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161.
Two new imidoylnitrenes and alkoxycarbonylnitrene form a sequence of reactivities : Only ROCON attacks CH bonds, it and ROC(NCN)N convert benzene to azepines. Benzene is not attacked by ROC(NSO2CH3)N, but all three nitrenes react with olefins, alcohols, etc. 相似文献
162.
Fabrication of nanoscale metallic spirals using phospholipid microtubule organizational templates 总被引:3,自引:0,他引:3
We describe the fabrication of metallic Cu spiral/helical nanostructures prepared via selective electroless metallization of a phospholipid microtubule template. The metallization template is created through selective, sequential adsorption of the oppositely charged polyelectrolytes, sodium poly(styrenesulfonate) (PSS) and poly(ethyleneimine) (PEI), onto nanoscale seams naturally occurring on the microtubule surface. A negatively charged Pd(II) nanoparticle catalyst is bound to the terminal cationic PEI layer of the multilayer film and initiates selective template metallization to form the helical Cu nanostructures. Details of the process are presented, and a mechanism and factors affecting the control of the feature critical dimensions are discussed. 相似文献
163.
The MNDO scheme has been reparametrized for hydrocarbons using both molecular binding energies and heats of formation at 0 K as experimental reference data. Compared with MNDO, there are only minor changes in the optimized parameters, and the results are essentially of the same accuracy. These tests justify the use of heats of formation at 298 K as reference data in the original MNDO parametrization. 相似文献
164.
Analysis, purification and properties of a 50,000-dalton membrane-associated phosphoprotein from human platelets 总被引:3,自引:0,他引:3
Recently, the development of a monospecific antiserum against a 46,000/50,000-dalton membrane protein from human platelets which was stoichiometrically and reversibly phosphorylated in intact human platelets in response to vasodilators was reported. Using this antiserum, the subcellular distribution and the purification of this vasodilator-stimulated phosphoprotein (VASP) from human platelets has now been analysed. The VASP of human platelets is primarily a membrane-associated protein and can be purified to apparent homogeneity by salt extraction and sequential ion-exchange and dye-ligand chromatography with a purification factor of 1200 and a yield of 13%. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis under reducing and non-reducing conditions indicated that purified monomers of this VASP are linked by interchain disulphide bonding. 相似文献
165.
1-, 2-cis-, 2-trans-, and 3-trans-heptenes (C7)are isomerized either very slowly or not at all with IrX(CO)L2 at 80°C in toluene and under N2. However, under the conditions of hydrogenation fast isomerisation takes place. With IrCl(CO)L2 as catalyst the rate of isomerisation decreases the order: 1-C7 ∼ 2-cis-C7 > 3-trans-C7 > 2-trans-C7. This sequence is independent of the ligand L in lrCl(CO)L2, however, with a particular isomer the rate of isomerisation is a function of L in the order L = PPh3 > P(C6H11)3 > P(OPh)3. 相似文献
166.
Losod, a new type of crystalline hydrated sodium aluminosilicate, Na12Al12Si12O48 · q H2O, has been prepared from reaction mixtures containing bulky quaternary alkylammonium ions, particularly azonia-spiro[4.4]nonane, besides sodium ions. Losod crystallizes from batches with a low sodium content (Na/Al ≤ 1 and Si/Al ≈? 1). The quaternary ammonium hydroxide primarily serves as a source of hydroxide ions and is not incorporated into the zeolite crystals. These bulky bases provide a useful means for controlling the alkalinity of the system independently of the concentration of the necessary cations built into the zeolite. The crystals of Losod are hexagonal (a = 12.91 and c = 10.54 Å) and the proposed framework structure shows a polytypic relationship to sodalite and cancrinite. Losod has reversible sorption and ion exchange properties typical of a small-pore zeolite and in essential agreement with the proposed structure. 相似文献
167.
168.
The syntheses of p-substituted 2-methyl-4-phenylbuten(1)-carboxylic acid derivatives are described, using Blanc's chloromethylation reaction, the Friedel-Crafts alkylation of unsaturated ketones or the Meerwein arylation; the formed intermediates react in subsequent steps to the title compounds. 相似文献
169.
Walter Harm 《Photochemistry and photobiology》1968,7(1):73-86
Abstract— Exposure of E. coli B/r and B at low average dose rates of u.v. radiation (2537 Å), produced either by fractionated doses or by continuous irradiation at a very low dose rate (80 ergs/mm2 /hr), results in much increased survival compared to single exposure at high dose rate. This increase is attributed to repair taking place during the irradiation period. The effect is small in the repair-deficient strains E. coli B8-1 _, and C syn- , and is absent in phage T1 and T4, which cannot undergo repair in the extracellular state. However, the prolonged time available for repair in these experiments accounts for only a very minor part of the increase in survival. The principal factor apparently is that the number of lesions present at any time remains relatively low. Presumably complete repair, not only the excision step, can occur in buffer during the irradiation period. This interpretation is supported by experiments in which cells were exposed to combinations of highly fractionated irradiation and single-dose irradiation. We therefore propose that mutual interference in repair, possibly by overlapping of repair regions in complementary DNA strands, reduces considerably the repair efficiency if many lesions are present. This hypothesis explains the 'shouldered' survival curves of B/r and possibly other E. coli strains as due to decreasing repair efficiency with increasing u.v. dose 相似文献
170.