ISNet—严格的多维NMR谱解析理论（Ⅰ）

ＩＳＮｅｔ（独立自旋偶合网络，Ｉｎｄｅｐｅｎｄｅｎｔ Ｃｏｕｐｌｉｎｇ Ｎｅｔｗｏｒｋ）是作者为了严格地从多维ＮＭＲ谱推导出溶液状态中复杂有机物的分子结构而建立的新概念。从数学上讲，ＩＳＮｅｔ可被视分子结构连接性的另一种表面形式，是一种图论表达。与分子结构图的共价表达不同之处在于，ＩＳＮｅｔ中的第一条国害理论上是二维ＮＭＲ谱图上的一个可观察的峰。本文建立ＩＳＮｅｔ概念，并讨论从实验波谱，运用ＩＳＮ     

ISNet－严格的多维NMR谱解析理论（I）

ＩＳＮｅｔ（独立自旋偶合网络,ＩｎｄｅｐｅｎｄｅｎｔＳｐｉｎＣｏｕｐｌｉｎｇＮｅｔｗｏｒｋ）是作者为了严格地从多维ＮＭＲ谱推导出溶液状态中复杂有机物的分子结构而建立的新概念。从数学上讲,ＩＳＮｅｔ可被视为分子结构连接性的另一种表达形式,是一种图论表达。与分子结构图的共价键表达不同之处在于,ＩＳＮｅｔ中的每一条边在理论上是二维ＮＭＲ谱图上的一个可观察的峰。本文建立ＩＳＮｅｔ概念,并讨论从实验波谱,运用ＩＳＮｅｔ分析理论导出各类分子结构的原理及其图论、模糊数学基础。     

AAindex数据库中傅里叶方法的多重氨基酸指数选择

波谱学方法研究蛋白质时,蛋白质序列的特征频率与蛋白质的位点、功能、空间结构对应.基于时间序列傅里叶变换的交叉谱原理,本文提出的“一个蛋白质关于多种氨基酸指数的一致谱”能够获取一个或多个蛋白质序列较显著的特征频率,再由特征频率去筛选与之对应的氨基酸指数.该方法与Lazovi(c)的筛选方法和筛选意义不同.结果显示,筛选出的氨基酸指数对应的性质多数与蛋白质的空间结构性质有关.蛋白质特征频率也许是用于特征提取的好方法,氨基酸指数筛选可被看作蛋白质数字表达的一种优化.     

pPre_ITMS:基于机器学习方法的串联质谱数据预处理系统

串联质谱技术被广泛应用于高通量的蛋白质鉴定.质谱中噪音峰和同位素峰的存在会降低蛋白质鉴定的准确性,同时增加计算负担.pPre_ITMS系统是针对离子阱数据,利用机器学习中的最大期望方法和决策树方法分别识别出质谱中的噪音基线和同位素峰的预处理系统.此外,pPre_ITMS系统采用三层独立模型增强系统鲁棒性,并提供了手动调节功能.利用pPre_ITMS系统可以简单、快速且可视化地对离子阱数据进行预处理.     

3-甲基-7-二乙氨基-1,4-氧氮杂萘-2-酮的波谱性质量子化学从头计算

以合成的重要荧光材料3-甲基-7-二乙氨基-1,4-氧氮杂萘-2-酮为例子,进行了一些有机含氮杂环化合物的红外、核磁性质Hartree-Fock(HF)和密度泛函(DFT)量子化学从头计算研究。通过系统构象搜寻,对低能量稳定构象进行了红外振动频率和1H、13C-NMR及偶合常数等光谱学性质的计算,并对计算结果进行详细的归属和解析。在化学位移计算方面,HF／631g(d)和DFT／BG3LYP／6311 g(2d,p)方法计算结果相当。但对于自旋偶合常数的计算,用HF／631g(d)方法不能得到准确的结果,只能用密度泛函大基组的方法才能得到比较准确的结果。计算结果表明有机分子光谱性质的理论计算尤其是核磁性质的计算是一种非常有效的辅助结构确定方法。     

高提升滤波在低对比度目标相关探测中的应用

光电混合联合变换器可实现对目标的实时探测、识别及自动定位。但低对比度目标的相关峰强度很弱,甚至得不到相关峰．影响了目标的识别率。利用高提升滤波处理技术和图像分割对功率谱进行增强处理,可以有效提高功率谱对比度,最大限度保留光谱图像的细节信息,提高光电联合相关系统的目标识别率。     

一种降低TAG覆盖多播网络加入延迟的方法

为了降低TAG(TopologyAware Grouping)覆盖多播网络的加入延迟,将IP多播技术融入TAG覆盖多播网络中,提出一种将网络划分成多个独立的域,域间以IP多播方式进行传输,域内以TAG覆盖多播方式进行传输的改进的TAG覆盖多播技术,从而降低多播传递树的深度,减小加入延迟。通过仿真实验,验证了该技术比MTAG方法更能有效减小TAG覆盖多播网络的加入延迟。     

基于机器学习的蛋白质编码问题研究

氨基酸序列编码问题一直是在蛋白质结构预测中导致算法输入空间较大的主要原因。只有对氨基酸序列进行更好的编码,才能为后续进行计算机分析打下基础。提出并实现了综合考虑了氨基酸序列的划分和长程作用效应,利用氨基酸正交编码区分每个氨基酸个体,利用基本正交矩阵获得氨基酸在物理、化学、生物上的相似性,利用分属概率来获得当前蛋白质序列中氨基酸构成不同二级结构的趋势的新的混合编码方法,从而改进了氨基酸残基序列编码,并利用现有算法比较了不同编码方式对蛋白质二级结构预测的影响,结果证实该编码方式能够提高蛋白质二级结构预测的准确性。     

基于机器学习的蛋白质编码问题研究

氨基酸序列编码问题一直是在蛋白质结构预测中导致算法输入空间较大的主要原因。只有对氨基酸序列进行更好的编码．才能为后续进行计算机分析打下基础。提出并实现了综合考虑了氨基酸序列的划分和长程作用效应,利用氨基酸正交编码区分每个氨基酸个体,利用基本正交矩阵获得氨基酸在物理、化学、生物上的相似性,利用分属概率来获得当前蛋白质序列中氨基酸构成不同二级结构的趋势的新的混合编码方法,从而改进了氨基酸残基序列编码,并利用现有算法比较了不同编码方式对蛋白质二级结构预测的影响,结果证实该编码方式能够提高蛋白质二级结构预测的准确性。     

利用混料设计和香农信息熵优化香烟主流烟气萃取溶液的配比

采用混料设计原理进行试验设计,结合香农信息熵作为色谱指纹图谱信息含量的评价指标,对寻找香烟烟气中主要成分萃取溶液的最佳配比进行了系统研究。以甲醇、乙醇和二氯甲烷为主要萃取溶液,通过自动进样将提取液进行气相色谱正交加速飞行时间质谱(GC/oa-TOF-MS)分析,结果表明:(1)二氯甲烷与乙醇的混合溶液提取效率最好,其色谱图信息明显高于以二氯甲烷与甲醇为混合溶液的所得色谱;(2)在二氯甲烷和乙醇的混合溶剂中,随着乙醇浓度增加,各物质出峰顺序基本一致,但其谱峰个数、峰宽及峰高变化明显;(3)当二氯甲烷和乙醇比率为0.8:0.2时,多个谱峰明显高于其他组之相同谱峰,并出现多个其他组没有的特征峰,得到谱峰分离度最好。     

Time-optimal control for hybrid systems based on the nitrogen-vacancy center

Fast and high fidelity quantum control is the key technology of quantum computing. The hybrid system composed of the nitrogen-vacancy center and nearby Carbon-13 nuclear spin is expected to solve this problem. The nitrogen-vacancy center electron spin enables fast operations for its strong coupling to the control field, whereas the nuclear spins preserve the coherence for their weak coupling to the environment. In this paper, we describe a strategy to achieve time-optimal control of the Carbon-13 nuclear spin qubit by alternating controlling the nitrogen-vacancy center electron spin as an actuator. We transform the qubit gate operation into a switched system. By using the maximum principle, we study the minimum time control of the switched system and obtain the time-optimal control of the qubit gate operation. We show that the $X$ gate and $Y$ gate operations are within 10 $\mu$s while the fidelity reaches 0.995.     

Mean interface magnon dispersion curves obtained by means of the matching procedure

A theoretical approach based on the matching procedure in the random-phase approximation has been developed to investigate the spin fluctuations dynamics on an interface of the Heisenberg biferromagnetic layers. The two ferromagnetic layers are considered directly coupled by magnetic exchange interactions. No electronic effects are considered. The analytical approach solves for the three-dimensional crystal spin field in the bulk and the interface domain, that arises owing to the reduced of magnetic translation symmetry for the system. The calculations presented here are an application of a theoretical method based on Green functions formalism discussed in previous work. Analytic expressions are obtained for the dispersion relations and spectral intensities of the localized spin-waves and the quantized bulk spin waves near an interface. The effects of varying the bulk-interface coupling exchange near the interface are studied. Also, the condition for the appearance of the acoustic and optical interface modes is discussed. Numerical examples of the modes are given and provide some indication of how the magnon spectrum is affected by interface parameters. These factors influence the energies of localized modes, as well as their frequency, intensity and attenuation.     

Controlling Spin Qubits in Quantum Dots

We review progress on the spintronics proposal for quantum computing where the quantum bits (qubits) are implemented with electron spins. We calculate the exchange interaction of coupled quantum dots and present experiments, where the exchange coupling is measured via transport. Then, experiments on single spins on dots are described, where long spin relaxation times, on the order of a millisecond, are observed. We consider spin-orbit interaction as sources of spin decoherence and find theoretically that also long decoherence times are expected. Further, we describe the concept of spin filtering using quantum dots and show data of successful experiments. We also show an implementation of a read out scheme for spin qubits and define how qubits can be measured with high precision. Then, we propose new experiments, where the spin decoherence time and the Rabi oscillations of single electrons can be measured via charge transport through quantum dots. Finally, all these achievements have promising applications both in conventional and quantum information processing. PACS: 03.67.Lx, 03.67.Mn, 73.23.Hk, 85.35.Be     

Dipolar relaxation mechanism of long-lived states of methyl groups

We analyze the symmetry properties of the dipolar Hamiltonian as the main relaxation mechanism responsible for the observed NMR spectra of long-lived states of methyl groups. Long-lived states exhibit relaxation times that are considerably longer than the spin–lattice relaxation time, \(T_{1}\). The analysis is complementary to previous studies and provides insight into the relaxation mechanism of long-lived states by focusing exclusively on the symmetry of the spin Hamiltonian. Our study shows that the dipole–dipole coupling between protons of a methyl group and between the protons and an external spin are both symmetry breaking interactions that can lead to relaxation pathways that transform the polarization from symmetry order to Zeeman order. The net contribution of the internal dipolar interaction to the NMR observation of long-lived states is zero. Our calculation is in good agreement with the reported features of the observed spectra and previous theoretical studies.     

Theory of Single Spin Detection with STM

We propose a mechanism for detection of a single spin center on a non-magnetic substrate. In the detection scheme, the STM tunnel current is correlated with the spin orientation. In the presence of magnetic field, the spin precesses and the tunnel current is modulated at the Larmor frequency. The mechanism relies on the effective spin-orbit interaction between the injected unpolarized STM current and the local spin center, which leads to the nodal structure of the spatial signal profile. Based on the proposed mechanism, the strongest spin-related signal can be expected for the systems with large spin-orbit coupling and low carrier concentration. PACS: 74.40.Gk; 72.70.+m; 73.63.Kv; 85.65.+h     

Electric dipole transition moments and permanent dipole moments for spin–orbit configuration interaction wave functions

A procedure for calculating electric dipole transition moments and permanent dipole moments from spin–orbit configuration interaction (SOCI) wave functions has been developed in the context of the COLUMBUS ab initio electronic structure programs. The SOCI procedure requires relativistic effective core potentials and their corresponding spin–orbit coupling operators to define the molecular Hamiltonian, electric dipole transition moment and permanent dipole moment matrices. The procedure can be used for any molecular system for which the COLUMBUS SOCI circuits are applicable. Example applications are reported for transition moments and dipole moments for a series of electronic states of LiBe and LiSr defined in diatomic relativistic ωω-coupling.     

Multipartite electronic entanglement purification using quantum-dot spin and microcavity system

This paper presents an entanglement purification protocol of multipartite electronic spin entangled state resorting to quantum-dot (QD) spin and micro cavity coupled system. The QD and microcavity coupling system is used to construct parity check detectors which provides a novel experimental platform of quantum information processing with photon and solid qubit. In this proposed protocol, the mixed multi-electron entangled state ensemble can be purified efficiently.     

On novel magnetic probe for fullerene characterization: Theoretical studies on NMR parameters of free and confined in fullerenes HD and H2 molecules

Chemical characterization and separation of individual fullerenes from a raw reaction mixture need new and efficient tools, including rapid spectroscopic techniques. Recent “molecular surgery” synthesis of endohedral complexes of fullerenes with selected atoms and small molecules has opened a new path for experimental and theoretical studies on structural and spectroscopic properties of these molecular systems. Among them are fullerenes with molecular hydrogen confined within a nanoscale cavity.In this work we report on quantum-chemical prediction of nuclear magnetic shielding (and chemical shift) and indirect spin–spin coupling constant in free HD and H₂ molecules, as well as models of confined dihydrogen using the coupled cluster with single and double excitations (CCSD) and density functional theory (DFT) levels of theory. Inspired with the recent experimental NMR studies on HD and H₂ molecules confined inside C₆₀ fullerene we systematically investigated the sensitivity of ¹H nuclear magnetic shielding of H₂ and indirect spin–spin coupling constant ¹J_HD in HD molecules to the interatomic separation in the gas phase, in the presence of benzene and inside fullerene cages of different size. The sensitivity of both NMR parameters to confinement is discussed in terms of very weak non-covalent interactions of HD and H₂ with fullerene cage.     

NMR spin relaxation methods for characterization of disorder and folding in proteins

The flexibility and dynamics of proteins directly influence the processes of protein folding, recognition, and function. NMR spin relaxation methods are used to assess the dynamics and mobility of proteins, for fast ps and ns motions as well as slower microsecond and ms events. The degree of protein flexibility and disorder as well as the changes in protein flexibility can be assessed by NMR spin relaxation methods at individual residues within the protein. In addition to probing protein dynamics, the changes in the NMR-derived order parameters can be used to estimate the entropic contributions of order-disorder transitions. Furthermore, kinetic processes in the ms time regime may be directly investigated to extract the rates of conformational interconversion, ligand binding, and protein folding processes. We show how a variety of dynamical information can be obtained from NMR relaxation measurements. We present examples that illustrate the use of NMR spin relaxation analysis for investigation of folding and disorder in proteins.     

Digital quantum simulation with Rydberg atoms

We discuss in detail the implementation of an open-system quantum simulator with Rydberg states of neutral atoms held in an optical lattice. Our scheme allows one to realize both coherent as well as dissipative dynamics of complex spin models involving many-body interactions and constraints. The central building block of the simulation scheme is constituted by a mesoscopic Rydberg gate that permits the entanglement of several atoms in an efficient, robust and quick protocol. In addition, optical pumping on ancillary atoms provides the dissipative ingredient for engineering the coupling between the system and a tailored environment. As an illustration, we discuss how the simulator enables the simulation of coherent evolution of quantum spin models such as the two-dimensional Heisenberg model and Kitaev’s toric code, which involves four-body spin interactions. We moreover show that in principle also the simulation of lattice fermions can be achieved. As an example for zcontrolled dissipative dynamics, we discuss ground state cooling of frustration-free spin Hamiltonians.