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排序方式: 共有183条查询结果,搜索用时 15 毫秒
1.
Daniel R. Coulter Ranty H. Liang Salvador Di Stefano Jovan Moacanin Amitava Gupta 《Chemical physics letters》1982,87(6):594-598
Transient emission studies following pulse radiolysis of solid poly(1-vinyl naphthalene) show existence of excited monomers and two excimers. Quenching experiments indicate that excimers are not formed directly by recombination of ions but probably by trapping of migrating monomeric excitation in performed traps whose density is approximately one in 103. 相似文献
2.
A kinetic method for the determination of codeine, based on its inhibitor action on the catalytic decomposition of hydrogen peroxide by cobalt(II), is presented. It has been found that the effect of codeine is most pronounced in the presence of 5% v/v ethylene glycol. The reaction is followed photometrically. Codeine can be determined in concentrations ranging from 0.80×10–5
M to 2.4×10–5
M. The method has been applied to the determination of codeine in pharmaceutical preparations. 相似文献
3.
A kinetic method for the determination of selenium(IV) traces is proposed, based on its inhibitory action on the oxidation of Nile Blue A by hydrogen peroxide in phosphate buffer (pH 10.5). A linear dependence was established between the rate of the proposed indicator reaction and selenium concentration in the range 9.5 × 10–2-1.58 ng cm–3. The experimental conditions of maximal selenium effect were established. Selenium, determined by the tangent method, was determined at concentrations over the range 0.22–1.26 ng cm–3, with relative standard deviations up to 4.5%. The reaction rate was followed spectrophotometrically. The effect of foreign ions on the accuracy of this method was also investigated. The method was applied to the determination of selenium in pharmaceutical preparations and wheat flour. 相似文献
4.
Gordana A. Milovanović 《Microchemical Journal》1983,28(3):437-457
A review on the determination of organic substances by kinetic-catalytic methods of analysis is given.Methods based on homogeneous catalyzed solution reactions as well as those based on heterogeneous catalyzed electrode reactions are discussed. 相似文献
5.
6.
Matilda Vojnović Ana J. Šetrajčić-Tomić Siniša M. Vučenović Jovan P. Šetrajčić 《Optical and Quantum Electronics》2018,50(4):198
Recent research in nano-optical engineering and in nanomedicine as well, seeks for methods of construction of various types of nano-markers, nano-carriers, and ways to deliver drugs to the exactly determined regions of body. In this process it is important to find methods of recognition of certain types of molecules. It is obvious that optical recognition would be the easiest and the most effective way to do it. Our research presents a model of a molecular ultrathin crystalline film and generated exciton system inside it and corresponding methodology of analysis of their optical characteristics. Properties of these spatially very restricted structures are very sensitive to their surrounding surfaces. Using the two-time Green’s functions adapted for crystalline structures with symmetry breaking, and graphical-numerical software, we have calculated the energy spectra and possible exciton states. We have shown that the appearance and the presence of localized states on the surfaces and in the boundary layers of the film depend on the thickness of the film and the film surroundings, presented through the perturbation of parameters on surfaces. Optical properties in these structures demonstrate discrete and very selective resonant absorption spectra, depending on the perturbation on their surfaces. 相似文献
7.
Milica V. Milovanovi Efrat Shimshoni 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
We study bulk and edge correlations in the compressible half-filled state, using a modified version of the plasma analogy. The corresponding plasma has anomalously weak screening properties, and as a consequence we find that the correlations along the edge do not decay algebraically as in the Laughlin (incompressible) case, while the bulk correlations decay in the same way. The results suggest that due to the strong coupling between charged modes on the edge and the neutral fermions in the bulk, reflected by the weak screening in the plasma analogue, the (attractive) correlation hole is not well defined on the edge. Hence, the system there can be modeled as a free Fermi gas of electrons. We finally comment on a possible scenario, in which the Laughlin-like dynamical edge correlations may nevertheless be realized. 相似文献
8.
9.
Miloš Milovanovi? 《Polymer Degradation and Stability》2006,91(12):3221-3229
The kinetics and mechanism of the thermal degradation of poly(diethyl fumarate) (PDEF) were studied by thermogravimetry, as well as by analysis of the thermolysis volatiles and polymer residue. The characteristic mass loss temperatures were determined, as were the overall thermal degradation activation energies of three PDEF samples of varying molar mass. Ethylene and ethanol were present in the thermolysis volatiles at degradation temperatures below 300 °C, while diethyl fumarate was also evidenced at higher degradation temperatures. The amount of monomer increased with increasing degradation temperature. The dependence of the molar mass of the residual polymer on the degradation time and temperature was established and the number of main-chain scissions per monomer unit, s/P0, calculated. A thermal degradation mechanism including de-esterification and random main-chain scission is proposed. The thermal degradation of PDEF was compared to the thermolysis of poly(ethyl methacrylate) (PEMA), poly(diethyl itaconate) (PDEI) and poly(ethyl acrylate) (PEA). 相似文献
10.
Vojislav Spasojevic Ana Mrakovic Marija Perovic Vladan Kusigerski Jovan Blanusa 《Journal of nanoparticle research》2011,13(2):763-771
Single-phase perovskite compound La0.7Ca0.3MnO3 was synthesised by a high-energy ball milling in a single step processing. Structure and morphology characterizations revealed
nanoparticle nature of this mixed valent manganite with the average particle diameter of 9 nm. Comprehensive set of magnetic
measurements showed that the system can be described as an ensemble of interacting magnetic nanoparticles where each particle
possesses high magnetic moment, i.e., superspin. Furthermore, magnetic behavior showed contributions from both superspin-glass
(SSG) and superparamagnetic (SP) states, and the prevailing properties depended on the experimental conditions. It was established
that SSG state dominated in low magnetic fields up to 500 Oe while in higher applied fields suppression of collective behavior
occurred and individual characteristics of nanoparticles prevailed. It was also concluded that the applied method of synthesis
produced system with high magnetic anisotropy as well as with the large nanoparticle shell whose thickness amounts 30% of
a particle diameter. 相似文献