Phase behavior of mixtures of polyoxyethylene(10) stearyl ether (Brij-76), 1-butanol, isooctane, and mixed polar solvents I. Water and formamide (or N,N-dimethyl formamide)

The isothermal phase diagram of the quaternary system polyoxyethylene(10) stearyl ether (Brij-76)/1-butanol/isooctane/water has been constructed at 30 degrees C with equal amounts of oil and water. A regular fishtail diagram was obtained, confirming the establishment of hydrophile-lipophile balance (HLB) in the system. Mixing of formamide (FA) [or N,N-dimethyl formamide (DMF)] with water as a cosolvent altered the HLB and decreased the solubilization capacity of the quaternary system. No three-phase body appeared at high FA or DMF content. Similar observations were noted for temperature-induced phase diagrams. The effect of DMF was more pronounced than that of FA in reducing the maximum solubilization capacity. The results have been summarized on the basis of HLB and mutual solubility of the components.     

Sequential separation by HDEHP of carrier-free101,105,106Rh,103,104,105,106,110,112Ag and104,105,107,109,111Cd produced in alpha-particle activated palladium

Carrier free^101,105,106Rh,^{103,104,105,106,110,112}Ag and^{104,105,107,109,111}Cd radioisotopes were produced simultaneously by -particle irradiation of palladium target material in a variable energy cyclotron. The radioisotopes produced were extracted and separated from the activated target by LLX using HDEHP as liquid cation exchanger. With the help of -ray spectrometry the presence of several radioisotopes in the activated target matrix and their purity at each step of the separation was confirmed.     

Interaction of coupled higher order nonlinear Schrödinger equation solitons

The novel inelastic collision properties of two-soliton interaction for an n-component coupled higher order nonlinear Schr?dinger equation are studied. Some interesting features of three soliton interactions, related to the integrability of the n-component coupled higher order nonlinear Schr?dinger equation are also discussed. Received 17 April 2002 Published online 2 October 2002 RID="a" ID="a"e-mail: abhijit@iitg.ernet.in RID="b" ID="b"e-mail: sasanka@iitg.ernet.in RID="c" ID="c"e-mail: sudipta@iitg.ernet.in     

Exotic electron states and tunable magneto-transport in a fractal Aharonov–Bohm interferometer

A Sierpinski gasket fractal network model is studied in respect of its electronic spectrum and magneto-transport when each ‘arm’ of the gasket is replaced by a diamond shaped Aharonov–Bohm interferometer, threaded by a uniform magnetic flux. Within the framework of a tight binding model for non-interacting, spinless electrons and a real space renormalization group method we unravel a class of extended and localized electronic states. In particular, we demonstrate the existence of extreme localization of electronic states at a special finite set of energy eigenvalues, and an infinite set of energy eigenvalues where the localization gets ‘delayed’ in space (staggered localization). These eigenstates exhibit a multitude of localization areas. The two terminal transmission coefficient and its dependence on the magnetic flux threading each basic Aharonov–Bohm interferometer is studied in details. Sharp switch on–switch off effects that can be tuned by controlling the flux from outside, are discussed. Our results are analytically exact.     

Benzofuran-derived cyclic beta-amino acid scaffold for building a diverse set of flavonoid-like probes and the discovery of a cell motility inhibitor

We report here a practical, enantioselective synthesis of benzofuran-derived, cyclic trans-beta-amino acid scaffold. In two cases, tricyclic derivatives having six- and eight-membered unsaturated lactams were obtained from this versatile scaffold. To explore the biological applications, these compounds were subjected to cell-based assays, using NIH3T3 mouse cells to examine their potency as cell motility inhibitors and identified 18 as a potent cell motility inhibitor (IC50 approximately 40 microM in chamber cell migration assay).     

Synthesis of polysubstituted benzothiophenes and sulfur-containing polycyclic aromatic compounds via samarium diiodide promoted three-component coupling reactions of thiophene-2-carboxylate

By the promotion of samarium diiodide, thiophene-2-carboxylate reacted with 2 equiv of ketones at the C-4 and C-5 positions to give diols such as 2 and 9. Because the intermediary organosamarium species were oxophilic but not too basic, the double hydroxyalkylations with various ketone substrates, including alkyl aryl ketones, acetylthiophenes, cyclohexanone, alpha-tetralone, and alpha-phenylacetophenones, were realized without complication of side reactions. The diol products underwent an acid-catalyzed dehydration to give dienes such as 3 and 10, which were treated with DDQ to give either polysubstituted thiophenes (e.g., 4 and 11) or benzothiophenes (e.g., 5, 13, and 14) depending on the reaction conditions. Oxidative annulations of 4,5-diarylthiophenes 11 and 4,5,6,7-tetraphenylbenzothiophenes 14 were carried out by photochemical or chemical methods to give the sulfur-containing polycyclic aromatic compounds, such as phenanthro[9,10-b]thiophene-2-carboxylate, piceno[13,14-b]thiophene-2-carboxylate, and tribenzo[fg,ij,rst]pentapheno[15,16-b]thiophene-2-carboxylates. This method is applicable to the preparation of polysubstituted thiophenes, benzothiophenes, and the related compounds possessing liquid crystalline, photochromic, and other functional properties.     

ICP-AES analysis of impurities in PuO2 after separation of Pu by TOPO impregnated XAD-4

Nuclear fuels should meet some specified characteristics to achieve their better performance in the reactor. Hence controlling and monitoring of trace level elements in the fuel materials are essential. Atomic emission spectroscopic methods are most popular for the trace level analysis. An ICP-AES procedure is described here for the trace level impurity analysis of PuO₂ produced through PUREX process. To avoid the Pu interference in the impurity analysis, initially the Pu was separated by extraction chromatography using TOPO impregnated XAD-4 resin. Magnitude of Pu interference in the impurities spectra lines was investigated. Moreover the recovery of impurity elements using the resin was established.