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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Essays in International Macroeconomics

Dmitriev, Mikhail January 2014 (has links)
Thesis advisor: Fabio Ghironi / Thesis advisor: Susanto Basu / My dissertation develops a set of tools for thinking about heterogeneity in economic models in an analytically tractable way. Many models use the representative agent framework, which greatly simplifies macroeconomic aggregation but abstracts from the heterogeneity we see in the real world. Models with heterogeneity in general equilibrium have too many moving parts, so that it is hard to disentangle cause and effect. First, my work in international macroeconomics incorporates heterogeneity via idiosyncratic shocks across countries in a simple and analytical way. Second, my work on financial frictions helps to understand the role of asymmetric information between lenders and borrowers in different contractual environments. Crucially, these insights can be incorporated into the models currently used by academics and central banks for policy analysis. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.
12

Strategic complementarity and endogenous heterogeneity in oligopolistic markets

Knauff, Malgorzata 10 January 2006 (has links)
The thesis consists of five chapters. The first of them contains introduction. Chapter 2 considers a broad class of two player symmetric games, which display a fundamental non-concavity when actions of both players are about to be the same. This implies that no symmetric equilibrium is possible. We distinguish different properties of the payoff functions, like strategic substitutes, complements and quasi-concavity, which are not necessarily imposed globally on the joint action space. For each of these cases we provide conditions to secure the existence of exclusively asymmetric equilibria. Moreover we consider the case of convex payoff functions. A number of applications from industrial organization and applied microeconomics literature are provided. In Chapter 3 we generalize to the extent possible the known results for the case of games with one-dimensional action sets to the general case of games with strategic complemantarities with action spaces that are complete lattices. One key issue addressed is the extent to which all equilibria tend to be symmetric for the general case of multi-dimensional (i.e. only partially ordered) strategy spaces. We find that the scope for asymmetric equilibrium behavior is definitely broader than in the one-dimensional case, though still quite limited. Another key question investigated here is whether asymmetric pure strategy Nash equilibria are always Pareto dominated by symmetric pure strategy Nash equilibria. While this need not hold in general for games with strategic complementarities, we identify different sufficient conditions that guarantee that such dominance holds. In Chapter 4 we deal with the effects of market transparency on prices in the Bertrand duopoly model. The analysis is intuitive and simple when we consider two types of strategic interaction between firms in an industry - strategic complementarities and substitutabilities. We present also traditional comparative statics analyses, demanding additionally some other regularity conditions, to cover those problems, when neither of these situations is the case. In the first case, the results are close to conventional wisdom, especially, when in the same time products are substitutes. Namely, equilibrium prices and profits are always decreasing in transparency level, while the consumer's surplus is increasing. For a special case when supermodularity holds, but products are not substitutes, the result on profits is not valid anymore. Considering price competition with strategic substitutes, an ambiguity in the direction of change of prices appears. This leads to ambiguity concerning equilibrium profits and surplus changes caused by increasing transparency. In Chapter 5 we provide general conditions for Cournot oligopoly with product differentiation to have monotonic reaction correspondences. We give a proof for the conditions stated by Vives (1999). Moreover we elaborate more general requirements. They allow for identifying increasing best responses even in case inverse demand is submodular, and similarly, decreasing best responses in case of supermodular inverse demand. Examples illustrating the scope of applicability of these results are provided.
13

Microbial adaptations and controlling mechanisms of surface-associated microhabitat heterogeneity in aquatic systems

Jeske, Jan Torsten January 2015 (has links)
Habitat heterogeneity is a driving factor for speciation and ecosystem functioning and is well studied in macro-ecology. Yet our understanding of microbial adaptations, and governing processes is incomplete. The here presented thesis aims at giving us a better understanding of patterns in micro-heterogeneity, and microbial adaptations to such heterogeneity with particular focus on surface-dominated, aquatic habitats. The most prominent microbial adaptation to surface associated mode of life is biofilm formation. Biofilms rely heavily on type IV pili. These pili systems are well studied in Bacteria, but largely unknown in Archaea. Therefore, the first part of this thesis focuses on resolving genetic and structural feature of the type IV like aap-pilus of the thermo-acidophilic Sulfolobus acidocaldarius. We found the aap-pilus to be indispensible for biofilm formation, and to be unparalleled in variability of its quaternary structure and cross regulation with other filaments. The second part of this thesis investigates particle colonization in the water column, focusing on diatoms as a model system, allowing an in situ assessment of different stages of particle colonization, and potential particle-specificity of the associated bacterial community. Opposing reports from marine systems, we did not observe diatom-specificity in the associated bacterial community. Instead we found bacterial community subsets, one likely originating from sediment resuspension, and the other being controlled by biofilm-forming populations (e.g. Flexibacter), able to attach to newly formed particle surfaces and subsequently facilitate secondary colonization by other bacteria. Finally, the habitat heterogeneity in top-layers of lake sediments were investigated in experimental microcosms. Cell-specific oxygen consumption rates were determined, to assess microbial activity across different scales. Individual activity rates differed strongly across all investigated scales, likely due to spatially heterogeneous distribution of nutrients with differing quality. Vice versa, the influence of microbial activity on micro-habitat-heterogeneity was investigated. We correlated sediment redox-state with bacterial community composition and populations. Our results indicate that habitat heterogeneity is generally beneficial for microorganism, and greater heterogeneity results in greater bacterial diversity. However, this heterogeneity-diversity relationship is limited and microorganisms actively stabilize their immediate redox environment to a preferred, community-specific, stable state, if cell abundances exceed a minimum threshold.
14

Adaptive genetic variation in Scots pine (Pinus sylvestris L.) in Scotland

Salmela, Matti Juhani January 2011 (has links)
Genetic differentiation in phenotypic traits among populations from heterogeneous environments is often observed in common-garden studies on forest trees, but data on adaptive variation in Scots pine (Pinus sylvestris L.) in Scotland are limited. As a result, current seed transfer guidelines are based on earlier molecular marker studies and do not take into account environmental or adaptive genetic variation. An analysis of spatial variation in climate showed substantial differences in temperature and precipitation among the native Scots pine sites in Scotland. To investigate whether differentiation in response to environmental variation has occurred in Scotland, a glasshouse-based common-garden trial of ~3,360 seedlings from 21 populations and 84 open-pollinated families was established in 2007. At the beginning of the 2nd growing season, timing of bud flush showed evidence of genetic differentiation among populations, with those from cooler origins generally flushing earlier. Variation was also found among families within populations, suggesting that the trait is genetically controlled. Populations and families showed different levels of variability in this trait which could be partly due to variable levels of temporal climate fluctuation in different parts of Scotland. Chlorophyll fluorescence was used to examine drought response in three-year old seedlings from five populations on sites that experience contrasting levels of annual rainfall. It was found that the response was not related to rainfall, but possibly to more complex moisture variables that also take into account additional factors such as evaporation. Also, photosynthetic capacity in response to cold winter temperatures varied significantly among eight populations that were kept outdoors, and the largest reduction was seen in seedlings from the mildest, most maritime coastal site. The following spring, height growth and needle flush started earlier in seedlings from cooler locations. Earlier studies on genetic diversity of native pinewoods have shown high levels of selectively neutral variation in this predominantly outcrossing conifer, and a mating system analysis with a limited number of microsatellite markers supported this pattern. Together, these data suggest that despite significant historic population size decrease, environmental gradients have resulted in genetic differentiation among native pinewoods. In order to minimise the risk of planting poorly-adapted stock and to maximise the success of replanting programmes, it is important that the origins of planting stock are carefully considered in management guidelines for the species.
15

Effects of Development Platform Heterogeneity in Testing of Heterogeneous systems: An Industrial Survey

V N ANJANAYA UDAY, MAJETI January 2016 (has links)
Context. Over the years, software has evolved to a large and complex system of systems. According to the literature, a heterogeneous system is defined as “a system comprised of n number of subsystems where at least one subsystem exhibits heterogeneity with respect to other subsystem”. The area of research in heterogeneous system has also received large attention in recent years, as a result of shift in technology and customer needs. In heterogeneous systems, heterogeneity may occur in different dimensions for different systems. Objectives. The main aim of this thesis is, “to investigate the effects of development platform heterogeneity in heterogeneous system on the test process”. The objectives to achieve our aim is to determine the influence of platform heterogeneity on software testing and also to investigate best practices for testing heterogeneous systems with different types of heterogeneity. Methods. An industrial survey and interviews with practitioners are considered as a research method in this thesis. The purpose of this survey is to help the testers to understand how the platform heterogeneity affects the test process. Results. In this research, the researcher had gathered data related to effects and best practices in heterogeneous systems from both survey and interviews. Conclusions. In this thesis, the researcher had investigated the effects of development platform heterogeneity in heterogeneous system on the test process and also identified the best practices for testing heterogeneous systems that exhibit different types of heterogeneity. Apart from these, the researcher also identified different types of development platforms used for development of a heterogeneous type of systems in the industry.
16

Immunohistochemical and Molecular Features of Melanomas Exhibiting Intratumor and Intertumor Histomorphologic Heterogeneity

Mejbel, Haider A., Arudra, Sri Krishna C., Pradhan, Dinesh, Torres-Cabala, Carlos A., Nagarajan, Priyadharsini, Tetzlaff, Michael T., Curry, Jonathan L., Ivan, Doina, Duose, Dzifa Y., Luthra, Raja, Prieto, Victor G., Ballester, Leomar Y., Aung, Phyu P. 01 November 2019 (has links)
Melanoma is a heterogeneous neoplasm at the histomorphologic, immunophenotypic, and molecular levels. Melanoma with extreme histomorphologic heterogeneity can pose a diagnostic challenge in which the diagnosis may predominantly rely on its immunophenotypic profile. However, tumor survival and response to therapy are linked to tumor genetic heterogeneity rather than tumor morphology. Therefore, understating the molecular characteristics of such melanomas become indispensable. In this study, DNA was extracted from 11 morphologically distinct regions in eight formalin-fixed, paraffin-embedded melanomas. In each region, mutations in 50 cancer-related genes were tested using next-generation sequencing (NGS). A tumor was considered genetically heterogeneous if at least one non-overlapping mutation was identified either between the histologically distinct regions of the same tumor (intratumor heterogeneity) or among the histologically distinct regions of the paired primary and metastatic tumors within the same patient (intertumor heterogeneity). Our results revealed that genetic heterogeneity existed in all tumors as non-overlapping mutations were detected in every tested tumor (n = 5, 100%; intratumor: n = 2, 40%; intertumor: n = 3, 60%). Conversely, overlapping mutations were also detected in all the tested regions (n = 11, 100%). Melanomas exhibiting histomorphologic heterogeneity are often associated with genetic heterogeneity, which might contribute to tumor survival and poor response to therapy.
17

Automated Scanning Microelectrode Analysis of Epithelial K^+ Transport in Malpighian Tubules of Drosophilia melanogaster: Evidence for Spatial and Temporal Heterogeneity / Automated K^+ Scanning Microelectrode Analysis

Rheault, Mark 09 1900 (has links)
Malpighian (renal) tubules of the fruit fly Drosophila melanogaster consist of three functional domains: a non-secretory distal segment, a secretory main segment and a reabsorptive lower segment. In this study a computer-controlled micropositioning system and a self-referencing K^+ microelectrode were used to measure K^+ concentration gradients of extracellular unstirred layers associated with specific epithelial domains. K^+ fluxes were calculated from the measured gradients. This is the first time: that an accurate assessment of the concentration gradients of the unstirred layer of Drosophila melanogaster could be assessed due to the enhanced sensitivity of this self-referencing technique over conventional ion-selective microelectrodes. The technique permits high resolution spatial and temporal mapping of the flux patterns in response to stimulation or inhibition of ion transport. Variations in K^+ transport over time and at different sites suggest that transport is non-uniform within any one functional domain. / Thesis / Master of Science (MSc)
18

Heterogeneous parallel computing

Jackson, Robert Owen January 1999 (has links)
No description available.
19

Modeling steam assisted gravity drainage in heterogeneous reservoirs using different upscaling techniques

Kumar, Dhananjay 10 October 2014 (has links)
This thesis presents different methods that improve the ability to relate the flow properties of heterogeneous reservoirs to equivalent anisotropic flow properties in order to predict the performance of the Steam Assisted Gravity Drainage (SAGD) process. Process simulation using full scale heterogeneous reservoirs are inefficient and so the need arises to develop equivalent anisotropic reservoirs that can capture the effect of reservoir heterogeneity. Since SAGD is highly governed by permeability in the reservoir, effective permeability values were determined using different upscaling techniques. First, a flow-based upscaling technique was employed and a semi-analytical model, derived by Azom and Srinivasan, was used to determine the accuracy of the upscaling. The results indicated inadequacy of flow-based upscaling schemes to derive effective direction permeabilities consistent with the unique flow geometry during the SAGD process. Subsequently, statistical upscaling was employed using full 3D models to determine relationships between the heterogeneity variables: k[subscript italic v]⁄k[subscript italic h] , correlation length and shale proportion. An iterative procedure coupled with an optimization algorithm was deployed to determine optimal k[subscript italic v] and k[subscript italic k] values. Further regression analysis was performed to explore the relationship between the variables of shale heterogeneity in a reservoir and the corresponding effective properties. It was observed that increased correlation lengths and shale proportions both decrease the dimensionless flow rates at given dimensionless times and that the semi-analytical model was more accurate for cases that contained lower shale proportions. Upscaled heterogeneous values inputted into the semi-analytical model resulted in underestimation of oil flow rate due to the inability to fully account for the impact of reservoir barriers and the configuration of flow streamlines during the SAGD process. Statistical upscaling using geometric averaging as the initial guess was used as the basis for developing a relationship between correlation length, shale proportion and k[subscript italic v]⁄k[subscript italic h]. The initial regression models did not accurately predict the anisotropic ratio because of insufficient data points along the regression surface. Subsequently a non-linear regression model that was 2nd order in both length and shale proportion was calibrated by executing more cases with varying levels of heterogeneity and the regression model revealed excellent matches to heterogeneous models for the prediction cases. / text
20

Molecular genetics of autosomal recessive spinocerebellar ataxias

Christodoulou, Kyproula January 1995 (has links)
No description available.

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