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21.
22.
以L-脯氨酸/吡啶为催化剂,茴香醛和丙二酸为原料,经Knoevenagel 缩合反应合成了对甲氧基肉桂酸.考察了带水剂种类、原料摩尔比、催化剂L-脯氨酸和吡啶用量、反应时间等对对甲氧基肉桂酸收率的影响.结果表明,在以正己烷为带水剂(用量50 mL),茴香醛用量5 mL(0.041 5 mol),丙二酸与茴香醛摩尔比1.2∶1,L-脯氨酸用量(以丙二酸质量计)4.0%,吡啶用量5 mL,反应时间3 h的条件下,对甲氧基肉桂酸重结晶收率达90.0%. 相似文献
23.
Laurus nobilis L., commonly known as daphne tree, is an evergreen that belongs to the Lauraceae family. Daphne trees produce grape-sized
shiny purplish berries having three parts: flesh, skin, and an inner kernel (single seed). This study examines supercritical
CO2 (SC-CO2) extraction of oil from daphne seeds. The oil yield of ground seeds varied from 14 to 28% depending on the method and particle
size used for oil recovery. Yields were similar for both petroleum ether and SC-CO2 extraction. The extraction yield decreased significantly with increasing particle size. The amount of extract collected increased
exponentially with increasing SC-CO2 pressure. The highest extraction yield was obtained at the highest temperature studied, 75°C. More than 45% of the oil was
lauric acid. SC-CO2 is a viable technique to obtain high-purity L. nobilis L. seed oil, which is a potential ingredient for the cosmetic industry. 相似文献
24.
An experiment to remove re-deposited layers and to release hydrogen using a glow discharge in oxygen (O-GDC) has been performed in the HT-7 superconducting tokamak. In the absence of magnetic fields, the O-GDC wall conditioning had produced rapid, controlled co-deposit removal. Average removal rates, 5.2 × 1022 H-atoms/h, 5.65 × 1021 D-atoms/h and 5.53 × 1022 C-atoms/h, respectively, were obtained during 145 min O-GDC experiment in the pressure range 0.5-1.5 Pa. The corresponding removal rate of co-deposited films was ∼1.19 μm/day (26.5 g/day for carbon) based on an area of 12 m2. Compared to thermo-oxidation and O-ICR experiment, high pressure O-GDC wall conditioning promoted the oxidation and improved the C and D atoms removal. In the O-GDC experiment, the removal rates of H-atoms and D-atoms as H2O, HDO and D2O were higher than that of H2 and D2 by factors of about 20 and 50, respectively. During the 145 min O-GDC experiment, about 14.5% O-atoms were converted into carbon oxides and hydroxides, and about 5.37 × 1022 O-atoms were adsorbed on the walls corresponding to a coverage of 4.5 × 1021 O/m2 on an wall area of 12 m2. In a 100 min helium glow discharge (He-GDC) following the O-GDC experiment, 1.53 × 1022 O-atoms, about 28.5% oxygen retained on the walls, were removed. The removal rate of H-atoms in He-GDC cleaning after O-GDC experiment was lower than that in He-GDC cleaning before O-GDC experiment, which indicates that the O-GDC wall conditioning had effectively reduced hydrogen retention on the walls. 相似文献
25.
介绍了作者研制的应用于固态雷达发射机上的L波段500W固态功放组件的工作原理、用途及其主要技术指标。描述了功放组件的设计过程和测试结果。该功放组件在窄脉宽条件下实现了快速上升沿,性能优良,工作稳定可靠。 相似文献
26.
The equilibrium moisture content (EMC) characteristics of high oleic sunflower seeds and kernels between 10 and 55°C were determined by equilibrating the samples to known relative humidities (RH) above saturated salt solutions. EMC of the kernels was lower than that of seeds in the range of 11 to 96% ERH and at 25 and 40°C. Hysteresis effect was found for the EMC properties of seeds and kernels at 25°C. Four EMC-ERH models (modified Henderson, Chung-Pfost, Halsey, and Guggenheim-Anderson-de Boer) and their estimated parameters were evaluated for goodness of fit. GAB and Halsey equations showed the best fitting of experimental data although GAB equation adjusted for temperature described the EMC data the best. Components of the seed as oil content or hull/kernel ratio did not explain the slight differences in EMC found between the varieties. 相似文献
27.
Recently a method that uses water droplets at the air–solution interface as an ordered template was reported for the preparation of ordered micrometer‐size honeycomb structures. Here we show that the method can also be used for formation of honeycomb‐like porous films from random copolymers with certain hydrophilicity, besides those polymers with defined structures such as block copolymers, starlike homopolymers, amd amphiphilic polymers. This demonstrates that the stabilization of water droplets is the key factor for the regular structure. Also we indicate that size and structure of the films can be regulated by such variables as concentration and atmospheric humidity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1846–1850, 2003 相似文献
28.
^17O系统的R矩阵分析 总被引:2,自引:1,他引:1
采用多道多能级R矩阵理论,全面系统地分析~(17)O系统中10.5 MeV激发能以下有关~(16)O(n,n)~(16)O·~(16)O(n,a)~(13)C和~(13)C(a,a)~(13)C的全部实验数据。有关~(16)O的中子反应截面计算值被收入中国评价数据库CENDL-2和美国的评价数据库ENDF/B-6。对在R矩阵分析中如何确定本底、道半径和边界条件等问题予以讨论。 相似文献
29.
30.
Core–shell type nanoparticles of poly(L ‐lactide)/poly(ethylene glycol) (LE) diblock copolymer were prepared by a dialysis technique. Their size was confirmed as 40–70 nm using photon correlation spectroscopy. The 1H‐NMR analysis confirmed the formation of core–shell type nanoparticles and drug loading. The particle size, drug loading, and drug release rate of the LE nanoparticles were slightly changed by the initial solvents that were used. The drug release behavior of LE core–shell type nanoparticles showed an initial burst during the first 12 h and then a sustained release until 100 h. The degradation behavior of LE block copolymer nanoparticles was divided into three phases: the initial rapid degradation phase, the stationary phase, and the rapid degradation phase until complete degradation. It was suggested that lidocaine release kinetics were predominantly governed by the diffusion mechanism in the initial burst phase and after that by both of the diffusion and degradation mechanisms. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2625–2634, 2002 相似文献