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51.
Y. P. Khanna E. M. Pearce B. D. Forman D. A. Bini 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2799-2816
The synthesis of some wholly aromatic polyamides based on unsubstituted and chloro- and nitro-substituted diamines by low temperature solution polymerization is described. Poly(1,3-phenylene isophthalamide) and poly(chloro-2,4-phenylene isophthalamide) were selected for further investigation. To study the two polyamides on a systematic basis their model diamides were synthesized. These materials were characterized with respect to chemical structure and purity by elemental analysis, infrared (IR), and nuclear magnetic resonance (NMR) spectroscopic techniques. The usefulness of the model compounds in the interpretation of the polymer spectra is also demonstrated. 相似文献
52.
Robin Forman 《Communications in Mathematical Physics》1992,147(3):485-526
We relate the determinants of differential and difference operators to the boundary values of solutions of the operators. Previous proofs of related results have involved considering one-parameter families of such operators, showing the desired quantities are equal up to a constant, and then calculating the constant. We take a more direct approach. For a fixed operator, we prove immediately that the two sides of our formulas are equal by using the following simple observation (Proposition 1.3):Let USU(n,C).Write U in block form
相似文献
53.
H Liu L J Forman J Montoya C Eggers C Barham M Delgado 《Journal of chromatography. A》1992,576(1):163-169
The derivatization of valproic acid and undecylenic acid with 4-bromomethyl-7-methoxycoumarin is described. The derivatives were detected by photodiode-array and fluorescence detectors. The optimum monitoring conditions and the stability of the suspension solution and derivatives were investigated. A high-performance liquid chromatographic (HPLC) method with isocratic or gradient elution has been established for the analysis. This method has been used for the determination of total and free valproic acid in serum. There is a satisfactory correlation between the results obtained by this HPLC method and those measured by the enzyme immunoassay. Some other common anti-epileptic drugs did not interfere with the analysis. The method is simple and fast and has better sensitivity and linearity than enzyme immunoassay. It is suited for routine therapeutic drug monitoring. 相似文献
54.
Wong A Fettinger JC Forman SL Davis JT Wu G 《Journal of the American Chemical Society》2002,124(5):742-743
We report solid-state 23Na NMR and X-ray crystallographic results for a self-assembled G-quadruplex channel formed by a guanine nucleoside, 5'-tert-butyl-dimethylsilyl-2',3'-O-isopropylidene guanosine (G 1). The study provides an unambiguous 23Na NMR identification for the Na+ ions inside a lipophilic G-quadruplex channel. The crystalline nature of the sample yields a remarkably high resolution in the 23Na multiple-quantum magic-angle spinning (MQMAS) spectrum, making it possible to extract very accurate 23Na NMR parameters for each of the three crystallographically distinct Na sites. The observation of a single Na+ ion from a 9-kDa system demonstrates the potential of solid-state 23Na NMR as a complementary technique to X-ray for detecting Na+ ions in biological structures. 相似文献
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58.
Tei Newman-Lehman Roberto Grana Kalyanasundaram Seshadri Forman Williams 《Proceedings of the Combustion Institute》2013,34(2):2147-2153
Knowledge of combustion of hydrocarbon fuels with nitrogen-containing oxidizers is a first step in understanding key aspects of combustion of hypergolic and gun propellants. Here an experimental and kinetic-modeling study is carried out to elucidate aspects of nonpremixed combustion of methane (CH4) and nitrous oxide (N2O), and ethane (C2H6) and N2O. Experiments are conducted, at a pressure of 1 atm, on flames stabilized between two opposing streams. One stream is a mixture of oxygen (O2), nitrogen (N2), and N2O, and the other a mixture of CH4 and N2 or C2H6 and N2. Critical conditions for extinction are measured. Kinetic-modeling studies are performed with the San Diego Mechanism. Experimental data and results of kinetic-modeling show that N2O inhibits the flame by promoting extinction. Analysis of the flame structure shows that H radicals are produced in the overall chain-branching step 3H2 + O2 ? 2H2O + 2H, in which molecular hydrogen is consumed. Hydrogen is also consumed in the overall step N2O + H2 ? N2 + H2O where stable products are formed. Inhibition of the flames by N2O is attributed to competition between these two overall steps. 相似文献
59.
Sun Y Frenkel AI Isseroff R Shonbrun C Forman M Shin K Koga T White H Zhang L Zhu Y Rafailovich MH Sokolov JC 《Langmuir : the ACS journal of surfaces and colloids》2006,22(2):807-816
We compared the characteristics of dodecanethiolate palladium nanoparticles synthesized by two different techniques, a one-phase method and a two-phase method. From transmission electron microscopy (TEM), we determined that the particle sizes were 46 +/- 10 angstroms and 20 +/- 5 angstroms for the one- and two-phase particles, respectively. Electron diffraction confirmed that their structure was face-centered cubic (fcc). The lattice constant a0 was 3.98 +/- 0.01 angstroms and 3.90 +/- 0.01 angstroms for the one- and two-phase particles, respectively. High-resolution TEM (HRTEM) showed that the one-phase particles had an ordered core surrounded by a disordered shell structure, while the two-phase particles appeared to be crystalline throughout. The particles were also analyzed with extended X-ray absorption fine structure (EXAFS). A cuboctahedral fcc model was used to fit the data, which implied particle sizes of less than 10 angstroms for both the one- and two-phase particles. The discrepancy between the two techniques was attributed to the presence of a disordered phase, which we presumed was composed of Pd-S compounds. Compared with the bulk palladium, lattice expansion was observed in both one- and two-phase particles by electron diffraction, HRTEM, and EXAFS. At the air/water interface, a uniform film that produced surface pressure/area isotherms could only be obtained from the two-phase particles. The one-phase particles did not wet the water surface. X-ray reflectivity data indicated that the Langmuir monolayer of the two-phase particles was only 13 angstroms thick. TEM revealed the diameter of the particles in this layer to be 23 angstroms; hence the particles assumed an oblate structure after spreading. EXAFS examination of a stack of 750 Langmuir monolayers indicated far fewer Pd-S compounds, which may have dissolved in the water. The data were consistent with a model of a monolayer of truncated cuboctahedron Pd particles that were 7 angstroms thick and 19 angstroms in diameter. 相似文献
60.
GS Agarwal 《Pramana》1984,22(3-4):303-312
Nonlinear oscillator models are constructed to treat the bistability in situations involving elementary excitations in solids.
Such models are shown to be useful not only in describing single photon but also multiphoton bistability. The resulting bistability
both with and without cavity is considered. The two-photon excitonic bistability in CuCl is in detail. The effect of local
field corrections can also be incorporated, in a simple manner, in such models. 相似文献
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