反射扩散过程的极集

本文利用Ｄｉｒｉｃｈｌｅｔ型中有产在容度的结论，从几何的观点刻画了反射扩散过程的极集。     

Free-release static coating of glass capillary columns: Coating with medium polar and polar stationary phases

Summary Principles are proposed to select solvents for the coating of glass capillary columns with medium-polar and polar stationary phases applying the free-release static-coating technique, practical examples are given, demonstrating that this technique is suitable to coat stationary phases like OV-1701 and Carbowaxes.     

Anisotropy Effects on Polar Optical Vibrations in a Freestanding Wurtzite Cylindrical Quantum Dot

The properties of polar optical phonon vibrations in a quasi-zero- dimensional (Q0D) anisotropic wurtzite cylindrical quantum dot (QD) are analyzed based on the dielectric continuum model and Loudon's uniaxial crystal model.The analytical electrostatic potentials of the phonon vibrations in the systems are deduced and solved exactly. The result shows that there exist four types of polar mixing optical phonon modes in the Q0D wurtzite cylindrical QD systems. The dispersive equations and electron-phonon coupling function for the quasi-confined-half-space (QC-HS) mixing modes are derived and discussed. It is found that once the radius or the height of the QD approach infinity, the dispersive equations of the QC-HS mixing modes in the Q0D cylindrical QD can naturally reduce to those of the QC and HS modes in Q2D QWs or Q1D QWWs systems. This has been analyzed reasonably from both of physical and mathematical viewpoints.     

A Review of Potential Use of Amazonian Oils in the Synthesis of Organogels for Cosmetic Application

New strategies for the delivery of bioactives in the deeper layers of the skin have been studied in recent years, using mainly natural ingredients. Among the strategies are organogels as a promising tool to load bioactives with different physicochemical characteristics, using vegetable oils. Studies have shown satisfactory skin permeation, good physicochemical stability mainly due to its three-dimensional structure, and controlled release using vegetable oils and low-molecular-weight organogelators. Within the universe of natural ingredients, vegetable oils, especially those from the Amazon, have a series of benefits and characteristics that make them unique compared to conventional oils. Several studies have shown that the use of Amazonian oils brings a series of benefits to the skin, among which are an emollient, moisturizing, and nourishing effect. This work shows a compilation of the main Amazonian oils and their nutraceutical and physicochemical characteristics together with the minority polar components, related to health benefits, and their possible effects on the synthesis of organogels for cosmetic purposes.     

Comparison of mechanistic models for correlation of activation energies of liquid‐phase addition of carbon‐centered radicals to terminal olefins

The performance of different models for the influence of enthalpy and polar effects on radical additions is compared for the extensive data set from the Fischer group, supplemented by additional data. The best correlations result from the Fischer–Radom (FR) model, but it also contains the largest number of adjustable radical‐dependent parameters not based on physical observables. Updating the literature values of , IP, and EA that are inputs to the FR model led to some deterioration in the quality of the correlations; this is symptomatic of remaining deficiencies in the thermochemical databases. In contrast, the Lalevee–Allonas–Fouassier (LAF) model gives poorer correlation but this is in part compensated because it uses the same inputs but with no adjustable parameters. Hammett‐type models based on polar and radical substituent constants rather than on molecular properties of the reactants perform even more poorly. In all cases, poorer correlation, as judged by increasing sd(ΔE), is accompanied by a systematic bias to over‐predict the lower E values and under‐predict the higher ones. The enthalpy contribution in the FR and LAF models is expressed as a linear Evans–Polanyi dependence of E on ΔH. Replacement by nonlinear Marcus dependences does not significantly improve performance. An attempt to significantly reduce the number of adjustable parameters in the FR model by anchoring them to a base set applicable to all radicals, which is then modulated for spin delocalization based on observable ESR hyperfine constants in the initial and adduct radicals, showed modest success. Copyright © 2008 John Wiley & Sons, Ltd.     

The Norwegian and the Englishman

I sketch the lives and work of the Norwegian physicist Kristian Birkeland (1867–1917) and the English mathematician Sydney Chapman (1888–1970), focusing particularly on Chapman’s controversy with Birkeland over the origin and development of auroras, a controversy that Chapman conducted with Birkeland for more than fifty years after Birkeland’s death. Sidney Borowitz is Professor Emeritus of Physics at New York University.     

电离层中性气体释放的早期试验效应研究

在电离层释放电子吸附类中性气体能够引起电离层电子密度耗空,在释放之后快速形成"电离层洞";同时,由于释放气体的快速膨胀,挤压背景等离子体,在电离层洞的外边缘产生"壳状"电子密度增强结构,电离层洞和电子密度增强结构同时存在是释放早期试验效应的显著特征.本文研究了电离层中性气体释放的早期试验效应,建立了释放早期电子密度的时空演化物理模型,仿真了释放早期电子密度的时空演化过程,同时采用射线追踪方法研究了释放后10 s和120 s不同频率信号在扰动区的传播效应,并反演得到了电离层垂直探测电离图,反演结果与一次火箭喷焰的实际观测结果吻合较好,初步验证了本模型的正确性.     

极性半导体的表面电子

有不少的极性半导休,电子与表面声学声子和体纵光学声子的耦合弱,但与表面光学声手的耦台强.本文同时考虑体纵光学声子、表面光学声子以及表面声学声予的影响,研究这类半导体的表面电予的性质,采用线性组合算符和拉格朗日乘子法,导出其有效哈密顿量和重正化质量。     

Polar structure of N,N′-dimethylurea crystals

In the crystal structure of N,N′-dimethylurea, there is one molecule in the asymmetric unit, but with two halves related by an axis of pseudosymmetry. All nonhydrogen atoms of each molecule lie on a plane. In the crystal the molecules are held together by hydrogen bonds in the direction of the “a” axis. They form parallel rows with the same sense orientation, so that the crystal has a polar structure.     

Solution of Hadwiger-Levi's Covering Problem for Duals of Cyclic 2k-Polytopes

For a collection C of convex bodies let h(C) be the minimum number m with the property that every element K of C can be covered by m or fewer smaller homothetic copies of K. Denote by C _d ^* the collection of all duals of cyclic d-polytopes, d 2. We show that h(C _2k ^* )=(k +1)2 for any k 2. We also prove the inequalities (d+1) (d+3)/4 h(C _d ^* ) (d+1) 2/2$ for any d 2.