bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced computational approaches to understand protein aggregation
Authors: Ghosh Deepshikha , Biswas Anushka , Radhakrishna Mithun
Published: April 2024

Protein aggregation is a widespread phenomenon implicated in debilitating diseases like Alzheimer's, Parkinson's, and cataracts, presenting complex hurdles for the field of molecular biology. In this review, we explore the evolving realm of computational methods and bioinformatics tools that have revolutionized our comprehension of protein aggregation. Beginning with a discussion of the multifaceted challenges associated with understanding this process and emphasizing the critical need for precise predictive tools, we highlight how computational techniques have become indispensable for understanding protein aggregation. We focus on molecular simulations, notably molecular dynamics (MD) simulations, spanning from atomistic to coarse-grained levels, which have emerged as pivotal tools in unraveling the complex dynamics governing protein aggregation in diseases such as cataracts, Alzheimer's, and Parkinson's. MD simulations provide microscopic insights into protein interactions and the subtleties of aggregation pathways, with advanced techniques like replica exchange molecular dynamics, Metadynamics (MetaD), and umbrella sampling enhancing our understanding by probing intricate energy landscapes and transition states. We delve into specific applications of MD simulations, elucidating the chaperone mechanism underlying cataract formation using Markov state modeling and the intricate pathways and interactions driving the toxic aggregate formation in Alzheimer's and Parkinson's disease. Transitioning we highlight how computational techniques, including bioinformatics, sequence analysis, structural data, machine learning algorithms, and artificial intelligence have become indispensable for predicting protein aggregation propensity and locating aggregation-prone regions within protein sequences. Throughout our exploration, we underscore the symbiotic relationship between computational approaches and empirical data, which has paved the way for potential therapeutic strategies against protein aggregation-related diseases. In conclusion, this review offers a comprehensive overview of advanced computational methodologies and bioinformatics tools that have catalyzed breakthroughs in unraveling the molecular basis of protein aggregation, with significant implications for clinical interventions, standing at the intersection of computational biology and experimental research.
Low turn-on voltage and 2.3 kV
β
-Ga2O3 heterojunction barrier Schottky diodes with Mo anode
Authors: Su Chunxu , Zhou Hong , Zhang Kun , Wang Chenlu , Sun Sihan , Gong Hehe , Ye Jiandong , Liu Zhihong , Dang Kui , Hu Zheyuan , Zhang Xiaodong , Wei Jie , Luo Xiaorong , Zhang Jincheng , Zhang Rong , Hao Yue
Published: April 2024

In this work, we propose combining a low work function anode metal and junction barrier Schottky structure to simultaneously achieve low turn-on voltage (Von) and high breakdown voltage (BV), which alleviates the dilemma that high BV requires high Schottky barrier height (SBH) and high Von. Molybdenum (Mo) is used to serve as the anode metal to reduce the SBH and facilitate fast turn-on to achieve a low Von. To resolve the low SBH related low BV issue, a p-NiO/n-Ga2O3-based heterojunction structure is used to enhance β-Ga2O3 sidewall depletion during the reverse state to improve the BV. With such a design, a low Von = 0.64 V(@1A/cm2) and a high BV = 2.34 kV as well as a specific on-resistance (Ron,sp) of 5.3 mΩ cm2 are demonstrated on a 10 μm-drift layer with a doping concentration of 1.5 × 1016 cm−3. β-Ga2O3 JBS diodes with low Von = 0.64 V and a power figure of merit of 1.03 GW/cm2 show great potential for future high-voltage and high-efficiency power electronics.
A variance-based optimization for determining ground and excited N-electron wave functions within the doubly occupied configuration interaction scheme
Authors: Alcoba Diego R. , Oña Ofelia B. , Torre Alicia , Lain Luis , Sierra Guadalupe , Massaccesi Gustavo E.
Published: April 2024

This work describes optimizations of N-electron system wave functions by means of the simulated annealing technique within the doubly occupied configuration interaction framework. Using that technique, we minimize the energy variance of a Hamiltonian, providing determinations of wave functions corresponding to ground or excited states in an identical manner. The procedure that allows us to determine electronic spectra can be performed using treatments of restricted or unrestricted types. The results found in selected systems, described in terms of energy, spin, and wave function, are analyzed, showing the performance of each method. We also compare these results with those arising from more traditional approaches that minimize the energy, in both restricted and unrestricted versions, and with those obtained from the full configuration interaction treatment.
From technical lignin to native lignin: Depolymerization, functionalization, and applications
Authors: Giardino Gavin J. , Wang Hongyan , Niu Jia , Wang Dunwei
Published: April 2024

Lignocellulose as a form of biomass is inedible. It represents a renewable feedstock for the synthesis of chemicals and materials. Its utilization has become an area of growing interest. Of lignocellulose components, lignin is comparatively under-explored and under-utilized, despite its abundance. This Focus Review recognizes this missed opportunity and presents a concise overview on some of the most recent progress involving the generation and application of functional materials derived from lignin. Between the two commonly encountered forms of lignin, technical lignin is a by-product of the paper production industry and is highly processed under harsh conditions. As such, it has generally been used for filler and resin materials. By comparison, native lignin is rich in chemical functionalities and holds great promise for downstream chemical synthesis. In recognition of these potentials, “lignin-first” strategies have emerged to directly convert native lignin to building blocks rich in functional groups, such as alcohols and carbonyls, while maintaining the integrity of the aromatic structures in lignin. The lignin-first strategy complements the already well explored field of technical lignin utilization. These chemoselective, lignin-first methods promise routes to native lignin valorization into high-value building blocks while keeping cellulose and hemicellulose intact and, therefore, are particularly appealing. This Focus Review first recognizes the importance of the traditional strategies for technical lignin utilization and highlights some of the newest developments. It then puts an emphasis on these lignin-first approaches for improved native lignin utilizations.
Plasma-enhanced chemical vapor deposition a-SiOCN:H low-Z thin films for bulk acoustic wave resonators
Authors: Berger Claudio , Schneider Michael , Pfusterschmied Georg , Schmid Ulrich
Published: April 2024

The 5th generation (5G) wireless telecommunication standards with newly defined frequency bands up to 6 GHz are currently established around the world. While outperforming surface acoustic wave (SAW) filters above 1 GHz, bulk acoustic wave (BAW) resonators in multiplexers for radio-frequency front-end (RFFE) modules continuously face higher performance requirements. In contrast to free-standing bulk acoustic resonators (FBARs), solidly mounted resonator (SMR) technology uses an acoustic Bragg mirror, which has already been successfully applied for several GHz applications. In this work, we investigate the potential of amorphous hydrogenated silicon-oxycarbonitride (a-SiOCN:H) thin films synthesized with low-temperature plasma-enhanced chemical vapor deposition (PECVD) as a low acoustic impedance (low-Z) material. Compared to the state-of-the-art where in Bragg mirrors up to now SiO2 is used as standard, the acoustic impedance ratio against the high-Z material tungsten (W) is enhanced for a better device performance. To limit the expected increase in viscous loss when the acoustic impedance is reduced, to a minimum, predominantly the mass density was reduced while keeping the mechanical elasticity high. By doing so, acoustic impedance values as low as 7.1 MRayl were achieved, thereby increasing the impedance ratio of high-Z to low-Z materials from 8:1 up to 14:1.
Tolerance and breakdown of topological protection in a disordered waveguide
Authors: Goudarzi Kiyanoush , Lee Moonjoo
Published: April 2024

We consider a disordered waveguide consisting of trivial dielectric and non-trivial magnetically anisotropic material. A topologically protected edge mode appears owing to the broken time-reversal symmetry of the non-trivial lattice. While the edge mode maintains under other position and radius disorders, the protection is immediately broken by applying a radius disorder to the non-trivial lattice. This breakdown originates from donor and acceptor modes occupying the topological bandgap. Furthermore, via the calculation of the Bott index, we show that Anderson localization occurs as a metal conducting gap changes to a topological gap along with increasing disorders.
Special role of indium nitride in the properties of related compounds and quantum structures
Authors: Gorczyca I. , Suski T. , Perlin P. , Grzegory I. , Staszczak G. , Aktas M.
Published: April 2024

This Review provides a thorough description of the experimental progress on the InN family and other relevant compounds. Although InN is of great interest, many of its properties are not well understood and are still puzzling researchers with a number of unexpected effects. These include a surprisingly small energy gap, sensitivity to applied pressure in terms of lattice stability, and poor miscibility with compounds with smaller lattice parameters, such as GaN and AlN. Special features of InN under pressure are highlighted, such as the effect of conduction band filling and the strong pressure dependence of the effective mass. Several negative and positive effects due to the presence of In have been observed. We highlight their implications for InN-based alloys and quantum structures, which are crucial materials in modern optoelectronics (light emitting diodes and laser diodes). These effects include In clustering, large piezoelectricity resulting in strong internal electric fields that reduce the optical gain in nitride heterostructures, and difficulties in growing high-In superlattices and other quantum structures. All of these effects pose challenges that need to be addressed. We show that theoretical explanations allow for the clarification of puzzling experimental observations. Discussed are (i) a reformulation of the rule describing the bandgap dependence on pressure in all III–V semiconductors; (ii) the very large bandgap curvatures in nitride alloys; and (iii) the discrepancies between theory and experiment in the optical emission from InN/GaN superlattices, leading to the conclusion that epitaxial growth of high In content InxGa1−xN (x > 0.3) quantum wells on GaN is not possible.
Flow of a colloidal solution in an orthogonal rheometer
Authors: Yanamundra Krishna Kaushik , Benjamin Chandler C. , Rajagopal Kumbakonam Ramamani
Published: April 2024

The flow of a colloidal solution between two parallel disks rotating with the same angular velocity about two non-coincident axes was studied. The problem has been approached from two perspectives, the first wherein the stress is expressed in terms of a power-law of kinematical quantities, and the second wherein we consider a non-standard model where the symmetric part of the velocity gradient is given by a power-law of the stress. For a range of power-law exponents, the class of models are non-invertible. By varying the material and geometric parameters, changes in the flow behavior at different Reynolds numbers were analyzed. We find that pronounced boundary layers develop even at low Reynolds numbers depending on the power-law exponents. The new class of stress power-law fluids and fluids that exhibit limiting stress also show the ability to develop boundary layers.
Molecular dynamics simulations of heat transport using machine-learned potentials: A mini-review and tutorial on GPUMD with neuroevolution potentials
Authors: Dong Haikuan , Shi Yongbo , Ying Penghua , Xu Ke , Liang Ting , Wang Yanzhou , Zeng Zezhu , Wu Xin , Zhou Wenjiang , Xiong Shiyun , Chen Shunda , Fan Zheyong
Published: April 2024

Molecular dynamics (MD) simulations play an important role in understanding and engineering heat transport properties of complex materials. An essential requirement for reliably predicting heat transport properties is the use of accurate and efficient interatomic potentials. Recently, machine-learned potentials (MLPs) have shown great promise in providing the required accuracy for a broad range of materials. In this mini-review and tutorial, we delve into the fundamentals of heat transport, explore pertinent MD simulation methods, and survey the applications of MLPs in MD simulations of heat transport. Furthermore, we provide a step-by-step tutorial on developing MLPs for highly efficient and predictive heat transport simulations, utilizing the neuroevolution potentials as implemented in the GPUMD package. Our aim with this mini-review and tutorial is to empower researchers with valuable insights into cutting-edge methodologies that can significantly enhance the accuracy and efficiency of MD simulations for heat transport studies.
Dual-comb interchanging absolute distance measurement with non-ambiguity range extension
Authors: Shao Xiaodong , Han Hainian , Yan Yu , Ma Junyi , Li Chengzhi , Wei Zhiyi
Published: April 2024

We demonstrate a rapid and high-precision dual-comb ranging method with a significantly extended non-ambiguity range (NAR). By reasonably setting the polarization combining and splitting of two optical combs, we can obtain two sets of interferograms of signal comb and local oscillator comb interchanging simultaneously. This method allows us to extend the NAR to tens to hundreds of kilometers without changing the repetition rate of the signal comb. With this scheme, we demonstrate a dynamic distance measurement when a moving target crosses a measurement dead zone that is 3–4 times the NAR. The standard deviation of the residual distance is 1.48 μm with a 925 μs update rate. This rapid, high-precision, and NAR extension absolute distance measurement scheme will have broad potential in various ranging applications.
Negative elastic wave refraction and focusing regulation of single-phase solid phononic crystals
Authors: Liu Fei-Yu , Wang Fa-Jie , Zhao Sheng-Dong
Published: April 2024

This paper presents the design of a single-phase solid phononic crystal (PnC) structure featuring a regular hexagonal perforation pattern. The structure manifests three negative refraction bands, encompassing one for transverse waves and two for longitudinal waves, thereby enabling simultaneous control of shear and longitudinal waves. Due to the high symmetry of the triangular lattice, the equal frequency curves corresponding to the negative refraction band approach circular shapes, suggesting a nearly isotropic negative refraction effect. This negative refraction effect is achieved through specific mass resonance modes closely related to the porous structure designed in this paper. Initially, we analyze the band structure of the PnC, followed by designing the PnC plate structure to achieve negative refraction control for transverse waves at a frequency of 32.4 kHz, with a negative refraction index of −1. Additionally, negative refraction control for longitudinal waves is attained at frequencies of 44 and 64.54 kHz. Subsequently, we scrutinize the influence of various conditions on negative refraction, including different structural parameters, incident angles, and operating frequencies, while verifying the robustness of the designed phonon crystal structure. Leveraging the negative refraction characteristics of the structure, we construct an elastic wave lens to achieve perfect imaging of shear and longitudinal waves. Finally, employing finite element simulation and analyzing focusing imaging characteristics with different source positions, we validate that the results closely align with theoretical expectations. The solid PnC structure designed in this study holds significant potential for applications in the fields of elastic wave imaging.
Influence of inflow conditions on simplified heavy vehicle wake
Authors: Han Shuai , Wang Fan , Zhang Jie
Published: April 2024

In the current study, the impact of various inflow conditions, including turbulent wind profiles and turbulent intensity, on the wake flow topology of a simplified ground transportation system (GTS) model was investigated using the improved delayed detached eddy simulation. The reliability and accuracy of the numerical method adopted in this paper were verified against the results comprising the aerodynamic drag and the wake flow structure of the GTS model obtained from the large eddy simulation and the experimental data. The research results indicate that turbulent winds characterized by logarithmic and uniform velocity profiles resulted in significantly different wake flow topologies yet exhibit the same dominant frequency. The turbulent intensity also plays a crucial role in the wake of the GTS model. It is observed that an increase in turbulence intensity corresponds with a rise in the aerodynamic drag. Specifically, when the turbulence intensity is set at 15%, there is a 3.68% increase in the aerodynamic drag of the GTS model compared to a case where the turbulence intensity was only 5%. In addition, the turbulent intensity is critical to the dominant frequency characteristics of the wake region of the GTS model. These results demonstrate that both the velocity profiles and the turbulence intensities significantly influence the wake flow topology and aerodynamic drag of the GTS model, providing a valuable reference for establishing appropriate inflow conditions and exploring the formation mechanism of flow topology in the wake of the GTS model.
Dynamic tuning of moiré superlattice morphology by out-of-plane deformation
Authors: Zhu Guangfei , Liu Rumeng , Tang Chun , Wang Lifeng
Published: April 2024

The moiré superlattice structure has become a subject of intense interest due to its unique and intriguing properties. Key to the success of its applications is the precise manipulation of morphologies that determines the ultimate functionalities. To achieve such a goal is, however, very challenging. In this work, we present an approach for tuning moiré superlattices of suspended van der Waals structures through out-of-plane deformation. By studying the influence of out-of-plane deformation on interlayer sliding and atomic reconstruction in bilayer van der Waals structures, it is observed that interlayer sliding can overcome van der Waals potential barriers, resulting in stacking mode variations. Detailed analysis show that contraction and rotation of moiré patterns are induced, and leads to changes in the wavelength of the moiré superlattice. The approach outlined here offers opportunities for controlling and manipulating moiré superlattices.
Suppression of cracking in drying colloidal suspensions with chain-like particles
Authors: Niu Zhaoxia , Zhao Yiping , Zhang Qiuting , Zhao Zhiyuan , Ge Dengteng , Zhou Jiajia , Xu Ye
Published: April 2024

The prevention of drying-induced cracking is crucial in maintaining the mechanical integrity and functionality of colloidal deposits and coatings. Despite exploring various approaches, controlling drying-induced cracking remains a subject of great scientific interest and practical importance. By introducing chain-like particles composed of the same material and with comparable size into commonly used colloidal suspensions of spherical silica nanoparticles, we can significantly reduce the cracks formed in dried particle deposits and achieve a fivefold increase in the critical cracking thickness of colloidal silica coatings. The mechanism underlying the crack suppression is attributed to the increased porosity and pore sizes in dried particle deposits containing chain-like particle, which essentially leads to reduction in internal stresses developed during the drying process. Meanwhile, the nanoindentation measurements reveal that colloidal deposits with chain-like particles exhibit a smaller reduction in hardness compared to those reported using other cracking suppression approaches. This work demonstrates a promising technique for preparing colloidal coatings with enhanced crack resistance while maintaining desirable mechanical properties.
Trap states and carrier diffusion lengths in NiO/β-Ga2O3 heterojunctions
Authors: Polyakov A. Y. , Yakimov E. B. , Saranin D. S. , Chernykh A. V. , Vasilev A. A. , Gostishchev P. , Kochkova A. I. , Alexanyan L. A. , Matros N. R. , Shchemerov I. V. , Pearton S. J.
Published: April 2024

We report the electrical properties, deep trap spectra, and diffusion lengths of non-equilibrium carriers in Ni Schottky diodes and NiO/Ga2O3 heterojunctions (HJs) prepared on the same n−/n+ β-Ga2O3 epi structures. The heterojunctions decrease the reverse current of Ga2O3 high-power rectifiers. In HJs, in contrast to Schottky diodes, the capacitance and AC conductance show a prominent frequency and temperature dependence, suggesting the presence of two temperature activation processes with activation energies of 0.17 and 0.1 eV. The deep trap spectra of the Schottky diodes and HJs differ by the absence in the HJ of deep electron traps E2* with level near Ec − 0.7 eV considered to be an important center of non-radiative recombination. This correlates with the observed increase in the diffusion length of non-equilibrium charge carriers in the HJs to 370 nm compared to 240 nm in the Schottky diodes. The diffusion length of charge carriers in p-NiO was found to be quite short, 30 nm. Possible reasons for the observed differences and possible origin of the minority-trap-like feature commonly reported to be present in the deep level spectra of HJs and also observed in our experiments are discussed.
Realization of high cryogenic thermoelectric performance for MgAgSb base alloy by regulation heat-treatment process
Authors: Qiu Fanghong , Chen Jun-Liang , Liao Yuntiao , Zhang Zhongwei , Liang Jisheng , Miao Lei , Zhou Qi , Peng Ying , Liu Chengyan , Gao Jie
Published: April 2024

MgAgSb alloy has attracted wide attention due to its inherent low thermal conductivity, excellent thermoelectric (TE) properties, and environmental friendliness. Although the TE performance has been deeply investigated for the temperature range over 300–700 K, while cryogenic range has seldom report. In this study, a systematic investigation on cryogenic TE performance of α-MgAgSb has been performed. α-MgAgSb alloy has been synthesized by ordinary ball milling followed spark plasma sintering process and then further regulated by heat treatment. The power factor of MgAgSb alloy after 10 days of heat-treating increased by 230%, which is attributed to the reduction of the impurity phase and the improvement of the crystallinity achieved by the optimization of heat treatment. The total thermal conductivity decreased by 18% to 1.15 W m−1 K−1, and the maximum ZT reached 0.264 at 173 K, which is 300% enhancement to untreated one. The ZTavg reached to 0.45 over 173–298 K, located at the pinnacle among cryogenic TE materials. In addition, the ZTeng value of 0.23 related to the highest device conversion efficiency of 5.2% demonstrates good device potential. This work reveals that the purity and the cryogenic TE properties of α-MgAgSb alloy can be effectively improved by heat-treating, and demonstrates the greatly potential of MgAgSb materials in the field of liquefied natural gas's cold energy recovery.
Numerical prediction and optimization of aerodynamic noise of straw crushers by considering the straw-crushing process
Authors: Zhao Yu , Zhai Zhiping , Gao Bo , Lan Yuezheng
Published: April 2024

Straw crops are struck and broken into soft filaments by the high-speed rotating hammers of straw crushers, which disturb the internal airflow field and generate much noise during the operation of straw crushers. To accurately estimate and reduce the aerodynamic noise of straw crushers at the design stage, in this study, first, the coupling method of the discrete element method, bonded-particle model, and computational fluid dynamics were used to obtain the acoustics source data. Next, the Ffowcs Williams–Hawkins theory and the indirect boundary element method were used to predict the aerodynamic noise generated during the straw crushing process. The multi-island genetic algorithm was used to optimize the aerodynamic noise of straw crushers. The results indicate that the simulated and measured total sound pressure levels (TSPLs) at the outlet and inlet differed by 1.43 and 2.12 dB(A), respectively. Additionally, aerodynamic noise at the inlet appears to be primarily influenced by the sound pressure level at the excitation fundamental frequency, while noise at the outlet is primarily influenced by the sound pressure level at the double frequency. Higher sound pressure levels were mainly concentrated at the fundamental frequency and its lower harmonic frequencies, and the sound pressure level gradually decreased with the increase in the frequency. After optimization, the aerodynamic noise TSPL at the inlet decreased from 100.87 to 88.58 dB(A) and at the outlet decreased from 102.26 to 89.62 dB(A). This study provides a methodological reference for aerodynamic noise prediction and the design of low-noise straw crushers.
Source–drain contact impacts on electrical performances and low frequency noise of InZnO thin-film transistors down to 7 K
Authors: Chen Yayi , Liu Xingji , Liu Yuan , Chen Rongsheng , Zhang Jianfeng , Wu Mingchao , Kwok Hoi-Sing , Zhong Wei
Published: April 2024

Source–drain contacts seriously affect low frequency noise (LFN) in amorphous IZO (a-IZO) thin-film transistors with bilayer ITO/Mo electrodes at cryogenic temperatures. In the range of 7–300 K, electrical and LFN performances of devices are measured, and the temperature dependence of channel resistances (Rch) and contact resistances (Rsd) is also analyzed. The carrier transport transition both occurs in a-IZO channels at 80 K and in ITO/Mo electrodes at 100 K, which causes the variation in Rsd and Rch. Below 80 K, the variable range hopping conduction dominates in the channels and contacts with Rsd/Rch ratio > 1. The LFN measured results indicate that the noise is contact-dominated. At higher temperatures above 120 K, the band conduction dominates in the channel, with Rsd/Rch ratio < 1, and the noise is channel-dominated. The main mechanism of noise transfers from the mobility fluctuation to the carrier number fluctuation. We consider that the contribution of contact noise to total LFN is determined by the Rsd/Rch ratio. This work provides comments for the selection of electrode materials in devices applied to cryogenic integration circuits.
Modular slot-die coater for in situ grazing-incidence x-ray scattering experiments on thin films
Authors: Reus Manuel A. , Baier Thomas , Lindenmeir Christoph G. , Weinzierl Alexander F. , Buyan-Arivjikh Altantulga , Wegener Simon A. , Kosbahn David P. , Reb Lennart K. , Rubeck Jan , Schwartzkopf Matthias , Roth Stephan V. , Müller-Buschbaum Peter
Published: April 2024

Multimodal in situ experiments during slot-die coating of thin films pioneer the way to kinetic studies on thin-film formation. They establish a powerful tool to understand and optimize the formation and properties of thin-film devices, e.g., solar cells, sensors, or LED films. Thin-film research benefits from time-resolved grazing-incidence wide- and small-angle x-ray scattering (GIWAXS/GISAXS) with a sub-second resolution to reveal the evolution of crystal structure, texture, and morphology during the deposition process. Simultaneously investigating optical properties by in situ photoluminescence measurements complements in-depth kinetic studies focusing on a comprehensive understanding of the triangular interdependency of processing, structure, and function for a roll-to-roll compatible, scalable thin-film deposition process. Here, we introduce a modular slot-die coater specially designed for in situ GIWAXS/GISAXS measurements and applicable to various ink systems. With a design for quick assembly, the slot-die coater permits the reproducible and comparable fabrication of thin films in the lab and at the synchrotron using the very same hardware components, as demonstrated in this work by experiments performed at Deutsches Elektronen-Synchrotron (DESY). Simultaneous to GIWAXS/GISAXS, photoluminescence measurements probe optoelectronic properties in situ during thin-film formation. An environmental chamber allows to control the atmosphere inside the coater. Modular construction and lightweight design make the coater mobile, easy to transport, quickly extendable, and adaptable to new beamline environments.
Numerical investigation of turbulence generation using Zakharov-like model equation
Authors: Kumar Praveen , Uma R. , Sharma R. P.
Published: April 2024

This study investigates the turbulence generation behavior with a Zakharov-like (ZL) equation in a fluid system. The model equation is derived using conservation equations (mass and momentum conservation), and the source of nonlinearity is the high amplitude of the acoustic wave. The Zakharov-like equation has been derived and then solved numerically, then turned into a modified nonlinear Schrödinger equation. Furthermore, modulation instability, or Benjamin–Feir instability, of the model equations, which leads to the emergence of Akhmediev breathers, is discussed. The numerical simulation uses a finite difference method for temporal evolution and a pseudo-spectral approach to determine spatial regimes. The outcomes indicate that the situation involving the nonlinear Schrödinger equation case displays a periodic pattern in space and time. The findings also demonstrate that the localization of structure and the Fermi, Pasta, and Ulam (FPU) recurrences are disrupted for the modified nonlinear Schrödinger equation and Zakharov-like equation cases. The energy spectrum exhibits a power law behavior that approximately follows k−1.65 in the ZL model equation case, and it is steeper than Kolmogorov's spectrum within the inertial sub-range.
Effect of fluid–structure interaction on the oblique water entry of the projectile under the influence of floating ice structure
Authors: Hu Xinyu , Wei Yingjie , Wang Cong
Published: April 2024

The water entry of a projectile constrained by polar floating ice presents a unique cross-media challenge. This paper investigates the dynamics of oblique water entry for a projectile influenced by floating ice using the fluid–structure interaction (FSI) method. The validity of the numerical method has been confirmed through experimental validation. The water entry process of a projectile from the side of the floating ice is examined. The evolution of the cavity and the movement patterns of objects as the distance between the projectile and the floating ice decreases toward collision are investigated. The influence of water on the critical collision distance between the projectile and the floating ice during oblique water entry is analyzed. Additionally, the physical mechanism of floating ice deflection through collision is investigated based on the theory of cavity dynamics. Subsequently, the study focuses on the oblique water entry process of a projectile colliding with the upper surface of the floating ice. Different entry angles determine the collision mode between the projectile and the floating ice surface. This study also examines how varying entry angles influence cavity evolution and object movement patterns during oblique collisions. Different collision modes between the projectile and the floating ice lead to asymmetric cavity evolution and various modes of object deflection motion. Finally, changes in the flow field and vortex structure during oblique collisions are studied to examine the influence of the FSI process between the projectile and the floating ice on the flow field.
Enhancing gas film stability by alternating superhydrophobic and hydrophobic surfaces for stable drag reduction
Authors: Yao Xiao , Yang Yi , Li Guoqiang , Song Yuegan , Wang Yuan , Xuan Sensen , Yin Huan , Zou Qinrui , Ren Hesong , Li Xiaoxin , Li Xiaohong
Published: April 2024

Superhydrophobic surfaces can significantly reduce the resistance of underwater vehicles, but as the speed increases, the gas film is prone to be destroyed, leading to a decrease in the drag reduction effect or even an increase in the drag. Therefore, enhancing the stability of the gas film is crucial for maintaining the drag reduction effect. Inspired by the honeycomb array pit structures, the high adhesion hydrophobic properties of rose petals, and the wetting gradient surface of Namib desert beetles, an alternating superhydrophobic and hydrophobic surface (ASHHs) was constructed by femtosecond laser to enhance the stability of the gas film. The high adhesion hydrophobic surface (HAHs) provides greater adhesive force, allowing the gas film to firmly pin at the junction of a low-adhesion superhydrophobic surface (LASHs) and HAHs, thereby enhancing the stability of the gas film. The critical failure velocity of ASHHs can reach 2.3 m/s, which is significantly greater than that of low-adhesion superhydrophobic surface samples (LASH-S) (1.7 m/s). ASHHs maintains a stable drag reduction effect of 37% at a velocity of 2.3 m/s, while that of LASH-S is only 6%. It is envisioned that such superhydrophobic surfaces that enhance gas film stability should find widespread applications in minimizing resistance and reducing energy consumption in the marine engineering field.
Experimental evidence for defect tolerance in Pb-halide perovskites
Authors: Jasti Naga Prathibha , Levine Igal , Feldman Yishay (Isai) , Hodes Gary , Aharon Sigalit , Cahen David
Published: April 2024

The term defect tolerance (DT) is used often to rationalize the exceptional optoelectronic properties of halide perovskites (HaPs) and their devices. Even though DT lacked direct experimental evidence, it became a “fact” in the field. DT in semiconductors implies that structural defects do not translate to electrical and optical effects (e.g., due to charge trapping), associated with such defects. We present pioneering direct experimental evidence for DT in Pb-HaPs by comparing the structural quality of 2-dimensional (2D), 2D-3D, and 3D Pb-iodide HaP crystals with their optoelectronic characteristics using high-sensitivity methods. Importantly, we get information from the materials’ bulk because we sample at least a few hundred nanometers, up to several micrometers, from the sample’s surface, which allows for assessing intrinsic bulk (and not only surface-) properties of HaPs. The results point to DT in 3D, 2D-3D, and 2D Pb-HaPs. Overall, our data provide an experimental basis to rationalize DT in Pb-HaPs. These experiments and findings will help the search for and design of materials with real DT.
Brain-inspired computing with fluidic iontronic nanochannels
Authors: Kamsma Tim M. , Kim Jaehyun , Kim Kyungjun , Boon Willem Q. , Spitoni Cristian , Park Jungyul , van Roij René
Published: April 2024

The brain’s remarkable and efficient information processing capability is driving research into brain-inspired (neuromorphic) computing paradigms. Artificial aqueous ion channels are emerging as an exciting platform for neuromorphic computing, representing a departure from conventional solid-state devices by directly mimicking the brain’s fluidic ion transport. Supported by a quantitative theoretical model, we present easy-to-fabricate tapered microchannels that embed a conducting network of fluidic nanochannels between a colloidal structure. Due to transient salt concentration polarization, our devices are volatile memristors (memory resistors) that are remarkably stable. The voltage-driven net salt flux and accumulation, that underpin the concentration polarization, surprisingly combine into a diffusionlike quadratic dependence of the memory retention time on the channel length, allowing channel design for a specific timescale. We implement our device as a synaptic element for neuromorphic reservoir computing. Individual channels distinguish various time series, that together represent (handwritten) numbers, for subsequent in silico classification with a simple readout function. Our results represent a significant step toward realizing the promise of fluidic ion channels as a platform to emulate the rich aqueous dynamics of the brain.
TiO2 multi-leg nanotubes for surface-enhanced Raman scattering
Authors: S Harini , Gupta Garima , Roy Somnath C , Yalavarthi Rambabu
Published: April 2024

In the recent past, significant research efforts have been put forth to fabricate cost-effective substrates for surface-enhanced Raman scattering (SERS) applications. Here we propose semiconducting TiO2 multi-leg nanotubes and Au nanoparticle-coated TiO2 multi-leg nanotubes (TiO2 MLNTs and Au/TiO2 MLNTs) as SERS substrates. The unique multi-leg architecture of TiO2 nanotubes demonstrated enhanced light-harvesting properties facilitated by an induced photonic absorption edge. Remarkable high SERS sensitivity is observed towards the detection of Methylene blue (MB), up to nM concentration (E.F. ∼104) using TiO2 MLNTs. The same is attributed to the resonantly matched photonic absorption edge of TiO2 MLNTs with the wavelength of incident laser probe light. On the other hand, the Au nanoparticle coating further leveraged the light absorption ability of TiO2 MLNTs with the aid of localized surface plasmon resonance mode. As such, Au/TiO2 MLNTs showed excellent enhancement in SERS sensitivity (E.F. ∼105
, for nM of MB) facilitated by the synergy between the plasmonic modes of Au and the photonic absorption mode of TiO2 MLNTs. UV-Vis diffuse reflectance and Raman spectroscopy measurements are highlighted to elucidate the light absorption and SERS sensitivity of the TiO2 and Au/TiO2 MLNTs.
Dual mode spin to charge conversion using inverse spin Hall effect in NiFe/FeMn/NiFe multilayer thin films
Authors: Panigrahi Brahmaranjan , Raja M Manivel , Murapaka Chandrasekhar , Haldar Arabinda
Published: April 2024

Microwave devices with more than one operating frequency and their ease of tunability are of great importance for high-frequency information processing. Magnetic thin films offer an unparalleled advantage of engineering different microwave bands that can be precisely tailored and reconfigured externally. Here, novel trilayer structures consisting of NiFe/FeMn/NiFe with varying antiferromagnetic FeMn layer thickness have been investigated by exploring their ferromagnetic resonance (FMR) properties and inverse spin Hall effect (ISHE) responses. Two-step magnetic hysteresis loops are observed for higher FeMn thickness (t ⩾ 12 nm), where the bottom NiFe layer shows a comparatively more significant shift due to the presence of strong interfacial exchange coupling. FMR study reveals two resonant modes associated with the two ferromagnetic layers, which are distinguishable for higher thicknesses of FeMn or at high excitation frequencies. The choice of FeMn thickness determines the operating frequencies, which can be finely tailored by optimizing the FeMn thickness. Gilbert damping parameter is found to be in the range of 0.009–0.012 where the presence of exchange bias adds to the the scattering mechanisms. Prominent ISHE responses are obtained from the bottom NiFe layer as compared to the top NiFe layer. Variation of FeMn thickness also shows a strong influence on the spin pumping (

V

sp

), and perpendicular anisotropic magnetoresistance (

V

AMR

⊥

) components. The results are correlated with the efficiency of spin flow and spin-to-charge conversion of the FeMn layer. Our systems can be used as an emerging alternative for microwave detectors and microwave energy harvesters.
In situ growth of Ag nanoparticles on the surface of MXene by γ-ray irradiation to fabricate EVA composite: the improvement of flame retardancy, smoke suppression, and mechanical properties
Authors: Xu Siyi , Li Danyi , Wang Wenrui , Lin Lin , Sun Ying , Li Jihao , Li Linfan
Published: April 2024

A large amount of toxic smoke and heat generated by the combustion of ethylene vinyl acetate copolymer (EVA) poses a significant threat to human fire escape evacuation. This work aims to use γ-ray to prepare e-MXene@Ag hybrid flame-retardant materials by the method of in-situ reduction, and EVA composites are prepared by melt blending to reduce the smoke and toxic gases produced during combustion significantly. Compared with pure EVA, the total heat release, total smoke release, and the production rate of CO and CO2 produced by the combustion of EVA composite with 1 wt% e-MXene@Ag1.0 decreased by 30.3%, 33.3%, 18.2%, and 20.1% respectively. The fire hazard reduction of EVA composite materials was due to the physical barrier, catalytic carbonization and adsorption of the e-MXene@Ag1.0 hybrid. In addition, e-MXene@Ag1.0 can also further increase the mechanical properties of EVA composites due to its own ‘multi-contact point limit structure’.
Analysis of defects dominating carrier recombination in CeO2 single crystal for photocatalytic applications
Authors: Zhang Endong , Brabec Christoph J , Kato Masashi
Published: April 2024

In photocatalytic water splitting and CO2 reduction, recently, cerium oxide (CeO2) has been widely investigated. Defects that can directly dominate carrier recombination are essential for the photocatalytic performance of CeO2. In this study, several photoluminescence (PL) peaks are observed on the (100) face of an undoped CeO2 single crystal, indicating the presence of defects. Moreover, we characterize carrier recombination using time-resolved photoluminescence (TR-PL) and microwave photoconductivity decay (μ-PCD) measurements. The temperature dependence of decay curves is the result of carrier trapping and emission at deep levels. These decay curves are observed separately using a 565 nm band-pass filter (BPF) based on the PL spectra. The trap energy level (

E

T

) and majority carrier capture cross-section (

σ

T

) of each defect are also analyzed using rate equations to fit the experimental results. The temperature-dependent time constants are well reproduced by a recombination model using hole traps HTinfrared and HTvisible at

E

T

of 0.76 and 0.55 eV from the conduction or valence band, with estimated

σ

T

of the order of 10−21 and 10−22 cm2 for without and with the BPF, respectively. These findings regarding the presence of multiple defects in a single crystal indicate the necessity to focus on defect control.
Charge–spin interconversion in nitrogen sputtered Pt via extrinsic spin Hall effect
Authors: Shashank Utkarsh , Kusaba Yu , Nakamura Junnosuke , Mathew Arun Jacob , Imai Koki , Senba Shinya , Asada Hironori , Fukuma Yasuhiro
Published: April 2024

We experimentally investigate the charge–spin interconversion by introducing a lighter impurity, namely nitrogen (N) into Pt by varying the nitrogen gas flow rate, Q from 0 to 20%, and studying the Onsager reciprocity of spin Hall effect (SHE) via complementary methods of spin-torque ferromagnetic resonance and spin-pumping inverse SHE measurements, respectively. We notice a reduction in the crystalline nature of Pt upon nitrogen incorporation. We observe the influence of extrinsic side-jump scattering induced SHE by measuring the spin Hall efficiency,

θ

SH

in a wide temperature range from 10 to 296 K. This work establishes the incorporation of N in Pt by using sputtering, to enhance the SHE via extrinsic scattering as well as to observe the reciprocal effects of charge–spin interconversion.
Anomalous Hall effect and magnetic transition in the kagome material YbMn6Sn6
Authors: Jiang Lei , Fan Feng-Ren , Chen Dong , Mu Qingge , Wang Yiyan , Yue Xiaoyu , Li Na , Sun Yan , Li Qiuju , Wu Dandan , Zhou Ying , Sun Xuefeng , Liang Hui
Published: April 2024

We investigate the magnetic and transport properties of a kagome magnet YbMn6Sn6. We have grown YbMn6Sn6 single crystals having a HfFe6Ge6 type structure with ordered Yb and Sn atoms, which is different from the distorted structure previously reported. The single crystal undergoes a ferromagnetic phase transition around 300 K and a ferrimagnetic transition at approximately 30 K, and the magnetic transition at low temperature may be correlated to the ordered Yb sublattice. Negative magnetoresistance has been observed at high temperatures, while the positive magnetoresistance appears at 5 K when the current is oriented out of kagome plane. We observe a large anisotropic anomalous Hall effect with the intrinsic Hall contribution of 141 Ω−1cm−1 for

σ

z
x

int

and 32 Ω−1cm−1 for

σ

x
y

int

, respectively. These values are similar to those in YMn6Sn6 with the same anisotropy. The magnetic transition and anomalous Hall behavior in YbMn6Sn6 highlights the influence of the ordered Yb atoms and rare earth elements on its magnetic and transport properties.
Recombination dynamics and manybody effect of excitons in large-area monolayer MoS2 capped with (111) NiO epitaxial layer
Authors: Mujeeb Faiha , Rana Gourab , Chakrabarti Poulab , Prasad Sahu Bhabani , Jeena Rupa , Datta Anindya , Dhar Subhabrata
Published: April 2024

CVD grown monolayer MoS2 films on c-sapphire substrates are vacuum annealed and capped with (111) NiO epitaxial films using pulsed laser deposition technique. Time, energy and polarization resolved optical techniques are used to understand the effect of capping on the excitonic properties of the monolayer MoS2. It has been observed that trion contribution in the photoluminescence (PL) spectra increases after the capping, suggesting an enhancement of electron concentration in the conduction band. This has been attributed to the capping driven reduction of physisorbed air molecules from the sulphur vacancy (

V

S

) sites. Note that the air molecules act as passivating agents for the

V

S

-donors. Low temperature polarization resolved PL spectroscopy and ultrafast pump and probe transient absorption spectroscopy (TAS) show an increase of the biexcitonic population in the system after the encapsulation. The TAS study further reveals longer lifetime for both A and B excitons in capped samples implying a reduction of non-radiative recombination rate of the excitons after the capping. It has also been observed that in the capped samples,

K

/

K

′

valleys are populated with trions under sufficiently high pump powers. This has been attributed to the lower non-radiative recombination rates of the high energy photoexcited carriers and the faster transfer of either electrons or holes from the high energy pockets to the

K

/

K

′

valleys. The study further reveals different many-body effects in excitons and trions.