排序方式: 共有14条查询结果,搜索用时 15 毫秒
1.
太赫兹回旋管可实现高功率输出,并具有一定的频率调谐范围,是核磁共振波谱系统理想的高功率太赫兹辐射源。设计了263 GHz,TE5,2基波连续调谐回旋管,通过磁场调节实现频率调谐范围为1.39 GHz,利用时域多模多频自洽非线性理论对设计的连续调谐回旋管非稳定振荡状态进行了研究。结果表明,在低次纵向谐波模式工作磁场范围内,当工作电流大于起振电流时,连续调谐回旋管先进入稳定状态,高次纵向谐波模式被抑制,工作模式TE5,2的输出功率随时间不变;当电流增大,纵向谐波模式间的竞争引起回旋管由稳定状态进入到非稳定振荡状态,工作模式TE5,2的输出功率随时间呈振荡变化且互作用效率大大降低;随着电流的进一步增大,回旋管又回到与低电流不同的稳定状态,互作用效率进一步降低。同时发现非稳定振荡状态的起始电流随着磁场增加而增大。本研究对需工作于稳定状态的面向DNP-NMR应用的连续调谐太赫兹回旋管的研制具有一定指导意义。 相似文献
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DNA damage repair through the nucleotide excision repair (NER) pathway is one of the major reasons for the decreased antitumor efficacy of platinum‐based anticancer drugs that have been widely applied in the clinic. Inhibiting the intrinsic NER function may enhance the antitumor activity of cisplatin and conquer cisplatin resistance. Herein, we report the design, optimization, and application of a self‐assembled lipid nanoparticle (LNP) system to simultaneously deliver a cisplatin prodrug together with siRNA targeting endonuclease xeroderma pigmentosum group F (XPF), a crucial component in the NER pathway. The LNP is able to efficiently encapsulate both the platinum prodrug and siRNA molecules with a tuned ratio. Both platinum prodrug and XPF‐targeted siRNA are efficiently carried into cells and released; the former damages DNA and the latter specifically downregulates both mRNA and protein levels of XPF to potentiate the platinum drug, leading to enhanced expression levels of apoptosis markers and improved cytotoxicity in both cisplatin‐sensitive and ‐resistant human lung cancer cells. Our results demonstrate an effective approach to utilize a multi‐targeted nanoparticle system that can specifically silence an NER‐related gene to promote apoptosis induced by cisplatin, especially in cisplatin‐refractory tumors. 相似文献
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纳米力学的数值模拟方法 总被引:8,自引:3,他引:8
纳米力学是一支新兴学科,主要研究100nm以下尺度上物质的行为和变化规律.物质在纳米尺度上所具有的特殊效应如量子效应、微尺度效应等导致了其特异的性能和行为.人们对纳米力学行为的认识,目前主要通过试验观测和数值模拟等方法.本文概要回顾了分子动力学模拟、蒙特卡罗模拟等纳米力学计算方法的研究进展及现状,提出了以量子力学为基础、多学科交叉、多层次融合发展纳米力学研究方法的构思,并对纳米力学研究方法所面临的问题及其发展趋势做了初步展望. 相似文献
4.
Yuan Tianzhong Zeng Jinsong Wang Bin Cheng Zheng Chen Kefu 《Cellulose (London, England)》2021,28(12):7651-7662
Cellulose - This study aims to investigate the relationship between mechanical fibrillation, morphological properties, and rheological behavior of cellulosic fiber. Three types of cellulosic fibers... 相似文献
5.
Tong T Zhang J Tian B Chen F He D Anpo M 《Journal of colloid and interface science》2007,315(1):382-388
The Ce-TiO2 catalysts were prepared by controlled hydrolysis of Ti(OC(4)H(9))(4) with water generated "in situ" via an esterification reaction between acetic acid and ethanol, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), atomic absorption flame emission spectroscopy (AAS), and nitrogen adsorption-desorption methods. Both of undoped TiO2 and Ce-TiO2 samples exclusively consist of primary anatase crystallites, which further form spherical aggregates with diameters ranging from 100 to 500 nm. The photocatalytic activity of Ce-TiO2 was investigated for the photocatalytic degradation of Rhodamine B (RB) aqueous solution both under UV and visible light irradiation. Doping of Ce(4+) effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.2 and 0.4%, respectively. The photocatalytic mechanisms of Ce-TiO2 catalysts were tentatively discussed. 相似文献
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Multipulse feed strategy for glycerol fed-batch fermentation 总被引:4,自引:0,他引:4
Dongming Xie Dehua Liu Haoli Zhu Tianzhong Liu 《Applied biochemistry and biotechnology》2001,95(2):103-112
During glycerol fed-batch fermentation, the process could be divided into multiple equal subintervals, and the feed operation
was performed in pulse form at the start of each subinterval. Based on the macrokinetic models, the multipulse feed strategy
for both glucose and corn steep slurry was determined by a general nonlinear optimization approach to maximize the final glycerol
productivity and still control the residual glucose at a low concentration. The experimental results in a 600-mL Airlift Loop
Reactor showed that the tested data with this strategy agreed well with the corresponding model prediction, and that the feed
mode with nonlinear optimization could improve the glycerol productivity significantly compared with those determined just
by limited experimental optimization in previous studies. 相似文献
8.
Highly ordered self-assembly with large area of Fe3O4 nanoparticles and the magnetic properties 总被引:4,自引:0,他引:4
Yang T Shen C Li Z Zhang H Xiao C Chen S Xu Z Shi D Li J Gao H 《The journal of physical chemistry. B》2005,109(49):23233-23236
Monodisperse Fe3O4 nanoparticles (NPs) with narrow size distribution are synthesized by a high-temperature solution-phase method. The diameter of the as-synthesized NPs is tuned from 2 to 14 nm by varying the reaction conditions. Highly ordered superlattice structures of the Fe3O4 NPs with areas extending over 0.8 microm x 0.7 microm have been successfully obtained. The magnetic properties are investigated in their different states, such as in the solid state and diluted in wax with different concentrations. Some magnetic properties enhanced by increasing interparticle distances, such as the remanent magnetization and coercive field at low temperature, were noticed. Furthermore, we also observed that the saturation magnetization changed with temperature as expected. The preliminary explanation for the properties mentioned above is proposed. 相似文献
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传统的镜头光学设计多半是在一初始模型(如专利)的基础上作一定程度的人工修改。然而借助光学设计软件的新技术,可以对初始模型作较大的改动,使之脱离原有的模式而得到一个更优化的结果。本文以一个35~70mm/F3.5~4.8变焦镜头的光学设计为例,简要地叙述了这一过程。 相似文献