DBU Promoted Facile Synthesis of New Thieno[2,3‐b]pyridine/quinoline Derivatives and Their Antimicrobial Evaluation

Several new thieno[2,3‐b]pyridine and thieno[2,3‐b]quinoline derivatives are synthesized in an efficient manner catalyzed by DBU as a base. Simple workup procedure, good yields, and mild reaction conditions are the salient features of this method. All the synthesized compounds are screened for antimicrobial activity against several organisms.     

Working group report: Low energy and flavour physics

This is a report of the low energy and flavour physics working group at WHEPP-8, held at the Indian Institute of Technology, Mumbai, India, during 5–16 January 2004.     

Radiating Kerr particle in Einstein universe

A generalized Kerr-NUT type metric is considered in connection with Einstein field equations corresponding to perfect fluid plus a pure radiation field. A general scheme for obtaining the exact solutions of these field equations is developed. Two physically meaningful particular cases are investigated in detail. One gives the field of a radiating Kerr particle embedded in the Einstein universe. The other solution may probably represent a deSitter-like universe pervaded by a pure radiation field.     

The transition width and critical current density measurements on slow-cooled YBa2Cu3O7−x superconductor

It is shown that by adopting a very gradual programmed cooling procedure in oxygen environment one can obtain a sharp transition (ΔT _c⋍1 K) in YBa₂Cu₃O_7−x while retaining the high-T _c value (⋍105 K) of samples prepared by a semi-wet route. This is attributed to a maximum occupancy of oxygen at 0 1/2 0 sites and a near-perfect ordering of vacancies at 1/2 0 0 sites in the orthorhombic unit cell which maximizes the availability of conduction paths in the form of continuous CuO₄ chains. Critical current densities (J _c) of 204 A cm⁻² are obtained for bulk samples at 77 K. It is suggested that the intergrain coupling is weak and thus limits the transportJ _c-values.     

Temperature hysteretic effect and its influence on colossal magnetoresistance of La0.33Nd0.33Ca0.33MnO3

Electrical resistance (R) measurements of a bulk La_0.33Nd_0.33Ca_0.33MnO₃ perovskite in magnetic fields up to 40 kOe have revealed anomalous temperature hysteretic effects both in 0 Oe and 20 kOe magnetic fields. The sharp peak observed in the R vs. T plot indicates the occurrence of metal-to-insulator (M-I) transition at a temperature of T _MI=110 K and 140 K, for cooling and warming paths, respectively. An applied magnetic field of 20 kOe reduces the resistance and shifts T _MI to 160 K and 185 K for cooling and warming, respectively. We have observed a much higher resistance in the cooling path than in the warming path leading to the hysteretic resistance ratio (R _cool/R _warm) of 200 at 110 K and 1.8 at 160 K for 0 Oe and 20 kOe, respectively. Record values of colossal magnetoresistance (CMR) have been achieved. The CMR value reaches nearly 99% in the temperature ranges of 90 K to 140 K and 90 K to 170 K for 20 kOe and 40 kOe magnetic fields in the cooling mode, respectively. The observed unusual behavior is attributed to the co-existence of La-rich and Nd-rich domains assumed to be distributed randomly in the compound.     

Peak effect studies in single crystals CeRu2 and 2H-NbS2

We have studied the peak effect (PE) phenomenon in single crystals of weakly pinned superconductors CeRu₂ and 2H-NbS₂. 2H-NbS₂ is iso-structural and iso-electronic to 2H-NbSe₂, whose similarity with CeRu₂ as regards the PE representing the order-to-disorder transformation of the flux line lattice was claimed some time ago. We report on the step change in equilibrium magnetization across the peak effect in CeRu₂. We also present the vortex phase diagram of 2H-NbS₂ obtained from the magnetization data, and compare the PE phenomenon in 2H-NbS₂ and 2H-NbSe₂.     

An experimental limit on the coupling of a light neutral pseudoscalar particle to hadrons

Detailed results of an experiment, looking for a short-lived neutral particle decaying by ane ⁺ e ⁻ pair in the decay of the 3.68 MeV (3/2) state in¹³C, whose decay is predominantly M1, are presented. An upper limit of 7 × 10⁻⁵ has been placed on the branching ratio for decay through such a particle with a mass in the range 1.7 to 1.9 MeV/c². This leads to an upper limit of 10⁻⁶ for the coupling of such a particle to nucleons. Such a limit rules out the explanation of thee ⁺ ande ⁻ peaks recently observed in heavy ion collisions, as due to the decay of a neutral particle.     

HPTLC Method for Determination of Colchicine in a Pharmaceutical Formulation

JPC – Journal of Planar Chromatography – Modern TLC - An HPTLC method, using an internal standard, for analysis of colchicine in a pharmaceutical formulation, has been established and...     

Synthesis,anti‐bacterial,anti‐asthmatic and anti‐diabetic activities of novel N‐substituted‐2‐(benzo[d]isoxazol‐3‐ylmethyl)‐1H‐benzimidazoles

Synthesis of a series of novel class of N‐substituted‐2‐(benzo[d]isoxazol‐3‐ylmethyl)‐1H‐benzimidazoles ( 4 ) by the condensation of o‐phenylenediamine ( 1 ) with benzo[d]isoxazol‐3‐yl‐acetic acid ( 2 ) and subsequent reactions with different types of electrophiles have been reported. Some compounds exhibited promising anti‐bacterial activity against Salmonella typhimurium, however poor activity against Staphylococcus aureus. The compound 4t was found to have high activity even at 1 μg/ml compared to Cephalexin against S. aureus. The biological activity against PDE‐IV for potential anti‐asthmatic effect and against DP‐IV and PTP‐1B for potential anti‐diabetic effects was disappointing.     

Altered Membrane Mechanics Provides a Receptor-Independent Pathway for Serotonin Action

Serotonin, an important signaling molecule in humans, has an unexpectedly high lipid membrane affinity. The significance of this finding has evoked considerable speculation. Here we show that membrane binding by serotonin can directly modulate membrane properties and cellular function, providing an activity pathway completely independent of serotonin receptors. Atomic force microscopy shows that serotonin makes artificial lipid bilayers softer, and induces nucleation of liquid disordered domains inside the raft-like liquid-ordered domains. Solid-state NMR spectroscopy corroborates this data at the atomic level, revealing a homogeneous decrease in the order parameter of the lipid chains in the presence of serotonin. In the RN46A immortalized serotonergic neuronal cell line, extracellular serotonin enhances transferrin receptor endocytosis, even in the presence of broad-spectrum serotonin receptor and transporter inhibitors. Similarly, it increases the membrane binding and internalization of oligomeric peptides. Our results uncover a mode of serotonin–membrane interaction that can potentiate key cellular processes in a receptor-independent fashion.