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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.
1

Multivariate dependencies in survival analysis / Amy Beatrix Salter.

Salter, Amy Beatrix January 1999 (has links)
Bibliography: leaves 177-181. / xiv, 181 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis investigates determinants of factors associated with retention of injecting drug users on the South Australian methadone program over the decade 1981 to mid 1991. Truncated multivariate survival models are proposed for the analysis of data from the program, and the theory of graphical chain models applied to the data. A detailed analysis is presented which gives further insight into the nature of the relationships that exist amongst these data. This provides an application of graphical chain models to survival data. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied Mathematics, 2000
2

Surgical trauma, inflammation and tissue injury : an experimental study /

Törkvist, Leif, January 1900 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.
3

Multivariate dependencies in survival analysis /

Salter, Amy Beatrix. January 1999 (has links) (PDF)
Thesis (Ph.D.) -- University of Adelaide, Dept. of App. Maths, 2000. / Bibliography: leaves 177-181.
4

Multivariate dependencies in survival analysis

Salter, Amy Beatrix. January 1999 (has links) (PDF)
Bibliography: leaves 177-181. This thesis investigates determinants of factors associated with retention of injecting drug users on the South Australian methadone program over the decade 1981 to mid 1991. Truncated multivariate survival models are proposed for the analysis of data from the program, and the theory of graphical chain models applied to the data. A detailed analysis is presented which gives further insight into the nature of the relationships that exist amongst these data. This provides an application of graphical chain models to survival data.
5

A multivariate frailty model for disease recurrences and survival.

Wen, Sijin. Chan, Wenyaw, Xiong, Momiao, January 2009 (has links)
Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1744. Advisers: Xuelin Huang; Ralph F. Frankowski. Includes bibliographical references.
6

Effects of sequential Campylobacter jejuni 81-176 lipooligosaccharide core truncations on stress survival and pathogenesis

Naito, Mizue 11 1900 (has links)
Campylobacterjejuni, a Gram-negative enteric pathogen, is the leading cause of bacterial gastroenteritis in the developed world. A C. jejuni strain 8 1-176 transposon library was used to screen for mutants over-producing a calcofluor white (CFW)-reactive polymer implicated in biofilm formation. This identified two lipooligosaccharide (LOS) core mutants: one defective for a two-domain glycosyltransferase (lgtF), and the other defective in a heptosyltransferase (waaF). To determine if other LOS core mutants displayed a similar phenotype, and to explore other biological outcomes of step-wise LOS truncations on C. jejuni stress resistance and pathogenesis, mutant strains defective for GaiT and CstII were also constructed. Silver stain and mass spectrometry analyses confirmed the sequential truncation of sialic acid (ΔcstII), galactose (ΔgalT), two glucoses (ΔlgtF), and heptose II (ΔwaaF). While the ΔlgtF and ΔwaaF mutants exhibited enhanced biofilm formation and ΔlgtF displayed increased sensitivity to complement killing, no effect for these phenotypes and only modest alterations in CFW reactivity were seen with partial outer core truncations. Deletion of LgtF had no effect on mouse colonization in vivo, or on invasion and intracellular survival in epithelial cells in vitro. In contrast, the ΔwaaF mutant exhibited a significant defect in intracellular survival in vitro. Interestingly, the mutants exhibited stepwise increases in susceptibility to the antimicrobial peptide LL-37, with /waaF and ΔlgtF being more susceptible and ΔgalT and ΔstII being more resistant than wild type. In contrast, all of the mutants were highly susceptible to polymyxin B. This is the first report of C. jejuni susceptibility to LL-37 and of LOS affecting polymyxin B resistance. Each of these appears to be independent of overt effects on outer membrane protein expression, membrane stability, or surface hydrophobicity. Together, our data indicate that the length and specific moieties of the LOS play important roles in C. jejuni biology, and suggest a dynamic interplay of the LOS with other stress resistance factors.
7

Effects of sequential Campylobacter jejuni 81-176 lipooligosaccharide core truncations on stress survival and pathogenesis

Naito, Mizue 11 1900 (has links)
Campylobacterjejuni, a Gram-negative enteric pathogen, is the leading cause of bacterial gastroenteritis in the developed world. A C. jejuni strain 8 1-176 transposon library was used to screen for mutants over-producing a calcofluor white (CFW)-reactive polymer implicated in biofilm formation. This identified two lipooligosaccharide (LOS) core mutants: one defective for a two-domain glycosyltransferase (lgtF), and the other defective in a heptosyltransferase (waaF). To determine if other LOS core mutants displayed a similar phenotype, and to explore other biological outcomes of step-wise LOS truncations on C. jejuni stress resistance and pathogenesis, mutant strains defective for GaiT and CstII were also constructed. Silver stain and mass spectrometry analyses confirmed the sequential truncation of sialic acid (ΔcstII), galactose (ΔgalT), two glucoses (ΔlgtF), and heptose II (ΔwaaF). While the ΔlgtF and ΔwaaF mutants exhibited enhanced biofilm formation and ΔlgtF displayed increased sensitivity to complement killing, no effect for these phenotypes and only modest alterations in CFW reactivity were seen with partial outer core truncations. Deletion of LgtF had no effect on mouse colonization in vivo, or on invasion and intracellular survival in epithelial cells in vitro. In contrast, the ΔwaaF mutant exhibited a significant defect in intracellular survival in vitro. Interestingly, the mutants exhibited stepwise increases in susceptibility to the antimicrobial peptide LL-37, with /waaF and ΔlgtF being more susceptible and ΔgalT and ΔstII being more resistant than wild type. In contrast, all of the mutants were highly susceptible to polymyxin B. This is the first report of C. jejuni susceptibility to LL-37 and of LOS affecting polymyxin B resistance. Each of these appears to be independent of overt effects on outer membrane protein expression, membrane stability, or surface hydrophobicity. Together, our data indicate that the length and specific moieties of the LOS play important roles in C. jejuni biology, and suggest a dynamic interplay of the LOS with other stress resistance factors.
8

FACTORS ASSOCIATED WITH SURVIVAL FOR A COHORT OF CLINICALLY CONFIRMED DIABETES CASES IN NOVA SCOTIA

Talbot, Pamela J. 10 August 2011 (has links)
Diabetes Care Program of Nova Scotia (DCPNS) Registry data were used to examine factors associated with survival for clinically confirmed diabetes mellitus (DM) cases. Type 1 (N=2,043) and type 2 (N=47,974) cases were followed from first Diabetes Centre visit until death/study end. Kaplan Meier curves and Cox proportional hazard models were used to explore differences in survival by sex, district health authority of care, and comorbidity status (hypertension and/or dyslipidemia). Median lifespan for type 1 cases was 12 years shorter than for type 2 cases. Hazard rate ratios for those with dyslipidemia, hypertension, or both compared to those with neither comorbidity were 1.63, 2.57, and 7.52 for type 1 cases and 0.95, 1.15, and 1.00 for type 2 cases. Disease progression and the relationship between comorbidity status and survival differed markedly for the type 1 and type 2 DM populations underscoring the need to examine these populations separately.
9

Estimation of Survival with a Combination of Prevalent and Incident Cases in the Presence of Length Bias

Makvandi-Nejad, Ewa 24 September 2012 (has links)
In studying natural history of a disease, incident studies provide the best quality estimates; in contrast, prevalent studies introduce a sampling bias, which, if the onset time of the disease follows a stationary Poisson process, is called length bias. When both types of data are available, combining the samples under the assumption that failure times in incident and prevalent cohorts come from the same distribution function, could improve the estimation process from a revalent sample. We verify this assumption using a Smirnov type of test and construct a likelihood function from a combined sample to parametrically estimate the survival through maximum likelihood approach. Finally, we use Accelerated Failure Time models to compare the effect of covariates on survival in incident, prevalent, and combined populations. Properties of the proposed test and the combined estimator are assessed using simulations, and illustrated with data from the Canadian Study of Health and Aging.
10

Bayesian survival analysis

Abrams, Keith Rowland January 1992 (has links)
In cancer research the efficacy of a new treatment is often assessed by means of a clinical trial. In such trials the outcome measure of interest is usually time to death from entry into the study. The time to intermediate events may also be of interest, for example time to the spread of the disease to other organs (metastases). Thus, cancer clinical trials can be seen to generate multi-state data, in which patients may be in anyone of a finite number of states at a particular time. The classical analysis of data from cancer clinical trials uses a survival regression model. This type of model allows for the fact that patients in the trial will have been observed for different lengths of time and for some patients the time to the event of interest will not be observed (censored). The regression structure means that a measure of treatment effect can be obtained after allowing for other important factors. Clinical trials are not conducted in isolation, but are part of an on-going learning process. In order to assess the current weight of evidence for the use of a particular treatment a Bayesian approach is necessary. Such an approach allows for the formal inclusion of prior information, either in the form of clinical expertise or the results from previous studies, into the statistical analysis. An initial Bayesian analysis, for a single non-recurrent event, can be performed using non-temporal models that consider the occurrence of events up to a specific time from entry into the study. Although these models are conceptually simple, they do not explicitly allow for censoring or covariates. In order to address both of these deficiencies a Bayesian fully parametric multiplicative intensity regression model is developed. The extra complexity of this model means that approximate integration techniques are required. Asymptotic Laplace approximations and the more computer intensive Gauss-Hermite quadrature are shown to perform well and yield virtually identical results. By adopting counting process notation the multiplicative intensity model is extended to the multi-state scenario quite easily. These models are used in the analysis of a cancer clinical trial to assess the efficacy of neutron therapy compared to standard photon therapy for patients with cancer of the pelvic region. In this trial there is prior information both in the form of clinical prior beliefs and results from previous studies. The usefulness of multi-state models is also demonstrated in the analysis of a pilot quality of life study. Bayesian multi-state models are shown to provide a coherent framework for the analysis of clinical studies, both interventionist and observational, yielding clinically meaningful summaries about the current state of knowledge concerning the disease/treatment process.

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