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排序方式: 共有241条查询结果,搜索用时 15 毫秒
1.
The evaluation of second derivatives of the electronic energy for nonvariational wave functions using an energy functional is discussed. It is shown that, in certain cases, the formation of the first-order relaxed density matrix leads to an efficient algorithm for the calculation of second-order response properties. Detailed formulas are given for second-order Møller–Plesset perturbation theory. © 1994 John Wiley & Sons, Inc. 相似文献
2.
Jaume Carbonell Jean -Marc Richard Slawomir Wycech 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(3):325-329
We study the Coulomb and threshold corrections to the low-energy scattering parameters for the proton-antiproton system, with numerical examples based on current optical models. Some commonly used expressions are shown to be inconsistent with our results. We check that the Trueman formula is valid for the level shifts of protonium, provided one takes properly into account the Coulomb corrections to the scattering lengths and volumes. 相似文献
3.
Timerbaev AR Aleksenko SS Polec-Pawlak K Ruzik R Semenova O Hartinger CG Oszwaldowski S Galanski M Jarosz M Keppler BK 《Electrophoresis》2004,25(13):1988-1995
Characterizing how platinum metallocomplexes bind to human serum albumin (HSA) is essential in evaluating anticancer drug candidates. Using cisplatin as a reference complex, the application of capillary electrophoresis (CE) to reliably assess drug/HSA interactions was validated. Since this complex is small compared to the size of the protein, the binding response could only be recognized when applying CE coupled to a (platinum) metal-specific mode of detection, namely inductively coupled plasma-mass spectrometry (ICP-MS). This coupling allowed for confirmation of a specific affinity of cisplatin and novel Pt complexes to HSA, measurement of the kinetics of binding reactions, and determination of the number of drug molecules attached to the protein. As the cisplatin/HSA molar ratio increased, the reaction rate became faster with a maximum on the kinetic curve appearing at about 50 h of incubation at 20 times excess of cisplatin. The reaction was characterized as a pseudo-first order reaction with the rate constant k = 0.003 min(-1) at 37 degrees C. When incubated with a 20-fold excess of cisplatin, HSA bound up to 10 mol of Pt per mol of the protein. This is indicative for a strong metal-protein coordination occurring at several HSA sites other than the only protein cysteine residue. Structural analogs of cisplatin, bearing aminoalcohol ligands, showed comparable protein binding reactivity and stoichiometry but a common equilibrium was not reached even after one week of incubation. Also apparent was a two-step mechanism of the binding reaction. Results demonstrated the suitability of CE-ICP-MS as a rapid assay for high-throughput studying of drug/HSA interactions. 相似文献
4.
Jerzy Lange Elzbieta Pytlewska Jan Plenkiewicz Tomasz Kulinski Janina Karolak-Wojciechowska Slawomir Rump 《Journal of heterocyclic chemistry》1997,34(2):389-396
Ethoxycarbonylalkylidene derivatives 2 and 6 of the title hydrazones were obtained in the reaction with ethyl pyruvate or ethyl aroylformate and ethyl acetoacetate, respectively, in methanol. Both compounds were mixtures of geometric isomers with high predominance of one of them. Nmr spectroscopy revealed an unexpected magnetic non-equivalence of the CH2 protons in the ester ethyl group of the major isomer of 6 . On heating (?200°) in an inert medium or on refluxing in ethanolic sodium ethoxide 2 cyclized to the corresponding pyridazino[6,1-c]-triazines 4 , whereas 6 formed pyrazolylpyridazines 7 . The structure of the latter was unambigously established by X-ray analysis. Alkylation of 4a with benzyl bromide in the presence of tetrabutylammonium bromide occurred selectively on the pyridazine N atom. 相似文献
5.
Sek S Tolak A Misicka A Palys B Bilewicz R 《The journal of physical chemistry. B》2005,109(39):18433-18438
Polyalanine derivatives containing cysteamine linker R-(Ala)14NH-(CH2)2-SH, where R is ferrocenecarbonyl or hydrogen, were synthesized and then used to form self-assembled monolayers on gold. The tilt angles and the packing density of the molecules within monolayer assemblies were determined by FTIR spectroscopy and scanning tunneling microscopy, respectively. Electrochemical properties of monolayer-modified electrodes were studied using cyclic voltammetry and impedance spectroscopy. Measurements of electron-transfer rates using electrochemical techniques and scanning tunneling spectroscopy revealed asymmetry dependent on the applied voltage. It is suggested that the observed electron-transfer behavior is connected with the electric field generated by the molecular dipole of the polyalanine helix. 相似文献
6.
J. Solecki M. Reszka S. Chibowski 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(2):261-265
Radioactivity of 90Sr and 137Cs in several species of herbs collected at Fajsawice and Góra Puawska located in Lublin (Poland) region was examined. Depending on the type of herb the radioactivity of strontium ranged from 0.004 to 1.808 Bq/kg dry weight whereas that from cesium varied from 0.053 to 9.853 Bq/kg. Calculated transfer factors of the radioisotopes in the plants studied revealed much stronger accumulation of strontium than cesium. Concentration of calcium and potassium in these plants has no influence on the concentration of measured radioisotopes. 相似文献
7.
S. Chibowski J. Solecki J. Szczypa 《Journal of Radioanalytical and Nuclear Chemistry》1997,220(2):183-190
An investigation of the presence of some radioactive isotopes in the bottom sediments of two lakes, Piaseczno and Masluchowskie (Middle East of Poland) has been performed. Similar measurements were done at the Zalew Zemborzycki artificial water reservoir, filled up few years after the most intensive period of atmospheric nuclear explosions. It was estimated, that the concentration of radionuclides, especially of artificial origin was much greater in natural lakes than in examined artificial one. That testifies for an accumulation of radioactive substances on the bottom of the water tanks. The confirmation of this thesis may be the fact, that 85% of137Cs detected in Zalew Zemborzycki comes from Chemobyl fallout while in natural lakes this isotope amounts only to 56–60%. Other isotopes, such as210Pb,226Ra, and224Ra were detected in significant amounts. The radioactivity of239,240Pu isotopes reaches 2.2–2.6 Bq/kg for the lakes and 0.7 for Zalew Zemborzycki. The238Pu to239,240Pu ratio suggests, that detected plutonium comes from world fallout. 相似文献
8.
J. Solecki 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):357-364
Summary Results
of studies of Na+, K+ and Cs+ influence on the
adsorption of 85Sr on soil samples of the different types of
successive horizons are presented. It was proved that the adsorption isotherms
in log-log coordinates are of straight-line type and may be described by the
Freundlich equation. Monovalent cations influence the coverage degree of the
soil surface by 85Sr (most often lowering it) in the following order
K+3Na+3Cs+.
The investigation of pH influence proved its essential meaning in the process.
The plateau of surface coverage degree versus pH lies above pH 5.5 or 6.5
depending on the soil type. Generally, in the studied system, the size of 85Sr
adsorption depends on the concentration of the isotope, pH of the solution,
type of monovalent cation, and on the soil properties.</p>
</p> 相似文献
9.
Marian Mikolajczyk Slawomir Grzejszczak Katarzyna Korbacz 《Tetrahedron letters》1981,22(32):3097-3100
A convenient synthesis of vinylphosphonates which involves addition of elemental selenium to phosphonate carbanions followed by alkylation and selenoxide elimination is described. A general approach to 1,4-dicarbonyl systems based on diethyl α-methylthiovinylphosphonate is also reported. 相似文献
10.
We construct a non-commutative *-algebra
which is a quantum deformation of the algebra of continuous functions on the closed unit disc
.
is generated by the Toeplitz operators on a suitable Hilbert space of holomorphic functions onU.Supported in part by the National Science Foundation under grant DMS/PHY 88-16214 相似文献