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61.
62.
In less than 2 hours, (Z)-alkenols of 97 – 98% stereoisomeric purity may be prepared and isolated (!) if a new type of “instant-ylids” is used. 相似文献
63.
Frank C. De Lucia Jr. Jennifer L. Gottfried Chase A. Munson Andrzej W. Miziolek 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1399-1404
Detecting trace explosive residues at standoff distances in real-time is a difficult problem. One method ideally suited for real-time standoff detection is laser-induced breakdown spectroscopy (LIBS). However, atmospheric oxygen and nitrogen contributes to the LIBS signal from the oxygen- and nitrogen-containing explosive compounds, complicating the discrimination of explosives from other organic materials. While bathing the sample in an inert gas will remove atmospheric oxygen and nitrogen interference, it cannot practically be applied for standoff LIBS. Alternatively, we have investigated the potential of double pulse LIBS to improve the discrimination of explosives by diminishing the contribution of atmospheric oxygen and nitrogen to the LIBS signal. These initial studies compare the close-contact (< 1 m) LIBS spectra of explosives using single pulse LIBS in argon with double pulse LIBS in atmosphere. We have demonstrated improved discrimination of an explosive and an organic interferent using double pulse LIBS to reduce the air entrained in the analytical plasma. 相似文献
64.
Birgit Krimmel Friederike Swoboda Sonja Solar Gottfried Reznicek 《Radiation Physics and Chemistry》2010,79(12):1247-1254
The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement –OCH3 by ?OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC–UV and LC–ESI–MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed. 相似文献
65.
Bernhard Traulich†Eilo Hildebrand‡Angelika Schimz‡Gottfried WagnerJanos K. Lanyi§ 《Photochemistry and photobiology》1983,37(5):577-579
Halobacterium halobium , strain L-33, which is deficient in bacteriorhodopsin (BR) but synthesizes increased amounts of halorhodopsin (HR), shows behavioral responses upon changes in fluence rate with visible light or with UV light. The observations support the earlier report (Schimz et al. , 1982). that BR is not essential for photosensing in H. halobium. In the UV-range, changes in light intensity elicit the maximal response at λ= 370 nm. In the visible range, changes in light intensity show the maximal response at Δ= 565 nm and a secondary peak at Δ= 590 nm. The latter corresponds to the absorption maximum of HR (Δmax = 588 nm). This light-energy converting retinal pigment of H. halobium thus appears to contribute to photosensory behavior. 相似文献
66.
Norman L. Allinger Helmut Hönig Ulrich Burkert Laszlo Asolnai Gottfried Huttner 《Tetrahedron》1984,40(18):3449-3453
The trans-syn-trans isomer of perhydrohenanthrene has the central ring in a boat conformation. A crystalline derivative (the dibenzoate of the cis 9,10-diol) was prepared, and the crystal structure was determined. The boat conformation is slightly twisted, as predicted by molecular mechanics. 相似文献
67.
Gottfried Heinisch Barbara Matuszczak Elisabeth Spielmann Myriam Witvrouw Christophe Pannecouque Erik De Clercq 《Journal of heterocyclic chemistry》2001,38(1):125-130
Two methods for the preparation of dialkylsubstituted dipyridazino[4,3‐b:3′,4′‐e][1,4]diazepinones and dipyridazino[3,4‐b:3′,4′‐e][1,4]diazepinones are reported. The new compounds were evaluated for their inhibitory effects against the replication of human immunodeficiency virus [HIV‐1(IIIB) and HIV‐2(ROD)] in MT‐4 cells. 相似文献
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70.
Gottfried Machata 《Fresenius' Journal of Analytical Chemistry》1986,324(3-4):231