Effects of a CPT-even and Lorentz-violating nonminimal coupling on the electron-positron scattering

We propose a new \emph{CPT}-even and Lorentz-violating nonminimal coupling between fermions and Abelian gauge fields involving the CPT-even tensor $(K_{F})_{\mu\nu\alpha\beta}$ of the standard model extension. We thus investigate its effects on the cross section of the electron-positron scattering by analyzing the process $e^{+}+e^{-}\rightarrow\mu^{+}+\mu^{-}$. Such a study was performed for the parity-odd and parity-even nonbirefringent components of the Lorentz-violating $(K_{F})_{\mu\nu\alpha\beta}$ tensor. Finally, by using experimental data available in the literature, we have imposed upper bounds as tight as $10^{-12}(eV)^{-1}$ on the magnitude of the CPT-even and Lorentz-violating parameters while nonminimally coupled.Comment: LaTeX2e, 06 pages, 01 figure

Radiative generation of the CPT-even gauge term of the SME from a dimension-five nonminimal coupling term

In this letter we show for the first time that the usual CPT-even gauge term of the standard model extension (SME) can be radiatively generated, in a gauge invariant level, in the context of a modified QED endowed with a dimension-five nonminimal coupling term recently proposed in the literature. As a consequence, the existing upper bounds on the coefficients of the tensor $(K_{F})$ can be used improve the bounds on the magnitude of the nonminimal coupling, $\lambda(K_{F}),$ by the factors $10^{5}$ or $10^{25}.$ The nonminimal coupling also generates higher-order derivative contributions to the gauge field effective action quadratic terms.Comment: Revtex style, two columns, 6 pages, revised final version to be published in the Physics Letters B (2013

Neutron Stars in Teleparallel Gravity

In this paper we deal with neutron stars, which are described by a perfect fluid model, in the context of the teleparallel equivalent of general relativity. We use numerical simulations to find the relationship between the angular momentum of the field and the angular momentum of the source. Such a relation was established for each stable star reached by the numerical simulation once the code is fed with an equation of state, the central energy density and the ratio between polar and equatorial radii. We also find a regime where linear relation between gravitational angular momentum and moment of inertia (as well as angular velocity of the fluid) is valid. We give the spatial distribution of the gravitational energy and show that it has a linear dependence with the squared angular velocity of the source.Comment: 19 pages, 14 figures. arXiv admin note: text overlap with arXiv:1206.331

Results of endoscopic biliary drainage in patients with malignant hilar stricture

In Malignant Hilar Biliary Stricture (MHBS) palliative biliary drainage is a frequent strategy, improving the quality of life, reducing pruritus, loss of appetite and relieving cholangitis. The endoscopic approach is an effective, although challenging procedure. This study aimed to evaluate technical and clinical success rates of biliary drainage by ERCP. This is a retrospective study including all patients with MHBS referred to Instituto do Cancer do Hospital de São Paulo (ICESP) submitted to biliary drainage by ERCP, between January 2010 and December 2017. Multivariable logistic regression was performed to evaluate predictors of clinical failure, as total bilirubin levels, Bismuth classification, number of hepatic sectors drained and presence of cholangitis. In total, 82 patients presenting unresectable MHBS were included in this study. 58.5% female and 41.5% male, with a mean age of 60±13 years. Bismuth classification grades II, IIIA, IIIB and IV were noted in 23.2%, 15.9%, 14.6% and 46.3%, respectively. Technical and clinical success was achieved in 92.7% and 53.7% respectively. At multivariable logistic-regression analyses, Bismuth IV strictures were related to higher clinical failure rates when compared to other strictures levels, with an Odds Ratio of 5.8 (95% CI 1.28‒20.88). In conclusion, endoscopic biliary drainage for malignant hilar biliary stricture had a high technical success but suboptimal clinical success rate. Proximal strictures (Bismuth IV) were associated with poor drainage outcomes

Casimir energy and black hole pair creation in Schwarzschild-de Sitter spacetime

Following the subtraction procedure for manifolds with boundaries, we calculate by variational methods, the Schwarzschild-de Sitter and the de Sitter space energy difference. By computing the one loop approximation for TT tensors we discover the existence of an unstable mode even for the non-degenerate case. This result seems to be in agreement with the sub-maximal black hole pair creation of Bousso-Hawking. The instability can be eliminated by the boundary reduction method. Implications on a foam-like space are discussed.Comment: 19 pages,RevTeX with package epsf and four eps figures. Added other references. Accepted for publication in Classical and Quantum Gravit

Biomarkers of disease differentiation: HCV recurrence versus acute cellular rejection

The wound-healing process induced by chronic hepatitis C virus (HCV) infection triggers liver damage characterized by fibrosis development and finally cirrhosis. Liver Transplantation (LT) is the optimal surgical treatment for HCV-cirrhotic patients at end-stage liver disease. However, acute cellular rejection (ACR) and HCV recurrence disease represent two devastating complications post-LT. The accurate differential diagnosis between both conditions is critical for treatment choice, and similar histological features represent a challenge for pathologists. Moreover, the HCV recurrence disease severity is highly variable post-LT. HCV recurrence disease progression is characterized by an accelerated fibrogenesis process, and almost 30% of those patients develop cirrhosis at 5-years of follow-up. Whole-genome gene expression (WGE) analyses through well-defined oligonucleotide microarray platforms represent a powerful tool for the molecular characterization of biological process. In the present manuscript, the utility of microarray technology is applied for the ACR and HCV-recurrence biological characterization in post-LT liver biopsy samples. Moreover, WGE analysis was performed to identify predictive biomarkers of HCV recurrence severity in formalin-fixed paraffin-embedded liver biopsies prospectively collected

On Higher Order Gravities, Their Analogy to GR, and Dimensional Dependent Version of Duff's Trace Anomaly Relation

An almost brief, though lengthy, review introduction about the long history of higher order gravities and their applications, as employed in the literature, is provided. We review the analogous procedure between higher order gravities and GR, as described in our previous works, in order to highlight its important achievements. Amongst which are presentation of an easy classification of higher order Lagrangians and its employment as a \emph{criteria} in order to distinguish correct metric theories of gravity. For example, it does not permit the inclusion of only one of the second order Lagrangians in \emph{isolation}. But, it does allow the inclusion of the cosmological term. We also discuss on the compatibility of our procedure and the Mach idea. We derive a dimensional dependent version of Duff's trace anomaly relation, which in \emph{four}-dimension is the same as the usual Duff relation. The Lanczos Lagrangian satisfies this new constraint in \emph{any} dimension. The square of the Weyl tensor identically satisfies it independent of dimension, however, this Lagrangian satisfies the previous relation only in three and four dimensions.Comment: 30 pages, added reference