Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 40 for “"null model"”.
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Building, applying, and communicating ecosystem understanding via freshwater forecasts over time and space
… variables across three waterbodies using diverse modeling methods. I developed daily, weekly, and fortnightly forecasts of chlorophyll-a at two drinking water reservoirs using a Bayesian linear model, and found process uncertainty dominated total forecast uncertainty. Additionally, I produced …
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Null Models For Cultural And Social Evolution
… be important in biology, has been proposed as a null model for cultural change, but has not developed into tests for selection on cultural features. Using inference in timeseries of alternative word forms and grammatical constructions, I demonstrate a cultural analog of natural selection on a …
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The role of organizational commitment and job satisfaction in progressive withdrawal behaviors: testing a comprehensive model with integrated methodology
This study examined several competing models for the hypothesized role that organizational commitment and job satisfaction play in withdrawal behaviors. These models were tested against a null or base model from which the other models were nested. The results supported the null model as best …
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Ecological Gradients in Diversity and Abundance: A Search for Patterns and Processes in Small Mammal Communities
… aims in mind, I examine the predictability of null models and biological diversity hypotheses for latitudinal and elevational gradients in diversity and abundance of small mammals. The unimodal distribution of diversity in North American desert rodents was highly consistent with the mid-domain …
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Theoretical and Algorithmic Solutions for Null models in Network Theory
… major example. In this framework, the concept of Null Model borrowed from the statistical sciences identifies the elective strategy to obtain a baseline points of modelling comparison [2]. Hereafter, a null model is a graph which matches one specific graph in terms of some structural features, but …
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The Effects of Multiple Predator Species on the Prey's Risk of Predation
… risks can either match the predictions of a null model of additivity (additive risk) or vary from them (non-additive risk) in either a positive (risk enhancement) or negative direction (risk reduction). Additivity, risk enhancement, and risk reduction have all been documented in nature, but …
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Determining the Influence of Abiotic and Biotic Predictors on Ecological Niche Models
… and are typically excluded from ecological niche models (ENMs). However, the role such interactions play in shaping species distributions is increasingly recognized, sparking the development of methods for their integration into ENMs.</p> <p>Among the most common approaches are those that limit …
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From Protein Folds to Chromatin: Topological Data Analysis and Deep Learning at Multiple Scales
… integrate geometric, topological, and spatial modeling with deep learning to elucidate these structure–function relationships. CASTpFold extends the Computed Atlas of Surface Topography of Proteins by combining computational geometry, topological data analysis, and AI-based structure prediction …
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An Examination of Student Understanding of the Use of Models in Science and Conceptual Understanding of Electricity and Magnetism
… college physics students' knowledge about models in science and their conceptual understanding with regard to electricity and magnetism. The data for this study was obtained through the administration of two instruments: Conceptual Survey of Electricity and Magnetism, a multiple choice …
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Selection of landscapes by male ruffed grouse during peak abundance.
… 5,349 hectares. I used information theoretic model selection to examine two sets of a priori models. The top model in the first set was the null model (intercepts only), but a model representing Shannon‘s Evenness Index was competing. This competing model contained the second greatest …
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Perceived Social Class, College Interest, and Post-Secondary Goals: An Application of the Scat Interest and Choice Model
… as a person variable in the interest and choice model of social cognitive career theory (Lent & Brown, 1996; Lent, Brown, & Hackett, 1994). The study first examined the relation of PSC to students' choice intention to pursue a college degree via cognitive self-evaluations (college self-efficacy, …
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The generation and maintenance of diversity in a rapid adaptive radiation
… Community-level diversity is investigated using null model analysis of species co-occurrence data. We detect signals of non-random community assembly at only the broadest and finest spatial scales. Based on the unique ecological and evolutionary characteristics of this assemblage we suggest that …
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How predictable : modeling rates of change in individuals and populations
… at the population level, in three pieces: i) a model of individual rate of change as a function of search and finite resources, ii) a structural model of population level change in urban economies, and iii) a statistical test for the deviation from a null model of rank chum of items in a …
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Cigarette and Smokeless Tobacco Product Use Among South Asian Americans and Health: The Role of Gender and Acculturation
… Users; and (4) Dual Users. Results: The overall model was significant compared to the null model [χ2 (15) = 107.1, p < 0.001]. With the Non-Users as the reference category in the MLR model, acculturation, physical health, and marital status were significant predictors of cigarette & SLT user …
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Molecular Evolution of Visual System Genes in Fishes
… improved upon through the presentation of a new null model that better accommodates among-site variation in selection. In Chapter Six, phylogenetic relationships within the βγ lens crystallin superfamily are clarified, and the functionally distinct γN family is shown to have evolved …
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Inheritance of Dorsal Fin Coloration in the Metriaclima Species Complex (Teleostei: Cichlidae) of Lake Malawi
… of asymmetry was less than predicted under a null model. UPGMA clustering resulted in M. thapsinogen and M. emmiltos grouping closer together than geographically proximate M. zebra. These data suggest the genetic basis for red dorsal fin coloration is allelic between M. thapsinogen and M. …
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Hormone-Sensitive Lipase - New roles in adipose tissue biology
… resistance in multiple tissues of the HSL null mice, which was almost fully compensated for by increased insulin secretion by the pancreatic beta-cells. The HSL null mice were resistant to high-fat diet (HFD)-induced obesity, with severely reduced WAT. A proteomic analysis suggested a local …
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Examining neotropical primate community structure at regional and local scales : insights from taxonomic and phylogenetic approaches
… However, comparing empirical distributions to a null model of range cohesion suggests mechanisms other than dispersal are setting a limit to the number of species capable of co-occurring throughout a species’ range. These differences in species associations across geographic ranges generate …
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Magnitude correlations and criticality in a self-similar model of seismicity
… proposed self-similar aftershock rates model of seismicity whose main distinguishing feature arises as a consequence of the dependency of the rates on the magnitude difference between trigger-triggered events. By means of a particular statistical measure we studied the level of magnitude …
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On the Rheology of Soft Cellular Materials, An Experimental Investigation of the Microstructure and Rheology of a Novel Tissue-Mimic Material
… the sample temperature. A fractional Maxwell model is used to model the creep response, revealing a correlation between the model’s parameters that persists across a wide range of sample preparation and measurement parameters. The final contribution addresses the question of how the sample’s …
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