共查询到17条相似文献,搜索用时 62 毫秒
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我们利用单杂质Anderson模型及运动方程等理论,通过求解格林函数的方法研究了通过T型量子点结构(耦合于铁磁电极和介观环量子点结构)的自旋极化输运过程.研究结果表明,与量子点相耦合的铁磁电极中的极化强度是控制量子点电子输运的重要参数,由此可以达到自旋阀效应.另外我们还发现与量子点相耦合的介观环中的磁通会影响电子自旋向上和自旋向下近藤共振峰的分裂程度,但若加入适当的外磁场,那么这样的分裂将被抵消。 相似文献
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肿瘤基因MYC在人类70%癌细胞中高表达,抑制其转录是治疗肿瘤的有效手段.c-MYC启动子区P1近端的核酸酶超敏元件Ⅲ1(NHE Ⅲ1)控制MYC基因近90%的转录激活.NHE Ⅲ1区域富含碱基G序列并且形成G-四链体(G4),调控c-MYC基因转录,是抗肿瘤药物靶标.但G4-DNA和G4-RNA的三维结构高度相似,小分子与其他G4(如端粒G4、mRNA G4、c-Kit G4等)的非特异性作用会产生小分子药物“脱靶”效应,同时小分子药物会诱导其他G4形成从而干扰正常细胞的功能,造成靶向c-MYC G4抗癌药物设计困难.本文综述了近些年靶向肿瘤因子c-MYC G4-DNA的小分子药物研究进展,及核磁共振(NMR)技术在G4-DNA和G4-RNA结构确定中的作用,为靶向c-MYC G4-DNA的小分子药物设计等相关研究工作提供参考. 相似文献
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有机-无机杂化钙钛矿(OIHPs)是现阶段较为新颖的光电子材料之一,已被广泛地应用于太阳能电池和发光领域。然而,该类材料已被证实具有较强的自旋轨道耦合和Rashba效应,并且具备较高的载流子迁移率和消光系数。因此,这为实现自旋注入和自旋调控提供了重要依据。本文从三个方面对有机-无机杂化钙钛矿的自旋光电子学展开论述,首先是自旋极化电子在钙钛矿自旋器件中的输运研究以及铁磁-钙钛矿自旋界面研究;其次,是该材料在激发态下的磁场效应研究;最后,就钙钛矿自旋光电子学未来发展进行了探讨和评论。 相似文献
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运用密度泛函理论,对甘氨酸丙氨酸依次交替组成的13 条丝素寡肽链进行结构优化,并计算了平均结合能、偶极矩,绘出寡肽链的振动红外光谱. 计算结果发现,随着寡肽链的生长,平均结合能单调变化,典型官能团的红外特征峰均发生频移. 但官能团的伸缩振动和弯曲振动表现出相反的红移和蓝移趋势. 揭示出丝素氨基肽链的物理化学性质在生长过程存在尺寸效应及各向异性. 该现象源于同类官能团之间的耦合效应,以及分子内氢键作用对伸缩振动和弯曲振动具有不同的影响.
关键词:
寡肽
红外光谱
尺寸效应
奇偶效应 相似文献
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利用基于多组态Dirac-Fock方法的程序包GRASP92和RATIP以及在此基础上最新发展的RERR06程序,计算了锂原子1s2nl(n=2,3; l=s, p) 的内壳层和外壳层的光电离截面. 计算中详细考虑了光电离过程中的弛豫效应. 结果表明:在锂原子内壳层电子的光电离过程中弛豫效应较强,而在外壳层电子的光电离过程中弛豫效应较弱. 另外,相应于不同态的内壳层光电离过程,其弛豫效应的影响也不同,对激发态的影响比对基态的影响大,对高激发态
关键词:
多组态Dirac-Fock方法
光电离截面
弛豫效应 相似文献
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通过求解Bogoliubov-deGennes方程,利用推广的Bonder-Tinklam-Klapwijk方法,计算铁磁/绝缘层/铁磁/绝缘层/超导结构中的微分电导(G)和散粒噪声(S)。研究发现系统中的微分电导和散粒噪声都随中间铁磁层厚度作两种不同周斯的振荡,其中通过增强铁磁材料中的交换劈裂和铁磁/超导界面的势垒强度,短周期分量可从长周期中分离出来,反之通过降低铁磁层中的交换劈裂和铁磁/超导界面的势垒强度,长周期分量可从短周期中分离出来,这一结果表明G和S中的两种不同周期的振荡分量分别来自入射电子与铁磁/超导界面处的Andreev反射和正常电子反射的量子干涉效应。 相似文献
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强流重离子加速器HIAF-BRing在加速完成后进行束团合并,为研究BRing中的束流负载效应对束团合并的影响,对238U35+束流进行了粒子跟踪模拟。模拟结果显示,在束团合并过程中,束流负载效应引起束团长度和束团中心位置的振荡,导致束流动量分散和束团长度的增长。束团合并过程中尾场电压以及不同束团间尾场的耦合导致的势阱畸变,是引起束团长度和束团中心振荡及束流发射度增长的原因。为了降低束流负载效应的影响,采用多谐波前馈系统进行补偿,达到了补偿束团合并过程中的束流负载效应的目的,从而确保了BRing中引出束流的品质,同时根据模拟结果确定了前馈系统需要覆盖的频率范围和需要补偿的最大尾场电压。 相似文献
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An analytical thermodynamic theory is applied to investigate the electrocaloric effect of ferroelectric BaTiO3/SrTiO3 bilayer thin films with different orientations at room temperature. Theoretical analysis indicates that the strong electrostatic coupling between the layers results in the suppression of ferroelectricity at a critical relative thickness which occurs approximately at 50%, 23%, and 12% of SrTiO3 fraction in the (001), (110), and (111) bilayer thin films, respectively. The ferroelectric bilayer thin films are respected to have the largest electrocaloric effect at this critical relative thickness. Moreover, the electrocaloric effect strongly depends on the orientation and the (110) oriented bilayer thin films have the largest electrocaloric effect. Consequently, control of the orientation and the relative thickness of SrTiO3 layer can be used to adjust the electrocaloric effect of ferroelectric bilayer thin films, which may provide the potential for practical application in refrigeration devices. 相似文献
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从小尺度热晕线性理论出发,在non-Kolmogorov谱的基础上,得到了non-Kolmogorov谱湍流下热晕相位补偿的Strehl比表达式,分析了湍流谱对高能激光的相位补偿的影响.研究结果表明湍流谱对湍流热晕效应的相位补偿有重要的影响.在相同的湍流菲涅耳数下,当谱指数越接近于3时补偿效果越差,谱指数接近于4时补偿效果越好.在相同大气相干长度条件下或在相同湍流折射率常量条件下,当谱指数接近于3时,Strehl比随热晕效应的增强而下降变快,当湍流谱指数逐渐接近于4时,Strehl比下降速度变慢.其原因是随着湍流谱指数的增大,湍流热晕相互作用引起的对数振幅起伏增长变慢. 相似文献
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Pedro Henrique Benites Aoki Priscila Alessio Jose Antonio De Saja Carlos Jos Leopoldo Constantino 《Journal of Raman spectroscopy : JRS》2010,41(1):40-48
The synergistic effect produced by nanoparticles when incorporated into different systems used as analytical tools represents a growing research field nowadays. On the other hand, the study of interactions involving pharmacological drugs and biological membranes using phospholipids as mimetic systems is a research field already well established. Here, we combine both the anionic phospholipid dipalmitoyl phosphatidyl glycerol (DPPG) and negative Ag nanoparticles (AgNP) to form layer‐by‐layer (LbL) multilayered films using the cationic polymer poly(allylamine hydrochloride) (PAH) as the supporting polyelectrolyte, which were further investigated in the presence of a phenothiazine compound (methylene blue—MB). The molecular architecture of the LbL films in terms of controlled growth, morphology with micro and nanometer spatial resolutions, and dispersion of both AgNP and MB within the DPPG matrix was determined combining spectroscopy [ultraviolet–visible (UV–Vis) absorption and micro‐Raman spectroscopy] and microscopy [scanning electron microscopy (SEM) and atomic force microscopy (AFM)]. The results showed that the LbL films can be grown in a controlled way at nanometer thickness scale with the surface morphology susceptible to the presence of both AgNP and MB. The surface‐enhanced phenomenon was applied to investigate the LbL films taking the advantage of the strong surface‐enhanced resonance Raman scattering (SERRS) signal presented by the MB molecules. Besides, as MB is a pharmacological drug of interest, its molecular arrangements when dispersed in LbL films containing DPPG, which is the biological membrane mimetic system here, were investigated. In this case, the AgNP played a key role in achieving the MB SERRS signal. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Photocatalytic, sono-photocatalytic oxidation of pharmaceutical drug of carbamazepine was successfully carried out using Ag/AgCl supported BiVO4 catalyst. For this purpose, firstly, photocatalytic oxidation was optimized by central composite design methodology and then synergistic effect of sonication was investigated. Low frequency (20 kHz) probe type and high frequency (850 kHz) plate type sonication at pulse and continuous mode were studied to degrade the carbamazepine (CBZ) containing wastewater. Pulse duties of 1:5 and 5:1 (on : off) were tested using the high frequency sonication system in the sono-photocatalytic oxidation of CBZ. The effects of frequency, power density measured from calorimetry by changing amplitudes were discussed in the sono-photocatalytic oxidation of CBZ. Complete carbamazepine removal was achieved at the optimum conditions of 5 ppm CBZ initial concentration with 1.5 g/L of catalysts loading and at an alkaline pH of 10 at the end of 4 h of photocatalytic reaction under visible LED light irradiation. Both low frequency and high frequency sonication systems caused an increase in photocatalytic efficiency in a shorter treatment time of 60 min. CBZ removal increased from 44% to 65.42% in low frequency sonication of 20 kHz at the amplitude of 20% (0.15 W/mL power density). In the case of high frequency ultrasonic system (850 kHz), CBZ removal increased significantly from 44% to 89.5 % at 75% amplitude (0.12 W/mL power density) within 60 min of reaction. Continuous mode sonication was observed to be more effective than that of pulse mode sonication not only for degradation efficiency and also for electrical energy consumption needed to degrade CBZ. Sono-catalytic oxidation was also conducted with simulated wastewater that contains SO42-, CO32–, NO3–, Cl- anions and natural organic component of fulvic acid. The CBZ degradation was inhibited slightly in the presence of NO3– and Cl-, and fulvic acid, however, the existence of SO42- and CO32– increased the degradation degree of CBZ. Toxicity tests were performed to determine the toxicity of untreated CBZ, and treated CBZ by photocatalytic, and sono-photocatalytic oxidations. 相似文献
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A self-consistent problem of interaction of two dipole atoms separated by an unrestricted distance with the field of a quasi-resonance
light wave was solved on the assumption that the investigated atoms are Lorentz linear oscillators and the polarizing fields
inside the system consist of the Coulomb and the retarded parts. The solution obtained was investigated for the case where
the atoms have the same polarizability and the distance between them is much smaller than the length of the external light
wave. Formulas for the electric fields inside a small object and outside it have been obtained. It is shown that inside a
small two-atom object there can take place longitudinal and transverse optical vibrations accompanied by corresponding dispersion
effects depending on the interatomic distance and the angle between the axis of the system and the direction of propagation
of the external light wave. The field outside the small object in the wave zone is linearly polarized when the external wave
has linear polarization. However, the direction of polarization of the corresponding waves is largely determined by their
frequency. It is also shown that the amplitude of the field outside the small object in the wave zone depends greatly on the
frequency of the external field and the interatomic distance. The effects observed are considered as a near-field effect in
optics of small objects. This phenomena makes it possible to investigate the structure of small objects with the use of optical
radiation.
Ul'yanovsk Branch of the Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 48 Goncharov Str., Ul'yanovsk,
432700, Russia; e-mail: gadomsky@quant.univ.simbirsk.su. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6,
pp. 765–770, November–December, 1999. 相似文献