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  • 2251.
    Abrahamsson, Christian
    et al.
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Social and Economic Geography.
    Thomas, Mary
    Ohio State University.
    Review section vision2008In: Environment and Planning D: Society and Space, Vol. 26, no 2, p. 192-194Article in journal (Other scientific)
  • 2252. Abrahamsson, Christina
    et al.
    Ahlund, Catherine
    Nordlander, Margareta
    Lind, Lars
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Sciences.
    A method for heart rate-corrected estimation of baroreflex sensitivity.2003In: J Hypertens, ISSN 0263-6352, Vol. 21, no 11, p. 2133-40Article in journal (Refereed)
  • 2253.
    Abrahamsson, Christoffer
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Theology, Department of Theology. Johannelunds Teologiska Högskola.
    En trumslagare för freden!: En kritisk granskning av Martin Luther King Jr:s ickevåldsideologi2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this Master thesis is to give an account of and review the ideology yhat King presented through his preaching, speeches and other sources. The metod I have chosen for this purpose is to systematize King’s ideology and the to critically analyze it. When doing so I have discoverd that King’s non-violent ideology is coherent, but that his argumentation is somewhat defective, especially when examing its plausibility.                      King’s non-violence ideology was based on a theocentric wordview and a natural law pholosophy. He tought that all men are created in the image of God and that all humans have the possibility to do good. King’s non-violence ideology is based on active resistance where people use love and civil disobedience as tools to enforce subversive changes. King was against all types of violent actions and stated that violence never leads to sustainable change, that violence is immoral and unworthy of any human. King also said that non-violence is the only way to combat societal problems in a long-term perspective.

  • 2254.
    Abrahamsson, Curt Johan David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, Jesús José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Fregelius, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bladh, Johan
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Magnetic thrust bearing for a 10 MW hydropower generator with a Kaplan turbine2018Conference paper (Refereed)
  • 2255.
    Abrahamsson, Ebba
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Informatics and Media.
    Waern-Bugge, Fredrik
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Informatics and Media.
    Framgångsfaktorer vid en agil övergång2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 2256.
    Abrahamsson, Elin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Sveriges lantbruksuniversitet.
    In situ-metoder för sanering av klorerade lösningsmedel: utvärdering med avseende på svenska förhållanden2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Currently, there are 428 areas contaminated with chlorinated solvents in Sweden. These substances have been used in Sweden’s industry as degreasing agents and solvents.Chlorinated solvents are more difficult to investigate and remediate compared to petroleum hydrocarbons, due to their complicated distribution in different media. Hence, it is important to increase the knowledge of remediation of chlorinated solvents. The remediation technology excavation is frequently used in Sweden for contaminated areas. Excavation means that soil is dug up and transported to treatment or landfills sites. Due to its climate impact, the use of more sustainable remediation technologies should be increased.

    This thesis aimed to evaluate in situ remediation technologies for soil and groundwater contaminated with chlorinated solvents with respect to functionality, sustainability, time and cost aspects. Furthermore, this thesis aimed to investigate which technologies are best suited for Swedish conditions. To evaluate suitability and functionality of remediation technologies,all technologies were described and a case study of five areas in Sweden contaminated with chlorinated solvents was conducted. The contaminant situation and site-specific conditions were described for each area. Thereafter, the evaluation and choice of remediation technology and remediation result were presented. The technologies studied in the case study were two types of chemical reduction, multi-phase extraction, biostimulation and thermal treatment.The five projects were then assessed using the Swedish Geotechnical Institute’s decision support tool for remediation technologies, SAMLA. The technologies were rated in SAMLA according to criteria related to environmental factors, social factors and costs. Furthermore,the remediation technologies were evaluated based on their strengths and limitations with respect to Swedish conditions, such as geology, climate and geochemistry. They were also evaluated based on their strengths and limitations according to implementation areas, cost,remediation time, energy consumption and use in Sweden.The assessment of the five projects in SAMLA produced similar results compared to previously conducted risk evaluations. The technologies that were chosen based on the risk evaluations were also rated highest in SAMLA. The choice of technology for each project was based on conditions for the area, such as geology and existing buildings. Conclusions were drawn indicating that all technologies can be implemented in Sweden with respect to geological conditions. However, site-specific conditions, such as high groundwater flow and heterogeneous soil, limit the implementation of a specific technology. Moreover, other sitespecific conditions than those already discussed have to be considered, for instance buildings or future exploitation. Future development of in situ remediation technologies may focus on implementation of a certain type of geology (highly permeable soils), where chlorinated solvents may be found more frequently.

  • 2257.
    Abrahamsson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Ekelund, My
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Human Exposure from Mercury in Rice in the Philippines2015Student paper other, 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the western part of the Philippines, in the Palawan province, studies have shown that large quantities of mercury are spread to the surrounding area during heavy rainfall. In addition, mercury is spread to rice fields and bioaccumulated in marine fish and seafood. The mercury originates from the abandoned Palawan Quicksilver Mine. Since mercury is toxic for the human body and new studies have shown that mercury accumulates in rice, it is important to investigate human exposure from mercury in rice.

    This project investigates the total amount of mercury and methylmercury (MeHg) accumulated in rice, soil and water from four different rice fields in Palawan. The soil samples have been taken directly from the fields and water samples have been taken from nearby streams and springs. Rice grains harvested earlier this year from the same fields have been collected from farmers. The soil, water and rice samples were analyzed in Manila and rice samples were as well analyzed in Sweden and China. Furthermore, this project contains a dietary survey and calculation of daily exposure values of MeHg. The survey investigates how often people eat fish and rice and if they have dental amalgam. It also investigates possible health problems related to mercury exposure from rice and fish consumption.

    The analyses from China show that rice samples from all barangays contain total mercury and MeHg. Analyses from Sweden also show that rice from the barangays contains total mercury but the levels were found to be higher than the ones analyzed in China. Furthermore, the health problems found in the diet survey were hard to relate to mercury exposure from rice since the health problems can be caused by other factors. When calculating daily exposure values, the values were found to be as high as the recommended maximum acceptable daily intake in one of the barangays. There might therefore be a risk of eating rice from these four barangays. It is important to consider that these daily exposure values were only based on MeHg exposure from rice consumption, not taking dental amalgam and fish consumption into consideration. This means that the daily exposure values might be even higher than the ones calculated in this study.

  • 2258.
    Abrahamsson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Educational Sciences, Department of Education.
    Vallien, Isa
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Educational Sciences, Department of Education.
    Blir våra elever kompetenta matematiker?: En studie om vilka möjligheter mellanstadieelever har att utveckla matematiska kompetenser när de arbetar med algebra i läroböcker2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna läroboksanalys har undersökt i vilken utsträckning elever ges möjlighet att utveckla matematiska kompetenser när de arbetar med algebra i läroböcker. Två läroböcker i samma läroboksserie har analyserats, en för årskurs 4 respektive årskurs 6. Detta för att kunna undersöka om det finns en progression, förvärvad kunskap som byggs vidare på, mellan läroböckerna.

    Enligt den teoretiska utgångspunkten som analysen baseras på finns sex matematiska kompetenser. Läroböckernas algebrauppgifter analyserades för att se vilken eller vilka av dessa kompetenser som gavs möjlighet att utvecklas i varje uppgift. Kompetenserna delades sedan in i nivåerna ingen, liten, medelstor eller stor utsträckning.

    Resultatet visade att samma matematiska kompetenser förekom i lika stor utsträckning i båda läroböckerna, med ett undantag. En kompetens förekom i ingen utsträckning i årskurs 4 och i liten utsträckning för årskurs 6. Två kompetenser förekom i liten utsträckning för årskurs 4 och tre kompetenser för årskurs 6. Samma kompetens utvecklas i medelstor utsträckning och stor utsträckning i båda läroböckerna. Progression identifierades i fyra kompetenser. En kompetens delades upp i två underkategorier för att se om en progression fanns mellan läroböckerna inom denna specifika kompetens. Det fanns en progression.

    Den matematiska kompetens som inte ges möjlighet att utvecklas har i tidigare forskning visats viktig. Att den inte ges möjlighet att utvecklas kan ha att göra med att den inte är med i läroplanen för grundskolan (Lgr11, 2018). En annan studie med samma teoretiska utgångspunkt har gjorts på nationella prov. I studierna förekom en kompetens i olika utsträckning på grund av att studierna valt att definiera den på olika sätt. Studierna visar i stort sett samma resultat vad gäller progression mellan årskurser.

    Slutsatsen är att kompetenserna hade behövt ges möjlighet att utvecklas i större utsträckning i läroböckerna, samt att Lgr11 skulle behöva ha med alla sex kompetenserna i läroplanen.

  • 2259.
    Abrahamsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Business Studies.
    Widfeldt, Jesper
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Business Studies.
    Aktiekapitalets funktioner: En studie av kapitalkravets funktioner utifrån åtta entreprenörers synvinklar2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Bakgrund och problem

    Aktiekapitalets nivå har sedan dess införande slitits mellan att uppfylla de funktioner som myndigheterna ämnar uppnå med ett kapitalkrav och att nivån inte ska utgöra ett ekonomiskt hinder för de entreprenörer som önskar använda aktiebolagsformen. Den ekonomiska utvecklingen, där större fokus har hamnat på småföretagande och entreprenörskap, har inneburit att funktionerna av aktiekapitalet har kommit att ifrågasättas. I dagsläget förs en debatt om huruvida kapitalkravet innebär ett hinder för nyetableringen av aktiebolag i Sverige. Detta resulterade i att regeringen år 2007 tillsatte en utredning för att undersöka möjligheten att sänka kapitalkravet. Myndigheternas syn på aktiekapitalets funktioner har inte ändrats under de senaste 35 åren, men hur uppfattar dagens moderna företagare, entreprenören, dessa funktioner? Frånvaron av entreprenörernas tankar i debatten gör att mycket lite kan sägas om hur väl dagens aktiekapital uppfyller sina tilltänkta funktioner.

    Forskningsfråga

    Stämmer entreprenörernas bild av aktiekapitalets funktioner överens med myndigheternas syn på dess funktioner?

    Syfte

    Huvudsyftet med denna uppsats är att undersöka hur entreprenörerna, utifrån deras egna verksamheter, har uppfattat myndigheternas tilltänkta funktioner med aktiekapitalet vid dagens nivå på kapitalkravet. Som bisyfte ämna författarna även undersöka om den föreslagna sänkningen av kapitalkravet ligger i linje med entreprenörernas syn på aktiekapitalets funktioner.

    Metod

    Studiens ansats är kvalitativ med ett deduktivt angreppssätt där en komparativ design har använts. Urvalet av respondenter har bestått av åtta stycken entreprenörer verksamma i konsultbranschen, med anknytning till Teknikbyn Science Park Västerås. Dataunderlaget har samlats in genom personliga semistrukturerade intervjuer.

    Slutsatser

    Utifrån undersökningen i denna uppsats kan författarna dra slutsatsen att det både finns en enighet och en skillnad i myndigheternas och entreprenörernas syn på aktiekapitalets funktioner vid dagens nivå på kapitalkravet. Utifrån studien kan slutsatsen dras att myndigheternas huvudargument, i dagsläget, för att behålla kapitalkravet är dess funktion som seriositetsspärr. Förslaget om en sänkning av kapitalkravet inte ligger i linje med entreprenörernas syn på denna funktion. Övriga argument för ett kapitalkrav uppfattas i dagsläget som antingen omoderna eller bristfälliga av de medverkande entreprenörerna vilket medför att en sänkning av aktiekapitalet inte skulle påverka några av dessa funktioner.

  • 2260.
    Abrahamsson, Eva
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Logopedi.
    Quick, Linnéa
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Logopedi.
    Datorbaserad fonologisk lästräning för barn med hörselnedsättning: En undersökning av fonologisk medvetenhet och ordavkodning2015Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Randomized controlled trials evaluating the effect of various forms of literacy training with reliable tests are lacking in Sweden today. The aim of the present study was to investigate whether a cross-over design and the use of phonologically matched wordlists specifically designed to detect transfer, would yield a more thorough method and reliable results. Six children with hearing impairment using hearing aids between 7 and 9 years of age took part in the study. The schools in which the children had their education were randomized into either an intervention group that started to practice phonics by means of a computer-assisted program after the first testing, or a control group that, continued as usual in school. Children were informed to practice daily with the program during four weeks in school. Children were tested with a battery of tests for phonological awareness, letter knowledge and word decoding at three occasions separated by four weeks. Results showed that the wordlists seemed reliable in establishing children’s decoding strategies as well as how word length affected reading speed. Both children who took part in the intervention and the control group improved their scores at the second testing. Thus, the computer-assisted reading intervention did not prove to be more effective than usual school activities. Due to a small number of participants, a large heterogeneity of the group and insufficient practice time, effects were difficult to detect. The present investigation should be considered a pilot study towards the use of more careful testing methods with adapted wordlists that enables the detection of transfer. But, to accomplish this, it is crucial to use a larger number of participants.

    Randomiserade kontrollerade studier som utvärderar effekten av olika former av läs- och skrivträning med tillförlitliga tester saknas i Sverige idag. Syftet med denna undersökning var att genomföra en interventionsstudie med cross-over design och använda fonologiskt matchade ordlistor specifikt utformade för att upptäcka transfer, för att ge utdelning för en mer grundlig metod och reliabla resultat. Sex barn mellan 7 och 9 års ålder som använde hörapparat deltog i studien. Skolorna som barnen gick i randomiserades till att antingen utgöra en interventionsgrupp, som började träna med ett ljudbaserat lästräningsprogram via dator efter första testningen, eller kontrollgrupp som fortsatte med vanlig skolundervisning. Barnen informerades att träna med programmet under fyra veckor dagligen i skolan. Barnen utförde ett testbatteri innehållande tester för fonologisk medvetenhet, bokstavskännedom och ordavkodning vid tre tillfällen med fyra veckors mellanrum. Resultaten visade att ordlistorna på ett reliabelt sätt kunde fastställa barns avkodningsstrategier samt hur ordlängd påverkade läshastigheten. Både interventions- och kontrollgruppen påvisade förbättring vid andra testningen. Dock kunde det inte påvisas att den datorbaserade lästräningen var mer effektiv än sedvanlig skolundervisning. Då deltagarantalet var litet, spridningen stor och träningstiden vid datorn var låg kan detta ha bidragit till att effekterna uteblev. Studien bör ses som en pilotstudie som går mot en noggrannare form av testmetod där användandet av anpassade ordlistor möjliggör upptäckt av transfer. För att åstadkomma detta är det emellertid avgörande att det ingår ett större deltagarantal.

  • 2261.
    Abrahamsson, Fredrik
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Educational Sciences, Department of Education.
    Då - nu - sedan? Lärarnas tolkning av historiemedvetande: En kvalitativ undersökning baserad på samtalsintervjuer med lärare i år 4-92011Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Den här undersökningen behandlar lärarnas tolkning av begreppet historiemedvetande. Totalt är åtta olika lärare intervjuade; hälften av dem undervisar i år 4-6 och hälften i år 7-9. Samtliga lärare som intervjuats arbetar på olika skolor i Östhammars Kommun.

    Undersökningen visar att lärarnas uppfattning och tolkning av styrdokumenten påverkar deras planering av undervisningen. Den visar också att frånvaron av en korrekt och gemensam definition av ett begrepp som förekommer i styrdokumenten skapar osäkerhet kring innebörd, tillämpning och bedömning. Frånvaron av en definition medför också att en fruktbar tolkning av begreppet inte kan existera och att det därmed medför svårigheter för att bedöma elevernas relation till detta begrepp, samt fördomar om hur elevernas relation till historiemedvetandet ser ut.

  • 2262.
    Abrahamsson, Gun
    et al.
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Business Studies.
    Helin, Sven
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Business Studies.
    Ekonomistyrning och förbättringsarbete. En fallstudie om hur ekonomistyrning kan stödja respektive hindra ständigt förbättringsarbete ,2000Licentiate thesis, monograph (Other scientific)
  • 2263.
    Abrahamsson, Gun
    et al.
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Business Studies.
    Helin, Sven
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Business Studies.
    Problemlösningsarbete på låg organisatorisk nivå: Två studier om implementering respektive konkretisering av idéer om kundorderstyrd tillverkning2004Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The two studies reported in this thesis are about problem solving at a low organisational level in an organisational unit in a Swedish manufacturing company, which has adopted ideas of World Class Manufacturing. In the first study, we analyse, from an organisational learning perspective, the implementation of the well-known concept Continuous Improvement at shop-floor level and how management accounting may facilitate or impede improvement work. A case study was conducted in two workgroups in one production unit for about seven months. In one of the groups, management accounting facilitated improvement work with high organisational scope and, in the other group, impeded the organisational scope. Our conclusion is that management accounting may facilitate a high organisational scope by supporting the leadership style, stressing co-operation, dialog and participation, or, by the way the manager uses management accounting, make boundaries distinct between groups of employees and between departments, and therefore impede improvements with high organisational scope. In the second study, we analyse, from a rule-based behavioural perspective, how ideas of World Class Manufacturing are institutionalised in cross-functional problem solving at a low organisational level. A case study was carried out in two cross-functional weekly group meetings for about nine months. Problems raised and solutions decided followed a repeated pattern. The actors draw on instrumental rules, which can be described as technical as well as economic. We concluded that ideas of World Class Manufacturing were institutionalised as different variants of World Class Manufacturing in the different functions at a low organisational level. At the meetings, contradictory instrumental rules were activated by the functions and treated according to interaction rules. Two overall patterns of action, articulated the two main interaction rules guiding actors in how to treat contradictory ideas of World Class Manufacturing.

  • 2264.
    Abrahamsson, Hanna
    et al.
    Uppsala University, Faculty of Educational Sciences, Department of Studies in Education, Culture and Media.
    Fridén, Karin
    Uppsala University, Faculty of Educational Sciences, Department of Studies in Education, Culture and Media.
    Fler tänker bättre än en - eller?: en studie om lärares uppfattningar om grupparbete som arbetsform2010Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med vårt examensarbete har varit att undersöka vad lärare har för uppfattningar om grupparbete som arbetsform i skolan. Det har vi undersökt genom att göra kvalitativa intervjuer med åtta lärare på olika skolor. Resultaten visade att alla lärarna ställde sig positiva till arbetsformen, men de var också snabba med att poängtera att det är en krävande arbetsform som förutsätter mycket arbete. Många av lärarna såg bland annat gruppindelningen som krävande där de visade sig använda olika metoder för att sätta samman väl fungerande grupper. Det rådde även delade meningar om i vilket ämne lärarna främst föredrog att använda sig av grupparbete. Några av lärarna förespråkade det i SO och NO medan ett par av dem tyckte att det var givande i ett teoretiskt ämne som matematik. Vid intervjuerna framgick det också att lärarna främst fokuserade på och framhävde de sociala förmågor som kan tränas vid grupparbete, och att de i mindre grad betonade de ämneskunskaper som eleverna kan tillägna sig i grupp. Samtliga lärare poängterade de sociala vinsterna eleverna får vid ett grupparbete och menade framförallt att grupparbete främjar elevernas samarbetsförmåga.

    Trots lärarnas positiva syn på arbetsformen tog alla upp nackdelar och svårigheter med metoden. Efter att ha forskat i ämnet tror vi att lärare generellt behöver tillägna sig mer kunskaper om hur arbetsformen kan användas. Detta för att få erfara fler fungerande grupparbeten och därmed vilja använda sig mer av grupparbete i sin undervisning. Vi menar dock att det inte bara hänger på läraren, utan även eleverna behöver få mer träning i hur man arbetar och samarbetar kollektivt.

     

     

  • 2265. Abrahamsson, Hasse
    et al.
    Ostlund-Lindqvist, Ann-Margret
    Nilsson, Ralf
    Simren, Magnus
    Gillberg, Per-Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Pharmacology.
    Altered bile acid metabolism in patients with constipation-predominant irritable bowel syndrome and functional constipation2008In: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 43, no 12, p. 1483-1488Article in journal (Refereed)
    Abstract [en]

    Objective. Bile acids are derived from cholesterol and are potent physiological laxatives. The aim of this study was to investigate whether bile acid synthesis is altered in constipation. Material and methods. Female patients with constipation (23 IBS-C, 4 functional constipation (FC)) were studied and compared with non-constipated subjects (16 IBS-D, 20 healthy women). Body mass index (BMI), blood lipids, lanosterol, sitosterol, colonic transit (oro-anal transit time (OATT), reference=4.3 days) and stool frequency were measured. C4 (7--hydroxy-4-cholesten-3-one) levels reflecting bile acid synthesis were measured at 0800 h and 1300 h. Results. When all the groups of constipated and non-constipated subjects were compared, it was found that only stool frequency and OATT differed between groups (p 0.001). When constipated patients were categorized according to OATT, absence of the usual C4 increase at lunchtime was noted in 82% of patients with delayed OATT compared with 17% in subjects with normal OATT (p 0.001). Symptom severity did not differ between groups. A subset of the patients with severely delayed OATT had markedly elevated C4 levels. Conclusions. Patients with IBS-C and FC have marked changes in bile acid synthesis in relation to colonic transit. The diurnal rhythm is altered in the slow transit colon when there is no C4 peak at lunchtime. Alterations in bile acid metabolism may be implicated in the pathophysiology of constipation.

  • 2266.
    Abrahamsson, Håkan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine.
    Characterization of calcium transport in mouse and clonal rat pancreatic ß-cells 1985Doctoral thesis, comprehensive summary (Other academic)
  • 2267.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kinetic Energy Storage and Magnetic Bearings: for Vehicular Applications2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the main challenges in order to make electric cars competitive with gas-powered cars is in the improvement of the electric power system. Although many of the energy sources currently used in electric vehicles have sufficientlyhigh specific energy, their applicability is limited due to low specific power. It would therefore be advantageous to create a driveline with the main energy storage separated from a smaller energy buffer, designed to have high power capabilities and to withstand frequent and deep discharge cycles. It has been found that rotating kinetic energy storage in flywheels is very well suited for this type of application.

    A composite shell, comprising an inner part made of glassfiber and an outer part made of carbonfiber, was analyzed analytically and numerically, designed, and constructed. The shell was fitted onto a metallic rotor using shrinkfitting. The cost of the shell, and the complexity of assembly, was reduced by winding the glass- and carbonfiber consecutively on a mandrel, and curing the complete assembly simultaneously. Thereby, the shell obtained an internal segmentation, without the need for fitting several concentric parts onto each other. The radial stress inside the composite shell was kept compressive thanks to a novel approach of using the permanent magnets of the integrated electric machine to provide radial mechanical load during rotation.

    Two thrust bearing units (one upper and one lower) comprising one segmented unit with the permanent magnets in a cylindrical Halbach configuration and one non-segmented unit in a up/down configuration were optimized, constructed and tested. Each thrust bearing unit generated 1040 N of repelling force, and a positive axial stiffness of 169 N/mm at the nominal airgap of 5 mm. 

    Two radial active magnetic bearings (one upper and one lower) were optimized, constructed and tested. By parameterizing the shape of the actuators, a numerical optimization of force over resistive loss from the bias currentcould be performed. The optimized shape of the electromagnets was produced by watercutting sheets of laminated steel. A maximum current stiffness of120 N/A at a bias current of 1.5 A was achieved.

    List of papers
    1. Prototype of electric driveline with magnetically levitated double wound motor
    Open this publication in new window or tab >>Prototype of electric driveline with magnetically levitated double wound motor
    Show others...
    2010 (English)In: Electrical Machines (ICEM), 2010 XIX International Conference on, 2010Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper presents the ongoing work of constructing a complete driveline for an electric road vehicle, using a flywheel as auxiliary energy storage. The flywheel energy storage system (FESS) is connected in series between the main energy storage (batteries) and the wheel motor of the vehicle, allowing the batteries to deliver power to the system in an optimized way, while at the same time making efficient use of regenerative braking. A double wound permanent magnet electric machine is used to electrically separate the two sides. In order to minimize losses, the machine has a double rotor configuration and is suspended with magnetic bearings. A bench test set-up is being constructed to investigate the properties of this system in detail. This set-up will achieve a level of power and energy close to that of a full scale system. This will allow measurements of complete drive cycles to be performed, improving the understanding of the constituting components and optimization of the complete system.

    Keywords
    electric drives, flywheels, magnetic bearings, permanent magnet machines, regenerative braking, road vehicles, auxiliary energy storage, double rotor configuration, double wound permanent magnet electric machine, electric driveline, electric road vehicle, flywheel energy storage system, magnetically levitated double wound motor, wheel motor
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-140370 (URN)
    Conference
    International Conference on Electrical Machines, ICEM
    Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2016-04-18Bibliographically approved
    2. Magnetic bearings in kinetic energy storage systems for vehicular applications
    Open this publication in new window or tab >>Magnetic bearings in kinetic energy storage systems for vehicular applications
    2011 (English)In: Journal of Electrical Systems, ISSN 1112-5209, Vol. 7, no 2, p. 225-236Article in journal (Refereed) Published
    Abstract [en]

    The rotating Kinetic Energy Storage System (KESS) is suitable as temporary energy storage in electric vehicles due to its insensitivity to the number of charge-discharge cycles and its relatively high specific energy. The size and weight of the KESS for a given amount of stored energy are minimized by decreasing the moment of inertia of the rotor and increasing its speed. A small and fast rotor has the additional benefit of reducing the induced gyroscopic moments as the vehicle turns. The very high resulting rotational speed makes the magnetic bearing an essential component of the system, with the Active Magnetic Bearing (AMB) being the most common implementation. The complexity and cost of an AMB can be reduced by integration with the electric machine, resulting in a bearingless and sensorless electric machine. This review article describes the usage of magnetic bearings for FESS in vehicular applications.

    Keywords
    Magnetic bearing, FESS, flywheel, energy storage, electric vehicle
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-165038 (URN)
    Available from: 2012-01-02 Created: 2012-01-02 Last updated: 2017-12-08Bibliographically approved
    3. Prototype of Kinetic Energy Storage System for Electrified Utility Vehicles in Urban Traffic
    Open this publication in new window or tab >>Prototype of Kinetic Energy Storage System for Electrified Utility Vehicles in Urban Traffic
    2012 (English)Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    Arlington, Virginia, USA: , 2012
    National Category
    Engineering and Technology
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-190197 (URN)
    Conference
    13th International Symposium on Magnetic Bearings
    Available from: 2013-01-07 Created: 2013-01-07 Last updated: 2017-04-06
    4. On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline
    Open this publication in new window or tab >>On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline
    Show others...
    2012 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 5, no 8, p. 2794-2817Article in journal (Refereed) Published
    Abstract [en]

    This paper presents experimental results on an innovative electric driveline employing a kinetic energy storage device as energy buffer. A conceptual division of losses in the system was created, separating the complete system into three parts according to their function. This conceptualization of the system yielded a meaningful definition of the concept of efficiency. Additionally, a thorough theoretical framework for the prediction of losses associated with energy storage and transfer in the system was developed. A large number of spin-down tests at varying pressure levels were performed. A separation of the measured data into the different physical processes responsible for power loss was achieved from the corresponding dependence on rotational velocity. This comparison yielded an estimate of the perpendicular resistivity of the stranded copper conductor of 2.5 x 10(-8) +/- 3.5 x 10(-9). Further, power and energy were measured system-wide during operation, and an analysis of the losses was performed. The analytical solution was able to reproduce the measured distribution of losses in the system to an accuracy of 4.7% (95% CI). It was found that the losses attributed to the function of kinetic energy storage in the system amounted to between 45% and 65%, depending on usage.

    Keywords
    kinetic energy storage, flywheel, electric machine, driveline, electric vehicle, losses
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-182543 (URN)10.3390/en5082794 (DOI)000308241500011 ()
    Available from: 2012-10-11 Created: 2012-10-11 Last updated: 2017-12-07Bibliographically approved
    5. A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings
    Open this publication in new window or tab >>A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings
    2014 (English)In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 50, no 9, article id 8101809Article in journal (Refereed) Published
    Abstract [en]

    Brushless dc coreless electric machines with double-rotor and single-stator configuration have very low losses, since the return path of the magnetic flux rotates with the permanent magnets. The eddy-current loss in the stator is additionally very small due to the lack of iron, making it ideal for kinetic energy storage. This paper presents a design for self-bearing rotor suspension, achieved by placing the stator windings skewed on a conical surface. A mathematical analysis of the force from a skewed winding confined to the surface of a cone was found. The parametric analytical expressions of the magnitude and direction of force and torque were verified by finite-element method simulations for one specific geometry. A dynamic model using proportional-integral-differential control was implemented in MATLAB/Simulink, and the currents needed for the self-bearing effect were found by solving an underdetermined system of linear equations. External forces, calculated from acceleration measurements from a bus in urban traffic, were added to simulate the dynamic environment of an electrical vehicle.

    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:uu:diva-212105 (URN)10.1109/TMAG.2014.2321104 (DOI)000343036900019 ()
    Available from: 2013-12-05 Created: 2013-12-05 Last updated: 2017-12-06Bibliographically approved
    6. Passive Axial Thrust Bearing for a Flywheel Energy Storage System
    Open this publication in new window or tab >>Passive Axial Thrust Bearing for a Flywheel Energy Storage System
    Show others...
    2013 (English)Conference paper, Published paper (Refereed)
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-212104 (URN)
    Conference
    The 1st Brazilian Workshop on Magnetic Bearings
    Available from: 2013-12-05 Created: 2013-12-05 Last updated: 2017-10-24
    7. High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings
    Open this publication in new window or tab >>High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings
    2014 (English)In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, no 6, p. 3012-3021Article in journal (Refereed) Published
    Abstract [en]

    This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.

    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Research subject
    Engineering Science with specialization in Science of Electricity
    Identifiers
    urn:nbn:se:uu:diva-212101 (URN)10.1109/TIE.2013.2259782 (DOI)000329055300039 ()
    Available from: 2013-12-05 Created: 2013-12-05 Last updated: 2017-12-06Bibliographically approved
  • 2268.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kinetic Energy Storage and Magnetic Bearings, for vehicular applications2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the main challenges in order to make electric cars competitive with gaspowered cars is in the improvement of the electric power system. Although many of the energy sources currently used in electric vehicles have sufficiently high specific energy, their applicability is limited due to low specific power. It would therefore be advantageous to create a driveline with the main energy storage separated from a smaller energy buffer, designed to have high power capabilities and to withstand frequent and deep discharge cycles. It has been found that rotating kinetic energy storage in flywheels is very well suited for this type of application. The work presented in this thesis and the included papers span a number of topcis Introductory overview - This section explains the concept of the modern flywheel, and investigates some of its properties. It illustrates the concepts with a number of examples, relevant for the usage of flywheels in vehicular applications. Experimental set-up - The construction of a complete electric driveline is ongoing within the division for Electricity at Uppsala University. An optimized electric machine has been constructed and connected with a programmable load, as well as with a DC power source through power electronics controlled by PWM. As a part of this system, an experimental set-up of an active magnetic bearing for two degrees-of-freedom has been constructed. The work with this device is described in detail and some preliminary results are presented. Self-bearing machine - The electric machine developed for the existing driveline is coreless, double wound and with a double rotor. In order to achieve magnetic bearing functionality in this device for all DOF, a novel Lorentz force self-bearing machine is suggested. The design is analyzed analytically and numerically.

  • 2269.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Magnetic bearings in kinetic energy storage systems for vehicular applications2011In: Journal of Electrical Systems, ISSN 1112-5209, Vol. 7, no 2, p. 225-236Article in journal (Refereed)
    Abstract [en]

    The rotating Kinetic Energy Storage System (KESS) is suitable as temporary energy storage in electric vehicles due to its insensitivity to the number of charge-discharge cycles and its relatively high specific energy. The size and weight of the KESS for a given amount of stored energy are minimized by decreasing the moment of inertia of the rotor and increasing its speed. A small and fast rotor has the additional benefit of reducing the induced gyroscopic moments as the vehicle turns. The very high resulting rotational speed makes the magnetic bearing an essential component of the system, with the Active Magnetic Bearing (AMB) being the most common implementation. The complexity and cost of an AMB can be reduced by integration with the electric machine, resulting in a bearingless and sensorless electric machine. This review article describes the usage of magnetic bearings for FESS in vehicular applications.

  • 2270.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    de Santiago, Juan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Oliveira, Janaína Gonçalves de
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Prototype of electric driveline with magnetically levitated double wound motor2010In: Electrical Machines (ICEM), 2010 XIX International Conference on, 2010Conference paper (Refereed)
    Abstract [en]

    This paper presents the ongoing work of constructing a complete driveline for an electric road vehicle, using a flywheel as auxiliary energy storage. The flywheel energy storage system (FESS) is connected in series between the main energy storage (batteries) and the wheel motor of the vehicle, allowing the batteries to deliver power to the system in an optimized way, while at the same time making efficient use of regenerative braking. A double wound permanent magnet electric machine is used to electrically separate the two sides. In order to minimize losses, the machine has a double rotor configuration and is suspended with magnetic bearings. A bench test set-up is being constructed to investigate the properties of this system in detail. This set-up will achieve a level of power and energy close to that of a full scale system. This will allow measurements of complete drive cycles to be performed, improving the understanding of the constituting components and optimization of the complete system.

  • 2271.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Gonçalves de Oliveira, Janaína
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    de Santiago, Juan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline2012In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 5, no 8, p. 2794-2817Article in journal (Refereed)
    Abstract [en]

    This paper presents experimental results on an innovative electric driveline employing a kinetic energy storage device as energy buffer. A conceptual division of losses in the system was created, separating the complete system into three parts according to their function. This conceptualization of the system yielded a meaningful definition of the concept of efficiency. Additionally, a thorough theoretical framework for the prediction of losses associated with energy storage and transfer in the system was developed. A large number of spin-down tests at varying pressure levels were performed. A separation of the measured data into the different physical processes responsible for power loss was achieved from the corresponding dependence on rotational velocity. This comparison yielded an estimate of the perpendicular resistivity of the stranded copper conductor of 2.5 x 10(-8) +/- 3.5 x 10(-9). Further, power and energy were measured system-wide during operation, and an analysis of the losses was performed. The analytical solution was able to reproduce the measured distribution of losses in the system to an accuracy of 4.7% (95% CI). It was found that the losses attributed to the function of kinetic energy storage in the system amounted to between 45% and 65%, depending on usage.

  • 2272.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hedlund, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Prototype of Kinetic Energy Storage System for Electrified Utility Vehicles in Urban Traffic2012Conference paper (Refereed)
  • 2273.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hedlund, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kamf, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings2014In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, no 6, p. 3012-3021Article in journal (Refereed)
    Abstract [en]

    This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.

  • 2274.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hedlund, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings2014In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 50, no 9, article id 8101809Article in journal (Refereed)
    Abstract [en]

    Brushless dc coreless electric machines with double-rotor and single-stator configuration have very low losses, since the return path of the magnetic flux rotates with the permanent magnets. The eddy-current loss in the stator is additionally very small due to the lack of iron, making it ideal for kinetic energy storage. This paper presents a design for self-bearing rotor suspension, achieved by placing the stator windings skewed on a conical surface. A mathematical analysis of the force from a skewed winding confined to the surface of a cone was found. The parametric analytical expressions of the magnitude and direction of force and torque were verified by finite-element method simulations for one specific geometry. A dynamic model using proportional-integral-differential control was implemented in MATLAB/Simulink, and the currents needed for the self-bearing effect were found by solving an underdetermined system of linear equations. External forces, calculated from acceleration measurements from a bus in urban traffic, were added to simulate the dynamic environment of an electrical vehicle.

  • 2275.
    Abrahamsson, Jonas
    et al.
    Queen Silvia Children’s Hospital, Gothenburg.
    Forestier, Erik
    Heldrup, Jesper
    Jahnukainen, Kirsi
    Jónsson, Olafur G.
    Lausen, Birgitte
    Palle, Josefine
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Women's and Children's Health, Pediatrics.
    Zeller, Bernward
    Hasle, Henrik
    Aarhus University Hospital Skejby, Aarhus.
    Response-Guided Induction Therapy in Pediatric Acute Myeloid Leukemia With Excellent Remission Rate2011In: Journal of Clinical Oncology, ISSN 0732-183X, E-ISSN 1527-7755, Vol. 29, no 3, p. 310-315Article in journal (Refereed)
    Abstract [en]

    Purpose

    To evaluate the early treatment response in children with acute myeloid leukemia (AML) using a response-guided induction strategy that includes idarubicin in the first course.

    Patients and Methods

    All Nordic children with AML younger than 15 years (n = 151) were treated on the Nordic Society for Pediatric Hematology and Oncology (NOPHO) AML 2004 protocol. After the first course of idarubicin, cytarabine, etoposide, and 6-thioguanin, patients with good response were allowed hematologic recovery before the second course, whereas patients with a poor (>= 15% blasts) or intermediate (5% to 14.9% blasts) were recommended to proceed immediately with therapy. Patients not in remission after the second course received fludarabine, cytarabine, and granulocyte colony-stimulating factor. Poor responders received allogeneic stem-cell transplantation (SCT) as consolidation.

    Results

    Seventy-four percent of patients had good response, 17% had intermediate response, and 7% had poor response after the first course. The overall remission frequency was 97.4%, with 92% in remission after the second course. The rate of induction death was 1.3%. Patients with an intermediate response had a lower event-free survival of 35% compared with good (61%) and poor responders (82%).

    Conclusion

    The NOPHO-AML 2004 induction strategy gives an excellent remission rate with low toxic mortality in an unselected population. Outcome is worse in patients with intermediate response but may be improved by intensifying consolidation in this group using SCT.

  • 2276.
    Abrahamsson, K., Choo, K.-S., Pedersén, M., Johansson, G. and Snoeijs, P.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology. Department of Ecology and Evolution, Plant Ecology. PLANT ECOLGY.
    Effects of temperature on the production of hydrogen peroxide and volatile halocarbons by brackish-water algae2003In: Phytochemistry, Vol. 64, p. 725-734Article in journal (Refereed)
  • 2277. Abrahamsson, K
    et al.
    Ekdahl, A
    Collén, J
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiological Botany.
    Pedersen, M
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiological Botany.
    Marine algae - a source of trichloroethylene and perchloroethylene1995In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 40, no 7, p. 1321-1326p. 1321-1326Article in journal (Refereed)
    Abstract [en]

    Our results show the natural production of two olefins, trichloroethylene and perchloroethylene, by various marine macroalgae and a microalga. We found significant difference in the ability of the algae to produce these compounds. The production rates for trichloroethylenevaried between 0.022 and 3,400 ng g-l fresh wt (FW)h-l and were generally higher than those for perchloroethylene(0.0026-8.2 ng g-l FW h-l). The two subtropicalalgae, Asparagopsis taxiformis and Falkenbergia hillebrandii,showed the highest formation rates. One axenicmarine red microalga, Porphyridium purpureum, was alsotested and it could also produce trichloroethylene and perchloroethylene.The measured rates suggest that the emissionof trichloroethylene and perchloroethylene from theoceans to the atmosphere may be of such a magnitude thatit cannot be neglected in the global atmospheric chlorinebudget.

  • 2278. Abrahamsson, K.
    et al.
    Pakhomovc,, E.A.
    Loréna, A.
    Fronemanc,, P.W.
    Bertilsson, Stefan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Chiericia,, M.
    Franssona, A.
    Variations of biochemical parameters along a transect in the Southern Ocean, with special emphasis on volatile halogenated organic compounds2004In: Deep Sea Research Part II:: Topical Studies in Oceanography, Vol. 51,, no 22-24, p. 2745-2756Article in journal (Refereed)
    Abstract [en]

    A number of parameters of biogeochemical interest were monitored along a north–southerly transect (S 43–S 63°) in the Atlantic Sector of the Southern Ocean from the 8th to the 20th of December 1997. Changes in total dissolved inorganic carbon (CT) and total alkalinity (AT) were mostly dependent on temperature and salinity until the ice edge was reached. After this point only a weak correlation was seen between these. Highest mean values of CT and AT were observed in the Winter Ice Edge (WIE) (2195 and 2319 μmol kg−1, respectively). Lowest mean AT (2277 μmol kg−1) was observed in the Sub-Antarctic Front (SAF), whereas lowest mean CT concentration (2068 μmol kg−1) was associated with the Sub-Tropical Front (STF). The pH in situ varied between 8.060 and 8.156 where the highest values were observed in the southern part of the Antarctic Polar Front (APF) and in the Summer Ice Edge (SIE) Region . These peaks were associated with areas of high chlorophyll a (chl a) and tribromomethane values. In the other areas the pH in situ was mainly dependent on hydrography. Bacterial abundance decreased more than one order of magnitude when going from north to south. The decrease appeared to be strongly related to water temperature and there were no elevated abundances at frontal zones. Microphytoplankton dominated in the SAF and APF, whereas the nano- and picoplankton dominated outside these regions.

    Volatile halogenated compounds were found to vary both with regions, and with daylight. For the iodinated compounds, the highest concentrations were found north of the STF. Brominated hydrocarbons had high concentrations in the STF, but elevated concentrations were also found in the APF and SIE regions. No obvious correlation could be found between the occurrence of individual halocarbons and chl a. On some occasions trichloroethene and tribromomethane related to the presence of nano- and microplankton, respectively.

  • 2279.
    Abrahamsson, Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Bachofner Gran, Clara
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    de Afonseca, Ana
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Eriksson, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Kalla, Christelle
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Lindqvist, Sandra
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Livscykelanalys av förbrukningsvaror: En studie för minskad klimatpåverkan inom Landstinget i Uppsala län2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Landstinget i Uppsala län (LUL) presenterade år 2014 ett miljöprogram med målet att minskasin klimatpåverkan inom bland annat transport, energi och förbrukningsmaterial. Syftet meddenna studie var att undersöka möjligheten för LUL att minska sina utsläpp av växthusgasergenom att välja mer miljövänliga varianter av två välanvända förbrukningsvaror inom vården:operationsset och tvättlappar. Detta utfördes genom att tillämpa metoden livscykelanalys(LCA), där tre varianter av operationsset, två sorters tvättlappar samt ett jämförbartavtorkningspapper följdes ”från vaggan till graven”.Studiens resultat skulle besvara frågan om vilken produkt inom de två användningsområdenasom avgav minst växthusgaser i form av koldioxid, metan samt lustgas under en livscykel, föratt uppfylla samma funktion inom avdelningarna operation samt geriatrik. Resultatet skullepresenteras i enheten koldioxidekvivalenter (eCO2). Dessutom identifieradesförbrukningsvarorna som medförde de minsta årsförbrukningskostnaderna för LUL.Operationsseten som undersöktes bestod av polylaktid (PLA), polypropen (PP) samt viskos.Avtorkningspappret bestod av pappersmassa och tvättlapparna bestod bland annat av viskossamt skumplast. Studien avgränsades till att inkludera växthusgasutsläpp från tillverkning avråmaterial, tillverkning av förpackningsmaterial, transporter samt förbränning.Efter utförd LCA kunde det observeras att en årsförbrukning av operationssetet i PLA släppteut minst växthusgaser med cirka 11 100 kg eCO2 per år, operationssetet i PP släppte ut mestmed 25 100 kg eCO2 per år och operationssetet i viskos bidrog med 20 300 kg eCO2 per år. Enårsförbrukning av avtorkningspappret bidrog med minst växthusgasutsläpp med 67,1 kg eCO2per år, medan tvättlappen i viskos släppte ut 134 kg eCO2 per år och tvättlappen i skumplastbidrog med det största utsläppsvärdet på 1 150 kg eCO2 per år.En årsförbrukning av båda operationsseten i PLA och PP kostade cirka 127 000 kr medansamma mängd av operationssetet i viskos ungefär kostade 125 000 kr. Avtorkningspappretkostade 4 790 kr för en årsförbrukning, tvättlappen i viskos kostade 21 000 kr och tvättlappeni skumplast kostade 19 800 kr.Resultatet från denna studie tydde på att LUL skulle kunna minska sin klimatpåverkan frånförbrukningsmaterial genom att upphandla operationssetet i PLA samt avtorkningspappretistället för de alternativen som används i dagsläget. Det finns en osäkerhet i resultatet då flertaletantaganden gjordes i brist på tillgänglig information. Resultatet anses dock ge en rimlig bild avmiljöpåverkan från produkterna då de minst klimatpåverkande förbrukningsvarorna till stor delutgjordes av förnyelsebart material.

  • 2280.
    Abrahamsson, Kurt V., 1934- Baltic University Programme
    Uppsala University.
    A sustainable Baltic region. Authors: Kurt-Viking Abrahamsson ...1997Other (Other scientific)
  • 2281.
    Abrahamsson, Kurt V. et al
    Uppsala University.
    A sustainable Baltic region. Authors: Kurt-Viking Abrahamsson ... Deltitel: Session 1 : The road towards sustainability : a historical perspective. Editor: Sverker Sörlin1997Other (Other scientific)
  • 2282.
    Abrahamsson, Leif R.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    A priori estimates for solutions of singular perturbations with a turning point1977In: Studies in applied mathematics (Cambridge), ISSN 0022-2526, E-ISSN 1467-9590, Vol. 56, p. 51-69Article in journal (Refereed)
  • 2283.
    Abrahamsson, Leif R.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Keller, Herbert B.
    Kreiss, Heinz-Otto
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Difference approximations for singular perturbations of systems of ordinary differential equations1974In: Numerische Mathematik, ISSN 0029-599X, E-ISSN 0945-3245, Vol. 22, p. 367-391Article in journal (Refereed)
  • 2284.
    Abrahamsson, Lillemor
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Domestic Sciences.
    Matvanor och behov under livscykeln1999In: Näringslära för högskolan, Liber AB Stockholm , 1999, p. 289-316Chapter in book (Other scientific)
  • 2285.
    Abrahamsson, Lillemor
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Domestic Sciences.
    Proteiner1999In: Näringslära för högskolan, Liber AB Stockholm , 1999, p. 79-101Chapter in book (Other scientific)
  • 2286.
    Abrahamsson, Lillemor
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Domestic Sciences.
    Andersson, Agneta
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Domestic Sciences. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences.
    Principles of nutritional assessment2006In: Scandinavian Journal of Food and Nutrition, ISSN 1748-2976, E-ISSN 1748-2984, Vol. 50, no 4, p. 177-177Article, book review (Other (popular science, discussion, etc.))
  • 2287.
    Abrahamsson, Lillemor
    et al.
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Domestic Sciences. kost.
    Andersson, Agneta
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Domestic Sciences. Medicinska vetenskapsområdet, Faculty of Medicine, Department of Public Health and Caring Sciences.
    Becker, Wulf
    Medicinska vetenskapsområdet, Faculty of Medicine, Department of Public Health and Caring Sciences. Klinisk nutrition och metabolism.
    Nilsson, Gerd
    Näringslära för högskolan2006Book (Other (popular scientific, debate etc.))
  • 2288. Abrahamsson, Lillemor
    et al.
    Andersson, Agneta
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Food, Nutrition and Dietetics.
    Nilsson, Gerd
    Näringslära för högskolan: Från grundläggande till avancerad nutrition2013 (ed. 6)Book (Other (popular science, discussion, etc.))
  • 2289.
    Abrahamsson, Lillemor
    et al.
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Domestic Sciences.
    Ekblad, Jenny
    Behov under livscykeln och varianter av kost2006In: Näringslära för högskolan, Liber AB, Stockholm , 2006, p. 356-393Chapter in book (Other (popular scientific, debate etc.))
  • 2290.
    Abrahamsson, Lillemor
    et al.
    Uppsala University, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Faculty of Social Sciences, Department of Domestic Sciences.
    Löf, Marie
    Proteiner2006In: Näringslära för högskolan, Liber AB, Stockholm , 2006, p. 131-165Chapter in book (Other (popular scientific, debate etc.))
  • 2291.
    Abrahamsson, Linda
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Mathematics, Mathematical Statistics.
    Statistical models of breast cancer tumour growth for mammography screening data2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 2292.
    Abrahamsson, Lotta
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Neuroscience, Logopedi.
    Ljung, Ida-Karin
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Neuroscience, Logopedi.
    Bliss i interaktion: - En samtalsanalytisk fallstudie av hur blissanvändare och tolkare tillsammans bygger upp yttranden2008Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 2293.
    Abrahamsson, Ludvig
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Economic History.
    Försäljning av statliga bolag. En jämförande studie av inställning till statligt ägande under två perioder.2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    I denna uppsats undersöks hur inställningen till statligt ägande förändrats från början av 1990-talet till mitten av 2000-talet. Genom att undersöka den borgerliga regeringens proposition om minskat statligt ägande från 1991/92 med den borgerliga regeringens proposition om minskat statligt ägande från 2006/07 skapas en förståelse om hur de båda förslagen liknar varandra och hur de skiljer sig åt. Till de båda propositionerna lägger oppositionspartierna fram sina åsikter i motioner. Motionerna undersöks och bidrar till att skapa en bredare förståelse för den ekonomiska och politiska förändring som analyseras.

    För att sätta undersökningen i en historisk kontext presenteras en historisk bakgrund. I den historiska bakgrunden diskuteras Sveriges ekonomiska och politiska förändring under 1980-talet fram till alliansregeringens tillträde 2006. Fokus ligger här på de nya ekonomiska idéer som växer fram och hur dessa idéer påverkar det politiska klimatet.

    Genomgånge av de två olika förslagen som undersökningen bygger på visar att det finns likheter men också vissa skillnader mellan de båda förslagen. Regeringen 1991/92 vill sälja av statliga företag för att skapa en mer dynamisk och effektiv marknad. Regeringen 2006/07 vill sälja av statliga företag för att skapa en mer dynamisk och effektiv marknad för att på så sätt skapa fler jobb och bryta utanförskapet.

    Resultatet av undersökningen visar att det finns skillnader i hur de två undersökta regeringarna förhåller sig till statligt ägande. De har olika mål med att sälja ut statliga bolag, den övergripande visionen är annorlunda. Anledningen till detta kan bero på flera olika faktorer. Beroende på hur resultatet tolkas i relation till den historiska kontexten kan flera olika förklaringar konstateras.

  • 2294.
    Abrahamsson, M. L. A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Tran, A.
    Sun, L.
    Åkermark, B.
    Styring, S.
    Mukhtar, E.
    Lindquist, S. E.
    Hammarström, L.
    Electron Transfer Kinetics for Ruthenium-Manganese Complexes Adsorbed onto Nanocrystalline TiO2 Films2001Article in journal (Refereed)
  • 2295.
    Abrahamsson, Malin L. A.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry.
    Electron Transfer in Ruthenium-Manganese Complexes for Artificial Photosynthesis: Studies in Solution and on Electrode Surfaces2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In today’s society there is an increasing need for energy, an increase which for the most part is supplied by the use of fossil fuels. Fossil fuel resources are limited and their use has harmful effects on the environment, therefore the development of technologies that produce clean energy sources is very appealing. Natural photosynthesis is capable of converting solar energy into chemical energy through a series of efficient energy and electron transfer reactions with water as the only electron source. Thus, constructing an artificial system that uses the same principles to convert sunlight into electricity or storable fuels like hydrogen is one of the major forces driving artificial photosynthesis research.

    This thesis describes supramolecular complexes with the intention of mimicking the electron transfer reactions of the donor side in Photosystem II, where a manganese cluster together with a tyrosine catalyses the oxidation of water. All complexes are based on Ru(II)-trisbipyridine as a photosensitizer that is covalently linked to electron donors like tyrosine or manganese. Photochemical reactions are studied with time-resolved transient absorption and emission measurements. Electrochemical techniques are used to study the electrochemical behavior, and different photoelectrochemical techniques are used to investigate the complexes adsorbed onto titanium dioxide surfaces. In all complexes, intramolecular electron transfer occurs from the linked donor to photo-oxidized Ru(III). It is also observed that coordinated Mn(II) quenches the excited state of Ru(II), a reaction that is found to be distance dependent. However, by modifying one of the complexes, its excited state properties can be tuned in a way that decreases the quenching and keeps the electron transfer properties. The obtained results are of significance for the development of multinuclear Ru-Mn complexes that are capable of multi-electron transfer.

    List of papers
    1. Ruthenium-Manganese Complexes for Artificial Photosynthesis: Factors Controlling Intramolecular Electron Transfer and Excited State Quenching Reactions
    Open this publication in new window or tab >>Ruthenium-Manganese Complexes for Artificial Photosynthesis: Factors Controlling Intramolecular Electron Transfer and Excited State Quenching Reactions
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    2002 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 41, no 6, p. 1534-1544Article in journal (Refereed) Published
    Abstract [en]

    Continuing our work toward a system mimicking the electron-transfer steps from manganese to P(680)(+) in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (k(ET)) values span a large range, 1 x 10(5)-2 x 10(7) s(-1), and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (lambda = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically lambda approximately 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium(III) electron-transfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.

    National Category
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-89491 (URN)10.1021/ic0107227 (DOI)11896722 (PubMedID)
    Available from: 2001-10-19 Created: 2001-10-19 Last updated: 2017-12-14Bibliographically approved
    2. A Biomimetic Model System for the Water Oxidizing Triad in Photosystem II
    Open this publication in new window or tab >>A Biomimetic Model System for the Water Oxidizing Triad in Photosystem II
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    1999 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 121, no 1, p. 89-96Article in journal (Refereed) Published
    Abstract [en]

    In plants, solar energy is used to extract electrons from water, producing atmospheric oxygen. This is conducted by Photosystem II, where a redox ”triad” consisting of chlorophyll, a tyrosine, and a manganese cluster, governs an essential part of the process. Photooxidation of the chlorophylls produces electron transfer from the tyrosine, which forms a radical. The radical and the manganese cluster together extract electrons from water, providing the biosphere with an unlimited electron source. As a partial model for this system we constructed a ruthenium(II) complex with a covalently attached tyrosine, where the photooxidized ruthenium was rereduced by the tyrosine. In this study we show that the tyrosyl radical, which gives a transient EPR signal under illumination, can oxidize a manganese complex. The dinuclear manganese complex, which initially is in the Mn(III)/(III) state, is oxidized by the photogenerated tyrosyl radical to the Mn(III)/(IV) state. The redox potentials in our system are comparable to those in Photosystem II. Thus, our synthetic redox “triad” mimics important elements in the electron donor ”triad” in Photosystem II, significantly advancing the development of systems for artificial photosynthesis based on ruthenium−manganese complexes.

    Keywords
    Electron-Transfer, Y-Z, Photosynthesis, Mechanism, Complexes, Tyrosine, Oxygen, Light
    National Category
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-89492 (URN)10.1021/ja981494r (DOI)
    Available from: 2001-10-19 Created: 2001-10-19 Last updated: 2017-12-14
    3. Hydrogen-Bond Promoted Intramolecular Electron Transfer to Photogenerated Ru(III): A Functional Mimic of TyrosineZ and Histidine 190 in Photosystem II
    Open this publication in new window or tab >>Hydrogen-Bond Promoted Intramolecular Electron Transfer to Photogenerated Ru(III): A Functional Mimic of TyrosineZ and Histidine 190 in Photosystem II
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    1999 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 121, no 29, p. 6834-6842Article in journal (Refereed) Published
    Abstract [en]

    As a model for redox components on the donor side of photosystem II (PS II) in green plants, a supramolecular complex 4 has been prepared. In this, a ruthenium(II) tris-bipyridyl complex which mimics the function of P680 in PS II, has been covalently linked to a tyrosine unit which bears two hydrogen-bonding substituents, dipicolylamine (dpa) ligands. Our aim is to mimic the interaction between tyrosineZ and a basic histidine residue, namely His190 in PSII, and also to use the dpa ligands for coordination of manganese. Two different routes for the synthesis of the compound 4 are presented. Its structure was fully characterized by 1H NMR, COSY, NOESY, 13C NMR, IR, and mass spectrometry. 1H NMR and NOESY gave evidence for the existence of intramolecular hydrogen bonding in 4. The interaction between the ruthenium and the substituted tyrosine unit was probed by steady-state and time-resolved emission measurements as well as by chemical oxidation. Flash photolysis and EPR measurements on 4 in the presence of an electron acceptor (methylviologen, MV2+, or cobalt pentaminechloride, Co3+) showed that an intermolecular electron transfer from the excited state of Ru(II) in 4 to the electron acceptor took place, forming Ru(III) and the methylviologen radical MV+ or Co2+. This was followed by intramolecular electron transfer from the substituted tyrosine moiety to the photogenerated Ru(III), regenerating Ru(II) and forming a tyrosyl radical. In water, the radical has a g value of 2.0044, indicative of a deprotonated tyrosyl radical. In acetonitrile, a radical with a g value of 2.0029 was formed, which can be assigned to the tyrosine radical cation. In both solvents the electron transfer is intramolecular with a rate constant kET > 1 × 107 s-1. This is 2 orders of magnitude greater than the one for a similar compound 3, in which no dpa arm is attached to the tyrosine unit. Therefore the hydrogen bonding between the substituted tyrosine and the dpa arms in 4 is proposed to be responsible for the fast electron transfer. This interaction mimics the proposed His190 and tyrosineZ interaction in the donor side of PS II.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-89493 (URN)10.1021/ja984048c (DOI)
    Available from: 2001-10-19 Created: 2001-10-19 Last updated: 2017-12-14
    4. Towards an artificial model for Photosystem II: A manganese(II,II) dimer covalently linked to ruthenium(II) tris-bipyridine via a tyrosine derivative
    Open this publication in new window or tab >>Towards an artificial model for Photosystem II: A manganese(II,II) dimer covalently linked to ruthenium(II) tris-bipyridine via a tyrosine derivative
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    2000 (English)In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 78, no 1, p. 15-22Article in journal (Refereed) Published
    Abstract [en]

    In order to model the individual electron transfer steps from the manganese cluster to the photooxidized sensitizer P680+ in Photosystem II (PS II) in green plants, the supramolecular complex 4 has been synthesized. In this complex, a ruthenium(II) tris-bipyridine type photosensitizer has been linked to a manganese(II) dimer via a substituted L-tyrosine, which bridges the manganese ions. The trinuclear complex 4 was characterized by electron paramagnetic resonance (EPR) and electrospray ionization mass spectrometry (ESI-MS). The excited state lifetime of the ruthenium tris-bipyridine moiety in 4 was found to be about 110 ns in acetonitrile. Using flash photolysis in the presence of an electron acceptor (methylviologen), it was demonstrated that in the supramolecular complex 4 an electron was transferred from the excited state of the ruthenium tris-bipyridine moiety to methylviologen, forming a methylviologen radical and a ruthenium(III) tris-bipyridine moiety. Next, the Ru(III) species retrieved the electron from the manganese(II/II) dimer in an intramolecular electron transfer reaction with a rate constant kET > 1.0 x 10(7) s(-1), generating a manganese(II/III) oxidation state and regenerating the ruthenium(II) photosensitizer. This is the first example of intramolecular electron transfer in a supramolecular complex, in which a manganese dimer is covalently linked to a photosensitizer via a tyrosine unit, in a process which mimics the electron transfer on the donor side of PS II.

    Keywords
    ruthenium complexes, manganese dimer complexes, artificial photosynthesis, electron transfer, photosystem II, ELECTRON-TRANSFER, MNIIMNIII COMPLEXES, PHOTOSYNTHESIS, PROTEINS, CATALASE, SPECTRA, ENZYMES, SYSTEMS, REDOX
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-89494 (URN)10.1016/S0162-0134(99)00200-7 (DOI)10714701 (PubMedID)
    Available from: 2001-10-19 Created: 2001-10-19 Last updated: 2017-12-14
    5. Ruthenium Trisbipyridyl Complexes Covalently Linked to Phenolate Ligands that Coordinates Manganese
    Open this publication in new window or tab >>Ruthenium Trisbipyridyl Complexes Covalently Linked to Phenolate Ligands that Coordinates Manganese
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    Article in journal (Refereed) In press
    Identifiers
    urn:nbn:se:uu:diva-89495 (URN)
    Available from: 2001-10-19 Created: 2001-10-19 Last updated: 2010-01-14Bibliographically approved
    6. Electron Transfer Kinetics for Ruthenium-Manganese Complexes Adsorbed onto Nanocrystalline TiO2 Films
    Open this publication in new window or tab >>Electron Transfer Kinetics for Ruthenium-Manganese Complexes Adsorbed onto Nanocrystalline TiO2 Films
    Show others...
    2001 (English)Article in journal (Refereed) In press
    Identifiers
    urn:nbn:se:uu:diva-89496 (URN)
    Available from: 2001-10-19 Created: 2001-10-19 Last updated: 2014-01-24Bibliographically approved
  • 2296.
    Abrahamsson, Malin L. A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Berglund Baudin, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Tran, A.
    Philouze, C.
    Berg, K.
    Raymond-Johansson, Mary Katherine
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Sun, L.
    Åkermark, B.
    Styring, S.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Ruthenium-Manganese Complexes for Artificial Photosynthesis: Factors Controlling Intramolecular Electron Transfer and Excited State Quenching Reactions2002In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 41, no 6, p. 1534-1544Article in journal (Refereed)
    Abstract [en]

    Continuing our work toward a system mimicking the electron-transfer steps from manganese to P(680)(+) in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (k(ET)) values span a large range, 1 x 10(5)-2 x 10(7) s(-1), and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (lambda = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically lambda approximately 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium(III) electron-transfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.

  • 2297.
    Abrahamsson, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Accelerator mass spectrometry group.
    Tuning of the Excited State Properties of Ruthenium(II)-Polypyridyl Complexes2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Processes where a molecule absorbs visible light and then converts the solar energy into chemical energy are important in many biological systems, such as photosynthesis and also in many technical applications e.g. photovoltaics. This thesis describes a part of a multidisciplinary project, aiming at a functional mimic of the natural photosynthesis, with the overall goal of production of a renewable fuel from sun and water. More specific, the thesis is focused on design and photophysical characterization of new photosensitizers, i.e. light absorbers that should be capable of transferring electrons to an acceptor and be suitable building blocks for supramolecular rod-like donor-photosensitizer-acceptor arrays.

    The excited state lifetime, the excited state energy and the geometry are important properties for a photosensitizer. The work presented here describes a new strategy to obtain longer excited state lifetimes of the geometrically favorable Ru(II)-bistridentate type complexes, without a concomitant substantial decrease in excited state energy. The basic idea is that a more octahedral coordination around the Ru will lead to longer excited state lifetimes. In the first generation of new photosensitizers a 50-fold increase of the excited state lifetime was observed, going from 0.25 ns for the model complex to 15 ns for the best photosensitizer. The second generation goes another step forward, to an excited state lifetime of 810 ns. Furthermore, the third generation of new photosensitizers show excited state lifetimes in the 0.45 - 5.5 microsecond region at room temperature, a significant improvement. In addition, the third generation of photosensitizers are suitable for further symmetric attachment of electron donor and acceptor motifs, and it is shown that the favorable properties are maintained upon the attachment of anchoring groups. The reactivity of the excited state towards light-induced reactions is proved and the photostability is sufficient so the new design strategy has proven successful.

    List of papers
    1. A tridentate Ligand for Preparation of Bisterpyridine-like Ruthenium(II) Complexes with an Increased Excited State Lifetime
    Open this publication in new window or tab >>A tridentate Ligand for Preparation of Bisterpyridine-like Ruthenium(II) Complexes with an Increased Excited State Lifetime
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    2004 (English)In: Inorganic Chemistry Communications, ISSN 1387-7003, E-ISSN 1879-0259, Vol. 7, no 3, p. 337-340Article in journal (Refereed) Published
    Abstract [en]

    A new tridentate polypyridine ligand, 6-(2-picolyl)-2,2-bipyridine, as well as its homoleptic Ru(II) complex has been prepared. Photophysical studies show a prolonged lifetime of the excited state compared to [Ru(tpy)2]2+, where tpy is 2,2:6,2″-terpyridine.

    Place, publisher, year, edition, pages
    Elsevier, 2004
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-95083 (URN)10.1016/j.inoche.2003.12.007 (DOI)
    Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2017-12-14Bibliographically approved
    2. A New Strategy for the Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes: Synthesis and Photophysical and Electrochemical Characterization of Six Mononuclear Ruthenium(II) Bisterpyridine-Type Complexes
    Open this publication in new window or tab >>A New Strategy for the Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes: Synthesis and Photophysical and Electrochemical Characterization of Six Mononuclear Ruthenium(II) Bisterpyridine-Type Complexes
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    2005 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, no 9, p. 3215-3225Article in journal (Refereed) Published
    Place, publisher, year, edition, pages
    ACS, 2005
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-95084 (URN)10.1021/ic048247a (DOI)15847430 (PubMedID)
    Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2017-12-14Bibliographically approved
    3. Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.
    Open this publication in new window or tab >>Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.
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    2008 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 47, no 9, p. 3540-3548Article in journal (Refereed) Published
    Abstract [en]

    The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane (1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane (2). A homoleptic ([Ru(2)(2)](2+)) and a heteroleptic complex ([Ru(ttpy)(2)](2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru(1)(2)](2+). The excited-state lifetime of the homoleptic Ru-II complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru-II complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru-II ion less octahedral in [Ru(2)(2)](2+) than in [Ru(1)(2))(2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ((MLCT)-M-3) and metal-centered ((MC)-M-3) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru-II complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (MLCT)-M-3 states to short-lived (MC)-M-3 states.

    Place, publisher, year, edition, pages
    ACS, 2008
    National Category
    Inorganic Chemistry Analytical Chemistry
    Research subject
    Analytical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-95085 (URN)10.1021/ic7019457 (DOI)000255380500018 ()18402440 (PubMedID)
    Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2017-12-14Bibliographically approved
    4. Six-membered Ring Chelate Complexes of Ru(II): Structural and photophysical effects
    Open this publication in new window or tab >>Six-membered Ring Chelate Complexes of Ru(II): Structural and photophysical effects
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    2007 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, no 24, p. 10354-10364Article in journal (Refereed) Published
    Abstract [en]

    The structural and photophysical properties of Ru(II)−polypyridyl complexes with five- and six-membered chelate rings were studied for two bis-tridentate and two tris-bidentate complexes. The photophysical effect of introducing a six-membered chelate ring is most pronounced for the tridentate complex, leading to a room-temperature excited-state lifetime of 810 ns, a substantial increase from 180 ns for the five-membered chelate ring model complex. Contrasting this, the effect is the opposite in tris-bidentate complexes, in which the lifetime decreases from 430 ns to around 1 ns in going from a five-membered to six-membered chelate ring. All of the complexes were studied spectroscopically at both 80 K and ambient temperatures, and the temperature dependence of the excited-state lifetime was investigated for both of the bis-tridentate complexes. The main reason for the long excited-state lifetime in the six-membered chelate ring bis-tridentate complex was found to be a strong retardation of the activated decay via metal-centered states, largely due to an increased ligand field splitting due to the complex having a more-octahedral geometry.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-95086 (URN)10.1021/ic7011827 (DOI)000251109500039 ()17975915 (PubMedID)
    Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2017-12-14Bibliographically approved
    5. A 3.0 mu s room temperature excited state lifetime of a bistridentate Ru-II-polypyridine complex for rod-like molecular arrays
    Open this publication in new window or tab >>A 3.0 mu s room temperature excited state lifetime of a bistridentate Ru-II-polypyridine complex for rod-like molecular arrays
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    2006 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, no 39, p. 12616-12617Article in journal (Refereed) Published
    Abstract [en]

    A bistridentate RuII-polypyridine complex [Ru(bqp)2]2+ (bqp = 2,6-bis(8'-quinolinyl)pyridine) has been prepared, which has a coordination geometry much closer to a perfect octahedron than the typical Ru(terpyridine)2-type complex. Thus, the complex displays a 3.0 mus lifetime of the lowest excited metal-to-ligand charge transfer (3MLCT) state at room temperature. This is, to the best of our knowledge, the longest MLCT state lifetime reported for a RuII-polypyridyl complex at room temperature. The structure allows for the future construction of rod-like, isomer-free molecular arrays by substitution of donor and acceptor moieties on the central pyridine units. This makes it a promising photosensitizer for applications in molecular devices for artificial photosynthesis and molecular electronics.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-95087 (URN)10.1021/ja064262y (DOI)000240795000014 ()17002333 (PubMedID)
    Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2017-12-14Bibliographically approved
    6. Bistridentate Ruthenium(II)polypyridyl-Type Complexes with Microsecond 3MLCT State Lifetimes: Sensitizers for Rod-Like Molecular Arrays
    Open this publication in new window or tab >>Bistridentate Ruthenium(II)polypyridyl-Type Complexes with Microsecond 3MLCT State Lifetimes: Sensitizers for Rod-Like Molecular Arrays
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    2008 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 46, p. 15533-15542Article in journal (Refereed) Published
    Abstract [en]

    A series of bistridentate ruthenium(II) polypyridyl-type complexes based on the novel 2,6-di(quinolin-8-yl)pyridine (dqp) ligand have been synthesized and their photophysical properties have been studied. The complexes are amenable to substitution in the 4-position of the central pyridine with conserved quasi-C2v symmetry, which allows for extension to isomer-free, rod-like molecular arrays for vectorial control of electron and energy transfer. DFT calculations performed on the parent [Ru(dqp) 2](2+) complex (1) predicted a more octahedral structure than in the typical bistridentate complex [Ru(tpy)2](2+) (tpy is 2,2':6',2"-terpyridine) thanks to the larger ligand bite angle, which was confirmed by X-ray crystallography. A strong visible absorption band, with a maximum at 491 nm was assigned to a metal-to-ligand charge transfer (MLCT) transition, based on time-dependent DFT calculations. 1 shows room temperature emission (Phi = 0.02) from its lowest excited ((3)MLCT) state that has a very long lifetime (tau = 3 micros). The long lifetime is due to a stronger ligand field, because of the more octahedral structure, which makes the often dominant activated decay via short-lived metal-centered states insignificant also at elevated temperatures. A series of complexes based on dqp with electron donating and/or accepting substituents in the 4-position of the pyridine was prepared and the properties were compared to those of 1. An unprecedented (3)MLCT state lifetime of 5.5 micros was demonstrated for the homoleptic complex based on dqpCO2Et. The favorable photosensitizer properties of 1, such as a high extinction coefficient, high excited-state energy and long lifetime, and tunable redox potentials, are maintained upon substitution. In addition, the parent complex 1 is shown to be remarkably photostable and displays a high reactivity in light-induced electron and energy transfer reactions with typical energy and electron acceptors and donors: methylviologen, tetrathiofulvalene, and 9,10-diphenylanthracene. This new class of complexes constitutes a promising starting point for the construction of linear, rod-like molecular arrays for photosensitized reactions and applications in artificial photosynthesis and molecular electronics.

    Place, publisher, year, edition, pages
    ACS, 2008
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-95088 (URN)10.1021/ja804890k (DOI)000263311300058 ()19006410 (PubMedID)
    Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2017-12-14Bibliographically approved
    7. Modulation of the lowest metal-to-ligand charge-transfer state in [Ru(bpy)(2)(N-N)](2+) systems by changing the N-N from hydrazone to azine: Photophysical Consequences
    Open this publication in new window or tab >>Modulation of the lowest metal-to-ligand charge-transfer state in [Ru(bpy)(2)(N-N)](2+) systems by changing the N-N from hydrazone to azine: Photophysical Consequences
    Show others...
    2006 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, no 23, p. 9580-9586Article in journal (Refereed) Published
    Abstract [en]

    Two Ru( II) complexes, [ Ru( bpy) L-2]( ClO4) 2 ( 1) and [ Ru( bpy)(2)L']( BF4) 2 ( 2), where bpy is 2,2'-bipyridine, L is diacetyl dihydrazone, and L' 1: 2 is the condensate of L and acetone, are synthesized. From X-ray crystal structures, both are found to contain distorted octahedral RuN62+ cores. NMR spectra show that the cations in 1 and 2 possess a C-2 axis in solution. They display the expected metal-to-ligand charge transfer ( (MLCT)-M-1) band in the 400 - 500 nm region. Complex 1 is nonemissive at room temperature in solution as well as at 80 K. In contrast, complex 2 gives rise to an appreciable emission upon excitation at 440 nm. The room-temperature emission is centered at 730 nm ( lambda(max)(em)) with a quantum yield ( em) of 0.002 and a lifetime ( tau(em)) of 42 ns in an air-equilibrated methanol - ethanol solution. At 80 K, Phi(em) = 0.007 and tau(em)= 178 ns, with a lambda(max)(em) of 690 nm, which is close to the 0 - 0 transition, indicating an (MLCT)-M-3 excited-state energy of 1.80 eV. The radiative rate constant ( 5 x 10(4) s(-1)) at room temperature and 80 K is almost temperature independent. From spectroelectrochemistry, it is found that bpy is easiest to reduce in 2 and that L is easiest in 1. The implications of this are that in 2 the lowest (MLCT)-M-3 state is localized on a bpy ligand and in 1 it is localized on L. Transient absorption results also support these assignments. As a consequence, even though 2 shows a fairly strong and long-lived emission from a Ru( II) -> bpy CT state, the Ru( II) -> L CT state in 1 shows no detectable emission even at 80 K.

    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-95089 (URN)10.1021/ic061116k (DOI)000241778900057 ()
    Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2017-12-14Bibliographically approved
    8. Structural and Spectral Investigation of Ruthenium(II) Polypyridyl Complexes by DFT Calculations
    Open this publication in new window or tab >>Structural and Spectral Investigation of Ruthenium(II) Polypyridyl Complexes by DFT Calculations
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    (English)In: Inorganic ChemistryArticle in journal (Refereed) Submitted
    Identifiers
    urn:nbn:se:uu:diva-95090 (URN)
    Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2013-05-17Bibliographically approved
  • 2298.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Becker, Hans-Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Microsecond (MLCT)-M-3 excited state lifetimes in bis-tridentate Ru(II)-complexes: significant reductions of non-radiative rate constants2017In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 39, p. 13314-13321Article in journal (Refereed)
    Abstract [en]

    In this paper we report the photophysical properties of a series of bis-tridentate Ru-II-complexes, based on the dqp-ligand (dqp = 2,6-di(quinolin-8-yl) pyridine), which display several microsecond long excited state lifetimes for triplet metal-to-ligand charge transfer ((MLCT)-M-3) at room temperature. Temperature dependence of the excited state lifetimes for [Ru(dqp)(2)](2+) and [Ru(dqp)(ttpy)](2+) (ttpy = 4'-tolyl-2,2': 6', 2 ''-terpyridine) is reported and radiative and non-radiative rate constants for the whole series are reported and discussed. We can confirm previous assumptions that the near-octahedricity of the bis-dqp complexes dramatically slows down activated decay at room temperature, as compared to most other and less long-lived bis-tridentate RuII-complexes, such as [Ru(tpy)(2)](2+) with tau = 0.25 ns at room temperature (tpy = 2,2': 6', 2 ''-terpyridine). Moreover, the direct non-radiative decay to the ground state is comparatively slow for similar to 700 nm room-temperature emission when considering the energy-gap law. Analysis of the 77 K emission spectra suggests that this effect is not primarily due to smaller excited state distortion than that for comparable complexes. Instead, an analysis of the photophysical parameters suggests a weaker singlet-triplet mixing in the MLCT state, which slows down both radiative and non-radiative decay.

  • 2299.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Becker, Hans-Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Bonnefous, Celine
    Chamchoumis, Charles
    Thummel, Randolph
    Six-membered Ring Chelate Complexes of Ru(II): Structural and photophysical effects2007In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, no 24, p. 10354-10364Article in journal (Refereed)
    Abstract [en]

    The structural and photophysical properties of Ru(II)−polypyridyl complexes with five- and six-membered chelate rings were studied for two bis-tridentate and two tris-bidentate complexes. The photophysical effect of introducing a six-membered chelate ring is most pronounced for the tridentate complex, leading to a room-temperature excited-state lifetime of 810 ns, a substantial increase from 180 ns for the five-membered chelate ring model complex. Contrasting this, the effect is the opposite in tris-bidentate complexes, in which the lifetime decreases from 430 ns to around 1 ns in going from a five-membered to six-membered chelate ring. All of the complexes were studied spectroscopically at both 80 K and ambient temperatures, and the temperature dependence of the excited-state lifetime was investigated for both of the bis-tridentate complexes. The main reason for the long excited-state lifetime in the six-membered chelate ring bis-tridentate complex was found to be a strong retardation of the activated decay via metal-centered states, largely due to an increased ligand field splitting due to the complex having a more-octahedral geometry.

  • 2300.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Tocher, Derek
    Nag, Samik
    Datta, Dipankar
    Modulation of the lowest metal-to-ligand charge-transfer state in [Ru(bpy)(2)(N-N)](2+) systems by changing the N-N from hydrazone to azine: Photophysical Consequences2006In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, no 23, p. 9580-9586Article in journal (Refereed)
    Abstract [en]

    Two Ru( II) complexes, [ Ru( bpy) L-2]( ClO4) 2 ( 1) and [ Ru( bpy)(2)L']( BF4) 2 ( 2), where bpy is 2,2'-bipyridine, L is diacetyl dihydrazone, and L' 1: 2 is the condensate of L and acetone, are synthesized. From X-ray crystal structures, both are found to contain distorted octahedral RuN62+ cores. NMR spectra show that the cations in 1 and 2 possess a C-2 axis in solution. They display the expected metal-to-ligand charge transfer ( (MLCT)-M-1) band in the 400 - 500 nm region. Complex 1 is nonemissive at room temperature in solution as well as at 80 K. In contrast, complex 2 gives rise to an appreciable emission upon excitation at 440 nm. The room-temperature emission is centered at 730 nm ( lambda(max)(em)) with a quantum yield ( em) of 0.002 and a lifetime ( tau(em)) of 42 ns in an air-equilibrated methanol - ethanol solution. At 80 K, Phi(em) = 0.007 and tau(em)= 178 ns, with a lambda(max)(em) of 690 nm, which is close to the 0 - 0 transition, indicating an (MLCT)-M-3 excited-state energy of 1.80 eV. The radiative rate constant ( 5 x 10(4) s(-1)) at room temperature and 80 K is almost temperature independent. From spectroelectrochemistry, it is found that bpy is easiest to reduce in 2 and that L is easiest in 1. The implications of this are that in 2 the lowest (MLCT)-M-3 state is localized on a bpy ligand and in 1 it is localized on L. Transient absorption results also support these assignments. As a consequence, even though 2 shows a fairly strong and long-lived emission from a Ru( II) -> bpy CT state, the Ru( II) -> L CT state in 1 shows no detectable emission even at 80 K.

43444546474849 2251 - 2300 of 252596
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