bluuebunny/crossref_metadata_2025 huggingface dataset:
Generalized N-rotor problems, synchronized subsystems, and associated solitons
Authors: Lohe M. A.
Published: August 2024

We consider systems of N particles interacting on the unit circle through 2π-periodic potentials. An example is the N-rotor problem that arises as the classical limit of coupled Josephson junctions and for various energies is known to have a wide range of behaviors such as global chaos and ergodicity, together with families of periodic solutions and transitions from order to chaos. We focus here on selected initial values for generalized systems in which the second order Euler–Lagrange equations reduce to first order equations, which we show by example can describe an ensemble of oscillators with associated emergent phenomena such as synchronization. A specific case is that of the Kuramoto model with well-known synchronization properties. We further demonstrate the relation of these models to field theories in 1+1 dimensions that allow static kink solitons satisfying first order Bogomolny equations, well-known in soliton physics, which correspond to the first order equations of the generalized N-rotor models. For the nonlinear pendulum, for example, the first order equations define the separatrix in the phase portrait of the system and correspond to kink solitons in the sine-Gordon equation.
Simultaneous analysis of collinear neutron time-of-flight (nToF) traces applied to pulsed fusion experiment
Authors: Mitrani James M. , Ampleford David J. , Chandler Gordon A. , Eckart Mark J. , Hahn Kelly D. , Jeet Justin , Kerr Shaun M. , Mannion Owen M. , Moore Alastair M. , Schlossberg David J. , Youmans Amanda E. , Grim Gary P.
Published: August 2024

On pulsed fusion experiments, the neutron time of flight (nToF) diagnostic provides critical information on the fusion neutron energy spectrum. This work presents an analysis technique that uses two collinear nToF detectors, potentially to measure nuclear bang time and directional flow velocities. Two collinear detectors may be sufficient to disambiguate the contributions of nuclear bang time and directional flow velocities to the first moment of the neutron energy spectrum, providing an independent measurement of nuclear bang time. Preliminary results from measured nToF traces on the National Ignition Facility and additional applications of this technique are presented.
Magneto-optical Kerr effect of noncollinear antiferromagnetic Mn3Ir films
Authors: Yamada Kihiro T. , Yamaguchi Kotarou , Kobayashi Yuta , Takamura Yota , Munekata Hiro , Ono Teruo , Moriyama Takahiro , Satoh Takuya
Published: August 2024

We present the magneto-optical Kerr effect (MOKE) of (111)-oriented antiferromagnetic L12-Mn3Ir films epitaxially grown on MgO (111) substrates. We observed that the amplitude and sign of the polar MOKE change depending on the growth temperature. The Mn3Ir films grown at 800 and 600 °C have rotation angles of 41.6 and −4.6 mdeg and ellipticity angles of −15.3 and 9.1 mdeg, respectively. Residual strains owing to heteroepitaxial growth on the order of a few tenths of a percent can play a critical role in determining the amplitude and sign of the MOKE of a noncollinear antiferromagnet, unlike ferromagnets.
Experimental evaluation of the influence of the diffuser inlet to nozzle exit cross sectional area ratio on pressure oscillation in a high-altitude test facility
Authors: Fouladi N. , Farahani M. , Parsa Delivand A. R. , Nojoumi A. A.
Published: August 2024

The ratio of diffuser inlet to nozzle exit area (Ad/Ae) is one of the most important parameters in designing and evaluating the performance of a high-altitude test facility (HATF). Typically, at motor pressures near start or operating pressure of the diffuser, the vacuum chamber pressure oscillates at a high Ad/Ae, which may be dangerous for the HATF. In the present study, the effect of the Ad/Ae on the starting and breakdown performance of a second throat exhaust diffuser (STED) has been investigated experimentally using a HATF supplied by high-pressure cold air apparatus. Upon examining the overall performance of the diffuser, it is observed that with an increase in Ad/Ae, the oblique sealing shock wave at the diffuser inlet undergoes significant changes in location and strength. This leads to a further reduction of the flow total pressure and a stronger separation of the flow along the diffuser. Consequently, flow instability arises during starting or breakdown phases near the STED starting or operating pressure. By frequency analysis, it is observed that as Ad/Ae increases, the number of oscillatory modes of the vacuum chamber pressure increases and the dominant frequency of the oscillations in these transient situations becomes larger. Additionally, there is a significant decrease in nozzle pressure related to the onset of pressure oscillations. Furthermore, with an increase in Ad/Ae from 1.27 to 7.81, the minimum starting pressure and breakdown pressure of STED increase by 20.33% and 28.47%, respectively. Also, the hysteresis range in performance of STED vanishes at high Ad/Ae values.
A low-cost and convenient route of fabricating GaN films with P-type mixed microcrystalline and amorphous structure deposited via Ga target of magnetron sputtering
Authors: Chen Xueqing , Li Nan , Xing Zerong , Zu Jiasheng , Meng Xianwei , Zhou Zhuquan , Li Qian , Tian Lifeng , Cui Yuntao , Liu Jing
Published: August 2024

GaN, a third-generation semiconductor, has gained widespread attention owing to its high temperature resistance, wide bandgap, and high critical breakdown electric fields. Magnetron sputtering has a broad potential in the field of low-cost growth of GaN on account of high efficiency, superior quality, and convenient operation. However, challenges caused from the pure Ga targets with a huge refrigeration system need to be resolved for wide practices. Here, a new and cost-effective Ga target for magnetron sputtering was fabricated by utilizing the wetting properties of CuGa2 and Ga. Mixed microcrystalline and amorphous GaN films were obtained via reactive magnetron sputtering employing the Ga target. The average deposition rate is about 1.68 nm/min, and the average roughness is ∼7.45 ± 0.26 nm under 100 W of sputtering power. In addition, the sputtered GaN films were found to be wide-bandgap and p-type semiconductors with high transmittance, as revealed by x-ray photoelectron spectroscopy and absorption spectra. The GaN films display a bandgap of ∼3.60 eV and a transmittance exceeding 88.5% in the visible range. Furthermore, field-effect transistors and metal–semiconductor–metal photodetectors have been fabricated using the obtained GaN films, demonstrating favorable response characteristics. The prospects of microcrystalline/amorphous GaN films in sensing, power devices, and flexible electronics were forecasted. Overall, a low-cost and pervasive route of target fabrication process expands the possibilities of using low melting point metals in magnetron sputtering.
Nonmodal linear stability analysis of hypersonic flow over an inclined cone
Authors: Liu Shuyi , Chen Xi , Wan Bingbing , Zhang Ligeng , Chen Jianqiang
Published: August 2024

Nonmodal linear stability analysis results are presented for hypersonic flow over a cone at 6° angle of attack complementing earlier modal stability analysis. Based on the parallel flow assumption, singular value decomposition is applied to obtain the optimal linear combination of global crossflow modes. The optimal disturbance exhibits significant transient growth in the initial short distance and progressively follows the path of the most unstable mode downstream. The largest transient energy gain is observed for disturbances at around 40 kHz close to the most amplified modal frequency and tends to increase with the Reynolds number. The optimal disturbance initially exhibits two amplitude peaks in the azimuthal direction, one lying in the leeward region where the unstable crossflow modes reside and the other in the windward region where the adjoint modes exist. As the optimal disturbance travels downstream, the second amplitude peak rapidly shifts toward the leeward side and reaches the optimal energy gain when it eventually merges with the first amplitude peak. The evolution process of the optimal disturbance indicates that the optimal disturbance might have exploited the locally crossflow instability through traveling from the windward side to the leeward side.
Effect of blade profile on the hydraulic performance of a double-suction centrifugal pump as turbine based on enstrophy dissipation theory
Authors: Wang Tao , Lei Lei , Liu Yunqi , Guo Qing , Huang Tengfei
Published: August 2024

Pump as turbine (PAT) is widely used in micro hydropower stations and chemical industries as an economical energy recovery device. The special impeller with forward-curved blades can significantly improve the efficiency of PAT and expand its high-efficiency range due to the suitable blade profile, which is more appropriate for PAT's operation mode than the backward-curved blades. To study the influence of the forward blade on a double-suction centrifugal PAT performance, three forward-curved blade schemes with different blade angle conditions are compared with the original backward-curved blade scheme. The three forward-curved blade schemes have the highest efficiency when the inlet angles are 60°, 90°, and 120°, respectively, and the appropriate blade outlet angle. The results showed that the forward-curved blade is suitable for high-flow rate operating conditions in double-suction centrifugal PAT. The PAT with a forward-curved blade impeller has higher efficiency and a broader high-efficiency region than the backward-curved blade impeller. The double-suction centrifugal PAT's main energy loss comes from the impeller's turbulent loss. The forward-curved blade reduces the impeller's turbulence loss and improves the PAT's efficiency at large flow rates. The research in this paper provides a theoretical basis for the design and application of double-suction centrifugal PAT.
Incompressible boundary layer flow past a hump with temperature-dependent viscosity
Authors: Aljohani Abdulrahman F. , Gajjar Jitesh S. B.
Published: August 2024

The problem of boundary layer flow past a hump placed on a flat surface, where viscosity is coupled with temperature, is investigated using triple-deck theory. The incompressible Navier–Stokes equations supplemented by the heat and viscosity equations are considered in the limit that the Reynolds number is large. The triple-deck scalings are adopted, and asymptotic expansions are used to obtain some novel triple-deck equations coupled with the thermal boundary layer. We have used the same viscosity–temperature dependence as in Jasmine and Gajjar [Int. J. Heat Mass Transfer 48, 1022–1037 (2005)], in which viscosity varies inversely proportional to the temperature. The linear analysis is performed, and the nonlinear equations are solved numerically. Our results show that increasing the characteristic constant of the viscosity leads to enhanced peaks and troughs in the pressure and in the skin friction over the hump, as compared to the constant viscosity case. This suggests that temperature-dependent viscosity is more likely to provoke separation.
Preparatory study of feasibility for a vertical viewing electron cyclotron emission diagnostic for the JT-60SA tokamak
Authors: Tokuzawa T. , Yoshida M. , Imazawa R. , Nakagawa S. , Inagaki S. , Kin F. , Chiba S. , Suzuki N. , Nasu T. , Fujisawa A. , Ida K.
Published: August 2024

A preparatory study is underway to investigate the feasibility study of high-energetic, non-thermal electron distribution function measurements using a vertical-viewing electron cyclotron emission (ECE) diagnostic on JT-60SA. The system is designed to detect broad ECE spectra (70–260 GHz) due to the second, third, and fourth harmonics using a focusing optics system with four quasi-optical mirrors in the upper port of JT-60SA. A Gaussian beam optics design is performed in vacuum, and ray tracing calculations are performed in plasma using the TRAVIS code to investigate density characteristics. A ceramic viewing dump is also designed to reduce the effects of multiple reflections from the opposing vacuum vessel surface.
Flow structures in large-scale bank erosion zone of Lower Yangtze River
Authors: Sun Qihang , Deng Shanshan , Zhu Yude , Liu Wanli , Yang Yunping , Yang Zongmo
Published: August 2024

The bank erosion process in the densely populated Lower Yangtze River can pose a great threat to riparian residents and industries. It is characterized by rapid development within a few hours, a large-scale soil collapse of 106 m3, and an arc shape. During its development, flow field inside the bank erosion area continuously evolves and interacts with the bank soil. However, the mechanisms behind the bank erosion process are still unclear. Therefore, laboratory experiments were conducted to investigate flow structures and turbulences inside bank erosion areas. A pulsed particle image velocimeter was employed to obtain high-quality velocity data inside the bank erosion zone. Results show that the bank erosion zone can be divided into a backflow zone, a mixing zone, and a mainstream zone, according to variations in flow structure; in the mixing zone, water flow is highly turbulent, and the mixing width gradually increases downstream because of the shear effects between the mainstream and backflow; the backflow zone can be subdivided into a central zone and a peripheral zone, based on the pattern of velocity changes along the radial axis from the backflow center to its periphery. A formula for calculating the flow velocity within the backflow zone was proposed, and we found that the velocity gradient in the peripheral zone was approximately four times higher than that in the central zone. This indicated that shear stress exerted by the flow near the backflow boundary was significantly intensified.
A photo rechargeable capacitor based on the p–n heterojunction of ZnO/ZIF-67 showing enhanced photovoltage
Authors: Lv Yanlong , Sun Xin , Mi Changhua , Gu Jianan , Wang Yanhong , Li Meicheng
Published: August 2024

The photo rechargeable device (PRD) has been continuously drawing attention because it combines energy conversion and storage in one device. As for the photoelectrode of PRD, the construction of heterojunction is of crucial importance to enhance the photo performance. In this work, a two-electrode photo rechargeable capacitor based on the p–n heterojunction of ZnO/ZIF-67 is fabricated. ZIF-67 not only serves as the energy storage material but also forms the p–n heterojunction together with ZnO. A fast volatilization method was adopted for the in situ growth of ZIF-67 on ZnO nanorods to ensure sufficient mass loading and fewer interface defects. The results show a photovoltage of 0.36 V (0.2 V higher than single ZnO), a specific capacitance of 759.0 mF/g, and an overall energy conversion efficiency of 0.49%. The enhanced photovoltage is attributed to the p–n heterojunction. Moreover, a practical button cell was also fabricated, with 91% Coulombic efficiency remaining after 3000 cycles in the dark.
Advancing the process understanding and localization in jet electrochemical machining with electrolyte confinement through fluid dynamic simulations and experiments
Authors: Ye Zhisen , Chen Xiaolei , Lin Yiming , Cheng Liang , Arshad Muhammad Hazak , Saxena Krishna Kumar , Zhang Yongjun
Published: August 2024

Functionality-oriented micro-structures, such as micro-dimples and grooves, are widely used in tribology and heat transfer. Jet electrochemical machining (JEM) is effective to fabricate micro-structures on metallic surfaces. However, in traditional JEM, the unrestricted electrolyte flowing can induce stray corrosion on workpiece, and thus, both surface quality and machining localization are reduced. In this paper, a novel electrolyte-confinement technique is proposed for JEM, a high-density liquid (perfluorotripropylamine, FTPA) is used to confine the electrolyte flowing region on workpiece when electrolyte exits nozzle, facilitating reduction in stray corrosion on workpiece and overcut of micro-structures. A multi-physics model including two-phase flow field and electric field is developed to analyze the electrolyte confined by FTPA, and both simulation and observation results show that the area of electrolyte flowing on the workpiece is confined well by FTPA, and the current density distribution becomes concentrated, which enhances the machining localization. Compared to traditional JEM, the etch factor of micro-dimple is improved by 2.5 times and there is no stray corrosion. The material removal rate is increased due to the concentration of current distribution on the workpiece surface. Furthermore, profile evolution of micro-dimples revealed that with feed depth increased, FTPA could flow into the micro-dimple to protect the sidewall from continuous dissolution, thus forming vertical sidewall. Additionally, electrolyte flowing region is still confined during the scanning motion of nozzle, and the etch factor increases from 0.41 to 8.8 compared to traditional JEM. Moreover, increasing inter-electrode gap could reduce electrolyte flowing region on workpiece, further enhancing machining localization.
Global well-posedness for two-phase fluid motion in the Oberbeck–Boussinesq approximation
Authors: Zhang Wei , Fu Jie , Hao Chengchun , Yang Siqi
Published: August 2024

This paper focuses on the global well-posedness of the Oberbeck–Boussinesq approximation for the unsteady motion of a drop in another bounded fluid separated by a closed interface with surface tension. We assume that the initial state of the drop is close to a ball BR with the same volume as the drop, and that the boundary of the drop is a small perturbation of the boundary of BR. To begin, we introduce the Hanzawa transformation with an added barycenter point to obtain the linearized Oberbeck–Boussinesq approximation in a fixed domain. From there, we establish time-weighted estimates of solutions for the shifted equation using maximal Lp–Lq regularities for the two-phase fluid motion of the linearized system, as obtained by Hao and Zhang [J. Differ. Equations 322, 101–134 (2022)]. Using time decay estimates of the semigroup, we then obtain decay time-weighted estimates of solutions for the linearized problem. Additionally, we prove that these estimates are less than the sum of the initial value and its own square and cube by estimating the corresponding non-linear terms. Finally, the existence and uniqueness of solutions in the finite time interval (0, T) was proven by Hao and Zhang [Commun. Pure Appl. Anal. 22(7), 2099–2131 (2023)]. After that, we demonstrate that the solutions can be extended beyond T by analyzing the properties of the roots of algebraic equations.
Influence of wall–fluid interaction on the relationship between mass transfer and nanopore width
Authors: Jiang Chuntao , Li Wuming , Liu Qingsheng
Published: August 2024

In this study, the influence mechanisms of the nanopore width on mass transfer characteristics for methane nanofluidic are explored by non-equilibrium multiscale molecular dynamics simulation systematically. The numerical results indicate that the diffusion coefficient increases with the increase in the nanopore width via the quasi-parabolic paths. In the middle of nanopore, the local diffusion coefficients increase with the increase in the wall–fluid interaction strength factor; however, the change of local diffusion coefficient is reversed in the fluid domain near the nanopore wall. Moreover, the results show that the residual decreases with the increase in the degree polynomial of 1h. According to these fitting functions, it can be found that the diffusion coefficient approaches 80% of that of bulk system when the nanopore width increases to 14 times the diameter of methane molecule. Furthermore, the velocity autocorrelation functions and the diffusion coefficients (x, y, and z direction) demonstrate that the methane nanofluid shows anisotropy characteristics. In addition, the mean interaction force potential and slip velocity also indicate that the wall–fluid interaction strength factor and the nanopore width significantly affect the mass transfer characteristics of nanofluidic. The numerical results would be helpful to comprehend the mass transfer characteristics of nanofluidics. It should be considered in the optimal design of nano-devices.
Artificial design of anisotropic magnetoelectric effect in Sr2IrO4/SrTiO3 superlattices
Authors: Wu Biao , Liu Xin , Wang Maoyuan , Lu Peipei , Wu Mei , Sun Yuanwei , Yan Dayu , Shi Youguo , Sun Nian Xiang , Sun Young , Wang Fa
Published: August 2024

Magnetoelectric response in thin films is highly desirable for high-throughput and high-density microelectronic applications, like magnetic sensors. To sensitively detect the direction of magnetic field, the anisotropic magnetoelectric effect is required. Here, we artificially design an anisotropic magnetoelectric response in Sr2IrO4/SrTiO3 superlattices, where a strong (negligible) magnetoelectric response for magnetic fields along the z-direction (xy-plane) of Sr2IrO4/SrTiO3 interface was observed. A combination of perturbative calculations with numerical results and density functional theory calculations reveals that only the effective z-component Zeeman field within the Sr2IrO4 layers can change the electron occupation of the neighboring SrTiO3 layers, which is proportional to the polarization. Via controlling the periodicity of the superlattices, we can further control the anisotropy of magnetoelectric responses. This atomic-scale design of 3d/5d superlattices paves an alternative way toward controllable magnetoelectric effects with thin film integrations.
Physics-informed neural networks for advection–diffusion–Langmuir adsorption processes
Authors: Huang Bo , Hua Haobo , Han Huan , He Sensen , Zhou Yuanye , Liu Shuhong , Zuo Zhigang
Published: August 2024

Advection–diffusion–Langmuir adsorption (ADLA) presents a complex problem in chemical engineering and biomedicine fields. This transport phenomenon can be described by the advection–diffusion–reaction (ADR) equations, which traditionally require intensive computational load at extreme conditions. In this paper, physics-informed neural networks (PINNs) are applied to solve the ADR equations due to their mesh-free and computationally efficient nature. Six cases are examined, including both diffusion-dominated and advection-dominated cases with varying Péclet numbers Pe and aspect ratios λ. To ensure stability and efficiency during training with the Adam optimizer, the gradients of the loss function are analyzed. Key gradient terms causing instability are identified, leading to recommendations for lower weights for these gradient terms. The validation results show that compared to the finite difference method, PINN achieves a concentration field error within 10% and an average adsorption amount error within 7.2% for diffusion-dominated cases. For advection-dominated cases, the errors are within 20% and 2.5%, respectively. In conclusion, PINNs can offer an efficient and accurate technique for solving ADR equations.
Apparatus for the room temperature measurement of low field Nernst and magneto-Seebeck coefficients
Authors: Porter C. E. , Crawford C. M. , Toberer E. S.
Published: August 2024

Nernst coefficient measurements are a classic approach to investigate charge carrier scattering in both metals and semiconductors. However, such measurements are not commonly performed, despite the potential to inform material design strategies in applications such as thermoelectricity. As dedicated instruments are extremely scarce, we present here a room temperature apparatus to measure the low field Nernst coefficient (and magneto-Seebeck coefficient) in bulk polycrystalline samples. This apparatus is specifically designed to promote accurate and facile use, with the expectation that such an instrument will make Nernst measurements de rigueur. In this apparatus, sample loading and electrical contacts are all pressure-based and alignment is automatic. Extremely stable thermal control (10 mK of fluctuation when ΔT = 1 K) is achieved from actively cooled thermoelectric modules that operate as heaters or Peltier coolers. Magneto-Seebeck measurements are integrated into the system to correct for residual probe offsets. Data from the apparatus are provided on bulk polycrystalline samples of bismuth, InSb, and SnTe, including raw data to illustrate the process of calculating the Nernst coefficient. Finally, we review how Nernst measurements, in concert with Seebeck, Hall, and electrical resistivity, can be analyzed via the Boltzmann equation in the relaxation time approximation to self-consistently predict the Fermi level, effective mass, and energy-dependent relaxation time.
Numerical dissipation induced by the low-pass filtering in nonlinear gyrokinetic simulations
Authors: Wang Zihao , Wang Shaojie
Published: August 2024

De-aliasing is an essential procedure for eliminating the aliasing error in nonlinear simulations, such as nonlinear gyrokinetic turbulence simulations. An ideal approach to de-aliasing in the periodic dimension is the Fourier truncation. Finite difference low-pass filtering applied in the non-periodic direction strongly dampens aliasing modes. At the same time, it induces numerical dissipation in the region of the physically realistic solution. It is shown analytically that the long-wave dissipation coefficient is proportional to the (Np−3) power of the wavenumber under desirable constraints satisfying the highest order of accuracy, where Np is the number of filter points. Numerical results after applying the optimized low-pass filtering to the nonlinear gyrokinetic turbulence simulation suggest that the nine-point format preserves intact mesoscopic zonal structures in tokamak plasma, and is therefore suitable for long-time nonlinear turbulence simulations.
Polymer assisted deposition of YIG thin films with thickness control for spintronics applications
Authors: Corcuera Rubén , Jiménez-Cavero Pilar , Pérez del Real Rafael , Rivadulla Francisco , Ramos Rafael , Morales-Aragonés José Ignacio , Sangiao Soraya , Magén César , Morellón Luis , Lucas Irene
Published: August 2024

The use of magnetic garnets in new technologies such as spintronic devices requires fine-structured thin films. Classical fabrication techniques for these materials, typically physical vapor deposition methods, lead to excellent magnetic behavior. However, availability and scalability for potential applications are well restricted. In this study, we propose an innovative approach to fabricating Yttrium Iron Garnet thin films with precise thickness control achieved through iterative layer deposition via a chemical synthesis route. Remarkably, the iterative deposition process results in films exhibiting exceptional crystallinity. Magnetic characterization provides saturation magnetization and coercivity values on par with those reported in literature, summed to narrow ferromagnetic resonance lines. Therefore, in this work we demonstrate the viability of polymer assisted deposition as a promising alternative thinking about scalability to conventional deposition techniques for this material. Notably, our findings reveal energy conversion efficiencies comparable to those achieved with materials synthesized via physical vapor deposition methods.
A Perspective on tellurium-based optoelectronics
Authors: Zha Jiajia , Tong Jingyi , Huang Haoxin , Xia Yunpeng , Dong Dechen , Tan Chaoliang
Published: August 2024

Tellurium (Te) has been rediscovered as an appealing p-type van der Waals semiconductor for constructing various advanced devices. Its unique crystal structure of stacking of one-dimensional molecular chains endows it with many intriguing properties including high hole mobilities at room temperature, thickness-dependent bandgap covering short-wave infrared and mid-wave infrared region, thermoelectric properties, and considerable air stability. These attractive features encourage it to be exploited in designing a wide variety of optoelectronics, especially infrared photodetectors. In this Perspective, we highlight the important recent progress of optoelectronics enabled by Te nanostructures, which constitutes the scope of photoconductive, photovoltaic, photothermoelectric photodetectors, large-scale photodetector array, and optoelectronic memory devices. Prior to that, we give a brief overview of basic optoelectronic-related properties of Te to provide readers with the knowledge foundation and imaginative space for subsequent device design. Finally, we provide our personal insight on the challenges and future directions of this field, with the intention to inspire more revolutionary developments in Te-based optoelectronics.
Transcription of HIV-1 at sites of intact latent provirus integration
Authors: Teixeira Ana Rafaela , Bittar Cintia , Silva Santos Gabriela S. , Oliveira Thiago Y. , Huang Amy S. , Linden Noemi , Ferreira Isabella A.T.M. , Murdza Tetyana , Muecksch Frauke , Jones R. Brad , Caskey Marina , Jankovic Mila , Nussenzweig Michel C.
Published: August 2024

HIV-1 antiretroviral therapy is highly effective but fails to eliminate a reservoir of latent proviruses, leading to a requirement for life-long treatment. How the site of integration of authentic intact latent proviruses might impact their own or neighboring gene expression or reservoir dynamics is poorly understood. Here, we report on proviral and neighboring gene transcription at sites of intact latent HIV-1 integration in cultured T cells obtained directly from people living with HIV, as well as engineered primary T cells and cell lines. Proviral gene expression was correlated to the level of endogenous gene expression under resting but not activated conditions. Notably, latent proviral promoters were 100–10,000× less active than in productively infected cells and had little or no measurable impact on neighboring gene expression under resting or activated conditions. Thus, the site of integration has a dominant effect on the transcriptional activity of intact HIV-1 proviruses in the latent reservoir, thereby influencing cytopathic effects and proviral immune evasion.
Recent progresses and applications on chiroptical metamaterials: a review
Authors: Wang Yan , Wu Zeyu , Yu Wenming , Liu Zhengqi
Published: August 2024

Chiroptical metamaterials have attracted considerable attention owing to their exciting opportunities for fundamental research and practical applications over the past 20 years. Through practical designs, the chiroptical response of chiral metamaterials can be several orders of magnitude higher than that of natural chiral materials. Chiroptical metamaterials therefore represent a special type of artificial structures for unique chiroptical activities. In this review, we present a comprehensive overview of the progresses in the development of chiroptical metamaterials. Chiroptical metamaterial progress enables applications, including asymmetric transmission, polarization conversion, chiral absorber, chiral imaging, chiral sensor and chiral emission. We also review fabrication techniques and design of chiroptical metamaterials based on deep learning. In the conclusion, we present possible further research directions in this field.
Properties of a continuous optical discharge sustained by short-wave infrared laser radiation in high pressure argon
Authors: Androsenko V N , Kotov M A , Solovyov N G , Shemyakin A N , Yakimov M Yu
Published: August 2024

This paper is devoted to the experimental study of the characteristics of a continuous optical discharge (COD) sustained by high power continuous wave laser radiation at a wavelength λ = 1.08 μm in high pressure argon. New data on the COD threshold laser power dependence of argon pressure in the range 20–50 bar is obtained. The COD threshold laser power is shown to be in good agreement with the data obtained by other authors and theoretical evaluations provided the contribution of plasma energy loss due to thermal radiation is taken into account properly. The maximum plasma temperature was estimated to be 20–21 kk or higher, favorable to obtain high UV spectral radiance. A study of the convective plume oscillations around COD in argon has been carried out. It is found that in the pressure range 25–35 bars the growth of the laser radiation power leads to a decrease in convection oscillation frequency from 33 to 29 Hz, while the radius of the convective plume grows accordingly. The oscillation frequency ν and characteristic radius of the convective plume r
0 were found to obey the similarity relation

ν
=
0.5

g

/

2

r
0

previously established in experiments with COD in xenon. These results are promising for using COD in argon as a high brightness broadband UV radiation source.
Effect of aliovalent substitution on the local structure of CaKFe4As4 superconductor
Authors: Tomassucci G , Tortora L , Minati F , Russo M , Duchenko A , Varsano F , Masi A , Campi G , Simonelli L , Martin-Diaconesu V , Boeri L , Mizokawa T , Saini N L
Published: August 2024

We have investigated the local structure of the iron-based CaKFe4As4 superconductor featuring distinct aliovalent substitutions at the Ca and K sites, that is CaKFe4As4, CaK0.9Sr0.1Fe4As4, CaK0.9Ba0.1Fe4As4 and Ca0.9Na0.1K0.9Ba0.1Fe4As4. Temperature-dependent Fe K-edge extended x-ray absorption fine structure (EXAFS) measurements are used to determine the near-neighbors bondlengths and their stiffness. The EXAFS analysis reveals that the Fe–As bondlength undergoes negligible changes by substitution, however, the Fe–Fe bondlength and the As height are affected by the Sr substitution. The superconducting transition temperatures of CaK0.9Sr0.1Fe4As4 and CaK0.9Ba0.1Fe4As4 are very similar even if the mean As heights are significantly different suggesting that the anion height may not be a unique parameter to describe the superconductivity in CaKFe4As4. The mean As heights show a peculiar temperature dependence characteristic of CaKFe4As4 system. Furthermore, the temperature-dependent mean square relative displacements reveal similar Fe–Fe bond stiffness in all samples, instead the Fe–As bond is substantially stiffer in case of CaK0.9Sr0.1Fe4As4. The local structure results are discussed in relation to the differing transport properties of aliovalent substituted 1144 superconductor.
Melting and freezing of a skyrmion lattice
Authors: Garanin Dmitry A , Soriano Jorge F , Chudnovsky Eugene M
Published: August 2024

We report comprehensive Monte–Carlo studies of the melting of skyrmion lattices (SkL) in systems of small, medium, and large sizes with the number of skyrmions ranging from 103 to over 105. Large systems exhibit hysteresis similar to that observed in real experiments on the melting of SkLs. For sufficiently small systems which achieve thermal equilibrium, a fully reversible sharp solid–liquid transition on temperature with no intermediate hexatic phase is observed. A similar behavior is found on changing the magnetic field that provides the control of pressure in the SkL. We find that on heating the melting transition occurs via a formation of grains with different orientations of hexagonal axes. On cooling, the fluctuating grains coalesce into larger clusters until a uniform orientation of hexagonal axes is slowly established. The observed scenario is caused by collective effects involving defects and is more complex than a simple picture of a transition driven by the unbinding and annihilation of dislocation and disclination pairs.
Enhancing TDCP-specified GNSS/INS tightly coupled filter robustness in cascaded for low-cost urban applications
Authors: Chen Chao , Zhao Xingwang , Ge Yulong , Xu Jian , Hu Chao , Yu Xuexiang
Published: August 2024

Integration of global navigation satellite systems (GNSS) with inertial navigation systems (INS) is commonly employed to enhance navigation performance. However, conventional integrated algorithms suffer from low-quality GNSS measurements due to either inaccurate pseudorange or difficulty in ambiguity resolution when utilizing carrier phase (CP) measurements in urban environments. We propose a new time-differenced CP (TDCP-) specified GNSS/INS tightly coupled integration algorithm for low-cost urban applications. The proposed method employs a dual-rate filter scheme, wherein the potential of TDCP observations and INS-derived positions are fully harnessed for state estimation with PR outlier inhibition and CP small cycle slip repair. Field test results in urban environments demonstrate that the integrated navigation scheme proposed is superior to conventional algorithms, with an average improvement of about 13.4%, 19.2%, and 25.5% in position, velocity, and attitude, respectively.
A novel spatio-temporal characteristic extraction network for bearing remaining useful life prediction
Authors: Jiang Li , Cao Biaobiao , Zhang Xin , Chen Bingyang , Wang Lei , Li Yibing
Published: August 2024

Remaining useful life (RUL) is an important index indicating the health status of equipment, which has attracted extensive attention. Nevertheless, many existing RUL prediction methods encounter difficulties in effectively capturing comprehensive degradation features hidden in the data. Moreover, within real-world industrial scenarios, noisy signals are inevitably collected in the raw signals, thereby posing a big challenge to the precision of RUL predictions. To address the aforementioned problems, a robust RUL estimation approach based on degradation intrinsic mode functions (IMFs) selection and spatio-temporal feature regression is developed in this paper. The former addresses the issue of deep learning models struggling to extract degradation features of rolling bearings due to interference factors in vibration signals, while the latter resolves the problem of incomplete degradation features extracted by traditional RUL models under complex operating conditions. Firstly, complete ensemble empirical mode decomposition with adaptive noise is adopted to process the raw signals, separating components with degradation features, ineffective components, and noise. Subsequently, an IMFs selection method employing fast dynamic time warping and cosine coefficients is designed to obtain the valuable degradation features. Finally, a spatio-temporal feature extraction network is presented to comprehensively and effectively capture both spatial and temporal features within the chosen degradation IMFs, achieving the prediction of RUL with high accuracy and strong robustness. The experimental part containing two case studies has validated the effectiveness and superiority of the proposed method.
Calibration of the spherical tip radius of Rockwell hardness diamond indenters using a confocal laser scanning microscope
Authors: Zackaria Mutaib , Felgner Andre , Menelao Febo , Ahbe Thomas , Brand Uwe , Tutsch Rainer
Published: August 2024

The precise form of an indenter is an essential part of hardness testing methods. It is therefore incumbent upon a user to ensure that the indenter geometry is calibrated before performing a hardness test. A geometric change of the tip radius by ±5 μm can cause a change of approximately 0.6 units of Rockwell hardness C scale (HRC) in a material with a hardness of 65 HRC. Keeping in mind that the measurement uncertainty is typically of the order of 0.3 HRC, it is critical to know the true value of the tip radius. Typically, tactile methods are used to determine the tip radius of a Rockwell hardness diamond indenter from the measured surface topography. Two main drawbacks of tactile measurements are the long duration of measurement and the limitation in capturing surface features of sizes smaller than the probe tip radius of 2 μm. Both could be overcome by using an optical 3D measurement. Confocal laser scanning microscopes (CLSM) allow a fast contactless 3D-mapping of the surface of Rockwell hardness diamond indenters and can be used to obtain geometric information such as the tip radius. The accuracy of these 3D measurements is still under question. Within this work, some of the influencing factors for fast 3D surface measurement are investigated. Using a CLSM with a 50x objective lens and a numerical aperture of 0.95, typical shape deviations of Rockwell diamond indenters are shown. Furthermore, an improved 3D based point cloud method for the evaluation of the indenter radius is presented. The aim of this paper is to explore the capabilities and limits of CLSM to obtain the 3D surface of a Rockwell hardness diamond indenter in order to calibrate the tip radius and compare their results with measurements from traceable stylus instruments.
Global convergence rates from relaxed Euler equations to Navier–Stokes equations with Oldroyd-type constitutive laws
Authors: Peng Yue-Jun , Zhao Liang
Published: August 2024

In a previous work (Peng and Zhao 2022 J. Math. Fluid Mech.
24 29), it is proved that the 1D full compressible Navier–Stokes equations for a Newtonian fluid can be approximated globally-in-time by a relaxed Euler-type system with Oldroyd’s derivatives and a revised Cattaneo’s constitutive law. These two relaxations turn the whole system into a first-order quasilinear hyperbolic one with partial dissipation. In this paper, we establish the global convergence rates between the smooth solutions to the relaxed Euler-type system and the Navier–Stokes equations over periodic domains. For this purpose, we use stream function techniques together with energy estimates for error systems. These techniques may be applicable to more complicated systems.
Dosimetry for repetitive transcranial magnetic stimulation: a translational study from Alzheimer’s disease patients to controlled in vitro investigations
Authors: Camera Francesca , Colantoni Eleonora , Casciati Arianna , Tanno Barbara , Mencarelli Lucia , Di Lorenzo Francesco , Bonnì Sonia , Koch Giacomo , Merla Caterina
Published: August 2024

Objective. Recent studies have indicated that repetitive transcranial magnetic stimulation (rTMS) could enhance cognition in Alzheimer’s Disease (AD) patients, but to now the molecular-level interaction mechanisms driving this effect remain poorly understood. While cognitive scores have been the primary measure of rTMS effectiveness, employing molecular-based approaches could offer more precise treatment predictions and prognoses. To reach this goal, it is fundamental to assess the electric field (E-field) and the induced current densities (J) within the stimulated brain areas and to translate these values to in vitro systems specifically devoted in investigating molecular-based interactions of this stimulation. Approach. This paper offers a methodological procedure to guide dosimetric assessment to translate the E-field induced in humans (in a specific pilot study) into in vitro settings. Electromagnetic simulations on patients’ head models and cellular holders were conducted to characterize exposure conditions and determine necessary adjustments for in vitro replication of the same dose delivered in humans using the same stimulating coil. Main results. Our study highlighted the levels of E-field and J induced in the target brain region and showed that the computed E-field and J were different among patients that underwent the treatment, so to replicate the exposure to the in vitro system, we have to consider a range of electric quantities as reference. To match the E-field to the levels calculated in patients’ brains, an increase of at least the 25% in the coil feeding current is necessary when in vitro stimulations are performed. Conversely, to equalize current densities, modifications in the cells culture medium conductivity have to be implemented reducing it to one fifth of its value. Significance. This dosimetric assessment and subsequent experimental adjustments are essential to achieve controlled in vitro experiments to better understand rTMS effects on AD cognition. Dosimetry is a fundamental step for comparing the cognitive effects with those obtained by stimulating a cellular model at an equal dose rigorously evaluated.
A terahertz broadband and narrowband switchable absorber based on joint modulation of vanadium dioxide and graphene surfaces
Authors: Zhang Ying , Zhou Xingtong , Li You
Published: August 2024

In this paper, a terahertz broadband and narrowband switchable absorber is proposed. The absorption performance tuning for both broadband and narrowband functions is realized based on the joint modulation of vanadium dioxide (VO2) and graphene surfaces. Concretely, while VO2 is in the metallic state, the absorber achieves broadband absorption function. The overall bandwidth of over 90% absorption is 4.04 THz corresponding to a relative bandwidth of 84%. Through regulating the conductivity of VO2, dynamic tuning of the absorption amplitude is obtained and the modulation depth is 96%. By manipulating the graphene Femi energy and VO2 conductivity simultaneously, dynamic tuning of the absorption bandwidth is realized. In particular, the spectral center frequency of broadband absorption remains stable without drifting during the tuning process. While VO2 is in the insulating state, the absorber achieves narrowband absorption function. Calculated results show that two separate perfect absorption peaks are formed, and the absorption amplitudes are 99.6% and 99.2% respectively. Through regulating the Fermi energy of graphene surface, the dynamic tuning of narrowband absorption frequency is realized. Compared with the ones reported in recent years, our absorber has the advantage on function realization, absorption characteristics and performance tuning.
ITER materials irradiation within the D–T neutron environment at JET: post-irradiation radioactivity analysis following the DTE2 experimental campaign
Authors: Packer L.W. , Batistoni P. , Bearcroft C. , Bradnam S.C. , Eardley E. , Fabbri M. , Fonnesu N. , Gilbert M.R. , Ghani Z. , Gorzkiewicz K. , Grove C.L. , Kierepko R. , Łaszyńska E. , Lengar I. , Litaudon X. , Loreti S. , Mietelski J.W. , Pillon M. , Savva M.I. , Shand C.R. , Stamatelatos I.E. , Turner A.N. , Vasilopoulou T. , Villari R. , Wójcik-Gargula A. , Žohar A. ,   JET Contributors
Published: August 2024

This work presents the results following the first irradiation of ITER materials samples in a tokamak D–T plasma environment operating at significant fusion power. The materials exposed to this nuclear environment at the Joint European Torus during the DTE2 experimental campaign that took place in 2021 include representative ITER samples from various components such as poloidal field coil jacket samples, toroidal field coil radial closure plate steels, EUROFER 97 steel, W and CuCrZr materials from the divertor, Inconel-718 and 316L stainless steel for blanket modules, as well as vacuum vessel forging samples. The experimental results discussed include high-resolution gamma spectrometry measurements and analysis conducted with the post-irradiated samples, of which there were 68 in total. These samples were exposed through different experimental campaigns, including deuterium, deuterium–tritium and tritium phases. Diagnostics that supported the analysis included 25 dosimetry foil-based neutron diagnostics and two ‘VERDI’ neutron spectrometry diagnostics. A further 12 samples for positron annihilation spectroscopy were also irradiated. The irradiation of all these samples took place in a long-term irradiation assembly located near the JET vacuum vessel. The post-irradiation analysis of the ITER material samples has yielded valuable insights into their material activation levels and radiation fields. Comparative assessments between experimental measurements and comprehensive neutronics simulations have demonstrated a significant level of agreement in this work, while also revealing some discrepancies in specific material instances. The data and interpretation from this work not only serve as a robust experimental foundation for enhancing the precision and predictability of neutronics simulation approaches for ITER and next-step devices but also present some opportunities for the refinement of simulation methodologies. In light of these findings, a series of recommendations have been proposed, aimed at improving confidence in nuclear predictions associated with materials that have been exposed to fusion nuclear environments and advancing understanding in this important domain.