985 resultados para Leibniz-Poisson Algebra
Resumo:
A full set of (higher-order) Casimir invariants for the Lie algebra gl(infinity) is constructed and shown to be well defined in the category O-FS generated by the highest weight (unitarizable) irreducible representations with only a finite number of nonzero weight components. Moreover, the eigenvalues of these Casimir invariants are determined explicitly in terms of the highest weight. Characteristic identities satisfied by certain (infinite) matrices with entries from gl(infinity) are also determined and generalize those previously obtained for gl(n) by Bracken and Green [A. J. Bracken and H. S. Green, J. Math. Phys. 12, 2099 (1971); H. S. Green, ibid. 12, 2106 (1971)]. (C) 1997 American Institute of Physics.
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Background: People with less education in Europe, Asia, and the United States are at higher risk of mortality associated with daily and longer-term air pollution exposure. We examined whether educational level modified associations between mortality and ambient particulate pollution (PM(10)) in Latin America, using several timescales. Methods: The study population included people who died during 1998-2002 in Mexico City, Mexico; Santiago, Chile; and Sao Paulo, Brazil. We fit city-specific robust Poisson regressions to daily deaths for nonexternal-cause mortality, and then stratified by age, sex, and educational attainment among adults older than age 21 years (none, some primary, some secondary, and high school degree or more). Predictor variables included a natural spline for temporal trend, linear PM(10) and apparent temperature at matching lags, and day-of-week indicators. We evaluated PM(10) for lags 0 and I day, and fit an unconstrained distributed lag model for cumulative 6-day effects. Results: The effects of a 10-mu g/m(3) increment in lag 1 PM(10) on all nonextemal-cause adult mortality were for Mexico City 0.39% (95% confidence interval = 0.131/-0.65%); Sao Paulo 1.04% (0.71%-1.38%); and for Santiago 0.61% (0.40%-0.83%. We found cumulative 6-day effects for adult mortality in Santiago (0.86% [0.48%-1.23%]) and Sao Paulo (1.38% [0.85%-1.91%]), but no consistent gradients by educational status. Conclusions: PM(10) had important short- and intermediate-term effects on mortality in these Latin American cities, but associations did not differ consistently by educational level.
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Background This study describes heat- and cold-related mortality in 12 urban populations in low- and middle-income countries, thereby extending knowledge of how diverse populations, in non-OECD countries, respond to temperature extremes. Methods The cities were: Delhi, Monterrey, Mexico City, Chiang Mai, Bangkok, Salvador, So Paulo, Santiago, Cape Town, Ljubljana, Bucharest and Sofia. For each city, daily mortality was examined in relation to ambient temperature using autoregressive Poisson models (2- to 5-year series) adjusted for season, relative humidity, air pollution, day of week and public holidays. Results Most cities showed a U-shaped temperature-mortality relationship, with clear evidence of increasing death rates at colder temperatures in all cities except Ljubljana, Salvador and Delhi and with increasing heat in all cities except Chiang Mai and Cape Town. Estimates of the temperature threshold below which cold-related mortality began to increase ranged from 15 degrees C to 29 degrees C; the threshold for heat-related deaths ranged from 16 degrees C to 31C. Heat thresholds were generally higher in cities with warmer climates, while cold thresholds were unrelated to climate. Conclusions Urban populations, in diverse geographic settings, experience increases in mortality due to both high and low temperatures. The effects of heat and cold vary depending on climate and non-climate factors such as the population disease profile and age structure. Although such populations will undergo some adaptation to increasing temperatures, many are likely to have substantial vulnerability to climate change. Additional research is needed to elucidate vulnerability within populations.
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Background: Worldwide strategies have been conducted in order to guarantee longer periods of exclusive breastfeeding for most children, especially those from developing countries. The evaluation of infant feeding practices and the identification of weaning risk factors are essential for public health policy planning. Methods: This cross-sectional study was carried out in Joinville, the biggest city of Santa Catarina State in the southern Brazilian region. The caregivers of children under 1 year of age were systematically selected for interview in previously drawn immunization units during the 2005 National Vaccination Campaign. A structured questionnaire was applied for collection of infant, maternal, and healthcare variables. A 24-hour food recall survey was included in order to evaluate infant feeding practices. Descriptive statistic analysis on breastfeeding prevalence and Poisson regression analysis of risk factors for discontinuing exclusive breastfeeding for infants up to 6 months of age were performed. Results: Caregivers of 1,470 infants were interviewed. The feeding inquiry showed an overall rate of breastfeeding of 72.5% and a frequency of exclusive breastfeeding of 43.7% and 53.9% among infants younger than 6 and 4 months of age, respectively. The findings associated with the interruption of exclusive breastfeeding for infants up to 6 months were: higher infant age (P < 0.001), pacifier use (P < 0.001), and lower maternal educational level (P = 0.013). Conclusions: In developing countries, specific strategies must be created for the delivery of information about breastfeeding and the effect of pacifier use, especially for less educated women.
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Sepsis is still a major cause of mortality in the intensive critical care unit and results from an overwhelming immune response to the infection. TNF signaling pathway plays a central role in the activation of innate immunity in response to pathogens. Using a model of polymicrobial sepsis by i.p. injection of cecal microflora, we demonstrate a critical role of TNFR1 and R2 activation in the deregulated immune responses and death associated with sepsis. A large and persistent production of TNF was found in wild-type (B6) mice. TNFR1/R2-deficient mice, compared with B6 mice, survive lethal polymicrobial infection with enhanced neutrophil recruitment and bacterial clearance in the peritoneal cavity. Absence of TNFR signaling leads to a decreased local and systemic inflammatory response with diminished organ injury. Furthermore, using TNFR1/R2-deficient mice, TNF was found to be responsible for a decrease in CXCR2 expression, explaining reduced neutrophil extravasation and migration to the infectious site, and in neutrophil apoptosis. In line with the clinical experience, administration of Enbrel, a TNF-neutralizing protein, induced however only a partial protection in B6 mice, with no improvement of clinical settings, suggesting that future TNF immunomodulatory strategies should target TNFR1 and R2. In conclusion, the present data suggest that the endogenous TNFR1/R2 signaling pathway in polymicrobial sepsis reduces neutrophil recruitment contributing to mortality and as opposed to pan-TNF blockade is an important therapeutic target for the treatment of polymicrobial sepsis. The Journal of Immunology, 2009, 182: 7855-7864.
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Background: Obesity is epidemic worldwide, and increases in cesarean delivery rates have occurred in parallel. Objective: This study aimed to determine whether cesarean delivery is a risk factor for obesity in adulthood in a birth cohort of Brazilian subjects. Design: We initiated a birth cohort study in Ribeirao Preto, southeastern Brazil, in 1978. A randomly selected sample of 2057 subjects from the original cohort was reassessed in 2002-2004. Type of delivery, birth weight, maternal smoking, and schooling were obtained after birth. The following data from subjects were collected at 23-25 y of age: body mass index (BMI; in kg/m(2)), physical activity, smoking, and income. Obesity was defined as a BMI >= 30. A Poisson multivariable model was performed to determine the association between cesarean delivery and BMI. Results: The obesity rate in adults born by cesarean delivery was 15.2% and in those born by vaginal delivery was 10.4% (P = 0.002). Adults born by cesarean delivery had an increased risk (prevalence ratio: 1.58; 95% CI: 1.23, 2.02) of obesity at adulthood after adjustments. Conclusion: We hypothesize that increasing rates of cesarean delivery may play a role in the obesity epidemic worldwide. Am J Clin Nutr 2011;93:1344-7.
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Low birth weight and preterm birth, and social disadvantage may negatively affect mental health of children, but findings have been inconsistent. To assess the influence of perinatal and social factors on mental health problems in children aged 7-9 years. A random sample of 805 births in So Luis, Brazil was studied in 1997/1998 and again in 2005/2006. Perinatal, socioeconomic and demographic variables were assessed within 24 h after delivery. The Strengths and Difficulties Questionnaire (SDQ) was used to assess mental health problems in the children. Simple and multiple Poisson regressions were used for statistical analysis. The overall prevalence of mental health problems in the total sample was 47.7%. The prevalences of emotional and conduct problems were 58.2 and 48.8%, respectively. Only paternal age (< 20 years) was associated with mental health problems as measured by the full SDQ scale (prevalence ratio PR = 1.27). Children born to single mothers (PR = 1.31) and those with birth weight from 1,500 to 2,499 g (PR = 1.18) and from 2,500 to 2,999 g (PR = 1.17) had a higher risk of emotional problems, but those from low income families had a lower risk (PR = 0.80). Children with a father of less than 20 years had a higher risk of having problems with their peers (PR = 1.75). A maternal education of 9 years or over was inversely associated with peer (PR = 0.70) and conduct problems (PR = 0.73). Girls had a lower risk of conduct (PR = 0.77) and hyperactivity problems (PR = 0.68). A maternal education of 4 years or less increased the risk of hyperactivity (PR = 1.48). Socioeconomic and demographic conditions were better predictors of mental health problems in children than birth weight or preterm birth. However, since most effect sizes were small most mental health problems were, unexplained by the variables in the study.
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There is evidence that intrauterine growth restriction, resulting in newborn girls that are small for gestational age (SGA), may be related to the onset of polycystic ovary syndrome (PCOS). Thus, we studied whether women born SGA have a higher prevalence of PCOS than women born appropriate for gestational age (AGA). This was a prospective birth cohort study of 384 women born at term between June 1, 1978, and May 31, 1979, in Ribeirao Preto, Brazil. After exclusion, 165 women effectively participated in this study, of whom 43 were SGA and 122 were AGA. The prevalence of PCOS was analysed. At a mean age of 29 years, the women agreed to follow the study protocol, which included: anamnesis, physical examination, serum tests [follicle stimulating hormone, luteinizing hormone, total and free testosterone, dehydroepiandrostenedione sulphate, 17-OH-progesterone, fasting insulin, sex steroid-binding globulin (SHBG) and fasting glucose] and pelvic ultrasound. Data regarding gestational age, birthweight, age at menarche and maternal data were obtained from the files of the cohort. The adjusted relative risk (RR) values of the SGA, insulin resistance, body mass index, maternal smoking and parity variables were analysed using Poisson regression with robust adjustment of variance for the prediction of PCOS. The prevalence of PCOS was higher in the SGA group than in the AGA group [adjusted RR = 2.44, 95% CI (1.39-4.28)]. Hyperandrogenism was more prevalent in the SGA women than in the AGA women (P = 0.011). Circulating SHBG was lower in the SGA women than in the AGA women (P = 0.041), but fasting insulinemia was similar in both groups. The prevalence of PCOS in SGA women was twice as high as in AGA women in our study population.
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Aim: The aim of this study was to assess the rise in multiple births and its influence on trends of low birth weight (LBW) rates in Porto Alegre, Brazil. Methods: This is a registry-based study of live births from 1994 to 2005 obtained from the national live birth information system. Chi-square tests for trends were assessed for LBW and multiple birth rates. The impact of multiple births on LBW trends was assessed by sequential modelling, including year and further adjustment for multiple births. Risk factors for multiple births were assessed using the Poisson regression. Results: A total of 263 252 live births were studied. The LBW rate increased from 9.70% to 9.88% (p < 0.001) and the multiple birth rate rose from 1.95% to 2.53% (p < 0.001). LBW rate increased among twins, from 57.14% to 63.46% (p = 0.001). The twin birth rate rose by 24.7%, while the rate of triplets or higher-order increased by 150%. Multiple births may be responsible for 23.9% of the increase in the LBW rate over the period. Mothers with higher levels of schooling, older mothers and mothers delivering in private hospitals were more likely to deliver multiple births. Conclusions: It seems that both the increase in multiple births and in the LBW among multiple births contributed to this rise in overall LBW rate.
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To estimate the 1-year prevalence of tension-type headache (TTH) and the degree of the association of TTH with some sociodemographic characteristics of a representative sample of the adult population of Brazil. This was an observational, cross-sectional, population-based study. We conducted telephone interviews on 3848 people, aged 18-79 years, randomly selected from the 27 states of Brazil. Trained lay interviewers administered the structured questionnaire. It included questions about the sociodemographic characteristics of the population, as well as questions about headache. The degree of the association was calculated through prevalence ratios, adjusted with Poisson regression by gender, age, years of education, marital status, household income, job status, body mass index (BMI), and physical exercise. The estimated 1-year gender- and-age-adjusted prevalence of TTH was 13.0% (95% CI: 11.8-14.2%); 15.4% in males and 9.5% in females. The prevalence of probable TTH was 22.6% (95% CI: 21.1-24.1%). Most (86.2%) subjects reported episodic TTH; 6.4% had chronic TTH. The prevalence was higher at 18-29 years of age (16.2%). TTH was 1.6 times more prevalent in men, and 1.54 times more in subjects with more than 11 years of education. There was no significant association of TTH with marital or job status, household income, BMI, and physical activity. This is the first nationwide epidemiological study of TTH in Brazil. The overall prevalence of TTH in Brazil is low, at 13%. TTH is significantly more prevalent in males and subjects with higher education level.
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The objectives of this study were to estimate the 1-year prevalence of chronic daily headache (CDH) and the degree of the association of CDH with some sociodemographic characteristics of the adult population of Brazil. This was a cross-sectional, population-based study. We conducted telephone interviews with 3848 people, aged 18-79 years, randomly selected from the 27 States of Brazil. The degree of the association was calculated through prevalence ratios, adjusted with Poisson regression by gender, age and some sociodemographic factors. The estimated 1-year gender- and age-adjusted prevalence of CDH was 6.9%. CDH was 2.4 times more prevalent in women, 1.72 times more in unemployed, 1.63 times more in subjects with high household income and two times greater in those who did not exercise. The overall prevalence of CDH in Brazil is high. CDH is significantly more prevalent in women, the unemployed, subjects with higher income, and in those who do not exercise.
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Purpose: The objective of the present study was to assess the prevalence of untreated caries in a Brazilian paediatric acquired immunodeficiency syndrome (AIDS) patient population and its association with sociodemographic, behavioural and clinical characteristics. Materials and Methods: The study group was comprised of 125 HIV-infected patients (aged 3 to 15 years) who had already manifested AIDS and were assisted in a specialised health care unit. Dental examinations followed the World Health Organization`s guidelines for oral health surveys. Family caregivers provided information about the socioeconomic standing and the behaviour of their children. Patients` medical records in the hospital provided information on the clinical status of patients. A Poisson regression analysis was used for assessing the covariates for the prevalence of untreated dental caries, as adjusted by age. Results: The prevalence of untreated caries was 58%; a higher prevalence was found in younger children with primary and mixed dentition. The prevalence of untreated caries associated significantly with lower socioeconomic status (household crowding and schooling of the caregiver), dietary habits (higher frequency of sugar consumption) and poorer clinical status (HIV viral load and symptom severity). Conclusions: The high burden of untreated caries on paediatric AIDS patients reinforced the importance of integrating the clinician with the interdisciplinary health care team that assisted these children. The identification of socioeconomic and behavioural factors associated with caries experience reinforced the importance of the attention that children with AIDS received within their own households for the prevention of dental disease, particularly a proper nutritional advisement and monitoring of dental hygiene.
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The Bariev model with open boundary conditions is introduced and analysed in detail in the framework of the Quantum Inverse Scattering Method. Two classes of independent boundary reflecting K-matrices leading to four different types of boundary fields are obtained by solving the reflection equations. The models are exactly solved by means of the algebraic nested Bethe ansatz method and the four sets or Bethe ansatz equations as well as their corresponding energy expressions are derived. (C) 2001 Elsevier Science B.V. All rights reserved.
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Most cellular solids are random materials, while practically all theoretical structure-property results are for periodic models. To be able to generate theoretical results for random models, the finite element method (FEM) was used to study the elastic properties of solids with a closed-cell cellular structure. We have computed the density (rho) and microstructure dependence of the Young's modulus (E) and Poisson's ratio (PR) for several different isotropic random models based on Voronoi tessellations and level-cut Gaussian random fields. The effect of partially open cells is also considered. The results, which are best described by a power law E infinity rho (n) (1<n<2), show the influence of randomness and isotropy on the properties of closed-cell cellular materials, and are found to be in good agreement with experimental data. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.