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101.
102.
Franz A. Mautner Harald Krischner Christoph Kratky 《Monatshefte für Chemie / Chemical Monthly》1988,119(8-9):921-927
Single crystals of Ca(N3)2·2 H2O have been prepared from aqueous solutions at room temperature. The crystals are monoclinic,a=1 159.0 (3),b=614.2 (2),c=785.5 (2) pm, =106.52 (2)°,Z=4, space group P21/n. The crystal structure was determined by single crystal X-ray diffraction (1 109 Mo-K-reflexions,R=0.052). Calcium atoms are surrounded by four azide groups and four water molecules. The coordination polyhedra are antiprism which are sharing azide groups and water molecules to form layers. The lattice constants and powder pattern agree well with values reported earlier for Ca(N3)2 · 1.5 H2O [1]. It was also shown, that Sr(N3)2 · 2 H2O is isotypic with Ca(N3)2 · 2 H2O. 相似文献
103.
Lubbad I Mayinda JP Chatelut M Vittori O 《Analytical and bioanalytical chemistry》2004,380(3):551-555
The contamination of drinking water and industrial wastewaters is a critical environmental problem. The nitrophenol, dinitrophenol, cadmium, and lead contaminants are classified as hazardous compounds. Their rapid determination may be obtained using differential pulse polarography with concentrated electrolyte. CaCl2, which is very soluble to levels exceeding 5 mol l–1, allows separation of coalescent peaks at 0.1 mol l–1. A systematic study undertaken from 0.1 to 5 mol l–1 shows good separation of lead and cadmium from the organic compounds, and optimization of the electrolyte concentration according to the objective is described. Preconcentration of real samples is necessary because pollution levels are usually very low. 相似文献
104.
Chengyu Wang 《Applied Surface Science》2007,253(10):4768-4772
Hydrophobic vaterite nanoparticles were prepared via crystallization of CaCO3 with oleic acid in methanol by mimicking the process of biomineralization. The molar ratio of oleic acid to calcium ion was varied from 0.1 to 0.5. By changing the concentration of the oleic acid, CaCO3 particles with different shapes and polymorphism were obtained. High concentration of the oleic acid gave stable vaterite crystals, the polymorph of which did not change when the composite was kept in water for more than one week. Fourier transform infrared spectroscopy (FT-IR) and TGA analysis of the obtained product indicated that the oleic acid was bound to the crystalline CaCO3. The contact angle of the modified vaterite reached 122°. We have succeeded in crystallization of hydrophobic CaCO3 nanoparticles in situ. 相似文献
105.
106.
Uri Yermiyahu Shlomo Nir Gozal Ben-Hayyim Uzi Kafkafi Gunther F. E. Scherer Thomas B. Kinraide 《Colloids and surfaces. B, Biointerfaces》1999,14(1-4):237-249
The hypotheses that genotypic differences in salinity tolerance may result from (i) differences in global surface charge density or (ii) from differences in global Ca2+ binding were tested. An attempt was made to correlate the differing salinity tolerance of four melon cultivars with surface properties of vesicles extracted from the plasma membrane (PM) of their root cells. Surface characterization involved measurements of electrophoretic mobility and sorption of 45Ca2+ to the vesicles in the presence of varying concentrations of Ca2+, Na+ and Mg2+. Irrespective of salinity tolerance, vesicles from the four cultivars yielded similar ζ potentials under similar conditions, indicating similar global surface charge densities. Sorption studies with vesicles from two cultivars differing in salinity tolerance predicted independently this result of equal surface charge density. The estimated global binding affinities of Ca2+, Na+ and Mg2+ to the PM of both cultivars were the same with binding coefficients of 50, 0.8 and 9 M−1, respectively. Consequently, the hypotheses enumerated above to interpret genotypic differences in salinity toxicity are rejected. However, vesicles from the salt-resistant strain sorbed 19% more Ca2+ per given amount of protein in the membrane, indicating the existence of a larger number of negatively charged surface sites per given amount of protein and a smaller amount of protein per given area of membrane. Genotypic differences in site-specific Ca2+-binding affinity (e.g. at ion channels) remain a viable hypothesis for genotypic differences in salinity tolerance. 相似文献
107.
自行研制了一种凹面光栅整体组合狭缝五通道原子吸收式血液五元素分析仪,用于人全血中5种元素Ca,Cu,Mg,Fe和Zn的测定.采用1支五元素空心阴极灯作为光源,以单反射方式聚焦在火焰中心,以凹面光栅为色散元件.设计了五元素锐线通过的整体组合狭缝.采用顺序注射变速恒流在线稀释的溶液注入方式.为消除干扰谱线对钙的原子吸收的影... 相似文献
108.
Starting from gypsum, a by-product of lactic acid fabrication process, novel “green” composites have been produced by melt-blending polylactide (PLA) and this filler after a previous specific dehydration to obtain anhydrite II (AII). Such a material is potentially interesting in biodegradable/rigid packaging and in technical applications requiring rigidity, heat resistance and dimensional stability. In order to obtain PLA-AII composites characterized by specific end-use flame retardant properties, the addition of selected organo-modified layered silicates (OMLS) was considered. Co-addition of AII and OMLS leads to PLA (nano)composites characterized by good (nano)filler dispersion, thermal stability and adequate mechanical resistance. The flame retardant properties as shown by cone calorimetry showed significant increase in the ignition time compared to neat PLA and a substantial decrease, i.e., ca. 40%, of the maximum rate of heat release, whereas the UL94 HB test was successfully passed revealing non-dripping effect and extensive char formation. The study represents a new approach in formulating novel PLA grades with improved characteristic features. 相似文献
109.
A gel of composition 3CaO·2SiO2 was synthesised by means of sol–gel route involving hydrolysis of tetramethyl orthosilicate (TMOS) with calcium nitrate in alcoholic medium, and polycondensation reaction. The gel was submitted to DTA and TGA analysis and the resulted material was examined by FTIR spectroscopy and X-ray powder diffractometry. The thermal treatments required for the gel into glass conversion led to a partially devitrified product. The XRD analysis showed that the structure obtained is highly depolymerised. 相似文献
110.
Long range correlation concerning hydrophilicity and flexibility along a number of 80 calcium binding protein sequences is confirmed by using spectral analysis and detrended fluctuations analysis methods, as well as by Hurst exponent calculations. There are no significant differences between the correlation properties concerning these properties for the two structural subfamilies, extended and compact, of the calcium binding proteins and they are also similar with the correlation properties revealed by other investigated proteins. This result sustains the hypothesis that the long range correlation of hydrophilicity and flexibility along the chain is a common feature of proteins. 相似文献