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81.
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83.
Summary Interference with the lead plate test for fluoride by borate and fluoborate can be eliminated by applying tests for silica and borate to the water drop, these tests allowing positive identification of the presence of silica and borate in the sample.
Part XX: Mikrochim. Acta [Wien]1964, 790. 相似文献
Zusammenfassung Die durch Borat und Fluoborat verursachte Störung des Fluoridnachweises nach dem Bleiplattenverfahren läßt sich durch Prüfung auf Kieselerde und Borat im Wassertropfen vermeiden, deren Anwesenheit in der Probe hiermit eindeutig feststellbar ist.
Résumé On peut éliminer l'interférence des fluorures avec les borates et les fluoborates dans l'essai à la lame de plomb en effectuant la recherche de la silice et des borates sur une goutte d'eau, ce qui permet l'identification positive de la présence de silice et de borate dans l'échantillon.
Part XX: Mikrochim. Acta [Wien]1964, 790. 相似文献
84.
A diode-pumped Nd:KGd(WO4)2 laser mode locked by a saturable Bragg reflector (SBR) is passively stabilized to suppress Q-switched mode locking and to extend the parameter range of continuous-wave mode locking. An indium phosphide plate exhibiting two-photon absorption and free-carrier absorption is used for passive stabilization. The intracavity pulse energy for the onset of stable continuous-wave mode locking is reduced by a factor of 4 compared with the laser without stabilization. By increasing the modulation depth of the SBR, pulse shortening by 30% is achieved and bandwidth-limited 6.2-ps pulses are measured. 相似文献
85.
The Carnivora are one of only four orders of terrestrial mammals living in Madagascar today. All four (carnivorans, primates, rodents and lipotyphlan insectivores) are placental mammals with limited means for dispersal, yet they occur on a large island that has been surrounded by a formidable oceanic barrier for at least 88 million years, predating the age of origin for any of these groups. Even so, as many as four colonizations of Madagascar have been proposed for the Carnivora alone. The mystery of the island's mammalian origins is confounded by its poor Tertiary fossil record, which leaves us with no direct means for estimating dates of initial diversification. Here we use a multi-gene phylogenetic analysis to show that Malagasy carnivorans are monophyletic and thus the product of a single colonization of Madagascar by an African ancestor. Furthermore, a bayesian analysis of divergence ages for Malagasy carnivorans and lemuriforms indicates that their respective colonizations were temporally separated by tens of millions of years. We therefore conclude that a single event, such as vicariance or common dispersal, cannot explain the presence of both groups in Madagascar. 相似文献
86.
An improved spectral editing method for solids is described which allows one to obtain a set of subspectra in roughly two-thirds the amount of time as our original CPPI editing method for the same signal to noise. This improvement is afforded by a new pulse sequence that is used to acquire a (13)CH + (13)CH(2) spectrum which has very little (13)CH(3) or nonprotonated carbon contamination. By using this new sequence the (13)CH-only subspectrum is obtained much more efficiently. Criteria for optimizing the signal to noise in the edited subspectra are discussed. Copyright 2000 Academic Press. 相似文献
87.
研究了Er∶Yb∶YCa4O(BO3)3(简称Er∶Yb∶YCOB)的多晶制备和单晶生长,用提拉法生长出光学质量优良的Er∶Yb∶YCOB单晶,测量了其吸收光谱和荧光光谱,分析了其能级和泵浦原理,并进行了以激光二极管为抽运源的激光试验,实现了Er∶Yb∶YCOB晶体的在1.55μm附近110mW的激光输出,且斜效率达18.9;. 相似文献
88.
Transport properties of very thin (2.5 monolayer) films of Ag epitaxially grown on clean Ge (001) substrates are reported. The films consist of a monolayer coverage plus isolated three dimensional islands. Below ~70°K the conductivity is dominated by the metal film and displays the temperature and electric and magnetic field dependences characteristic of metallic weak localization in two dimensions. Below ~2°K the resistance drops rapidly in a manner resembling an incomplete superconducting transition. The resistance is restored by application of a magnetic field of ~20 KGauss at 0.6°K. 相似文献
89.
Christopher J. Burns Robert D. Groneberg Joseph M. Salvino Gerard McGeehan Stephen M. Condon Robert Morris Matthew Morrissette Rose Mathew Shelley Darnbrough Kent Neuenschwander Anthony Scotese Stevan W. Djuric John Ullrich Richard Labaudiniere 《Angewandte Chemie (International ed. in English)》1998,37(20):2848-2850
One common synthetic route creates small-molecule libraries directed toward two functionally distinct target families. The novel structural template 1 can independently display the necessary pharmacophore patterns for inhibition of members of two different biomolecular target families, the matrix metalloproteinases (MMPs) or the phosphodiesterases (PDEs). The incorporation of multiple target family directed design elements into combinatorial library design could help expedite the pharmaceutical lead discovery process. Z=OR′ (PDE4), H (MMPs). 相似文献
90.
Two hydrated uranyl arsenates, Cs2(UO2)[(UO2)(AsO4)]4(H2O)2 (CsUAs) and Rb2(UO2)[(UO2)(AsO4)]4(H2O)4.5 (RbUAs), were synthesized by hydrothermal methods. Intensity data were collected at room temperature using MoKα radiation and a CCD-based area detector. The crystal structure of RbUAs was solved by direct methods, whereas the structure model of the phosphate Cs2(UO2)[(UO2)(PO4)]4(H2O)2 was used for CsUAs; both were refined by full-matrix least-squares techniques on the basis of F2 to agreement indices (CsUAs, RbUAs) wR2=0.061,0.041, for all data, and R1=0.032,0.021, calculated for 5098, 4991 unique observed reflections (|Fo|>4σF), respectively. The compound CsUAs is orthorhombic, space group Cmc21, Z=4, a=15.157(2), b=14.079(2), c=13.439(2) Å, V=2867.9(1) Å3. RbUAs is monoclinic, space group C2/m, Z=4, a=13.4619(4), b=15.8463(5), c=14.0068(4) Å, β=92.311(1)°, V=2985.52(2) Å3. The structures consist of sheets of arsenate tetrahedra and uranyl pentagonal bipyramids, with composition [(UO2)(AsO4)]−, that are topologically identical to the uranyl silicate sheets in uranophane-beta. These sheets are connected by a uranyl pentagonal bipyramid in the interlayer that shares corners with two arsenate tetrahedra on each of two adjacent sheets and whose fifth equatorial vertex is an H2O group, resulting in an open framework with alkali metal cations in the larger cavities of the structures. CsUAs is isostructural with its phosphate analogue, and has two Cs atoms and a H2O group in its structural cavities. RbUAs is not isostructural with its phosphate analogue, although it has a homeotypic framework. Its structural cavities are occupied by three Rb atoms and four H2O groups; one Rb position and three of the interstitial H2O groups are half-occupied. The partial occupancies of these positions probably result from the accommodation of the larger As atoms (relative to P) in the framework and resultant larger cavities. 相似文献