Electron energy-distribution functions in gases

Numerical calculation of the electron energy distribution functions in the regime of drift tube experiments is discussed. The discussion is limited to constant applied fields and values of E/N (ratio of electric field strength to neutral density) low enough that electron growth due to ionization can be neglected. (GHT

Evaluation of angular scattering models for electron-neutral collisions in Monte Carlo simulations

In Monte Carlo simulations of electron transport through a neutral background gas, simplifying assumptions related to the shape of the angular distribution of electron-neutral scattering cross sections are usually made. This is mainly because full sets of differential scattering cross sections are rarely available. In this work simple models for angular scattering are compared to results from the recent quantum calculations of Zatsarinny and Bartschat for differential scattering cross sections (DCS's) from zero to 200 eV in argon. These simple models represent in various ways an approach to forward scattering with increasing electron energy. The simple models are then used in Monte Carlo simulations of range, straggling, and backscatter of electrons emitted from a surface into a volume filled with a neutral gas. It is shown that the assumptions of isotropic elastic scattering and of forward scattering for the inelastic collision process yield results within a few percent of those calculated using the DCS's of Zatsarinny and Bartschat. The quantities which were held constant in these comparisons are the elastic momentum transfer and total inelastic cross sections

Composição química e de ácidos graxos do músculo longissimus dorsi e da gordura subcutânea de tourinhos Red Norte e Nelore Chemical composition and of fatty acids of the muscle longissimus dorsi and backfat of Red Norte and young Nellore bulls

Objetivou-se com este trabalho avaliar a composição química e o perfil de ácidos graxos do músculo longissimus dorsi e da gordura subcutânea de tourinhos Red Norte e Nelore terminados em confinamento. Utilizaram-se 44 animais, sendo 22 Red Norte com peso vivo inicial médio de 367±30 kg e 22 do grupo Nelore com peso vivo inicial médio de 361±30 kg. Os animais receberam ração à vontade durante 112 dias e foram abatidos com 519 e 482 kg, respectivamente. Amostras do músculo longissimus dorsi e da gordura subcutânea foram coletadas 24 horas após abate entre a 12ª e 13ª costelas para análise da composição centesimal e do perfil de ácidos graxos. As análises de ácidos graxos foram realizadas por meio de cromatografia gasosa, em coluna capilar de 100 m. Não houve diferença na composição química da carne entre os grupos genéticos. Nos animais Red Norte, foram maiores os teores dos ácidos graxos pentadecanoico, palmítico, palmitoleico, linoleico e ácido linoleico conjugado (CLA), enquanto nos animais Nelore foi encontrado o maior teor de ácido oleico. O músculo longissimus dorsi apresentou maiores teores dos ácidos láurico, heptadecenoico, esteárico, linoleico, &#945;-linolênico e araquidônico. Em comparação ao músculo longissimus dorsi, na gordura subcutânea foram maiores os teores dos ácidos mirístico, miristoleico, pentadecanoico, palmítico, palmitoleico, oleico e CLA. Os animais Red Norte apresentaram maiores teores de ácidos graxos saturados em comparação aos Nelore. Em bovinos, o perfil de ácidos graxos depositados no músculo é diferente do observado na gordura subcutânea. O perfil de ácidos graxos da carne de tourinhos difere entre grupos genéticos.<br>The objective of this study was to evaluate the chemical composition and the fatty acid profile of the longissimus dorsi muscle and the backfat thickness of Red Norte and Nellore young bulls finished in feedlot. Fourty-four animals (22 Red Norte with initial average weight of 367±30 kg and 22 Nellore at initial average weight of 361±30 kg) were used. The animals were fed ad libitum during 112 days, slaughtered at 519 and 482 kg, respectively. Samples of the longissimus dorsi muscle and backfat thickness were collected 24 hours after slaughter between the 12th and 13th ribs for analysis of the chemical composition and the fatty acids profile. Fatty acid analyses were performed by gas chromatography with a 100-m capillary column. There was no difference for the chemical composition of the meat between the genetic groups. Red Norte animals showed higher contents of pentadecanoic, palmitic, palmitoleic, linoleic and conjugated linoleic acid (CLA) fatty acids, while Nellore animals had the highest content of oleic acid. The muscle longissimus dorsi showed greater concentrations of lauric, heptadecenoic, stearic, linoleic, &#945;-linoleic and arachidonic acids. Comparing the fatty acid deposited in the longissimus dorsi muscle with backfat thickness, the latter showed higher contents of miristic, miristoleic, pentadecanoic, palmitic, palmitoleic, oleic and CLA acids. Red Norte animals showed higher contents of saturated fatty acid than Nellore. In bovine, the profile of fatty acids deposited in the muscle is different than the that in the backfat thickness. The fatty acids profile of the meat from young bulls differs between genetic groups