Gravitational collapse with tachyon field and barotropic fluid

A particular class of space-time, with a tachyon field, \phi, and a barotropic fluid constituting the matter content, is considered herein as a model for gravitational collapse. For simplicity, the tachyon potential is assumed to be of inverse square form i.e., V(\phi) \sim \phi^{-2}. Our purpose, by making use of the specific kinematical features of the tachyon, which are rather different from a standard scalar field, is to establish the several types of asymptotic behavior that our matter content induces. Employing a dynamical system analysis, complemented by a thorough numerical study, we find classical solutions corresponding to a naked singularity or a black hole formation. In particular, there is a subset where the fluid and tachyon participate in an interesting tracking behaviour, depending sensitively on the initial conditions for the energy densities of the tachyon field and barotropic fluid. Two other classes of solutions are present, corresponding respectively, to either a tachyon or a barotropic fluid regime. Which of these emerges as dominant, will depend on the choice of the barotropic parameter, \gamma. Furthermore, these collapsing scenarios both have as final state the formation of a black hole.Comment: 18 pages, 7 figures. v3: minor changes. Final version to appear in GR

Determination of contamination with Clostridium botulinum in two species of processed and non prosecced fish

Background and Objective: The Clostridium botulinum is one of the most important causative of food poisoning. Spores of Clostridium botulinum spread out in the soil, the sea sediments, the marine environments and the marine animals. In recent years use of the marine food products like as fish and cultured fish are elevated. The aim of this study was done to compare between processing and non processing fish infected by predominant type of Clostridium botulinum. Materials and Methods: This descriptive study was done on the 146 samples of fish in two species of processed and non prosecced that collected from Gilan province in Iran during 2008. These samples included the Liza auratus Fish (45 processed fish and 28 non processed fish) and the Salmo Trutta caspius Fish (34 processing fish and 39 non processing fish). The samples examined according to the APHA2000 and FDA2003 protocols. Data Analyzed with SPSS-13 and Chi-Square test. Results: 16 (11%) of samples (13% of the processed fish and 7.5% of non processed fish) were confirmed that infected by Clostridium botulinum. Also the dominant type of exotoxin was Type E. The Type E exotoxin was determined from 11 of the samples (6 processed fish and 5 non processed fish). Conclusion: This study showed that fish are infected by Clostridium botulinum special the type E. also use of fish in bad preparation (half cooking and add material in its stomach) may cause the food poisoning

The acute effects of cardiac resynchronization therapy on severity of mitral regurgitation in end-stage heart failure patients

"nBackground: Cardiac resynchronization therapy (CRT) has proved as an efficient treatment in patients with end stage Heart failure. Previous studies showed the beneficial long term effects of CRT on the severity of mitral regurgitation (MR). The aim of this study was to evaluate acute effects of CRT on severity of MR."n "nMethods: This study was a double blind randomized trial performed from 1387 to 1388 in Imam Khomeini Hospital. Echocardiographic parameters including severity of MR were measured before and after CRT implantation with different echocardiographic methods."n "nResults: Patients had a significant improvement in severity of MR (14% Vs. 11% P<0/05), in increasing ejection fraction (18/04 Vs. 24/42 P<0/05) and in decreasing end systolic diameters (6/14 Vs. 5/98 P<0/05) and end diastolic diameters (7 Vs. 6/8 P<0/05) after CRT implantation. The reduction of MR was significantly correlated with the improvement of ejection fraction (P=0.07)."n "nConclusion: The mechanism of decreasing severity of MR is not yet truly understood and may be different in acute and chronic phases. Correction of left ventricular dyssynchrony might influence the improvement of MR severity. Also, synchronization of papillary muscle and increased transmitral pressure with more forceful mitral valve closure, decreases regurgitation fraction and volumes is proposed for these beneficial effects. If posterior papillary muscle is involved in dyssynchrony, the acute reduction of MR following CRT is expected but if the dyssynchrony is mainly at the lateral parts of left ventricle MR might be improved in longer durations