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991.
David E. Portlock Anil C. Ghosh William E. Schwarzel Richard R. Kurtz Eliahu Boger Haldean C. Dalzell Raj K. Razdan 《Journal of heterocyclic chemistry》1976,13(4):781-788
Novel cyclol derivatives (Table 1, 15, 16 ) similar in structure to the peptide portion of ergocornine were synthesized. Detailed experimental procedures are given for the preparation of the cis- 13a and the unknown trans- 14a cyclol esters. 相似文献
992.
The use of sodium citrate as a reagent for the separation of silver group metals has been described. Silver, lead and mercurous ions are all capable of forming soluble citrate complexes, but they differ in their stability. The lead complex is not decomposed by soluble chlorides, whereas silver and mercurous complexes yield the insoluble chlorides. The fact that lead sulphate is soluble in a hot solution of sodium citrate has been utilized for the detection of lead, when present as insoluble sulphate, in a mixture. 相似文献
993.
Diffusion is often accompanied by a reaction or sorption which can induce temperature inhomogeneities. Monte Carlo simulations of Lennard-Jones atoms in zeolite NaCaA are reported with a hot zone presumed to be created by a reaction. Our simulations show that localized hot regions can alter both the kinetic and transport properties. Further, enhancement of the diffusion constant is greater for larger barrier height, a surprising result of considerable significance to many chemical and biological processes. We find an unanticipated coupling between reaction and diffusion due to the presence of hot zone in addition to that which normally exists via concentration. 相似文献
994.
995.
An efficient procedure is described for catalyst recycling and easy product isolation in alkene epoxidation with hydrogen peroxide catalyzed by water-soluble iron(III) porphyrins in environmentally benign and ambient temperature ionic liquids. 相似文献
996.
Jean-Paul Allouche Dinesh S. Thakur 《Proceedings of the American Mathematical Society》1999,127(5):1309-1312
Using the techniques of automata theory, we give another proof of the function field analogue of the Mahler-Manin conjecture and prove transcendence results for the power series associated to higher divisor functions .
997.
The electrical resistance of the critical binary liquid system C6H12+(CH3CO)2O is measured both in the pure form and when the system is doped with small amounts (≈ 100 ppm) of H2O impurities. Near Tc, the resistance varies as dR/dT = A1+A2 (T-Tc)-b with b ≈ 0.35. Neither the critical exponent b nor the amplitude ratio A1/A2 are affected by the impurities. A sign reversal of dR/dT is noticed at high temperatures T ? Tc. 相似文献
998.
Ratna S. Phadke N. Vasanth Kumar R. V. Hosur Anil Saran Girjesh Govil 《International journal of quantum chemistry》1981,20(1):85-92
In our earlier studies using quantum chemical methods we had proposed that propranolol has an extended structure. These results were confirmed using proton NMR . We have now carried out extensive magnetic resonance and model building studies to examine the interaction of this drug with model membranes. The effect of propranolol on organization of lipid bilayers has been studied using ESR spin labeling technique. Spin label Tempo and spin labeled stearic acid (5 SASL ) have been used to monitor changes in the fluidity of model membranes. Presence of the drug is found to fluidize the lipids. In case of 0.2M dipalmitoyl phosphatidyl choline (DPPC), presence of drug (0.1M) is found to decrease the gel-liquid crystalline phase transition temperature by about 10°C. The order parameter measured from the spectrum of 5 SASL shows a 4% decrease on incorporation of the drug in membranes. 13C spin lattice relaxation time (T1) measurements have been carried out for different nuclear sites of the drug. The aromatic moiety shows a high degree of molecular rigidity when the drug is bound to the lipid bilayers. The oxypropanolamine group is however relatively flexible. It appears from these studies that the aromatic group binds strongly to the hydrophobic regions of the lipid bilayer, while the oxypropanolamine moiety remains relatively free and lies in the hydrophilic region. The 13C chemical shifts indicate the involvement of the β-hydroxyl group in hydrogen bonding with the lipids. The NH group may be involved in electrostatic interactions with the negatively charged phosphate group of the lipid bilayers. 相似文献
999.
Summary Regression and classification problems can be viewed as special cases of the problem of function estimation. It is rather
well known that a two-layer perceptron with sigmoidal transformation functions can approximate any continuous function on
the compact subsets ofRP if there are sufficient number of hidden nodes. In this paper, we present an algorithm for fitting perceptron models, which
is quite different from the usual backpropagation or Levenberg-Marquardt algorithm. This new algorithm based on backfitting
ensures a better convergence than backpropagation. We have also used resampling techniques to select an ideal number of hidden
nodes automatically using the training data itself. This resampling technique helps to avoid the problem of overfitting that
one faces for the usual perceptron learning algorithms without any model selection scheme. Case studies and simulation results
are presented to illustrate the performance of this proposed algorithm. 相似文献
1000.
Sandeep Kumar D.R. Sharma N. Thakur N.S. Negi V.S. Rangra 《Journal of Molecular Liquids》2007,130(1-3):70-73
The dielectric relaxation time (τ) of binary mixtures of different molar concentrations of pyridine (C5H5N) and chlorobenzene (C6H5Cl) in benzene solution at different temperatures (25, 30, 35 and 40 °C) has been calculated by using standard microwave techniques and Gopala Krishna's single frequency (9.875 GHz) concentration variation method. The energy parameters (ΔHε, ΔFε, and ΔSε) for the dielectric relaxation process of the binary mixture containing 0.5 mol fraction of pyridine have been calculated at the respective temperatures. Comparisons have been made with the corresponding energy parameters for the viscous flow (ΔHη, ΔFη, and ΔSη). From the observations it is found that the dielectric relaxation process can be treated as the rate process. Based upon above studies, solute–solvent type of molecular associations arising from the interaction of chlorobenzene and benzene and pyridine and benzene molecules has been proposed. No solute–solute type of molecular association has been observed. 相似文献