Substituent Effect on the Tautomerization of 1‐Arylazonaphthalen‐2‐ols by Mass Spectrometric Analysis

An electron‐ionization (EI) mass spectra of a series of 1‐arylazonaphthalen‐2‐ols was obtained for studying the substituent effect on the fragmentation. The correlation between the ratio, molecular ion and fragment ion, and Hammett’s constants is applied to examine the effect of the substituent on the fragmentation. The negative correction between the ratio, I_{molecular ion}/(I_171amu + I_143amu + I_115amu), and Hammett’s constants indicates an electron‐withdrawing group destabilized the molecular ion. An unusual long‐range hydrogen transfer demonstrates an important role in the fragmentation process     

On the diophantine equation x 2 + 2 a · 3 b · 11 c = y n

In this note, we find all the solutions of the Diophantine equation x ² + 2 ^a · 3 ^b · 11 ^c = y ⁿ , in nonnegative integers a, b, c, x, y, n ≥ 3 with x and y coprime.     

A mode coupling theory description of the short- and long-time dynamics of nematogens in the isotropic phase

Optical heterodyne-detected optical Kerr effect (OHD-OKE) experimental data are pre-sented on nematogens 4-(trans-4-n-octylcyclohexyl)isothiocyanatobenzene (8-CHBT), and 4-(4-pentyl-cyclohexyl)-benzonitrile (5-PCH) in the isotropic phase. The 8-CHBT and 5-PCH data and previously published data on 4-pentyl-4-biphenylcarbonitrile (5-CB) are analyzed using a modification of a schematic mode coupling theory (MCT) that has been successful in describing the dynamics of supercooled liquids. At long time, the OHD-OKE data (orientational relaxation) are well described with the standard Landau-de Gennes (LdG) theory. The data decay as a single exponential. The decay time diverges as the isotropic to nematic phase transition is approached from above. Previously there has been no theory that can describe the complex dynamics that occur at times short compared to the LdG exponential decay. Earlier, it has been noted that the short-time nematogen dynamics, which consist of several power laws, have a functional form identical to that observed for the short time behavior of the orientational relaxation of supercooled liquids. The temperature-dependent orientational dynamics of supercooled liquids have recently been successfully described using a schematic mode coupling theory. The schematic MCT theory that fits the supercooled liquid data does not reproduce the nematogen data within experimental error. The similarities of the nematogen data to the supercooled liquid data are the motivation for applying a modification of the successful MCT theory to nematogen dynamics in the isotropic phase. The results presented below show that the new schematic MCT theory does an excellent job of reproducing the nematogen isotropic phase OHD-OKE data on all time scales and at all temperatures.     

关于Reed列表染色猜想的一些结果

构造了一个图G,给G的每个顶点v一个颜色列表,使得每个列表Lv的大小至少为每个顶点v的邻域NG(v)与每个Vc交集的最大数目,但是这个图不存在一个正常的列表染色,从而推翻了R eed的一个猜想.     

Axial intensity distribution of truncated Bessel-Gauss beams in a turbulent atmosphere

By means of the extended Huygens-Fresnel integral formula in the paraxial approximation and based on the fact that a hard aperture function can be expanded into a finite sum of complex Gaussian functions, an approximate analytical expression for Bessel-Gauss beams propagating in a turbulent atmosphere truncated by an aperture has been derived. The result is more convenient for studying the axial intensity distribution properties of Bessel-Gauss beams with different topological charges in a turbulent atmosphere than the usual way by using diffraction integral directly. Utilizing the analytical expression, the axial intensity distribution of such kind of beam in a turbulent atmosphere is investigated numerically in detail. Results show that the intensity distribution on the axis changes with the variation of the beam topological charge m, the wavelength and beam waist width of the initial beam and the turbulent strength.     

甲基丙烯酸甲酯-苯乙烯-N-苯基马来酰亚胺三元共聚物的研究

研究了甲基丙烯酸甲酯-苯乙烯-N-苯基马来酰亚胺三元共聚体系的组成以及分子量分布对共聚物的耐热及物理机械性能的影响.实验结果表明:在一定条件下如果适当控制混合单体比例,可望获得一种综合性能较优越的共聚物材料.     

Properties of as-cast and structurally relaxed Zr-based bulk metallic glasses

We have studied the influence of the arc melting procedure of Nb-containing Zr-based bulk metallic glasses (BMGs) on their thermal and mechanical properties. We found that the strength and plastic strain to failure, determined at room temperature, increases by the addition of a few percentage of Nb into the Zr-based BMGs. High-resolution transmission-electron microscopy results show that the addition of 2 at.% Nb introduces the formation of as-cast nanocrystals. At the same time, thermal analyses indicate an increase in glass forming ability with the small addition of Nb. Contrary to the reported results in other amorphous alloys, we found that the plastic strain increases further after heat-induced structural relaxation in the Zr-based BMGs.     

相位反射产生的激光场空洞现象及其与激光等离子体参数相关性研究

理论研究和数值模拟研究表明激光在等离子体中诱导的等离子体密度调制可以起类似布拉格反射镜的作用，使得后面的入射光在等离子体平均密度远低于临界密度的区域就对入射光产生相位反射.相位反射的发生会影响激光在等离子体中的传播，例如激光在等离子体中相对传播时会出现激光场空洞现象.进一步的理论和数值模拟研究表明，相位反射持续发生的时间以及反射率的高低与等离子体的密度、等离子体区域的长度、激光强度以及脉宽等因素密切相关，这些都会对激光在等离子体中的传输产生影响. 关键词： 相位反射 密度调制 激光等离子体 粒子模拟     

Selective hydrogenation of nitrobenzene top-Aminophenol by the polymer-supported palladium-based mono- and bimetallic catalyst

In acidic reaction medium, polymer-supported monometallic palladium catalyst, PVP-PdCl₂ [(PVP=poly(N-vinyl-pyrrolidone)], is used to catalyze the hydrogenation of nitrobenzene top-aminophenol and aniline. The addition of a second transition metal compound or a very small amount of 2-mercaptopyrimidine gives rise to an increase in the selectivity forp-aminophenol.     

Gold nanocages as contrast agents for spectroscopic optical coherence tomography

We describe gold nanocages as a new class of potential contrast agent for spectroscopic optical coherence tomography (OCT). Monodispersed gold nanocages of an approximately 35 nm edge length exhibit strong optical resonance, with the peak wavelength tunable in the near-infrared range. We characterized the optical properties of the nanocage by using OCT experiments along with numerical calculations, revealing an absorption cross section approximately 5 orders of magnitude larger than conventional dyes. Experiments with tissue phantoms demonstrated that the nanocages provide enhanced contrast for spectroscopic as well as conventional intensity-based OCT imaging.