Publikationer från Stockholms universitet
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Vilken betydelse har lärares kön och ålder för gymnasielevers betyg?
No full textI den här uppsatsen undersöks vilken betydelse lärares kön och ålder har för gymnasieelevers betyg. Uppsatsen behandlar följande två frågeställningar: • Har lärares kön betydelse för vilka betyg gymnasieelever får? • Har lärares ålder betydelse för vilka betyg gymnasieelever får? För att besvara dessa frågor insamlades betygskataloger från kommunala gymnasieskolor i Stockholms kommun. En betygskatalog är en lista över eleverna i en viss undervisningsgrupp där det framgår vilket betyg eleverna har fått på kursen och vilken lärare som har satt betyget. Resultaten visade att lärarnas kön inte hade någon nämnvärd betydelse för elevernas betyg. I den analys som kontrollerade för elevers kön och etnicitet samt vilken skola och vilket gym-nasieprogram eleven går på fanns ingen statistiskt signifikant skillnad mellan vilka betyg kvinnliga och manliga lärare satte. Resultatet är förenligt med tidigare svensk forskning. Detta tyder på att lärares kön inte har någon större betydelse för elevers betyg. Resultaten visade att lärarnas ålder hade en viss betydelse för elevernas betyg. Framför allt fanns en skillnad mellan vilka betyg unga lärare (23-30 år) och övriga lärare satte. De unga lärarna satte signifikant högre betyg. Om unga lärare verkligen sätter högre betyg är det ut-ifrån tidigare forskning rimligt att anta att detta beror på att de är mer generösa med betygen. Det är mindre rimligt att utifrån tidigare forskning anta att det beror på att unga lärare har en mer positiv effekt på elevers skolprestationer jämfört med övriga lärare. Resultatet ska dock tolkas med försiktighet. För att med större säkerhet kunna uttala sig krävs studier som under-söker betyg i relation till elevers resultat på nationella prov. I en sådan studie kan man under-söka om unga lärare sätter högre betyg i relation till vad eleverna presterat på de nationella proven.
Konsulternas mångfald : Om organisationskonsulters mångfaldsbegrepp
No full textSyftet med uppsatsen är att analysera mångfaldskonsulters syn på mångfald och mångfaldsarbete utifrån nyinstitutionell teori och sociologen Lauren B. Edelmans begrepp om lagens ledarskapifiering. Uppsatsens analysdel är baserad på intervjuer med 14 mångfaldskonsulter. Analysen visar att mångfaldskonsulter använder ett "brett" begrepp om mångfald, som inkluderar både diskrimineringslagens kategorier och därtill ickerättsliga dimensioner som kompetens, färdigheter, arbetssätt och klädstil. Det breda mångfaldsbegreppet tillsammans med en betoning på organisationsnytta snarare än rättvisemotiv tolkas i denna uppsats som en ledarskapifiering av lagen – en tolkningsprocess varigenom diskrimineringslagen och dess rättviseprinciper retoriskt omgestaltas för att bättre överensstämma med arbetsgivarintressen. Ledarskapifieringen gör därtill mångfaldsbegreppet vagt, något som inte behöver försvåra utan tvärtom kan underlätta konsulternas arbete: en löst förpackad mångfaldsidé utvidgar tolkningsutrymmet för vad mångfaldsarbete kan vara, vilket i sin tur kan skapa en större marknad för mångfaldskonsulternas tjänster
Emergent Weyl Fermions and the Metal to Weyl-Semimetal phase transition in WTe2,via broadband High Resolution NMR
No full textWeyl Fermions (WFs) in the type-II Weyl Semimetal (WSM) WTe2 are difficult to resolve experimentally because the Weyl bands disperse in an extremely narrow region of the (E-k) space. Here, by using DFT-assisted high-resolution 125Te solid-state NMR (ssNMR) in the temperature range 50K - 700K, we succeeded in detecting low energy WF excitations and monitor their evolution with temperature. Remarkably, WFs appear to emerge at T∼120K; at lower temperatures WTe2 behaves as a metal. This intriguing metal-to-WSM phase transition is shown to be induced by the rapid raise of the Fermi level with temperature, crossing solely the electron and hole pockets in the low-T metallic phase, while crossing the Weyl bands near the nodal points - a prerequisite for the emergence of WFs - only for T>120K
Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings: Part I
No full textEvaluation of climate model simulations is a crucial task in climate research. In a work consisting of three parts, we propose a new statistical framework for evaluation of simulated responses to climate forcings, based on the concept of latent (unobservable) factors. Here, in Part I, we suggest several latent factor models of different complexity that can be used for evaluation of temperature data from climate model simulations against climate proxy data from the last millennium. Each factor model is developed for use with data from a single region, which can be of any size. To be able to test the hypotheses of interest, we have applied the technique of confirmatory factor analysis. We also elucidate the link between our factor models and the statistical methods used in Detection and Attribution (D\&A) studies. In particular, we demonstrate that our factor models can be used as an alternative approach to the methods used in D\&A studies. An additional advantage of their use is that they, in contrast to the commonly used D\&A methods, make it, in principle, possible to investigate whether the forcings of interest act additively or if any interaction effects exist.In Part II we investigate and illustrate the expansion of factor models to structural equation models, which permits the statistical modelling of more complicated climatological relationships. The performance of some of our statistical models suggested in Part I and Part is evaluated and compared in a numerical experiment, whose results are presented in Part III
Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings: Part III
No full textEvaluation of climate model simulations is a crucial task in climate research. In a work consisting of three parts, we propose a new statistical framework for evaluation of simulated responses to climate forcings, based on the concept of latent (unobservable) variables. In Part I, several latent factor models were suggested for evaluation of temperature data from climate model simulations, forced by a varying number of forcings, against climate proxy data from the last millennium. In Part II, focusing on climatological characteristics of forcings, we deepen the discussion by suggesting two alternative latent variable models that can be used for evaluation of temperature simulations forced by five specific forcings of natural and anthropogenic origin. The first statistical model is formulated in line with confirmatory factor analysis (CFA), accompanied by a more detailed discussion about the interpretation of latent temperature responses and their mutual relationships. Introducing further causal links between some latent variables, the CFA model is extended to a structural equation model (SEM), which allows us to reflect more complicated climatological relationships with respect to all SEM's variables. Each statistical model is developed for use with data from a single region, which can be of any size. Here, in Part III, the performance of both these statistical models and some models suggested in Part I is evaluated and compared in a pseudo-proxy experiment, in which the true unobservable temperature is replaced by temperature data from a selected climate model simulation. The present analysis involves seven regional data sets. Focusing first on the ability of the models to provide an adequate and climatologically defensible description of the unknown underlying structure, we may conclude that given the climate model under consideration, the SEM model in general performed best. As for the factor model, its assumptions turned out to be too restrictive to describe the observed relationships in all but one region. The performance of another factor model, reflecting the assumptions typically made in many D\&A studies, can be characterised as unacceptable due to its high sensitivity to insignificant coefficient estimates. Regarding the fourth statistical model analysed - a factor model with two indicators and one latent factor - it can be recommended to apply it with caution due to its sensitivity to departures from the independence assumptions among the model variables, which can make the interpretation of the latent factor unclear. The conclusions above have been confirmed in some form of a cross-validation study, presuming the availability of several data sets within each region of interest. Importantly, the present pseudo-proxy experiment is performed only for zero noise level, implying that the five SEM models and one factor model await further investigation to fully test their performance for realistic levels of added noise
A Stable, Fully Implicit, Second Order Method for Viscous Free Surface Stokes Flow
No full textWe present a fully implicit finite element method for the type of viscous free surface problems which are common in glaciology and geodynamics. Standard fully implicit solvers suffer from convergence issues for large time-steps; we address this by incorporating a stabilization term that vanishes upon convergence. This approach enables the use of significantly larger time-steps, thereby substantially improving the efficiency of simulations. Furthermore, we leverage the fully implicit solver to develop second-order time-stepping schemes that mitigate the high errors associated with first-order methods for large time steps
Exact completion and constructive theories of sets
No full textIn the present paper we use the theory of exact completions to study categorical properties of small setoids in Martin-Loef type theory and, more generally, of models of the Constructive Elementary Theory of the Category of Sets, in terms of properties of their subcategories of choice objects (i.e. objects satisfying the axiom of choice). Because of these intended applications, we deal with categories that lack equalisers and just have weak ones, but whose objects can be regarded as collections of global elements. In this context, we study the internal logic of the categories involved, and employ this analysis to give a sufficient condition for the local cartesian closure of an exact completion. Finally, we apply this result to show when an exact completion produces a model of CETCS