A new model for gravitational potential perturbations in disks of spiral galaxies. An application to our Galaxy

We propose a new, more realistic, description of the perturbed gravitational potential of spiral galaxies, with spiral arms having Gaussian-shaped groove profiles. We investigate the stable stellar orbits in galactic disks, using the new perturbed potential. The influence of the bulge mass on the stellar orbits in the inner regions of a disk is also investigated. The new description offers the advantage of easy control of the parameters of the Gaussian profile of its potential. We find a range of values for the perturbation amplitude from 400 to 800 km^2 s^{-2} kpc^{-1} which implies a maximum ratio of the tangential force to the axisymmetric force between 3% and 6%, approximately. Good self-consistency of arm shapes is obtained between the Inner Lindblad resonance (ILR) and the 4:1 resonance. Near the 4:1 resonance the response density starts to deviate from the imposed logarithmic spiral form. This creates bifurcations that appear as short arms. Therefore the deviation from a perfect logarithmic spiral in galaxies can be understood as a natural effect of the 4:1 resonance. Beyond the 4:1 resonance we find closed orbits which have similarities with the arms observed in our Galaxy. In regions near the center, in the presence of a massive bulge, elongated stellar orbits appear naturally, without imposing any bar-shaped potential, but only extending the spiral perturbation a little inward of the ILR. This suggests that a bar is formed with a half-size around 3 kpc by a mechanism similar to that of the spiral arms. The potential energy perturbation that we adopted represents an important step in the direction of self-consistency, compared to previous sine function descriptions of the potential. Our model produces a realistic description of the spiral structure, able to explain several details that were not yet understood.Comment: 12 pag., 11 fig. Accepted for publication in A&A, 2012 December 1

Discovery of optical pulsations in V2116 Ophiuchi/GX 1+4

We report the detection of pulsations with $\sim 124$ s period in V2116 Oph, the optical counterpart of the low-mass X-ray binary GX 1+4. The pulsations are sinusoidal with modulation amplitude of up to 4% in blue light and were observed in ten different observing sessions during 1996 April-August using a CCD photometer at the 1.6-m and 0.6-m telescopes of Laborat\'orio Nacional de Astrof\'{\i}sica, in Brazil. The pulsations were also observed with the $UBVRI$ fast photometer. With only one exception the observed optical periods are consistent with those observed by the BATSE instrument on board the Compton Gamma Ray Observatory at the same epoch. There is a definite correlation between the observability of pulsations and the optical brightness of the system: V2116~Oph had $R$ magnitude in the range $15.3-15.5$ when the pulsed signal was detected, and $R = 16.0-17.7$ when no pulsations were present. The discovery makes GX 1+4 only the third of $\sim 35$ accretion-powered X-ray pulsars to be firmly detected as a pulsating source in the optical. The presence of flickering and pulsations in V2116 Oph adds strong evidence for an accretion disk scenario in this system. The absolute magnitude of the pulsed component on 1996 May 27 is estimated to be $M_V \sim -1.5$. The implied dimensions for the emitting region are 1.1 R_{\sun}, 3.2 R_{\sun}, and 7.0 R_{\sun}, for black-body spectral distributions with $T = 10^5$ K, $2 \times 10^4$ K, and $1 \times 10^4$ K, respectively.Comment: 9 pages, 3 figures in PostScript, latex, accepted for publication on the Astrophysical Journal Letter

Apparent digestibility of conventional and alternative feedstuffs by hybrid tambacu juveniles.

Abstract: The apparent digestibility coefficients (ADC's) of dry matter (DM), crude protein (CP), and gross energy (GE) of conventional feedstuffs (cottonseed meal-CSM, soybean meal-SBM, wheat bran-WHB, corn-COR) and regional alternative feedstuffs (common bean residue meal-CBR, mesquite meal-MES, pasta by-product meal-PBM) were determined for hybrid juvenile tambacu Colossoma macropomum × Piaractus mesopotamicus. The apparent DM and GE digestibility of feedstuffs decreased (p0.05) were found among ADC's of PBM and COR. The lowest CP ADC among energy sources was observed in MES; the lowest CP ADC among plant protein sources was observed in CBR. Information about the ADC's of conventional and alternative feedstuffs for tambacu is essential to formulate low-cost diets and can contribute to regional development

Experimental Adhesion Prevention Studies: A Comparative Study in a Rabbit Model

Background: Adhesions formation after abdominal surgery is a problem that causes many complications in the patient’s future life. In this study we compare the possible individual effects of Ringer ́s lactate, Adept® and Mesofol® and the combined effects of Adept® and Mesofol® in the prevention of post surgical adhesions formation in a standardised rabbit model.Materials and Methods: 90 rabbits were divided into 9 groups. The same experimental method was used in all rabbits to produce adhesions, consisting of cecal and sigmoid abrasion and excision of parietal peritoneum. The rabbits were operated after 2 weeks to assess the adhesions occurring. The results were analysed using the chi-square test and the Fisher exact test when needed.Results: Comparison of adhesion stages demonstrated a significant difference between the control group and the Adept® groups (p<0.05) in both branches. The adhesion grade of the combined treatment groups (G5 and G9) was not statistically significant (p>0.05). In the Mesofol® group and the combined group, four and two rabbits, respectively, developed granulomas. Conclusions: Adept® used individually reduced the adhesion grade. The Adept® and Mesofol® combination was less effective in reducing adhesion formation in comparison to the Adept® group by itself. On the other hand, in our experimental study, the usage of Mesofol®, alone or in combination, caused foreign body granulomas in 6 animals. Although the literature is very sufficient in comparison several materials for decreasing adhesion formation, we believe that our study provides more valuable evidence in this area. Due to the appearance of six cases of foreign body granulomas, detailed studies focused on this matter are needed in the future. Keywords: Post-operative adhesions; comparative study; prevention; rabbit model. Introdução: A formação de aderências após a cirurgia abdominal é um problema que causa muitas complicações na vida futura do doente. Neste estudo, comparamos os possíveis efeitos individuais do Ringer lactato, Adept® e do Mesofol®, e os efeitos combinados do Adept® e do Mesofol® na prevenção da formação de aderências pós-cirúrgicas num modelo padronizado de coelhos.Materiais e Métodos: 90 coelhos foram divididos em nove grupos. O mesmo método experimental foi utilizado em todos os coelhos para favorecer a produção de aderências, realizando abrasão do cego e da sigmoideia e excisão do peritoneu parietal. Os coelhos foram operados após duas semanas para avaliar a ocorrência de aderências. Os resultados foram analisados por meio do teste do qui-quadrado e do teste exacto de Fisher, quando necessário.Resultados: A comparação em estadios de aderência demonstrou uma diferença significativa entre o grupo controlo e os grupos Adept® (p <0,05) em ambos os ramos. O grau de aderências dos grupos de tratamento combinado (G5 e G9) não foi estatisticamente significativo (p <0,05). No grupo do Mesofol® e no grupo combinado, quatro e dois coelhos, respectivamente, desenvolveram granulomas. Conclusões: Adept® utilizado individualmente reduziu o grau de aderências. O Adept® combinado com o Mesofol® foi menos eficaz na redução da formação de aderências em comparação com o grupo do Adept®, por si só. Por outro lado, o uso de Mesofol® isoladamente ou em conjunto podem aumentar o risco de granulomas. Estudos mais detalhados são necessários, e futuros estudos sobre a eficácia de um material para diminuir a formação de aderências deve incluir uma comparação de controle de diversos materiais num mesmo modelo.Palavras-Chave: aderências pós-operatórias; estudo comparativo; prevenção; modelo animal em coelhos

Differential molecular signature in patients from African origin with triple-negative breast cancer

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Field-enlarging transformations and chiral theories

A field-enlarging transformation in the chiral electrodynamics is performed. This introduces an additional gauge symmetry to the model that is unitary and anomaly-free and allows for comparison of different models discussed in the literature. The problem of superfluous degrees of freedom and their influence on quantization is discussed. Several "mysteries" are explained from this point of view.Comment: 14 pages, LaTeX-file, BI-TP 93/0

COMPUTER ANALYSIS OF THE GMAW AND GMAW-CW WELDING THERMAL CYCLES

A novel process of welding GMAW-CW (Gas Metal Arc Welding-Cold Wire) had been developed with it resemblance to the GMAW (Gas Metal Arc Welding), the GMAW-CW has an additional wire fed into de weld pool, allowing better deposition rates, while maintaining weld characteristics. However, there is a more complex situation related to the HAZ (Heat Affected Zone) and weld geometry prediction than the GMAW conventional. The welding energy is a high metallurgical important parameter because together with the geometric characteristics of the gasket and the preheat level is decisive in thermal cycles imposed to the material, and therefore in the possible microstructural transformations and behavior of the joint. The behavior of representative curves of thermal cycling reflects important aspects regarding the conditions used in welding. Usually such factors as the type of process, use or non- pre or post- heating, heat input, multipass welding, are able to establish differences in the form of a heat cycle curve. In this work, it was applied the dual ellipsoidal model of heat input, adapted to the GMAW-CW and compared to the same model over the GMAW, using existing experimental data and predicting the HAZ dimensions in function of weld and welding parameters. The results found had less than 10% error from experimental data in a more refined version of the model, whereas the difficulties to predict cold wire addition influences were not trivial