André Luiz Lopes da Silveira

Guanine and adenine nucleotidase activities in rat cerebrospinal fluid

Adenine and guanine nucleotides have been shown to exert multiple roles in central and peripheral nervous systems, and the sequential breakdown of these nucleotides by enzymatic systems is an important step in the modulation of their extracellular effects. The aim of this study was to investigate whether nucleotide hydrolysis also occurs in the cerebrospinal fluid (CSF) of rats. CSF was able to hydrolyze all guanine and adenine nucleotides investigated (2.0 mM): GDPz.Gt;ADP=ATP=GTPz.Gt;AMP=GMP. More detailed studies with the diphosphate nucleotides showed that the hydrolysis of ADP and GDP was linear with incubation time and protein concentration. The apparent K(M) (Henry-Michaelis-Menten constant) and V (maximal velocity) values for ADP and GDP were 164.3+/-54.7 microM and 12.2+/-3.8 nmol P(i)/min per mg protein, and 841.0+/-90.2 microM and 22.8+/-8.0 nmol P(i)/min per mg protein. The sum of ADP, GDP and UDP hydrolysis (2.0 mM) upon individual incubations with CSF was similar to the hydrolysis observed when all three nucleotides were incubated together. This pattern of hydrolysis strongly suggests the involvement of more than one enzyme activity. The higher maximum activity for GDP and UDP compared to ADP is compatible with presence of a soluble NTDPase5.

Improvements in large‐scale drainage networks derived from digital elevation models

[1] This paper presents an improved algorithm for deriving drainage networks for coarse-gridded distributed hydrological models based on relatively fine resolution digital elevation models. The proposed algorithm aims to reproduce actual drainage networks more closely when applied in regions with meandering rivers running in parallel and for cell sizes of the order of 10 kilometers. To achieve this goal, the COTAT algorithm of Reed (2003) was improved, introducing another parameter related to the minimum upstream flow path into the cell besides the area threshold. The proposed algorithm was tested by applying it to the catchments of the rivers Tapajos (530,000 km 2 ) and Grande (145,000 km 2 ) in South America. Results show that drainage networks are generally improved by the proposed algorithm, needing only minor manual corrections.

Cumulative equations for continuous time Chicago hyetograph method

O metodo de Chicago e um dos metodos classicos em hidrologia para definicao de hietogramas de projeto com base nas curvas de intensidade-duracao-frequencia (curvas IDF). O hietograma do metodo de Chicago apresenta as intensidades por funcoes continuas no tempo, uma para antes e outra para depois do pico. O pico e posicionado arbitrariamente em um instante zero e as equacoes usam tempos contados de forma reversa (antes do pico) ou normal (depois do pico). A duracao para antes do pico e determinada por um fator de pico entre zero e um multiplicado pela duracao total do hietograma. Para facilitar o emprego do metodo de Chicago a presente nota tecnica apresenta equacoes com tempo zero na origem do hietograma e valores obtidos de forma cronologica ate a sua duracao total. As equacoes aqui apresentadas sao de precipitacoes cumulativas que representam a integral exata no tempo dos volumes das intensidades do Metodo de Chicago, ou seja, a cada instante de tempo a partir de zero (inicio da chuva) tem-se o valor exato da lâmina acumulada precipitada. Por desacumulacao podem-se obter as lâminas precipitadas sequenciais do hietograma. Ha uma vantagem de manuseio dessas equacoes que as tornam facilmente programaveis em planilhas eletronicas.

Estudo da ocorrência de fluxos no perfil vertical do vento na baixa atmosfera com análise das componentes principais (ACP) e a sua relação com a precipitação no Rio Grande do Sul

This study analyses the relation between Low-Level Jets (LLJ) and Flows in the vertical wind profiles generating convection at the synoptic scale, and associated events of rainfall, using vertical wind profiles obtained by radiosonde at the Salgado Filho International Airport in Porto Alegre, the State of Rio Grande do Sul. The LLJs involved in this large-scale transport tend to be associated with nocturnal convective events and with the generation of Mesoscale Convective Complexes (MCCs), giving high rainfall intensities, which may have important economic consequences. To describe the relations involved, the study uses a statistical method principal component analysis. Use of this method makes it possible to understand the complex interactions operating at meteorological scales involved in synoptic processes, from macro- to meso-scale. In such complexity, the part played by LLJs and Flows in this interaction is to effect transport in the lower atmosphere, thereby coupling regional meteorology and water circulation at the continental scale.