bluuebunny/crossref_metadata_2025 huggingface dataset:
A control strategy for the sterile insect technique using exponentially decreasing releases to avoid the hair-trigger effect
Authors: Leculier Alexis , Nguyen Nga
Published: June 2023

In this paper, we introduce a control strategy for applying the Sterile Insect Technique (SIT) to eliminate the population ofAedesmosquitoes which are vectors of various deadly diseases like dengue, zika, chikungunya… in a wide area. We use a system of reaction-diffusion equations to model the mosquito population and study the effect of releasing sterile males. Without any human intervention, and due to the so-calledhair-trigger effect, the introduction of only a few individuals (eggs or fertilized females) can lead to the invasion of mosquitoes in the whole region after some time. To avoid this phenomenon, our strategy is to keep releasing a small number of sterile males in the treated zone and move this release forward with a negative forcing speedcto push back the invasive front of wild mosquitoes. By using traveling wave analysis, we show in the present paper that the strategy succeeds in repulsing the population while consuming a finite amount of mosquitoes in any finite time interval even though we treat a moving half-space {x>ct}. Moreover, we succeed in constructing a ‘forced’ traveling wave for our system moving at the same speed as the releases. We also provide some numerical illustrations for our results.
Therapieoptionen von primären Motilitätsstörungen des Ösophagus
Authors: Denzer Ulrike , Müller Michaela , Kreuser Nicole , Thieme René , Hoffmeister Albrecht , Feisthammel Juergen , Niebisch Stefan , Gockel Ines
Published: June 2023

Ösophagusmotilitätsstörungen sind Erkrankungen, bei denen es aufgrund einer Veränderung der neuromuskulären Strukturen zu Fehlfunktionen des Schluckakts kommt. Das Leitsymptom ist daher die Dysphagie für feste und/oder flüssige Speisen, häufig begleitet von Symptomen wie Thoraxschmerz, Regurgitation, Sodbrennen, und Gewichtsverlust. Die Ösophagusmanometrie ist der Goldstandard in der Diagnostik. Endoskopie und Radiologie dienen dem Ausschluss entzündlicher oder maligner Veränderungen.

Durch die Einführung der hochauflösenden Ösophagusmanometrie (HRM) hat sich die Diagnostik der Ösophagusmotilitätsstörungen verbessert und mit der Chicago-Klassifikation zu einer neuen Einteilung geführt, die im letzten Jahrzehnt mehrfach modifiziert wurde, zuletzt 2020 mit der Chicago-Klassifikation v4.0. Verglichen mit der Vorversion v3.0 finden sich einige wichtige Änderungen, die anhand der im klinischen Alltag wichtigsten Ösophagusmotilitätsstörungen vorgestellt werden.
Divergent Synthesis of Isochroman-4-ols, 1,3-Dihydroisobenzo­furans, and Tetrahydro-2H-indeno[2,1-b]furan-2-ones via Epoxidation/Cyclization Strategy of (E)-(2-Stilbenyl/Styrenyl)methanols
Authors: Ploypradith Poonsakdi , Jongcharoenkamol Jira , Jancharoen Kitsana , Batsomboon Paratchata , Ruchirawat Somsak
Published: June 2023

Starting from (E)-(2-stilbenyl/styrenyl)methanols, two distinct scaffolds, namely isochroman-4-ols and 1,3-dihydroisobenzofurans (phthalans), could be synthesized via an epoxidation/cyclization strategy. Indenes, readily accessible from the same starting materials, could undergo epoxidation/ring-opening/cyclization to provide tetrahydro-2H-indeno[2,1-b]furan-2-ones. Stilbene/styrene/indene epoxidation by m-CPBA or DMDO converted the nucleophilic olefin into the electrophilic epoxide, which subsequently underwent the regioselective ring-opening either by the hydroxy or the ester group to furnish the corresponding products with stereocontrol at the newly formed stereogenic centers. The reaction proceeded under substrate control to yield each product type exclusively.
Perforator-Based Propeller Flap with Additional Venous Pedicle for Lower Limb Reconstruction
Authors: Mishra Jiten Kumar , Sahu Shamendra Anand , Bodhey Narendra Kuber , Sindhuja Abi , V. Abhijith
Published: June 2023

Propeller flaps are effective reconstructive tools for small-to-medium sized defects of the lower limb and a reasonable alternative to free flaps. A major vessel of the lower limb remains undisturbed while raising the flap and the flap donor and recipient areas are addressed in the same operative field. Perforator-based propeller flaps are based on single perforator arising from a major vessel and during rotation of the larger paddle there is a possibility of kink in the venous component leading to congestion of flap. In our modification, one superficial vein of the lower limb namely the great saphenous or short saphenous vein was included in the flap territory to enhance the retrograde or antegrade venous drainage of the flap. We observed, no flap congestion or necrosis in the postoperative period. Also, the patency of the incorporated vein was confirmed using handheld and color Doppler.
PMM2-CDG T237M Mutation in a Patient with Cerebral Palsy-Like Phenotypes Reported from South India
Authors: Sreedevi N. , Swapna N. , Maruthy Santosh , Meghavathi H.S. , Sylvester Charles
Published: June 2023

Congenital disorder of glycosylation (CDG) is an autosomal recessively inherited disorder. Hypotonia, stroke-like episodes, and peripheral neuropathy are also associated with the condition that typically develops during infancy. The patient, a 12-year-old girl born to healthy consanguineous parents, was diagnosed with cerebral palsy as a child. The affected patient has hypotonia, inadequate speech, strabismus, and developmental delay with mild mental retardation, which are key symptoms of CDG. Whole-exome sequencing (WES) identified the known missense pathogenic variant PMM2 c.710 C > T, p.T237M in the patient coding for the phosphomannomutase 2 (PMM2) confirming molecular testing of CDG. The patient's parents carried heterozygous PMM2 c.710 C > T variants. This study highlights the importance of WES in patients with a developmental disability or other neurological conditions, which is also useful in screening risk factors in couples with infertility or miscarriage issues.
CT and MRI in the Preoperative Planning of Balloon Dilation of the Eustachian Tube: Literature Review
Authors: Borshchenko Maria , Eremeeva Kseniya , Svistushkin Valery
Published: June 2023

Balloon dilatation of the Eustachian tube (BET) is a surgical treatment method for Eustachian tube dysfunction (ETD), which relieves the symptoms in the majority of cases. However, there are potential intraoperative risks associated with BET; the decision-making process with regard to indications for BET is not standardized up to date. The objective of this study was to review the role of computed tomography (CT) and magnetic resonance imaging (MRI) in the preoperative planning of BET. The literature review is based on a database search performed in August 2022.

BET is classified into transtympanic and nasopharyngeal. CT of the temporal bone provides good visualization of the site of obstruction, which allows to choose the adequate approach. Transtympanic approach is associated with risks of internal carotid artery damage due to possible carotid canal anomalies. This risk can be prevented with preoperative CT scan of the temporal bone. In case of nasopharyngeal BET, there is no sufficient data considering risks of possible artery damage, although CT can provide accurate measurements of ET. MRI is useful for differential diagnosis of conditions imitating ETD, such as endolymphatic hydrops and nasopharyngeal carcinoma. Thus, it is feasible to perform CT and MRI before BET to personalize the management of ETD patients.
Evaluating Earplug Performance over a 2-Hour Work Period with a Fit-Test System
Authors: Gong Wei , Murphy William J. , Meinke Deanna K. , Feng Huiling Amy , Stephenson Mark R.
Published: June 2023

Workers rely on hearing protection devices to prevent occupational noise-induced hearing loss. This study aimed to evaluate changes in attenuation over time for properly fit devices when worn by workers exposed to hazardous noise. Earplug fit testing was accomplished on 30 workers at a brewery facility with three types of foam and three types of premolded earplugs. The personal attenuation ratings (PARs) were measured before and after a 2-hour work period while exposed to hazardous noise levels. The minimum acceptable initial PAR was 15 dB. Average decreases in PAR ranged from −0.7 to −2.6 dB across all six earplug types. Significant changes in PAR were observed for the Foam-1 (p = 0.009) and Premold-3 (p = 0.004) earplugs. A linear mixed regression model using HPD type and study year as fixed effects and subject as random effect was not significant for either fixed effect (α = 0.05). Ninety-five percent of the final PAR measurements maintained the target attenuation of 15 dB. Properly fitting earplugs can be effective at reducing worker's noise exposures over time. The potential for a decrease in attenuation during the work shift should be considered when training workers and establishing the adequacy of protection from hazardous noise exposures.
A motorized rotation mount for the switching of an optical beam path in under 20 ms using polarization control
Authors: Raghuram Adarsh P. , Mortlock Jonathan M. , Bromley Sarah L. , Cornish Simon L.
Published: June 2023

We present a simple motorized rotation mount for a half-wave plate that can be used to rapidly change the polarization of light. We use the device to switch a high power laser beam between different optical dipole traps in an ultracold atom experiment. The device uses a stepper motor with a hollow shaft, which allows a beam to propagate along the axis of the motor shaft, minimizing inertia and mechanical complexity. A simple machined adapter is used to mount the wave plate. We characterize the performance of the device, focusing on its capability to switch a beam between the output ports of a polarizing beam splitter cube. We demonstrate a switching time of 15.9(3) ms, limited by the torque of the motor. The mount has a reaction time of 0.52(3) ms and a rotational resolution of 0.45(4)°. The rotation is highly reproducible, with the stepper motor not missing a step in 2000 repeated tests over 11 h.
Mehler–Fock transforms and retarded radiative Green functions in hyperbolic and spherical spaces
Authors: Durand Loyal
Published: June 2023

We develop the theory of causal radiation Green functions on hyperbolic and hyperspherical spaces using a constructive approach based on generalized Mehler–Fock transforms. This approach focuses for HRd on the kernel of the transformation expressed in terms of hyperbolic angles θ with 0 ≤ θ < ∞. The kernel provides an explicit representation for the generalized delta distribution, which acts as the source term for the radiation, and allows for an easy implementation of the causality or retardation condition and determination of the Green function. We obtain the corresponding kernel distribution on SRd by analytic continuation of the kernel distribution of an appropriate Helmholtz equation on HRd and then show that this construction leads to the proper retarded Green function for the wave equation. That result is then used to establish the validity of a new generalized Mehler–Fock transformation for 0 ≤ θ < π. The present results clarify and extend those obtained recently by Cohl et al. [SIGMA 14, 136 (2018)].
Transmission electron microscopy studies of organic–inorganic hybrid perovskites: Advances, challenges, and prospects
Authors: Du Hong-Qiang , Jiang Yang , Rothmann Mathias Uller , Bach Udo , Cheng Yi-Bing , Li Wei
Published: June 2023

In the last few years, organic–inorganic hybrid perovskites (OIHPs) have attracted immense research and industry attention for their application as light absorbers in solar cells and light-emitting diodes. Characterizing OIHP materials and optoelectronic devices using transmission electron microscopy (TEM)-based techniques has played a large role in understanding their structural, compositional, and electronic properties. However, the highly energetic and electrically charged electron beam radiation used in TEM can result in damage to the pristine structure, as OIHPs are unstable and highly sensitive to electron beams. This damage potentially obscures intrinsic information and leads to a serious misunderstanding of the microscopic structure–property–performance relationship for OIHP optoelectronic devices. To address this issue, we first review the electron and ion beam-induced degradation mechanism of OIHPs, followed by a review of the development of ultra-low-dose TEM techniques that can able to minimize this damage, thus can able to obtain reliable, intrinsic structural information about OIHPs from the atomic to micrometer length scales. Finally, we suggest a protocol for appropriate TEM specimen preparation and characterization techniques. This protocol can help ensure that future TEM studies of OIHPs give reliable information, thereby enabling a deeper understanding and optimization of the performance and long-term stability of OIHP optoelectronic devices.
Surface plasmonic coupling of Au nanoparticle arrays with ultrathin hexagonal boron nitride nanosheets for Raman enhancement
Authors: Gao Jinling , Zhan Wei , Xiao Yuhan , Zhu Xingrui , Gao Wei , Yin Hong
Published: June 2023

Integration of hexagonal boron nitride (h-BN) with plasmonic nanostructures that possess nanoscale field confinement will enable unusual properties; hence, the manipulation and understanding of the light interactions are highly desirable. Here, we demonstrate the surface plasmonic coupling of Au nanoparticles (ANPs) with ultrathin h-BN nanosheets (BNNS) in nonspecific nanocomposites leading to a great enhancement of the Raman signal of E2g in both experimental and theoretical manner. The nanocomposites were fabricated from liquid-exfoliated atomically thin BNNS and diblock copolymer-based ANPs with excellent dispersion through a self-assembly approach. By precisely varying the size of ANPs from 3 to 9 nm, the Raman signal of BNNS was improved from 1.7 to 71. In addition, the underlying mechanism has been explored from the aspects of electromagnetic field coupling strength between the localized surface plasmons excited from ANPs and the surrounding dielectric h-BN layers, as well as the charge transfer at the BNNS/ANPs interfaces. Moreover, we also demonstrate its capability to detect dye molecules as a surface enhanced Raman scattering (SERS) substrate. This work provides a basis for the self-assembly of BNNS hierarchical nanocomposites allowing for plasmon-mediated modulation of their optoelectronic properties, thereby showing the great potential not only in the field of SERS but also in large-scale h-BN-based plasmonic devices.
Effects of the neutral dynamics model on the particle-in-cell simulations of a Hall thruster plasma discharge
Authors: Faraji F. , Reza M. , Knoll A.
Published: June 2023

The dynamics of the neutral atoms in Hall thrusters affects several plasma processes, from ionization to electrons' mobility. In the context of Hall thruster's particle-in-cell (PIC) modeling, the neutrals are often treated kinetically, similar to the plasma species, and their interactions with themselves and the ions are resolved using the direct-simulation Monte–Carlo (DSMC) algorithm. However, the DSMC approach is computationally resource demanding. Therefore, modeling the neutrals as a 1D fluid has been also pursued in simulations that do not involve the radial coordinate and, hence, do not resolve the neutrals' radial expansion. In this article, we present an extensive study on the sensitivity of the PIC simulations of Hall thruster discharge to the model used for the neutral dynamics. We carried out 1D axial PIC simulations with various fluid and kinetic models of the neutrals as well as self-consistent quasi-2D axial-azimuthal simulations with different neutrals’ fluid descriptions. Our results show that the predictions of the simulations in either 1D or 2D configurations are highly sensitive to the neutrals' model, and that different treatments of the neutrals change the spatiotemporal evolution of the discharge. Moreover, we observed that considering the ion-neutral collisions causes a significant variation in the neutral temperature, thus requiring that the neutrals' energy equation to be included as well in their fluid system of equations. Finally, the self-consistent axial-azimuthal simulations highlighted that a neutrals’ model based on the continuity conservation equation only is not an appropriate choice and leads to physically unexpected high-frequency global discharge oscillations.
Shear banding predictions for wormlike micellar systems under a contraction–expansion complex flow
Authors: López-Aguilar J. Esteban , Tamaddon-Jahromi Hamid R. , Manero Octavio
Published: June 2023

This study focuses on computational modeling of shear-banded wormlike micellar solutions (WLM) in a complex planar Couette flow, driven by a moving top plate over a rounded-corner 4:1:4 obstruction. The BMP+_τp model is used, which is constructed within an Oldroyd-B-like form, coupled with a thixotropic fluidity-based structure equation. Solute energy dissipation drives fluid–structure adjustment in a construction–destruction dynamics affected by viscoelasticity. This model reproduces conventional WLM features, such as shear thinning, extensional hardening/softening, viscoelasticity, apparent yield stress, and shear banding, with a bounded extensional viscosity and an N1Shear upturn at high deformation rates. The BMP+_τp characterization for shear banding is based on extremely low solvent fractions and appropriate shear-banding intensity parameters. Flow structure is analyzed through velocity, stress, and fluidity, whereupon banded and non-banded response is contrasted at appropriately selected flow rates. Solutions are obtained with our hybrid fe-fv algorithm, capturing essential shear-banded flow features reported experimentally. For a fluid exhibiting banding, banded solutions are generated at a flow rate within the flow curve unstable branch. In the fully developed simple shear flow regions, a split velocity profile is observed, with different viscosity bands at equal stress levels, enhanced with a shock-capture procedure. Non-banded solutions are derived for the lowest and highest flow rates sampled, located in the stable branches. Within the constriction zone, banded profiles are lost due to the mixed non-homogeneous deformation. Shear-banding fluids display less intense viscosity/stress features, correlated with their relatively stronger shear thinning response. The constriction resistance provokes a pressure-level adjustment, leading to fully developed Couette-like constant values upstream–downstream.
Refining and relating fundamentals of functional theory
Authors: Liebert Julia , Chaou Adam Yanis , Schilling Christian
Published: June 2023

To advance the foundation of one-particle reduced density matrix functional theory (1RDMFT), we refine and relate some of its fundamental features and underlying concepts. We define by concise means the scope of a 1RDMFT, identify its possible natural variables, and explain how symmetries could be exploited. In particular, for systems with time-reversal symmetry, we explain why there exist six equivalent universal functionals, prove concise relations among them, and conclude that the important notion of v-representability is relative to the scope and choice of variable. All these fundamental concepts are then comprehensively discussed and illustrated for the Hubbard dimer and its generalization to arbitrary pair interactions W. For this, we derive by analytical means the pure and ensemble functionals with respect to both the real- and complex-valued Hilbert space. The comparison of various functionals allows us to solve the underlying v-representability problems analytically, and the dependence of its solution on the pair interaction is demonstrated. Intriguingly, the gradient of each universal functional is found to always diverge repulsively on the boundary of the domain. In that sense, this key finding emphasizes the universal character of the fermionic exchange force, recently discovered and proven in the context of translationally invariant one-band lattice models.
Microstructural evolution of periclase under irradiation by molecular dynamics simulations
Authors: Chartier Alain , Fossati Paul , Van Brutzel Laurent , Dorosh Orest , Jagielski Jacek
Published: June 2023

The response of MgO periclase to irradiation is investigated by means of molecular dynamics simulations, mimicking irradiation by Frenkel pairs accumulation. Both the calculated lattice and volume swellings, which refer, respectively, to the lattice and total volume changes reproduce well the experimental measures. The two diverge at around 0.2 dpa, above which lattice and volume swellings follow separate trends. Below this value, dislocation loops nucleate from point defects clusters, built up by progressive aggregation of both magnesium and oxygen interstitials. Very small 12⟨110⟩ loops lying in {001} planes and made of (MgO)6 interstitials could be characterized. They serve as seeds for the subsequent growth of dislocation loops in all three {110}, {001}, and {111} planes, which then follows a sublinear law. The 12⟨110⟩ loops lying in the {011} planes become dominant as loop diameters increase beyond 15 nm. Above 0.2 dpa, we observe (i) the relative decrease of lattice swelling mainly because the very dense dislocations loops recombine and stabilize into less dense dislocation forests and, concomitantly, (ii) the fast increase of volume swelling caused by the occurrence of significant voids of up to 32 vacancies.
In situ detection of delamination and critical current degradation caused by the thermal stress in epoxy impregnated REBa2Cu3O7−δ coils
Authors: Yang Zhirong , Song Peng , Li Yiran , Shao Liangjun , Xiao Mianjun , Guan Mingzhi , Qu Timing
Published: June 2023

Epoxy impregnated superconducting coils have better structural integrity and thermal stability. However, for REBa2Cu3O7−δ (REBCO, RE=Rare earth) coils, the mismatch of thermal expansion coefficients between epoxy and REBCO tapes is a serious problem. In this work, the temperature distribution, stress evolution during the cooling process, critical current distribution, and delamination sites inside REBCO coils impregnated using Stycast 2850FT have been studied. We measured the temperature distribution and the hoop strain in the penultimate turn of impregnated coils during the cooling process and analyzed the thermal stress evolution. No damage was observed for coils with the ratio between outer and inner diameter Ro/Ri<1.93. The delamination behavior occurred in coils with Ro/Ri>2.37, where the coils even exhibited a two-stage delamination. The delamination mechanism of REBCO coils was proposed from three aspects: the mechanical analysis, the critical current degradation, and the microscopic analysis. In this work, we found that the actual delamination behavior may appear earlier than the steady-state temperature, and temperature distribution will push the radial stress peak toward the inner radius of the coil, making the inner turn more susceptible to delamination. Multiple delamination locations were accurately predicted and confirmed. The measured compressive hoop strain first increased from −4212 με to −4684 με with the increase in Ro/Ri and then decreased to −3835 με obviously due to delamination. This work reveals in detail the delamination mechanism in impregnated REBCO coils, which is of great significance for the development of damage-free coils.
Significantly enhanced thermal conductivity of the aramid nanofiber composite film with GO and Ag nanoflakes for thermal management application
Authors: Zeng Zhenghong , Xu Cenkai , Ren Junwen , Yang Zefeng , Wu Guangning , Wei Wenfu
Published: June 2023

The development of composite materials with excellent thermal conductivity is attracting extensive attention to meet the increasing heat concentration challenges in both power and electronic equipment. Previous strategies for improving the thermal conductivities usually accompanied by the cost of mechanical strength. Herein, we propose a new strategy for developing both mechanically strong and thermally conductive composite films. The aramid nanofibers (ANF) are well prepared with introducing Ag nanoflakes and graphene oxide (GO) via vacuum-assisted filtration and hot-pressing treatment. Results indicate the synergistic effects of low dimension materials have resulted in a tightly arranged phonon network construction. The in-plane thermal conductivity of the prepared ANF/Ag/GO film reaches 9.84 W m−1 K−1, about 371% higher than that of pure ANF. Meanwhile, the strong hydrogen bond formed between the functional group of GO and the amide group of ANFs plays a synergistic strengthening and toughening role at the complex interface, and the tensile strength reaches 231 MPa. We believe that these findings shed some light on the design and fabrication of multifunctional materials for thermal management applications.
Robust composite repetitive control with disturbance observer for high-precision tracking of piezo-actuated nano-stages with measurement delays
Authors: Zhang Zhiming , Yan Peng
Published: June 2023

In this paper, a robust composite control strategy in the framework of unified infinite-dimensional H∞ optimal control is developed to support nano-scale periodic tracking with improved non-harmonic disturbance attenuation of piezo-actuated nano-stages with sensor-induced measurement delays. In particular, we analyze the electromechanical coupled dynamics and derive a multi-perturbation model, where an extended Youla–Kucera parameterization-based repetitive controller with a disturbance observer is constructed to optimize control performances on high-precision tracking and perturbation rejection. The controller parameters are solved by using a unified infinite-dimensional H∞ optimization method. Comprehensive experiments on a piezo-actuated stage are conducted, where comparative results with representative methods, such as the conventional repetitive control and proportional-integral-derivative control, demonstrate significant performance improvements in hysteresis compensation, trajectory tracking, and disturbance suppression of the proposed method.
Nucleation of cubic boron nitride on boron-doped diamond via plasma enhanced chemical vapor deposition
Authors: Brown Jesse M. , Vishwakarma Saurabh , Smith David J. , Nemanich Robert J.
Published: June 2023

Cubic boron nitride (c-BN), with a small 1.4% lattice mismatch with diamond, presents a heterostructure with multiple opportunities for electronic device applications. However, the formation of c-BN/diamond heterostructures has been limited by the tendency to form hexagonal BN at the interface. In this study, c-BN has been deposited on free standing polycrystalline and single crystal boron-doped diamond substrates via electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD), employing fluorine chemistry. In situ x-ray photoelectron spectroscopy (XPS) is used to characterize the nucleation and growth of boron nitride (BN) films as a function of hydrogen gas flow rates during deposition. The PECVD growth rate of BN was found to increase with increased hydrogen gas flow. In the absence of hydrogen gas flow, the BN layer was reduced in thickness or etched. The XPS results show that an excess of hydrogen gas significantly increases the percent of sp2 bonding, characteristic of hexagonal BN (h-BN), particularly during initial layer growth. Reducing the hydrogen flow, such that hydrogen gas is the limiting reactant, minimizes the sp2 bonding during the nucleation of BN. TEM results indicate the partial coverage of the diamond with thin epitaxial islands of c-BN. The limited hydrogen reaction is found to be a favorable growth environment for c-BN on boron-doped diamond.
Analysis of electromagnetic scattering from hypersonic vehicle coated with non-uniform plasma sheath based on FVTD method
Authors: Liu Yu-Guo , Zhang Shuai , Gao Tie-Suo , Xu Yong , Jiang Tao , Song Zi-Xuan
Published: June 2023

The finite volume time domain (FVTD) method is proposed to accurately calculate the electromagnetic (EM) scattering of hypersonic vehicles coated with non-uniform plasma sheath. The plasma sheath in the actual flight environment is accurately established by solving the Navier–Stokes equations and combining appropriate thermochemical models. The radar cross section (RCS) of metal and uniform medium coated metal targets calculated by FVTD are in good agreement with those simulated by the software FEKO (MoM) and the Mie series. The calculated RCS of the vehicle under the reentry condition is consistent with the flight test data, too. The calculated electron number density distribution is consistent with the flight experiment results. The body fitted structure EM grid is adopted. The EM grid independence of the target coated with plasma sheath is studied. Then, the scattering and plasma EM parameters of the vehicle during the actual reentry are studied. The reentry altitude is from 78 to 55 km, and the reentry velocity is from 6406 to 6350 m/s. With the reentry altitude decreasing, the plasma angular frequency and collision frequency increased gradually. The scattering of different incident conditions and different wall catalytic conditions is analyzed in depth. This paper provides a valuable reference for vehicles' detection, recognition, and stealth during reentry flights.
Diffusion-controlled reactions with non-Markovian binding/unbinding kinetics
Authors: Grebenkov Denis S.
Published: June 2023

We develop a theory of reversible diffusion-controlled reactions with generalized binding/unbinding kinetics. In this framework, a diffusing particle can bind to the reactive substrate after a random number of arrivals onto it, with a given threshold distribution. The particle remains bound to the substrate for a random waiting time drawn from another given distribution and then resumes its bulk diffusion until the next binding and so on. When both distributions are exponential, one retrieves the conventional first-order forward and backward reactions whose reversible kinetics is described by generalized Collins–Kimball’s (or back-reaction) boundary condition. In turn, if either of distributions is not exponential, one deals with generalized (non-Markovian) binding or unbinding kinetics (or both). Combining renewal technique with the encounter-based approach, we derive spectral expansions for the propagator, the concentration of particles, and the diffusive flux on the substrate. We study their long-time behavior and reveal how anomalous rarity of binding or unbinding events due to heavy tails of the threshold and waiting time distributions may affect such reversible diffusion-controlled reactions. Distinctions between time-dependent reactivity, encounter-dependent reactivity, and a convolution-type Robin boundary condition with a memory kernel are elucidated.
Hybrid-VPIC: An open-source kinetic/fluid hybrid particle-in-cell code
Authors: Le Ari , Stanier Adam , Yin Lin , Wetherton Blake , Keenan Brett , Albright Brian
Published: June 2023

Hybrid-VPIC is an extension of the open-source high-performance particle-in-cell (PIC) code VPIC incorporating hybrid kinetic ion/fluid electron solvers. This paper describes the models that are available in the code and gives an overview of applications of the code to space and laboratory plasma physics problems. Particular choices in how the hybrid solvers were implemented are documented for reference by users. A few solutions for handling numerical complications particular to hybrid codes are also described. Special emphasis is given to the computationally taxing problem of modeling mix in collisional high-energy-density regimes, for which more accurate electron fluid transport coefficients have been implemented for the first time in a hybrid PIC code.
Ferroelectric behavior of sputter deposited Al0.72Sc0.28N approaching 5 nm thickness
Authors: Zheng Jeffrey X. , Fiagbenu Merrilyn Mercy Adzo , Esteves Giovanni , Musavigharavi Pariasadat , Gunda Akhil , Jariwala Deep , Stach Eric A. , Olsson Roy H.
Published: June 2023

Ferroelectric Al1−xScxN has raised much interest in recent years due to its unique ferroelectric properties and complementary metal oxide semiconductor back-end-of-line compatible processing temperatures. Potential applications in embedded nonvolatile memory, however, require ferroelectric materials to switch at relatively low voltages. One approach to achieving a lower switching voltage is to significantly reduce the Al1−xScxN thickness. In this work, ferroelectric behavior in 5–27 nm films of sputter deposited Al0.72Sc0.28N has been studied. We find that the 10 kHz normalized coercive field increases from 4.4 to 7.3 MV/cm when reducing the film thickness from 27.1 to 5.4 nm, while over the same thickness range, the characteristic breakdown field of a 12.5 μm radius capacitor increases from 8.3 to 12.1 MV/cm. The 5.4 nm film demonstrates ferroelectric switching at 5.5 V when excited with a 500 ns pulse and a switching speed of 60 ns.
Large-eddy simulations of flow and aeroacoustics of twin square jets including turbulence tripping
Authors: Mihaescu Mihai , Karnam Aatresh , Gutmark Ephraim
Published: June 2023

In this study, we investigate the flow and aeroacoustics of twin square (i.e., aspect ratio of 1.0) jets by implicit large-eddy simulations (LESs) under a nozzle pressure ratio of 3.0 and a temperature ratio of 1.0 conditions. A second-order central scheme coupled with a modified Jameson's artificial dissipation is used to resolve acoustics as well as to capture discontinuous solutions, e.g., shock waves. The flow boundary layer inside of the nozzle is tripped, using a small step in the convergent section of the nozzle. The time-averaged axial velocity and turbulent kinetic energy of LES with boundary layer tripping approaches better to particle image velocimetry experimental data than the LES without turbulence tripping case. A two-point space–time cross-correlation analysis suggests that the twin jets are screeching and are coupled to each other in a symmetrical flapping mode. Intense pressure fluctuations and standing waves are observed between the jets. Spectral proper orthogonal decomposition (SPOD) confirms the determined mode and the relevant wave propagation. The upstream propagating mode associated with the shock-cell structures is confined inside jets. Far-field noise obtained by solving Ffowcs Williams and Hawkings equation is in good agreement with the measured acoustic data. The symmetrical flapping mode of twin jets yields different levels of the screech tone depending on observation planes. The tonalities—the fundamental tone, second and third harmonics—appear clearly in the far-field, showing different contributions at angles corresponding to the directivities revealed by SPOD.
Low frequency photothermal excitation of AFM microcantilevers
Authors: Deolia Akshay , Raman Arvind , Wagner Ryan
Published: June 2023

Photothermal excitation at frequencies below the mechanical resonance of the atomic force microscopy (AFM) microcantilever can be utilized in force modulation microscopy, fast force displacement curve acquisition, and tip-based mass spectroscopy. To understand the microcantilever bending response in these modes, accurate models of the thermoelastic response of the AFM microcantilever are needed. We study the sub-resonance photothermal vibrational response of coated and uncoated AFM microcantilevers as a function of laser modulation frequency and spot location. The sub-resonance microcantilever response shows distinct thermoelastic regimes. Below the microcantilever's thermal roll-off frequency, the vibration amplitude is mostly constant. Past this frequency, the vibration amplitude decreases with increasing frequency. At modulation frequencies below the thermal roll-off frequency, the most efficient photothermal laser spot to excite harmonic motion is near the free end of both coated and uncoated microcantilevers. For the tested coated microcantilevers, the most efficient photothermal laser location migrates from near the free end of the microcantilever to near the fixed end as modulation frequency increases. For the tested uncoated microcantilever, the most efficient photothermal laser location remains unchanged at the tested frequencies. To predict the bending response of the coated microcantilever, a bilayer bending model is implemented. At low frequencies, this model underpredicts the bending response compared to experiments by up to 90%. This may be due to neglecting microcantilever bending contributed by a through-thickness temperature gradient. Our results illustrate different aspects of the frequency-dependent photothermal laser spot optimization that can guide users to maximizing microcantilever response to a given input power.
Model for 1/f flux noise in superconducting aluminum devices: Impact of external magnetic fields
Authors: Nava Aquino José Alberto , de Sousa Rogério
Published: June 2023

Superconducting quantum interference devices and related circuits made of aluminum are known to display 1/ω flux noise, where ω is frequency. A recent experiment showed that the application of an external magnetic field in the 10–100 G range changed the noise to a single Lorentzian peaked at ω = 0. Here, it is shown that a model based on independent impurity spin flips with coexisting cross and direct mechanisms of spin relaxation may explain these experiments. The model shows that application of an external magnetic field can be used to reduce the impact of flux noise in qubits.
Tutorial: Real-time coherent terahertz imaging of objects moving in one direction with constant speed
Authors: Yasui Takeshi , Abraham Emmanuel
Published: June 2023

Pulsed terahertz (THz) electric fields enable various coherent THz imaging modes, such as reflection tomography, spectral imaging, and computed tomography (CT) for nondestructive inspection, quality control, and material characterization. The extension of coherent THz imaging modes to moving objects has been regarded as key to their social implementation. This Tutorial focuses on two-dimensional spatiotemporal (2D-ST) THz imaging of objects moving in one direction with constant speed as a promising means of enabling real-time coherent THz imaging. In 2D-ST THz imaging, the temporal waveform and line image of the THz pulse are simultaneously acquired without the need for mechanical scanning of the time delay and sample position using a combination of non-collinear 2D free-space electro-optic sampling with THz line-imaging optics. This 2D-ST THz imaging boosts the imaging rates of THz reflection tomography, THz spectral imaging, and THz CT to levels that are applicable to moving objects. The advanced THz reflection tomography and THz spectral imaging that result from the assistance of 2D-ST THz imaging achieve real-time line imaging of cross sections and spectral signatures, respectively. Subsequently, this enables in-line total inspection of objects moving on a translation stage or a conveyor belt. A THz CT system using real-time line projection of a THz beam is effectively applied to a 2D spectral cross section of a continuously rotating object. 2D-ST THz imaging enables the functional THz imaging of moving objects in various practical applications.
Stochastic models of free-molecular nanopore flows
Authors: Kratzer Matthew M. , Bhatia Suresh K. , Klimenko Alexander Y.
Published: June 2023

In gas transport systems of the nanoscale, fluid–surface interactions become the main forces governing the evolution of the flow state. In ideal nanoscale systems, such as atomically smooth carbon nanotubes, the characteristic lengths reduce to such an extent that the non-equilibrium entrance region comprises a large proportion of the domain. In this regime, the added effective resistance induced by the non-equilibrium entrance region becomes large enough that classical effusion models break down. The mechanisms behind the resistance in this regime are still poorly understood. A stochastic model of interfacial resistance is developed here, which allows for the determination of the effective diffusion coefficient via a novel finite-difference solution. We use this method to model free-molecular gas flow through long nanotubes, showing that such non-equilibrium effects may be present in systems of length scales currently within manufacturing capabilities. Finally, this model is used to discuss gas separation through aligned carbon nanotube arrays, with a focus on the effect of membrane length on the separation of a H2–CH4 mixture.
Disordering two-dimensional magnet-particle configurations using bidispersity
Authors: Tsuchikusa K. , Yamamoto K. , Katsura M. , de Paula C. T. , Modesto J. A. C. , Dorbolo S. , Pacheco-Vázquez F. , Sobral Y. D. , Katsuragi H.
Published: June 2023

In various types of many-particle systems, bidispersity is frequently used to avoid spontaneous ordering in particle configurations. In this study, the relation between bidispersity and disorder degree of particle configurations is investigated. By using magnetic dipole–dipole interaction, magnet particles are dispersed in a two-dimensional cell without any physical contact between them. In this magnetic system, bidispersity is introduced by mixing large and small magnets. Then, the particle system is compressed to produce a uniform particle configuration. The compressed particle configuration is analyzed by using Voronoi tessellation for evaluating the disorder degree, which strongly depends on bidispersity. Specifically, the standard deviation and skewness of the Voronoi cell area distribution are measured. As a result, we find that the peak of standard deviation is observed when the numbers of large and small particles are almost identical. Although the skewness shows a non-monotonic behavior, a zero skewness state (symmetric distribution) can be achieved when the numbers of large and small particles are identical. In this ideally random (disordered) state, the ratio between pentagonal, hexagonal, and heptagonal Voronoi cells becomes roughly identical, while hexagons are dominant under monodisperse (ordered) conditions. The relation between Voronoi cell analysis and the global bond orientational order parameter is also discussed.
Thickness modulation of incline-grown Bi2O2Se for the construction of high-performance phototransistors
Authors: Fan Sidi , Wu Yuting , Li Weisheng , Gao Jun , Yang Weiyu , Deng Jiajun , Cao Rui , Liu Xiaolong
Published: June 2023

Newly emerging two-dimensional (2D) Bi2O2Se has received intense research interest due to its unique band structure and ultrafast optical properties. However, the device performance of Bi2O2Se-based photodetectors is far from the expectation because of the undesirable contact issues of the contaminates from the fabrication process or the high Schottky barrier caused by the large work function mismatch. In this work, highly efficient photodetection based on an “all-Bi2O2Se” device geometry has been demonstrated. By controlling the growth conditions, Bi2O2Se flakes with thicknesses of 8–15 nm (thin) and >40 nm (thick) are obtained. The thin one is a typical n-type semiconductor, while the thick one shows the degenerated n-type behavior with a higher Fermi level. Two thick flakes are adopted as 2D contacts for the absorption layer of thin flake, leading to the upward movement of the thin flake band structures. By tailoring the Schottky barrier frame at the interface junction, the high barriers are eliminated, which boost the transport and collection of photo-generated electrons. The photodetector demonstrates strong photoresponse to visible and near-infrared light. High photoresponsivity and specific detectivity of 3.34 × 104 A/W and 6.61 × 1013 Jones, respectively, are achieved under the 640 nm light illumination.
Surface defects related to polishing cycle in ß-Ga2O3 crystals grown by floating zone
Authors: Perrier Coralie , Traoré Aboulaye , Ito Toshimitsu , Umezawa Hitoshi , Gheeraert Etienne , Ferrandis Philippe
Published: June 2023

We report an investigation on ß-Ga2O3 Schottky barrier diodes performed on substrates grown by floating-zone method using structural characterization techniques (secondary-ion mass spectrometry, inductively coupled plasma-mass spectroscopy, and atomic force microscopy) and electrical measurements (current-voltage, capacitance-voltage, Hall effect, and capacitance deep-level transient spectroscopy). Four distinct electron trap levels labeled ES, E1, E2, and E3 were found in the range of 1 eV below the Ga2O3 conduction band minimum. Among them, E1, E2, and E3 show signatures similar to those reported in the literature for Czochralski and edge-defined film-fed grown ß-Ga2O3 substrates. Trap ES was found near the surface, and we could establish a link between this defect and the damage induced by the substrate polishing technique. The level related to ES was identified at ∼0.31 eV below the conduction band minimum. An energy band above 0.31 eV was also detected and is associated with states at the metal–semiconductor interface. We demonstrated that the interface states and surface deep traps are not uniformly distributed on the ß-Ga2O3 surface. Furthermore, they contribute to the reverse leakage current and the on-state conduction degradation of the diodes.
Observation of nontrivial Zak phase induced topological states in glow discharge plasma
Authors: Li Jianfei , Yao Jingfeng , Wang Ying , Zhou Zhongxiang , Kudryavtsev Anatoly A. , Lan Zhihao , Yuan Chengxun
Published: June 2023

Plasma blackout, which contains ablative impurities, strongly attenuates the signal of the reentry spacecraft. Traditional methods focus on mitigating electron densities and impurities around the antenna, and metamaterial-based electromagnetic methods have yet to be proven experimentally. We simulate the plasma blackout problem using laboratory plasma supported by gas discharge technology. Alumina pillars are embedded in the plasma background to form plasma photonic crystals, while topological phase transitions are achieved by shrinking and expanding pillars within a unit cell. The topological edge states (TESs) that are insensitive to weak impurities in the transport path are verified theoretically and experimentally. We introduce the glide-reflection (GR) symmetry in the nontrivial lattices to obtain the gapless edge states, which are exclusively observed in the acoustic systems. Meanwhile, the Δω of the gapless TES increases with the electron densities, ensuring a wide communication bandwidth. Furthermore, the strong coupling of heterostructure with GR symmetry in plasma photonic crystals is elucidated. Our work not only provides a new approach to the blackout communication problem but can also serve as a nascent experimental platform to investigate topological electromagnetic phenomena.
Resonant dynamics of three-dimensional skyrmionic textures in thin film multilayers
Authors: Srivastava Titiksha , Sassi Yanis , Ajejas Fernando , Vecchiola Aymeric , Ngouagnia Yemeli Igor , Hurdequint Hervé , Bouzehouane Karim , Reyren Nicolas , Cros Vincent , Devolder Thibaut , Kim Joo-Von , de Loubens Grégoire
Published: June 2023

Skyrmions are topological magnetic solitons that exhibit a rich variety of dynamics, such as breathing and gyration, which can involve collective behavior in arrangements like skyrmion lattices. However, such localized excitations typically lie in the gap of the spin wave spectrum and do not couple to propagating modes. By combining magnetic force microscopy, broadband ferromagnetic resonance, and micromagnetics simulations, we show that in thin-film multilayers of [Pt/FeCoB/AlOx]20 a high-frequency (>12 GHz) mode accompanies the skyrmion lattice phase, which involves the coherent precession of the skyrmion cores that results in the generation of 50–80 nm wavelength spin waves flowing into the uniformly magnetized background. This observation is made possible by a Gilbert damping constant of ∼0.02, which is nearly an order of magnitude lower than in similar ultrathin materials. The simulations also reveal a complex three-dimensional spin structure of the skyrmion cores, which plays a key role for spin wave generation.