Warm Asymmetric Nuclear Matter and Proto-Neutron Star

Asymmetric nuclear matter equation of state at finite temperature is studied in SU(2) chiral sigma model using mean field approximation. The effect of temperature on effective mass, entropy, and binding energy is discussed. Treating the system as one with two conserved charges the liquid-gas phase transition is investigated. We have also discussed the effect of proton fraction on critical temperature with and without $\rho$-meson contribution. We have extended our work to study the structure of proto-neutron star with neutron free charge-neutral matter in beta-equilibrium. We found that the mass and radius of the star decreases as it cools from the entropy per baryon S = 2 to S = 0 and the maximum temperature of the core of the star is about 62 MeV for S = 2.Comment: 25 pages, 16 figure

Energetics and electronic structure of carbon doped aluminum clusters

The energetics and the electronic structure of AlnC clusters (n=3, 4, 5; 11, 12, 13) have been studied by a global optimization of their geometry without any symmetry constraint. The total energies of these clusters both in neutral and charged states are calculated using an all-electron basis and the generalized gradient approximation to the density functional theory. While Al4C and Al12C clusters share some characteristic features of closed shell structures, namely enhanced stability and low electron affinity compared to their neighboring sizes, their ionization potentials exhibit different behavior. These decrease steadily from Al3C to Al5C while that of Al12C is higher than its neighbors. Carbon is found to form planar structures in small AlnC clusters (n=3, 4, 5) irrespective of their charge state although neutral Al4C possesses a nearly degenerate tetrahedral isomer lying slightly higher in energy from the planar configuration. The results agree well with experimental and previous theoretical data. In larger AlnC (n=11, 12, 13) clusters, carbon occupies an interior site. In Al12C, carbon occupies the center of an icosahedron while it is off-centered in Al11C and Al13C. As an electron is attached, the near degeneracies of the neutral Al4C is lifted whereas nondegenerate isomers of neutral Al12C yield nearly degenerate anions. Both these features produce complicated photoelectron spectra making identification of their adiabatic electron affinity a difficult problem. With the exception of neutral Al12C, the bonding of carbon to aluminum atoms is governed primarily by covalent interaction. The above calculations were also performed with a simplified basis by freezing the atomic cores of aluminum. In most cases, this simple basis yields results in good agreement with all electron calculations

Evolution of the electronic structure and properties of neutral and charged aluminum clusters: A comprehensive analysis

Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to calculate the global equilibrium geometries and electronic structure of neutral, cationic, and anionic aluminumclusters containing up to 15 atoms. The total energies of these clusters are then used to study the evolution of their binding energy, relative stability, fragmentation channels, ionization potential, and vertical and adiabatic electron affinities as a function of size. The geometries are found to undergo a structural change from two dimensional to three dimensional when the cluster contains 6 atoms. An interior atom emerges only when clusters contain 11 or more atoms. The geometrical changes are accompanied by corresponding changes in the coordination number and the electronic structure. The latter is reflected in the relative concentration of the s and p electrons of the highest occupied molecular orbital. Aluminum behaves as a monovalent atom in clusters containing less than seven atoms and as a trivalent atom in clusters containing seven or more atoms. The binding energy evolves monotonically with size, but Al7, Al+7, Al−7, Al−11, and Al−13 exhibit greater stability than their neighbors. Although the neutral clusters do not conform to the jellium model, the enhanced stability of these charged clusters is demonstrated to be due to the electronic shell closure. The fragmentation proceeds preferably by the ejection of a single atom irrespective of the charge state of the parent clusters. While odd-atom clusters carry a magnetic moment of 1μB as expected, clusters containing even number of atoms carry 2μB for n⩽10 and 0 μB for n\u3e10.The calculated results agree very well with all available experimental data on magnetic properties,ionization potentials,electron affinities, and fragmentation channels. The existence of isomers of Al13 cluster provides a unique perspective on the anomaly in the intensity distribution of the mass spectra. The unusual stability of Al7 in neutral, cationic, and anionic form compared to its neighboring clusters is argued to be due to its likely existence in a mixed-valence state

Novel electronic and magnetic properties of BN sheet decorated with hydrogen and fluorine

First principles calculations based on density functional theory reveal some unusual properties of BN sheet functionalized with hydrogen and fluorine. These properties differ from those of similarly functionalized graphene even though both share the same honeycomb structure. (1) Unlike graphene which undergoes a metal to insulator transition when fully hydrogenated, the band gap of the BN sheet significantly narrows when fully saturated with hydrogen. Furthermore, the band gap of the BN sheet can be tuned from 4.7 eV to 0.6 eV and the system can be a direct or an indirect semiconductor or even a half-metal depending upon surface coverage. (2) Unlike graphene, BN sheet has hetero-atomic composition, when co-decorated with H and F, it can lead to anisotropic structures with rich electronic and magnetic properties. (3) Unlike graphene, BN sheets can be made ferromagnetic, antiferromagnetic, or magnetically degenerate depending upon how the surface is functionalized. (4) The stability of magnetic coupling of functionalized BN sheet can be further modulated by applying external strain. Our study highlights the potential of functionalized BN sheets for novel applications.Comment: 18 pages, 6 figures, and 1 tabl

Nature human Interface:An Ecocritical Study of Anita Desai’s Fire on the Mountain

The idea of distinction or conflict between nature and human being is possibly the result of scientific prudence. Progress in science and technology develops the idea of nature as a mechanical system which may be used and exploited in the process of satisfying human desires. It results in the acceleration of changes in the balance of the environment. Thus, it is the need of the twentyfirst century to explore the primordial relation of human with nature in science and philosophy, history and literature, perhaps the main objective is to save it. Again human dependence on environment for instrumental as well as intrinsic purpose is undeniable and ubiquitous. In the process of searching for fulfillment amidst desperation, human being finds nature as probably a suitable space. This paper makes an attempt to study how nature plays vital role in reshaping and restructuring human life as well as how human developmental practices (both scientific and cultural) corrupt and desecrate the environment. Moreover, it carries out the study of Anita Desai's Fire on the Mountain, in the backdrop of Ecocritical ideas, in order to justify Desai's vision of nature and its relationship with the human in the novel

Caging of Ni clusters by benzene molecules and its effect on the magnetism of Ni clusters

Global optimization of the geometry of small Ni clusters interacting with benzene molecules yields equilibrium structures where the Ni atoms find themselves caged between the benzene molecules. This leads to quenching of the Ni magnetic moment in most of the complexes even though the structure of the caged Ni clusters remain relatively unchanged from their otherwise free gas phase geometry. The accuracy of these predictions, based on density functional theory with generalized gradient approximation for exchange and correlation, is established by the good agreement achieved between the calculated and available experimental dissociation energies and ionization potentials

Reinventing the Cultural History of Colonial Odisha through Creative Nonfiction: A Study of J.P Das's A Time Elsewhere

Historical fictions and narrating the historical facts through creative nonfiction are different concepts, as in the former the details are fictionalised with the imaginative dialogues and events and in the later the historical facts are presented in a creative way that does not affect or disturb the authenticity of the facts. Here the epithet "Creative" refers to the use of literary techniques and novelistic narrative modes to tell the "true stories" or the factually accurate prose and does not mean the narration of imaginary events and the nonexistent things1. It is true that history in an objective way details the significant events with utmost exactness. So the question comes while narrating the history in a creative way will not the creative process interfere with the facts? Again, in the process of analysis and interpretation of facts to narrate, the personal ideological bias of the author may be implicitly present in the text and the narrative takes the way as the author intends; for which the reliability on the factuality of the presented facts will be in doubt. The central concern of this paper is to study J P Das's A Time Elsewhere to explore how the cultural history of Orissa has been presented with factual accurateness of events, creativity and the cardinal principles of History writing, moreover to study the aforementioned writing as creative nonfiction