Effect of dispersion on the diffusion zone in two-phase laminar flows in microchannels

Aim of the present work is to investigate the reaction–diffusion process of a two species system under laminar flow in a T-shaped microchannel. A zone formed at the interface between the aqueous solutions of these two species is affected by advection and diffusion. Through theoretical analyses and experimental results, the effect of dispersion has been shown to influence this diffusion zone. We have defined a parameter called effective diffusivity, to account for the dispersion effects and observed it to be a function of the channel Peclet number. In the limiting case of low Peclet number, this parameter is constant and turns out to be equal to the molecular diffusivity. We have also related effective diffusivity and the dispersion coefficient through scaling estimates.     

Natural convective heat transfer in water enclosed between pairs of differentially heated vertical plates

This paper presents the results of an experimental study of buoyancy-driven convective heat transfer between three parallel vertical plates, symmetrically spaced with water as the intervening medium. The centre plate was electrically heated, while the other side plates were water-cooled forming two successive parallel vertical channels of dimensions 20 cm × 3.5 cm × 35 cm (length W, gap L, height H) each. Top, bottom and sides of the channels were open to water in the chamber which is the novel aspect of this study. Plate surface temperature and bath temperature at different levels of height from the bottom of channel were measured by K-type thermocouples. Experimental data have been correlated as under:

Breakup of 42 MeV 7Li projectiles in the fields of 12C and 197Au nuclei

Inclusive cross sections of α particles and tritons from the breakup of 42 MeV ⁷Li by ¹²C and ¹⁹⁷Au targets are presented and analysed in the framework of the Serber model. Spectral distortions due to the targets and relevant reaction mechanisms are discussed.     

Supramolecular Gels Derived from the Salts of Variously Substituted Phenylacetic Acid and Dicyclohexylamine: Design,Synthesis, Structures,and Dye Adsorption

A well‐studied supramolecular synthon, namely, secondary ammonium monocarboxylate (SAM), was exploited to generate a new series of organic salts derived from variously substituted phenylacetic acid and dicyclohexylamine as potential low‐molecular‐weight gelators. As much as 25 % of the SAM salts under study were gelators. The gels were characterized by rheology, and the morphology of the gel networks was studied by high‐resolution electron microscopy. Single‐crystal and powder XRD data were employed to study structure–property (gelation) correlations. One of the gels could adsorb a hydrophobic dye (Nile Red) more efficiently than that of a hydrophilic dye (Calcein) from dimethyl sulfoxide; this might provide useful clues towards the development of stain‐removing gels.     

Interaction of divalent metal ions with uracil III. Complexes of MnII,FeII, CoII,NiII and CuII with uracil acting as bidentate ligand

Summary Some novel nonelectrolytic complexes of uracil in its anionic form with divalent metal ions were synthesised by heating to reflux a methanolic solution of uracil and a metal salt at pHca. 7.5. The isolated complexes are formulated as [ML₂(H₂O)₂] where M = Mn, Fe, Co, Ni, or Cu; L = C₄H₃N₂O₂ Electronic spectra indicate the hexacoordination of the metal ion in all the complexes and also the presence of a weak metal-oxygen interaction. The disappearance of the (NH) band and also the appreciable change both in intensity and position the characteristic bands of the 2-keto group of the uracil in the infrared spectra of all the complexes indicate the chelation of the uracil through C(2)=O and N(3).     

Non-intrinsic superconductivity in InN epilayers: Role of Indium Oxide

In recent years there have been reports of anomalous electrical resistivity and the presence of superconductivity in semiconducting InN layers. By a careful correlation of the temperature dependence of resistivity and magnetic susceptibility with structural information from high-resolution x-ray diffraction measurements, we show that superconductivity is not intrinsic to InN and is seen only in samples that show traces of oxygen impurity. We hence believe that InN is not intrinsically a superconducting semiconductor.     

pH-Responsive Biocompatible Fluorescent Core-Shell Nanogel for Intracellular Imaging and Control Drug Release

This study reports a fluorescence iron core-carbonized biocompatible hybrid poly(ethylene glycol) (PEG)-oriented nanogel (Fe₂O₃@C@PEG-COOH nanogel). The fluorescence Fe₂O₃@C@PEG-COOH nanogel is prepared using a facile one-pot polycondensation reaction without organic solvents or catalysts. The properties of the fluorescenceFe₂O₃@C@PEG-COOH nanogel are investigated by fluorescence spectroscopy, transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis. A change in pH as a stimulus can trigger the release of loaded doxorubicin (DOX). Under acidic conditions, the nanogel releases the highly loaded drug slowly compared to the neutral and basic conditions, which is important for cancer treatment. The synthesized fluorescenceFe₂O₃@C@PEG-COOH nanogel is well dispersed in water and shows fluorescence with high photostability, good biocompatibility with a paramagnetic nature. Furthermore, the nanogel can act as a potential fluorescent probe for cell imaging.     

Thermal dehydration and decomposition of nickel chloride hydrate (NiCl2·xH2O)

The dehydration and decomposition characteristics of an undried and a partly dried sample of NiCl₂·xH₂O have been investigated by isothermal and non-isothermal (TG and DTA) methods in static air as well as flowing nitrogen environment. While the isothermal weight loss method fails to distinguish between different steps of reaction, TG curves upto 800°C reveal as many as five steps in static air and four steps in nitrogen atmosphere. However, both methods indicate that NiCl₂ is stable upto 400°C above which dehydrochlorination takes place in presence of water vapour. The intermediate products of dehydration and decomposition at different temperatures have been characterized by chemical analysis, X-ray diffraction, infrared and diffuse reflectance spectroscopy. All these methods reveal the presence of water in samples calcined at even 400°–600°C. Thermodynamic functions for different steps of dehydration have been calculated and discussed in the light of the possible structural changes occurring in the partially dehydrated products.The authors wish to express their sincere thanks to Mr. D. N. Dey, Head, Pyrometallurgy Division for his keen interest and constant support during the course of investigation. Thanks are also due to Director, Regional Research Laboratory, Bhubaneswar for his kind permission to publish this paper. One of the authors (S. K. M.) is thankful to the Council of Scientific and Industrial Research, New Delhi for awarding a Junior Research Fellowship.