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排序方式: 共有107条查询结果,搜索用时 15 毫秒
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Claudius Lenz Sebastian Dörner Dr. Alexander Sherwood Prof. Dr. Dirk Hoffmeister 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(47):12166-12171
Psilocin ( 1 ) is the dephosphorylated and psychotropic metabolite of the mushroom natural product psilocybin. Oxidation of the phenolic hydroxy group at the C-4 position of 1 results in formation of oligomeric indoloquinoid chromophores responsible for the iconic blueing of bruised psilocybin-producing mushrooms. Based on previous NMR experiments, the hypothesis included that the 5,5’-coupled quinone dimer of 1 was the primary product responsible for the blue color. To test this hypothesis, ring-methylated 1 derivatives were synthesized to provide stable analogs of 1 dimers that could be completely characterized. The chemically oxidized derivatives were spectroscopically analyzed and compared to computationally derived absorbance spectra. Experimental evidence did not support the original hypothesis. Rather, the blue color was shown to stem from the quinoid 7,7’-coupled dimer of 1 . 相似文献
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D. Rudolph D.G. Sarantites C. Andreoiu C. Fahlander D.P. Balamuth R.J. Charity M. Devlin J. Eberth A. Galindo-Uribarri P.A. Hausladen D. Seweryniak L.G. Sobotka Th. Steinhardt 《The European Physical Journal A - Hadrons and Nuclei》2002,14(2):137-146
Prompt proton decay lines in 58Cu have been studied by means of high-resolution in-beam particle-γ coincidence spectroscopy using the GAMMASPHERE Ge-detector
array in conjunction with a dedicated set of ancillary detectors including four ΔE-E silicon-strip telescopes. High-spin states in 58Cu have been populated via the heavy-ion fusion-evaporation reaction 28Si(36Ar, 1α1p1n) at 148 MeV beam energy. The full-width at half maximum for the proton peak could be reduced significantly compared
to earlier experiments. The results indicate that only one prompt proton decay branch exists in the decay-out of the well-deformed
band of 58Cu.
Received: 11 March 2002 / Accepted: 10 April 2002 相似文献
87.
Baumann D Dymarsky A Klebanov IR McAllister L Steinhardt PJ 《Physical review letters》2007,99(14):141601
We investigate whether explicit models of warped D-brane inflation are possible in string compactifications. To this end, we study the potential for D3-brane motion in a warped conifold that includes holomorphically embedded D7-branes involved in moduli stabilization. The presence of the D7-branes significantly modifies the inflaton potential. We construct an example based on a very simple and symmetric embedding due to Kuperstein, z1= const, in which it is possible to fine-tune the potential so that slow-roll inflation can occur. The resulting model is rather delicate: inflation occurs in the vicinity of an inflection point, and the cosmological predictions are extremely sensitive to the precise shape of the potential. 相似文献
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Georg Bechler Claudius Steinhardt Jochen Mackert Robert Klein 《European Journal of Operational Research》2021,288(3):902-917
Recent advances in customer choice analysis demonstrated the strong impact of compromise alternatives on the behaviour of decision-makers in a wide range of decision situations. Compromise alternatives are characterized by an intermediate performance on some of the relevant attributes. For instance, price compromises are well known in the sense that customers tend to buy neither the cheapest, nor the most expensive alternative, but the mid-priced one. However, thus far, the literature on product line optimization has not considered such context effects.In this paper, we propose a model-based approach for optimal product line selection which incorporates customers’ preferences for compromise alternatives. We consider customer choice in a realistic, sophisticated fashion by applying an established utility model that integrates compromise variables into a multinomial logit model. We formulate the resulting optimization problem as a mixed-integer linear program. The challenging feature for modelling – making the formulation substantially more complicated than existing ones without compromises – are the endogenous effects of selected products on other alternatives’ utilities that need to be adequately captured via compromise variables. Based on data we collected by a stated choice experiment in a retail setting, we perform a computational study and demonstrate the superiority of our product line selection approach compared to a reference model that does not take compromises into account. Even under uncertainty of the estimated utility parameters, profit gains of, on average, 23% can be achieved in our experimental setting. 相似文献
90.
We note that the essential idea of inflation, that the Universe underwent a brief period of accelerated expansion followed by a long period of decelerated expansion, can be encapsulated in a "closure condition" which relates the amount of accelerated expansion during inflation to the amount of decelerated expansion afterward. We present a protocol for systematically testing the validity of this condition observationally. 相似文献