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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

Social Determinants of Racial and Ethnic Disparities in Perinatal Morbidity: Social Origins of Perinatal Health Study

Salinas-Miranda, Abraham A. 01 January 2013 (has links)
BACKGROUND: The social causation of preterm birth remains elusive, without an adequate explanatory framework. Thus, this study proposed and evaluated a conceptual model of the social determinants of perinatal health for the understanding of perinatal health disparities. METHODS: A prospective cohort study was conducted with pregnant women between 20 and 35 weeks gestation who were participating in two Healthy Start programs in Central Florida, from July 2011-August 2013. Perinatal health was operationalized based on gestational age, birth weight, and healthy start infant risk screen score. The predictors were: early life adversity, social position, maternal health-related quality of life, maternal stress, racism and discrimination, lack of social support, father involvement during pregnancy, intimate partner violence, and adverse maternal behaviors. Data collection consisted of a self-administered survey and birth outcome data was obtained from Healthy Start administrative databases. The statistical framework was structural equation modeling. RESULTS: The study sample was racially and ethnically diverse (N, Hispanics=72; N, non-Hispanic blacks=61; and N, non-Hispanic whites=48). The majority of mothers in this study were single or not married (cumulative 76%), US born (74.6%), and with English speaking preference (74.6%). The sample tended to cluster in low income groups (cumulative 58% less than $25,000 annual household income) and with education levels of less than high school (79.6%). A greater proportion of Hispanic mothers were married (66.7%) compared to non-Hispanic blacks (34.4%) and non-Hispanic whites (47.9%). Only 41.7% had completed high school, compared to 63.9% non-Hispanic blacks and 64.6% non-Hispanic whites. Nearly all non-Hispanic blacks and non-Hispanic whites were born in the US, compared to only 43.1% Hispanic mothers. Only 40% of non-Hispanic blacks reported on currently living with the baby's father at the time of the survey, compared to 66.2% for Hispanic mothers, and 58.3% for non-Hispanic whites. Furthermore, non-Hispanic blacks reported a greater proportion of discriminatory experiences in daily situations (mean = 4.74), compared to the other groups (mean for Hispanics was 2.14, and mean for non-Hispanic whites was 1.95). Non-Hispanic whites reported the greater proportion of daily alcohol use (mean 3.8 beverages per month), compared to other groups (Hispanic mean was 0.69, and non-Hispanic blacks mean was 1.68). Non-Hispanic white mothers also presented a higher mean of adverse childhood experiences before 18 years of life (mean = 3.4), compared to other groups (mean for Hispanics was 1.63, mean for non-Hispanic blacks was 2.48). With the exception of the confirmatory factor analysis for intimate partner violence (low correlations with common factor), all other confirmatory factor analyses demonstrated an acceptable Chi-square to degrees of freedom ratio (<6), and the RMSEA was less than 0.08 (minimum for acceptance). Thus, structural equation models were estimated subsequently. The first model was a model of direct effects between social position and perinatal health (hypothesis 1: direct effects), which demonstrated a good fit as indicated by X2/DF ratio of 1.4 (Chi-Square = 19, DF =13) and a RMSEA of 0.05. However, the direct effect of social position was very small and non-significant (Beta=-.02, p-value =.76), supporting the conclusion that a simple direct effect of social position on perinatal health was not found in this population. The second model explored indirect effects of social position through intermediate factors (hypothesis 2: indirect effects), which demonstrated a good fit to the data, as indicated by a Chi-square/df ratio = 1.45 and RMSEA=.05. Social support was a statistically significant mediator between social position (Beta=0.284, p<0.05) and perinatal health (Beta=0.22, p<0.05). The third model incorporated adverse childhood experiences as predictor of social position effects. Adverse childhood experiences were significantly associated with social position (Beta=.363, p<0.05) and moderated the effects of social position on social support and perinatal health. In the presence of adverse childhood experiences, the social position was significantly associated to maternal health-related quality of life (Beta=-0.226, p<0.05) and maladaptive maternal behaviors (Beta=0.654, p<0.05). CONCLUSION: This study demonstrated synergistic effects of social determinants of health. Controlling for all factors considered, social support was significantly associated with perinatal health, which presents implications for strengthening prenatal programs that provide support to pregnant women. Findings need to be replicated in larger studies with the US general population. Policy makers and researchers need to pay greater attention to the role of early life adversity on perinatal health outcomes.
22

Positive Psychology in Education: Hope and time perspective from Rasch, latent growth curve model, and phenomenological research approaches

Ring, Joseph January 2016 (has links)
The primary purposes of this study were to identify motivational typologies of growth and stability and identify people who have crossed a boundary in terms of levels of hope and time perspective. This study draws upon two fields, philosophy and psychology. The philosophical framework traces its roots back to American pragmatism and Alfred North Whitehead’s Process Philosophy. The second set of theories proposed for investigation came from the relatively recent empirical endeavor known as positive psychology. Specifically, I tested the construct validity and predictive utility of hope and time perspective as predictors of academic time management and academic outcomes in a Japanese sample. The participants were 467 students attending one of the largest private universities in Japan. Several instruments were used to measure the relationship between hope and time perspective as independent variables and self-reported academic outcomes. The instruments were the Hope Disposition Survey, the Zimbardo Time Perspective Inventory, self-reported TOEIC and GPA scores, and the Vocabulary Size Test. The research design was a quantitative and qualitative mixed-methods research plan. Two relatively recent constructs from the area of positive psychology research known as hope theory (a goal-oriented construct) and the Zimbardo Time Perspective Inventory were utilized for empirical investigation. The use of a mixed-method research design allowed this study to add to our knowledge of the roles of hope and time management in goal directed behavior. The analytical tools included the Rasch model, confirmatory factor analyses (CFA), structural equation modeling (SEM), and latent growth curve modeling (LGM). The qualitative analysis was a phenomenological investigation (similar to a case study) into the relationship between affect, cognition, and motivation utilizing a Process Philosophy framework. Results of the Rasch and CFA indicated that hope and time perspective were viable constructs for this sample. The hope SEM results indicated that hope had a positive relationship with academic outcomes as hypothesized. The time perspective SEM indicated that future time perspective had a positive relationship and that present-hedonism had a negative relationship with academic behavior as hypothesized. LGM results indicated that study time management had a non-linear relationship with the academic calendar. Both sets of results must be considered with caution due to a design flaw in the data collection instruments and high levels of attrition for the LGMs. Finally, the interview results indicated that students in the sample were extrinsically motivated by situational variables such as professor signals of how to, how much, when to, and what to study and that transitions from secondary to tertiary level studies were difficult for students with low levels of hope. The results were interpreted to suggest that levels of student engagement in the sample were at a less than desirable level when compared to OECD or North American university expectations. However, results were considered to be generally supportive of hope and time perspective theory. / Applied Linguistics
23

Individual and age-related differences in face-cognition

Hildebrandt, Andrea 01 September 2010 (has links)
Experimentelle und neurophysiologische Studien weisen auf eine Spezifität der Gesichterkognition hin. In der differentiellen Psychologie wird ein Schwerpunkt auf die Differenzierbarkeit sozio-kognitiver Leistungen von akademischen Fähigkeiten gelegt. Dabei werden bislang kaum Versuche unternommen, Messmodelle zu etablieren, die in neurokognitiven Modellen verankert sind. Basierend auf neuartigen Versuchen zur Etablierung solcher Modelle ist es das Ziel dieser Dissertation, die Robustheit dieser Modelle aus einer entwicklungspsychologischen Perspektive zu betrachten und diese zu erweitern. Zudem werden altersbedingte Leistungsunterschiede in der Gesichterkognition auf der Ebene latenter Faktoren ermittelt und die Hypothese altersbedingter kognitiver Dedifferenzierung mit modernen Methoden kritisch untersucht. Das Hauptziel ist die Erbringung entwicklungspsychologischer Evidenz für die Spezifität der Gesichterkognition. In einem ersten - primär methodologischen - Manuskript wird erstmalig in der Literatur die Implementierung von Funktionen der Beobachtungsgewichtung aus der nicht-parametrischen Regression für Strukturgleichungsanalysen vorgeschlagen. Diese Methode ergänzt Multigruppenanalysen bei der Untersuchung kognitiver Dedifferenzierung. Weitere vier Manuskripte adressieren Fragestellungen zur Gesichterkognition und zeigen: 1) Gesichterwahrnehmung, Gesichtergedächtnis und die Schnelligkeit der Gesichtererkennung sind separierbare Prozesse über die gesamte erwachsene Lebensspanne; 2) die Schnelligkeit der Gesichtererkennung kann nicht von der Schnelligkeit der Emotions- und Objekterkennung faktoriell getrennt werden; 3) Gesichterwahrnehmung und Gesichtergedächtnis können bis zum späten Alter von allgemeinen kognitiven Fähigkeiten getrennt werden, und 4) eine leichte Dedifferenzierung zwischen Objekt- und Gesichterkognition tritt auf der Ebene von Akkuratheitsmessungen auf. Implikationen sind in den Manuskripten ausführlich diskutiert und im Epilog zusammengefasst. / Cognitive-experimental and neuropsychological studies provided strong evidence for the specificity of face cognition. In individual differences research, face tasks are used within a broader variety of tasks, usually with the intention to measure some social skills. Contemporary individual differences research still focuses on the distinction between social-emotional vs. academic intelligence, rather than establishing measurement models with a solid basis in experimental and neuropsychological work. Building upon recent efforts to establish such measurement models this dissertation aimed to extend available models and assess their robustness across age. Furthermore, it investigates mean age differences for latent factors, critically looks at phenomena of dedifferentiation with novel and innovative analytic methods, and attempts to provide more evidence on the uniqueness and communalities of face cognition throughout adulthood. In a first primarily methodological manuscript, we propose for the first time in the literature an implementation of functions to weight observations used in nonparametric regression approaches into structural equation modeling context, which can fruitfully complement traditionally used multiple-group approaches to investigate factorial dedifferentiation. In the following four manuscripts, we investigated individual and age-differences in face cognition. Results show that: 1). Face perception, face memory and the speed of face cognition remain differentiable throughout adulthood; 2). The speed of face cognition is not differentiable from the speed of perceiving emotional expressions in the face and complex objects, like houses; 3). Face perception and memory are clearly differentiable from abstract cognition throughout adulthood; and 4). A slight dedifferentiation occurs between face and object cognition. Implications are discussed in the manuscripts and the epilogue.
24

Equações estruturais aplicadas a modelos causais de câncer de pulmão / Structural equation models applied to lung cancer causal models

Baltar, Valéria Troncoso 21 February 2011 (has links)
Introdução: O câncer de pulmão (CP) é o tipo de câncer que mais mata no mundo e o cigarro ainda é sua causa mais importante. Além disso, a alimentação tem sido associada ao CP, por ser fonte de vitaminas e aminoácidos que fazem parte do metabolismo do carbono (MC). O MC é considerado mecanismo chave na manutenção da integridade do DNA e na regulação da expressão gênica, que, dessa forma, deve estar relacionado à carcinogênese. A ativação da imunidade está associada ao envelhecimento em indivíduos saudáveis, assim como a uma série de patologias, incluindo o câncer. Objetivo: Estudar como o MC, a ativação da imunidade e o tabaco estão relacionados ao risco de CP em um estudo caso-controle aninhado à coorte do EPIC (European Prospective Investigation into Cancer and Nutrition). Métodos: Para avaliar se os níveis plasmáticos de cotinina são um bom biomarcador da exposição ao tabaco, foram utilizados modelos lineares generalizados. Para avaliar os efeitos do tabaco, do MC e da ativação da imunidade no risco de CP, foram aplicados modelos de equações estruturais (MEE) de duas maneiras diferentes (com e sem variáveis latentes). Resultados: Com base nas respostas aos questionários de qualidade de vida, com relação às questões sobre fumo ativo e passivo, a cotinina se mostrou um bom biomarcador de exposição recente ao tabaco (tanto o aumento da exposição passiva quanto ativa foram significativas, P<0,001 e P<0,001 respectivamente). Em um MEE com variáveis observadas, incluindo o MC e a via de ativação da imunidade, a metionina e o folato como causas proximais apresentaram uma forte e inversa associação com o risco de CP. O aumento em um desvio-padrão nos níveis séricos de metionina e de folato significou uma redução no risco de 19 por cento (P<0,01) e 12 por cento (P=0,03) respectivamente. Em um MEE com variáveis latentes (cada uma representando o conjunto de vitaminas e aminoácidos importantes para promover: metilação de DNA, síntese de núcletídeos e imune ativação), foram encontrados efeitos protetores diretos da metilação do DNA (P=0,018) e da imune ativação (P=0,037); por outro lado, a síntese de nucletídeos não apresentou efeito no risco do câncer (P=0,098). Nas duas abordagens de MEE o cigarro permaneceu como a causa de maior impacto. Conclusões: A cotinina mostrou-se um bom biomarcador da exposição ao tabaco (ativa e passivamente). Confirmou-se que a via de metilação é um fator de proteção contra o CP. A ativação da imunidade apresentou um efeito direto de proteção contra o CP no modelo com variáveis latentes, equanto que, a síntese de nucletídeos não apresentou relação com o CP. O tabaco continua sendo o fator de maior impacto no risco de CP / Background: Lung cancer (LC) continues to be the most common cancer death in the world. Tobacco exposure continues to be the most important cause. In addition, micronutrient intake has been linked to LC, because they are the main source of vitamins and amino acids involved in the one-carbon metabolism (OCM) which is considered key in maintaining DNA integrity, regulating gene expression, and may thus affect carcinogenesis. Immune activation is involved in the aging process in normal healthy individuals as well as in a number of pathologies, including cancer. Objectives: To investigate how OCM, immune activation and tobacco are related to LC incidence in a nested case-control study from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Methods: To validate plasma cotinine levels as a good biomarker for tobacco exposure, a generalized linear model was applied. To evaluate the effects of tobacco, OCM and immune activation in LC, structural equation models (SEM) were applied in two different ways. Results: Based on questions about smoking, passive smoking and number of cigarettes smoked, it was shown that cotinine is a good biomarker for tobacco exposure (passive and active exposure with significant relation, p<0.001 and P<0.001, respectively). In a SEM model with only observed variables, including OCM and immune activation, methionine and folate as proximal causes presented a strong and inverse relation with LC risk. An increase in one standard deviation of serum levels of methionine and folate meant a 19 per cent (P<0.01) and 12 per cent (P<0.01) reduction in LC risk, respectively. In a SEM including latent variables (each one including vitamins and amino acids important to promote DNA methylation, nucleotide synthesis and immune activity), a direct and protective effect for DNA methylation (p=0.018) and immune activation was found (p=0.037), whereas nucleotide synthesis did not present a significant total effect. In both approaches of SEM, tobacco exposure remains with the highest impact on LC risk. Conclusions: It was found that cotinine is a good biomarker of tobacco exposure (active and passive). It was confirmed that methylation protects against LC. Immune activation presented a direct protective effect in the latent model, while nucleotide synthesis was not confirmed to be related to LC risk. Tobacco effect remains as the factor with highest impact in lung cancer
25

Influência dos fatores de situação socioeconômica, de aceitação da gravidez e da assistência pré-natal na mortalidade fetal: análise com modelagem de equações estruturais / Influence of socioeconomic situation and acceptance of pregnancy factors and prenatal care on fetal mortality: analysis through structural equation modeling

Alencar, Gizelton Pereira 18 February 2009 (has links)
Introdução. As hipóteses levantadas sobre as relações entre as variáveis de exposição e o óbito fetal, via diversos mecanismos, são desenhadas em um diagrama a partir de um quadro conceitual feito pelo pesquisador. Testes sobre essas relações podem ser feitos por meio da modelagem por equações estruturais (MEE). Objetivo. Este estudo objetiva compreender o papel da situação socioeconômica (SSE), da não-aceitação da gravidez (nAdG) e assistência pré-natal na mortalidade fetal, na região sul do município de São Paulo, em 2000. Métodos. Foram construídas variáveis latentes para representar a situação socioeconômica e a não-aceitação da gravidez, a partir de dados da pesquisa do tipo caso-controle sobre mortalidade fetal no município de São Paulo, feita em 2000. Foi testado um modelo para o desfecho óbito fetal com as variáveis latentes, a assistência pré-natal, intercorrências (hipertensão, diabetes gestacional, sangramento vaginal) e retardo de crescimento intra-uterino (RCIU) por meio do MEE. A SSE foi formada por escolaridades da mãe e do chefe da família, classificação socioeconômica e renda per capita; a nAdG foi formada a partir das reações da mãe, pai e família, tentativa de aborto e se a gravidez foi planejada. Resultados. O modelo final apontou a relação entre a situação socioeconômica e não-aceitação da gravidez sobre a mortalidade fetal, passando pelo cuidado de pré-natal inadequado, modelo no qual intercorrências e RCIU também tem efeito sobre o desfecho. Conclusões. Os resultados sugerem que aceitação negativa da gravidez e o efeito da situação socioeconômica desfavorável, mediados pela atenção de pré-natal, podem ser amenizadas com uma maior qualidade nas visitas de pré-natal, especialmente em mães de maior vulnerabilidade social. / Introduction. The hypothesis about the relations among exposure variables and the fetal death are written as a diagram designed from a conceptual framework given by the researcher. Tests on these relations can be performed using structural equation modeling (SEM). Objective. This study aim to understand the role of socioeconomic situation (SES), non-acceptance of pregnancy (nAoP) and prenatal care on fetal mortality, in region south of the city of São Paulo, in 2000. Methodology. The measurement models were created to the latent variables SES and nAoP, from case-control study on fetal mortality in Sao Paulo city, in 2000. It was tested a model with SES, nAoP, prenatal care, medical complications (hypertension, gestational diabetes, vaginal bleeding), intra-uterine growth retardation (IUGR) on the outcome, performed by SEM. Results. The SES was composed by mothers and household heads years of study, socioeconomic classification index, and income per capita income; The AoP was composed by reactions of mother, father and family, attempted abortion and planned gestation. The final model showed the effect of SES and AoP on fetal death mediated by prenatal care, in a model where medical complications and IUGR also has an effect. Conclusion. The results suggests that negative acceptance of pregnancy and unfavorable socioeconomic situation, mediated by prenatal care, could be minimized improving the quality of prenatal care especially to those who are more social vulnerable.
26

A Livable City Study in China Using Structural Equation Models

Song, Yang January 2011 (has links)
The concept of livable city was put forward naturally and began to gain more attention when people care more about human needs during the economic development. In this paper, we define a livable city as an urban area takes the residents' demand as first priority. It has a pleasant ecological environment, a mature community with rich public resources such as culture, transportation and medical system, and being economically well developed. Our study first reviews the theory development and literature on the subject. Then we set up a structural equation model (SEM) to verify the theory based on early works and find the dimensions that are important to the development of livable city. Using the data from China City Yearbook, 2007, a SEM analysis was performed. The result showed that a well developing economic system has positive influence on a city's livability.
27

The role of information in transit use by undergraduate and graduate students in Brazil and Denmark

MONTEIRO, Mayara Moraes 29 February 2016 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-09-02T13:18:26Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) vs. definitiva_Dissertação_Mayara Moraes Monteiro.pdf: 4228121 bytes, checksum: 54dc912414b3c77351997697e1806b2d (MD5) / Made available in DSpace on 2016-09-02T13:18:26Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) vs. definitiva_Dissertação_Mayara Moraes Monteiro.pdf: 4228121 bytes, checksum: 54dc912414b3c77351997697e1806b2d (MD5) Previous issue date: 2016-02-29 / CNPq / With the fast improvement of technology, accompanied by changes in the lifestyle and the growth of cities, that made the Public Transport (PT) system more complex, delivery of integrated information on PT systems in an efficient and clear way are of the outmost importance but not always available. This study sought to understand the relation between travel information, PT use intentions and non-habitual travel (at night). The hypothesis is that PT use intentions are related to the perceived usefulness and the ease-of-use of the system, which are related to information quality and real-time information availability. The hypothesized relations are anchored theoretically in the Extended Technology Acceptance Model and validated empirically in two sources of data: (i) Copenhagen (Denmark), characterized by a highly integrated PT system with an advanced web-based information system; (ii) Recife and Natal (Brazil), characterized by a lower perceived Level Of Service (LOS) and non-integrated information sources. The data was collected through a tailor-made survey answered for 1,123 university students in Denmark and Brazil. Structural equation models were employed for explaining the use of PT as a function of the observed respondent characteristics and the latent constructs. The results show: (i) information quality is essential for explaining PT use; (ii) perceived information quality is directly and positively related to perceived LOS, convenience and familiarity with the PT system; (iii) the use of real-time information is positively related to information quality and familiarity, while it is negatively associated with perceived PT security; (iv) PT use at night is positively related to habitual PT use and information search / Com a rápida melhoria da tecnologia, acompanhada por mudanças no estilo de vida, e o crescimento das cidades, que tornou o transporte público (TP) muito mais complexo, entregar informação integrada do sistema de transporte de uma forma eficiente e clara é de extrema importância, mas nem sempre está disponível. Este estudo procurou entender a relação entre informações sobre viagens, intenções de uso de TP e viagens não habituais (à noite). A hipótese é que as intenções de uso de TP estão relacionadas com a percepção sobre a utilidade e a facilidade de uso do sistema, que estão relacionados com a qualidade da informação e a disponibilidade de informação em tempo real. As relações hipotéticas são ancoradas teoricamente na Extensão do Modelo de Aceitação Tecnológica e validado empiricamente através de duas fontes de dados: (i) Copenhague (Dinamarca), caracterizado por um sistema de transporte altamente integrado com um avançado sistema de informação baseado na web; (ii) Recife e Natal (Brasil), caracterizadas por um nível de percepção do nível de serviço como mais baixo e fontes de informação não integradas. Os dados foram recolhidos através de um questionário feito sob medida e respondido por 1.123 estudantes universitários na Dinamarca e no Brasil. Modelos de equações estruturais foram utilizados para explicar a utilização do TP em função das características observadas dos respondentes e os construtos latentes. Os resultados mostram: (i) a qualidade da informação é essencial para explicar o uso do TP; (ii) a percepção da qualidade da informação está direta e positivamente relacionada com a percepção do nível de serviço, conveniência e familiaridade com o sistema de TP; (iii) o uso da informação em tempo real está positivamente relacionado com a qualidade da informação e familiaridade, enquanto está associado negativamente com a percepção de segurança do TP; (iv) utilização do TP à noite está positivamente relacionada com a utilização habitual do TP e a busca de informações
28

Equações estruturais aplicadas a modelos causais de câncer de pulmão / Structural equation models applied to lung cancer causal models

Valéria Troncoso Baltar 21 February 2011 (has links)
Introdução: O câncer de pulmão (CP) é o tipo de câncer que mais mata no mundo e o cigarro ainda é sua causa mais importante. Além disso, a alimentação tem sido associada ao CP, por ser fonte de vitaminas e aminoácidos que fazem parte do metabolismo do carbono (MC). O MC é considerado mecanismo chave na manutenção da integridade do DNA e na regulação da expressão gênica, que, dessa forma, deve estar relacionado à carcinogênese. A ativação da imunidade está associada ao envelhecimento em indivíduos saudáveis, assim como a uma série de patologias, incluindo o câncer. Objetivo: Estudar como o MC, a ativação da imunidade e o tabaco estão relacionados ao risco de CP em um estudo caso-controle aninhado à coorte do EPIC (European Prospective Investigation into Cancer and Nutrition). Métodos: Para avaliar se os níveis plasmáticos de cotinina são um bom biomarcador da exposição ao tabaco, foram utilizados modelos lineares generalizados. Para avaliar os efeitos do tabaco, do MC e da ativação da imunidade no risco de CP, foram aplicados modelos de equações estruturais (MEE) de duas maneiras diferentes (com e sem variáveis latentes). Resultados: Com base nas respostas aos questionários de qualidade de vida, com relação às questões sobre fumo ativo e passivo, a cotinina se mostrou um bom biomarcador de exposição recente ao tabaco (tanto o aumento da exposição passiva quanto ativa foram significativas, P<0,001 e P<0,001 respectivamente). Em um MEE com variáveis observadas, incluindo o MC e a via de ativação da imunidade, a metionina e o folato como causas proximais apresentaram uma forte e inversa associação com o risco de CP. O aumento em um desvio-padrão nos níveis séricos de metionina e de folato significou uma redução no risco de 19 por cento (P<0,01) e 12 por cento (P=0,03) respectivamente. Em um MEE com variáveis latentes (cada uma representando o conjunto de vitaminas e aminoácidos importantes para promover: metilação de DNA, síntese de núcletídeos e imune ativação), foram encontrados efeitos protetores diretos da metilação do DNA (P=0,018) e da imune ativação (P=0,037); por outro lado, a síntese de nucletídeos não apresentou efeito no risco do câncer (P=0,098). Nas duas abordagens de MEE o cigarro permaneceu como a causa de maior impacto. Conclusões: A cotinina mostrou-se um bom biomarcador da exposição ao tabaco (ativa e passivamente). Confirmou-se que a via de metilação é um fator de proteção contra o CP. A ativação da imunidade apresentou um efeito direto de proteção contra o CP no modelo com variáveis latentes, equanto que, a síntese de nucletídeos não apresentou relação com o CP. O tabaco continua sendo o fator de maior impacto no risco de CP / Background: Lung cancer (LC) continues to be the most common cancer death in the world. Tobacco exposure continues to be the most important cause. In addition, micronutrient intake has been linked to LC, because they are the main source of vitamins and amino acids involved in the one-carbon metabolism (OCM) which is considered key in maintaining DNA integrity, regulating gene expression, and may thus affect carcinogenesis. Immune activation is involved in the aging process in normal healthy individuals as well as in a number of pathologies, including cancer. Objectives: To investigate how OCM, immune activation and tobacco are related to LC incidence in a nested case-control study from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Methods: To validate plasma cotinine levels as a good biomarker for tobacco exposure, a generalized linear model was applied. To evaluate the effects of tobacco, OCM and immune activation in LC, structural equation models (SEM) were applied in two different ways. Results: Based on questions about smoking, passive smoking and number of cigarettes smoked, it was shown that cotinine is a good biomarker for tobacco exposure (passive and active exposure with significant relation, p<0.001 and P<0.001, respectively). In a SEM model with only observed variables, including OCM and immune activation, methionine and folate as proximal causes presented a strong and inverse relation with LC risk. An increase in one standard deviation of serum levels of methionine and folate meant a 19 per cent (P<0.01) and 12 per cent (P<0.01) reduction in LC risk, respectively. In a SEM including latent variables (each one including vitamins and amino acids important to promote DNA methylation, nucleotide synthesis and immune activity), a direct and protective effect for DNA methylation (p=0.018) and immune activation was found (p=0.037), whereas nucleotide synthesis did not present a significant total effect. In both approaches of SEM, tobacco exposure remains with the highest impact on LC risk. Conclusions: It was found that cotinine is a good biomarker of tobacco exposure (active and passive). It was confirmed that methylation protects against LC. Immune activation presented a direct protective effect in the latent model, while nucleotide synthesis was not confirmed to be related to LC risk. Tobacco effect remains as the factor with highest impact in lung cancer
29

Influência dos fatores de situação socioeconômica, de aceitação da gravidez e da assistência pré-natal na mortalidade fetal: análise com modelagem de equações estruturais / Influence of socioeconomic situation and acceptance of pregnancy factors and prenatal care on fetal mortality: analysis through structural equation modeling

Gizelton Pereira Alencar 18 February 2009 (has links)
Introdução. As hipóteses levantadas sobre as relações entre as variáveis de exposição e o óbito fetal, via diversos mecanismos, são desenhadas em um diagrama a partir de um quadro conceitual feito pelo pesquisador. Testes sobre essas relações podem ser feitos por meio da modelagem por equações estruturais (MEE). Objetivo. Este estudo objetiva compreender o papel da situação socioeconômica (SSE), da não-aceitação da gravidez (nAdG) e assistência pré-natal na mortalidade fetal, na região sul do município de São Paulo, em 2000. Métodos. Foram construídas variáveis latentes para representar a situação socioeconômica e a não-aceitação da gravidez, a partir de dados da pesquisa do tipo caso-controle sobre mortalidade fetal no município de São Paulo, feita em 2000. Foi testado um modelo para o desfecho óbito fetal com as variáveis latentes, a assistência pré-natal, intercorrências (hipertensão, diabetes gestacional, sangramento vaginal) e retardo de crescimento intra-uterino (RCIU) por meio do MEE. A SSE foi formada por escolaridades da mãe e do chefe da família, classificação socioeconômica e renda per capita; a nAdG foi formada a partir das reações da mãe, pai e família, tentativa de aborto e se a gravidez foi planejada. Resultados. O modelo final apontou a relação entre a situação socioeconômica e não-aceitação da gravidez sobre a mortalidade fetal, passando pelo cuidado de pré-natal inadequado, modelo no qual intercorrências e RCIU também tem efeito sobre o desfecho. Conclusões. Os resultados sugerem que aceitação negativa da gravidez e o efeito da situação socioeconômica desfavorável, mediados pela atenção de pré-natal, podem ser amenizadas com uma maior qualidade nas visitas de pré-natal, especialmente em mães de maior vulnerabilidade social. / Introduction. The hypothesis about the relations among exposure variables and the fetal death are written as a diagram designed from a conceptual framework given by the researcher. Tests on these relations can be performed using structural equation modeling (SEM). Objective. This study aim to understand the role of socioeconomic situation (SES), non-acceptance of pregnancy (nAoP) and prenatal care on fetal mortality, in region south of the city of São Paulo, in 2000. Methodology. The measurement models were created to the latent variables SES and nAoP, from case-control study on fetal mortality in Sao Paulo city, in 2000. It was tested a model with SES, nAoP, prenatal care, medical complications (hypertension, gestational diabetes, vaginal bleeding), intra-uterine growth retardation (IUGR) on the outcome, performed by SEM. Results. The SES was composed by mothers and household heads years of study, socioeconomic classification index, and income per capita income; The AoP was composed by reactions of mother, father and family, attempted abortion and planned gestation. The final model showed the effect of SES and AoP on fetal death mediated by prenatal care, in a model where medical complications and IUGR also has an effect. Conclusion. The results suggests that negative acceptance of pregnancy and unfavorable socioeconomic situation, mediated by prenatal care, could be minimized improving the quality of prenatal care especially to those who are more social vulnerable.
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Towards a flexible statistical modelling by latent factors for evaluation of simulated responses to climate forcings

Fetisova, Ekaterina January 2017 (has links)
In this thesis, using the principles of confirmatory factor analysis (CFA) and the cause-effect concept associated with structural equation modelling (SEM), a new flexible statistical framework for evaluation of climate model simulations against observational data is suggested. The design of the framework also makes it possible to investigate the magnitude of the influence of different forcings on the temperature as well as to investigate a general causal latent structure of temperature data. In terms of the questions of interest, the framework suggested here can be viewed as a natural extension of the statistical approach of 'optimal fingerprinting', employed in many Detection and Attribution (D&amp;A) studies. Its flexibility means that it can be applied under different circumstances concerning such aspects as the availability of simulated data, the number of forcings in question, the climate-relevant properties of these forcings, and the properties of the climate model under study, in particular, those concerning the reconstructions of forcings and their implementation. It should also be added that although the framework involves the near-surface temperature as a climate variable of interest and focuses on the time period covering approximately the last millennium prior to the industrialisation period, the statistical models, included in the framework, can in principle be generalised to any period in the geological past as soon as simulations and proxy data on any continuous climate variable are available.  Within the confines of this thesis, performance of some CFA- and SEM-models is evaluated in pseudo-proxy experiments, in which the true unobservable temperature series is replaced by temperature data from a selected climate model simulation. The results indicated that depending on the climate model and the region under consideration, the underlying latent structure of temperature data can be of varying complexity, thereby rendering our statistical framework, serving as a basis for a wide range of CFA- and SEM-models, a powerful and flexible tool. Thanks to these properties, its application ultimately may contribute to an increased confidence in the conclusions about the ability of the climate model in question to simulate observed climate changes. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 3: Manuscript.</p>

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