Growth of large La2−xSrxCuO4 single crystals using tilting-mirror-type infrared heating image furnace

Large single crystals of La_2−xSr_xCuO₄ (LSCO) high-T_c superconductors were grown by the infrared heating floating zone (IR-FZ) method using a tilting-mirror-type image furnace. The maximum diameter of the LSCO crystals increased to 10 mm in the tilting-mirror-type image furnace from 6 mm in the conventional image furnace. CuO rich feeds were required for the crystal growth using the tilting-mirror-type image furnace to compensate for the lack of CuO caused by the significant evaporation of CuO during the growth. The evaporation of CuO was affected by the tilting angle of the mirrors of the image furnace and by feed diameter. The optimized growth conditions were as follows: mirror tilting angle, 20°; feed diameter, 10 mm∅; and feed composition 50.7 mol% CuO.     

High energy neutrinos from gamma-ray bursts with precursor supernovae

The high energy neutrino signature from proton-proton and photo-meson interactions in a supernova remnant shell ejected prior to a gamma-ray burst provides a test for the precursor supernova, or supranova, model of gamma-ray bursts. Protons in the supernova remnant shell and photons entrapped from a supernova explosion or a pulsar wind from a fast-rotating neutron star remnant provide ample targets for protons escaping the internal shocks of the gamma-ray burst to interact and produce high energy neutrinos. We calculate the expected neutrino fluxes, which can be detected by current and future experiments.     

Synthesis and Characterization of High-Quality Polycrystalline Sample NiV2O6 by Solid-State Reaction Technique

Physics of the Solid State - Employing the solid-state reaction route, good quality polycrystalline sample NiV2O6 is prepared that has effective application in rechargeable Li-ion batteries. The...     

Modified signed-digit trinary addition using synthetic wavelet filter

The modified signed-digit (MSD) number system has been a topic of interest as it allows for parallel carry-free addition of two numbers for digital optical computing. In this paper, harmonic wavelet joint transform (HWJT)-based correlation technique is introduced for optical implementation of MSD trinary adder implementation. The realization of the carry-propagation-free addition of MSD trinary numerals is demonstrated using synthetic HWJT correlator model. It is also shown that the proposed synthetic wavelet filter-based correlator shows high performance in logic processing. Simulation results are presented to validate the performance of the proposed technique.     

Gamma-ray bursts in the swift-Fermi era

Gamma-ray bursts （GRBs） are among the most violent occurrences in the universe. They are pow- erful explosions, visible to high redshift, and thought to be the signature of black hole birth. They are highly luminous events and provide excellent probes of the distant universe. GRB research has greatly advanced over the past 10 years with the results from Swift, Fermi and an active followup community. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.     

Engineering of Cysteine Residues Leads to Improved Production of a Human Dipeptidase Enzyme in <Emphasis Type="Italic">E. coli</Emphasis>

Low yields, poor folding efficiencies and improper disulfide bridge formation limit large-scale production of cysteine-rich proteins in Escherichia coli. Human renal dipeptidase (MDP), the only human β-lactamase known to date, is a homodimeric enzyme, which contains six cysteine residues per monomer. It hydrolyses penem and carbapenem β-lactam antibiotics and can cleave dipeptides containing amino acids in both d- and l-configurations. In this study, MDP accumulated in inactive form in high molecular weight, disulfide-linked aggregates when produced in the E. coli periplasm. Mutagenesis of Cys361 that mediates dimer formation and Cys93 that is unpaired in the native MDP led to production of soluble recombinant enzyme, with no change in activity compared with the wild-type enzyme. The removal of unpaired or structurally inessential cysteine residues in this manner may allow functional production of many multiply disulfide-linked recombinant proteins in E. coli.     

Facile Synthesis of Hypercrosslinked Hollow Microporous Organic Capsules for Electrochemical Sensing of CuII Ions

A very simple and facile methodology is used to prepare dithiocarbamate-functionalized hollow microporous organic capsules (HMOCs-DTC), which exhibit excellent stability, a high surface area, and appropriate microporous architecture. In this strategy, SiO₂ particles are used as templates to construct PS-DVB-MAA microspheres, and then dithiocarbamate groups are grafted onto them. The dithiocarbamate-functionalized hypercrosslinked microporous organic capsules (HMOCs-DTC/GC) are then used as an electrode material for the detection of Cu^II ions. Cyclic voltammetry (CV) and electron impedance spectroscopy (EIS) are exploited to study the electrochemical potential of the designed material. The placement of functional groups (dithiocarbamate) at the mesopore interface effectively enhances the mass transfer, which facilitates the more selective detection of Cu^II ions. The high sensitivity of the modified electrode is expressed in terms of current (I_p) enhancement at extremely low concentrations of Cu^II ions. Thus, a functional and robust porous material (HMOCs-DTC) presents a sensitive sensing ability, displaying the calibration response over a wide linear range (2.50×10⁻¹¹–3.50×10⁻¹⁰ m ), with a lowest limit of detection of 1.02×10⁻¹¹ m . Indeed, these HMOCs present a new class of porous polymers possessing extraordinarily high scalability but avoiding complex and expensive synthetic methodologies, promoting its practical utilization.     

Recent advances in sodium alginate-based membranes for dehydration of aqueous ethanol through pervaporation

Sodium alginate (SA) is a progressive material for membrane fabrication. The technological development of SA-based membranes has made a significant contribution to the separation techniques, especially in aqueous organic solutions. The outstanding performance of SA is attributed to its outstanding structural flexibility and hydrophilicity. In view of structural characteristics, SA membranes have immense utilization in the pervaporation separation of organics. Among various organics, dehydration of aqueous ethanol is employed as a standard to check the success of pervaporation (PV) membrane. Because ethanol and water have comparable molecular sizes, thus difficult to extract water from aqueous ethanol mixtures than it is for other organics. A literature survey shows that wide-ranging data are available on the PV performance of SA and its modified membranes. In this context, the present review addresses the recent advances made in SA membranes for enhanced ethanol dehydration performance during the last decade. Available data since 2010 has been compiled for grafted, crosslinked, blend, mixed matrix, and composite hybrid sodium alginate membranes in terms of separation factor, permeation flux, and pervaporation separation index PSI. The data are assessed with reference to the effect of feed composition, membrane selectivity, flux, and swelling behavior.     

Superconductivity of Li under pressure

The superconductivity of Li under pressure is studied by a density functional method. Structural and elastic properties, transition temperature (T_c), density of states (DOS), are considered for the material at ambient and at higher pressures. The calculations, particularly of T_c and DOS as a function of pressure, are compared with other available results. This is in view of the wide difference between the previously predicted maximum T_c-value and those observed by both magnetic susceptibility and electrical resistivity experiments. The present calculations yield better estimates of T_c and other parameters with respect to measured values.