Photoluminescence properties of Gd:ZnO nano phosphor

Journal of Sol-Gel Science and Technology - Gd (0.1, 0.5, 1.0?mol%) doped ZnO nano phosphor, prepared by wet chemical method followed by sintering in air at 700?°C, was...     

Design and Synthesis of Imidazole and Triazole Pyrazoles as Mycobacterium Tuberculosis CYP121A1 Inhibitors

The emergence of untreatable drug-resistant strains of Mycobacterium tuberculosis is a major public health problem worldwide, and the identification of new efficient treatments is urgently needed. Mycobacterium tuberculosis cytochrome P450 CYP121A1 is a promising drug target for the treatment of tuberculosis owing to its essential role in mycobacterial growth. Using a rational approach, which includes molecular modelling studies, three series of azole pyrazole derivatives were designed through two synthetic pathways. The synthesized compounds were biologically evaluated for their inhibitory activity towards M. tuberculosis and their protein binding affinity (K_D). Series 3 biarylpyrazole imidazole derivatives were the most effective with the isobutyl ( 10 f ) and tert-butyl ( 10 g ) compounds displaying optimal activity (MIC 1.562 μg/mL, K_D 0.22 μM ( 10 f ) and 4.81 μM ( 10 g )). The spectroscopic data showed that all the synthesised compounds produced a type II red shift of the heme Soret band indicating either direct binding to heme iron or (where less extensive Soret shifts are observed) putative indirect binding via an interstitial water molecule. Evaluation of biological and physicochemical properties identified the following as requirements for activity: LogP >4, H-bond acceptors/H-bond donors 4/0, number of rotatable bonds 5–6, molecular volume >340 ų, topological polar surface area <40 Ų.     

GeneralizedM-diffusion model of molecular rotations

The widely usedM-model of rotational diffusion of molecules in fluid phases is generalized. The ordinaryM-model assumes that intermolecular collisions causeinstantaneous changes in the orientation of an otherwise free rotor. The present scheme takes cognizance of the ubiquitous intermolecular torques which should make the molecular orientation a continuously variable random function of time. It is assumed here that the component of the angular velocity, which is conjugate to the angle specifying the orientation of the molecule, is a stationary Gaussian-Markov process. The ordinaryM-model emerges then as a special case of the more general treatment presented here. The results derived for the dipole correlation function of a linear rotor on the basis of the generalized scheme are applied to a series of infrared data. The observed agreement is highly satisfactory. The present analysis affords a justification for the Gordon scheme which generalizes theM-model by assigning to the mean rate of collision anad-hoc dependence on the angular speed of the rotor. It is argued also that the model treated here incorporates certain memory effects which are ignored in the ordinaryM-model, and may yield, in some cases, results which are similar to those based on certain memory function formalisms.     

Direct generation of a voltage and current by gas flow over carbon nanotubes and semiconductors

We report here a direct generation of measurable voltages and currents when a gas flows over a variety of solids even at the modest speed of a few meters per second. The underlying mechanism is an interesting interplay of Bernoulli's principle and the Seebeck effect: Pressure differences along streamlines give rise to temperature differences across the sample; these in turn produce the measured voltage. The electrical signal is quadratically dependent on the Mach number M and proportional to the Seebeck coefficient of the solids. Results are presented for doped Si and Ge, single wall and multiwall carbon nanotubes, and graphite. Our results show that gas flow sensors and energy conversion devices can be constructed based on direct generation of electrical signals.     

Low-lying intrinsic structures in <Superscript>254</Superscript>Es

Low-lying two-quasiparticle bandhead energies for the Z = 99 odd-odd nucleus ²⁵⁴Es are evaluated using a simple phenomenological model with the inclusion of the residual p-n interaction. Configurations of the intrinsic levels directly fed in ²⁵⁴Es from the parent ²⁵⁸Md are discussed in the light of this model. Our analysis predicts the occurrence of ten K≤5 bandheads in ²⁵⁴Es with excitation energies E _x≤300keV. Structures of these as yet unidentified low-lying intrinsic levels and their expected locations are discussed in the light of available experimental information.     

Pyrochlore “dynamic spin-ice” Pr2Sn2O7 and monoclinic Pr2Ti2O7: A comparative temperature-dependent Raman study

Here we report a temperature-dependent Raman study of the pyrochlore “dynamic spin-ice” compound Pr₂Sn₂O₇ and compare the results with its non-pyrochlore (monoclinic) counterpart Pr₂Ti₂O₇. In addition to phonon modes, we observe two bands associated with electronic Raman scattering involving crystal field transitions in Pr₂Sn₂O₇ at ∼135 and 460 cm⁻¹ which couple strongly to phonons. Anomalous temperature dependence of phonon frequencies that are observed in pyrochlore Pr₂Sn₂O₇ are absent in monoclinic Pr₂Ti₂O₇. This, therefore, confirms that the strong phonon-phonon anharmonic interactions, responsible for the temperature-dependent anomalous behavior of phonons, arise due to the inherent vacant sites in the pyrochlore structure.