排序方式: 共有75条查询结果,搜索用时 15 毫秒
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Elmira Solati Maryam Mashayekh Davoud Dorranian 《Applied Physics A: Materials Science & Processing》2013,111(3):689-694
Electrically pumped ultraviolet random lasing was achieved in metal-insulator-semiconductor (MIS) diodes based on ZnO films at room temperature. The ZnO films were grown by plasma assisted molecular beam epitaxy. Two different kinds of insulator layers, SiO x (0<x≤2) and AlO x (0<x≤1.5) were deposited by electron beam evaporation. X-ray diffraction experiments found these oxide layers were amorphous (or microcrystals), and X-ray photoelectron spectroscopy confirmed the Si and Al were fully oxidized. Compared with devices using SiO x as the insulator layer, diodes with evaporated AlO x layers showed a lower working threshold forward current (~20 mA to ~26 mA) and higher emission intensity. Periodic features indicating formation of closed-loop paths were deduced by the power Fourier transform of electroluminescence spectra. The cavity length of both devices increased as forward currents increased, while a larger cavity length was always obtained in the AlO x -involved device under the same working current. The improved performance was attributed to larger hole amount in AlO x layers. These results revealed that evaporated AlO x can serve as good electron blocking and hole supplying layers for hetero-structures. 相似文献
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A domino approach to naphtho[2,1-b]furan-2(1H)-one derivatives from (Z)-4-arylidene-2-phenyl-5(4)-oxazolones (azlactones) and 2-naphthols catalyzed by p-TSA with reasonably moderate to high yields, has been developed. This protocol illustrates attractive features including a unique and convenient process. 相似文献
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Askhat Sabitov Katarzyna Gawe-Bben Zuriyadda Sakipova Marcelina Strzpek-Gomka Uliana Hoian Elmira Satbayeva Kazimierz Gowniak Agnieszka Ludwiczuk 《Molecules (Basel, Switzerland)》2021,26(9)
Plants belonging to the Rosa genus are known for their high content of bioactive molecules and broad spectrum of healing and cosmetic activities. Rosa platyacantha Schrenk is a wild-type species abundant in the mountainous regions of Kazakhstan. The phytochemical composition as well as the bioactivity of R. platyacantha extracts have not been fully investigated to date. In this study, various parts of R. platyacantha plant, collected in Almaty region, Kazakhstan, were used to prepare five hydroalcoholic extracts (R1–R5). The extracts were compared for the content of phytochemicals and selected biological activities, which are important for the potential cosmetic application of R. platyacantha. Extract R3, prepared from flower buds, showed the most significant antioxidant and tyrosinase inhibitory potential, decreasing the monophenolase and diphenolase activities of tyrosinase. Extract R3 showed also collagenase inhibitory activity and cytotoxicity against human melanoma cells A375, being less cytotoxic for noncancerous skin keratinocytes HaCaT. Analysis of fractions E and F, obtained from R3 extracts, revealed that quercetin, kaempferol, rutin, and their derivatives are more likely responsible for the tyrosinase inhibitory properties of R. platyacantha extracts. 相似文献
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Nedialko B. Dimitrov Dennis P. Michalopoulos David P. Morton Michael V. Nehme Feng Pan Elmira Popova Erich A. Schneider Gregory G. Thoreson 《Annals of Operations Research》2011,187(1):207-228
We describe a model for deploying radiation detectors on a transportation network consisting of two adversaries: a nuclear-material smuggler and an interdictor. The interdictor first installs the detectors. These installations are transparent to the smuggler, and are made under an uncertain threat scenario, which specifies the smuggler??s origin and destination, the nature of the material being smuggled, the manner in which it is shielded, and the mechanism by which the smuggler selects a route. The interdictor??s goal is to minimize the probability the smuggler evades detection. The performance of the detection equipment depends on the material being sensed, geometric attenuation, shielding, cargo and container type, background, time allotted for sensing and a number of other factors. Using a stochastic radiation transport code (MCNPX), we estimate detection probabilities for a specific set of such parameters, and inform the interdiction model with these estimates. 相似文献
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Dr. Elmira Mohammadi Lukáš Petera Dr. Homa Saeidfirozeh Antonín Knížek Dr. Petr Kubelík Dr. Roman Dudžák Dr. Miroslav Krůs Dr. Libor Juha Prof. Svatopluk Civiš Rémi Coulon Dr. Ondřej Malina Dr. Juri Ugolotti Dr. Václav Ranc Prof. Michal Otyepka Prof. Jiří Šponer Dr. Martin Ferus Dr. Judit E. Šponer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(52):12075-12080
Terrestrial volcanism has been one of the dominant geological forces shaping our planet since its earliest existence. Its associated phenomena, like atmospheric lightning and hydrothermal activity, provide a rich energy reservoir for chemical syntheses. Based on our laboratory simulations, we propose that on the early Earth volcanic activity inevitably led to a remarkable production of formic acid through various independent reaction channels. Large-scale availability of atmospheric formic acid supports the idea of the high-temperature accumulation of formamide in this primordial environment. 相似文献
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Two N-thiophosphorylated thiosemicarbazides of the common formula RC(S)NHP(S)(OiPr)2 [R = PhNHNH- (1); EtN(NH2)- (2)] have been synthesized and characterized by IR, 1H and 31P spectroscopy, and the single crystal X-ray diffraction method. Single crystal X-ray diffraction studies showed the thiosemicarbazides form both intra- and intermolecular hydrogen bonds, which in turn lead to polymeric chain formation. Moreover, according to the X-ray data of the phenylsubstituted thiosemicarbazide, the formation of intermolecular H?η6-phenyl interactions were established. 相似文献
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Spin crossover in a series of six cyanide-bridged iron(II) tetranuclear square complexes was analyzed using density functional theory (DFT) methods. As the spin crossover between the low-spin (LS) and high-spin (HS) states can occur only for two of four iron ions, we characterized energetically and structurally the [LS-LS], [HS-LS], and [HS-HS] spin-state isomers. For all studied complexes, the energy of the mixed [HS-LS] spin state does not deviate essentially from the halfway point between the energies of homogeneous spin states, thereby satisfying the conditions for an one-step transition between the [LS-LS] and [HS-HS]. This fact reflects the weak elastic coupling between the environments of transiting centers. The two-step spin transition observed in one complex can appear only due to the crystal packing effects. We also evaluated the strength of exchange coupling between the paramagnetic ions in the [HS-HS] state. 相似文献