Mariza Camargo

Unified Approach for Variable Collision‐Frequency Models in Rarefied Gas Dynamics

Abstract An analytical version of the discrete‐ordinates method is used to develop solutions for some problems of the rarefied gas dynamics, based on a variable collision‐frequency model (CLF model) of the linearized Boltzmann equation. As much as possible, the solution is developed following a unified procedure for all problems considered, and the computational algorithm is implemented for three specific cases: the classical BGK model (constant collision frequency), the Williams model (the collision frequency is proportional to the magnitude of the velocity), and the rigid‐sphere model. Finite‐channel and half‐space problems are treated. In particular, numerical results obtained for the Poiseuille flow problem, the thermal‐creep problem and the thermal‐slip problem, are presented.

Collaborative Brazilian Pediatric Renal Transplant Registry (CoBrazPed-RTx): A Report From 2004 to 2013

BACKGROUND The Collaborative Brazilian Pediatric Renal Transplant Registry started in 2004 as a multicenter initiative aiming to analyze, report, and share the results of pediatric kidney transplantation in Brazil. Data from all pediatric kidney transplants performed between January 2004 and December 2013 were recorded electronically and periodically updated. All patients under 18 years old from the participating centers were enrolled. Demographic data, etiology of chronic kidney disease, and patient and graft survival were analyzed. From a total of 2443 pediatric kidney transplants performed in Brazil during the study period, we report data from 1751 pediatric renal transplants performed in 13 centers enrolled in the collaborative study. Median age at transplantation was 12.4 years, and most of recipients were male (56%). The most common underlying renal etiologies were obstructive uropathy (31%) and glomerulopathy (26%). METHODS According to donor source, 1155 (66%) of transplants were performed with deceased donors (DD). Initial immunosuppression consisted mainly of tacrolimus, mycophenolate, steroids, and induction therapy with anti-IL-2R antibodies. RESULTS One-year graft survival (death-censored) was 93% and 90% (log rank test, P < .01), respectively, for living donor (LD) and DD. Graft losses (15%) were most frequently caused by vascular thrombosis, chronic allograft nephropathy, death with functioning kidney, acute rejection, and recurrent renal disease. Recipients of DD had 2.02 (95% confidence interval: 1.14-3.59) times the hazard of graft loss compared with those of LD (P = .015). Patient survival rates at 1 and 5 years were 98% and 97% for LD and 97% and 93% for DD, respectively. The mortality rate was 3.8%, mainly as the result of infection and cardiovascular disease. CONCLUSIONS The results of this collaborative pediatric transplant study are comparable to international registries. Our effort has been able to maintain an exchange of information, both among the participating centers and with other international registries.

Avaliação de Propriedades de Reflectância e Transmitância: Um Problema de Transferência Radiativa em Meio Homogêneo Unidimensional

Neste trabalho uma solucao e proposta para a equacao de transferencia radiativa em meio homogeneo unidimensional, buscando avaliar densidade de radiacao e propriedades espectrais tais como reflectancia e transmitancia, que podem, por exemplo, estar associadas a caracterizacao de uma vegetacao. Resultados numericos obtidos com o metodo analitico de ordenadas discretas (ADO), para diferentes formulacoes das condicoes no contorno do meio, sao discutidos e comparados aos de outros trabalhos que fizeram uso de metodos analiticos classicos, no tratamento de problemas unidimensionais e homogeneos relacionados a area de transferencia radiativa. A analise dos resultados mostra que a formulacao ADO e precisa e computacionalmente eficiente.

DEGRADAÇÃO DE SACOLAS PLÁSTICAS CONVENCIONAIS E OXIBIODEGRADÁVEIS

O uso de sacolas plasticas e comum no cotidiano das pessoas, porem seu acumulo no meio ambiente e um problema serio causado pela sociedade moderna. Dessa forma, torna-se fundamental estudar a degradacao destas para entender os processos que podem ocorrer quando descartadas indevidamente pela sociedade. Diante disso, sacolas plasticas convencionais e oxibiodegradaveis foram submetidas a exposicao as intemperies (chuva, umidade, oscilacao de temperatura do ar, radiacao solar) sob a areia, para avaliar a degradacao natural das amostras em funcao de suas respectivas perdas de massa. Notou-se que as sacolas convencionais e oxibiodegradaveis apresentaram perda de massa, porem ambas apresentaram comportamento similares frente as intemperies. As sacolas oxibiodegradaveis nao apresentaram degradacao total durante o periodo de estudo (12 meses).

Estimativa de Recarga de Aquífero e Enquadramento dos Corpos de Água em Sub-Bacias Parcialmente Florestadas no Noroeste do Rio Grande do Sul

Groundwater has become an important source for water supply, due the increase of restriction for surface water supply, today with scarcity and poor quality conditions. This study aims to estimate the groundwater recharge of SASG and the surface water quality from two small watershed. The watersheds, with different land use, are located at northwest of Rio Grande do Sul State. The groundwater recharge was calculated base on the drain flow rate data, collected in dry conditions. To estimate the runoff time in each watershed it was calculated the concentration time. The flow rate on a dry period was considered as water withdraw from the aquifer. The monitoring program included physical and chemical data from surface water measured during a hydrological year. The land use was mapped base on Google Earth images. The recharge was estimated in 0,58252 m 3 /year/m 2 in the watershed 1 and 0,95476 m 3 /year/m 2 in the watershed 2. The watershed 2 has higher forest land use. According to the water use classification, indicated in the legislation, the surface water is classified as from Class 1.