bluuebunny/crossref_metadata_2025 huggingface dataset:
Lie-group method solutions for a viscous flow in a dilating-squeezing permeable channel with velocity slip
Authors: Mandal Sougata , Ghosh Sukhendu
Published: April 2023

The investigation focuses on the effects of wall velocity slip on the solution of a viscous, laminar, incompressible channel flow subjected to small-scaled contraction and expansion of the weakly permeable walls. The study of such flow systems is often contextual for fluid transport in biological organisms. In the considered flow configuration, the vertically moving porous walls enable the fluid to enter or exit with a constant rate. The tangential slip velocity of the flow at the porous walls is modeled with the Navier slip boundary condition. The flow dynamics inside the channel is governed by the full Navier–Stokes equations. The Lie symmetry analysis and the invariant method are adopted to reduce the number of independent variables in the system of governing equations. Consequently, a single fourth-order ordinary differential equation is obtained, which is solved analytically by the double perturbation method and the variation of iteration method. The solutions are compared for different arrangements. Furthermore, the approximated analytical solutions are likened to the numerical solutions obtained from a fourth-order Runge–Kutta solver embedding the Shooting method to check the accuracy. It is observed that the boundary layers are formed, and the flow rapidly turns near the walls, when suction and wall contraction coexist. Alternatively, if injection and wall expansion are paired, the flow adjacent to the walls is delayed. The existence of wall velocity slip advances the near-wall velocity and cuts down the speed of centerline velocity. It results in a change in the volumetric flow rate and shear rate. The overall pressure is also varied by higher wall velocity slip. The results are explored for different values of the permeation Reynold number and the dimensionless wall dilation rate to capture all possible impacts of the flow parameters. The current analysis rectifies the existing errors in the work of Boutros et al. [“Lie-group method solution for two-dimensional viscous flow between slowly expanding or contracting walls with weak permeability,”Appl. Math. Model. 31(6), 1092–1108 (2007)] with the no-slip boundary condition and discusses the overall influences of slip boundary condition on the Lie symmetry solution of the flow system.
An experimental and analytical study of wind turbine wakes under pressure gradient
Authors: Dar Arslan Salim , Gertler Abraham Starbuck , Porté-Agel Fernando
Published: April 2023

This work is dedicated to the systematic investigation of wind turbine wakes under the effect of pressure gradients. Wind tunnel experiments are carried out with a wind turbine positioned on straight ramps of increasing angle such that it experiences an approximately linear flow speed-up/slow-down from the induction region into the far wake. Fifteen ramp angles are studied: 7 favorable (FPG), 7 adverse (APG), and 1 zero pressure gradient. The wake center is shown to follow the base flow streamline originating from a virtual turbine hub height. A quasi-linear relationship between the pressure gradient and near wake length is demonstrated. Far wake characteristics, such as the recovery of the wake center velocity deficit and wake growth rate, are observed to systematically vary with the pressure gradient. The wake recovery rate increases (decreases) with the increase in the FPG (APG), and the wake growth rate shows a linear increase from most favorable to most adverse pressure gradient. The turbine power coefficient decreases significantly with increasing APG to a greater degree than the increase in power coefficient under FPG. The engineering approach of superposing the wake deficit predicted by the standard Gaussian model on the modified base flow is shown to work for very moderate pressure gradients. In light of this, a threshold in terms of flow speed-up/slow-down along the wake trajectory is established, below which the engineering approach can be reasonably employed. Finally, a physics-based model for wakes under the pressure gradient is tested. A new theoretical relation for near wake length under the pressure gradient is proposed. Using the theoretical near wake length, the pressure gradient model predicts the turbine wakes for all cases with good accuracy and shows a significant improvement from the engineering approach.
Improved piezoelectric properties through manganese-doping in phase coexistence region in lead strontium zirconate titanate (PSZT) thin films
Authors: Priyadarsini V. , Pradeep Athul , Jumana P. J. , Kanno Isaku , Kumar V.
Published: April 2023

In the quaternary system PbTiO3-PbZrO3-SrTiO3-SrZrO3, compositions that lie close to the antiferroelectric tetragonal and ferroelectric rhombohedral (AFET-FER) phase boundary have potential applications in micro-actuators. However, in thin films, this phase boundary is reported to shift significantly to the zirconium-rich region. Hence, it is necessary to seek alternative approaches to stabilize the tetragonal AFE phase in such compositions. Therefore, this study explores the effect of B-site Mn3+-doping on their structure. Dielectric, ferroelectric, and piezoelectric characteristics of such thin films have been compared with those with increasing Zr/Ti ratios to understand the efficacy of this approach. Transverse piezoelectric coefficient, e31,f, and bipolar strain are found to be higher in Mn3+-doped thin films. Furthermore, large strains and e31,f in thin films have been correlated with structural modifications revealed by systematic Raman spectroscopic investigations.
Polarization study of single color centers in aluminum nitride
Authors: Cannon J. K. , Bishop S. G. , Hadden J. P. , Yağcı H. B. , Bennett A. J.
Published: April 2023

Color centers in wide-bandgap semiconductors are a promising class of solid-state quantum light source, many of which operate at room temperature. We examine a family of color centers in aluminum nitride, which emits close to 620 nm. We present a technique to rapidly map an ensemble of these single photon emitters, identifying all emitters, not just those with absorption dipole parallel to the laser polarization. We demonstrate a fast technique to determine their absorption polarization orientation in the c-plane, finding they are uniformly distributed in orientation, in contrast to many other emitters in crystalline materials.
Bond formation insights into the Diels–Alder reaction: A bond perception and self-interaction perspective
Authors: Schulze Wanja Timm , Schwalbe Sebastian , Trepte Kai , Croy Alexander , Kortus Jens , Gräfe Stefanie
Published: April 2023

The behavior of electrons during bond formation and breaking cannot commonly be accessed from experiments. Thus, bond perception is often based on chemical intuition or rule-based algorithms. Utilizing computational chemistry methods, we present intrinsic bond descriptors for the Diels–Alder reaction, allowing for an automatic bond perception. We show that these bond descriptors are available from localized orbitals and self-interaction correction calculations, e.g., from Fermi-orbital descriptors. The proposed descriptors allow a sparse, simple, and educational inspection of the Diels–Alder reaction from an electronic perspective. We demonstrate that bond descriptors deliver a simple visual representation of the concerted bond formation and bond breaking, which agrees with Lewis’ theory of bonding.
High level ab initio and density functional study of TeF6+ and TeCl6+: Attainability of +7 oxidation state for tellurium
Authors: Kim Joonghan , Park Eunji , Park Jeongmin , Kim Jungyoon , Yoon Kihwan , Oh Dakyeung , Lee Junho , Kim Tae Wu , Kim Tae Kyu
Published: April 2023

Discovery of a new oxidation state for an element expands its chemistry. A high oxidation state, such as +7, is rare for sp-block elements except for halogens. In this study, we determined that Te can attain a +7 oxidation state through the existence of a distorted octahedron (DOH) structure of TeCl6+ based on coupled cluster singles and doubles with perturbative triples calculations. We propose a new type of isomerization that resembles pseudorotation. The octahedron structure of TeF6+ bearing one elongated axial bond isomerizes to a DOH via an associated pseudorotation.
Simulation of superfluid fountain effect using smoothed particle hydrodynamics
Authors: Kincl Ondřej , Schmoranzer David , Pavelka Michal
Published: April 2023

This paper investigates the applicability of smoothed particle hydrodynamics in simulations of superfluid helium-4. We devise a new approach based on Hamiltonian mechanics suitable for simulating thermally driven and weakly compressible flows with free surfaces. The method is then tested in three cases, including a simulation of the fountain effect. We obtain remarkable agreement with referential and theoretical results. The simulations provide new physical insight, such as the pressure and temperature fields in a vessel experiencing the fountain effect.
Active steering of omni-droplets on slippery cross-scale arrays by bi-directional vibration
Authors: Wu Sizhu , Xiang Le , Jiang Shaojun , Li Chuanzong , Zhao Zhipeng , Deng Qiyu , Xie Shuting , Jiao Yunlong , Chen Chao , Lao Zhaoxin , Wang Liqiu
Published: April 2023

Directed droplet manipulation is paramount in various applications, including chemical micro-reaction and biomedical analysis. The existing strategies include some kinds of gradients (structure, inherent wettability, and charge density), whereas they suffer from several limitations, such as low velocity, limited volume range, poor durability, and inefficient environmental suitability. Moreover, active bi-directional reversal of omni-droplets remains challenging because one kind of microstructure at a single scale cannot acquire two kinds of net results of mechanical interaction. Herein, we report an active and directional steering of omni-droplets utilizing bi-directional (vertical and horizontal) vibration on slippery cross-scale structures consisting of macro millimeter-scale circular arc arrays and micro/nanometer-scale slant ratchet arrays, which are fabricated by femtosecond laser patterned oblique etching and lubricant infusion. The physical mechanism of active droplet steering lies in the relative competition between the forces under vertical and horizontal vibration, which mainly arise from the circular arc arrays and slant ratchet arrays, respectively. Various steering modes, including climbing and programmable manipulation, can be realized. Our work is applicable to a wide range of potential applications, including circuit on/off and droplet-based chemical micro-reaction, particularly in the field of high-throughput omni-droplets operation.
Transient form of polyvinyl alcohol-based devices with configurable resistive switching behavior for security neuromorphic computing
Authors: Sun Jing , Wang Zhan , Wang Saisai , Cao Yaxiong , Gao Haixia , Wang Hong , Ma Xiaohua , Hao Yue
Published: April 2023

Physically transient resistive switching devices, a form of memory devices with the ability of achieving physical disappearance in a controllable manner, hold tremendous potentials in multiple security applications. Herein, we demonstrated a physically transient form of memristive device composed of Ag/polyvinyl alcohol/W with configurable resistive switching functionality for security neuromorphic computing. The resistive switching type of the transient device could be modulated effectively by controlling the compliance current during the set process, which was well interpreted by the filament model. Typical synaptic functions pertained to short-term plasticity (STP) and its transition from STP to long-term plasticity were vividly mimicked in this transient memristive device. Importantly, both the synaptic functions and physical form of the transient devices were capable of disappearing instantly upon immersing in de-ionized water, and the dissolution characteristics of the constituent transient materials were investigated experimentally to reveal the degradation mechanism of the device. This transient form of artificial synapse provides foreseeing perspectives on information security enhancement for neuromorphic computing systems.
Observing soft x-ray magnetization-induced second harmonic generation at a heterojunction interface
Authors: Sumi T. , Horio M. , Senoo T. , Kubota Y. , Yamaguchi G. , Wada T. , Miyamoto M. , Yamaguchi K. , Tsujikawa Y. , Sato Y. , Niibe M. , Hirata Y. , Miyauchi Y. , Oshima D. , Kato T. , Owada S. , Tono K. , Yabashi M. , Matsuda I.
Published: April 2023

Second harmonic generation (SHG) spectroscopy in the visible and infrared regions has been a useful tool to selectively probe electronic properties at surfaces and interfaces. By examining variation of SHG under a magnetic field, one can also evaluate magnetic properties at the surfaces/interfaces. When multiple elements are involved in SHG, however, it is difficult to separate their contributions. In order to meet the demand of studying increasingly complex magnetic multilayer materials, element selectivity is desired. Here, using an Fe-based multilayer sample with broken inversion symmetry, we present observation of magnetization-induced SHG in the soft x-ray regime around the Fe M-shell absorption edge. Significant variation of SHG signal was captured depending on the direction of the magnetic moment, assuring sensitivity of the measurement likely enhanced by the Fe M-edge inner-shell resonance. The present methodology paves the way for element specific studies of magnetic properties at buried interfaces.
Equation of state based on the first principles
Authors: Chefranov Sergey G.
Published: April 2023

An alternative to the well-known complete form of the Mie–Grüneisen equation of state (EOS) for water is suggested. A closed analytical description of the self-consistent EOS for an arbitrary medium based only on the first law of thermodynamics and on a new form of virial theorem is obtained. This form of the virial theorem (allowing a variable power-law exponent of the particles interaction potential) is a result of the generalization of the known method of similarity [Feynman et al., “Equation of state of elements based on the generalized Fermi–Thomas theory,” Phys. Rev. 75, 1561 (1949)]. In the new EOS, the description of the internal potential energy as a solution of a nonlinear Riemann–Hopf type equation is proposed.
Bruce–Vincent transference numbers from molecular dynamics simulations
Authors: Shao Yunqi , Zhang Chao
Published: April 2023

Transference number is a key design parameter for electrolyte materials used in electrochemical energy storage systems. However, the determination of the true transference number from experiments is rather demanding. On the other hand, the Bruce–Vincent method is widely used in the lab to approximately measure transference numbers of polymer electrolytes, which becomes exact in the limit of infinite dilution. Therefore, theoretical formulations to treat the Bruce–Vincent transference number and the true transference number on an equal footing are clearly needed. Here, we show how the Bruce–Vincent transference number for concentrated electrolyte solutions can be derived in terms of the Onsager coefficients, without involving any extrathermodynamic assumptions. By demonstrating it for the case of poly(ethylene oxide)–lithium bis(trifluoromethane)sulfonimide system, this work opens the door to calibrating molecular dynamics (MD) simulations via reproducing the Bruce–Vincent transference number and using MD simulations as a predictive tool for determining the true transference number.
Computing chemical potentials of adsorbed or confined fluids
Authors: Schmid Rochus , Cheng Bingqing
Published: April 2023

The chemical potential of adsorbed or confined fluids provides insight into their unique thermodynamic properties and determines adsorption isotherms. However, it is often difficult to compute this quantity from atomistic simulations using existing statistical mechanical methods. We introduce a computational framework that utilizes static structure factors, thermodynamic integration, and free energy perturbation for calculating the absolute chemical potential of fluids. For demonstration, we apply the method to compute the adsorption isotherms of carbon dioxide in a metal-organic framework and water in carbon nanotubes.
Deep UV transparent conductive Si-doped Ga2O3 thin films grown on Al2O3 substrates
Authors: Yang Zhenni , Xu Xiangyu , Wang Yan , Kuang Siliang , Chen Duanyang , Qi Hongji , Zhang K. H. L.
Published: April 2023

β-Ga2O3 is attracting considerable attention for applications in power electronics and deep ultraviolet (DUV) optoelectronics owing to the ultra-wide bandgap of 4.85 eV and amendable n-type conductivity. In this work, we report the achievement of Si-doped β-Ga2O3 (Si:β-Ga2O3) thin films grown on vicinal α-Al2O3 (0001) substrates with high electrical conductivity and DUV transparency of promising potential as transparent electrodes. The use of Al2O3 substrates with miscut angles promotes step-flow growth mode, leading to substantial improvement of crystalline quality and electrical properties of the Si:β-Ga2O3 films. A high conductivity of 37 S·cm−1 and average DUV transparency of 85% have been achieved for 0.5% Si-doped film grown on a 6° miscut substrate. High-resolution x-ray and ultraviolet photoemission spectroscopy were further used to elucidate the surface electronic properties of the grown Si:β-Ga2O3 films. An upward surface band bending was found at the surface region of Si:β-Ga2O3 films. Interestingly, all the Si:β-Ga2O3 films have a very low work function of approximately 3.3 eV, which makes Si:β-Ga2O3 suitable materials for efficient electron injection. The present Si:β-Ga2O3 films with high conductivity, DUV transparency, and low work function would be useful as the DUV transparent electrode to develop advanced DUV optoelectronic devices.
The effect of menisci on vortex streets on soap film flows
Authors: Kim Ildoo
Published: April 2023

In soap film experiments, the insertion of an external object is necessary to produce vorticity. However, this insertion causes local thickness changes, or simply meniscus, near the object. Because the meniscus formation may alter the flow near the object, the characterization of a meniscus is of considerable importance for the accurate interpretation of data. In this study, we insert cylindrical cones made of aluminum, titanium, and glass to measure the size of the menisci by using a long-range microscope. In all material tested, we find that the size of the meniscus is less than 0.2 mm, much shorter than the capillary length. In addition, by comparing the formation of vortex streets behind objects of different materials, we conclude that the meniscus acts as an added length to the size of the object itself. This added length effect can be non-negligible if the size of an object is comparable to the size of a meniscus.
A comparison of lattice Boltzmann schemes for sub-critical shallow water flows
Authors: De Rosis Alessandro
Published: April 2023

In this paper, we test the numerical properties of several variants of the lattice Boltzmann method (LBM) for simulating the shallow water flows. Specifically, we perform a systematic comparison of five different schemes: (i) the single-relaxation-time LBM, the (ii) raw-moments-based and (iii) central-moments-based multiple-relaxation-time LBMs, and the (iv) two-stages and (v) one-stage simplified LBMs. Concerning the latter, traditional simplified schemes require a fractional step two-stages technique. Building on the work Delgado-Gutiérrez et al. [“A single-step and simplified graphics processing unit lattice Boltzmann method for high turbulent flows,” Int. J. Numer. Methods Fluids 93, 2339–2361 (2021)], we derive a one-stage approach, where the procedure spans the grid points just once per time step. All the aforementioned LBMs are tested against five well-consolidated benchmark problems, and their numerical performance is assessed. Overall, populations-based schemes show superior accuracy and convergence properties. We link this behavior to the higher numerical dissipation introduced by the simplified models.
Direct simulation of stably stratified wall-bounded turbulence using the lattice Boltzmann method
Authors: Wong Ron Chik-Kwong
Published: April 2023

The lattice Boltzmann method (LBM) is employed to simulate stratified plane Couette (SPC) flows in their statistically stationary turbulent state. The aim is to assess the suitability of the LBM for direct simulation of wall-bounded, sheared turbulence under the influence of stable stratification. The SPC flow is generated by two parallel plates moving in opposite directions with velocities ± U w, and the buoyancy is fixed at ± b w at the upper and lower plates, respectively. The Reynolds number Re = U w h / ν, where h is the half-gap height, and ν is the kinematic viscosity, varies from 1000 to 3000. The Richardson number Ri = b w h / U w 2 is set to 0 or 0.01. The LBM results are compared to direct numerical simulations using the conventional pseudo-spectral method, and good agreement is found in various turbulence statistics, such as mean and fluctuation velocity and buoyancy, Reynolds stress, turbulent heat flux, dissipation rate, wall fluxes of momentum and heat, and longitudinal and transverse turbulence spectra. The results from grid-sensitivity tests indicate that the uniform isotropic grid spacing Δ x in LBM needs to be no greater than approximately the near-wall viscous length scale δ ν to achieve adequate resolution of stratified wall-bounded turbulence.
Shear instability at the interface between fluid and granular medium in a horizontal rotating cylinder
Authors: Dyakova Veronika , Polezhaev Denis
Published: April 2023

The stability of the interface between a low-viscosity fluid and a granular medium in a horizontal rotating cylinder is experimentally studied. Two cases are studied, namely, (i) plastic particles in a more dense fluid and (ii) plastic particles in a less dense fluid. We consider a moderate rotation when particles can form an axisymmetric core in the cylinder center or an annular layer near the cylindrical wall under the action of centrifugal force. The buoyancy force acting on the particles of the granular core fluidizes the granular bed and induces the rotation of the suspended particles with a velocity different from that of the rotating fluid. In the same way, the gravitational force tends to fluidize the surface of an annular layer of granular material in experiments with a fluid with a density less than that of grains. The observations revealed that the suspended particles arrange themselves into regular ripples at the interface. In the present study, the stability threshold and the size of regular ripples are studied in dependence on the rotation rate, the relative density of two media, and the volume of granular material. The instability is found to be of the same nature as the Kelvin–Helmholtz instability observed in classical fluids but with characteristics that can differ due to the specificity of the granular rheology.
Laser absorption study of the N2+ O → NO + N and NO + O → O2+ N Zeldovich reactions in shock-heated N2O mixtures
Authors: Streicher Jesse W. , Krish Ajay , Hanson Ronald K.
Published: April 2023

The fast decomposition of nitrous oxide (N2O) into molecular nitrogen (N2) and atomic oxygen (O) was leveraged to probe the N2 + O and NO + O Zeldovich reactions behind reflected shocks in experiments spanning 2000–6800 K and 0.04–1.67 atm in 1% and 5% N2O diluted in either argon (Ar) or N2, respectively. One infrared (IR) and two ultraviolet (UV) laser absorption diagnostic systems probed N2O and NO. The IR laser system probed N2O in isolation, while the two UV laser systems probed a combination of N2O, NO, and O2 using an online/offline method. The resulting absorbance time-histories were used to infer the NO rotational temperature and the number densities of N2O and NO. The number density time-histories were used to infer (1) the N2O dissociation rate to form N2 and O ( k d N 2 O − [ M ]), (2) the reaction rate of N2O and O to form two NO ( k d N 2 O − O , 1), (3) the NO + O Zeldovich reaction rate ( k z NO − O), and (4) the N2 + O Zeldovich reaction rate ( k z N 2 − O). The experiments were insensitive to the reaction rate of N2O and O to form O2 and N2 ( k d N 2 O − O , 2) at high temperatures. Generally, k d N 2 O − [ M ] was inferred from IR and UV offline data, with k d N 2 O − O , 1, k z NO − O, and k z N 2 − O inferred from UV online data in Ar and N2 dilution. Each inferred reaction rate shows consistency with literature, while extending data to higher temperatures with reduced uncertainty. The reduced uncertainty is sufficient to enable comparisons of the data to various high-temperature quantum chemistry models.
Cernox thermometer under hydrostatic pressure for enhanced temperature accuracy
Authors: Kang Woun
Published: April 2023

Sensors that can be used in a pressurized environment are few. Thus, it is generally considered that the accuracy of temperature measurements decreases in experiments carried out under pressure. Based on a commercially available cryogenic temperature sensor, Cernox from Lake Shore Cryotronics, Inc., we developed and tested an enclosure that enables Cernox to be directly used inside a cylindrical pressure cell, next to the specimen under investigation. To isolate the Cernox thermometer from the pressurized medium inside the pressure cell, we combined the principles of an encapsulated Pt sensor and a cylindrical clamped piston cell. The encapsulated Cernox allows for precise measurement and control of the specimen’s temperature. It is also beneficial for accurately determining small changes in physical properties, such as temperature, or measuring the amount of hysteresis in the first-order phase transition. It would also be useful for accurately controlling the sample’s temperature when the sample approaches the transition temperature from one side.
Thermal transport properties of nanoporous silicon with significant specific surface area
Authors: Isaiev Mykola , Mankovska Yuliia , Kuryliuk Vasyl , Lacroix David
Published: April 2023

This paper studies thermal transport in nanoporous silicon with a significant specific surface area. First, the equilibrium molecular dynamics approach was used to obtain the dependence of thermal conductivity on a specific surface area. Then, a modified phonon transport kinetic theory-based approach was developed to analyze thermal conductivity. Two models were used to evaluate the phonon mean free path in the porous materials. The first model assumes that the dependence of the mean free path only relies on the specific surface area, and the second one also considers the mean free path variation with the porosity. Both approaches approximate molecular dynamics data well for the smaller porosity values. However, the first model fails for highly porous matrixes, while the second one matches well with molecular dynamics simulations across all considered ranges of the porosities. This work illustrates that the phonon mean free path dependence with the porosity/volume fraction of composite materials is essential for describing thermal transport in systems with significant surface-to-volume ratio.
Acoustic emission in bulk normal and superfluid 3He
Authors: Noble M. T. , Midlik Š. , Colman L. , Schmoranzer D. , Tsepelin V.
Published: April 2023

We present measurements of the damping experienced by custom-made quartz tuning forks submerged in 3He covering frequencies from 20 to 600 kHz. Measurements were conducted in the bulk of normal liquid 3He at temperatures from 1.5 K down to 12 mK and in superfluid 3He-B well below the critical temperature. The presented results complement earlier work on tuning fork damping in 3He, removing possible ambiguities associated with acoustic emission within partially enclosed volumes and extend the probed range of frequencies, leading to a clearly established frequency dependence of the acoustic losses. Our results validate existing models of damping and point toward the same mechanism of wave emission of first sound in normal 3He and liquid 4He and zero sound in superfluid 3He. We observe a steep frequency dependence of the damping ≈f5.5, which starts to dominate around 100 kHz and restricts the use of tuning forks as efficient sensors in quantum fluids. The acoustic emission model can predict the limiting frequencies for various devices, including micro-electromechanical and nano-electromechanical structures developed for quantum turbulence and single vortex dynamics research.
Energy-conserving coupled trajectory mixed quantum–classical dynamics
Authors: Villaseco Arribas Evaristo , Maitra Neepa T.
Published: April 2023

The coupled-trajectory mixed quantum–classical method (CTMQC), derived from the exact factorization approach, has successfully predicted photo-chemical dynamics in a number of interesting molecules, capturing population transfer and decoherence from first principles. However, due to the approximations made, CTMQC does not guarantee energy conservation. We propose a modified algorithm, CTMQC-E, which redefines the integrated force in the coupled-trajectory term so to restore energy conservation, and demonstrate its accuracy on scattering in Tully’s extended coupling region model and photoisomerization in a retinal chromophore model.
Origin of the two-dimensional hole gas and criteria for its existence in the III-nitride heterostructures
Authors: Lingaparthi R. , Dharmarasu N. , Radhakrishnan K.
Published: April 2023

The existence of the two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) in the same III-nitride heterostructure is advantageous for the development of complementary nitride electronics. However, it is still unclear whether the buried-2DHG and the top 2DEG can coexist in the same III-nitride heterostructure. This study has addressed this long-standing question. Using charge distribution model, a systematic analysis is done and proposed surface acceptor states as the origin of the two-dimensional hole gas (2DHG). Using this centralized analysis, factors affecting the formation of both surface and buried-2DHG in the nitride heterostructures are presented. Furthermore, it is proved that the buried-2DHG is absent in III-nitride heterostructures, particularly under the 2DEG. In the absence of buried-2DHG at the GaN/AlXGa1-XN interface, a hole trap is observed, which not only balances the charge distribution but also reduces the electric field in the GaN channel layer.
Planar turbulent wakes under pressure gradient: Integral and self-similarity analyses
Authors: Wei Tie , Liu Xiaofeng , Li Zhaorui , Livescu Daniel
Published: April 2023

By using a combination of integral and self-similarity analyses, the generalized analytical solutions for the mean transverse velocity and Reynolds shear stress are rigorously derived for the first time for the far field of planar turbulent wakes under arbitrary pressure gradients. Specifically, by assuming self-similarity for the mean axial velocity, the analytical formulation for the mean transverse velocity is obtained from the integral of the mean continuity equation, and the analytical formulation for the Reynolds shear stress is obtained from the integral of the momentum equation. The generalized analytical formulations for the mean transverse velocity and Reynolds shear stress consist of multiple components, each with its unique scale and physical mechanism. In the zero pressure gradient limit, the generalized formulations recover the single-scale equations reported by Wei, Liu, and Livescu. Furthermore, simpler approximate formulations for the mean transverse velocity and Reynolds shear stress are also obtained, and show excellent agreement with the experimental measurements. The findings provide new insights into the properties of planar turbulent wakes under pressure gradients, filling some long-standing gaps in the existing literature.
Lizards exploit the changing optics of developing chromatophore cells to switch defensive colors during ontogeny
Authors: Zhang Gan , Yallapragada Venkata Jayasurya , Halperin Topaz , Wagner Avital , Shemesh Michal , Upcher Alexander , Pinkas Iddo , McClelland Harry L. O. , Hawlena Dror , Palmer Benjamin A.
Published: April 2023

Many animals undergo changes in functional colors during development, requiring the replacement of integument or pigment cells. A classic example of defensive color switching is found in hatchling lizards, which use conspicuous tail colors to deflect predator attacks away from vital organs. These tail colors usually fade to concealing colors during ontogeny. Here, we show that the ontogenetic blue-to-brown tail color change in
Acanthodactylus beershebensis
lizards results from the changing optical properties of single types of developing chromatophore cells. The blue tail colors of hatchlings are produced by incoherent scattering from premature guanine crystals in underdeveloped iridophore cells. Cryptic tail colors emerge during chromatophore maturation upon reorganization of the guanine crystals into a multilayer reflector concomitantly with pigment deposition in the xanthophores. Ontogenetic changes in adaptive colors can thus arise not via the exchange of different optical systems, but by harnessing the timing of natural chromatophore development. The incoherent scattering blue color here differs from the multilayer interference mechanism used in other blue-tailed lizards, indicating that a similar trait can be generated in at least two ways. This supports a phylogenetic analysis showing that conspicuous tail colors are prevalent in lizards and that they evolved convergently. Our results provide an explanation for why certain lizards lose their defensive colors during ontogeny and yield a hypothesis for the evolution of transiently functional adaptive colors.
STED imaging of endogenously tagged ARF GTPases reveals their distinct nanoscale localizations
Authors: Wong-Dilworth Luis , Rodilla-Ramirez Carmen , Fox Eleanor , Restel Steffen D. , Stockhammer Alexander , Adarska Petia , Bottanelli Francesca
Published: April 2023

ADP-ribosylation factor (ARF) GTPases are major regulators of cellular membrane homeostasis. High sequence similarity and multiple, possibly redundant functions of the five human ARFs make investigating their function a challenging task. To shed light on the roles of the different Golgi-localized ARF members in membrane trafficking, we generated CRISPR-Cas9 knockins (KIs) of type I (ARF1 and ARF3) and type II ARFs (ARF4 and ARF5) and mapped their nanoscale localization with stimulated emission depletion (STED) super-resolution microscopy. We find ARF1, ARF4, and ARF5 on segregated nanodomains on the cis-Golgi and ER-Golgi intermediate compartments (ERGIC), revealing distinct roles in COPI recruitment on early secretory membranes. Interestingly, ARF4 and ARF5 define Golgi-tethered ERGIC elements decorated by COPI and devoid of ARF1. Differential localization of ARF1 and ARF4 on peripheral ERGICs suggests the presence of functionally different classes of intermediate compartments that could regulate bi-directional transport between the ER and the Golgi. Furthermore, ARF1 and ARF3 localize to segregated nanodomains on the trans-Golgi network (TGN) and are found on TGN-derived post-Golgi tubules, strengthening the idea of distinct roles in post-Golgi sorting. This work provides the first map of the nanoscale organization of human ARF GTPases on cellular membranes and sets the stage to dissect their numerous cellular roles.
How can AI accelerate advances in physiology?
Authors: McCulloch Andrew D.
Published: April 2023

Combining machine learning with mechanistic computational modeling is enabling the discovery of novel genotype-phenotype relationships in heart disease.
Supplementary comparison of national standard instruments in the field of magnetic flux density and magnetic flux measurements by sensing coils
Authors: Maslova Tatiana I , Serdiukov Sergey V , А Volegova Ekaterina , Albrecht Martin , Ulvr Michal , Harmon Stuart , He Jian
Published: April 2023

Main text

The COOMET.EM-S26 (1715) supplementary comparison of national standard instruments in the field of magnetic flux density and magnetic flux measurements by sensing coils has been organized within the CCEM framework to test the abilities of the metrology institutes to measure magnetic flux density and magnetic flux.

Five NMIs participated in the supplementary comparison COOMET.EM-S26 (1715). Ural Research Institute for Metrology (UNIIM) (since 2020 it has been called Affiliated Branch of D.I. Mendeleev Institute for Metrology (VNIIM-UNIIM)), Russian Federation, acted as the coordinating laboratory of the comparison.

The comparison on DC magnetic flux density and magnetic flux was carried out through the measurement of the coil constant of transfer standard coils. In general, very good agreement of the results has been observed.

To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.

The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
Anticancer effects of DBD plasma-activated saline within different discharge modes
Authors: Xu Shengduo , Jing Xixi , Zhang Jishen , Liu Dingxin , Zhang Hao , Wang Zifeng , Chen Min , Zhou Renwu , Xu Yujing , Xu Han , Xu Dehui , Wang Xiaohua , Rong Mingzhe
Published: April 2023

With a change in ambient temperature and discharge power, air discharge plasma can switch between two typical modes, namely the ozone mode and the NO
x
mode. Here, we analyze the physicochemical properties and anticancer effects of air dielectric barrier discharge (DBD) plasma-activated saline (PAS) treated by ozone-riched gas produced in an ozone discharge mode, NO
x
-riched gas produced in a NO
x
discharge mode, and a mixture of both produced in the combined two modes simultaneously. The results show that gaseous and aqueous reactive oxygen species (ROS) and reactive nitrogen species (RNS) generated by plasma vary in different discharge modes, correlating to the amount of high-valance nitroxides. In the ozone mode, ozone and minor N2O5 are generated in the gaseous phase and are transformed to aqueous ROS and RNS. In the NO
x
mode, low-valance RNS are generated in the gaseous phase but are transformed into less aqueous RNS. For the PAS produced by the mixed gases, not only the highest concentrated ROS are generated, but also the most abundant gaseous high-valence RNS are produced and transformed to aqueous RNS in the saline. In vitro experiments reveal that, although A375 cells incubated with these three PASs (30%) could all inhibit their viability by enhancing intracellular oxidative stress and inducing cell apoptosis, the PAS produced by the mixed gases has the strongest anticancer effects. Further studies suggest that high-valence RNS play a key role in PAS-induced anticancer effects.
Reducing damage of sputtering and improving conductivity of transparent electrodes for efficient semi-transparent perovskite solar cells
Authors: Liu Jie , Wu Yulin , Zhao Zeren , Wu Shan , Tang Xuan , Wang Jinyao , Mehmood Bilal , Yue Shizhong , Qu Shengchun , Wang Zhijie , Liu Kong , Liu Xiaoliang
Published: April 2023

Sputtered indium tin oxide (ITO) is widely used as an electrode in semi-transparent and tandem perovskite solar cells. However, damage from sputtering to under layers and the limited conductivity of ITO are still the two main obstacles that hinder further performance improvement of the devices. In this work, the effects and mechanism of sputtering damage and poor conductivity of ITO are investigated based on a traditional perovskite solar cell with bathocuproine (BCP) buffer layer. In order to suppress the sputtering damage, tin oxide (SnO2) is deposited on C60 to replace the BCP buffer layer. However, it is found that the deposition of SnO2 on the non-reactive C60 by atomic layer deposition will result in island growth of SnO2 film, which is the key reason for large dark current in solar cells. Fortunately, the phenomenon is inhibited by decorating C60 surface with WO3 thin film. In order to improve the conductivity of the transparent electrode, an ITO/Au/ITO multilayer architecture is designed. The fill factor (FF) and power conversion efficiency (PCE) of the semi-transparent solar cells (ST-PSCs) with the modified buffer layer and electrodes reached 76.4% and 17.62%, respectively, showing an improvement of FF and PCE when compared to the device with BCP buffer layer and ITO electrode. It is revealed that the optimization also increases the short circuit current of the solar cells. These results provide new strategies for damage reduction of sputtering and performance improvement of ST-PSCs.
A new complex system fault detection method based on belief rule base for unreliable interval values
Authors: Zhou Guohui , Zhao Erkai , Yang Ruohan , Feng Zhichao , Cheng Xiaoyu , He Wei
Published: April 2023

Failures to equipment such as milling machines and inertial navigation systems (INSs) can affect their normal operation, resulting in economic losses and personal injury in severe cases. Therefore, fault detection is of great importance. Belief rule base (BRB) is an expert system that plays an important role in fault detection. The traditional BRB has some problems in the explosion of the number of combination rules, the process of model inference, and the process of parameter optimization. To better deal with the above problems, this paper proposes a complex system fault detection method based on an interval-valued BRB fault detection interval-valued (FDIV) and provides the construction and inference process of the method. In the method construction, the form of interval value and disjunction rules are introduced to solve the problem of the number explosion of combination rules, the indicator reliability is added to improve the accuracy of the method, and a new calculation method of rule availability is proposed. In the inference process, twice fusions are made based on evidence reasoning (ER) analysis algorithm and ER rule algorithm respectively to deal with the interval uncertainties. Moreover, the proposed FDIV method is optimized by the projection covariance matrix adaptive evolutionary strategy algorithm projection covariance matrix adaptive evolutionary strategy (P-CMA-ES). Finally, the effectiveness of the proposed method was verified through the research on milling fault detection and the experimental verification of INS fault detection. The superiority of the model was also confirmed through comparative experiments.
Origami-inspired soft-rigid hybrid contraction actuator and its application in pipe-crawling robot
Authors: Liu Jianbin , Ma Guoyu , Ma Zhuo , Zuo Siyang
Published: April 2023

A vacuum-driven inclined hexagonal prism soft-rigid hybrid contraction actuator inspired by Kresling origami pattern and with low driving pressure, high contraction ratio, and fast response was proposed. The advantages of soft-rigid hybrid vacuum contraction actuators over conventional positive-type oscillators were investigated. Under 30 kPa vacuum pressure, the actuator can realize a torsional angle of 87°, contraction ratio of 59%, contracting response time of 0.2 s, and restoring response time of 0.42 s. The design and fabrication of the proposed actuator were discussed. A mathematical model treating all creases as a combination of linear and torsion springs, which is firstly considered compared with previously proposed models of Kresling origami-based actuators, was established to predict the output performance. The excellent output force prediction performance of the proposed method was validated experimentally. To investigate the application potential of the proposed modular actuator, six actuators were assembled on a pipe-crawling robot that can crawl in horizontal, vertical, elbow rigid pipes as well as flexible pipes with inner diameters ranging from 55 to 71 mm. The robot achieved a maximum crawling velocity of 34.8 mm s−1 (0.226 body lengths per second) and maximum load of 1000 g (12.5 times its own weight) in tests. Thus, the excellent application potential of the proposed actuator was validated.
Design and fabrication of 3D-printed composite metastructure with subwavelength and ultrawide bandgaps
Authors: Muhammad  , Kennedy John , Ogun Oluwaseyi
Published: April 2023

Architected composite metastructures can exhibit a subwavelength ultrawide bandgap (BG) with prominent emerging applications in the structural vibration and noise control and, elastic wave manipulation. The present study implemented both forward and inverse design methods based on numerical simulations and machine learning (ML) methods, respectively to design and fabricate an architected composite metastructure exhibiting subwavelength and ultrawide BGs. The multilayer perceptron and radial basis function neural networks are developed for the inverse design of the composite metastructure and their accuracy and computation time are compared. The band structure revealed the presence of subwavelength and ultrawide BGs generated through local resonance and structural modes of the periodic composite lattice. Both in-plane and out-of-plane local resonant modes of the periodic lattice structure were responsible for inducing the BGs. The findings are confirmed by calculating numerical wave transmission curves and experiment tests on the fabricated supercell structures, utilizing 3D-printing technology. Both numerical and experimental results validate the ML prediction and the presence of subwavelength and ultrawide BG was observed. The design approach, research methodology and proposed composite metastructure will have a wide range of application in the structural vibration control and shock absorption.
Asymmetric full mode-converting transmission of elastic waves
Authors: Chai Yijun , Yao Shengjie , Yang Xiongwei , Li Yueming
Published: April 2023

Asymmetric transmission in which wave energy propagates only in one direction attracts significant attention in various fields because of its rich physics and potential applications. In this work, we propose an elastic mode-converting metamaterial, which allows a full-power mode-converting transmission from longitudinal waves to transverse waves in the forward direction, while completely restricts the L wave transmission in the inverse direction. The metamaterial is designed by simply cutting two arrays of periodic silts on a matrix by exploring a straight design methodology, and thus very friendly for fabrication and application. Eigen-frequency analysis shows that the bilayer metamaterial exhibits two modes with significantly close natural frequencies around the working frequency, one for full-power mode-converting transmission, and the other for asymmetric transmission. Ultrasonic experiments are carried out to validate the proposed design. Our work offers a simple and efficient way for the realization of a complete one-way mode-converting transmission, and could be critically useful in designing diode-like meta-devices for novel wave manipulations.