What the Frog's Nose Tells the Frog's Brain

The olfactory system has the challenging task of responding to thousands of structurally dissimilar odors. In the last decade, advances in molecular biology and genomics have made it possible to obtain an understanding of the diversity of olfactory receptors (Mombaerts, 1999; Buck, 2000). In the mouse, for example, there are over 1,000 different olfactory receptor genes (Zhang and Firestein, 2002), and each olfactory receptor neuron (ORN) expresses only one of these olfactory receptors through a remarkable mechanism that includes feedback by the olfactory receptor protein excluding expression of all other olfactory receptor genes (Serizawa et al., 2003). Therefore, it is thought that each ORN will respond to a set of structurally related odors that stimulate the particular olfactory recepto

Modelos unifactoriales de tipos de interés : aplicación al mercado colombiano

Este trabajo presenta una primera aproximación a la implementación de los modelos unifactoriales de tipos de interés de Hull y White (1990) y Black y Karasinski (1991) para el mercado colombiano. Se encuentra que ambos modelos replican exactamente la estructura a plazos de tasas de interés del mercado. No obstante, debido a la insistencia de instrumentos derivados de tasas de interés lo suficientemente líquidos no es posible realizar la calibración implícita de estos modelos. Este proceso se reemplazó por la estimación del parámetro de volatilidad utilizando un modelo EGARCH sobre la Tasa de Interés Interbancaria. La metodología utilizada servirá para valorar derivados de tasas de interés en el mercado colombiano, principalmente, en sus primeras fases de desarrollo.43 p.This work presents a first approximation for implementing the Hull and White (1990) and the Black and Karasinski (1991) One-Factor Interest Rate Models in the Colombian market. Both models fit exactly the Colombian term structure of interest rates. Nevertheless, due to the unavailability of interest rate derivatives in our market, implicit calibration was not possible. This process was replaced by the estimation of the volatility using an EGARCH model for the Interbank Interest Rate. This approach will hand out with the pricing of interest rate derivatives in the Colombian Market, mainly, in its early steps of development

Indirect detection of gravitino dark matter including its three-body decays

It was recently pointed out that in supersymmetric scenarios with gravitino dark matter and bilinear R-parity violation, gravitinos with masses below Mw typically decay with a sizable branching ratio into the 3-body final states W^*+lepton and Z^*+neutrino. In this paper we study the indirect detection signatures of gravitino dark matter including such final states. First, we obtain the gamma ray spectrum from gravitino decays, which features a monochromatic contribution from the decay into photon+neutrino and a continuum contribution from the three-body decays. After studying its dependence on supersymmetric parameters, we compute the expected gamma ray fluxes and derive new constraints, from recent FERMI data, on the R-parity breaking parameter and on the gravitino lifetime. Indirect detection via antimatter searches, a new possibility brought about by the three-body final states, is also analyzed. For models compatible with the gamma ray observations, the positron signal is found to be negligible whereas the antiproton one can be significant.Comment: 21 pages,16 figures v2: one numerical error corrected, one figure added, main results unchange