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981.
S.A. Studenikin M. Byszewski D.K. Maude M. Potemski A. Sachrajda Z.R. Wasilewski M. Hilke L.N. Pfeiffer K.W. West 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):73
Microwave induced resistance oscillations (MIROs) were studied experimentally over a very wide range of frequencies ranging from 20 GHz up to 4 THz, and from the quasi-classical regime to the quantum Hall effect regime. At low frequencies regular MIROs were observed, with a periodicity determined by the ratio of the microwave to cyclotron frequencies. For frequencies below 150 GHz the magnetic field dependence of MIROs waveform is well described by a simplified version of an existing theoretical model, where the damping is controlled by the width of the Landau levels. In the THz frequency range MIROs vanish and only pronounced resistance changes are observed at the cyclotron resonance. The evolution of MIROs with frequency is presented and discussed. 相似文献
982.
Photoluminescence (PL), photoluminescence excitation (PLE) and selective excitation (SE-PL) studies were performed in an attempt to identify the origin of the emission bands in a pseudomorphic In0.05Ga0.95N/GaN film. Besides the InGaN near-band-edge PL emission centred at 3.25 eV an additional blue band centred at 2.74 eV was observed. The lower energy PL peak is characterized by an energy separation between absorption and emission–the Stokes’ shift–(500 meV) much larger than expected. A systematic PLE and selective excitation analysis has shown that the PL peak at 2.74 eV is related to an absorption band observed below the InGaN band gap. We propose the blue emission and its related absorption band are associated to defect levels, which can be formed inside either the InGaN or GaN band gap. 相似文献
983.
984.
I. G. Gverdtsiteli A. I. Guldamashvili E. M. Diasamidze S. A. Zaslavsky A. N. Kalinin M. A. Kumakhov 《辐射效应与固体损伤》2013,168(3):171-174
Experiments on the dependence of penetration of boron ions channelled into silicon are described. 相似文献
985.
Kun-Jen Chung Jui-Jung Liao Shy-Der Lin Sheng-Tu Chuang Hari M. Srivastava 《Mathematical Methods in the Applied Sciences》2020,43(6):3099-3116
In the year 2006, Teng et al considered an appropriate economic production quantity (EPQ) model in which the manufacturer receives the supplier's trade credit and provides trade credit to the customer simultaneously. The following two payment methods were discussed by Teng et al: The main purpose of this paper is summarized below: Finally, with a view to further motivating the interested researchers for using the methodology and mathematical analytic techniques in several other contexts in the field, we have chosen to include, in Section 12, a number of related recent works in the field. 相似文献
986.
The Schrödinger equation is solved for a particle confined within the ellipsoidal potential well using the perturbation theory and the Hamiltonian diagonalization method. The explicit expressions are obtained for the energy levels that are size and shape dependent and appropriate wave functions. The calculated energy levels are in a good qualitative and quantitative agreement with the result obtained by numerical solution of the Schrödinger equation. It is revealed that for the lowest states of a given symmetry the region of validity of the perturbation approximation is much larger than it follows from the usual condition of applicability of the perturbation theory. The optical properties of nanoparticles of a prolate and oblate ellipsoidal shape are discussed. 相似文献
987.
《Biomedical chromatography : BMC》2018,32(5)
Lipoic acid (LA) is used extensively as a therapeutic agent for the treatment of various diseases. Many methods have been reported for the determination of LA plasma levels and its metabolites after its supplementation, but available information concerning endogenous plasma levels is still scarce. Studies which directly focused on determining the endogenous plasma levels provided highly controversial results, <4.9 nmol/L or 143.7–197.0 nmol/L. The main aim of this study was to verify the levels of free LA in the plasma of 40 individuals (17 women, 23 men). This group was nonsupplemented with LA and met the conditions for incorporation into the blood donors register. We measured the levels of LA using an HPLC method with very sensitive coulometric detection after previous sample preparation including deproteination and solid‐phase extraction with a Phenyl cartridge. Our limit of detection was 1.85 nmol/L and was better than the values reported in studies that directly focused on determining the endogenous plasma levels of LA: 2.4 and 4.9 nmol/L respectively. However, the levels of free LA in the plasma of nonsupplemented voluntary blood donors were not detectable in all cases. The presented results of our study show that endogenous concentrations of LA are <1.85 nmol/L. 相似文献
988.
Vasanthy Karmegam Chinthaka M. Udamulle Gedara Michael C. Biewer Mihaela C. Stefan 《Journal of polymer science. Part A, Polymer chemistry》2018,56(22):2547-2553
Side chain engineering has been used for tuning the opto-electronic properties of organic semiconductors. In this work, a series of pyrimidine-based donor-acceptor (D-A) conjugated polymers functionalized with electron-withdrawing or electron-donating side chains were synthesized. The opto-electronic properties of the pyrimidine D-A conjugated polymers were investigated focusing on the dependence on the electron withdrawing strength of the acceptor moiety, while maintaining the same donor moiety. Fine-tuning of the energy levels was achieved by introducing electron donating (alkoxy [ OR] and alkylthio [ SR]) or electron withdrawing (alkylsulfinyl [ SOR] and alkylsulfonyl [ SO2R]) side chains onto the acceptor moiety. The effects of side chain modification have been investigated through DFT calculations, UV–vis analysis, and electrochemical measurements. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2547–2553 相似文献
989.
990.
Ayşe Tekin Dede 《International Journal of Mathematical Education in Science & Technology》2019,50(2):292-314
Socio-cultural theories in mathematics education field recently emphasize the importance of the collective argumentation within small-group work. Since mathematical modelling tasks require a process in which students search for a solution for real life problems through small-group work, the arguments in this process become an issue of concern. This study examines the arguments constructed within the mathematical modelling cycle by considering the participants’ modelling processes. In this context, four primary pre-service mathematics teachers worked on a modelling task and their arguments were explained through the components of Toulmin’s argumentation schema. Findings revealed that the data and the claims of most of the arguments corresponded to the starting and ending points of the modelling transition in which the current arguments constructed. The existence of the arguments corresponded through warrant-claim originated from inquiring the assumptions in the modelling cycle. In addition, the participants made assumptions as warrants to support their arguments and as rebuttals to show the degree of certainty of claims in intra-group challenging situations. Both the warrants and the backings depended on modelling context as well as mathematics context. 相似文献