bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of distance between sample surface and geometrical focal point on CN emission intensity from femtosecond laser-induced PMMA plasmas
Authors: Wang Qiuyun , Chen Anmin , Qi Hongxia , Xu Wanpeng , Zhang Dan , Wang Ying , Li Suyu , Jiang Yuanfei , Jin Mingxing
Published: July 2019

In this study, a femtosecond laser is used to ablate polymethyl methacrylate and produce plasma with CN molecules to investigate the influence of the distance between the sample surface and geometrical focal point on CN emission intensity in air. The laser wavelength is 800 nm with a pulse width of 50 fs, and the laser energy ranges from 0.1 mJ to 1.5 mJ. It is determined that the spectral characteristics of the CN molecule depend on the distance between the sample surface and geometrical focal point, as well as the energy of the femtosecond laser. At the same energy, the spectral intensity of the CN molecule first increases, and then decreases with an increase in the distance. The position with the strongest spectral emission is not the geometrical focal point of the focusing lens, but away from the geometrical focal point. As the laser energy increases, the position with the strongest spectral emission moves toward the focusing lens. In addition, the vibration temperature and full width at half maximum (FWHM) are also calculated by fitting CN spectral data for specific distances and energies. The vibration temperature and FWHM of CN at the position with strongest emission are the lowest, and the vibration temperature and FWHM at the left side (close to the lens) of the strongest emission position are higher than those at the right side (away from the lens) of the strongest emission position.
Verification and application of resonance broadened quasi-linear (RBQ) model with multiple Alfvénic instabilities
Authors: Gorelenkov N. N. , Duarte V. N. , Collins C. S. , Podestà M. , White R. B.
Published: July 2019

The resonance broadened quasilinear (RBQ) model for the problem of relaxing the hot ion distribution function in constant-of-motion 3D space [Gorelenkov et al., Nucl. Fusion 58, 082016 (2018)] is presented with the self-consistent evolution of multiple Alfvén eigenmode amplitudes. The RBQ model represents the generalization of the earlier published model [Berk et al., Nucl. Fusion 35, 1661 (1995)] by carefully examining the wave particle interaction in the presence of realistic Alfvén eigenmode (AE) structures and pitch angle scattering with the help of the guiding center code ORBIT. One aspect of the generalization is that the RBQ model goes beyond the local perturbative-pendulumlike approximation for the wave particle dynamics near the resonance. An iterative procedure is introduced to account for eigenstructures varying within the resonances. It is found that a radially localized mode structure implies a saturation level 2–3 times smaller than that predicted by an earlier bump-on-tail quasilinear model that employed uniform mode structures. We apply the RBQ code to a DIII-D plasma with an elevated q-profile where the beam ion profiles exhibit stiff transport properties [Collins et al., Phys. Rev. Lett. 116, 095001 (2016)]. The properties of AE driven fast ion distribution relaxation are studied for validations of the applied RBQ model in DIII-D discharges. Initial results show that the model is robust, is numerically efficient, and can predict fast ion relaxation in present and future burning plasma experiments.
Polarization by light reflection at metallic surfaces observed in the shape of the Balmer-α line of low density plasmas
Authors: Dickheuer Sven , Marchuk Oleksandr , Krasikov Yuri , Mertens Philippe , Brandt Christian , Ertmer Stephan , Börner Petra , Reiter Detlev , Göths Beatrix , von Bovert Kalle , Kreter Arkadi
Published: July 2019

The degree of linear polarization of light reflected at metallic surfaces is obtained from the shape of the Balmer-α line measured in a low density plasma. The measurements of the polarization properties of metallic surfaces utilize only the high-resolution emission spectra induced by fast reflected H atoms (≈100 eV) in ArH plasmas. The measurements are performed at two different lines-of-sight to the target surfaces of Mo and Cu. Only at the observation angle close to the Brewster one, a significant drop of the measured red-shifted signal is detected for the Mo target: the red-shifted emission reduces by ≈50% depending on whether the transverse (S) or the parallel (P) polarization component of the reflected light is selected. In contrast to this, a very weak change of emission is observed for the Cu surface for the same angle. The spectra measured in front of the Mo target were modeled utilizing the energy and angular distribution of reflected atoms and excitation of the cross section of Ar-H collision combined in a Doppler-shifted emission model. A good agreement with the theoretical calculations is found for polarization components (except for the weak P polarization at 70°). Finally, the undercosine distribution of the reflected atoms with b ≈ 0.2 (b is the power of the cosine distribution) shows the best agreement with the spectra measured at both lines-of-sight.
Density measurement of liquid 22MnB5 by aerodynamic levitation
Authors: Le Maux Dylan , Courtois Mickaël , Pierre Thomas , Lamien Bernard , Le Masson Philippe
Published: July 2019

This study is part of the general context of thermophysical characterization of liquid metals with an aerodynamic levitation device and laser heating. The density measurements vs temperature of pure and alloyed metals are determined during cooling of the sample. The temperature and shape of the sample are measured, respectively, with a bichromatic pyrometer and filmed by a high-speed camera. The sample visualization is performed by backlighting, which has been preferred to self-illumination. The post-treatment process consists in a binarisation of each recorded image, and then, an ellipse is fitted on the detected edge. The density is directly calculated with the ellipse volume and the sample weight. The good agreement of experimental results on pure metals with the literature validates the method. Then, an industrial steel of unknown liquid density is characterized from 1750 K to 2250 K.
Radiation flux study of hohlraum used to create uniform and strongly coupled warm dense matter
Authors: Zhang Zhiyu , Zhao Yang , Zhang Jiyan , Hu Zhimin , Jing Longfei , Qing Bo , Xiong Gang , Lv Min , Du Huabing , Yang Yimeng , Zhan Xiayu , Yu Ruizhen , Mei Yu , Yang Jiamin
Published: July 2019

A hohlraum used to create uniform and strongly coupled warm dense matter and its radiation flux study on the SG-III prototype laser facility are described. Time evolution of the radiation temperature from laser entrance hole (LEH) and the incident radiation temperature at the target surface are obtained using flat response X-ray diode detectors. Then, a calculation of the radiation flux evolution for this hohlraum is carried out using a view-factor method, and the calculated results agree well with the experimental data within the error bar. Using the incident radiation at the target surface as a source, the validity to create uniform and strongly coupled warm dense matter by this hohlraum is verified.
Effect of discharge behaviors on equivalent capacitance between electrodes in dielectric barrier discharge of atmospheric pressure helium
Authors: Hao Yanpeng , Fang Qiang , Wan Hairong , Han Yuying , Yang Lin , Li Licheng
Published: July 2019

Columnar pattern discharges and multipulse uniform discharges were generated in atmospheric helium with a background air pressure of 40 Pa to study the effect of discharge behaviors on the equivalent capacitance between the electrodes. Applied voltages, discharge currents, Lissajous figures, and discharge images from the bottom of the electrode under various applied voltages were measured. Based on the Lissajous figures, the equivalent capacitances between electrodes and the transferred charge were calculated. It was found that the equivalent capacitance is about 9.6 pF at the applied voltages below the discharge inception voltage, and increases from 13.2 pF at the incipient discharge voltage to 21.4 pF at a applied voltage above the discharge inception voltage, at which a multipulse uniform glow discharge covering the entire electrode surface appears, with an equivalent capacitance increase in 62%. If the applied voltage is decreased from the incipient discharge voltage, columnar patterned discharges below the incipient discharge voltage will appear; it increased from 9.6 pF of a single column discharge to 13.1 pF of a local uniform discharge, with an increase in 36%. At applied voltages further below the inception voltage, the discharge disappears and the equivalent capacitance returns to 9.6 pF. The correlation coefficient between the equivalent capacitance and the transferred charge was calculated under various discharge behaviors. The results show that the transferred charge during discharges caused the change of the equivalent capacitance between electrodes. From this understanding, an amendment is proposed for a previously simplified electrical equivalent circuit.
Electrochemical stability and light-harvesting ability of silicon photoelectrodes in aqueous environments
Authors: Campbell Quinn , Dabo Ismaila
Published: July 2019

We study the factors that affect the photoactivity of silicon electrodes for the water-splitting reaction using a self-consistent continuum solvation model of the solid-liquid interface. This model allows us to calculate the charge-voltage response, Schottky barriers, and surface stability of different terminations while accounting for the interactions between the charge-pinning centers at the surface and the depletion region of the semiconductor. We predict that the most stable oxidized surface does not have a favorable Schottky barrier, which further explains the low solar-to-hydrogen performance of passivated silicon electrodes.
Applying Tersoff-potential and bond-softening models in a molecular dynamics study of femtosecond laser processing
Authors: Lee Byoung Seo , Park Seungho
Published: July 2019

In the molecular dynamics study of short-pulsed laser processing of semiconductors, potential models capable of describing the atomistic behavior during high electronic excitations is the most critical issue at the current stage. This study of the molecular dynamics adopts the Tersoff-potential model to analyze the ultrafast laser processing of silicon. The model was modified to include electronic excitation effects by reducing the attraction of the antibonding state by half. It offers an excellent description of the experimental behavior during nonthermal melting. Subpicosecond melting is achieved above certain threshold levels of superheating and carrier density as required in experiments. Energy conservation is demonstrated with a bandgap energy of the order obtained in experiments. The modification of the potential mimics an absorption of bandgap energy and a subsequent lattice heating on a time scale within 0.3 ps. The melting kinetics establishes a correlation between nonthermal melting and thermal bulk melting. For superheating of less than two, the electronic melting of bond softening proceeds via homogeneous nucleation. The associated thermal theory, corrected with a limit on the nucleus radius to bond length, is still valid for the higher superheating regime. The original Tersoff model shows that this superheating by a factor of two is isothermal for spallation—the lowest-energy ablative mechanism. Its proximity to the evaporating point suggests the role of thermal boiling during spallation.
Effects of noise-induced coherence on the fluctuations of current in quantum absorption refrigerators
Authors: Holubec Viktor , Novotný Tomáš
Published: July 2019

We investigate the effects of noise-induced coherence on average current and current fluctuations in a simple model of a quantum absorption refrigerator with degenerate energy levels. We describe and explain the differences and similarities between the system behavior when it operates in the classical regime, where the populations and coherences in the corresponding quantum optical master equation decouple in a suitably chosen basis, and in the quantum regime, where such a transformation does not exist. The differences between the quantum and the classical cases are observable only close to the maximum current regime, where the system steady-state becomes nonunique. This allows us to approximate the system dynamics by an analytical model based on a dichotomous process that explains the behavior of the average current both in the classical and in the quantum cases. Due to the nonuniqueness, the scaled cumulant generating function for the current at the vicinity of the critical point exhibits behavior reminiscent of the dynamical first-order phase transition. Unless the system parameters are fine-tuned to a single point in the parameter space, the corresponding current fluctuations are moderate in the quantum case and large in the classical case.
Understanding the secondary separation from an inclined square cylinder with sharp and rounded trailing edges
Authors: Kumar Deepak , Sourav Kumar , Yadav Pavan Kumar , Sen Subhankar
Published: July 2019

The steady separated flow past a square cylinder at 45° incidence and having a sharp/rounded base is a unique kind of separated flow around a symmetric bluff obstacle. At low Reynolds numbers (Re ≈ 6–8), this flow displays diverse features that are not known to be displayed by common symmetric bluff bodies, such as circular/square cylinders at zero incidence. The uniqueness of this flow was first highlighted by Kumar et al. [“Steady separation of flow from an inclined square cylinder with sharp and rounded base,” Comput. Fluids 171, 29–40 (2018)] in their recent numerical investigation concerning the onset of initial separation. They reported detailed flow kinematics resulting from separation of the laminar boundary layer via secondary mode, primary mode, and their combination. In this work, based on stabilized finite-element computations, the fluid dynamic aspects of primary and secondary separation are delved. The parameters considered are the normalized corner radius at the cylinder base and Re. Exploration of the influence of base radius on the occurrence/absence of the secondary separation is the main objective. The occurrence of secondary separation is a function of base radius. It occurs only with small or no rounding at the base, i.e., when the pressure gradient close to the base is favorable or mildly adverse. Irrespective of the base radius, the onset of secondary separation occurs at a constant Re value of 7.3. The drag decays as Re−0.62; it becomes invariant when Re is held constant. A new nondimensional parameter η accommodating the effects of pressure recovery and radius of curvature is introduced. The drag exhibits no sensitivity to η.
Probing ion species separation and ion thermal decoupling in shock-driven implosions using multiple nuclear reaction histories
Authors: Sio H. , Larroche O. , Atzeni S. , Kabadi N. V. , Frenje J. A. , Gatu Johnson M. , Stoeckl C. , Li C. K. , Forrest C. J. , Glebov V. , Adrian P. J. , Bose A. , Birkel A. , Regan S. P. , Seguin F. H. , Petrasso R. D.
Published: July 2019

Simultaneously measured DD, DT, and D3He reaction histories are used to probe the impacts of multi-ion physics during the shock phase of inertial confinement fusion implosions. In these relatively hydrodynamiclike (burn-averaged Knudsen number ⟨NK⟩ ∼0.3) shock-driven implosions, average-ion hydrodynamic DUED simulations are able to reasonably match burnwidths, nuclear yields, and ion temperatures. However, kinetic-ion FPION simulations are able to better simulate the timing differences and time-resolved reaction rate ratios between DD, DT, and D3He reactions. FPION simulations suggest that the D3He/DT reaction rate ratio is most directly impacted by ion species separation between the 3He and T ions, whereas the D3He/DD reaction rate ratio is affected by both ion species separation and ion temperature decoupling effects.
Modeling of intense terahertz wave generation with controlled field distribution
Authors: Chaudhary Sheetal , Singh Kunwar Pal , Singh Beer Pal ,   Manendra , Malik Anil K
Published: July 2019

We report the results of a theoretical model and numerical investigations for an efficient intensity distribution-tunable terahertz (THz) radiation generation by two color Hermite cosh Gaussian lasers pumped in periodic density gas plasma. The effect of various laser parameters like b (decentered parameter of the cosh function), s (mode index of the Hermite function), δ (initial phase difference between two lasers), and νen (electron neutral collision frequency) on the THz field distribution, amplitude, and efficiency is investigated. The largest peak of the THz field is obtained for s=1, b=0, δ=0, π, 2π, and ω≈ωp (resonant excitation) at x=0 (forward emission in the direction of the laser propagation axis). It is found that THz radiation is highly intense for s=1, b=0, νen=0, and ω≈ωp compared to any other set of laser and plasma parameters. This study also reveals that the THz peak field and efficiency decrease monotonically with electron collision frequency. The THz field of ∼G V m−1 with an efficiency of ∼3% for the optimum laser and plasma parameters can be obtained in this scheme.
Fermionic limit of the Calogero-Sutherland system
Authors: Khoroshkin S. M. , Matushko M. G.
Published: July 2019

We present a construction of an integrable model as a projective type limit of Calogero-Sutherland models of N fermionic particles, when N tends to infinity. Explicit formulas for limits of Dunkl operators and of commuting Hamiltonians by means of vertex operators are given.
Reduced density profile of small particles near a large particle: Results of an integral equation theory with an accurate bridge function and a Monte Carlo simulation
Authors: Nakamura Yuka , Arai Shota , Kinoshita Masahiro , Yoshimori Akira , Akiyama Ryo
Published: July 2019

Solute–solvent reduced density profiles of hard-sphere fluids were calculated by using several integral equation theories for liquids. The traditional closures, Percus–Yevick (PY) and the hypernetted-chain (HNC) closures, as well as the theories with bridge functions, Verlet, Duh–Henderson, and Kinoshita (named MHNC), were used for the calculation. In this paper, a one-solute hard-sphere was immersed in a one-component hard-sphere solvent and various size ratios were examined. The profiles between the solute and solvent particles were compared with those calculated by Monte Carlo simulations. The profiles given by the integral equations with the bridge functions were much more accurate than those calculated by conventional integral equation theories, such as the Ornstein–Zernike (OZ) equation with the PY closure. The accuracy of the MHNC–OZ theory was maintained even when the particle size ratio of solute to solvent was 50. For example, the contact values were 5.7 (Monte Carlo), 5.6 (MHNC), 7.8 (HNC), and 4.5 (PY), and the first minimum values were 0.48 (Monte Carlo), 0.46 (MHNC), 0.54 (HNC), and 0.40 (PY) when the packing fraction of the hard-sphere solvent was 0.38 and the size ratio was 50. The asymptotic decay and the oscillation period for MHNC–OZ were also very accurate, although those given by the HNC–OZ theory were somewhat faster than those obtained by Monte Carlo simulations.
Lift force acting on a pair of clean bubbles rising in-line
Authors: Kusuno Hiroaki , Yamamoto Hiroya , Sanada Toshiyuki
Published: July 2019

In this study, we experimentally observed the motion of a pair of bubbles initially positioned in line, especially focusing on the intermediate Reynolds number case, i.e., 20 < Re < 60. We observed three types of motion at different Reynolds numbers. At a low Reynolds number (Re < 20), the trailing bubble collided with the leading bubble like a pair of rigid spheres. At a high Reynolds number (100 < Re), the trailing bubble moved out from the original vertical line joining the two bubbles. At intermediate Reynolds numbers (20 < Re < 60), small differences in bubble size affected the motion. When the leading bubble was larger than or equal to the trailing bubble, the trailing bubble first approached the leading bubble and later moved out from the initial vertical line owing to a lift force. When the leading bubble was smaller than the trailing bubble, the trailing bubble first approached the leading bubble, and then a repulsive force acted on both bubbles so that both of them moved out from the vertical line in opposite directions. These motions are attributed to two effects, the first is potential effects at short distance between bubbles, and the second is the wake of the leading bubble.
Effect of plasma on the intrapulse distortion of linear frequency modulated pulse
Authors: Song Lihao , Li Xiaoping , Bai Bowen , Liu Yanming , Wang Junjie
Published: July 2019

This study analyzes intrapulse nonuniform amplitude distortion of the LFM (linear frequency modulated) pulse propagating through a plasma by conducting theoretical analysis and experiments. The FDTD-IFFT method is proposed to calculate the propagation of the linear frequency modulated (LFM) signal in plasma, and the nonuniform pulse amplitude distortion is verified by a comparison of experimental and theoretical results. The plasma will cause amplitude distortion of the signal which is characterized by two metrics: (1) the pulse amplitude difference ΔG and (2) the pulse amplitude nonuniformity degree ψ values. The degree of nonuniform distortion is determined by the carrier frequency, the bandwidth, electron density, and the collision frequency. The results shows that when the carrier frequency is close to the cut-off frequency of electron density, ΔG and ψ reach positive peak values, the amplitude shows an increasing trend, and pulse amplitude nonuniformity distortion is most serious. Moreover, ΔG is negative when the cut-off frequency of electron density is far greater than the carrier frequency, and the collision frequency is high. The pulse amplitude shows a decreasing trend under this condition. The higher the electron density and the collision frequency, the larger the ψ value and the absolute value of negative ΔG and the more serious intrapulse nonuniform distortion. The intrapulse distortion will cause a signal to noise ratio variation in a pulse which will seriously affect the signal detection. The conclusions of this study are crucial for the application of electronic systems on vehicles under a plasma and for deepening the understanding of the effect of plasma on electromagnetic waves.
Comprehensive Zakharov-type model for parametric instabilities in the corona of direct-drive targets
Authors: Sary G. , Gremillet L. , Canaud B.
Published: July 2019

We report on two-dimensional simulations of parametric instabilities excited by a single, intense (2 × 1016 W cm−2), wavelength-sized laser speckle immersed in a nonuniform CH plasma close to the quarter-critical density. A first set of simulations is performed using a Zakharov-type reduced model. This newly developed simulation tool, which we present in detail, describes Stimulated Raman Scattering (SRS), Two-Plasmon Decay (TPD), Stimulated Brillouin Scattering, and secondary decays involving ion acoustic waves. Because of the high speckle intensity considered, strong electron plasma waves (EPWs) are driven via TPD, whose beating induces fast-collapsing ion cavities. Yet, Zakharov equations are notoriously incapable of modeling collapse arrest due to their neglect of kinetic processes dissipating energy from small-scale EPW packets, thus resulting in nonphysical density evolution. Transit-time damping is such a process, and we show that its inclusion in the reduced model allows for a self-consistent description of all phases of the collapse. The accuracy of our model is checked against a second simulation, performed using a particle-in-cell (PIC) code run under similar conditions. Good qualitative agreement is obtained, particularly in regard to the cavities' dynamics. Still, an excessive SRS reflectivity is predicted by the reduced model, which we ascribe to missing kinetic effects. The influence of electron trapping and heating on the decay of EPWs and saturation of SRS is assessed based on the PIC simulation.
Crystalline clusters in mW water: Stability, growth, and grain boundaries
Authors: Leoni Fabio , Shi Rui , Tanaka Hajime , Russo John
Published: July 2019

With numerical simulations of the mW model of water, we investigate the energetic stability of crystalline clusters both for Ice I (cubic and hexagonal ice) and for the metastable Ice 0 phase as a function of the cluster size. Under a large variety of forming conditions, we find that the most stable cluster changes as a function of size: at small sizes, the Ice 0 phase produces the most stable clusters, while at large sizes, there is a crossover to Ice I clusters. We further investigate the growth of crystalline clusters with the seeding technique and study the growth patterns of different crystalline clusters. While energetically stable at small sizes, the growth of metastable phases (cubic and Ice 0) is hindered by the formation of coherent grain boundaries. A fivefold symmetric twin boundary for cubic ice, and a newly discovered coherent grain boundary in Ice 0, promotes cross nucleation of cubic ice. Our work reveals that different local structures can compete with the stable phase in mW water and that the low energy cost of particular grain boundaries might play an important role in polymorph selection.
Fourth order expressions for the electronic absorption lineshape of molecular excitons
Authors: Jang Seogjoo J.
Published: July 2019

The line shape of electronic absorption spectroscopy reflects the information on quantum dynamical processes accompanying the electronic excitation, and its accurate description is an important component for validating theoretical models and assumptions. The present work provides detailed expressions for the absorption line shape of molecular excitons that are valid up to the fourth order of exciton-bath interactions within the quantum master equation approach. These expressions can serve as the basis for developing general and systematic methods to model the line shape for a broad class of molecular exciton systems and environments. For the bath model of linearly coupled harmonic oscillators, more detailed expressions employing the spectral densities of the bath are presented. These expressions are then tested for a linear aggregate of identical chromophores each coupled to the harmonic oscillator bath. Calculation results for a super-Ohmic spectral density with exponential cutoff demonstrate the feasibility of calculations and also offer insights into the utility and difficulty of going beyond the second order approximation.
Experimental study of second-mode wave on a flared cone at Mach 6
Authors: Liu Xiaolin , Yi Shihe , Xu Xiwang , Shi Yang , Ouyang Tianci , Xiong Haoxi
Published: July 2019

Second-mode instability plays an important role in the transition of a hypersonic boundary layer. The second-mode wave on a flared cone at Mach 6 has been investigated experimentally through the Nanoparticle-tracer based Planar Laser Scattering (NPLS) technique in this paper. Different behaviors of the second-mode wave ranging from linear growth to deformation are visualized under different unit Reynolds numbers. The propagation velocity of the second-mode wave is quantitatively calculated, and the spectral properties of the second-mode wave have been analyzed by the power spectrum density. The characteristic frequency of the second-mode wave calculated from the NPLS images agrees well with the results measured by the transducers. Evolution of the wall-normal distribution of disturbance shows that high frequency harmonics are generated during the growth process of the second-mode wave and its normal distribution range shrinks with the increase in its frequency. The bispectral analysis indicates that the high degree of phase coupling may be the reason for the deformation of the second-mode wave. The nonlinear interaction between the disturbance waves is strong during the deformation stage of the second-mode waves.
Interplay between quantum paraelectricity and thermoelectricity in the photo-Seebeck effect in a SrTiO3 single crystal
Authors: Shiraishi Yuuka , Tanabe Kenji , Taniguchi Hiroki , Okazaki Ryuji , Terasaki Ichiro
Published: July 2019

We report the electrical conductivity and the Seebeck coefficient of a SrTiO3 single crystal under 405-nm laser illumination from 10 to 30 K. We find that the photoconductivity exponentially increases with decreasing temperature, suggesting a gradual metal-insulator transition. Assuming the carrier mobility reported in the preceding studies, we have evaluated the carrier concentration to be 8×109cm−3 at maximum, which corresponds to 10−7ppm impurities in the case of chemical doping. Such ultralow doping is realized only when the energy of the incident light is slightly lower than the bandgap. In this situation, the incident light penetrates the whole sample with a small probability of electron–hole creation. We find that the observed photo-Seebeck coefficient seriously disagrees with the calculated values from the carrier concentration. In order to remedy this discrepancy, we have proposed a phenomenological model in which the quantum paraelectric behavior of SrTiO3 screens the thermoelectric voltage.
Studies on virtual electrode and ion sheath characteristics in a cylindrical inertial electrostatic confinement fusion device
Authors: Bhattacharjee D. , Jigdung D. , Buzarbaruah N. , Mohanty S. R. , Bailung H.
Published: July 2019

An experiment on the formation of virtual electrode and ion sheath characteristics has been carried out in a hot cathode discharge plasma produced inside a cylindrical inertial electrostatic confinement fusion device. The plasma parameters such as electron temperature and plasma density are evaluated by using a Langmuir probe. Transition from a single potential well to multiple potential wells, i.e., virtual electrodes inside the cathode grid, is observed when the bias voltage applied to the cathode is increased from –1000 to –5000 V. An emissive probe has been used for the measurement of plasma potential due to its greater accuracy than the conventional Langmuir probe. Ion sheath potential structures and presheath characteristics for different cathode potentials have been investigated using the emissive probe and are found to be consistent with the Debye sheath model. A detailed discussion on the obtained results has been presented in this paper.
Characterization of hydration water in supercooled water-trehalose solutions: The role of the hydrogen bonds network
Authors: Iorio A. , Camisasca G. , Rovere M. , Gallo P.
Published: July 2019

The structural and dynamical properties of hydration water in aqueous solutions of trehalose are studied with molecular dynamics simulation. We simulate the systems in the supercooled region to investigate how the interaction with the trehalose molecules modifies the hydrogen bond network, the structural relaxation, and the diffusion properties of hydration water. The analysis is performed by considering the radial distribution functions, the residence time of water molecules in the hydration shell, the two body excess entropy, and the hydrogen bond water-water and water-trehalose correlations of the hydration water. The study of the two body excess entropy shows the presence of a fragile to strong crossover in supercooled hydration water also found in the relaxation time of the water-water hydrogen bond correlation function, and this is in agreement with predictions of the mode coupling theory and of previous studies of the oxygen-oxygen density correlators [A. Iorio et al., J. Mol. Liq. 282, 617 (2019); Sci. China: Phys., Mech. Astron. 62, 107011 (2019)]. The water-trehalose hydrogen bond correlation function instead evidences a strong to strong crossover in the relaxation time, and this crossover is related to a trehalose dynamical transition. This signals the role that the strong interplay between the soluted molecules and the surrounding solvent has in determining the dynamical transition common to both components of the system that happens upon cooling and that is similar to the well known protein dynamical transition. We connect our results with the cryoprotecting role of trehalose molecules.
Entrance effects in concentration-gradient-driven flow through an ultrathin porous membrane
Authors: Rankin Daniel J. , Bocquet Lydéric , Huang David M.
Published: July 2019

Transport of liquid mixtures through porous membranes is central to processes such as desalination, chemical separations, and energy harvesting, with ultrathin membranes made from novel 2D nanomaterials showing exceptional promise. Here, we derive, for the first time, general equations for the solution and solute fluxes through a circular pore in an ultrathin planar membrane induced by a solute concentration gradient. We show that the equations accurately capture the fluid fluxes measured in finite-element numerical simulations for weak solute–membrane interactions. We also derive scaling laws for these fluxes as a function of the pore size and the strength and range of solute–membrane interactions. These scaling relationships differ markedly from those for concentration-gradient-driven flow through a long cylindrical pore or for flow induced by a pressure gradient or an electric field through a pore in an ultrathin membrane. These results have broad implications for transport of liquid mixtures through membranes with thickness on the order of the characteristic pore size.
A hybrid, bottom-up, structurally accurate, Go¯-like coarse-grained protein model
Authors: Sanyal Tanmoy , Mittal Jeetain , Shell M. Scott
Published: July 2019

Coarse-grained (CG) protein models in the structural biology literature have improved over the years from being simple tools to understand general folding and aggregation driving forces to capturing detailed structures achieved by actual folding sequences. Here, we ask whether such models can be developed systematically from recent advances in bottom-up coarse-graining methods without relying on bioinformatic data (e.g., protein data bank statistics). We use relative entropy coarse-graining to develop a hybrid CG but Go¯-like CG peptide model, hypothesizing that the landscape of proteinlike folds is encoded by the backbone interactions, while the sidechain interactions define which of these structures globally minimizes the free energy in a unique native fold. To construct a model capable of capturing varied secondary structures, we use a new extended ensemble relative entropy method to coarse-grain based on multiple reference atomistic simulations of short polypeptides with varied α and β character. Subsequently, we assess the CG model as a putative protein backbone forcefield by combining it with sidechain interactions based on native contacts but not incorporating native distances explicitly, unlike standard Go¯ models. We test the model’s ability to fold a range of proteins and find that it achieves high accuracy (∼2 Å root mean square deviation resolution for both short sequences and large globular proteins), suggesting the strong role that backbone conformational preferences play in defining the fold landscape. This model can be systematically extended to non-natural amino acids and nonprotein polymers and sets the stage for extensions to non-Go¯ models with sequence-specific sidechain interactions.
Tunable low-field magnetoresistance properties in (La0.7Ca0.3MnO3)1−x:(CeO2)x vertically aligned nanocomposite thin films
Authors: Gao Xingyao , Li Leigang , Jian Jie , Huang Jijie , Sun Xing , Zhang Di , Wang Haiyan
Published: July 2019

Vertically aligned nanocomposite (VAN) (La0.7Ca0.3MnO3)1−x:(CeO2)x thin films have been deposited on SrTiO3 (001) substrates by pulsed laser deposition. Enhanced low-field magnetoresistance properties and tunable metal-insulator transition temperature (TMI) have been demonstrated via modulating the composition of (La0.7Ca0.3MnO3)1−x:(CeO2)x (x = 0, 0.05, 0.1, and 0.2). By increasing the atomic percentage of the CeO2 phase to 20%, a maximum magnetoresistance value of 51.8% can be achieved and the TMI value can be tuned from 113 K to 210 K. The enhanced magnetoresistance properties are attributed to the disordered grain boundary and tunneling structure generated by the insulating CeO2 phase. The change in the TMI value is attributed to the strain state in the La0.7Ca0.3MnO3 phase. Furthermore, high ferromagnetic anisotropy and enhanced magnetization have been demonstrated in the VAN system. This work demonstrates the power of multifunctionalities and property tuning in VAN thin films.
On the magnetic properties of nanodiamonds: Electronic g-tensor calculations
Authors: Masys Š. , Rinkevicius Z. , Tamulienė J.
Published: July 2019

The electronic g-tensor calculations are carried out for various paramagnetic defects introduced into hydrogenated diamond nanocrystal C35H36, showing that such a system can be successfully used to model magnetic properties of nanodiamonds (NDs) with paramagnetic centers containing no vacancies. In addition, it is revealed that, depending on the geometric positions in ND, paramagnetic centers of the same type produce noticeable variations of the g-tensor values. A side-by-side comparison of the performance of effective nuclear charge and spin-orbit mean field (SOMF) approaches indicates that the latter is more sensitive to the quality of basis sets, especially concerning diffuse functions, the inclusion of which is found to be nonbeneficial. What is more, the SOMF method also exhibits a much more pronounced gauge-origin dependence. Compared to electronic charge centroid, spin centers (SCs) demonstrate a superior suitability as gauge origins, providing a better agreement with diamagnetic and paramagnetic contributions of g-tensor obtained employing gauge-including atomic orbitals (GIAOs). Therefore, SCs can be recommended for the g-tensor calculations of NDs whenever GIAOs are not available.
Mass measurement of graphene using quartz crystal microbalances
Authors: Dolleman Robin J. , Hsu Mick , Vollebregt Sten , Sader John E. , van der Zant Herre S. J. , Steeneken Peter G. , Ghatkesar Murali K.
Published: July 2019

Current wafer-scale fabrication methods for graphene-based electronics and sensors involve the transfer of single-layer graphene by a support polymer. This often leaves some polymer residue on the graphene, which can strongly impact its electronic, thermal, and mechanical resonance properties. To assess the cleanliness of graphene fabrication methods, it is thus of considerable interest to quantify the amount of contamination on top of the graphene. Here, we present a methodology for the direct measurement of the mass of the graphene sheet using quartz crystal microbalances (QCMs). By monitoring the QCM resonance frequency during removal of graphene in an oxygen plasma, the total mass of the graphene and contamination is determined with sub-graphene-monolayer accuracy. Since the etch-rate of the contamination is higher than that of graphene, quantitative measurements of the mass of contaminants below, on top, and between graphene layers are obtained. We find that polymer-based dry transfer methods can increase the mass of a graphene sheet by a factor of 10. The presented mass measurement method is conceptually straightforward to interpret and can be used for standardized testing of graphene transfer procedures in order to improve the quality of graphene devices in future applications.
Enhanced catalytic hydrogen evolution reaction in phosphorene nanosheet via cobalt intercalation
Authors: Zhang Wen-liang , Zhang Kai , Wu Xiao-jun
Published: July 2019

Searching alternatives to Pt-based catalyst for producing hydrogen via water splitting has gathered enormous attention to develop renewable energy. Phosphorene has been investigated widely for its large surface area, low cost, and high carrier mobility, however, the poor activity in hydrogen evolution reaction (HER) and low conductivity limit its practical application. Herein, on the basis of first-principles calculations, we demonstrate that the catalytic HER in phosphorene can be enhanced significantly with cobalt intercalations. The Co-intercalated phosphorene is metallic with charge transfer from Co atoms to phosphorene, which could enhance the catalytic activity of phosphorene. In addition, the calculated Gibbs free energy of hydrogen adsorption on Co-intercalated phosphorene bilayer is comparable to that on Pt(111) surface, independent of the degree of hydrogen coverage. Our study implies that the Co intercalation provides an effective approach to enhance the catalytic HER in phosphorene.
A translation-based heterolingual pun and translanguaging
Authors: Sato Eriko
Published: July 2019

This paper examines six English translations of the Japanese novelBotchanwith a focus on a complex pun that pairs a multi-morphemic sentence-ending in the Matsuyama dialect with the name of a traditional Japanese food. One English translation renders it as a heterolingual SL-TL pun, which is made comprehensible for TT readers without using footnotes and without distorting the culture of the ST. The SL item in this pun is seamlessly integrated into the TT’s linguistic environment at the morpho-syntactic level and is provided with layers of scaffolding at varied linguistic levels which are naturally presented as if they are a part of textual message. This heterolingual pun is analyzed as a manifestation of translanguaging. The paper proposes a research methodology whereby translanguaging perspectives are applied to translation studies in order to explain varied heterolingual translation phenomena, including foreignization.
Editing of the gut microbiota reduces carcinogenesis in mouse models of colitis-associated colorectal cancer
Authors: Zhu Wenhan , Miyata Naoteru , Winter Maria G. , Arenales Alexandre , Hughes Elizabeth R. , Spiga Luisella , Kim Jiwoong , Sifuentes-Dominguez Luis , Starokadomskyy Petro , Gopal Purva , Byndloss Mariana X. , Santos Renato L. , Burstein Ezra , Winter Sebastian E.
Published: July 2019

Chronic inflammation and gut microbiota dysbiosis, in particular the bloom of genotoxin-producing E. coli strains, are risk factors for the development of colorectal cancer. Here, we sought to determine whether precision editing of gut microbiota metabolism and composition could decrease the risk for tumor development in mouse models of colitis-associated colorectal cancer (CAC). Expansion of experimentally introduced E. coli strains in the azoxymethane/dextran sulfate sodium colitis model was driven by molybdoenzyme-dependent metabolic pathways. Oral administration of sodium tungstate inhibited E. coli molybdoenzymes and selectively decreased gut colonization with genotoxin-producing E. coli and other Enterobacteriaceae. Restricting the bloom of Enterobacteriaceae decreased intestinal inflammation and reduced the incidence of colonic tumors in two models of CAC, the azoxymethane/dextran sulfate sodium colitis model and azoxymethane-treated, Il10-deficient mice. We conclude that metabolic targeting of protumoral Enterobacteriaceae during chronic inflammation is a suitable strategy to prevent the development of malignancies arising from gut microbiota dysbiosis.
Electric structure of shallow D-wave states in Halo EFT
Authors: Braun J , Elkamhawy W , Roth R , Hammer H-W
Published: July 2019

We compute the electric form factors of one-neutron halo nuclei with shallow D-wave states up to next-to-leading order and the E2 transition from the S-wave to the D-wave state up to leading order in Halo effective field theory (Halo EFT). The relevant degrees of freedom are the core and the halo neutron. The EFT expansion is carried out in powers of R
core/R
halo, where R
core and R
halo denote the length scales of the core and the halo, respectively. We propose a power counting scenario for weakly-bound states in one-neutron Halo EFT and discuss its implications for higher partial waves in terms of universality. The scenario is applied to the

5

2

+

first excited state and the

1

2

+

ground state of 15C. We obtain several universal correlations between electric observables and use data for the E2 transition

5

2

+

→

1

2

+

together with ab initio results from the No-Core Shell Model to predict the quadrupole moment.
The experimental dose ranges influence the LETd dependency of the proton minimum RBE (RBEmin)
Authors: Rørvik Eivind , Thörnqvist Sara , Ytre-Hauge Kristian S
Published: July 2019

Cell experiments have shown the proton relative biological effectiveness (RBE) to vary with dose and linear energy transfer (LET), which has led to development of variable RBE models. The RBE is normally estimated from two independent functions, the RBEmax and RBEmin, describing the extreme RBE at low and high doses. While there is consensus that RBEmax increases with increasing LET, the RBEmin is not uniformly defined and its dependency on LET is deviating. In this work, we analysed this dependency and its sensitivity to variations of the experimental dose range.

We performed a literature search to find data from existing monoenergetic proton cell survival experiments with (α/β)
x
values below 5 Gy and dose averaged LET (LETd) values below 20 keV µm−1. From the experiments the doses and their corresponding survival data were extracted. Based on these data, multiple restricted databases were generated by sequential exclusion of low dose data in the experiments followed by a linear-quadratic (LQ) fit. The quadratic component from the LQ-fit was used to estimate RBEmin. The LETd dependency of RBEmin was determined by fitting a linear function to the RBEmin values estimated from the restricted databases.

Our analysis showed the LETd dependency of RBEmin to be significantly influenced by the experimental dose range. By including experiments with doses below 1 Gy in the database, we found that RBEmin increased with increasing LETd. By excluding the low dose experiments in our database, the RBEmin became constant for all LETd values. For an LETd value of 5 keV µm−1, a restricted database including the data with the lowest doses gave an RBEmin of 1.4  ±  0.1, while databases with only high dose data (>2 Gy) gave an RBEmin of 1.0  ±  0.1. None of our restricted databases gave a decreasing RBEmin with increasing LETd.

Our study showed that RBEmin has a small yet significant dependency on LETd for tissues with low (α/β)
x
ratio. The LETd dependency of RBEmin varied substantially with the experimental dose range. Including experiments with high minimum dose in RBE models may lead to underestimation of the RBE.