Thermal Background Corrections to the Neutrino Electromagnetic Vertex in Models with Charged Scalar Bosons

We calculate the correction to the neutrino electromagnetic vertex due to background of electrons in a large class of models, as the supersymmetric model with explicit breaking of R-parity, where charged scalar bosons couple to leptons and which are able to provide an astrophysically interesting value for the neutrino magnetic (electric) moment, $\mu_\nu\sim 10^{-12}\:\mu_B$. We show that the medium contribution to the chirality flipping magnetic (electric) dipole moment is not significant, however a new chirality flipping, but helicity conserving, term arises. It signals the presence of ${\cal CP}$ and ${\cal CPT}$ asymmetries in the medium and is associated to the longitudinal photon and therefore disappears in the vacuum. We estimate the contribution of this new term to the rate of the plasmon decay process $\gamma_{pl}\rightarrow \nu\nu$ in the core of degenerate stars, showing that it can be comparable with the contribution coming from the vacuum magnetic (dipole) moment. We also calculate the correction to the effective potential of a propagating neutrino in presence of a magnetic field due to a chirality preserving contribution to the diagonal magnetic moment from the medium. This contribution is identical for particles and antiparticles and so need not to vanish for Majorana neutrinos.Comment: DFPD 93/TH/75, SISSA 93/183/A preprint, 25 pages + 4 figures available by e-mail reques

The burden of Stroke in Pakistan

Epidemiologic literature on stroke burden, patterns of stroke is almost non existent from Pakistan. However, several hospital-based case series on the subject are available, mainly published in local medical journals. Despite the fact that true stroke incidence and prevalence of stroke in Pakistan is not known, the burden is assumed to be high because of highly prevalent stroke risk factors (hypertension, diabetes mellitus, coronary artery disease, dyslipidemia and smoking) in the community. High burden of these conventional stroke risk factors is further compounded by lack of awareness, poor compliance hence poor control, and inappropriate management/treatment practices. In addition certain risk factors like rheumatic valvular heart disease may be more prevalent in Pakistan. We reviewed the existing literature on stroke risk factors in community, the risk factor prevalence among stroke Patients, patterns of stroke, out come of stroke, availability of diagnostic services/facilities related to stroke and resources for stroke care in Pakistan