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91.
D. K. Bhattacharyya N. C. Dutta A. De 《Journal of Radioanalytical and Nuclear Chemistry》1990,140(1):121-131
The uptake of 22 cations at tracer concentrations has been studied over hydrous tin dioxide exchanger material. A granular variety of tin dioxide was prepared from the reaction of tin(IV) chloride with NaOH solution, and the formula of the material was ascertained to be SnO2·1.7 H2O. Radiochemical separation of carrier-free234Th from238U and113mIn from113Sn was achieved over a tin dioxide column. The separated products were of high radionuclidic purity. The overall separation procedures are very simple and quick with quantitative yield. 相似文献
92.
Jain SL Bhattacharyya P Milton HL Slawin AM Crayston JA Woollins JD 《Dalton transactions (Cambridge, England : 2003)》2004,(6):862-871
Seven new pyridine dicarboxamide ligands H2L(1-7) have been synthesised from condensation reactions involving pyridine-2,6-dicarboxylic acid (H2dipic), pyridine-2,6-dicarbonyl dichloride or 2,6-diaminopyridine with heterocyclic amine or carboxylic acid precursors. Crystallographic analyses of N,N'-bis(2-pyridyl)pyridine-2,6-dicarboxamide monohydrate (H2L8 x H2O), N,N'-bis[2-(2-pyridyl)methyl]pyridine-2,6-dicarboxamide and N,N'-bis[2-(2-pyridyl)ethyl]pyridine-2,6-dicarboxamide monohydrate revealed extensive intramolecular hydrogen bonding interactions. 2,6-Bis(pyrazine-2-carboxamido)pyridine (H2L6) and 2,6-bis(pyridine-2-carboxamido)pyridine (H2L7) reacted with copper(II) acetate monohydrate to give tricopper(II) complexes [Cu3(L)2(mu2-OAc)2]. X-Ray crystallography confirmed deprotonation of the amidic nitrogen atoms and that the (L6,7)2- ligands and acetate anions hold three copper(II) ions in approximately linear fashion. H2L8. Reacted with copper(II) tetrakis(pyridine) perchlorate to give [Cu(L8)(OH2)]2 x 2H2O, in which (L8)2- was tridentate through the nitrogen atoms of the central pyridine ring and the deprotonated carboxamide groups at one copper centre, with one of the terminal pyridyl rings coordinating to the other copper atom in the dimer. The corresponding reaction using H2L7 gave [Cu3(L7)2(py)2][ClO4]2, which transformed during an attempted recrystallisation from ethanol under aerobic conditions to a tetracopper(II) complex [Cu4(L7)2(L7-O)2]. 相似文献
93.
In flash photolysis of an oxygenated aqueous potassium persulphate solution at pH 12.5 the decay of the ozonide radical has been found to follow order kinetics which has been explained by reactions O?3 + O? ? 2 O?2 and O?3 + HO2 → 2 O2 + OH? 相似文献
94.
This article addresses the problem of oscillating laminar electrokinetic liquid flow in an infinitely extended circular microchannel. Based on the Debye-Huckel approximation for low surface potential at the channel wall, a complex variable approach is used to obtain an analytical solution for the flow. The complex counterparts of the flow rate and the current are linearly dependent on the pressure gradient and the external electric field. This property is used to show that Onsager's principle of reciprocity continues to be valid (involving the complex quantities) for the stated problem. During oscillating pressure-driven flow, the electroviscous effect for a given value of the normalized reciprocal electrical double-layer (EDL) thickness is observed to attain a maximum at a certain normalized frequency. In general, an increasing normalized frequency results in a reduction of EDL effects, leading to (i). a volumetric flow rate in the case of streaming potential approaching that predicted by the theory without EDL effects, and (ii). a reduction in the volumetric flow rate in the case of electroosmosis. 相似文献
95.
R.?T.?Savalia K.?N.?Lad A.?PratapEmail author G.?K.?Dey S.?Banerjee 《Journal of Thermal Analysis and Calorimetry》2004,78(3):745-751
The formation of nano-quasicrystals on isothermal annealing of melt-spun ribbons of Zr69.5Al7.5Ni11Cu12 metallic glass has been investigated using transmission electron microscopy (TEM). The crystallization study of this metallic glass has been carried out using differential scanning calorimetry (DSC) in non-isothermal (linear heating) mode. It exhibits two-stage crystallization where the first stage corresponds to the precipitation of icosohedral nano-quasicrystalline phase. This has been confirmed with the help of TEM investigations. The crystallization parameters like the activation energy (E
c) and frequency factor (k
0) have been derived using the Kissinger peak shift analysis. The activation energies for the first and second crystallization peak are found to be 278 and 295 kJ mol–1, respectively. The frequency factors obtained for the two peaks are respectively 7.16·1019 and 1.42·1020 s–1. E
c, k
0 and the Avrami exponent (n) have also been derived by fitting the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation for the transformed volume fraction (x) to the crystallization data. JMAK results of E
c for the first and second crystallization peak turn out to be 270 and 290 kJ mol–1 respectively. However, k
0 and n are found to be heating rate dependent as reported in similar studies. The values of n for the first crystallization stage ranges between 1.66 and 2.57 indicating diffusion-controlled transformation in agreement with earlier reports. 相似文献
96.
Summary In NH4NO3+NH4OH buffered 10% (v/v) dioxan-water media (pH 7.0–8.5), thePseudo-first-order rate constant for the formation of the title complexes M(baen),i.e. ML, conforms to the equation 1/kobs=1/k+1/(kKo.s · TL), where TL stands for the total ligand concentration in the solution, Ko.s is the equilibrium constant for the formation of an intermediate outer sphere complex and k is the rate constant for the formation of the complex ML from the intermediate. Under the experimental conditions the free ligand (pKa>14) exists virtually exclusively in the undissociated form (baenH2 or LH2) which is present mostly as a keto-amine in the internally hydrogen-bonded state. Although the observed formation-rate ratio kCu/kNi is of the order of 105, as expected for systems having normal behaviour, the individual rate constants are very low (at 25°C, kCu=50 s–1 and kNi=4.7×10–4s–1) due to the highly negative S values (–84.2±3.3 JK–1M–1 for CuL and –105.8±4.1 JK–1M–1 for NiL); the much slower rate of formation of the nickel(II) complex is due to higher H value (41.2±1.0 kJM–1 for CuL and 78.2±1.2 kJM–1 for NiL) and more negative S value compared to that of CuL. The Ko.s values are much higher than expected for simple outer-sphere association between [M(H2O)6] and LH2 and may be due to hydrogen bonding interaction.In acid media ([H+], 0.01–0.04 M) these complexes M(baen) dissociate very rapidly into the [M(H2O)6]2+ species and baenH2, followed by a much slower hydrolytic cleavage of the ligand into its components,viz. acetylacetone and ethylenediamine (protonated). For the dissociation of the complexes kobs=k1[H+]+k2[H+]2. The reactions have been studied in 10% (v/v) dioxan-water media and also ethanolwater media of varying ethanol content (10–25% v/v) and the results are in conformity with a solvent-assisted dissociativeinterchange mechanism involving the protonated complexes. 相似文献
97.
Banerjee A Grewer C Ramakrishnan L Jäger J Gameiro A Breitinger HG Gee KR Carpenter BK Hess GP 《The Journal of organic chemistry》2003,68(22):8361-8367
The synthesis and characterization of a new photolabile protecting group (caging group) for carboxylic acids, the 2-(dimethylamino)-5-nitrophenyl (DANP) group, is described. This compound has a major absorption band in the visible wavelength region with a maximum near 400 nm (epsilon400 = 9077 M(-1) cm(-1) at pH 7.4 and 21 degrees C). The caging group is attached through an ester linkage to the carboxyl functionality of beta-alanine, which activates the inhibitory glycine receptor in the mammalian central nervous system. Such caged compounds play an important role in transient kinetic investigations of fast cellular processes. Upon photolysis of DANP-caged beta-alanine, the caging group is released within 5 micros. Quantum yields of 0.03 and 0.002 were obtained in the UV region (308 and 360 nm) and the visible region (450 nm), respectively. Laser-pulse photolysis experiments, using 337 or 360 nm light, were performed with the caged compound equilibrated with HEK 293 cells transiently transfected with cDNA encoding the alpha1 homomeric, wild-type glycine receptor. The experiments demonstrated that neither DANP-caged beta-alanine nor its byproducts inhibit or activate the glycine receptors on the cell surface. Under physiological conditions, the DANP-caged beta-alanine is water-soluble and stable and can be used for transient kinetic measurements. 相似文献
98.
Susanta Banerjee Pranav K. Gutch Chhaya Saxena 《Journal of polymer science. Part A, Polymer chemistry》1995,33(10):1719-1725
Six new polyether azomethines were synthesized by melt and solution polycondensation of six different diamines with 4,4′-[1,4-phenylene bis(oxy)] bisbenzaldehyde. The polymers synthesized by solution method are yellow to white in color and had inherent viscosities up to 0.59 dL/g in concentrated H2SO4. The polymers obtained by melt condensation show higher viscosity. Except polymer IV , others are insoluble in common organic solvents. The polymers were characterized by IR, x-ray, elemental analysis, and DSC study. The thermal stability of the polymers was evaluated by TGA and IGA study. Polymers I-III are highly thermally and thermooxidatively stable and exhibit no appreciable decomposition up to 420°C both in air and nitrogen atmosphere. It was shown that the curing of the polyazo-methines takes place by opening up of the ? CH?N? linkages at higher temperature. The electrical conductivities of the virgin and iodine doped polymers were as high as 10?11?10?16 and 10?6?10?8S cm?1, respectively, at 30°C. Electronic spectra of the undoped polymers ( I-III ) indicated a large bathochromic shift of the ? – ?* absorptions band (376 nm) due to ? C?N? bonds of the model compound. This can be attributed to extensive delocalization of the electrons along the polymer chain. © 1995 John Wiley & Sons, Inc. 相似文献
99.
Titanium phosphate as ion exchanger for column operation has been prepared by mixing TiCl4 and H3PO4 in suitable proportion. The ratio of titanium: phosphate was obtained to be 1:2.02. The uptake of Na+, K+, Rb+, Cs+, Ag+, Ca2+, Sr2+, Ba2+, Pb2+, Sc3+, Co3+, Y3+, Tb3+, Zr4+ and Th4+ cations at very small concentrations has been studied on this exchanger. The data indicated that the different cations are adsorbed in the exchanger by different mechanisms. Radiochemical separations of carrier free95Nb from95Zr, UX1 from U and45Ca from46Sc have been achieved by adopting very simple chemical procedures through a column of titanium phosphate. The -spectrum of the separated95Nb, UX1 and46Sc showed that the products are of high radionuclidic purity. The individual separation procedures took less than 20 min and the yields are quantitative. 相似文献
100.
Yang J Bhattacharyya A Masliyah JH Kwok DY 《Journal of colloid and interface science》2003,261(1):21-31
This paper has addressed analytically the problem of laminar flow in microchannels with rectangular cross-section subjected to a time-dependent sinusoidal pressure gradient and a sinusoidal electric field. The analytical solution has been determined based on the Debye-Hückel approximation of a low surface potential at the channel wall. We have demonstrated that Onsager's principle of reciprocity is valid for this problem. Parametric studies of streaming potential have shown the dependence of the electroviscous effect not only on the Debye length, but also on the oscillation frequency and the microchannel width. Parametric studies of electroosmosis demonstrate that the flow rate decreases due to an increase in frequency. The obtained solutions for both the streaming potential and electroosmotic flows become those for flow between two parallel plates in the limit of a large aspect ratio. 相似文献