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Gradient theory (GT), a form of density functional theory (DFT), was applied to water, methanol, and ethanol using the cubic perturbed hard body (CPHB) equation of state (EOS). Compared to the standard form of classical nucleation theory (CNT), the GT results for water showed an improved temperature dependence, but the supersaturation dependence was slightly poorer. GT and several forms of CNT were also found to be in good agreement with a single high T molecular dynamics rate for TIP4P water. The rates predicted by GT for methanol and ethanol were improved by several orders of magnitude compared to CNT, but no improvement in the predicted temperature dependence of the rates was found. 相似文献
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Marine proteomics: generation of sequence tags for dissolved proteins in seawater using tandem mass spectrometry 总被引：3，自引：1，他引：3
Matthew J. Powell Jennifer N. Sutton Carlos E. Del Castillo Aaron T. Timperman 《Marine Chemistry》2005,95(3-4):183-198
Dissolved proteins in seawater samples from the Gulf of Mexico were concentrated using tangential flow ultrafiltration and methanol/chloroform/water precipitation. Following concentration and purification, two different separation methods were employed. In one method, intact proteins were separated by SDS–PAGE and digested enzymatically in-gel. In the second method, the peptides resulting from a solution proteolytic digest of the whole protein pellet mixture were separated by capillary HPLC. In both methods, the final chromatographic separation was coupled on-line with a mass spectrometer using an electrospray interface, and peptide CID spectra were collected using tandem mass spectrometry (MS). De novo sequencing of the peptide tandem mass spectra generated short amino acid sequences (peptide tags) that were used to search databases for protein class and source information. Trends of conserved sequences for two specific classes of proteins were observed: membrane/envelope proteins and enzymes. Similarity searching of peptide tags produced identification of conserved sequences from several protein homologues originating from many different species, including: long chain fatty acyl CoA synthetase, anthranilate synthase, ribulose bisphosphate carboxylase, and luminal binding protein. These results provide new insight into the sources and production mechanisms for dissolved organic matter (DOM), as there is direct evidence for dissolved proteins other than the bacterial outer membrane proteins reported by Tanoue et al. Furthermore, the data presented herein support the idea that physical protection and selective preservation are not mutually exclusive survival mechanisms, but rather these two models are dependent upon one another for explaining the survival of refractory dissolved proteins in seawater. 相似文献
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Eleven Chinese immature source rock concentrates from the immature oil formations in four different depressions were extracted ultrasonically with a mixture of CS2 and N-methyl-2-pyrrolidinone (CS2/NMP) at room temperature. The samples were also extracted with CHCl3 and a mixture of methanol/acetone/chloroform (MAC) for comparison. The solvent system CS2/NMP is very efficient for the extraction of immature source rock concentrates, giving much higher extraction yields than CHCl3 or MAC. The composition of the extracts using different solvent mixtures is also different. Model compound tests indicate that no chemical reactions have taken place between the NMP and the substrates in the extraction. These results suggest that there are abundant non-covalent bond interactions in the organic matter of the immature source rock concentrates. The fact that CS2/NMP mixed solvent extracts more than MAC and CHCl3 is not only because it can dissolve higher molecular weight fractions, but also because it has stronger ability to disrupt the complex interactions existing between the soluble and insoluble fractions. Biomarker distributions in the saturated hydrocarbon fractions are different for different solvent systems, suggesting that care should be taken when comparing the biomarker parameters in source rocks when using different solvents for extraction. 相似文献
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N. Watanabe A. Nagaoka H. Hidaka T. Shiraki T. Chigai A. Kouchi 《Planetary and Space Science》2006,54(11):1107-1114
Experiments on the hydrogenation of CO on pure CO and CO-H2O mixed ice have been performed at temperatures between 8 and 20 K. We obtained temperature and compositional dependence of the effective reaction rate constants. Results indicate that hydrogenation proceeds efficiently on pure solid CO and CO-H2O mixed ice at temperatures below 10 and 20 K, respectively. Rate constants for pure CO decreased significantly at 12 K compared to those obtained with CO-H2O mixed ice. Hydrogenation of CO at temperatures greater than 12 K were catalyzed by the H2O adjacent to the CO. The importance of the experimental results for some relevant astrophysical environments has also been outlined. 相似文献
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固载杂多酸催化合成富马酸二甲酯 总被引：2，自引：0，他引：2
以富马酸与甲醇为原料，固载杂多酸PW12／C为催化剂合成了富马酸二甲酯。详细探讨了影响酯化反应的各种因素，得出了富马酸与甲醇反应的最佳条件，即m（催化剂）∶m（富马酸）8∶100，n（富马酸）∶n（甲醇）＝1∶8，回流搅拌反应3h。在该条件下，酯化产率为91.6%。结果表明，此法催化剂用量少，催化活性高，反应时间短，酯收率高，反应工艺简单。 相似文献
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A field trial for in-situ bioremediation of 1,2-DCA 总被引：2，自引：0，他引：2
Historic spillages of chlorinated hydrocarbons at a vinyl chloride plant in the Rotterdam Botlek area in The Netherlands have lead to contamination of the underlying aquifer. The principal contaminant is 1,2-dichloroethane (1,2-DCA). The contamination is temporarily contained by a pump-and-treat system. A field trial was carried out to investigate the feasibility of treating the dissolved phase of 1,2-DCA via reductive dechlorination by injection of an aqueous solution of methanol, ammonium chloride and sodium chloride into the confined aquifer using an array of eight boreholes. Biodegradation of 1,2-DCA was localised. This was attributed to limited mixing of the carbon substrate within the test zone. In addition, clogging of recharge wells complicated groundwater circulation. 相似文献
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David J. Clifford Patrick G. Hatcher Robert E. Botto John V. Muntean Beverly Michels Ken B. Anderson 《Organic Geochemistry》1997,27(7-8)
Soluble polylabdanoids isolated by sequential solvent extraction have been characterized by liquid-state 13C- and 1H NMR and 13C-1H HMQC (heteronuclear correlation) NMR spectroscopy in addition to solid-state NMR and Py-GC-MS techniques. Two Holocene resins originating from Santander, Colombia and Mombasa, Kenya were analyzed. Soluble polymers were isolated by extraction with a 1:1 (v/v) methylene chloride-methanol mixture following sequential extractions with methylene chloride and methanol. The molecular weight of polymer extracts was shown by GPC analyses to exceed that of non-polymeric occluded terpenoids. Py-GC-MS, solid-state 13C CP/MAS and 13C cross-polarization/depolarization NMR spectroscopy results indicated that chemical compositions of soluble polymers isolated from immature resins are highly representative of the structure of corresponding insoluble polymers, i.e. polylabdatrienes. These data provide evidence for cross-linking or cyclization of side-chain olefinic carbons during or shortly after polymerization. Generally, the characterization of soluble resin polymers by liquid-state NMR spectroscopy has proven to be an excellent means for investigating the maturation mechanism of polylabdanoid resinites, and has potential for furthering the application of Class I resinites as geothermal indicators. 相似文献
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