Abstract

Several novel phases with large strangeness fraction such as, hyperon matter, quarkphase and Bose-Einstein condensates of antikaons are theoretically predicted at the highdensity core of neutron stars. Within the framework of the traditional meson exchangepicture known as the relativistic mean field (RMF) model, we study the equation ofstate (EoS) in the dense matter at the core of compact stars, formed in the core collapsesupernovas.The EoS of hot and dense matter plays a fundamental role in the understanding ofcore-collapse supernova. A phase transition from hadronic to exotic phases might occurin the early post-bounce phase of a core collapse supernova. We investigate the emergenceof strange hyperons in the dynamical collapse of a non-rotating massive star to a blackhole. We follow the dynamical formation and collapse of a protoneutron star (PNS) fromthe gravitational collapse of a 40M star adopting the newly constructed Shen hyperonicEOS. We also study the neutrino signals that may be used as a probe to core collapsesupernova. We compare the results with those of Shen nuclear EoS and understand therole of strange hyperons in the core collapse.Finally we discuss about our ongoing work on generating a full table of antikaon EoSfor a wide spectrum of temperature, density and proton fraction, which should be usefulfor supernova simulations.

Abstract

A protein called DNA Polymerases is capable of creating new DNA strands by incorporating the monomeric units of DNA called nucleotides opposite the single stranded parent DNA in a Watson Crick manner (A:T and G:C). DNA polymerases are therefore centrally involved in the replication of DNA. In order to carry out this crucial function, these replicative DNA polymerase molecules exhibit extremely high accuracy and processivity (measure of the no. of nucleotides added by a polymerase per association with a DNA). The presence of damaged nucleotides in the genome (DNA code for any organism) is highly inhibitory to the activity of these DNA Polymerases. DNA can be damaged by a variety of external (radiation, chemicals) and internal (free radicals, reactive intermediates) agents. Replicative DNA Polymerases are not capable of stabilizing the damaged nucleotide and the correct incoming nucleotide in their active sites which leads to the stalling of the replication machinery. To overcome this predicament it is seen that all organisms have specialized DNA Polymerases grouped under the Y-family of DNA Polymerases. The members of this family usually exhibit low-fidelity (ability to pair in Watson Crick manner) and low-processivity and are able to incorporate nucleotides opposite various kinds of damaged nucleotides. It is believed that once these molecules help the replication machinery cross the damage they are replaced by normal replicative DNA Polymerases. In addition, it has also been suggested that the low-fidelity of these molecules is exploited to generate adaptive mutations that can relieve selection pressure arising from adverse environmental conditions. This might be especially true in case of prokaryotes (bacterial organisms) where the expression of these molecules is controlled by transcriptional mechanisms that deal with stress. We have carried out structural and functional studies on one of theY-family protein in Mycobacterium smegmatis (bacterial organism similar toTuberculosis and non pathological), MsDpo4. The aim is to provide atopological and chemical description of MsDpo4 in order to understand the relation between structure and function in case of Y- Family DNA Polymerases in prokaryotes. We have seen that this protein prefers Watson-Crick mode of base pairing and it is also capable of promoting mismatches. Steady-state kinetic analysis shows that this protein exhibits significant ability to promote G:T and T:G mismatches and thus has the biochemical capacity to participate in adaptive mutagenesis. MsDpo4 is also capable of carrying out synthesis across the damaged DNA. The structure of MsDpo4 has been determined to a resolution of 2.6 Ã…. The structure suggests that one of the domain of this protein exhibits conformational heterogeneity. The possible implications of this observation will be discussed.

Abstract

Double beta decay (DBD), first predicted in 1935 by Maria Goeppert-Mayer, has evolved from a marginal activity in nuclear physics to one of the top priority research areas of the physics worldwide, for understanding neutrinos primarily and also for constraining the nuclear structure models to a large extent. In last 75 years, a large progress has been made in the field of double beta decay studies, experimentally as well as theoretically, resulting in successful observation of two neutrino double beta decay for several nuclei and pinning down the mass of neutrino to sub eV scale (~0.2-0.5 eV; depending on the choice of nuclear matrix element) – through a single claim for the observation of neutrinoless double beta decay of 76Ge. Though, this clam, still needs to be verified by other experiments for 76Ge and other candidate nuclei as well, it has greatly boosted up the research projects related to this particular lepton violating process. More importantly, Indian efforts, however at primitive stage presently, are also on to develop a state of the art double beta decay experiment at India based Neutrino Observatory (INO). In the present talk, I will discuss our results for DBD and also present an overview of the current status along with future prospects of DBD studies.

Abstract

Oriented assemblies of small crystals forming larger structuresare common in nature and crucial for forthcoming technologies asthey circumvent the difficulties of structural manipulation atmicroscopic scale. We have discovered two distinctive concentricassemblies of zinc oxide rods, wherein each rod has an intrinsicallypositive and a negative polar end induced by the noncentrosymmetricarrangement of Zn and O atoms. All the rods in a single assemblyemanate out of a central core maintaining a single polar direction.Due to growth along the two polar surfaces with different atomicarrangements, these assemblies are distinct in their intrinsicproperties and exhibit strong UV luminescence in the exterior ofZn-polar assemblies, unlike the O-polar assemblies. We have reportedsurface-enhanced Raman scattering (SERS) from Ag and Au nanoparticlesdecorated on thin carbon nanowalls (CNWs) grown by microwave plasmachemical vapor deposition. The Ag morphology is controlled byexposing the CNWs to oxygen plasma and through the electrodepositionprocess by varying the number of deposition cycles. The SERSsubstrates are capable of detecting low concentrations of rhodamine6G and bovine serum albumin, showing much higher Raman enhancementthan ordinary planar HOPG with Ag decoration. The major factorscontributing to this behavior include: high density of Agnanoparticles, large surface area, high surface roughness, and theunderlying presence of vertically oriented CNWs. The relativelysimple procedure of substrate preparation and nanoparticledecoration suggests that this is a promising approach forfabricating ultrasensitive SERS substrates for biological andchemical detection at the single-molecule level, while alsoenabling the study of fundamental SERS phenomena.

Abstract