High pressure X-ray diffraction study on p-FeS2, m-FeS2 and MnS2 to 340 kbar: A possible high spin-low spin transition in MnS2

Pyrite p-FeS₂, marcasite m-FeS₂ and MnS₂2 have been investigated using the high-pressure X-ray diffraction technique to 340 kbar. MnS2 undergoes a pressure-induced phase transition at about 140 kbar from the pyrite to the marcasite type phase with a volume contraction of about 15%. The high-pressure marcasite type m-MnS₂ is found to belong to the B type of marcasite with an axial ratio $\text{c}\text{a}\text{= 0.76}$ and $\text{c}\text{b}\text{= 0.62.}$ p-FeS₂ and m-FeS₂ do not undergo any phase transition in the pressure range investigated. The high spin p-MnS₂ has been found to be much more compressible (B_o = 760 kbar, B′_o = 5.4) than the low spin p-FeS₂ (B_o = 2154 kbar, B′_o = 5.5) and m-FeS₂ (B₀ = 1465 kbar, B′_o = 4.9) while the high-pressure m-MnS₂ has comparable compressibility (B_o = 2138 kbar, B′₀ = 5.0) with those of low spin p-FeS₂ and m-FeS₂. The p-MnS₂-m-MnS₂ phase transition might be accompanied by a high spin-low spin transition of Mn²⁺.     

Temperature and pressure dependence of the crystal structure of InTe: A new high pressure phase of InTe

InTe has been investigated using high pressure x-ray diffraction technique to 340 kbar InTe undergoes a pressure induced phase transition from the tetragonal TISe-type (B37) to the NaCl-type (B1) phase We have discovered a further pressure induced phase transition from the NaCl-type to the CsCl type (B2) phase at about 150 kbar The crystal structure of the tetragonal TISe-type InTe has been reinvestigated with x-ray diffractometer data Temperature variation of the lattice constants of the tetragonal InTe has been obtained in the range 297 to 505 K.     

Pressure induced phase transition in MnTe2

Energy dispersive high-pressure powder X-ray experiments have been performed for MnTe₂ up to a pressure of 20 GPa. MnTe₂ undergoes a discontinuous transformation from the cubic pyrite type structure to the orthorhombic marcasite type structure at 7.0±0.5 GPa upon increasing pressure. The transformation is accompanied by a large reduction in the specific volume (ΔV/V=0.18) which probably reflects different magnetic properties of the two modifications of MnTe₂.     

Monitoring Membrane Protein Conformational Heterogeneity by Fluorescence Lifetime Distribution Analysis Using the Maximum Entropy Method

Due to the inherent difficulty in crystallizing membrane proteins, approaches based on fluorescence spectroscopy have proved useful in elucidating their conformational characteristics. The ion channel peptide gramicidin serves as an excellent prototype for monitoring membrane protein conformation and dynamics due to a number of reasons. We have analyzed conformational heterogeneity in membrane-bound gramicidin using fluorescence lifetime distribution analysis of tryptophan residues by the maximum entropy method (MEM). MEM represents a model-free and robust approach for analyzing fluorescence lifetime distribution. In this paper, we show for the first time, that fluorescence lifetime distribution analysis using MEM could be a convenient approach to monitor conformational heterogeneity in membrane-bound gramicidin in particular and membrane proteins in general. Lifetime distribution analysis by MEM therefore provides a novel window to monitor conformational transitions in membrane proteins.     

Study of electron donor-acceptor complexes of tri-n-octyl amine with [60]- and [70]fullerenes and some other electron acceptors by absorption spectrophotometric method

Electron donor-acceptor (EDA) complexes of tri-n-octylamine (TOA) with [60]- and [70]fullerenes and some other electron acceptors have been studied in chloroform medium by absorption spectrophotometric technique. Charge transfer (CT) absorption bands are observed in the visible region. Vertical ionization potential of TOA was determined utilizing CT transition energy. Oscillator strengths, transition dipole strengths and resonance energies for all the complexes have been calculated. [60]Fullerene/TOA and [70]fullerene/TOA complexes are found to decay slowly with time. Kinetics of these reactions have been studied and activation energies for such processes have been estimated. Ab initio calculations suggest that complexation of [70]fullerene with TOA is enthalpy favoured.     

Optical and electrical properties of p-type transparent conducting CuAlO2 thin film synthesized by reactive radio frequency magnetron sputtering technique

Thin films of p-type transparent conducting CuAlO₂ have been synthesized through reactive radio frequency magnetron sputtering on silicon and glass substrates at substrate temperature 300°C. Reactive sputtering of a target fabricated from Cu and Al powder (1:1.5) was performed in Ar+O₂ atmosphere. The deposition parameters were optimized to obtain phase pure, good quality CuAlO₂ thin films. The films were characterized by studying their structural, morphological, optical and electrical properties.     

Trace formulas for relative Schatten class perturbations

We derive trace formulas for a pair of self-adjoint operators $H+V$ and H under the assumption that ${(H?\mathrm{i})}^{?1}V$ is in a Schatten class. This extends the trace formulas of [8], where V alone is assumed to be in a Schatten class. Our trace formulas apply, in particular, in the setting of differential operators and are based on Taylor-like approximations of operator functions. This significantly improves non-Taylor based trace formulas of [10].     

Ag2CO3-catalyzed cycloaddition of organic azides onto terminal alkynes: A green and sustainable protocol accelerated by aqueous micelles of CPyCl

Using catalytic amount of Ag₂CO₃ a simple, efficient and copper free green protocol has been developed to synthesize 1,4-disubstituted 1,2,3-triazoles regioselectively. Here, the cationic surfactant, cetylpyridinium chloride (CPyCl) in water provides a micellar media and accelerates the subsequent Ag(I)-catalysed azide-alkyne cycloaddition (AgAAC) reaction by increasing the concentration of reactants in the micellar pseudophase. Our method is found to be environmentally friendly from E-factor measurement. The surfactant, CPyCl is found to be nontoxic.     

Thermally exfoliated graphene oxide reinforced stress responsive conductive nanocomposite hydrogel

Lightweight and flexible biosensors that can sustain mechanical deformation and can be adhered to human skin is an interesting field of study. In the current article, a systematic study on development of thermally exfoliated graphene oxide (TEGO)–reinforced poly(vinyl alcohol) (PVA)–based conductive hydrogel nanocomposites has been reported. The free‐standing hydrogels were synthesized using controlled and repetitive freeze‐thaw cycles. The samples were then studied for their mechanical as well as electrical properties. The hydrogels were characterized for their microstructural, chemical, and rheological properties to understand the observed macroscopic properties. Additionally, a study on the behavior of hydrogels immersed in phosphate‐buffered saline (PBS) was carried out to investigate their hydrolytic stability within simulated biological environment. Overall, the nanocomposite hydrogels demonstrated excellent static and dynamic mechanical performance, stability in PBS, considerable electrical conductivity, and significant electrical response to applied external stress, establishing their potential for use as flexible biosensors.