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61.
62.
Cyclization cascades involving C-C bond formations followed by lactonization reactions provide fast access to structurally complex tricyclic indane and tetrahydronaphthalene derivatives. 相似文献
63.
We study deterministic discounted optimal control problems associated with discrete-time systems. It is shown that, for small discount rates, the controllability properties of the underlying system can guarantee the convergence of the discounted value function to the value function of the average yield. An application in the theory of exponential growth rates of discrete inclusions is presented. This application motivates the analysis of infinite-horizon optimal control problems with running yields that are unbounded from below. 相似文献
64.
65.
Electromagnetic and nuclear fission of238U in the reaction of 100, 500, and 1000 A·MeV208Pb with238U
S. Polikanov W. Brüchle H. Folger E. Jäger T. Krogulski M. Schädel E. Schimpf G. Wirth T. Aumann J. V. Kratz E. Stiel N. Trautmann 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(3):221-227
The folding- and azimuthal-angle and velocity distributions for the238U fission fragments have been measured in reactions with 100, 500, and 1000 A·MeV208Pb. These distributions were used to decompose the fission cross section into its electromagnetic and nuclear components. The fraction of electromagnetic fission was found to be 0.16±0.07, 0.48±0.08, and 0.60±0.04, respectively. The electromagnetic fission cross section as a function of the208Pb nucleus energy is compared with theoretical predictions. The measured fission cross section from nuclear reactions (≈1.5 b) is approximately constant between 100 and 1000 A·MeV. 相似文献
66.
67.
Dietrich PM Horlacher T Girard-Lauriault PL Gross T Lippitz A Min H Wirth T Castelli R Seeberger PH Unger WE 《Langmuir : the ACS journal of surfaces and colloids》2011,27(8):4808-4815
Carbohydrate films on gold based on dimannoside thiols (DMT) were prepared, and a complementary surface chemical analysis was performed in detail by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), near-edge X-ray absorption fine structure (NEXAFS), FT-IR, and contact angle measurements in order to verify formation of ω-carbohydrate-functionalized alkylthiol films. XPS (C 1s, O 1s, and S 2p) reveals information on carbohydrate specific alkoxy (C-O) and acetal moieties (O-C-O) as well as thiolate species attached to gold. Angle-resolved synchrotron XPS was used for chemical speciation at ultimate surface sensitivity. Angle-resolved XPS analysis suggests the presence of an excess top layer composed of unbound sulfur components combined with alkyl moieties. Further support for DMT attachment on Au is given by ToF-SIMS and FT-IR analysis. Carbon and oxygen K-edge NEXAFS spectra were interpreted by applying the building block model supported by comparison to data of 1-undecanethiol, poly(vinyl alcohol), and polyoxymethylene. No linear dichroism effect was observed in the angle-resolved C K-edge NEXAFS. 相似文献
68.
Altun M Kramer HB Willems LI McDermott JL Leach CA Goldenberg SJ Kumar KG Konietzny R Fischer R Kogan E Mackeen MM McGouran J Khoronenkova SV Parsons JL Dianov GL Nicholson B Kessler BM 《Chemistry & biology》2011,18(11):1401-1412
Converting lead compounds into drug candidates is a crucial step in drug development, requiring early assessment of potency, selectivity, and off-target effects. We have utilized activity-based chemical proteomics to determine the potency and selectivity of deubiquitylating enzyme (DUB) inhibitors in cell culture models. Importantly, we characterized the small molecule PR-619 as a broad-range DUB inhibitor, and P22077 as a USP7 inhibitor with potential for further development as a chemotherapeutic agent in cancer therapy. A striking accumulation of polyubiquitylated proteins was observed after both selective and general inhibition of cellular DUB activity without direct impairment of proteasomal proteolysis. The repertoire of ubiquitylated substrates was analyzed by tandem mass spectrometry, identifying distinct subsets for general or specific inhibition of DUBs. This enabled identification of previously unknown functional links between USP7 and enzymes involved in DNA repair. 相似文献
69.
A method for measuring local current density, not requiring segmentation of the electrode or spatial scanning, is presented. The motion of colloidal particles in response to local current density, characterized by the intensity of the light they scatter, is the fundamental phenomenon of the technique. The scattering was produced and measured with the electrochemical total internal reflection microscope, a tool that places an electrochemical cell within a total internal reflection apparatus. The electrolysis of water and the oxidation of ferrocene monocarboxylic acid were used as test reactions. Light scattered by a probe particle produced an "image" of current density; scattered light was converted to local current density by a function derived herein. Numerical simulations supplemented experimental evidence that local current density controlled the probe particle's vertical motion. The spatial resolution of the method was approximately the length scale of the probe particle, in this case 5.7 μm. The resolution of current density was better than 100 nA cm(-2). The method might find use in high throughput screening of electrocatalysts. 相似文献
70.
Forster J Rösner B Khusniyarov MM Streb C 《Chemical communications (Cambridge, England)》2011,47(11):3114-3116
A new mechanism for enhancing the visible light absorption of a homogeneous polyoxovanadate system is described. The photoactive pentanuclear {V(5)} isopolyoxovanadate cluster is formed in situ by a thermally-induced condensation reaction starting from a tetranuclear {V(4)} precursor. Upon irradiation with visible light, {V(5)} undergoes a light induced reduction reaction resulting in the formation of a 2-electron reduced {V(10)} cluster. Simultaneously, the oxidant methanol is selectively oxidized to formaldehyde. The {V(10)} cluster can subsequently be re-oxidized using H(2)O(2) or O(2). 相似文献