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排序方式: 共有137条查询结果,搜索用时 46 毫秒
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The problem of constructing confidence intervals of a fixed length for the location parameter based on a random size sample is considered. It is proposed to use the confidence interval $$\theta _p^* - u\sqrt p /\sigma< \theta< \theta _p^* + u\sqrt p /\sigma $$ , whereθ p * is an adaptive estimator,σ 2 is the Fisher information, and p?1 is the mean of the sample size. Nonparametric bounds are given for the limit as p → 0 confidence probability. Bibliography: 5 titles. 相似文献
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A quantitative estimate is given of the robustness of the characterization of the distribution with a density by the property of asymptotic -admissibility of the sample variance as an estimator of the population variance with a quadratic loss function.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 61, pp. 75–83, 1976. 相似文献
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Dr. Zhijia Wang Mikhail Ivanov Dr. Yuting Gao Laura Bussotti Prof. Paolo Foggi Huimin Zhang Prof. Nino Russo Prof. Bernhard Dick Prof. Jianzhang Zhao Prof. Mariangela Di Donato Dr. Gloria Mazzone Prof. Liang Luo Prof. Matvey Fedin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1091-1102
Spin–orbit charge-transfer intersystem crossing (SOCT-ISC) is useful for the preparation of heavy atom-free triplet photosensitisers (PSs). Herein, a series of perylene-Bodipy compact electron donor/acceptor dyads showing efficient SOCT-ISC is prepared. The photophysical properties of the dyads were studied with steady-state and time-resolved spectroscopies. Efficient triplet state formation (quantum yield ΦT=60 %) was observed, with a triplet state lifetime (τT=436 μs) much longer than that accessed with the conventional heavy atom effect (τT=62 μs). The SOCT-ISC mechanism was unambiguously confirmed by direct excitation of the charge transfer (CT) absorption band by using nanosecond transient absorption spectroscopy and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The factors affecting the SOCT-ISC efficiency include the geometry, the potential energy surface of the torsion, the spin density for the atoms of the linker, solvent polarity, and the energy matching of the 1CT/3LE states. Remarkably, these heavy atom-free triplet PSs were demonstrated as a new type of efficient photodynamic therapy (PDT) reagents (phototoxicity, EC50=75 nm ), with a negligible dark toxicity (EC50=78.1 μm ) compared with the conventional heavy atom PSs (dark toxicity, EC50=6.0 μm, light toxicity, EC50=4.0 nm ). This study provides in-depth understanding of the SOCT-ISC, unveils the design principles of triplet PSs based on SOCT-ISC, and underlines their application as a new generation of potent PDT reagents. 相似文献
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Sergey L. Veber Matvey V. Fedin Sergey V. Fokin Renad Z. Sagdeev Victor I. Ovcharenko Elena G. Bagryanskaya 《Applied magnetic resonance》2010,37(1-4):693-701
We report the X-band (9 GHz) electron paramagnetic resonance (EPR) study of series of bis(o-semiquinonato)copper(II) complexes with different ligands. It was found previously, that exchange interactions in spin triads of these compounds are very sensitive to the structure of the ligand coordinated to the central copper(II) ion. Ligand moderates the copper–radical and radical–radical exchange interactions and strongly changes the magnetic properties of the compound. Depending on a ligand, ferromagnetic or antiferromagnetic character of exchange dominates in the system. The EPR study of these complexes allowed us to obtain information on zero-field splitting parameters and their distributions in the studied compounds. The EPR results compliment previously obtained spectroscopic data on these compounds and suggest the pronounced plasticity of the clusters manifested in the broad distributions of their rhombicity parameters. 相似文献
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Atom-economic Approach to the Synthesis of α-(Hetero)aryl-substituted Furan Derivatives from Biomass
Leonid V. Romashov Kirill S. Kozlov Matvey K. Skorobogatko Alexander Y. Kostyukovich Valentine P. Ananikov 《化学:亚洲杂志》2022,17(1):e202101227
An atom-economic ring construction approach to the synthesis of α-(hetero)arylfurans based on renewable furanic platform chemicals has been developed. Corresponding compounds have been prepared in good to excellent yields via [2+2+2] and [4+2] cycloaddition reactions using metal-catalyzed or photoredox protocols. Easily available HMF-based 2-hydroxymethyl-5-ethynylfuran and 2-hydroxymethyl-5-cyanofuran were used as starting materials. A synthetic route with an improved carbon economy factor has been implemented to achieve sustainability aim. The possible application of arylfurans as molecular conductors has been investigated by DFT calculations, which revealed excellent charge transfer properties. As a future perspective, integration of biomass processing strategy into manufacturing of molecular electronics was pointed out to achieve the aim of sustainability. 相似文献
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Dr. Wawrzyniec Kaszub Andrea Marino Dr. Maciej Lorenc Prof. Eric Collet Prof. Elena G. Bagryanskaya Prof. Evgeny V. Tretyakov Prof. Victor I. Ovcharenko Prof. Matvey V. Fedin 《Angewandte Chemie (International ed. in English)》2014,53(40):10636-10640
Molecular compounds with photoswitchable magnetic properties have been intensively investigated over the last decades due to their prospective applications in nanoelectronics, sensing and magnetic data storage. The family of copper‐nitroxide‐based molecular magnets represents a new promising type of photoswitchable compounds. We report the first study of these appealing systems using femtosecond optical spectroscopy. We unveil the mechanism of ultrafast (<50 fs) spin state photoswitching and establish its principal differences compared to other photoswitchable magnets. On this basis, we propose potential advantages of copper‐nitroxide‐based molecular magnets for the future design of ultrafast magnetic materials. 相似文献
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There exists a considerable debate in the literature about the applicability of -stable distributions as they appear in Lévy"s central limit theorems. A serious drawback of Lévy"s approach is that, in practice, one can never know whether the underlying distribution is heavy tailed, or just has a long but truncated tail. Limit theorems for stable laws are not robust with respect to truncation of the tail or with respect to any change from 'light" to 'heavy" tail, or conversely. In this talk we provide a new 'pre-limiting" approach that helps overcome this drawback of Lévy-type central limit theorems. 相似文献
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