bluuebunny/crossref_metadata_2025 huggingface dataset:
Anomalous viscosity-time behavior of polysaccharide dispersions
Authors: Kampf Nir , Wachtel Ellen J. , Zilman Anton , Ben-Shalom Noah , Klein Jacob
Published: July 2018

Using viscosity and dynamic light scattering (DLS) measurements, we monitored the changes in the properties of dispersions of chitosan (a cationic polysaccharide) in acidic solution over a period of up to 700 h. Different polymer concentrations, weight average molecular weights, and degrees of deacetylation were examined. We found that the solution rheology and chitosan aggregates continue to change even up to 700 h. It was observed, remarkably, using both capillary and cone and plate viscometry that the viscosity decreased significantly during the storage period of the chitosan dispersions, with a rapid initial decrease and a slow approach to the steady state value. DLS measurements over this period could be interpreted in terms of a gradual decrease in the size of the chitosan aggregates in the dispersion. This behavior is puzzling, insofar as one expects the dissolution of compact polymer aggregates with time into individual polymer chains to increase the viscosity rather than decrease it as observed: We attribute this apparently anomalous behavior to the fact that the chitosan aggregates are rigid crystalline rod-like entities, which dissolved with time from dispersion of overlapping rods (with high viscosity) into solution of individual random coils (with lower viscosity). A detailed model comparing the hydrodynamic behavior of the initial overlapping rod-like aggregates with the subsequent free coils in solution is in semi-quantitative agreement with our observation.
Influence of neutral beam attenuation on beam emission spectroscopy and charge exchange recombination spectroscopy
Authors: Yu Y. , Wang H. J. , Chen Z. , Chen R. , Lan T. , Li Y. Y. , Zang Q. , Zhang J. , Zhao H. L. , Mao S. F. , Lyu B. , Ye M. Y. , Wan B. N.
Published: July 2018

Neutral beam attenuation is simulated by means of consulting the ADAS (Atomic Data and Analysis Structure) database based on experimentally diagnosed radial plasma density and electron temperature profiles on the Experimental Advanced Superconducting Tokamak (EAST). Two-dimensional distributions of beam emission and charge exchange recombination photon flux are simulated, taking neutral beam attenuation into account, together with comparison with experimental results of Beam Emission Spectroscopy (BES) and Charge eXchange Recombination Spectroscopy (CXRS). A photon number which is over 1014 promises a sufficient photon flux for typical detectors of BES, CXRS, and UltraFast-CXRS (UF-CXRS) diagnostics. Evidence shows that the ADAS database overvalues neutral beam injection effective stopping coefficient on the EAST tokamak. The joint diagnostic of BES and UF-CXRS which is under development to measure plasma pressure with a high temporal resolution of 1 μs will have strong signals in a radial range of 0.6 < ρ < 0.8. The steep gradients of plasma density and C6+ density at ρ ∼ 1 bring great difficulty to edge plasma investigation by this joint diagnostic.
Transparent ZnO:Al2O3 films with high breakdown voltage and resistivity
Authors: Liu Shiying , Liu Shan , Zhou Yaoyao , Piao Yongjun , Li Guojian , Wang Qiang
Published: July 2018

Transparent ZnO films with high breakdown voltage and resistivity were deposited by the radio frequency-assisted evaporation method. In this paper, we have investigated on the structural, optical, and electrical properties of ZnO:Al2O3. The preferred orientation of the columnar structured in situ-grown film was along (002). The resistivity of the films was five orders of magnitude larger than the current's highest resistivity. The breakdown voltage of the film (8571 V/mm) was five times higher than the highest reported breakdown voltage for a ZnO semiconductor. Furthermore, the ZnO:Al2O3 film was transparent in the visible and infrared regions even though the film had an Al content of about 7% and a thickness of 100 nm. The high-frequency dielectric constant of the ZnO:Al2O3 film was higher than that of Al2O3. The possible reasons for the transparent ZnO:Al2O3 film behavior were second-phase Al2O3, lower carrier concentration, and strong bound electrons. Less defects and strong bonding contribute 4 orders of magnitude improvement to the high resistivity of ZnO films. The obtained results suggest that ZnO:Al2O3 can be used as an insulator layer between the p-n junction in order to improve the efficiency of the solar cell device.
Chaos in small networks of theta neurons
Authors: Laing Carlo R.
Published: July 2018

We consider small networks of instantaneously coupled theta neurons. For inhibitory coupling and fixed parameter values, some initial conditions give chaotic solutions while others give quasiperiodic ones. This behaviour seems to result from the reversibility of the equations governing the networks’ dynamics. We investigate the robustness of the chaotic behaviour with respect to changes in initial conditions and parameters and find the behaviour to be quite robust as long as the reversibility of the system is preserved.
Ultra-short period Ga-free superlattice growth on GaSb
Authors: Sarney W. L. , Svensson S. P. , Yakes M. K. , Xu Y. , Donetsky D. , Belenky G.
Published: July 2018

This work describes a thorough investigation of the structural properties of intended binary InAs/InSb strained layer superlattices (SLS) on GaSb substrates for infrared detection. The designed periods were as short as possible, with the InSb layers approaching one to two molecular monolayers. None of the examined growth conditions produced complete InSb layers. All samples showed a significant loss of Sb. The Sb that was incorporated was found to exhibit a spread in the growth direction, mainly due to step formation, and secondly due to forward diffusion. All structures, therefore became an InAs1-xSbx/InAs1-ySby SLS. The intended InAs layer had a Sb composition of x ∼ 0.003–0.010 and the intended InSb layer had composition y, ranging from ∼0.24–0.43. All terrace steps appeared to be in the same direction, resulting in a weak tilt of the SLS relative to the substrate normal. We discuss the implications for growth of high-Sb-concentration InAsSb/InAs structures.
First-principles study on thermoelectric properties of half-Heusler compounds CoMSb (M = Sc, Ti, V, Cr, and Mn)
Authors: Minami Susumu , Ishii Fumiyuki , Mizuta Yo Pierre , Saito Mineo
Published: July 2018

We have performed systematic density functional calculations and evaluated thermoelectric properties (Seebeck coefficient and anomalous Nernst coefficient) of half-Heusler compounds CoMSb (M = Sc, Ti, V, Cr, and Mn). The carrier concentration dependence of the Seebeck coefficient in nonmagnetic compounds is in good agreement with experiments. We found that the half-metallic ferromagnetic CoMnSb shows a large anomalous Nernst effect originating from Berry curvature near the Brillouin zone boundary. These results help us understand the mechanism of a large anomalous Nernst coefficient and give us a clue to design high performance magnetic thermoelectric materials.
Imaging the three-dimensional orientation and rotational mobility of fluorescent emitters using the Tri-spot point spread function
Authors: Zhang Oumeng , Lu Jin , Ding Tianben , Lew Matthew D.
Published: July 2018

Fluorescence photons emitted by single molecules contain rich information regarding their rotational motions, but adapting single-molecule localization microscopy (SMLM) to measure their orientations and rotational mobilities with high precision remains a challenge. Inspired by dipole radiation patterns, we design and implement a Tri-spot point spread function (PSF) that simultaneously measures the three-dimensional orientation and the rotational mobility of dipole-like emitters across a large field of view. We show that the orientation measurements done using the Tri-spot PSF are sufficiently accurate to correct the anisotropy-based localization bias, from 30 nm to 7 nm, in SMLM. We further characterize the emission anisotropy of fluorescent beads, revealing that both 20-nm and 100-nm diameter beads emit light significantly differently from isotropic point sources. Exciting 100-nm beads with linearly polarized light, we observe significant depolarization of the emitted fluorescence using the Tri-spot PSF that is difficult to detect using other methods. Finally, we demonstrate that the Tri-spot PSF detects rotational dynamics of single molecules within a polymer thin film that are not observable by conventional SMLM.
Measurement of cryogenic target position and implosion core offsets on OMEGA
Authors: Grimble W. , Marshall F. J. , Lambrides E.
Published: July 2018

Cryogenic target implosions currently performed on the University of Rochester's OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] are of deuterium–tritium-filled polystyrene shells held at near the triple point temperature (∼20 K) inside a cooled shroud that must be retracted from around the target just before the target is illuminated by OMEGA. As a consequence, impulses may be imparted to the target stalk, causing the target to depart from its ideal position centered at the aim point of the laser beams. The positions of cryogenic targets at the start of the laser pulse are determined in this work by comparing the positions of images of the cryogenic target implosion to that of a non-cryogenic target implosion that is accurately centered on the aim point of the beams. Images are taken from an array of up to five digitally recorded, x-ray pinhole cameras. Positions of the resultant implosion cores are determined along a single line of sight from x-ray images of these cores taken with an x-ray microscope operating in the time-integrated mode. The offsets of the cryogenic-target cores relative to the non-cryogenic-target cores are found to have a magnitude and direction consistent with the core forming in the direction of the target offset at the start of the laser pulse. The inferred offsets are therefore consistent with each other within errors. Neutron yields are seen to be affected by the target offset although with considerable scatter.
Energy characteristics of the electrical explosion of two intertwined wires made of dissimilar metals
Authors: Pervikov A. , Glazkova E. , Lerner M.
Published: July 2018

In this article, we present the results of the research into the characteristics of the conditions of heating and explosive destruction of Al-Cu, Fe-Ti, Fe-Cu, and Fe-Pb wires under a pulse of current with the density of 107 A/cm2. It has been shown that the energy that is deposited into the wire may depend on the relation between the thermophysical parameters and specific electric resistivity of the metals. It has been determined that under a pulse of current, the wires may explode synchronously or non-synchronously. During a synchronous explosion of wires, a single voltage pulse is generated. In the case of non-synchronous explosion, the wires explode in a succession, thus generating two voltage pulses. We suggested a dimensionless parameter that allows for predicting whether an electrical explosion of two wires of dissimilar metals is synchronous or non-synchronous. According to the research findings, non-synchronous nature of wire explosion may impact the formation of bimetallic particles through the explosion of two intertwined wires made of dissimilar metals.
Ultraviolet relaxation dynamics in uracil: Time-resolved photoion yield studies using a laser-based thermal desorption source
Authors: Ghafur Omair , Crane Stuart W. , Ryszka Michal , Bockova Jana , Rebelo Andre , Saalbach Lisa , De Camillis Simone , Greenwood Jason B. , Eden Samuel , Townsend Dave
Published: July 2018

Wavelength-dependent measurements of the RNA base uracil, undertaken with nanosecond ultraviolet laser pulses, have previously identified a fragment at m/z = 84 (corresponding to the C3H4N2O+ ion) at excitation wavelengths ≤232 nm. This has been interpreted as a possible signature of a theoretically predicted ultrafast ring-opening occurring on a neutral excited state potential energy surface. To further investigate the dynamics of this mechanism, and also the non-adiabatic dynamics operating more generally in uracil, we have used a newly built ultra-high vacuum spectrometer incorporating a laser-based thermal desorption source to perform time-resolved ion-yield measurements at pump wavelengths of 267 nm, 220 nm, and 200 nm. We also report complementary data obtained for the related species 2-thiouracil following 267 nm excitation. Where direct comparisons can be made (267 nm), our findings are in good agreement with the previously reported measurements conducted on these systems using cold molecular beams, demonstrating that the role of initial internal energy on the excited state dynamics is negligible. Our 220 nm and 200 nm data also represent the first reported ultrafast study of uracil at pump wavelengths <250 nm, revealing extremely rapid (<200 fs) relaxation of the bright S3(1ππ*) state. These measurements do not, however, provide any evidence for the appearance of the m/z = 84 fragment within the first few hundred picoseconds following excitation. This key finding indicates that the detection of this specific species in previous nanosecond work is not directly related to an ultrafast ring-opening process. An alternative excited state process, operating on a more extended time scale, remains an open possibility.
Measurement of electron temperature fluctuations on J-TEXT via correlation ECE
Authors: Zhou H. , Yang Z. J. , Xie X. L. , Zhang C. , Pan X. M. , Cai Q. X. , Ruan B. W.
Published: July 2018

The capabilities of the joint-Texas experimental tokamak correlation electron cyclotron emission (CECE) diagnostic have recently been extended with an upgrade. Four new yttrium iron garnet (YIG) filters from 4 GHz to 18 GHz with a bandwidth of 90 ∼ 230 MHz are added to the previous 4 channels. Optical optimization of the transmission line has improved the poloidal resolution, which allows kθ < 3.08 cm−1. The improvement of video amplifiers allows the frequency and amplitude gain to be adjusted discretely from 200 kHz to 1 MHz and from 200 to 1000, respectively, for different situations. A controller is designed to remotely adjust the center frequency of the YIG filters. Based on the CECE, the distribution and the effect of magnetohydrodynamic instabilities on electron temperature fluctuations have been observed. The experiment results show good performance of the upgraded CECE diagnostic.
A multiplexer-based multi-channel microwave Doppler backward scattering reflectometer on the HL-2A tokamak
Authors: Shi Zhongbing , Zhong Wulyu , Yang Zengchen , Liang Anshu , Wen Jie , Jiang Min , Shi Peiwan , Fu Binzhong , Chen Chengyuan , Liu Zetian , Ding Xuantong , Yang Qingwei
Published: July 2018

The Doppler backward scattering (DBS) reflectometer has become a well-established and versatile diagnostic technique for the measurement of density fluctuations and flows in magnetically confined fusion experiments. In this work, a novel multiple fixed-frequency array source with a multiplexer technique is developed and applied in the multi-channel DBS system. The details of the system design and laboratory tests are presented. Preliminary results of Doppler shift frequency spectra measured by the multi-channel DBS reflectometer systems are obtained. Characteristics of plasma rotation and turbulence before and after supersonic molecular beam injection are analyzed.
Nonlinear shear and dilatational rheology of viscoelastic interfacial layers of cellulose nanocrystals
Authors: van den Berg Merel E. H. , Kuster Simon , Windhab Erich J. , Sagis Leonard M. C. , Fischer Peter
Published: July 2018

We present a nonlinear rheological investigation of model rod-like particles at the air/water interface in dilatation and shear. Cellulose nanocrystals were modified to vary their surface hydrophobicity, creating a range of surface-active particles with varying contact angle. The interfacial rheological properties were studied using a series of frequency sweeps in small amplitude oscillatory shear as well as strain sweeps under large amplitude oscillatory shear (LAOS) and large amplitude oscillatory dilatation (LAOD) to include the nonlinear behavior. A multi-mode Maxwell model was used to fit the frequency sweeps that were obtained during formation of the interfacial layer. A shift toward longer relaxation times was found, more pronounced for particles with higher hydrophobicity. Lissajous plots in LAOS revealed strain stiffening, yielding, and unconstrained flow of the interfacial layers. Lissajous plots in LAOD revealed strain hardening in compression and strain softening in expansion, increasing with surface pressure and with particle hydrophobicity. While interfacial layers commonly show gel or solid-like behavior, our findings imply a weakly aggregated system. The rheological behavior indicates the formation of larger clusters for particles with high hydrophobicity compared to smaller clusters for particles with low hydrophobicity. The particle-particle interactions therefore vary with hydrophobicity, suggesting that capillary interactions are important for the formation of these microstructures.
Linear-field plasma jet arrays excited by high-voltage alternating current and nanosecond pulses
Authors: Zhou Ruoyu , Zhang Bo , Zhou Renwu , Liu Feng , Fang Zhi , Ostrikov Kostya (Ken)
Published: July 2018

Atmospheric pressure plasma jet arrays can expand the treatment dimension of a single jet to large scales effectively, and the arrays with a good downstream uniformity have a great potential for applications in the materials surface treatment and biomedicine. In this paper, a linear-field jet array with a ring-ring electrode structure in Ar is excited by alternating current (AC) and nanosecond (ns) pulse voltage, and the characteristics and downstream uniformity of the array and their dependence on the applied voltage and gas flow rate are investigated and compared through optical, electrical, and Schlieren diagnosis. The electrical and hydrodynamic interactions between the jets in the array are analyzed and discussed. The results show that the ns pulse excited jet arrays can generate relatively large-scale plasma with better uniformity, longer plumes, and higher intensity active species with a higher energy efficiency than the AC excited ones. No visible deviation of the plume and gas flow trajectories in the light emission and Schlieren images is observed for the ns pulse excited arrays. On the other hand, deviation of plume trajectories is shown to depend on the applied voltage and the gas flow rate for the AC excited arrays. The shorter duration of the interaction of the ns pulse excited jet arrays compared with that of the AC excited jet arrays results in the weaker effects of the Coulomb repellence force and the gas heating, which helps to maintain the uniformity of jet arrays. The reported results can help to design controllable and scalable plasma jet arrays in the economic Ar with good uniformity and higher energy efficiency for material surface and biomedical treatments.
Measuring dynamic fast ion spatial profiles with fusion protons in the Madison Symmetric Torus
Authors: Magee R. M. , Anderson J. K. , Korepanov S. , Frausto L. , Boguski J. , Bonofiglo P. J. , Kim J. , McConnell R.
Published: July 2018

Neutral beam injected fast ions play a dominant role in both the field reversed configuration (FRC) at TAE Technologies and the Madison Symmetric Torus (MST) reversed field pinch (RFP), making fast ion diagnosis a major pillar of both research programs. And as strongly self-organized plasmas, the FRC and RFP similarly exhibit dynamic relaxation events which can redistribute fast ions. Recently, a collaboration between TAE Technologies and the University of Wisconsin was conducted to develop a method for measuring a fast changing fast ion spatial profile with a fusion proton detector and to investigate commonalities between the two plasmas. The steerable detector was designed and built at TAE and installed on MST. The fusion proton emission profile resulting from injection of a 25 kV deuterium neutral beam is measured with better than 5 cm spatial resolution and 100 μs temporal resolution over the course of several 10s of shots. The fast ion density profile, forward modeled by tracing the orbits of the 3 MeV protons through a reconstructed magnetic equilibrium, is observed to flatten during global magnetic tearing mode activity, dropping by 30% in the core and increasing by a similar amount at the edge. The equilibrium profile is observed to be consistent with measurements made with a collimated neutron detector.
On the low magnetic field effect in radical pair reactions
Authors: Lewis Alan M. , Fay Thomas P. , Manolopoulos David E. , Kerpal Christian , Richert Sabine , Timmel Christiane R.
Published: July 2018

Radical pair recombination reactions are known to be sensitive to the application of both low and high magnetic fields. The application of a weak magnetic field reduces the singlet yield of a singlet-born radical pair, whereas the application of a strong magnetic field increases the singlet yield. The high field effect arises from energy conservation: when the magnetic field is stronger than the sum of the hyperfine fields in the two radicals, S → T± transitions become energetically forbidden, thereby reducing the number of pathways for singlet to triplet interconversion. The low field effect arises from symmetry breaking: the application of a weak magnetic field lifts degeneracies among the zero field eigenstates and increases the number of pathways for singlet to triplet interconversion. However, the details of this effect are more subtle and have not previously been properly explained. Here we present a complete analysis of the low field effect in a radical pair containing a single proton and in a radical pair in which one of the radicals contains a large number of hyperfine-coupled nuclear spins. We find that the new transitions that occur when the field is switched on are between S and T0 in both cases, and not between S and T± as has previously been claimed. We then illustrate this result by using it in conjunction with semiclassical spin dynamics simulations to account for the observation of a biphasic-triphasic-biphasic transition with increasing magnetic field strength in the magnetic field effect on the time-dependent survival probability of a photoexcited carotenoid-porphyrin-fullerene radical pair.
FPGA-based implementation of chaotic oscillators by applying the numerical method based on trigonometric polynomials
Authors: Pano-Azucena A. D. , Tlelo-Cuautle E. , Rodriguez-Gomez G. , de la Fraga L. G.
Published: July 2018

Chaotic systems are integrated via numerical methods but the main challenge is determining the correct time-step. For instance, traditional numerical methods like Forward Euler (FE) and 4th-order Runge-Kutta (RK), have been applied to simulate and to implement chaotic oscillators into embedded systems like the field-programmable gate array (FPGA). However, if one does not choose the correct time-step, numerical methods may induce artificial chaos suppression or can engender the appearance of spurious solutions. To cope with these issues when solving chaotic systems, one can apply numerical methods for problems having oscillatory characteristics. In this manner, we show that methods like the one based on trigonometric polynomials are ad hoc in simulating chaotic oscillators because provide better accuracy than FE, and as also shown herein requires lower FPGA resources compared to 4th-order RK. To demonstrate the usefulness of the method based on trigonometric polynomials, five chaotic oscillators are simulated and compared to the traditional FE, 4th-order RK and ODE45 (available into MatlabTM). The comparison considers time-execution and number of calls for evaluating the mathematical models of the oscillators. The experimental results when implementing the methods within an FPGA demonstrate that the method based on trigonometric polynomials has similar accuracy than ODE45, similar time-execution compared to FE, and its FPGA implementation requires lower hardware resources than RK. Therefore, we conclude that trigonometric polynomials is much better than FE and RK when one knows a priori that the problem has oscillatory characteristics.
Fe substitution-controlled anti-polar phase in multiferroic TbMn2O5
Authors: Cho Kwanghee , Seong Keeyeon , Lee Seongsu , Park Soonyong
Published: July 2018

Magnetic multiferroics TbMn2O5 shows rich magnetic phases that are strongly coupled to multiple electrical phases. Herein, we report that Fe substitutions in TbMn2O5 can selectively and completely suppress the lower-temperature anti-polar phase, whereas the higher-temperature ferroelectric phase is almost intact down to T ≈ 10 K. Neutron diffraction on the single crystalline TbMn2-xFexO5 (x ≈ 0.06) shows that the commensurate magnetic phase persists down to T ≈ 1.7 K, indicating that the commensurability, which is responsible for the exchange-striction mechanism, plays a deterministic role on the ferroelectric polarization in TbMn2O5.
Band alignment of In2O3/β-Ga2O3 interface determined by X-ray photoelectron spectroscopy
Authors: Sun Shun-Ming , Liu Wen-Jun , Wang Yong-Ping , Huan Ya-Wei , Ma Qian , Zhu Bao , Wu Su-Dong , Yu Wen-Jie , Horng Ray-Hua , Xia Chang-Tai , Sun Qing-Qing , Ding Shi-Jin , Zhang David Wei
Published: July 2018

The energy band alignment of the atomic-layer-deposited In2O3/β-Ga2O3 (2¯01) interface is evaluated by X-ray photoelectron spectroscopy. The X-ray diffraction pattern reveals that the In2O3 film grown at 160 °C is amorphous, while it becomes polycrystalline at a higher deposition temperature of 200 °C. The bandgaps, determined by reflection electron energy loss spectroscopy, are 4.65, 3.85, and 3.47 eV for β-Ga2O3, polycrystalline In2O3, and amorphous In2O3, respectively. Both amorphous and polycrystalline In2O3/β-Ga2O3 interfaces have Type I alignment. The conduction and valence band offsets at the polycrystalline (amorphous) In2O3/β-Ga2O3 interface are 0.35 and 0.45 eV (0.39 and 0.79 eV), respectively. These observations suggest that polycrystalline In2O3 as an intermediate semiconductor layer is beneficial to the barrier reduction of metal/Ga2O3 contact.
Perspective: Multireference coupled cluster theories of dynamical electron correlation
Authors: Evangelista Francesco A.
Published: July 2018

Predicting the electronic structure and properties of molecular systems that display strong electron correlation effects continues to remain a fundamental theoretical challenge. This perspective discusses the recent progress and current challenges in multireference wave function methods for dynamical electron correlation, focusing on systematically improvable methods that go beyond the limitations of configuration interaction and perturbation theory.
Spatially resolved optical activation of Eu ions by laser irradiation in implanted hexagonal MoO3 microrods
Authors: Almodóvar P. , Díaz-Guerra C. , Ramírez-Castellanos J. , González-Calbet J. M. , Peres M. , Lorenz K.
Published: July 2018

An effective optical activation of Eu ions in implanted h-MoO3 microrods can be achieved by ultraviolet (325 nm) or red (633 nm) laser irradiation in a confocal microscope, contrary to the case of rapid thermal annealing or conventional annealing treatments. Eu3+ photoluminescence emission is triggered by h-MoO3 to α-MoO3 or h-MoO3 to η-Mo4O11 phase transformations induced by the laser beam, as revealed by Raman microscopy and spectroscopy. The formation of such phases was found to depend on laser wavelength, power density, and irradiation time. The possibility to induce controlled activation of luminescent rare earth ions at a desired position and with high precision by laser irradiation is of interest for potential applications of this material in optoelectronics.
Terrace morphology on fused silica surfaces by Ar+ ion bombardment with Mo co-deposition
Authors: Chen Dekang , Yang Gaoyuan , Li Jinyu , Hirsch Dietmar , Liu Ying , Frost Frank , Hong Yilin
Published: July 2018

The morphology evolution of self-organized nanopatterns induced during Ar+ ion bombardment (IB) with Mo co-deposition on fused silica (SiO2) surfaces at different incidence angles and fluences was investigated by using atomic force microscopy and transmission electron microscopy. For pure IB at incidence angles from 30° to 70°, SiO2 surfaces evolve from being flat, via ripples, to direction-transversed ripples. In contrast, at the same ion fluence and incidence angles, the simultaneous Mo co-deposition leads to significant terraced structures with significantly enhanced roughness and wavelength. Our observations show that the concurrent Mo co-deposition during IB can reduce the critical incidence angle and the fluence level of terrace formation. Owing to the guidance of the IB-induced morphology, at incidence angles where a well-ordered ripple-mode can be generated, well-ordered terrace morphology is more likely to be formed. Terraced structures are initiated and further grow until the appearance of the nonlinear phase, i.e., where the ripple amplitude is sufficiently high. The enhanced terrace morphology on smooth SiO2 results from the interplay between pure IB and Mo co-deposition. The phase separation is attributed to the formation of crystalline MoOx on the side facing the impurity.
Widely tunable harmonic frequency comb in a quantum cascade laser
Authors: Piccardo Marco , Chevalier Paul , Anand Sajant , Wang Yongrui , Kazakov Dmitry , Mejia Enrique A. , Xie Feng , Lascola Kevin , Belyanin Alexey , Capasso Federico
Published: July 2018

Self-starting harmonic frequency combs in quantum cascade lasers exhibit skipping of several tens of longitudinal modes of the cavity, producing widely spaced frequency combs which may be used for a number of applications, such as the generation of high-spectral-purity microwave and terahertz tones. Under pure electrical injection, the spacing of such combs is fixed by fundamental laser parameters and can hardly be controlled. Here, we demonstrate that harmonic frequency combs in quantum cascade lasers can be induced by optical injection of an external seed provided by a tunable source. This scheme enables wide tunability of the harmonic comb spacing, allowing the skipping between 44 and 171 longitudinal modes in a single device.
Anomalous energy shift of laterally confined two-dimensional excitons
Authors: Ono Shota , Ogura Tomohiro
Published: July 2018

We theoretically investigate the energy of the ground state exciton confined to two-dimensional (2D) monolayers with circular shape. Within an effective mass approach employing a nonlocal screening effect on the Coulomb potential energy, we demonstrate how the exciton energy is correlated with the radius of the circle, electron-hole reduced mass, and 2D susceptibility. In addition, we show that a dead layer around the circle edge, into which the electron-hole pair cannot penetrate, is necessary for understanding the energy shift recently observed in monolayer WSe2 quantum dots.
Influence of the cathode material in the cathode fall characteristics of a hydrogen hollow cathode glow-discharge
Authors: Gonzalez-Fernandez V. , Grützmacher K. , Pérez C. , de la Rosa M. I.
Published: July 2018

In this work, we present Doppler free two photon optogalvanic measurements to determine the local electric field strength (E-field) in the cathode fall region of a hollow cathode discharge, operated in pure hydrogen, via the Stark splitting of the 2S level of hydrogen. The main aim of this article is the comparison of the measurements made with different cathode materials, stainless steel, and tungsten; both of them are widely used in the low-pressure discharges. Sputtering of stainless steel is the principle cause of the differences observed for the E-field variation, and the differences are analyzed in the frame of the sputtered material in a wide range of discharge conditions. Complementary images of the discharge luminosity allow for the conclusion; the cathode dark zone corresponds in good approximation to the cathode fall length.
The photoelectron spectra of the isomeric 1- and 2-methyltetrazoles; their equilibrium structures and vibrational analysis by ab initio calculations
Authors: Palmer Michael H. , Coreno Marcello , de Simone Monica , Grazioli Cesare , Hoffmann Søren Vrønning , Jones Nykola C. , Peterson Kirk A. , Aitken R. Alan , Rouxel Cécile
Published: July 2018

New synchrotron based studies of the photoelectron ionization spectra (PES) for the isomeric 1- and 2-methyltetrazoles (1- and 2-MeTet) show markedly higher resolution than previous reports. The unusual spectral profiles suggest that a considerable overlay of the ionic states occurs for both molecules. Under these circumstances of near degeneracy of two or more ionic states, mutual annihilation of vibrational fine structure occurs for all except the strongest vibrational states; the PES just reflects the resultants rather than full spectra. Theoretical determination of the adiabatic ionization energies (AIEs) proved a challenge; the most successful method was second order Møller-Plesset perturbation theory (MP2). These calculations suggest that the lowest PES bands for both isomers contain ionization both from lone pair σ-orbitals (2A′) on the N-atoms (LPN) and π-orbitals (2A″). The lowest experimental AIEs are as follows: 1-MeTet is 10.315 eV assigned to 12A′, while 2-MeTet is 10.543 eV assigned to 12A″. Franck-Condon analysis shows that the lowest ionization energy regions of both spectra are dominated by IE from the LPN 2A′ manifold, even though the 2A″ states have a higher absolute intensity. In this example, we have utilized a VUV Rydberg state to assist simplification of the PES; more frequently, the PES assignment is simpler and assists the location of Rydberg states in the VUV. The very slow spectral onset for 2-MeTet demonstrates the importance of vertical ionization energy calculations since maxima are more readily measured than slow onsets. These were performed at the equilibrium structure of the X1A′ state, using both multi-reference multi-root configuration interaction and the ionization potential variant of the equations-of-motion coupled cluster method, with single and double excitations (EOMIP-CCSD). This enabled the principal ionization bands to be identified over a wider range of energy. Attempts to study the higher ionic states by EOMIP-CCSD showed that several states of each symmetry are close to degenerate for 1-MeTet, in particular. A multi-configuration self-consistent field study confirmed the small separation of ionic states, but state switching during the optimization process largely disabled this method.
Evaluation of lattice curvature and crystalline homogeneity for 2-inch GaN homo-epitaxial layer
Authors: Seo Okkyun , Kim Jae Myung , Song Chulho , Lou Yanfang , Kumara L. S. R. , Hiroi Satoshi , Chen Yanna , Katsuya Yoshio , Irokawa Yoshihiro , Nabatame Toshihide , Koide Yasuo , Sakata Osami
Published: July 2018

We evaluated the lattice curvature, crystallinity, and crystalline homogeneity of a GaN layer on a free standing GaN substrate using lattice orientation measurements, θ rocking curves, and reciprocal space mapping from synchrotron X-ray diffraction topography, and X-ray diffraction. The lattice curvature of the 2-inch GaN homo-epitaxial layer was a concave bend, which had a curvature radius of approximately 20.7 m. The GaN layer was epitaxially grown on the GaN substrate and had good crystallinity with a high homogeneity.
On quasi-periodic waves and rogue waves to the (4+1)-dimensional nonlinear Fokas equation
Authors: Wang Xiu-Bin , Tian Shou-Fu , Feng Lian-Li , Zhang Tian-Tian
Published: July 2018

Under investigation in this paper is the (4+1)-dimensional nonlinear Fokas equation, which is an important physics model. With the aid of Bell’s polynomials, an effective and straightforward method is presented to succinctly construct the bilinear representation of the equation. By using the resulting bilinear formalism, the soliton solutions and Riemann theta function periodic wave solutions of the equation are well constructed. Furthermore, the extended homoclinic test method is employed to construct the breather wave solutions and rogue wave solutions of the equation. Finally, a connection between periodic wave solutions and soliton solutions is systematically established. The results show that the periodic waves tend to solitary waves under a limiting procedure.
Non-adiabatic molecular dynamics simulations of non-charge-transfer and charge-transfer scattering in H+ +CO2 at ELab=30 eV
Authors: Yan Yun-An , Morales Jorge A.
Published: July 2018

The H+ +CO2 reaction at high energies is relevant in atmospheric chemistry, astrophysics, and proton cancer therapy research. Therefore, we present herein a complete investigation of H+ +CO2 at ELab=30 eV with the simplest-level electron nuclear dynamics (SLEND) method. SLEND describes nuclei via classical mechanics and electrons with a single-determinantal Thouless wavefunction. The 3402 SLEND conducted simulations from 42 independent CO2 target orientations provide a full description of all the reactive processes and their mechanisms in this system: non-charge-transfer scattering (NCTS), charge-transfer scattering (CTS), and single C=O bond dissociation; all this valuable information about reactivity is not accessible experimentally. Numerous details of the projectile scattering patterns are provided, including the appearance and coalescence of primary and secondary rainbow angles as a function of the target orientation. SLEND NCTS and CTS differential cross sections (DCSs) are evaluated in conjunction with advanced semi-classical techniques. SLEND NCTS DCS agrees well with its experimental counterpart at all the measured scattering angles, whereas SLEND CTS DCS agrees well at high scattering angles but less satisfactorily at lower ones. Remarkably, both NCTS and CTS SLEND DCSs predict the primary rainbow angle signatures in agreement with the experiment.
Network modeling of inflammatory dynamics induced by biomass smoke leading to chronic obstructive pulmonary disease
Authors: Yu Hai-shan , Pan Zhi-chao , Liao Jie-lou
Published: July 2018

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disorder characterized by airflow obstruction and progressive damage of lung tissues. As currently more than 3 billion people use biomass fuel for cooking and heating worldwide, exposure to biomass smoke (BS) is recognized as a significant risk factor for COPD. Recent clinical data have shown that BS-COPD patients have a Th2-type inflammatory profile significantly different from that in COPD induced by cigarette smoke. As COPD is essentially proinflammatory, however, the mechanism underlying this Th2-type anti-inflammatory profile remains elusive. In this work, a network model is applied to study BS-induced inflammatory dynamics. The network model involves several positive feedback loops, activations of which are responsible for different mechanisms by which clinical phenotypes of COPD are produced. Our modeling study in this work has identified a subset of BS-COPD patients with a mixed M1- and Th2-type inflammatory profile. The model’s prediction is in good agreement with clinical experiments and our in silico knockout simulations have demonstrated several important network components that play an important role in the disease. Our modeling study provides novel insight into BS-COPD progression, offering a rationale for targeted therapy and personalized medicine for treatment of the disease in future.
Dissipaton equation of motion theory versus Fokker-Planck quantum master equation
Authors: Liu Yang , Xu Rui-xue , Zhang Hou-dao , Yan YiJing
Published: July 2018

The quest of exact and nonperturbative methods on quantum dissipation with nonlinear coupling environments remains in general a great challenge. In this review we present a comprehensive account on two approaches to the entangled system-and-environment dynamics, in the presence of linear-plus-quadratic coupling bath. One is the dissipaton-equation-of-motion (DEOM) theory that has been extended recently to treat the nonlinear coupling environment. Another is the extended Fokker-Planck quantum master equation (FP-QME) approach that will be constructed in this work, based on its DEOM correspondence. We closely compare these two approaches, with the focus on the underlying quasi-particle picture, physical implications, and implementations.
Modelling climate change impacts on early and late harvest grassland systems in Portugal
Authors: Yang Chenyao , Fraga Helder , van Ieperen Wim , Santos João A.
Published: July 2018

Climate change projections for Portugal showed warming and drying trends, representing a substantial threat for the sustainability of forage production in perennial grassland. The objective of the present study was to assess climate change impacts on seasonal dry matter yield (DMY) in three locations (North-west-, Central-inner and South-Portugal) with different climatic conditions, for two grassland production systems deviating in growing season length, either early cuts in spring (ES) or late cuts in summer (LS). Impacts were estimated using the STICS (Simulateur mulTIdisciplinaire pour les Cultures Standard) crop model, by comparing a historical baseline period (1985–2006) with simulated projections over future periods (2021–2080). For this purpose, the STICS crop model was driven by high-resolution climate data from a coupled Global Climate Model/Regional Climate Model chain. As a result, we obtained that, during the baseline period, DMY of LS was consistently much higher than that of ES in all three locations. For LS, significant reductions in mean DMY were forecasted during 2061–2080, ranging from mild (–13%) in the north to severe (–31%) in the south of Portugal. In contrast, seasonal DMY was largely maintained for ES among sites until 2080, benefiting from low water deficits, the expected atmospheric CO2 rise and the forecasted temperature increase during cool season. Thus, the yield gap was projected to gradually decrease between the two regimes, in which mean DMY for ES was foreseen to exceed that of LS over 2061–2080 in the southern site. Moreover, ES was projected to have very low exposure to extreme heat and severe water stresses. Conversely, LS, subjected to high summer water deficit and irrigation needs, was projected to experience increased summertime water stress (9–11%) and drastically increased heat stress (33–57%) in 2061–2080, with more pronounced heat stress occurring in the south. Frequency of occurrence of extreme heat stress was projected to gradually increase in summer over successive study periods, with a concomitant increased intensity of DMY response to inter-annual variability of heat stress during 2061–2080. Heat stress tended to be more important than water stress under the prescribed irrigation strategy for LS, potentially being the main limiting factor for summertime DMY production under climate change scenario.
Building oral health capacity in a women's health service
Authors: Durey Angela , Lee Susan Kaye , Adebayo Bola , Slack-Smith Linda
Published: July 2018

Adult women in Australia are more likely than men to have no teeth, more missing teeth or have a dental hospital admission. Experiences of war, family and domestic violence, mental health or alcohol and other drug use problems may also negatively affect women’s oral health. Yet, oral health is often excluded from primary healthcare. Little is known about what helps or inhibits primary healthcare service workers to promote oral health to women in need. Identifying the perceptions and experiences of such workers is a step towards a strategy to develop resources to support them in raising oral health issues with disadvantaged clients. This paper presents findings from a qualitative study conducted at a community-based women’s health service, which used focus groups to investigate workers’ perceptions of promoting oral health and accessing services for their clients. Findings indicated how structural issues informed oral healthcare, where workers generally did not consider oral health their responsibility, were reluctant to raise the issue with clients and had limited oral health knowledge and resources. To overcome these barriers, workers identified the need for oral health resources and better linkages to the dental system to help support their clients.
Mavacamten stabilizes an autoinhibited state of two-headed cardiac myosin
Authors: Rohde John A. , Roopnarine Osha , Thomas David D. , Muretta Joseph M.
Published: July 2018

Significance

Small-molecule allosteric effectors designed to target and modulate striated and smooth myosin isoforms for the treatment of disease show promise in preclinical and clinical trials. Beta-cardiac myosin is an especially important target, as heart disease remains a primary cause of death in the United States. One prevalent type of heart disease is hypertrophic cardiomyopathy (HCM), which is hypothesized to result from dysregulated force generation by cardiac myosin. Mavacamten is a potent cardiac myosin ATPase activity inhibitor that improves cardiac output in HCM animal models. Our results show that mavacamten selectively stabilizes a two-headed–dependent, autoinhibited state of cardiac myosin in solution. The kinetics and energetics of this state are consistent with the autoinhibited superrelaxed state previously observed only in intact sarcomeres.
Combined computational and experimental investigation of the La
2
CuO

4–
x

S

x

(0 ≤
x
≤ 4) quaternary system
Authors: He Hua , Yee Chuck-Hou , McNally Daniel E. , Simonson Jack W. , Zellman Shelby , Klemm Mason , Kamenov Plamen , Geschwind Gayle , Zebro Ashley , Ghose Sanjit , Bai Jianming , Dooryhee Eric , Kotliar Gabriel , Aronson Meigan C.
Published: July 2018

Significance

Discovery of new materials enabling new technologies, from novel electronics to better magnets, has so far relied on serendipity. Computational advances show promise that new materials can be designed in a computer and not in the lab, a proposal called “Materials by Design.” We present here a detailed comparison between theory and experiment, carrying out the synthesis of a high-temperature superconductor in an X-ray beam to elucidate the sequence of chemical reactions as the compound forms. Parallel computations of the stabilities of possible compounds that could form from the selected elements accurately predict the observed reactions. Paired with our chemical intuition, this methodology provides understanding and potentially control of the essential chemical principles responsible for stabilizing virtually any compound.
Oxidative stress is tightly regulated by cytochrome
c
phosphorylation and respirasome factors in mitochondria
Authors: Guerra-Castellano Alejandra , Díaz-Quintana Antonio , Pérez-Mejías Gonzalo , Elena-Real Carlos A. , González-Arzola Katiuska , García-Mauriño Sofía M. , De la Rosa Miguel A. , Díaz-Moreno Irene
Published: July 2018

Significance

Dysfunction of mitochondria, the powerhouses of living cells, favors the onset of human diseases, namely neurodegenerative diseases, cardiovascular pathologies, and cancer. Actually, respiratory cytochrome
c
has been found to be phosphorylated at tyrosine 97 during the insulin-induced neuroprotection response following a brain ischemic injury. Here, we report that the decrease in neuronal death could be directly ascribed to changes in mitochondrial metabolism—including lower production of reactive oxygen species—and cell homeostasis induced by cytochrome
c
phosphorylation. Our findings thus provide the basis for understanding the molecular mechanism and potential use of phosphomimetic species of cytochrome
c
, thereby yielding new opportunities to develop more efficient therapies against acute pathologies.