基于原子操纵技术的人工量子结构研究

扫描隧道显微镜原子操纵技术是指利用扫描探针在特定材料表面以晶格为步长搬运单个原子或分子的技术.它是纳米尺度量子物理与器件研究领域一种独特而有力的研究手段.利用这种手段,人们能够以原子或分子为单元构筑某些常规生长或微加工方法难以制备的人工量子结构,通过对格点原子、晶格尺寸、对称性、周期性的高度控制,实现对局域电子态、自旋序、以及能带拓扑特性等量子效应的设计与调控.原子操纵技术与超快测量及自动控制技术的结合,使得人们能够进一步研究原子级精准的量子器件,因而该技术成为探索未来器件新机理、新工艺的重要工具.本文首先简介原子操纵方法的发展过程和技术要点,然后分别介绍人工电子晶格、半导体表面人工量子点、磁性人工量子结构、人工结构中的信息存储与逻辑运算、单原子精度原型器件等方面的最新研究进展,以及单原子刻蚀和自动原子操纵等方面的技术进展,最后总结并展望原子操纵技术的应用前景和发展趋势.     

Quantum Hacking on an Integrated Continuous-Variable Quantum Key Distribution System via Power Analysis

In quantum key distribution (QKD), there are some security loopholes opened by the gaps between the theoretical model and the practical system, and they may be exploited by eavesdroppers (Eve) to obtain secret key information without being detected. This is an effective quantum hacking strategy that seriously threatens the security of practical QKD systems. In this paper, we propose a new quantum hacking attack on an integrated silicon photonic continuous-variable quantum key distribution (CVQKD) system, which is known as a power analysis attack. This attack can be implemented by analyzing the power originating from the integrated electrical control circuit in state preparation with the help of machine learning, where the state preparation is assumed to be perfect in initial security proofs. Specifically, we describe a possible power model and show a complete attack based on a support vector regression (SVR) algorithm. The simulation results show that the secret key information decreases with the increase of the accuracy of the attack, especially in a situation with less excess noise. In particular, Eve does not have to intrude into the transmitter chip (Alice), and may perform a similar attack in practical chip-based discrete-variable quantum key distribution (DVQKD) systems. To resist this attack, the electrical control circuit should be improved to randomize the corresponding power. In addition, the power can be reduced by utilizing the dynamic voltage and frequency scaling (DVFS) technology.     

Physical layer orthogonal frequency‐division multiplexing acquisition and timing synchronization security

Orthogonal frequency‐division multiplexing (OFDM) has become the manifest modulation choice for 4G standards. Timing acquisition and carrier frequency offset synchronization are prerequisite to OFDM demodulation and must be performed often. Most of the OFDM methods for synchronization were not designed with security in mind. In particular, we analyze the performance of a maximum likelihood synchronization estimator against highly correlated jamming attacks. We present a series of attacks against OFDM timing acquisition: preamble whitening, the false preamble attack, preamble warping, and preamble nulling.The performance of OFDM synchronization turns out to be very poor against these attacks, and a number of mitigation strategies and security improvements are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

双温度氩-氮等离子体热力学和输运性质计算

获得覆盖较宽温度和压力范围内的等离子体热力学和输运性质是开展等离子体传热和流动过程数值模拟的必要条件.本文通过联立Saha方程、道尔顿分压定律以及电荷准中性条件求解等离子体组分;采用理想气体动力学理论计算等离子体热力学性质;基于Chapman-Enskog方法求解等离子体输运性质.利用上述方法计算了压力为0.1, 1.0和10.0 atm (1 atm=101325 Pa),电子温度在300—30000 K范围内,非局域热力学平衡(电子温度不等于重粒子温度)条件下氩-氮等离子体的热力学和输运性质.结果表明压力和非平衡度会影响等离子体中各化学反应过程,从而对氩-氮等离子体的热力学及输运性质有较大的影响.在局域热力学平衡条件下,计算获得的氩-氮等离子体输运性质和文献报道的数据符合良好.     

盐酸四环素中可交换氢和氢键的核磁共振波谱研究

四环素类抗生素是一类广谱抗生素,对革兰氏阳性菌、革兰氏阴性菌、支原体、衣原体和立克次体感染均具有抗菌活性.本文运用一维（1D）和二维（2D）核磁共振（NMR）技术对盐酸四环素中可交换氢和氢键进行研究,并将研究结果与RNA和蛋白质结合的四环素以及游离药物的晶体结构进行比较,进一步讨论了药物中的氢键构架与药物活性的相关性.最后对盐酸四环素及其同系物的¹H和¹³C NMR信号进行了全归属和分析,并对文献归属结果进行了细微校正.这些结果有助于进一步探索该类药物在更复杂的生物或环境系统中的构效关系.     

A new ESIPT-based fluorescent probe for highly selective and sensitive detection of HClO in aqueous solution

A new ESIPT-based fluorescent probe, PHC2, for the detection of hypochlorous acid has been rationally designed and developed. Endowed by the specific reaction between hypochlorous acid and phenyl azo group, PHC2 features high degree of selectivity and sensitivity for HClO with a low detection limit (13.2 nM) under physiological conditions in neutral aqueous solution.     

Template-directed syntheses of two 3D metal oxalates: in situ N-methylation and crystal structures

Two isomorphic organically templated zinc/cobalt oxalates, (dmdabco)[Zn₂(C₂O₄)₃]·4H₂O (1), and (dmdabco)[Co₂(C₂O₄)₃]·4H₂O (2) (C₂O₄^2? = oxalate; dmdabco = N,N′-dimethyl-1,4-diazabicyclo[2,2,2]octane), have been prepared under solvothermal conditions and characterized by X-ray structural analyses. The dmdabco²⁺ templating agent was derived from simple in situ N-alkylation between methanol and 1,4-diazabicyclo[2,2,2]octane (dabco). Distinct from conventional Eschweiler-Clarke methylation containing excess formic acid and formaldehyde, such one-step methylation from methanol molecules is convenient. Both 1 and 2 exhibit a uninodal 3-connected 3-D interrupted open-framework, in which oxalate ligands have in-plane and out-of-plane connection modes.     

Synthesis of nano/micro scale ZSM-5 from kaolin and its catalytic performance

Nano/micro scale ZSM-5 zeolites were synthesized by using natural kaolin as raw material. The effect of particle size on the catalytic performance of ZSM-5 zeolite for the methanol to olefins conversion was evaluated in a fixed-bed reactor. The results indicated the crystal size had a significant effect on the catalytic stability and the products distribution. ZSM-5 with nanosize showed better tolerance to coke formation, longer catalytic lifetime, and higher selectivity to propylene. The selectivity to propylene on nanosized ZSM-5 was on average 4.5% higher than on the submicron sample and 10% higher than on microsized ZSM-5. After the reaction was conducted for 20 h the ZSM-5 catalyst synthesized from kaolin showed longer lifetime and higher propylene selectivity than the sample synthesized with chemical materials The reason can be explained by the occurence of such elements as Fe, P, and especially Ti.     

Determination of copper(II) based on its inhibitory effect on the cathodic electrochemiluminescence of lucigenin

A simple method is described for the determination of copper(II) ions based on the cathodic electrochemiluminescence (ECL) of lucigenin which is quenched by Cu(II). The blue ECL is best induced at ?0.45 V (vs. Ag/AgCl) at a scan rate of 50 mV·s^?1. Under optimum conditions, the calibration plot is linear in the 3.0 to 1000 nM Cu(II) concentration range. The limit of detection is 2.1 nM at a signal-to-noise ratio of 3. Compared to other analytical methods, the one presented here is simple, fast, selective and cost-effective. It has been successfully applied in the analysis of copper ions in spiked tap water samples with recoveries ranging from 93.0% (at 50 nM concentration) to 105.7% (at 150 nM).

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Graphical abstract The inhibitory effect of Cu(II) on the cathodic electrochemiluminescence of lucigenin enables determination of Cu(II) with a 2.1 nM detection limit.

     

Photometric determination of free cholesterol via cholesterol oxidase and carbon nanotube supported Prussian blue as a peroxidase mimic

Microchimica Acta - The authors describe a photometric method for the determination of free cholesterol based on the oxidation of cholesterol by the catalytic action of the enzyme...