bluuebunny/crossref_metadata_2025 huggingface dataset:
Brownian motion of poly(divinylbenzene) nanoparticles in water
Authors: Lin Ching-Bin , Lee Chia-Wei , Ouyang Hao , Yang Fuqian , Lee Sanboh
Published: March 2023

Understanding the motion of nanoparticles in liquid is of practical importance for drug delivery and fluid flow in nanofluidic systems. In this work, we use a nanoparticle tracking analyzer to investigate the Brownian motion of polydivinylbenzene (PDVB) nanoparticles in water and a video camera to record the aggregation of PDVB aggregates on the water surface. Using water as the liquid medium precludes the possible complex interaction between the liquid medium and the PDVB nanoparticles, which can possibly alter the random characteristics of the motion of the PDVB nanoparticles. The diffusivity of the PDVB nanoparticles determined from the mean square displacements of the PDVB nanoparticles has the same activation energy as that for the intrinsic viscosity of the corresponding aqueous suspension of the PDVB nanoparticles. The correlation between the diffusivity for the motion of the PDVB nanoparticles in water and the intrinsic viscosity of the corresponding aqueous suspension follows the Stokes–Einstein relation. The capillary effect and the interaction between PDVB aggregates and the liquid media enable the aggregation of the PDVB aggregates on the water surface, which follows the first-order reaction with activation energy larger than that for the random motion of the PDVB nanoparticles in water.
Calibrating single-qubit gates by a two-dimensional Rabi oscillation
Authors: Huang You , T Amawi Mohammad , Poggiali Francesco , Shi Fazhan , Du Jiangfeng , Reinhard Friedemann
Published: March 2023

We present and analyze a simple scheme to calibrate single–qubit gates. It determines the amplitude and phase difference between a quadrature pair of drives, as well as their common detuning from the qubit resonance. The method is based on a two–dimensional Rabi oscillation, a sequence of two pulses of varying length sourced from the drive pair. We demonstrate error diagnosis using this scheme on an ensemble of nitrogen-vacancy centers in diamond and point out subtle pitfalls in its implementation.
RKKY interactions mediated by topological states in transition metal doped bismuthene
Authors: Lopes Emmanuel V. C. , Vernek E. , Schmidt Tome M.
Published: March 2023

We have investigated magnetic interactions between transition metal ions in bismuthene topological insulators with protected edge states. We find that these topological states have a crucial role in the magnetic interactions in 2D topological insulators. Using first-principles and model Hamiltonian, we make a comparative study of transition metal doped bulk and nanoribbon bismuthene. While a direct overlap between the transition metal prevails in gapped bulk bismuthene, at the borders of nanoribbons, a long-range magnetism is present. The exchange interactions are well described by a Ruderman–Kittel–Kasuya–Yosida-like Hamiltonian mediated by massive and topological states. Our results show a dominance of antiferromagnetism promoted by the topological states, preserving the spin-locked Dirac crossing states due to a global time-reversal symmetry preservation. This extended magnetic interactions mediated mainly by massless electrons can increase the spin diffusion length being promising for fast dissipationless spintronic devices.
Fourier spectral theory of pulsed photothermal radiometry, signal analysis, and parametric measurements in two-layered media
Authors: Baradaran Shokouhi Elnaz , Mandelis Andreas
Published: March 2023

A theoretical model of pulsed photothermal radiometry based on conduction-radiation theory is introduced for a two-layered medium with a first layer having optical and thermal properties different from those of the semi-infinite substrate. This geometry closely represents the optical and thermal properties of biotissues, a major intended application. The theory derives the spatial distribution of the frequency spectrum of the pulsed photothermal signal from the composite two-layer boundary-value problem and matches the spectral frequency domain results to the measured photothermal transients through an efficient inverse Fourier transformation algorithm, which involves the optical, thermal, and geometric parameters of the experimental system. This approach avoids the complicated and computationally expensive analytical Laplace transform approach usually adopted in similar studies and yields a complete conduction–radiation description of photothermal signals without simplifying, yet restrictive, approximations encountered in the literature. Numerical and experimental tests of the model using intralipid solution as layer 1 and semi-infinite solid samples such black rubber and anodized aluminum as layer 2 of the medium are described. The radiation heat transfer coefficients from the air–intralipid and intralipid–solid interfaces were introduced to complement the conductive blackbody-radiated infrared signal component at the detecting camera. The best-fitted parameters and heat transfer coefficients are compared to theoretical and experimental data, and the results of these tests were found to be consistent with the theoretical model.
Enhancing the mechanical and energy release performance of nano-aluminum@fluororubber (nAl@F2311) core–shell microstructured composite materials
Authors: Geng Hengheng , Liu Rui , Deng Peng , Ren Hui , Ge Chao , Wang Haifu , Chen Pengwan
Published: March 2023

Aluminum (Al)-based reactive materials have recently attracted much attention due to their excellent chemical energy release characteristics. However, there still exists a great challenge to improve the mechanical properties and energy density of Al-based reactive materials. In this work, we reported that core–shell nano-aluminum@fluororubber (nAl@F2311) composites with good mechanical properties and high energy release characteristics were designed and fabricated by the electrical exploding wires method. The results showed that Al nanospheres were coated by F2311 uniformly to form the nAl@F2311 core–shell microstructure with high Al contents. Quasi-static/Split Hopkinson Pressure Bar dynamic compression test results showed axial splitting failure mode of nAl@F2311 composites. nAl@F2311-10 composites with 90 wt. % Al contents had higher compressive strength, with quasi-static and dynamic compressive strength of 117.6 and 304.6 MPa, respectively. nAl@F2311-15 composites with 85 wt. % Al contents had a lower ignition threshold. Furthermore, the impact-induced energy release test showed higher fluorine contents will accelerate energy release, reduce impact ignition threshold, and improve the reaction efficiency of nAl@F2311 composites. The high reaction efficiency (97.79%) of the nAl@F2311-15 composites was obtained at an impact velocity of 1090 m/s. This offered a concept-of-proof work to design and fabrication of nanostructured reaction materials, which had high strength and energy release performance.
The third-order nonlinear optical susceptibility of the quantum dot as a three-level system in a hybrid structure
Authors: Biranvand Neda , Bahari Ali
Published: March 2023

To increase the optical nonlinearity effects in hybrid structures comprising a quantum dot and a nanoparticle, a quantum dot is taken as a three-level system. Under the dipole–dipole interactions between the quantum dot and the nanoparticle, the density matrix elements are derived within the rotating approximation. Under the quasi-static approximation by taking the nanoparticle polarization as a function of its geometry, the induced fields around the quantum dot in the presence of one/two nanoparticle(s) are obtained and the increasing factors of the local fields are calculated. The third-order nonlinear optical susceptibility of quantum dot is achieved by using the perturbation expansion theory of density matrix for different geometries of the nanoparticle, and the effects of the structural parameters are investigated to optimize the nonlinear optical response of the system. It can be seen that the presence of two nanorods results in great optical nonlinearities in the hybrid structure, being suitable for on/off switches, quantum communication, and quantum computing applications.
Topological optimization of a composite square lattice structure for bandgap property based on an improved multi-parameter genetic algorithm
Authors: Wang Xueqi , Li Dong
Published: March 2023

This paper proposed a two-dimensional composite square lattice structure containing two kinds of inclusions (polymethylmethacrylate and T2 copper). To maximize the relative widths of the gaps between the adjacent energy bands of the phononic crystals (PnCs), an improved multi-parameter genetic algorithm was adopted in this paper. The material distribution and ligament sizes were considered simultaneously by ternary encoding and binary encoding. The propagation wave behaviors of the composite lattice structures were studied by the finite element method. The effects of different lattice shapes and other relevant influencing parameters on the bandgaps were discussed. The results showed that the lattice shape, ligament width, and material density affect the width and the location of the bandgaps, and the effectiveness of the proposed method was demonstrated by a transmission spectrum experiment.
An integral method to determine mean skin friction in turbulent boundary layers
Authors: Li Dong , Liu Yuqi , Luo Kun , Fan Jianren
Published: March 2023

This study is concerned with accurately determining the mean skin friction in a zero-pressure-gradient turbulent boundary layer. By assuming a linear relation for the weighted total shear stress in the near-wall region, an integral method to evaluate the skin friction is proposed. The method requires the wall-normal profiles of the mean streamwise velocity and Reynolds shear stress within the range of y/δ≤0.4 at only one streamwise location, where δ is the boundary layer thickness. A number of direct numerical simulation and experimental data available in the literature are employed to validate the accuracy of the method over a wide range of Reynolds numbers. The skin friction coefficient obtained using the proposed method is found to be within ±4% in agreement with the published values in both the smooth- and rough-wall turbulent boundary layers. A comparison of the present approach with several existing methods is presented, showing that the proposed skin friction relation is robust and accurate.
Multi-site reaction dynamics through multi-fragment density matrix embedding
Authors: Li Chenghan , Yang Junjie , Zhang Xing , Kin-Lic Chan Garnet
Published: March 2023

The practical description of disordered chemical reactions, where the reactions involve multiple species at multiple sites, is presently a challenge using correlated electronic structure methods due to their high computational cost and steep scaling. Here, we describe the gradient theory of multi-fragment density matrix embedding theory, which potentially provides a minimal computational framework to model such processes at the correlated electron level. We present the derivation and implementation of the gradient theory, its validation on model systems and chemical reactions using density matrix embedding, and its application to a molecular dynamics simulation of proton transport in a small water cluster, a simple example of multi-site reaction dynamics.
Tailoring Bi2Sr2CaCu2O8+δ
surface Josephson junctions
Authors: Wei Zihan , Du Hongmei , Li Dingding , Jiang Mei Ping , Zhang Ping , Chen Shixian , Lyu Yang-Yang , Sun Hancong , Wang Yong-Lei , Koelle Dieter , Kleiner Reinhold , Wang Huabing , Wu Peiheng
Published: March 2023

Bi2Sr2CaCu2O8+δ (BSCCO) single crystals are promising for high-temperature superconducting electronic devices with ultimate performance. Recently, tailoring superconductivity in ultra-thin BSCCO locally has received wide attention and interest. In this work, we focus on controlling the superconductivity of the uppermost CuO2 double layer of the BSCCO crystal. Gold electrodes are deposited onto the freshly cleaved BSCCO surface by a high-vacuum in situ evaporation technique at room temperature, and then surface Josephson junctions (SJJs) between the two outermost superconducting CuO2 double layers are fabricated as a probe to evaluate the superconductivity of the uppermost double layer. We find that the junction transition temperature Tc′ as well as its critical current density jc depend systematically and reproducibly on the deposition rate of the gold electrode. The electric properties of the SJJs, spanning the range from completely degraded to almost as good as the intrinsic Josephson junctions inside the bulk, systematically reveal the evolutionary process of superconductivity of the uppermost BSCCO layer, extending the range for practical applications.
The vortex ring state of a rotor and its comparison with the collapse of an annular jet in counterflow
Authors: Pickles D. J. , Green R. B. , Busse A.
Published: March 2023

The vortex ring state (VRS) of a rotor is associated with the development of the trailed vortex system in powered descending flight, where the topology of the vortex wake changes from its usual helical form into a toroidal form. In the VRS, the toroidal vortex ring envelops the entire rotor, and it sheds and reforms in an unsteady manner. In previous attempts to understand the basic phenomenology of the VRS, the focus was on the role of the trailed vortices in the transition to the VRS: computational and experimental work utilized rotor models to generate the trailing vortex wake, and mechanisms for the emergence of the VRS were postulated based on the interaction of the trailed vortices. In this paper, a different approach is taken: a set of experiments on a core annular jet flow are described, where the jet flow in counterflow is used to simulate a rotor in powered descent. It is shown that this leads to the formation of a flow field that shares many of the features of the VRS of a rotor system. This brings into question the role of the rotor blade trailing vortices in the development of the rotor wake VRS, and it is proposed instead that the interaction between the mean flow and counterflow drives the VRS phenomenon.
Investigation of ultrafast excited-state dynamics at the nanoscale with terahertz field-induced electron tunneling and photon emission
Authors: Katayama Ikufumi , Kimura Kensuke , Imada Hiroshi , Kim Yousoo , Takeda Jun
Published: March 2023

The combination of terahertz (THz) pulses with scanning tunneling microscopy (STM) enables us to investigate ultrafast dynamics at material surfaces with high spatial (nanoscale) and temporal (femtosecond) resolution. In this Perspective, we review the basic principles of THz-STM, outline the related literature, and discuss its future outlook capable of advancing nanoscience, especially by introducing further combination of THz-STM with scanning tunneling luminescence spectroscopy, which can extract more fruitful information about nanoscale materials via obtaining luminescence spectra compared to just observing the net tunneling current induced by THz pulses in THz-STM. By shining THz pulses onto an STM tip, we can observe plasmon luminescence locally confined between the tip and the surface, whose spectrum changes with tip conditions. The combined approach is a stepping stone toward investigating the ultrafast excited-state dynamics of nanoscale materials with high spatiotemporal resolution.
Leidenfrost limit enhancement via supersonically sprayed iron carboxylate framework for convection cooling
Authors: Joshi Bhavana , Khadka Ashwin , Aldalbahi Ali , Rahaman Mostafizur , Yarin Alexander L.
Published: March 2023

Device cooling schemes are required to reduce the local temperature of solar panels and solar air heaters, while maintaining their radiative heat to maximize energy conversion. Therefore, an efficient cooling scheme was developed using textured surfaces augmented by highly porous materials for increasing their total surface area. In this study, highly porous iron carboxylate framework, MIL-100(Fe), Materials of Institute Lavoisier, was introduced to substrates to provide a highly textured surface. This significantly reduced the temperature of the surface that was subject to radiative heat during both air and mist (or aerosol) cooling. In the case of mist cooling, the proposed MIL-100(Fe)-coated substrates were superhydrophilic, which promoted close contact between the impacting aerosols and the heated surface. Single drop impact and evaporation experiments were conducted to quantify the rate of heat removal provided by the proposed MIL-100(Fe) coatings. These coatings provided an increase in the Leidenfrost limit from 140 to 200 °C. As such, the highly wettable and porous MIL-100(Fe)-coated layers promoted rapid evaporative cooling. The proposed layers were analyzed using scanning electron microscopy, x-ray diffraction, atomic force microscopy, and Brunauer–Emmett–Teller data to elucidate the reason for their increased heat transfer rate.
An improved gas–liquid–solid coupling model with plastic failure for hydraulic flushing in gassy coal seam and application in borehole arrangement
Authors: Yang Lei , Fan Chaojun , Wen Haiou , Luo Mingkun , Sun Hao , Jia Ce
Published: March 2023

Hydraulic flushing can increase the efficiency of gas extraction by artificially modifying the coal reservoir. Considering the plastic failure of coal mass, an improved gas–liquid–solid coupling model for hydraulic flushing and gas extraction is constructed. The parameter evolution in the hydraulic flushing process was numerically investigated to determine the optimal borehole arrangement of hydraulic flushing. The results show that the relative permeability of gas gradually increases with the initial dewatering. The gas rates of both regular extraction and hydraulic flushing enhanced extraction show an increasing–decreasing trend. An increased and delayed peak gas rate is observed comparing with the regular extraction, caused by the hydraulic flushing induced new fractures. The area around of borehole is divided into the failure zone, the plastic softening zone, and the elastic zone after hydraulic flushing. The failure zone has the greatest increase in coal permeability, followed by the plastic softening zone, while the elastic zone keeps no significant change. The larger difference between the horizontal stress and vertical stress, the more obvious the elliptical shape of the permeability change area near the borehole, as well as the pressure drop in the elliptical zone. With the increase in the hydraulic flushing radius, the permeability increasing zone and gas pressure decreasing zone gradually increase. Subsequently, the equivalent effective radius and equivalent influencing radius were obtained, as well as the optimal borehole spacing for hydraulic flushing by cross-layer drilling. Finally, the optimal borehole spacing is obtained for different borehole diameters and efficient extraction times. These provide a theoretical guidance for field application of hydraulic flushing in a low-permeable coal seam.
Modulation of potassium conductances optimizes fidelity of auditory information
Authors: Kaczmarek Leonard K.
Published: March 2023

Potassium channels in auditory neurons are rapidly modified by changes in the auditory environment. In response to elevated auditory stimulation, short-term mechanisms such as protein phosphorylation and longer-term mechanisms such as accelerated channel synthesis increase the amplitude of currents that promote high-frequency firing. It has been suggested that this allows neurons to fire at high rates in response to high sound levels. We have carried out simple simulations of the response to postsynaptic neurons to patterns of neurotransmitter release triggered by auditory stimuli. These demonstrate that the amplitudes of potassium currents required for optimal encoding of a low-amplitude auditory signal differ from those for louder sounds. Specifically, the cross-correlation of the output of a neuron with an auditory stimulus is improved by increasing potassium currents as sound amplitude increases. Temporal fidelity for low-frequency stimuli is improved by increasing potassium currents that activate at negative potentials, while that for high-frequency stimuli requires increases in currents that activate at positive membrane potentials. These effects are independent of the firing rate. Moreover, levels of potassium currents that maximize the fidelity of the output of an ensemble of neurons differ from those that maximize fidelity for a single neuron. This suggests that the modulatory mechanisms must coordinate channel activity in groups of neurons or an entire nucleus. The simulations provide an explanation for the modulation of the intrinsic excitability of auditory brainstem neurons by changes in environmental sound levels, and the results may extend to information processing in other neural systems.
Refinement mechanism and optimization for compact strip production process
Authors: Liu Kai , Cheng Shusen , Wei Xingwen , Li Jipeng , Feng Yongping , Volkova Olena
Published: March 2023

To avoid the fracture of cold-rolled sheets, this study investigated the refinement mechanism for the compact strip production process and proposed an optimised method. The primary austenite grain size was 50–475 µm, and the grain size of the hot-rolled strips was 3.6–4.8 µm. The Gleeble-3500 simulator was applied to simulate the hot rolling process. Grain refinement was realised through dynamic recrystallization and the supply of more nucleation sites for transformation by sub-structures. Increasing the coiling temperature from 620 to 730 °C increased the ferrite fraction from 3.95 to 24.16%. The adjacent cementite distance changed from 0.33 to 0.84 µm, resulting in decreased yield and tensile strengths and increased elongation. Thus, the fracture of cold-rolled sheets was avoided.
Vision rescue via unconstrained in vivo prime editing in degenerating neural retinas
Authors: Qin Huan , Zhang Wenliang , Zhang Shiyao , Feng Yuan , Xu Weihui , Qi Jia , Zhang Qian , Xu Chunxiu , Liu Shanshan , Zhang Jia , Lei Yushuang , Liu Wanqin , Feng Shuyu , Wang Jingjing , Fu Xuefei , Xu Zifen , Li Ping , Yao Kai
Published: March 2023

Retinitis pigmentosa (RP) is an inherited retinal dystrophy causing progressive and irreversible loss of retinal photoreceptors. Here, we developed a genome-editing tool characterized by the versatility of prime editors (PEs) and unconstrained PAM requirement of a SpCas9 variant (SpRY), referred to as PESpRY. The diseased retinas of Pde6b-associated RP mouse model were transduced via a dual AAV system packaging PESpRY for the in vivo genome editing through a non-NGG PAM (GTG). The progressing cell loss was reversed once the mutation was corrected, leading to substantial rescue of photoreceptors and production of functional PDE6β. The treated mice exhibited significant responses in electroretinogram and displayed good performance in both passive and active avoidance tests. Moreover, they presented an apparent improvement in visual stimuli-driven optomotor responses and efficiently completed visually guided water-maze tasks. Together, our study provides convincing evidence for the prevention of vision loss caused by RP-associated gene mutations via unconstrained in vivo prime editing in the degenerating retinas.
Orbital distortion and electric field control of sliding ferroelectricity in a boron nitride bilayer
Authors: Liu Meng , Ji Hongyan , Fu Zhaoming , Wang Yeliang , Sun Jia-Tao , Gao Hong-Jun
Published: March 2023

Recent experiments confirm that two-dimensional boron nitride (BN) films possess room-temperature out-of-plane ferroelectricity when each BN layer is sliding with respect to each other. This ferroelectricity is attributed to the interlayered orbital hybridization or interlayer charge transfer in previous work. In this work, we attempt to understand the sliding ferroelectricity from the perspective of orbital distortion of long-pair electrons. Using the maximally localized Wannier function method and first-principles calculations, the out-of-plane pz
orbitals of BN are investigated. Our results indicate that the interlayer van der Waals interaction causes the distortion of the N pz
orbitals. Based on the picture of out-of-plane orbital distortion, we propose a possible mechanism to tune the ferroelectric polarization by external fields, including electric field and stress field. It is found that both the polarization intensity and direction can be modulated under the electric field. The polarization intensity of the system can also be controlled by stress field perpendicular to the plane. This study will provide theoretical help in the device design based on sliding ferroelectrics.
Low-temperature and elastic properties of the 1/1 Tsai-type quasicrystal approximant GdCd6 investigated by ultrasonic measurements
Authors: Yoshida Taichi , Jin Kensuke , Wakiya Kazuhei , Nakamura Mitsuteru , Yoshizawa Masahito , Muro Yuji , Nakanishi Yoshiki
Published: March 2023

Low-temperature and elastic properties of the quasicrystal approximant GdCd6 have been investigated by means of an ultrasonic measurement. Salient elastic anomalies were observed in the temperature and magnetic field dependence of the principal elastic constants, most probably being associated with the successive multiple magnetic phase transitions showing up at low temperatures. Based on the experimental data, a magnetic field vs temperature phase diagram was constructed. In a zero magnetic field, at least four phases appear to exist. However, the phase diagram both for the magnetic field applied for H//

⟨
100
⟩

and H//

⟨
110
⟩

is richer, and interestingly some phase boundaries correspond to the development of field-induced phases, leading to the intricate magnetic phase diagram possibly with multiple ordered phases. We discuss the elastic and electronic properties at low temperatures, and also the nature of the multiple magnetic phase transitions of GdCd6.
Particle-based simulation of atom and ion transport in HiPIMS: effect of the plasma potential distribution on the ionized flux fraction
Authors: Kozák Tomáš
Published: March 2023

We present a three-dimensional particle-based computer simulation of high-power impulse magnetron sputtering (HiPIMS) discharges which enables us to simulate the transport of atoms and ions in the discharge and the corresponding plasma parameters. The simulation requires a definition of the plasma potential and electron density distribution (not calculated self-consistently), for which parametric analytical formulae were devised. A numerical algorithm is used to constrain the simulation by an experimental target current waveform, which ensures that the simulation results are closely tied to the experimental discharge conditions. Simulations of a HiPIMS discharge with Ti target show the capability to calculate the spatial distributions of target material atoms and ions and also to quantify the process-gas rarefaction. We evaluated, among others, the ion return probability and the ionized fraction of the target material flux onto the substrate for various values of the potential difference across the magnetic presheath in front of the target racetrack, which is responsible for attracting most of the plasma ions towards the target. It is shown that this parameter of the plasma potential distribution strongly affects the ion return probability and, thus, it must be known quite precisely to reliably predict the ionized flux fraction on the substrate. Other parameters, such as the composition of the ion flux onto the target are less sensitive. The simulation can be run in a reasonably short time and can easily be extended by adding more plasma species (excited states or doubly ionized species) and their interactions.
The transport dynamics of tens of micrometer-sized water droplets in RF atmospheric pressure glow discharges
Authors: Nayak Gaurav , Meyer Mackenzie , Oinuma Gaku , J Kushner Mark , J Bruggeman Peter
Published: March 2023

Charging of particles having diameters of tens of microns has been extensively studied at atmospheric pressure in the context of, for example, electrostatic precipitators where the focus was on unipolar charging. The ambipolar charging of particles in atmospheric pressure plasmas, and of droplets in particular, has received less attention. The plasma activation of droplets is of interest for water purification, fertilizer production and materials synthesis, all of which depend on the transport of the droplets through the plasma, which in turn depends on their charging. In this paper, we report on the transport dynamics of water droplets, tens of microns in diameter, carried by the gas flow through an atmospheric pressure radiofrequency glow discharge sustained in helium. The droplets pass through the plasma with minimal evaporation and without reaching the Rayleigh limit. The droplet trajectory in the presence and absence of the plasma provides insights on the forces acting on the droplet. The measurements were analyzed using results from a three-dimensional fluid model and a two-dimensional plasma hydrodynamics model. We found that the transport dynamics as the droplet enters and leaves the plasma are due to differential charging of the droplet in the plasma gradients of the bounding sheaths to the plasma.
Temperature effects on the performance of ferroelectric FET with random grain phase variation for non-volatile memory application
Authors: Li Qiang , Li Ming-Hao , Hsu Hsiao-Hsuan , Ying Lei-Ying , Zhang Bao-Ping , Zheng Zhi-Wei
Published: March 2023

We report the temperature effects on the performance of ferroelectric field-effect transistor (FeFET)-based non-volatile memory (NVM) considering random grain phase variation in the ferroelectric layer through simulation. Based on the FE temperature effect model that accounts for both the transistor and ferroelectric degradation, we demonstrate that: (1) at a certain temperature, the memory window (MW) decreases with pronounced effect on low threshold voltage shift and its variation increases as the FE phase decreases; (2) with the temperature increases, the MW decreases with pronounced effect on high threshold voltage shift. The random grain phase variation further exacerbates the MW distribution, thus degrading the sensing margin. These results may provide insights for device design of high-performance FeFET-based NVMs.
Superconductivity emerging from a pressurized van der Waals kagome material Pd3P2S8
Authors: Wang Qi , Qiu Xiao-Le , Pei Cuiying , Gong Ben-Chao , Gao Lingling , Zhao Yi , Cao Weizheng , Li Changhua , Zhu Shihao , Zhang Mingxin , Chen Yulin , Liu Kai , Qi Yanpeng
Published: March 2023

Kagome materials have been reported to possess abundant and peculiar physical properties, which provide an excellent platform to explore exotic quantum states. We present a discovery of superconductivity in van der Waals material Pd3P2S8 composed of Pd kagome lattice under pressure. Pd3P2S8 displays superconductivity for those pressures where the semiconducting-like temperature dependence of the resistivity turns into a metallic one. Moreover, it is found that the increased pressure results in a gradual enhancement of superconducting transition temperature, which finally reaches 6.83 K at 79.5 GPa. Combining high-pressure x-ray diffraction, Raman spectroscopy and theoretical calculations, our results demonstrate that the observed superconductivity induced by high pressure in Pd3P2S8 is closely related to the formation of amorphous phase, which results from the structural instability due to the enhanced coupling between interlayer Pd and S atoms upon compression.
Hi-COLA: fast, approximate simulations of structure formation in Horndeski gravity
Authors: Wright Bill S. , Sen Gupta Ashim , Baker Tessa , Valogiannis Georgios , Fiorini Bartolomeo
Published: March 2023

We introduce Hi-COLA, a code designed to run fast, approximate N-body simulations of non-linear structure formation in reduced Horndeski gravity. Given an input Lagrangian, Hi-COLA dynamically constructs the appropriate field equations and consistently solves for the cosmological background, linear growth, and screened fifth force of that theory. Hence Hi-COLA is a general, adaptable, and useful tool that allows the mildly non-linear regime of many Horndeski theories to be investigated for the first time, at low computational cost. In this work, we first describe the screening approximations and simulation setup of Hi-COLA for theories with Vainshtein screening. We validate the code against traditional N-body simulations for cubic Galileon gravity, finding 2.5% agreement up to k
max = 1.2 h/Mpc. To demonstrate the flexibility of Hi-COLA, we additionally run the first simulations of an extended shift-symmetric gravity theory. We use the consistency and modularity of Hi-COLA to dissect how the modified background, linear growth, and screened fifth force all contribute to departures from ΛCDM in the non-linear matter power spectrum. Hi-COLA can be found at https://github.com/Hi-COLACode/Hi-COLA.
Low-light-level spin–orbit splitting via structured light cross-Kerr interaction in coherent atomic media
Authors: Zhao Lu , Su Yingjie
Published: March 2023

We explore the spin–orbit coupling (SOC) mechanism for structured light in coherent atomic media with low-light-level cross-Kerr nonlinearity. Using the five-level M-type electromagnetic induced transparency (EIT) system as a prototype, we show that spin–orbit splitting for a weak spinor image can be generated by a weak trigger field carrying orbital angular momentum (OAM) at low-light intensity. By quantum-optical analogy, the paraxial focusing and defocusing of the two pseudo-spin states in the spinor image can be governed by a Pauli-like equation. More importantly, by changing the EIT parameters, especially the topological charge of the weak trigger field, the SOC-induced radial quantization of the spinor image can be rather significant, giving rise to positive or negative OAM-OAM mode separation in free space. This suggests that the separation can be flexibly controlled due to strong image-vortex interaction based on few-photon cross-Kerr modulation. Our findings may have the potential for all-optical OAM multiplexing and demultiplexing of structured light fields toward few-photon quantum control and multimode communication.
Solving Schrodinger equations using a physically constrained neural network*
Authors: Pu Kai-Fang , Li Han-Lin , Lü Hong-Liang , Pang Long-Gang
Published: March 2023

Deep neural networks (DNNs) and auto differentiation have been widely used in computational physics to solve variational problems. When a DNN is used to represent the wave function and solve quantum many-body problems using variational optimization, various physical constraints have to be injected into the neural network by construction to increase the data and learning efficiency. We build the unitary constraint to the variational wave function using a monotonic neural network to represent the cumulative distribution function (CDF)

. Using this constrained neural network to represent the variational wave function, we solve Schrodinger equations using auto-differentiation and stochastic gradient descent (SGD) by minimizing the violation of the trial wave function

to the Schrodinger equation. For several classical problems in quantum mechanics, we obtain their ground state wave function and energy with very low errors. The method developed in the present paper may pave a new way for solving nuclear many-body problems in the future.
Determining the change in performance from replacing a separator with an anion exchange membrane for alkaline water electrolysis
Authors: Ferriday T.B. , Middleton P.H. , Kolhe M.L.
Published: March 2023

The emphasis on energy storage has caused renewed interest in alkaline water electrolysis (AWE), where the novel anion exchange membrane (AEM) has opened new pathways to further improve this mature technology. The comparison between the novel and the mature is most commonly performed on uneven grounds, as the ionic conductivity of the 30 wt.% (6.89 M) KOH electrolyte used in AWE is significantly greater than the 1.0 M employed in AEM water electrolysis. Through this paper, the performance of a zero-gap water electrolyser is systematically tested utilising either a separator or an AEM in a 1.0 M KOH electrolyte over several temperatures. Catalysed with only untreated nickel foam, the cell configuration with the AEM displayed predictably enough a notably lower series resistance and thereby a lower overpotential. However, the cell with the separator displayed better innate thermal stability, and showed stable results at 25°C, 40°C and 70°C. These findings exhibit the potential of additional R&D efforts in both separators and AEMs.
Discrete element analysis for effects of recoating blade and surface morphology of substrate on powder spreading quality
Authors: Tang Cheng Ming , Zhao Ji Bin , Zhao Yu Hui , Wang Zhi Guo
Published: March 2023

A discrete element method model was established to simulate 316L stainless steel powder spreading process in selective laser melting. The effects of recoating blade speed, assigned gap width and substrate surface morphology on the powder spreading quality was studied. The results showed that lower recoating speed and larger gap width benefited the quality of powder layer. When the angle between the moving direction of recoater and laser scanning direction was greater than 45 °, the density level of the powder layer on the SLM processing surface was higher than that of the flat substrate and more uniform. The quality of the powder layer on the milled surface varied with position obviously, and the maximum density was between the other two types of surfaces, while uniformity of the powder layer was worse than the other two surfaces. This study shows that the quality of powder layer can be controlled by adjusting the setting parameters of the recoater and the surface morphology of the substrate.
Evaluation of viscosity reduction effect of oil-soluble viscosity reducer on crude oil
Authors: Lei Haoran , Huang Chen , Liu Jiangbo , Dou Miao , Gu Xuefan
Published: March 2023

In this paper, several crude oil viscosity reducers were selected to evaluate their performance on the heavy oil Henan Oilfield, China. Through investigation, the viscosity reducing ability of these viscosity reducers were relatively general. Among them, EVA had the highest performance, reaching a viscosity reduction rate of 45.6%. The results were characterized by DSC analysis, wax crystal micromorphology analysis of saturated hydrocarbons and IR spectroscopy. Finally, possible viscosity reduction mechanism was discussed.
Focus on plastics from land to aquatic ecosystems
Authors: van Emmerik Tim H M , González-Fernández Daniel , Laufkötter Charlotte , Blettler Martin , Lusher Amy , Hurley Rachel , Ryan Peter G
Published: March 2023

Plastic pollution in oceans and rivers is of growing concern. Aquatic ecosystems play an important role in transport and storage of plastic waste from land-based storage to riverine and marine environments. This focus issue brings together new insights on the sources, transport dynamics, fate, and impact of plastic pollution through aquatic environments. The work collected in this focus issue shows that urban areas, transportation infrastructure, and wastewater treatment plants are consistently identified as sources for micro-, meso-, and macroplastics. Transport dynamics of plastics over land and through rivers were found to be driven by human factors, flood and storm events, and hydrodynamics, and combinations thereof. Most plastics were found not to make it to the open sea, but rather beach, float in coastal waters, or accumulate on land and within river systems. When exposed to the environment, both conventional and biodegradable plastics degrade into smaller pieces. Yet, the degradation and fragmentation of plastics in the environment remain unresolved. Future work should focus on transferability of new river and region specific insights, collection and exploration of large-scale and novel datasets, source and entry point identification, and understanding fundamental transport mechanisms. This focus issue provides new insights on sources, transport, fate, and impact of plastics, but also emphasizes that need for further work on plastics in aquatic ecosystems.
Mean first exit times of Ornstein–Uhlenbeck processes in high-dimensional spaces
Authors: Kersting Hans , Orvieto Antonio , Proske Frank , Lucchi Aurelien
Published: March 2023

The d-dimensional Ornstein–Uhlenbeck process (OUP) describes the trajectory of a particle in a d-dimensional, spherically symmetric, quadratic potential. The OUP is composed of a drift term weighted by a constant

θ
⩾
0

and a diffusion coefficient weighted by σ > 0. In the absence of drift (i.e. θ = 0), the OUP simply becomes a standard Brownian motion (BM). This paper is concerned with estimating the mean first-exit time (MFET) of the OUP from a ball of finite radius L for large

d
≫
0

. We prove that, asymptotically for

d
→
∞

, the OUP takes (on average) no longer to exit than BM. In other words, the mean-reverting drift of the OUP (scaled by

θ
⩾
0

) has asymptotically no effect on its MFET. This finding might be surprising because, for small

d
∈

N

, the OUP exit time is significantly larger than BM by a margin that depends on θ. As it allows for the drift to be ignored, it might simplify the analysis of high-dimensional exit-time problems in numerous areas.

Finally, our short proof for the non-asymptotic MFET of OUP, using the Andronov–Vitt–Pontryagin formula, might be of independent interest.
Family of nonstandard integrable and superintegrable classical Hamiltonian systems in non-vanishing magnetic fields
Authors: Hoque Md Fazlul , Šnobl Libor
Published: March 2023

In this paper, we present the construction of all nonstandard integrable systems in magnetic fields whose integrals have leading order structure corresponding to the case (i) of theorem 1 in Marchesiello and Šnobl (2022 J. Phys. A: Math. Theor.
55 145203). We find that the resulting systems can be written as one family with several parameters. For certain limits of these parameters the system belongs to intersections with already known standard systems separating in Cartesian and / or cylindrical coordinates and the number of independent integrals of motion increases, thus the system becomes minimally superintegrable. These results generalize the particular example presented in section 3 of Marchesiello and Šnobl (2022 J. Phys. A: Math. Theor.
55 145203).
Validation of FABDEM, a global bare-earth elevation model, against UAV-lidar derived elevation in a complex forested mountain catchment
Authors: Marsh Christopher B , Harder Phillip , Pomeroy John W
Published: March 2023

Space-based, global-extent digital elevation models (DEMs) are key inputs to many Earth sciences applications. However, many of these applications require the use of a ‘bare-Earth’ DEM versus a digital surface model (DSM), the latter of which may include systematic positive biases due to tree canopies in forested areas. Critical topographic features may be obscured by these biases. Vegetation-free datasets have been created by using statistical relationships and machine learning to train on local-scale datasets (e.g., lidar) to de-bias the global-extent datasets. Recent advances in satellite platforms coupled with increased availability of computational resources and lidar reference products has allowed for a new generation of vegetation- and urban-canopy removals. One of these is the Forest And Buildings removed Copernicus DEM (FABDEM), based on the most recent and most accurate global DSM Copernicus-30. Among the more challenging landscapes to quantify surface elevations are densely forested mountain catchments, where even airborne lidar applications struggle to capture surface returns. The increasing affordability and availability of UAV-based lidar platforms have resulted in new capacity to fly modest spatial extents with unrivalled point densities. These data allow an unprecedented ability to validate global sub-canopy DEMs against representative UAV-based lidar data. In this work, the FABDEM is validated against up-scaled lidar data in a steep and forested mountain catchment considering elevation, slope, and Terrain Position Index (TPI) metrics. Comparisons of FABDEM with SRTM, MERIT, and the Copernicus-30 dataset are made. It was found that the FABDEM had a 24% reduction in elevation RMSE and a 135% reduction in bias compared to the Copernicus-30 dataset. Overall, the FABDEM provides a clear improvement over existing deforested DEM products in complex mountain topography such as the MERIT DEM. This study supports the use of FABDEM in forested mountain catchments as the current best-in-class data product.
COVID-19 Vaccine Safety Surveillance in Early Pregnancy in the United States: Design Factors Affecting the Association Between Vaccine and Spontaneous Abortion
Authors: Vazquez-Benitez Gabriela , Haapala Jacob L , Lipkind Heather S , DeSilva Malini B , Zhu Jingyi , Daley Matthew F , Getahun Darios , Klein Nicola P , Vesco Kimberly K , Irving Stephanie A , Nelson Jennifer C , Williams Joshua T B , Hambidge Simon J , Donahue James , Fuller Candace C , Weintraub Eric S , Olson Christine , Kharbanda Elyse O
Published: March 2023

In the Vaccine Safety Datalink (VSD), we previously reported no association between coronavirus disease 2019 (COVID-19) vaccination in early pregnancy and spontaneous abortion (SAB). The present study aims to understand how time since vaccine rollout or other methodological factors could affect results. Using a case-control design and generalized estimating equations, we estimated the odds ratios (ORs) of COVID-19 vaccination in the 28 days before a SAB or last date of the surveillance period (index date) in ongoing pregnancies and occurrence of SAB, across cumulative 4-week periods from December 2020 through June 2021. Using data from a single site, we evaluated alternative methodological approaches: increasing the exposure window to 42 days, modifying the index date from the last day to the midpoint of the surveillance period, and constructing a cohort design with a time-dependent exposure model. A protective effect (OR = 0.78, 95% confidence interval: 0.69, 0.89), observed with 3-cumulative periods ending March 8, 2021, was attenuated when surveillance extended to June 28, 2021 (OR = 1.02, 95% confidence interval: 0.96, 1.08). We observed a lower OR for a 42-day window compared with a 28-day window. The time-dependent model showed no association. Timing of the surveillance appears to be an important factor affecting the observed vaccine-SAB association.