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971.
Nitrogen ylides represent an important class of nucleophilic or bifunctional reagents. This digest summarizes the application of diverse nitrogen ylides for the construction of important and interesting carbo- or heterocycles in the reactions with a variety of electrophiles, especially under the catalysis of an organic compound.  相似文献   
972.
The chartreuse monoclinic Ni-dpbz (Ni(L)[Ni(CN)4], (L = 1,4-Bis(4-pyridyl)benzene, or dpbz) crystal assumes a pillared structure with layers defined by 2-D Ni[Ni(CN)4]n nets and dpbz ligands as pillars, linking between coordinated Ni sites. In addition to the hysteretic adsorption/desorption feature of Ni-dpbz, in half of the parallelepiped-shape space enclosed by the pillars and nets, an additional dpbz ligand was found to link between the open ends of two four-fold Ni sites. This arrangement results in an unusual 5-fold pseudo square-pyramid environment for Ni and a significantly long Ni–N distance of 2.369(4) Å. The presence of disordered dimethyl sulfoxide (DMSO) solvent molecules give rise to the formula of Ni(dpbz)[Ni(CN)4]·½dpbz·0.44DMSO. Sorption isotherms showed flexible behavior during the adsorption and desorption of CO2.  相似文献   
973.
《Analytical letters》2012,45(12):897-904
Abstract

Titanocene nitrogen fixation in tetrahydrofuran was significantly affected by traces of water. Water was reduced to hydrogen by titanocene monochloride. In turn, hydrogen was reduced to hydride by titanocene. Analogy with nitrogenase catalysis is discussed.  相似文献   
974.
Here we present an operational method to improve accuracy and information content of ground-based measurements of stratospheric NO2. The motive is to improve the investigation of trends in NO2, and is important because the current trend in NO2 appears to contradict the trend in its source, suggesting that the stratospheric circulation has changed. To do so, a new software package for retrieving NO2 vertical profiles from slant columns measured by zenith-sky spectrometers has been created. It uses a Rodgers optimal linear inverse method coupled with a radiative transfer model for calculations of transfer functions between profiles and columns, and a chemical box model for taking into account the NO2 variations during twilight and during the day. Each model has parameters that vary according to season and location. Forerunners of each model have been previously validated. The scheme maps random errors in the measurements and systematic errors in the models and their parameters on to the retrieved profiles. Initialisation for models is derived from well-established climatologies. The software has been tested by comparing retrieved profiles to simultaneous balloon-borne profiles at mid-latitudes in spring.  相似文献   
975.
INTRODUCTIONAdsorption separation process may be advantageous compared to the conventionally usedmethod based on organic solvent extraction due to its low energy consumption, convenientoperation and high concentrating ability [11. Currently, however, the ability of the commerciallyavailable adsorbentS to selectively adsorb one solute or even families of compounds with similarchemical structUre from a complex system such as the extraction solUtion of Chinese herbalmedicines is limited and…  相似文献   
976.
Photoacoustic NO2 traces detection based on continuous and pulsed lasers emitting at 532 nm is presented. Both systems were calibrated with known NO2-pure air mixtures. A minimum detectable volume concentration of 20 parts in 109 (S/N=1) and 15 parts in 109 for the resonant and pulsed regime, respectively, were obtained. These values were limited by electrical and acoustical noise of the microphone and electronics. Measurements of NO2 concentrations in urban air are compared with home-manufactured mixtures. Traces of nitrogen dioxide from two different car exhausts are also detected and quantitatively assigned from the calibration curves.  相似文献   
977.
The structure and NO reactivity of Zr-deposited Pd surfaces were investigated by X-ray photoelectron spectroscopy, low-energy electron diffraction, infrared reflection absorption spectroscopy, and temperature-programmed desorption. Zr on Pd(1 0 0) was oxidized to ZrO2 by exposure to O2 at 773 K. Heating at 823 K in a vacuum led to decomposition of ZrO2 to Zr metal and O2. The activation energy for ZrO2 decomposition changed remarkably at ΘZr = 0.4. For ΘZr > 0.4, a hexagonal structure was observed for ZrO2/Pd(1 0 0); no ordered structure was observed for ΘZr < 0.4. Deposited Zr had no significant effect on the adsorption and decomposition of NO on Pd(1 0 0) but resulted in a creation of new NO dissociation sites on Pd(3 1 1). Zr on Pd(3 1 1) was oxidized to ZrOX by oxygen produced from NO dissociation. Heating at 823 K in a vacuum led to decomposition of ZrOX to Zr metal and O2.  相似文献   
978.
FITRS combined with15N and18O isotope substitution and TPD have revealed that nitrates are the most abundant ad-NOx species on over-exchanged Cu- and Co-ZSM-5 zeolites. the transformation rates of such species under the action of a propane—oxygen mixture were found to be comparable and sufficiently high to afford steady-state catalytic activities. A scheme of the reaction mechanism including C, N-containing intermediates detected in work is suggested.  相似文献   
979.
Nitridated iron is a promising material for potential applications in permanent magnets. Recent work on stabilization of nitridated iron in a foil form through nitrogen ion implantation and annealing motivates to study effect of thermal annealing on the surface of nitrogen-implanted iron. In this work, we show effect of annealing on chemical state and magnetism of nitrogen implanted epitaxial iron films. It is observed that nitrogen in the lattices only stays at the lower temperatures than 450 °C. In addition, significant reduction and lattice modification are taken placed, when the film is annealed at 450 °C. The increases of saturation magnetization and coercivity, where it is annealed at 450 °C, are likely to be triggered by reduction of oxygen contents at the surface and thinning of Fe2O3.  相似文献   
980.
The pH dependence of the conformation of poly-(L-lysine) with 4.6 mol% of its side chain amino groups attached to an azo dye, 4′ -dimethyl aminoazobenzene-4-carboxylic acid, has been studied. Circular dichroic spectra showed that in acidic as well as in neutral media the polymer exists in the random coil conformation, like that of poly-(L-lysine). In basic medium the polypeptide acquires a β-structure, unlike poly-(L-lysine) which exists in an α-helical conformation.  相似文献   
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