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31.
翁坤荣 《广东微量元素科学》1996,3(4):66-71
人类缺钙是世界性普遍存在的问题,中国人由于膳食结构缺陷及传统饮食习惯而使食物中钙的吸收受到影响,因而缺钙尤其普遍。 相似文献
32.
Yiyi Weng Xingxing Ding Joo C. A. Oliveira Xiaobin Xu Nikolaos Kaplaneris Meijie Zhu Hantao Chen Zhuo Chen Lutz Ackermann 《Chemical science》2020,11(34):9290
There is a strong demand for novel native peptide motifs for post-synthetic modifications of peptides without pre-installation and subsequent removal of directing groups. Herein, we report an efficient method for peptide late-stage C(sp3)–H arylations assisted by the unmodified side chain of asparagine (Asn) without any exogenous directing group. Thereby, site-selective arylations of C(sp3)–H bonds at the N-terminus of di-, tri-, and tetrapeptides have been achieved. Likewise, we have constructed a key building block for accessing agouti-related protein (AGRP) active loop analogues in a concise manner.An efficient method for peptide late-stage C(sp3)-H arylations assisted by unmodified side chain of asparagine (Asn) without any exogenous directing group has been reported. 相似文献
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34.
本文对Michigan大学S.Hatamian等人在“微波共振跃迁法测量电子偶素2~3S_1-2~3P_J精细结构”实验中所用拟合公式进行了审慎的分析和推证,修正了该公式的功率增宽项,并就Mainz大学R.Ley等人对该公式的批评作了评价。最后,采用新、旧拟合公式对Michigan组实验数据进行拟合并讨论其结果。 相似文献
35.
With the development of transgenic crops, regulations to label the genetically modified organisms (GMOs) and their derived products have been issued in many countries. Polymerase chain reaction (PCR) methods are thought to be reliable and useful techniques for qualitative and quantitative detection of GMOs. These methods are generally needed to amplify the transgene and compare the amplified results with that of a corresponding reference gene to get the reliable results. Specific primers were developed for the rapeseed (Brassica napus), high-mobility-group protein I/Y(HMG-I/Y) single-copy gene and PCR cycling conditions suitable for the use of this sequence as an endogenous reference gene in both qualitative and quantitative PCR assays. Both methods were assayed with 15 different rapeseed varieties, and identical amplified products were obtained with all of them. No amplification was observed when templates were the DNA samples from the other species of Brassica genus or other species, such as broccoli, stem mustard, cauliflower, Chinese cabbage, cabbage, sprouts, Arabidopsis thaliana, carrot, tobacco, soybean, mung bean, tomato, pepper, eggplant, plum, wheat, maize, barley, rice, lupine, and sunflower. This system was specific for rapeseed. Limits of detection and quantitation in qualitative and quantitative PCR systems were about 13 pg DNA (about 10 haploid genomes) and about 1.3 pg DNA (about 1 haploid genome), respectively. To further test the feasibility of this HMG-I/Y gene as an endogenous reference gene, samples containing transgenic rapeseed GT73 with the inserted glyphosate oxidoreductase (GOX) gene were quantitated. These demonstrated that the endogenous PCR detection systems were applicable to the qualitative and quantitative detection of transgenic rapeseed. 相似文献
36.
A complexing process is developed to prepare Y-Ba-Cu-O superconducting fibers. The process is not identical to typical sol-gel processes; here the resulting gel network is built up by hydrogen bonding linkage among complexing species in non-aqueous solution. Cu acetate, [Cu(OAC)2], Ba methoxyethoxide [Ba(ORE)2] and Y acetate [Y(OAC)3] are used as precursors for preparing homogeneous gels while -methacrylic acid (HOAA) and diethylenetriamine (DETA) as complexing agents, and methoxyethanol (REOH) as solvent. Fibers drawn from a sol obtained through reduced pressure present no or little deformation at 80°MoC via adjusting the amount of DETA and HOAA. Cu(OAC)2, Ba(ORE)2 and Y(OAC)3 in the complexing process have been demonstrated to form gels without hydrolysis and condensation at ambient atmosphere. The relationships between the drawing behavior of sols and gel structure with different amounts of DETA and HOAA are suggested. The concentration region of drawing the gel fibers with no or little deformation heated at 80°MoC is also found. 相似文献
37.
Thermally induced phase separation technique was utilized to fabricate biodegradable poly(l ‐lactic acid) (PLLA) macrocellular foams which were capable of being applied in tissue engineering. The block copolymer Pluronic F127 composed of (polyethyleneoxide)‐(polypropyleneoxide)‐(polyethyleneoxide) [(PEO)‐(PPO)‐(PEO)] was used as a porogen. Water/dioxane mixtures with different volume ratios were used as solvents. The addition of Pluronic F127 could induce an appearance of large pores (50–200 μm) besides small pores (10–20 μm) or a change from a solid–liquid phase separation to a liquid–liquid phase separation. The role of Pluronic F127 depends on the water/dioxane ratios in the PLLA/dioxane/water system. The X‐ray diffraction patterns and porosity measurement results showed that Pluronic F127 was crystallized and existed on the pore wall. The effect of Pluronic F127 on changing pore structure is attributed to the occurrence of the interaction of the lipophilic PPO blocks in Pluronic F127 with PLLA clews, consequently, this results in PLLA aggregation and early phase separation on cooling. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
38.
微波辐照增强原煤磁分离脱硫机理探讨 总被引:5,自引:0,他引:5
采用~(57)Fe穆斯堡尔谱学方法,研究微波-磁分离法脱硫机理及微波辐照深度对脱硫率的影响。结果表明,微波选择性介质加热,可以激励煤中顺磁性黄铁矿FeS_2热解,使其转化为非化学计量的磁黄铁矿Fe_(1-x)S(0相似文献
39.
40.
The activation method of determination of trace amounts of Hg in human urine has been studied by introducing a simple amalgam deposition method. Human urine samples were obtained from the alkali chloride, electrolysis plant equipped with Hg cells. The capacity of Cu powder for Hg quantity, the pH conditions, and the shaking time were described. The results showed that the Hg contents in workers' urine samples varied from 33 ppb to 60 ppb depending on working conditions. 相似文献