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991.
992.
993.
Chong Soo Han 《Reaction Kinetics and Catalysis Letters》1996,57(2):247-254
The adsorption of oxygen on ZnO
has been studied by observing the nonohmic characteristics of contacted ZnO
crystals. When the sample assembly was evacuated at 773 K, there was a negative peak at the bias of 10 mV in the(I-kV) vs. V plot. When the assembly was exposed to oxygen at 298–573 K, the mean conductivity decreased and a negative peak at the bias of 50–230 mV was found in the(I-kV) vs. V plot. To analyze the experimental results, a simple model was developed assuming the contact to be of two semiconductor surfaces separated by a finite distance. From the experimental results and theoretical suggestions, we estimated the height of surface barrier during oxygen adsorption. 相似文献
994.
Chong LT Bandyopadhyay P Scanlan TS Kuntz ID Kollman PA 《Journal of computational chemistry》2003,24(12):1371-1377
Direct hydroxide attack on the scissile carbonyl of the substrate has been suggested as a likely mechanism for esterase antibodies elicited by phosphonate haptens, which mimic the transition states for the alkaline hydrolysis of esters.1 The unique amidase activity of esterase antibody 43C9 has been attributed to nucleophilic attack by an active-site histidine residue.2 Yet, the active site of 43C9 is strikingly similar to those of other esterase antibodies, particularly 17E8. We have carried out quantum mechanical calculations, molecular dynamics simulations, and free energy calculations to assess the mechanism involving direct hydroxide attack for 43C9. Results support this mechanism and suggest that the mechanism is plausible for other antiphosphonate antibodies that catalyze the hydrolysis of (p-nitro)phenyl esters. 相似文献
995.
Stephen R. Langhoff Richard L. Jaffe Delano P. Chong 《International journal of quantum chemistry》1983,23(3):875-886
The valence-shell vertical ionization potentials of Cl2 were calculated by perturbation corrections to the Koopmans theorem using a traditional effective core potential based on a Phillips–Kleinman derivation and an improved effective core potential obtained by Christiansen, Lee, and Pitzer. Comparison of the results with an all-electron calculation demonstrated the reliability of the Christiansen–Lee–Pitzer effective core potential, which was then used to compute the vertical ionization potentials of ClN3 and ClNCO. The results shed new light in the interpretation of the photoelectron spectra of these molecules. 相似文献
996.
Yu CJ Wang H Wan Y Yowanto H Kim JC Donilon LH Tao C Strong M Chong Y 《The Journal of organic chemistry》2001,66(9):2937-2942
We have synthesized two novel phosphoramidites with a ferrocenyl moiety at the 2'-ribose position linked through a butoxy linker. Using automated DNA/RNA synthesis techniques, oligonucleotides containing ferrocene at various positions were prepared and characterized by HPLC, MALDI-TOF mass spectrometry, and electrochemistry. Thermal stability studies of the ferrocene-modified DNA duplexes revealed that introduction of one or two ferrocenyl complexes does not result in an observed change of the T(m) values of the corresponding DNA duplexes when compared to the nonmodified hybrids. These data indicate that the introduction of a ferrocenyl group at the 2'-position of the ribose ring containing either a purine or pyrimidine base has no effect on the stability of the modified DNA. The electrochemical behavior of the ferrocene-containing DNA was examined by cyclic voltammetry. The modified 2'-ferrocene-oligonucleotides are electrochemically active and can be used as signaling probes for the electronic detection of nucleic acids on bioelectronic sensors. 相似文献
997.
应用ESR技术对一变质系列煤的自由基特性进行了实验研究,探讨了煤中自由基的起源、性质和数量的变化,并将其与煤的大分子结构相关联。结果表明,煤自由基特性在煤化过程中的规律性较好。 相似文献
998.
999.
1000.
Warren T. Ford Glenn H. Beasley Berni P. Chong James W. Neely 《Journal of polymer science. Part A, Polymer chemistry》1982,20(5):1213-1229
Carbonaceous adsorbents are obtained by thermolysis of sulfonated macroreticular polystyrene ion exchange resins at 300-500°C. The hard, spherical, carbonaceous particles react exothermally with elemental chlorine to form products containing up to 38% Cl. The chlorinated particles react readily with polyamines to form anion exchange resins with capacities of up to 2.2 meq/g dry resin. Less than 60% of the nitrogen atoms in the particles are utilized as ion exchange sites. The carbonaceous particles can also be chloromethylated with chloromethyl methyl ether or chlorinated with sulfuryl chloride and then aminated with polyamines to form anion exchange resins, sulfonated with sulfuric acid or chlorosulfonic acid to form strongly acidic cation exchange resins, or chlorosulfonated and then aminated with polyamines to form anion exchange resins. Model structures of the thermolyzed resins containing polycyclic aromatic hydrocarbon fragments are proposed to explain their chemical reactivities. 相似文献