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  • 151.
    Lu, Yifei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Deep neural networks and fraud detection2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 152.
    Lundin, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Sequential Testing for Diffusion Processes2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 153.
    Lundin, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Time and speed dependency of swimming bursts in guppies2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 154.
    Magnusson, Hanna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    A Risk Surplus Model using Hawkes Point Processes2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 155.
    Makris, Georgios D.
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för neurovetenskap, Psykiatri, Akademiska sjukhuset.
    Reutfors, Johan
    Karolinska Inst, Karolinska Univ Hosp, Dept Med Solna, Clin Epidemiol Unit, Stockholm, Sweden..
    Larsson, Rolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik. Sweden..
    Isacsson, Goran
    Karolinska Inst, Ctr Mol Med, Dept Mol Med & Surg, Stockholm, Sweden.;Tiohundra AB, Dept Psychiat, Norrtalje, Sweden..
    Osby, Urban
    Karolinska Inst, Ctr Mol Med, Dept Mol Med & Surg, Stockholm, Sweden.;Tiohundra AB, Dept Psychiat, Norrtalje, Sweden..
    Ekbom, Anders
    Karolinska Inst, Karolinska Univ Hosp, Dept Med Solna, Clin Epidemiol Unit, Stockholm, Sweden..
    Ekselius, Lisa
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för neurovetenskap, Psykiatri, Akademiska sjukhuset.
    Papadopoulos, Fotios C.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för neurovetenskap, Psykiatri, Akademiska sjukhuset.
    Serotonergic medication enhances the association between suicide and sunshine2016Ingår i: Journal of Affective Disorders, ISSN 0165-0327, E-ISSN 1573-2517, Vol. 189, s. 276-281Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: An association between suicide and sunshine has been reported. The effect of sunshine on hormones and neurotransmitters such as serotonin has been hypothesized to exert a possible triggering effect on susceptible individuals. The aim of this study is to examine if there is an association between sunshine and suicide, adjusting for season, and if such an association differs between individuals on different antidepressants. Methods: By using Swedish Registers and the Swedish Meteorological and Hydrological Institute we obtained information, including forensic data on antidepressive medication for 12,448 suicides and data on monthly sunshine duration. The association between monthly suicide and sunshine hours was examined with Poisson regression analyses while stratifying for sex and age and controlling for time trend and season. These analyses were repeated in different groups of antidepressant treatment. Results: We found a significantly increased suicide risk with increasing sunshine in both men and women. This finding disappeared when we adjusted for season. Among both men and women treated with selective serotonin reuptake inhibitors (SSRIs) there was a positive association between sunshine and suicide even after adjustment for season and time trend for suicide. Pair comparisons showed that the sunshine-suicide association was stronger among men treated with SSRIs compared to other antidepressant medications or no medication at all. Limitations: Other meteorological factors were not controlled (i.e. temperature) for in the analyses. Conclusions: There is an enhanced association between sunshine and suicide among those with SSRI medication, even after adjusting for season. This may have interesting theoretical and clinical implications.

  • 156.
    Malik, Adam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Analysis of a bluffing game2014Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 157.
    Mann, Richard P.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Garnett, Roman
    The entropic basis of collective behaviour2015Ingår i: Journal of the Royal Society Interface, ISSN 1742-5689, E-ISSN 1742-5662, Vol. 12, nr 106, artikel-id 20150037Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We identify a unique viewpoint on the collective behaviour of intelligent agents. We first develop a highly general abstract model for the possible future lives these agents may encounter as a result of their decisions. In the context of these possibilities, we show that the causal entropic principle, whereby agents follow behavioural rules that maximize their entropy over all paths through the future, predicts many of the observed features of social interactions among both human and animal groups. Our results indicate that agents are often able to maximize their future path entropy by remaining cohesive as a group and that this cohesion leads to collectively intelligent outcomes that depend strongly on the distribution of the number of possible future paths. We derive social interaction rules that are consistent with maximum entropy group behaviour for both discrete and continuous decision spaces. Our analysis further predicts that social interactions are likely to be fundamentally based on Weber's law of response to proportional stimuli, supporting many studies that find a neurological basis for this stimulus-response mechanism and providing a novel basis for the common assumption of linearly additive 'social forces' in simulation studies of collective behaviour.

  • 158.
    Mann, Richard P.
    et al.
    Univ Leeds, Sch Math, Dept Stat, Leeds, W Yorkshire, England;Alan Turing Inst, London, England.
    Spaiser, Viktoria
    Univ Leeds, Sch Polit & Int Studies, Leeds 3, W Yorkshire, England.
    Bergström, Lina
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutet för bostads- och urbanforskning (IBF). Delft Univ Technol, Fac Architecture & Built Environm, OTB Res Built Environm, Delft, Netherlands.
    Sumpter, David J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Choice modelling with Gaussian processes in the social sciences: A case study of neighbourhood choice in Stockholm2018Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, nr 11, artikel-id e0206687Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a non parametric extension of the conditional logit model, using Gaussian process priors. The conditional logit model is used in quantitative social science for inferring interaction effects between personal features and choice characteristics from observations of individual multinomial decisions, such as where to live, which car to buy or which school to choose. The classic, parametric model presupposes a latent utility function that is a linear combination of choice characteristics and their interactions with personal features. This imposes strong and unrealistic constraints on the form of individuals' preferences. Extensions using non-linear basis functions derived from the original features can ameliorate this problem but at the cost of high model complexity and increased reliance on the user in model specification. In this paper we develop a non-parametric conditional logit model based on Gaussian process logit models. We demonstrate its application on housing choice data from over 50,000 moving households from the Stockholm area over a two year period to reveal complex homophilic patterns in income, ethnicity and parental status.

  • 159.
    Mann, Richard P.
    et al.
    University of Leeds - School of Mathematics.
    Spaiser, Viktoria
    School of Politics and International Studies, University of Leeds.
    Hedman, Lina
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutet för bostads- och urbanforskning (IBF).
    Sumpter, David J.T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Non-Linear Choice Modelling with Gaussian Processes: A Case Study of Neighbourhood Choice in Stockholm2016Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We present a non-parametric extension of the conditional logit model, using Gaussian pro- cess priors. The conditional logit model is used in quantitative social science for inferring interaction effects between personal features and choice characteristics from observations of individual multinomial decisions, such as where to live, which car to buy or which school to choose. The classic, parametric model presupposes a latent utility function that is a linear combination of choice characteristics and their interactions with personal features. This imposes strong and unrealistic constraints on the form of individuals’ preferences. Extensions using non-linear basis functions derived from the original features can ameliorate this problem but at the cost of high model complexity and increased reliance on the user in model specification. In this paper we develop a novel, non-parametric conditional logit model based on Gaussian process logit models. We demonstrate its application on housing choice data from over 50,000 moving households from the Stockholm area over a two year period to reveal complex homophilic patterns in income, ethnicity and parental status.

  • 160.
    Mansky, Maximilian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Mapping from physical events to words using neural networks: A case study on football2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 161.
    Markesjö, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Different Replicator Equations in Symmetric and Asymmetric Games2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 162.
    Markesjö, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Quantitative analysis of the decline int he ratio of Swedish limited companies with bank loans between 1998 and 20152018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 163.
    Marras, Stefano
    et al.
    CNR, IAMC, I-09170 Torregrande, Oristano, Italy..
    Noda, Takuji
    Kyoto Univ, Grad Sch Informat, Dept Social Informat, Kyoto 6068501, Japan..
    Steffensen, John F.
    Univ Copenhagen, Marine Biol Sect, DK-3000 Helsingor, Denmark..
    Svendsen, Morten B. S.
    Univ Copenhagen, Marine Biol Sect, DK-3000 Helsingor, Denmark..
    Krause, Jens
    Leibniz Inst Freshwater Ecol & Inland Fisheries, D-12587 Berlin, Germany.;Humboldt Univ, Fac Life Sci, D-10115 Berlin, Germany..
    Wilson, Alexander D. M.
    Carleton Univ, Dept Biol, Fish Ecol & Conservat Physiol Lab, Ottawa, ON K1S 5B6, Canada..
    Kurvers, Ralf H. J. M.
    Leibniz Inst Freshwater Ecol & Inland Fisheries, D-12587 Berlin, Germany..
    Herbert-Read, James
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Boswell, Kevin M.
    Florida Int Univ, Marine Sci Program, Dept Biol Sci, North Miami, FL 33181 USA..
    Domenici, Paolo
    CNR, IAMC, I-09170 Torregrande, Oristano, Italy..
    Not So Fast: Swimming Behavior of Sailfish during Predator-Prey Interactions using High-Speed Video and Accelerometry2015Ingår i: Integrative and Comparative Biology, ISSN 1540-7063, E-ISSN 1557-7023, Vol. 55, nr 4, s. 719-727Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synopsis Billfishes are considered among the fastest swimmers in the oceans. Despite early estimates of extremely high speeds, more recent work showed that these predators (e.g., blue marlin) spend most of their time swimming slowly, rarely exceeding 2 m s(-1). Predator-prey interactions provide a context within which one may expect maximal speeds both by predators and prey. Beyond speed, however, an important component determining the outcome of predator-prey encounters is unsteady swimming (i.e., turning and accelerating). Although large predators are faster than their small prey, the latter show higher performance in unsteady swimming. To contrast the evading behaviors of their highly maneuverable prey, sailfish and other large aquatic predators possess morphological adaptations, such as elongated bills, which can be moved more rapidly than the whole body itself, facilitating capture of the prey. Therefore, it is an open question whether such supposedly very fast swimmers do use high-speed bursts when feeding on evasive prey, in addition to using their bill for slashing prey. Here, we measured the swimming behavior of sailfish by using high-frequency accelerometry and high-speed video observations during predator-prey interactions. These measurements allowed analyses of tail beat frequencies to estimate swimming speeds. Our results suggest that sailfish burst at speeds of about 7 m s(-1) and do not exceed swimming speeds of 10 m s(-1) during predator-prey interactions. These speeds are much lower than previous estimates. In addition, the oscillations of the bill during swimming with, and without, extension of the dorsal fin (i.e., the sail) were measured. We suggest that extension of the dorsal fin may allow sailfish to improve the control of the bill and minimize its yaw, hence preventing disturbance of the prey. Therefore, sailfish, like other large predators, may rely mainly on accuracy of movement and the use of the extensions of their bodies, rather than resorting to top speeds when hunting evasive prey.

  • 164.
    McCormick, Stephen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    A note on mass-minimising extensions2015Ingår i: General Relativity and Gravitation, ISSN 0001-7701, E-ISSN 1572-9532Artikel i tidskrift (Refereegranskat)
  • 165.
    McCormick, Stephen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    First Law of Black Hole Mechanics as a Condition for Stationarity2014Ingår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918Artikel i tidskrift (Refereegranskat)
  • 166.
    McCormick, Stephen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Gluing Bartnik extensions, continuity of the Bartnik mass, and the equivalence of definitions2020Ingår i: Pacific Journal of Mathematics, ISSN 0030-8730, E-ISSN 1945-5844, Vol. 304, nr 2, s. 629-653Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the context of the Bartnik mass, there are two fundamentally different notions of an extension of some compact Riemannian manifold (Omega, gamma) with boundary. In one case, the extension is taken to be a manifold without boundary in which (Omega, gamma) embeds isometrically, and in the other case the extension is taken to be a manifold with boundary where the boundary data is determined by a partial derivative Omega. We give a type of convexity condition under which we can say both of these types of extensions indeed yield the same value for the Bartnik mass. Under the same hypotheses we prove that the Bartnik mass varies continuously with respect to the boundary data. This also provides a method to use estimates for the Bartnik mass of constant mean curvature (CMC) Bartnik data, to obtain estimates for the Bartnik mass of non-CMC Bartnik data. The key idea for these results is a method for gluing Bartnik extensions of given Bartnik data to other nearby Bartnik data.

  • 167.
    McCormick, Stephen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    The asymptotically flat scalar-flat Yamabe problem with boundary2017Ingår i: Journal of Geometric Analysis, ISSN 1050-6926, E-ISSN 1559-002XArtikel i tidskrift (Refereegranskat)
  • 168.
    McCormick, Stephen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    The phase space for the Einstein-Yang-Mills equations and the first law of black hole thermodynamics2014Ingår i: Advances in Theoretical and Mathematical Physics, ISSN 1095-0761, E-ISSN 1095-0753Artikel i tidskrift (Refereegranskat)
  • 169.
    McCormick, Stephen
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Miao, Pengzi
    On a Penrose-like inequality in dimensions less than eight2017Ingår i: International mathematics research notices, ISSN 1073-7928, E-ISSN 1687-0247Artikel i tidskrift (Refereegranskat)
  • 170.
    Mitrea, Irina
    et al.
    Temple Univ, Philadelphia, USA.
    Ott, Katharine
    Bates Coll, Lewiston, USA.
    Tucker, Warwick
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Invertibility Properties of Singular Integral Operators Associated with the Lam, and Stokes Systems on Infinite Sectors in Two Dimensions2017Ingår i: Integral equations and operator theory, ISSN 0378-620X, E-ISSN 1420-8989, Vol. 89, nr 2, s. 151-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we establish sharp invertibility results for the elastostatics and hydrostatics single and double layer potential type operators acting on , , whenever is an infinite sector in . This analysis is relevant to the layer potential treatment of a variety of boundary value problems for the Lam, system of elastostatics and the Stokes system of hydrostatics in the class of curvilinear polygons in two dimensions, such as the Dirichlet, the Neumann, and the Regularity problems. Mellin transform techniques are used to identify the critical integrability indices for which invertibility of these layer potentials fails. Computer-aided proofs are produced to further study the monotonicity properties of these indices relative to parameters determined by the aperture of the sector and the differential operator in question.

  • 171.
    Mohammad, Asadzadeh
    et al.
    Chalmers University of Technology and the University of Gothenburg.
    Bartoszek, Krzysztof
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Convergence of Finite Volume Scheme for a Three-Dimensional Poisson Equation2014Ingår i: Journal of Mathematical Sciences, Vol. 202, nr 2, s. 130-153Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We construct and analyze a finite volume scheme for numerical solution of a three-dimensional Poisson equation. We derive optimal convergence rates in the discrete H1 norm and sub-optimal convergence in the maximum norm, where we use the maximal available regularity of the exact solution and minimal smoothness requirement on the source term. The theoretical results are justified through implementing some canonical examples in 3D.

  • 172.
    Munkhammar, Joakim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Mattsson, Lars
    Nordita, Stockholms University.
    Rydén, Jesper
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Polynomial probability distribution estimation using the method of moments2017Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, nr 4, s. 1-14, artikel-id e0174573Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We suggest a procedure for estimating Nth degree polynomial approximations to unknown (or known) probability density functions (PDFs) based on N statistical moments from each distribution. The procedure is based on the method of moments and is setup algorithmically to aid applicability and to ensure rigor in use. In order to show applicability, polynomial PDF approximations are obtained for the distribution families Normal, Log-Normal, Weibull as well as for a bimodal Weibull distribution and a data set of anonymized household electricity use. The results are compared with results for traditional PDF series expansion methods of Gram–Charlier type. It is concluded that this procedure is a comparatively simple procedure that could be used when traditional distribution families are not applicable or when polynomial expansions of probability distributions might be considered useful approximations. In particular this approach is practical for calculating convolutions of distributions, since such operations become integrals of polynomial expressions. Finally, in order to show an advanced applicability of the method, it is shown to be useful for approximating solutions to the Smoluchowski equation.

  • 173.
    Munkhammar, Joakim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Widén, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Rydén, Jesper
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    On a probability distribution model combining household power consumption, electric vehicle home-charging and photovoltaic power production2015Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 142, s. 135-143Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we develop a probability distribution model combining household power consumption, electric vehicle (EV) home-charging and photovoltaic (PV) power production. The model is set up using a convolution approach to merge three separate existing probability distribution models for household electricity use, EV home-charging and PV power production. This model is investigated on two system levels: household level and aggregate level of multiple households. Results for the household level show the power consumption/production mismatch as probability distributions for different time bins. This is further investigated with different levels of PV power production. The resulting yearly distribution of the aggregate scenario of multiple uncorrelated households with EV charging and PV power production is shown to not be normally distributed due to the mismatch of PV power production and household power consumption on a diurnal and annual basis.

  • 174.
    Nannyonga, Betty
    et al.
    Makerere Univ, Coll Nat Sci, Sch Phys Sci, Dept Math, Kampala, Uganda..
    Sumpter, David J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Modelling optimal allocation of resources in the context of an incurable disease2017Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, nr 3, artikel-id e0172401Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nodding syndrome has affected and led to the deaths of children between the ages of 5 and 15 in Northern Uganda since 2009. There is no reliable explanation of the disease, and currently the only treatment is through a nutritional programme of vitamins, combined with medication to prevent symptoms. In the absence of a proper medical treatment, we develop a dynamic compartmental model to plan the management of the syndrome and to curb its effects. We use incidence data from 2012 and 2013 from Pader, Lamwo and Kitgum regions of Uganda to parameterize the model. The model is then used to look at how to best plan the nutritional programme in terms of first getting children on to the programme through outreach, and then making sure they remain on the programme, through follow-up. For the current outbreak of nodding disease, we estimate that about half of available resources should be put into outreach. We show how to optimize the balance between outreach and follow-up in this particular example, and provide a general methodology for allocating resources in similar situations. Given the uncertainty of parameter estimates in such situations, we perform a robustness analysis to identify the best investment strategy. Our analysis offers a way of using available data to determine the best investment strategy of controlling nodding syndrome.

  • 175.
    Nedelcu, Robert
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för kirurgiska vetenskaper, Käkkirurgi.
    Olsson, Pontus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Nyström, Ingela
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion. Uppsala Univ, Dept Informat Technol, Ctr Image Anal, Box 337, S-75105 Uppsala, Sweden..
    Rydén, Jesper
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Thor, Andreas
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för kirurgiska vetenskaper, Käkkirurgi.
    Accuracy and precision of 3 intraoral scanners and accuracy of conventional impressions: A novel in vivo analysis method2018Ingår i: Journal of Dentistry, ISSN 0300-5712, E-ISSN 1879-176X, Vol. 69, s. 110-118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective: To evaluate a novel methodology using industrial scanners as a reference, and assess in vivo accuracy of 3 intraoral scanners (IOS) and conventional impressions. Further, to evaluate IOS precision in vivo.

    Methods: Four reference-bodies were bonded to the buccal surfaces of upper premolars and incisors in five subjects. After three reference-scans, ATOS Core 80 (ATOS), subjects were scanned three times with three IOS systems: 3M True Definition (3M), CEREC Omnicam (OMNI) and Trios 3 (TRIOS). One conventional impression (IMPR) was taken, 3M Impregum Penta Soft, and poured models were digitized with laboratory scanner 3shape D1000 (D1000). Best-fit alignment of reference-bodies and 3D Compare Analysis was performed. Precision of ATOS and D1000 was assessed for quantitative evaluation and comparison. Accuracy of IOS and IMPR were analyzed using ATOS as reference. Precision of IOS was evaluated through intra-system comparison.

    Results: Precision of ATOS reference scanner (mean 0.6 mu m) and D1000 (mean 0.5 mu m) was high. Pairwise multiple comparisons of reference-bodies located in different tooth positions displayed a statistically significant difference of accuracy between two scanner-groups: 3M and TRIOS, over OMNI (p value range 0.0001 to 0.0006). IMPR did not show any statistically significant difference to IOS. However, deviations of IOS and IMPR were within a similar magnitude. No statistical difference was found for IOS precision.

    Conclusion: The methodology can be used for assessing accuracy of IOS and IMPR in vivo in up to five units bilaterally from midline. 3M and TRIOS had a higher accuracy than OMNI. IMPR overlapped both groups. Clinical significance: Intraoral scanners can be used as a replacement for conventional impressions when restoring up to ten units without extended edentulous spans.

  • 176.
    Netsvetov, Maksym
    et al.
    Natl Acad Sci Ukraine, Inst Evolutionary Ecol, 37 Lebedev St, UA-03143 Kiev, Ukraine.
    Prokopuk, Yulia
    Natl Acad Sci Ukraine, Inst Evolutionary Ecol, 37 Lebedev St, UA-03143 Kiev, Ukraine.
    Didukh, Yakiv
    Natl Acad Sci Ukraine, MG Kholodny Inst Bot, 2 Tereshchenkivska St, UA-01601 Kiev, Ukraine.
    Romenskyy, Maksym
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Climatic sensitivity of Quercus robur L. in floodplain near Kyiv under river regulation2018Ingår i: Dendrobiology, ISSN 1641-1307, E-ISSN 2083-8387, Vol. 79, s. 20-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climate change has a significant impact on natural ecosystems, particularly on floodplain forests that are among the most transformed ecosystems in the world. The climate sensitivity of dominant species is likely to play a key role in determining the susceptibility of flooded forests to climate changes. Here, we use dendrochronological approaches and local climate records from 1880 to 2015 to assess the response in pedunculate oak (Quercus robur L.) trees growing in a floodplain of the Dnipro River near Kyiv to climatic variables. Correlation analysis reveals the strongest positive association of the Q. robur tree-ring width chronology with May-June precipitation, May-June temperature, and May self-calibrating Palmers drought severity indices (scPDSI). The moving-window correlation analysis points to positive association with the scPDSI after the 1950s, when local river regulation was implemented. The positive correlation with current March precipitation is the least expected change in the oak growth-to-climate relationship that occurred in the aftermath of human alterations in the local river and regional climate changes. This study discusses the probable ecological consequences and ecophysiological mechanisms of observable climate-to-growth relationships and their temporal stability.

  • 177. Nicolis, Gregoire
    et al.
    Nicolis, Stamatios C.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Probabilistic Network Approach to Decision-Making2015Ingår i: Open systems & information dynamics, ISSN 1230-1612, E-ISSN 1573-1324, Vol. 22, nr 2, artikel-id 1550012Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A probabilistic approach to decision-making is developed in which the states of the underlying stochastic process, assumed to be of the Markov type, represent the competing options. The principal parameters determining the dominance of a particular option versus the others are identified and the transduction of information associated to the transitions between states is quantified using a set of entropy-like quantities.

  • 178.
    Norrman, Michaela
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Hahlin, Lina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Hur tänker Instagram?: En statistisk analys av två Instagramflöden2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 179.
    Olauson, Jon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bergkvist, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Rydén, Jesper
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Simulating intra-hourly wind power fluctuations on a power system level2017Ingår i: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 20, nr 6, s. 973-985Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In wind integration studies, sub-hourly, load synchronous wind data are often preferable. These datasets can be generatedby a hybrid approach, combining hourly measurements or output from meteorological models with a stochastic simulationof the high-frequency fluctuations. This paper presents a method for simulating aggregated intra-hourly wind power fluc-tuations for a power system, taking into account the time-varying volatility seen in measurements. Some key elements inthe modelling were transformations to stationarity, the use of frequency domain techniques including a search for appropri-ate phase angles and an adjustment of the resulting time series in order to get correct hourly means. Generation data fromDenmark and Germany with 5 and 15 min temporal resolution were used for training models. It is shown that the distribu-tion and non-stationarity of simulated deviations from hourly means closely follow those of measurements. Power spectraldensities and step change distributions agree well. Of particular importance is that the results are good also when the train-ing and objective power systems are not the same. The computational cost is low in comparison with other approaches forgenerating high-frequency data.

  • 180.
    Olauson, Jon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Edström, Per
    Sweco.
    Rydén, Jesper
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Wind turbine performance decline in Sweden2017Ingår i: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 20, nr 12, s. 2049-2053Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that Swedish wind turbines constructed before 2007 lose 0.15 capacity factor percentage points per year, corresponding to a lifetime energy loss of 6%. A gradual increase of downtime accounts for around one third of the deterioration and worsened efficiency for the remaining. Although the performance loss in Sweden is considerably smaller than previously reported in the UK, it is statistically significant and calls for a revision of the industry practice for wind energy calculations. The study is based on two partly overlapping datasets, comprising 1,100 monthly and 1,300 hourly time series spanning 5–25 years each.

  • 181.
    Papakonstantinou, Konstantinos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Pricing of Barrier Options Using a Two-Volatility Model2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 182.
    Persson, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Cirkulära data och dess statistiska tillämpningar2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 183.
    Persson, Erik K
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    What is the link between temperature, carbon dioxide and methane? A multivariate Granger causality analysis based on ice core data from Dome C in Antarctica2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 184.
    Pihlström, Ralf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    On some Spectral Properties of Stochastic Similarity Matrices for Data Clustering2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 185.
    Prepic, Asmir
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    An Application of A Bayesian Extreme Value Mixture Model to Reinsurance Excess-of-Loss Pricing and Extreme Value Threshold Selection2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 186.
    Précenth, Rasmus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Word Embeddings and Gender Stereotypes in Swedish and English2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 187.
    Ranganathan, Shyam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Non-linear dynamic modelling for panel data in the social sciences2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Non-linearities and dynamic interactions between state variables are characteristic of complex social systems and processes. In this thesis, we present a new methodology to model these non-linearities and interactions from the large panel datasets available for some of these systems. We build macro-level statistical models that can verify theoretical predictions, and use polynomial basis functions so that each term in the model represents a specific mechanism. This bridges the existing gap between macro-level theories supported by statistical models and micro-level mechanistic models supported by behavioural evidence. We apply this methodology to two important problems in the social sciences, the demographic transition and the transition to democracy.

    The demographic transition is an important problem for economists and development scientists. Research has shown that economic growth reduces mortality and fertility rates, which reduction in turn results in faster economic growth. We build a non-linear dynamic model and show how this data-driven model extends existing mechanistic models. We also show policy applications for our models, especially in setting development targets for the Millennium Development Goals or the Sustainable Development Goals.

    The transition to democracy is an important problem for political scientists and sociologists. Research has shown that economic growth and overall human development transforms socio-cultural values and drives political institutions towards democracy. We model the interactions between the state variables and find that changes in institutional freedoms precedes changes in socio-cultural values. We show applications of our models in studying development traps.

    This thesis comprises the comprehensive summary and seven papers. Papers I and II describe two similar but complementary methodologies to build non-linear dynamic models from panel datasets. Papers III and IV deal with the demographic transition and policy applications. Papers V and VI describe the transition to democracy and applications. Paper VII describes an application to sustainable development.

    Delarbeten
    1. Bayesian Dynamical Systems Modelling in the Social Sciences
    Öppna denna publikation i ny flik eller fönster >>Bayesian Dynamical Systems Modelling in the Social Sciences
    2014 (Engelska)Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, nr 1, s. e86468-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Data arising from social systems is often highly complex, involving non-linear relationships between the macro-level variables that characterize these systems. We present a method for analyzing this type of longitudinal or panel data using differential equations. We identify the best non-linear functions that capture interactions between variables, employing Bayes factor to decide how many interaction terms should be included in the model. This method punishes overly complicated models and identifies models with the most explanatory power. We illustrate our approach on the classic example of relating democracy and economic growth, identifying non-linear relationships between these two variables. We show how multiple variables and variable lags can be accounted for and provide a toolbox in R to implement our approach.

    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-219971 (URN)10.1371/journal.pone.0086468 (DOI)000330240500135 ()
    Tillgänglig från: 2014-03-12 Skapad: 2014-03-09 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
    2. Parsimonious dynamical systems using the LASSO and the bootstrap - a summary
    Öppna denna publikation i ny flik eller fönster >>Parsimonious dynamical systems using the LASSO and the bootstrap - a summary
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nationell ämneskategori
    Matematik
    Forskningsämne
    Statistik
    Identifikatorer
    urn:nbn:se:uu:diva-261623 (URN)
    Tillgänglig från: 2015-09-02 Skapad: 2015-09-02 Senast uppdaterad: 2016-01-27
    3. The Demographic Transition and Economic Growth: Implications for Development Policy
    Öppna denna publikation i ny flik eller fönster >>The Demographic Transition and Economic Growth: Implications for Development Policy
    (Engelska)Ingår i: Palgrave CommunicationsArtikel i tidskrift (Refereegranskat) Accepted
    Nationell ämneskategori
    Nationalekonomi
    Identifikatorer
    urn:nbn:se:uu:diva-261286 (URN)
    Tillgänglig från: 2015-09-01 Skapad: 2015-09-01 Senast uppdaterad: 2016-01-27
    4. Setting development goals using stochastic dynamical system models
    Öppna denna publikation i ny flik eller fönster >>Setting development goals using stochastic dynamical system models
    (Engelska)Ingår i: World Development, ISSN 0305-750X, E-ISSN 1873-5991Artikel i tidskrift (Refereegranskat) Submitted
    Nationell ämneskategori
    Ekonomi och näringsliv
    Identifikatorer
    urn:nbn:se:uu:diva-261628 (URN)
    Tillgänglig från: 2015-09-02 Skapad: 2015-09-02 Senast uppdaterad: 2017-12-04
    5. The Dynamics of Democracy, Development and Cultural Values
    Öppna denna publikation i ny flik eller fönster >>The Dynamics of Democracy, Development and Cultural Values
    2014 (Engelska)Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, nr 6, s. e97856-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Over the past decades many countries have experienced rapid changes in their economies, their democratic institutions and the values of their citizens. Comprehensive data measuring these changes across very different countries has recently become openly available. Between country similarities suggest common underlying dynamics in how countries develop in terms of economy, democracy and cultural values. We apply a novel Bayesian dynamical systems approach to identify the model which best captures the complex, mainly non-linear dynamics that underlie these changes. We show that the level of Human Development Index (HDI) in a country drives first democracy and then higher emancipation of citizens. This change occurs once the countries pass a certain threshold in HDI. The data also suggests that there is a limit to the growth of wealth, set by higher emancipation. Having reached a high level of democracy and emancipation, societies tend towards equilibrium that does not support further economic growth. Our findings give strong empirical evidence against a popular political science theory, known as the Human Development Sequence. Contrary to this theory, we find that implementation of human-rights and democratisation precede increases in emancipative values.

    Nationell ämneskategori
    Matematik
    Identifikatorer
    urn:nbn:se:uu:diva-234216 (URN)10.1371/journal.pone.0097856 (DOI)000341869000014 ()
    Tillgänglig från: 2014-10-15 Skapad: 2014-10-15 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
    6. Understanding Democracy and Development Traps Using a Data-Driven Approach
    Öppna denna publikation i ny flik eller fönster >>Understanding Democracy and Development Traps Using a Data-Driven Approach
    2015 (Engelska)Ingår i: Big Data, ISSN 2167-6461, Vol. 3, nr 1, s. 22-33Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Methods from machine learning and data science are becoming increasingly important in the social sciences, providing powerful new ways of identifying statistical relationships in large data sets. However, these relationships do not necessarily offer an understanding of the processes underlying the data. To address this problem, we have developed a method for fitting nonlinear dynamical systems models to data related to social change. Here, we use this method to investigate how countries become trapped at low levels of socioeconomic development. We identify two types of traps. The first is a democracy trap, where countries with low levels of economic growth and/or citizen education fail to develop democracy. The second trap is in terms of cultural values, where countries with low levels of democracy and/or life expectancy fail to develop emancipative values. We show that many key developing countries, including India and Egypt, lie near the border of these development traps, and we investigate the time taken for these nations to transition toward higher democracy and socioeconomic well-being.

    Nationell ämneskategori
    Data- och informationsvetenskap Statsvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-261283 (URN)10.1089/big.2014.0066 (DOI)000355563100003 ()
    Tillgänglig från: 2015-09-01 Skapad: 2015-09-01 Senast uppdaterad: 2018-01-11Bibliografiskt granskad
    7. Analysing Mechanisms for Meeting Global Emissions Target - A Dynamical Systems Approach
    Öppna denna publikation i ny flik eller fönster >>Analysing Mechanisms for Meeting Global Emissions Target - A Dynamical Systems Approach
    2014 (Engelska)Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Global emissions beyond 44 gigatonnes of carbondioxide equivalent (GtCO2e) in 2020 can potentially lead the world to an irreversible climate change. Employing a novel dynamical system modeling approach, we predict that in a business-asusual scenario, it will reach 61 GtCO2e by 2020. Testing estimated parameters, we nd that limiting the burden of emission reduction to the top 25 global emitters, does not increase their encumbrance. In absence of emission cuts, technology and preferences for environmental quality have to improve by at least 2.6 percent and 3.5 percent if the emission target has to be met by 2020.

    Förlag
    s. 40
    Serie
    Working paper / Department of Economics, Uppsala University (Online), ISSN 1653-6975 ; 2014:10
    Nationell ämneskategori
    Nationalekonomi
    Forskningsämne
    Nationalekonomi
    Identifikatorer
    urn:nbn:se:uu:diva-235543 (URN)
    Tillgänglig från: 2014-11-05 Skapad: 2014-11-05 Senast uppdaterad: 2016-01-27Bibliografiskt granskad
  • 188.
    Ranganathan, Shyam
    et al.
    Virginia Polytech Inst & State Univ, Dept Stat, Blacksburg, VA 24061 USA.
    Nicolis, Stamatios
    Univ Libre Bruxelles, Fac Sci, Serv Chim Phys & Biol Theor, Campus Plaine,CP 231, Brussels, Belgium.
    Bali Swain, Ranjula
    Stockholm Sch Econ, Mistra Ctr Sustainable Markets, Stockholm, Sweden.; Sodertorn Univ, Stockholm, Sweden.
    Sumpter, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Setting development goals using stochastic, dynamical system models2017Ingår i: Plos One, Vol. 12, nr 2, artikel-id e0171560Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Millennium Development Goals (MDG) programme was an ambitious attempt to encourage a globalised solution to important but often-overlooked development problems. The programme led to wide-ranging development but it has also been criticised for unrealistic and arbitrary targets. In this paper, we show how country-specific development targets can be set using stochastic, dynamical system models built from historical data. In particular, we show that the MDG target of two-thirds reduction of child mortality from 1990 levels was infeasible for most countries, especially in sub-Saharan Africa. At the same time, the MDG targets were not ambitious enough for fast-developing countries such as Brazil and China. We suggest that model-based setting of country-specific targets is essential for the success of global development programmes such as the Sustainable Development Goals (SDG). This approach should provide clear, quantifiable targets for policymakers.

  • 189.
    Rindstedt, Aron
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Programming aspects in a combinatorial sparse linear solver2014Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 190. Romanczuk, P.
    et al.
    Romensky, Maxym
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Scholz, D.
    Lobaskin, V.
    Schimansky-Geier, L.
    Motion of Euglena gracilis: Active fluctuations and velocity distribution2015Ingår i: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 224, nr 7, s. 1215-1229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the velocity distribution of unicellular swimming algae Euglena gracilis using optical microscopy and active Brownian particle theory. To characterize a peculiar feature of the experimentally observed distribution at small velocities we use the concept of active fluctuations, which was recently proposed for the description of stochastically self-propelled particles [Romanczuk, P. and Schimansky-Geier, L., Phys. Rev. Lett. 106, 230601 (2011)]. In this concept, the fluctuating forces arise due to internal random performance of the propulsive motor. The fluctuating forces are directed in parallel to the heading direction, in which the propulsion acts. In the theory, we introduce the active motion via the depot model [Schweitzer, et al., Phys. Rev. Lett. 80(23), 5044 (1998)]. We demonstrate that the theoretical predictions based on the depot model with active fluctuations are consistent with the experimentally observed velocity distributions. In addition to the model with additive active noise, we obtain theoretical results for a constant propulsion with multiplicative noise.

  • 191.
    Romensky, Maksym
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Scholz, Dimitri
    Lobaskin, Vladimir
    Hysteretic dynamics of active particles in a periodic orienting field2015Ingår i: Journal of the Royal Society Interface, ISSN 1742-5689, E-ISSN 1742-5662, Vol. 12, nr 108, artikel-id 20150015Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Active motion of living organisms and artificial self-propelling particles has been an area of intense research at the interface of biology, chemistry and physics. Significant progress in understanding these phenomena has been related to the observation that dynamic self-organization in active systems has much in common with ordering in equilibrium condensed matter such as spontaneous magnetization in ferromagnets. The velocities of active particles may behave similar to magnetic dipoles and develop global alignment, although interactions between the individuals might be completely different. In this work, we show that the dynamics of active particles in external fields can also be described in a way that resembles equilibrium condensed matter. It follows simple general laws, which are independent of the microscopic details of the system. The dynamics is revealed through hysteresis of the mean velocity of active particles subjected to a periodic orienting field. The hysteresis is measured in computer simulations and experiments on unicellular organisms. We find that the ability of the particles to follow the field scales with the ratio of the field variation period to the particles' orientational relaxation time, which, in turn, is related to the particle self-propulsion power and the energy dissipation rate. The collective behaviour of the particles due to aligning interactions manifests itself at low frequencies via increased persistence of the swarm motion when compared with motion of an individual. By contrast, at high field frequencies, the active group fails to develop the alignment and tends to behave like a set of independent individuals even in the presence of interactions. We also report on asymptotic laws for the hysteretic dynamics of active particles, which resemble those in magnetic systems. The generality of the assumptions in the underlying model suggests that the observed laws might apply to a variety of dynamic phenomena from the motion of synthetic active particles to crowd or opinion dynamics.

  • 192.
    Romensky, Maxym
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Lobaskin, V.
    Orientational hysteresis in swarms of active particles in external field2015Ingår i: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 224, nr 7, s. 1359-1376Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Structure and ordering in swarms of active particles have much in common with condensed matter systems like magnets or liquid crystals. A number of important characteristics of such materials can be obtained via dynamic tests such as hysteresis. In this work, we show that dynamic hysteresis can be observed also in swarms of active particles and possesses similar properties to the counterparts in magnetic materials. To study the swarm dynamics, we use computer simulations of the active Brownian particle model with dissipative interactions. The swarm is confined to a narrow linear channel and the one-dimensional polar order parameter is measured. In an oscillating external field, the order parameter demonstrates dynamic hysteresis with the shape of the loop and its area varying with the amplitude and frequency of the applied field, swarm density and the noise intensity. We measure the scaling exponents for the hysteresis loop area, which can be associated with the controllability of the swarm. Although the exponents are non-universal and depend on the system's parameters, their limiting values can be predicted using a generic model of dynamic hysteresis. We also discuss similarities and differences between the swarm ordering dynamics and two-dimensional magnets.

  • 193.
    Romenskyy, Maksym
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Herbert-Read, James E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Ward, Ashley J. W.
    Univ Sydney, Sch Biol Sci, Sydney, NSW, Australia..
    Sumpter, David J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Body size affects the strength of social interactions and spatial organization of a schooling fish (Pseudomugil signifer)2017Ingår i: Royal Society Open Science, E-ISSN 2054-5703, Vol. 4, nr 4, artikel-id 161056Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    While a rich variety of self-propelled particle models propose to explain the collective motion of fish and other animals, rigorous statistical comparison between models and data remains a challenge. Plausible models should be flexible enough to capture changes in the collective behaviour of animal groups at their different developmental stages and group sizes. Here, we analyse the statistical properties of schooling fish (Pseudomugil signifer) through a combination of experiments and simulations. We make novel use of a Boltzmann inversion method, usually applied in molecular dynamics, to identify the effective potential of the mean force of fish interactions. Specifically, we show that larger fish have a larger repulsion zone, but stronger attraction, resulting in greater alignment in their collective motion. We model the collective dynamics of schools using a self-propelled particle model, modified to include varying particle speed and a local repulsion rule. We demonstrate that the statistical properties of the fish schools are reproduced by our model, thereby capturing a number of features of the behaviour and development of schooling fish.

  • 194.
    Romenskyy, Maksym
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik. Imperial Coll London, Dept Life Sci, London SW7 2AZ, England.
    Spaiser, Viktoria
    Univ Leeds, Sch Polit & Int Studies, Leeds LS2 9JT, W Yorkshire, England.
    Ihle, Thomas
    Ernst Moritz Arndt Univ Greifswald, Inst Phys, Felix Hausdorff Str 6, D-17489 Greifswald, Germany.
    Lobaskin, Vladimir
    Univ Coll Dublin, Sch Phys, Dublin 4, Ireland.
    Polarized Ukraine 2014: opinion and territorial split demonstrated with the bounded confidence by model, parametrized XY Twitter data2018Ingår i: Royal Society Open Science, E-ISSN 2054-5703, Vol. 5, nr 8, artikel-id 171935Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multiple countries have recently experienced extreme political polarization, which, in some cases, led to escalation of hate crime, violence and political instability. Besides the much discussed presidential elections in the USA and France, Britain's Brexit vote and Turkish constitutional referendum showed signs of extreme polarization. Among the countries affected, Ukraine faced some of the gravest consequences. In an attempt to understand the mechanisms of these phenomena, we here combine social media analysis with agent-based modelling of opinion dynamics, targeting Ukraine's crisis of 2014. We use Twitter data to quantify changes in the opinion divide and parametrize an extended bounded confidence XY model, which provides a spatio-temporal description of the polarization dynamics. We demonstrate that the level of emotional intensity is a major driving force for polarization that can lead to a spontaneous onset of collective behaviour at a certain degree of homophily and conformity. We find that the critical level of emotional intensity corresponds to a polarization transition, marked by a sudden increase in the degree of involvement and in the opinion bimodality.

  • 195.
    Rundin, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Decentraliserat eller centraliseratpassningsnätverk: en studie om relationen mellan passningsnätverk och resultat i fotbollsmatcher2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 196.
    Ryden, Jesper
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    A Statistical Analysis of Trends for Warm and Cold Spells in Uppsala by Means of Counts2015Ingår i: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 97, nr 3, s. 431-436Artikel i tidskrift (Refereegranskat)