Hyperon production in pp collisions

We report on a study of the proton induced hyperon production reactions. We discuss the theoretical efforts made towards understanding the existing data and the uncertainties involved in the calculations. Our recent calculations of the missing mass spectra for the pp → K ⁺ Λp reaction which involve a proper coupled channel treatment of the final state Λp interaction are presented. Significant differences in the results using different models of the hyperon-nucleon interaction are found.     

Fast ethylamine gas sensing based on intermolecular charge-transfer complexation

We have investigated the fast ethylamine gas sensing of 2-chloro-3,5-dinitrobenzotrifluoride(CDBF) loaded poly(acrylonitrile) nanofiber based on an intermolecular charge-transfer complexation.Reversible response and recovery were achieved using alternating gas exposure.This system shows a fast ethylamine gas sensing within 0.4 s.     

Multifragmentation and the phase transition: A systematic study of the multifragmentation of 1A GeV Au, La and Kr

A systematic analysis of the multifragmentation (MF) in fully reconstructed events from 1A GeV Au, La and Kr collisions with C has been performed. Detailed comparisons of the various fragment properties are presented as a function of excitation energy, E*_th. The charged particle multiplicity from MF stage shows a saturation beyond E*_th ∼ 8 MeV/nucleon for Kr. The universal behavior of intermediate mass fragment yields and of the size of the largest fragment is observed only for Au and La when scaled with size of the system. The Kr data are found to lack this property. Moments of the fragment size distribution show that the Kr MF is different than the MF of Au and La. A power law behavior is observed for Au and La with exponent τ>2, while for Kr τ<2. The results are compared with the statistical multifragmentation model (SMM). A single value of all the parameters of the model fits the data for all the three systems. The breakup of Au and La is consistent with a continuous phase transition. The data indicate that both E*_th and the isotope ratio temperature T _Hc-DT decrease with increase in system size at the critical point. The breakup temperature obtained from SMM also shows the same trend as seen in data. This trend is attributed primarily to the increasing Coulomb energy with finite size effects playing a smaller role. The percolation and Ising model studies for finite size neutral matter show behavior which is opposite to the one seen in the present work. EOS Collaboration     

Density Functional Theory Study of Optical and Electronic Properties of (TiO2)n=5,8,68 Clusters for Application in Solar Cells

A range of solution-processed organic and hybrid organic−inorganic solar cells, such as dye-sensitized and bulk heterojunction organic solar cells have been intensely developed recently. TiO₂ is widely employed as electron transporting material in nanostructured TiO₂ perovskite-sensitized solar cells and semiconductor in dye-sensitized solar cells. Understanding the optical and electronic mechanisms that govern charge separation, transport and recombination in these devices will enhance their current conversion efficiencies under illumination to sunlight. In this work, density functional theory with Perdew-Burke Ernzerhof (PBE) functional approach was used to explore the optical and electronic properties of three modeled TiO₂ brookite clusters, (TiO₂)_n=5,8,68. The simulated optical absorption spectra for (TiO₂)₅ and (TiO₂)₈ clusters show excitation around 200–400 nm, with (TiO₂)₈ cluster showing higher absorbance than the corresponding (TiO₂)₅ cluster. The density of states and the projected density of states of the clusters were computed using Grid-base Projector Augmented Wave (GPAW) and PBE exchange correlation functional in a bid to further understand their electronic structure. The density of states spectra reveal surface valence and conduction bands separated by a band gap of 1.10, 2.31, and 1.37 eV for (TiO₂)₅, (TiO₂)₈, and (TiO₂)₆₈ clusters, respectively. Adsorption of croconate dyes onto the cluster shifted the absorption peaks to higher wavelengths.     

Relative wavefunctions, vertex functions and coupling constants for the virtual decay of 4He

The d + d, t + p and h + n relative wavefunctions and their asymptotic normalizations are considered in the framework of the generator coordinate method (GCM) and compared with ATMS (amalgamation of two-body correlation into multiple scattering processes) method which used the realistic Reid soft core interaction. The asymptotic normalization of relative wavefunctions provide various coupling constants, the cluster probability amplitude (the so-called Z ^1/2-factor) and matter RMS radii. These wavefunctions are also used to obtain ⁴He − d − d, ⁴He − t − p and ⁴He − h − n vertex functions in the virtual decay of ⁴He. The extrapolation of vertex functions for negative values of q ² upto the corresponding poles provide the vertex constants which are comparable with other estimates. It is noticed that in GCM the coupling constants C ² for ⁴He − d − d vertex is less than 2 as has been obtained in the forward dispersion relation technique.     

Quasielastic reactions around the coulomb barrier in 16O+118Sn

Measurement of elastic and quasielastic reaction cross sections were done in ¹⁶O + ¹¹⁸Sn system at two different energies above the barrier. Attempts are being made to understand the results in the framework of coupled reaction channel model.     

Amorphization and recrystallization study of lithium insertion into manganese dioxide

Various polymorphs of MnO(2) are widely used as electrode materials in Li/MnO(2) batteries. Electrolytic manganese dioxide (EMD) is the most electrochemically active form of MnO(2) and is very difficult to characterize. Their structural details are still largely unknown owing to the poor quality of X-ray diffraction (XRD) patterns obtained from most MnO(2) samples. Simulated amorphisation and crystallization technique was used to derive microstructural models for Li-MnO(2) which included most microstructural details that one would expect to find in the real material. Specifically, pyrolusite-MnO(2), comprising about 25,000 atoms, was amorphised (strain-induced) under molecular dynamics (MD) and different concentrations of lithium ions were inserted. Each system was then crystallized under MD simulation. The resulting models conformed to the pyrolusite polymorph, with microstructural features including: extensive micro-twinning and more general grain-boundaries, stacking faults, dislocations and isolated point defects and defect clusters. Molecular graphical images, showing the atom positions for the microstructural features together with simulated XRD patterns they give rise to, are presented and compared with measured XRD. The calculated XRD are in accord with experiment thus validating the structural models.