bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation characteristics of longitudinal modes in dusty plasmas
Authors: Shahzad Aamir , Sohail Amjad , Manzoor Alina , Ikram Muhammad , Loya Adil , Ur Rehman Amam , Shakoori Muhammad Asif
Published: January 2023

The space-time correlation function has been obtained in strongly coupled dusty plasmas (SCDPs) using equilibrium molecular dynamics (EMD) simulations. The simulated results for three-dimensional (3D) SCDPs with suitable normalization are computed over a wide domain of plasma parameters (Γ, κ) in a microcanonical ensemble. The EMD simulations indicate that different modes of propagated wave in SCDPs are analyzed for four different values of wave number (k). New investigations of normalized longitudinal current correlation function CL(k, t) show that the amplitude of oscillation and frequency of propagated modes increase with an increase in k. The obtained results for longitudinal modes of oscillation indicate that the dust particles remain in damping behavior at the low Γ, damped oscillation with decreasing amplitude inside decaying exponential envelope at intermediate Г, and sinusoidal oscillation at high Г, depending on κ. The system size (N) does not significantly affect the propagated modes of oscillation, while the periodic oscillation shifts toward higher Γ with increasing N and κ. The computations show that normalized longitudinal CL(k, t) current correlation particularly depend on Coulomb coupling (Γ), Debye screening (κ), and wave number (k). In our simulations, the frequency and the amplitude of oscillation of the dust particles decrease with an increment of κ and system size (N), but the frequency increases and the amplitude decreases with increasing Γ, as expected. It has been demonstrated that the EMD method is used to study the different propagated modes in dusty plasma systems and can be used to predict the damping behavior, damped oscillation, and periodic phenomena in 3D strongly coupled SCDPs.
Collision rates estimated from exact N-body simulations of a one-dimensional plasma
Authors: Gravier Etienne , Drouot Thomas , Lesur Maxime , Guillevic Alejandro , Lo-Cascio Guillaume , Moritz Jérôme , Escande Dominique , Manfredi Giovanni
Published: January 2023

In a plasma, the charged particles interact via long-range forces, and this interaction causes the plasma to exhibit collective effects. If the graininess or coupling parameter g goes to zero (ideal collisionless plasma), two-body collisions are negligible, while collective effects dominate the dynamics. In contrast, when g≈1 collisions play a significant role. To study the transition between a collisionless and a collisional regime, a N-body code was developed and used in this work. The code solves exactly, in one spatial dimension, the dynamics of N infinite parallel plane sheets for both ion and electron populations. We illustrate the transition between individual and collective effects by studying two basic plasma phenomena, the two-stream instability and Langmuir waves, for different values of g. The numerical collision rates given by the N-body code increase linearly with g for both phenomena, although with proportionality factors that differ by roughly a factor of two, a discrepancy that may be accounted for by the different initial conditions. All in all, the usual collision rates published in the literature (Spitzer collisionality) appear to compare rather well with the rates observed in our simulations.
Interaction at a distance: Xenon migration in Mb
Authors: Turan Haydar Taylan , Boittier Eric , Meuwly Markus
Published: January 2023

The transport of ligands, such as NO or O2, through internal cavities is essential for the function of globular proteins, including hemoglobin, myoglobin (Mb), neuroglobin, truncated hemoglobins, or cytoglobin. For Mb, several internal cavities (Xe1 through Xe4) were observed experimentally and they were linked to ligand storage. The present work determines barriers for xenon diffusion and relative stabilization energies for the ligand in the initial and final pocket, linking a transition depending on the occupancy state of the remaining pockets from both biased and unbiased molecular dynamics simulations. It is found that the energetics of a particular ligand migration pathway may depend on the direction in which the transition is followed and the occupancy state of the other cavities. Furthermore, the barrier height for a particular transition can depend in a non-additive fashion on the occupancy of either cavity A or B or simultaneous population of both cavities, A and B. Multiple repeats for the Xe1 → Xe2 transition reveal that the activation barrier is a distribution of barrier heights rather than one single value, which is confirmed by a distribution of transition times for the same transition from unbiased simulations. Dynamic cross correlation maps demonstrate that correlated motions occur between adjacent residues or through space, residue Phe138 is found to be a gate for the Xe1 → Xe2 transition, and the volumes of the internal cavities vary along the diffusion pathway, indicating that there is dynamic communication between the ligand and the protein. These findings suggest that Mb is an allosteric protein.
A comprehensive approach for discrete resilience of complex networks
Authors: Casablanca Rocío M. , Criado Regino , Mesa Juan A. , Romance Miguel
Published: January 2023

The research and use of the term resilience in various types of technological, physiological, and socioeconomic systems has become very topical in recent years since this term has been applied in different fields with different meanings and connotations. One of the most common meanings of resilience is related to a positive idea that addresses recovery from failures. This study proposes to establish a theoretical and mathematical framework for discrete resilience that allows different systems to be quantitatively compared from this point of view. Also, a definition and a local view of the concept of resilience applicable to different characteristic measures in the field of complex networks is provided. Furthermore, several computational experiments are presented on the values of this new parameter in different types of synthetic and real-world networks, supplying a new set of conceptual tools for network science research.
The impact of accelerating diode resonances on L-band high-power long-pulse relativistic backward wave oscillator operation
Authors: Zhou Ning , Zhang Xiaoping , Dang Fangchao , Ge Xingjun , Zhang Peng , Deng Rujin
Published: January 2023

An L-band high-power relativistic backward wave oscillator is designed. In the simulation, microwaves centered at 1.6 GHz are generated, with the power of 3.6 GW and the efficiency of 40%. In the preliminary experiment, the pulse duration of the device was only 45 ns, presenting a pulse-shortening phenomenon. Through the 3D particle-in-cell simulation analysis, it was found that the accelerating diode resonances significantly impact the operation of the L-band high power relativistic backward wave oscillator, and the resonance of a TE11 mode in the accelerating diode played the primary role in the pulse shortening. Moreover, we found that choosing the appropriate distance between the cathode baffle and the end of the annular cathode is beneficial to effectively suppress the starting oscillation of the parasitic TE11 mode. In the improved experiment, we changed the distance between the cathode baffle and the end of the annular cathode from previous 5.4 to 4.6 cm. Eventually, when the diode voltage is 650 kV and the diode current is 14 kA, microwaves centered at 1.58 GHz are generated with the power of 3.3 GW, the efficiency of 36%, and the pulse duration above 104 ns.
Self-excitation of radio waves in the metal–insulator–metal structure doped with metal nanowires
Authors: Bordo V. G.
Published: January 2023

The effect of self-excitation of radio waves in the metal–insulator–metal structure doped with metal nanowires is predicted and its theory is developed. Both the transient stage of self-excitation and the steady-state regime of self-oscillation are analyzed in a fully analytical form. The numerical estimates demonstrate that this effect can be used for diverse practical purposes, in particular, for radio frequency wireless power harvesting. These findings extend the approach developed in nano-optics to the field of electrical engineering.
Spin–orbit coupling corrections for the GFN-xTB method
Authors: Jha Gautam , Heine Thomas
Published: January 2023

Spin–orbit coupling (SOC) is crucial for correct electronic structure analysis in molecules and materials, for example, in large molecular systems such as superatoms, for understanding the role of transition metals in enzymes, and when investigating the energy transfer processes in metal–organic frameworks. We extend the GFN-xTB method, popular to treat extended systems, by including SOC into the hamiltonian operator. We followed the same approach as previously reported for the density–functional tight-binding method and provide and validate the necessary parameters for all elements throughout the Periodic Table. The parameters have been obtained consistently from atomic SOC calculations using the density–functional theory. We tested them for reference structures where SOC is decisive, as in the transition metal containing heme moiety, chromophores in metal–organic frameworks, and in superatoms. Our parameterization paves the path for incorporation of SOC in the GFN-xTB based electronic structure calculations of computationally expensive molecular systems.
A plano–convex thick-lens velocity map imaging apparatus for direct, high resolution 3D momentum measurements of photoelectrons with ion time-of-flight coincidence
Authors: Davino Michael , McManus Edward , Helming Nora G. , Cheng Chuan , Moǧol Gönenç , Rodnova Zhanna , Harrison Geoffrey , Watson Kevin , Weinacht Thomas , Gibson George N. , Saule Tobias , Trallero-Herrero Carlos A.
Published: January 2023

Since their inception, velocity map imaging (VMI) techniques have received continued interest in their expansion from 2D to 3D momentum measurements through either reconstructive or direct methods. Recently, much work has been devoted to the latter of these by relating electron time-of-flight (TOF) to the third momentum component. The challenge is having a timing resolution sufficient to resolve the structure in the narrow (<10 ns) electron TOF spread. Here, we build upon the work in VMI lens design and 3D VMI measurement by using a plano–convex thick-lens (PCTL) VMI in conjunction with an event-driven camera (TPX3CAM) providing TOF information for high resolution 3D electron momentum measurements. We perform simulations to show that, with the addition of a mesh electrode to the thick-lens geometry, the resulting plano–convex electrostatic field extends the detectable electron cutoff energy range while retaining the high resolution. This design also extends the electron TOF range, allowing for a better momentum resolution along this axis. We experimentally demonstrate these capabilities by examining above-threshold ionization in xenon, where the apparatus is shown to collect electrons of energy up to ∼7 eV with a TOF spread of ∼30 ns, both of which are improved compared to a previous work by factors of ∼1.4 and ∼3.75, respectively. Finally, the PCTL-VMI is equipped with a coincident ion TOF spectrometer, which is shown to effectively extract unique 3D momentum distributions for different ionic species in a gas mixture. These techniques have the potential to lend themselves to more advanced measurements involving systems where the electron momentum distributions possess non-trivial symmetries.
Preferential decomposition of the major anion in a dual-salt electrolyte facilitates the formation of organic-inorganic composite solid electrolyte interphase
Authors: Qi Feng , Yu Peiping , Zhou Qiwei , Liu Yue , Sun Qitao , Ma Bingyun , Ren Xinguo , Cheng Tao
Published: January 2023

The performance of a lithium metal battery (LMB) with liquid electrolytes depends on the realization of a stable solid electrolyte interphase (SEI) on the Li anode surface. According to a recent experiment, a high-concentrated (HC) dual-salt electrolyte is effective in modulating the SEI formation and improving the battery performance. However, the underlying reaction mechanism between this HC dual-salt electrolyte and the lithium metal anode surface remains unknown. To understand the SEI formation mechanism, we first performed 95 ps ab initio Molecular Dynamics (AIMD) simulation and then extend this AIMD simulation to another 1 ns by using Hybrid ab Initio and Reactive Molecular Dynamics (HAIR) to investigate the deep reactions of such dual-salt electrolytes consists of lithium difluorophosphate and lithium bis(trifluoromethanesulfonyl)imide in dimethoxyethane (DME) solvent at lithium metal anode surface. We observed the detailed reductive decomposition processes of DFP− and TFSI−, which include the formation pathway of CF3 fragments, LiF, and LixPOFy, the three main SEI components observed experimentally. Furthermore, after extending the simulation to 1.1 ns via the HAIR scheme, the decomposition reactions of DME solvent molecules were also observed, producing LiOCH3, C2H4, and precursors of organic oligomers. These microscopic insights provide important guidance in designing the advanced dual-salt electrolytes for developing high-performance LMB.
Symmetry-breaking rhythms in coupled, identical fast–slow oscillators
Authors: Awal Naziru M. , Epstein Irving R. , Kaper Tasso J. , Vo Theodore
Published: January 2023

Symmetry-breaking in coupled, identical, fast–slow systems produces a rich, dramatic variety of dynamical behavior—such as amplitudes and frequencies differing by an order of magnitude or more and qualitatively different rhythms between oscillators, corresponding to different functional states. We present a novel method for analyzing these systems. It identifies the key geometric structures responsible for this new symmetry-breaking, and it shows that many different types of symmetry-breaking rhythms arise robustly. We find symmetry-breaking rhythms in which one oscillator exhibits small-amplitude oscillations, while the other exhibits phase-shifted small-amplitude oscillations, large-amplitude oscillations, mixed-mode oscillations, or even undergoes an explosion of limit cycle canards. Two prototypical fast–slow systems illustrate the method: the van der Pol equation that describes electrical circuits and the Lengyel–Epstein model of chemical oscillators.
Acoustothermal phase change and acoustically driven atomization for cold liquid microthrusters
Authors: Horesh Amihai , Connacher William , Friend James
Published: January 2023

Over the years, a diverse range of physical and chemical phenomena have been explored and applied to devise reliable, small thrusters for stationkeeping and orientation of spacecraft. Commercial space flight is accelerating this need. Here, we consider acoustically driven melting of a frozen working fluid in the nozzle of an acoustic device, followed by acoustofluidic atomization from the nozzle to produce thrust. Fifty-five MHz acoustic waves generated by piezoelectric transducers couple into liquid and transfer energy in the form of both acoustic radiation and streaming, producing a directed atomized spray. A challenge in this system, as with most liquid-thrust systems, is the risk of phase change due to the extreme thermal environment in space, particularly in the freezing of the working fluid. Though acoustic energy is known to produce rapid and controllable heating, it so far has not been used to produce phase changes. The atomization produces capillary pressure sufficient to draw in fluid from a reservoir, though we do use a simple pressure-driven pump to support greater atomization rates. We provide a simple energy conservation model to explain the acoustothermal interaction and validate this with experiments. The specific impulse and thrust of this type of thruster are quite modest at 0.1–0.4 s and 12.3 μN, respectively, but the thruster component is small, light, and is without moving parts, a fascinating potential alternative to current technologies.
Seebeck, Peltier, and Soret effects: On different formalisms for transport equations in thermogalvanic cells
Authors: Kjelstrup Signe , Kristiansen Kim R. , Gunnarshaug Astrid F. , Bedeaux Dick
Published: January 2023

Thermogalvanic cells convert waste heat directly to electric work. There is an abundance of waste heat in the world and thermogalvanic cells may be underused. We discuss theoretical tools that can help us understand and therefore improve on cell performance. One theory is able to describe all aspects of the energy conversion: nonequilibrium thermodynamics. We recommend to use the theory with operationally defined, independent variables, as others have done before. These describe well-defined experiments. Three invariance criteria serve as a basis for any description: of local electroneutrality, entropy production invariance, and emf’s independence of the frame of reference. Alternative formalisms, using different sets of variables, start with ionic or neutral components. We show that the heat flux is not the same in the two formalisms and derive a new relationship between the heat fluxes. The heat flux enters the definition of the Peltier coefficient and is essential for the understanding of the Peltier heat at the electrode interfaces and of the Seebeck coefficient of the cell. The Soret effect can occur independently of any Seebeck effect, but the Seebeck effect will be affected by the presence of a Soret effect. Common misunderstandings are pointed out. Peltier coefficients are needed for the interpretation and design of experiments.
Calculation of exciton couplings based on density functional tight-binding coupled to state-interaction state-averaged ensemble-referenced Kohn–Sham approach
Authors: Kim Tae In , Lee In Seong , Kim Hwon , Min Seung Kyu
Published: January 2023

We introduce the combination of the density functional tight binding (DFTB) approach, including onsite correction (OC) and long-range corrected (LC) functional and the state-interaction state-averaged spin-restricted ensemble-referenced Kohn–Sham (SI-SA-REKS or SSR) method with extended active space involving four electrons and four orbitals [LC-OC-DFTB/SSR(4,4)], to investigate exciton couplings in multichromophoric systems, such as organic crystals and molecular aggregates. We employ the LC-OC-DFTB/SSR(4,4) method to calculate the excitonic coupling in anthracene and tetracene. As a result, the LC-OC-DFTB/SSR(4,4) method provides a reliable description of the locally excited (LE) state in a single chromophore and the excitonic couplings between chromophores with reasonable accuracy compared to the experiment and the conventional SSR(4,4) method. In addition, the thermal fluctuation of excitonic couplings from dynamic nuclear motion in an anthracene crystal with LC-OC-DFTB/SSR(4,4) shows a similar fluctuation of excitonic coupling and spectral density with those of first-principle calculations. We conclude that LC-OC-DFTB/SSR(4,4) is capable of providing reasonable features related to LE states, such as Frenkel exciton with efficient computational cost.
Influence of thermocapillary flow induced by a heated substrate on atomization driven by surface acoustic waves
Authors: Muñoz J. , Arcos J. , Bautista O. , Méndez F.
Published: January 2023

Thermocapillary flow on the mechanism of interfacial destabilization prior to atomization of a sessile Newtonian droplet subjected to surface acoustic waves (SAWs) is analyzed. We assumed that an interfacial temperature distribution is induced on the free surface of the millimeter-sized water droplet since the droplet is on a heated substrate. Given the dependence of surface tension on interfacial temperature, shear stresses combined with SAWs lead to the development of thermocapillary flow. The evolution equation for a small-scale droplet under the combined influence of SAW atomization and thermocapillary flow is derived via an asymptotic approach to the hydrodynamic equations, arising the acoustic capillary and Marangoni numbers. In this limit, our simplified droplet model can predict capillary instability leading to atomization once a critical amplitude is reached for the induced capillary waves at the liquid droplet. In doing so, our model also represents the influence of the thermocapillary effect on the interfacial deformation of the droplet and shows how the Marangoni flow promoted by a heated substrate counteracts the acoustic stress, leading to a virtually uniform droplet aspect ratio and thus larger aerosol diameters compared to the isothermal case. These results are supported by the development of a novel analytical expression that has allowed us to estimate the characteristic aerosol size under thermocapillary flow and SAW excitation, and to postulate thermocapillary flow as a new valuable means of explaining the regulation of the characteristic aerosol size at SAW atomization.
Tunable rapid electron transport in titanium oxide thin films
Authors: Li Runze , Yan Faguang , Deng Yongcheng , Shang Yaxuan , Sheng Yu
Published: January 2023

Rapid electron transport triggers many novel physical phenomena and becomes a critical point for high-speed electronics. Two-dimensional electron gas (2DEG) has drawn great attention due to its high electron mobility, and this has been observed in different materials, such as semiconductor, oxide interfaces, and 2D materials. In this paper, we report, for the first time, the existence and electrical manipulation of 2DEG in the Schottky quantum well, which was formed in the titanium oxide thin films. We take the asymmetry interface electron scattering effect into consideration when studying the electrical transport properties of our multilayer thin films. We found electrons would be transferred from the low-mobility semiconducting and metallic conductive channels to the high-mobility 2DEG conductive channel with an in-plane applied electric field. Therefore, electron concentration and mobility of the 2DEG formed in the Schottky quantum well could be tuned, and the nano-devices exhibited non-linear voltage–current curves. The differential resistivity of the nano-devices could decrease by two orders with increasing electric field at room temperature. Weak electron localization of electrons was experimentally observed in our nano-devices at low temperature, which further demonstrated the existence of 2DEG in the Schottky quantum well. Our work will provide us new physics about the rapid electron transport in the multilayer thin films and bring novel functional devices for the modern microelectronic industry.
Enhanced piezoelectric response of Aurivillius ferroelectrics by constructing a novel solid solution and combining traditional chemical substitution
Authors: Guan Shangyi , Wu Xiaojun , Shi Wei , Wu Yutong , Xu Hongfei , Lang Rong , Chen Yu , Tan Zhi , Xing Jie , Zhu Jianguo , Chen Qiang
Published: January 2023

With the increasing demand for high-temperature piezoelectric ceramics, excellent piezoelectricity and high Curie temperature are required simultaneously. Herein, combining the advantages of constructing new-type solid solutions and traditional A-site doping strategy, Aurivillius ferroelectrics (Na0.5Bi0.5)0.5−x/2(Li0.5Ce0.5)x/2Bi2.5Ti0.5Nb1.5O9 (NBTN-LC100x, x = 0–0.16) were designed to achieve the large piezoelectric response and high Curie temperature simultaneously. The existence of a pseudo-tetragonal phase boundary together with the reduction of domain size produces a large piezoelectric coefficient (d33 ∼ 24.6 pC/N) with a fairly high TC (∼825 °C). Moreover, pseudo-tetragonal distortion might be responsible for the excellent thermal stability of d33 against thermal depolarization temperature (Td). For NBTN-LC12, high-temperature electric resistivity is still above 1 × 105 Ω cm at 600 °C. The improved comprehensive properties of NBTN-LC100x ceramics demonstrate that the construction of a novel Aurivillius ferroelectrics is a promising way to explore high-temperature sensor materials.
Surface states passivation in GaN single crystal by ruthenium solution
Authors: Kumar Navneet , Kumar Ashish , Chand Fakir
Published: January 2023

GaN single crystal samples were cleaned and passivated with ruthenium solution. Photoluminescence (PL) and scanning tunneling spectroscopy (STS) were used to characterize the passivated surface. PL study showed an effective increase in band edge emission after passivation. I–V (current–voltage) and dI/dV (differential conductance) spectra measurements of GaN single crystal samples using ambient STS revealed the variation in the density of states (local), shifting of Fermi-level position, and onset/offset of valence and conduction bands. We found a significant change in I–V and dI/dV measurements after surface treatment, which means modification in surface electronic properties. The ruthenium solvent passivates the surface states, converting the surface into a highly ordered and air oxidation-resistant state. Finally, Ni/GaN Schottky diodes were fabricated to demonstrate improved device characteristics after passivation, which was a direct indication of improved GaN interface due to ruthenium passivation.
Strain induced power enhancement of far-UVC LEDs on high temperature annealed AlN templates
Authors: Knauer A. , Kolbe T. , Hagedorn S. , Hoepfner J. , Guttmann M. , Cho H. K. , Rass J. , Ruschel J. , Einfeldt S. , Kneissl M. , Weyers M.
Published: January 2023

High temperature annealed AlN/sapphire templates exhibit a reduced in-plane lattice constant compared to conventional non-annealed AlN/sapphire grown by metalorganic vapor phase epitaxy (MOVPE). This leads to additional lattice mismatch between the template and the AlGaN-based ultraviolet-C light emitting diode (UVC LED) heterostructure grown on these templates. This mismatch introduces additional compressive strain in AlGaN quantum wells resulting in enhanced transverse electric polarization of the quantum well emission at wavelengths below 235 nm compared to layer structures deposited on conventional MOVPE-grown AlN templates, which exhibit mainly transverse magnetic polarized emission. In addition, high temperature annealed AlN/sapphire templates also feature reduced defect densities leading to reduced non-radiative recombination. Based on these two factors, i.e., better outcoupling efficiency of the transverse electric polarized light and an enhanced internal quantum efficiency, the performance characteristic of far-UVC LEDs emitting at 231 nm was further improved with a cw optical output power of 3.5 mW at 150 mA.
Toward achieving cost-effective hexagonal BN semi-bulk crystals and BN neutron detectors via halide vapor phase epitaxy
Authors: Alemoush Z. , Hossain N. K. , Tingsuwatit A. , Almohammad M. , Li J. , Lin J. Y. , Jiang H. X.
Published: January 2023

Presently, thermal neutron detectors fabricated from boron-10 enriched hexagonal boron nitride (h-10BN) ultrawide bandgap semiconductor grown by metal organic chemical vapor deposition (MOCVD) hold the record high detection efficiency among all solid-state detectors at 59%. To overcome the short comings of MOCVD growth, including inherently low growth rate and unavoidable impurities such as carbon in metal organic source, we demonstrate here the growth of natural hexagonal boron nitride (h-BN) semi-bulk wafers using halide vapor phase epitaxy (HVPE), which is an established technique for producing GaN semi-bulk crystals at a high growth rate. Electrical transport characterization results revealed that these HVPE grown materials possess an electrical resistivity of 1 × 1013 Ω cm, and a charge carrier mobility and lifetime product of 2 × 10−4 cm2/V s. Detectors fabricated from a 100 μm thick h-BN wafer have demonstrated a thermal neutron detection efficiency of 20%, corresponding to a charge collection efficiency of ∼60% at an operating voltage of 500 V. This initial demonstration opens the door for mass producing high efficiency h-BN semiconductor neutron detectors at a reduced cost, which could create unprecedented applications in nuclear energy, national security, nuclear waste monitoring and management, the health care industry, and material sciences.
Investigation of the derivation and consistency of the quasi-two-dimensional flamelet models for non-premixed flames
Authors: Yu Panlong , Kurose Ryoichi , Watanabe Hiroaki
Published: January 2023

Three non-premixed quasi-two-dimensional flamelet (Q2DF) models can be derived via integrating one-dimensional flamelet libraries, which are generated by premixing the third stream with the fuel stream or (and) the oxidizer stream as the premix fraction (η) varied from zero to unity. These models are attractive and considered effective substitutes for two-dimensional flamelet (2DF) formulations; however, the connections between these Q2DF models and 2DF equations have not been clearly illustrated formerly. In this work, the 2DF formulations are converted from the space defined by two mixture fractions (Z1×Z2) to that used for each Q2DF model (ξ×η) in which ξ designates a newly defined mixture fraction. For moderate Reynolds number conditions, it is considered that the Q2DF models and the 2DF formulations are equivalents as the one-dimensional (1D) flamelet elemental libraries are integrated upon sufficient grids of η. To confirm this, the two-dimensional (2D) direct numerical simulations (DNS) and three-dimensional (3D) large-eddy simulation (LES) are performed to provide reference data since it is readily to associate the 2DF formulations with variable transports in physical space. The 2D DNS cases present various three-feed systems characterized by different third streams and ensure a well-mixed mixture in moderate η, while the 3D LES case is performed with a large flux of pure CO2 as the third stream. Three Q2DF models are compared by using the same tracking parameters obtained from, respectively, the DNSs and LES. The comparisons based on the DNS cases demonstrate that the Q2DF models can reproduce the DNS data with quite satisfying accuracy, and it is confirmed that the accuracy has nothing to do with the type of the third stream. Through the LES results and the related comparisons, it can be concluded that the Q2DF models are reliable to predict the experimental measurements, and on the condition of a sufficient η resolution, the three Q2DF models can give the same prediction in the whole range of η.
Kinetic-enhanced carbon fiber for rechargeable zinc–air batteries
Authors: Li Yang , Wang Bin , Wang Hao-Fan , Tang Cheng
Published: January 2023

Metal-free catalysts are made by the elements with infinite reserve in nature and, therefore, show the potential for large-scale applications in energy devices including metal–air batteries. The construction of metal–air batteries prefers using self-supporting catalysts with favorable activity as well as fast kinetics. However, it is challenging due to the limited electropositivity of metal-free catalysts for O–O bond formation in oxygen evolution reaction (OER), scaling relationship restrictions between OER and oxygen reduction reaction, and difficulty in porosity construction on the monolith electrode surface. In this contribution, through developing a facile methodology of quenching high-temperature carbon clothes in liquid nitrogen, a self-supported carbon cloth with bifunctional active graphene skin and fast kinetics is well constructed to serve as the air cathode in metal–air batteries. Regulated oxygen species and three-dimensionally hierarchical porosity are well constructed on the carbon fiber surfaces, contributing high intrinsic activity and prominently enhanced kinetics, which leads to favorable performances in aqueous as well as flexible rechargeable zinc–air batteries. The work proposed a promising strategy in the rational design and smart synthesis of fast-kinetic monolith electrodes, which refreshes concepts and strategies of advanced material fabrication, and also bridges material science and practical energy devices.
The loss of the property of locality of the kernel in high-dimensional Gaussian process regression on the example of the fitting of molecular potential energy surfaces
Authors: Manzhos Sergei , Ihara Manabu
Published: January 2023

Kernel-based methods, including Gaussian process regression (GPR) and generally kernel ridge regression, have been finding increasing use in computational chemistry, including the fitting of potential energy surfaces and density functionals in high-dimensional feature spaces. Kernels of the Matern family, such as Gaussian-like kernels (basis functions), are often used which allow imparting to them the meaning of covariance functions and formulating GPR as an estimator of the mean of a Gaussian distribution. The notion of locality of the kernel is critical for this interpretation. It is also critical to the formulation of multi-zeta type basis functions widely used in computational chemistry. We show, on the example of fitting of molecular potential energy surfaces of increasing dimensionality, the practical disappearance of the property of locality of a Gaussian-like kernel in high dimensionality. We also formulate a multi-zeta approach to the kernel and show that it significantly improves the quality of regression in low dimensionality but loses any advantage in high dimensionality, which is attributed to the loss of the property of locality.
We don’t know the half of it: morphological and molecular evidence reveal dramatic underestimation of diversity in a key pollinator group (Nemestrinidae)
Authors: Theron Genevieve L. , Anderson Bruce , Cozien Ruth J. , Ellis Allan G. , Grenier Florent , Johnson Steven D. , Newman Ethan , Pauw Anton , van der Niet Timotheüs
Published: January 2023

Nemestrinidae (tangle-veined flies) are important pollinators of numerous southern African plant species. Despite their known ecological importance, the family has received little taxonomic attention in recent years and the systematics of the group is poorly understood. In this study we aimed to assess the phylogenetic relationships and species diversity among three southern African nemestrinid genera from the Nemestrininae subfamily: Prosoeca, Moegistorhynchus and Stenobasipteron, with a specific focus on the largest among these, Prosoeca. We reconstructed a molecular phylogeny using both mitochondrial and nuclear (COI, 16S rRNA, 28S rRNA and CAD) DNA sequence data. Both morphology and molecular species delimitation methods (Automatic Barcode Gap Discovery and the Bayesian Poisson Tree Process) were used to estimate species diversity. The topology from the combined analysis places a monophyletic Moegistorhynchus as the sister group to a paraphyletic Prosoeca with Stenobasipteron nested inside Prosoeca. In all three genera, almost half of the putative species sampled did not match the concept of described species based on morphology. Analysis of phylogenetic diversity showed that undescribed putative species make a substantial contribution to the overall phylogenetic diversity among the sampled species. Comparisons among biogeographic regions suggested that diversity is concentrated in multiple biodiversity hotspots and biomes, particularly in Fynbos and Grassland biomes. The numerous undescribed species and paraphyly of Prosoeca both emphasise the need for increased taxonomic attention for this ecologically important group of flies in particular, and for southern African insect taxa in general.
Using integrative taxonomy to distinguish cryptic halfbeak species and interpret distribution patterns, fisheries landings, and speciation
Authors: Riley Indiana J. , DiBattista Joseph D. , Stewart John , Schilling Hayden T. , Suthers Iain M.
Published: January 2023

Context Species classification disputes can be resolved using integrative taxonomy, which involves the use of both phenotypic and genetic information to determine species boundaries. Aims Our aim was to clarify species boundaries of two commercially important cryptic species of halfbeak (Hemiramphidae), whose distributions overlap in south-eastern Australia, and assist fisheries management. Methods We applied an integrative taxonomic approach to clarify species boundaries and assist fisheries management. Key results Mitochondrial DNA and morphological data exhibited significant differences between the two species. The low level of mitochondrial DNA divergence, coupled with the lack of difference in the nuclear DNA, suggests that these species diverged relatively recently (c. 500 000 years ago) when compared with other species within the Hyporhamphus genus (>2.4 million years ago). Genetic differences between the species were accompanied by differences in modal gill raker counts, mean upper-jaw and preorbital length, and otolith shape. Conclusions On the basis of these genetic and morphological differences, as well as the lack of morphological intergradation between species along the overlapping boundaries of their geographical distributions, we propose that Hyporhamphus australis and Hyporhamphus melanochir remain valid species. Implications This study has illustrated the need for an integrative taxonomic approach when assessing species boundaries and has provided a methodological framework for studying other cryptic fish species in a management context.
Agonist of growth hormone-releasing hormone improves the disease features of spinal muscular atrophy mice
Authors: Boido Marina , Gesmundo Iacopo , Caretto Anna , Pedrolli Francesca , Schellino Roberta , Leone Sheila , Cai Renzhi , Sha Wei , Ghigo Ezio , Schally Andrew V. , Vercelli Alessandro , Granata Riccarda
Published: January 2023

Spinal muscular atrophy (SMA) is a severe autosomal recessive neuromuscular disease affecting children and young adults, caused by mutations of the survival motor neuron 1 gene (
SMN1
). SMA is characterized by the degeneration of spinal alpha motor neurons (αMNs), associated with muscle paralysis and atrophy, as well as other peripheral alterations. Both growth hormone-releasing hormone (GHRH) and its potent agonistic analog, MR-409, exert protective effects on muscle atrophy, cardiomyopathies, ischemic stroke, and inflammation. In this study, we aimed to assess the protective role of MR-409 in SMNΔ7 mice, a widely used model of SMA. Daily subcutaneous treatment with MR-409 (1 or 2 mg/kg), from postnatal day 2 (P2) to euthanization (P12), increased body weight and improved motor behavior in SMA mice, particularly at the highest dose tested. In addition, MR-409 reduced atrophy and ameliorated trophism in quadriceps and gastrocnemius muscles, as determined by an increase in fiber size, as well as upregulation of myogenic genes and inhibition of proteolytic pathways. MR-409 also promoted the maturation of neuromuscular junctions, by reducing multi-innervated endplates and increasing those mono-innervated. Finally, treatment with MR-409 delayed αMN death and blunted neuroinflammation in the spinal cord of SMA mice. In conclusion, the present study demonstrates that MR-409 has protective effects in SMNΔ7 mice, suggesting that GHRH agonists are promising agents for the treatment of SMA, possibly in combination with SMN-dependent strategies.
Study of fatigue crack growth behaviour of Al-Mg and Al-Mg-Sc-Zr alloys
Authors: Li Zhiliang , Jiang Feng , Liu Lele , Wang Ying
Published: January 2023

Fatigue crack growth behaviour of Al-Mg and Al-Mg-Sc-Zr alloys is studied under different orientations and stress ratios. The microstructures and the fracture morphologies of each alloy are observed. For both alloys, they have Brass, S and Goss texture; while only Al-Mg alloy has Cube texture which indicates recrystallisation; as fatigue crack propagated, intergranular fracture transformed into transgranular fracture accompanied with gradually coarser crack surfaces. Al-Mg alloy is featured by large recrystallised grain, favourable plasticity, rougher crack surfaces, and with relatively strong crack growth resistance before rapid growth. While Al-Mg-Sc-Zr alloy with small grain size and relatively smoother crack surfaces, shown cyclic stability at higher Δ K level.
Superscattering of Underwater Sound via Deep Learning Approach
Authors: Miao Wenjie , Linghu Zhiang , Du Qiujiao , Peng Pai , Liu Fengming
Published: January 2023

We design a multilayer cylindrical structure to realize superscattering of underwater sound. Because of the near degeneracy of resonances in multiple channels of the structure, the scattering contributions from these resonances can overlap to break the single-channel limit of subwavelength objects. However, tuning the design parameters to achieve the target response is an optimization process that is tedious and time-consuming. Here, we demonstrate that a well-trained tandem neural network can deal with this problem efficiently, which can not only forwardly predict the scattering spectra of the multilayer structure with high precision, but also inversely design the required structural parameters efficiently.
Strain-Enabled Control of Chiral Magnetic Structures in MnSeTe Monolayer
Authors: Wang Zhiwen , Liang Jinghua , Yang Hongxin
Published: January 2023

Chiral magnetic states are promising for future spintronic applications. Recent progress of chiral spin textures in two-dimensional magnets, such as chiral domain walls, skyrmions, and bimerons, have been drawing extensive attention. Here, via first-principles calculations, we show that biaxial strain can effectively manipulate the magnetic parameters of the Janus MnSeTe monolayer. Interestingly, we find that both the magnitude and the sign of the magnetic constants of the Heisenberg exchange coupling, Dzyaloshinskii–Moriya interaction and magnetocrystalline anisotropy can be tuned by strain. Moreover, using micromagnetic simulations, we obtain the distinct phase diagram of chiral spin texture under different strains. Especially, we demonstrate that abundant chiral magnetic structures including ferromagnetic skyrmion, skyrmionium, bimeron, and antiferromagnetic spin spiral can be induced in the MnSeTe monolayer. We also discuss the effect of temperature on these magnetic structures. The findings highlight the Janus MnSeTe monolayer as a good candidate for spintronic nanodevices.
On the unit component of the Newman–Unti group
Authors: Schmeding Alexander
Published: January 2023

In this short note we identify the unit component of the Newman–Unti (NU) group in the fine very strong topology. In previous work, this component has been endowed with an infinite-dimensional Lie group structure, while the full NU-group does not support such a structure.
Multi-functional application potential of Ruddlesden–Popper perovskite-based heterostructure PtSe2/Cs2PbI4 with tunable electronic properties
Authors: Liao Cheng-Sheng , Liu Biao , Yang Jun-Liang , Cai Meng-Qiu
Published: January 2023

Heterogeneous stacking based on two-dimensional Ruddlesden–Popper (RP) perovskite is a desired strategy for the reasonable combination of stability and efficiency. Constructing heterostructures with tunable optoelectronic properties further provide opportunities to design multi-functional devices. Herein, we present a first-principle research to investigate the geometric and electronic structures of RP perovskite heterostructure PtSe2/Cs2PbI4 and its tunable electronic properties induced by thickness modulation and external strains. The results indicate that the heterostructure based on Cs2PbI4 monolayer and PtSe2 monolayer has a type-II band alignment, which is suitable for the photovoltaic applications. With the layer number of PtSe2 in heterostructure increases from monolayer to bilayer, the band alignment of PtSe2/Cs2PbI4 heterostructure can switch from type-II to type-I, which is beneficial for the luminescence device applications. However, when the thickness of PtSe2 in heterostructure further increases to trilayer, the heterostructure exhibits metallic characteristic with a p-type Schottky barrier. In addition, we find the strain engineering is an effective knob in tuning the electronic properties of PtSe2/Cs2PbI4 heterostructures with different thickness. These findings reveal the potential of PtSe2/Cs2PbI4 heterostructure as a tunable hybrid material with substantial prospect in multi-functional applications.
Impact of humidity and flowrate on the thoron measurement sensitivity of electrostatic radon monitors
Authors: He Chunyu , Wang Hao , Zhang Lei , Guo Qiuju
Published: January 2023

The accurate measurement of thoron activity concentration is an important issue in both thoron exposure evaluation and in reducing its influence on radon measurement. For radon monitors based on electrostatic collection technique and an alpha spectrometry analyser, air humidity and sampling flowrate are key factors influencing the sensitivity of thoron activity concentration measurement. For the purpose of improving thoron measurement sensitivity and stability, theoretical derivation and experimental studies were systemically performed in this study. The results show that thoron measurement sensitivity decreases as a negative exponential function with absolute humidity increasing, and the sensitivity of thoron is much lower than that of radon under the same conditions, which is mainly caused by the small value of the concentration ratio of thoron inside to outside of the chamber. When the air exchange rate of the measurement chamber (sampling flowrate/inner volume) increases, the measurement sensitivity of thoron gas first increases rapidly and then decreases slowly after reaching its maximum at the air exchange rate of 0.24 s−1. In practice, in the normal air exchange rate range (for example <0.05 s−1), increasing the sampling flowrate could greatly improve the thoron measurement sensitivity, which consequently suggests an effective way to update thoron measurement under the present conditions of the monitor.
Novel absolute length measurement method for etalon sensor using optical comb pulsed interference and harmonic etalon reflections
Authors: Masuda Shusei , Kadoya Shotaro , Michihata Masaki , Takahashi Satoru
Published: January 2023

A Fabry–Perot interferometer, also called an etalon, is used in various applications such as resonant structures for lasers, wavelength filters, length and frequency standards, and sensors. When the etalon is used as sensor, both the high resolution and simplicity of the measurement mechanism are required. We propose a method using an optical comb and an etalon harmonically. Using this method, it is possible to achieve measurements with resolution of less than a few nanometers and improved sensitivity. This method can be implemented with a simple system, and traceability can be easily achieved from the characteristics of the optical comb without the need for a high-precision wavelength meter. In this study, in addition to proposing a method, we implemented measurement system including a repetition frequency scanning optical comb and verified it experimentally. The repeatability of the measurement was approximately 3.0 nm (σ = 2) when 175 mm etalon was used. The measured absolute value of the etalon length was compared to the coordinate measuring machine (CMM) measurement results and difference between the two values was <1 μm that indicated the absolute values agreed well with the maximum permissible length error range of the CMM. The etalon displacement was measured, and the result was compared to that of the conventional He–Ne interferometer. The difference between the two was less than 1 nm, indicating the validity of the measurement and its applicability as sensor. These results demonstrated that the proposed measurement method is feasible and functional for etalon sensor.