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121.
Rubidium amide‐ammonia(3/2), RbNH2·2/3NH3, was synthesized from Rubidiumhydride, RbH, in liquid ammonia at ?78 °C. The compound crystallizes in the cubic space group I213 with Z = 4, a = 10.0490(12) Å, and V = 1014.77(20) Å as isometric colorless crystals. The crystal structure was solved from single‐crystal X‐ray data. The structure contains a three‐dimensional network of amide anions and ammonia molecules, which are interconnected via hydrogen bonds. 相似文献
122.
Nikolaus Kocher Carola Selinka Dirk Leusser Daniel Kost Inna Kalikhman Dietmar Stalke 《无机化学与普通化学杂志》2004,630(12):1777-1793
The homologous series of parent octamethylcyclotetrasilazane (c‐NH‐SiMe2‐)4, ( 1 ), the lithium complex [(THF)2Li2(c‐N‐SiMe2‐NH‐SiMe2‐)2]2, ( 2 ), containing the cyclic dianion, and [(THF)2LiAl(c‐N‐SiMe2‐)4]2, ( 3 ), accommodating the unprecedented tetraanion [Me2SiN]4‐ was synthesized to investigate the nature of the covalent Si‐N single bond in the presence of various metals. These model compounds show a wide diversity of Si‐N(H), Si‐N(M), Si‐N(H, M) and M‐N bonds and serve as bench‐mark systems to study polar bonds by high‐resolution low‐temperature X‐ray structure analysis. Experimental charge density studies reveal highly polar Si‐N bonds with remarkable ionic contribution, even in the non‐metallated starting material 1 . The Li‐N and Li‐O bonds have to be classified as almost purely ionic bonds with topological properties not far from those determined for NaCl. 相似文献
123.
Hartwig Möller Nikolaus Seiler und Gottfried Werner 《Fresenius' Journal of Analytical Chemistry》1968,243(1):126-129
Zusammenfassung Es werden Erfahrungen mit der Kombination von automatischem Aminosäurenanalysator und Szintillations-Durchflußzelle zur Bestimmung der spezifischen Radioaktivität 14C-markierter Aminosäuren im Gehirn mitgeteilt. Die Erfassungsgrenze beträgt 3 · 10–4 Ci/ml Eluat, die Reproduzierbarkeit 5–1% vom Mittelwert im Meßbereich von 1 · 10–3 bis 5 · 10–2 Ci.
A method for the determination of the specific radioactivity of free amino-acids in tissue extracts of mammals
Some experiences are given with a measuring device for the determination of the specific radioactivity of 14C-labelled brain amino-acids. The apparatus consists of an automatic amino-acid analyzer combined with a flow cell filled with anthracene. The reproducibility of the method is ±5% to ±1% m.e. in the range of 1×10–3 Ci to 5×10–2 Ci. A quantitative determination of 3×10–4 Ci/ml eluant is still possible.相似文献
124.
An investigation of hypersonic boundary‐layer flow along a flat plate is being presented. The high Mach number investigated calls for the consideration of the chemical reactions and the change in thermodynamical properties for temperatures up to T = 6000 K. For the current investigation a test case at M = 20 and the atmospheric conditions at an altitude of H = 50 Km is chosen. The differences to the ideal‐gas result is demonstrated. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
125.
K. Ertel U. Kohl J. Lehmann M. Merschdorf W. Pfeiffer A. Thon S. Voll G. Gerber 《Applied physics. B, Lasers and optics》1999,68(3):439-445
Received: 6 November 1998 相似文献
126.
Two stereoisomeric pentacyclic oxindole alkaloids from Uncaria tomentosa: uncarine C and uncarine E
Ilias Muhammad Ikhlas A. Khan Nikolaus H. Fischer Frank R. Fronczek 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):480-482
The chloroform solvate of uncarine C (pteropodine), (1′S,3R,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octahydro‐1′‐methyl‐2‐oxospiro[3H‐indole‐3,6′(4′aH)‐[1H]pyrano[3,4‐f]indolizine]‐4′‐carboxylic acid methyl ester, C21H24N2O4·CHCl3, has an absolute configuration with the spiro C atom in the R configuration. Its epimer at the spiro C atom, uncarine E (isopteropodine), (1′S,3S,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octahydro‐1′‐methyl‐2‐oxospiro[3H‐indole‐3,6′(4′aH)‐[1H]pyrano[3,4‐f]indolizine]‐4′‐carboxylic acid methyl ester, C21H24N2O4, has Z′ = 3, with no solvent. Both form intermolecular hydrogen bonds involving only the oxindole, with N?O distances in the range 2.759 (4)–2.894 (5) Å. 相似文献
127.
Nikolaus Hofreiter 《Monatshefte für Mathematik》1941,49(1):219-227
Ohne ZusammenfassungGedächtnisrede, die der Verf. am 7. Juni 1940 in der Wiener Mathematischen Gesellschaft hielt. 相似文献
128.
129.
Rita França Rodrigues Palmira Ferreira da Silva Prof. Karina Shimizu Dr. Adilson A. Freitas Dr. Sergey A. Kovalenko Dr. Nikolaus P. Ernsting Prof. Frank H. Quina Prof. António Maçanita Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(6):1397-1402
The red flavylium cations of anthocyanins form ground‐state charge‐transfer complexes with several naturally occurring electron‐donor copigments, such as hydroxylated flavones and hydroxycinnamic or benzoic acids. Excitation of the 7‐methoxy‐4‐methyl‐flavylium–protocatechuic acid complex results in ultrafast (240 fs) internal conversion to the ground state of the complex by way of a low‐lying charge‐transfer state. Thus, both uncomplexed anthocyanins, whose excited state decays by fast (5–20 ps) excited‐state proton transfer, and anthocyanin–copigment complexes have highly efficient mechanisms of deactivation that are consistent with the proposed protective role of anthocyanins against excess solar radiation in the vegetative tissues of plants. 相似文献
130.
The article reviews the use of electrochemical biosensors for detecting lactate, a key metabolite of the anaerobic glycolytic
pathway. This compound plays an important role in (sports) medicine, in the nutritional sector, in food quality control and
touches environmental concerns. Amperometric biosensors offer a sensitive and selective means to monitor organic analytes
like lactate. A detailed study on different aspects of amperometric lactate biosensor preparation is described: the main configuration
aspects are compiled regarding electrode materials, biorecognition elements, immobilization methods, mediators and cofactors
as well as fields of application. Comparative studies are conducted correlating different configuration aspects and performance
of the resulting biosensors. This review contains 214 references from the years 1974 to 2007.
Correspondence: Beate Strehlitz, UFZ, Helmholtz Centre for Environmental Research – UFZ, Environmental and Biotechnology Centre
(UBZ), Permoserstrasse 15, D-04318 Leipzig, Germany 相似文献