The total quasi-steady-state approximation for fully competitive enzyme reactions

none3The validity of the Michaelis-Menten-Briggs-Haldane approximation for single enzyme reactions has recently been improved by the formalism of the total quasi-steady-state approximation. This approach is here extended to fully competitive systems, and a criterion for its validity is provided. We show that it extends the Michaelis-Menten-Briggs-Haldane approximation for such systems for a wide range of parameters very convincingly, and investigate special cases. It is demonstrated that our method is at least roughly valid in the case of identical affinities. The results presented should be useful for numerical simulations of many in vivo reactions.noneM. PEDERSEN; BERSANI AM; BERSANI EPedersen, MORTEN GRAM; Bersani, Am; Bersani, E

Índices de conforto térmico e respostas fisiológicas de bezerros da raça holandesa em bezerreiros individuais com diferentes coberturas Thermal comfort indexes and physiological responses of holstein calves in individual houses with different roofings

Este trabalho avaliou a eficiência de abrigos para bezerros, a partir de índices de conforto térmico (carga térmica radiante, índice de temperatura de globo e umidade e índice de globo negro), pela comparação entre abrigos cobertos por telha de cimento-amianto e telha de cimento- celulose. O experimento foi implantado num sistema de abrigos convencionais, tipo boxe, com cinco tratamentos: telhados de cimento-amianto, cimento-celulose, cimento-celulose pintado de branco e telhado duplo de cimento-celulose, todos expostos ao sol, e telhado de cimento-celulose em área sombreada. Foram realizadas cinco repetições (um bezerro por repetição), de setembro a novembro de 2002, em Pirassununga - SP. As variáveis fisiológicas registradas foram freqüência respiratória e temperatura retal. Os abrigos expostos ao sol e com telha de cimento-amianto apresentaram os índices menos satisfatórios quanto ao conforto térmico animal, em relação aos demais abrigos ao sol. Os abrigos com telhas de cimento-celulose e em área sombreada apresentaram os melhores índices de conforto térmico animal. Os resultados das variáveis fisiológicas foram melhores para o tratamento posicionado à sombra. Encontrou-se relação entre os resultados de conforto térmico e os fisiológicos, em especial para a freqüência respiratória.<br>This work was focused in the efficiency of housing for calves, based on thermal comfort indexes (radiant thermal load, black globe humidity index and black globe index). It was compared animal housing covered with commercial corrugated sheets produced with asbestos cement and cellulose cement tiles. The experiment was carried out in a system of conventional housing, box type, with five treatments: roofs with asbestos cement tiles, cellulose cement tiles, cellulose cement painted tiles and double layer of cement cellulose tiles, all of them exposed to the sunlight and cement cellulose roof under shade. The experiment involved five replications (one calf per replication), during the spring time of 2002, in Pirassununga, State of São Paulo, Brazil. Physiological variables of thermoregulation (respiration rate and rectal temperature) were registered. The housing directly exposed to the sunlight and covered with asbestos cement sheets presented the less satisfactory results for the animal thermal comfort in comparison with the other treatments also exposed to the sun. The housing covered with cellulose cement tiles under shade showed the best results of thermal comfort. The results of the physiological variables were significantly better for the treatment positioned under shade. A satisfactory relation between the thermal comfort indexes and the physiological results (especially respiration rate) were found for the conditions of the present work