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31.
Highly ordered mesoporous silica can be regenerated from a mesoporous carbon CMK-3 that is a negative replica of mesoporous silica SBA-15, indicating reversible replication between carbon and inorganic materials. 相似文献
32.
A method is described for the potentiometric titration of milligram quantities of the uranium(IV) ion in the presence of iron. This is accomplished by complexing the iron with 1.10-phcnanthroline. The uranium can then be titrated with standard ceric sulfate without interference from the iron. 相似文献
33.
Contributions to the Chemistry of Phosphorus. 143. Li4P26 and Na4P26, the First Salts with Hexacosaphosphid(4?) Ions The hexacosaphosphides Li4P26 ( 1 ) and Na4P26 ( 2 ) are formed besides other polyphosphides in the reaction of white phosphorus with lithium dihydrogenphosphide or sodium. 1 also results from the decomposition of Li2HP7 in tetrahydrofuran at room temperature and can be obtained pure as a crystalline solvent adduct Li4P26 · 16 THF. According to 2D?31P-NMR spectroscopic investigations the P264? ion is a conjucto-phosphane of two P7(5)?-and two P9(3)?-unit groups with structures analogous to norbornane and deltacyclane, respectively. 相似文献
34.
F. L. Hahn 《Mikrochimica acta》1955,43(1):170-175
Zusammenfassung Eisen(II)sulfat reduziert in saurer Lösung Silbernitrat zu metallischem Silber; diese Reaktion wird durch Goldspuren katalysiert. Bei Abwesenheit von Trägerkeimen liegt die molare Grenzkonzentration für Gold bei etwa 10–8, bei Gegenwart von Keimen dagegen bei 10–11 bis 10–12. Eine geregelte Keimzahl wird durch Zusatz kleinster Bariummengen erhalten, die eine an sich kaum wahrnehmbare Bariumsulfattrübung bilden. Zur praktischen Anwendung geeignet dürfte eine Abänderung der Reaktion sein, bei der als Reduktor Hydrazin in alkalischer, Tartrat und Ammoniak enthaltender Lösung benutzt wird.
Summary In acid solution, iron(II) sulfate reduces silver nitrate to metallic silver. This reaction is catalyzed by traces of gold. In the absence of carrier nuclei, the molar limiting concentration for gold is about 10–8, but in the presence of nuclei this limit is 10–11 to 10–12. A controlled number of nuclei is obtained by adding very small amounts of barium, which produce a barely visible turbidity of barium sulfate. — For practical application, it may be possible to use a modified form of the reaction, in which the reductant is hydrazine acting in an alcaline solution containing tartrate and ammonia.
Résumé En solution acide le sulfate de fer (II) réduit le nitrate d'argent à l'état d'argent métallique; cette réaction est catalysée par des traces d'or. En l'absence des germes, la concentration limite pour l'or est environ 10–8, mais en présence des germes cette limite est 10–11 à 10–12. On peut obtenir un nombre connu de germes par addition d'une très petite quantité de baryum qui produira un trouble àpeine visible dû au sulfate de baryum formé. En pratique on peut employer une forme de réaction différente, l'agent réducteur étant l'hydrazine agissant en milieu alcalin en présence de tartrate et d'ammoniaque.相似文献
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36.
Armstrong TA Bettoni D Bharadwaj V Biino C Borreani G Broemmelsiek D Buzzo A Calabrese R Ceccucci A Cester R Church M Dalpiaz P Dalpiaz PF Dibenedetto R Dimitroyannis D Fabbri MG Fast J Gianoli A Ginsburg CM Gollwitzer K Hahn A Hasan M Hsueh S Lewis R Luppi E Macrí M Majewska AM Mandelkern M Marchetto F Marinelli M Marques J Marsh W Martini M Masuzawa M Menichetti E Migliori A Mussa R Palestini S Pallavicini M Pastrone N Patrignani C Peoples J Pesando L Petrucci F Pia MG Pordes S Rapidis P 《Physical review letters》1992,69(16):2337-2340
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38.
The luminescence of solid xenon at 20 K has been excited optically in the wavelength range 1550Åto 1150Å. The 1760Å emission band due to a transition of the molecule is found in agreement with α? or e?-excitation. The excitation spectrum yields a relatively high quantum efficiency of the Γ(3/2) exciton series indicating efficient self-trapping. The Γ(1/2) exciton series and conduction band states have a low quantum efficiency. 相似文献
39.
Jae C. Schwartz John E. P. Syka Ian Jardine 《Journal of the American Society for Mass Spectrometry》1991,2(3):198-204
By using a modified ion trap mass spectrometer, resolution in excess of 30,000 (FWHM) at m I z 502 is demonstrated. The method of increasing resolution in the ion trap mass spectrometer operated in the mass-selective instability mode depends on decreasing the rate of scanning the primary radio frequency amplitude as well as using resonance ejection at the appropriate frequency and amplitude. A theoretical basis for the method is introduced. 相似文献
40.
Systemic and pulmonary circulations constitute a complex organ that serves multiple important biological functions. Consequently, any pathological processing affecting the vasculature can have profound systemic ramifications. Endothelial and smooth muscle are the two principal cell types composing blood vessels. Critically, endothelial proliferation and migration are central to the formation and expansion of the vasculature both during embryonic development and in adult tissues. Endothelial populations are quite heterogeneous and are both vasculature type- and organ-specific. There are profound molecular, functional, and phenotypic differences between arterial, venular and capillary endothelial cells and endothelial cells in different organs. Given this endothelial cell population diversity, it has been challenging to determine the origin of endothelial cells responsible for the angiogenic expansion of the vasculature. Recent technical advances, such as precise cell fate mapping, time-lapse imaging, genome editing, and single-cell RNA sequencing, have shed new light on the role of venous endothelial cells in angiogenesis under both normal and pathological conditions. Emerging data indicate that venous endothelial cells are unique in their ability to serve as the primary source of endothelial cellular mass during both developmental and pathological angiogenesis. Here, we review recent studies that have improved our understanding of angiogenesis and suggest an updated model of this process.Subject terms: Cell lineage, Chemotaxis 相似文献