Employer demands for flexible work practices have seen an increase in the diversity of employment relationships illustrated by a global growth of people working in contingent or precarious positions. Increasing evidence suggests that precarious employment is associated with poorer occupational health and safety (OHS) outcomes in terms of injury rates, disease risk and psychological wellbeing. This study used a cross sectional survey of 255 employees to compare the OHS experiences of temporary (N = 156, 61.2%) and permanent (N = 99, 38.8%) workers employed in three companies involved in the seasonal processing of primary agriculture products (dairy, meat and produce) in two regions of New Zealand. This research identified a clearly definable group of temporary workers (seasonals), who exhibit different characteristics to those commonly associated with precarious employment as they have an expectation of reasonable lengths of fairly secure employment (seasons exceed eight months). Many respondents only undertook one period of employment per year and were re-engaged in subsequent seasons. There are limited opportunities for alternative employment adjacent to these plants. This creates a dependant employment market, potentially putting labour in a weak bargaining position. This is countered by a high overall level of union membership (N = 181, 71%) and the operation of collective employment contracts. This may be atypical in seasonal industries. Injury numbers were similar (permanent N = 49, 49.5%, temporary N = 73, 46.8%) and serious injuries (permanent N = 23, 23.2%, temporary N = 31, 19.9%). Once a factor was introduced to compensate for exposure time, thereby creating a frequency rate, results showed a statistically significant difference with temporary workers suffering injuries and serious injuries with less exposure than their permanent counterparts (t (193.821) = -5.566, p < 0.05 and (t (236.928) = -2.160, p < 0.05 respectively). There was a significant difference in chronic injuries with permanent employees being more likely to have a chronic injury (F91,253) = 20.456, p<0.05). Most importantly, using the General Linear Model (logistic regression), when all other influences were controlled for, this research found employment status remained influential in determining whether a respondent was injured at work or not.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1978. / Typescript (photocopy). Includes bibliographical references (leaves 141-148). Also issued in print.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 38-40). Also issued in print.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1981. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 38-40).

Thesis (M.S.)--University of Michigan, Ann Arbor, 1978. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 141-148).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 237-242).

Thesis (M.Soc.Sc.)--University of Hong Kong, 1986. / Also available in print.

Resumo: Neste trabalho é feito o estudo do fenômeno da captura gravitacional temporária e do conceito de esfera de influência, considerando o papel da velocidade relativa. Este estudo foi feito através de simulações numéricas do problema circular restrito de três corpos e através do monitoramento da energia do problema de dois corpos. No caso da captura gravitacional temporária nós acompanhamos a variação de energia do problema de dois corpos (partícula-corpo secundário), de uma partícula que sofre um encontro próximo com um corpo massivo (um planeta, por exemplo). A evolução dessa energia mostra se a partícula foi capturada, ou não, para algumas condições iniciais específicas. Este procedimento resultou na obtenção de funções matemáticas que permitem o cálculo do chamado raio de captura em função da velocidade relativa. No estudo numérico da esfera de influencia, a variação da energia do problema de dois corpos no tempo também foi acompanhada, mas desta vez nós acompanhamos a energia do problema partícula-corpo central, para uma partícula que sofre um encontro próximo com o corpo secundário. A evolução desta energia mostra se a partícula foi afetada significativamente, ou não, pela influência gravitacional do corpo secundário, para condições iniciais específicas. Este procedimento resulta na obtenção de funções matemáticas que permitem o cálculo do raio da esfera de influência em função da velocidade relativa. Finalmente, a manobra de swing-by foi aplicada no estudo do caso dos asteróides Vesta e Magnya com o objetivo de explicar sua distante localização orbital em relação aos demais membros da família do asteróide Vesta. Este estudo mostrou que uma mudança na órbita do Magnya não seria proporcionada apenas pelo swing-by, e que ele deveria sofrer a ação de outros mecanismos para causar tal mudança. / Abstract: This work studies the phenomenom of the temporary gravitational capture and the concept of sphere of influence, taking into account the relative velocity. It has been done through numerical simulations of the restricted three-body problem, and through the analysis of the two-body energy. In the case of the temporary gravitational capture we followed the temporal variation of the two-body energy (particle-secondary body) of a particle that suffers a close enconter with a massive body (a planet, for instance). The evolution of such energy shows if the particle was captured or not, for some specific initial conditions. This procedure results in mathematical functions to calculate the so called capture radius as a function of the relative velocity. In the numerical study of the sphere of influence, we also followed the temporal variation of the two-body energy but, at this time, we followed the energy particle-central body of a particle that suffers a close encounter with a massive body (called secondary body). The evolution of such energy shows if the particle was significantly affected by the gravitational influence of the secondary body or not, for some specific initial conditions. This procedure results in mathematical functions to calculate the sphere of influence as a function of the relative velocity. Finally, the swing-by maneuver was applied in the study of the case of the asteroids Vesta and Magnya, in order to explain its distant orbital localization relative to the localization of the others members of the Vesta's family. This study showed that a change in the orbit of Magnya would not be proporcioned only by the swing-by, and that the asteroid Magnya should suffer the action of others mechanisms to cause it. / Orientador: Othon Cabo Winter. / Coorientador: Antonio Fernando B. de A. Prado. / Banca: Ernesto Vieira Neto. / Banca: Roberto Vieira Martins. / Mestre

OBJECTIVES: To evaluate in vitro the coronal leakage of endodontically treated teeth sealed with temporary restorative materials with or without coating sealants, and subjected to brushing and thermocycling. MATERIALS AND METHODS: One hundred two extracted human premolars and molars, were endodontically accessed, and restored with 3 types of temporary restorations: 1. Cavit (3M ESPE), 2. Ketac Molar (3M ESPE), 3. Riva Light Cure GlC (SDI). Each type of restoration had one subgroup with a coating (Cavit-Ketac Glaze, Ketac Molar- Ketac Glaze, Riva Light Cure GIC – Riva Coat) and the other without coating. Restored teeth were placed in artificial saliva at 37°C for 24 hours. Teeth were divided into 3 treatment subgroups: Group A: No treatment, soaked at 37° C artificial saliva; Group B: Teeth underwent thermocycling; Group C: teeth underwent both thermocycling and brushing. Thermocycling included 500 cycles between 5°C to 55°C. Tooth brushing was simulated in a brushing machine using 190g weight applied to 16,800 linear strokes. The control group was not exposed to thermocycling or brushing. Leakage was detected by immersion of specimens in 2% methylene blue dye for 24 hours. Specimens were epoxy embedded and sectioned longitudinally. The leakage scores were evaluated from photographs by longitudinal dye penetration depth scored 0 for no leakage and 4 for maximum leakage to the bottom of restoration. Statistical analysis was done to examine the effect of coating and post-treatment on leakage scores. RESULTS: All tested temporary restorative materials with coating had lower leakage than without coating in all experimental groups. CONCLUSIONS: The leakage of temporary restorative materials can be reduced by surface coating, however, thermocycling and brushing treatment can still generate some leakage. / 2020-06-28T00:00:00Z

Boston University. University Professors Program Senior theses. / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / 2999-01-01