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  • 51. Aftabi, Pedram
    et al.
    Roustaie, Mahasa
    Alsop, G.Ian
    Talbot, Christopher J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    InSAR mapping and modelling of an active Iranian salt extrusion2010Inngår i: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 167, nr 1, s. 155-170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Interferometric synthetic aperture radar (InSAR) imaging is a powerful technique that is increasingly used to extract detailed 3D information on Earth surface structures, including exposed diapiric surfaces. We have used InSAR to map, for the first time, the cumulative surface deformation in a 6 km × 3 6 km region surrounding an active salt diapir (Syahoo) and its associated surface salt flow (or namakier) exposed in the Zagros Mountains of southern Iran. Images provided by the European Space Agency were acquired in 12 increments (ranging in length between 35 and 1248 days) over a 14 year interval between July 1992 and May 2006. The deformation of the salt surface is non-steady, with (extrapolated) rates of displacement varying between surficial uplifts of +1.4 mm day-1 (+511 mm a-1) and subsidence of -2.2 mm day-1 (-803 mm a-1). Growth of a central topographic dome occurs following short wet intervals to create a salt fountain morphology, which then slowly decays during the intervening long dry periods. Salt associated with dynamic 'bulging' of the central dome during wet intervals may flow laterally via gravity spreading into the surrounding salt sheet, resulting in deflation and subsidence of the dome, which is counteracted by growth and inflation of the adjacent namakiers. Salt 'bulges' that migrate down the namakier, resulting in local inflationary and deflationary cycles of the surface, may be regarded as episodic pulses of gravity spreading. Areas of inflation and deflation are also observed to commonly reverse during dry to wet periods, as the overall salt system effectively self regulates as it continually strives for dynamic equilibrium. As long as the source of salt remains undepleted, gravity spreading of the dome ultimately results in more buoyancy-driven salt flowing up the diapiric neck to replenish and feed the extrusion and maintain the gross fountain morphology.

  • 52. Agapitov, Oleksiy
    et al.
    Krasnoselskikh, Vladimir
    Khotyaintsev, Yuri V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Rolland, Guy
    A statistical study of the propagation characteristics of whistler waves observed by Cluster2011Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, s. L20103-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    VLF waves play a crucial role in the dynamics of radiation belts, and are responsible for the loss and the acceleration of energetic electrons. Modeling wave-particle interactions requires the best possible knowledge for how wave energy and wave-normal directions are distributed in L-shells and for the magnetic latitudes of different magnetic activity conditions. In this work, we performed a statistical study for VLF emissions using a whistler frequency range for nine years (2001-2009) of Cluster measurements. We utilized data from the STAFF-SA experiment, which spans the frequency range from 8.8 Hz to 3.56 kHz. We show that the wave energy distribution has two maxima around L similar to 4.5 = 6 and L similar to 2, and that wave-normals are directed approximately along the magnetic field in the vicinity of the geomagnetic equator. The distribution changes with magnetic latitude, and so that at latitudes of similar to 30 degrees, wave-normals become nearly perpendicular to the magnetic field. The observed angular distribution is significantly different from Gaussian and the width of the distribution increases with latitude. Since the resonance condition for wave-particle interactions depends on the wave normal orientation, our results indicate that, due to the observed change in the wave-normal direction with latitude, the most efficient particle diffusion due to wave-particle interaction should occur in a limited region surrounding the geomagnetic equator.

  • 53. Agerstrand, Marlene
    et al.
    Berg, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Miljötoxikologi.
    Bjorlenius, Berndt
    Breitholtz, Magnus
    Brunström, Björn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Miljötoxikologi.
    Fick, Jerker
    Gunnarsson, Lina
    Larsson, D. G. Joakim
    Sumpter, John P.
    Tysklind, Mats
    Ruden, Christina
    Improving Environmental Risk Assessment of Human Pharmaceuticals2015Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, nr 9, s. 5336-5345Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents 10 recommendations for improving the European Medicines Agency's guidance for environmental risk assessment of human pharmaceutical products. The recommendations are based on up-to-date, available science in combination with experiences from other chemical frameworks such as the REACH-legislation for industrial chemicals. The recommendations concern: expanding the scope of the current guideline; requirements to assess the risk for development of antibiotic resistance; jointly performed assessments; refinement of the test proposal; mixture toxicity assessments on active pharmaceutical ingredients with similar modes of action; use of all available ecotoxicity studies; mandatory reviews; increased transparency; inclusion of emission data from production; and a risk management option. We believe that implementation of our recommendations would strengthen the protection of the environment and be beneficial to society. Legislation and guidance documents need to be updated at regular intervals in order to incorporate new knowledge from the scientific community. This is particularly important for regulatory documents concerning pharmaceuticals in the environment since this is a research field that has been growing substantially in the last decades.

  • 54.
    Agic, Heda
    et al.
    Department of Earth Science, University of California at Santa Barbara, Santa Barbara, USA.
    Högström, Anette
    Tromsø Universitetsmuseum.
    Jensen, Sören
    Área de Paleontología, Universidad de Extremadura, Avenida de Elvas s/n, Badajoz, Spain.
    Ebbestad, Jan Ove R.
    Uppsala universitet, Enheten för musik och museer, Evolutionsmuseet.
    Meinhold, Guido
    Geowissenschaftliches Zentrum der Universität Göttingen, Germany.
    Taylor, Wendy L.
    Department of Geological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
    Palacios, Teodor
    Área de Paleontología, Universidad de Extremadura, Avenida de Elvas s/n, Badajoz, Spain.
    Høyberget, Magne
    Rennesveien 14, N-4513 Mandal, Norway.
    Life through the 'Varanger ice ages': microfossil record of late Neoproterozoic glacial-interglacial units from arctic Norway2018Inngår i: Geological Society of America Abstracts with Programs, Geological Society of America, 2018, Vol. 50Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The late Neoproterozoic strata in Finnmark (Arctic Norway) provide a good sedimentary record of Neoproterozoic glaciations on the Baltica paleocontinent. The lower Vestertana Group exposed on the Digermulen Peninsula contains two glaciogenic units, the Smalfjord and Mortensnes formations. Chemostratigraphic correlation dated the Smalfjord diamictite to the Marinoan glaciation (650-635 Ma), yet its age was also proposed to be older, per correlation to glacial units in central and southern Scandinavia. The diamictites are bracketing shales and siltstones of the interglacial Nyborg Formation. Stratigraphic, paleontological, and sedimentological data are presented from the interglacial-glacial succession, investigated by the Digermulen Early Life Research Group. Palynological analysis yielded well-preserved organic-walled microfossils (OWM) from the Nyborg Fm., and from fine-grained diamictite matrix in the Mortensnes Fm. via a modified extraction method.

    The interglacial Nyborg Fm. hosts a moderate diversity assemblage of prokaryotic and eukaryotic OWM, as well as acanthomorphic acritarchs such as Ceratosphaeridium, ?Cavaspina, and a novel process-bearing form. Organically preserved, enigmatic multicellular eukaryotic fossils occur in the upper Nyborg Fm. The Mortensens glacial assemblage is less diverse and contains bacterial filaments, leiosphaerids, toroidal forms, and Micrhystridium-type minute acanthomorphs.

    The presence of Doushantuo-Pertatataka type acritarchs in the Nyborg Fm., and small acanthomorphs in the Mortensnes diamictite corroborate an early Ediacaran age for the interglacial-glacial succession on Digermulen. In addition to the trace fossil and body-fossil record of Ediacara-biota in the overlying Stáhpogieddi Formation, the microfossil biostratigraphy suggests Marinoan and Gaskiers glaciation equivalent ages of the Varanger glaciations in Finnmark. Protistan diversity in the succession declined through and following the glaciation, until late Ediacaran.

  • 55.
    Agic, Heda
    et al.
    Department of Earth Science, University of California at Santa Barbara, Santa Barbara, USA.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Högström, Anette
    Tromsø Universitetsmuseum.
    Ebbestad, Jan Ove R.
    Uppsala universitet, Enheten för musik och museer, Evolutionsmuseet.
    Jensen, Sören
    Área de Paleontología, Universidad de Extremadura, Avenida de Elvas s/n, Badajoz, Spain.
    Meinhold, Guido
    Geowissenschaftliches Zentrum der Universität Göttingen, Germany.
    Palacios, Teodor
    Área de Paleontología, Universidad de Extremadura, Avenida de Elvas s/n, Badajoz, Spain.
    Taylor, Wendy L.
    Department of Geological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
    Novis, Linn K.
    Tromsø Universitetsmuseum.
    Unusual organic-walled microfossil from the late Neoproterozoic Nyborg Formation, Digermulen Peninsula, Arctic Norway2017Inngår i: ISECT 2017, 2017Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The late Neoproterozoic Nyborg Formation is exposed in the Tanafjord area, Finnmark, Arctic Norway, on Digermulen and Varanger Peninsulas. The succession is composed of ~400 m of interbedded shales, siltstone and purple to grey sandstone, deposited between Neoproterozoic low latitude glacial deposits. The Nyborg Fm. lies on top of the Smalfjord diamictite, and is overlain by the Mortensnes diamictite (the latter was attributed to both Marinoan (650-635 Ma) and Gaskiers (579 Ma) glaciations) and the Ediacaran-Cambrian Stáhpogieddi Formation. Thus, the Nyborg Fm. represents late Neoproterozoic, probably the last Cryogenian interglacial interval. Presented material was collected in 2014 by members of Digermulen Early Life Research Group, from organic-rich, grey-green shales and siltstones of the Nyborg Mbr. D, uppermost Nyborg Fm. between Árasulluokta and Guvssájohka valleys. Organic-walled microfossils were extracted from shale via standard palynological acetolysis in hydrofluoric acid, and studied via light and scanning electron microscopy. Microfossils from the Nyborg Fm. include Synsphaeridium-type aggregated cells, unbranched bacterial filaments (Polythrichoides and Siphonophycus), sphaeromorph and envelope-bearing acritarchs (leiosphaerids, Stictosphaeridium, Simia), and previously unrecognized aggregated tubular microfossils. These taxa are long-ranging, but common in glacial-interglacial units worldwide, and thus broadly corroborate the Cryogenian age of the Nyborg sediments. The novel fossil, up to 300 μm in size, is a parenchymatous meshwork of interconnected organic-walled tubes that terminate in cup-shaped apices 4-11 µm in diameter. Irregular tube clusters are truncated both in macerates and in thin sections, suggesting post mortem transport. Elemental EDXS analysis indicates that extracted meshwork microfossils are predominantly composed of carbonaceous material and also associated with small amounts of titanium and vanadium. Considering the branching and adjoined body plan of carbonaceous fossil, it was likely multicellular and of eukaryotic affinity. As such, it may represent an important step in the evolution of complex multicellularity and morphological complexity several million years before the appearance of Ediacaran organisms.

  • 56.
    Agić, Heda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    A new species of small acritarch with porous wall structure from the early Cambrian of Estonia, and implications for the fossil record of eukaryotic picoplankton2015Inngår i: Palynology, ISSN 0191-6122, E-ISSN 1558-9188, Vol. 40, nr 3, s. 343-356Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Proterozoic-Phanerozoic transition records a general trend of decrease in phytoplankton cell size, in contrast tothe earlier and much larger Ediacaran acritarchs. Particularly minute, unornamented but sculptured organic-walledmicrofossils have been recovered from the lower Cambrian Lükati Formation in northern Estonia. The lack of anysignificant thermal alteration in the formation allowed for excellent preservation of fine microstructures on thesemicrofossils. Among the rich palynomorph assemblage in Lükati, a new species of tiny, spheroidal eukaryoticmicrofossil is recorded: Reticella corrugata gen. et sp. nov. It is characterised by a corrugated and flexible vesicle wallthat is densely perforated by nano-scale pores. Despite its unique morphology, the new species shares diagnosticcharacters with fossil and extant prasinophyte algae. R. corrugata is among the smallest microfossils with typicaleukaryotic morphology (conspicuous wall sculpture) and contributes to the diversity of the size class of smallacritarchs. Size, abundance, inferred prasinophyte affinity and eukaryotic wall sculpture make this new taxon alikely member of the early eukaryotic picoplankton.

  • 57.
    Agić, Heda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Fossil Focus: Acritarchs2016Inngår i: Palaeontology Online, Vol. 6, nr 11, s. 1-13Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 58.
    Agić, Heda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Microfossils of eukaryotic cysts through time: A study of Precambrian-Ordovician organic-walled microbiota2014Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 59.
    Agić, Heda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    One of the most important events in the history of life is the evolution of the complex, eukaryotic cell. The eukaryotes are complex organisms with membrane-bound intracellular structures, and they include a variety of both single-celled and multicellular organisms: plants, animals, fungi and various protists. The evolutionary origin of this group may be studied by direct evidence of past life: fossils. The oldest traces of eukaryotes have appeared by 2.4 billion years ago (Ga), and have additionally diversified in the period around 1.8 Ga. The Mesoproterozoic Era (1.6-1 Ga) is characterised by the first evidence of the appearance complex unicellular microfossils, as well as innovative morphologies, and the evolution of sexual reproduction and multicellularity. For a better understanding of the early eukaryotic evolution and diversification patterns, a part of this thesis has focused on the microfossil records from various time periods and geographic locations. Examination of microfossil morphology, cell wall microstructure and biochemical properties, reflect their intracellular complexity and function, and allow reconstructions of their life cycle, as well as observing the evolutionary pattern of change from Mesoproterozoic, to Cambrian-Ordovician transition. Several case studies included assemblages deriving from Mesoproterozoic, Neoproterozoic and early Paleozoic time intervals that show disparate morphotypes and innovative features indicative of algal clades. The Mesoproterozoic Ruyang Group in northern China has yielded a diverse microfossil assemblage that provides important clues about the diversification of different eukaryotic groups. Furthermore these microfossils contributed an additional evidence for the emergence of the crown group Eukarya by 1.7-1.4 Ga. In another part of this thesis, examination of wall microstructure and chemical properties via Raman spectroscopy has been used to assess the biological affinities of various Neoproterozoic problematic carbonaceous compression fossils. Studies on the early Phanerozoic (c. 545-485 Ma) assemblages from Estonia reconstructed patterns of the early radiations of phytoplankton and its evolutionary innovations. A continuing theme in this thesis has been using a combination of evidence of microfossils’ fine-scale morphology, ecology and chemical properties to determine their function in life, in addition to their systematic position.

    Delarbeid
    1. Affnity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China
    Åpne denne publikasjonen i ny fane eller vindu >>Affnity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China
    2015 (engelsk)Inngår i: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 89, nr 1, s. 28-50Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Light microscope and scanning electron microscope observations on new material of unicellularmicrofossils Dictyosphaera macroreticulata and Shuiyousphaeridium macroreticulatum, from the MesoproterozoicRuyang Group in China, provide insights into the microorganisms’ biological affinity, life cycle and cellularcomplexity. Gigantosphaeridium fibratum n. gen. et sp., is described and is one of the largest Mesoproterozoicmicrofossils recorded. Phenotypic characters of vesicle ornamentation and excystment structures, properties ofresistance and cell wall structure in Dictyosphaera and Shuiyousphaeridium are all diagnostic of microalgalcysts. The wide size ranges of the various morphotypes indicate growth phases compatible with the development ofreproductive cysts. Conspecific biologically, each morphotype represents an asexual (resting cyst) or sexual (zygotic cyst)stage in the life cycle, respectively. We reconstruct this hypothetical life cycle and infer that the organism demonstrates areproductive strategy of alternation of heteromorphic generations. Similarly in Gigantosphaeridium, a metabolicallyexpensive vesicle with processes suggests its protective role as a zygotic cyst. In combination with all these charactersand from the resemblance to extant green algae, we propose the placement of these ancient microorganisms in the stemgroup of Chloroplastida (Viridiplantae). A cell wall composed of primary and secondary layers in Dictyosphaera andShuiyouisphaeridium required a high cellular complexity for their synthesis and the presence of an endomembranesystem and the Golgi apparatus. The plastid was also present, accepting the organism was photosynthetic. The biotareveals a high degree of morphological and cell structural complexity, and provides an insight into ongoing eukaryoticevolution and the development of complex life cycles with sexual reproduction by 1200Ma.

    sted, utgiver, år, opplag, sider
    Cambridge Journals, 2015
    Emneord
    organic-walled microfossils; early eukaryotes; Mesoproterozoic; Dictyosphaera; Shuiyousphaeridium; algae; evolution; intracellular complexity
    HSV kategori
    Forskningsprogram
    Geovetenskap med inriktning mot historisk geologi och paleontologi; Biologi med inriktning mot systematik
    Identifikatorer
    urn:nbn:se:uu:diva-247264 (URN)10.1017/jpa.2014.4 (DOI)000351478500003 ()
    Forskningsfinansiär
    Swedish Research Council, 621-2009-4445
    Tilgjengelig fra: 2015-03-16 Laget: 2015-03-16 Sist oppdatert: 2017-12-04bibliografisk kontrollert
    2. Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton - a window into the early eukaryote evolution
    Åpne denne publikasjonen i ny fane eller vindu >>Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton - a window into the early eukaryote evolution
    2017 (engelsk)Inngår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, s. 101-130Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Mesoproterozoic Era was an important time for the initial diversification of eukaryotic groups and the appearance of the first complex morphologies. While eukaryotes evolved around 2.4 Ga, the first microfossils with ornamentation and sculpture occur in the 1.8-1.6 Ga successions worldwide. Shales and siltstones of the Ruyang Group, Shanxi Province, North China Craton, record a high diversity of such organic-walled microfossils. Recently, the depositional ages of this succession has been constrained to 1.75-1.40 Ga via   zircon U-Pb dating. This dating extends back the time of the first appearance of complex eukaryotic characters (e.g. processes, complex wall structure) in the fossil record. We have conducted a biostratigraphic investigation on of the samples throughout the fossiliferous Ruyang Group to provide an estimate of the early eukaryotic diversity in the Mesoproterozoic. Light- and scanning electron microscope studies have documented 26 species, including several that are reported for the first time, and some that were previously known only from younger, Neoproterozoic strata. Fossil diversity is high in the upper Baicaoping Formation, declines in the middle and reaches its peak in the upper Beidajian Formation. Novel morphologies among the unicellular Ruyang biota include a variety of processes, from tube-like extensions to hirsute spines, vesicles with velutinous outer membranes, as well as numerous specimens with internal bodies of varying sizes. We have also recorded the globally distributed Mesoproterozoic taxa Dictyosphaera, Shuiyousphaeridium, and Tappania. Key characters displayed by the Ruyang biota are consistent with reproductive structures (especially cysts among modern protists. These microfossils provide an additional evidence for the emergence of the crown group Eukarya by 1.7-1.4 Ga.

    Emneord
    Mesoproterozoic, Ruyang Group, organic-walled microfossils, eukaryotic evolution, North China, Dictyosphaera.
    HSV kategori
    Forskningsprogram
    Geovetenskap med inriktning mot historisk geologi och paleontologi
    Identifikatorer
    urn:nbn:se:uu:diva-265216 (URN)10.1016/j.precamres.2017.04.042 (DOI)000404697200006 ()
    Prosjekter
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
    Forskningsfinansiär
    Swedish Research Council, 621-2009-4445
    Tilgjengelig fra: 2015-10-25 Laget: 2015-10-25 Sist oppdatert: 2018-02-22bibliografisk kontrollert
    3. Raman spectroscopy and microstructural comparison of carbonaceous compression and body fossils from the Neoproterozoic of Siberian and Eastern European platforms
    Åpne denne publikasjonen i ny fane eller vindu >>Raman spectroscopy and microstructural comparison of carbonaceous compression and body fossils from the Neoproterozoic of Siberian and Eastern European platforms
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Macroscopic, organic-walled fossils preserved as carbonaceous compressions and body fossils are commonly occurring in the Neoproterozoic-Cambrian successions worldwide. Most of these fossils, including studied here Chuaria, Tawuia, and Beltemelliformis, have been accepted as algae, and Sabellidites as an early metazoan. They possess limited characters for biological identification and differ in gross morphology of spherodial vs. tubular millimetre-sized specimens. Consequently, other methods than morphologic observations are needed to elucidate their affinities and, ultimately, phylogeny. Here we present a comparison of the Raman spectrographic signatures and new scanning electron microscope (SEM) observations on different carbonaceous compression and body fossils from the Khajpakh Formation (Siberian Platform), and Nekrasovo Formation (East European Platform), referred to the Tonian-Cryogenian transitional interval (c. 840-700 Ma) and the lowermost Cambrian stage, respectively. Data from the Raman spectroscopy of the walls of non-mineralised organisms reveal their chemical properties, and, in additions to microstructural characters, may be used to resolve the fossils’ phylogenetic affinities. To test the basic recognition of organic matter in studied photosynthetic organisms vs. animals, we have examined algal compression fossils and organically-preserved body-fossil. Differences in the Raman spectroscopic signature between various taxa have been observed. Vibrational absorption bands similar to those characteristic of α-chitin signature have been detected in the organic wall of Sabellidites, consistent with its metazoan identity. Distinct organic matter spectra of the macroalgae Chuaria, Tawuia and Beltanelliformis, and the possible early annelid Sabellidites indicate that Raman spectroscopy could be a useful method in identifying different branches of the early eukaryotes. Additionally, the recognition of the earliest metazoans among un-diagnostic tubular fossils by biochemical signatures and wall ultrastructure, could provide the minimum age of their origins.

    Emneord
    Neoproterozoic, Cambrian, tubular fossils, organic body fossils, Raman spectroscopy, SEM, East European Platform, Siberian Platform
    HSV kategori
    Forskningsprogram
    Geovetenskap med inriktning mot historisk geologi och paleontologi
    Identifikatorer
    urn:nbn:se:uu:diva-265206 (URN)
    Prosjekter
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
    Forskningsfinansiär
    Swedish Research Council, 621-2012-1669
    Tilgjengelig fra: 2015-10-25 Laget: 2015-10-25 Sist oppdatert: 2015-12-04
    4. Ecdysozoan-like sclerites among Ediacaran microfossils
    Åpne denne publikasjonen i ny fane eller vindu >>Ecdysozoan-like sclerites among Ediacaran microfossils
    2015 (engelsk)Inngår i: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 152, nr 6, s. 1145-1148Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    We report the occurrence of organically preserved microfossils from the subsurface Ediacaran strata overlying the East European Platform in Poland, in the form of sclerites and cuticle fragments of larger organisms. They are morphologically similar to those known from Cambrian strata and associated with various metazoan fossils of recognized phyla. The Ediacaran age of the microfossils is evident from the stratigraphic position below the base of the Cambrian System and above the isotopically dated tuff layers at c. 551±4Ma. Within this strata interval, other characteristic Ediacaran microorganisms co-occur such as cyanobacteria, vendotaenids, microalgae, Ceratophyton,Valkyria and macroscopic annelidan Sabellidites. The recent contributions of organic sclerites in revealing the scope of the Cambrian explosion are therefore also potentially extendable back to the Ediacaran Period when animals first appear in the fossil record.

    sted, utgiver, år, opplag, sider
    Cambridge: Cambridge University Press, 2015
    Emneord
    Ediacaran metazoans; small carbonaceous fossils; Poland; organic preservation; refractory biopolymers
    HSV kategori
    Forskningsprogram
    Geovetenskap med inriktning mot historisk geologi och paleontologi
    Identifikatorer
    urn:nbn:se:uu:diva-264156 (URN)10.1017/S001675681500045X (DOI)000367730400013 ()
    Forskningsfinansiär
    Swedish Research Council, 621-2012-1669, 621-2011-4703
    Tilgjengelig fra: 2015-10-06 Laget: 2015-10-06 Sist oppdatert: 2017-12-01bibliografisk kontrollert
    5. A new species of small acritarch with porous wall structure from the early Cambrian of Estonia, and implications for the fossil record of eukaryotic picoplankton
    Åpne denne publikasjonen i ny fane eller vindu >>A new species of small acritarch with porous wall structure from the early Cambrian of Estonia, and implications for the fossil record of eukaryotic picoplankton
    2015 (engelsk)Inngår i: Palynology, ISSN 0191-6122, E-ISSN 1558-9188, Vol. 40, nr 3, s. 343-356Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The Proterozoic-Phanerozoic transition records a general trend of decrease in phytoplankton cell size, in contrast tothe earlier and much larger Ediacaran acritarchs. Particularly minute, unornamented but sculptured organic-walledmicrofossils have been recovered from the lower Cambrian Lükati Formation in northern Estonia. The lack of anysignificant thermal alteration in the formation allowed for excellent preservation of fine microstructures on thesemicrofossils. Among the rich palynomorph assemblage in Lükati, a new species of tiny, spheroidal eukaryoticmicrofossil is recorded: Reticella corrugata gen. et sp. nov. It is characterised by a corrugated and flexible vesicle wallthat is densely perforated by nano-scale pores. Despite its unique morphology, the new species shares diagnosticcharacters with fossil and extant prasinophyte algae. R. corrugata is among the smallest microfossils with typicaleukaryotic morphology (conspicuous wall sculpture) and contributes to the diversity of the size class of smallacritarchs. Size, abundance, inferred prasinophyte affinity and eukaryotic wall sculpture make this new taxon alikely member of the early eukaryotic picoplankton.

    Emneord
    Cambrian, Estonia, organic-walled microfossils, picoplankton, prasinophytes, small acritarchs
    HSV kategori
    Forskningsprogram
    Geovetenskap med inriktning mot historisk geologi och paleontologi
    Identifikatorer
    urn:nbn:se:uu:diva-265208 (URN)10.1080/01916122.2015.1068879 (DOI)000386047200007 ()
    Prosjekter
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
    Forskningsfinansiär
    Swedish Research Council, 621-2012-1669
    Tilgjengelig fra: 2015-10-25 Laget: 2015-10-25 Sist oppdatert: 2017-11-10bibliografisk kontrollert
    6. Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils
    Åpne denne publikasjonen i ny fane eller vindu >>Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils
    2016 (engelsk)Inngår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 138, nr 2, s. 278-294Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Unicellular organic-walled microfossils from the Cambrian-Ordovician transition in Estonia (ca. 490-480 million years ago) exhibit rare characters reflecting their function as reproductive algal cysts. The studied assemblages record the evolutionary history of phytoplankton in the early Paleozoic Era: novel morphologies appearing through the Cambrian and subsequently diversifying in the Ordovician. Well preserved specimens were extracted following a standard palynological method and studied by light transmitted microscopy. The galeate plexus acritarchs Caldariola, Priscogalea and Stelliferidium have revealed exceptionally preserved morphological elements and a rare structure among both fossil and extant protists – an opening with operculum (lid) in reproductive cysts, in addition to lavish vesicle ornamentation and sculpture. Analogous morphology is observed in the living dasycladalean alga Acetabularia (Chlorophyta), which possesses an intrinsic lid-forming apparatus used during organism’s reproductive stage. Based on the observations on the fossil material and studies on the Acetabularia lid-formation, we propose a model of operculum formation in the galeate plexus microorganisms. Due to strong morphological and ecological similarities between galeate fossils and dasycladalean cysts, and the antiquity of this algal order, galeates may be positioned within green algae, more specifically Dasycladales. Unique morphology of the operculum-bearing microbiota would have required a high degree of intracellular complexity for its development, suggesting that advanced intracellular machinery was present already in the early Paleozoic phytoplankton. Additionally, minute prasinophyte microfossils Reticella corrugata  are reported for the first time in the Upper Cambrian strata. 

    Emneord
    acritarchs, Baltica, cyst-formation, Dasycladales, Estonia, galeate plexus, microfossils, operculum, Ordovician, palaeobiology
    HSV kategori
    Forskningsprogram
    Geovetenskap med inriktning mot historisk geologi och paleontologi
    Identifikatorer
    urn:nbn:se:uu:diva-265207 (URN)10.1080/11035897.2015.1116603 (DOI)000379763500001 ()
    Prosjekter
    Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
    Forskningsfinansiär
    Swedish Research Council, 621-2012-1669Danish National Research Foundation, DNRF53
    Tilgjengelig fra: 2015-10-25 Laget: 2015-10-25 Sist oppdatert: 2017-12-01bibliografisk kontrollert
  • 60.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Univ Calif Santa Barbara, Dept Earth Sci, Santa Barbara, CA 93106 USA.
    Högström, Anette E. S.
    UiT Arctic Univ Norway, Arctic Univ Museum Norway, N-9037 Tromso, Norway.
    Moczydlowska, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Jensen, Sören
    Univ Extremadura, Area Paleontol, E-06006 Badajoz, Spain.
    Palacios, Teodoro
    Univ Extremadura, Area Paleontol, E-06006 Badajoz, Spain.
    Meinhold, Guido
    Keele Univ, Sch Geog Geol & Environm, Keele ST5 5BG, Staffs, England;Univ Gottingen, Dept Sedimentol & Environm Geol, Goldschmidtstr 3, D-37077 Gottingen, Germany.
    Ebbestad, Jan Ove R.
    Uppsala universitet, Enheten för musik och museer, Evolutionsmuseet.
    Taylor, Wendy L.
    Univ Cape Town, Dept Geol Sci, ZA-7701 Rondebosch, South Africa.
    Höyberget, Magne
    Rennesveien 14, N-4513 Mandal, Norway.
    Organically-preserved multicellular eukaryote from the early Ediacaran Nyborg Formation, Arctic Norway2019Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, artikkel-id 14659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Eukaryotic multicellularity originated in the Mesoproterozoic Era and evolved multiple times since, yet early multicellular fossils are scarce until the terminal Neoproterozoic and often restricted to cases of exceptional preservation. Here we describe unusual organically-preserved fossils from mudrocks, that provide support for the presence of organisms with differentiated cells (potentially an epithelial layer) in the late Neoproterozoic. Cyathinema digermulense gen. et sp. nov. from the Nyborg Formation, Vestertana Group, Digermulen Peninsula in Arctic Norway, is a new carbonaceous organ-taxon which consists of stacked tubes with cup-shaped ends. It represents parts of a larger organism (multicellular eukaryote or a colony), likely with greater preservation potential than its other elements. Arrangement of open-ended tubes invites comparison with cells of an epithelial layer present in a variety of eukaryotic clades. This tissue may have benefitted the organism in: avoiding overgrowth, limiting fouling, reproduction, or water filtration. C. digermulense shares characteristics with extant and fossil groups including red algae and their fossils, demosponge larvae and putative sponge fossils, colonial protists, and nematophytes. Regardless of its precise affinity, C. digermulense was a complex and likely benthic marine eukaryote exhibiting cellular differentiation, and a rare occurrence of early multicellularity outside of Konservat-Lagerstatten.

  • 61.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Is cyst formation in early eukaryotes a requirement for their preservation in the fossil record?2015Inngår i: Abstracts of the Astrobiology Science Conference 2015: Habitability, Habitable Worlds and Life: EARTH’S EARLY BIOSPHERE: LIFE ON AN “ALIEN” PLANET, 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Most of the Archaean-Proterozoic fossil record consists of non-biomineralizing microorganisms or their signatures. Body fossils of bacteria and early eukaryotes are preserved in siliciclastics, shales and carbonates, and are usually studied by preparation of thin sections or extraction from the rock matrix via acid maceration.The first eukaryotic organic-walled microfossils (OWM) appear at least by 1.8 Ga and undergo morphological diversification and evolutionary radiation in the Mesoproterozoic. There are no preserved eukaryotic-grade microfossils except OWM until the onset of biomineralization much later in the Neoproterozoic, evident in the record of testate amoebae (VSM) and microfossils with scaly elements.OWM are a less conspicuous component of the fos-sil record than taxa with skeletal or shelly elements. Organic matter decays quickly upon death of the organism, due to autolytic enzymes or degradation via het-erotrophy. However, species producing vegetative cells, resting cysts, zygotes, or spores, show considerable resistance to autolysis. Case studies on extractable carbonaceous OWM indicate they are preserved due to complex refractory molecules in the structure of their sturdy vesicle walls. Living analogues across protistan clades utilise such sporopollenin-like compounds for the cyst wall construction during reproductive phase. Algaenan-containing trilaminar sheath structure (TLS) is secreted during aplanospore formation in extant chlorophyte alga Haematococcus. TLS has also been documented in Leiosphaeridia acritarchs from the Cambrian Lükati Formation in Estonia. Leiosphaeridia is a long ranging morphotype, dating as far back as 1.8 Ga. Presence of TLS in these fossils suggests their function as reproductive cyst. Dictyosphaera-Shuiyousphaeridium plexus from the Mesoproterozoic Ruyang Group, China, also exhibits cyst-like morphology and unique elements of wall reinforcement: internally secreted organic platelets.In addition to these early OWM, many Meso-Neoproterozoic taxa such as Tappania, Trachyhystrychosphaera and Kildinella contain cyst-like characters: 1) reproductive openings, 2) ornamentation, 3) occa-sionally preserved internal bodies and 4) acetolysis-resistant vesicle walls – properties observed among extant encysting protists.Ornamented (process-bearing) microfossils in par-ticular bear strong similarities with zygotes of living unicellular algae. Property of acetolysis-resistant vesicle is a result of sporopollenin-like macromolecules in the wall, synthesized most commonly by the autotrophic eukaryotes. Presence of such recalcitrant organic walls requires significant metabolic investment by the microorganism, which suggests a protective and/or reproductive function. This also allows for easier, and more detailed preservation in the rock record.One of the concerns arising from the studies on the early eukaryotic fossils is the bias towards encysting organisms. The eventual search for the fossil record on other planetary bodies could face the same challenges as the Precambrian palaeobiology: fossilisation and eventual detection might be problematic for any unicellular eukaryotic-grade organisms if they have not evolved reproduction via encystment, or cyst formation as means of coping with adverse environmental conditions.

  • 62.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Raman spectra analysis and comparison of Neoproterozoic organic-walled mesofossils2012Inngår i: The 2012 Fermor Meeting of the Geological Society: The Neoproterozoic Era: Evolution, Glaciation, Oxygenation / [ed] Fairchild I., Condon D., Lenton T., Shields-Zhou G., Brasier M.D., London, 2012, Vol. 1, s. 86-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Skeletal material first appears in the rock record in the terminal Ediacaran, leaving most of the Earth’s history only to minute organic fossils. Aside from abundant acritarchs (unicellular organic-walled phytoplankton) present from at least ~2.5 Ga, other Proterozoic organic fossils of complex (eukaryotic) organisms include fungi and macroscopic algae of still debated taxonomy. Often preserved as flattened carbonaceous filaments in several morphologies: (1) rounded, (2) stick-like elongate and (3) branching, these Neoproterozoic fossils, including Chuaria, Morania, Beltanelloides, Vendotaenia, possess limited characters and differ little in gross morphology. As a result, other methods are needed to elucidate their biological affinities and, ultimately, phylogeny.

    Here we present the comparison of the Raman spectra analysis of different macroalgal genera from Yakutia, Siberia, as well as that of a putative polychaete Sabellidites from the East European Platform, dated to the early Cryogenian (840-700 Ma) and lowermost Cambrian respectively.

    Data from the vibrational modes of organic molecules from the wall of unmineralised organisms reveal their chemistry and partially wall ultrastructure, presumably an indication of their relationships. Polyaromatic chain hydrocarbons and n-aliphatic pyrolysates suggest algal affinity for some of the Neoproterozoic organic problematica, yet most of the Raman spectra results are still difficult to fully identify, partially owing to the thermal maturity of the host rocks. However, there are clear differences between various groups, differentiating between parts of a single plexus (cf previous studies of Chuaria-Tawuia suggesting them to be components of a multicellular plant) and elements from other taxa. Additionally, the distinct organic matter spectra of Chuaria and Sabellidites indicate that Raman spectroscopy could be a useful method in identifying different branches of the early eukaryotes.

    As they are usually shallow-water and dependant on sunlight, the record of sturdy photosynthetic macroorganisms in the  Neoproterozoic strengthens the evidence that limits the extent of the harsh environmental conditions during the Cryogenian period, at least during the Kaigas and Sturtian glaciations.

  • 63.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Raman spectroscopy and microstructural comparison of carbonaceous compression and body fossils from the Neoproterozoic of Siberian and Eastern European platformsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Macroscopic, organic-walled fossils preserved as carbonaceous compressions and body fossils are commonly occurring in the Neoproterozoic-Cambrian successions worldwide. Most of these fossils, including studied here Chuaria, Tawuia, and Beltemelliformis, have been accepted as algae, and Sabellidites as an early metazoan. They possess limited characters for biological identification and differ in gross morphology of spherodial vs. tubular millimetre-sized specimens. Consequently, other methods than morphologic observations are needed to elucidate their affinities and, ultimately, phylogeny. Here we present a comparison of the Raman spectrographic signatures and new scanning electron microscope (SEM) observations on different carbonaceous compression and body fossils from the Khajpakh Formation (Siberian Platform), and Nekrasovo Formation (East European Platform), referred to the Tonian-Cryogenian transitional interval (c. 840-700 Ma) and the lowermost Cambrian stage, respectively. Data from the Raman spectroscopy of the walls of non-mineralised organisms reveal their chemical properties, and, in additions to microstructural characters, may be used to resolve the fossils’ phylogenetic affinities. To test the basic recognition of organic matter in studied photosynthetic organisms vs. animals, we have examined algal compression fossils and organically-preserved body-fossil. Differences in the Raman spectroscopic signature between various taxa have been observed. Vibrational absorption bands similar to those characteristic of α-chitin signature have been detected in the organic wall of Sabellidites, consistent with its metazoan identity. Distinct organic matter spectra of the macroalgae Chuaria, Tawuia and Beltanelliformis, and the possible early annelid Sabellidites indicate that Raman spectroscopy could be a useful method in identifying different branches of the early eukaryotes. Additionally, the recognition of the earliest metazoans among un-diagnostic tubular fossils by biochemical signatures and wall ultrastructure, could provide the minimum age of their origins.

  • 64.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Canfield, Donald
    University of Southern Denmark.
    Cyst and operculum formation in Cambrian-Ordovician galeate acritarchs from Estonia: implications for the algal phylogeny and blooms in the early Paleozoic2014Inngår i: 4th International Palaeontological Congress Abstract Volume: The history of life: a view from the Southern Hemisphere, 2014, s. 913-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Unicellular organic-walled microfossils have been recovered from the Cambrian Lükati Formation and the Tremadocian Varangu Formation exposed in northern Estonia. Due to a combination of main morphological and biochemical characters, mainly a) excystment opening, b) processes, c) acetolysis-  resistant vesicle wall, microfossils have been interpreted as reproductive cysts of green algae. Both microfossil assemblages reflect the evolutionary patterns though the early Palaeozoic: from the Cambrian radiation of morphologically innovative taxa to increase in diversity and more disparate Ordovician forms. Combined light transmitted and scanning electron microscopy on the Middle Cambrian to Tremadocian galeate plexus acritarchs CaldariolaPriscogalea and Stelliferidium, revealed exceptionally preserved morphological elements and rare structure among fossil and extant microbiota – an opening with operculum (lid) in reproductive cyst, in addition to lavish vesicle ornamentation and sculpture. Operculum formation model is reconstructed from fossils at different stages of operculum position and attachment. Comparative morphology shows strong similarity of galeates to the reproductive cysts of the extant algae of Dasycladales (Chlorophyta), where the lid covering the cyst opening is determined by an intrinsic lid-forming apparatus during the organism’s reproductive stage. Opercula in Cambro-Ordovician galeate acritarchs and Dasycladales may be considered a homologous character. Unique morphology of the operculum-bearing microbiota would have required a degree of intracellular sophistication for its development, suggesting advanced intracellular machinery present already in the early Palaeozoic phytoplankton. Additionally, a new species of minute, sphaeromorphic and aggregated eukaryotic microfossils is recorded. It possesses a vesicle wall with corrugated sculpture and perforated by nano-scale pores. These minute early Cambrian microfossils have diagnostic characters of prasinophyte algae.

  • 65.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Canfield, Donald
    University of Southern Denmark .
    Reproductive cyst and operculum formation in the Cambrian-Ordovician galeate-plexus microfossils2016Inngår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 138, nr 2, s. 278-294Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Unicellular organic-walled microfossils from the Cambrian-Ordovician transition in Estonia (ca. 490-480 million years ago) exhibit rare characters reflecting their function as reproductive algal cysts. The studied assemblages record the evolutionary history of phytoplankton in the early Paleozoic Era: novel morphologies appearing through the Cambrian and subsequently diversifying in the Ordovician. Well preserved specimens were extracted following a standard palynological method and studied by light transmitted microscopy. The galeate plexus acritarchs Caldariola, Priscogalea and Stelliferidium have revealed exceptionally preserved morphological elements and a rare structure among both fossil and extant protists – an opening with operculum (lid) in reproductive cysts, in addition to lavish vesicle ornamentation and sculpture. Analogous morphology is observed in the living dasycladalean alga Acetabularia (Chlorophyta), which possesses an intrinsic lid-forming apparatus used during organism’s reproductive stage. Based on the observations on the fossil material and studies on the Acetabularia lid-formation, we propose a model of operculum formation in the galeate plexus microorganisms. Due to strong morphological and ecological similarities between galeate fossils and dasycladalean cysts, and the antiquity of this algal order, galeates may be positioned within green algae, more specifically Dasycladales. Unique morphology of the operculum-bearing microbiota would have required a high degree of intracellular complexity for its development, suggesting that advanced intracellular machinery was present already in the early Paleozoic phytoplankton. Additionally, minute prasinophyte microfossils Reticella corrugata  are reported for the first time in the Upper Cambrian strata. 

  • 66.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Yin, Leiming
    Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.
    Affnity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China2015Inngår i: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 89, nr 1, s. 28-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Light microscope and scanning electron microscope observations on new material of unicellularmicrofossils Dictyosphaera macroreticulata and Shuiyousphaeridium macroreticulatum, from the MesoproterozoicRuyang Group in China, provide insights into the microorganisms’ biological affinity, life cycle and cellularcomplexity. Gigantosphaeridium fibratum n. gen. et sp., is described and is one of the largest Mesoproterozoicmicrofossils recorded. Phenotypic characters of vesicle ornamentation and excystment structures, properties ofresistance and cell wall structure in Dictyosphaera and Shuiyousphaeridium are all diagnostic of microalgalcysts. The wide size ranges of the various morphotypes indicate growth phases compatible with the development ofreproductive cysts. Conspecific biologically, each morphotype represents an asexual (resting cyst) or sexual (zygotic cyst)stage in the life cycle, respectively. We reconstruct this hypothetical life cycle and infer that the organism demonstrates areproductive strategy of alternation of heteromorphic generations. Similarly in Gigantosphaeridium, a metabolicallyexpensive vesicle with processes suggests its protective role as a zygotic cyst. In combination with all these charactersand from the resemblance to extant green algae, we propose the placement of these ancient microorganisms in the stemgroup of Chloroplastida (Viridiplantae). A cell wall composed of primary and secondary layers in Dictyosphaera andShuiyouisphaeridium required a high cellular complexity for their synthesis and the presence of an endomembranesystem and the Golgi apparatus. The plastid was also present, accepting the organism was photosynthetic. The biotareveals a high degree of morphological and cell structural complexity, and provides an insight into ongoing eukaryoticevolution and the development of complex life cycles with sexual reproduction by 1200Ma.

  • 67.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Yin, Leiming
    Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.
    Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton - a window into the early eukaryote evolution2017Inngår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, s. 101-130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mesoproterozoic Era was an important time for the initial diversification of eukaryotic groups and the appearance of the first complex morphologies. While eukaryotes evolved around 2.4 Ga, the first microfossils with ornamentation and sculpture occur in the 1.8-1.6 Ga successions worldwide. Shales and siltstones of the Ruyang Group, Shanxi Province, North China Craton, record a high diversity of such organic-walled microfossils. Recently, the depositional ages of this succession has been constrained to 1.75-1.40 Ga via   zircon U-Pb dating. This dating extends back the time of the first appearance of complex eukaryotic characters (e.g. processes, complex wall structure) in the fossil record. We have conducted a biostratigraphic investigation on of the samples throughout the fossiliferous Ruyang Group to provide an estimate of the early eukaryotic diversity in the Mesoproterozoic. Light- and scanning electron microscope studies have documented 26 species, including several that are reported for the first time, and some that were previously known only from younger, Neoproterozoic strata. Fossil diversity is high in the upper Baicaoping Formation, declines in the middle and reaches its peak in the upper Beidajian Formation. Novel morphologies among the unicellular Ruyang biota include a variety of processes, from tube-like extensions to hirsute spines, vesicles with velutinous outer membranes, as well as numerous specimens with internal bodies of varying sizes. We have also recorded the globally distributed Mesoproterozoic taxa Dictyosphaera, Shuiyousphaeridium, and Tappania. Key characters displayed by the Ruyang biota are consistent with reproductive structures (especially cysts among modern protists. These microfossils provide an additional evidence for the emergence of the crown group Eukarya by 1.7-1.4 Ga.

  • 68.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Yin, Leiming
    Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.
    Morphology of the Proterozoic eukaryotic microfossils as a reflection of their intracellular complexity2014Inngår i: 4th International Palaeontological Congress Abstract Volume: The history of life: a view fom the southern hemisphere / [ed] Esperanza CERDEÑO, 2014, s. 256-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mesoproterozoic is a time of increasing diversity of microscopic life and appearance of intricate new cell morphologies. First eukaryotes may have evolved around 2.4 Ga, but the first microbiota with intricate sculpture and ornamentation are found in the younger, 1.8.-1.6 Ga successions worldwide. Such microfossils were uncovered from the Ruyang Formation in Shanxi, China and Roper Group, Northern Territories, Australia, dating back to 1.6-1.0 Ga ago. Some of these unicellular organic-walled fossils share characters with Ediacaran and Phanerozoic fossils, as well as extant green microalgae. Key characters among some Precambrian acritarchs are acetolysis-resistant vesicle with multi-layered walls; vesicle ornamentation by diverse processes that are produced during cyst formation; and excystment openings for the release of gametes or daughter-cells. Combination of these morphological elements, also present in extant phytoplankton, reflects the fossils’ protective function as reproductive cysts, indicating that complex life cycles and reproduction were well under way in Mesoproterozoic. Several case studies of microfossil morphology likely induced by intrinsic eukaryotic mechanisms are presented.

    Distinctive vesicle wall composed of the primary layer reinforced by polygonal platelets in Mesoproterozoic taxa Dictyosphaera and Shuiyouisphaeridium, as well as the sophisticated vesicle-wall patterning on the fossil sphaeromorphs Valeria and younger Cerebrosphaera would have required a certain degree of complexity for their formation, as observed in the present day analogues among eukaryotic protists. This suggests the activity of the key eukaryotic organelles and cellular mechanisms and signalling for the cyst formation. Considering that Golgi apparatus and the endoplasmatic reticulum are the organelles regulating eukaryotic secretory pathway and synthesis of biopolymers used in cell-wall construction, they would have been required for the complex morphology observed in these Precambrian taxa. Therefore, the presence of GA and ER in the eukaryotic cell is inferred at the minimum age of 1.6-1.4 Ga. Similarly, morphology of acritarchs of the Cambrian galeate plexus, namely openings with opercula, is likely induced by the activity of the LFA organelle (lid-forming apparatus) as in the extant dasycladalean alga Acetabularia.

    Additionally, several new morphotypes from the Ruyang Formation are presented. These unicellular fossils bear a velutinous outer membrane surrounding an internal sphere, which suggests a protective function of a reproductive or a resting cyst.

    Cyst-like morphology varies in disparity, but its key features are consistent through Mesoproterozoic, Neoproterozoic and early Palaeozoic.

  • 69.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ward, L.
    Juarez Rivera, M.
    Kerrigan, Z.
    Petryshyn, V.A.
    Corsetti, F.A.
    Tripati, A.
    Lateral growth of Late Pleistocene stromatolites from Walker Lake (Nevada) and proxy constraints on environmental change2014Inngår i: 2014 GSA Annual Meeting in Vancouver, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Walker Lake, a terminal sodium bicarbonate lake in Western Nevada (Great Basin, USA) contains numerous carbonate structures, including stromatolites. The lake is a remnant of the larger Pleistocene Lake Lahontan system that has been isolated for the last ~12 ka. Stromatolites of unique macroscale morphology were collected at the ancient Lahontan shoreline during the 2014 International Geobiology Course.

    Initial observations of a stromatolite bed revealed a bowl-shaped carbonate framework composed of stacked, weakly laminated, vertical and horizontal petal-like structures with copious pore space. One laterally-oriented petal was taken off of the main structure and studied. Petrographical observations exhibit two types of alternating microfabrics and three transitions in microfabric. Both sparry crystal fans of calcite, and convex layers of fine micrite with occasional trapped crystals and fossils, were observed.

    Calibrated 14C ages (IntCal13) for the proximal and the distal end of the stromatolite are 35,540 YBP and 33,580 YBP, respectively. Clumped isotope (D47)-based estimates of temperature steadily increase throughout most of this interval, from the beginning of accretion, to the middle of the structure. By the distal end, values are at their peak, and at the tip temperatures decrease again. D47-temperatures correspond to microfabric, with textural changes associated with evidence for climatic fluctuations.

    We suggest the stromatolite formation may have been initiated during warmer intervals, induced by the chemical precipitation of calcite fans which served as a substrate for a biofilm growth. Microbial activity trapped the fine sediment and formed micrite. Colder conditions propagated fan precipitation. Microfabric alternation throughout the stromatolite records environmental change in the span of ca. 2000 years of Lake Lahontan history, likely in response to lake level fluctuations.

  • 70.
    Agić, Heda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ward, Lewis
    California Institute of Technology.
    Juarez Rivera, Marisol
    University of California-Davis.
    Kerrigan, Zak
    University of Rhode Island.
    Petryshyn, Victoria A.
    University of California, Los Angeles.
    Corsetti, Frank A.
    University of Southern California.
    Tripati, Aradhna
    University of California, Los Angeles.
    Lateral growth of Late Pleistocene stromatolites from Walker Lake (Nevada) and proxy constrains on environmental change2014Inngår i: Geological Society of America Abstracts with Programs, Geological Society of America , 2014, s. 300-4-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Walker Lake, a terminal sodium bicarbonate lake in Western Nevada (Great Basin, USA) contains numerous carbonate structures, including stromatolites. The lake is a remnant of the larger Pleistocene Lake Lahontan system that has been isolated for the last ~12 ka. Stromatolites of unique macroscale morphology were collected at the ancient Lahontan shoreline during the 2014 International Geobiology Course.

    Initial observations of a stromatolite bed revealed a bowl-shaped carbonate framework composed of stacked, weakly laminated, vertical and horizontal petal-like structures with copious pore space. One laterally-oriented petal was taken off of the main structure and studied. Petrographical observations exhibit two types of alternating microfabrics and three transitions in microfabric. Both sparry crystal fans of calcite, and convex layers of fine micrite with occasional trapped crystals and fossils, were observed.

    Calibrated 14C ages (IntCal13) for the proximal and the distal end of the stromatolite are 35,540 YBP and 33,580 YBP, respectively. Clumped isotope (D47)-based estimates of temperature steadily increase throughout most of this interval, from the beginning of accretion, to the middle of the structure. By the distal end, values are at their peak, and at the tip temperatures decrease again. D47-temperatures correspond to microfabric, with textural changes associated with evidence for climatic fluctuations.

    We suggest the stromatolite formation may have been initiated during warmer intervals, induced by the chemical precipitation of calcite fans which served as a substrate for a biofilm growth. Microbial activity trapped the fine sediment and formed micrite. Colder conditions propagated fan precipitation. Microfabric alternation throughout the stromatolite records environmental change in the span of ca. 2000 years of Lake Lahontan history, likely in response to lake level fluctuations.

  • 71. Agostini, Andrea
    et al.
    Corti, Giacomo
    Zeoli, Antonio
    Mulugeta, Genene
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Evolution, pattern, and partitioning of deformation during oblique continental rifting: Inferences from lithospheric-scale centrifuge models2009Inngår i: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 10, s. Q11015-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oblique rifting is investigated through centrifuge experiments that reproduce extension of a continental lithosphere containing a preexisting weakness zone. During extension, this weakness localizes deformation, and different rift obliquity is obtained by varying its trend with respect to the stretching direction. Model results show that deformation is mostly controlled by the obliquity angle a (defined as the angle between the orthogonal to the rift trend and the extension direction). For low obliquity (alpha < 45 degrees), rifting is initially characterized by activation of large, en echelon boundary faults bordering a subsiding rift depression, with no deformation affecting the rift floor. Increasing extension results in the abandonment of the boundary faults and the development of new faults within the rift depression. These faults are orthogonal to the direction of extension and arranged in two en echelon segments linked by a complex transfer zones, characterized by strike-slip component of motion. In these models, a strong strain partitioning is observed between the rift margins, where the boundary fault systems have an oblique-slip motion, and the valley floor that away from the transfer zones is affected by a pure extension. Moderate obliquity (alpha = 45 degrees) still results in a two-phase rift evolution, although boundary fault activity is strongly reduced, and deformation is soon transferred to the rift depression. The fault pattern is similar to that of low-obliquity models, although internal faults become slightly oblique to the orthogonal to the direction of extension. Deformation partitioning between the rift margins and the valley floor is still observed but is less developed than for low-obliquity rifting. For high obliquity (alpha > 45 degrees), no boundary faults form, and the extensional deformation affects the rift depression since early stages of extension. Dominance of the strike-slip motion over extension leads to the development of oblique-slip and nearly pure strike-slip faults, oblique to both the rift trend and the orthogonal to the extension direction, with no strain partitioning between the margins and the rift floor. These results suggest that oblique reactivation of preexisting weaknesses plays a major role in controlling rift evolution, architecture, and strain partitioning, findings that have a significant relevance for natural oblique rifts.

  • 72.
    Agustsson, Kristjan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Kristjansdottir, Sigridur
    Flovenz, Olafur G
    Gudmundsson, Olafur
    Induced Seismic Activity during Drilling of Injection Wells at the Hellisheiði Power Plant, SW Iceland.2015Inngår i: Induced Seismic Activity during Drilling of Injection Wells at the Hellisheiði Power Plant, SW Iceland., 2015Konferansepaper (Fagfellevurdert)
  • 73. Ahl, Martin
    et al.
    Bergman, Stefan
    Bergström, Ulf
    Eliasson, Thomas
    Ripa, Magnus
    Weihed, Pär
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. Luleå tekniska universitet, Geovetenskap och miljöteknik.
    Geochemical classification of plutonic rocks in central and northern Sweden2001Rapport (Annet vitenskapelig)
  • 74.
    Ahlberg, K., Almgren, E., Wright, H.E., Ito, E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Holocene stable-isotope stratigraphy at Lough Gur, County Limerick, Western Ireland2001Inngår i: The Holocene, Vol. 11, nr 3, s. 375-380Artikkel i tidsskrift (Fagfellevurdert)
  • 75.
    Ahlberg, Per. E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Blom, H.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi, Paleontologigruppen.
    Clack, J. A.
    The axial skeleton of the Devonian Tetrapod Ichthyostega2003Inngår i: The Gross Symposium 2. Advances in Palaeoichthyology. Riga, Latvia., 2003, s. 7-8Konferansepaper (Fagfellevurdert)
  • 76.
    Ahlberg, Per E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Blom, Henning
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Brazeau, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Clément, Gaël
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Snitting, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    The virtual Eusthenopteron: inside the head of a Devonian lobe-fin with CT.2005Konferansepaper (Fagfellevurdert)
  • 77.
    Ahlberg, Per E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Blom, Henning
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Brazeau, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Clément, Gaël
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Snitting, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    The virtual Eusthenopteron: inside the head of a Devonian lobe-fin with CT. In A. Ivanov and G. Young (eds.), Middle Palaeozoic Vertebrates from Laurussia: Relationships with Siberia, Kazakhstan, Asia and Gondwana. Ichthyolith Issues Special Publication 9:3–4.2005Annet (Annet vitenskapelig)
  • 78.
    Ahlberg, Per E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Clack, J. A.
    Blom, H.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi, Paleontologigruppen.
    The axial skeleton of the Devonian Tetrapod Ichthyostega.2003Inngår i: 51st symposium of vertebrate palaeontology and comparative anatomy, Oxford University Museum of Natural History, Oxford, 2003, s. 3-Konferansepaper (Fagfellevurdert)
  • 79.
    Ahlberg, Per E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Clack, Jennifer A.
    Palaeontology: A firm step from water to land2006Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 440, nr 7085, s. 747-749Artikkel i tidsskrift (Fagfellevurdert)
  • 80.
    Ahlberg, Per Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för fysiologi och utvecklingsbiologi, Evolutionär organismbiologi.
    Sky konspiratörernas dimma - I: Uppsala Nya Tidning (UNT), 27 dec2008Annet (Annet (populærvitenskap, debatt, mm))
  • 81. Ahlers, R.
    et al.
    Cleaver, F
    Rusca, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Schwartz, K.
    Unleashing Entrepreneurs or Controlling Unruly Providers?: The Formalisation of Small-scale Water Providers in Greater Maputo, Mozambique2013Inngår i: Journal of Development Studies, ISSN 0022-0388, E-ISSN 1743-9140, Vol. 49, nr 4, s. 470-482Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The existing legal and policy framework regulating water service provision in Greater Maputo, Mozambique appears fixated on the official service areas. In doing so it inadequately addresses the geographically varied service provision modalities which characterise the city. We argue that the predominant legal and policy framework does little to support development of improved services in areas unserved by the formal utility. Although ad hoc measures recognising small-scale providers as a temporary alternative to service provision by a formal utility have been implemented, these measures appear designed to increase control over these providers rather than support the service delivery capacity of small-scale providers.

  • 82.
    Ahlgren, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    Organic Phosphorus Compounds in Aquatic Sediments: Analysis, Abundance and Effects2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Phosphorus (P) is often the limiting nutrient in lacustrine and brackish eco-systems, and enhanced input of P into an aquatic system might therefore negatively impact the environment. Because modern waste water manage-ment have reduced external P input to surface waters, internal P loading from the sediment has become one of the main P sources to aquatic ecosys-tems, in which relatively unknown organic P compounds seem to be more active in P recycling than previously thought.

    This thesis focus is on improving analysis methods for organic P com-pounds in lacustrine and brackish sediments, as well as determining which of these compounds might be degraded, mobilized and subsequently recycled to the water column and on what temporal scale this occur. In both lacustrine and brackish environments, the most labile P compound was pyrophosphate, followed by different phosphate diesters. Phosphate monoesters were the least labile organic P compounds and degraded the slowest with sediment depth. In regulated lakes, it was shown that pyrophosphate and polyphos-phate compound groups were most related to lake trophic status, thus indi-cating their involvement in P cycling. This thesis also indicates faster P turn-over in sediment from the brackish environment compared to sediment from the lacustrine environment.

    A comparison of organic P extraction procedures showed that pre-extraction with EDTA, and NaOH as main extractant, was most efficient for total P extraction. Using buffered sodium dithionite (BD) as a pre-extractant and NaOH as main extractant was most efficient for extracting the presuma-bly most labile organic P compound groups, pyrophosphate and polyphos-phate. Furthermore, it was determined that organic P compounds associated with humic substances were more recalcitrant than other P compounds, that the BD step used in traditional P fractionation might extract phosphate monoesters, and that NMR is a statistically valid method for quantification of organic P compounds in sediment extracts.

    Delarbeid
    1. Depth attenuation of biogenic phosphorus compounds in lake sediment measured by 31P NMR
    Åpne denne publikasjonen i ny fane eller vindu >>Depth attenuation of biogenic phosphorus compounds in lake sediment measured by 31P NMR
    Vise andre…
    2005 (engelsk)Inngår i: Environmental Science and Technology, ISSN 0013-936, Vol. 39, nr 3, s. 867-872Artikkel i tidsskrift (Fagfellevurdert) Published
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-94212 (URN)
    Tilgjengelig fra: 2006-03-31 Laget: 2006-03-31 Sist oppdatert: 2017-11-30bibliografisk kontrollert
    2. Characterization of phosphorus in sequential extracts from lake sediments using P-31 nuclear magnetic resonance spectroscopy
    Åpne denne publikasjonen i ny fane eller vindu >>Characterization of phosphorus in sequential extracts from lake sediments using P-31 nuclear magnetic resonance spectroscopy
    Vise andre…
    2006 (engelsk)Inngår i: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 63, nr 8, s. 1686-1699Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Phosphorus (P) compounds in three different lake surface sediments were extracted by sequential P extraction and identified by P-31 nuclear magnetic resonance (P-31 NMR) spectroscopy. The extraction procedure primarily discriminates between inorganic P-binding sites but most extraction steps also contained P not reacting (nrP) with the molybdenum complex during P analyses. In all three lakes, the nrP dominated in the NaOH extracts. Nonreactive P from the dystrophic lake was dominated by potentially recalcitrant P groups such as orthophosphate monoesters, while the nrP in the two more productive lakes also contained polyphosphates, pyrophosphate, and organic P groups such as P lipids and DNA-P that may be important in remineralization and recycling to the water column. In addition, polyphosphates showed substantial dynamics in settling seston. The Humic-P pools (P associated with humic acids) showed strong signals of orthophosphate monoesters in all three lakes, which supported the assumption that P-containing humic compounds are indeed recovered in this fraction, although other organic P forms are also present. Thus, in addition to expanding the understanding of which organic P forms that are present in lake sediments, the P-31 NMR technique also demonstrated that the chemical extraction procedure may provide some quantification of recalcitrant versus labile organic P forms.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-94213 (URN)10.1139/F06-070 (DOI)000239655100003 ()
    Tilgjengelig fra: 2006-03-31 Laget: 2006-03-31 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    3. Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments: A P-31 nuclear magnetic resonance study
    Åpne denne publikasjonen i ny fane eller vindu >>Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments: A P-31 nuclear magnetic resonance study
    Vise andre…
    2006 (engelsk)Inngår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 51, nr 5, s. 2341-2348Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The composition and abundance of phosphorus extracted by NaOH-ethylenediaminetetraacetic acid from anoxic Northwest Baltic Sea sediment was characterized and quantified using solution P-31 nuclear magnetic resonance. Extracts from sediment depths down to 55 cm, representing 85 yr of deposition, contained 18.5 g m(-2) orthophosphate. Orthophosphate monoesters, teichoic acid P, microbial P lipids, DNA P, and pyrophosphate corresponded to 6.7, 0.3, 1.1, 3.0, and 0.03 g P m(-2), respectively. The degradability of these compound groups was estimated by their decline in concentration with sediment depth. Pyrophosphate had the shortest half-life (3 yr), followed by microbial P lipids with a half-life of 5 yr, DNA P (8 yr), and orthophosphate monoesters (16 yr). No decline in concentration with sediment depth was observed for orthophosphate or teichoic acid P.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-94214 (URN)000240673800036 ()
    Tilgjengelig fra: 2006-03-31 Laget: 2006-03-31 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    4. Biogenic phosphorus in oligotrophic mountain lake sediments: Differences in composition measured with NMR spectroscopy
    Åpne denne publikasjonen i ny fane eller vindu >>Biogenic phosphorus in oligotrophic mountain lake sediments: Differences in composition measured with NMR spectroscopy
    Vise andre…
    2006 (engelsk)Inngår i: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 40, nr 20, s. 3705-3712Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Phosphorus (P) composition in alkaline sediment extracts from three Swedish oligotrophic mountain lakes was investigated using P-31-NMR spectroscopy. Surface sediments from one natural lake and two mature reservoirs, one of which has received nutrient additions over the last 3 years, were compared with respect to biogenic P composition. The results show significant differences in the occurrence of labile and biogenic P species in the sediments of the different systems. The P compound groups that varied most between these three systems were pyrophosphate and polyphosphates, compound groups known to play an important role in sediment P recycling. The content of these compound groups was lowest in the reservoirs and may indicate a coupling between anthropogenic disturbances (i.e., impoundment) to a water system and the availability of labile P species in the sediment. A statistical study was also conducted to determine the accuracy and reliability of using P-31-NMR spectroscopy for quantification of sediment P forms.

    Emneord
    phosphorus species, P-31-NMR spectroscopy, reservoirs, oligotrophication, method validation, P-31-NMR accuracy
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-94215 (URN)10.1016/j.watres.2006.09.006 (DOI)000242988600005 ()17070896 (PubMedID)
    Tilgjengelig fra: 2006-03-31 Laget: 2006-03-31 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    5. Degradation rates of organic phosphorus in lake sediment
    Åpne denne publikasjonen i ny fane eller vindu >>Degradation rates of organic phosphorus in lake sediment
    Vise andre…
    2007 (engelsk)Inngår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 82, nr 1, s. 15-28Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Phosphorus (P) binding groups were identified in phytoplankton, settling particles, and sediment profiles by 31P NMR spectroscopy from the Swedish mesotrophic Lake Erken. The 31P NMR analysis revealed that polyphosphates and pyrophosphates were abundant in the water column, but rapidly mineralized in the sediment. Orthophosphate monoesters and teichoic acids degraded more slowly than DNA-P, polyphosphates, and P lipids. Humic acids and organic acids from phytoplankton were precipitated from the NaOH extract by acidification and identified by 31P NMR spectroscopy. The precipitated P was significantly more recalcitrant than the P compound groups remaining in solution, but does not constitute a major sink of P as it did not reach a stable concentration with depth, which indicates that it may eventually be degraded. Since P also precipitated from phytoplankton, the origin of humic-P can not be related solely to allochthonous P.

    Emneord
    Organic P, 31P NMR, Lake sediment, Degradation rates
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-97627 (URN)10.1007/s10533-006-9049-z (DOI)000244070900002 ()
    Tilgjengelig fra: 2008-10-15 Laget: 2008-10-15 Sist oppdatert: 2017-12-14bibliografisk kontrollert
    6. Sediment Phosphorus Extractants for Phosphorus-31 Nuclear Magnetic Resonance Analysis: A Quantitative Evaluation
    Åpne denne publikasjonen i ny fane eller vindu >>Sediment Phosphorus Extractants for Phosphorus-31 Nuclear Magnetic Resonance Analysis: A Quantitative Evaluation
    Vise andre…
    2007 (engelsk)Inngår i: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 36, nr 3, s. 892-898Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with 31P nuclear magnetic resonance (31P-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-94217 (URN)10.2134/jeq2006.0235 (DOI)000246430500028 ()17485721 (PubMedID)
    Tilgjengelig fra: 2006-03-31 Laget: 2006-03-31 Sist oppdatert: 2017-12-14bibliografisk kontrollert
  • 83.
    Ahlgren, Joakim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi. Institutionen för biokemi och organisk kemi, Organisk kemi I. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    Reitzel, Kasper
    Danielsson, Rolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi. Institutionen för biokemi och organisk kemi, Organisk kemi I. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    Gogoll, Adolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi. Institutionen för biokemi och organisk kemi, Organisk kemi I. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Rydin, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi. Institutionen för biokemi och organisk kemi, Organisk kemi I. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
    Biogenic phosphorus in oligotropic mountain lake sediments: Differences in composition measured with NMR spectroscopy2006Inngår i: Water Research, nr 40, s. 3705-3712Artikkel i tidsskrift (Fagfellevurdert)
  • 84.
    Ahlgren Mattsson, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Jämförelse av portrycksmätning i Uppsalalera mellan portrycksmätare och dissipationstest2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Portrycket är en viktig parameter för att bestämma jordens egenskaper, såsom dränering, permeabilitet och stabilitet (då portrycket har en påverkan på den effektiva spänningen i jorden). Portrycket kan mätas med portrycksmätare men det kan även mätas under ett Cone penetrating test (CPT) med ett s.k. dissipationstest. Fördelar med ett dissipationstest jämfört med traditionell portrycksmätning skulle vara att det skulle spara tid och pengar, då man slipper trycka ner portrycksmätare och sedan vänta på att få portrycket ifrån dem, istället kan portrycket mätas under sondering med CPT.Detta självständiga arbete har som syfte att jämföra portrycksmätningar mellan portrycksmätning med BAT-spets och dissipationstest under CPT-sondering för att se hur bra mätvärden dissipationstester ger och om de eventuellt kan ersätta portrycksmätare. Fältförsöken av metoderna skedde i Uppsalalera, på en tomt i Kungsängen i Uppsala.Två stationer med BAT-spetsar på 5 meter, 7,5 meter och 10 meters djup sattes ner i leran. Sondering med CPT genomfördes sedan, där borren stoppades på samma djup som BAT-spetsarna. CPT:n stoppades på dessa djup i drygt 24 timmar, för att tillåta det generade portrycket som skapades när borren trycks ner i leran att skingras åt sidan. Jämviktsportrycket kommer vara det portryck som finns kvar efter att det generade portrycket har försvunnit. Portrycken från de två olika metoderna jämfördes sedan för att se hur nära dissipationstestet kommer värdena från portrycksmätningen med BAT-spetsarna.Resultatet av dissipationstesterna blev att inga av dem nådde referensvärdena från BAT-spetsarna efter 24 timmar. Beroende på användningsklass ligger dissipationstesterna inom den tillåtna minsta noggrannheten. Dissipationstest är antagligen inte så praktiskt tillämpbart i jordar med låg permeabilitet.

  • 85.
    Ahlm, L.
    et al.
    Stockholm University.
    Krejci, R.
    Stockholm University.
    Nilsson, E. D.
    Stockholm University.
    Martensson, E. M.
    Stockholm University.
    Vogt, M.
    Stockholm University.
    Artaxo, P.
    Emission and dry deposition of accumulation mode particles in the Amazon Basin2010Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, nr 21, s. 10237-10253Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Size-resolved vertical aerosol number fluxes of particles in the diameter range 0.25-2.5 mu m were measured with the eddy covariance method from a 53 m high tower over the Amazon rain forest, 60 km NNW of Manaus, Brazil. This study focuses on data measured during the relatively clean wet season, but a shorter measurement period from the more polluted dry season is used as a comparison. Size-resolved net particle fluxes of the five lowest size bins, representing 0.25-0.45 mu m in diameter, were in general dominated by deposition in more or less all wind sectors in the wet season. This is an indication that the source of primary biogenic aerosol particles may be small in this particle size range. Transfer velocities within this particle size range were observed to increase linearly with increasing friction velocity and increasing particle diameter. In the diameter range 0.5-2.5 mu m, vertical particle fluxes were highly dependent on wind direction. In wind sectors where anthropogenic influence was low, net upward fluxes were observed. However, in wind sectors associated with higher anthropogenic influence, deposition fluxes dominated. The net upward fluxes were interpreted as a result of primary biogenic aerosol emission, but deposition of anthropogenic particles seems to have masked this emission in wind sectors with higher anthropogenic influence. The net emission fluxes were at maximum in the afternoon when the mixed layer is well developed, and were best correlated with horizontal wind speed according to the equation log(10)F = 0.48.U + 2.21 where F is the net emission number flux of 0.5-2.5 mu m particles [m(-2) s(-1)] and U is the horizontal wind speed [ms(-1)] at the top of the tower.

  • 86.
    Ahlm, L.
    et al.
    Stockholm University.
    Nilsson, E. D.
    Stockholm University.
    Krejci, R.
    Stockholm University.
    Martensson, E. M.
    Stockholm University.
    Vogt, M.
    Stockholm University.
    Artaxo, P.
    A comparison of dry and wet season aerosol number fluxes over the Amazon rain forest2010Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, nr 6, s. 3063-3079Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Vertical number fluxes of aerosol particles and vertical fluxes of CO(2) were measured with the eddy covariance method at the top of a 53 m high tower in the Amazon rain forest as part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) experiment. The observed aerosol number fluxes included particles with sizes down to 10 nm in diameter. The measurements were carried out during the wet and dry season in 2008. In this study focus is on the dry season aerosol fluxes, with significant influence from biomass burning, and these are compared with aerosol fluxes measured during the wet season. Net particle deposition fluxes dominated in daytime in both seasons and the deposition flux was considerably larger in the dry season due to the much higher dry season particle concentration. The particle transfer velocity increased linearly with increasing friction velocity in both seasons. The difference in transfer velocity between the two seasons was small, indicating that the seasonal change in aerosol number size distribution is not enough for causing any significant change in deposition velocity. In general, particle transfer velocities in this study are low compared to studies over boreal forests. The reasons are probably the high percentage of accumulation mode particles and the low percentage of nucleation mode particles in the Amazon boundary layer, both in the dry and wet season, and low wind speeds in the tropics compared to the midlatitudes. In the dry season, nocturnal particle fluxes behaved very similar to the nocturnal CO(2) fluxes. Throughout the night, the measured particle flux at the top of the tower was close to zero, but early in the morning there was an upward particle flux peak that is not likely a result of entrainment or local pollution. It is possible that these morning upward particle fluxes are associated with emission of primary biogenic particles from the rain forest. Emitted particles may be stored within the canopy during stable conditions at nighttime, similarly to CO(2), and being released from the canopy when conditions become more turbulent in the morning.

  • 87. Ahmad, M R
    et al.
    Esa, M R M
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Measurement of bit error rate at 2,4 GHz due to lightning interference2012Inngår i: Proceeding of the 31st International Conference on Lightning Protection ICLP 2012, 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper analyzes the interference of lightning flashes with wireless communication systems operating in the microwave band at 2.4 GHz. A bit error rate (BER) measurement method was used to evaluate BER during 3 heavy thunderstorms on January 25, March 17 and March 20, all in year 2011. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW) conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-of-sight (LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higher recorded BER. The maximum recorded BER was 9.9·101 and the average recorded BER was 9.95·10 -3 during the thunderstorms with the average fair weather BER values under the influence of adjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10 -6 respectively. We conclude that wireless communication systems operating at 2.4 GHz microwave frequency can be significantly interfered by lightning.

  • 88.
    Ahmad, Mohd Riduan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Universiti Teknikal Malaysia Melaka.
    Interaction of Lightning Flashes with Wireless Communication Networks: Special Attention to Narrow Bipolar Pulses2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this thesis, the features of electric field signatures of narrow bipolar pulses (NBPs) generated by cloud flashes are investigated and their effects on wireless communication systems are studied. A handful amount of NBPs (14.5%) have been observed to occur as part of cloud-to-ground flashes in South Malaysia. Occurrence of NBPs in Sweden has been reported for the first time in this thesis. The electric field waveform characteristics of NBPs as part of cloud-to-ground flashes were similar to isolated NBPs found in Sweden and South Malaysia and also to those isolated NBPs reported by previous studies from various geographical areas. This is a strong indication that their breakdown mechanisms are similar at any latitudes regardless of geographical areas.

    A comparative study on the occurrence of NBPs and other forms of lightning flashes across various geographical areas ranging from northern regions to the tropics is presented. As the latitude decreased from Uppsala, Sweden (59.8°N) to South Malaysia (1.5°N), the percentage of NBP emissions relative to the total number of lightning flashes increased significantly from 0.13% to 12%. Occurrences of positive NBPs were more common than negative NBPs at all observed latitudes. However, as latitudes decreased, the negative NBP emissions increased significantly from 20% (Sweden) to 45% (South Malaysia). Factors involving mixed-phase region elevations and vertical extents of thundercloud tops are invoked to explain the observed results. These factors are fundamentally latitude dependent.

    In this thesis, the interaction between microwave radiations emitted by cloud-to-ground and cloud flashes events and bits transmission in wireless communication networks are also presented. To the best of our knowledge, this is the first time such effects are investigated in the literature. Narrow bipolar pulses were found to be the strongest source of interference that interfered with the bits transmission.

    Delarbeid
    1. Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms
    Åpne denne publikasjonen i ny fane eller vindu >>Signatures of Narrow Bipolar Pulses as Part of Cloud-to-Ground Flashes in Tropical Thunderstorms
    2014 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Emneord
    Narrow bipolar pulse; Return stroke; Tropical thunderstorm.
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233624 (URN)
    Tilgjengelig fra: 2014-10-07 Laget: 2014-10-07 Sist oppdatert: 2017-12-05
    2. Narrow bipolar pulses and associated microwave radiation
    Åpne denne publikasjonen i ny fane eller vindu >>Narrow bipolar pulses and associated microwave radiation
    2013 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    sted, utgiver, år, opplag, sider
    Stockholm: , 2013
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-212898 (URN)
    Konferanse
    Progress in Electromagnetics Research Symposium
    Tilgjengelig fra: 2013-12-16 Laget: 2013-12-16 Sist oppdatert: 2015-01-23
    3. Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden
    Åpne denne publikasjonen i ny fane eller vindu >>Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden
    Vise andre…
    2014 (engelsk)Inngår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Artikkel i tidsskrift (Fagfellevurdert) Submitted
    Emneord
    Electric field; Narrow bipolar pulse; Sweden.
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233636 (URN)
    Tilgjengelig fra: 2014-10-07 Laget: 2014-10-07 Sist oppdatert: 2017-12-05
    4. Latitude Dependence of Narrow Bipolar Pulse Emissions
    Åpne denne publikasjonen i ny fane eller vindu >>Latitude Dependence of Narrow Bipolar Pulse Emissions
    Vise andre…
    2015 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 128, s. 40-45Artikkel i tidsskrift (Fagfellevurdert) Published
    Emneord
    Latitude; Narrow bipolar pulse; Thunderstorm.
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233638 (URN)10.1016/j.jastp.2015.03.005 (DOI)000355717500005 ()
    Tilgjengelig fra: 2014-10-07 Laget: 2014-10-07 Sist oppdatert: 2017-12-05bibliografisk kontrollert
    5. Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses
    Åpne denne publikasjonen i ny fane eller vindu >>Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses
    2014 (engelsk)Inngår i: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, s. 810-813Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    In this paper, temporal characteristics of several initial electric field pulses of preliminary breakdown process (PBP) from very close negative cloud-to-ground (CG) flashes are compared to close narrow bipolar pulses (NBPs) to observe any similarity that may exists. Interestingly, we found that the initial PBP pulses are similar to close NBP with zero crossing time less than 5 mu s, do not preceded by any slow field change and followed by pronounce static component. As NBPs are believed to be a result of relativistic runaway electron avalanches discharge, this finding is an indication that the initial electric field pulses of PBP are perhaps the result of the same discharge mechanism.

    sted, utgiver, år, opplag, sider
    IEEE conference proceedings, 2014
    Emneord
    Narrow bipolar pulse; Preliminary breakdown pulse; Relativistic runaway electron avalanches.
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-233639 (URN)000358572100153 ()978-1-4799-3544-4 (ISBN)
    Konferanse
    International Conference on Lightning Protection (ICLP), OCT 11-18, 2014, Tsinghua Univ, Shanghai, PEOPLES R CHINA
    Tilgjengelig fra: 2014-10-07 Laget: 2014-10-07 Sist oppdatert: 2015-09-03bibliografisk kontrollert
    6. Lightning interference in multiple antennas wireless communication systems
    Åpne denne publikasjonen i ny fane eller vindu >>Lightning interference in multiple antennas wireless communication systems
    Vise andre…
    2012 (engelsk)Inngår i: Journal of Lightning Research, ISSN 1652-8034, Vol. 4, s. 155-165Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    This paper analyzes the interference of lightning flashes with multiple antennas wireless communicationsystems operating in the microwave band at 2.4 GHz and 5.2 GHz. A bit error rate (BER) measurement method was usedto evaluate BER and packet error rate (PER) during 5 heavy thunderstorms on January 25 and March 17 to 20, 2011,respectively. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW)conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-ofsight(LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higherrecorded BER. The maximum recorded BER was 9.9·10-1 and the average recorded BER and PER were 2.07·10-2 and2.44·10-2 respectively during the thunderstorms with the average fair weather BER and PER values under the influence ofadjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10-6 respectively. Weconclude that multiple antennas wireless communication systems operating at the microwave frequency can besignificantly interfered by lightning.

    sted, utgiver, år, opplag, sider
    Bentham open, 2012
    HSV kategori
    Forskningsprogram
    Teknisk fysik med inriktning mot atmosfäriska urladdningar
    Identifikatorer
    urn:nbn:se:uu:diva-190902 (URN)
    Tilgjengelig fra: 2013-01-09 Laget: 2013-01-09 Sist oppdatert: 2016-02-03
    7. Interference from cloud-to-ground and cloud flashes in wireless communication system
    Åpne denne publikasjonen i ny fane eller vindu >>Interference from cloud-to-ground and cloud flashes in wireless communication system
    2014 (engelsk)Inngår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 113, s. 237-246Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this study, cloud-to-ground (CG) flash and intra-cloud (IC) flash events that interfere with the transmission of bits in wireless communication system operating at 2.4 GHz were analyzed. Bit error rate (BER) and consecutive lost datagram (CLD) measurement methods were used to evaluate BER and burst error from 3 tropical thunderstorms on November 27, 28, and 29 during 2012 northeastern monsoon in Malaysia. A total of 850 waveforms from the electric field change recording system were recorded and examined. Out of these, 94 waveforms of very fine structure were selected which matched perfectly with the timing information of the recorded BER. We found that both CG and IC flashes interfered significantly with the transmission of bits in wireless communication system. The severity of the interference depends mainly on two factors namely the number of pulses and the amplitude intensity of the flash. The interference level becomes worst when the number of pulses in a flash increases and the amplitude intensity of pulses in a flash intensifies. During thunderstorms, wireless communication system has experienced mostly intermittent interference due to burst error. Occasionally, in the presence of very intense NBP event, wireless communication system could experience total communication lost. In CG flash, it can be concluded that PBP is the major. source of interference that interfered with the bits transmission and caused the largest burst error. In IC flash, we found that the typical IC pulses interfered the bits transmission in the same way as PBP and mixed events in CG flash and produced comparable and in some cases higher amount of burst error. NBP has been observed to interfere the bits transmission more severely than typical IC and CG flashes and caused the most severe burst error to wireless communication system.

    Emneord
    Bit error rate, Cloud flash, Cloud-to-ground flash, Interference, Microwave radiation, Wireless system
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-228679 (URN)10.1016/j.epsr.2014.03.022 (DOI)000337554200032 ()
    Tilgjengelig fra: 2014-07-22 Laget: 2014-07-21 Sist oppdatert: 2017-12-05bibliografisk kontrollert
  • 89.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Esa, Mona Riza Binti Mohd
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, E.
    Wireless Communications and Networking Lab, Macquarie University, Sydney, Australien.
    Lightning interference in multiple antennas wireless communication systems2012Inngår i: Journal of Lightning Research, ISSN 1652-8034, Vol. 4, s. 155-165Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper analyzes the interference of lightning flashes with multiple antennas wireless communicationsystems operating in the microwave band at 2.4 GHz and 5.2 GHz. A bit error rate (BER) measurement method was usedto evaluate BER and packet error rate (PER) during 5 heavy thunderstorms on January 25 and March 17 to 20, 2011,respectively. In addition, BER measurements also were done on January 21 and March 30, 2011 under fair weather (FW)conditions providing a baseline for comparison. The Transmitter-Receiver separation was fixed at 10 meter with line-ofsight(LOS) consideration. We infer that lightning interfered with the transmitted digital pulses which resulted in a higherrecorded BER. The maximum recorded BER was 9.9·10-1 and the average recorded BER and PER were 2.07·10-2 and2.44·10-2 respectively during the thunderstorms with the average fair weather BER and PER values under the influence ofadjacent channel interference (ACI) and co-channel interference (CCI) being 1.75·10-5 and 7.35·10-6 respectively. Weconclude that multiple antennas wireless communication systems operating at the microwave frequency can besignificantly interfered by lightning.

  • 90.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Occurrence of Narrow Bipolar Event as Part of Cloud-to-Ground Flash in Tropical Thunderstorms2014Konferansepaper (Fagfellevurdert)
  • 91.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Similarity between the Initial Breakdown Pulses of Negative Ground Flash and Narrow Bipolar Pulses2014Inngår i: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP), IEEE conference proceedings, 2014, s. 810-813Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, temporal characteristics of several initial electric field pulses of preliminary breakdown process (PBP) from very close negative cloud-to-ground (CG) flashes are compared to close narrow bipolar pulses (NBPs) to observe any similarity that may exists. Interestingly, we found that the initial PBP pulses are similar to close NBP with zero crossing time less than 5 mu s, do not preceded by any slow field change and followed by pronounce static component. As NBPs are believed to be a result of relativistic runaway electron avalanches discharge, this finding is an indication that the initial electric field pulses of PBP are perhaps the result of the same discharge mechanism.

  • 92.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Baharudin, Zikri Abadi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Universiti Teknikal Malaysia Melaka.
    Hettiarachchi, Pasan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Latitude Dependence of Narrow Bipolar Pulse Emissions2015Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 128, s. 40-45Artikkel i tidsskrift (Fagfellevurdert)
  • 93.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hettiarachchi, Pasan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Baharudin, Zikri Abadi
    Universiti Teknikal Malaysia Melaka.
    Electric Field Signature of Narrow Bipolar Pulse Observed in Sweden2014Inngår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Artikkel i tidsskrift (Fagfellevurdert)
  • 94.
    Ahmad, Mohd Riduan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Mohd Esa, Mona Riza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Johari, Dalina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ismail, Mohd Muzafar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Chaotic Pulse Train in Cloud-to-Ground and Cloud Flashes of Tropical Thunderstorms2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we report for the first time the observation of chaotic pulse train (CPT) preceding natural subsequent negative return strokes and also CPT occurrence in IC flashes from tropical thunderstorms in South Malaysia. In CG flashes, all CPTs were occurred in between return strokes with 41.1% have occurred between the first and second return strokes. The maximum number of CPT in one sequence is 3, which can be observed between the first and third return strokes only. In IC flashes, all CPTs were observed to occur in between IC flash pulses.

  • 95.
    Ahmad, Mohd Riduan
    et al.
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Periannan, Dinesh
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Sabri, Muhammad Haziq Mohammad
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Abd Aziz, Mohamad Zoinol Abidin
    UTEM, Durian Tunggal, Melaka, Malaysia.
    Esa, Mona Riza Mohd
    UTM, Inst Voltan Tinggi & Arus Tinggi IVAT, Johor Bharu, Malaysia.
    Lu, Gaopeng
    Chinese Acad Sci, Beijing, Peoples R China.
    Zhang, Hongbo
    Chinese Acad Sci, Beijing, Peoples R China.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Emission Heights of Narrow Bipolar Events in a Tropical Storm over the Malacca Strait2017Inngår i: 2017 International Conference On Electrical Engineering And Computer Science (Icecos), IEEE , 2017, s. 305-309Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Emission heights for narrow bipolar events (NBEs) have been reported mostly from observations at mid latitudes but none have been reported from tropical regions. In this paper, we are reporting for the first time the heights of NBE emissions from a tropical storm over the Malacca Strait, a narrow water passage between the Malay Peninsula and Sumatra Island. A total of 49 positive NBEs (+NBEs) were detected from the storm. The NBE activity can be divided into two stages according to the emission heights and radar reflectivity data. The first stage (or S1) lasted for only 6 minutes, started with the first detected NBE, and produced 20 NBEs (41%). The emission heights ranged between 12.0 and 16.7 km. Radar reflectivity data showed that the storm reached maximum values at 55 dBZ within the period S1. In contrast, the second stage (S2) lasted longer (32 minutes) and produced 29 NBEs (59%). The emission heights were lower and ranged from 8.5 to 13.7 km. Radar reflectivity data showed that the storm reached maximum values at 50 dBZ within the period S2.

  • 96.
    Ahmad, M.R.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rashid, M.
    Aziz, M.H.A.
    Esa, M.R.M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dutkiewicz, E.
    Analysis of Lightning-induced Transient in 2.4 GHz Wireless Communication System2011Inngår i: Proceeding of IEEE International Conference on Space Science and Communication (IconSpace), Penang, Malaysia, pp225-230, 2011Konferansepaper (Fagfellevurdert)
  • 97. Ahmad, Noor Azlinda
    et al.
    Baharudin, Zikri A
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fernando, M.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Radiation field spectra of long-duration cloud flashes2015Inngår i: Atmospheric Science Letters, ISSN 1530-261X, E-ISSN 1530-261X, Vol. 16, nr 2, s. 91-95Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The preliminary results of radiation electric fields produced by long-duration cloud flashes have been Fourier analyzed to determine the frequency spectrum in the range of 10kHz-10MHz. The flashes were recorded within a distance of less than 20km. The spectrum was normalized to 50km distance and it shows a f(-1) dependence within the entire frequency range.

  • 98.
    Ahmad, Noor Azlinda
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fernando, Mahendra
    Baharudin, Z. A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rahman, Mahbubur
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Cooray, Vernon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Saleh, Ziad
    Dwyer, Joseph R.
    Rassoul, Hamid K.
    The first electric field pulse of cloud and cloud-to-ground lightning discharges2010Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, nr 2-3, s. 143-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, the first electric field pulse of cloud and cloud-to-ground discharges were analyzed and compared with other pulses of cloud discharges. Thirty eight cloud discharges and 101 cloud-to-ground discharges have been studied in this analysis. Pulses in cloud discharges were classified as [`]small', [`]medium' and [`]large', depending upon the value of their relative amplitude with respect to that of the average amplitude of the five largest pulses in the flash. We found that parameters, such as pulse duration, rise time, zero crossing time and full-width at half-maximum (FWHMs) of the first pulse of cloud and cloud-to-ground discharges are similar to small pulses that appear in the later stage of cloud discharges. Hence, we suggest that the mechanism of the first pulse of cloud and cloud-to-ground discharges and the mechanism of pulses at the later stage of cloud discharges could be the same.

  • 99.
    Ahmadi, Omid
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Application of the Seismic Reflection Method in Mineral Exploration and Crustal Imaging: Contributions to Hardrock Seismic Imaging2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The seismic reflection method has been used extensively in mineral exploration and for imaging crustal structures within hardrock environments. In this research the seismic reflection method has been used and studied to address problems associated with hardrock settings. Papers I and II, address delineating and imaging a sulfide ore body and its surrounding rocks and structures in Garpenberg, central Sweden, at an active mine. 3D ray-tracing and finite-difference modeling were performed and the results suggest that although the detection of the ore body by the seismic reflection method is possible in the area, the presence of backfilled stopes in the mine makes seismic imaging of it difficult. In paper III the deeper structures of the Pärvie fault system in northern Sweden were revealed down to about 8 km through 2D seismic reflection profiling. The resulting images were interpreted using microearthquake data as a constraint. Based on the interpretation, some locations were suggested for future scientific deep drilling into the fault system. In paper IV, the seismic signature of complex geological structures of the Cue-Weld Range area in Western Australia was studied using a portion of a deep 2D seismic reflection profile. The pronounced reflections on the seismic images were correlated to their corresponding rock units on an available surface geological map of the study area. 3D constant velocity ray-tracing was performed to constrain the interpretation. Furthermore, the proposed structural model was tested using a 2D acoustic finite-difference seismic modeling method. Based on this study, a new 3D structural model was proposed for the subsurface of the area. These studies have investigated the capability of the seismic reflection method for imaging crustal structures within challenging hardrock and complex geological settings and show some its potential, but also its limitations.

    Delarbeid
    1. High-resolution 2D seismic imaging and forward modeling of a polymetallic sulfide deposit at Garpenberg, central Sweden
    Åpne denne publikasjonen i ny fane eller vindu >>High-resolution 2D seismic imaging and forward modeling of a polymetallic sulfide deposit at Garpenberg, central Sweden
    2013 (engelsk)Inngår i: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 78, nr 6, s. B339-B350Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    We acquired a high-resolution 2D seismic profile to test the capability of the seismic method in imaging a sulfide ore body at Garpenberg, central Sweden. Delineation of the geologic structures, which surround and host the ore body, is another goal of the survey. Due to the 3D geology of the structures, a cross-dip correction performed to image out-of-the-plane reflections, resulting in a clear high amplitude anomaly at a time and location to that to be expected from near the top of the ore body. Furthermore, DMO processing and migration are applied to the data, providing images of four main reflection groups. The reflections have been interpreted as corresponding to geologic rock units in the area that partly interfere with the potential ore body signal. To further investigate the seismic response of the ore body, forward modeling by ray-tracing is applied using the ore body geometry as mapped by drilling. We use two ray-tracing approaches: standard 3D ray-tracing and an exploding reflector approach. Seven representative samples from the mine area are used to determine P-wave velocities. The measurements show a considerable contrast between the ore body and host rock. By comparing the modeled and observed data, we find that the high amplitude signal in the real seismic section most likely emanates from near the top of one concentrated ore which lies inside the larger mapped ore body that has been modeled as a resource. The base of the ore body is only observed on the synthetic data whereas a signal penetration analysis suggests that the seismic signal penetrated efficiently along the entire survey line. Presence of disseminated ore and lower fold toward the northern end of the profile could be combined reasons that make imaging the base of the ore body difficult.

    Emneord
    2D, processing, ray tracing, modeling
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-210135 (URN)10.1190/geo2013-0098.1 (DOI)000330223800003 ()
    Tilgjengelig fra: 2013-11-01 Laget: 2013-11-01 Sist oppdatert: 2017-12-06
    2. The effect of the backfilled stopes on seismic imaging of a sulfide deposit in Garpenberg, central Sweden
    Åpne denne publikasjonen i ny fane eller vindu >>The effect of the backfilled stopes on seismic imaging of a sulfide deposit in Garpenberg, central Sweden
    2015 (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    HSV kategori
    Forskningsprogram
    Geofysik med inriktning mot fasta jordens fysik
    Identifikatorer
    urn:nbn:se:uu:diva-259140 (URN)
    Tilgjengelig fra: 2015-07-27 Laget: 2015-07-27 Sist oppdatert: 2015-08-28
    3. Revealing the deeper structure of the end-glacial Parvie fault system in northern Sweden by seismic reflection profiling
    Åpne denne publikasjonen i ny fane eller vindu >>Revealing the deeper structure of the end-glacial Parvie fault system in northern Sweden by seismic reflection profiling
    2015 (engelsk)Inngår i: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 6, nr 2, s. 621-632Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A new seismic reflection survey for imaging deeper levels of the end-glacial Parvie fault system in northern Sweden was acquired in June 2014. The Parvie fault system hosts the largest fault scarp so far documented in northern Scandinavia, both in terms of its length and calculated magnitude of the earthquake that generated it. Present-day microearthquakes occur along the length of the fault scarp on the eastern side of the scarp, in general agreement with an east-dipping main fault. In the central section of the fault system, where there is a number of subsidiary faults east of the main Parvie scarp, it has been unclear how the earthquakes relate to the structures mapped at the surface. A seismic profile across the Parvie fault system acquired in 2007, with a mechanical hammer as a source, showed a good correlation between the surface mapped faults and moderate to steeply dipping reflections. The most pronounced reflectors could be mapped to about 3 km depth. In the new seismic survey, for deeper penetration an explosive source with a maximum charge size of 8.34 kg in 20 m deep shot holes was used. Reflectors can now be traced to deeper levels with the main 65A degrees east-dipping fault interpreted as a weakly reflective structure. As in the previous profile, there is a strongly reflective 60A degrees west-dipping structure present to the east of the main fault that can now be mapped to about 8 km depth. Extrapolations of the main and subsidiary faults converge at a depth of about 11.5 km, where current earthquake activity is concentrated, suggesting their intersection has created favorable conditions for seismic stress release. Based on the present and previous seismic reflection data, we propose potential locations for future boreholes for scientific drilling into the fault system. These boreholes will provide a better understanding of the reflective nature of the fault structures and stress fields along the faults at depth.

    HSV kategori
    Forskningsprogram
    Geofysik med inriktning mot fasta jordens fysik
    Identifikatorer
    urn:nbn:se:uu:diva-259138 (URN)10.5194/se-6-621-2015 (DOI)000357128400020 ()
    Tilgjengelig fra: 2015-07-27 Laget: 2015-07-27 Sist oppdatert: 2017-12-04bibliografisk kontrollert
    4. Seismic signatures of complex geological structures in the Cue-Weld range area, Murchison domain, Yilgarn Craton, Western Australia
    Åpne denne publikasjonen i ny fane eller vindu >>Seismic signatures of complex geological structures in the Cue-Weld range area, Murchison domain, Yilgarn Craton, Western Australia
    2016 (engelsk)Inngår i: Tectonophysics, Vol. 689, s. 56-66Artikkel i tidsskrift, Meeting abstract (Fagfellevurdert) Published
    Abstract [en]

    The Murchison domain forms the northwest part of the Youanmi Terrane, a tectonic unit within the Neoarchean Yilgarn Craton in Western Australia. In the Cue-Weld Range area the Murchison domain has experienced a complex magmatic and deformation history that resulted in a transposed array of greenstone belts that host significant iron, gold, and base metal deposits. In this study, we interpret the upper 2 s (about 6 km) of a deep crustal seismic profile TOGA-YU1, near the town of Cue, and correlate rock units and structures in outcrop with corresponding reflections. We performed 3D constant velocity ray-tracing and calculate the corresponding travel times for the reflectionsfor time domain pre-stack and post-stack seismic data. This allows us to link shallow reflections with mafic volcanic rocks of the Glen Group and basaltic rocks of the Polelle Group in outcrop. Based on our interpretation and published geological maps and data, we propose a model in which the local stratigraphy represents a refolded thrust system. To test our hypothesis, we applied 2D acoustic finite difference forward modeling. The corresponding synthetic data were processed in the same way as the acquired data. Comparisons between the acquired and the synthetic data show that the model is consistent with observations. We propose a new model for the subsurface of the Cue-Weld Range area and argue that some of the lithologies in the area are repeated structurally at different levels. Our approach highlights the benefit of imaging and modeling of deep seismic transects to resolve local structural complexity in Archean granite-greenstone terrains.

    Emneord
    Seismic interpretation; 3D structural model; Ray-tracing; Finite difference modeling; Weld range; Murchison domain
    HSV kategori
    Forskningsprogram
    Geofysik med inriktning mot fasta jordens fysik; Geovetenskap med inriktning mot mineralogi, petrologi och tektonik
    Identifikatorer
    urn:nbn:se:uu:diva-259139 (URN)10.1016/j.tecto.2016.02.020 (DOI)000387522100006 ()
    Tilgjengelig fra: 2015-08-01 Laget: 2015-07-27 Sist oppdatert: 2017-01-25bibliografisk kontrollert
  • 100.
    Ahmadi, Omid
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Hedin, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Malehmir, Alireza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    Juhlin, Christopher
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik.
    3D Seismic Interpretation and Forward Modeling: an approach to providing reliable results from 2D seismic data2013Inngår i: Proceedings of the 12th Biennial Meeting: Mineral Deposit Research for a High-Tech World / [ed] Johnson, E., 2013, Vol. 1-4, s. 50-53Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Accurate 3D interpretations is challenging when only 2D seismic reflection data are available. This can be compensated for by using additional data. Here we present two case studies where 2D seismic reflection data have been used in combination with geological/geophysical data to create and verify 3D interpretations of specific structures targeted for scientific deep drilling and mining. In the first case, a surface geological map and high resolution 2D seismic reflection data were used to create a 3D lithological model of the subsurface structures in an area around a scientific deep drilling site. This model was also compared to results from constrained 3D inverse modeling of gravity data. In the second case, seismic forward ray-trace modeling was used to delineate a massive sulfide ore body by using high resolution 2D seismic reflection data. By comparison of the generated synthetic data with the real data, it was found that the top of the ore body was detected.

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