Superconductivity in doped FeTe1-xSx (x= 0.00 to 0.25) single crystals

We report self flux growth and characterization of FeTe1-xSx (x= 0.00 to 0.25) single crystal series. Surface X-ray diffraction (XRD) exhibited crystalline nature with growth in (00l) plane. Micro-structural (electron microscopy) images of representative crystals showed the slab-like morphology and near stoichiometric composition. Powder XRD analysis (Rietveld) of single crystals exhibited tetragonal structure with P4/nmm space group and decreasing a and c lattice parameters with increase in x. Electrical resistivity measurements (R-T) showed superconductivity with Tconset at 9.5K and 8.5K for x =0.10 and x =0.25 respectively. The un-doped crystal exhibited known step like anomaly at around 70K. Upper critical field Hc2(0), as calculated from magneto transport for x =0.25 crystal is around 60Tesla and 45Tesla in H//ab and H//c directions. Thermal activation energy [U0(H)] calculated for x =0.10 and 0.25 crystals followed weak power law, indicating single vortex pinning at low fields. Mossbauer spectra for FeTe1-xSx crystals at 300K and 5K are compared with non superconducting FeTe. Both quadrupole splitting (QS) and isomer shift (IS) for S doped crystals were found to decrease. Also at 5K the hyperfine field for x =0.10 superconducting crystal is decreased substantially from 10.6Tesla (FeTe) to 7.2Tesla. For x =0.25 crystal, though small quantity of un-reacted Fe is visible at room temperature, but unlike x =0.10, the low temperature (5K) ordered FeTe hyperfine field is nearly zero.Comment: 20 Pages Text + Figs: Accepted Mat. Res. Exp, Mat. Rex. Exp. (2018

DEVELOPMENT AND EVALUATION OF CLOBETASOL–LOADED SOLID LIPID NANOPARTICLES FOR TOPICAL TREATMENT OF PSORIASIS

Objective: The current research was structured to achieve a maximum topical delivery for the drug clobetasol-17-propionate (CP) and to predict the effects of various independent variables like lipid: drug ratio, surfactant, and homogenization time on particulate characters and performance solid lipid nanoparticles (SLNs). Methods: CP loaded SLNs were formulated by Emulsification–Homogenization method and optimized using 33 full factorial designs (Design-Expert software 11.0). Drug loaded SLNs were evaluated for various parameters like particle size, surface charge, polydispersity index, entrapment efficiency, surface morphology, thermal analysis, in vitro drug release through skin (Franz diffusion cell), drug deposition study and stability. Results: The optimized formulation (SLNs) attains a minimal Particle size of 133.3±3.66 nm, Poly dispersibility index of 0.179±0.081, % entrapment efficiency of 78.1±1.11 and Zeta potential of-36.2±0.11mV. Skin permeation study of CP loaded SLNs suspension showed prolonged drug release up to 24h. Maximum drug deposition was obtained after developing the drug into SLNs (48.22µg/ml) when compared to the pure drug (19.12µg/ml). Conclusion: SLNs were promising colloidal particulate carriers by which prolonged drug release and improved skin permeation was achieved for the drug Clobetasol 17- propionate

Electronic structure and Fermi surface topology of binary and ternary compounds

To explore the material properties, electronic structure calculations are very much useful and can be obtained from the well known density functional theory(DFT) calculations. In the present thesis, we have focussed on the Fermi surface calculations and try to link the same with other physical properties. In addition, we have also explored the pressure effect on properties of the system. For the present study, we have selected different types of compounds which are Ni-based Heusler compounds, Nb-based A-15 compounds, Sn-based binary compounds and few magnetic compounds(one Zr-based Heusler compound and other Mn-based compounds). Electronic structure, mechanical, vibrational properties of Ni-based Heusler compounds, Ni2XAl (X=Ti, Zr, Hf, V, Nb, and Ta), Ni2NbGa and Ni2NbSn, are presented both at ambient and under compression. Among the mentioned compounds, Ni2NbAl, Ni2NbGa and Ni2NbSn are experimentally reported as superconductors at ambient and our calculated superconducting transition temperature (Tc) and electron-phonon coupling constant (λep) values are in good agreement with the experiments. In addition, we have predicted superconducting nature in Ni2VAl with electron-phonon coupling constant (λep) around 0.68, which leads to superconducting transition temperature (Tc) around ∼4 K (by using coulomb pseudopotential μ∗ = 0.13), which is a relatively high transition temperature for Ni based Heusler alloys and are compared with other Ni2NbY (Y = Al, Ga and Sn) compounds. From the calculated Fermi surfaces, flat Fermi sheets are observed along X

Analysis of an unswept propfan blade with a semiempirical dynamic stall model

The time history response of a propfan wind tunnel model with dynamic stall is studied analytically. The response obtained from the analysis is compared with available experimental data. The governing equations of motion are formulated in terms of blade normal modes which are calculated using the COSMIC-NASTRAN computer code. The response analysis considered the blade plunging and pitching motions. The lift, drag and moment coefficients for angles of attack below the static stall angle are obtained from a quasi-steady theory. For angles above static stall angles, a semiempirical dynamic stall model based on a correction to angle of attack is used to obtain lift, drag and moment coefficients. Using these coefficients, the aerodynamic forces are calculated at a selected number of strips, and integrated to obtain the total generalized forces. The combined momentum-blade element theory is used to calculate the induced velocity. The semiempirical stall model predicted a limit cycle oscillation near the setting angle at which large vibratory stresses were observed in an experiment. The predicted mode and frequency of oscillation also agreed with those measured in the experiment near the setting angle