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941.
This paper reports comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC-TOF MS) analysis of Pogostemon cablin Benth (Cablin Parchouli) volatile oil. The suitable column system and operation conditions were chosen on the basis of the properties of composition of the volatile oil. One-dimensional gas chromatography (ID-GC) and GC x GC, GC-MS and GC x GC-TOF MS were compared under appropriate conditions, and the enhanced sensitivity and superior resolution of GC x GC were demonstrated. 394 components were tentatively identified by GC x GC-TOF MS. 相似文献
942.
943.
IntroductionMolecularnonlinearoptics (NLO)hasattractedin creasinginterestoverthepasttenyears ,becauseoftheirpotentialapplicationsinvariousfieldsincludingtelecom munications ,opticaldatastorageandprocessingandopti calpowerlimitation .1,2 Itiswellknownthatthep… 相似文献
944.
研究了RE,Al及Al-RE合金对Zn-2%(质量分数,下同)Ni合金组织中Zn-Ni合金相粒子的细化作用,利用扫描电镜(SEM)及能谱分析(EDS)等方法分析了合金凝固组织特点。结果表明:在Zn-2%Ni合金中,加入0.02%~1%RE会产生新的Zn—RE—Ni合金相粒子,对Zn-Ni合金相粒子没有明显的细化作用;加入0.02%~1%Al,虽然对Zn-Ni合金粒子有细化作用,但此合金组织不适宜在热镀锌中运用。在铝浓度较低(〈0.1%)时。凝固组织中的合金相粒子尺寸不均匀;当铝浓度较高(〉0.2%)时,高熔点、低密度β-NiAl相核心长大,合金相粒子易上浮,出现比重偏析;加入0.02%~0.2%Al-RE时,能形成细小弥散而均匀分布的异质晶核β-NiAl相,促进了γ-Ni2Zn5相的生成,获得细小且均匀分布的γ-Ni2Zn5相。Al-RE合金细化效果明显优于RE和Al,其最佳加入浓度为0.05%~0.1%。 相似文献
945.
946.
Conclusions A short synthesis of R,E-14-methyl-8-hexadecenal (trans-trogodermal) from 1,1-ethylene-dioxy-8-acetoxy-9-decene and R-(-)-1-bromo-4-methylhexane was realized.Translated from Izvestiya Akademii Nauk SSSR, Seriya, Khimicheskaya, No. 4, pp. 903–906, April, 1987. 相似文献
947.
A novel BOD biosensor has been fabricated from a microbial membrane on an oxygen electrode; a porous inorganic Al2O3 sol-gel matrix was used to immobilize the yeast. Use of the sensor is convenient and rapid compared with the official BOD5 method. The gelation time required to form the microorganism membrane was less than 15 min. There was linear relationship between the response (sensor current) and BOD values ranging from 10-50 mg x L(-1). The lifetime of the BOD biosensor was more than 30 days at ambient temperature. 相似文献
948.
In this article, silicone rubber (SR)/clay nanocomposites were synthesized by a melt‐intercalation process using synthetic Fe‐montmorillonite (Fe‐MMT) and natural Na‐MMT which were modified by cetyltrimethyl ammonium bromide (CTAB). This study has been designed to determine if the presence of structural iron in the matrix can result in radical trapping and then enhance thermal stability, affect the crosslinking degree and elongation. The SR/clay nanocomposites were characterized by X‐ray diffraction (XRD) patterns and transmission electron microscopy (TEM). Exfoliated and intercalated nanocomposites were obtained. Thermo gravimetric analysis (TGA) and mechanical performance were applied to test the properties of the SR/clay nanocomposites. The presence of iron significantly increased the onset temperature of thermal degradation in SR/Fe‐MMT nanocomposites. The thermal stability, gel fraction and mechanical property of SR/Fe‐MMT were different from the SR/Na‐MMT nanocomposites. So the iron not only in thermal degradation but in the vulcanization process acted as an antioxidant and radicals trap. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
949.
950.
LC/MS3‐Guided biotransformation of p‐coumaric acid (=(2E)‐3‐(4‐hydroxyphenyl)prop‐2‐enoic acid; CA) with H2O2/Momordica charantia peroxidase at pH 5.0 and 45° in the presence of acetone has resulted in the isolation of three CA trimers, triCA1 ( 1 ), triCA2 (trans‐ 2 ), and triCA3 (cis‐ 2 ), and seven CA dimers, diCA1–diCA7, i.e., 3 – 9 , among which seven (triCA1–triCA3 and diCA1–diCA4) are new compounds and three (diCA5–diCA7) are known compounds. The structures were established by 2D‐NMR such as HSQC, HMBC, and NOESY measurements. The possible mechanism for the formation of the products is also discussed (Schemes 1–3). This is the first time that the biotansformation of p‐coumaric acid catalyzed by peroxidase in vitro was achieved. Compounds triCA3 (cis‐ 2 ), diCA1 ( 3 ), diCA5 ( 7 ), and diCA7 ( 9 ) exhibit a stronger antioxidative activity than the parent CA. 相似文献