Modeling highly pathogenic avian influenza transmission in wild birds and poultry in West Bengal, India.

Wild birds are suspected to have played a role in highly pathogenic avian influenza (HPAI) H5N1 outbreaks in West Bengal. Cluster analysis showed that H5N1 was introduced in West Bengal at least 3 times between 2008 and 2010. We simulated the introduction of H5N1 by wild birds and their contact with poultry through a stochastic continuous-time mathematical model. Results showed that reducing contact between wild birds and domestic poultry, and increasing the culling rate of infected domestic poultry communities will reduce the probability of outbreaks. Poultry communities that shared habitat with wild birds or those indistricts with previous outbreaks were more likely to suffer an outbreak. These results indicate that wild birds can introduce HPAI to domestic poultry and that limiting their contact at shared habitats together with swift culling of infected domestic poultry can greatly reduce the likelihood of HPAI outbreaks

The Universe With Bulk Viscosity

Exact solutions for a model with variable $G$, $\Lambda$ and bulk viscosity are obtained. Inflationary solutions with constant (de Sitter-type) and variable energy density are found. An expanding anisotropic universe is found to isotropize during its course of expansion but a static universe is not. The gravitational constant is found to increase with time and the cosmological constant decreases with time as $\Lambda \propto t^{-2}$.Comment: 7 LateX pages, no figure

The color of polarization in cuprate superconductors

A technique for the identification of individual anisotropic grains in a heterogeneous and opaque material involves the observation of grain color in reflected light through crossed polarizers (color of polarization). Such colors are generally characteristic of particular phases. When grains of many members of the class of hole carrier cuprate superconductors are so viewed, using a xenon light source (600 K color temperature), a characteristic color of polarization is observed. This color was studied in many of these cuprate superconductors and a strong correlation was found between color and the existence of superconductivity. One of the members of the electron carrier cuprate superconductors (Nd(1.85)Ce(.15)CuO(4-x) was examined and found that it possesses the same color of polarization as all the electron hole carrier cuprate superconductors so far examined. The commonality of the characteristic color in the cuprate superconductors indicated that the presence of this color is independent of the nature of charge carriers. The correlation of this color with existence of superconductivity suggests that the origin of the color relates to the origin of superconductivity in the cuprate superconductors. Photometric techniques are also discussed

Anemia in Antiretroviral Naïve HIV/AIDS Patients: A Study from Eastern India

Background: Hematological manifestations are common throughout the course of HIV infection. Impact of anemia is the most significant among them. The present study was undertaken to evaluate the etiologies underlying anemia in HIV/AIDS. Methods This was a non randomized cross sectional observational study conducted in a tertiary care hospital of India over a period of 2 years. One hundred and fifty HIV patients were screened. Thorough clinical and laboratory evaluation was done in 50 randomly selected anemic cases. Results: Proper etiological diagnosis could be reached in 46 patients. Among them correlation between Hb% and CD4 count was statistically insignificant (p = 0.074, r = 0.47) whereas it was significant with absolute lymphocyte and CD4 count (p = 0.006, r = 0.41). There was better correlation of bone marrow iron status with percent saturation of transferrin (p = 0.003, r = 0.54) than with serum ferritin (p = 0.055, r = 0.09). Bone marrow iron status did not have any relationship with CD4 count. Anemia of chronic disease was the commonest etiology (37%) followed by HIV related myelodysplastic syndrome (31%), iron deficiency anemia (13%), bone marrow suppression due to direct involvement by some infective process (7%). Aplastic anemia, multiple myeloma, Hodgkin’s disease, pure red cell aplasia, hemophagocytic lymphohistiocytosis and vitamin B12 deficiency were detected in one case (2%) each. Conclusions: Etiologies of anemia in HIV/AIDS are multifactorial with anemia of chronic disease being the commonest. For screening of iron deficiency in this group, percent saturation is a better tool than serum ferritin. Absolute lymphocyte count can sometimes be used as a surrogate marker of immunological status in antiretroviral naïve HIV patients, particularly in resource poor areas

Free Energy Self-Averaging in Protein-Sized Random Heteropolymers

Current theories of heteropolymers are inherently macrpscopic, but are applied to folding proteins which are only mesoscopic. In these theories, one computes the averaged free energy over sequences, always assuming that it is self-averaging -- a property well-established only if a system with quenched disorder is macroscopic. By enumerating the states and energies of compact 18, 27, and 36mers on a simplified lattice model with an ensemble of random sequences, we test the validity of the self-averaging approximation. We find that fluctuations in the free energy between sequences are weak, and that self-averaging is a valid approximation at the length scale of real proteins. These results validate certain sequence design methods which can exponentially speed up computational design and greatly simplify experimental realizations.Comment: 4 pages, 3 figure

Freezing Transition of Random Heteropolymers Consisting of an Arbitrary Set of Monomers

Mean field replica theory is employed to analyze the freezing transition of random heteropolymers comprised of an arbitrary number ($q$) of types of monomers. Our formalism assumes that interactions are short range and heterogeneity comes only from pairwise interactions, which are defined by an arbitrary $q \times q$ matrix. We show that, in general, there exists a freezing transition from a random globule, in which the thermodynamic equilibrium is comprised of an essentially infinite number polymer conformations, to a frozen globule, in which equilibrium ensemble is dominated by one or very few conformations. We also examine some special cases of interaction matrices to analyze the relationship between the freezing transition and the nature of interactions involved.Comment: 30 pages, 1 postscript figur

Random walks in the space of conformations of toy proteins

Monte Carlo dynamics of the lattice 48 monomers toy protein is interpreted as a random walk in an abstract (discrete) space of conformations. To test the geometry of this space, we examine the return probability $P(T)$, which is the probability to find the polymer in the native state after $T$ Monte Carlo steps, provided that it starts from the native state at the initial moment. Comparing computational data with the theoretical expressions for $P(T)$ for random walks in a variety of different spaces, we show that conformational spaces of polymer loops may have non-trivial dimensions and exhibit negative curvature characteristic of Lobachevskii (hyperbolic) geometry.Comment: 4 pages, 3 figure