bluuebunny/crossref_metadata_2025 huggingface dataset:
Hole-punching for enhancing electrocatalytic activities of 2D graphene electrodes: Less is more
Authors: Gao Yunxiang , Zhang Lipeng , Xia Zhenhai , Li Chang Ming , Dai Liming
Published: August 2020

Using a polymer-masking approach, we have developed metal-free 2D carbon electrocatalysts based on single-layer graphene with and without punched holes and/or N-doping. A combined experimental and theoretical study on the resultant 2D graphene electrodes revealed that a single-layer graphene sheet exhibited a significantly higher electrocatalytic activity at its edge than that over the surface of its basal plane. Furthermore, the electrocatalytic activity of a single-layer 2D graphene sheet was significantly enhanced by simply punching microholes through the graphene electrode due to the increased edge population for the hole-punched graphene electrode. In a good consistency with the experimental observations, our density function theory calculations confirmed that the introduction of holes into a graphene sheet generated additional positive charge along the edge of the punched holes and hence the creation of more highly active sites for the oxygen reduction reaction. The demonstrated concept for less graphene material to be more electrocatalytically active shed light on the rational design of low-cost, but efficient electrocatalysts from 2D graphene for various potential applications ranging from electrochemical sensing to energy conversion and storage.
Ground and excited state exciton polarons in monolayer MoSe2
Authors: Goldstein Thomas , Wu Yueh-Chun , Chen Shao-Yu , Taniguchi Takashi , Watanabe Kenji , Varga Kalman , Yan Jun
Published: August 2020

Monolayer transition metal dichalcogenide semiconductors, with versatile experimentally accessible exciton species, offer an interesting platform for investigating the interaction between excitons and a Fermi sea of charges. Using hexagonal boron nitride encapsulated monolayer MoSe2, we study the impact of charge density tuning on the A and B series of exciton Rydberg states, including A:1s, A:2s, B:1s, and B:2s. The doping dependence of the A:2s state provides an opportunity to examine such interactions with greatly reduced exciton binding energy and more spatially diffuse structures, and we found that the impact of the Fermi sea becomes much more dramatic compared to the A:1s state. Using photoluminescence upconversion, we verify that the B:2s exciton state displays similar behavior when interacting with the Fermi sea despite being well above the bare bandgap in energy. Photoluminescence and reflection spectra of the A:1s state show clear evidence that the interaction of the exciton with a Fermi sea is best described by the exciton–polaron model, rather than a trion model. Our experimental results demonstrate that overall features of charge interaction are quite generic and highly robust, offering key insights into the dressed many body states in a Fermi sea.
On the genesis and evolution of barchan dunes: Hydrodynamics
Authors: Khosronejad Ali , Kang Seokkoo , Farhadzadeh Ali , Sotiropoulos Fotis
Published: August 2020

Barchans are an important signature of turbulent atmospheric and aquatic flows on parts of the Earth’s surface where the supply of sediments is scarce. Khosronejad and Sotiropoulos [“On the genesis and evolution of barchan dunes: Morphodynamics,” J. Fluid Mech. 815, 117–148 (2017)] demonstrated that high-fidelity hydro-morphodynamic large-eddy simulation (LES) can replicate sub-aqueous barchan fields exhibiting the geometric features and morphodynamic interactions observed in nature. Herein, we first validate the ability of our LES method to simulate mean flow and turbulence statistics over a frozen barchan dune created in a control laboratory experiment. We then analyze our high-fidelity LES datasets to elucidate the hydrodynamic phenomena that drive the previously identified morphodynamic interactions at various stages of subaqueous barchan dune evolution, from flatbed to quasi-equilibrium. We uncover and quantify the hydrodynamic mechanisms that cause (i) the initiation of crescent microfeatures on the initial flatbed; (ii) the development of three-dimensional barchan dunes; and (iii) several other phenomena that occur during the barchan field maturation, such as the birth of new small barchans and the exposure of the underlying bedrock in the wake of the barchans. Defining a dimensionless timescale, i.e., the saturation timescale, as a function of the saturation length scale, we attempt to categorize for the first time various temporal stages of barchan field development. We show that the barchan field has specific characteristics corresponding to each of the barchan stage developments in terms of both the flow field and the bed topology. Comparing the simulation results of transverse and barchan dunes, we illustrate that the two dune types have similar topographic and hydrodynamics characteristics until bedrock exposure occurs.
Retardation of droplet transport in confined microchannel by interfacial jamming of nanoparticles
Authors: Luo Zheng Yuan , Bai Bo Feng
Published: August 2020

Despite its significance in droplet microfluidics and enhanced oil recovery, the dynamics of single droplets in confined microchannels still remains an unsolved fundamental problem, especially when the droplet is covered with nanoparticles. In this study, we present a numerical investigation on the transport of a nanoparticle-covered droplet through a confined microchannel with a square cross section. This work is realized via developing a level-set-based computational methodology with the nanoparticle–fluid, nanoparticle–nanoparticle, and nanoparticle–interface interactions all taken into account. We find that the interfacial convection drags the nanoparticles to the droplet rear and induces their local jamming and assembly into closely packed structures. More importantly, the interfacial jamming of the nanoparticles leads to nearly complete immobilization of the droplet surface, where the surface velocity is decreased by about two orders of magnitude compared to the clean surface. As a final consequence, the transport of the whole droplet through the confined microchannel is significantly retarded; specifically, the droplet-induced extra pressure loss in the microchannel is remarkably enlarged. Although the nanoparticle-induced surface immobilization is similar to the results from the surfactant-induced Marangoni stress, the immobilization-induced reduction in the surface velocity for the nanoparticle-covered droplet is much more significant than the surfactant-laden droplet. As a result, the effects of interfacial jamming of nanoparticles on the droplet motion, e.g., the extra pressure loss in the microchannel, are much stronger than that of the surfactant-induced Marangoni stress.
Fatigue and retention in the growth window of ferroelectric Hf0.5Zr0.5O2 thin films
Authors: Lyu Jike , Fina Ignasi , Sánchez Florencio
Published: August 2020

The growth window of epitaxial Hf0.5Zr0.5O2 is established taking into account the main ferroelectric properties that films have to present simultaneously: high remanent polarization, low fatigue, and long retention. Defects in the film and imprint field depend on deposition temperature and oxygen pressure, with an impact on fatigue and retention, respectively. Fatigue increases with substrate temperature and pressure, and retention is short if low temperature is used. The growth window of epitaxial stabilization of ferroelectric Hf0.5Zr0.5O2 is narrower when all major ferroelectric properties (remanence, endurance, and retention) are considered, but deposition temperature and pressure ranges are still sufficiently wide.
Multisensory graphene-skin for harsh-environment applications
Authors: Shaikh Sohail F. , Hussain Muhammad M.
Published: August 2020

Monitoring the environment using electronic systems in harsh environments requires materials and processes that can withstand harsh environments. Environmental harshness can come from the surrounding temperature, varying pressure, intense radiation, reactive chemicals, humidity, salinity, or a combination of any of these conditions. Here, we present graphene as a candidate for a multisensory flexible platform in harsh-environment applications. We designed sensors for harsh environments like high temperature (operating range up to 650 °C), high salinity, and chemical harsh environments (pH sensing) on a single flexible polyimide sheet. The high-temperature graphene sensor gives a sensitivity of 260% higher than the Pt-based sensor. The temperature sensor acts between metal and a thermistor, thereby providing an opportunity to classify the region depending on temperature (<210 °C linear and > 210 °C up to 650 °C as quadratic). Improved performances are observed for salinity and pH sensing in comparison with existing non-graphene solutions. The simple transfer free fabrication technique of graphene on a flexible platform and laser-induced graphene on a flexible polyimide sheet opens the potential for harsh-environment monitoring and multisensory graphene skin in future applications.
Numerical study of unsteady viscoelastic flow past two side-by-side circular cylinders
Authors: Peng Sai , Xiong Yong-Liang , Xu Xiao-Yang , Yu Peng
Published: August 2020

In this study, numerical simulation is conducted to understand the two-dimensional viscoelastic flows past two side-by-side circular cylinders at a Reynolds number of 100. The Peterlin approximation of the finitely extensible nonlinear elastic model is adopted to describe the non-linear modulus of elasticity and the finite extendibility of polymer macromolecules. The flow behavior and time-averaged forces that act on the two cylinders are investigated over a wide range of parameter space, i.e., the Weissenberg number (We), from 0 to 8, and the spacing between the two cylinders (LD), from 0.1D to 3.0D (D denotes the diameter of each cylinder). Similar to the corresponding Newtonian flow, the viscoelastic flow gradually undergoes six transitions as LD increases. However, these transitions are delayed in the viscoelastic flow, particularly at a high We. As a result, three distinct flow modes remain within the above-mentioned LD range at a high We. With increasing We, the total drag acting on the two cylinders increases for all LD values, and the repulsive force between the two cylinders gradually decreases for a lower LD value but increases for a higher LD value. Both the intensity and frequency of force fluctuation decrease as We increases. The findings of the present study may provide new insight into the multi-body wake dynamics in the viscoelastic flow.
From hard spheres and cubes to nonequilibrium maps with thirty-some years of thermostatted molecular dynamics
Authors: Hoover William Graham , Hoover Carol Griswold
Published: August 2020

This is our current research perspective on models providing insight into statistical mechanics. It is necessarily personal, emphasizing our own interest in simulation as it developed from the National Laboratories’ work to the worldwide explosion of computation of today. We contrast the past and present in atomistic simulations, emphasizing those simple models that best achieve reproducibility and promote understanding. Few-body models with pair forces have led to today’s “realistic” simulations with billions of atoms and molecules. Rapid advances in computer technology have led to change. Theoretical formalisms have largely been replaced by simulations incorporating ingenious algorithm development. We choose to study particularly simple, yet relevant, models directed toward understanding general principles. Simplicity remains a worthy goal, as does relevance. We discuss hard-particle virial series, melting, thermostatted oscillators with and without heat conduction, chaotic dynamics, fractals, the connection of Lyapunov spectra to thermodynamics, and finally simple linear maps. Along the way, we mention directions in which additional modeling could provide more clarity and yet more interesting developments in the future.
A GPU implementation of classical density functional theory for rapid prediction of gas adsorption in nanoporous materials
Authors: Zhou Musen , Wu Jianzhong
Published: August 2020

Nanoporous materials are promising as the next generation of absorbents for gas storage and separation with ultrahigh capacity and selectivity. The recent advent of data-driven approaches in materials modeling provides alternative routes to tailor nanoporous materials for customized applications. Typically, a data-driven model requires a large amount of training data that cannot be generated solely by experimental methods or molecular simulations. In this work, we propose an efficient implementation of classical density functional theory with a graphic processing unit (GPU) for the fast yet accurate prediction of gas adsorption isotherms in nanoporous materials. In comparison to serial computing with the central processing unit, the massively parallelized GPU implementation reduces the computational cost by more than two orders of magnitude. The proposed algorithm renders new opportunities not only for the efficient screening of a large materials database for gas adsorption but it may also serve as an important stepping stone toward the inverse design of nanoporous materials tailored to desired applications.
Design exploration and optimization under uncertainty
Authors: Mishra Aashwin Ananda , Mukhopadhaya Jayant , Alonso Juan , Iaccarino Gianluca
Published: August 2020

Computational strategies that explicitly quantify uncertainties are becoming increasingly used in aerospace applications to improve the consistency in reliability, robustness, and performance of designs. A major source of uncertainty in simulations is due to the structural assumptions invoked in the formulation of turbulence models. Accounting for the turbulence model-form uncertainty has been described as “the greatest challenge” in simulation-based engineering design. Despite its importance, design exploration and optimization under turbulence model-form uncertainty is an avenue that has not been investigated in depth in prior literature. In this investigation, we outline methodologies for the design analysis, exploration, and robust optimization under model-form uncertainty due to Reynolds averaged Navier–Stokes models. We exhibit how interval uncertainty estimates enable the use of alternative criteria for decision making under uncertainty in engineering design. It is shown that such criteria can lead to different design choices in design exploration. Finally, we carry out design optimization under mixed uncertainties by using the perturbation framework in conjunction with polynomial chaos expansions. We introduce an approach for engineering design optimization under uncertainty that utilizes physics-based uncertainty estimation along with decision theory criteria under uncertainty to produce designs that are more robust to turbulence model uncertainties. These methodologies are illustrated via their application to complex turbulent flow cases, pertinent to aerospace design applications.
Numerical investigation of magnetic multiphase flows by the fractional-step-based multiphase lattice Boltzmann method
Authors: Li Xiang , Dong Zhi-Qiang , Yu Peng , Niu Xiao-Dong , Wang Lian-Ping , Li De-Cai , Yamaguchi Hiroshi
Published: August 2020

In the present study, a fractional-step-based multiphase lattice Boltzmann (LB) method coupled with a solution of a magnetic field evolution is developed to predict the interface behavior in magnetic multiphase flows. The incompressible Navier–Stokes equations are utilized for the flow field, while the Cahn–Hilliard equation is adopted to track the interface, and these governing equations are solved by reconstructing solutions within the LB framework with the prediction–correction step based on a fractional-step method. The proposed numerical model inherits the excellent performance of kinetic theory from the LB method and integrates the good numerical stability from the fractional-step method. Meanwhile, the macroscopic variables can be simply and directly calculated by the equilibrium distribution functions, which saves the virtual memories and simplifies the computational process. The proposed numerical model is validated by simulating two problems, i.e., a bubble rising with a density ratio of 1000 and a viscosity ratio of 100 and a stationary circular cylinder under an external uniform magnetic field. The interfacial deformations of a ferrofluid droplet in organic oil and an aqueous droplet in ferrofluid under the external magnetic field are, then, simulated, and the underlying mechanisms are discussed. Moreover, the rising process of a gas bubble in the ferrofluid is investigated, which shows that the rising velocity is accelerated under the effect of the external magnetic field. All the numerical examples demonstrate the capability of the present numerical method to handle the problem with the interfacial deformation in magnetic multiphase flows.
Asymptotic analysis of solutions of ordinary differential equations with distribution coefficients
Authors: Savchuk A. M. , Shkalikov A. A.
Published: August 2020

Ordinary differential equations of the formon the finite intervalare under consideration. Here the functionsandare absolutely continuous and positive and the coefficients of the differential expressionare subject to the conditionswheredenotes theth antiderivative of the functionin the sense of distributions. Our purpose is to derive analogues of the classical asymptotic Birkhoff-type representations for the fundamental system of solutions of the above equation with respect to the spectral parameter asin certain sectors of the complex plane. We reduce this equation to a system of first-order equations of the formwhereis a positive function,is a matrix with constant elements, the elements of the matricesandare integrable functions, andas. For systems of this kind, we obtain new results concerning the asymptotic representation of the fundamental solution matrix, which we use to make an asymptotic analysis of the above scalar equations of high order.

Bibliography: 44 titles.
Optimal position of compact sets and the Steiner problem in spaces with Euclidean Gromov-Hausdorff metric
Authors: Malysheva O. S.
Published: August 2020

We study the geometry of the metric space of compact subsets of

considered up to an orientation-preserving motion. We show that, in the optimal position of a pair of compact sets (for which the Hausdorff distance between the sets cannot be decreased), one of which is a singleton, this point is at the Chebyshev centre of the other. For orientedly similar compacta we evaluate the Euclidean Gromov-Hausdorff distance between them and prove that, in the optimal position, the Chebyshev centres of these compacta coincide. We show that every three-point metric space can be embedded isometrically in the space of compacta under consideration. We prove that, for a pair of optimally positioned compacta all compacta that lie in between in the sense of the Hausdorff metric also lie in between in the sense of the Euclidean Gromov-Hausdorff metric. For an arbitrary

-point boundary formed by compact sets of a set

that are neighbourhoods of segments, the Steiner point realizes the minimal filling and also belongs to the set

.

Bibliography: 14 titles.
Journal publication productivity, impact, and quality among Applied Linguistics and TESOL academics in the Group of
Eight Australian Universities
Authors: Riazi Mehdi , Cooper Heather , Calvey Grai
Published: August 2020

This article reports on a study in which journal publication performance of Applied Linguistics and TESOL
(AL/TESOL) academics in the Group of Eight (Go8) Australian universities was examined for each academic rank (Lecturer to
Professor) and across apparent genders (females and males). Journal publication performance was defined in terms of productivity
(number of articles), academic impact (number of citations to those articles), and quality (journal impact factor and quartile
rankings). To this end, journal publications of 65 Go8 AL/TESOL academics were identified over 19 years (2000–2018 inclusive).
Normative research profiles are provided for each academic level and across two genders and are discussed in light of the
literature. Where appropriate, a critical view has also developed concerning issues such as “publish or perish” and “gender gap”
in academic publication. Results and discussion of results can contribute to a better understanding of AL/TESOL journal article
production in Go8 universities as a reference group.
Diglossia and language ideology Petrarch on linguistic variation and differentiation
Authors: Spreafico Marco
Published: August 2020

Petrarch’s metalinguistic observations are scattered throughout his work, rare and for the most part elliptical. The present article closely examines Petrarch’s statements about language to arrive at an alternative interpretation to that of previous scholarship. We analyse the ideas, attitudes and beliefs that inform Petrarch’s conception of the difference between Latin and the vernacular languages. The first section provides a critique of the now prevailing view on Petrarch’s metalinguistic thinking. Mirko Tavoni and Silvia Rizzo hypothesize that Petrarch ‘was not conscious of being bilingual’, since he considered Latin and vernaculars as different stylistic varieties of one and the same language. In the remaining two sections we propose an alternative account. Comparing statements made by contemporaries of Petrarch and investigating their origin and rationale, we suggest that Petrarch’s conception and practice cannot be accounted for within a modern perspective of national language and are better captured by the notion of diglossia, in which two linguistic varieties are delimited by the contexts of their use.
Crisis in the Linguistic Society of America
Authors: Newmeyer Frederick J.
Published: August 2020

This article discusses and analyses the 1970 election for President of
the Linguistic Society of America. In that year, Dwight Bolinger
challenged the official candidate Martin Joos and defeated him easily. We see that it was
mainly personal and generational factors, rather than intellectual ones, that led to
Bolinger’s victory.
Peroxisome retention involves Inp1-dependent peroxisome–plasma membrane contact sites in yeast
Authors: Krikken Arjen M. , Wu Huala , de Boer Rinse , Devos Damien P. , Levine Tim P. , van der Klei Ida J.
Published: August 2020

Retention of peroxisomes in yeast mother cells requires Inp1, which is recruited to the organelle by the peroxisomal membrane protein Pex3. Here we show that Hansenula polymorpha Inp1 associates peroxisomes to the plasma membrane. Peroxisome–plasma membrane contact sites disappear upon deletion of INP1 but increase upon INP1 overexpression. Analysis of truncated Inp1 variants showed that the C terminus is important for association to the peroxisome, while a stretch of conserved positive charges and a central pleckstrin homology-like domain are important for plasma membrane binding. In cells of a PEX3 deletion, strain Inp1-GFP localizes to the plasma membrane, concentrated in patches near the bud neck and in the cortex of nascent buds. Upon disruption of the actin cytoskeleton by treatment of the cells with latrunculin A, Inp1-GFP became cytosolic, indicating that Inp1 localization is dependent on the presence of an intact actin cytoskeleton.
Wnts regulate planar cell polarity via heterotrimeric G protein and PI3K signaling
Authors: Landin Malt Andre , Hogan Arielle K. , Smith Connor D. , Madani Maxwell S. , Lu Xiaowei
Published: August 2020

In the mammalian cochlea, the planar cell polarity (PCP) pathway aligns hair cell orientation along the plane of the sensory epithelium. Concurrently, multiple cell intrinsic planar polarity (referred to as iPCP) modules mediate planar polarization of the hair cell apical cytoskeleton, including the kinocilium and the V-shaped hair bundle essential for mechanotransduction. How PCP and iPCP are coordinated during development and the roles of Wnt ligands in this process remain unresolved. Here we show that genetic blockade of Wnt secretion in the cochlear epithelium resulted in a shortened cochlear duct and misoriented and misshapen hair bundles. Mechanistically, Wnts stimulate Gi activity by regulating the localization of Daple, a guanine nucleotide exchange factor (GEF) for Gαi. In turn, the Gβγ complex signals through phosphoinositide 3-kinase (PI3K) to regulate kinocilium positioning and asymmetric localizations of a subset of core PCP proteins, thereby coordinating PCP and iPCP. Thus, our results identify a putative Wnt/heterotrimeric G protein/PI3K pathway for PCP regulation.
The very low number of calcium-induced permeability transition pores in the single mitochondrion
Authors: Neginskaya Maria A. , Strubbe Jasiel O. , Amodeo Giuseppe F. , West Benjamin A. , Yakar Shoshana , Bazil Jason N. , Pavlov Evgeny V.
Published: August 2020

Mitochondrial permeability transition (PT) is a phenomenon of stress-induced increase in nonspecific permeability of the mitochondrial inner membrane that leads to disruption of oxidative phosphorylation and cell death. Quantitative measurement of the membrane permeability increase during PT is critically important for understanding the PT’s impact on mitochondrial function. The elementary unit of PT is a PT pore (PTP), a single channel presumably formed by either ATP synthase or adenine nucleotide translocator (ANT). It is not known how many channels are open in a single mitochondrion during PT, which makes it difficult to quantitatively estimate the overall degree of membrane permeability. Here, we used wide-field microscopy to record mitochondrial swelling and quantitatively measure rates of single-mitochondrion volume increase during PT-induced high-amplitude swelling. PT was quantified by calculating the rates of water flux responsible for measured volume changes. The total water flux through the mitochondrial membrane of a single mitochondrion during PT was in the range of (2.5 ± 0.4) × 10−17 kg/s for swelling in 2 mM Ca2+ and (1.1 ± 0.2) × 10−17 kg/s for swelling in 200 µM Ca2+. Under these experimental conditions, a single PTP channel with ionic conductance of 1.5 nS could allow passage of water at the rate of 0.65 × 10−17 kg/s. Thus, we estimate the integral ionic conductance of the whole mitochondrion during PT to be 5.9 ± 0.9 nS for 2 mM concentration of Ca2+ and 2.6 ± 0.4 nS for 200 µM of Ca2+. The number of PTPs per mitochondrion ranged from one to nine. Due to the uncertainties in PTP structure and model parameters, PTP count results may be slightly underestimated. However, taking into account that each mitochondrion has ∼15,000 copies of ATP synthases and ANTs, our data imply that PTP activation is a rare event that occurs only in a small subpopulation of these proteins.
Direct Strong Measurement of a High-Dimensional Quantum State*
Authors: Zhang Chen-Rui , Hu Meng-Jun , Xiang Guo-Yong , Zhang Yong-Sheng , Li Chuan-Feng , Guo Guang-Can
Published: August 2020

It is of great importance to determine an unknown quantum state for fundamental studies of quantum mechanics, yet it is still difficult to characterize systems of large dimensions in practice. Although the scan-free direct measurement approach based on a weak measurement scheme was proposed to measure a high-dimensional photonic state, how weak the interaction should be to give a correct estimation remains unclear. Here we propose and experimentally demonstrate a technique that measures a high-dimensional quantum state with the combination of scan-free measurement and direct strong measurement. The procedure involves sequential strong measurement, in which case no approximation is made similarly to the conventional direct weak measurement. We use this method to measure a transverse state of a photon with effective dimensionality of 65000 without the time-consumed scanning process. Furthermore, the high fidelity of the result and the simplicity of the experimental apparatus show that our approach can be readily used to measure the complex field of a beam in diverse applications such as wavefront sensing and quantitative phase imaging.
Multi-Core Conformal Lenses*
Authors: Zhu Xinghong , Zhao Pengfei , Chen Huanyang
Published: August 2020

We propose multi-core conformal lenses by combining conformal transformation optics with absolute instruments. Depending on the cores and incident angles, the conformal lenses have tunable functionalities like focusing, reflection, and transparency, thereby providing a feasible general method for designing multi-functional devices.
de Haas-van Alphen Quantum Oscillations in BaSn3 Superconductor with Multiple Dirac Fermions*
Authors: Zhang Gaoning , Shi Xianbiao , Liu Xiaolei , Xia Wei , Su Hao , Chen Leiming , Wang Xia , Yu Na , Zou Zhiqiang , Zhao Weiwei , Guo Yanfeng
Published: August 2020

Characterization of Fermi surface of the BaSn3 superconductor (T
c ∼ 4.4 K) by de Haas–van Alphen (dHvA) effect measurement reveals its non-trivial topological properties. Analysis of non-zero Berry phase is supported by the ab initio calculations, which reveals a type-II Dirac point setting and tilting along the high symmetric K–H line of the Brillouin zone, about 0.13 eV above the Fermi level, and other two type-I Dirac points on the high symmetric Γ–A direction, but slightly far below the Fermi level. The results demonstrate BaSn3 as an excellent example hosting multiple Dirac fermions and an outstanding platform for studying the interplay between nontrivial topological states and superconductivity.
Symmetry-Assisted Protection and Compensation of Hidden Spin Polarization in Centrosymmetric Systems
Authors: Zhang Yingjie , Liu Pengfei , Sun Hongyi , Zhao Shixuan , Xu Hu , Liu Qihang
Published: August 2020

It was recently noted that in certain nonmagnetic centrosymmetric compounds, spin–orbit interactions couple each local sector that lacks inversion symmetry, leading to visible spin polarization effects in the real space, dubbed “hidden spin polarization (HSP)". However, observable spin polarization of a given local sector suffers interference from its inversion partner, impeding material realization and potential applications of HSP. Starting from a single-orbital tight-binding model, we propose a nontrivial way to obtain strong sector-projected spin texture through the vanishing hybridization between inversion partners protected by nonsymmorphic symmetry. The HSP effect is generally compensated by inversion partners near the Γ point but immune from the hopping effect around the boundary of the Brillouin zone. We further summarize 17 layer groups that support such symmetry-assisted HSP and identify hundreds of quasi-2D materials from the existing databases by first-principle calculations, among which a group of rare-earth compounds LnIO (Ln = Pr, Nd, Ho, Tm, and Lu) serves as great candidates showing strong Rashba- and Dresselhaus-type HSP. Our findings expand the material pool for potential spintronic applications and shed light on controlling HSP properties for emergent quantum phenomena.
Structure-Spin-Transport Anomaly in Quasi-One-Dimensional Ba9Fe3Te15 under High Pressure
Authors: Zhang Jun , Jin Mei-Ling , Li Xiang , Wang Xian-Cheng , Zhao Jian-Fa , Liu Ying , Duan Lei , Li Wen-Min , Cao Li-Peng , Chen Bi-Juan , Wang Li-Juan , Sun Fei , Wang Yong-Gang , Yang Liu-Xiang , Xiao Yu-Ming , Deng Zheng , Feng Shao-Min , Jin Chang-Qing , Zhu Jin-Long
Published: August 2020

Recently, a series of novel compounds Ba3MX5 (M = Fe, Ti, V; X = Se, Te) with hexagonal crystal structures composed of quasi-1-dimensional (1D) magnetic chains has been synthesized by our research team using high-pressure and high-temperature methods. The initial hexagonal phases persist to the maximum achievable pressure, while spin configurations and magnetic interactions may change dramatically as a result of considerable reductions in interchain separations upon pressurization. These compounds therefore offer unique possibilities for studying the evolution of intrinsic electronic structures in quasi-1D magnetic systems. Here we present a systematic investigation of Ba9Fe3Te15, in which the interchain separations between trimerized 1D chains (∼ 10.2 Å) can be effectively modulated by external high pressure. The crystal structure especially along the 1D chains exhibits an abnormal expansion at ∼5 GPa, which accompanies trimerization entangled anomalous mixed-high-low spin transition. An insulator-metal transition has been observed under high pressure as a result of charge-transfer gap closing. Pressure-induced superconductivity emerges at 26 GPa, where the charge-transfer gap fully closes, 3D electronic configuration forms and local spin fully collapses.
Enhancement of Curie Temperature under Built-in Electric Field in Multi-Functional Janus Vanadium Dichalcogenides*
Authors: Ji Shilei , Wu Hong , Zhou Shuang , Niu Wei , Wei Lujun , Li Xing-Ao , Li Feng , Pu Yong
Published: August 2020

Functionalized two-dimensional materials with multiferroicity are highly desired to be next-generation electronic devices. Here we theoretically predict a family of Janus vanadium dichalcogenides VXX’ (X/X’ = S, Se, Te) monolayers with multiferroic properties, combing ferromagnetism, ferroelasticity and piezoelectricity. Due to the unpaired electrons on the V atom, the Janus VXX’ monolayers have intrinsic long-range ferromagnetic orders. Particularly, the Curie temperature of 1T-VSeTe monolayer is up to 100 K, which is greatly higher than 2D 1T-VSe2 and 1T-VTe2. Furthermore, the six Janus VXX’ monolayers have similar crater-like ferroelastic switching curves. Compared to black phosphorus, 2H-VSSe monolayer has the similar ferroelastic switching signal and 4 times lower energy barrier. In addition, the out-of-plane piezoelectricity induced by the structure asymmetry in the vertical direction gives the 2H-VXX’ monolayers the potential to be piezoelectric materials. It is found that a built-in electric field in the vertical direction due to the different electronegativity values of chalcogen atoms induces the changes of electronic structures, which leads to the appearance of three different types of band gaps in the three H-phase structures. Recently, the experimental growth of the Janus MoSSe monolayers and the electrochemical exfoliation of ferromagnetic monolayered VSe2 make the Janus VXX’ monolayers possibly fabricated in experiments.
Pressure-Dependent Phonon Scattering of Layered GaSe Prepared by Mechanical Exfoliation*
Authors: Zheng Yu-Lu , Li Liang , Li Fang-Fei , Zhou Qiang , Cui Tian
Published: August 2020

Few-layered gallium selenide (GaSe) is obtained by using the mechanical exfoliation method, and its properties are characterized by photoluminescence and Raman spectroscopy. The pressure-dependent phonon scatterings of bulk, few-layered, oxidized few-layered GaSe are characterized up to 30 GPa by using a diamond anvil cell with inert argon used as the pressure transmission medium. All the GaSe samples processed a phase transition around 28 GPa. A new vibration mode at 250 cm−1 is found in oxidized few-layered GaSe by Raman spectra, which is indexed as the Raman vibration mode of α-Se.
Polymorphism and Flexibility of DNA in Alcohols*
Authors: Zhang Nan , Li Ming-Ru , Xu Hui-Ting , Zhang Feng-Shou
Published: August 2020

Molecular dynamics simulations are performed to investigate the polymorphism and flexibility of DNA in water, ethylene glycol (EG) and ethanol (EA) solutions. DNA in EG resembles the structure of DNA in water exhibiting B-DNA. In contrast, the DNA is an A-DNA state in the EA. We demonstrate that one important cause of these A↔B state changes is the competition between hydration and direct cation coupling to the phosphate groups on DNA backbones. To DNA structural polymorphism, it is caused by competition between hydration and cation coupling to the base pairs on grooves. Unlike flexible DNA in water and EA, DNA is immobilized around the canonical structure in EG solution, eliminating the potential biological effects of less common non-canonical DNA sub-states.
The 2020 plasma catalysis roadmap
Authors: Bogaerts Annemie , Tu Xin , Whitehead J Christopher , Centi Gabriele , Lefferts Leon , Guaitella Olivier , Azzolina-Jury Federico , Kim Hyun-Ha , Murphy Anthony B , Schneider William F , Nozaki Tomohiro , Hicks Jason C , Rousseau Antoine , Thevenet Frederic , Khacef Ahmed , Carreon Maria
Published: August 2020

Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, CH4 activation into hydrogen, higher hydrocarbons or oxygenates, and NH3 synthesis. Other applications are already more established, such as for air pollution control, e.g. volatile organic compound remediation, particulate matter and NOx removal. In addition, plasma is also very promising for catalyst synthesis and treatment. Plasma catalysis clearly has benefits over ‘conventional’ catalysis, as outlined in the Introduction. However, a better insight into the underlying physical and chemical processes is crucial. This can be obtained by experiments applying diagnostics, studying both the chemical processes at the catalyst surface and the physicochemical mechanisms of plasma-catalyst interactions, as well as by computer modeling. The key challenge is to design cost-effective, highly active and stable catalysts tailored to the plasma environment. Therefore, insight from thermal catalysis as well as electro- and photocatalysis is crucial. All these aspects are covered in this Roadmap paper, written by specialists in their field, presenting the state-of-the-art, the current and future challenges, as well as the advances in science and technology needed to meet these challenges.
Molecular transport across a two-dimensional nanomesh membrane–graphdiyne
Authors: Xu Jiyu , Meng Sheng
Published: August 2020

The purification and separation technologies are of great importance to industry and agriculture in modern society. Two-dimensional (2D) crystals emerge as superior membrane materials showing desirable molecular permeability and selectivity. Among them, 2D materials with a nanomesh structure show the greatest potential in molecular transport and separation. Here, we highlight the recent theoretical progresses in molecular transport across 2D graphdiyne membrane with the nanomesh structure. Firstly, the nonlinear and activated water flow were demonstrated through the graphdiyne membranes under external hydrostatic pressure. Then, the superior proton conductivity and perfect selectivity were shown for graphdiyne membrane at ambient conditions. Lastly, graphdiyne was shown to exhibit perfect small gas molecule permeability and selectivity at the atmospheric conditions. The mechanisms for molecular transport and selectivity are also discussed.
Quartet condensation induced by the isovector pairing force
Authors: Sambataro M , Sandulescu N
Published: August 2020

The phenomenon of quartet condensation in the ground state of an isovector pairing Hamiltonian for an even–even N = Z system is investigated. For this purpose we follow the evolution of the ground state from an unperturbed regime up to a strongly interacting one in a formalism of collective pairs. These pairs are those resulting from the diagonalization of the pairing Hamiltonian in a space of two particles coupled to isospin T = 1. The ground state is found to rapidly evolve from a product of distinct T = 0 quartets, each one formed by two of the above pairs, to a condensate of identical quartets built only with the pair corresponding to the lowest energy. This finding establishes a link between the complicated structure of the exact ground state and the simple approximation scheme of the quartet condensation model. The mechanism at the basis of this quartet condensation turns out to be the same which is responsible for the development of a pair condensate in the ground state of a like-particle pairing Hamiltonian.
Microscopic description of quadrupole-octupole coupling in actinides with the Gogny-D1M energy density functional
Authors: Rodríguez-Guzmán R , Humadi Y M , Robledo L M
Published: August 2020

The interplay between quadrupole and octupole degrees of freedom is discussed in a series of U, Pu, Cm and Cf isotopes both at the mean-field level and beyond. In addition to the static Hartree–Fock–Bogoliubov approach, dynamical beyond-mean-field correlations are taken into account via both parity restoration and symmetry-conserving generator coordinate method calculations based on the parametrization D1M of the Gogny energy density functional. Physical properties such as correlation energies, negative-parity excitation energies as well as reduced transition probabilities B(E1) and B(E3) are discussed in detail and compared with the available experimental data. It is shown that, for the studied nuclei, the quadrupole-octupole coupling is weak and to a large extent the properties of negative parity states can be reasonably well described in terms of the octupole degree of freedom alone.
On the validation of a priori estimates of standard displacement uncertainties in T3-stereocorrelation
Authors: Minguet C , Soulas F , Lafargue-Tallet T , Chalumeau E , Pommies M , Peiffer R , Hild F
Published: August 2020

Uncertainty quantification is crucial for any measurement technique. The present work aims at validating a priori estimates of displacement uncertainties. Images acquired prior to fourteen thermomechanical tests were analyzed via FE-based stereocorrelation to determine actual displacement uncertainties, which were compared to a priori estimates. For the studied experimental database, a very good agreement was observed between a priori and a posteriori estimates of standard displacement uncertainties.
Investigation on the cause of the furnace effect of high-temperature fixed points
Authors: Yamada Yoshiro
Published: August 2020

Investigation into the cause of the furnace effect, encountered in the realization of high-temperature fixed points (HTFPs), was conducted at the copper point. Modifications of the cavity design reduced the furnace effect, which indicates that the furnace effect is caused by the interaction between the furnace and the cavity through reflection at the cavity side wall, linked to the design of the HTFP cells. It was shown that the effect could be mitigated by applying a small aperture at the cavity opening. The difference of the realized temperature from that in the absence of the furnace effect was considered, and it was shown that the effect at the copper point in a HTFP furnace was estimated to be around 14 mK or less, the realized temperature being lower than the true temperature.
Preferred growth direction of III–V nanowires on differently oriented Si substrates
Authors: Zeng Haotian , Yu Xuezhe , Fonseka H Aruni , Boras Giorgos , Jurczak Pamela , Wang Tao , Sanchez Ana M , Liu Huiyun
Published: August 2020

One of the nanowire (NW) characteristics is its preferred elongation direction. Here, we investigated the impact of Si substrate crystal orientation on the growth direction of GaAs NWs. We first studied the self-catalyzed GaAs NW growth on Si (111) and Si (001) substrates. SEM observations show GaAs NWs on Si (001) are grown along four <111> directions without preference on one or some of them. This non-preferential NW growth on Si (001) is morphologically in contrast to the extensively reported vertical <111> preferred GaAs NW growth on Si (111) substrates. We propose a model based on the initial condition of an ideal Ga droplet formation on Si substrates and the surface free energy calculation which takes into account the dangling bond surface density for different facets. This model provides further understanding of the different preferences in the growth of GaAs NWs along selected <111> directions depending on the Si substrate orientation. To verify the prevalence of the model, NWs were grown on Si (311) substrates. The results are in good agreement with the three-dimensional mapping of surface free energy by our model. This general model can also be applied to predictions of NW preferred growth directions by the vapor-liquid-solid growth mode on other group IV and III–V substrates.
Effects of Rashba-spin–orbit coupling on superconducting boron-doped nanocrystalline diamond films: evidence of interfacial triplet superconductivity
Authors: Bhattacharyya Somnath , Mtsuko Davie , Allen Christopher , Coleman Christopher
Published: August 2020

Among the many remarkable properties of diamond, the ability to superconduct when heavily doped with boron has attracted much interest in the carbon community. When considering the nanocrystalline boron doped system, the reduced dimensionality and confinement effects have led to several intriguing observations most notably, signatures of a mixed superconducting phase. Here we present ultra-high-resolution transmission electron microscopy imaging of the grain boundary and demonstrate how the complex microstructure leads to enhanced carrier correlations. We observe hallmark features of spin–orbit coupling (SOC) manifested as the weak anti-localization effect. The enhanced SOC is believed to result from a combination of inversion symmetry breaking at the grain boundary interfaces along with antisymmetric confinement potential between grains, inducing a Rashba-type SOC. From a pronounced zero bias peak in the differential conductance, we demonstrate signatures of a triplet component believed to result from spin mixing caused by tunneling of singlet Cooper pairs through such Rashba-SOC grain boundary junctions.
Anthropogenic forcing enhances rainfall seasonality in global land monsoon regions
Authors: Deng Shulin , Sheng Chen , Yang Ni , Song Lian , Huang Qiuyan
Published: August 2020

Understanding how humanity’s influence on the climate affects rainfall seasonality around the world is immensely important for agriculture production, ecology protection, and freshwater resource management. In this study, we qualitatively and quantitatively analyzed the potential influence of anthropogenic forcing on rainfall seasonality in global land monsoon (GM) regions using the Coupled Model Intercomparison Project Phase 5 (CMIP5) general circulation models. We discovered that anthropogenic forcing enhances rainfall seasonality over many parts of GM regions, and was evident in the South Asian and the most parts of the South American and the South African monsoon regions. Anthropogenic forcing partially but clearly contributed to the increasing trend of rainfall seasonality over many parts of GM regions from 1960 to 2012. Moreover, anthropogenic forcing also increased the probability of more pronounced rainfall seasonality in almost all GM regions. The results provide valuable information for agriculture, ecology, and freshwater resource management under climate warming induced by anthropogenic forcing.
Dynamic softening mechanism of 2 vol.% nano-sized SiC particle reinforced Al-12Si matrix composites during hot deformation
Authors: Wang Zhen , Wang Aiqin , Xie Jingpei
Published: August 2020

The hot deformation behavior of the 2 vol.% nano-SiCp/Al-12Si composites prepared by powder metallurgy is complicated due to the simultaneous presence of nano-sized SiC particles and micro-sized precipitated Si particles. In this paper, the isothermal heat compression test and the transmission electron microscope analysis technique were used to analyze the softening mechanism of the 2 vol.% nano-SiCp/Al-12Si composites based on Z parameters and deformation temperature, and the nucleation mechanism of dynamic recrystallization of the 2 vol.% nano-SiCp/Al-12Si composites was analyzed. The results showed that, when LnZ > 55.02, T ≤ 753 K, the cross slip of dislocation was the main softening mechanism; when LnZ < 55.76, T ≥ 733 K, the softening mechanism mainly includes the cross slip, climbing of dislocation, and untangling of three-dimensional dislocation network; when lnZ ≤ 53.65, T ≥ 773 K, the dynamic recovery and dynamic recrystallization were the main softening mechanism of the composites. The dynamic recrystallization nucleation mechanisms of the 2 vol.% nano-SiCp/Al-12Si composites include the sub-grain combination nucleation and grain boundaries bulging nucleation.