CALCULATION OF THE YOUNG''''S MODULUS OF AN ADSORBED POLYMER LAYER

Polymer layers adsorbed to a surface or in a confined environment often change their mechanical properties. There is even the possibility of solidification of the confined layer. To judge the stiffness of such a layer, we used the Hertz model to calculate the Young's modulus of the polymer layer in the confinement of AFM experiments with silicon nitride tip with a radius of curvature of R≈50 nm and a glass sphere attached to the cantilever R = 5μm. Since there is no visible indentation of the layer in the AFM experiments, the layer is either penetrated very easily, or the indentation is too small to be seen in a force curve. The latter would be the case for a polymer layer with a Young's modulus above 4×108 Pa in case of an experiment with a silicon nitride tip and 4×105 Pa in case of a glass sphere.     

气泡室中"胚胎"气泡成长为可见气泡的模型建立及初步的理论计算

建立了气泡室中“胚胎”气泡成长为可见气泡模型.初步计算表明,“胚胎”气泡在成长为可见气泡的过程中,它不仅要从其周围吸收热量,而且还有分子进入到它的里面.理论上可以合理解释能量相同的中子和质子入射到气泡室所产生的径迹上的气泡半径是不同的,中子在气泡室中产生的径迹细长,而质子在气泡室中产生的径迹粗短;可以合理解释在同一径迹上某个区域内可以有半径大小相差不多的气泡存在;也可以合理解释电荷数较多的入射粒子较能量相同但电荷数不同的入射粒子,其在气泡室中径迹上气泡的半径要大;理论上预测入射粒子刚进入气泡室时,其径迹上有大气泡破裂现象发生.通过选择合适的工作物质可以提高气泡室的灵敏度和探测效率.     

Separation of small molecules using novel rolltruded membranes. I. Apparatus and preliminary results

A novel membrane production technique, rolltrusion, has been developed for the preparation of permselective polymeric membranes for both gas and vapor separations and pervaporation applications. Pinhole-free thin films with a regulated three-dimensional morphology comprising crystalline and amorphous regions have been produced with improved mechanical properties in three dimensions. Because rolltrusion is a solid-state processing technique, it is not restricted by solubility constraints inherent in the common solvent-based thinfilm production techniques. Consequently it can be extended to include commercially available engineering plastics that have not been used as membranes previously because of their limited solvent solubility. These polymers are interesting because of their applicability to temperatures in excess of 200 to 300°C in harsh chemical environments, compared with the ca. 150°C ceiling usually encountered in the most rugged of solvent-cast polymers. In the first part of this series we detail an automated experimental permeation apparatus that permits testing of both single-component and multicomponent gases and vapors over a temperature range of ?73 to 273°C. Currently, modifications to the permeation cell are underway to permit pervaporation studies in the apparatus. To illustrate the operation of the apparatus, and to some degree the effect of rolltrusion processing, experimental permeability, diffusivity, solubility, and actual gas separation factors (via gas chromatography) are detailed for several light gases in rolltruded isotactic poly(propylene) (iPP) and in the thermally and chemically resistant thermoplastic, poly(ether ether ketone) (PEEK). Permeation temperatures to at least 225°C have been studied using PEEK, representing the first published experimental permeability and gas-separation results for such engineering polymers at temperatures above 200 °C. © 1992 John Wiley & Sons, Inc.     

气泡室中"胚胎"气泡的联并成长为可见气泡的理论计算

借助岛的联并理论,可以很好地解决气泡室中"胚胎"气泡成长为可见气泡问题.理论计算表明,联并后的大"胚胎"气泡在成长为可见气泡的过程中,气泡的半径不仅与工作物质如液体的表面张力系数、饱和蒸汽压和流体的沸点有关,而且还与"胚胎 "气泡从其周围吸收热量和"胚胎"气泡联并的个数有关.理论上可以合理解释能量相同的中子和质子入射到气泡室所产生的径迹粗短;也可以合理解释电荷数较多的入射粒子较能量相同但电荷数不同的入射粒子,其在气泡室中径迹上气泡的半径要大.     

Measurement of the η production in proton-proton collisions with the COSY time-of-flight spectrometer

The reaction pp → ppη was measured at excess energies of 15 and 41 MeV at an external target of the Jülich Cooler Synchrotron COSY with the time-of-flight spectrometer. About 25000 events were measured for the excess energy of 15 MeV and about 8000 for 41 MeV. Both protons of the process ppη were detected with an acceptance of nearly 100% and the η was reconstructed by the missing-mass technique. For both excess energies the angular distributions are found to be nearly isotropic. In the invariant-mass distributions strong deviations from the pure phase space distributions are seen. Received: 24 May 2002 / Accepted: 20 September 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: e.roderburg@fz-juelich.de Communicated by M. Gar?on     

Initial-state nuclear effects in proton-nucleus collisions

Two important initial-state nuclear effects in hadron-nucleus collisions are considered. The ratios of inclusive differential cross-sections for Drell-Yan dimuon production are calculated. The calculated results are compared to the E866 data. It is shown that the consideration of multiple soft rescatterings of incident quarks in nuclei and initial-state quark energy loss effects allow to get a good agreement between the calculated results and the experimental data.     

Energetic AT1 Spectra of He in Circularly Polarized Laser

A new analytic model for ATIspectra of He in circularly polarized laser is proposed.The model gives a way to describe the effects of the final state Coulomb interaction and the joint interaction of the atomic potential and laser field. The experimental spectra by Mohideen et al. can be quite well described. The peak intensity contradiction, which appeared in previous literatures, can be considerably eliminated.     

Investigation on the influence of atomic potentials on the above threshold ionization

We systematically investigate the influence of atomic potentials on the above-threshold ionization （ATI） spectra in one-dimensional （1D） cases and compare them with the three-dimensional （3D） case by numerically solving the time-dependent Schrrdinger equation. It is found that the direct ionization plateau and the rescattering plateau of the ATI spectrum in the 3D case can be well reproduced by the 1D ATI spectra calculated from the supersolid-core potential and the soft-core potential, respectively. By analyzing the factors that affect the yield of the ATI spectrum, we propose a modified-potential with which we can reproduce the overall 3D ATI spectrum. In addition, the influence of the incident laser intensities and frequencies on the ATI spectra calculated from the proposed modified potential is studied.     

On the space of measurable functions and its topology determined by the Choquet integral

Let (X,A,μ) be a finite nonadditive measure space and M be the set of all finite measurable functions on X. The topology on M, which is determined by the Choquet integral with respect to μ, is investigated. The relationship between this topology and the one determined by the Sugeno integral is examined. Some interesting examples are included.     

Low-energy structure in the ionization of argon: Comparison of experiment with theory

The above-threshold ionization of argon in an intense 70-fs,400-nm linearly polarized laser pulse has been investigated by the velocity map imaging techniques,combined with an attosecond-resolution quantum wave packet dynamics method.There is a quantitative agreement in all dominant features between the experiment and the theory.Moreover,a peak-splitting phenomenon in the first energy peak has been observed at high pulse intensity.Further,through the theoretical analysis,an ac Stark splitting with evident resonant and nonresonant ionization pathways has been found to be the physical reason for the experimental observations.