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961.
962.
The structures of B32 and B32H2–32 with Ih symmetry have been investigated by means of ab initio calculations at STO-3G level. The relationship between molecular orbitals of them has been analyzed and their bonding properties have been discussed. Then the possibility of their existence, as well as the similarity and difference between B32 (B32H2–32) and C60 (C60H60) have been inferred. 相似文献
963.
Günter Block Dieter Hirschfeld Ilse-Marie Lichtenauer Annette Pohl 《Mikrochimica acta》1992,107(3-6):279-282
The aim of the first part of the paper is to give some advice for the faultless metallographic preparation of vacuum plasma sprayed coatings. Several coating/substrate combinations using metals, alloys and ceramics were investigated to derive some general rules. The second part deals with a preparation technique for cross-sections- of physical vapour deposition coatings. This technique was optimized for TiN and Ti(C, N) coatings on hardmetals which were examined in an analytical transmission electron microscope. 相似文献
964.
本文对CT联合血清同型半胱氨酸(HCY)、β2-微球蛋白(β2-M)在下肢动脉狭窄闭塞性疾病中的诊断价值进行分析。选取上海市金山区中西医结合医院收治的120例疑似下肢动脉狭窄闭塞性疾病患者进行研究,选取同期健康体检者120例作为对照组,对患者进行CT检查、血清HCY和β2-M水平检查,并比较了CT诊断下肢动脉狭窄闭塞情况、两组患者血清HCY和β2-M水平,以明确CT、HCY、β2-M诊断价值及误诊率、漏诊率。结果显示,120例疑似患者中,CT检测出646节段病变血管,其中轻度狭窄155节段,中度狭窄257节段,重度狭窄143节段,血管完全闭塞91节段;研究组患者血清HCY、β2-M水平明显高于对照组,两组比较差异有统计学意义(P<0.05);HCY的AUC为0.863,截断值>21.75(μmol/L),诊断敏感性为79.00%,特异性为80.00%,β2-M的AUC为0.837,截断值>2.98(μmol/mL),诊断敏感性为75.25%,特异性为65.21%;CT诊断阳性率为67.50%,HCY诊断阳性率为69.17%,β2-M诊断阳性率为67.50%,三者联合诊断阳性率为82.50%,联合诊断阳性率高于CT、HCY、β2-M单独诊断阳性率(P<0.05);CT、HCY、β2-M单一检测对下肢动脉狭窄闭塞性疾病均有较高灵敏度、特异性及准确度,但三者联合诊断灵敏度、特异性及准确度最高,误诊率、漏诊率最低。本文证实了采用CT联合血清HCY、β2-M诊断下肢动脉狭窄闭塞性疾病诊断灵敏度、特异性及准确度高,误诊率、漏诊率低。 相似文献
965.
Curing of diglycidyl ether of bisphenol-A (DGEBA) with phosphorus containing amide amines i.e. bis[3(3’-aminobenzamido phenyl)]methyl
phosphine oxide (MB),bis[3(4’-aminobenzamido phenyl)]methyl phosphine oxide (PB), tris[3(3’-aminobenzamidophenyl)] phosphine
oxide (MT) and tris[3(4’-aminobenzamido phenyl)] phosphine oxide (PT)and conventionally used curing agent 4,4’-diaminodiphenyl
sulfone (D) was studied by DSC. The amines MB, PB, MT and PT were synthesised in the laboratory and were characterized by
determining elemental composition, melting point, and amine equivalent. Structural characterization was done by 1H-NMR and FTIR. The onset temperature of curing depended on the nucleophilicity of the amines and was in the orderMT≈MB<PT<PB<D.
The exothermic peak temperatures were in the orderD>PB>PT>MT≈MB. The char residue of cured epoxy resin was significantly higher
when phosphorus was incorporated in the cured network. Using mixed amine formulations based on amine D and P-containing amines
and the molar ratio of these amines could easily control the curing characteristics. A linear relationship between char yield
and P-content was observed in such formulations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
966.
N. A. Talzhanov D. T. Sadyrbekov F. M. Smagulova R. M. Mukanov V. A. Raldugin M. M. Shakirov A. V. Tkachev G. A. Atazhanova B. I. Tuleuov S. M. Adekenov 《Chemistry of Natural Compounds》2005,41(2):178-181
Chemical components from the aerial part of the Kazakhstan population of Artemisia pontica, from which the rarely encountered flavonoids 7-O-methyl- and 4′,7-di-O-methyl-esters of apigenin were isolated for the first time, were identified. The complete chemical composition of the essential oil was established using GC-MS.__________Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 143–145, March–April, 2005. 相似文献
967.
968.
The mercury(II)-catalysed replacement of cyanide in hexacyanoferrate(II) by p-nitrosodiphenylamine (p-NDA) in aqueous solution has been investigated spectrophotometrically by measuring the change in absorbance of the green complex ion, [Fe(CN)(5).p-NDA](3-), at 640 nm. Activation parameters of the catalysed and uncatalysed reactions have been calculated. The effects of the dielectric constant and water content of the medium on reaction rates are used to explain the formation of a polar activated complex and suggest an I(d) mechanism for the catalysed reaction. The varying catalytic activity of Hg(II) as a function of concentration has been discussed. 相似文献
969.
This paper concerns the application of excess adsorption isotherms, measured for solvent mixture/adsorbent systems, to the characterization of TLC data. For this purpose the excess adsorption isotherms for three liquid mixtures: cyclohexane/ benzene, benzene/acetone, and carbon tetrachloride/ethyl acetate on silica gel at 20°C have been measured. These mixtures have been used as binary mobile phases in TLC measurements. It has been shown for a given solute in binary mobile phase that the quantity RM is a simple function of the excess adsorption. Parameters of this function have been used to characterize chromatographic systems with binary mobile phases. 相似文献
970.
CrystalandMolecularStructureof3,4-diphenyl-5-ethyl-5-methyl-1,3,4-diazaphospholidin-2-thione-4-oxide¥FengKe-Sheng;ChenRu-Yu(I... 相似文献