Métodos estatísticos para controle do processo produtivo de clínquer de cimento Portland

O cimento é fabricado a partir da moagem de uma mistura constituída de calcário, escória de alto forno, gesso, materiais de características pozolânicas e de clínquer. O clínquer representa em média 50% da mistura que constitui o cimento, sendo obtido através da exposição da mistura de calcário e argila às temperaturas superiores à 1450ºC. O mesmo é responsável pelo endurecimento do cimento na presença de água. O processo de fabricação de clínquer ocorre em forno rotativo. Para verificar a qualidade do clínquer produzido são coletadas amostras pontuais e ensaios são realizados para definir as concentrações do óxido de cálcio livre e silicato tricálcico. De posse destes resultados os controladores do forno atuam no processo. Entretanto, durante o intervalo entre as analises, o operador realiza o controle através da observação de variáveis que estão relacionadas à qualidade do clínquer. Diante desta situação, a presente pesquisa, buscou verificar a inter-relação entre as variáveis do processo. Utilizando essas variáveis foram desenvolvidos modelos matemáticos para estimar valores de dois parâmetros de controle do processo de fabricação de clínquer para cimento portland: óxido de cálcio livre e silicato tricálcico.Os modelos desenvolvidos poderão ser utilizados como ferramenta de apoio no controle do processo produtivo do clínquer, pois durante todo o tempo de funcionamento do forno, os operadores teriam a estimativa de valores de referências de óxido de cálcio livre de silicato tricálcico e não apenas quando coletadas as amostras, tornando o controle mais eficaz e pró ativo

Homocysteine: validation and comparison of two methods using samples from patients with pulmonary hypertension

Introduction and objective:The determination of homocysteine plasma levels has been reported as a risk marker of interest in severe diseases involving endothelial injury and associated with the development or progression of atherosclerotic lesions and thrombus formation. The aims of this study were to validate method for quantification of plasma homocysteine by high performance liquid chromatography (HPLC) with fluorimetric detection, and to compare the results obtained from patients with pulmonary hypertension by HPLC with those obtained by spectrophotometric enzymatic cycling (S-Ec) method.Materials and methods:The validation parameters, such as linearity, matrix effect, precision, accuracy, detection and quantitation limits, and robustness of the method were evaluated aiming to demonstrate that it is suitable for the intended use. The data obtained in the quantification of homocysteine using the validated method (HPLC) and the spectrophotometric enzymatic cycling (S-Ec) method, were compared.Results:The method was precise, accurate, and robust; it also had good recovery and showed no matrix effect. The linearity covered a range of 5.0-85.0 µmol/l and the limits of detection and quantification were 1.0 µmol/l and 3.4 µmol/l, respectively. The results obtained for homocysteine determination by HPLC and S-Ec methods were comparable.Conclusion:The validated HPLC method showed good performance for quantification of plasma homocysteine levels, while S-Ec method provided results for homocysteine comparable with those obtained by the validated method; therefore, this methodology is a potential alternative of automated method for clinical laboratories

Atividade fí­sica e pressão arterial em crianças obesas

This study aimed to evaluate the chronic effect of an exercise program in resting blood pressure values of school children aged six to nine years old with overweight and obesity in public schools of the city of OuroPreto, Minas Gerais - Brazil, comparing the systolic and diastolic blood pressure of these students before and after an intervention program. Method: This is a randomized clinical study of intervention, quasi-experimental, double-blind, pragmatic, with the study of the individual unit. Seventy-nine children participated in the interventional study and were considered a convenient sample. These subjects were allocated by randomization into two groups: the intervention group (n = 40) and the control group (n = 39) practised physical activity three times a week for 50 minutes and were followed for 4 months. The exercise intensity was determined by open-circuit spirometry. Blood pressure was measured three times consecutively and the average was used. Results: After the intervention, there was no evidence of significant chronic effects of a regular program of exercises on basal levels of blood pressure of obese children between 6 and 9 years old. Conclusion: In this study, there was no evidence of significant effects from a program of regular physical activity on basal levels of blood pressure of obese children between 6 and 9 years old.Objetivo: o presente estudo tem como objetivo avaliar o efeito crônico de um programa de atividade fí­sica nos valores de pressão arterial basal de escolares de seis a nove anos com sobrepeso e obesidade das escolas públicas do municí­pio de Ouro Preto, Minas Gerais. Método: Trata-se de um estudo clí­nico aleatorizado de intervenção, quase-experimental, duplo-cego, pragmático, tendo como unidade de estudo o indiví­duo. Foram alocadas por aleatorização inconsciente em dois grupos: o grupo-intervenção (n=40) submetido í  atividade fí­sica três vezes por semana de 50 minutos de duração e o grupo-controle (n=39) e acompanhados por quatro meses. A intensidade do exercí­cio foi determinada por meio de espirometria de circuito aberto. A pressão arterial foi aferida três vezes, consecutivamente e a media foi utilizada. Setenta e nove crianças participaram do estudo intervencional. Resultado: Após a intervenção, não foram evidenciados efeitos significativos de um programa regular de atividade fí­sica sobre os ní­veis basais da Pressão Arterial de crianças obesas entre 6 e 9 anos. Conclusão: No presente estudo, não foram evidenciados efeitos significativos de um programa regular de atividade fí­sica sobre os ní­veis basais da Pressão Arterial de crianças obesas entre 6 e 9 anos

Physical activity and blood pressure in obese children

This study aimed to evaluate the chronic effect of an exercise program in resting blood pressure values of school children aged six to nine years old with overweight and obesity in public schools of the city of OuroPreto, Minas Gerais - Brazil, comparing the systolic and diastolic blood pressure of these students before and after an intervention program. Method: This is a randomized clinical study of intervention, quasi-experimental, double-blind, pragmatic, with the study of the individual unit. Seventy-nine children participated in the interventional study and were considered a convenient sample. These subjects were allocated by randomization into two groups: the intervention group (n = 40) and the control group (n = 39) practised physical activity three times a week for 50 minutes and were followed for 4 months. The exercise intensity was determined by open-circuit spirometry. Blood pressure was measured three times consecutively and the average was used. Results: After the intervention, there was no evidence of significant chronic effects of a regular program of exercises on basal levels of blood pressure of obese children between 6 and 9 years old. Conclusion: In this study, there was no evidence of significant effects from a program of regular physical activity on basal levels of blood pressure of obese children between 6 and 9 years old

Impact of a physical activity program on plasma concentrations of adiponectin, leptin and ghrelin in overweight and obese schoolchildren: A randomized controlled trial

Introduction: Child obesity has important consequences on the child’s health and is related to the risk of developing chronic diseases. That brings up the need for research assessing the impact of obesity - and overweight - reduction programs with close attention to methodology aspects and precise indicators of the impact of such programs. Goal: Assessing the impact of a physical activity program on the plasma concentrations of adiponectin, leptin, and ghrelin in overweight and obese schoolchildren. Methods: Randomized controlled trial, double-blind, with 6- to 9-year-old overweight and obese school- children. A sample of 79 schoolchildren ran- domly distributed into control and intervention groups was subjected to a physical activity program. The levels of adiponectin, leptin, ghrelin, body mass index, body fat percentage, an- thropometry, lipid profile and glycemia were evaluated. The program’s impact was assessed through multivariate linear regression models. Result: When comparing the groups, a significant difference was found for adiponectin, which shows an increase in the proportion of subjects with higher adiponectin concentrations for the intervention group and a reduction in body mass index and body fat percentage. Conclusion: The impact of the intervention program was positive in increasing adiponectin levels associated with a reduction in body mass index and body fat percentage