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981.
铝合金中锌、铁的快速测定--原子吸收分光光度法 总被引:6,自引:0,他引:6
样品以盐酸溶解,加入过氧化氢助溶,蒸至近干.加入1 1盐酸提取,移入100mL容量瓶中,分取部分溶液于50mL容量瓶中,调整盐酸酸度为5%,用水稀至刻度,摇匀后,以空气-乙炔火焰水相直接测定锌和铁。为了消除大量基体元素的影响,在标准系列中加入相当量的铝。此方法快捷、简便,亦可用于锰、镁、铜、铅、镍的测定。 相似文献
982.
Phosphatidylcholine acyltransferase (lecithin:cholesterol acyltransferase or LCAT; EC 2.3.1.43) activity was found to be present
in pig ovarian follicular fluid (POFF), in addition to pig serum (PS). The cholesterol esterification rate in both POFF and
PS is linear with incubation time up to 2 hr. The mean absolute rate of POFF-cholesterol esterification was 8.1±0.4 nmoles
per ml per hr approximately one-fourth of that in PS. However, the fractional rate (percent of labeled cholesterol esterified
per hr) of POFF-cholesterol esterification was similar to that observed in PS. There was little variation of absolute rate
of cholesterol esterification in the fluid obtained from different sizes of follicles. Fatty acid or triacylglycerol did not
participate in the reaction of cholesterol esterification in POFF. No appreciable change in enzymatic activity was found from
storing POFF at 4 C for periods of time up to 24 hr or at −70 C up to 2 months, but activity was lost thereafter. On the other
hand, PS showed a much longer period of stability (5 days at 4 C and 9 months at −70 C). A discrepancy between the fatty acid
composition of cholesteryl esters formed by the LCAT reaction and the fatty acid composition at the C-2 position of phosphatidylcholine
led us to propose a two-step mechanism for the LCAT reaction. It is concluded that the LCAT of POFF, as well as that of plasma,
is specific for individual fatty acids rather than for the fatty acid composition of phosphatidylcholine. The fatty acid concentration
of lysophosphatidylcholine decreased during prolonged incubation times (6 to 21 hr) suggesting that the increased lysophosphatidylcholine
formed as a product of the LCAT reaction may be reused as substrate for the LCAT reaction or for hydrolysis by lysophosphatidylcholine
hydrolase.
Presented at the AOCS Meeting, New York, May 1977. 相似文献
983.
984.
985.
Woo Gi Lee Jin Suk Lee Byung Geon Park Mi Sun Kim Soon Chul Park Ho Nam Chang 《Korean Journal of Chemical Engineering》1996,13(5):453-456
Chemostat and total cell retention cultures with internal filter system ofSaecharomyc.es cerevisiae H1-7 were carried out to produce ethanol from wood hydrolysate. Maximum ethanol productivity obtained in a chemostat with
the aeration rate of 1 vvm was 3.79 g/(L·h). This was 20% higher than that in a chemostat without aeration. However, the substrate
was not completely consumed at the dilution rate with the maximum productivity. The realistic productivity, which has higher
than 99% conversion rate of substrate, was. 2.95 g/(L·h). The maximum productivity in the total cell retention culture was
6.65 g/(L·h) at the dilution rate of 0.19 h1 and the residual glucose concentration was negligible. 相似文献
986.
M. -K. Chang E. J. Conkerton D. C. Chapital P. J. Wan O. P. Vadhwa J. M. Spiers 《Journal of the American Oil Chemists' Society》1996,73(2):263-265
Chinese melon (Momordica charantia L.), also known as bitter gourd, is a tropical crop, grown throughout Asian countries for use as food and medicinals. In
1993, four cultivars of Chinese melon were grown in Mississippi and the seeds were collected. Oil contents of the seeds ranged
from 41 to 45% and the oils contained 63–68% eleostearic acid and 22–27% stearic acid. Industrially important tung oil, a
“fast-drying oil” used in paints and varnishes, contains 90% eleostearic and 2–3% stearic acid. The ratio of stearic to eleostearic
in Chinese melon seed oil is ten times greater than that in tung oil. The higher ratio should reduce the rate of drying and
crosslinking and could be advantageous in the paint industry. The defatted meals contained 52–61% protein and would be a good
source of methionine. 相似文献
987.
为了提高轿车侧面耐撞性,设计耐撞性能强的B柱成为主要课题之一.目前的优化方法很难将B柱侵入量和侵入速度同时控制在理想范围内.因此,提出泡沫铝材料填充在汽车B柱内代替B柱加强板的方法,缓冲侧面碰撞冲击.通过建立泡沫铝有限元模型与材料特性分析,确定仿真泡沫铝主要材料参数.进而根据中国新车评价规程C-NCAP要求,建立轿车整车侧面碰撞有限元模型,采用LS-DYNA软件进行仿真分析.结果表明,泡沫铝填充后的B柱侵入量和侵入速度都有明显降低.泡沫铝材料塑性变形和整体弯曲变形能够吸收1.51kJ的能量,是B柱加强板的3倍.填充泡沫铝前后仿真结果表明,轿车B柱填充泡沫铝是一种提高轿车侧面耐撞性的方法. 相似文献
988.
本文建立了他励直流电动机虚拟模型,通过模型进行仿真算法分析,并利用虚拟技术,在仿真平台上实现仿真,在上位机上显示数据,对单闭环直流调速系统进行可行性研究与优化。仿真做的主要前期工作为模型建立,通过电枢回路方程和动力方程进而推导出电动机的数学模型方程,并对模型进行分析计算。后期工作对所建立的模型进行仿真,并调试出模型数据,进而得到仿真结果。设计的虚拟模型建立在虚拟仿真平台上,利用平台的模拟和数字输入输出端口进行信号的采集和传递,并利用仿真平台强大的内部资源进行运算分析,从而达到期望的研究效果。 相似文献
989.
Jiaqing Chang Mingshan Chi Teng Shen Zhongwei Liang 《Journal of Adhesion Science and Technology》2020,34(10):1128-1143
AbstractVarious inks with different properties are widely used in the printed electronic industry. In order to obtain high quality inkjet printing, it is necessary to study the droplet formation process and its influencing factors comprehensively. Only in this way, the incentive conditions and liquid physical parameters of droplet ejection can be obtained and optimized. Firstly, the calculation model of the droplet ejection process is established for a tubular print head and the boundary conditions are set according to the driving characteristics. Secondly, the free surface flow is calculated in the simulation software and sequential pictures of the droplet formation processes are captured to validate the availability of the numerical algorithm. Finally, the droplet formation processes of the tubular piezoelectric print head are simulated under different incentive conditions, different viscosities and different surface tensions. Too small a driving energy is insufficient to cause the head to eject droplets. Excessive excitation energy will result in larger or multiple satellite droplets. Additionally, the thinning process of the liquid neck is examined carefully in this paper. Results show that surface tension and viscosity have a significant effect on the thinning speed of the liquid neck, but the effect is not as significant as previous studies. 相似文献
990.