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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.
21

Friends of My Enemies: A Longitudinal Investigation into Supply Base Management

January 2016 (has links)
abstract: In this dissertation research, I expand the definition of the supply network to include the buying firm’s competitors. Just as one buyer-supplier relationship impacts all other relationships within the network, the presence of competitor-supplier relationships must also impact the focal buying firm. Therefore, the concept of a “competitive network” made up of a focal firm, its competitors and all of their combined suppliers is introduced. Utilizing a unique longitudinal dataset, this research explores how the organic structural changes within the new, many-to-many supply network impact firm performance. The investigation begins by studying the change in number of suppliers used by global auto manufacturers between 2004 and 2013. Following the Great Recession of 2008-09, firms have been growing the number of suppliers at more than twice the rate they had been reducing suppliers just a few years prior. The second phase of research explores the structural changes to the network resulting from this explosive growth in the number of suppliers. The final investigation explores a different flow – financial flow -- and evaluates its association with firm performance. Overall, this dissertation research demonstrates the value of aggregating individual supply networks into a macro-network defined as the competitive network. From this view, no one firm is able to control the structure of the network and the change in structure directly impacts firm performance. A new metric is introduced which addresses the subtle changes in buyer-supplier relationships and relates significantly to firm performance. The analyses expand the body of knowledge through the use of longitudinal datasets and uncovers otherwise overlooked dynamics existing within supply networks over the past decade. / Dissertation/Thesis / Doctoral Dissertation Business Administration 2016
22

HIV Evolution: Biogeography and Intra-Individual Dynamics

January 2013 (has links)
abstract: The entire history of HIV-1 is hidden in its ten thousand bases, where information regarding its evolutionary traversal through the human population can only be unlocked with fine-scale sequence analysis. Measurable footprints of mutation and recombination have imparted upon us a wealth of knowledge, from multiple chimpanzee-to-human transmissions to patterns of neutralizing antibody and drug resistance. Extracting maximum understanding from such diverse data can only be accomplished by analyzing the viral population from many angles. This body of work explores two primary aspects of HIV sequence evolution, point mutation and recombination, through cross-sectional (inter-individual) and longitudinal (intra-individual) investigations, respectively. Cross-sectional Analysis: The role of Haiti in the subtype B pandemic has been hotly debated for years; while there have been many studies, up to this point, no one has incorporated the well-known mechanism of retroviral recombination into their biological model. Prior to the use of recombination detection, multiple analyses produced trees where subtype B appears to have first entered Haiti, followed by a jump into the rest of the world. The results presented here contest the Haiti-first theory of the pandemic and instead suggest simultaneous entries of subtype B into Haiti and the rest of the world. Longitudinal Analysis: Potential N-linked glycosylation sites (PNGS) are the most evolutionarily dynamic component of one of the most evolutionarily dynamic proteins known to date. While the number of mutations associated with the increase or decrease of PNGS frequency over time is high, there are a set of relatively stable sites that persist within and between longitudinally sampled individuals. Here, I identify the most conserved stable PNGSs and suggest their potential roles in host-virus interplay. In addition, I have identified, for the first time, what may be a gp-120-based environmental preference for N-linked glycosylation sites. / Dissertation/Thesis / Ph.D. Molecular and Cellular Biology 2013
23

Exploring the changing multidimensional experiences of frail older people towards the end of life : a narrative study

Lloyd, Anna Elizabeth January 2015 (has links)
Background Palliative care services have widened beyond cancer in recent years, yet frail older adults rarely receive such services. There is a need to understand the dynamic multidimensional end-of-life experiences of this group in order to assess how or if a palliative approach could be beneficial. Physical end-of-life trajectories for frail older people have been described but there remains little person centred research that describes changing experiences across physical, social, psychological and existential dimensions. Aims and objectives To explore the changing multidimensional experiences of frail older people towards the end of life and to reflect on the utility of a qualitative longitudinal multi-perspective design for this population. Methods Thirteen cognitively intact, community dwelling older adults considered to be moderately or severely frail, using a clinical frailty scale, and thirteen nominated informal carers participated in up to three narrative interviews over eighteen months. Eight nominated professionals were also interviewed. The interviews were participant led, audio-recorded and fully transcribed. The ‘voice centred relational’ narrative method, incorporating analyses of multidimensional experience, was used to analyse the data. The data were then analysed longitudinally to compile case studies for each older person. Findings The narratives of these frail older people approaching the end of life illustrate patterns of multidimensional experience that differ from the end-of-life trajectories of other groups. All participants experienced physical decline however three possible patterns of psychological, social and existential experience emerged. These were stable, regressive and tragic according to the capacity to hold on to core values, and maintain a sense of self and of belonging in the world and are illustrated using visual trajectories. When the sense of self was threatened these frail older people lacked valued alternative identities and struggled with the absence of clear causative factors to explain their circumstances. The participants frequently described fears of burdening others, of moving to a nursing home or of developing dementia more than fears of dying. Losses and sustaining factors are described for physical, social, psychological and existential dimensions revealing the importance of social and community networks for supporting frail older people. There were constraints and benefits to using a qualitative longitudinal multi-perspective method, however the method enabled a deep, contextualised and rich understanding of the dynamic experiences of frail older people. Conclusion Frail older people may be supported towards the end of life by considering ways to promote the integration of the self. This may involve promoting valued alternative identities, protecting personhood through social and health care practices and by investigating ways to alleviate or make tolerable greatest fears. Community health and social care structures and social and community networks appear essential for addressing the end-of-life needs of frail older people. A qualitative, longitudinal, multi-perspective design was beneficial for investigating the experiences of frail older people.
24

A Framework for the Discovery and Tracking of Ideas in Longitudinal Text Corpora

Mei, Mei 24 May 2022 (has links)
No description available.
25

Dropout in Couple Therapy: An Exploration of the Trajectories of Couples Dropping Out

Lybbert, Ragan A. 06 June 2022 (has links)
Dropout is a problematic phenomenon which wastes community, clinician, client, and researcher resources. Clients who dropout from therapy end up the same, or worse than, those who did not seek out therapy at all. While there is a relatively deep and broad understanding of dropout from individual therapy, an exhaustive review of couple therapy dropout literature reveals a very inconsistent and non-conclusive body of research. This may stem from a lack of a consistently used theory to guide research endeavors in this important realm. Primarily, this seems to stem from treating dropout as a static event rather than a process occurring across time. This study seeks to remedy this and shed new light on dropout from couple therapy by using a growth mixture model analysis to tease out which trajectories of change of predictor variables across time are more likely to predict dropout from couple therapy. While the results of this study did not reveal any significant relationships between class membership and dropout (likely due to a too small sample size), the study did find that there were distinct classes (trajectories of change) among the predictor variables across time.
26

The Effect of Social Skills on Academic Achievement of Linguistically Diverse Elementary Students: Concurrent and Longitudinal Analysis

Yoon Sung, Young ji 02 April 2009 (has links)
Due to the difference in cultures and languages, language minority students, who are mostly immigrant students, are confronted with more demands than are mainstream students (Ogden, Sorlie, & Hagen, 2007). Further, when they are limited in English proficiency (LEP), they tend to perform at lower levels in school and to be at risk of school failure. Based on the previous studies that addressed the importance of students' social skills for school success, this study examined the social development of the language minority immigrant students from kindergarten to fifth grade and investigated the longitudinal effect of their social skills on their academic performance in comparison with the English-speaking mainstream students. Using a nationally representative database, the Early Childhood Longitudinal Study – Kindergarten Class of 1998-1999 (ECLS-K), this study first investigated the concurrent association between social skills and the academic achievement of fifth-grade students, and the profiles of their social skills during the first six years of schooling to identify the relative importance of various aspects of social skills that are related to academic performance. Next, the language minority student group, which was further divided based on their LEP status at kindergarten, was examined and compared with the mainstream student group with respect to their development patterns and levels of social skills from kindergarten to fifth grade. As a final step, the longitudinal effect of students' social skills on their reading and math performance was estimated and tested using the two-level hierarchical growth model. The result identified approaches to learning as the most important aspect of social skills related to academic achievement. Language minority immigrant students from families living in poverty displayed extremely unstable development in all aspects of social skills, including their approaches to learning. In addition, the longitudinal effect of the social skills on reading and math performance was significant for all students but larger for the students in poverty regardless of the language minority status. The positive effect of improved social skills was the largest for the group of students who displayed the most unstable social development, which were the language minority immigrant students who did not show LEP at kindergarten and who were living in poverty. This result suggests the needs of students living in poverty, especially language minority students, for relevant supports and intervention. / Ph. D.
27

A Monte Carlo Evaluation of Growth Mixture Models: Effects of Varying Distributional Parameters on Grouping Outcomes

Shader, Tiffany M. January 2019 (has links)
No description available.
28

Family Matters: Relationship Dynamics Surrounding the Death of a Child in Later Life

Mellencamp, Kagan A. 19 December 2022 (has links)
No description available.
29

Modeling Treatment Outcome: Improving Clinical Meaning Through the Use of Nonlinear Growth Curve Models

Stensland, Michael D. 30 June 2004 (has links)
No description available.
30

EMPIRICAL APPLICATION OF DIFFERENT STATISTICAL METHODS FOR ANALYZING CONTINUOUS OUTCOMES IN RANDOMIZED CONTROLLED TRIALS

Zhang, Shiyuan 10 1900 (has links)
<p>Background: Post-operative pain management in total joint replacement surgery remains to be ineffective in up to 50% of patients and remains to have overwhelming impacts in terms of patient well-being and healthcare burden. The MOBILE trial was designed to assess whether the addition of gabapentin to a multimodal perioperative analgesia regimen can reduce morphine consumption or improve analgesia of patients following total joint arthroplasty. We present here empirical application of these various statistical methods to the MOBILE trial.</p> <p>Methods: Part 1: Analysis of covariance (ANCOVA) was used to adjust for baseline measures and to provide an unbiased estimate of the mean group difference of the one year post-operative knee flexion scores in knee arthroplasty patients. Robustness test were done by comparing ANCOVA to three comparative methods: i) the post-treatment scores, ii) change in scores, iii) percentage change from baseline.</p> <p>Part 2: Morphine consumption, taken at 4 time periods, of both the total hip and total knee arthroplasty patients was analyzed using linear mixed-effects model (LMEM) to provide a longitudinal estimate of the group difference. Repeated measures ANOVA and generalized estimating equations were used in a sensitivity analysis to compare robustness of the methods. Additionally, robustness of different covariance matrix structures in the LMEM were tested, namely first order auto-regressive compared to compound symmetry and unstructured.</p> <p>Results: Part 1: All four methods showed similar direction of effect, however ANCOVA (-3.9, 95% CI -9.5, 1.6, p=0.15) and post-treatment score (-4.3, 95% CI -9.8, 1.2, p=0.12) method provided the highest precision of estimate compared to change score (-3.0, 95% CI -9.9, 3.8, p=0.38) and percent change (-0.019, 95% CI -0.087, 0.050, p=0.58).</p> <p>Part 2: There was no statistically significant difference between the morphine consumption in the treatment group and the control group (1.0, 95% CI -4.7, 6.7, p=0.73). The results remained robust across different longitudinal methods and different covariance matrix structures.</p> <p>Conclusion: ANCOVA, through both simulation and empirical studies, provides the best statistical estimation for analyzing continuous outcomes requiring covariate adjustment. More wide-spread of the use of ANCOVA should be recommended amongst not only biostatisticians but also clinicians and trialists. The re-analysis of the morphine consumption aligns with the results of the MOBILE trial that gabapentin did not significantly reduce morphine consumption in patients undergoing major replacement surgeries. More work in area of post-operative pain is required to provide sufficient management for this patient population.</p> / Master of Science (MSc)

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