Transport properties of Ti3Ir compound at low temperature

Electrical resistivity and magnetoresistivity of Ti₃Ir compound have been measured in the temperature range 2.0 K ≤T ≤ 300 K in absence as well as in presence of magnetic field upto 7.7 T. The low temperature resistivity shows aT ² behaviour whereas the high temperature resistivity shows a linear behaviour. The magnetoresistivity is positive and cannot be explained by simple s-d scattering model. The enhancement of the coefficient A of theT ² term and the deviation from the quadratic field dependence of the resistivity may be due to the anisotropy in the compound. This work has been performed under the grant by the Department of Science and Technology, Govt. of India.     

Experimental investigation of heat transfer performance of corrugated tube with spring tape inserts

Turbulent forced convection in a corrugated tube with spring tape is investigated experimentally, for Reynolds numbers from 10,000 to 50,000. The working fluid is air. Experiments are performed for different pitch and spring ratios. Results show that Nusselt numbers can be increased considerably, depending on pitch and spring ratios. An overall assessment, considering the friction losses, is achieved using the thermo-hydraulic performance parameter. The latter is observed to take values larger than unity for all cases, where quite high values around 2.8 occur for cases with smallest pitch and spring ratios. Predictive Nusselt number and friction factor correlations are proposed.     

Investigation of Noise-Induced Escape Rate: A Quantum Mechanical Approach

A quantum system coupled to a heat-bath in non-equilibrium environment is considered to study the problem of noise-induced escape rate from a metastable state in the moderate to strong friction limit (Kramers’ regime). It is known that starting from an initial coherent state representation of bath oscillators, one can derive a c-number generalized quantum Langevin equation where the quantum correction terms appear as a coupled infinite set of hierarchy of equations. For practical purpose, one should truncate these equations after a certain order. In our present development, we calculate the quantum correction terms in a closed analytical form based on a systematic perturbation technique and then derive the lowest order quantum correction factor exactly in the case of an Ohmic dissipative bath. Finally, to demonstrate its applicability, the effective equation of motions has been used to study the barrier crossing dynamics which incorporates the quantum correction factors.     

Polarization-encoded all-optical quaternary multiplexer and demultiplexer - A proposal

Multi-valued logic is positioned as a coming generation technology that can execute arithmetic functions faster and with less interconnect than binary logic. Furthermore, nonbinary data storage would require less physical space than binary data. The application of multi-valued digital signals can provide considerable relief of capacity constraints. In electronics many proposals have already been reported. But, here for the first time we propose an all-optical circuit for designing quaternary (four-valued) multiplexer and demultiplexer with the help of some polarization-encoded basic quaternary logic gates (quaternary min and quaternary delta literal). Nonlinear interferometer-based optical switch can take an important role here. The principles and possibilities of design of all-optical quaternary multi-valued multiplexer and demultiplexer circuits are proposed and described.     

Palladium-mediated intramolecular aryl amination on furanose derivatives: an expedient approach to the synthesis of chiral benzoxazocine derivatives and tricyclic nucleosides

Pd-catalyzed intramolecular arylamination on sugar derivatives has been accomplished by using bulky biaryl phosphine ligands. An application of this methodology on a variety of D-glucose-derived substrates, 2a-f, led to the synthesis of highly functionalized cis-fused tricyclic oxazocines, 3a-e. The products could subsequently be transformed to the optically active benzoxazocine derivative 4 and tricyclic nucleoside 6. This is the first example of the synthesis of eight-membered rings via intramolecular cycloamination of furanose derivatives, which provides a very useful method for the catalytic synthesis of medium-ring heterocycles.     

Synthesis and binding ability of bile acid-based receptors for recognition of flavin analogues

Novel cholaphanes 6a,b, based on lithocholic and deoxycholic acids, were synthesised through 3a,b by a sequence of reactions involving Cs-salt methodology of macrocyclisation. Cholaphanes 6a,b and acyclic steroidal receptors 3a,b bind flavin analogues via three hydrogen bonds in CHCl₃.     

Indium(I) iodide promoted cleavage of diphenyl diselenide and disulfide and subsequent palladium(0)-catalyzed condensation with vinylic bromides. A simple one-pot synthesis of vinylic selenides and sulfides

[reaction: see text] Diphenyl diselenide (and disulfide) undergo facile reaction with indium(I) iodide and the corresponding intermediate complex condenses in situ with a variety of substituted vinyl bromides in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0) [Pd(PPh3)4] in THF at room temperature to produce vinylic selenides and sulfides in good yields. The conversion of (E)-vinyl bromides is remarkably stereoselective giving (E)-vinyl selenides (and sulpfides) whereas the stereoselectivity in reaction of (Z)-vinyl bromides is not very good.     

Stresses produced in slightly compressible,finitely deformed elastic media due to a normal moving load

In this paper, the stresses developed in slightly compressible, finitely deformed half-space due to normal moving load has been discussed. It has been observed that this type of media have much effect on the existing normal and shearing stresses due to the load. The numerical calculations have been done for developed stresses at different depths. It has been observed that the stresses increase significantly in case of slightly compressible, deformed media.     

Aggregation Behavior of pHLIP in Aqueous Solution at Low Concentrations: A Fluorescence Study

pH (low) insertion peptide (pHLIP) is a 36-residue peptide derived from the third transmembrane helix of the membrane protein bacteriorhodopsin. The hydrophobicity of this peptide makes it prone to aggregation even at low concentrations, but this has not been studied in detail. In this work, we characterized monomeric and aggregated forms of pHLIP in aqueous solution (pH 8) at low concentrations (~μM) using fluorescence-based approaches, complemented by circular dichroism (CD) spectroscopy. We show here that monomeric and aggregated pHLIP display differential red edge excitation shift (REES) and CD spectra. These spectroscopic features allowed us to show that pHLIP aggregates even at low concentrations. A detailed knowledge of the aggregation behavior of pHLIP under these conditions will be useful for monitoring and quantifying its interaction with membranes.