Dissertations / Theses on the topic 'Heterogeneity'
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Lamberti, Giuseppe. "Modelling with heterogeneity." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/309295.
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When collecting survey data for a specific study it is usual to have some background information, in the form for example, of socio-demographic variables. In our context, these variables may be useful in identifying potential sources of heterogeneity. Resolving the heterogeneity may mean to perform distinct analyses based on the main variables for distinct and homogeneous segments of the data, defined in terms of the segmentation variables. In 2009 Gastón Sánchez proposed an algorithm PATHMOX with the aim to automatic detecting heterogeneous segments within the PLS-PM methodology. This technique, based on recursive partitioning, produces a segmentation tree with a distinct path models in each node. At each node PATHMOX searches among all splits based on the segmentation variables and chooses the one resulting in the maximal difference between the PLS-PM models in the children nodes. Starting from the work of Sanchez the purpose of the thesis is to extend PATHMOX in the following points:
1. Extension to the PATHMOX approach to detect which constructs differentiate segments. The PATHMOX approach uses a F-global test to identify the best split in heterogeneous segments. Following the same approach it is possible to extend the testing to find which the endogenous constructs are and which are the relationships between constructs responsible of the difference between the segments.
2. Extension to the PATHMOX approach to deal with the factor invariance problem. Originally PATHMOX adapted the estimation of constructs to each detected segment, that is, once a split is performed the PLS-PM model is recalculated in every child. This leads to the problem of invariance: if the the estimation of the latent variables are recalculated in each terminal node of the tree, we cannot be sure to compare the distinct behavior of two individuals who belong to two different terminal nodes. To solve this problem we will propose a invariance test based on the X^2 distribution, where the goal of to test whether the measurement models of each terminal node can be considered equal or not among them.
3. Extension to the PATHMOX approach to overcome the parametric hypothesis of F-test. One critic to the PATHMOX approach, applied in the context of partial least square path modeling, is that it utilizes a parametric test based on the hypothesis that the residuals have a normal distribution to compare two structural models. PLS-PM in general, is utilized to model data that come from survey analysis. These data are characterized by an asymmetric distribution. This situation produces skewness in the distribution of data. As we know, PLS-PM methodology, is based in the absence of assumptions about the distribution of data. Hence, the parametric F test used in PATHMOX may represent a limit of the methodology. To overcome this limit, we will extend the test in the context of LAD robust regression.
4. Generalization of PATHMOX algorithm to any type of modeling methodology. The PATHMOX algorithm has been proposed to analyze heterogeneity in the context of the partial least square path modeling. However, this algorithm can be applied to many other kind of methodologies according to the appropriate split criterion. To generalize PATHMOX we will consider three distinct scenarios: Regression analysis (OLS, LAD, GLM regression) and Principal Component Analysis.
5. Implement the methodology, using the R software as specific library.Cuando se realiza un estudio científico, el análisis hace énfasis sobre las variables recogidas para responder a las preguntas que se quieren hallar durante el mismo estudio. Sin embargo en muchos análisis se suele recoger más variables, como por ejemplo variables socio demográfico: sexo, status social, edad. Estas variables son conocidas como variables de segmentación, ya que pueden ser útiles en la identificación de posibles fuentes de heterogeneidad. Analizar la heterogeneidad quiere decir realizar distintas análisis para distintos colectivos homogéneos definidos a partir de las variables de segmentación. Muchas veces, si hay algún conocimiento previo, esta heterogeneidad puede ser controlada mediante la definición de segmentos a priori. Sin embargo no siempre se dispone de conocimiento suficiente para definir a priori los grupos. Por otro lado muchas variables de segmentación podrían ser disponibles para analizar la heterogeneidad de acuerdo con un apropiado algoritmo. Un algoritmo desarrollado con este objetivo fue PATHMOX, propuesto por Gastón Sanchez en 2009. Esta técnica, utilizando particiones recursivas, produce un árbol de segmentación con distintos modelos asociados a cada nodo. Para cada nodo, PATHMOX busca entre todas las variables de segmentación aquella que produce una diferencia máxima entre los modelos de los nodos hijos. Tomando como punto de partida el trabajo de Gastón Sanchez esta tesis se propone: 1. Extender PATHMOX para identificar los constructos responsables de la diferencias. PATHMOX nos permite detectar distintos modelos en un data-set sin identificar grupos a priori. Sin embargo, PATHMOX es un criterio global. Pera identificar las distintas ecuaciones y coeficientes responsables de las particiones, introduciremos los test F-block y F-coefficient. 2. Extender PATHMOX para solucionar el problema de la invariancia. En el contexto del PLS-PM (Partial Least Squares Path Modeling), PATHMOX funciona fijando las relaciones causales entre las variables latentes y el objetivo es identificar modelos con coeficientes path lo más posible distintos sin poner ninguna restricción sobre el modelo de medida. Por lo tanto, cada vez que una diferencia significativa es identificada, y dos nodos hijos vienen definidos, las relaciones causales entre las variables latentes son las mismas en ambos modelos "hijos", pero la estimación de cada variable latente se recalcula y no podemos estar seguros de comparar el comportamiento de dos individuos distintos que pertenecen a dos nodos diferentes. Para resolver este problema propondremos un test de invariancia basado en la distribución X^2, donde el objetivo del test es verificar si los modelos de cada nodo terminales se puede considerar igual o no entre ellos. 3. Extender PATHMOX para superar la hipótesis paramétrica del F-test. Una crítica a PATHMOX, aplicadas en el contexto del PLS-PM, es que el algoritmo utiliza una prueba paramétrica, basada en la hipótesis de que los residuos tienen una distribución normal, para comparar dos modelos estructurales. Para superar este límite, extenderemos el test para comparar dos regresiones robustas LAD en el contexto del PLS. 4. La generalización del algoritmo PATHMOX a cualquier tipo de metodología. El algoritmo PATHMOX ha sido propuesto para analizar la heterogeneidad en el contexto PLS-PM. Sin embargo, este algoritmo se puede aplicar a muchos otros tipos de metodologías de acuerdo con un apropiado criterio de partición. Para generalizar PATHMOX consideraremos tres escenarios distintos: modelos de regresión (modelos OLS, LAD, GLM) y el análisis en componentes principales. 5. Implementar la metodología, utilizando el software R como librería específica.
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Cleutjens, Jacobus Peter Marie. "Basement membrane heterogeneity." Maastricht : Maastricht : Rijksuniversiteit Limburg ; University Library, Maastricht University [Host], 1989. http://arno.unimaas.nl/show.cgi?fid=5472.
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Heslop, Louise. "Satellite cell heterogeneity." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395478.
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Terzi, Ayse, Kees Koedijk, Charles N. Noussair, and Rachel Pownall. "Reference Point Heterogeneity." FRONTIERS MEDIA SA, 2016. http://hdl.handle.net/10150/621274.
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It is well-established that, when confronted with a decision to be taken under risk, individuals use reference payoff levels as important inputs. The purpose of this paper is to study which reference points characterize decisions in a setting in which there are several plausible reference levels of payoff. We report an experiment, in which we investigate which of four potential reference points: (1) a population average payoff level, (2) the announced expected payoff of peers in a similar decision situation, (3) a historical average level of earnings that others have received in the same task, and (4) an announced anticipated individual payoff level, best describes decisions in a decontextualized risky decision making task. We find heterogeneity among individuals in the reference points they employ. The population average payoff level is the modal reference point, followed by experimenter's stated expectation of a participant's individual earnings, followed in turn by the average earnings of other participants in previous sessions of the same experiment. A sizeable share of individuals show multiple reference points simultaneously. The reference point that best fits the choices of the individual is not affected by a shock to her income.
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Shachat, Jason Matthew 1967. "Heterogeneity and equilibrium." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/289566.
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The research reported in this dissertation explores the observable effects that individual heterogeneity implies in strategic environments. The first chapter provides a focused experimental test of mixed strategy play in strictly competitive games. The experiment directly tests whether serial correlation results from subjects' inability to generate sequences of actions that appear to be time independent, or instead from the play of non-equilibrium strategies. This is achieved by allowing the subjects to generate actions via a simple randomizing device. It is found that serial correlation is not reduced and that subjects adopt a wide variety of non-equilibrium mixed strategies. This wide variety of mixtures potentially explains the seeming paradox of minimax winning proportions with a high variance of win rates across pairs of players. In the second chapter a theoretical model is developed for simultaneous move games in which the observable outcomes are allocations of monetary payoffs or commodity bundles, not expected utility levels. It is assumed that the players' mappings from the uncertain money amounts or commodity bundle allocations to expected utility levels are heterogeneous and are private information. The third chapter applies this framework to investigate the incentives to form agricultural marketing pools.
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Boedeker, Peter. "Comparison of Heterogeneity and Heterogeneity Interval Estimators in Random-Effects Meta-Analysis." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157553/.
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Meta-analyses are conducted to synthesize the quantitative results of related studies. The random-effects meta-analysis model is based on the assumption that a distribution of true effects exists in the population. This distribution is often assumed to be normal with a mean and variance. The population variance, also called heterogeneity, can be estimated numerous ways. Accurate estimation of heterogeneity is necessary as a description of the distribution and for determining weights applied in the estimation of the summary effect when using inverse-variance weighting. To evaluate a wide range of estimators, we compared 16 estimators (Bayesian and non-Bayesian) of heterogeneity with regard to bias and mean square error over conditions based on reviews of educational and psychological meta-analyses. Three simulation conditions were varied: (a) sample size per meta-analysis, (b) true heterogeneity, and (c) sample size per effect size within each meta-analysis. Confidence or highest density intervals can be calculated for heterogeneity. The heterogeneity estimators that performed best over the widest range of conditions were paired with heterogeneity interval estimators. Interval estimators were evaluated based on coverage probability, interval width, and coverage of the estimated value. The combination of the Paule Manel estimator and Q-Profile interval method is recommended when synthesizing standardized mean difference effect sizes.
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Yegorov, Yuri. "Spatial Heterogeneity and Equilibrium." Doctoral thesis, Universitat Pompeu Fabra, 1999. http://hdl.handle.net/10803/7592.
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This thesis consists of five chapters, based on four different articles. All of them are devoted to different aspects of spatial heterogeneity and its impact on economic equilibrium in space. The concept of heterogeneous continuous space is discussed in the introductory chapter.The first model "Equilibrium in Continuous Space under Decentralized Production" addresses the issue of the impact of differences across locations in exogeneous productivity on the structure of equilibrium prices, production and trade. The goal is to describe the general equilibrium in a spatially decentralized economy, when production, consumption and markets are distributed in continuous space and transportation costs are essentially linear. It is shown that an autarky equilibrium can exist only if transport costs are high enough. In the general case, the general equilibrium in this model includes some endogeneously determined trade areas, with flows of goods across space, and autarky areas where production and consumption activities take place only at the same point. An analytical solution in explicit functions is obtained; it contains equilibrium prices, labor supply and flows of goods as functions of the spatial variable. The model can be applied to a set of practical questions in regional economics. In particular, it is able to describe persistent price differentials across regions and non-local consequences of road construction and transportation cost shocks for the economy. The differences across locations in population density may have either historical or economic reasons.
The second model "Hotelling's Revival" extends a well-known research of H.Hotelling (1929) to the two-dimensional case with spatially heterogeneous demand density, preserving the rest of his classical assumptions. It is shown that the problem of demand discontinuity in the one-dimensional model, which was discovered by d'Aspremont, Gabszewich and Thisse (1979), disappears in this case. This also holds for any bounded distribution of consumers on any compact set on a plane, which can describe real geographical situations. Demand continuity still holds for any transport costs, strictly increasing in distance and not necessarily linear. Although this is sufficient for the existence of Nash equilibrium in mixed strategies, in pure strategies it exists only for some subset of cases. Examples of both existence and non-existence are constructed, and for some family of densities the separation point between the two cases is found.
The third model addresses locational choice of heterogeneous consumers, when land is also heterogeneous in quality. It is based on two articles. The first, "Dacha Pricing", is presented in chapter 4 and studies the problem of locational rent in a city-neighbourhood when utility includes both the impact of transport costs and time for transportation. For the case of identical agents the problem is solved explicitly and comparative statics with respect to exogeneous changes in transport cost and speed is studied. For the case of agents who are heterogeneous with respect to their income, a solution is also obtained. The model explains some evidence about dacha pricing in Russia and its dynamics during the transition period. The second article related to this model is "Location and Land Size Choice by Heterogeneous Agents". It generalizes the first one and form a separate chapter 5. A new approach about the general equilibrium allocation of heterogeneous divisible good (like land) among a continuum of heterogeneous consumers is proposed. The model is based on continuity of primitives which allow not only to finding a general equilibrium solution in a class of continuous functions, but also to treat the solution to a continuous problem as the limit of the corresponding sequence of discrete problems. This solves one of Berliant's paradoxes, related to spatial economics. The multiplicity of equilibria is shown to take place.
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Pinto, Eugenio. "Heterogeneity and input reallocation." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3903.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Economics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Jonnalagadda, Deepa. "HETEROGENEITY IN PLATELET EXOCYTOSIS." UKnowledge, 2013. http://uknowledge.uky.edu/biochem_etds/8.
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Platelet exocytosis is essential for hemostasis and for many of its sequelae. Platelets release numerous bioactive molecules stored in their granules enabling them to exert a wide range of effects on the vascular microenvironment. Are these granule cargo released thematically in a context-specific pattern or via a stochastic, kinetically-controlled process? My work describes platelet exocytosis using a systematic examination of platelet secretion kinetics. Platelets were stimulated for increasing times with different agonists (i.e. thrombin, PAR1-agonist, PAR4-agonist, and convulxin) and micro-ELISA arrays were used to quantify the release of 28 distinct α-granule cargo molecules. Agonist potency directly correlated with the speed and extent of release. PAR4-agonist induced slower release of fewer molecules while thrombin rapidly induced the greatest release. Cargo with opposing actions (e.g. pro- and anti-angiogenic) had similar release profiles, suggesting limited thematic response to specific agonists. From the release time-course data, rate constants were calculated and used to probe for underlying patterns. Probability density function and operator variance analyses were consistent with three classes of release events, differing in their rates. The distribution of cargo into these three classes was heterogeneous suggesting that platelet secretion is a stochastic process potentially controlled by several factors such as cargo solubility, granule shape, and/or granule-plasma membrane fusion routes.
Sphingosine 1 phosphate (S1P) is a bioactive lipid that is stored in platelets. S1P is essential for embryonic development, vascular integrity, and inflammation. Platelets are an abundant source of S1P due to the absence of the enzymes that degrade it. Platelets release S1P upon stimulation. My work attempts to determine how this bioactive lipid is released from platelets. Washed platelets were stimulated with agonists for defined periods of time and the supernatant and pellet fractions were separated by centrifugation. Lipids were separated by liquid phase extraction and S1P was quantified with a triple quadrapole mass spectrometer. A carrier molecule (BSA) is required to detect release of S1P. Further, there is a dose-dependent increase in total S1P with increasing BSA. S1P release shows characteristics similar to other platelet granule cargo e.g. platelet factor IV (PF4). Platelets from Unc13-d Jinx mice and VAMP8-/- mice, which are secretion-deficient (dense granule, alpha granule and lysosome), were utilized to understand the process of S1P release. S1P release was more affected in Unc13-d Jinx mice mirroring their dense granule secretion defect. Fluorescence microscopy and sub-cellular fractionation were used to examine localization of S1P in platelets. S1P was observed to be enriched in a granule population. These studies indicate the existence of two pools of S1P, a readily extractable agranular pool, sensitive to BSA, and a granular pool that requires the secretion machinery for release. The secretion machinery of platelets in addition to being involved in the release of normal granule cargo is thus proved to be involved in the release of bioactive lipid molecules like S1P.
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Marks, John. "Michel Foucault : towards heterogeneity." Thesis, Nottingham Trent University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357156.
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Mealor, Michael A. "Spatial heterogeneity in ecology." Thesis, University of Stirling, 2005. http://hdl.handle.net/1893/53.
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This project predominantly investigated the implications of spatial heterogeneity in the ecological processes of competition and infection. Empirical analysis of spatial heterogeneity was carried out using the lepidopteran species Plodia interpunctella. Using differently viscous food media, it was possible to alter the movement rate of larvae. Soft Foods allow the movement rate of larvae to be high, so that individuals can disperse through the environment and avoid physical encounters with conspecifics. Harder foods lower the movement rate of larvae, restricting the ability of individuals to disperse away from birth sites and avoid conspecifics encounters. Increasing food viscosity and lowering movement rate therefore has the effect of making uniform distributed larval populations more aggregated and patchy. Different spatial structures changed the nature of intraspecific competition, with patchy populations characterised by individuals experiencing lower growth rates and greater mortality because of the reduced food and space available within densely packed aggregations. At the population scale, the increased competition for food individuals experience in aggregations emerges as longer generational cycles and reduced population densities. Aggregating individuals also altered the outcome of interspecific competition between Plodia and Ephestia cautella. In food media that allowed high movement rates, Plodia had a greater survival rate than Ephestia because the larger movement rate of Plodia allowed it to more effectively avoid intraspecific competition. Also the faster growth rate, and so larger size, of Plodia allowed it to dominate interspecific encounters by either predating or interfering with the feeding of Ephestia. In food that restricts movement, the resulting aggregations cause Plodia to experience more intraspecific encounters relative to interspecific, reducing its competitive advantage and levelling the survival of the two species. Spatial structure also affected the dynamics of a Plodia-granulosis virus interaction and the evolution of virus infectivity. Larval aggregation forced transmission to become limited to within host patches, making the overall prevalence of the virus low. However potentially high rates of cannibalism and multiple infections within overcrowded host aggregations caused virus-induced mortality to be high, as indicated by the low host population density when virus is presented. Also aggregated host populations cause the evolution of lower virus infectivity, where less infective virus strains maintain more susceptible hosts within the aggregation and so possess a greater transmission rate. The pattern of variation in resistance of Plodia interpunctella towards its granulosis virus was found using two forms of graphical analysis. There was a bimodal pattern of variation, with most individuals exhibiting either low or high levels of resistance. This pattern was related to a resistance mechanism that is decreasingly costly to host fitness.
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Osypiw, Jacqueline Connett. "Heterogeneity of rat hepatocytes." Thesis, Liverpool John Moores University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261422.
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Restivo, Andrea. "Core-mantle boundary heterogeneity." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271844.
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Gonçalves, Carlos Augusto. "Characterisation of formation heterogeneity." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/35033.
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The characterisation of formation heterogeneities requires a multidisciplinary study of data acquired using a large number of numerical geophysical and geological measurements and a rigorous evaluation of the precision and accuracy of the data. Another essential aspect of the appraisal of any measurement is the quality assessment and quality control of the data. In this work multivariate statistical techniques and an Artificial Neural Network (ANN) are used provide lithofacies characterisation and to identify heterogeneities in complex formations as well as to evaluate the boundaries they generate. The precision and accuracy of the data from different sources are very important and are considered here by using sample support in the integration of measurements at different scales. We use examples from two holes of the Ocean Drilling Program and two oilfield holes to show the differences in characterisation obtained with each technique. Multivariate Statistical Analysis are initially used to group the petrophysical, geophysical and geological parameters extracted from the downhole measurements into distinct geologically definable zones. This technique has the advantage of being quasi-independent of any pre-determined ideas we have about the whole dataset, and has proved very reliable in formation characterisation. Thus the result obtained here is used as a basis for comparison with that obtained from the Neural Network. Artificial Neural Network is used to characterise the different lithology sequences present in each well. Neural Networks are relatively new tools and have proved very useful in applications where conventional computing methods are inadequate. Another application is the possibility of determining quantitative petrophysical parameters from well logs and core data in uncored intervals. The results are presented as a comparison between the two techniques. We show that both methods are very encouraging. When comparing the ANN derived petrophysical parameter logs with actual core measurements and other petrophysical parameters prediction techniques we see a good match. Low quality petrophysical measurements can be determined by a mismatch between the responses.
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Branford, White Harriet A. "Heterogeneity in Ewing sarcoma." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:7af59b69-e68f-41af-b5f0-8a7d278f6fd7.
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Ewing sarcoma, an aggressive primary bone and soft tissue tumour is characterised by the expression of the chimeric transcription factor EWS-FLI1 in 90% of patients. This alters expression of many genes including activation of the Insulin Growth Factor (IGF) pathway via IGFBP3 supression. Phase I/II trials with an IGF-1 inhibitor have demonstrated tumour regression in a modest number of Ewing sarcoma patients. The aim of this thesis was to identify mechanisms contributing to the heterogeneity of resistance in Ewing sarcoma following inhibition with OSI-906, a dual kinase inhibitor of IGF-1 (IGF-1R) and Insulin (IR) receptors. The hypothesis was that mechanisms of resistance relate to heterogeneity of responses to signalling pathway activation and inhibition. Through selection, disruption of the pathway would identify subpopulations of cells both sensitive and resistant in their response allowing for interrogation of resistance mechanisms. A genome wide approach was taken to model the resistance profile of cell lines. Through developing a method of unbiased quantification, a panel of validated Ewing sarcoma cell lines (EuroBoNet) were imaged and segmented to assess the responses of biomarkers on signalling pathway activation. Heterogeneity was confirmed between cell lines. The application to diagnostic biopsies led to the identification of prognostic classifiers and cellular subpopulations with clinical prognostic significance. The distribution of Ki67 was found to be predictive of survival and cells with lower levels of CD99 in the cytoplasm were most discriminative. Parallel sequencing strategies (RNA-seq, whole exome sequencing, and aCGH/ SNP array) for genome-wide screening was carried out for point mutations, copy number changes and rearrangements. Systematic detection was used to characterise genomic rearrangements and functional validation performed. Resistant clones, formed via ENU mutagenesis of cell lines, were sequenced in order to demonstrate the resistance profile of OSI-906. In summary heterogeneity of Ewing sarcoma at the genomic and proteomic level can influence the signalling dependency of tumours and response to inhibitors. Genomic and proteomic profiling of tumour cells may be relevant to future developments of novel therapies.
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Coghill, David Rockwell. "Heterogeneity in hyperkinetic disorder." Thesis, University of Dundee, 2010. https://discovery.dundee.ac.uk/en/studentTheses/afa9d9e9-eadb-49bf-8c83-db47eb0cadd9.
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It is increasingly recognised that the broadly defined behavioural phenotype of attention deficit – hyperactivity disorder (ADHD) is a heterogeneous condition and that this heterogeneity is seen across all levels of analysis from the genetic and environmental causes to the associated neuropsychological deficits, the clinical presentation and response to treatment. This work investigated whether the more restrictive and clinically homogeneous hyperkinetic disorder (HKD) phenotype is associated with reduced neuropsychological heterogeneity compared with the broader ADHD phenotype. Using a well known, broad based battery of neuropsychological tasks from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and a computerised Go/NoGo task in a large well described group of boys with rigorously diagnosed HKD who were stimulant medication naïve at baseline, it was demonstrated that the neuropsychological heterogeneity in the HKD boys was very similar to that seen previously in children with ADHD. Interestingly, and contrary to popular opinion, the strongest associations were with more simple recognition memory tasks with a low executive demand. Although there were significant associations between HKD and deficits on a range of tasks with high executive demands these were less strong. Could this neuropsychological heterogeneity be a function of different developmental issues or comorbidity? With respect to development there was evidence that boys with HKD lagged behind the healthy boys with respect to the development of their neuropsychological performance. However the pattern of development was similar with the performance of the HKD boys paralleling that of the healthy boys, suggesting that the neuropsychological heterogeneity seen in HKD is not accounted for by developmental issues. With respect to the relationship between neuropsychological functioning and comorbidity, the impact of comorbid oppositional defiant disorder (ODD) and conductdisorder (CD), it was found that all three clinical groups (pure HKD, HKD + ODD and HKD + CD) demonstrated deficits on several tasks compared with the healthy boys. Compared with healthy boys each of the three clinical groups was associated with at least one unique neuropsychological deficit. This suggests that comorbidity between HKD and both ODD and CD may contribute to the neuropsychological heterogeneity in the HKD boys. Is there an association between clinical and neuropsychological responses to the treatment of HKD with the stimulant drug methylphenidate (MPH)? Detailed analyses were conducted to investigate heterogeneity of clinical and neuropsychological response in these boys to MPH. As predicted in previous studies there is evidence for clinical heterogeneity in response with between 68 and 78% of boys with HKD responding to MPH treatment at either one or both of the doses. The precise proportion responding was dependent on the scale and definition of response used. Clinical response was not predicted by age but was predicted to a degree by severity of symptoms at baseline and it was generally true that better response was predicted by lower (better) scores at baseline. Baseline performance on a component reflecting recognition memory performance at baseline predicted clinical response to the lower (0.3 mg/kg/dose), but not the higher (0.6, mg/kg/dose) dose of MPH with poorer baseline neuropsychological performance predicting a better clinical response. Whilst there was improvement on some neuropsychological measures following administration of MPH there was little association between clinical and neuropsychological responses to medication. Clinical response was only associated with neuropsychological response on a single measure from a single task (Go/NoGo Block 2 Errors to Distractors), a task that did not itself discriminate between the HKD boys and healthy Controls at baseline.
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Bretan, Pedro Luis Accioli Nobre. "Firm heterogeneity and lobbying." reponame:Repositório Institucional do FGV, 2006. http://hdl.handle.net/10438/109.
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Previous issue date: 2006-12-18The structure of protection across sectors is usually interpreted as the result of competition among lobbies to influence politicians, but little attention has been devoted to the importance of individual firms in this process. This paper builds a model incorporating firm heterogeneity into a lobbying setup `a la Grossman and Helpman (1994), in a monopolistic competitive environment. We obtain that increased sectorial dispersion cause a fall in equilibrium tariff provided that the exporter’s cutoff is above the mean of the distribution. Also, higher average productivity brings about a fall in the equilibrium tariff, whereas an increase in export costs cause an increase in the tariff. JEL Classification codes: D43, D7, F12, F13, L11
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De, Snaijer Mark. "On the heterogeneity of firms /." Berlin : Dissertation.de Verlag im Internet, 1999. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Hoermann, Gudrun. "Mortality heterogeneity and life insurance /." [S.l.] : [s.n.], 2009. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000293554.
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Hutnik, Cindy Mary-Lynn. "The conformational heterogeneity of proteins." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5844.
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Time-correlated single photon counting and steady-state fluorescence spectroscopy were used to investigate the conformational properties of select proteins. Specifically, the role of naturally associated metal ions in modulating the conformation of members from two families of metalloproteins was examined. Two homologous bacterial copper-containing azurins were purified from Pseudomonas fluorescens (ATCC 13525) and Pseudomonas aeruginosa (ATCC 10145). The intrinsic fluorescence of the native Cu(II) single tryptophan-containing protein, as well as experimentally prepared Cu(I), Ni(II), Co(II) and metal-free derivatives demonstrated that the metal centre of these redox proteins played an important role in the conformational heterogeneity of the protein. Such an effect was strongly dependent on the nature of the metal ion. From the calcium-binding superfamily, the single-tryptophan containing isotype III component of parvalbumin was purified from codfish. The previous notion that this protein was a Ca(II)/Mg(II)-specific protein was shown to be due to an experimental artefact arising from the use of the soluble chelator EGTA. The Ca(II)-specific conformational changes of cod III parvalbumin were compared with those of the highly homologous Ca(II)-binding tumour protein oncomodulin. Since native tumour oncomodulin was devoid of tryptophan, a site-specific mutant of oncomodulin with tryptophan in the identical position of the parvalbumin tryptophan was examined. The results showed that the ability of oncomodulin to function as a modulator (unlike parvalbumin) may be due to relatively subtle Ca(II)-specific conformational changes. Details of these changes were obtained by an examination of a number of oncomodulin mutant proteins in which the non-fluorescent phenylalanine, and the highly fluorescent tryptophan had been substituted into various positions of the two Ca(II)-binding loops. The results demonstrated that the binding of the first equivalent of Ca(II) induced greater than 90% of the conformational changes experienced by various probed positions, but that the second equivalent of Ca(II) played an important role in orienting the two Ca(II)-binding loops relative to each other.
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Boneng, Yus T. "Weibull frailty for modelling heterogeneity." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ61968.pdf.
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Vamvakidou, Alexandra P. T̈ozeren Aydin. "Phenotypic heterogeneity of breast tumors /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1777.
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Botman, Dennis Petrus Johannes. "Globalization, heterogeneity, and imperfect information." [Amsterdam : Amsterdam : Thela Thesis] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/59482.
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McCarthy, Sean Patrick. "Studies on human macrophage heterogeneity." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238184.
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Michelacci, Claudio. "Growth with cross-sectional heterogeneity." Thesis, London School of Economics and Political Science (University of London), 1998. http://etheses.lse.ac.uk/2243/.
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Different agents experience different histories and pursue different economic functions. This implies that once a picture of the economic system is taken, a lot of cross-sectional heterogeneity appears. This thesis consists of four essays each one of them makes a case where the intrinsic heterogeneity of the economic system is crucial for understanding macroeconomic performance. Firstly, it shows when and how an increase in the level of business cycle volatility harms the growth process in a Keynesian world where the decision to free resources and to take advantage of them lies on different agents. Secondly, it analyses the effects of an increase in research effort in a Schumpeterian world where innovation requires an entrepreneur to implement a valuable invention. In this context the observed decreasing returns in R&D might be the outcome of lack of entrepreneurial skills rather than any vanishing of investment opportunities. Thirdly, it extends the Solow-Swan growth model allowing for cross-sectional heterogeneity. In doing so it reconciles apparently conflicting results on cross-sectional convergence and stochastic output dynamics. Finally, it argues that cross-sectional heterogeneity is an important transmission mechanism. In the context of a stylized vintage model it is shown how the mechanism generating heterogeneity in the real world also generates persistence in the aggregate fluctuations. Moreover, as aggregate shocks create very high degree of persistence without affecting either the number of firms in the market or technological progress, this degree of persistence is simply attributed to cross-sectional heterogeneity.
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Cullen, Mark Allan. "Heterogeneity of the fossilisation process." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299718.
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Robinson, Monique Samantha Chantal. "An investigation into platelet heterogeneity." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271085.
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Mathis, Robert Austin. "Intra-tumor heterogeneity and evolution." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113432.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Although the treatment of cancer is a major focus of biomedical research, many cancers are extremely hard to treat. Tumors likely resist treatment because each tumor is heterogeneous, and can evolve. Although tumor evolution has long been appreciated, it remains incompletely understood. In this thesis, I will explore two questions related to cancer heterogeneity and evolution: how evolution can affect plastic phenotypes, and the role of purifying selection in cancer evolution. Different cell states or phenotypes have been observed within tumors, and they are associated with treatment resistance and metastasis. The observation that these phenotypes are plastic leads to a conundrum: how can selection act on such an unstable phenotype? We determined that plasticity, in the form of cell state bias, varies widely across clones in a tumor. These different biases are heritable, with each cell faithfully passing its differentiation bias to its daughters. Simulations revealed that this makes plasticity an evolvable phenotype--- in a changing environment, an optimal state bias will be selected. The second question explored in this thesis is the role of purifying selection in cancer evolution. It is widely thought that tumor evolution is dominated by positive selection. We posited that, as in the evolution of species, purifying selection would prevent the fixation of deleterious mutations in tumors. Through computational analysis of tumor genomes, we determined that purifying selection acts to remove deleterious mutations. Genes under purifying selection must be important to tumors in vivo, as only mutations in these genes would be problematic. Consistent with this prediction, most genes under purifying selection in tumors were essential in cancer cell lines. To find genes essential to tumors but not generally cell-essential, we developed a method to find genes under increased purifying selection in one tumor type over others. This revealed a number of pathways under selection in melanomas, but not other tumor types, such as DNA damage pathways. By seeking genes important to tumors, but not generally essential, our analysis revealed potential therapeutic targets. Purifying selection offers an unprecedented view into which genes are essential to tumors in vivo, a finding predominantly inaccessible through experimentation.
by Robert Austin Mathis.
Ph. D.
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Scott, Alison Catherine. "Heterogeneity in high-shear granulation." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621989.
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Larsen, Morten. "Benthic mineralization and microscale heterogeneity." Thesis, University of the Highlands and Islands, 2012. https://pure.uhi.ac.uk/portal/en/studentthesis/benthic-mineralization-and-microscale-heterogeneity(24f26190-b99d-4fda-b070-8944b117734e).html.
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Traditionally, marine sediments are viewed as horizontally layered structures. However, in recent decades there has been growing awareness of the naturally occurring microscale heterogeneity affecting the biogeochemical functioning. Studies on microscale dynamics have been facilitated by recent developments of high resolution sensors for 2-dimensional chemical imaging. The presented work has contributed to this development by introducing a simple, robust and inexpensive 2-dimensional imaging system, which has made the approach accessible to a much wider user-group. The presented study utilizes the advances in chemical imaging to study benthic processes in systems, where the natural function of microscale heterogeneity has been ignored or improperly appreciated. The results confirm the importance of natural heterogeneity in benthic ecosystem functioning including: trace metal mobilization, microbial abundance/activity and localized increased concentrations of electron donors. The combined findings highlight the need for high spatial resolution to achieve a full conceptual and quantitative understanding of benthic microbial systems. The current work has opened a number of avenues for future work on microscale patchiness. This especially includes; I) Plant and microorganism effects on rhizosphere biogeochemistry; II) Microscale heterogeneity of microbial abundance, diversity and function; III) Fauna induced microscale heterogeneity and structure.
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Lee, Soyoung. "Micro Heterogeneity and Macro Implications." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1591019323932109.
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Ribeiro, Joel Gustavo Silva. "European heterogeneity in Horizon 2020." Master's thesis, FEUC, 2016. http://hdl.handle.net/10316/31844.
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Relatório de estágio do mestrado em Economia (Economia de Crescimento e Políticas Estruturais), apresentado à Faculdade de Economia da Universidade de Coimbra, sob a orientação de Pedro Godinho.Este relatório de estágio, efetuado na ISA – Intelligent Sensing Anywhere, onde trabalhamos de perto com os programas de incentivos europeus, discute a heterogeneidade europeia em Investigação & Desenvolvimento e na Inovação, nomeadamente no programa Horizonte 2020 (via proxy “SME instrument”). Esta questão torna-se relevante com a dificuldade da Europa em competir com a concorrência asiática enquanto, dentro da união, os novos membros aparentam ser incapazes de convergir na direção da vanguarda em inovação. Nós analisamos os dados da participação no “SME instrument” (um canal exclusivo a PMEs – Pequenas e médias empresas) para expor os padrões de participação dos países e as tendências atuais. Os resultados corroboram firmemente a hipótese de não-convergência entre EU15 e EU13, no entanto, apesar disto, existem casos discordantes, como a Estónia e a Eslovénia, casos aqui desenvolvidos em dois casos de estudos. Novas questões também emergiram como o aparecimento de uma periferia Sul na Europa e indicadores de apatia nos países do ‘coração’ europeu. Concluímos com uma serie de recomendações de politicas para reverter o atual cenário e trazer convergência para a excelência, reforçando assim o papel da Europa no sistema de I&D e Inovação mundial.
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McSheffrey, Robert (Robert Michael) Carleton University Dissertation Psychology. "The heterogeneity of the gifted." Ottawa, 1989.
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Wiermann, Christian. "Four Essays on Individual Heterogeneity." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-23571.
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Rudland, Victoria Louise. "HETEROGENEITY OF GESTATIONAL DIABETES MELLITUS." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15872.
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Gestational diabetes mellitus (GDM) is a complex, heterogeneous disorder. As the prevalence of GDM increases, it is increasingly important to identify subgroups of women within the GDM umbrella whose pathophysiology and associated pregnancy risk necessitates a different management approach in order to optimise maternal and neonatal outcomes. Glucokinase maturity-onset diabetes of the young (GCK-MODY) and islet autoimmunity are two such clinical entities. Recently, new pregnancy-specific screening criteria (NSC) for GCK-MODY were proposed to identify women with GDM who warrant GCK genetic testing. We tested the NSC and HbA1c in a multiethnic GDM cohort. The prevalence of GCK-MODY in women with GDM was ~1%. The NSC performed well for Anglo-Celtic women, but less well for women from other ethnic backgrounds. Antepartum HbA1c was not higher in those with GCK-MODY. We report the first two cases of antepartum fetal GCK genotyping and demonstrate how knowledge of fetal GCK genotype guides the management of maternal hyperglycaemia. We examined the prevalence, clinical significance and antepartum to post-partum trajectory of glutamic acid decarboxylase autoantibodies (GADA), insulinoma-associated antigen-2 autoantibodies (IA-2A), insulin autoantibodies (IAA) and zinc transporter 8 autoantibodies (ZnT8A) in a multiethnic GDM cohort. 9.9% of women were positive for one islet autoantibody antepartum. No participant had multiple islet autoantibodies. ZnT8A were the most common islet autoantibody. For women with positive GADA, IA-2A or IAA antepartum, islet autoantibody positivity typically persisted post-partum and 20% of women had post-partum glucose levels consistent with diabetes. In contrast, women with positive ZnT8A antepartum typically demonstrated normal ZnT8A titres post-partum and normal post-partum glucose tolerance. ZnT8A may be a marker for islet autoimmunity in a proportion of women with GDM, but the clinical relevance of ZnT8A in GDM needs further research.
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POSCHKE, Markus. "Firm heterogeneity and macroeconomic performance." Doctoral thesis, European University Institute, 2007. http://hdl.handle.net/1814/10310.
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Defence date: 7 December 2007Examining Board: Prof. Omar Licandro, (EUI) ; Prof. Salvador Ortigueira, (EUI) ; Prof. Russell Cooper, (University of Texas at Austin) ; Prof. Jaume Ventura, (CREI, Universitat Pompeu Fabra)
PDF of thesis uploaded from the Library digital archive of EUI PhD theses
The regulation of entry and aggregate productivity Euro Area economies have lower firm turnover rates, lower total factor and labor productivity, and higher capital intensity than the Unites States. I argue that differences in entry cost contribute to this pattern by affecting firms' technology choice. Introducing technology choice into a standard heterogeneous firm model, small differences in administrative entry cost suffice to explain 10-20% of differences in total factor productivity and the capital-output ratio. The productivity difference arises because higher equilibrium capital intensity acts as an entry barrier and protects low-productivity incumbents. Both firm heterogeneity and technology choice are crucial for strengthening results compared to previous studies. 2 Employment protection, firm selection, and growth This paper analyzes the effect of ring costs on aggregate productivity growth. For this purpose, a model of endogenous growth through selection and imitation is developed. It is consistent with recent evidence on firm dynamics and on the importance of reallocation for productivity growth. In the model, growth is driven by selection among heterogeneous incumbent firms, and is sustained as entrants imitate the best incumbents. In this framework, firing costs not only induce misallocation of labor, but also affect growth by affecting firms' exit decisions. Importantly, charging firing costs only to continuing firms raises growth by promoting selection. Also charging them to exiting firms is akin to an exit tax, hampers selection, and reduces growth { by 0.1 percentage points in a calibrated version of the model. With job turnover very similar in the two settings, this implies that the treatment of exiting firms matters for welfare. In addition, the impact on growth rates is larger in sectors where firms face larger idiosyncratic shocks, as in services. This fits evidence that recent EU-US growth rate differences are largest in these sectors and implies that firing costs can play a role here. A brief empirical analysis of the impact of firing costs on the size of exiting firms supports the model's conclusions. 3 The labor market, the decision to become an entrepreneur, and the firm size distribution Why do some people become entrepreneurs, and how do labor markets affect this choice? This paper addresses this question using a matching model with occupational choice and heterogeneity in both ability as a worker and ex ante unknown productivity of firm start-ups. Key effects are the following: labor market conditions affect incentives to start firms differently for workers and the unemployed, with repercussions on aggregate productivity; and they affect the expected value of firm creation due to the possibility of failure. These effects go beyond the standard impact of labor market conditions on firms' employment policy and value. The correlation of observed productive ability and potential productivity significantly shapes the firm size distribution, suggesting that the empirical correlation is positive but far from perfect. Finally, the model allows for a comparatively flexible lower tail of the firm size distribution and can explain the existence and persistence of small, lowproductivity firms with low profits: their owners have low outside options in the labor market.
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Acosta, Ojeda Carmelo Alexis. "Heterogeneity-awareness in multithreaded multicore processors." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/6016.
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During the last decades, Computer Architecture has experienced a great series of revolutionary changes. The increasing transistor count on a single chip has led to some of the main milestones in the field, from the release of the first Superscalar (1965) to the state-of-the-art Multithreaded Multicore Architectures, like the Intel Core i7 (2009).Moore's Law has continued for almost half of a century and is not expected to stop for at least another decade, and perhaps much longer. Moore observed a trend in the process technology advances. So, the number of transistors that can be placed inexpensively on an integrated circuit has increased exponentially, doubling approximately every two years. Nevertheless, having more available transistors can not be always directly translated into having more performance.
The complexity of state-of-the-art software has reached heights unthinkable in prior ages, both in terms of the amount of computation and the complexity involved. If we deeply analyze this complexity in software we would realize that software is comprised of smaller execution processes that, although maintaining certain spatial/temporal locality, imply an inherently heterogeneous behavior. That is, during execution time the hardware executes very different portions of software, with huge differences in terms of behavior and hardware requirements. This heterogeneity in the behaviour of the software is not specific of the latest videogame, but it is inherent to software programming itself, since the very beginning of Algorithmics.
In this PhD dissertation we deeply analyze the inherent heterogeneity present in software behavior. We identify the main issues and sources of this heterogeneity, that hamper most of the state-of-the-art processor designs from obtaining their maximum potential. Hence, the heterogeneity in software turns most of the current processors, commonly called general-purpose processors, into overdesigned. That is, they have much more hardware resources than really needed to execute the software running on them. This fact would not represent a main problem if we were not concerned on the additional power consumption involved in software computation.
The final goal of this PhD dissertation consists in assigning each portion of software exactly the amount of hardware resources really needed to fully exploit its maximal potential; without consuming more energy than the strictly needed. That is, obtaining complexity-effective executions using the inherent heterogeneity in software behavior as steering indicator. Thus, we start deeply analyzing the heterogenous behaviour of the software run on top of general-purpose processors and then matching it on top of a heterogeneously distributed hardware, which explicitly exploit heterogeneous hardware requirements. Only by being heterogeneity-aware in software, and appropriately matching this software heterogeneity on top of hardware heterogeneity, may we effectively obtain better processor designs.
The PhD dissertation is comprised of four main contributions that cover both multithreaded single-core (hdSMT) and multicore (TCA Algorithm, hTCA Framework and MFLUSH) scenarios, deeply explained in their corresponding chapters in the PhD dissertation memory. Overall, these contributions cover a significant range of the Heterogeneity-Aware Processors' design space. Within this design space, we have focused on the state-of-the-art trend in processor design: Multithreaded Multicore (CMP+SMT) Processors.
We make special emphasis on the MPsim simulation tool, specifically designed and developed for this PhD dissertation. This tool has already gone beyond this PhD dissertation, becoming a reference tool by an important group of researchers spread over the Computer Architecture Department (DAC) at the Polytechnic University of Catalonia (UPC), the Barcelona Supercomputing Center (BSC) and the University of Las Palmas de Gran Canaria (ULPGC).
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Bauducco, Sofia. "Optimal policy heterogeneity and limited commitment." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7394.
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Esta tesis contribuye a la literatura de política fiscal y monetaria óptima. Primero analizo cómo el resultado de tasas impositivas suaves, que habitualmente se obtiene en modelos de política fiscal óptima, se ve alterado en un contexto de división internacional de riesgo con compromiso parcial. Encuentro que la presencia de compromiso parcial altera significativamente la dinámica de las variables fiscales, con respecto al caso de compromiso total. La volatilidad de la tasa impositiva aumenta. En segundo lugar, estudio la política fiscal y monetaria en un modelo con shocks idiosincráticos no asegurables a la productividad laboral. Encuentro que, cuando el gobierno es utilitarista, la autoridad monetaria fija la tasa de interés nominal a cero. Los efectos agregados de bienestar son pequeños, mientras que los efectos individuales son grandes. Los beneficiarios de la inflación son agentes pobres con baja productividad, mientras que los agentes de clase media y alta siempre son perdedores.This thesis contributes to the literature on optimal fiscal and monetary policy. First, I analyze how the tax-smoothing result obtained in models of optimal fiscal policy is altered in a context of international risk sharing with limited commitment. I find that the presence of limited commitment alters substantially the dynamics of the fiscal variables with respect to the full commitment case. In particular, the volatility of the tax rate increases. Second, I study the optimal monetary and fiscal policy mix in a model in which agents are subject to idiosyncratic uninsurable shocks to their labor productivity. I find that, for a utilitarian government, the monetary policy-maker sets nominal interest rates to zero. Although the aggregate welfare costs of inflation are small, individual costs and benefits are large. Net winners from inflation are poor, less productive agents, while middle-class and rich households are always net losers.
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Caracciolo, Giacomo. "Essays on heterogeneity and macroeconomic dynamics." Doctoral thesis, Universitat Pompeu Fabra, 2019. http://hdl.handle.net/10803/668366.
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Limited asset market participation is a well-known stylized fact and a widespread phenomenon
even in developed economies. While existing models have already examined
the effects of social security and its reforms on welfare and inequality, little attention
has been devoted to the role of public pensions in the context of limited asset market
participation. I develop a quantitative overlapping generations general equilibrium
model where heterogenous agents face a financial friction limiting access to capital markets.
I examine how, in presence of the market imperfection, a public pay-as-you-go
system affects consumption and wealth inequality and compare the results with a standard
model that does not account for limited asset market participation. In a second
exercise, I study the implications, in terms of inequality, of an increase in the retirement
age in response to a population ageing shock. I find that limited asset participation is
important for the analysis of the impact of social security on overall inequality and on
inequality within age groups.
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Chang, Kwangpil. "Essays on heterogeneity in choice modeling." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ34537.pdf.
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Nilsson, William. "Equality of opportunity, heterogeneity and poverty." Doctoral thesis, Umeå : Umeå University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-518.
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Bauducco, Sofia. "Optimal policym heterogeneity and limited commitment." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7394.
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Esta tesis contribuye a la literatura de política fiscal y monetaria óptima. Primero analizo cómo el resultado de tasas impositivas suaves, que habitualmente se obtiene en modelos de política fiscal óptima, se ve alterado en un contexto de división internacional de riesgo con compromiso parcial. Encuentro que la presencia de compromiso parcial altera significativamente la dinámica de las variables fiscales, con respecto al caso de compromiso total. La volatilidad de la tasa impositiva aumenta. En segundo lugar, estudio la política fiscal y monetaria en un modelo con shocks idiosincráticos no asegurables a la productividad laboral. Encuentro que, cuando el gobierno es utilitarista, la autoridad monetaria fija la tasa de interés nominal a cero. Los efectos agregados de bienestar son pequeños, mientras que los efectos individuales son grandes. Los beneficiarios de la inflación son agentes pobres con baja productividad, mientras que los agentes de clase media y alta siempre son perdedores.This thesis contributes to the literature on optimal fiscal and monetary policy. First, I analyze how the tax-smoothing result obtained in models of optimal fiscal policy is altered in a context of international risk sharing with limited commitment. I find that the presence of limited commitment alters substantially the dynamics of the fiscal variables with respect to the full commitment case. In particular, the volatility of the tax rate increases. Second, I study the optimal monetary and fiscal policy mix in a model in which agents are subject to idiosyncratic uninsurable shocks to their labor productivity. I find that, for a utilitarian government, the monetary policy-maker sets nominal interest rates to zero. Although the aggregate welfare costs of inflation are small, individual costs and benefits are large. Net winners from inflation are poor, less productive agents, while middle-class and rich households are always net losers.
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Durnin, Anne Theresa. "Secretory heterogeneity among anterior pituitary gonadotrophs." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358632.
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Hulme, T. "Seismic scattering from small-scale heterogeneity." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604769.
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This dissertation is concerned with the scattering of waves by features which are on a sub-wavelength length scale. Although these features cannot be easily resolved, they may still cause significant wave scattering, and the general problem is to understand the situations under which this occurs, and the effects that it may have. A specific example of this generic problem is given by considering seismic wave propagation through sedimentary sequences. Channelisation in such sequences causes lateral variation on a length scale (5-30 m) that is comparable to, or smaller than, typical wavelengths used in seismic exploration. The effects of this variation on wave propagation are investigated using a combination of numerical modelling and experimental work. The Mount Messenger formation in North Taranaki, New Zealand is taken as a prototype sedimentary sequence. This sequence provides a superb exposure of slightly dipping turbidites and has been the subject of previous detailed outcrop studies. Field observations taken from this sequence have been used to build well-constrained, albeit simplified, models of typical channel and other sub-wavelength features. The elastic wave equation is solved for these models using new methodology, which reformulates the classical partial differential boundary value problem as a set of two first order initial value problems. A spectral expansion means that these initial value problems become ordinary differential equations, which can then be solved to a very high degree of precision. The resulting synthetic seismograms show that the sub-wavelength geometrical formations cause significant wave scattering, and that this scattering can introduce artefacts after simple processing steps. A high-resolution seismic reflection experiment has been carried out on the Mount Messenger formation, and processed sections from this experiment display features which can be interpreted as being analogous to the artefacts seen in the synthetic results.
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Lopes, Carlos J. "THE PUBLIC SECTOR, MIGRATION, AND HETEROGENEITY." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/38.
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Questions on the optimal size of government always provoke intense political debate. At the center of this is the public goods problem, where certain goods and services are “under-provided” by the market due to problems with rivalry and excludability. These goods are usually provided by the public sector and financed through taxes. Questions emerge over the optimal level of provision, as different individuals value these goods differently. This dissertation consists of two studies which address preferences for the size of government from different perspectives.
The first study provides a method that can be used to estimate demand for changes in levels of public provision. Using individual level Census data on migration from 1990 and 2000, I demonstrate how preferences are revealed through migration responses. Though policy convergence precludes the estimation of optimal levels for different demographic groups, I find that balanced-budget increases in education expenditures tend to attract most demographic groups while other expenditures tend to repel most individuals. Young, college educated, relatively high-income individuals tend to be more responsive to, and therefore appear to have higher preference intensity for, fiscal changes. This is true even when controlling for their increased propensity to migrate. Evidence inconsistent with welfare migration is found, suggesting that policies intended to address the race-to-the-bottom in welfare benefits may be counterproductive. In addition, the ability of the Tiebout migration process to homogenize a jurisdiction is limited by relatively small fiscal changes among jurisdictions and similar migration responses among demographic groups.
The second study empirically explores the effect of ethnic heterogeneity on government size for countries throughout the world. In the developed world, heterogeneity is found to reduce the size of budgetary government, consistent with previous studies and predictions in the literature. In the undeveloped world, however, heterogeneity is found to increase the size of non-budgetary government and may increase the overall size of government.
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Frühwirth-Schnatter, Sylvia, Regina Tüchler, and Thomas Otter. "Bayesian analysis of the heterogeneity model." SFB Adaptive Information Systems and Modelling in Economics and Management Science, WU Vienna University of Economics and Business, 2002. http://epub.wu.ac.at/678/1/document.pdf.
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In the present paper we consider Bayesian estimation of a finite mixture of models with random effects which is also known as the heterogeneity model. First, we discuss the properties of various MCMC samplers that are obtained from full conditional Gibbs sampling by grouping and collapsing. Whereas full conditional Gibbs sampling turns out to be sensitive to the parameterization chosen for the mean structure of the model, the alternative sampler is robust in this respect. However, the logical extension of the approach to the sampling of the group variances does not further increase the efficiency of the sampler. Second, we deal with the identifiability problem due to the arbitrary labeling within the model. Finally, a case study involving metric Conjoint analysis serves as a practical illustration. (author's abstract)Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"
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Sandin, Rickard. "Heterogeneity in oligopoly : theories and tests." Doctoral thesis, Handelshögskolan i Stockholm, Samhällsekonomi (S), 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:hhs:diva-867.
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This dissertation consists of five separate chapters, of which the three first three are empirical and the last two are theoretical. Chapter 1: Competition in Interrelated Markets: An Empirical Study. (Co-authored with Marcus Asplund.)This chapter studies competition in small, concentrated and interrelated markets. Our data set consists of price information from 543 driving schools in 250 local markets in Sweden, which gives a large sample to test hypotheses on how market structure influences competition. The results show that if prices in nearby markets are low, and the distances to them are short, it reduces prices, as suggested in models of spatial competition. Moreover, we find that prices in closely located markets are interdependent. It is also shown that prices are increasing in firm concentration within a market, as most theories of oligopoly predict. Chapter 2: Estimating the Number of Firms and Capacity in Small Markets. (Co-authored with Marcus Asplund.)Many oligopoly theories predict that there will be a positive correlation between market size and the equilibrium number of firms, and some also imply that competition is more intense in larger markets. We test these predictions with a sample of 535 driving schools in 249 markets. With an ordered Probit, a Tobit, and a Poisson model we estimate the relation between the number of firms, capacity, and market size. We find a strong positive correlation between market size and the number of firms. The results show that the per firm market size is increasing in the number of firms in the market. The market size per capacity unit is smaller in large markets. Since the industry produces a fairly homogenous good, we argue that this is evidence that competition is increasing in market size. Chapter 3: The Survival of New Products. (Co-authored with Marcus Asplund.)We study the product turnover in an industry and, in particular, the survival of new products. The data set consists of monthly sales of all products sold in the Swedish beer market over the time period of 1989-1995. The death rates of newly introduced products are high - out of 199 products an estimated 25 percent were withdrawn within 18 months and 50 percent within approximately 48 months. We use parametric duration models with time varying covariates to estimate survival functions. Our results show that products with low and decreasing market shares have higher hazard rates. Moreover, the hazard rates are dependent on the characteristics of the producer. Products from firms with a large number of other products, and (to a lesser extent) the largest market shares are more likely to be withdrawn. Chapter 4: Uniform Subsidy Reductions in International Oligopoly.This chapter studies the effect of production subsidies used as strategic instruments by two rivalling countries whose firms differ in production efficiency. In particular, it examines the welfare effects of a uniform subsidy reduction from the Cournot-Nash equilibrium under different assumptions regarding technology and taste. It is found that the net exporter (usually the efficient country) gains while the net importer (usually the inefficient country) loses from a uniform subsidy reduction. Results show that a non-linear demand function or marginal cost functions with different slopes across countries is necessary to obtain an increase in total welfare.Chapter 5: Subsidies in Oligopoly Markets: A Welfare Comparison between Symmetric and Asymmetric Costs. (Co-authored with Stephen F. Hamilton.)This chapter studies welfare effects of uniform production subsidies in oligopoly markets, comparing cases of symmetric and asymmetric costs. Cost asymmetry reduces the impact relative to the symmetric-cost case if the deman function is concave and magnifies the impact if demand is convex. The welfare difference increases with the degree of market power and the cost differential in the industry.Diss. Stockholm : Handelshögsk. : 1997
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Berrish, Taher S. "Metabolic heterogeneity in impaired glucose tolerance." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321310.
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Reid, Alistair Gordon. "Genomic heterogeneity in Philadelphia positive leukaemias." Thesis, Anglia Ruskin University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269108.
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DIAS, RODRIGO ARAUJO CARDOSO. "WELLS PRODUCTIVITY IN HIGH HETEROGENEITY RESERVOIRS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32970@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
A previsão da produção de poços tem um papel crucial na engenharia de petróleo. Logo, a modelagem do escoamento no reservatório e no poço é fundamental em diversos problemas nessa área. Na maioria esmagadora dos problemas, a equação de Darcy é a escolha para prever o comportamento do fluxo em rochas petrolíferas. O grande sucesso do uso da equação de Darcy, infelizmente, levou sua aplicação para fora do âmbito dos problemas para os quais esta se aplica. A equação clássica de Darcy apresenta limitações quando aplicadas em meios porosos altamente heterogêneos, por exemplo com cavidades conectadas por redes de fraturas, com vugs e cavernas. Ao longo dos anos, outras modelagens foram propostas e derivadas de outros pontos de vista para tratar o escoamento em meios porosos, por exemplo, através do processo de média de volume ou através de teoria de mistura. O presente trabalho utiliza as equações médias em meios porosos. O modelo desenvolvido contabiliza termos adicionais para a equação de quantidade de movimento linear que são relevantes em várias situações práticas, e envolve a solução conjunta das equações de conservação. No modelo desenvolvido neste trabalho, o escoamento no reservatório é resolvido de forma acoplada ao escoamento ao longo do poço, considerando a possibilidade de utilização de diferentes tipos de completação. As previsões dos campos de pressão e velocidade, assim como a produtividade de poços de petróleo utilizando o modelo desenvolvido são comparadas com as previsões do modelo baseado na equação de Darcy. Mostra-se que para determinadas situações, em especial em reservatórios carbonáticos, altamente heterogêneos, grandes diferenças podem ser obtidas. A previsão da produtividade de um poço a partir da equação de Darcy pode ser significativamente super-estimada.
Predicting wellbore production plays a crucial role in petroleum engineering. Therefore, the modeling of the ow in reservoir and in wellbore is fundamental in several problems in this area. In the overwhelming majority problems, Darcy s equation is the choice to predict the behavior of ow in reservoirs. The great success of Darcy s equation, unfortunately, took its application out of the scope of the problems for which it applies. The classic Darcy s equation presents limitations when applied in highly heterogeneous porous media, for example with cavities connected by fracture networks, with vugs and caves. Over the years, other models have been proposed and derived from other points of view to treat ow in porous media, for example through the average volume process or through mixture theory. The present work considers the average volume process in porous media. The developed model includes additional terms for the linear momentum equation that are relevant in several practical situations, and involves the joint solution of conservation equations. In the model developed in this work, the ow in the reservoir is solved coupled to the wellbore ow, considering the possibility of using different completion types. The pressure and velocity fields predictions as well as the productivity of oil wellbores using the developed model are compared with the predictions of the model based on the Darcy s equation. It is shown that for certain situations, especially in highly heterogeneous carbonate reservoirs, large differences can be obtained. The prediction of the productivity of a wellbore from the Darcy s equation can be significantly overestimated.