Evolution of coercivity and its angular dependence in CoFe nanostructures subjected to field cooling

Evolution of coercivity and its angular dependence in CoFe nanostructures subjected to field cooling has been investigated in this work. Spherical CoFe grains with an average diameter of 30 nm were grown on a silicon substrate using electron beam evaporation. Further, the as‐deposited sample was subjected to field cooling. The morphology and topography of the sample before and after field cooling were characterized by atomic force microscopy and SEM. Magnetic force microscopy indicated that there is a good uniformity of magnetization throughout the sample after field cooling. Vibrating sample magnetometer measurements indicate that the coercivity in CoFe nanostructures is dependent on shape of the nanostructures. Copyright © 2013 John Wiley & Sons, Ltd.     

Selective reductions. 56. Exploration of the B-haloisopinocampheylboranes for asymmetric reduction of ketones

A series of diisopinocampheylhaloboranes and monoisopinocampheyldihaloboranes were synthesized by the reaction of the corresponding boranes with the respective HX or X₂ (X = halogen) or by the hydroboration of α-pinene with the corresponding haloboranes. Stabilities of these haloboranes in various solvents were studied. Most of these haloboranes proved capable of reducing prochiral ketones to the alcohols with significant optical induction. When tested against a representative aromatic and aliphatic prochiral ketone, acetophenone and 3-methyl-2-butanone, respectively, α-phenethyl alcohol in 65–98% ee and 3-methyl-2-butanol in 28–59% ee were obtained. Some of them exhibited anomalous behavior.     

Third-order nonlinear optical studies of newly synthesized polyoxadiazoles containing 3,4-dialkoxythiophenes

The third-order nonlinear optical properties of newly synthesized soluble polyoxadiazoles containing 3,4-dialkoxythiophenes were investigated by using Z-scan and degenerate four-wave mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of χ⁽³⁾ determined from both the experiments. Z-scan results indicate a negative nonlinear refractive index, n₂, whose magnitude is of the order of 10⁻¹⁰ esu for all the copolymers. The variation of nonlinear response among the copolymers clearly indicates the dependence of χ⁽³⁾ on donor and acceptor type of units present in these copolymers. The copolymers exhibit strong reverse saturable absorption and good optical limiting properties at 532 nm.     

Scattering matrix for Raman effect in cubic crystals

The scattering matrix for Raman effect in cubic crystals for any general orientation of the crystal and any angle of scattering is given. The averages of the matrix over all possible orientations is also given and checks with the well known value of 6/7 for the depolarisation of degenerate lines for transverse scattering. The scattering matrix for backward scattering in terms of polar angles and for some special cases are also given.     

Anomalous superfluidity in (2+1)-dimensional two-color lattice QCD

We study thermodynamics of strongly coupled lattice QCD with two colors of staggered fermions in 2+1 dimensions. The partition function of this model can be written elegantly as a statistical mechanics of dimers and baryon loops. The model is invariant under an SO(3) x U(1) symmetry. At low temperatures, we find evidence for superfluidity in the U(1) symmetry sector while the SO(3) symmetry remains unbroken. The finite temperature phase transition appears to belong to the Kosterlitz-Thouless universality class, but the superfluid density jump rho(s) (T(c)) at the critical temperature T(c) is anomalously higher than the normal value of 2T(c)/pi. We show that, by adding a small SO(3) symmetry breaking term to the model, the superfluid density jump returns to its normal value, implying that the extra symmetry causes anomalous superfluid behavior. Our results may be of interest to researchers studying superfluidity in spin-1 systems.     

An improved HPLC method with the aid of a chemometric protocol: simultaneous analysis of amlodipine and atorvastatin in pharmaceutical formulations

Statistical experimental design and Derringer's desirability function were applied to develop an improved RP-HPLC method for the simultaneous analysis of amlodipine and atorvastatin in pharmaceutical formulations. Four independent factors were considered: acetonitrile content in the mobile phase; buffer pH; buffer concentration; and flow rate. The preliminary screening step was carried out, according to a 2(4-1) fractional factorial design, to identify the significant factors affecting the analysis time response. Then central composite design was applied for a response surface study, in order to examine in depth the effects of the most important factors. Subsequently, Derringer's desirability function was employed to simultaneously optimize the six responses: retention factor of first peak; two resolutions; and three retention times, each having a different target. This procedure allowed deduction of two separate optimum conditions, intended for the analysis of quality control and plasma samples, within the experimental domain. The predicted optimum for the quality control samples was: methanol-acetonitrile-15 mM K(2)HPO(4) buffer (pH 5.33) (10:42.08:47.92, v/v/v) as the mobile phase and 1.12 mL/min as the flow rate. The method using this optimized condition showed higher sensitivity and shorter analysis time than the previously published reports. The optimized assay condition was validated according to International Conference on Harmonization guidelines.