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51.
Uwe Schmidt Luis Werner Merle Arrowsmith Andrea Deissenberger Alexander Hermann Alexander Hofmann Stefan Ullrich James D. Mattock Alfredo Vargas Holger Braunschweig 《Angewandte Chemie (International ed. in English)》2020,59(1):325-329
The reaction of aryl‐ and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3‐trans‐dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis‐1,2‐μ‐H‐3‐hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base‐stabilized B3H4+ analogues. 相似文献
52.
Raymundo Cea-Olivares Rubn Alfredo Toscano Marcela Lpez Patricia García 《Heteroatom Chemistry》1993,4(4):313-317
Three 1,1-dithioacids containing an additional functional group, 2-pyrrolidone-1-carbodithioic acid, 2-hydroxycyclopentene-1-carbodithioic acid, and 2-pyrrolidone-1,3-bis(carbodithioic) acid, were reacted with the Group 15 heterocycles 2-chloro-1,3-dithia-2-arsa- and stiba-cyclopentanes (CIMS2C2H4; M = As, Sb). The dithiocomplexes obtained were characterized by spectroscopic methods and elemental analyses. The X-ray structure determination of the 2-pyrrolidonedithiocarbamate of 1,3-dithia-arsacyclopentane shows a monodentate behavior of the dithiocarbamate entity and the absence of participation of the carbonyl oxygen in the coordination. 相似文献
53.
The cationic bioxazoline Pd(II) complex 2 catalyzes the alternating copolymerization of carbon monoxide with styrene and 4-methylstyrene, respectively, to yield a highly isotactic optically active polymer at room temperature and low carbon monoxide pressure (1–4 atm). 相似文献
54.
Quantification of veterinary antibiotics (sulfonamides and trimethoprim) in animal manure by liquid chromatography-mass spectrometry 总被引:22,自引:0,他引:22
Haller MY Müller SR McArdell CS Alder AC Suter MJ 《Journal of chromatography. A》2002,952(1-2):111-120
A fast and cost effective method was developed to extract and quantify residues of veterinary antimicrobial agents (antibiotics) in animal manure by liquid-liquid extraction and liquid chromatography-mass spectrometry. The compounds investigated include six sulfonamides, one metabolite, and trimethoprim. The method was performed without sample clean up. Recoveries from spiked manure slurry samples (spike level = 1 mg/kg) were as follows: sulfaguanidine (52%), sulfadiazine (47%), sulfathiazole (64%), sulfamethazine (89%), its metabolite N4-acetyl-sulfamethazine (88%), sulfamethoxazole (84%), sulfadimethoxine (51%), and trimethoprim (64%). Relative standard deviations of the recoveries were less than 5% within the same day and less than 20% between days. The limit of quantification was below 0.1 mg/kg liquid manure slurry for all compounds and calibration curves obtained from extracts of spiked samples were linear up to a level of 5 mg/kg liquid manure, except for trimethoprim (0.01-0.5 mg/kg). Analysis of six grab samples taken in Switzerland from manure pits on farms where medicinal feed had been applied revealed total sulfonamide concentrations of up to 20 mg/kg liquid manure. 相似文献
55.
Direct and inverse problems for first-order in time linear evolution problems without initial conditions, i.e. related to
the unbounded time-intervals (−∞, 0] and
\mathbbR{\mathbb{R}}, are considered in the framework of Banach spaces. Some degenerate in time problems related to a bounded time-interval are
also considered.
The approach for solving the previous problems is related to both C
0-and Analytic Semigroup Theory. 相似文献
56.
Alfredo?Macías Abel?Camacho Luis?F.?Barragán-Gil Claus?L?mmerzahl 《General Relativity and Gravitation》2010,42(3):489-508
The canonical quantization for N = 1 supergravity in the context of gravitational minisuperspace described by Gowdy T
3 and Bianchi class A cosmological models is analyzed in order to search for physical states. There are indeed physical states
in the minisuperspace sector of the theory. This fact entails that the non-physical states conjecture has a restricted validity,
and in consequence it cannot be considered a general result. 相似文献
57.
Emma Sotelo-Gonzalez María T. Fernandez-ArgüellesJose M. Costa-Fernandez Alfredo Sanz-Medel 《Analytica chimica acta》2012
Quantum dot (QD) nanoparticles (NPs) are increasingly used as highly valuable fluorescent biomarkers and as sensitive (bio)chemical probes. Interestingly, if certain metal impurities are incorporated during the NPs synthesis, phosphorescent QDs with analytical potential can be obtained. 相似文献
58.
Alfredo Peris 《Proceedings of the American Mathematical Society》1999,127(12):3601-3603
Contrary to the case of polynomials on Banach spaces, in which it is known that no hypercyclic homogeneous polynomial of degree exists on any Banach space, we construct for each a chaotic -homogeneous polynomial on the Fréchet space .
59.
Polar Diterpenoids from Leaf-Glands of Plectranthus argentatus S. T. BLAKE From the red leaf-glands of the Australian Plectranthus argentatus the following novel diterpenoids were isolated: coleon-U-quinone ( 1 ), 8α,9α-epoxycoleon-U-quinone ( 3 ), 6β-formyloxy-7α-hydroxyroyleanone ( 7 ), and 5,6-dihydrocoleon U ( 10 ), besides the already known compounds 6β, 7α-dihydroxyroyleanone ( 4 ), 7α-acetoxy-6β-hydroxyroyleanone ( 5 ), and 7α-formyloxy-6β-hydroxyroyleanone ( 6 ). Epoxydation of 1 by perborate led in 32% yield to the epoxyquinone 3 . 相似文献
60.
Alfredo De Rossi Gaetano Assanto Stefano Trillo William E. Torruellas 《Optics Communications》1998,150(1-6):390-398
We have identified a family of (2+1)D spatial solitary waves which can stably propagate in bulk media in the presence of coexisting diffraction, self-focusing Kerr and quadratic nonlinearities. In a conspicuous range of excitation conditions close to the stationary solutions, the emerging wavepackets are immune to the detrimental occurrence of filamentation and collapse, typical of pure Kerr media. The presence of a second-order contribution to the cubic nonlinear response is, therefore, able to prevent optical damage in applications relying on self-guidance. We show that the cross-phase modulation plays an important effect on stability. Our estimate shows that the effects of the cubic susceptibility cannot be neglected below a certain beam size in realistic crystals (e.g. KTP or similar). 相似文献