Modelling of Ion Transport in Solids with a General Bond Valence Based Force-Field

Empirical bond length - bond valence relations provide insight into the link between structure of and ion transport in solid electrolytes. Building on our earlier systematic adjustment of bond valence (BV) parameters to the bond softness, here we discuss how the squared BV mismatch can be linked to the absolute energy scale and used as a general Morse-type interaction potential for analyzing low-energy pathways in ion conducting solid or mixed conductors either by an energy landscape approach or by molecular dynamics (MD) simulations. For a wide range of Lithium oxides we could thus model ion transport revealing significant differences to an earlier geometric approach. Our novel BV-based force-field has also been applied to investigate a range of mixed conductors, focusing on cathode materials for lithium ion battery (LIB) applications to promote a systematic design of LIB cathodes that combine high energy density with high power density. To demonstrate the versatility of the new BV-based force-field it is applied in exploring various strategies to enhance the power performance of safe low cost LIB materials (LiFePO4, LiVPO4F, LiFeSO4F, etc.).Received: 11 October 2010; Revised: 26 October 2010; Accepted: 28 October 201

SYNTHESIS AND CHARACTERIZATION OF A NOVEL MUCOADHESIVE DERIVATIVE OF PSYLLIUM SEED POLYSACCHARIDE

Objective: In the present study, thiol-functionalization of psyllium seed polysaccharide (PSY) was cross-linked with thioglycolic acid by esterification in an attempt to reveal the mucoadhesive properties of thiolated psyllium seed polysaccharide (TPSY).Methods: The crosslinking was carried out by the microwave-assisted method. A simplex centroid design was employed to systematically study the mucoadhesive strength, mucoadhesive retention time and drug release profile. Comparative evaluation of carbopol-based ciprofloxacin hydrochloride (HCl) tablets containing PSY and TPSY was carried out. Acute oral toxicity studies and repeated oral toxicity for TPSY were also conducted.Results: Thiol-functionalization was confirmed by-SH stretch in Fourier Transform infra-red spectra at 2353 cm-1. Thiolation was observed in thiolated PSY (TPSY) by a change in the surface morphology of psyllium from fibrous to granular and resulted in 82 %swelling in deionized water. TPSY was found to contain 102.35 mmol of thiol groups/g as determined by the Ellman's method. The percent increase in mucoadhesive strength of TPSY was found to be 50.31 % as compared to PSY and 128.30 % as compared to carbopol. The percent increase in mucoadhesive retention time of TPSY was found to be 110 % as compared to PSY and 50 % as compared to carbopol.Conclusion: Mucoadhesion strength and mucoadhesive retention time were greater of tablets containing a higher amount of TPSY. Further, the acute oral toxicity studies and repeated oral toxicity for TPSY proved it as non-toxic and hence safe for human use

Effect of Mg Doping on the Structural and Optical Properties of CdS Nanoparticles Synthesized by co-Precipitation Method

Cd1 – xMgxS (x = 0.00, 0.05, 0.10, 0.15 and 0.20) nanoparticles were synthesized by co-precipitation method for the first time. Compositional, morphological, structural and optical studies of the as prepared samples were carried out by X-ray diffraction (XRD), Energy dispersive analysis of X-rays (EDAX), Scanning electron microscopy (SEM), Diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) techniques. XRD studies revealed the structural phase transition from cubic to hexagonal and increase in the average grain size of the nanoparticles (lie in the range 1.4 nm to 2.8 nm) with increasing Mg content. EDAX spectra rules out the existence of impurities in the samples. Bandgap widening was observed in all the samples compared to bulk CdS (2.42 eV). Decrease in bandgap (3.02 eV to 2.54 eV), luminescence quenching and red shift of luminescence peak position were observed with increasing Mg in Cd1 – xMgxS. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3028

Solution combustion derived nanocrystalline Zn2SiO4 : Mn phosphors: A spectroscopic view

Manganese doped nanocrystalline willemite powder phosphors Zn2-xMnxSiO4 (0.1less than or equal toxless than or equal to0.5) have been synthesized by a low-temperature initiated, self-propagating, gas producing solution combustion process. The phosphors have been characterized by using x-ray diffraction (XRD), energy dispersive spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), and photo luminescence (PL) spectroscopic techniques. The lattice parameters calculated from XRD confirm that Zn2-xMnxSiO4 has a rhombohedral space group R (3) over barH. The XRD patterns confirm that Zn2-xMnxSiO4 phosphor samples undergo a phase transformation from beta-willemite to alpha-willemite phase at 950 degreesC. The EPR spectra of Mn2+ ions exhibit resonance signals at gcongruent to3.24 and gcongruent to2.02, with a sextet hyperfine structure centered around gcongruent to2.02. The EPR signals of Mn2+ give a clear indication of the presence of two different Mn2+ sites. The magnitude of the hyperfine splitting (A) indicates that the Mn2+ is in an ionic environment. The number of spins participating in resonance (N), the paramagnetic susceptibility (chi), and the zero-field splitting parameter (D) have been evaluated as function of x. It is interesting to observe that the variation of N with temperature obeys Boltzmann. The paramagnetic susceptibility is calculated from the EPR data at various temperatures and the Curie constant and Curie paramagnetic temperature was evaluated from the 1/chi versus T graph. The luminescence of Mn2+ ion in Zn2SiO4 shows a strong green emission peak around 520 nm from the synthesized phosphor particles under UV excitation (251 nm). The luminescence is assigned to a transition from the upper T-4(1)-->(6)A(1) ground state. The mechanism involved in the generation of a green emission has been explained in detail. The effect of Mn content on luminescence has also been studied. (C) 2004 American Institute of Physics

Synthesis, characterization and TL studies of porous CaSiO3 ceramic powders

Nanocryst. porous CaSiO3 ceramic powders have been synthesized by a novel low temp. initiated self-​propagating, gas producing soln. combustion process and characterized by XRD, SEM, EDS (energy dispersive spectroscopy)​, porosity, surface area and thermoluminescence (TL) studies. The effect of temp. on cryst. phase formation, amt. of porogens and particle size of porous CaSiO3 have been investigated. Single phase β-​CaSiO3 and α-​CaSiO3 were formed at 950° and 1200°C resp. The phase transformation temps. of combustion derived CaSiO3 were found to be low compared to the powders obtained via solid state reaction method. The microstructure and morphol. were studied by SEM and it was noted that with increase in calcination temp., the samples became more porous and the pore diam. increased from 0.25 to 8 μm. The samples calcined at 950°C for 3 h had 17.5​% porosity, however, the porosity increased to 31.6​% on calcination at 1200°C for 3 h. The surface areas of the as-​formed and calcined (at 950° and 1200°C) CaSiO3 samples were found to be 31.93, 0.585 and 3.48 m2·g-​1 resp. The TL intensity in powder sample was more intense when compared to the pelletized CaSiO3 and it was further obsd. that there was a shift in glow peak temps. in pelletized sample. This is attributed to the interparticle spacing and pressure-​induced defects

Pigeonpea perspective in India

Pigeonpea occupies a prominent place in Indian rainfed agriculture. It is an integral component of in various agro ecologies of the country mainly inter cropped with cereals, pulses and oilseeds and millets. It is the second most important pulse crop next to chickpea, covering an area of around 4.42 m ha (occupying about 14.5% of area under pulses) and production of 2.86 MT (contributing to 16% of total pulse production) and productivity of about 707 kg/ha. It is mainly consumed as dry split dhal throughout the country besides several other uses of various parts of pigeonpea plant. Enhancing the productivity of the crop assumes specific significance in India mainly to combat protein malnutrition as it is the main source of protein to the predominant vegetarian population. Based on the crop duration and climatic condition the crop is grouped under four agro ecological zones with varied plant type requirements and location specific constraints for each zone. Systematic crop improvement efforts were launched at ICRSIAT since its inception in 1972. It focused during first decade (1972 to 1980) on collection, evaluation, maintenance and sharing of germplasm and yield enhancement research. During 1980 to 2000 ICRISAT research priorities were development of stable sources of resistance for wilt and Sterility Mosaic Diseases which are highly devastating and endemic in India in almost all the agro ecologies of pigeonpea cultivation. From 2000, concerted efforts are in progress on CGMS based hybrid development. Spectacular achievement by ICRISAT in recent past in the crop is deciphering its genome sequence and it has ushered pigeonpea in to genomic era. Subsequently lot of genomic information is in the process of development through molecular approaches like Genome Wide Association Studies (GWAS), Nested Association Mapping (NAM). Multiparent Advance Generation Inter Crosses (MAGIC) and Introgression Libraries (IL) etc. These approaches are under process of utilization for crop improvement

Modification of the ground state in Sm-Sr manganites by oxygen isotope substitution

The effect of $^{16}$O $\to$ $^{18}$O isotope substitution on electrical resistivity and magnetic susceptibility of Sm$_{1-x}$Sr$_x$MnO$_3$ manganites is analyzed. It is shown that the oxygen isotope substitution drastically affects the phase diagram at the crossover region between the ferromagnetic metal state and that of antiferromagnetic insulator (0.4 $< x <$ 0.6), and induces the metal-insulator transition at for $x$ = 0.475 and 0.5. The nature of antiferromagnetic insulator phase is discussed.Comment: 4 pages, 3 eps figures, RevTeX, submitted to Phys. Rev. Let

Fast variability from black-hole binaries

Currently available information on fast variability of the X-ray emission from accreting collapsed objects constitutes a complex phenomenology which is difficult to interpret. We review the current observational standpoint for black-hole binaries and survey models that have been proposed to interpret it. Despite the complex structure of the accretion flow, key observational diagnostics have been identified which can provide direct access to the dynamics of matter motions in the close vicinity of black holes and thus to the some of fundamental properties of curved spacetimes, where strong-field general relativistic effects can be observed.Comment: 20 pages, 11 figures. Accepted for publication in Space Science Reviews. Also to appear in hard cover in the Space Sciences Series of ISSI "The Physics of Accretion onto Black Holes" (Springer Publisher

Modelling of strain effects in manganite films

Thickness dependence and strain effects in films of $La_{1-x}A_xMnO_3$ perovskites are analyzed in the colossal magnetoresistance regime. The calculations are based on a generalization of a variational approach previously proposed for the study of manganite bulk. It is found that a reduction in the thickness of the film causes a decrease of critical temperature and magnetization, and an increase of resistivity at low temperatures. The strain is introduced through the modifications of in-plane and out-of-plane electron hopping amplitudes due to substrate-induced distortions of the film unit cell. The strain effects on the transition temperature and transport properties are in good agreement with experimental data only if the dependence of the hopping matrix elements on the $Mn-O-Mn$ bond angle is properly taken into account. Finally variations of the electron-phonon coupling linked to the presence of strain turn out important in influencing the balance of coexisting phases in the filmComment: 7 figures. To be published on Physical Review

Fluorescent carbon dioxide indicators

Over the last decade, fluorescence has become the dominant tool in biotechnology and medical imaging. These exciting advances have been underpinned by the advances in time-resolved techniques and instrumentation, probe design, chemical / biochemical sensing, coupled with our furthered knowledge in biology. Complementary volumes 9 and 10, Advanced Concepts of Fluorescence Sensing: Small Molecule Sensing and Advanced Concepts of Fluorescence Sensing: Macromolecular Sensing, aim to summarize the current state of the art in fluorescent sensing. For this reason, Drs. Geddes and Lakowicz have invited chapters, encompassing a broad range of fluorescence sensing techniques. Some chapters deal with small molecule sensors, such as for anions, cations, and CO2, while others summarize recent advances in protein-based and macromolecular sensors. The Editors have, however, not included DNA or RNA based sensing in this volume, as this were reviewed in Volume 7 and is to be the subject of a more detailed volume in the near future