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71.
Axisymmetric flow of thin pure liquid film on a spinning horizontal annular disk is studied under the action of air shear at the liquid–air interface and evaporation. The non-linear evolution equation that is obtained by singular perturbation method is solved analytically, for small Reynolds number, by using the method of characteristic and numerically by the use of Newton–Kantorovich method for any Reynolds number. Font breakdown time and its location from the center of the disk is predicted both by analytically and numerically. The result shows that the thinning of the initial film increases as air stress increase, same result is also escalated in presence of evaporation. 相似文献
72.
73.
Shyamaprosad Goswami Abhishek Manna Sima Paul Avijit K. Das Prasanta K. Nandi Anup Kumar Maity Partha Saha 《Tetrahedron letters》2014
5(Benzothiazol-2-yl)-4-hydroxyisophthalaldehyde (BHI), an intense ESIPT containing molecule in mixed media loses its properties due to resonance-assisted H-bond (RAHB) in absolute water. Due to resonance-assisted H-bond the o-aldehyde is more reactive than the other one. With addition of cysteine/homocysteine into this solution the o-aldehyde group gets transformed into thiazolidine/thiazine ring, respectively, and the phenolic proton becomes free enough for transfer to nitrogen of the benzothiazole ring in excited state, that is, the ESIPT of BHI is turned on. Thus we can detect cysteine/homocysteine in water as well as in live cells. 相似文献
74.
Simple Organic Salts Having a Naphthalenediimide (NDI) Core Display Multifunctional Properties: Gelation,Anticancer and Semiconducting Properties 下载免费PDF全文
Following a supramolecular synthon rationale, a dicarboxylic acid derivative having a naphthalenediimide (NDI) core, namely, bis‐N‐carboxymethyl naphthalenediimide ( NDI‐G ), was reacted with n‐alkyl amines with varying alkyl chain lengths to generate a new series of primary ammonium dicarboxylate (PAD) salts. The majority of the salts (≈85 %) were found to gel various polar solvents. The gels were characterized by dynamic rheology and high‐resolution electron microscopy. Single‐crystal and powder X‐ray diffraction analyses were used to study the supramolecular synthon present in one of the gelator salts (i.e., S8 ). Charge‐transfer (CT)‐induced gelation with donor molecules such as anthracene methanol ( Ant ) and pyrene ( Py ) was also possible with S8 . The CT complex ( S8.Ant ) displayed anticancer activity as probed by cell migration assay on the highly aggresive breast cancer cell line MDA‐MB‐231 . The DMSO gel of S8.Ant also displayed semiconducting behavior. To the best of our knowledge, simple organic salts with an NDI core that display such mulitifunctional properties are hitherto unknown. 相似文献
75.
76.
Time-resolved and steady-state fluorescence measurements have been performed on monomeric and dimeric forms of yeast hexokinase-PI. Observation of similar emission spectra and fluorescence decay parameters for both the forms of the enzyme suggests that tryptophan residue(s) are not likely to be present at the subunit-subunit interface and the process of dimerization does not perturb the local environment of tryptophan(s). The fluorescence decay of tryptophans in enzyme could be fitted to a bi-exponential function with two lifetime components, tau1 approximately 2.2 ns and tau2 approximately 3.9 ns. Binding of glucose, which is known to convert the 'open' conformation of the enzyme to a 'closed' active conformation, results in approximately 30% reduction in emission intensity and a selective decrease in tau1 from approximately 2.2 to approximately 1.1 ns. These effects can be reversed by the addition of trehalose 6-phosphate (an inhibitor of yeast hexokinase), suggesting that the trehalose 6-phosphate inhibits the enzyme by binding to its 'open' inactive conformation rather than competing with glucose to bind to the 'closed' active conformation. Binding of nucleotide ligands (ATP, ADP and adenyl-(beta,gamma-methylene)-diphosphate (AMPPCP)) to the monomeric or dimeric form of enzyme quenched the steady-state fluorescence by approximately 4-8%, but had no measurable effect on the distribution of lifetimes or on their magnitudes. Addition of nucleotides to the enzyme-glucose complex also did not produce any further change in fluorescence decay parameters. These results indicate that it is highly unlikely that the formation of a ternary enzyme-glucose-nucleotide complex from the binary enzyme-glucose complex is accompanied by a large conformational change in the enzyme, as has been surmised in some earlier studies. 相似文献
77.
Sunil K. Maity Narayan C. Pradhan Anand V. Patwardhan 《Journal of molecular catalysis. A, Chemical》2006,250(1-2):114-121
The reaction between benzyl chloride and aqueous ammonium sulfide was carried out in an organic solvent – toluene, using tetrabutylammonium bromide (TBAB) as phase transfer catalyst (PTC). Two products, namely dibenzyl sulfide (DBS) and benzyl mercaptan (BM), were identified in the reaction mixture. The selectivity of DBS was maximised by changing various parameters such as NH3/H2S mole ratio, stirring speed, catalyst loading, concentration of benzyl chloride, volume of aqueous phase, and temperature. The highest selectivity of DBS obtained was about 90% after 445 min of reaction with excess benzyl chloride at 60 °C. Complete conversion of benzyl chloride could be achieved at the cost of very low selectivity of DBS and very high selectivity of BM. The apparent activation energy for the kinetically controlled reaction was found to be 12.3 kcal/mol. From the detailed study of the effects of various parameters on the reaction, a suitable mechanism was established which could explain the course of the reaction. 相似文献
78.
A variant of the orthogonal gradient method of orbital optimization in the INDO-MCSCF framework has been used to study the
photochemical decomposition of the HNO molecule into H + NO in the lowest1.3A″ states. A complete geometry optimization has been carried out at all points of the reaction path which appears to be almost
barrierless. The one-electron density matrix extracted from the optimized wavefunction at each point has been used to generate
the relevant sets of quantum chemical valence parameters. A sharp transition is noted in the N-H bond order and hydrogen free
valence index when plotted as functions of rNH. This enables us to locate the transition region easily. 相似文献
79.
A radiometric procedure for quantitative analysis of traces of silver in galena has been demonstrated. The mineral sample was dissolved in HNO3 (31) and silver present in the solution was precipitated as insoluble AgI by adding an excess amount of131I-labeled KI solution and was coprecipitated with zirconium hydrogen phosphate, Zr(HPO4)2, in 0.5N H2SO4 medium. The method of radiometric analysis of silver which was estimated from the knowledge of the loss of131I activity in solution, was found to be effective in determination of the element even below ppb level. Applicability of the radiometric procedure in routine analysis or preconcentration of traces of silver in galena has been stressed. 相似文献
80.
Polymerization of MMA was carried out in near-bulk and in fairly dilute solutions in DMF at 40° with (1) CPB-BZ2O2 combination as the redox initiator in the dark and (2) CPB as the sole photoinitiator in visible light. Rp was proportional to ([CPB] [BZ2O2])0.18 for the redox polymerization and to [CPB]0.35 for the photopolymerization both in near-bulk (10% DMF, v/v) and in high dilution (50% DMF, v/v). Polymerization was inhibited by hydroquinone in each case indicating a radical mechanism. Effect of several solvents/additives on the polymerization revealed that dimethyl formamide, acetonitrile and pyridine acted as rate enhancing solvents in the redox polymerization while in the photopolymerization they acted as normal diluents; benzene, methanol, acetone and chloroform exhibited inert nature while formamide and acetamide behaved as retarding additives in both types of polymerization. Initiator transfer of the degradative type reasonably explains kinetic nonidealities. 相似文献