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91.
Mildred M. Maguire Huang Do Son Kim Nguyen Chau Vo Douglas Smith Grant Koher Gregg Doutt Martyn C.R. Symons 《Journal of organometallic chemistry》1984,269(2):183-189
Exposure of (C5H5)2MO(CH3)2 and (C5H5)2W(CH3)2, prepared from the corresponding dichlorides, to 20Co γ-rays at 77 K gave H2C.CML3 carbene species characterised by their ESR spectra, together with a central feature possibly due to the parent cations. Dilute solutions in CD3OD gave features assigned to the parent anions which were converted on bleaching with visible light into methyl radicals, and H2C.ML3 radicals. From the magnitude of the 1H and 183W hyperfine coupling constants, it is deduced that the SOMO for H2C.WL3 radicals is strongly localised on carbon.Dilute solutions in aqueous sulphuric acid also gave species with A(2H) = 20 G, identified as the carbene derivatives, H2C.Ml3. These were formed on annealing, as signals assigned to HSO4 · radicals were lost. 相似文献
92.
Nguyen Q. A. Tucker M. P. Boynton B. L. Keller F. A. Schell D. J. 《Applied biochemistry and biotechnology》1998,(1):77-87
Selective thinning of forests in the western United States will generate a large, sustainable quantity of softwood residues
that can be an attractive feedstock for fuel ethanol production. The major species available from thinning of forests in northern
California and the eastern Rocky Mountains include white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii), and Ponderosa pine (Pinus ponderosa). Douglas fir chips were soaked in 0.4% sulfuric acid solution, then pretreated with steam at 200 – 230°C for 1 – 5 min.
After pretreatment, 90 – 95% of the hemicellulose and as much as 20% of the cellulose was solubilized in water, and 90% of
the remaining cellulose can be hydrolyzed to glucose by cellulase enzyme. The prehydrolysates, at as high as 10% total solid
concentration, can be readily fermented by the unadapted yeastSaccharomyces cerevisiae D5A. 相似文献
93.
J. Edward Schneider Jr. Tahereh Tabatabaie Lindsay Maidt Renee Horning Smith Xuan Nguyen Quentin Pye Robert A. Floyd 《Photochemistry and photobiology》1998,67(3):350-357
A spectrum of oxidative lesions was observed in a bacteriophage-based model system that is very sensitive to the photodynamic activity of selected dyes. When suspensions of the intact bacteriophage Qβ were exposed to methylene blue plus light (MB+L), inactivating events, or "hits" occurred that were oxygen-dependent and that were associated with the formation of several specific lesions: (1) carbonyl moieties on proteins, (2) 8-oxo-7,8-dihydroguanine (8-oxoGua), and (3) single-strand breaks (ssb) in the RNA genome and (4) RNA-protein crosslinks. Formation of carbonyl groups associated with protein in the Qβ phage preparation correlated positively with photoinactivation of the phage with increasing doses of either of the sensitizers MB or rose bengal. Strand breaks in the Qβ genomic RNA were observable at high MB concentrations but appeared not to be significant at the lower concentrations of MB, as full-length Qβ RNA was observable well beyond the 99% inactivation point in MB dosage. It was shown that the number of 8-oxoGua lesions were unlikely to be sufficient to account for the number of lethal events. Following exposure to MB+L, crosslink formation between Qβ RNA and protein was observed by virtue of the location of RNA at the interface of phenol-aqueous extractions of phage suspensions. A significant increase over background of RNA-protein complexes (including full-length Qβ RNA) was observed at the lowest concentration of MB tested (0.5 μ M ), which corresponded roughly to an average of 2 lethal hits per phage or approximately 13% survival compared to the zero MB control (100% survival). Due to its close correlation with Qβ inactivation and its expected lethality, RNA-protein crosslink formation may be important as an inactivating lesion in bacteriophage Qβ following MB+L exposure. 相似文献
94.
The separation characteristics of alkylchloroformate-derivatised amino acids (AAs) by using comprehensive two-dimensional gas chromatography (GC×GC) is reported. The use of a low-polarity/polar column set did not provide as good a separation performance as that achieved with a polar/non-polar column set, where the latter appeared to provide less correlation over the separation space. The degree of component correlation in each column set was estimated by using the correlation coefficient (r2; for 1tR and 2tR data) with the low-polarity/polar and polar/low-polarity sets returning correlation coefficients of 0.86, and 0.00 respectively, under the respective conditions employed for the experiments. The 1.5-m non-polar 2D column (0.1-mm ID; 0.1-m film thickness) gave peak halfwidths of the order of 50–80 ms. Linearity of detection was good, over a three order of magnitude concentration range, with typical lower detection limit of ca. 0.01 mg L–1, compared with 0.5 mg L–1 for normal GC operation with splitless injection. The method was demonstrated for analysis of AAs in a range of food and beverage products, including wine, beer and honey. The major AA in these samples was proline. The Heineken beer sample had a relatively more complex and more abundant AA content compared with the other beer sample. The wine and honey samples also gave a range of AA compounds. Repetition of the sample preparation/analysis procedure for the honey sample gave acceptable reproducibility for individual AAs. 相似文献
95.
20-Deoxoluteone has been synthesized from sclareol. Sclareol was brominated with phosphorus tribromide to form a mixture of primary allyl bromides, from which, by the malonic synthesis, a mixture of bicyclogeranylgeranylacetic acids was obtained which was cyclized with fluorosulfonic acid to form a mixture of two diastereomeric -lactones. The predominating lactone was converted by successive reduction with lithium tetrahydroaluminate, oxidation with oxalyl chloride in dimethyl sulfoxide, reaction with methylmagnesium iodide, and oxidation by the chromium trioxide/pyridine complex into 20-deoxyluteone.Institute of Chemistry, Moldavian SSR Academy of Science, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 346–353, May–June, 1990. 相似文献
96.
Résumé Le thiocarbohydrazide est un réactif d'accès facile précipitant quantitativement les aldéhydes et quelques cétones. Les points de fusion sont nets. Les précipités formés se prêtent à la gravimétrie. Nous avons étudié avec la thermobalance leur domaine de stabilité et fourni la température à ne pas dépasser pour le séchage à poids constant.
Summary Thiocarbohydrazide is a readily available reagent which quantitatively precipitates aldehydes and some ketones. The melting points are sharp. The resulting precipitates are suitable for gravimetry. Their regions of stability have been investigated with the thermobalance and the temperatures which should not be exceeded in drying to a constant weight have been found.
Zusammenfassung Thiocarbohydrazid ist ein leicht zugängliches Reagens zur quantitativen Fällung der Aldehyde und mancher Ketone. Die Schmelzpunkte der Niederschläge sind scharf. Diese eignen sich zur gravimetrischen Auswertung. Ihre Stabilität wurde mit Hilfe der Thermowaage untersucht und die Höchsttemperaturen für ihre Trocknung bis zur Gewichtskonstanz bestimmt.相似文献
97.
Nguyen Ai Viet 《Czechoslovak Journal of Physics》1981,31(3):269-274
In this paper the analytical expression is derived for the third-order optical harmonic coefficients x
abcd
v
(,,) of the atomic hydrogen at very low frequencies 0 in many level of the discrete energy spectrum.The author expresses his thank to Prof. Nguyen Van Hieu for suggesting the problem and fruitful discussions. 相似文献
98.
Spin gapless semiconductor like Ti2MnAl film as a new candidate for spintronics application 下载免费PDF全文
Wuwei Feng Xiao Fu Caihua Wan Zhonghui Yuan Xiufeng Han Nguyen Van Quang Sunglae Cho 《固体物理学:研究快报》2015,9(11):641-645
A novel Heusler ferrimagnet Ti2MnAl film has been grown on Si(001) substrate using magnetron sputtering. Characteristics of its magnetic and transport properties reveal the spin‐gapless‐semiconductor (SGS) nature of the stoichiometric Ti2MnAl, in agreement with theoretical prediction. The as‐grown SGS‐like Ti2MnAl film demonstrated high Curie temperature, nearly compensated ferrimagnetic properties with small coercivity and low magnetization. It also showed semiconductor‐like behavior at room temperature allowing good compatibility with commercial Si‐based semiconductor. In this regards, Ti2MnAl film is a potential candidate material for spintronics application, especially for the minimization of energy consumption of device. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
99.
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