bluuebunny/crossref_metadata_2025 huggingface dataset:
An asymmetric interdependent networks model for cyber-physical systems
Authors: Jiang Jiang , Xia Yongxiang , Xu Sheng , Shen Hui-Liang , Wu Jiajing
Published: May 2020

Cyber-physical systems (CPSs) are integrations of information technology and physical systems, which are more and more significant in society. As a typical example of CPSs, smart grids integrate many advanced devices and information technologies to form a safer and more efficient power system. However, interconnection with the cyber network makes the system more complex, so that the robustness assessment of CPSs becomes more difficult. This paper proposes a new CPS model from a complex network perspective. We try to consider the real dynamics of cyber and physical parts and the asymmetric interdependency between them. Simulation results show that coupling with the communication network makes better robustness of power system. But since the influences between the power and communication networks are asymmetric, the system parameters play an important role to determine the robustness of the whole system.
Imaging system with brightness amplification for a metal-nanopowder-combustion study
Authors: Li L. , Mostovshchikov A. V. , Ilyin A. P. , Antipov P. A. , Shiyanov D. V. , Gubarev F. A.
Published: May 2020

This work discusses an optical system with brightness amplification—a laser monitor, as well as the system's application for real-time imaging of the surface of metal nanopowders during high-temperature combustion. The advantage of the laser monitor is its combination of microscopic magnification, laser backlighting, and narrow-band filtering, which, together with high-speed video recording, makes it possible to visualize the nanopowder surface through the intense background lighting produced by a high-temperature burning sample. We used two laser-monitor schemes with short and long focal lengths to study the dynamics of the combustion process at different spatial resolutions. For compounds whose combustion is accompanied by intense scattering of the combustion products, we recommend using the laser monitor with increased monitoring distance via a mirror-imaging scheme. This proposed technique allows real-time monitoring of the high-temperature-combustion processes accompanied by intensive lighting and product scattering at a distance of 50 cm from the optical system. Both systems allow quantitative characterization of the combustion process by registering the average output of the brightness amplifier together with the overall brightness of glowing. The combustion of nanoAl + nanoFe and nanoAl + nanoFe + microAl powder mixtures was visualized using a laser monitor for the first time and compared with the combustion of aluminum nanopowder without additives.
Design of microresonators to minimize thermal noise below the standard quantum limit
Authors: Sharifi S. , Banadaki Y. M. , Cullen T. , Veronis G. , Dowling J. P. , Corbitt T.
Published: May 2020

Microfabricated resonators play a crucial role in the development of quantum measurement, including future gravitational wave detectors. We use a micro-genetic algorithm and a finite element method to design a microresonator whose geometry is optimized to maximize the sub-Standard Quantum Limit (SQL) performance including lower thermal noise (TN) below the SQL, a broader sub-SQL region, and a sub-SQL region at lower frequencies. For the proposed design, we study the effects of different geometries of the mirror pad and cantilever microresonator on sub-SQL performance. We find that the maximum ratio of SQL to TN is increased, its frequency is decreased, and the sub-SQL range is increased by increasing the length of the microresonator cantilever, increasing the radius of the mirror pad, decreasing the width of the microresonator cantilever, and shifting the laser beam location from the mirror center. We also find that there exists a trade-off between the maximum ratio of SQL to TN and the sub-SQL bandwidth. The performance of this designed microresonator will allow it to serve as a test-bed for quantum non-demolition measurements and to open new regimes of precision measurement that are relevant for many practical sensing applications, including advanced gravitational wave detectors.
Visible and near-infrared dual-band photodetector based on gold–silicon metamaterial
Authors: Wang Kai , Hu Haifeng , Lu Shan , Jin Meihua , Wang Yanjie , He Tao
Published: May 2020

A photodetector with a controllable response spectrum and high responsivity shows great potential in practical photoelectric applications. Here, we design and experimentally demonstrate a visible and near-infrared (NIR) dual-band photodetector by integrating the out-of-plane Au gratings and n+-Si groove substrate metamaterial (ASGM). Simulation, experimental, and calculation results indicate that the absorption spectrum can be tailored by surface plasmon resonances (SPRs) of different interfaces and Si-groove resonance. Visible-light absorption is caused by Si-groove resonance, SPRs of the Au–air interface, and high-frequency mode SPRs of the Au–Si interface. NIR absorption is induced by the SPRs of the Au–Si interface. Moreover, out-of-plane coupling between upper and lower Au gratings gives rise to an enhanced electric field and broadened SPR absorption. The respective photoresponsivity in the visible and NIR band is more than 7 and 3 mA/W without an external bias, with a maximum responsivity of 13 mA/W at 535 nm. The photoresponse of such ASGM-based dual-band photodetectors can be modulated so that they may be used in various fields like medical imaging, optical communication, and aerography.
Broadband free space impedance in Co2Z hexaferrites by substitution of high valency heavy transition metal ions for miniaturized RF devices
Authors: Kulik Piotr , Winter Gavin , Sokolov Alexander , Murphy Katherine , Yu Chengju , Qian Kun , Fitchorova Ogheneyunume , Harris Vincent G.
Published: May 2020

Polycrystalline samples of Z-type hexaferrites, having nominal compositions Ba3Co2+xFe24−2xMxO41, where M = Ir, Hf, or Mo and x = 0 and 0.05, were processed via ceramic protocols in pursuit of low magnetic and dielectric losses, as well as equivalent permittivity and permeability over the VHF–UHF band. Fine process control was conducted to ensure optimal magnetic properties. Organic dispersants, i.e., isobutylene and maleic anhydride, were employed to achieve maximum densities. Crystallographic structure, characterized by x-ray diffraction, revealed that the dopants did not adversely affect the crystal structure and phase purity of the Z-type hexaferrite. An increase in permeability and size reduction factor is shown to be linearly proportional to the ionic radii of the dopants. This trend is consistent with local bonding distortions giving rise to increased exchange energy (J) as predicted by the Goodenough–Kanamori–Anderson rules and superexchange theory. We posit that these distortions increase the magnetocrystalline anisotropy energy affecting the frequency dependent complex permeability. For Mo doping of x = 0.05, a bandwidth of 400 MHz exists at a center frequency of 650 MHz where the permittivity and permeability are very nearly equal, i.e., Z = 377 ± 5 Ω. These results give rise to low loss, i.e., tan δε/ε′ = 0.0006 and tan δμ/μ′ = 0.038 at 650 MHz, with considerable size reduction (×9). The miniaturization and optimized performance of magnetodielectric materials for antenna at VHF–UHF frequencies using cost-effective and volumetric processing methodologies are demonstrated.
Iron oxide–Si nanoparticle magnetic core–shell induced by the interaction of d-orbitals of Fe2+ with reconstructed Si dimer-like defects
Authors: Elhalawany Noha , Mantey Kevin , Hoang Tuan , Bahceci Ersin , Xu Jiacheng , Ates Hakan , Gorin Dmitry , Yamani Zain , Nayfeh Munir H.
Published: May 2020

Redox-type charge exchange between Si nanoparticles and aqueous metal ions mx+ was recently used to synthesize core–shell nanocomposites in which their functionalities have been integrated. The process requires the electron (hole) affinities of the two to be different, with the efficiency of the charge exchange being strongly dependent on their difference. In this paper, we examine the interaction of Fe ions and red luminescent Si nanoparticles where the metal ion has comparable electron affinity to that of the Si nanoparticle. Scanning electron microscopy and fluorescent spectroscopy imaging show the formation of red luminescent core-shell clusters ranging from 100 nm to 500 nm. A permanent magnet is found to pull the structures indicating the formation of a magnetic phase. We use first principle atomistic computations at the unrestricted Hartree–Fock-DFT (density functional theory) level to obtain the charging energies and affinities of various ions of Fe and the Si nanoparticle. The computations indicate that Fe2+ cannot be oxidized to Fe3+ by the nanoparticle and it cannot strip one or two electrons from the nanoparticle and freely separate, resulting in bound complexes. Our analysis shows that a magnetic phase of iron oxide results from charge delocalization over the complex and a simultaneous interaction of the iron d-orbitals with the oxygen’s lone electrons and the nanoparticle’s reconstruction dimer-like defects. The core-shell integration at the nanoscale affords double functionality of luminescence and magnetism enhancing sensing, tracking, and delivery and enabling a variety of applications, including controlled drug delivery, underground oil and water exploration, and recovery.
Magnus force of rotating microscopic magnetic particles
Authors: Liebendorfer Adam
Published: May 2020

Dropping the particles in fluids in the presence of a rotating magnetic field, researchers deduce force from trajectory measurements for particles as small as 80 μm.
A new system for high-speed terahertz wireless communication
Authors: Patrick Chris
Published: May 2020

Experimental demonstration of wireless transmission beyond 100 Gbit/s brings terahertz wireless communication closer to high-speed wireless applications.
OH* and CH* chemiluminescence characteristics in low swirl methane-air flames
Authors: Liu Yao , Tan Jianguo , Wan Minggang , Yao Xiao
Published: May 2020

Chemiluminescence information is of great significance for characterization of flame structure and combustion characteristics. An atmospheric low swirl burner was developed to investigate the chemiluminescence characteristics of OH* and CH* in low swirl flames, with the equivalence ratio varying from 0.8 to 1.2 and the swirl number from 0.2 to 0.6. The chemiluminescence images were captured via ICCD cameras coupled with narrow-bandpass filters, and an Abel inversion method was introduced to transform the line-of-sight-integrated image into two-dimensional radial distributions. The results show that the distribution of CH* is smaller than that of OH* and concentrated more upstream of the flame near the burner. The equivalence ratio has a relatively more direct influence on chemical reactions, while the swirl number has a more evident effect on the flame structure. As the equivalence ratio increases, the peak value of OH* and CH* increases and the peak position moves downstream of the flame, suggesting that the chemical reactions become more intense. In contrast, the height and width of chemiluminescence distribution increase linearly with increasing swirl number. Moreover, it is found that the equivalence ratio and swirl number can be feasibly estimated based on chemiluminescence measurement results, using the correlation between them derived from this study.
Finite
β
effects on short wavelength ion temperature gradient modes
Authors: Jagannath M. , Chowdhury J. , Ganesh R. , Villard L.
Published: May 2020

The electromagnetic effect is studied on the short wavelength branch of the ion temperature gradient mode in the linear regime for the first time using a global gyrokinetic model. The short wavelength ion temperature gradient mode growth rate is found to be reduced in the presence of electromagnetic perturbations at finite plasma β. The effect on real frequency is found to be weak. The threshold value of ηi is found to increase for the mode as the magnitude of β is increased. The global mode structure of the short wavelength branch of the ion temperature gradient mode is compared with the conventional branch. The magnetic character of the mode, measured as the ratio of mode average square values of electromagnetic potential to electrostatic potential, is found to increase with increasing values of the plasma β. The mixing length estimate for flux shows that the maximum contribution still comes from the long wavelengths modes. The magnitude of the flux decreases with increasing β.
On negative eigenvalues of two-dimensional Schrödinger operators with singular potentials
Authors: Karuhanga Martin , Shargorodsky Eugene
Published: May 2020

We present upper estimates for the number of negative eigenvalues of two-dimensional Schrödinger operators with potentials generated by Ahlfors regular measures of arbitrary fractional dimension α ∈ (0, 2]. The estimates are given in terms of integrals of the potential with a logarithmic weight and of its L log L type Orlicz norms. In the case α = 1, our results are stronger than the known ones about Schrödinger operators with potentials supported by Lipschitz curves.
Flexibilities of wavelets as a computational basis set for large-scale electronic structure calculations
Authors: Ratcliff Laura E. , Dawson William , Fisicaro Giuseppe , Caliste Damien , Mohr Stephan , Degomme Augustin , Videau Brice , Cristiglio Viviana , Stella Martina , D’Alessandro Marco , Goedecker Stefan , Nakajima Takahito , Deutsch Thierry , Genovese Luigi
Published: May 2020

The BigDFT project was started in 2005 with the aim of testing the advantages of using a Daubechies wavelet basis set for Kohn–Sham (KS) density functional theory (DFT) with pseudopotentials. This project led to the creation of the BigDFT code, which employs a computational approach with optimal features of flexibility, performance, and precision of the results. In particular, the employed formalism has enabled the implementation of an algorithm able to tackle DFT calculations of large systems, up to many thousands of atoms, with a computational effort that scales linearly with the number of atoms. In this work, we recall some of the features that have been made possible by the peculiar properties of Daubechies wavelets. In particular, we focus our attention on the usage of DFT for large-scale systems. We show how the localized description of the KS problem, emerging from the features of the basis set, is helpful in providing a simplified description of large-scale electronic structure calculations. We provide some examples on how such a simplified description can be employed, and we consider, among the case-studies, the SARS-CoV-2 main protease.
Effects of mechanical fields on mobile charges in a composite beam of flexoelectric dielectrics and semiconductors
Authors: Qu Yilin , Jin Feng , Yang Jiashi
Published: May 2020

We study the interaction between mechanical fields and the motion of charge carriers in a composite beam of flexoelectric (nonpiezoelectric) and semiconductor layers. The macroscopic theory of flexoelectricity and the drift-diffusion theory of semiconduction are used. They are coupled by doping and mobile charges in Gauss's equation of electrostatics. A one-dimensional electromechanical model is established for the bending of the beam. Solutions from the model show that bending of the beam induces redistribution of charge carriers through the electric field produced by flexoelectric coupling. This provides a new means for constructing electromechanical semiconductor devices and extends piezotronic devices.
Low-energy switching of antiferromagnetic CuMnAs/GaP using sub-10 nanosecond current pulses
Authors: Omari K. A. , Barton L. X. , Amin O. , Campion R. P. , Rushforth A. W. , Kent A. J. , Wadley P. , Edmonds K. W.
Published: May 2020

The recently discovered electrical-induced switching of antiferromagnetic (AF) materials that have spatial inversion asymmetry has enriched the field of spintronics immensely and opened the door for the concept of antiferromagnetic memory devices. CuMnAs is one promising AF material that exhibits such electrical switching ability and has been studied to switch using electrical pulses of length millisecond down to picosecond but with little focus on the nanosecond regime. We demonstrate here the switching of CuMnAs/GaP using nanosecond pulses. Our results showed that in the nanosecond regime, low-energy switching and a high readout signal with highly reproducible behavior down to a single pulse can be achieved. Moreover, a comparison of the two switching methods of orthogonal switching and polarity switching was made on the same device, and it showed distinct behaviors that can be exploited selectively for different future memory/processing applications.
Substrate dependent terahertz response of monolayer WS2
Authors: Dong H. M. , Tao Z. H. , Li L. L. , Huang F. , Xu W. , Peeters F. M.
Published: May 2020

We investigate experimentally the terahertz (THz) optoelectronic properties of monolayer (ML) tungsten disulfide (WS2) placed on different substrates using THz time-domain spectroscopy (TDS). We find that the THz optical response of n-type ML WS2 depends sensitively on the choice of the substrate. This dependence is found to be a consequence of substrate induced charge transfer, extra scattering centers, and electronic localization. Through fitting the experimental results with the Drude–Smith formula, we can determine the key sample parameters (e.g., the electronic relaxation time, electron density, and electronic localization factor) of ML WS2 on different substrates. The temperature dependence of these parameters is examined. Our results show that the THz TDS technique is an efficient non-contact method that can be utilized to characterize and investigate the optoelectronic properties of nano-devices based on ML WS2.
Separation of electron–electron and electron–proton correlation in multicomponent orbital-optimized perturbation theory
Authors: Fajen O. Jonathan , Brorsen Kurt R.
Published: May 2020

The multicomponent orbital-optimized second-order Møller–Plesset perturbation theory (OOMP2) method is the first multicomponent MP2 method that is able to calculate qualitatively accurate protonic densities, protonic affinities, and geometrical changes due to nuclear quantum effects in multicomponent systems. In this study, two approximations of the multicomponent OOMP2 method are introduced in an effort to demonstrate that, in orbital-optimized multicomponent methods, performing the orbital-optimization process with only electron–proton correlation is sufficient to obtain accurate protonic properties. Additionally, these approximations should reduce the computational expense of the multicomponent OOMP2 method. In the first approximation, the first-order wave function is written as a linear combination of one-electron one-proton excitations rather than as a linear combination of one-electron one-proton and two-electron excitations as in the original multicomponent OOMP2 method. Electron–electron correlation is included perturbatively after the orbital-optimization procedure has converged. In the second approach, the first approximation is further modified to neglect all terms in the orbital-rotation gradients that depend on the two-electron molecular-orbital integrals, which, assuming a fixed-sized protonic basis set, reduces the computational scaling for the orbital-optimization iterations to Ne3, where Ne is a measure of the electronic system size, compared to the Ne5 scaling of the original multicomponent OOMP2 method. The second approximation requires one Ne5 step after orbital convergence to compute the electron–electron correlation energy. The accuracy of the calculated protonic densities, protonic affinities, and optimized geometries of these approximations is similar or improved relative to the original multicomponent OOMP2 method.
Optical second harmonic generation imaging and x-ray diffraction of Cs1 − xRbxH2PO4 proton conductor series
Authors: Price Alex D. , Aguilar Angela C. , Botez Cristian E. , Li Chunqiang
Published: May 2020

The solid acid compound CsH2PO4 (CDP) is a superprotonic conductor for intermediate temperature range fuel cell applications. Doping CDP with rubidium can alter its transition temperature from normal phase to superprotonic phase. Powder samples of Cs1 − xRbxH2PO4 (0 ≤ x ≤ 1) were synthesized with 10 at. % intervals of x and analyzed at room temperature. A powder x-ray diffraction study showed three major structures between the various samples: monoclinic P21/m for x ≤ 0.5 samples, monoclinic P21/c for x = 0.8 samples, tetragonal I-42d for x = 0.9 and 1 samples, and a mixture of these structures in the x = 0.6 and 0.7 samples. Optical second harmonic generation (SHG) microscopy was performed on these samples, and a unique quadrupolar behavior in an SHG polar plot was found and correlated with the monoclinic P21/c structure in the x = 0.8 sample and some part of the x = 0.6 and 0.7 samples. Although in principle this P21/c structure is centrosymmetric with no SHG signal, the loss of local symmetry while maintaining the overall super structure can possibly explain this phenomenon. The tetragonal I-42d structure is noncentrosymmetric and shows dipolar behavior in the SHG polar plot from x = 0.9 and 1 samples and part of the x = 0.6 and 0.7 samples. The monoclinic P21/m structure is centrosymmetric with no SHG signal from the x ≤ 0.5 samples. Our discovery confirms the early finding of phases of Cs1 − xRbxH2PO4 (0 ≤ x ≤ 1) superprotonic conductor series at room temperature and indicates the potential of developing SHG microscopy to study the phases of these compounds at an intermediate working temperature in situ.
Influence of the surface stress on the size-dependent elastic behavior of silicon nanowires
Authors: Nasr Esfahani Mohammad , Jabbari Masoud
Published: May 2020

A recent study has highlighted an existing controversy among experimental measurements and theoretical models on the size-dependent elastic behavior of silicon nanowires. Some measurements have depicted a significant size-dependent elastic response, while several studies report a negligible change on the elastic modulus of silicon nanowires through size reduction. To address such contrast, this work studies the surface stress contribution on the size-dependent elastic behavior of silicon nanowires. Molecular dynamics simulations are employed to investigate the influence of size, crystal orientation, boundary condition, and the residual surface stress on the incorporation of the surface stress in the mechanical properties of silicon nanowires. This is accomplished by a primary atomic stress analysis. The implication of the surface stress on the bending behavior is then calculated for silicon nanowires along ⟨100⟩ and ⟨110⟩ crystal orientations having {100} and {100}/{110} transverse surfaces, respectively. This study demonstrates, for the first time, the role played by the surface stress to reduce the elastic modulus of ⟨110⟩ silicon nanowires, which is comparable with experimental measurements on wires with the same size and crystal orientation. The present work enlightens the incorporation of the surface stress on the mechanical behavior of silicon nanowires for the explanation of existing studies and implementation for future investigations.
Modeling charge transport in high-mobility molecular semiconductors: Balancing electronic structure and quantum dynamics methods with the help of experiments
Authors: Nematiaram Tahereh , Troisi Alessandro
Published: May 2020

Computing the charge mobility of molecular semiconductors requires a balanced set of approximations covering both the electronic structure of the Hamiltonian parameters and the modeling of the charge dynamics. For problems of such complexity, it is hard to make progress without independently validating each layer of approximation. In this perspective, we survey how all terms of the model Hamiltonian can be computed and validated by independent experiments and discuss whether some common approximations made to build the model Hamiltonian are valid. We then consider the range of quantum dynamics approaches used to model the charge carrier dynamics stressing the strong and weak points of each method on the basis of the available computational results. Finally, we discuss non-trivial aspects and novel opportunities related to the comparison of theoretical predictions with recent experimental data.
Characterization of charge carrier behavior in photocatalysis using transient absorption spectroscopy
Authors: Miao Tina Jingyan , Tang Junwang
Published: May 2020

Photocatalysis is a promising sustainable method to generate solar fuels for the future, as well as having other applications such as water/air purification. However, the performance of photocatalysts is often limited by poor charge carrier dynamics. To improve charge carrier dynamics, it is necessary to characterize and understand charge carrier behavior in photocatalytic systems. This critical review will present Transient Absorption Spectroscopy (TAS) as a useful technique for understanding the behavior of photoexcited charges in semiconductor photocatalysts. The role of TAS amongst other techniques for characterizing charge carrier behavior will be outlined. Basic principles behind TAS will be introduced, and interpretation of TAS spectra and kinetics will be discussed in the context of exemplar literature. It will be demonstrated that TAS is a powerful technique to obtain fundamental understanding of the behavior of photoexcited charges.
Alkali atoms attached to vortex-hosting helium nanodroplets
Authors: García-Alfonso Ernesto , Coppens Francois , Barranco Manuel , Pi Martí , Stienkemeier Frank , Halberstadt Nadine
Published: May 2020

Light absorption or fluorescence excitation spectroscopy of alkali atoms attached to 4He droplets is investigated as a possible way for detecting the presence of vortices. To this end, we have calculated the equilibrium configuration and energetics of alkali atoms attached to a 4He1000 droplet hosting a vortex line using 4He density functional theory. We use them to study how the dipole absorption spectrum of the alkali atom is modified when the impurity is attached to a vortex line. Spectra are found to be blue-shifted (higher frequencies) and broadened compared to vortex-free droplets because the dimple in which the alkali atom sits at the intersection of the vortex line and the droplet surface is deeper. This effect is smaller for lighter alkali atoms and all the more so when using a quantum description since, in this case, they sit further away from the droplet surface on average due to their zero-point motion. Spectral modifications due to the presence of a vortex line are minor for np ← ns excitation and therefore insufficient for vortex detection. In the case of higher n′p ← ns or n′s ← ns (n′ > n) excitations, the shifts are larger as the excited state orbital is more extended and therefore more sensitive to changes in the surrounding helium density.
Assignment of vibrational states within configuration interaction calculations
Authors: Mathea Tina , Rauhut Guntram
Published: May 2020

The assignment of vibrational states is an integral part of quantum chemical calculations, which supports the analysis of experimental infrared spectra. In variational calculations, usually, it is the leading coefficient of the configuration interaction vector, which provides the state identity. However, this concept will possibly fail in case of special coordinate systems, such as, for example, localized normal coordinates, or within calculations for overtones of non-Abelian molecules, when a real valued configuration basis has been employed. A combination of both renders a proper assignment fairly tedious. We present a route to overcome this problem by using a highly efficient calculation of multidimensional overlap integrals based on the Smolyak quadrature. Beside this, a general protocol for the symmetry assignment of vibrational states will be discussed, which completes a general assignment. Extensive benchmark calculations are provided for the fundamental modes and overtones of chloromethane, CH3Cl, in canonical and localized normal coordinates based on accurate potential energy surfaces obtained from explicitly correlated coupled-cluster theory. In addition, the linear CNNC molecule has been studied, for which hardly any reference data do exist.
Role of photoelectric charge fluctuation in dust detachment from the lunar surface
Authors: Mishra S. K.
Published: May 2020

Electrostatic processes are argued to be of fundamental importance in understanding the particle dynamics and complex dusty plasma environment over airless bodies—the Moon has been of particular interest. Based on the theory of electrostatic charge fluctuation corresponding to the photoemission current, the fundamental problem of dust detachment from the lunar surface is addressed. By applying the charge fluctuation at the microscopic scale, we have quantified the magnitude of fluctuating charge density over the sunlit lunar surface and illustrated that it could induce a sufficient electric field to overcome the dust–surface adhesive van der Waals bonding through the electrostatic Coulomb repulsion. The analysis takes into account the dynamic equations for the statistical variables, viz., the mean charge and the variance, corresponding to the charge distribution over the microscopic spots exposed to the solar radiation. The photoemission under the influence of extreme ultraviolet Lyman α radiation in the solar spectrum and subsequent collection of the emitted photoelectrons are accounted for as the dominant charging processes of the lunar surface. Based on analysis and calculations, the fluctuating charge is illustrated to be a significant function of the spot size, which may induce significantly high electric field fluctuations locally. As an illustrative example, it is shown that one square micrometer spot may acquire ∼15 electronic charges and might induce a local electric field equivalent to ∼10 kV/m, which can support the detachment of the submicrometer dust particles from the lunar surface.
Multiple temperature model of nonlinear coupled constitutive relations for hypersonic diatomic gas flows
Authors: Yuan Zhenyu , Jiang Zhongzheng , Zhao Wenwen , Chen Weifang
Published: May 2020

The rotational energy of diatomic gases would be activated by the process of intermolecular collisions in high-temperature hypersonic flows. In this paper, a multi-temperature nonlinear coupled constitutive model has been proposed for simulating the transfer of energy between translational and rotational motions in hypersonic non-equilibrium flows. In this model, the nonlinear coupled constitutive equations are modified by introducing a rotational energy relaxation model and a changeable viscosity ratio related to local temperature. To confirm its accuracy, the new model is applied to investigate steady shock wave structures and high-speed gas flows around a cylinder and across a flat plate. The computational results are compared with the multi-temperature Navier–Stokes (NS) equations, the direct simulation Monte Carlo (DSMC) solutions, and the experiment data. The final results show the new model would reproduce the NS results at low Knudsen numbers but behave quite differently from the NS results as the non-equilibrium degree is enhanced. The new model is in better agreement with the DSMC solutions and the experimental data than the NS solutions in the far-from-equilibrium regions, which demonstrates the potential of the new relaxation model in the simulation of hypersonic non-equilibrium flows.
Offering subterranean clover can reduce methane emissions compared with perennial ryegrass pastures during late spring and summer in sheep
Authors: Muir S. K. , Kennedy A. J. , Kearney G. , Hutton P. , Thompson A. N. , Vercoe P. , Hill J.
Published: May 2020

Sheep production systems in south-west Victoria are based predominantly on perennial ryegrass pastures, resulting in highly seasonal growth and declining feed quantity and nutritive value in late spring and summer. These changes result in reduced animal performance and increased CH4 emissions per kg DM intake. A potential alternative to the feedbase used in south-west Victoria that provides high quality and quantity of feed in late spring and early summer are legume-based pastures, such as clovers and lucerne. This experiment examined the impact of legume-based pastures on the growth rates and CH4 emissions of Maternal Composite ewes during late spring and early summer. In 2014, 240 Maternal Composite ewes grazed either perennial ryegrass (Lolium perenne L.), lucerne (Medicago sativa L.), subterranean clover (Trifolium subterraneum L.) or arrowleaf clover (Trifolium vesiculosum Savi.) pastures for 6 weeks during late spring and early summer (November and December). Sheep grazing subterranean clover were heavier at the end of the experiment than sheep grazing perennial ryegrass. Methane measurements using portable accumulation chambers indicated lower daily CH4 emissions (g/day) from sheep grazing subterranean clover (23.5 g/day) than from sheep grazing lucerne (27.3 g/day) and perennial ryegrass (32.3 g/day) pastures. Methane emissions and liveweight changes appeared to be associated with the nutritive characteristics of the forage offered. Legume-based pastures provide sheep producers in south-west Victoria an option to increase growth rates and decrease CH4 emissions during a period when perennial ryegrass pastures are declining in nutritive value.
Enzyme-mediated depletion of serum
l
-Met abrogates prostate cancer growth via multiple mechanisms without evidence of systemic toxicity
Authors: Lu Wei-Cheng , Saha Achinto , Yan Wupeng , Garrison Kendra , Lamb Candice , Pandey Renu , Irani Seema , Lodi Alessia , Lu Xiyuan , Tiziani Stefano , Zhang Yan Jessie , Georgiou George , DiGiovanni John , Stone Everett
Published: May 2020

Extensive studies in prostate cancer and other malignancies have revealed that
l
-methionine (
l
-Met) and its metabolites play a critical role in tumorigenesis. Preclinical and clinical studies have demonstrated that systemic restriction of serum
l
-Met, either via partial dietary restriction or with bacterial
l
-Met–degrading enzymes exerts potent antitumor effects. However, administration of bacterial
l
-Met–degrading enzymes has not proven practical for human therapy because of problems with immunogenicity. As the human genome does not encode
l
-Met–degrading enzymes, we engineered the human cystathionine-γ-lyase (hMGL-4.0) to catalyze the selective degradation of
l
-Met. At therapeutically relevant dosing, hMGL-4.0 reduces serum
l
-Met levels to >75% for >72 h and significantly inhibits the growth of multiple prostate cancer allografts/xenografts without weight loss or toxicity. We demonstrate that in vitro, hMGL-4.0 causes tumor cell death, associated with increased reactive oxygen species, S-adenosyl-methionine depletion, global hypomethylation, induction of autophagy, and robust poly(ADP-ribose) polymerase (PARP) cleavage indicative of DNA damage and apoptosis.
Altered photoreceptor metabolism in mouse causes late stage age-related macular degeneration-like pathologies
Authors: Cheng Shun-Yun , Cipi Joris , Ma Shan , Hafler Brian P. , Kanadia Rahul N. , Brush Richard S. , Agbaga Martin-Paul , Punzo Claudio
Published: May 2020

Significance

The main cause for blindness in the elderly worldwide is age-related macular degeneration (AMD). What causes AMD remains unknown. The high metabolic demands of photoreceptors are thought to contribute to disease pathogenesis, yet whether photoreceptor metabolism differs in individuals with AMD has not been determined. Here, we show that photoreceptor metabolism does differ between diseased and nondiseased individuals. Mimicking the metabolic profile of diseased individuals in mouse resulted in the similar advanced pathologies as those that cause blindness in humans. A disease model with photoreceptors as a contributing factor explains also why AMD affects preferentially the macula; it is the region of highest photoreceptor density. The data might open new avenues to study the role of PRs in disease pathogenesis.
Untangling the sequence of events during the S
2
→ S
3
transition in photosystem II and implications for the water oxidation mechanism
Authors: Ibrahim Mohamed , Fransson Thomas , Chatterjee Ruchira , Cheah Mun Hon , Hussein Rana , Lassalle Louise , Sutherlin Kyle D. , Young Iris D. , Fuller Franklin D. , Gul Sheraz , Kim In-Sik , Simon Philipp S. , de Lichtenberg Casper , Chernev Petko , Bogacz Isabel , Pham Cindy C. , Orville Allen M. , Saichek Nicholas , Northen Trent , Batyuk Alexander , Carbajo Sergio , Alonso-Mori Roberto , Tono Kensuke , Owada Shigeki , Bhowmick Asmit , Bolotovsky Robert , Mendez Derek , Moriarty Nigel W. , Holton James M. , Dobbek Holger , Brewster Aaron S. , Adams Paul D. , Sauter Nicholas K. , Bergmann Uwe , Zouni Athina , Messinger Johannes , Kern Jan , Yachandra Vittal K. , Yano Junko
Published: May 2020

In oxygenic photosynthesis, light-driven oxidation of water to molecular oxygen is carried out by the oxygen-evolving complex (OEC) in photosystem II (PS II). Recently, we reported the room-temperature structures of PS II in the four (semi)stable S-states, S
1
, S
2
, S
3
, and S
0
, showing that a water molecule is inserted during the S
2
→ S
3
transition, as a new bridging O(H)-ligand between Mn1 and Ca. To understand the sequence of events leading to the formation of this last stable intermediate state before O
2
formation, we recorded diffraction and Mn X-ray emission spectroscopy (XES) data at several time points during the S
2
→ S
3
transition. At the electron acceptor site, changes due to the two-electron redox chemistry at the quinones, Q
A
and Q
B
, are observed. At the donor site, tyrosine Y
Z
and His190 H-bonded to it move by 50 µs after the second flash, and Glu189 moves away from Ca. This is followed by Mn1 and Mn4 moving apart, and the insertion of O
X
(H) at the open coordination site of Mn1. This water, possibly a ligand of Ca, could be supplied via a “water wheel”-like arrangement of five waters next to the OEC that is connected by a large channel to the bulk solvent. XES spectra show that Mn oxidation (τ of ∼350 µs) during the S
2
→ S
3
transition mirrors the appearance of O
X
electron density. This indicates that the oxidation state change and the insertion of water as a bridging atom between Mn1 and Ca are highly correlated.
Multiple areas of the cerebral cortex influence the stomach
Authors: Levinthal David J. , Strick Peter L.
Published: May 2020

Significance

Despite the longstanding appreciation that how we move, think, and feel has an impact on stomach function, the areas of the cerebral cortex that are the origin of these influences are largely unknown. Here we identify the cortical areas that influence the rat stomach. Output neurons in the rostral insula are the major cortical source of influence over parasympathetic control of the stomach, whereas output neurons in sensorimotor areas of the cortex are the major source of influence over sympathetic control. Thus, cortical areas involved in action, interoception, and emotion differentially influence stomach function.
Viral infection impacts transposable element transcript amounts in
Drosophila
Authors: Roy Marlène , Viginier Barbara , Saint-Michel Édouard , Arnaud Frédérick , Ratinier Maxime , Fablet Marie
Published: May 2020

Transposable elements (TEs) are genomic parasites that are found in all genomes, some of which display sequence similarity to certain viruses. In insects, TEs are controlled by the Piwi-interacting small interfering RNA (piRNA) pathway in gonads, while the small interfering RNA (siRNA) pathway is dedicated to TE somatic control and defense against viruses. So far, these two small interfering RNA pathways are considered to involve distinct molecular effectors and are described as independent. Using Sindbis virus (SINV) in
Drosophila
, here we show that viral infections affect TE transcript amounts via modulations of the piRNA and siRNA repertoires, with the clearest effects in somatic tissues. These results suggest that viral acute or chronic infections may impact TE activity and, thus, the tempo of genetic diversification. In addition, these results deserve further evolutionary considerations regarding potential benefits to the host, the virus, or the TEs.
Language sources and the reconstruction of early languages
Authors: Bauer Brigitte L. M.
Published: May 2020

This article argues that with the original emphasis on dialectal variation, using primarily literary texts from
various regions, analysis of Old French has routinely neglected social variation, providing an incomplete picture of its grammar.
Accordingly, Old French has been identified as typically featuring e.g. “pro-drop”, brace constructions, and single negation. Yet
examination of these features in informal texts, as opposed to the formal texts typically dealt with, demonstrates that these
documents do not corroborate the picture of Old French that is commonly presented in the linguistic literature. Our reconstruction
of Old French grammar therefore needs adjustment and further refinement, in particular by implementing sociolinguistic data. With
a broader scope, the call for inclusion of sociolinguistic variation may resonate in the investigation of other early languages,
resulting in the reassessment of the sources used, and reopening the debate about social variation in dead languages and its role
in language evolution.
Ubiquitin links smoothened to intraflagellar transport to regulate Hedgehog signaling
Authors: Desai Paurav B. , Stuck Michael W. , Lv Bo , Pazour Gregory J.
Published: May 2020

In the absence of Hedgehog ligand, patched-1 (Ptch1) localizes to cilia and prevents ciliary accumulation and activation of smoothened (Smo). Upon ligand binding, Ptch1 is removed from cilia, and Smo is derepressed and accumulates in cilia where it activates signaling. The mechanisms regulating these dynamic movements are not well understood, but defects in intraflagellar transport components, including Ift27 and the BBSome, cause Smo to accumulate in cilia without pathway activation. We find that in the absence of ligand-induced pathway activation, Smo is ubiquitinated and removed from cilia, and this process is dependent on Ift27 and BBSome components. Activation of Hedgehog signaling decreases Smo ubiquitination and ciliary removal, resulting in its accumulation. Blocking ubiquitination of Smo by an E1 ligase inhibitor or by mutating two lysine residues in intracellular loop three causes Smo to aberrantly accumulate in cilia without pathway activation. These data provide a mechanism to control Smo’s ciliary level during Hedgehog signaling by regulating the ubiquitination state of the receptor.
Pronounced structural crossover in water at supercritical pressures
Authors: Cockrell C , Dicks O A , Brazhkin V V , Trachenko K
Published: May 2020

There have been ample studies of the many phases of H2O in both its solid and low pressure liquid states, and the transitions between them. Using molecular dynamics simulations we address the hitherto unexplored deeply supercritical pressures, where no qualitative transitions are thought to take place and where all properties are expected to vary smoothly. On the basis of these simulations we predict that water at supercritical pressures undergoes a structural crossover across the Frenkel line at pressures as high as 45 times the critical pressure. This provides a new insight into the water phase diagram and establishes a link between the structural and dynamical properties of supercritical water. Specifically, the crossover is demonstrated by a sharp and pronounced at low pressures, and smooth at high pressures, signified by changes in the pair distribution functions and local coordination which coincide with the dynamical transition (the loss of all oscillatory molecular motion) at the Frenkel line on the phase diagram.
Theoretical polarization of zero phonon lines in point defects
Authors: Davidsson Joel
Published: May 2020

In quantum technologies, point defects in semiconductors are becoming more significant. Understanding the frequency, intensity, and polarization of the zero phonon line is important. The last two properties are the subject of this paper. I present a method for calculating these properties and show the importance of using wave functions from both the ground and excited state. The validity of this method is demonstrated on the divacancy in 4H-SiC. Here, the calculated polarization and radiative lifetimes are in excellent agreement with experimental measurements. In general, this method can help to identify point defects and estimate suitable applications.
Proteins at curved fluid–fluid interfaces in a coarse-grained model
Authors: Zhao Yani , Cieplak Marek
Published: May 2020

We employ an empirical coarse-grained model with a proposed Gaussian-like interfacial potential to describe proteins at curved fluid–fluid interfaces such as occurring in bubbles and droplets. We consider the air–water and oil–water interfaces. We study the mass distributions and the geometry of the aqueous proteins as a function of the radius of curvature for protein G and two lipid transfer proteins. At curved interfaces the distortion of the proteins is different than at flat interfaces. We find that the proteins come closer to the surface of a bubble than to the surface of similarly curved droplet. In addition, the bubbles adsorb more proteins. We identify the pinning residues. We demonstrate the existence of the second layer in the density profile for sufficiently dense solutions.
Evaluation of irradiation effects on the microstructure and properties of Ag-sheathed Bi-2212 superconducting round wire for future application in CFETR
Authors: Li Zuoguang , Zhu Hongmei , Qiu Changjun , Yang Dongsheng , Qin Jinggang , Zhou Chao
Published: May 2020

The Chinese Fusion Engineering Test Reactor (CFETR) is designed to build a fusion engineering Tokamak reactor generating fusion power of 200–1500 MW, and to test the breeding tritium during fusion reaction. This may require a maximum magnetic field up to 15 T in the central solenoid and toroidal field coils. New superconducting materials should be developed for satisfying the next-generation fusion reactors with critical requirements. Recently, Bi2Sr2CaCu2Ox (denoted as Bi-2212) is considered as one of the most promising potential superconductors to be used as the magnets in CFETR, however, they will be subjected to harsh irradiation under operating conditions. The irradiation effects of the high-energy helium ions on the Ag-sheathed Bi-2212 superconducting round wire have been explored for the first time in this work. The microstructure and the critical current at 4.2 K of the superconducting wire before and after irradiation have been carefully investigated. Room-temperature x-ray diffraction (XRD) profiles showed that all the peaks shifted rightward significantly with a broadened (111)Ag peak, indicating that the high-energy He+ irradiation resulted in appreciable defects and strain in the superconducting wire. Meanwhile, the in-situ high-temperature XRD tests showed that the lattice constant and the thermal expansion coefficient were deduced in the irradiated sample to be due to the presence of the generated defects. After irradiation, the grain size of the Ag sheath was refined, and the lattice of Bi-2212 superconductor was distorted obviously, as confirmed by transmission electronic microscopy. The critical current IC at 4.2 K of the superconducting wires in the field of 0–12T determined by the four-probe technique, decreased substantially after irradiation because of the lattice distortion and the consequently induced strain in the Bi-2212 superconductor. This work provides a solid basis for evaluating and understanding the irradiation effects upon the Ag-sheathed Bi-2212 superconducting wire, more promising for future application in CFETR.