A teoria do valor extremo é aplicada em áreas de pesquisa tais como hidrologia, estudos de poluição, engenharia de materiais, controle de tráfego e economia. A distribuição valor extremo ou Gumbel é amplamente utilizada na modelagem de valores extremos de fenômenos da natureza e no contexto de análise de sobrevivência para modelar o logaritmo do tempo de vida. A modelagem de valores extremos de fenômenos da natureza tais como velocidade de vento, nível da água de rio ou mar, altura de onda ou umidade é importante em estatística ambiental pois o conhecimento de valores extremos de tais eventos é crucial na prevenção de catátrofes. Ultimamente esta teoria é de particular interesse pois fenômenos extremos da natureza têm sido mais comuns e intensos. A maioria dos artigos sobre teoria do valor extremo para modelagem de dados considera amostras de tamanho moderado ou grande. A distribuição Gumbel é frequentemente incluída nas análises mas a qualidade do ajuste pode ser pobre em função de presença de ouliers. Investigamos modelagem estatística de eventos extremos com base na teoria de valores extremos. Consideramos um modelo de regressão valor extremo introduzido por Barreto-Souza & Vasconcellos (2011). Os autores trataram da questão de corrigir o viés do estimador de máxima verossimilhança para pequenas amostras. Nosso primeiro objetivo é deduzir ajustes para testes de hipótese nesta classe de modelos. Derivamos a estatística da razão de verossimilhanças ajustada de Skovgaard (2001) e cinco ajustes da estatística da razão de verossimilhanças sinalizada, que foram propostos por Barndorff-Nielsen (1986, 1991), DiCiccio & Martin (1993), Skovgaard (1996), Severini (1999) e Fraser et al. (1999). As estatísticas ajustadas são aproximadamente distribuídas como uma distribuição $\\chi^2$ e normal padrão com alto grau de acurácia. Os termos dos ajustes têm formas compactas simples que podem ser facilmente implementadas em softwares disponíveis. Comparamos a performance do teste da razão de verossimilhanças, do teste da razão de verossimilanças sinalizada e dos testes ajustados obtidos neste trabalho em amostras pequenas. Ilustramos uma aplicação dos testes usuais e suas versões modificadas em conjuntos de dados reais. As distribuições das estatísticas ajustadas são mais próximas das respectivas distribuições limites comparadas com as distribuições das estatísticas usuais quando o tamanho da amostra é relativamente pequeno. Os resultados de simulação indicaram que as estatísticas ajustadas são recomendadas para inferência em modelo de regressão valor extremo quando o tamanho da amostra é moderado ou pequeno. Parcimônia é importante quando os dados são escassos, mas flexibilidade também é crucial pois um ajuste pobre pode levar a uma conclusão completamente errada. Uma revisão da literatura foi feita para listar as distribuições que são generalizações da distribuição Gumbel. Nosso segundo objetivo é avaliar a parcimônia e flexibilidade destas distribuições. Com este propósito, comparamos tais distribuições através de momentos, coeficientes de assimetria e de curtose e índice da cauda. As famílias mais amplas obtidas pela inclusão de parâmetros adicionais, que têm a distribuição Gumbel como caso particular, apresentam assimetria e curtose flexíveis enquanto a distribuição Gumbel apresenta tais características constantes. Dentre estas distribuições, a distribuição valor extremo generalizada é a única com índice da cauda que pode ser qualquer número real positivo enquanto os índices da cauda das outras distribuições são zero. Observamos que algumas generalizações da distribuição Gumbel estudadas na literatura são não identificáveis. Portanto, para estes modelos a interpretação e estimação de parâmetros individuais não é factível. Selecionamos as distribuições identificáveis e as ajustamos a um conjunto de dados simulado e a um conjunto de dados reais de velocidade de vento. Como esperado, tais distribuições se ajustaram bastante bem ao conjunto de dados simulados de uma distribuição Gumbel. A distribuição valor extremo generalizada e a mistura de duas distribuições Gumbel produziram melhores ajustes aos dados do que as outras distribuições na presença não desprezível de observações discrepantes que não podem ser acomodadas pela distribuição Gumbel e, portanto, sugerimos que tais distribuições devem ser utilizadas neste contexto. / The extreme value theory is applied in research fields such as hydrology, pollution studies, materials engineering, traffic management, economics and finance. The Gumbel distribution is widely used in statistical modeling of extreme values of a natural process such as rainfall and wind. Also, the Gumbel distribution is important in the context of survival analysis for modeling lifetime in logarithmic scale. The statistical modeling of extreme values of a natural process such as wind or humidity is important in environmental statistics; for example, understanding extreme wind speed is crucial in catastrophe/disaster protection. Lately this is of particular interest as extreme natural phenomena/episodes are more common and intense. The majority of papers on extreme value theory for modeling extreme data is supported by moderate or large sample sizes. The Gumbel distribution is often considered but the resulting fit may be poor in the presence of ouliers since its skewness and kurtosis are constant. We deal with statistical modeling of extreme events data based on extreme value theory. We consider a general extreme-value regression model family introduced by Barreto-Souza & Vasconcellos (2011). The authors addressed the issue of correcting the bias of the maximum likelihood estimators in small samples. Here, our first goal is to derive hypothesis test adjustments in this class of models. We derive Skovgaard\'s adjusted likelihood ratio statistics Skovgaard (2001) and five adjusted signed likelihood ratio statistics, which have been proposed by Barndorff-Nielsen (1986, 1991), DiCiccio & Martin (1993), Skovgaard (1996), Severini (1999) and Fraser et al. (1999). The adjusted statistics are approximately distributed as $\\chi^2$ and standard normal with high accuracy. The adjustment terms have simple compact forms which may be easily implemented by readily available software. We compare the finite sample performance of the likelihood ratio test, the signed likelihood ratio test and the adjusted tests obtained in this work. We illustrate the application of the usual tests and their modified versions in real datasets. The adjusted statistics are closer to the respective limiting distribution compared to the usual ones when the sample size is relatively small. Simulation results indicate that the adjusted statistics can be recommended for inference in extreme value regression model with small or moderate sample size. Parsimony is important when data are scarce, but flexibility is also crucial since a poor fit may lead to a completely wrong conclusion. A literature review was conducted to list distributions which nest the Gumbel distribution. Our second goal is to evaluate their parsimony and flexibility. For this purpose, we compare such distributions regarding moments, skewness, kurtosis and tail index. The larger families obtained by introducing additional parameters, which have Gumbel embedded in, present flexible skewness and kurtosis while the Gumbel distribution skewness and kurtosis are constant. Among these distributions the generalized extreme value is the only one with tail index that can be any positive real number while the tail indeces of the other distributions investigated here are zero. We notice that some generalizations of the Gumbel distribution studied in the literature are not indetifiable. Hence, for these models meaningful interpretation and estimation of individual parameters are not feasible. We select the identifiable distributions and fit them to a simulated dataset and to real wind speed data. As expected, such distributions fit the Gumbel simulated data quite well. The generalized extreme value distribution and the two-component extreme value distribution fit the data better than the others in the non-negligible presence of outliers that cannot be accommodated by the Gumbel distribution, and therefore we suggest them to be applied in this context.

Les troubles du contrôle postural (TCP) sont une cause majeure d’invalidité dans la maladie de Parkinson (MP) au stade évolué et sont fréquemment associés aux RBD (REM sleep behavior disorders). Les substrats anatomiques des TCP sont mal connus. Ils reposent en partie sur des lésions de la région locomotrice mésencéphalique (noyau pédonculopontin-PPN et noyau cunéiforme), également impliquée dans le contrôle du sommeil/vigilance et oculomoteur. Les saccades oculaires sont un modèle de contrôle moteur dont la quantification est robuste et les réseaux largement élucidés. Dans la MP au stade évolué, il existe une altération des saccades volitionnelles qui pourrait être associée aux TCP. Des dysfonctions des sous-réseaux du PPN pourraient participer à la survenue des TCP, du sommeil/vigilance et oculomoteurs.Notre objectif est de préciser les corrélats physiologiques et anatomo-fonctionnels des TCP, et le substrat de l’association clinique entre TCP et RBD dans la MP. Nous confrontons l’étude de l’initiation du pas (ajustements posturaux anticipatoires-APA) et d’autres tests de marche-équilibre à l’étude des saccades, et analysons les réseaux locomoteurs, de vigilance et oculomoteurs du PPN en IRM fonctionnelle. Nous montrons pour la première fois que les patients avec instabilité posturale ont un allongement de la latence des antisaccades et de la durée des APA, inter-corrélés. La durée des APA est corrélée aux anomalies de connectivité fonctionnelle entre le PPN et la SMA/préSMA. La présence de RBD est sous-tendue par des anomalies du réseau PPN-cortex cingulaire antérieur. L’allongement de la latence des antisaccades est associé à une désorganisation du réseau PPN-FEF. / Postural control (PC) impairment is a major cause of disability in Parkinson’s Disease (PD) and is frequently associated with RBD (REM-sleep behavior disorders-RBD). The networks underlying PC impairment in PD are not well known. They include lesions of the mesencephalic locomotor region (pedunculopontine nucleus-PPN, and cuneiform nucleus), which is also involved in the control of sleep/vigilance. Saccades are a model of motor control, their quantification is reliable and their networks have been largely elucidated. PD patients at evolved stages have predominant volitional saccades alterations which could be associated with some aspects of postural control disorders. Dysfunctions of specific PPN networks could be involved in PC impairment, sleep/vigilance and oculomotor disorders. Our goal is to specify the neurophysiological and anatomo-functional correlates of postural control impairment and to specify the substrates underlying the co-occurrence of postural control disorders and RBD in PD. We confront the study of gait initiation (anticipatory postural adjustments-APA) with the antisaccades paradigm, and we analyze the PPN functional locomotor, vigilance and oculomotor networks. We show for the first time that PD patients with postural instability have prolonged antisaccades latencies and APA duration, and that these disorders are intercorrelated. APA duration is correlated with PPN-SMA/préSMA functional connectivity abnormalities, the presence of RBD is associated with disruptions in the PPN-anterior cingular cortex network and prolonged antisaccade latencies are possibly underlined by PPN-FEF functional disorganization.

No description available.

L’objectif de ce travail est de déterminer l’influence des réductions de mobilité ostéo-articulaire passive et active sur la capacité posturo-cinétique. La réduction de mobilité passive est analysée à travers un mouvement d’élévation des membres supérieurs à vitesse maximale au cours duquel seront mesurés des indices électromyographiques (Tibial antérieur, Soléaire) et biomécaniques (plateforme de force, accéléromètre). La réduction de mobilité active est étudiée à partir d’un examen posturographique combiné à un mouvement de compression d’une barre dynamométrique et à l’enregistrement de la cinématique respiratoire. L’analyse de la composante passive révèle que, dès 50% de perte de mobilité au niveau de la région cervicale, la capacité posturo-cinétique (CPC) est perturbée. Le blocage passif des articulations des chevilles et du rachis cervical semble davantage réduire la CPC que celui des genoux ou du rachis lombaire. L’étude de la composante active montre que l'augmentation de la tension musculaire active le long du tronc est susceptible de perturber l'équilibre postural, mais uniquement lorsqu'elle dépasse un certain niveau. Ainsi les deux composantes, passive et active, de la mobilité ostéo-articulaire, paraissent chacune jouer un rôle dans la capacité à compenser les perturbations associées au maintien postural ou à l’exécution du mouvement. / The aim of this study was to determine the influence of passive and active components of osteoarticular mobility on the capacity posturo-kinetic. The passive component was analyzed through a paradigm of upper limb elevation at maximum velocity, during which electromyographic (Tibialis anterior, soleus) and biomechanical (force platform, accelerometer) parameters were measured. The active component was studied from an experimental paradigm associating a posturaphic examination with a bimanual compression of a dynamometric bar. Results analysis showed that the posturo-kinetic capacity (PKC) was reduced when the loss of mobility exceeded 50% at the neck level. Passively blocking the ankle joints and the cervical spine seemed more likely to reduce the PKC than blocking the knee or the lumbar spine. The study of the active component showed that the increase in active muscle tension along the trunk may impair body balance, but only when it exceeds a certain level. Thus the two components, passive and active, of the osteoarticular mobility, appeared as significant factors in the ability to compensate for the disturbances associated with postural maintenance or movement execution.

Studiens syfte var att beskriva hur undervisning i grundskolan utformas för nyanlända elever samt hur utformningen av undervisningen inverkar på elevernas lärande och inkludering. Frågorna som belystes var; Hur motiverar olika skolor sin utformning av undervisning för nyanlända elever? Hur utformar de olika skolorna stöttning och extra anpassningar, så att nyanlända elevers lärande underlättas? Hur beskrivs synen på inkluderande undervisning och hur omsätts den i verksamheten på olika skolor? Studien genomfördes med kvalitativ fenomenografisk metod. Nio halvstrukturerade intervjuer genomfördes med rektor, specialpedagog och lärare på tre olika skolor. Resultatet visade att undervisning för nyanlända elever utformades olika skolor emellan samt att kunskap och erfarenhet var viktigt för att kunna utforma god undervisning. Vidare, att alla skolor strävade efter en inkluderande undervisning och att extra anpassningar eller stöttning genomfördes, för att elevernas individuella förutsättningar att nå målen skulle tillvaratas. Viljan fanns, men inte alltid kunskaperna eller förutsättningarna. Några verksamma åtgärder för ökad måluppfyllelse identifierades i studien. Stöttning var en förutsättning för att nå de individuella målen.Undervisning som var kognitivt utmanande samt utgick från elevernas kunskaper och erfarenheter och användande av modersmål i undervisningen lyftes som verksamma redskap, för att få eleverna engagerade i läsande och skrivande samt stärka språket. Samarbete inom skolan mellan olika yrkeskategorier, men också ett samarbete med vårdnadshavare var en förutsättning. Ökad inkludering nåddes när åtgärder vidtogs, som skapade goda förutsättningar för nyanlända elever att lyckas i skolan. Inkluderingssträvan var en ständigt pågående demokratisk process för alla människors rättigheter och lika värde. Den utgick ifrån idén att elevers olikheter var en tillgång, där elever erbjöds möjligheter att uppleva gemenskap och aktivt deltagande med hög pedagogisk vinst. / The purpose of the study was to describe how teaching is designed in elementary school for newly arrived pupils, and to review the effects of this teaching. The questions being analyzed were: What is the motivation of the different schools in how they create their supportive teaching structure for the newly arrived students? How do the different schools organize their scaffolding, and how do they make adjustments, so that the learning of new arrivals is supported? How is inclusive education described, and how is it transformed into activities at different schools? The study used a qualitative phenomenographic methodology. Nine half-structured interviews were conducted with the principal, special educator and teacher at three different schools. The results showed that teaching for newly arrived pupils varies between schools, and that knowledge and experience is important in order to create a good teaching environment. Further, all schools aimed for an inclusive education, and that additional adjustments or supporting structures were implemented to ensure that the pupils' individual needs for achieving their goals were met. Not all schools had the knowledge or the right conditions for the implementation of an inclusive education, but all three had the will to try. Some methods for increased goal achievement have been identified as being particularly active in the study. Scaffolding was a prerequisite for reaching pupils’ individual goals, and one challenge was to decide on the right kind of pedagogy for the individual pupil. Education that was cognitively challenging, and on the pupil’s mother tongue, can all be used as active tools in order to get pupils involved in reading and writing and with the goal of strengthening their language. Collaboration within the schools’ different occupational categories, as well as cooperation with caregivers, were needed. Inclusion was achieved when the right action was taken to create good learning conditions for newly arrived pupils to succeed in school. The inclusion endeavor was ultimately based on an ongoing democratic process for all human rights and equal values. It was based on the idea that pupils' differences were an asset, offering students the opportunity to experience community and active participation with high educational gains.

The purpose of this study was to highlight the type of actions that can facilitate people with Asperger syndrome to get and keep a job in the regular labour market. Four interviews were done with people who have been diagnosed with Asperger syndrome and who got a job in the regular labour market. The study shows that efforts from society and friends at work have played a role when they had got their jobs and when they managed to keep it. The study shows that these efforts have strengthened their self-image and confidence. The study also shows that adaptations in the work, the ability to control over social contacts and the importance of having a job may have contributed to the respondents stayed in the workplace. The study also shows that counseling has played a role in the investigated people’s career development and helped them to find a job. The study draws no general conclusions when the result concerns four peoples own views.  However, the above factors have played a role for the respondents. The result cannot be interpreted to apply to all persons who have Asperger syndrome, it is important to see the individual behind the diagnosis. / Syftet med studien var att belysa vilken typ av insatser som kan underlätta för personer med Aspergers syndrom att få och behålla ett arbete på den reguljära arbetsmarknaden.  Fyra intervjuer genomfördes med personer som har diagnosen Aspergers syndrom och som har ett arbete på den reguljära arbetsmarknaden. Studien visar att insatser från samhället och från arbetskamrater i kombination med en egen drivkraft har haft betydelse när de respondenterna fått sitt arbete och när de klarat av att behålla det. Insatserna har stärkt självbild och självförtroende. Studien visar även att anpassningar i arbetet, möjlighet att själv styra över sociala kontakter samt betydelsen av att ha ett arbete kan ha bidragit till att respondenterna stannat kvar på sin arbetsplats. Studien visar också att studie- och yrkesvägledning har haft betydelse för respondenternas karriärutveckling samt hjälpt dem till arbete. Studien drar inga generella slutsatser då resultatet avser fyra personers egna uppfattningar. Dock konstateras att ovanstående faktorer har haft betydelse för respondenterna. Slutsatserna kan heller inte tolkas att gälla alla personer som har Aspergers syndrom, det är viktigt att se individen bakom diagnosen.

Tidigare forskning visar att det finns brister i den samsyn och samverkan mellan skolpersonal som är en framgångsfaktor för hög måluppfyllelse i grundskolan (Nilholm & Göransson, 2013; SOU 2010:95; www.skolinspektionen.se; m fl). Mentorer, lokala elevhälsoteam och skolledare är de aktörer som ansvarar för utbildningen till elever med olika förutsättningar. Graden av samsyn dessa aktörer emellan är därför intressant. Denna studies syfte har varit att identifiera och beskriva eventuella mönster i mentorers, lokala elevhälsoteams och skolledares uppfattningar om extra anpassningar och särskilt stöd, utifrån frågeställningar om anledningar till olika insatser, vem/vilka som ska ansvara för insatserna samt om orsaker till bristande insatser. En totalundersökning i en kommun har genomförts via webbenkät och kvantitativ multivariat analys. Utgångspunkterna har varit socialkonstruktivistisk teori om ett kontextberoende lärande tillsammans med andra, och ett relationellt perspektiv på skolsvårigheter.  Studien visar att störst samsyn finns kring det faktum att inte alla elever med behov ges tillräckligt stöd i skolorna, och att tid för arbete för dessa elever saknas i personalens scheman. Viss samsyn finns också angående när elever ska ges stöd, men i mindre grad gällande vem/vilka som ska utföra insatserna. Studien har också visat att en relativt stor andel av respondenterna upplever bristande samsyn med kollegor gällande att se/tolka behov hos elever, avgöra lämpliga åtgärder samt utföra åtgärderna, samtidigt som alla tre grupperna i hög grad är överens om att de själva sällan eller aldrig har bristande kompetens gällande just att tolka behov och avgöra/utforma åtgärder.  Resultaten visar att samsyn och samverkan behöver vidareutvecklas inom skolorna via strategiska kontaktytor. Utifrån resultaten och teorin bör samtalen handla om uppdragsuppfattning, elevsyn och gemensamma strategier för ökad inkludering, delaktighet och måluppfyllelse. / Previous research shows that there are shortcomings in the consensus and collaboration among school personnel, a success factor for high achievement in primary school (Nilholm & Göransson, 2013; SOU 2010:95; www.skolinspektionen.se; m fl). Mentors, local student health teams and school leaders are those responsible for the education of students with different qualifications. The degree of consensus between these actors is therefore interesting. The purpose of this study has been to identify and describe any patterns of mentors' , local student health teams' and school leaders' perceptions about additional adjustments and special support, based on the questions of reasons for different actions, who/which is responsible for action and reasons for lack of action.  A total survey in a municipality has been conducted via online questionnaire and quantitative multivariate analysis. The starting point has been the social constructivist theory of context-dependent learning with others, and a relational perspective on school difficulties.    The study shows that the greatest consensus is about the fact that not all students in need are given sufficient support, and that time to work for these students is lacking in staff schedules. Some consensus is also about which students should receive support, but less so regarding which staff should perform it. The study has also shown that a relatively large proportion of respondents perceive lack of consensus with colleagues regarding interpreting the needs of pupils, determining appropriate actions and bringing them into action, while all three groups largely agree that themselves rarely or never lack of expertise regarding just that;  interpreting the needs and determining/performing measures.   The results show that consensus and collaboration need to be developed within schools through strategic contacts. Based on the results and theory, the discourse should be about assignment, perception of difficulties and concerted strategies for greater inclusion, participation and achievement.

Σε παγκόσμια κλίμακα αλλά και εντός των ελληνικών συνόρων κερδίζει συνεχώς έδαφος η άποψη, τόσο από το καταναλωτικό κοινό όσο και από την πλευρά των πολιτικών παραγόντων, ότι οι τιμές της λιανικής βενζίνης δεν αντανακλούν το κόστος του αργού πετρελαίου. Συγκεκριμένα υπάρχει διάχυτη η πεποίθηση ότι οι τιμές της βενζίνης αποκρίνονται ασύμμετρα στις μεταβολές της τιμής του αργού πετρελαίου-ενώ δηλαδή οι αυξήσεις περνούν άμεσα στις τιμές, δεν ισχύει το ίδιο και στην περίπτωση μείωσης των τιμών του αργού πετρελαίου. Με αφορμή αυτήν την άποψη, ελέγξαμε για ύπαρξη ασύμμετρων αποκρίσεων της τιμής της βενζίνης με δεδομένα για την Ελλάδα από την περίοδο 30 Σεπτεμβρίου του 2002 έως τις 15 Απριλίου του 2009. Βρήκαμε ότι, θετικές ασυμμετρίες στην τιμή ισορροπίας (όταν η τιμή της αμόλυβδης είναι πάνω από την τιμή ισορροπίας όπως αυτή ορίζεται από την τιμή του πετρελαίου) εμμένουν και δεν τείνουν να εξαλειφθούν, ενώ αντιθέτως, αρνητικές αποκλίσεις της τιμής της αμόλυβδης από την «δίκαιη» τιμή της τείνουν να εξαλειφθούν σε σύντομο χρονικό διάστημα. Η διαπίστωση αυτή μπορεί να ερμηνευτεί από τα χαρακτηριστικά που διέπουν την ελληνικά αγορά πετρελαιοειδών και περιορίζουν την ανάπτυξη του ανταγωνισμού-ο εφοδιασμός των επιχειρήσεων λιανικής εμπορίας γίνεται για παράδειγμα με την χρήση συμβάσεων εμπορικής συνεργασίας μεταξύ πρατηριούχων και εταιριών εμπορίας πετρελαιοειδών-που περιλαμβάνουν περιοριστικούς του ανταγωνισμού όρους στη διακίνηση των εμπορευμάτων. Αναφορικά με τους λόγους της ασύμμετρης απόκρισης των τιμών λιανικής βενζίνης, εκτός από τις αιτίες που αναφέρονται στην κλασσική Βιβλιογραφία (Δύναμη της αγοράς, δαπανηρή προσαρμογή της παραγωγής και των αποθεμάτων, κόστη έρευνας κτλ) αναφερθήκαμε και σε δευτερεύουσες αιτιάσεις οι οποίες μπορεί να αποδειχθούν εξίσου σημαντικές (η ύπαρξη μελλοντικών συμβολαίων, η σχετική ζήτηση, η επιλογή λογιστικών πρακτικών, η επίδραση των οικονομικών κύκλων και των δομικών αλλαγών). Επιπλέον, αναφερθήκαμε στις κυριότερες από την πληθώρα των σχετικών μελετών που έχουν πραγματοποιηθεί παγκοσμίως και ειδικότερα στα υποδείγματα που έχουν προταθεί ως καταλληλότερα για την ανάλυση του ζητήματος της ασύμμετρης απόκρισης των λιανικών τιμών της βενζίνης αλλά και στους λόγους για τους οποίους αυτά δίνουν διαφορετικά αποτελέσματα. / World-wide and within the borders of Greece, is gaining continually ground, both to the consumers and politicians, the opinion that, retail gasoline prices don’t reflect the crude oil cost. Specifically, there is a strong belief that gasoline prices, respond asymmetrically to crude oil price changes - while for example, the increases pass through immediately to prices, the same doesn’t hold in the case of crude oil prices reduction. With incentive this point of view, we tested for the existence of asymmetric responses of gasoline price with data for Greece, for the period 30 September 2002 to 15 April 2009. We found that, positive asymmetries in equilibrium price (when unleaded gasoline price is above the equilibrium price as it is determined from the oil price) persist and don’t tend to eliminate, whereas, negative deviations of unleaded gasoline price from it’s “fair” price, tend to eradicate in short time. This finding, can be interpreted by the characteristics that rule the Greek oil market and restrict the development of competition – the supply of retail trade companies, is held for instance, with the use of commercial co-operation contracts, between the owners of the gas stations and the oil products trading firms, that incorporate competition restrictive conditions in the distribution of the commodities. As regard the reasons of asymmetric response of retail gasoline prices, apart from the causes that have been referred in the classic bibliography, (market power, costly output and inventories adjustment, search costs, etc), we mentioned and secondary reasons that may proved to be the same important (the existence of future contracts, the relative demand, the choice of the accounting practices, the effect of economic cycles and structural changes). Furthermore, we referred to the main, from the plentitude of the relative studies that have taken place worldwide and particularly to the models that have been suggested as proper for the analysis of the issue of asymmetric response of retail gasoline prices, as well as and to the causes for which they yield different results.

Syftet med denna studie är att utforska erfarenheter kring användandet av digitala verktyg hos gymnasieelever som får extra anpassningar beträffande språk-, läs- och skrivlärande. Metoden som använts är kvalitativa intervjuer med fyra gymnasieelever, och som teoretisk ansats utgår studien från ett sociokulturellt perspektiv på lärande. Utifrån syfte och frågeställningar presenteras resultatet av intervjuerna i form av fyra teman som samtliga handlar om digitala verktyg i undervisningen. Dessa är specialpedagogiskt stöd i grundskolan, bevis på att vara annorlunda, pedagogiskt och specialpedagogiskt redskap samt för- och nackdelar. Resultatet i studien visar att eleverna under sin grundskoletid inte fått tillräckligt med specialpedagogiskt stöd. Bristen har bland annat inneburit avsaknad av digital teknik, vilken hade kunnat ge stöd i att kompensera för elevernas läs- och skrivsvårigheter. I gymnasieundervisningen använder man däremot aktivt digitala verktyg för lärande. Dock saknas kunnig vägledning av dessa verktyg i klassrummet, varpå eleverna måste gå till en specialpedagog för att få hjälp och stöd. Sammantaget visar resultatet att eleverna upplever att skrivandet har påverkats positivt av användandet av digitala verktyg, men att det behövs ökad kompetens hos lärare beträffande elever med extra anpassningar i svenskämnet. / The aim of this study is to explore the experiences in the use of digital tools in upper secondary school by students who receive additional adjustments regarding language and literacy learning. The method used is qualitative interviews with four students, and the theoretical base of the study is a socio-cultural perspective of learning. Based on the aim and the questions at issue, the results of the interviews are presented in the form of four common themes, concerning digital tools for learning. These are special education support in primary school, proof of being different, special education and educational tools, and also advantages and disadvantages. The results of the study show that students have not received enough special education in elementary school. The shortage has, among other things, led to the absence of digital technology, which could have provided support to compensate for students' reading and writing difficulties. In upper secondary school, active digital tools for learning are used. However, there is a lack of expert guidance of these tools in the classroom, whereupon the students have to go to a special education teacher for help and support. Overall, the results show that the students feel that writing has been positively influenced by the use of digital tools, but that teachers need a higher degree of competence to deal with students with additional adjustments in the Swedish courses.

A large theoretical and empirical literature has studied the response in prices to changes in demands and costs. Three of the essays in this thesis are empirical studies of price-setting. The most important reason for studying the properties of price adjustments is the possible link between pricing and the business cycle. One family of models deals with price rigidities. If prices adjust slowly to changes in costs or demand, it will magnify fluctuations in output. A second family of models examines price changes due to changes in intensity of competition. Many of these models build on the idea that changes in demand affect the possibility of maintaining implicit collusion. Cyclical changes in the intensity of competition may cause a cyclical pricing pattern that magnifies fluctuations in output. Another line of research models the effects of liquidity constraints on the business cycle. One possible effect is that prices in markets where consumers have switching costs may increase, if the firms are hit by increased liquidity constraints. As increased liquidity constraints are common in recessions, prices will get a counter-cyclical tendency, which magnifies fluctuations in output. Another reason for studying price-setting patterns is that they can give an indication of the form of interaction between competing firms, which are of importance for competition policy. The fourth essay models sex discrimination formally. It shows that it is possible that sex discrimination in the labor market might be due to self-fulfilling sex stereotypes on the distribution of time out for child care between men and women. Both an even and an uneven distribution of time out for child care are possible equilibria in the model. The four essays can be read separatelyEssay 1 Price Responses to Seasonal Demand Changes in the Swedish Gasoline MarketA common idea in a number of papers on cyclical pricing is that implicit price collusion may be affected by changes in demand. In these models, tacit collusion is modeled as a game where agents balance gains from deviating from the collusive price, thereby gaining a short-run profit, against the gains from maintaining collusion in future periods. If demand fluctuates, the gains from deviating is high in periods of high demand; collusion may still be sustainable, however, if the collusive price is allowed to vary with demand. A lower price in high demand states reduces the gains from deviating, since it reduces the gain from each unit sold in these demand states. Hence, in order to equalize the profit from deviating and the profit from sticking to the implicit agreement, the price must move in the opposite direction to demand. Changes in demand can, naturally, be correlated with other factors affecting the price, such as cost changes. Thus, prices do not necessarily fall when demand increases in the data. According to the theory the, however, increase in demand should add a tendency to lower prices in order to make implicit collusion sustainable. The basic idea that changes in demand should affect prices if firms are engaged in implicit collusion has been employed in a number of papers, with different models for different assumptions on the pattern of demand changes. The demand for gasoline in Sweden follows a seasonal cycle, with demand being 42 percent higher in July than in January. Haltiwanger and Harrington provide a theory for implicit collusion over deterministic cycles, such as the seasonal cycle. Borenstein and Shepard (1996) tested Haltiwanger and Harrington’s model on the American gasoline retail market and found support for the theory. In this essay the model is tested for Swedish data, but no support for this theory is found. It is also investigated whether the effects on margins of the demand fluctuations induced by tax increases are compatible with theories of implicit collusion, but this is found not to be the case.Essay 2 Price Adjustments by a Gasoline Retail ChainEssay 2 is joint with Marcus Asplund and Richard Friberg. Stickiness of prices is an important building block in many business cycle models. This has spurred an empirical literature on price adjustments. Different types of price rigidities have different policy implications. Price setting can be state dependent, e.g. prices are adjusted when costs have changed by at least some minimal amount since the last price adjustment, or time-dependent e.g. adjusted once a week or once a year. Another issue is whether prices are equally rigid downwards as upwards. The second essay examines price responses in the Swedish gasoline retail market to changes in the Rotterdam spot price of gasoline, exchange rates and taxes. The main results are that cost changes are not fully passed through in the short run, but gradually moves towards the long-run equilibrium. Prices are stickier downwards than upwards. There is a minimum absolute size of price changes. Only very limited evidence of time-dependent price setting is found.Essay 3 Prices, Margins and Liquidity Constraints: Swedish Newspapers 1990-1996Essay 3 is written with Marcus Asplund and Niklas Strand. Chevalier and Scharfstein (1996) provide a model where consumer switching costs in combination with liquidity constraints give rise to a counter-cyclical tendency in prices. Customer stocks can be viewed as an investment, when consumers have switching costs when changing suppliers. Firms can exploit captured customers by setting a high price to raise short-run profits. However, a high price will induce consumers to search for alternatives, and customers once lost are costly to win back. Liquidity constraints, for instance in recessions, may force firms to sacrifice long-run profits for short-run gains. In this case, firms may have to cut back on investments in customer stocks by raising prices. Using firm level data from the Swedish daily newspaper industry, we test the effects of liquidity constraints on prices in markets with consumer switching costs. The newspaper industry is of particular interest, since firms set prices in two markets, the subscription market, where switching costs are high, and the advertising market, where switching costs are low. With accounting data from newspaper firms we can, by solvency, broadly categorize them as being more or less liquidity constrained. When Sweden enters a recession at the beginning of the nineties, we find a relative increase in subscription prices and margins for liquidity constrained firms. This is not the case for advertising prices, however. The results support the theory.Essay 4 Statistical Discrimination and Sex Stereotypes in the Labor MarketTime out for child care is unevenly distributed between the sexes. Parental leave benefits are usually exclusively given to the mother or distributed to both parents according to their choice. In Sweden, one month is reserved for each parent, however. One reason for this is to give the child better contact with both parents, but increased equality between the sexes in the labor market has also been put forward as an argument. This argument implicitly rests on the idea that sex stereotypes create sex discrimination, and that sex discrimination affects the distribution of time out for child care between the sexes. Essay 4 investigates if the uneven distribution of time out for child care can be explained by self-fulfilling sex stereotypes. It provides a model of distribution of time out for child care based on statistical discrimination and human capital investments. The model has three equilibria. In one equilibrium, time out for child care is evenly distributed between the sexes. In the second equilibrium, there is full specialization. The third equilibrium is an intermediate case, where time out for child care is unevenly distributed without full specialization There are no differences in ability or variance of ability between the sexes, the only differences between the equilibria are the self-fulfilling expectations of firms and workers. / Diss. (sammanfattning) Stockholm : Handelshögsk., 2001