POSITRON LIFETIME STUDY OF THERMALLY INDUCED MICROSTRUCTURAL CHANGES IN NISTARI SILK FIBER

Positron lifetime measurements have been made in natural polymer-Nistari silk fibers as a function of isochronalannealing temperature in the range of 27℃ to 280℃. The variations in the positron results indicate the structural changesoccurring in the Nistari silk fibers and determine the glass transition temperature as 170℃. Activation energies weremeasured separately for the crystalline and amorphous regions indicating the versatility of the technique. These values areclose to the N--H bond dissociation energy, suggesting N--H bond dissociation as the most probable process occurringduring thermal treatment As an extension of the positron results, the molecular weight of the Nistari silk fibers wasdetermined to be 10.7×10~5 based on free volume, which lies within the range suggested for the silk fibers. There seems to bean indication that cross-linking changes the spiral structure of cotton fibers to network type. However, this needs to be validated by other techniques.

Investigating the effect of entrance channel mass asymmetry on fusion reactions using the Skyrme energy density formalism

In the present investigations,the fusion crosssections for the formation of 200Pb compound nucleus(CN)using 16O+184 W,30Si+170Er,and 40Ar+160Gd nuclear reactions at energies above the Coulomb barrier were calculated to understand the effect of entrance channel mass asymmetry(α)on the fusion reactions;the Skyrme energy density formalism(SEDF)was used for this calculation.The SEDF uses the Hartree-Fock-Bogolyubov(HFB)computational program with Skyrme forces such as SkM*,SLy4,and SLy5 to obtain the nucleus-nucleus potential parameters for the above reactions.Using the SEDF model with SkM*,SLy4,and SLy5 interaction forces,the theoretical fusion cross-sections were determined above the barrier energy and compared with the available experimental fusion cross-sections.The results show a close agreement between the theoretical and experimental values for all selected systems at energies well above the barrier.However,near the barrier energies,the theoretical values were observed to be higher than the experimental values.

Steady-State and Time-Resolved Fluorescence Studies of Anthrylacrylic Ester

The photophysical properties of Anthrylacrylic ester were investigated in various solvents using steady-state and time-resolved fluorescence techniques. The dual fluorescence was observed in various solvents of different polarity functions. The emission bands observed are around 400 nm (band I) and 480 nm (band II) for 350 nm and 390 nm excitation at low concentrations (10–5 mol·dm–3) but at higher concentrations (10–3 mol·dm–3) only the emission (band II) at 480 nm alone was observed. The emission band observed around 400 nm shifts from 390 nm to 420 nm (shift 30 nm) when the excitation wavelength was varied from 300 nm to 380 nm and the emission band at 480 nm shifts from 430 nm to 510 nm (shift 80 nm) for the change of excitation wavelength from 380 nm to 400 nm. However, both emissions were observed for 380 nm excitation at lower concentrations. Solvatochromic shifts of electronic absorption and fluorescence emissions (band I & II) as a function of polarity functions were analyzed and the changes in dipole moment of the molecule was estimated (Δμ = 3.36 D & 5.98 D). Fluorescence decays monitored over each emission maxima showed bi-exponential behavior, and yielded two lifetime components respectively in the range 0.97 - 7.1 ns (at λem = 400 nm) and 0.34 - 7.23 ns (at λem = 480 nm). Based on the steady-state and time-resolved emission measurements emission band I (400 nm) and emission band II (480 nm) are respectively assigned as due to locally excited state (Trans-forms) and due to isomers (Cis-form).

Comparative analysis of entanglement measures based on monogamy inequality

We evaluate the monogamy inequality for symmetric, non-symmetric pure states of importance in terms of squared concurrence, squared entanglement of formation, squared negativity of partial transpose and compare the corresponding tangles. We show that though concurrence and concurrence tangle are zero for two special classes of mixed entangled states, both negativity tangle and entanglement of formation（EOF） tangle turn out to be non-zero. A comparison of different tangles is carried out in each case and it is shown that while the concurrence tangle captures the genuine multiqubit entanglement in N-qubit pure states with N distinct spinors（containing GHZ and superposition of W-, obverse W states）either negativity tangle or EOF tangle is to be used as a better measure of entanglement in the W-class of states with two distinct spinors and in the special classes of mixed multiqubit states.

1-D Paracrystalline Model to Simulate a Bragg Reflection: Computation of Crystallite Size and Lattice Strain

A simple and elegant method to simulate single order reflection profile based on 1-D paracrystalline model has been proposed here. For variety of polymer films this approach has been applied to compute microcrystalline parameters like crystallite size and lattice strain. Other metallic oxide compounds are also analysed using this approach. Employing this model, X-ray diffraction patterns from various polymer samples have been analysed and corresponding microstructure parameters have been reported in this article.

Preparation and Characterization of MMT Doped PVA/SA Polymer Composites

Blends of PVA/SA polymer doped with Montmorillonite were prepared by solution casting technique. Doping of nanoparticles to the polymer matrix does affect the structural and conducting properties. To analyze such changes, these films were subjected to X-ray diffraction, FT-IR spectroscopy, UV-visible absorbance and impedance analysis. Microstructural parameters were computed using in-house program employing X-ray data. Electrical conductivity of these polymer composites was derived using obtained impedance values to understand the conducting property. The results thus obtained are reported in this work.

Cynodon dactylon extract ameliorates cognitive functions and cerebellar oxidative stress in whole body irradiated mice

Objective: To explore the effect of hydroalcoholic extract of Cynodon dactylon on the whole body radiation-induced oxidative status of the cerebellum and cognitive impairments in mice. Methods: Swiss albino mice were randomly divided into the control group, radiation control group, low dose and high dose Cynodon dactylon extract treated groups and pre-treated with Cynodon dactylon extract before irradiation. Cynodon dactylon extract was administered for 7 d daily in low dose(0.25 g/kg) and high dose(1 g/kg). On day 7, mice were irradiated with a sublethal dose of 5 Gy gamma rays. Motor coordination was assessed by elevated rotarod test and spatial memory was studied by water maze test. Subsequently, biochemical markers(glutathione, lipid peroxidation and nitric oxide levels) in the cerebellum were evaluated. Results: The gamma irradiated group showed significant impairment in motor coordination and spatial memory compared to normal mice. Mice treated by Cynodon dactylon extract prior to gamma radiation showed good improvement in both paradigms compared to the radiation control group. Moreover, glutathione level was increased, while lipid peroxidation and nitric oxide levels were significantly reduced in mice receiving low dose and high dose of Cynodon dactylon extract compared to the radiation control group. Conclusions: The present study suggests the neuroprotective role of Cynodon dactylon against radiation-induced cognitive impairment and oxidative stress on the cerebellum of mice.

A Hirshfeld Surface Analysis and Crystal Structure of 2’-[1-(2-Fluoro-Phenyl)-1H-tetrazol-5-Yl]-4-Methoxy-Biphenyl-2-Carbaldehyde

The title compound, C21H15FN4O2 is synthesized and characterized by 1H NMR, LC-MS and finally confirmed by single crystal X-ray diffraction method. This molecule crystallizes in the monoclinic crystal system and space group P21/c, with crystal parameters a = 9.4386(5) A, b = 20.8082(1) A, c = 9.4338(6) A, β = 99.566(2)0, Z = 4 and V = 1826.98(19) A3. The mean planes of fluro-phenyl moiety makes a dihedral angle of 21.51 (7)0 with biphenyl moiety. The molecules are connected by hydrogen bonds of the type C---H...O and C---H...F. In addition, crystal structure is stabilized with π … π (exhibits intramolecular interaction) and C---O... π interactions. The intercontacts in the crystal structure are analyzed using Hirshfeld surfaces computational method.