Metallo-Anti-aromatic Al4Na4 and Al4Na3- compounds: A theoretical investigation

We propose a theoretical investigation in this paper to understand the bonding and structural properties of neutral Al4Na4 and anion Al4Na3- clusters. We show that the Al4 species in Al4Na4 and Al4Na3- clusters is a rectangular planar structure with alternate pi-bonds and hence satisfying the basic criteria for anti-aromaticity. We prove that the Al4Na4 and Al4Na3- clusters are metallo-anti-aromatic compounds

Symmetry Energy in the Equation of State of Asymmetric Nuclear Matte

The symmetry energy is an important quantity in the equation of state of isospin asymmetric nuclear matter. This currently unknown quantity is key to understanding the structure of systems as diverse as the neutron-rich nuclei and neutron stars. At TAMU, we have carried out studies, aimed at understanding the symmetry energy, in a variety of reactions such as, the multifragmentation of $^{40}$Ar, $^{40}$Ca + $^{58}$Fe, $^{58}$Ni and $^{58}$Ni, $^{58}$Fe + $^{58}$Ni, $^{58}$Fe reactions at 25 - 53 AMeV, and deep-inelastic reactions of $^{86}$Kr + $^{124,112}$Sn, $^{64,58}$Ni (25 AMeV), $^{64}$Ni + $^{64,58}$Ni, $^{112,124}$Sn, $^{232}$Th, $^{208}$Pb (25 AMeV) and $^{136}$Xe + $^{64,58}$Ni, $^{112,124}$Sn, $^{232}$Th, $^{197}$Au (20 AMeV). Here we present an overview of some of the results obtained from these studies. The results are analyzed within the framework of statistical and dynamical models, and have important implications for future experiments using beams of neutron-rich nuclei.Comment: 10 pages, 4 figures, talk presented at VI Latin American Symposium on Nuclear Physics and Application

Structural, electronic and bonding properties of zeolite Sn-Beta: A periodic density functional theory study

The structural, electronic and the bonding properties of the Sn-BEA are investigated by using the periodic density functional theory. Each of the 9 different T-sites in the BEA were substituted by the Sn atom and all the 9 geometries were completely optimized using the plane wave basis set in conjunction with the ultra-soft pseudopotential. On the basis of the structural and the electronic properties, it has been demonstrated that the substitution of the Sn atom in the BEA framework is an endothermic process and hence the incorporation of the Sn in the BEA is limited. The lowest unoccupied molecular orbitals (LUMO) energies have been used to characterize the Lewis acidity of each T-site. On the basis of the relative cohesive energy and the LUMO energy, T2 site is shown to be the most favorable site for the substitution of Sn atom in the BEA framework.Comment: 17 pages, 5 figures, 2 Table

Adaptation of Different Compomers to Primary Teeth Cavities

Background: Compomers remain the material of choice for restoration of primary teeth as they combine the best of GIC and composites. However, as it is a resinous material, attentionis focused on polymerization shrinkage causing gaps at restoration cavity interface. Gaps represent decreased efficacy of adaptation. Aim: To evaluate the marginal adaptation of compomers (Dyract, Compoglass, and F-2000) in class I and V cavities in primary molars. Materials and methods: Sixty noncarious primary molars were divided for three compomers (20), which were subdivided to two groups. Standard class I and V cavities (10 each) were prepared and restored. The cavity interface was examined and observations analyzed. The cavities were etched prior to restoration and margins were exposed. The cavosurface margins were inspected under stereomicroscope for surface gaps. Then buccolingually sectioned, they were examined for marginal gaps. Two specimens each were selected for SEM. Chi-square test was used to determine statistical significance (p < 0.05). Results: All compomers showed good adaptation at cavosurface, with class I better than V. Compoglass and Dyract were better adapted to cavity walls than F-2000. SEM revealed close interlaced adaptation of filling material to etched cavity. Conclusion: This study has shown that compomers provide good adaptation at cavity margins with compules (Compoglass and Dyract) being a better mode of dispensing than syringe tubes (F-2000). SEM showed gaps and pooling of adhesive and air in few samples.&nbsp

PRODUCTION AND OPTIMIZATION OF CITRIC ACID BY ASPERGILLUS NIGER USING MOLASSES AND CORNCOB

Objective: The present study made an attempt to produce commercially valuable citric acid by the fungal strain Aspergillus niger from molasses and corncob using submerged fermentation, as the best alternative to the sugar substrate.Methods: Three types of production media were prepared including control (sucrose) by following standard fermentation conditions. The acid production was indicated by the reduction of pH levels. The citric acid content and residual sugars of the final hydrolysate were estimated by the Marrier and Boulet method and Anthrone Sulphuric acid method respectively.Results: The control production medium gave yield of 4.6 milligrams per milliter (mg/ml) at pH 3.0 on 10th day. The medium containing molasses and other compositions gave the yield of 10.4 mg/ml, whereas corncob medium and other compositions gave the yield of 5.3 mg/ml at pH 2.5. The medium containing molasses and corncob separately with 5 percent (%) sucrose gave the highest yield of 12.6 mg/ml and 6.7 mg/ml at pH 3.0 respectively. Different factors affecting citric acid production by fermentation were also studied. Sucrose was found superior for maximum citric production at optimum incubation temperature at 30 degree Celsius (â°C). The nitrogen supplements, ammonium sulphate and ammonium chloride at a concentration of 0.25 % and 0.5% respectively gave the highest yield, whereas the methanol concentration of 2% was found optimum for obtaining maximum yield of citric acid.Conclusion: Molasses and corncob when replaced with sucrose in the fermentation medium produced significant amount of citric acid. The results imply the effective use of molasses and corncob as an alternative substrate for the production of commercially valuable, citric acid with a cost effective approach

Effective nucleon mass and the nuclear caloric curve

Assuming a schematic form of the nucleon effective mass as a function of nuclear excitation energy and mass, we provide a simple explanation for understanding the experimentally observed mass dependence of the nuclear caloric curve. It is observed that the excitation energy at which the caloric curve enters into a plateau region, could be sensitive to the nuclear mass evolution of the effective nucleon mass.Comment: 5 pages, 5 figures, Accepted for publication in Phys. Rev. C. Minor changes mad

Domination number of a bipartite semigraph when it is a cycle

Semigraph is a generalization of graph, with two or more vertices on edges which allows multiplicity in every concept of graph when it comes to semigraph. When number of vertices on the edges are restricted to two the semigraph is a graph, so every graph is a semigraph. In this article we deal with the variety of bipartite semigraphs, namely bipartite, s-bipartite and e-bipartite and bounds for their domination number (adjacent domination number and end vertex adjacent domination number) in particular when the semigraph is a cycle and also about possible size of the bipartite sets when the bipartite semigraph is a cycle.Publisher's Versio

Tracing the evolution of the symmetry energy of hot nuclear fragments from the compound nucleus towards multifragmentation

The evolution of the symmetry energy coefficient of the binding energy of hot fragments with increasing excitation is explored in multifragmentation processes following heavy-ion collisions below the Fermi energy. In this work, high-resolution mass spectrometric data on isotopic distributions of projectile-like fragments from collisions of 25 MeV/nucleon 86Kr and 64Ni beams on heavy neutron-rich targets are systematically compared to calculations involving the Statistical Multifragmentation Model. The study reveals a gradual decrease of the symmetry energy coefficient from 25 MeV at the compound nucleus regime (E*/A < 2 MeV) towards 15 MeV in the bulk multifragmentation regime (E*/A > 4 MeV). The ensuing isotopic distributions of the hot fragments are found to be very wide and extend towards the neutron drip-line. These findings may have important implications to the composition and evolution of hot astrophysical environments, such as core-collapse supernova.Comment: 5 pages, 4 figures, submitted to Phys. Rev.