• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2741
  • 1484
  • 654
  • 395
  • 280
  • 99
  • 82
  • 65
  • 59
  • 49
  • 45
  • 42
  • 31
  • 31
  • 31
  • Tagged with
  • 7617
  • 1050
  • 702
  • 699
  • 673
  • 615
  • 606
  • 548
  • 496
  • 489
  • 442
  • 427
  • 420
  • 399
  • 367
  • 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.
261

Nominal record linkage : the development of computer strategies to achieve the family-based record linkage of nineteenth century demographic data

Welford, John Anthony January 1989 (has links)
This thesis was originally submitted for examination in March 1983. Following the result of the viva in October of that year an appeal was lodged, and the subsequent proceedings lasted for almost four years. In October 1987 formal notification was made that the thesis could be revised and resubmitted. The prolonged length of the appeal proceedings has meant that the computing environment within which the research was set has developed significantly from the position in 1983. Indeed, in purely practical terms, the computing systems which were used at that time are no longer operational. The opportunity for making modifications and refinements to the record linkage system, and for incorporating additional primary source materials (even were sufficient human resources available), has therefore been removed. Under these circumstances, the record linkage strategies described in the revised thesis are precisely the same as those presented in the 1983 submission. For this reason and because of the extensive delays in carrying out the appeal proceedings it has not seemed appropriate to provide a full review of developments in the record linkage field beyond this date. Reference has, however, been made to the subsequent, crucial impact of the findings of the present research on the progress of the later phases of the 1851 Census National Sample Project, which I co-directed with Professor Michael Anderson at the University of Edinburgh. The entire conceptual and strategic approach to the organisation of family information in this project grew directly from perceptions which were central to the present research. Reference has also been made to the influence of the present research on the development of the SASPAC package, a computing system for handling the 1981 Population Census Small Area Statistics data for Great Britain. I was the chief systems designer of SASPAC, and the design and implementation methods which were adopted in this development drew heavily on the experience gained from the present research. Finally, the opportunity has been taken (in the new Section 10.2), to present the findings of some fresh analyses of 1851 household census data which serve to confirm the validity of the linkage strategies which have been developed.
262

Theoretical perspectives on the dynamics of communities with intraguild predation

Maciel, Gabriel Andreguetto [UNESP] 23 February 2011 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:25:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-23Bitstream added on 2014-06-13T19:53:27Z : No. of bitstreams: 1 maciel_ga_me_ift.pdf: 510710 bytes, checksum: febf0f526cd25a0f287f0521556976fc (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Predação intraguilda é um tipo de interação muito comum entre as espécies e pode influenciar fortemente na composição das comunidades ecológicas. Ela ocorre quando dois consumidores que compartilham de um mesmo recurso, e portanto competem, também apresentam comportamento predatório entre si. O consumidor que preda o seu competidor é frequentemente chamado de predador intraguilda, enquanto aquele que é predado é conhecido como presa intraguilda. Nesse trabalho nós investigamos alguns aspectos teóricos sobre esse tipo de interação. Primeiramente analisamos um experimento com ácaros predadores que foi realizado para testas as predições da teoria sobre padrões de exclusão em um gradiente de produtividade. Embora esse experimento foi cuidadosamente projetado para testar afirmações da teoria, seus resultados não concordam com ela. Utilizando um modelo bem simples para predação intraguilda que serve como uma representação daquele sistema, nós mostramos que: se levarmos em conta a dinâmica durante os transientes, e não apenas os resultados no equilíbrio, em que a teoria usual se baseia, e considerarmos que quando uma população atinge níveis muito baixos corresponde a uma extinção na realidade, os resultados experimentais concordam com a teoria. Em seguida nós estudamos questões que dizem respeito a influência dos diferentes estágios de vida dos indivíduos para a dinâmica da predação intraguilda. Nós introduzimos um modelo com estrutura de estágio em ambos os consumidores e consideramos a predação ocorrendo apenas dos adultos do predador intraguilda sobre os juvenis da presa intraguilda. Tem-se acreditado que essa interação dependente de estágio pode ter grandes efeitos sobre a dinâmica, uma vez que a pressão predatória sobre a presa intraguilda é reduzida... / Intraguild predation is a widespread interaction between species and can strongly influence communities composition. It occurs when two consumers which share a common resource, and hence compete, also engage into predation. The consumer which can prey on its competitor is often referred to as the intraguild predator while the other is called intraguild prey. In this work we investigate some theoretical aspects about these interactions. First we analyse an experiment with predatory mites which was carried to test patterns of exclusion along a productivity gradient, predicted by theory. Although this experiment was carefully designed to test the theoretical assertions, their results do not agree with theory. Through a very simple model for intraguild predation which serves as a representation of that system, we show that: if the short-term dynamics is taken into account rather than only equilibrium states, in which the usual theory is based, and we consider that populations that attain levels very close to zero are extinct, experimental results meet theory. Then we study questions concerning the influence of different life stages of individuals on the dynamics of intraguild predation. We introduce a model with stage structure in both consumers and consider predation occurring only from adults of the intraguild predator on juveniles of the intraguild prey. This stage dependent interaction was believed t ohave great effects on the dynamics, once predation pressure on the intraguild prey is reduced, and has been proposed as one feature that could promote coexistence. We check the outcomes of the system along a productivity gradient and show that stage structure do not induce great qualitative changes on the dynamics and the more likely resulting dynamics continues being the extinction of one of the consumers... (Complete abstract click electronic access below)
263

Non-zero trajectories for long-run net migration assumptions in global population projection models

Abel, Guy 16 May 2018 (has links) (PDF)
BACKGROUND Little attention is given to the role of migration in global population projection models. Most demographers set future levels of net migration on trajectories towards zero in all countries, nullifying the impact of migration on long-run projected populations. Yet as fertility and mortality rates fall, the role of migration on future population change is becoming more pronounced. OBJECTIVES In this paper we develop future long-run migration scenarios to provide a range of possible outcomes. METHODS Our alternative migration scenarios are linked to the Shared Socioeconomic Pathways (SSP), widely used in research on global environmental change. These are utilized as inputs for a global cohort component projection model to obtain population totals up until 2100 for all countries. CONTRIBUTION The results illustrate the important role of migration assumptions in long-run projections, especially in post-demographic-transition countries. Further, they provide plausible alternatives to projections based on the commonly used, but poorly justified, convergence towards a zero net migration assumption.
264

Pharmacokinetics, cell kinetics and pharmacodynamics : a Bayesian approach

Olaeta, Haritz January 2002 (has links)
No description available.
265

Vulnerabilidades e mobilidade pendular na Região Metropolitana da Baixada Santista / Vulnerabilities and commuting in the Baixada Santista Metropolitan Area

Silva, Robson Bonifácio da, 1978- 12 August 2018 (has links)
Orientador: Daniel Joseph Hogan / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Filosofia e Ciências Humanas / Made available in DSpace on 2018-08-12T22:35:32Z (GMT). No. of bitstreams: 1 Silva_RobsonBonifacioda_M.pdf: 1529430 bytes, checksum: 7dc4e377238d310c48accc814fedc4bb (MD5) Previous issue date: 2009 / Resumo: Esta dissertação é uma tentativa de relacionar o movimento pendular, considerado uma das modalidades da mobilidade espacial da população, com as vulnerabilidades socioambientais e sociodemográficas, já que acreditamos que as diversas formas de mobilidade populacional podem se constituir em elementos importantes para o avanço dos estudos sobre a vulnerabilidade, pois atuam na distribuição de perigos e afetam a exposição a riscos das pessoas. Inicialmente apresentamos um quadro geral do movimento sobre a Região Metropolitana da Baixada Santista e caracterizamos as pessoas que realizam o movimento pendular na região. Em seguida trabalhamos os conceitos de vulnerabilidade, especialmente a sociodemográfica e a socioambiental, ativos e estrutura de oportunidades. Por último, comparamos as pessoas que realizam o movimento pendular com as que não realizam, com o objetivo de identificar diferenças entre esses dois grupos de pessoas e a sua exposição a maior ou menor vulnerabilidade. Procuramos verificar também se há situações nas quais tais grupos apresentam maior enfrentamento da vulnerabilidade e quais os ativos que ambos mobilizam, tanto para enfrentá-la quanto para se recuperarem dos danos sócio-demográficos e socioambientais / Abstract: The purpose of this study is to relate commuting to social demographic and social environmental vulnerabilities. Many studies believe that several kinds of mobility can be considered as important elements to the understanding of the concept of the vulnerability. Initially we present the characteristics of the commuting and the commuters in the Baixada Santista Metropolitan Area. After, we work on the concepts of vulnerability, assets and structure of opportunities. Finally, we compare the people who commute to those who don't, trying to identify the differences between those two groups of people and their exposure to vulnerable situations. We also try to confirm the existence of situations in which different groups show a higher vulnerability and which assets they can mobilize to deal with the difficulties of life, especially to those related to social demographic and social environmental risks / Mestrado / Mestre em Demografia
266

Population ecology of Pleuroptya ruralis (Scopoli) (Pyralidae:Pyraustinae)

Romanowski, Helena Piccoli January 1991 (has links)
A natural population of Pleuroptya ruralis has been studied for three years with the following aims: (1) to elucidate its life history; (2) to study the variations in the larval and adult densities; (3) to identify the mortality factors acting upon them; (4) to investigate possible relationships between the intensity of the mortality factors and the spatial distribution (horizontal and vertical) of P. ruralis ; (5) to describe the role of the major mortality factors in determining the size of the population studied; (6) to assess the potential of the system for further studies about the mechanism of population regulation. P. ruralis caterpillars were individually labelled and followed throughout their development on a natural growth of their food plant, Urtica dioica (the nettle), near Leeds, Yorkshire, United Kingdom. Parasitism and predation as well as the distribution and movements of the larvae on the host plant were assessed. Caterpillars were also collected and reared in the laboratory for identification of the parasitoid species and to provide support for the field results. Adults were studied in the field by the mark- release- recapture method. Potential female fertility was investigated in the laboratory. The population suffered a dramatic decline in numbers during the period of this study. The main factors determining the observed population levels were the interactions between the weather, time spent in development, deviations in the sex ratio, bird predation towards the completion of pre-adult development and parasitization by a braconid (Macrocentrus grandii). Other parasitoids also had some effect, notably Diadegma sp. Predation also had a strong impact on the population of M. grandii. Birds appear to concentrate their attack in the part of the plant in which they are more likely to find the prey. Weather also influenced adult activity and availability of nectar sources in the field, and starvation of females reduced fecundity in the laboratory. Thus, egg shortfall may also have been important in the decrease of population size. The field method used with the caterpillars provided detailed and valuable information about individual and spatial variation and it is suggested that the system 'nettles / P. ruralis / natural enemies' can be a powerfull tool for studies on the mechanisms of population regulation.
267

Population Study of Aminoglycoside Pharmacokinetics at a Hospital in South Carolina

Barzanjy, Shaban, Nguyen, Yen January 2005 (has links)
Class of 2005 Abstract / Objectives: To determine the pharmacokinetic parameters of a patient population from drug concentration measurements records created by the pharmacokinetic service at a regional hospital in South Carolina, to predict peak and trough concentrations from three large dose-extended interval (LDEI) protocols to determine which method produce the highest percentage of concentrations that fall in the desired ranges, and to compare pharmacokinetic parameters of overweight and normal weight patients. Methods: This was a descriptive, retrospective study that used clinical data from 121 of 208 patient data forms. The collected data included patient age, gender, weight, height, serum creatinine (Scr), measured serum peak and trough concentrations, time of dosing, dose and dosing interval. These were used to determine individual pharmacokinetic parameters and predict peak and trough concentrations from three LDEI dosing protocols. Results: Method II produced the highest percentage of patients with peaks and troughs falling into the target range (95.9%). The Hartford method produced the highest percentage (79.3%) of patients achieving peak concentrations >20mg/L. All three methods achieved low troughs of <2mg/L, <1mg/L, <0.5mg/L, and <0.1mg/L at least 95%, 80%, 70%, and 50% of the time, respectively. No statistical significance was found between the group having actual body weight/ideal body weight ratio (ABW/IBW) greater than 1.2 and another group having ABW/IBW <1.2 for ABW, volume of distribution (V), elimination half-life (T1/2) and aminoglycoside clearance (Clag). Also, when overweight patients were excluded, a higher correlation between elimination rate constant (k) and creatinine clearance (CrCl) was found than when all patients were combined. In other words, as k increases, CrCl increases. Implications: Even though Method II produced the greatest percentage of peak and trough concentrations within its stated target range, the Hartford method may be the best dosing protocol to use since it achieves high peak concentrations (>20mg/L) while maintaining low trough concentrations. In addition, based on our data, we can assume that overweight people affect the predicted k value. There was no statistical significance between actual and predicted pharmacokinetic characteristics in overweight patients.
268

Dimensions of global population projections: what do we know about future population trends and structures?

Lutz, Wolfgang, KC, Samir January 2010 (has links) (PDF)
The total size of the world population is likely to increase from its current 7 billion to 8-10 billion by 2050. This uncertainty is because of unknown future fertility and mortality trends in different parts of the world. But the young age structure of the population and the fact that in much of Africa and Western Asia, fertility is still very high makes an increase by at least one more billion almost certain. Virtually, all the increase will happen in the developing world. For the second half of the century, population stabilization and the onset of a decline are likely. In addition to the future size of the population, its distribution by age, sex, level of educational attainment and place of residence are of specific importance for studying future food security. The paper provides a detailed discussion of different relevant dimensions in population projections and an evaluation of the methods and assumptions used in current global population projections and in particular those produced by the United Nations and by IIASA.
269

Beautiful but lacking diversity : population genetics of Pacific Dogwood (Cornus nuttallii Audobon ex Torr. & A. Gray)

Keir, Karolyn R. 11 1900 (has links)
In the past, conifers have been the primary focus of population and conservation genetic studies in Pacific Northwest (PNW) trees. These studies have provided tremendous insight as to how genetic diversity varies across species ranges for these wind-pollinated and mostly wind-dispersed species. With this study of Pacific dogwood (Cornus nuttallii), a broadleaved, PNW species, which utilizes biological vectors for pollen and seed dispersal, we hope to broaden our understanding of tree evolutionary dynamics. Marker development for C. nuttallii found few useful polymorphisms. Of eight microsatellite markers (SSRs) developed from a closely related species, three were monomorphic, while the other five averaged only 4.4 alleles/locus. Furthermore, only a single base pair substitution was found in the rpl16 region of the chloroplast genome after sequencing 2,262 non-coding base pairs in 100 individuals. This lack of diversity, which was found to be ubiquitous throughout the range of C. nuttallii, suggests this species may have endured a prolonged bottleneck in a single glacial refugium prior to recolonization. The cpDNA phylogeographic pattern and a significant decline in both SSR allelic richness (r² = 0.42, p<0.01), and expected heterozygosity (r² = 0.51, p<0.01) support this theory. Low levels of population structure, documented in both chloroplast (D = 0.153) and nuclear genomes (FST = 0.071, RST = 0.036) may suggest high levels of contemporary gene flow between populations are also influencing current patterns of diversity. Despite variation being the precursor for adaptation, a comparison of QST (0.088 for first-year height and 0.113 for bud burst timing) with a refined FST estimate (0.053), indicated that C. nuttallii had either retained or recovered significant phenotypic variation for differential selection to act. Such uniformly low diversity raises the issue of how genetic conservation efforts should proceed with this and other species sharing a similar degree of genetic depauperateness. So that signs of decline may be detected, we suggest population monitoring, especially for those populations occurring at high elevations. Furthermore, we advocate the transfer of seeds from the nearest southern source, in the event that restorative efforts are required to assist this species to cope with the rapidly changing climate. / Forestry, Faculty of / Graduate
270

Small mammal herbivory and plant recruitment in grassland

Hulme, Philip Eric January 1990 (has links)
No description available.

Page generated in 0.112 seconds