The superconducting phase transition and gauge dependence

The gauge dependence of the renormalization group functions of the Ginzburg-Landau model is investigated. The analysis is done by means of the Ward-Takahashi identities. After defining the local superconducting order parameter, it is shown that its exponent $\beta$ is in fact gauge independent. This happens because in $d=3$ the Landau gauge is the only gauge having a physical meaning, a property not shared by the four-dimensional model where any gauge choice is possible. The analysis is done in both the context of the $\epsilon$-expansion and in the fixed dimension approach. It is pointed out the differences that arise in both of these approaches concerning the gauge dependence.Comment: RevTex, 3 pages, no figures; accepted for publication in PRB; this paper is a short version of cond-mat/990527

Open vessel microwave extraction of metals in biological and botanical materials.

The complete sample decomposition is not always necessary when measurements are carried out using optical techniques. Depending on both technique employed and sample matrix characteristics, an extraction procedure can be completely suitable for quantitative determinations. To implement this approach is essential to perform a critical evaluation of the behavior of each element, of the extractor solution, and of the temperature and time of extraction. The temperature can be controlled adopting microwave-assisted procedures that guarantee fast heating and repeatability. In this work an open-vessel microwave system (Star 6, CEM) was employed to investigate the efficiency of the extraction procedures. The extraction of Al, Ca, Cu, Fe, Mg, Mn,:and Zn was evaluated in biological (bovine liver, SRM 1577b, NIST) and botanical (apple leaves, SRM 1515, NIST; trace elements in spinach leaves, SR!vf 1570a, NIST; and commercial teas) materials. The extraction procedures were investigated using 1 or 10% v/v hydrochloric or nitric acid solutions. An alkaline solution containing a mixture of water- soluble tertiary amines (CFA-C, Spectrasol) was also tested. All procedures were carried out at temperatures in the range 80-105 oC during time intervals shorter than 10 min. The analytes were determined by flame and graphite furnace atomic absorption spectrophotometry (Intralab, model Gemini AA12/1475 and Varian model 800, respectively), and by inductively coupled plasma atomic emission spectrometry (AtomScan 25, TJA). Copper, Mn, and Zn were quantitatively extracted from biological and botanical materials with all solutions employed. The complete extraction of these elements from biological materials was easier than from botanical materials and it was also observed that acid solutions were more efficient than the CFA-C mixture for botanical samples. Calcium and Mg were quantitatively extracted in some tea samples and it was found that Mg is weaker bound to the matrix than Ca. Aluminum and Fe were poorly extracted in all samples

Performance and digestive characteristics in dairy cattle maintained under grazing regime and supplemented with linseed.

Linseed is characterized by the rich unsaturated fatty acids and slow release of oil in the rumen. The objective of the present study was to evaluate the intake, rumen degradability, and digestibility of dairy cattle maintained under grazing regime and supplemented with linseed. Twelve Girolando (¾ Holstein × ¼ Gir) cows with a mean age of 5.2 ± 1.9 years and body weight of 583.9 ± 67.6 kg were used. The cows were maintained in a rotational grazing system on the mombaça grass (Panicum maximum) and divided into 2 experimental groups. The CONTR (n = 6) group received only the base diet (pasture) and the LINS group (n = 6) received pasture plus linseed. Initially, a fifteen-day adaptation period was established to stabilize the desired consumption amount. After this period, the animals received 800 g of linseed for 126 d. The ruminal degradability was evaluated using 2 males with a cannula in the rumen, and they were provided the same experimental diet. The measured dry matter production of pasture did not show differences during the experimental period. The intake of crude protein and ethereal extract was higher, whereas neutral detergent fiber content was lower in the cows supplemented with linseed. However, this did not alter the weight gain and digestibility coefficients, except the digestibility coefficient of the ethereal extract. At the ruminal level, linseed showed low effective and potential degradability with negative effect on grass degradability.Título em português: Desempenho e características digestivas em bovinos leiteiros mantidos em regime de pastoreio suplementados com linhaça

Viabilidade econômica de um sistema de produção de cabras leiteiras no Submédio do São Francisco.

O objetivo desse trabalho foi fazer um levantamento dos custos de produção visando determinar a receita mínima para garantir a viabilidade de um sistema de produção de leite de cabra na região do submédio do rio São Francisco. Os dados foram coletados durante o período de julho de 2007 a junho de 2008. Foram determinados os índices produtivos do rebanho, os custos operacionais efetivos, custos indiretos e o custo total e a relação benefício/custo. A produção média de leite foi de 1,2 L/cabra/dia, com 90 cabras em lactação, por um período de seis meses. Os custos com mão-de-obra e ração concentrada corresponderam a 60,8% dos custos operacionais. A pesquisa registrou resultados economicamente insatisfatórios em diversos índices econômicos. A relação benefício/custo foi de 0,68% e o ponto de nivelamento foi de 33372 L/ano. A situação mínima desejada seria a produtividade média de 1,8 L/ cabra/dia e o preço de R$ 1,00/ L de leite. Na situação desejada, a relação benefício/custo seria 1,11% e o ponto de nivelamento de 25576 L/ano. No período avaliado, o sistema de produção do sistema de cabras leiteiras mostrou-se ineficiente

Inquérito soro-epidemiológico anti-Brucella abortus em rebanhos caprinos na região semi-árida do Submédio São Francisco, PE.

A brucelose é uma doença infecto-contagiosa crônica comum a diversas espécies animais. O animal infectado é a principal fonte de infecção para o homem e outros animais. Objetivou-se com este estudo realizar um levantamento soro-epidemiológico da brucelose nos rebanhos caprinos na região semi-árida do Submédio São Francisco. Foram coletadas 144 amostras de soros de caprinos, rocedentes de três propriedades localizadas em municípios da região Submédio São Francisco no Estado de Pernambuco. As amostras foram obtidas por meio de venopunção da jugular e encaminhadas ao Laboratório de Microbiologia e Imunologia Animal da Universidade Federal do Vale do São Francisco, para realização do teste do antígeno acidificado tamponado (TAAT). Neste trabalho, todas as amostras analisadas (n=144), mostraram resultado negativo no TAAT. A infecção natural pela Brucella abortus não ocorre nos rebanhos de caprinos estudados na região semi-árida do Submédio São Francisco. No entanto, em virtude da presença de caprinos sororeagentes para esta enfermidade em estados vizinhos, salienta-se a importância de estudos como esse no Estado de Pernambuco e em outros estados geograficamente próximos