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排序方式: 共有135条查询结果,搜索用时 62 毫秒
81.
A. Lucaciu M. V. Frontasyeva E. Steinnes Ye. N. Cheremisina C. Oprea T. B. Progulova L. Staicu L. Timofte 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(2):457-458
This is the first systematic study of air pollution from heavy metals and other trace elements throughout several industrialized
areas and national parks of Eastern Romanian Carpathians using the moss biomonitoring technique. Samples ofHylocomium splendens collected at 120 sites were analyzed by epithermal neutron activation analysis at the pulsed fast reactor IBR-2 at JINR,
Dubna, for a wide range of elements including heavy metals and rare earths (Na, Mg, Al, Cl,K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni
(by (n,p) reaction), Cu, Zn, As, Se, Br, Rb, Sr, Zr, Mo, Ag, Sn, Sb, I, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Yb, Hf, Ta, W,
Au, Th, and U). Copper, lead and cadmium were determined by AAS. Certified Reference Standards of mosses produced for interlaboratory
comparisons in the European moss-survey 1995 were used to ensure the quality of the measurements. To present results in the
form of coloured contour maps the geographical information system GIS-INTEGRO was used. The regional extent of pollution with
specific metals was determined. Results reported are well consistent with those obtained in numerous recent projects carried
out in Germany, the Netherlands, Poland, Bulgaria and other countries. 相似文献
82.
83.
在水溶液中,Bi(Ⅲ)与溴化四丁基铵和KI形成不溶于水的三元缔合物BiI-4·TBAB+,此三元缔合物沉淀浮于盐水相上层形成界面清晰的液-固两相。当溶液中溴化四丁基铵和KI的浓度分别为5.0×10-4mol/L和3.0×10-3mol/L,pH=3时,Bi(Ⅲ)可与Zr(Ⅳ)、Ce(Ⅲ)、U(Ⅵ)和Mg(Ⅱ)定量分离,Bi(Ⅲ)的浮选率达到100%。对合成水样中Bi(Ⅲ)的分离和测定,效果良好。该方法具有选择性高,操作简便和不污染环境等特点,在微量铋的分离和富集分析中有一定的实用价值。 相似文献
84.
单粒子气溶胶的基质辅助激光解吸/电离飞行时间质谱技术具有快速在线检测环境大气生物气溶胶的潜力.以a-环糊精为分析物,实验研究了吡啶羧酸、2,5-二羟基苯甲酸、芥子酸、阿魏酸四种常用基质材料的效果,考察基质与分析物的摩尔比对分析物单粒子激光质谱信号的影响.实验结果表明阿魏酸做基质时质谱命中率及分析物质谱信号峰检测效率最高,吡啶羧酸做基质时的分析物质谱信号峰激发率最高,信号峰强度最强.吡啶羧酸对分析物摩尔比为100:1时,分析物质谱信号检测效率最高. 相似文献
85.
We show that catm(X)=cat(jm), where catm(X) is Fox?s m-dimensional category, jm:X→X[m] is the mth Postnikov section of X and cat(X) is the Lusternik-Schnirelmann category of X. This characterization is used to give new “Bochner-type” bounds on the rank of the Gottlieb group and the first Betti number for manifolds of non-negative Ricci curvature. Finally, we apply these methods to obtain Bochner-type theorems for manifolds of almost non-negative sectional curvature. 相似文献
86.
Gabriela Niculae Nicoleta Badea Aurelia Meghea Ovidiu Oprea Ioana Lacatusu 《Photochemistry and photobiology》2013,89(5):1085-1094
The coencapsulation of two UV filters, butyl‐methoxydibenzoylmethane (BMDBM) and octocrylene (OCT), into lipid nanocarriers was explored to develop stable cosmetic formulations with broad‐spectrum photoprotection and slow release properties. Different types of nanocarriers in various concentrations of the two UV filters were tested to find the combination with the best absorption and release properties. Solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) have been the two types of lipid nanocarriers used. The NLCs were based on either medium chain triglycerides (MCT) or squalene (Sq). The following physicochemical properties of the nanocarriers have been evaluated: particle size, morphology, zeta potential (ZP), entrapment efficiency, loading capacity, and thermal behavior. The nanocarriers have been formulated into creams containing low amounts of UV filters (2.5% BMDBM and 1% OCT). The best photoprotection results were obtained with the cream based on NLCs prepared with MCT, having a sun protection factor (SPF) of 17.2 and an erythemal UVA protection factor (EUVA–PF) of 50.8. The photostability of the encapsulated BMDBM filter was confirmed by subjecting the nanocarriers‐based creams to in vitro irradiation. The prolonged UV‐protection efficacy was coupled with a slow in vitro release of the synthetic UV filters, which followed the Higuchi release model. 相似文献
87.
88.
Emil Ioan Muresan Spiridon Oprea Theodor Malutan Mihai Vata 《Central European Journal of Chemistry》2007,5(3):715-726
The esterification reaction of palmitic acid with epichlorohydrin catalyzed by an anionic macroporous resin was studied. Purolite
A-500 resin proved to be a very effective catalyst in the synthesis of 3-chloro-2-hydroxypropyl palmitate. The effects of
certain parameters such as speed of agitation, catalyst particle size, catalyst loading, temperature, initial molar ratio
between reactants on the rate of reaction were studied. It was found that the overall rate is intrinsically kinetically controlled.
The structure of synthesized ester was confirmed by FTIR and 1H NMR analyses.
相似文献
89.
A study is reported of the crystallization behaviour of some glass compositions which belong in the system MgO-Al2O3-SiO2 and which lead to vitreous ceramics with α-cordierite as a main phase. DTA, X-ray diffraction and dilatometric analysis were
used to investigate the influence of the type and concentration of the nucleation agents. The activation energies of crystallization
were calculated and the crystalline phases were identified.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
90.