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A lithium ion battery cathode structure was produced which has the potential for excellent capacity retention and good thermal management. In these cathodes, the active cathode material (lithium iron phosphate) was carbon bonded to a thermally and electrically conductive carbon fiber paper (CFP) support. Electrochemical testing was performed on Swagelok cells consisting of CFP cathodes and lithium anodes. High specific energy, near-theoretical capacity, and good cycling performance were demonstrated for 0.11 and 0.37 mm thick CFP cathodes. [ABSTRACT FROM AUTHOR]

Today most of commercial Li-ion batteries (LIBs) are manufactured using toxic solvents and synthetic polymer binders. In order to lower the cost and the environmental impact of LIBs an effort must be made to identify low-cost and environmentally friendly materials and processes. In this work, flexible, self-standing and easily recyclable LiFePO cathodes are obtained using cellulose fibers as biosourced binder and a quick, aqueous filtration process, easily upscalable capitalizing the well-established papermaking know-how. The obtained paper-cathodes show very good mechanical properties, with Young's modulus as high as 100 MPa, discharge capacity values up to 110 mAh g and very good cycling performances, comparable with conventional polymer-bonded LiFePO cathodes. Moreover, a complete paper-cell, constituted by a paper-cathode, a paper-separator and a paper-anode is presented, showing good cycling performances in terms of specific capacity, efficiency and stability. [ABSTRACT FROM AUTHOR]

Abstract: Porous conducting carbon paper acts as an electrode backing material in a fuel cell. It not only assists in the flow of electrons and gases but also provides mechanical support to the MEA. The electrically conducting carbon paper (porosity ∼70%) was prepared using laminated assembly of chopped carbon fiber porous preforms and applying combined paper making and composite making technique. The green paper was subjected to different heat treatment temperatures (HTT), which was found to influence the characteristics of the paper significantly. The processing of the paper was carried out at a very fast carbonization rates, 900°C/h as compared to 10–20°C/h used conventionally, making the complete process highly cost efficient. The paper when used in the unit fuel cell assembly showed I–V performance comparable to that of the commercially available Toray carbon paper. [Copyright &y& Elsevier]

Abstract: The mono-energetic conversion electrons from the decay of Kr represent a unique tool for energy calibration and systematic studies of the tritium beta spectrum measured in neutrino mass determination experiments. For this reason, the corresponding parent isotope was produced in reactions Kr(p,xn)Rb. The behaviour of Rb () and its daughter product Kr () was examined, when the Rb was trapped in a cation-exchanger chromatographic paper or in zeolite. Using gamma spectroscopy measurements, recommendations for the production of a Rb/Kr radionuclide generator based on these cation-exchangers and suitable for the neutrino mass determination experiment KATRIN were deduced. [Copyright &y& Elsevier]

The discovery over 100 years ago that cathode rays were composed of negatively charged corpuscles-subsequently named electrons-was an historic event in the development of science, demonstrating for the first time that particles smaller than atoms existed and initiating other investigations into the nature of matter, as well as marking the beginning of the electronics industry. The research investigations of J. J. Thomson, leading up to the crucial experiments identifying the particle and determining its charge-to-mass ratio as reported in the Philosophical Magazine, are here described. [ABSTRACT FROM AUTHOR]

Abstract: We show that the numerical code used in the above mentioned paper does not take into account the multiple scattering effects of electromagnetic fields properly and is, therefore, incorrect. [Copyright &y& Elsevier]

Just over 100 years ago, Henry Moseley carried out a systematic series of experiments which showed that the frequencies of the X-rays emitted from an elemental target under bombardment by cathode rays were characteristic of that element and could be used to identify the charge on its atomic nucleus. This led to a reorganization of the periodic table, with chemical elements now arranged on the basis of atomic number Z rather than atomic weight A, as had been the case in previous tables, including those developed by Mendeleev. Moseley also showed that there were four 'missing elements' before gold. With further measurements up to uranium Z=92, the Swedish physicist Manne Siegbahn identified two more missing elements. This paper provides an introduction to Moseley and his experiments and then traces attempts to 'discover' missing elements by X-ray spectroscopy. There were two successes with hafnium (Z=72) and rhenium (Z=75), but many blind alleys and episodes of self-deception when dealing with elements 43, 61, 85 and 87. These all turned out to be radioactive, with extremely small natural abundances: all required synthesis by a nuclear reaction, with radiological characterization in the first instance. Finally, the paper moves on to consider the role of X-ray spectroscopy in exploring the periodic table beyond uranium. Although the discovery of artificial radioactive elements with Z>92 again depended on nucleosynthesis and radiological characterization, measurement of the frequencies or energies of characteristic X-rays remains the ultimate goal in proving the existence of an element. [ABSTRACT FROM AUTHOR]

High-temperature and high-pressure (HTHP)-treated diamonds have attracted attention all over the world due to their vivid colors. In order to explore a new method for the rapid and non-destructive identification of HTHP-treated diamonds, in this paper, five IaAB-type diamonds yielded in Russia were selected as the research object and treated with HTHP. The HTHP-treated diamonds were investigated by DiamondViewTM, cathodoluminescence, micro-infrared spectrometry (micro-IR), low-temperature photoluminescence (PL) spectrometry, and three-dimensional (3D) fluorescence spectrometry. The results show that under DiamondViewTM and cathode rays, the five samples were all non-phosphorescent with different luminous patterns, such as regular annular bands, multiple groups of intersecting linear stripes, or jagged stripes. In the low-temperature PL spectra, most HTHP-treated diamonds exhibited stronger luminescence peaks at 637 nm compared to 575 nm. But there were also exceptions, such as the purple-red sample showing the opposite luminescence peak. In the 3D fluorescence spectrum of the HTHP-treated diamonds, the fluorescence peak mainly appeared in the range of 440–450 nm, accompanied by a broad band of 350–500 nm and even longer wavelengths. Meanwhile, some samples also exhibited fluorescence peaks at longer wavelengths, such as 353 nm, 676 nm, and 665 nm. These results make it possible to identify HTHP-treated diamonds by using luminescence characteristics, providing a new method for the non-destructive and rapid detection of HTHP-treated diamonds. [ABSTRACT FROM AUTHOR]

In this paper, a high-power Ka-band traveling-wave tube (TWT) driven by a sheet electron beam is proposed and demonstrated by means of the simulation and experimental methods. The single grating rectangular waveguide with large width-to-height ratio is used as the slow-wave structure (SWS). An $E$ -plane bend energy coupler is put forward to feed this wide SWS. An irregular transition structure between the input waveguide and the SWS is suggested and designed, which is beneficial to suppress the self-excited oscillation. For a practical electron beam (20 mm $\times \,\, 1$ mm, 150.1 kV, 850 A, and 20-ns), the output power of this single rectangular grating sheet beam TWT is larger than 750 kW from 34.5 to 35.4 GHz. The maximum power is 1.21 MW at 35 GHz, corresponding to a gain of 20.4 dB. [ABSTRACT FROM PUBLISHER]

A new small-angle scattering technique in reflection geometry is described which enables a topological study of rough surfaces. This is achieved by using long-wavelength soft X-rays which are scattered at wide angles but in the low-Q range normally associated with small-angle scattering. The use of nanometrewavelength radiation restricts the penetration to a thin surface layer which follows the topology of the surface, while moving the scattered beam to wider angles preventing shadowing by the surface features. The technique is, however, only applicable to rough surfaces for which there is no specular reflection, so that only the scattered beam was detected by the detector. As an example, a study of the surfaces of rough layers of silicon produced by the deposition of nanoparticles by blade-coating is presented. The surfaces of the blade-coated layers have rough features of the order of several micrometers. Using 2 nm and 13 nm X-rays scattered at angular ranges of 5° ≤ θ 51° and 5° ≤ θ ≤ 45°, respectively, a combined range of scattering vector of 0.00842 Å -1 ≤ Q ≤ 0.4883 Å -1 was obtained. Comparison with previous transmission SAXS and USAXS studies of the same materials indicates that the new method does probe the surface topology rather than the internal microstructure. [ABSTRACT FROM AUTHOR]

In charged particle beams, one of the roles played by space charge is to couple the transverse and longitudinal dynamics of the beam. This can lead to very complex phenomena which are generally studied using computer simulations. However, in some cases models based on phenomenological or analytic approximations can provide valuable insight into the system behavior. In this paper, we employ such approximations to investigate the conditions under which all the slices of a space charge dominated electron beam with slowly varying current could be focused to a waist with the same radius and at the same location, independent of slice current, and show that this can be accomplished approximately if the initial transverse-longitudinal correlation introduced onto the beam by the electron gun is chosen to compensate for the transverse-longitudinal correlation introduced onto the beam in the drift section. The validity of our approximations is assessed by use of progressively more realistic calculations. We also consider several design elements of electron guns that affect the initial correlations in the beams they generate. [ABSTRACT FROM AUTHOR]

Insertion of ultra-thin polymeric interlayers (ILs) between the poly(3,4-ethylenedioxythiophene): polystyrene sulphonate hole injection and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) light emission layers of polymer light emitting diodes (PLEDs) can significantly increase their efficiency. In this paper, we investigate experimentally a broad range of probable causes of this enhancement with an eye to determining which IL parameters have the most significant effects. The importance of hole injection and electron blocking was studied through varying the IL material (and consequently its electronic energy levels) for both PLED and hole-only diode structures. The role of IL conductivity was examined by introducing a varying level of charge-transfer doping through blending the IL materials with a strong electron-accepting small molecule in concentrations from 1% to 7% by weight. Depositing ILs with thicknesses below the exciton diffusion length of 15nm allowed the role of the IL as a physical barrier to exciton quenching to be probed. IL containing PLEDs was also fabricated with Lumation Green Series 1300 (LG 1300) light emission layers. On the other hand, the PLEDs were modeled using a 3D multi-particle Kinetic Monte Carlo simulation coupled with an optical model describing how light is extracted from the PLED. The model describes charge carrier transport and interactions between electrons, holes, singlets, and triplets, with the current density, luminance, and recombination zone (RZ) locations calculated for each PLED. The model shows F8BT PLEDs have a narrow charge RZ adjacent to the anode, while LG 1300 PLEDs have a wide charge RZ that is evenly distributed across the light emitting layer. Varying the light emitting layer from F8BT to Lumation Green Series 1300, we therefore experimentally examine the dependence of the IL function, specifically in regard to anode-side exciton quenching, on the location of the RZ. We found an exponential dependence of F8BT PLED luminance on the difference, δ, in the highest occupied to lowest unoccupied molecular orbital energy gap between the light emitting polymer and a semiconducting polymeric IL, with δ consequently the most important parameter determining efficiency. Understanding the exponential effect that wider energy gap IL materials have on exciton quenching may allow δ to be used to better guide PLED structure design. [ABSTRACT FROM AUTHOR]

X-ray screening systems have been used to safeguard environments in which access control is of paramount importance. Security checkpoints have been placed at the entrances to many public places to detect prohibited items, such as handguns and explosives. Generally, human operators are in charge of these tasks as automated recognition in baggage inspection is still far from perfect. Research and development on X-ray testing is, however, exploring new approaches based on computer vision that can be used to aid human operators. This paper attempts to make a contribution to the field of object recognition in X-ray testing by evaluating different computer vision strategies that have been proposed in the last years. We tested ten approaches. They are based on bag of words, sparse representations, deep learning, and classic pattern recognition schemes among others. For each method, we: 1) present a brief explanation; 2) show experimental results on the same database; and 3) provide concluding remarks discussing pros and cons of each method. In order to make fair comparisons, we define a common experimental protocol based on training, validation, and testing data (selected from the public \mathbb GDX ray database). The effectiveness of each method was tested in the recognition of three different threat objects: 1) handguns; 2) shuriken (ninja stars); and 3) razor blades. In our experiments, the highest recognition rate was achieved by methods based on visual vocabularies and deep features with more than 95% of accuracy. We strongly believe that it is possible to design an automated aid for the human inspection task using these computer vision algorithms. [ABSTRACT FROM AUTHOR]

The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this "barrier" confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation. [ABSTRACT FROM AUTHOR]

Slow trapping phenomenon in AlGaN/GaN HEMTs has been extensively analyzed and described in this paper. Thanks to a detailed investigation, based on a combined pulsed and transient investigation of the current/voltage characteristics (carried out over on an 8-decade time scale), we report a detailed description of the properties of trap levels located in the gate-drain surface, and in the region under the gate of AlGaN/GaN HEMTs. More specifically, the following, relevant results have been identified: (i) the presence of surface trap states may determine a significant current collapse, and reduction of the peak transconductance. During a current transient measurement, the emission of electrons trapped at surface states proceeds through hopping, as demonstrated by means of temperature-dependent measurements. The activation energy of the de-trapping process is equal to 99 meV. (ii) The presence of a high density of defects under the gate may induce a significant shift in the threshold voltage, when devices are submitted to pulsed transconductance measurements. The traps responsible for this process have an activation energy of 0.63 eV, and are detected only on samples with high gate leakage, since gate current allows for a more effective charging/de-charging of the defects. [ABSTRACT FROM AUTHOR]

Context. Cyg OB2 #9 is one of a small set of non-thermal radio emitting massive O-star binaries. The non-thermal radiation is due to synchrotron emission in the colliding-wind region. Cyg OB2 #9 has only recently been discovered to be a binary system, and a multi-wavelength campaign was organized to study its 2011 periastron passage. Aims. We want to better determine the parameters of this system and model the wind-wind collision. This will lead to a better understanding of the Fermi mechanism that accelerates electrons up to relativistic speeds in shocks and its occurrence in collidingwind binaries.We report here on the results of the radio observations obtained in the monitoring campaign and present a simple model to interpret the data. Methods. We used the Expanded Very Large Array (EVLA) radio interferometer to obtain 6 cm and 20 cm continuum fluxes during the Cyg OB2 #9 periastron passage in 2011. We introduce a simple model to solve the radiative transfer in the stellar winds and the colliding-wind region, and thus determine the expected behaviour of the radio light curve. Results. The observed radio light curve shows a steep drop in flux sometime before periastron. The fluxes drop to a level that is comparable to the expected free-free emission from the stellar winds, suggesting that the non-thermal emitting region is completely hidden at that time. After periastron passage, the fluxes slowly increase. We use the asymmetry of the light curve to show that the primary has the stronger wind. This is somewhat unexpected if we use the astrophysical parameters based on theoretical calibrations. But it becomes entirely feasible if we take into account that a given spectral type-luminosity class combination covers a range of astrophysical parameters. The colliding-wind region also contributes to the free-free emission, which can help explain the high values of the spectral index seen after periastron passage. Combining our data with older Very Large Array (VLA) data allows us to derive a period P = 860:0 ± 3:7 days for this system. With this period, we update the orbital parameters that were derived in the first paper of this series. Conclusions. A simple model introduced to explain only the radio data already allows some constraints to be put on the parameters of this binary system. Future, more sophisticated, modelling that will also include optical, X-ray, and interferometric information will provide even better constraints. [ABSTRACT FROM AUTHOR]

The new contribution of this paper is to develop a cylindrical representation of an already known multiphysics model for embedded nanowire superlattices (NWSLs) of wurtzite structure that includes a coupled, strain dependent 8-band k·p Hamiltonian in cylindrical coordinates and investigate the influence of coupled piezo-electromechanical effects on the barrier localization and critical radius in such NWSLs. The coupled piezo-electromechanical model for semiconductor materials takes into account the strain, piezoelectric effects, and spontaneous polarization. Based on the developed 3D model, the band structures of electrons (holes) obtained from results of modeling in Cartesian coordinates are in good agreement with those values obtained from our earlier developed 2D model in cylindrical coordinates. Several parameters such as lattice mismatch, piezo-electric fields, valence, and conduction band offsets at the heterojunction of AlxGa1-xN/GaN superlattice can be varied as a function of the Al mole fraction. When the band offsets at the heterojunction of AlxGa1-xN/GaN are very small and the influence of the piezo-electromechanical effects can be minimized, then the barrier material can no longer be treated as an infinite potential well. In this situation, it is possible to visualize the penetration of the Bloch wave function into the barrier material that provides an estimation of critical radii of NWSLs. In this case, the NWSLs can act as inversion layers. Finally, we investigate the influence of symmetry of the square and cylindrical NWSLs on the band structures of electrons in the conduction band. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of optical pulses on the electron emission properties of metal-oxide-semiconductor (MOS) cathodes based on nanocrystalline silicon (nc-Si). The emission current is enhanced by about two orders of magnitude by the irradiation of 405 nm laser light. The increase of the emission current under irradiation was proportional to incident laser power. The differential quantum efficiency of the nc-Si based MOS diode itself was estimated to be 3 × 10-2. However, the value of the photoemission current was only 3 × 10-7 due to the short mean free path of hot electron for Pt used as the gate electrode. We obtained a pulsed electron beam from the cathode device by a pulsed laser. The result shows that MOS type cathodes have a suitable structure for optically generating a train of short electron bunches. [ABSTRACT FROM AUTHOR]

This paper addresses the effect of target plasma electrons on the charge state of energetic ions, penetrating a target composed of bound as well as plasma electrons. Dynamic screening of the projectile Coulomb potential by the plasma electrons brings about a depression in the ionization energy of the ionic projectiles, as has been verified experimentally. This in turn makes the ionization cross-sections larger, while making the recombination cross-section smaller, thereby causing an increase in the ion charge state compared to the case of a gas target. The effect of the plasma environment, where the valence electrons are treated as plasma, is illustrated here for a 2 MeV carbon beam penetrating amorphous carbon targets of varying densities. [ABSTRACT FROM AUTHOR]

Abstract  Fe(VI) batteries based on unusual ferrate cathodic charge storage have been studied for quite a few years. So far, a class of Fe(VI) compounds have been successfully synthesized and studied as the cathodic materials in both alkaline and nonaqueous battery systems. This paper provides a summary of the syntheses of a range of Fe(VI) cathodes including the alkali Fe(VI) salts Li2FeO4, K x Na(2−x)FeO4, K2FeO4, Rb2FeO4, Cs2FeO4, as well as alkali earth Fe(VI) salts CaFeO4, SrFeO4, BaFeO4, and a transition metal Fe(VI) salt Ag2FeO4. Two synthesis routes summarized in this paper are the solution phase synthesis and the solid-state synthesis. Preparation of coating-stabilized (coated with KMnO4, SiO2, TiO2, or ZrO2) Fe(VI) cathodes and preparation of thin-film reversible Fe(VI/III) cathodes are also presented. Fe(VI) analytical methodologies summarized in this paper include Fourier transform infrared spectrometry, titrimetric (chromite), ultraviolet-visible spectroscopy, X-ray diffraction, inductively coupled plasma spectroscopy, Mössbauer spectrometry, potentiometric, galvanostatic, and cyclic voltammetry. Cathodic charge transfer of Fe(VI) is also briefly presented. [ABSTRACT FROM AUTHOR]

In the paper by Kliem, Karlický, and Benz ( Astron. Astrophys. 360, 715, ) it was suggested, that plasmoids formed during the bursty regime of solar flare reconnection can be “visualised” in the radio spectra as drifting pulsating structures via accelerated particles trapped inside the plasmoid. In the present paper we investigate this idea in detail. First, simple statistical analysis supporting this hypothesis is presented. Then, by using the 2.5-D MHD (including gravity) model solar flare reconnection in the inhomogeneous, stratified atmosphere is simulated and the formation and subsequent ejection of the plasmoid is demonstrated. The ejected plasmoid, which is considered to be a trap for accelerated electrons, is traced and its plasma parameters are computed. To estimate the associated plasma radio emission we need to know locations of accelerated electrons and corresponding plasma frequencies. General considerations predict that these electrons should be distributed mainly along the magnetic separatrix surfaces and this was confirmed by using a particle-in-cell simulation. Finally, under some simplifying assumptions the model dynamic radio spectrum is constructed. The relation between the global frequency drift and the plasmoid motion in the inhomogeneous ambient atmosphere is studied. The results are discussed with respect to the observed drifting pulsation structures and their possible utilisation for flare magnetic field diagnostics. [ABSTRACT FROM AUTHOR]

The concept of physically based distributions used in studies concerning gas electrical breakdowns is introduced in this paper. The non-stationary exponential distribution of the breakdown voltages and time delays with time dependent distribution parameter is theoretically derived based on physical grounds starting from a binomial distribution for electron occurrence in the interelectrode gap. The experimental distributions of breakdown voltages Ub and time delays td are obtained by applying linearly rising (ramp) voltage pulses to the discharge tube with a hard galvanic layer of gold on the cathode and modeled by multi-component non-stationary exponential distribution, as well as by a Weibull distribution for the sake of comparison. In order to fit the experimental data, the multi-component voltage/time dependent distribution parameter YP is introduced, where Y is electron yield (number of generated electrons in the interelectrode gap per second), and P is breakdown probability (the probability of one electron to cause a breakdown). It is shown that multi-component non-stationary exponential distribution is suitable for modeling of the experimental data when time varying voltage pulses are applied to the discharge tube. [ABSTRACT FROM AUTHOR]

In this paper Mie scattering of light by dust particles having Mathis, Rumpl, and Nordsieek power law distribution of size has been incorporated in the formulation of the kinetics of an illuminated complex plasma which takes into account the ionization of neutral atoms by an external agency, ion-electron recombination, photoemission of electrons by the dust particles, and accretion of electrons and ions on the surface of the particles; the number and energy balance of the constituent species has also been taken into account. An interesting conclusion is that unlike the usual case (when Mie scattering is neglected) the charge on a particle is not proportional to the radius and that for certain sets of parameters the smaller particles are negatively charged while the larger particles, carry positive charge. [ABSTRACT FROM AUTHOR]

This paper deals with aging phenomena in polymers under electric stress. In particular, we focus our efforts on the development of a novel theoretical method accounting for the discharge process (partial discharge) in well known defects present in polymers, which are essentially tiny air gaps embedded in a polymeric matrix. Such defects are believed to act as trigger points for the partial discharges and their induced aging process. The model accounts for the amplitude as well as the energy distribution of the electrons during their motion, particularly at the time in which they impact on the polymer surface. The knowledge of the number of generated electrons and of their energy distributions is fundamental to evaluate the amount of damage caused by an avalanche on the polymer-void interface and get novel insights of the basic phenomena underlying the relevant aging processes. The calculation of such quantities would require generally the combined solution of the Boltzmann equation in the energy and space/time domains. The proposed method simplifies the problem, taking into account only the main phenomena involved in the process and provides a partial discharge (PD) model virtually free of adjustable parameters. This model is validated by an accurate experimental procedure aimed at reproducing the same conditions of the simulations and regarding air gaps embedded in polymeric dielectrics. The experimental results confirm the validity and accuracy of the proposed approach. [ABSTRACT FROM AUTHOR]

We consider the interaction between electrons and molecular vibrations in the context of electronic transport in nanoscale devices. We present a method based on nonequilibrium Green’s functions to calculate both equilibrium and nonequilibrium electronic properties of a single-molecule junction in the presence of electron-vibron interactions. We apply our method to a model system consisting of a single electronic level coupled to a single vibration mode in the molecule, which is in contact with two electron reservoirs. Higher-order diagrams beyond the usual self-consistent Born approximation (SCBA) are included in the calculations. In this paper we consider the effects of the double-exchange diagram and the diagram in which the vibron propagator is renormalized by one electron-hole bubble. We study in detail the effects of the first- and second-order diagrams on the spectral functions for a large set of parameters and for different transport regimes (resonant and off-resonant cases), both at equilibrium and in the presence of a finite applied bias. We also study the linear response (linear conductance) of the nanojunction for all the different regimes. We find that it is indeed necessary to go beyond the SCBA in order to obtain correct results for a wide range of parameters. [ABSTRACT FROM AUTHOR]

Ultrafast melting and resolidification of a submicron gold particle subject to pico- to femtosecond laser pulse are studied in this paper. The nonequilibrium heat transfer in the electrons and lattice is described using a two-temperature model, and the locations of the solid-liquid interface are determined using an interfacial tracking method. The interfacial velocity, as well as elevated melting temperature and depressed solidification temperature, is obtained by considering the interfacial energy balance and nucleation dynamics. The results showed that the maximum melting depth, peak interfacial temperature, and velocity increase with the decreasing particle size and pulse width or with the increasing laser fluence. [ABSTRACT FROM AUTHOR]

In this paper a remote phonon scattering of channel electrons in a field-effect transistor (FET) with a high dielectric constant (κ) insulator in between the gate and the channel is studied theoretically. The spectrum of phonons confined in the high κ layer and its modification by the gate screening is investigated. Only two phonon modes of five participate in the remote electron-phonon scattering. The gate suppresses one of the modes but increases scattering by the other. Numerical results for the channel mobility limited only by remote phonon scattering were obtained for a Si FET with a HfO2 layer and a SiO2 layer in between the channel and metallic gate. A surprising result is the reduction of the mobility compared to the case when the gate screening is absent. The dependence of the mobility on the widths of HfO2 and interfacial SiO2 layers on channel concentration and temperature was studied. The accuracy of the calculations based on the Boltzmann equation is discussed. Finally, a comparison of our results with available experimental data leads to the conclusion that the remote phonon scattering is not the dominating scattering mechanism. [ABSTRACT FROM AUTHOR]

The generator coordinate (GC) method is a variational approach to the quantum many-body problem in which interacting many-body wave functions are constructed as superpositions of (generally nonorthogonal) eigenstates of auxiliary Hamiltonians containing a deformation parameter. This paper presents a time-dependent extension of the GC method as a new approach to improve existing approximations of the exchange-correlation (XC) potential in time-dependent density-functional theory (TDDFT). The time-dependent GC method is shown to be a conceptually and computationally simple tool to build memory effects into any existing adiabatic XC potential. As an illustration, the method is applied to driven parametric oscillations of two interacting electrons in a harmonic potential (Hooke’s atom). It is demonstrated that a proper choice of time-dependent generator coordinates in conjunction with the adiabatic local-density approximation reproduces the exact linear and nonlinear two-electron dynamics quite accurately, including features associated with double excitations that cannot be captured by TDDFT in the adiabatic approximation. [ABSTRACT FROM AUTHOR]

The paper studies the role of electrons and holes mobility in determining the external quantum efficiency (EQE) in photodetectors based on a 1:1 in weight blend of poly(3-hexylthiophene) (P3HT) and C61-butyric acid methyl ester (PCBM). In order to fairly correlate the optoelectronic properties (efficiency and transient photocurrent) measured on photodetectors with the transport properties measured on field effect transistors, the photodetectors and the transistors have been produced with an identical planar geometry, where in both cases the charges flow occurs in the same direction with respect to the substrate. The measurements have been performed on devices based on pristine P3HT, on pristine PCBM, and on P3HT:PCBM 1:1 blend, before and after annealing, and have revealed the importance of a balanced carrier transport, showing that quantum efficiency increases as long as the mobility of electrons, which are the slowest carrier, increases. On the other end, the response time is mainly affected by the extension of the effective area. [ABSTRACT FROM AUTHOR]

Fundamental issues associated with the application of the nuclear-electronic orbital (NEO) approach to hydrogen transfer systems are addressed. In the NEO approach, specified nuclei are treated quantum mechanically on the same level as the electrons, and mixed nuclear-electronic wavefunctions are calculated with molecular orbital methods. The positions of the nuclear basis function centers are optimized variationally. In the application of the NEO approach to hydrogen transfer systems, the hydrogen nuclei and all electrons are treated quantum mechanically. Within the NEO framework, the transferring hydrogen atom can be represented by two basis function centers to allow delocalization of the proton vibrational wavefunction. In this paper, the NEO approach is applied to the [He-H-He]+ and [He-H-He]++ model systems. Analyses of technical issues pertaining to flexibility of the basis set to describe both single and double well proton potential energy surfaces, linear dependency of the hydrogen basis functions, multiple minima in the basis function center optimization, convergence of the number of hydrogen basis function centers, and basis set superposition error are presented. The accuracy of the NEO approach is tested by comparison to grid calculations for these model systems. [ABSTRACT FROM AUTHOR]

This paper presents results concerning measurements of the dissociative recombination (DR) of dihydrogen sulfide ions. In combination with the ion storage ring CRYRING an imaging technique was used to investigate the breakup dynamics of the three-body channel in the DR of 32SD2+. The two energetically available product channels S(3P)+2D(2S) and S(1D)+2D(2S) were both populated, with a branching fraction of the ground-state channel of 0.6(0.1). Information about the angle between the two deuterium atoms upon dissociation was obtained together with information about how the available kinetic energy was distributed between the two light fragments. The recombination cross sections as functions of energy in the interval of 1 meV to 0.3 eV in the center-of-mass frame are presented for 34SH2+. The thermal rate coefficient for the DR of 34SH2+ was determined to be (4.8±1.0)×10-7(T/300)-0.72±0.1 cm3 s-1 over this interval. [ABSTRACT FROM AUTHOR]

The quality of electron beam welds depends upon a number of parameters like accelerating voltage, beam current, focus settings, vacuum level, working distance and welding speed. Even if these parameters are tightly controlled, there can be variations in the beam that can affect the quality of the welds, due to changes in cathode and electrode geometry and cathode emission. To ensure the quality of the beam prior to carrying out the welds, a probe device has been developed using the slit-probing method. This paper describes the design of the probe and signal processing of the acquired signals. The novel design of the probe facilitates the alignment of the probe in the vacuum chamber and its verification using the acquired signals. The acquired signals are also processed to characterise the electron beam to indicate the quality of the welds. The sensitivity of the analysis method has been enhanced by the use of wavelet decomposition and features vectors. Trials have been carried out focussed on aero engine manufacture to verify that it is possible to detect changes in the electron beam characteristics before they cause weld defects. [ABSTRACT FROM AUTHOR]

This paper deals with the investigations of ceramic-metal sealed-off pseudospark switches with an auxiliary glow discharge in the trigger unit. The switches are produced commercially by the Pulsed Technology Ltd., Ryazan, Russia. Attention is concentrated on the switch TPI1–10k/50 (pulsed current—10 kA and anode voltage—up to 50 kV). The schematic design of the devices and the principles of function are described. It is demonstrated that the switch is able to operate with an electric circuit corresponding to the classical hydrogen thyratron and to the thyratron with a grounded grid. In both cases, a delay time to triggering in the vicinity of 100 ns and a nanosecond jitter in the delay time are achievable. [ABSTRACT FROM PUBLISHER]

Secondary electrons produced by Compton scattering and photoelectric effect contribute to the photon field through conversion mechanisms like bremsstrahlung and inner-shell impact ionization (ISII). Because electrons interact continuously, the solution of the coupled transport problem is complex and time consuming. For this reason, photon transport codes frequently neglect the effects due to secondary electrons. Both of these contributions have been computed by means of the ad hoc code KERNEL that uses the Monte Carlo code PENELOPE specific for coupled transport. The correction on the intensity of the characteristic lines due to ISII was treated in a recent paper of our group. This paper adds the continuous contribution to the radiation field due to bremsstrahlung by secondary electrons. The bremsstrahlung emission is studied in terms of angle, space, and energy. The continuous contribution is stored in a data library for selected photon source energies in the interval 1-150 keV and for all the elements Z = 1-92. For intermediate source energies, the single element contribution is obtained by interpolating the data library. An example is presented on how to use the data library to include bremsstrahlung in the simulation of a synchrotron experiment. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of trans-bis-(3-aminoflavone)dichloridoplatinum(II) (trans-Pt(3-af )2Cl2; TCAP) for use as a potential anticancer compound, and the evaluation of its structure by elemental and spectral analyses, and X-ray crystallography. The complex demonstrated a significant cytotoxic effect against human and murine cancer cell lines, as well as weaker toxicity towards healthy cells (human peripheral blood lymphocytes) in comparison with cisplatin. Various biochemical and morphological methods confirm that the proapoptotic activity of trans-Pt(3-af )2Cl2 is markedly higher than the reference cisplatin. Our results suggest that trans-Pt(3-af )2Cl2 may have a different antitumour specificity from that of cisplatin. [ABSTRACT FROM AUTHOR]

A new form of diffraction lines has been identified, similar to Rutherford, Kikuchi and Kossel lines. This paper highlights some of the properties of these lines and shows how they can be used to eliminate the need for sample/source matching in Lonsdale's triple convergent line method in lattice-parameter determination. [ABSTRACT FROM AUTHOR]

In this paper, an experimental investigation of pseudospark discharge behaviors was conducted under nanosecond pulsed voltages using a flexible discharge chamber. The breakdown voltages of the pseudospark discharge gap were measured for a wide range of gas pressures, anode-cathode gap distances, and cathode aperture diameters to find the match of gap distance and cathode aperture diameter at a certain gas pressure with the nanosecond pulsed voltage. According to the experimental results, an empirical relationship was obtained. The roles of the parameters in the empirical relationship during the discharge were analyzed. The breakdown characteristics were also consistent with the Paschen’s law in the pseudospark under nanosecond pulsed voltages, when the gap distance was replaced by the effective gap distance. In the end, a possible reason was put forward to explain the difference between the empirical relationships obtained under dc voltages and nanosecond pulsed voltages. [ABSTRACT FROM PUBLISHER]

The micro-focusing performance for hard X-rays of a fixed-geometry elliptical Kirkpatrick-Baez (K-B) mirrors assembly fabricated, tested and finally implemented at the micro-probe beamline 8-BM of the Advanced Photon Source is reported. Testing of the K-B mirror system was performed at the optics and detector test beamline 1-BM. K-B mirrors of length 80 mm and 60 mm were fabricated by profile coating with Pt metal to produce focal lengths of 250 mm and 155 mm for 3 mrad incident angle. For the critical angle of Pt, a broad bandwidth of energies up to 20 keVapplies. The classical K-B sequential mirror geometry was used, and mirrors were mounted on micro-translation stages. The beam intensity profiles were measured by differentiating the curves of intensity data measured using a wire-scanning method. A beam size of 1.3 mm (V) and 1.2 µm (H) was measured with monochromatic X-rays of 18 keV at 1-BM. After installation at 8-BM the measured focus met the design requirements. In this paper the fabrication and metrology of the K-B mirrors are reported, as well as the focusing performances of the full mirrors-plus-mount set-up at both beamlines. [ABSTRACT FROM AUTHOR]

Synchrotron radiation from third-generation high-brilliance storage rings is an ideal source for X-ray microbeams. The aim of this paper is to describe a microfocusing scheme that combines both a toroidal mirror and Kirkpatrick-Baez (KB) mirrors for upgrading the existing optical system for inelastic X-ray scattering experiments at sector 3 of the Advanced Photon Source. SHADOW ray-tracing simulations without considering slope errors of both the toroidal mirror and KB mirrors show that this combination can provide a beam size of 4.5 mm (H) x 0.6 mm (V) (FWHM) at the end of the existing D-station (66 m from the source) with use of full beam transmission of up to 59%, and a beam size of 3.7 mm (H) x 0.46 mm (V) (FWHM) at the front-end of the proposed Estation (68 m from the source) with a transmission of up to 52%. A beam size of about 5 mm (H) x 1 mm (V) can be obtained, which is close to the ideal case, by using high-quality mirrors (with slope errors of less than 0.5 mrad r.m.s.). Considering the slope errors of the existing toroidal and KB mirrors (5 and 2.9 mrad r.m.s., respectively), the beam size grows to about 13.5 mm (H) x 6.3 mm (V) at the end of the D-station and to 12.0 mm (H) x 6.0 mm (V) at the front-end of the proposed E-station. The simulations presented here are compared with the experimental measurements that are significantly larger than the theoretical values even when slope error is included in the simulations. This is because of the experimental set-up that could not yet be optimized. [ABSTRACT FROM AUTHOR]

When an un-gated thermionic cathode is operated in a radio-frequency gun, some fraction of the emitted electrons will return to the cathode due to the change in sign of the electric field in the gun. This back-bombardment current causes heating of the cathode, and this reduces the ability of the cathode heater to control the bunch charge. In this paper, we investigate the fundamental factors in single-frequency back-bombardment for a short-gap electron gun. Simulations revealed that the back-bombardment power depends strongly on the operating frequency and the bunch charge. Additionally, the use of a two-frequency TM010/TM{020} electron gun to mitigate this effect was investigated which revealed that the effectiveness of this technique depends strongly upon single-frequency back-bombardment power but with the optimal reduction in back-bombardment power (62% of the baseline) occurring in the low-frequency limit. [ABSTRACT FROM PUBLISHER]

In this paper, low energy electron beam (5-20 keV, 0-500 μAs/cm2) induced damage on a GaN/InGaN/GaN near-surface quantum well structure is studied. Exposure to low energy electron beam is shown to significantly reduce the optical quality of the structure. It is also observed that reducing the electron beam energy causes larger PL intensity reduction. This can be explained by considering the beam penetration depth, which is shown to be smaller with lower e-beam energies. The damage is believed to be attributed to enhanced dislocation mobility upon low energy electron beam irradiation. However, further studies are needed to confirm the mechanism. These results should be taken into consideration in low energy electron beam related sample characterization and preparation. [ABSTRACT FROM AUTHOR]