bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation studies of divertor power exhaust with neon seeding for CFETR with GW-level fusion power
Authors: Liu X. J. , Xu G. L. , Ding R. , Jia G. Z. , Sang C. F. , Si H. , Nian F. F. , Yang Z. S. , Li G. Q. , Chan V. S. , Deng G. Z. , Gao S. L. , Gao X.
Published: September 2020

A conventional single null divertor geometry has been proposed for Chinese fusion engineering testing reactor (CFETR) with fusion power up to gigawatt level. Modeling using the SOLPS5.0 code package shows promising results for divertor power exhaust by seeding with neon (Ne) and deuterium (D2). Partial detachment for both inner and outer divertor targets can be achieved with a peak heat load lower than 3 MW/m2. The effective ion charge number, Zeff, at the core boundary is below three, which can be further reduced by increasing the upstream D2 puffing rate. A higher D2 puffing rate helps to increase electron density (ne) in scrape-off layer (SOL) and the impurity screening ability. Based on the SOLPS modeling results, the lifetime of tungsten (W) divertor targets has been estimated by using the DIVIMP code, which indicates that W sputtering is mainly contributed by Ne ions at a far SOL region due to high electron and ion temperature (Te and Ti) there. Upstream D2 puffing can reduce the W erosion rate and W impurity concentration inside the separatrix due to decreasing Te and Ti at the far SOL region. The modeling results show a viable operation regime for the CFETR divertor.
Fragility and correlated dynamics in supercooled liquids
Authors: Banerjee Atreyee , Wales David J.
Published: September 2020

A connection between the super-Arrhenius behavior of dynamical properties and the correlated dynamics for supercooled liquids is examined for a well known glass forming binary Lennard-Jones mixture and its repulsive counterpart, the Weeks–Chandler–Andersen potential, over a range of densities. When considering short time nonergodic trajectory segments of a longer ergodic trajectory, we observe that, independent of the potentials and densities, the apparent diffusivity follows Arrhenius behavior until low temperatures. Comparing the two potentials, where the ergodic diffusivities are known to be rather different, we find that the short-time nonergodic part is similar throughout the temperature range. By including a correlation factor in the nonergodic diffusivity, a rescaled value is calculated, which provides a reasonable estimate of the true ergodic diffusivity. The true diffusion coefficient and the correction factor collapse to a master plot for all densities at any given time interval. Hence, our results confirm a strong connection between fragility and dynamical correlation.
First-principles study on effects of local Coulomb repulsion and Hund's coupling in ferromagnetic semiconductor CrGeTe3
Authors: Ko Eunjung , Son Young-Woo
Published: September 2020

Based on a first-principles computational method treating the local Coulomb repulsion of U and Hund's coupling of J separately, we investigate the effects of these important interactions on the electronic and magnetic structures of a layered ferromagnetic semiconductor CrGeTe3. We show that explicit inclusion of a density functional for the coupling J is critical to obtain proper bandgaps of a single-layer and bulk systems with a reasonable U, unlike a usual approximation treating those together. After obtaining reliable U and J, we also study the effects of strain on its energy gap. Within 2% of tensile and compressive strains, respectively, there is no strain-induced semiconductor-to-metal transition, contrary to the results without J, thus highlighting important roles of exchange interactions.
Multivariate optimization applied for the economic competitiveness analysis of photothermal systems into industrial heat production: An approach based on artificial intelligence
Authors: May Tzuc O. , Bassam A. , Anguebes-Franseschi F. , Ricalde Luis J. , Flota-Bañuelos Manuel , Castillo Téllez Margarita
Published: September 2020

This work studies the economic feasibility of using a hybrid solar energy system to satisfy the thermal demand in industrial processes. From an artificial intelligence perspective, a modeling and computational optimization methodology was developed for the design of a hybrid solar thermal plant. Modeling is applied to satisfy the needs of a pasteurization process in the region of Jalisco, Mexico. Scenarios with four different types of fossil fuels used in the backup system were analyzed. According to the optimization results, all the backup fossil fuel scenarios demonstrate economic viability. Furthermore, the present value studies indicate that under the appropriate climatic conditions, for the four auxiliary fuel scenarios, the optimization methodology can produce economically attractive configurations of the solar thermal plant for investors. The presented methodological procedure can be easily adapted and used to analyze the financial competitiveness of other solar thermal technologies for the industrial heat generation.
Ultrafast demagnetization of ferromagnetic semiconductor InMnAs by dual terahertz and infrared excitations
Authors: Mashkovich E. A. , Grishunin K. A. , Munekata H. , Kimel A. V.
Published: September 2020

Subpicosecond pumping of ferromagnetic semiconductor InMnAs in the ranges of intra- and interband electronic transitions can result in an efficient demagnetization of the medium up to 60% of the initial magnetic moment. Here, we report about the efficiency of ultrafast demagnetization by a duo of terahertz and infrared pulses that trigger intra- and interband electronic transitions, respectively. Varying the intensities of the pulses and the delay between them, we study the degree of demagnetization caused by the pulse duo. It is shown that the result of the excitation does not depend on the pulse sequence. Our findings indicate that both intra- and interband electronic transitions result in ultrafast demagnetization of the semiconductor via the very same mechanism, which evolves at a ps timescale. Independent of the origin of the electronic transition, ultrafast demagnetization is a result of a temperature increase in the free charge carriers (holes).
Determination of carrier recombination velocity at inclined grain boundaries in multicrystalline silicon through photoluminescence imaging and carrier simulation
Authors: Mitamura Kazuki , Kutsukake Kentaro , Kojima Takuto , Usami Noritaka
Published: September 2020

We present a quantification method of carrier recombination velocity of a general grain boundary (GB) by combining steady state photoluminescence (PL) imaging and carrier simulation under uniform illumination. To improve the accuracy and versatility, inclination angles of GBs, which can be obtained from front and rear optical images, were included in the carrier simulation model. As a consequence, simulated PL profiles successfully reproduced the tendency of experiments to exhibit shift of the minimal position from the GB on the front surface to the direction of inclination. Furthermore, by fitting simulated PL profiles with experiments, the carrier recombination velocity was evaluated for various GBs based on the improved model to consider the inclination angle.
Electrically stable Ag nanowire network anodes densely passivated by a conductive amorphous InSnTiO layer for flexible organic photovoltaics
Authors: Lan Shuai , Shin Hae-In , Kim Han-Ki
Published: September 2020

An electrically stable Ag nanowire (Ag NW) network was fabricated by passivating with a conductive amorphous InSnTiO (ISTO) layer. It could be used in flexible transparent conductive electrodes for flexible organic photovoltaics. By plasma damage-free sputtering of amorphous ISTO on Ag NWs, sulfurization of Ag NWs was effectively prevented without sacrificing sheet resistance (44.5 Ω/sq.), optical transmittance (87.2%), or mechanical flexibility. Flexible organic solar cells (OSCs) fabricated on ISTO covered Ag NW network anodes showed slightly higher power conversion efficiency (5.94%) than reference OSCs with ITO anodes (5.79%). These results demonstrate that passivation of Ag NWs by amorphous conductive ISTO is a useful approach to improving the reliability of Ag NW network electrodes for high-performance flexible OSCs because the amorphous compact structure can effectively prevent the diffusion of sulfur from ambient air.
Mn-intercalated MoSe2 under pressure: Electronic structure and vibrational characterization of a dilute magnetic semiconductor
Authors: Chen Shunda , Johnson Virginia L. , Donadio Davide , Koski Kristie J.
Published: September 2020

Intercalation offers a promising way to alter the physical properties of two-dimensional (2D) layered materials. Here, we investigate the electronic and vibrational properties of 2D layered MoSe2 intercalated with atomic manganese at ambient and high pressure up to 7 GPa by Raman scattering and electronic structure calculations. The behavior of optical phonons is studied experimentally with a diamond anvil cell and computationally through density functional theory calculations. Experiment and theory show excellent agreement in optical phonon behavior. The previously Raman inactive A2u mode is activated and enhanced with intercalation and pressure, and a new Raman mode appears upon decompression, indicating a possible onset of a localized structural transition, involving the bonding or trapping of the intercalant in 2D layered materials. Density functional theory calculations reveal a shift of the Fermi level into the conduction band and spin polarization in MnxMoSe2 that increases at low Mn concentrations and low pressure. Our results suggest that intercalation and pressurization of van der Waals materials may allow one to obtain dilute magnetic semiconductors with controllable properties, providing a viable route for the development of new materials for spintronic applications.
In-situ spectroscopic analysis of the recombination kinetics in UVB LEDs during their operation
Authors: Ruschel Jan , Glaab Johannes , Mahler Felix , Kolbe Tim , Einfeldt Sven , Tomm Jens W.
Published: September 2020

The recombination kinetics in the quantum well (QW) active region of ultraviolet light emitting diodes have been measured in situ during device operation. Non-radiative recombination is enhanced with increasing operation time. Saturation effects allow us to estimate that the density of non-radiative recombination centers in the QW layers increases by ∼5 × 1015 cm−3 after operation. Corresponding defects are proposed to be present in the pristine device already. The recombination kinetics after optical excitation can be controlled by an additionally applied DC. The experimental approach allows the direct comparison and quantification of the effects of optically and electrically generated non-equilibrium carriers on the QW luminescence.
Hydrogen desorption from silicane and germanane crystals: Toward creation of free-standing monolayer silicene and germanene
Authors: Araidai Masaaki , Itoh Mai , Kurosawa Masashi , Ohta Akio , Shiraishi Kenji
Published: September 2020

We investigate hydrogen desorptions from monolayer and multilayer graphane analogs, namely, silicane (SiH) and germanane (GeH), by the first-principles calculations. It is found from the calculated pressure–temperature diagrams of the monolayer and multilayer SiH and GeH crystals that the hydrogen atoms can be removed by heating and reducing hydrogen partial pressure. We also perform thermal-desorption-spectroscopy measurements for the multilayer crystals in order to demonstrate the validity of the theoretical calculations, and it turns out that the theoretical results are worth believing. Our theoretical results for monolayer SiH/GeH crystals indicate monolayer SiH and GeH crystals possess high potential to find their application as a precursor to free-standing monolayer silicene and germanene, respectively.
Molecular second-quantized Hamiltonian: Electron correlation and non-adiabatic coupling treated on an equal footing
Authors: Sibaev Marat , Polyak Iakov , Manby Frederick R. , Knowles Peter J.
Published: September 2020

We introduce a new theoretical and computational framework for treating molecular quantum mechanics without the Born–Oppenheimer approximation. The molecular wavefunction is represented in a tensor-product space of electronic and vibrational basis functions, with electronic basis chosen to reproduce the mean-field electronic structure at all geometries. We show how to transform the Hamiltonian to a fully second-quantized form with creation/annihilation operators for electronic and vibrational quantum particles, paving the way for polynomial-scaling approximations to the tensor-product space formalism. In addition, we make a proof-of-principle application of the new Ansatz to the vibronic spectrum of C2.
Joint evaluation of internal quantum efficiency and light extraction efficiency for AlGaN-based deep ultraviolet LEDs considering optical polarization properties
Authors: Lu Huimin , Chen Mengru , Wang Hui , Yu Tongjun , Wang Jianping
Published: September 2020

In this work, a joint evaluation method for the internal quantum efficiency (IQE) and light extraction efficiency (LEE) for AlGaN-based deep ultraviolet (DUV) light emitting diodes (LEDs) is proposed by fully considering the optical polarization properties. In this method, the IQE curve varying with the forward current can be reconstructed from a few measurement data at a small injection level. The corresponding LEE can be determined using the composition of spontaneous emission light with transverse electric and transverse magnetic components at different forward currents. The proposed method is applied for the efficiency evaluation of the AlGaN-based LED sample and verified by comparing with the EQE result deduced from the measured light output power–current (L–I) characteristic. It is demonstrated that the very low EQE and significant efficiency droop is from not only IQE but also LEE for AlGaN-based DUV LEDs.
Effects of anisotropic scattering on the onset of phototactic bioconvection with diffuse and collimated irradiation
Authors: Panda M. K.
Published: September 2020

The ability of many photosynthetic micro-organisms (algae) to detect a localized light source in their environment and move toward (away from) it is known as positive (negative) phototaxis. The phototactic algae absorb the incident light and scatter it isotropically or anisotropically thereafter across the suspension, which is illuminated by both diffuse and collimated irradiation. In this paper, we use the generic model of Panda et al. [“Effects of both diffuse and collimated incident radiation on phototactic bioconvection,” Phys. Fluids 28, 124104 (2016)] for phototaxis and investigate the effects of anisotropic (forward) scattering at the onset of phototactic bioconvection. In the motionless basic state, the up and down swimming caused by positive and negative phototaxis is balanced by diffusion due to randomness in the swimming behavior of algae. The forward scattering improves the underwater light distribution (radiation field) by propagating the light deeper into the algal suspension. At the equilibrium state, the bimodal (respectively, unimodal) base concentration profiles are shifted into the unimodal (respectively, bimodal) ones due to forward scattering for some fixed governing parameters when self-shading (absorption) is insignificant. As a result of forward scattering, for some parameter values, the most unstable solution shifts from mode 1 to mode 2 and a single oscillatory branch bifurcates from the stationary branch or disappears at bioconvective instability when self-shading (absorption) is significant. The dominant bioconvection pattern wavelength at instability is also qualitatively in good agreement with the experimental observations as the forward scattering coefficient is varied.
Monitoring laser-induced magnetization in FeRh by transient terahertz emission spectroscopy
Authors: Awari N. , Semisalova A. , Deinert J.-C. , Lenz K. , Lindner J. , Fullerton E. , Uhlíř V. , Li J. , Clemens B. , Carley R. , Scherz A. , Kovalev S. , Gensch M.
Published: September 2020

In this study, a conceptually different approach for investigating magnetic phase transitions in ultra-thin films is presented. THz emission from a laser-excited material is used to monitor the magnetization dynamics during the laser-driven antiferromagnetic to ferromagnetic transition in FeRh. The emitted THz signal is calibrated against static magnetometry data measurements, giving a direct measure of the absolute magnetic moment of the sample on the sub-picosecond timescale. The technique is, therefore, highly complementary to conventional time-resolved experiments such as time resolved magneto-optic Kerr effect (MOKE) or x-ray magnetic circular dichroism.
Experimental investigations on flow over a circular cylinder placed in a circular pipe
Authors: Arumuru Venugopal , Agrawal Amit , Prabhu S. V.
Published: September 2020

Flow over a circular cylinder placed inside a circular pipe is studied experimentally to understand the influence of Reynolds numbers (ReD = DUav/υ, where D is the diameter of the pipe, Uav is the average velocity in the pipe, and υ is the kinematic viscosity of the fluid) and blockage effects. In the present configuration, the influence of confinement, aspect ratio, upstream turbulence, shear, and end conditions coexists together. The wake dynamics of such a configuration are seldom reported in the literature. The Reynolds number range covered in the present study is ReD = 200–2.0 × 105. Four different flow regimes are defined based on the Reynolds number: steady, unsteady laminar, transition, and turbulent. In the unsteady laminar regime, the Strouhal number (St = fd/Uav, where f is the frequency of vortex shedding and d is the diameter of the bluff body) increases gradually. In the transition regime, a gradual fall in St is observed for all blockage ratios (d/D). In the turbulent regime, the upstream flow becomes fully turbulent, and the Strouhal number remains constant. The spanwise pressure distribution is influenced due to the blockage effects near the wall. The separation point moves 20° toward the rear stagnation point close to the wall compared to the center in the turbulent regime. A universal relation for the drag coefficient is proposed based on the pressure at the stagnation and separation points. The universal Strouhal number defined based on the wake width and velocity at the separation (Us) is shown to be independent of the blockage ratio. The results presented in the manuscript are relatively new in the domain of confined bluff body flows and will serve to enhance the general understanding of confined bluff body vortex dynamics.
Probing the trap states in N–i–P Sb2(S,Se)3 solar cells by deep-level transient spectroscopy
Authors: Lian Weitao , Tang Rongfeng , Ma Yuyuan , Wu Chunyan , Chen Chao , Wang Xiaomin , Fang Fang , Zhang Jianwang , Wang Zheng , Ju Huanxin , Zhu Changfei , Chen Tao
Published: September 2020

In this study, we provide fundamental understanding on defect properties of the Sb2(S,Se)3 absorber film and the impact on transmission of photo-excited carriers in N–i–P architecture solar cells by both deep level transient spectroscopy (DLTS) and optical deep level transient spectroscopy (ODLTS) characterizations. Through conductance–voltage and temperature-dependent current–voltage characterization under a dark condition, we find that the Sb2(S,Se)3 solar cell demonstrates good rectification and high temperature tolerance. The DLTS results indicates that there are two types of deep level hole traps H1 and H2 with active energy of 0.52 eV and 0.76 eV in the Sb2(S,Se)3 film, and this defect property is further verified by ODLTS. The two traps hinder the transmission of minority carrier (hole) and pinning the Fermi level, which plays a negative role in the improvement of open-circuit voltage for Sb2(S,Se)3 solar cells. This research suggests a critical direction toward the efficiency improvement of Sb2(S,Se)3 solar cells.
Molecular theory of Langevin dynamics for active self-diffusiophoretic colloids
Authors: Robertson Bryan , Schofield Jeremy , Gaspard Pierre , Kapral Raymond
Published: September 2020

Active colloidal particles that are propelled by a self-diffusiophoretic mechanism are often described by Langevin equations that are either postulated on physical grounds or derived using the methods of fluctuating hydrodynamics. While these descriptions are appropriate for colloids of micrometric and larger size, they will break down for very small active particles. A fully microscopic derivation of Langevin equations for self-diffusiophoretic particles powered by chemical reactions catalyzed asymmetrically by the colloid is given in this paper. The derivation provides microscopic expressions for the translational and rotational friction tensors, as well as reaction rate coefficients appearing in the Langevin equations. The diffusiophoretic force and torque are expressed in terms of nonequilibrium averages of fluid fields that satisfy generalized transport equations. The results provide a description of active motion on small scales where descriptions in terms of coarse grained continuum fluid equations combined with boundary conditions that account for the presence of the colloid may not be appropriate.
A mean-field model of linker-mediated colloidal interactions
Authors: Rogers W. Benjamin
Published: September 2020

Programmable self-assembly is one of the most promising strategies for making ensembles of nanostructures from synthetic components. Yet, predicting the phase behavior that emerges from a complex mixture of many interacting species is difficult, and designing such a system to exhibit a prescribed behavior is even more challenging. In this article, I develop a mean-field model for predicting linker-mediated interactions between DNA-coated colloids, in which the interactions are encoded in DNA molecules dispersed in solution instead of in molecules grafted to particles’ surfaces. As I show, encoding interactions in the sequences of free DNA oligomers leads to new behavior, such as a re-entrant melting transition and a temperature-independent binding free energy per kBT. This unique phase behavior results from a per-bridge binding free energy that is a nonlinear function of the temperature and a nonmonotonic function of the linker concentration, owing to subtle entropic contributions. To facilitate the design of experiments, I also develop two scaling limits of the full model that can be used to select the DNA sequences and linker concentrations needed to program a specific behavior or favor the formation of a prescribed target structure. These results could ultimately enable the programming and tuning of hundreds of mutual interactions by designing cocktails of linker sequences, thus pushing the field toward the original goal of programmable self-assembly: these user-prescribed structures can be assembled from complex mixtures of building blocks through the rational design of their interactions.
Experimental study of multiple magnetic transitions in micrometer and nano-grain sized Ni3TeO6-type oxide
Authors: Panneer Muthuselvam I. , Saranya K. , Sankar R. , Bhowmik R. N. , Kavitha L.
Published: September 2020

We report the experimental results of dc and ac magnetic susceptibility (χdc and χac) and specific heat (CP) measurements of the powdered Ni3TeO6-type oxide. Upon decreasing the grain size from micrometer (bulk) to nanometer range, the magnetic measurements have indicated multiple transitions, viz., a cusp at paramagnetic to ferrimagnetic (FIM) transition temperature (TC) ∼ 78 K, an antiferromagnetic (AFM) transition temperature (TN) ∼ 52 K, and a re-entrant spin glass (RSG) transition at Tm2 ∼ 7.49 K. The ferrimagnetic transition temperature TC is found to be highly sensitive to dc magnetic fields, where superposition of a small dc field (10 Oe) in the ac susceptibility measurement or the application of a dc magnetic field of up to 100 Oe in the dc magnetic measurement is enough to suppress the observed TC at 78 K. The CP(T) measurement also revealed a RSG state at lower temperatures for the sample with nano-sized grains. The absence of any sharp peak at TC in the CP(T) curves implies the absence of a true long-range FIM spin order in the samples. The coexistence of a RSG state with multiple magnetic transitions is understood as an effect of competitive AFM and FIM phases in the Ni3TeO6-type structure.
Phase-field simulation of two-dimensional topological charges in nematic liquid crystals
Authors: Liang Deshan , Ma Xingqiao , Liu Zhuhong , Jafri Hasnain Mehdi , Cao Guoping , Huang Houbing , Shi Sanqiang , Chen Long-Qing
Published: September 2020

The concept of topological quantum number, or topological charge, has been used extensively to describe topological defects or solitons. Nematic liquid crystals contain both integer and half-integer topological defects, making them useful models for testing the rules that govern topological defects. Here, we investigated topological defects in nematic liquid crystals using the phase-field method. If there are no defects along a loop path, the total charge number is described by an encircled loop integral. We found that the total charge number is conserved, and the conservation of defects number is determined by a boundary during the generation and annihilation of positive–negative topological defects when the loop integral is confined. These rules can be extended to other two-dimensional systems with topological defects.
Numerical investigation of quasi-sessile droplet absorption into wound dressing capillaries
Authors: Andredaki M. , Georgoulas A. , Marengo M.
Published: September 2020

The key concept in wound dressing design and development is the fact that keeping a wound moist accelerates healing. Therefore, the selection of the appropriate wound dressing type is vital. The absorption of wound exudate by wound dressings can be considered as a microfluidic phenomenon that can be investigated either by performing high resolution laboratory experiments or by utilizing high resolution Computational Fluid Dynamics numerical simulations. As an initial step, in the present paper, the effects of the pore size (wound dressing porosity), the liquid (wound exudate) viscosity, and the initial droplet diameter are numerically investigated using a simplified analog of the phenomenon that consists of a quasi-sessile droplet being absorbed by a single cylindrical pore. For this purpose, an enhanced Volume Of Fluid model, developed in the general context of OpenFOAM, is validated and applied. It is found that distinct droplet absorption rates exist with specific relationships derived using best-fit lines that can predict the absorption rates for particular values of pore size and liquid viscosity. For the examined Eo and Oh number ranges (0.0015 < Eo < 0.15 and 0.0035 < Oh < 0.095), these distinct droplet absorption rates are directly linked with four different droplet evolution regimes that are grouped in a well-defined flow map. Finally, it is shown that the resulting liquid absorption rates are not significantly affected by the initial droplet diameter and that an appropriate wound dressing porosity can be selected by an estimation of the wound exudate physical properties.
Ultrafast dynamics and short-lived carriers in Cu nitride and oxynitride layers
Authors: Sergides Marios , Zervos Matthew , Othonos Andreas
Published: September 2020

Ultrafast carrier dynamics in copper nitride (Cu3N) have been investigated using femtosecond pump-probe spectroscopy. Cu3N films were prepared on fused SiO2 substrates coated with thin Cu layers under NH3:O2 flow. The obtained differential transmission data revealed discrete maxima in the spectra at different probing energies. Lower energy maxima are attributed to direct bandgap transitions, while transient transmission peaks at higher energies are due to probing defect state transitions in the material. These states originate from crystalline structure defects and are energetically located close to the conduction and valence bands. The recombination times extracted from the data were of the order of few picoseconds which raises the question of how suitable this material is for energy conversion applications. Ultrafast pump-probe spectra obtained at a low temperature of 78 K revealed almost no shifting of the transition energies compared to room temperature spectra, although small differences in decay times were observed due to the absence of thermal effects. Measurements using longer probing wavelengths in the infrared region indicated state filling of defect states within the bandgap for wavelengths between 800 nm and 1400 nm while probing at longer wavelengths (1400–1600 nm) revealed initial free-carrier absorption and re-excitation of carriers to higher energy defect states above the conduction band. In addition, copper oxynitride layers were produced and studied in a similar fashion to investigate the effects of oxygen on the band structure and recombination times.
Unusual conduction mechanism of n-type β-Ga2O3: A shallow donor electron paramagnetic resonance analysis
Authors: von Bardeleben H. J. , Cantin J. L.
Published: September 2020

We have investigated the conduction mechanism in n-type, Si doped β-Ga2O3 bulk samples and evidenced carrier dynamics in the GHz frequency range at room temperature by electron paramagnetic resonance (EPR) spectroscopy. The Si shallow donor EPR and conduction electron spin resonance (CESR) spectra show an unusual temperature dependence of the linewidth and line shape, which reveals a variable range hopping conduction and donor clustering. The temperature dependence of the EPR signal intensity can be fitted with two thermally activated processes with energies of 4 meV and 40 meV in the below and above 40 K temperature range. The value of 40 meV is attributed to the ionization energy of the Si shallow donor, indicating that hopping proceeds via the conduction band. Above T = 130 K and up to room temperature, the conduction electron spin resonance (CESR) can be observed with a decreasing linewidth of ΔB < 1 G, which indicates negligible spin flip scattering. To illustrate the unusual behavior of the shallow donor in Ga2O3, we have analyzed the hydrogen shallow donor in ZnO, for which we observe a different “classical” behavior, characterized by donor localization below 40 K and thermal ionization in the conduction band above T = 90 K. In ZnO, the CESR can only be observed in a small temperature range at 90 K due to excessive line broadening for higher temperatures.
COVID-19 in the United States: Trajectories and second surge behavior
Authors: James Nick , Menzies Max
Published: September 2020

This paper introduces a mathematical framework for determining second surge behavior of COVID-19 cases in the United States. Within this framework, a flexible algorithmic approach selects a set of turning points for each state, computes distances between them, and determines whether each state is in (or over) a first or second surge. Then, appropriate distances between normalized time series are used to further analyze the relationships between case trajectories on a month-by-month basis. Our algorithm shows that 31 states are experiencing second surges, while four of the 10 largest states are still in their first surge, with case counts that have never decreased. This analysis can aid in highlighting the most and least successful state responses to COVID-19.
Anisotropic thermionic response of Weyl semimetals with application in thermionic cooling
Authors: Zuber J. W. , Zhang C.
Published: September 2020

We demonstrate that Weyl semimetals can exhibit intriguing thermionic properties. The emission current varies significantly in systems with different Weyl point separation, the key topological parameter of such materials. The emission is highly anisotropic along directions parallel and perpendicular to the Weyl point separation. For large separations, emission is higher along the perpendicular direction. However, for smaller separations, there exists a changeover temperature at which the dominant emission direction changes from parallel to perpendicular when increasing temperature. The optimal cooling efficiency of a single barrier device can approach 80% of the theoretical limit in the perpendicular direction, 5% greater than a conventional parabolic material. Our results suggest that this class of material has potential applications in thermionic cooling and power generation.
Essential Electron Transport for Device Physics
Authors: Levi A. F. J.
Published: September 2020

Essential Electron Transport for Device Physics introduces key elements of electron transport most applicable to the study of semiconductor electron devices. It is a convenient reference and summary of fundamental knowledge to be understood before exploring more sophisticated electron device models and concepts.

The contents serve as a foundation for scientists and engineers, without the need to invest in specialized detailed study.
Program description and implementation findings of MyCare: enhancing community mental health care in Tasmania, Australia
Authors: O'Donnell Renee , Ayton Darshini , Pizzirani Bengianni , Savaglio Melissa , Fast Debra , Vicary Dave , Skouteris Helen
Published: September 2020

Since 2014, Tasmania has experienced unprecedented rates of hospitalisations related to mental health issues. To address reliance on such acute-based care, government funding was invested to enhance community-based care, which, in turn, led to the development of MyCare. This paper represents the initial phase of a larger body of work (i.e. an effectiveness-controlled trial of MyCare) that describes the MyCare program and the successful implementation strategy underpinning the program. The implementation of MyCare was evaluated with 41 key stakeholders (staff, clients and senior executives) using semistructured interviews and focus groups, informed by the Consolidated Framework for Implementation Research (CFIR). According to stakeholders, three CFIR constructs that were directly addressed by the program, namely Tension for Change, Evidence Strength and Quality, and Available Resources for Implementation, facilitated the successful implementation of MyCare. In contrast, a feature of the program that impeded implementation was Patient Needs and Resources, which restricted program access to those with the most severe mental health issues. The reporting of implementation strategies underpinning mental health programs is rare. This study describes the implementation strategy underpinning a community-based mental health program that was successful in facilitating program uptake. We encourage other researchers to not only report on implementation findings, which may help avoid replication failure, but also to apply these innovative implementation processes (i.e. address the tension for change and ensure the program is evidence informed and that sufficient resources are available for implementation) within mental health programs to aid successful uptake.
Enabling early detection of osteoarthritis from presymptomatic cartilage texture maps via transport-based learning
Authors: Kundu Shinjini , Ashinsky Beth G. , Bouhrara Mustapha , Dam Erik B. , Demehri Shadpour , Shifat-E-Rabbi Mohammad , Spencer Richard G. , Urish Kenneth L. , Rohde Gustavo K.
Published: September 2020

Significance

Many diseases lack visual cues in early stages, eluding image-based detection. Today, osteoarthritis is diagnosed at an irreversible stage after bone damage has occurred. This research demonstrates that osteoarthritis detection in healthy individuals may be possible 3 y prior to symptoms or bone damage. We describe a technique combining mass transport theory with statistical pattern recognition, discovering sensitive cartilage phenotypes that predict future osteoarthritis progression with high accuracy. As our approach is based on mass transport principles, the cartilage phenotype defining predictive ability can be directly visualized, a key contribution of this work. This research demonstrates that transport-based learning might enable early osteoarthritis detection and visualization at a potentially reversible stage.
Localized foundering of Indian lower crust in the India–Tibet collision zone
Authors: Shi Danian , Klemperer Simon L. , Shi Jianyu , Wu Zhenhan , Zhao Wenjin
Published: September 2020

Significance

Although plate tectonics explains subduction of oceanic crust, the areally distributed deformation observed in continental collision requires more complex explanations of the geometric interaction of two colliding continents and the mechanics of plateau formation. Our seismic images reveal variations of the India–Tibet collision parallel to the Himalaya. Our observation of localized thinning of Indian lower crust, that is sufficiently extreme as to require material loss presumably into the underlying mantle, is an advance in explaining the apparent lack of mass balance in the India–Asia collision that requires loss of continental material. These zones of lower-crustal thinning and likely foundering represent slab segmentation (slab tears) that can geometrically accommodate the curvature of the Himalayan arc.
Unusually efficient CUG initiation of an overlapping reading frame in
POLG
mRNA yields novel protein POLGARF
Authors: Loughran Gary , Zhdanov Alexander V. , Mikhaylova Maria S. , Rozov Fedor N. , Datskevich Petr N. , Kovalchuk Sergey I. , Serebryakova Marina V. , Kiniry Stephen J. , Michel Audrey M. , O’Connor Patrick B. F. , Papkovsky Dmitri B. , Atkins John F. , Baranov Pavel V. , Shatsky Ivan N. , Andreev Dmitry E.
Published: September 2020

Significance

In this study, we describe a previously unknown mechanism of de novo protein-coding gene evolution. We show that the
POLG
gene, which encodes the catalytic subunit of mitochondrial DNA polymerase, is in fact a dual coding gene. Ribosome profiling, phylogenetic conservation, and reporter construct analyses all demonstrate that
POLG
mRNA possesses a conserved CUG codon which serves as a start of translation for an exceptionally long overlapping open reading frame (260 codons in human) present in all placental mammals. We called the protein encoded in this alternative reading frame POLGARF. We provide evidence that the evolution of
POLGARF
was incepted upon insertion of an MIR transposable element of the SINE family.
A map of decoy influence in human multialternative choice
Authors: Dumbalska Tsvetomira , Li Vickie , Tsetsos Konstantinos , Summerfield Christopher
Published: September 2020

Significance

Imagine you are deciding between two goods: A is simple but inexpensive, B is luxurious but more costly. Introducing a less advantageous option (e.g., lower quality than A, same price) should not alter your choice between A and B. However, this principle is often violated; three classic biases known as “decoy effects” have been identified, each describing a stereotyped choice pattern in the presence of irrelevant information. Through behavioral testing in human participants and computer simulations, we show that these decoy effects are special cases of a wider principle, whereby stimulus value information is encoded in a relative, rather than an absolute, format. This work clarifies the origin of three behavioral phenomena that are widely studied in psychology and economics.
A phenolic small molecule inhibitor of RNase L prevents cell death from ADAR1 deficiency
Authors: Daou Salima , Talukdar Manisha , Tang Jinle , Dong Beihua , Banerjee Shuvojit , Li Yize , Duffy Nicole M. , Ogunjimi Abiodun A. , Gaughan Christina , Jha Babal K. , Gish Gerald , Tavernier Nicolas , Mao Daniel , Weiss Susan R. , Huang Hao , Silverman Robert H. , Sicheri Frank
Published: September 2020

Significance

The OAS–RNase L system is an innate immunity pathway activated by viral infection. Viral dsRNA stimulates OAS enzymes to produce short 2′,5′-oligoadenylates (2-5A) that activate RNase L, resulting in cleavage of single-stranded (ss) RNA. We discovered a small-molecule inhibitor of RNase L that rescues the toxic phenotype of cells deficient in the dsRNA-editing enzyme ADAR1. ADAR1 destabilizes dsRNA to prevent OAS activity.
ADAR1
mutations are responsible for a subset of cases of Aicardi-Goutières syndrome (AGS), a severe neurodevelopmental and inflammatory genetic disease of children with no effective medical therapy. We posit that an RNase L inhibitor may have utility against cases of AGS in which RNase L is activated and other indications where overactivation of RNase L is harmful.
Influenza A virus causes maternal and fetal pathology via innate and adaptive vascular inflammation in mice
Authors: Liong Stella , Oseghale Osezua , To Eunice E. , Brassington Kurt , Erlich Jonathan R. , Luong Raymond , Liong Felicia , Brooks Robert , Martin Cara , O’Toole Sharon , Vinh Antony , O’Neill Luke A. J. , Bozinovski Steven , Vlahos Ross , Papagianis Paris C. , O’Leary John J. , Brooks Doug A. , Selemidis Stavros
Published: September 2020

Significance

Influenza infection during pregnancy is associated with increased maternal and perinatal complications. Here, we show that, during pregnancy, influenza infection leads to viral dissemination into the aorta, resulting in a peripheral “vascular storm” characterized by enhanced inflammatory mediators; the influx of Ly6C monocytes, neutrophils, and T cells; and impaired vascular function. The ensuing vascular storm induced hypoxia in the placenta and fetal brain and caused an increase in circulating cell free fetal DNA and soluble Flt1 release. We demonstrate that vascular dysfunction occurs in response to viral infection during pregnancy, which may explain the high rates of morbidity and mortality in pregnant dams, as well as the downstream perinatal complications associated with influenza infection.
America’s electorate is increasingly polarized along partisan lines about voting by mail during the COVID-19 crisis
Authors: Lockhart Mackenzie , Hill Seth J. , Merolla Jennifer , Romero Mindy , Kousser Thad
Published: September 2020

Are voters as polarized as political leaders when it comes to their preferences about how to cast their ballots in November 2020 and their policy positions on how elections should be run in light of the COVID-19 outbreak? Prior research has shown little party divide on voting by mail, with nearly equal percentages of voters in both parties choosing to vote this way where it is an option. Has a divide opened up this year in how voters aligned with the Democratic and Republican parties prefer to cast a ballot? We address these questions with two nationally diverse, online surveys fielded from April 8 to 10 and June 11 to 13, of 5,612 and 5,818 eligible voters, respectively, with an embedded experiment providing treated respondents with scientific projections about the COVID-19 outbreak. We find a nearly 10 percentage point difference between Democrats and Republicans in their preference for voting by mail in April, which had doubled in size to nearly 20 percentage points in June. This partisan gap is wider still for those exposed to scientific projections about the pandemic. We also find that support for national legislation requiring states to offer no-excuse absentee ballots has emerged as an increasingly polarized issue.
Studies of lincosamide formation complete the biosynthetic pathway for lincomycin A
Authors: Wang Shao-An , Lin Chia-I , Zhang Jiawei , Ushimaru Richiro , Sasaki Eita , Liu Hung-wen
Published: September 2020

Significance

Lincomycin A is an antibiotic used clinically in the treatment of Gram-positive bacterial infections. Its biosynthesis has attracted much attention due to its unique sulfur-containing thiooctose core. Despite significant progress in our understanding of lincomycin biosynthesis, the mechanism by which GDP-ᴅ-
erythro
-α-ᴅ-
gluco
-octose maturates to GDP-ᴅ-α-ᴅ-lincosamide remains obscure. Herein, the long-sought missing link is established to consist of two epimerizations: a 6,8-dehydration and a transamination reaction catalyzed by four enzymes. Furthermore, unlike other epimerases that function regiospecifically, a single enzyme is found to catalyze epimerization at two different loci. Also, the dehydration is shown to be an α,γ-dehydration catalyzed by two enzymes. This study thus completes the description of the lincomycin biosynthetic pathway and highlights the complex mechanistic subtleties of unusual sugar biosynthesis.
Rapid onsets of warming events trigger mass mortality of coral reef fish
Authors: Genin Amatzia , Levy Liraz , Sharon Galit , Raitsos Dionysios E. , Diamant Arik
Published: September 2020

Significance

Our study reveals a hitherto overlooked effect of warming on coral reefs. Traditionally, ecological studies of warming events focused on maximum temperatures and duration, rather than the rate of warming at the onset. Here, we show that onsets can trigger widespread mortality of reef fish. Hundreds of thermally stressed fish, belonging to dozens of species, became fatally infected with a common pathogen in the Red Sea. Differential susceptibility led to selective mortality, with disproportional death among predators and benthic feeders. A reassessment of past reports suggests that extreme onset might have been an overlooked trigger of fish kills elsewhere. Warming tropical and subtropical reefs may face an increasing frequency of extreme onsets, eliciting calamities far beyond coral bleaching.
Tree planting has the potential to increase carbon sequestration capacity of forests in the United States
Authors: Domke Grant M. , Oswalt Sonja N. , Walters Brian F. , Morin Randall S.
Published: September 2020

Several initiatives have been proposed to mitigate forest loss and climate change through tree planting as well as maintaining and restoring forest ecosystems. These initiatives have both inspired and been inspired by global assessments of tree and forest attributes and their contributions to offset carbon dioxide (CO
2
) emissions. Here we use data from more than 130,000 national forest inventory plots to describe the contribution of nearly 1.4 trillion trees on forestland in the conterminous United States to mitigate CO
2
emissions and the potential to enhance carbon sequestration capacity on productive forestland. Forests and harvested wood products uptake the equivalent of more than 14% of economy-wide CO
2
emissions in the United States annually, and there is potential to increase carbon sequestration capacity by ∼20% (−187.7 million metric tons [MMT] CO
2
±9.1 MMT CO
2
) per year by fully stocking all understocked productive forestland. However, there are challenges and opportunities to be considered with tree planting. We provide context and estimates from the United States to inform assessments of the potential contributions of forests in climate change mitigation associated with tree planting.
Melatonin promotes sleep by activating the BK channel in
C. elegans
Authors: Niu Longgang , Li Yan , Zong Pengyu , Liu Ping , Shui Yuan , Chen Bojun , Wang Zhao-Wen
Published: September 2020

Significance

Melatonin (Mel) promotes sleep through G protein-coupled Mel receptors. However, the downstream molecular target(s) of the Mel receptors to produce the sleep effect remains enigmatic. The study shows that a potassium channel, the BK channel, plays a role in sleep and that Mel promotes sleep by activating this channel through a specific Mel receptor.
Evolution of vertebrate gill covers via shifts in an ancient Pou3f3 enhancer
Authors: Barske Lindsey , Fabian Peter , Hirschberger Christine , Jandzik David , Square Tyler , Xu Pengfei , Nelson Nellie , Yu Haoze Vincent , Medeiros Daniel M. , Gillis J. Andrew , Crump J. Gage
Published: September 2020

Significance

The evolution of jaws in early vertebrates provided such a predatory advantage that 99% of vertebrate species living today are jawed. What is often overlooked, however, is another structural innovation that happened concurrently and may have been equally critical to the lineage’s success: the evolution of musculoskeletal gill covers to actively drive oxygenated water over the gills. Here, we identify the first essential gene for gill cover formation in modern vertebrates, Pou3f3, and uncover the genomic element that brought Pou3f3 expression into the pharynx more than 430 Mya. Remarkably, small changes in this deeply conserved sequence account for the single large gill cover in living bony fish versus the five separate covers of sharks and their brethren.