• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 64
  • 56
  • 8
  • 7
  • 6
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 169
  • 55
  • 20
  • 18
  • 16
  • 16
  • 15
  • 15
  • 14
  • 14
  • 13
  • 13
  • 12
  • 12
  • 12
  • 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.
1

The scaling of organ weights in six Old World monkey species

Larson, Susan G. January 1982 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 174-180).
2

Scaling the Diversity of Botanical Form and Function

Price, Charles Anthony January 2006 (has links)
Recent theoretical and empirical advances, in particular the fractal branching model of West, Brown and Enquist (WBE model), have highlighted the importance of exchange surfaces in understanding the integration of whole plant form, and functional traits. Key insights have arisen from an increased understanding of how the properties of distributive vessel networks influence whole plant metabolic and physiological traits. Here I show that an extension of WBE model, one in which network geometry is continuously variable, provides a robust foundation to understand the diversity of scaling relationships in plants and the organs of which they are composed. Central to the original WBE model has been the assumption of energy minimization as a selective force shaping the evolution of internal and external plant surface areas and morphology. Here I demonstrate how additional selection on traits not detailed in the original WBE formulation can lead to departures from strict energy minimization, and can thus explain much of the variation and covariation in observed scaling central tendencies in plant gross morphology observed within, and across natural plant communities. I test the predictions from this model extension with data from both regional and global datasets, from the leaf to whole plant level, across herbaceous, succulent, woody, annual and perennial taxa. These data demonstrate that the model extension is quite robust and should serve as a foundation upon which more detailed future models can be constructed.
3

Ontogenetic allometry of the postcranial skeleton in platyrrhines, with special emphasis on its relationship to the evolution of small body size in the callitrichidae /

Levitch, Linda Charlotte. January 1987 (has links)
Thesis (Ph. D.)--University of Washington, 1987. / Vita. Bibliography: leaves [144]-166.
4

A contravention of established principles of interspecific allometric metabolic scaling in developing silkworms, Bombyx mori

Blossman-Myer, Bonnie. Burggren, Warren W., January 2007 (has links)
Thesis (Ph. D.)--University of North Texas, May, 2007. / Title from title page display. Includes bibliographical references.
5

Asymmetric Branching in Biological Resource Distribution Networks

Brummer, Alexander B., Brummer, Alexander B. January 2017 (has links)
There is a remarkable relationship between an organism's metabolic rate (resting power consumption) and the organism's mass. It may be a universal law of nature that an organism's resting metabolic rate is proportional to its mass to the power of 3/4. This relationship, known as Kleiber's Law, appears to be valid for both plants and animals. This law is important because it implies that larger organisms are more efficient than smaller organisms, and knowledge regarding metabolic rates are essential to a multitude of other fields in ecology and biology. This includes modeling the interactions of many species across multiple trophic levels, distributions of species abundances across large spatial landscapes, and even medical diagnostics for respiratory and cardiovascular pathologies. Previous models of vascular networks that seek to identify the origin of metabolic scaling have all been based on the unrealistic assumption of perfectly symmetric branching. In this dissertation I will present a theory of asymmetric branching in self-similar vascular networks (published by Brummer et al. in [9]). The theory shows that there can exist a suite of vascular forms that result in the often observed 3/4 metabolic scaling exponent of Kleiber's Law. Furthermore, the theory makes predictions regarding major morphological features related to vascular branching patterns and their relationships to metabolic scaling. These predictions are suggestive of evolutionary convergence in vascular branching. To test these predictions, I will present an analysis of real mammalian and plant vascular data that shows: (i) broad patterns in vascular networks across entire animal kingdoms and (ii) within these patterns, plant and mammalian vascular networks can be uniquely distinguished from one another (publication in preparation by Brummer et al.). I will also present results from a computational study in support of point (i). Namely, that asymmetric branching may be the optimal strategy to balance the simultaneous demands of maximizing the number of nutrient exchange sites (capillaries or leaves) versus hydraulic resistance to resource transport (publication in preparation by Brummer et al.). Finally, I report on improved methods of estimating whole organism metabolism based solely on measurements of vasculature.
6

Morphometric variability and allometric relationships in the seagrass Thalassia testudinum in Florida Bay /

Hackney, John W. January 2003 (has links) (PDF)
Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Includes bibliographical references (leaves : 110-116).
7

Modelling in physiology and human performance : the influence of body size

Batterham, Alan Mark January 1997 (has links)
This thesis examined the validity of allometric models (Y = aXbg) in scaling physiological and human performance data (Y) for differences in body size (X). 1) Anaerobic performance. External peak power output (PPO) derived from supramaximalleg ergometry was compared in young adult males and females, using a multivariate allometric model. Estimated fat free mass (FFM) and thigh muscle-and-bone cross-sectional area served as indicators of involved musculature. Male PPO was greater than female (P < 0.05), after allometric adjustment for body size differences. This finding is questionable, however, as the within-gender goodness-of-fit values for the regression models were very poor. 2) Cardiac dimensions. The proper relationships between echocardiographic dimensions [left ventricular (LV) mass, and LV internal dimensions] and various indicators of overall body size [height, body mass (BM), FFM, and body surface area (BSA)] were examined in young, apparently healthy, adult males and females. Scaling by FFM was associated with the least residual error in these samples. The obtained relationships were generally dimensionally consistent, that is, LV mass proportional to FFM to the first power, and LV internal dimensions related to the 1/3 power ofFFM. 3) Methodological issues. The multivariate allometric scaling of peak oxygen uptake by height and BM was investigated. Regression diagnostics revealed that the obtained exponents were unstable, and potentially numerically inaccurate, due to severe collinearity between height and BM in the sample. For elite weightlifting performance, detailed examination of the allometric regression residuals revealed that the model was poorly specified. Re-specification of the model using secondorder polynomials provided the optimal scaling of this data set.
8

The evolution of convergence, growth, and diet under an adaptive landscape framework

Wynd, Brenen Michael 23 March 2022 (has links)
Macroevolutionary patterns of adaptation are a product of natural selection acting on genetic and developmental variation within populations, the basis of microevolution. In microevolution, an adaptive landscape is used to visualize the relationship between phenotype and fitness, through a series of peaks and valleys. The adaptive landscape, as a concept suggests that there is some phenotypic optimum, or a combination of phenotypes, that result in a maximum fitness. This peak is not stable but is a reflection of interactions between the environment and the flora and fauna within. To expand the adaptive landscape to macroevolutionary scales is to assume that there is some optimum that a species or population is adapted to, and that numerous species can be compared to one another on the same landscape. The world of phylogenetic comparative methods uses the theory of the adaptive landscape in investigating the trajectory of trait change but is often limited to extant organisms. The fossil record often represents a major gap in the use of adaptive landscape theory, due in part to the incomplete nature of specimens or difficulties in untangling evolutionary relationships. Within this gap, the Triassic Period (252.2 – 201.5 MA) is sparsely represented, due to the often highly incomplete nature of Triassic fossils and our constantly evolving understanding of their phylogenetic relationships. However, the Triassic Period is bookended by mass extinctions, and is thus a useful case study to explore the utility of adaptive landscape theory for organisms in a time of rapid environmental change. My dissertation explores convergence and growth through an adaptive landscape framework, to reconstruct how species were evolving, or populations adapting, to a changing environment. The first chapter of my dissertation explores the evolution of a long snout in reptiles, with exploration of convergent evolution for both extant and extinct reptiles across the tree of life. The second chapter of my dissertation explores a statistical method to incorporate variation due to fossilization in estimating and quantifying growth curves. This second chapter was necessary to explore the third chapter of my dissertation, the ontogeny of a large-bodied mammal relative, Exaeretodon argentinus. With my third chapter, I quantify growth curves, compare them across other proto mammals closely related to Exaeretodon, and explore how diet may have changed over the lifetime of a single individual. These chapters focus on the adaptive landscape over different scales (population vs clade), and serve as a basis for future work in estimating dietary evolution. / Doctor of Philosophy / Evolutionary studies are often divided into macroevolution and microevolution. Microevolution can be thought of as the primary process of evolution, such as evolution by natural selection. Macroevolution, however, relates to patterns in evolution, such as the repeated evolution of flight in insects, birds, bats, and many extinct reptiles known only from fossils. Surprisingly, we lack any convincing models that can accurately relate evolution by natural selection with macroevolutionary patterns. One idea to bridge this gap is the adaptive landscape, an 80-year-old concept that relates a trait to the fitness of a population or a species. The adaptive landscape provides a visual representation of evolution through a series of peaks and valleys. Peaks embody high fitness, reflecting a population that is well adapted to their environment. Valleys on the other hand represent extinction traps, where populations are maladapted to their environment, and are in decline and at a higher risk of extinction. The adaptive landscape essentially quantifies how different traits of a population relate to their environment. My dissertation seeks to explore evolution through the lens of the adaptive landscape, to better reconstruct hypotheses about how animals interact with their environments, particularly in extinct animals known from fossils. I view the adaptive landscape with a macroevolutionary lens by redescribing a fossil reptile and investigating the repeated evolution of a long snout in reptiles. I then attempt to look at the adaptive landscape at a microevolutionary scale, by investigating patterns of growth in a 230-million-year-old mammal relative. My dissertation views evolution across scales and sets the stage for future work to better connect those scales.
9

PREDICTION OF HUMAN SYSTEMIC, BIOLOGICALLY RELEVANT PHARMACOKINETIC (PK) PROPERTIES USING QUANTITATIVE STRUCTURE PHARMACOKINETIC RELATIONSHIPS (QSPKR) AND INTERSPECIES PHARMACOKINETIC ALLOMETRIC SCALING (PK-AS) APPROACHES FOR FOUR DIFFERENT PHARMACOLOGICAL CLASSES OF COMPOUNDS

Gottipati, Gopichand 01 January 2014 (has links)
This research developed and validated QSPKR models for predicting in-vivo human, systemic biologically relevant PK properties (i.e., reflecting the disposition of the unbound drug) of four, preselected, pharmacological classes of drugs, namely, benzodiazepines (BZD), neuromuscular blocking agents (NMB), triptans (TRP) and class III antiarrhythmic agents (AAR), as well as PK allometric scaling (PK-AS) models for BZD and NMB, using pertinent human and animal systemic PK information (fu, CLtot, Vdss and fe) from published literature. Overall, lipophilicity (logD7.4) and molecular weight (MW) were found to be the most important and statistically significant molecular properties, affecting biologically relevant systemic PK properties, and the observed relationships were mechanistically plausible: For relatively small MW and lipophilic molecules, (e.g., BZD), an increase in logD7.4 was associated with a decrease in fu, an increase in Vdssu and CLnonrenu, suggesting the prevalence of nonspecific hydrophobic interactions with biological membranes/plasma proteins as well as hepatic partitioning/DME binding. Similar trends were observed in fu and Vdssu for intermediate to large MW, hydrophilic molecules (e.g., NMB). However, although similar trends were observed in fu and Vdssu for relatively hydrophilic, intermediate MW molecules (e.g., TRP), and a heterogeneous class (e.g., Class III AAR), logD7.4 and MW were found to be highly correlated, i.e., the indepdendent effects of logD7,4 and MW cannot be assessed NMB, TRP and Class III AAR show mechanistically diverse clearance pathways, e.g., hepatobiliary, extrahepatic, enzymatic/chemical degradation and renal excretion; therefore, effects of the logD7.4 and/or MW are note generalizable for any of the clearances across classes. PK-AS analyses showed that Vdssu and Vdss scaled well with body weight across animal species (including humans) for BZD. Overall, within the limitations of the methods (and the sample size), ‘acceptable’ predictions (i.e., within 0.5- to 2.0-fold error range) were obtained for Vdssu and Vdss for BZD (and fu correction resulted in improvement of the prediction); however, none of the CLtot predictions were acceptable, suggesting major, qualitative interspecies differences in drug metabolism, even after correcting for body weight (BW). NMB undergo little extravascular distribution owing to their relatively large MW and charged nature, and, as a result, a high percentage of acceptable predictions was obtained for Vdss (based on BW). Similarly, the prediction of CLren (based on BW and glomerular filtration rate, GFR) was acceptable, suggesting that NMB are cleared by GFR across species, and there are no interspecies differences in their tubular handling. On the other hand, CLtot (and/or CLnonren) could not be acceptably predicted by PK-AS, suggesting major differences in their clearance mechanisms across animal species.
10

Macromineral requirements for maintenance and growth of Saanen goats /

Castillo Vargas, Julián Andrés January 2017 (has links)
Orientador: Izabelle Auxiliadora Molina de Almeida Teixeira / Coorientador: Amélia Katiane de Almeida / Banca: Nilza Kazue Sakomura / Banca: José Gilson Louzada Regadas Filho / Banca: Carla Joice Härter / Abstract: The objective of this study was to evaluate the effect of sex on the net macromineral requirements for maintenance and growth of Saanen goats from 5 to 45 kg body weight (BW). For this purpose, three dataset were used: the first dataset was assembled to evaluate the effect of sex on the net requirements for maintenance of Ca (NCam), P (NPm), Mg (NMgm), and K (NKm), estimated using the comparative slaughter technique (CST). This dataset was composed by 154 individual records (53 castrated males, 46 females, and 55 intact males) from three comparative slaughter studies. The second dataset, was constructed to evaluate the effect of sex on NCam, NMgm, and NKm, estimated using the minimum endogenous losses method (MEL). This dataset was assembled with 155 individual records (67 castrated males, 40 females, and 48 intact males) from four feeding trials. The third dataset was constructed to evaluate the effect of sex on the net requirements for growth of Ca (NCag), P (NPg), Mg (NMgg), Na (NNag), and K (NKg) considering or not the degree of maturity of the goat on the estimations. This dataset comprised by 209 individual records (69 castrated males, 69 females, and 71 intact males) from six comparative slaughter studies. Mineral requirements for maintenance using CST were calculated from the intercept of the linear regression between mineral retention and the mineral intake. Using the MEL, mineral requirements for maintenance were calculated from the intercept of a linear regression ... (Complete abstract click electronic access below) / Resumo: O objetivo deste estudo foi avaliar o efeito do sexo nas exigências liquidas de macrominerais para mantença e crescimento para caprinos Saanen de 5 a 45 kg de peso corporal (PC). Para esse fim, foram utilizados três bancos de dados: o primeiro banco de dados foi construído para avaliar o efeito do sexo sobre as exigências líquidas de Ca (NCam), P (NPm), Mg (NMgm) e K (Nkm) para mantença estimadas pelo método do abate comparativo (CST). O banco de dados foi composto por 154 observações individuais (53 machos castrados, 46 fêmeas e 55 machos inteiros) provenientes de três estudos de abate comparativo. O segundo banco de dados, foi construído para avaliar o efeito do sexo sobre as NCam, NMgm e NKm no corpo de caprinos Saanen, estimadas pelo método das perdas endógenas mínimas (MEL). Este banco de dados foi composto por 155 observações individuais (67 machos castrados, 40 fêmeas e 48 machos inteiros) provenientes de quatro ensaios de alimentação. O terceiro banco de dados foi construído para avaliar o efeito do sexo sobre as exigências líquidas de Ca (NCag), P (NPg), Mg (NMgg), Na (NNag) e K (NKg) para crescimento, considerando e não considerando o grau de maturidade do caprino, na estimativa destas. Este banco de dados foi composto por 209 observações individuais (69 machos castrados, 69 fêmeas e 71 machos inteiros) provenientes de seis estudos de abate comparativo. As exigências de minerais para mantença, obtidas pelo CST foram calculadas como o intercepto da regressão linear e... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Page generated in 0.0532 seconds