Configurational temperature control for atomic and molecular systems

A new configurational temperature thermostat suitable for molecules with holonomic constraints is derived. This thermostat has a simple set of motion equations, can generate the canonical ensemble in both position and momentum space, acts homogeneously through the spatial coordinates, and does not intrinsically violate the constraints. Our new configurational thermostat is closely related to the kinetic temperature Nosé-Hoover thermostat with feedback coupled to the position variables via a term proportional to the net molecular force. We validate the thermostat by comparing equilibrium static and dynamic quantities for a fluid of n-decane molecules under configurational and kinetic temperature control. Practical aspects concerning the implementation of the new thermostat in a molecular dynamics code and the potential applications are discussed

COUPLING CHIRAL BOSONS TO GRAVITY

The chiral boson actions of Floreanini and Jackiw (FJ), and of McClain,Wu and Yu (MWY) have been recently shown to be different representations of the same chiral boson theory. MWY displays manifest covariance and also a (gauge) symmetry that is hidden in the FJ side, which, on the other hand, displays the physical spectrum in a simple manner. We make use of the covariance of the MWY representation for the chiral boson to couple it to background gravity showing explicitly the equivalence with the previous results for the FJ representationComment: 8 pages, Latex, no figure

Pregnancy with autoimmune hepatitis

AIM: The aim of this study was to review our experience with gestations in autoimmune hepatitis patients. BACKGROUND: There are only limited data describing pregnancy in patients with autoimmune hepatitis. PATIENTS AND METHODS: Retrospective analysis of pregnancies with autoimmune hepatitis followed in Centro Hospitalar do Porto, Portugal in the last ten years. RESULTS: We reported nine pregnancies in seven patients with autoimmune hepatitis. Two patients had documented liver cirrhosis prior to the pregnancy. In this study, 66.7% of patients were treated with azathioprine and 88.9% with prednisolone. Clinical improvements were observed in 11.1% of pregnancies and 22.2% exacerbations were diagnosed. There were six live births and two preterm deliveries (preterm delivery rate of 33%). We also report three first trimester miscarriages (early gestation miscarriage rate of 33%). There were no neonatal or maternal deaths. CONCLUSION: The favorable obstetric outcome is a realistic expectation in patients with autoimmune hepatitis. Tight monitoring and control of asymptomatic and unpredictable exacerbations, which are unrelated to the severity of the underlying disease, are essential to the prognosis of the current pregnancyinfo:eu-repo/semantics/publishedVersio

Superspace Formulation for the BRST Quantization of the Chiral Schwinger Model

It has recently been shown that the Field Antifield quantization of anomalous irreducible gauge theories with closed algebra can be represented in a BRST superspace where the quantum action at one loop order, including the Wess Zumino term, and the anomalies show up as components of the same superfield. We show here how the Chiral Schwinger model can be represented in this formulation.Comment: 11 pages, Late

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