Studying the Properties of Calcium Fluoride Nanopowder after Irradiation with a Nanosecond Electron Beam

Technical Physics Letters - Using vacuum evaporation by a pulsed electron beam, mesoporous CaF2 nanopowders with a specific surface area of up to 91.5 m2/g were obtained. The effect of nanosecond...     

Dynamics of an Electron in Generalized Fibonacci Lattices

1.IntroductionSincetheremarkabledisc0veryofquasicrystals[1]andthesuccessfulfabricati0nofsemiconduct0rsu-perlatticesarrangedinaFib0naccisequencel']1muchattentionhasbeenpaidt0thestudyofelectr0nicpropertiesofquasiperiodicsystems.Withregardtoone-dimensional(lD)case,Fibonaccilatticeshavewellbeen.tudied[3'4].Numericalandanalyticalre-sultsshowthat1DFibonaccilatticeshavefractal-Iikespectraandcriticaleigenstates.Recently,thereisagrowingiflterestinthegeneralizedFibonaccilattices(GFL)[sl61,whichechib…     

Anomalous Electron Spectrum and Its Relation to Peak Structure of Electron Scattering Rate in Cuprate Superconductors

The recent discovery of a direct link between the sharp peak in the electron quasiparticle scattering rate of cuprate superconductors and the well-known peak–dip–hump structure in the electron quasiparticle excitation spectrum is calling for an explanation. Within the framework of the kinetic-energy-driven superconducting mechanism, the complicated line-shape in the electron quasiparticle excitation spectrum of cuprate superconductors is investigated. It is shown that the interaction between electrons by the exchange of spin excitations generates a notable peak structure in the electron quasiparticle scattering rate around the antinodal and nodal regions. However, this peak structure disappears at the hot spots, which leads to that the striking peak–dip–hump structure is developed around the antinodal and nodal regions, and vanishes at the hot spots. The theory also confirms that the sharp peak observed in the electron quasiparticle scattering rate is directly responsible for the remarkable peak–dip–hump structure in the electron quasiparticle excitation spectrum of cuprate superconductors.     

Propagation of an Electron Beam in Atmosphere at Altitudes from 15 to 100 km: Numerical Experiment

The propagation of a relativistic electron momentum in the atmosphere is investigated. The motion of electrons under the effect of the geomagnetic and electric force fields, scattering, ionization, the formation of secondary electrons, the perturbation of the atmospheric conductivity, and the distribution of electric field are numerically simulated. The previous conclusion by Neubert et al. [1] is substantiated, according to which the inclusion of the vertical geomagnetic field reduces by almost two orders of magnitude the radial collision blurring of the electron beam and increases accordingly the density of energy release and ionization during the injection from an altitude of 60 km downward. The results are given of simulation of the beam injection at an altitude of 60 km downward or horizontally in the presence of a horizontal or vertical geomagnetic field, as well as of the injection from an altitude of 15 km upward along a quasi-stationary thunderstorm electric field of 5 kV/m beyond the clouds, whose magnitude and polarity correspond to the field jumps that are observed in nature. Based on the calculation results, the degree of ionization, conductivity, and the relaxation time of these parameters in the electron beam trace are estimated. The estimates show that, in the vicinity of the beam trace, because of its polarization, there is a possibility of ten- and hundredfold investigation of the electric field, of discharges in the atmosphere, or of the attainment of the runaway threshold for background relativistic electrons. The possibility is discussed of application of a light electron accelerator for the initiation of observable optical atmospheric phenomena such as blue jets, blue starters, and red sprites.     

Features of Measuring the Electrical Conductivity of Distilled Water in Contact with Air

Measurement Techniques - The paper describes the results of experiments on measuring the electrical conductivity (specific conductance) of distilled water during prolonged contact with air. To...     

利用等离子体预处理增强涤纶织物电子束辐照亲水改性的效果

利用电子束辐照接枝亲水性单体可提高涤纶织物的亲水性,但涤纶大分子本身结构规整且结晶度较高,造成改性时接枝率偏低,引入预处理可以提高改性效果。先通过正交试验得到等离子体预处理的最佳方案,再分别对涤纶织物原样、无预处理接枝改性和经等离子体预处理后接枝改性的涤纶织物进行接枝率、回潮率、接触角、红外光谱(FT-IR)及扫描电子显微镜(SEM)的测试,结果表明,相比无预处理直接进行接枝改性的涤纶织物,增加等离子体预处理可以使接枝率提高1.64倍,回潮率增加75%,接触角也由87.95°急剧减小以至于无法测出具体数值,亲水性有了更为明显的改善。此外,断裂强力和白度测试结果也表明,辐照接枝前引入等离子体预处理对涤纶织物的物理性能影响较小,均在可接受范围内。     

Electron Holographic Observations at Boundaries Aligned Parallel and Nonparallel to the Incident Beam

The changes in phase profiles across heterointerfaces and the ability to detect intergranular amorphous phases were investigated using off-axis electron holography in a field-emission transmission electron microscope. The boundaries were viewed in the conventional edge-on orientation, and also after tilting so that the boundary was no longer parallel to the incident beam. Reconstructed phase images of W/Si multilayers demonstrate that the boundaries are still apparent even at substantial tilts (up to 6°), and that the shape of the phase profile changes as expected with tilt. Detection of thin (<1nm) glassy phases at grain boundaries in Ti-doped Al₂O₃ with minor silicon impurities was then explored. The amorphous aluminosilicate phase displays a significantly larger phase shift than the adjoining alumina grains, and can be apparent at tilts up to nearly 10°. An undecorated boundary shows very little change in phase at the interface.     

真空电子束焊机中的PLC应用技术

本文介绍了电子束焊机的组成及工作原理，并对电子束焊机的控制原理和使用进行分析，提出用三菱公司的FX系列的可编程逻辑控制器对电子束焊机进行逻辑控制，工作台控制则要用PLC的高速输出口和PLC特殊模块功能技术，实现了工作台的精密控制，结合电子束焊机对控制系统要求及焊接工艺需要，分别对控制软件的作用和软件构成进行了详细的说明，控制系统硬件及软件经过设备的运行表明，控制系统的硬件，软件功能完善，工作可靠。     

Characterization of Dynamics in Materials Using Time-Resolved Electron Microscopy Incorporating Electron Counting and Electron Correlation Spectroscopy

Time-resolved electron microscopy incorporating electron counting and electron correlation spectroscopy can be used to quantify the dynamics in materials faster than the shot noise limit of the real-time observation in conventional transmission electron microscopy. An imaging electron beam current, temporally modulated by the dynamics of the specimen, is selected by the aperture in the image plane, and is measured by means of an electron counting technique. Applications of the method to the study of the dynamics of superconducting vortices and to the observation of nanovibrations of materials associated with elastic properties are discussed.     

Special Features in the Realization of Film Boiling on Wire Heaters. Distilled Water

The existence of a region of self-oscillatory instability of heat transfer is revealed under conditions of film boiling of water subcooled to the saturation temperature. In the case of short heaters, whose length is commensurable with the Taylor instability wavelength, the process is regular. For heaters of the same length, the form of oscillations and their characteristics are fully reproducible. An increase in the heater length results in the emergence of spatially distributed oscillations. It is found that an increase in subcooling on the interface between the modes of boiling is accompanied by the formation of a structure consisting of a system of single domains of continuously decreasing size. The formation of this structure causes a significant change in the temperature distribution in the zone adjoining that of nucleate boiling, which considerably reduces the film stability. A single domain of the film mode of boiling was stable at any temperature of the liquid. The singularities of realization of minimal-size domains of the film mode of boiling under conditions of stabilization of the integral mean temperature of the heater are investigated. It is found that the minimal zone of the film mode of boiling is a system of three elementary domains.     

Effects of Synchronization and Switching off Chemical Self-Oscillations upon Periodic Exposure to Light

Technical Physics Letters - The effect of synchronization of chemical concentration self-oscillations of the Briggs–Rauscher reaction under the periodic external effect of white light was...     

Quantitative Proteomics Study Reveals Changes in the Molecular Landscape of Human Embryonic Stem Cells with Impaired Stem Cell Differentiation upon Exposure to Titanium Dioxide Nanoparticles

The increasing number of nanoparticles (NPs) being used in various industries has led to growing concerns of potential hazards that NP exposure can incur on human health. However, its global effects on humans and the underlying mechanisms are not systemically studied. Human embryonic stem cells (hESCs), with the ability to differentiate to any cell types, provide a unique system to assess cellular, developmental, and functional toxicity in vitro within a single system highly relevant to human physiology. Here, the quantitative proteomics approach is adopted to evaluate the molecular consequences of titanium dioxide NPs (TiO₂ NPs) exposure in hESCs. The study identifies ≈328 unique proteins significantly affected by TiO₂ NPs exposure. Proteomics analysis highlights that TiO₂ NPs can induce DNA damage, elevated oxidative stress, apoptotic responses, and cellular differentiation. Furthermore, in vivo analysis demonstrates remarkable reduction in the ability of hESCs in teratoma formation after TiO₂ NPs exposure, suggesting impaired pluripotency. Subsequently, it is found that TiO₂ NPs can disrupt hESC mesoderm differentiation into cardiomyocytes. The study unveils comprehensive changes in the molecular landscape of hESCs by TiO₂ NPs and identifies the impact which TiO₂ NPs can have on the pluripotency and differentiation properties of human stem cells.     

Modeling and Experimental Validation of the Electron Beam Selective Melting Process

Electron beam selective melting (EBSM) is a promising additive manufacturing (AM) technology. The EBSM process consists of three major procedures: ① spreading a powder layer, ② preheating to slightly sinter the powder, and ③ selectively melting the powder bed. The highly transient multi-physics phenomena involved in these procedures pose a significant challenge for in situ experimental observation and measurement. To advance the understanding of the physical mechanisms in each procedure, we leverage high-fidelity modeling and post-process experiments. The models resemble the actual fabrication procedures, including ① a powder-spreading model using the discrete element method (DEM), ② a phase field (PF) model of powder sintering (solid-state sintering), and ③ a powder-melting (liquid-state sintering) model using the finite volume method (FVM). Comprehensive insights into all the major procedures are provided, which have rarely been reported. Preliminary simulation results (including powder particle packing within the powder bed, sintering neck formation between particles, and single-track defects) agree qualitatively with experiments, demonstrating the ability to understand the mechanisms and to guide the design and optimization of the experimental setup and manufacturing process.     

Electron Beam Technologies for Preparation of Polymeric Materials Used for Waste Water Treatment, Agriculture, and Medicine

Radiation research results in the field of polymeric materials, obtained in the last few years by electron beam irradiation of aqueous solutions containing appropriate monomer mixtures, such as acrylamide, acrylic acid and vinyl acetate, are presented. Two types of polymeric flocculants for waste water treatment and three kinds of hydrogels for agriculture and medicine are described. The effects of radiation absorbed dose, radiation absorbed dose rate, and chemical composition of the irradiated solutions upon the polymeric materials characteristics are discussed. The required absorbed dose levels to produce the polymeric flocculants are in the range of 0.3 to 9 kGy and 4 kGy to 12 kGy for hydrogels. Some experimental results obtained by testing polymeric flocculants with waste water from food industry are given. Polymeric material processing was developed on a pilot plant level with ALID-7 electron linear accelerator of 5.5 MeV and 0.7 kW, built in the Electron Accelerator Laboratory of the Institute of Atomic Physics, Bucharest. A new facility permitting the application of simultaneous electron beam and microwave irradiation is presently under investigation. Preliminary results demonstrated that some polymeric flocculant characteristics, such as linearity, were improved by simultaneous electron beam and microwave treatment. Also, the absorbed dose levels decreased and intrinsic viscosity increased, respectively, by about two times by this new material processing method.     

Electron Spin Resonance and Infrared Spectroscopy Study of the Polyvinylpyrrolidone-C60 Composite

Recently we have found from ESR spectra that the electron charge transfer take place in the polyvinylpyrrolidone-C₆₀ composite. In this paper the polystyrene-C₆₀, polyvinylchloride-C₆₀, poly(ethylene glycol)-C₆₀, and poly(ethylene oxide)-C₆₀ composites are prepared and probed by the ESR technique for comparison. They show no signal which might be referred to the electron transfer. Along with this, we continue ESR study of the polyvinylpyrrolidone-C₆₀ composite and also present IR spectra, which indicate the involvement of the carbonyl group of polyvinylpyrrolidone into the electron charge transfer process.     

Electron Spin Resonance and Infrared Spectroscopy Study of the Polyvinylpyrrolidone-C60 Composite

Abstract

Recently we have found from ESR spectra that the electron charge transfer take place in the polyvinylpyrrolidone-C₆₀ composite. In this paper the polystyrene-C₆₀, polyvinylchloride-C₆₀, poly(ethylene glycol)-C₆₀, and poly(ethylene oxide)-C₆₀ composites are prepared and probed by the ESR technique for comparison. They show no signal which might be referred to the electron transfer. Along with this, we continue ESR study of the polyvinylpyrrolidone-C₆₀ composite and also present IR spectra, which indicate the involvement of the carbonyl group of polyvinylpyrrolidone into the electron charge transfer process.