Geometry and Elasticity of Strips and Flowers

We solve several problems that involve imposing metrics on surfaces. The problem of a strip with a linear metric gradient is formulated in terms of a Lagrangian similar to those used for spin systems. We are able to show that the low energy state of long strips is a twisted helical state like a telephone cord. We then extend the techniques used in this solution to two–dimensional sheets with more general metrics. We find evolution equations and show that when they are not singular, a surface is determined by knowledge of its metric, and the shape of the surface along one line. Finally, we provide numerical evidence by minimizing a suitable energy functional that once these evolution equations become singular, either the surface is not differentiable, or else the metric deviates from the target metric.     

Kinetics and mechanism of the reaction of alkoxymethylidene malonate and malononitrile with hydrazines and anilines

The kinetics and mechanism of the nucleophilic vinylic substitution of dialkyl (alkoxymethylidene)malonates (alkyl: methyl, ethyl) and (ethoxymethylidene)malononitrile with substituted hydrazines and anilines R¹–NH₂ (R¹: (CH₃)₂N, CH₃NH, NH₂, C₆H₅NH, CH₃CONH, 4‐CH₃C₆H₄SO₂NH, 3‐ and 4‐X‐C₆H₄; X: H, 4‐Br, 4‐CH₃, 4‐CH₃O, 3‐Cl) were studied at 25 °C in methanol. It was found that the reactions with all hydrazines (the only exception was the reaction of (ethoxymethylidene)malononitrile with N,N‐dimethylhydrazine) showed overall second‐order kinetics and k_obs were linearly dependent on the hydrazine concentration which is consistent with the rate‐limiting attack of the hydrazine on the double bond of the substrate. Corresponding Brønsted plots are linear (without deviating N‐methyl and N,N‐dimethylhydrazine), and their slopes (β_Nuc) gradually increase from 0.59 to 0.71 which reflects gradually increasing order of the C–N bond formed in the transition state. The deviation of both methylated hydrazines is probably caused by the different site of nucleophilicity/basicity in these compounds (tertiary/secondary vs. primary nitrogen). A somewhat different situation was observed with the anilines (and once with N,N‐dimethylhydrazine) where parabolic dependences of the kinetics gradually changing to linear dependences as the concentration of nucleophile/base increases. The second‐order term in the nucleophile indicates the presence of a steady‐state intermediate ‐ most probably T^±. Brønsted and Hammett plots gave β_Nuc = 1.08 and ρ = ?3.7 which is consistent with a late transition state whose structure resembles T^±. Copyright © 2013 John Wiley & Sons, Ltd.     

Polarity of the Medium and Quenching of Fluorescence of Caratenoids and Phthalimides

The relation for the dependence of the rate of radiationless energy conversion of the S ₁ state k _q on the polarity of the medium, obtained previously by the author, has been used to interpret the known literature data on the lifetime of the S ₁ state of solutions of some caratenoids and phthalimides. It has been shown that in alcohols and water (normal and deuterated ones) the fluorescence quenching of 4-amino-, 4-methylamino-, and 4-dimethylamino-N-methylphthalimides (4AMP, 4MAMP, and 4DMAMP) as well as of peridinine in alcohols is due to H-bond formation. It has been established that a twofold increase in the number of amine atoms of hydrogen on passing from 4MAMP to 4AMP, as well as deuteration of solvents in the case of 4DMAMP, is followed by a decrease in k _q by a factor of 1.6 and 1.75, respectively. The mechanism of quenching in complexes formed with solvent molecules by means of the H-bond is discussed. It has been concluded that the quenching of fluorescence of phthalimides in such complexes is mainly due to the intersystem crossing initiated by the oscillations of the protons or deuterons of the H-bonds.     

Infrared Spectra and Configuration of Anion Radical and Dianion of Benzil and Benzil-18o

Abstract

Infrared spectra of the products of one- and two -step reduction of both benzil and benzil-¹⁸0 have been investigated in dimethylsulfoxide-d₆ and tetrahydrofurane solutions. Anion-radicals have been obtained by electrochemical reduction of benzil and benzil-¹⁸0; dinegative ions have been prepared by reduction of the same ketones with potassium mirror in vacuo. The band assignment has been performed using the group vibrational concept and isotopic shift data. The previous assignment of the C[dbnd]O stretching band of benzil anion-radical-has been discussed and corrected. Two bands in the infrared spectra of benzil dianion have been found to be sensitive upon ¹⁸0 isotope labelling. This result certifies the presence of cis-configuration of benzil dianion in the investigated solutions. A decrease of ca. 290 cm-¹ has been found for vC[dbnd]O after the transformation of the neutral benzil into an anion-radical. Conversion of benzil anion-radical into dianion has been accompanied by an additional vC[dbnd]O downward shift of 105 cm^?1     

单链核糖体失活蛋白的Raman和红外光谱

我们测定了两种单链核糖体失活蛋白(肥皂草素和天花粉蛋白)的FTIR和FTRaman光谱。利用FTIR光谱酰胺Ⅲ区域对蛋白质的二级结构进行定量分析,计算了各种二级结构的含量。从肥皂草素和天花粉蛋白的二级结构分析可见,二者在结构上具有某种相似性,为二者功能上的相似性提供了依据。     

黑克、布劳、及伯曼-温采尔代数的诱导及分导系数和量子经典李代数的耦合与重新耦合系数

本文总结了计算黑克、布劳、及伯曼 温采尔代数在各种工数链下诱导及分导系数的线性方程方法(LEM)。特别强调了关于A,B,C,D型李代数及其量子情形与其中心代数之间的舒尔 魏尔 布劳双关性关系。这一关系使我们能够利用相应中心代数的诱导及分导系数计算出经典李代数及其量子情形的耦合与重新耦合系数。讨论了从该方法得到B,C,D型李代数不可约表示克罗内克积分解的应用。基于LEM还得到了处理对应于置换群CG系列问题的黑克代数张量积的方法。     

Geometry and scaling laws of excursion and iso-sets of enstrophy and dissipation in isotropic turbulence

Motivated by interest in the geometry of high intensity events of turbulent flows, we examine the spatial correlation functions of sets where turbulent events are particularly intense. These sets are defined using indicator functions on excursion and iso-value sets. Their geometric scaling properties are analysed by examining possible power-law decay of their radial correlation function. We apply the analysis to enstrophy, dissipation and velocity gradient invariants Q and R and their joint spatial distributions, using data from a direct numerical simulation of isotropic turbulence at Re_λ ≈ 430. While no fractal scaling is found in the inertial range using box-counting in the finite Reynolds number flow considered here, power-law scaling in the inertial range is found in the radial correlation functions. Thus, a geometric characterisation in terms of these sets’ correlation dimension is possible. Strong dependence on the enstrophy and dissipation threshold is found, consistent with multifractal behaviour. Nevertheless, the lack of scaling of the box-counting analysis precludes direct quantitative comparisons with earlier work based on multifractal formalism. Surprising trends, such as a lower correlation dimension for strong dissipation events compared to strong enstrophy events, are observed and interpreted in terms of spatial coherence of vortices in the flow.     

“电路原理”、“信号与系统”和“自动控制原理”课程的整合与优化

"电路原理"、"信号与系统"和"自动控制原理"三门课程是光电信息科学与工程等专业的专业基础课。若分别采用各自独立的教学内容和方法,内容交叉、重复,浪费学时,没有从整个课程体系系统化的角度把握有关内容。因此,提出了适用于光电信息科学与工程等专业的以上三门课程的教学改革方案,从根本上系统地将这三门课程进行整合、优化为"电路、信号和控制系统"课程。在教学实践中,进行了有关内容的教学尝试,缩短了教学时间,提高了教学质量。     

Equation of state and thermal expansivity of LiF and NaF

The high-pressure and high-temperature behaviors of LiF and NaF have been studied up to 37 GPa and 1000 K. No phase transformations have been observed for LiF up to the maximum pressure reached. The B1 to B2 transition of NaF at room temperature was observed at ～28 GPa, this transition pressure decreases with temperature. Unit-cell volumes of LiF and NaF B1 phase measured at various pressures and temperatures were fitted using a P–V–T Birch–Murnaghan equation of state. For LiF, the determined parameters are: α₀ = 1.05 (3)×10^?4 K^?1, dK/dT = ?0.025 (2) GPa/K, V ₀ = 65.7 (1) Å³, K ₀ = 73 (2) GPa, and K′ = 3.9 (2). For NaF, α₀ = 1.34 (4)×10^?4 K^?1, dK/dT = ?0.020 (1) GPa/K, V ₀ = 100.2 (2) Å³, K ₀ = 46 (1) GPa, and K′ = 4.5 (1).     

受控核聚变两大途径的对比与结合

目前人们探索受控核聚变主要是从两个方向着手：磁约束受控核聚变和惯性约束受控核聚变，但目前还无法判定到底哪一种途径更为可取，文章首先对这两种途径进行对比，指出各自的特点和困难，在此基础上提出了一种结构相对简单，成本相对较低的三轴六极磁镜系统设想，希望能将磁约束和惯性约束和惯性约束结合起来，以实现受控核聚变反应。     

酸碱染料离子的缔合及等色化

本文阐述了等色染料离子对形成的实验方法,等色染料离子对的缔全机理及其形式,用吸收光谱的能级图,从电子理论角度论述了等色染料离子对的缔合效应等色化,溶剂效应等以化机理。列表示出等色染料离子对的高灵敏度,从而证明了等色染料离子对的萃取光度,浮选光度及萃取荧光光度法是高灵敏度和超灵敏度的新体系,为金属痕量和超痕量分析开辟了更为宽广的前景。     

氩和氪气体团簇靶的制备及特性研究

 采用瑞利散射法和Mach-Zehnder（M-Z）干涉法分别测量氩、氪团簇的尺寸和密度，讨论了影响团簇尺寸和密度的因素，并比较氩团簇和氪团簇特性的异同点。通过改变诊断光和喷嘴阀门的相对延迟时间，获得了团簇尺寸和密度随时间的变化情况，发现氩、氪团簇的尺寸和密度均在3~25 ms达到最大值；在气体背景压强1.2~6.0 MPa下，测量了喷嘴轴线上的密度分布，发现离喷嘴喉部越远，气体密度越低，并且气体密度随压强呈线性上升。     

高光谱成像技术在果蔬品质与安全无损检测中的原理及应用

水果和蔬菜的品质与安全是消费者最为关心的问题。传统的化学检测方法是一种费时费力的破坏性检测技术。随着成像和光谱技术的快速发展,高光谱成像技术已经广泛应用于农产品品质与安全的快速无损检测中。高光谱成像技术融合了传统的成像和光谱技术的优点,可以同时获取被检测物体的空间信息和光谱信息,因此该技术既可以像检测物体的外部品质,又可以像光谱技术一样检测物体的内部品质和品质安全。目前,已经有大量的基于高光谱成像技术检测水果和蔬菜品质与安全的研究性论文发表,为了深入了解高光谱成像技术的检测原理并跟踪国内外最新的研究进展,综述了高光谱成像技术在水果和蔬菜外部品质、内部品质和品质安全检测中的原理、发展和应用。另外,还简要介绍和讨论了高光谱成像系统的构成、常用的数据分析方法、发展趋势及面临的挑战。     

HeII的粘度理论分析与计算

在一般的分析与计算中,超流氦的粘度往往成为一个被忽视甚至被省略的一个物理量。但是在某些低温系统中,需要完成超流氦长距离输送,粘度成为确定其流动阻力损失的一个重要物理量。目前各具特色的理论和计算关系式很多,但是迄今为止,还没有任何一种理论体系或计算关系式可以适用于所有的物质或所有的温度和压力范围,因此如何应用和借鉴现有的粘度理论或关系式以及实验结果,实现对HeII这种特殊流体粘度的分析和计算是一项十分重要的工作。     

星载测量通信系统模拟器设计与实现

为了在地面对星载测量通信系统之间互联互通性能进行测试评估,设计了一种可替代星载测量通信系统的地面模拟器,该模拟器由收发信机,时频单元,信道仿真器以及管理控制计算机构成,收发信机采用双FPGA架构设计,支持星间信号的收发处理,在功能性能指标方面与星载设备具有良好的一致性,信道仿真器能够实现信号传输延时、多普勒以及衰落特性的实时仿真,可显著增强试验场景的真实性以及评估结论的可信性。互联互通试验过程表明,该模拟器功能齐全、性能可靠、操控简单并且易于搬运,试验结果有效验证了星间互联互通方案的可行性。     

Investigation of radiation damage and hardness of H- and He-implanted SiC

In this study, an investigation was conducted in order to determine the effects of high-dose H and He ion implantation on the structure of 3C-SiC and 6H-SiC as well as the effects on material hardness in order to understand the role of H and He produced in SiC by neutron-induced transmutations as described by Heinisch et al. [J. Nucl. Mater. 2004, 327, 175–181.]. H and He ions were implanted into polycrystalline 3C-SiC on a Si substrate and single-crystal bulk 6H-SiC, respectively, at an ion energy of 100 keV, and the total dose that was used for both species was 10¹⁷ ions/cm² in the temperature range of 473–573 K. The specimens were annealed at 1000°C for 20 min in an inert Ar atmosphere. The damaged region in the He-implanted 6H-SiC had a high density of small bubbles, but no cracks were observed. Severe cracking was observed along the damaged region in the H-implanted 3C-SiC specimens as well as a high density of hydrogen platelets. Neither specimen displayed any amorphization. Nanoindentation hardness measurements showed a marked increase in the hardness of the annealed He-implanted 6H-SiC, which was ascribed to the creation of point defects inhibiting interplanar slip. There was also a large decrease in hardness corresponding to the depth of the ion damage.     

黄芩素的分离纯化与结构表征

以聚酰胺为柱层析吸附剂,以乙醇-氯仿混合溶剂梯度洗脱,从中药黄芩的甲醇提取液中分离出有效成分黄芩素的粗品。 通过对有效成分进行重结晶等纯化处理,得到了一种黄色短棱柱晶状产物。 利用红外光谱(FTIR)、紫外-可见光谱(UV-Vis)、质谱(MS)、氢谱(1H-NMR)及碳谱(13C-NMR)等分析测试手段,对产物的组成和结构进行了表征。 红外光谱测定结果表明,产物的结构中含有共轭芳香体系和单取代苯;紫外-可见光谱和质谱表明,产物为黄酮而非黄酮苷化合物,A环上含有三个酚羟基, B环无羟基和其他基团取代;核磁共振氢谱及碳谱表明,产物的结构中含15个碳原子, 三组羟基质子。 同时,文章还对所有1H-NMR和13C-NMR信号进行了归属,对FTIR光谱特征吸收峰所对应的官能团及其振动形式进行了指认,给出了化合物及碎片离子在质谱中的裂解方式,最终将黄色短棱柱晶状产物鉴定为5,6,7-三羟基黄酮,即黄芩素,分子式为C₁₅H₁₀O₅。     

Structure and properties of some chiralanes and chirolanes

The molecular structures, spectra and properties of six chiralanes and chirolanes (approximately spheroidal, saturated, cage hydrocarbons) have been determined by density functional theory (DFT) quantum chemistry calculations. The main features determined are: molecular geometry, partial atomic charges, standard enthalpy of formation, IR, nuclear magnetic resonance (NMR) and circular dichroism (CD) spectra. On the basis of the calculated standard enthalpies of formation and highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gaps, we suggest that chiralanes/chirolanes are potential synthetic targets. We have calculated the anomalously large downfield ¹³C-NMR shifts for endohedral carbons in the spectra of [5.5] and [5.7]chiralanes.