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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.
361

Brood ecology and population dynamics of King Eiders

Mehl, Katherine Rose 14 July 2004 (has links)
Birth and death processes and the extent of dispersal directly affect population dynamics. Knowledge of ecological factors that influence these processes provides insight into natural selection and understanding about changes in population size. King eiders (Somateria spectabilis) breed across the arctic region of North America and winter in polar oceanic waters of the western and eastern regions of the continent. Here I studied a local population of King Eiders at Karrak Lake, Nunavut, where I used analysis of naturally-occurring stable isotopes (13C, 15N) from feathers, in conjunction with banding data, to investigate the extent of dispersal among winter areas and the influence of winter area on subsequent breeding. In addition, I used capture-mark-recapture methods to (1) investigate the relative contributions of survival and recruitment probabilities to local population dynamics, and (2) to test hypotheses about the influence of specific ecological factors on those probabilities or their components, e.g., nest success, duckling survival. Isotopic data suggested that female King Eiders were not strongly philopatric to wintering areas between years. Individuals that wintered in western seas initiated nests earlier and had slightly larger clutch sizes during early nest initiation relative to females that wintered in the east. Female condition during incubation did not vary by winter area. Female King Eiders of known breeding age were at least 3-years-old before their first breeding attempt. Age of first successful breeding attempt did not appear to be influenced by body size. However, after reaching breeding age, larger females apparently experienced greater breeding propensity. Adult survival rate (1996-2002) was estimated as 0.87 and recapture probabilities varied with time and ranged from 0.31 to 0.67. There is no evidence of survival advantages related to larger size. Population growth for this local study area was high, estimated at 20%/year with larger females contributing more to the population growth than smaller females. With continued population growth, density-dependent effects on components of recruitment appeared to emerge; the proportion of the female population that nested successfully declined with increasing population size. The probability of breeding successfully did not correlate with Mayfield estimates of nest success. To gain insight into King Eider brood ecology I, respectively, monitored 111 and 46 individually-marked ducklings from broods of 23 and 11 radio-marked King Eiders during 2000 and 2001. Total brood loss accounted for 84% of all duckling mortality with most brood loss (77%) less than 2 days after hatch. Estimated apparent survival rates of ducklings to 22 days of age were 0.10 for those that remained with radio-marked females, 0.16 for all ducklings, including those that had joined other broods, and 0.31 for broods. Ducklings brooded by larger females experienced higher survival than those brooded by smaller females, and ducklings that hatched earlier in the breeding season survived at higher rates. Overland brood movements of 1 km or more occurred in both years, and survival was greatest for ducklings that dispersed from Karrak Lake to smaller ponds than on Karrak Lake itself, the central nesting area. Estimates of duckling survival, combined with relative contributions to the population by adults, suggest that ecological factors such as body size can influence population growth. Furthermore, low duckling survival and delayed maturity, emphasize the need of high adult survival for population growth to occur. These data, in combination with evidence of dispersal among wintering areas have helped contribute to a broader understanding of North American King Eider demographics.
362

A case study of three pupils at Wandering Spirit Native Survival School in Toronto

Pellerin, Judith A. 03 July 2007 (has links)
The purpose of this study was to describe how three pupils in the senior room of Wandering Spirit Survival School in Toronto responded behaviorally to the cultural and academic experiences provided. Participant observation was used to collect data for the study during the period of September 10 to November 15, 1981. Information concerning pupil behavior was gathered during: periods of total-class instruction and periods of individual instruction by the regular classroom teacher; individually-assigned task time; class sessions with visiting resource persons; free time; Ojibway and French language instruction; instruction at Winchester Public School; Sacred Circle feasts; and recess. Pupil seatwork was collected and studied. Additional information was obtained through interviews with the three Subjects and with the director.<p>The study was conducted over a period of ten weeks and totalled ninety-seven hours fifty-one minutes of observation time. The Subjects were students in the senior room of Wandering Spirit Survival School, an alternative school for native children in Toronto, and their class consisted of thirteen pupils from grades five to eight. The procedures of this study yielded descriptive data of each Subject's behavior during the various types of activities observed. From the behavioral data, an account described each S's behavior over the ten-week study period, as it occurred in various situations and with various instructors/resource persons.' Frequency of behavior and changes in behavior were noted. The behavior of Ss was also discussed in light of the cultural and academic goals of the school. The data suggested that the school was partially meeting its cultural goals and was failing to meet its academic goals in the case of the three Ss studied.<p>Wandering Spirit Survival School aimed at providing a safe, nonthreatening environment for its pupils. The atmosphere of the school and the cultural activities of the Sacred Circle, feasts, and Ojibway language instruction were found to be useful in creating a sense of pride in being Indian for the three Ss of the study. More could have been done in providing pupils with a knowledge and understanding of native heritage, native history, and contemporary native issues. Although Ojibway language was taught three times a week, the three Ss of the study had not learned to read, write, or speak any of the language during the ten weeks of this study.<p>A second goal of Wandering Spirit Survival School was to prepare pupils academically so that, if they chose, they could successfully continue their education beyond grade eight. Observations suggested that the three Ss of the study were not being academically prepared for high school according to this study. The Ss spent a great deal of class instruction time engaged in other activities: talking, drawing pictures, walking around, playing with articles at their desks, leaving the room Their behavior was the same regardless of who the instructor was. The Ss were most attentive during audio-visual presentations and during lessons involving activity on the part of pupils. However, the teaching done at the school involved, for the most part, the use of textbooks and workbooks.<p>The teacher appeared to hold higher expectations for Jim than for Donald and Agnes. These expectations were reflected in the small amount<br> [Abstract truncated. Pages iv - v missing from thesis.]
363

<i>Escherichia coli</i>O157; prevalence, survival, and stress responses during prolonged heat and cold shocks

Vidovic, Sinisa 30 January 2008 (has links)
<i>Escherichia coli</i> O157 is a food borne pathogen of increasing public health concern worldwide. Cattle have been implicated as the primary reservoir of <i>E. coli</i> O157. The fact that the livestock industry has rapidly expanded in Saskatchewan makes it imperative to have a clear scientific understanding of the prevalence of <i>E. coli</i> O157 in this province as well as its survival in soil under ambient conditions.<p>Longitudinal and point studies were employed to determine the prevalence of <i>E. coli</i> O157 among Saskatchewans cattle. During a 2-year period, 23 feedlot and cattle operations were examined and an overall prevalence of 15.6% was reported. The most important finding was that the prevalence rates were highly dependent on cattle density. All <i>E. coli</i> O157 isolates obtained from this study were characterized by using multiplex PCR, RAPD fingerprinting, a Vero cell cytotoxicity assay and antibiotic susceptibility tests. This characterization revealed a surprisingly highly virulent and heterogenous population of <i>E. coli</i> O157 isolates. <p>Subsequently, the survival characteristics of <i>E. coli</i> O157:H7 ATCC 43894 in sterile soil and manure-amended soil microcosms, as well as in situ under ambient environmental conditions were examined. Findings from this work indicated that desiccation had the most lethal effect on cell viability, whereas nutritionally-rich soils significantly increased survival times of the pathogen population. <p>A final study was designed to examine the survival strategy of hyper- and hypothermally adapted <i>E. coli</i> O157 cells exposed to high and low temperatures, with specific focus on the role of RpoS. Using wild type and its rpoS null allele <i>E. coli</i> O157 strains, in combination with 2D PAGE, It was found that both heat and cold post-acclimation stimulons consisted of two large sub-groups: (i) stress proteins, and (ii) housekeeping proteins. Comparative proteomic analyses revealed that the GroEL/S chaperonin complex and Pnp ribonuclease played a crucial role in growth resumption during high and low temperatures, respectively. Notably, RpoS had no control over key stress proteins in either stress stimulon. RpoS, however, showed a significantly more pronounced role during cold temperatures, where it was seen to regulate key proteins involved in homoeoviscous adaptation as well as various housekeeping proteins of both stress stimulons.
364

Statistical modeling of longitudinal survey data with binary outcomes

Ghosh, Sunita 20 December 2007 (has links)
Data obtained from longitudinal surveys using complex multi-stage sampling designs contain cross-sectional dependencies among units caused by inherent hierarchies in the data, and within subject correlation arising due to repeated measurements. The statistical methods used for analyzing such data should account for stratification, clustering and unequal probability of selection as well as within-subject correlations due to repeated measurements. <p>The complex multi-stage design approach has been used in the longitudinal National Population Health Survey (NPHS). This on-going survey collects information on health determinants and outcomes in a sample of the general Canadian population. <p>This dissertation compares the model-based and design-based approaches used to determine the risk factors of asthma prevalence in the Canadian female population of the NPHS (marginal model). Weighted, unweighted and robust statistical methods were used to examine the risk factors of the incidence of asthma (event history analysis) and of recurrent asthma episodes (recurrent survival analysis). Missing data analysis was used to study the bias associated with incomplete data. To determine the risk factors of asthma prevalence, the Generalized Estimating Equations (GEE) approach was used for marginal modeling (model-based approach) followed by Taylor Linearization and bootstrap estimation of standard errors (design-based approach). The incidence of asthma (event history analysis) was estimated using weighted, unweighted and robust methods. Recurrent event history analysis was conducted using Anderson and Gill, Wei, Lin and Weissfeld (WLW) and Prentice, Williams and Peterson (PWP) approaches. To assess the presence of bias associated with missing data, the weighted GEE and pattern-mixture models were used.<p>The prevalence of asthma in the Canadian female population was 6.9% (6.1-7.7) at the end of Cycle 5. When comparing model-based and design- based approaches for asthma prevalence, design-based method provided unbiased estimates of standard errors. The overall incidence of asthma in this population, excluding those with asthma at baseline, was 10.5/1000/year (9.2-12.1). For the event history analysis, the robust method provided the most stable estimates and standard errors. <p>For recurrent event history, the WLW method provided stable standard error estimates. Finally, for the missing data approach, the pattern-mixture model produced the most stable standard errors <p>To conclude, design-based approaches should be preferred over model-based approaches for analyzing complex survey data, as the former provides the most unbiased parameter estimates and standard errors.
365

Comparison of proportional hazards and accelerated failure time models

Qi, Jiezhi 30 March 2009 (has links)
The field of survival analysis has experienced tremendous growth during the latter half of the 20th century. The methodological developments of survival analysis that have had the most profound impact are the Kaplan-Meier method for estimating the survival function, the log-rank test for comparing the equality of two or more survival distributions, and the Cox proportional hazards (PH) model for examining the covariate effects on the hazard function. The accelerated failure time (AFT) model was proposed but seldom used. In this thesis, we present the basic concepts, nonparametric methods (the Kaplan-Meier method and the log-rank test), semiparametric methods (the Cox PH model, and Cox model with time-dependent covariates) and parametric methods (Parametric PH model and the AFT model) for analyzing survival data.<p> We apply these methods to a randomized placebo-controlled trial to prevent Tuberculosis (TB) in Ugandan adults infected with Human Immunodificiency Virus (HIV). The objective of the analysis is to determine whether TB preventive therapies affect the rate of AIDS progression and survival in HIV-infected adults. Our conclusion is that TB preventive therapies appear to have no effect on AIDS progression, death and combined event of AIDS progression and death. The major goal of this paper is to support an argument for the consideration of the AFT model as an alternative to the PH model in the analysis of some survival data by means of this real dataset. We critique the PH model and assess the lack of fit. To overcome the violation of proportional hazards, we use the Cox model with time-dependent covariates, the piecewise exponential model and the accelerated failure time model. After comparison of all the models and the assessment of goodness-of-fit, we find that the log-logistic AFT model fits better for this data set. We have seen that the AFT model is a more valuable and realistic alternative to the PH model in some situations. It can provide the predicted hazard functions, predicted survival functions, median survival times and time ratios. The AFT model can easily interpret the results into the effect upon the expected median duration of illness for a patient in a clinical setting. We suggest that the PH model may not be appropriate in some situations and that the AFT model could provide a more appropriate description of the data.
366

Risk and Predictive Factors for Liver Cancer : Analysis of Data from a Cohort Study

Sookthai, Disorn January 2011 (has links)
The association between the risk of liver cancer and blood chemistry was investigated in a cohort study with 95,150 men and women from two counties in Sweden. In 1963-65, blood tests and physical measurements were undertaken. All individuals were then followed up until 2007, and a total of 312 were diagnosed with liver cancer. Using survival analysis and logistic regression, significant risk factors were identified. Stepwise Cox proportional hazards regression applied to a main effect model revealed that Glutamic Pyruvate Transaminase (GPT) and Thymol Turbidity (TYM) were the most significant risk factors (p&lt;0.0001), followed by Protein-Bound Hexoses (HEX)  (p=0.002), sex (p=0.02), and Serum Iron (p= 0.03). Increasing the level of GPT expressed in U/L from normal (&lt;21) to slightly elevated (21, 31) or substantially elevated (&gt;31) raised the hazard of experiencing liver cancer by a factor of 1.45 and 4.09, respectively. In addition, GPT was found to be the most significant risk factor in almost all age groups among both men and women. However, there was no evidence that elevated GPT levels within the normal range (&lt;21), influenced the risk of liver cancer. Additional subgroup analyses revealed that TYM was highly significant within the group with normal GPT, and a high level of HEX (≥134 mg/dl) increased the hazard 1.55 times in comparison with the lowest HEX group (&lt;115 mg/dl). BMI was significant only in the male subgroup  (p&lt;0.01) and, in the obesity group, the hazard of experiencing liver cancer was 1.99 times higher than in the normal BMI group. A significant three-way interaction between GPT, BMI and gender was present (p=0.05) with a robust significant two-way interaction between GPT and BMI (p&lt;0.01) in the male subgroup.
367

Contrasting survival strategies of hatchery and wild red drum: implications for stock enhancement

Beck, Jessica Louise 15 May 2009 (has links)
Post-release survival of hatchery fishes is imperative to the success of any supplemental stocking program. The purpose of this research was to identify differences between hatchery and wild red drum (Sciaenops ocellatus) and determine if pre-release exposure techniques improve survival of hatchery individuals. Objectives were to contrast survival skills of hatchery and wild red drum from different locations, and examine if exposure to natural stimuli (e.g., habitat, predators, live prey) enhances survival skills in naïve hatchery red drum. Laboratory trials using high-speed videography (250 frames per second, fps) and field mesocosm experiments were used to investigate differences in prey-capture (e.g., attack distance, mean attack velocity, capture time, maximum gape, time to maximum gape, gape cycle duration, and foraging behaviors) and anti-predator performance (e.g., reaction distance, response distance, maximum velocity, time to maximum velocity, mean acceleration, and maximum acceleration) of hatchery and wild red drum. Results indicated that anti-predator performance measures differed significantly between hatchery and wild red drum. Variability in prey-capture and anti-predator performance for hatchery and wild red drum was high (CV range: 5.6 – 76.5%), and was greatest for hatchery fish for the majority of performance variables tested. Exposure to habitat (Spartina alterniflora marsh) did not appear to afford any obvious survival benefits to hatchery red drum, although survival skills did vary according to ontogenetic stage. Hatchery red drum exposed to natural predators (pinfish, Lagodon rhomboides) exhibited significantly greater attack distances during feeding events, and anti-predator performance variables were 20 – 300% in these individuals versus naïve red drum. In predation experiments with free-ranging pinfish predators, mortality rates (Z) ranged from 0.047 – 0.060 h-1 · predator-1; however no significant differences in mortality were found between fish reared with and without predators. Hatchery red drum reared on live prey (Artemia franciscana, mysid shrimp) demonstrated enhanced prey-capture and foraging behaviors as well as anti-predator performance relative to fish reared on artificial (pellet) diets. Findings of this research indicate that several behavioral patterns differed between hatchery and wild red drum; however, these differences can be mediated through the use of various pre-release exposure techniques.
368

Research on the strategy for small and medium enterprises¡¦ model transition

SU, KUO-TSAIR 17 August 2004 (has links)
­^¤åºK­n(Abstract) Since the government adopted the ¡§ Patience and Goodwill¡¨ policy to decelerate the ongoing industries¡¦ emigration, it inevitably results the deterioration on Taiwan political and economic environments and of being prone to the world factory ¡VChina. We could see that small to medium size companies are facing the dilemma- emigrating to China or stay. All industries in Taiwan have been forced to upgrade either for survive or business longevity This case study based on the competitive advantage theory and it evaluate the strategies incurred during small to medium size companies¡¦ internal upgrading; moreover, further identify its causes, directions and the condition within the whole process to find out the confronting and solution The goal is to find the way out, structure, and module. Herewith provide clear explanation and examination in order to further formulating for subject companies under circumstances of operating and business expansion. Meanwhile, the re-examination and adjustment of the formula either as being references and instruction for subject companies or fundament for future research after long-term operation. In this research analysis, (1) analyses external fastener industry environment and classify the success factors. (2) Analyses the subject company internal structure and characters to identify its key factor to success in the industry, (3) Marketing analysis. By applying the ¡§ Five forces framework and ¡§ SWOT¡¨ in order to- Firstly, realize the potential market opportunity and expanding space; Secondly, try to identify its core competency and competitive advantage. Thirdly, construct its sustainable competitive advantage to maintain its strength and finally lead to development and benefited prolong operation in the market place. The disclose of study: (1) Most of traditional industries have been on the progress of upgrading (2) Most of upgrading traditional manufacturers/suppliers have complete the basic operational upgrading. (3) Observing two tips from the smile curve, the early adopters have been benefited from upgrading changes. (4) The research subject ¡VS company, from a small size trading company to nowadays a multinational company, the continuous upgrading by adoption of positioning strategy is similarly develop toward two sides of the curve and the effects has been appealed. All above findings support there should have a model of best practice be generated for all the subject companies or similar industry reference Key words: sustainable competitive advantages, key success factors, key survival factor.
369

Medical cost and treatment outcome related factors for HCC

Huang, Ching-Fen 02 January 2006 (has links)
Background: Hepatocellular carcinoma (HCC) is the leading cause of cancer in Taiwan, which consumes high medical expense among the total healthcare expenditure and becomes the significant burden to the finance of National Health Insurance (NHI). However, population-based statistics about the cost with the survival rate is rare. Objective: Through analyzing the data from the Bureau of National Health Insurance and hospital clinical files, we estimated the medical expenditure for treating HCC patients and the factors associated with treatment outcome. Methods: The National Health Insurance data from 1996 to 2002 with ICD-9 code 155 were used, which include age, gender, visiting time, and medical cost for inpatient or outpatient visits. The population-based data were analyzed to estimate 1-5 year survival probability and medical cost of HCC patients. In hospital-based data, 189 patients from 1991 to 2004 were recorded by clinical chart and 62 of them diagnosed during 2002 and 2004 were further selected to match the claim data. These informations were used for computing survival or recurrence probability, related factors, and medical cost. Results: For all incident cases in 1997, the average 5-year cumulated cost was NT$ 219,398, while the cumulated cost for those patients survived more than five years was NT$ 491,288. The survival probability was 30.8% for more than one year, 20.9% for more than two years, 15.2% for more than three years, 11.3% for more than four years, and 9.7% for more than five years in 1997 respectively. Female and those age >45-65 years old seemed to have better survival outcomes than male and those age ¡Ø45 years old or >65 years old , the averaged medical cost per treated case surviving more than five years were T$2,457,214 for male and NT$ 1,987,874 for female. Hospital clinical data indicated that TNM stages, therapy choice, liver cirrhosis, and ascites are risk factors for surviving. Although pre-TACE treatment has higher expenditure, its five-year survival probability is better than other treatments in this research. Conclusions: This paper presents medical cost with survival probability and its associated factors for HCC patients and further estimates the medical cost per life saved for treating HCC patients. Our findings can offer the policy-maker, provider, and patient to evaluate the intervention or prevention program in the future.
370

Clinical results of nonsurgical treatment for spinal metastases

Iwata, Hisashi, Yamamura, Shigeki, Sugiura, Hideshi, Kobayashi, Hidetoshi, Inagaki, Jiro, Takahashi, Mitsuru, Katagiri, Hirohisa 01 December 1998 (has links)
名古屋大学博士学位論文 学位の種類 : 博士(医学)(論文) 学位授与年月日:平成11年1月22日 片桐浩久氏の博士論文として提出された

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