SO4●－自由基氧化酪氨酸反应中的溶剂效应

研究了水-乙腈混合溶液中SO4●－自由基氧化酪氨酸的反应.实验结果表明，SO4●－自由基氧化酪氨酸的反应机制不因乙腈的加入而改变，但所产生的瞬态粒子的动力学行为受到较大影响.随介质中乙腈体积分数的增加，SO4●－的衰变速率减慢而酪氨酸中性自由基（TyrO●）的衰变速率加快.我们认为这两种自由基所呈现出来的相反的溶剂效应是由于其所带电荷的不同.随介质中乙腈体积分数的增加，SO4●－氧化酪氨酸的反应速率减慢.这一实验结果意味着，在有机溶剂存在的情况下TyrO●/ TyrOH的氧化还原电势可能发生了变化，从而旁证了关于TyrO●/ TyrOH的氧化还原电势因酪氨酸从游离状态变到肽或蛋白质中而发生变化的推测.     

Co—Mo／MgO—Al2O3水煤气耐硫变换催化剂失活的研究

利用Ｘ－射线衍射，扫描电镜，拉曼光谱，等离子发射光谱和比表面测定等方法研究了不同状态下失活及新鲜催化剂的结构，杂种类及含量。结果表明，超温使催化剂晶化明显，制备方法对催化剂结构有直接影响，再生使其强度降低，条形催化剂比较容易粉化，无机杂质是次要的失活原因。     

Chiral selective tunneling induced graphene nanoribbon switch

An armchair graphene nanoribbon switch has been designed based on the principle of the Klein paradox. The resulting switch displays an excellent on-off ratio performance. An anomalous tunneling phenomenon, in which electrons do not pass through the graphene nanoribbon junction even when the conventional resonance condition is satisfied, is observed in our numerical simulations. A selective tunneling rule is proposed to explain this interesting transport behavior based on our analytical results. Based on this selective rule, our switch design can also achieve the confinement of an electron to form a quantum qubit.      

Geometrically distinct solutions for Klein–Gordon–Maxwell systems with super-linear nonlinearities

This paper is concerned with the following Klein–Gordon–Maxwell system $\left\{\begin{array}{c}-△u+V\left(x\right)u-(2\omega +\varphi )\varphi u=f(x,u),x\in {\mathbb{R}}^3,\hfill \\ △\varphi =(\omega +\varphi )u^2,x\in {\mathbb{R}}^3,\hfill \end{array}\right.$where $\omega >0$ is a constant, $V$ and $f$ are periodic with respect to $x$. By combining deformation type arguments, Lusternik–Schnirelmann theory and some new tricks, we prove that the above system admits infinitely many geometrically distinct solutions under weaker superlinear conditions instead of the common super-cubic conditions on $f$. Our result seems new and extends the previous results in the literature.     

通过不同烷基链取代调控喹吖啶酮分子在Ag(110)表面上的自组织结构

采用低能电子衍射、扫描隧道显微镜、第一性原理密度泛函理论计算以及分子力学计算,分别对不同烷基链取代的喹吖啶酮(QA)分子在Ag(110)基底上的吸附和生长进行了研究.QA和Ag基底的相互作用主要来自分子中O原子和Ag基底的共价键,它决定了分子的取向和最优吸附位置;而烷基链决定了分子吸附层的取向,QA分子间的排列可以通过烷基链的长度来调节.由此借助调节烷基链的长度,能够可控地制备具有不同物理性质的单层分子薄膜.     

光子晶体垂直腔面发射850nm波长激光器研究

文章报道了国内首次研制成功的光子晶体垂直腔面发射850nm波长激光器, 实现了连续电注入激射.发现器件能否激射直接依赖于光子晶体结构参数,而激光器的阈值、输出功率、输出模式等与光子晶体的晶格常数、占空比、腔的大小等因素有关.     

广义非对称Hartmann势Klein-Gordon方程的严格解(英文)

在标量势和矢量势相等的条件下,严格求解了在广义非对称Hartmann势场中粒子运动的Klein Gordon方程;并利用束缚态边界条件,获得了束缚态能谱表达式和由超几何函数表示出的波函数.     

An alternating periodic－chaotic ISI sequence of HH neuron under external sinusoidal stimulus

A study of Hodgkin－Huxley (HH) neuron under external sinusoidal excited stimulus is presented in this paper. As is well known, the stimulus frequency is to be considered as a bifurcate parameter, and numerous phenomena, such as synchronization, period, and chaos appear alternatively with the changing of the stimulus frequency. For the stimulus frequency less than 2f_B (f_B being the base frequency in this paper), the simulation results demonstrate that the single HH neuron could completely convey the sinusoidal signal in anti-phase into interspike interval (ISI) sequences. We also report, perhaps for the first time, another kind of phenomenon, the beat phenomenon, which exists in the phase dynamics of the ISI sequences of the HH neuron stimulated by a sinusoidal current. It is shown furthermore that intermittent transition results in the general route to chaos.     

Nordström,Ehrenfest, and the Role of Dimensionality in Physics

In the summer of 1916, Finnish physicist Gunnar Nordström (1881–1923) arrived in Leiden to carry out research with Paul Ehrenfest (1880–1933), Hendrik A. Lorentzs successor in the chair of theoretical physics. Nordström had recently published the first five-dimensional unified model of the universe, a theory that went virtually unnoticed by the physics community. Ehrenfests personal journals reveal that Nordströms visit coincided with a flowering of Ehrenfests own interest in dimensionality, which resulted in his well-known paper on the connection between the fundamental laws of physics and the three-dimensionality of space. I examine Nordströms and Ehrenfests collaboration and explore the relationship between their ideas and the Kaluza-Klein model of five-dimensional unification.Paul Halpern is Professor of Physics at the University of the Sciences in Philadelphia. He received a Guggenheim Fellowship in 2002 to study the history of dimensionality in science.