On the thermal and double episode emissions in GRB 970828

Following the recent theoretical interpretation of GRB 090618 and GRB 101023, we here interpret GRB 970828 in terms of a double episode emission: the first episode, observed in the first 40 s of the emission, is interpreted as the proto-black-hole emission; the second episode, observed after t$_0$+50 s, as a canonical gamma ray burst. The transition between the two episodes marks the black hole formation. The characteristics of the real GRB, in the second episode, are an energy of $E_{tot}^{e^+e^-} = 1.60 \times 10^{53}$ erg, a baryon load of $B = 7 \times 10^{-3}$ and a bulk Lorentz factor at transparency of $\Gamma = 142.5$. The clear analogy with GRB 090618 would require also in GRB 970828 the presence of a possible supernova. We also infer that the GRB exploded in an environment with a large average particle density $\, \approx 10^3$ part/cm$^3$ and dense clouds characterized by typical dimensions of $(4 - 8) \times 10^{14}$ cm and $\delta n/n \propto 10$. Such an environment is in line with the observed large column density absorption, which might have darkened both the supernova emission and the GRB optical afterglow.Comment: 7 pages, 10 figures, submitted to Ap

General Relativistic Radiant Shock Waves in the Post-Quasistatic Approximation

An evolution of radiant shock wave front is considered in the framework of a recently presented method to study self-gravitating relativistic spheres, whose rationale becomes intelligible and finds full justification within the context of a suitable definition of the post-quasistatic approximation. The spherical matter configuration is divided into two regions by the shock and each side of the interface having a different equation of state and anisotropic phase. In order to simulate dissipation effects due to the transfer of photons and/or neutrinos within the matter configuration, we introduce the flux factor, the variable Eddington factor and a closure relation between them. As we expected the strength of the shock increases the speed of the fluid to relativistic values and for some critical ones is larger than light speed. In addition, we find that energy conditions are very sensible to the anisotropy, specially the strong one. As a special feature of the model, we find that the contribution of the matter and radiation to the radial pressure are the same order of magnitude as in the mant as in the core, moreover, in the core radiation pressure is larger than matter pressure.Comment: To appear in Journal of Physics:Conference Series:"XXIX Spanish Relativity Meeting (ERE 2006): Einstein's Legacy: From the Theoretical Paradise to Astrophysical Observations

Realistic Exact Solution for the Exterior Field of a Rotating Neutron Star

A new six-parametric, axisymmetric and asymptotically flat exact solution of Einstein-Maxwell field equations having reflection symmetry is presented. It has arbitrary physical parameters of mass, angular momentum, mass--quadrupole moment, current octupole moment, electric charge and magnetic dipole, so it can represent the exterior field of a rotating, deformed, magnetized and charged object; some properties of the closed-form analytic solution such as its multipolar structure, electromagnetic fields and singularities are also presented. In the vacuum case, this analytic solution is matched to some numerical interior solutions representing neutron stars, calculated by Berti & Stergioulas (Mon. Not. Roy. Astron. Soc. 350, 1416 (2004)), imposing that the multipole moments be the same. As an independent test of accuracy of the solution to describe exterior fields of neutron stars, we present an extensive comparison of the radii of innermost stable circular orbits (ISCOs) obtained from Berti & Stergioulas numerical solutions, Kerr solution (Phys. Rev. Lett. 11, 237 (1963)), Hartle & Thorne solution (Ap. J. 153, 807, (1968)), an analytic series expansion derived by Shibata & Sasaki (Phys. Rev. D. 58 104011 (1998)) and, our exact solution. We found that radii of ISCOs from our solution fits better than others with realistic numerical interior solutions.Comment: 13 pages, 13 figures, LaTeX documen

Frecuencia elevada del alelo ε4 del gen de apolipoproteína E en una muestra de pacientes con síndrome Down

La enfermedad de Alzheimer es la entidad más frecuente enpacientes con síndrome Down (SD) y a su vez uno de losfactores de riesgo para el desarrollo de esta entidad es lapresencia del alelo ε4 de apolipoproteína E. En el presenteestudio se evaluó el genotipo de apolipoproteína E en ungrupo de pacientes de ambos sexos con síndrome Down.Los resultados muestran que hay una frecuencia aumentadapara el alelo ε4 en esta población cuando se hizo la comparacióncon los valores previamente encontrados para unamuestra de la población del Departamento de Risaralda queno presentaban SD la cual se tomó como control

Frecuencia elevada del alelo ε4 del gen de apolipoproteína E en una muestra de pacientes con síndrome Down

La enfermedad de Alzheimer es la entidad más frecuente enpacientes con síndrome Down (SD) y a su vez uno de losfactores de riesgo para el desarrollo de esta entidad es lapresencia del alelo ε4 de apolipoproteína E. En el presenteestudio se evaluó el genotipo de apolipoproteína E en ungrupo de pacientes de ambos sexos con síndrome Down.Los resultados muestran que hay una frecuencia aumentadapara el alelo ε4 en esta población cuando se hizo la comparacióncon los valores previamente encontrados para unamuestra de la población del Departamento de Risaralda queno presentaban SD la cual se tomó como control

Frecuencia elevada del alelo ε4 del gen de apolipoproteína E en una muestra de pacientes con síndrome Down

La enfermedad de Alzheimer es la entidad más frecuente enpacientes con síndrome Down (SD) y a su vez uno de losfactores de riesgo para el desarrollo de esta entidad es lapresencia del alelo ε4 de apolipoproteína E. En el presenteestudio se evaluó el genotipo de apolipoproteína E en ungrupo de pacientes de ambos sexos con síndrome Down.Los resultados muestran que hay una frecuencia aumentadapara el alelo ε4 en esta población cuando se hizo la comparacióncon los valores previamente encontrados para unamuestra de la población del Departamento de Risaralda queno presentaban SD la cual se tomó como control