On the Bödewadt–Rosenblat flow

Fluid motion induced by the torsional oscillations (of angular velocity bΩcosω T) of an infinite disk in contact with an incompressible viscous rotating (with angular velocity aΩ) fluid of semi-infinite extent is analysed when the amplitude parameter α( = b/a) varies from zero to infinity. Composite solutions valid over the whole of the flow regime and specific expressions for the shearing stress components at the disk and for the axial flow in the far region are obtained for low and high frequencies of torsional oscillations. Using the method of matched asymptotic expansions, we find that the region of the mean flow increases with α and reaches a maximum before settling down to the Rosenblat profile. Series expressions (for α < 1) are deduced for physical quantities of interest when the fluid in the far field and the disk are rotating with different angular velocities (in the same or in the opposite sense), which agree well with the known numerical results. (Received: April 7, 2003; revised: September 29, 2005)     

Effect of hydrophobic modifications in antimicrobial peptides

With increasing resistance development against conventional antibiotics, there is an urgent need to identify novel approaches for infection treatment. Antimicrobial peptides may offer opportunities in this context, hence there has been considerable interest in identification and optimization of such peptides during the last decade in particular, with the long-term aim of developing these to potent and safe therapeutics. In the present overview, focus is placed on hydrophobic modifications of antimicrobial peptides, and how these may provide opportunities to combat also more demanding pathogens, including multi-resistant strains, yet not provoking unacceptable toxic responses. In doing so, physicochemical factors affecting peptide interactions with bacterial and eukaryotic cell membranes are discussed. Throughout, an attempt is made to illustrate how physicochemical studies on model lipid membranes can be correlated to result from bacterial and cell assays, and knowledge from this translated into therapeutic considerations.     

Synthesis and Characterization of Novel Acyclic Enediynes

A novel group of symmetrical and asymmetrical acyclic enediynes has been synthesized by using Sonogashira coupling conditions and characterized spectroscopically.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Equilibrium Sorption of Hexavalent Chromium from Aqueous Solution Using Iron(III)-Loaded Chitosan-Magnetite Nanocomposites As Novel Sorbent

This work describes magnetic separation of hexavalent chromium by iron(III)-loaded chitosan-magnetite nanocomposites. The Cr(VI) uptake data, studied at 25°C and 45°C, was well fitted into the Freundlich isotherm. The values of constant K_F and 1/n were found to be 1.515, 1.266 and 1.006 (mg g^?1) (l mg^?1)^1/n and 0.76, 0.77, and 0.71, respectively. The Dubinin-Kaganer-Radushkevich isotherm was applied to determine mean sorption energy E. The value of E was found to be in the 8.977 to 9.90 kJ mol^?1 range, thus indicating the chemical nature of the sorption process. The kinetics of Cr(VI) uptake was best interpreted by the Power function model. The intraparticle diffusion of sorbate was confirmed by the Bangham equation, and various thermodynamic parameters were also evaluated. Finally, a plausible mechanism has been suggested to understand the sorption process. The intraparticle diffusion was found to occur and later on confirmed by the Bangham equation. Finally, a plausible mechanism has been suggested for the observed Cr(VI) uptake on this newly developed sorbent. The various thermodynamic parameters were also evaluated.     

Development of Poly(ethylene glycol) Based Amphiphilic Copolymers for Controlled Release Delivery of Carbofuran

The formation of micelles in a solvent that is selective for one of the blocks is one of the most important and useful properties of block copolymers. We had synthesized copolymers of polyethylene glycol and various dimethyl esters, which self assemble into nano micellar aggregates in aqueous media. In the present work, we have utilized these nano micelles for the encapsulation of carbofuran, [2,3–dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate], a systemic insecticide-nematicide, for the development of controlled release formulation.     

Coordination diversity in palladium(II)-picolinamide ligand complexes: structural and quantum chemical studies

The separation of different metal ions can be successfully accomplished by using picolinamide-based ligands. We herein report the first X-ray structure of picolinamide-based ligands of the type C₅H₄NCONR₂ (where R=ⁱC₃H₇ (L1) and ⁱC₄H₉ (L2)) and C₅H₄NCONHR (R=^tC₄H₉ (L3)) with palladium(II) ion. We have synthesized and characterized the structures of two palladium complexes, [PdCl₂(L1)₂] (1) and [PdCl₂L3] (3). In 1, ligand L1 forms a 2?:?1 complex with palladium(II) chloride, whereas in 3, the ligand L3 forms a 1?:?1 complex. Further, in 1, the ligand L1 acts as a monodentate ligand and is bound only through pyridyl-N atom, whereas in 3, the ligand L3 acts as a bidentate chelating ligand and is bound through both the pyridyl-N and amido-O atoms to the Pd(II) center. Electronic structure calculations are carried out to understand the experimental coordination diversity in the Pd complexes. Our calculations clearly suggest that a combination of steric hindrance of the ligand and the electronic effect of metal ions may modulate the coordination preferences.     

A study on seasonal variability of <Superscript>222</Superscript>Rn–<Superscript>220</Superscript>Rn parameters in dwellings around a thermal power plant,India

A novel ethylene diamine tetraacetic acid derivative of 4-nitroimidazole (EDTA-4-EtNHNM) was successfully synthesized as a carrier molecule and it was radiolabeled with ^99mTc in high yield to obtain ^99mTc-EDTA-4-EtNHNM, which was hydrophilic and had good in vitro stability. The tumor cell experiment and the biodistribution study in mice bearing S180 tumor showed that this complex exhibited a hypoxic selectivity and had high accumulation in tumor tissue with major clearance through urinary tract. High tumor uptake and tumor/muscle ratio of the complex suggests promise towards further evaluation.     

Design of a Hybrid Fiber-Optic Network Using 3-D Optical Code Sequences

We present the design of a 3-dimensional (3-D) noncoherent optical hybrid network. We also report the design of a new family of 3-D codes for fiber optic hybrid networks. We show that the hybrid network allows for shorter bit times and a higher number of users, given a set chip rate, compared to previously conceived networks. These newly designed hybrid single-pulse-per-row (HSPR) codes have very low autocorrelation side-lobes and very small cross-correlation peaks. We compare the performance of our hybrid model using our codes with the Optical Orthogonal Codes (OOCs) and Temporal/Spatial (T/S) codes and show that the new network can support a greater number of users and higher data rates than those using OOCs and T/S codes.     

Composite of discotic liquid crystal and gold nanoparticles: A comperative band gap study

Nanocomposites of discotic liquid crystal namely 2, 3, 6, 7, 10, 11-hexabutyloxytryphenylene (HAT4) in existence of variable concentration of gold nanoparticles (GNPs) have been studied at room temperature and zero pressure. The absorption spectra of nanocomposites are captured by a Shimadzu UV–VIS Spectrophotometer, model UV-1800, in the wavelength range 900–200?nm. In this paper using the Tauc’s relation, the absorption spectra fitting method was applied to estimate the optical band gap. Nanocomposites are prepared by mixing of GNPs with four concentrations in pure HAT4 viz. 0.2, 0.6, 1.2 and 3?wt%. From the investigation of absorption spectra, it has been observed that with the enhance of GNPs concentration in pure HAT4 band gap has decreased for lower concentrations but for higher concentration (3?wt%) it increases.