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991.
The new hydroxymethylosmium complex (η-C5Me5)Os(CO)2CH2OH has been prepared and its conversion to (η-C5Me5)Os(CO)2H, CO, and H2 either thermally (half life 3 h at 174°C) or by UV irradiation has been studied. Deuterium labelling experiments established that a methylene hydrogen of the hydroxymethyl ligand becomes the hydride hydrogen of the product, and a mechanism is proposed for this process. 相似文献
992.
The anhydrate, dihydrate, and trihydrate phases of chemically pure magnesium stearate and magnesium palmitate have been prepared and characterized as to their structural characteristics. The magnesium palmitate materials were obtained as significantly larger crystals than were the magnesium stearate materials, and the crystals of the dihydrate phase of either material were found to be the most fully developed. The crystal structures of all materials were judged to be very similar to each other, differing primarily in the magnitude of the long (001) crystal spacing. Thermal analysis studies revealed that the water of hydration contained within the dihydrate phases of either magnesium stearate or magnesium palmitate was more tightly bound than was the water of hydration within the corresponding trihydrate phases. These findings provide further support for the structural picture where the water contained in these lattice structures is present between the intermolecular planes. 相似文献
993.
Bursten BE Chisholm MH Clark RJ Firth S Hadad CM MacIntosh AM Wilson PJ Woodward PM Zaleski JM 《Journal of the American Chemical Society》2002,124(12):3050-3063
The compounds ((t)BuCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)C(t)Bu)(3) (M(4)OXA), where M = Mo or W, are shown by analysis of powder X-ray diffraction data to have extended lattice structures wherein oxygen atoms from the oxalate and pivalate ligands of one M(4)OXA molecule are linked to metal atoms of neighboring molecules. Raman, resonance Raman, electronic absorption (2-325 K in 2-MeTHF), and emission spectra are reported, together with corresponding spectra of the mu-O(2)(13)C(13)CO(2) isotopomers. To aid in the assignment, the Raman spectra of K(2)C(2)O(4).H(2)O and K(2)(13)C(2)O(4).H(2)O have also been recorded. The visible region of the electronic spectra is dominated by intense, fully allowed MLCT transitions, M(2) delta to oxalate pi*, which show pronounced thermochromism and extensive vibronic progressions associated with the oxalate ligand at low temperatures. With excitation into these charge-transfer bands, strong resonance enhancement is seen for Raman bands assigned to the oxalate nu(1)(a(g)) and, to a lesser extent, nu(2)(a(g)) modes. Electronic structure calculations for the model compounds (HCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)CH)(3), employing density functional theory (gradient corrected and time-dependent) with the Gaussian 98 and ADF 2000 packages, predict the planar oxalate D(2h) configuration to be favored, which maximizes M(2) delta to oxalate pi* back-bonding, and indicate low barriers (<8 kcal mol(-1)) to rotation about the oxalate C-C bonds. 相似文献
994.
Single-stage anaerobic codigestion for mixture wastes of simulated Korean food waste and waste activated sludge 总被引:2,自引:0,他引:2
Nam Hyo Heo Soon Chul Park Jin Suk Lee Ho Kang Don Hee Park 《Applied biochemistry and biotechnology》2003,107(1-3):567-579
Korean food waste was treated with a single-stage anaerobic codigester (SSAD) using waste activated sludge (WAS) generated
from a municipal wastewater treatment plant. The stability and performance of the system was analyzed. The C/N ratio was improved
with increasing food waste fraction of feed mixture. The pH, alkalinity, and free ammonia nitrogen concentration were the
parameters used to evaluate the digester’s stability. The experimentally determined values of the parameters indicated that
there were no methane inhibitions in the digester. Digester performance was determined by measuring the total chemical oxygen
demand TCOD), volate solids (VS) removal, methane content in biogas, methane production rate (MPR), and specific methane productivity.
Methane content in biogas and MPR were significantly dependent on hydraulic retention time (HRT) and ratio of food waste to
WAS. The methane content in biogas decreased at shorter HRT or higher organic loading rate (OLR) with increased food waste
fraction. Concerning the performance of the codigester, the optimum operating condition of the SSAD was found to be at an
HRT of 10 d with a feed mixture ratio of 50% food waste and 50% WAS. A TCOD removal efficiency of 53.6% and a VS removal efficiency
of 53.7% were obtained at an OLR of 5.96 kg of TCOD/(m3·d) and 3.14 kg of VS/(m3·d), respectively. A maximum MPR of 1.15 m3 CH4/(m3·d) and an SMP of 0.37 m3 CH4/kg of VSfeed were obtained at an HRT of 10 d with a methane content of 63%. 相似文献
995.
Dahl A Eriksson PS Persson AI Karlsson G Davidsson P Ekman R Westman-Brinkmalm A 《Rapid communications in mass spectrometry : RCM》2003,17(19):2195-2202
It is known that proliferation and survival of neural stem/progenitor cells in vitro not only depend on exogenous factors, but also on autocrine factors secreted into the conditioned medium. It is also well known that the identification of bioactive proteins secreted into the conditioned medium poses a substantial challenge. Recently, neural stem/progenitor cells were shown to secrete a survival factor, cystatin C, into the conditioned medium. Here, we demonstrate an approach to identify other low molecular weight proteins in conditioned medium from cultured adult rat hippocampal progenitor cells. A combination of preparative two-dimensional gel electrophoresis (2-DE) and mass spectrometry was utilized in the analysis. We were able to identify a number of proteins, which include Rho-guanine nucleotide dissociation inhibitor 1, phosphatidylethanolamine binding protein (PEBP), also termed Raf-1 kinase interacting protein, polyubiquitin, immunophilin FK506 binding protein 12 (FKBP12) and cystatin C. The presence of PEBP and FKBP12 in conditioned medium was confirmed immunologically. All nestin-positive progenitor cells showed immunoreactivity for antibodies against PEBP and FKBP12. To our knowledge we are the first to use this preparative proteomic approach to search for stem cell factors in conditioned medium. The method could be used to identify novel bioactive proteins secreted by stem/progenitor cells in vitro. Identification of bioactive proteins in vitro is of potential importance for the understanding of the regulatory mechanisms of the cells in vivo. 相似文献
996.
Jeffrey K. Hecht Don T. Dix 《Journal of polymer science. Part A, Polymer chemistry》1972,10(2):369-377
Indene has been copolymerized with polar monomers in the presence of ethylaluminum sesquichloride. The polymers have molecular weights in the 7,000–10,000 range and soften at temperatures above 150°C. The NMR spectra of the copolymers are discussed with reference to polymer structures and chain conformations. Indene is comparable to cyclopentene in reactivity in copolymerizations with methyl acrylate but is much more reactive than cyclopentene toward methyl methacrylate. 相似文献
997.
Abstract— The clinically important phenothiazine drugs, particularly chlorpromazine, often elicit phototoxic and photoallergic reactions. We have used the spin traps 2-methyl-2-nitrosopropane (MNP) and 5,5-dimethyl-pyrroline-N-oxide (DMPO) to define the radical photolysis pathways of chlorpromazine and promazine. In the absence of oxygen the dechlorination product of chlorpromazine is trapped by MNP. The reactivity of the dechlorination product is similar to that of the phenyl radical as shown by its ability to extract hydrogen atoms from donors. Our results suggest that the dechlorination product is sufficiently reactive to account for the observation that chlorpromazine is more phototoxic than its parent promazine. In the presence of oxygen both chlorpromazine and promazine form a superoxide-dismutase-insensitive oxygen-centered intermediate which, when trapped by DMPO, rapidly decays to DMPO-OOH and subsequently to DMPO-OH. In addition, chlorpromazine readily undergoes photoelectron ejection only when it is excited into the second excited singlet state (Δ < 280 nra). This previously unknown wavelength dependence of photoionization should be considered in establishing the mechanism of chlorpromazine photosensitization. 相似文献
998.
Mary Ann B. Meador Diane C. Malarik Michael A. Olshavsky 《Journal of polymer science. Part A, Polymer chemistry》1992,30(2):305-312
1,4,5,8-Tetrahydro-1,4;5,8-diepoxyanthracene reacts with various anthracene end-capped polymide oligomers to form Diels-Alder cycloaddition copolymers. The polymers are soluble in common organic solvents, and dehydrate thermally at temperatures of 300–350°C to give thermal oxidatively stable pentiptycene units along the polymer backbone. Because of their high softening points and good thermal oxidative stability, the polymers are candidates for matrix resins for high temperature composite applications. To assess their usefulness for such applications, several parameters have been studied affecting the properties of the final polymer. These parameters include varying the formulated molecular weight of the end-capped prepolymers, and use of meta-substituted aromatic diamine in place of some of the para-substituted diamine. Processability of the resins was studied using rheometric spectrometry, and a processing scheme was devised. Finally, several formulations of neat resins were compression molded into coupons, and evaluated for longterm stability in air at 315 and 371°C. The best combination of good processability and thermal oxidative stability was obtained from polymers synthesized with small amounts of meta-diamine substitution and higher formulated molecular weight prepolymers. 相似文献
999.
John A. Berry Ann Prescott David W.A. Sharp John M. Winfield 《Journal of fluorine chemistry》1977,10(3):247-254
Rhenium and uranium hexafluorides oxidise elemental iodine in iodine pentafluoride at ambient temperature to give the I2+ cation. With UF6 an additional reaction occurs to give β-uranium pentafluoride as one product, β-UF5 is soluble in acetonitrile without disproportionation and is also formed from the reduction of UF6 by MeCN. Copper, cadmium, and thallium metals are oxidised by ReF6 in MeCN giving CuI, CdII, and TlI hexafluororhenates(V) but the reactions are complicated by reaction between ReF6 and the solvent. 相似文献
1000.
The presence of an additional double bond can change the regioselectivity of the Wacker oxidation of a 1-alkene moiety to give the aldehyde product. 相似文献