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991.
《Journal of Coordination Chemistry》2012,65(3-4):327-336
Abstract The calcium vanadyl tartrate complex [Ca(VO)(d,l-C4H2O6)(H2O)4] has been synthesized and characterized by spectroscopic methods. Its crystal structure was solved by X-ray methods. The compound is monoclinic, space group P21/c, with a = 8.0282(5), b = 17.1568(8), c = 7.6113(3)Å, β = 94.269(4)° and Z = 4. The structure consists of centrosymmetric vanadyl tartrate dimers, [(VO)(d,l-C4H2O6)]2 4-, and calcium cations placed between them. As a result, dimers form chains in the [101] direction. Neighbouring chains are linked by the coordination of the calcium ion to the oxygen atom of a vanadyl group of a different chain, thus forming a two-dimensional structure. Different layers are linked by hydrogen bonds. Spectroscopic studies show the existence of intra-dimeric interactions between vanadium atoms. 相似文献
992.
《中国化学会会志》2017,64(8):962-968
SiO2 (activated or mesoporous silica)/Mg(magnesiothermic or metal sintering aid)/C(activated or polymeric carbon)/N2 (atmosphere) systems were used in the one‐step synthesis of β‐SiC and β‐Si3N4 whiskers. In this study, a mixture of the active precursors was allowed to react via a self‐sustaining reaction (high‐energy ball milling process). Scanning electron micrographs and X‐ray diffraction (XRD ) analysis showed that the rod‐like SiC whiskers (~800 µm) were synthesized in situ by the direct carbothermal reduction of silicon nitride (or silicon) with activated carbon in N2 (or Ar) atmosphere. The results show that β‐Si3N4 (without β‐SiC ) was fully formed after 5 h of milling with four different morphologies, namely whisker tip (droplet/no droplet) and nonuniform whiskers (short hexagonal/rhombohedral/rod‐like) with a length of 0.1–400 µm. By adding metal sintering aids, the liquid phase Mg–Si–O–N and the rate of carbothermal reduction increased (enhanced densification via particle rearrangement) and their hexagonal whiskers tended to assume a rod‐like shape. The effect of the concentration of CO (reduction of α‐Fe2O3 to Fe by CO ) on the whisker synthesis suggests that, in addition to the concentration of CO , the nature of the family of mesoporous silica/carbon template is an important factor in the synthesis of β‐SiC and β‐Si3N4 whiskers. The possible chemical reactions were investigated by studying the unwanted phases (MgO , Si, SiC , Fe2O3 , Fe3O4 , FeO , Fe, Fe3C , MgCO3 ) of comparable XRD graphs. 相似文献
993.
以L型丙交酯(LLA)、乙交酯(GA)和三亚甲基碳酸酯(TMC)为原料,辛酸亚锡为催化剂,通过开环聚合制备了丙交酯-三亚甲基碳酸酯二元共聚物(PLT)和丙交酯-三亚甲基碳酸酯-乙交脂(PLTG)三元共聚物。采用核磁共振氢谱、傅里叶红外光谱、体积排阻色谱、差热扫描、力学性能测试、血液相容性实验表征了产物的结构与性能,研究了共聚物组成对其结晶能力、热性能和力学性能的的影响。结果表明:所得聚合物的数均分子量均在8×10~4以上,多分散系数在2.0以下。共聚物中的TMC和GA链段使其结晶能力、玻璃化转变温度和拉伸强度与L型聚丙交酯相比均有所下降。三元共聚物PLTG的拉伸强度可达到22.3 MPa,断裂伸长率达到168.7%。另外,共聚物的血液相容性优良。 相似文献
994.
An efficient cesium carbonate-mediated synthesis of phenothiazine derivatives from S-2-acetamidophenyl ethanethioates and ortho-dihaloarenes has been developed. This protocol affords an efficient approach for the construction of phenothiazine derivatives without the need of transition-metal catalyst or ligand. A plausible mechanism is proposed. 相似文献
995.
以中国西南碳酸岩盐地区的红枫湖及环湖河流水体为研究对象,采用液-液萃取和ICP-MS测试方法,对水中溶解态稀土元素浓度进行了测定,借以探讨碳酸盐岩水体环境下稀土元素的地球化学行为和环境效应。研究结果表明,红枫湖湖水溶解态稀土含量相对较低,∑REE总浓度分布于14.3~27.2 ng.kg-1之间,平均含量为18.24 ng.kg-1,明显低于地表水体浓度平均值。环湖河水溶解态∑REE浓度分布于4.07~102.28 ng.kg-1,平均为24.12 ng.kg-1。湖水和河水的页岩(PAAS)标准化的溶解态稀土元素配分模式都显示了显著的重稀土富集特征以及Ce元素负异常,而水化学络合计算结果显示,水体中溶解态稀土几乎以占绝对优势的碳酸盐无机络合形态存在,其他络合方式所占比例非常微小。这些都显示与相对偏碱性的水化学环境有关。 相似文献
996.
Dr. Binglin Sui Xinglei Liu Dr. Mengyuan Wang Prof. Kevin D. Belfield 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10351-10354
A highly water‐soluble, fluorescence turn‐on sensor for Ca2+ is reported. The sensor affords high selectivity in sensing Ca2+ over other biologically important metal cations. The dissociation constant of the sensor in binding Ca2+ is 0.92 mm . Fluorescence microscopy experiments demonstrate that the sensor is cell‐impermeable and capable of detecting extracellular Ca2+. 相似文献
997.
Preparation,characterization, and bioavailability of a phosphorylated human‐like collagen calcium complex 下载免费PDF全文
Chenhui Zhu Yanru Chen Jianjun Deng Wenjiao Xue Xiaoxuan Ma Junfeng Hui Daidi Fan 《先进技术聚合物》2015,26(10):1217-1225
The aim of this study was to determine whether a phosphorylated human‐like collagen calcium (PHLC–Ca) complex showed a higher bioavailability than other calcium supplements. To improve the calcium‐binding ability of human‐like collagen (HLC), modified HLC was prepared by introducing a reactive phosphate group using a dry‐heating method, followed by the formation of PHLC–Ca in MOPS buffer. PHLC–Ca was characterized using atomic absorption spectrophotometry, Fourier transform infrared (FTIR), fluorescence quenching, circular dichroism (CD), and ultraviolet–visible absorption (UV–vis) spectroscopy. The calcium uptake test showed that the bioavailability of PHLC–Ca was higher than that of CaCl2 and G‐Ca. Data from a mouse model of osteoporosis suggested that PHLC–Ca is superior for treating osteoporosis than CaCl2 or G‐Ca. These results indicate that PHLC–Ca is a desirable calcium supplement for use in daily life and clinical application. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
998.
999.
Chau N. Tang Hunaid B. Nulwala Krishnan Damodaran Palwinder Kaur David R. Luebke 《Journal of polymer science. Part A, Polymer chemistry》2011,49(9):2024-2032
CO2‐based, crosslinked poly(hydroxyl urethane)s (PHUs) are accessed via a set of efficient reactions based on the addition chemistry of thiol‐ene and amines‐cyclic carbonates. This strategy to utilize 5‐membered cyclic carbonates produced from CO2 is robust, facile, modular, and atomically efficient in nature. The thiol‐ene reaction was utilized to access bis(cyclic carbonate), tris(cyclic carbonate), and tetrakis(cyclic carbonate) in quantitative yield from 4‐vinyl‐1,3‐dioxolan‐2‐one and thiols. Multi‐functional cyclic carbonates were simply mixed with diethylenetriamine and/or 1,6‐diaminohexane to generate crosslinked PHUs from 25 to 80 °C. These materials are easy to scale‐up and are potential candidates in many applications such as coatings, binders, and resins. The resulting polymers have glass transition temperatures between ?1 and 16 °C and thermal decomposition temperatures from 190 to 230 °C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
1000.
Anhydrous potassium carbonate has been utilized as an inexpensive, safe, and efficient basic catalyst for the synthesis of flavanones starting either from 2′-hydroxychalcones or from 2′-hydroxyacetophenones. In both the cases the favored reaction condition was either refluxing in a solvent with added catalyst or microwave irradiation on the catalyst. 相似文献