bluuebunny/crossref_metadata_2025 huggingface dataset:
Chaperones Skp and SurA dynamically expand unfolded OmpX and synergistically disassemble oligomeric aggregates
Authors: Chamachi Neharika , Hartmann Andreas , Ma Mai Quynh , Svirina Anna , Krainer Georg , Schlierf Michael
Published: February 2022

Significance

Outer membrane proteins (OMPs) are crucial for the survival of bacteria. The two chaperones 17-kilodalton protein (Skp) and survival factor A (SurA) play key roles in OMP maturation by keeping unfolded OMP proteins soluble in the periplasm. However, their functionalities are incompletely understood. Here, we establish connections between structural and energetic features employed by the two chaperones when interacting with unfolded OmpX. We find that expansion, accompanied with fast polypeptide chain reconfiguration, prevents unfolded OmpX from misfolding and aggregating. Moreover, chaperone interaction with unfolded OmpX is thermodynamically calibrated, allowing for a fine-tuned association of chaperones with OMPs in the adenosine triphosphate-depleted periplasm. We further discovered that Skp and SurA act together as disaggregases and are able to disassemble oligomeric OMP aggregates, revealing remarkable functionalities of this periplasmic chaperone system.
Conservation of chromatin conformation in carnivores
Authors: Corbo Marco , Damas Joana , Bursell Madeline G. , Lewin Harris A.
Published: February 2022

Significance

We found the three-dimensional (3D) structure of chromatin at the chromosome level to be highly conserved for more than 50 million y of carnivore evolution. Intrachromosomal contacts were maintained even after chromosome rearrangements within carnivore lineages, demonstrating that the maintenance of 3D chromatin architecture is essential for conserved genome functions. These discoveries enabled the identification of orthologous chromosomal DNA segments among related species, a method we call 3D comparative scaffotyping. The method has application for putative chromosome assignment of chromosome-scale DNA sequence scaffolds produced by de novo genome sequencing. Broadly applied to biodiversity genome sequencing efforts, the approach can reduce costs associated with karyotyping and the physical mapping of DNA segments to chromosomes.
A position sensing method for 2D scanning mirrors
Authors: Ghazinouri Behrad , He Siyuan , Tai Trevor S
Published: February 2022

This paper presents a cost-effective position sensing method for 2D scanning mirrors. The method uses only one 1D PSD (position sensitive detector) located at the backside of the 2D scanning mirror plate to retrieve the 2D rotation angle about the two axes separately in real time. Any 2D scanning mirror with resonant vibration about one axis and quasi-static vibration such as sinusoidal, saw tooth, triangular oscillation about the other axis can use this method. The two vibration axes are orthogonal to each other to form the scanning patterns, which are most desired in scanning 3D LiDAR systems. 3D scanning LiDAR is the targeted application for this research. The method uses timing measurement to measure the resonant vibration angle and Lagrange interpolation polynomial approximation to retrieve the quasi-static vibration angle. A prototype has been built to measure the 2D rotation angle of a 2D micromirror. The measured angle using the proposed method was verified using a 2D PSD. The largest errors for the vertical/horizontal angles were 9.6% and 5.36% respectively. The position sensing mechanism is also integrated to a scanning 2D micromirror based LiDAR system to demonstrate it as real time capability.
Single-layer metalens for achromatic focusing with wide field of view in the visible range
Authors: Luo Shilin , Zhang Fei , Lu Xinjian , Xie Ting , Pu Mingbo , Guo Yinghui , Wang Yanqin , Luo Xiangang
Published: February 2022

Metalenses have attracted extensive attention due to their capability of flexible wavefront manipulation by subwavelength nanostructures. However, the development of metalenses has been deeply limited by the field of view (FOV) and spectral bandwidth. Existing wide FOV and achromatic metalenses usually adopt cascaded metasurfaces to correct aberrations, resulting in inevitable challenges for nano-fabrication technologies. In this paper, we design a wide FOV metalens with a numerical aperture of 0.24 which can provide a diffraction-limited FOV for over 40° at three discrete wavelengths of 473 nm (blue), 532 nm (green), and 632.8 nm (red). The metalens involves only a single layer of metasurface integrated on a flat substrate to correct aberration. This method considerably simplifies the architectures compared with the cascaded metalenses and conventional bulky optical systems. In addition, an achromatic wide FOV metalens with an operating wavelength range from 492 to 592 nm is further designed to demonstrate the generality of the proposed method. The simulated results indicate that metalenses have a great achromatic and diffraction-limited focusing performance within a large incident angle region, which is expected to have promising applications in imaging, holography, machine vision, and other fields.
How effective is the Brink–Axel hypothesis for astrophysical weak rates?
Authors: Nabi Jameel-Un , Nayab Mazhar , Johnson Calvin W
Published: February 2022

We explore the effectiveness of the Brink–Axel hypothesis (BAH) for the computation of stellar electron capture (EC) and β-decay (BD) rates, namely that the transition strength function depends only upon the transition energy and not upon the details of the initial state. For this purpose, we calculated Gamow–Teller (GT) strength distributions for a selection of sd-shell nuclides, using two different microscopic models, namely the proton–neutron quasiparticle random phase approximation and the full configuration-interaction shell model, taking into account the first 100 states of both the initial and final nuclides. The GT transition strengths among these levels evolve with initial state energy. These transition strength functions we folded into weak-interaction mediated rates in stellar matter, specifically EC and BD rates, for a range of densities 10 g cm−3 ⩽ ρ ⩽ 1011 g cm−3 and range of temperatures 1 GK ⩽ T ⩽ 30 GK. When transitions from excited states were approximated using the BAH, augmented by so-called ‘back-resonance’ transitions, the rates were affected by up to three orders of magnitude or more at high temperatures and densities. Thus the BAH is not a reliable approximation for the calculation of stellar rates, especially in high temperature–density environments.
Investigation of a kind of neutrino mass matrix
Authors: Huang Chao-Shang , Li Wen-Jun
Published: February 2022

We carry out diagonalization of a kind of Majorana neutrino mass matrix

M
=

M

ν

M

ν

†

of which the real part and imaginary part are commutative. For the matrix M, it is shown in a model-independent way that δ = ±π/2, which implies the maximal strength of CP violation in neutrino oscillations and atmospherical mixing angle would be in the ranges, π/4 < θ
23 < 3π/4, or −3π/4 < θ
23 < −π/4. It is shown that the Hermitian Majorana neutrino mass matrix M has only five real parameters and furthermore, only one free real parameter (A or D) if using the measured values of three mixing angles and mass squared differences as inputs.
Towards modeling cluster structure of 8Be with chiral interaction
Authors: Fukui Tokuro
Published: February 2022

How the nuclear force behaves in cluster states, in particular those consisting of the α clusters, has been investigated so far, but not yet elucidated. Today the chiral effective field theory (EFT) is established and it would shed new light on the microscopic understanding of the cluster states. We aim to address a possible source of the attraction in the cluster states of 8Be in view of the pion exchange. Namely, we investigate whether the two-pion-exchange interaction acts as a dominant attraction in the α + α system as predicted by a previous work. We describe theoretically the cluster structure of 8Be by the Brink model, for which the effective interaction is designed from the realistic nuclear force derived through the chiral EFT. The two-body matrix elements of the chiral interaction with the local-Gaussian bases are formulated within the approximation of the spin–isospin saturation forming an α particle. Introducing a global prefactor to the chiral interaction phenomenologically, the ground and low-lying excited states of 8Be, the scattering phase shift of the α–α system as well, are satisfactorily depicted. The attraction in the cluster states is found to be stemming from the two-pion-exchange contributions dominantly, along with nonnegligible short-range terms. The present work can be the foundation towards constructing realistic cluster models, by which the cluster states will be revealed microscopically in the next step.
Modeling polarons in density functional theory: lessons learned from TiO2
Authors: Reticcioli Michele , Diebold Ulrike , Franchini Cesare
Published: February 2022

Density functional theory (DFT) is nowadays one of the most broadly used and successful techniques to study the properties of polarons and their effects in materials. Here, we systematically analyze the aspects of the theoretical calculations that are crucial to obtain reliable predictions in agreement with the experimental observations. We focus on rutile TiO2, a prototypical polaronic compound, and compare the formation of polarons on the (110) surface and subsurface atomic layers. As expected, the parameter U used to correct the electronic correlation in the DFT + U formalism affects the resulting charge localization, local structural distortions and electronic properties of polarons. Moreover, the polaron localization can be driven to different sites by strain: due to different local environments, surface and subsurface polarons show different responses to the applied strain, with impact on the relative energy stability. An accurate description of the properties of polarons is key to understand their impact on complex phenomena and applications: as an example, we show the effects of lattice strain on the interaction between polarons and CO adsorbates.
Strain-relaxation induced transverse resistivity anomaly in epitaxial films through lithography engineering
Authors: Chen Peng , Liu Pei , Wang Yongzuo , Li Xiaolin , Yun Jijun , Gao Cunxu
Published: February 2022

The exotic transverse resistivity in magnetic materials has received intense research because of possible new emergent physics. Here, we report the strain-relaxation induced transverse resistivity anomaly in Mn2CoAl epitaxial films through lithography engineering. The anomalous Hall resistivity

ρ

x
y

A
H

decreases from 0.48 to 0.17 μΩ cm at 10 K when the widths of the Hall bar decreases from 40 to 1 μm, and the temperature dependence of

ρ

x
y

A
H

reverses for the 1.4 μm deep-etched samples. Importantly, Hall resistivity anomalies appear in the 1 μm-wide and 1.4 μm-wide deep-etched Hall bar samples, which can be well explained by the two-channel transport mechanism. We believe that these observations can be attributed to the strain relaxation effect when the Hall bar width is narrowed to around 1 μm. Our work shows that the induced strain relaxation can possibly lead to the alternation of the materials’ electronic structure, and the size effect should be considered when the sample size is reduced to about 1 μm.
Measurement uncertainty quantification for myocardial perfusion using cardiac positron emission tomography imaging
Authors: Partarrieu Ignacio X , Jagan Kavya , Fenwick Andrew , Han Chunlei , Siekkinen Reetta , Teuho Jarmo , Saraste Antti , Smith Nadia A S
Published: February 2022

Perfusion, the flow of blood, and hence oxygen, is essential to the functioning of the heart. Reduced perfusion (or ischemia), is a reliable indicator of the presence of significant obstructive coronary artery disease (CAD), which is one of the biggest causes of death in Europe. Myocardial perfusion imaging is a non-invasive technique used in the diagnosis, management and prognosis of CAD and is a key component in the triage of patients into treatment and non-treatment groups. Cardiac positron emission tomography (PET) is an imaging technique with high sensitivity and specificity to CAD, however perfusion measurements are difficult to calibrate against a common reference standard, and confidence in them is generally not quantified in terms of measurement uncertainty. There are a number of steps involved in measuring perfusion using cardiac PET—from patient preparation to data analysis—each associated with potential sources of uncertainty. The absence of measurement uncertainty quantification can lead to inaccuracies in measurement results, a lack of comparability between devices or scanning facilities, and is likely to be detrimental to a decision-making process. In this paper, we identify some of the sources of measurement uncertainty in the cardiac PET perfusion measurement pipeline. We assess their relative contribution by performing a sensitivity analysis using experimental data of a flow phantom acquired on a PET scanner. The results of this analysis will inform users of how parameter choices in their imaging pipeline affect the output of their measurements, and serves as a starting point to develop an uncertainty quantification method.
An intelligent fault diagnosis method for roller bearings using an adaptive interactive deviation matrix machine
Authors: Pan Haiyang , Xu Haifeng , Zheng Jinde , Liu Qingyun , Tong Jinyu
Published: February 2022

Support matrix machines (SMMs) take a matrix as the modeled element and can fully mine the structural information of matrix samples. However, relying solely on a pair of parallel hyperplanes limits the performance of SMMs in classifying complex data. Therefore, this paper proposes an adaptive interactive deviation matrix machine (AIDMM). In the AIDMM, a sensitive margin parameter is introduced to construct two deviation hyperplanes, so that the parameter margin between the two deviation hyperplanes becomes flexible. Compared to the original fixed maximum-margin method, the parameter-margin AIDMM can better adjust the boundary of the deviation hyperplane according to the data, which contributes to improving insensitivity to noise and enhancing robustness. In addition, a multi-rank projection matrix is introduced to obtain a low-rank solution, which gives AIDMM a better fitting ability and avoids the problem of large training errors. Two roller bearing fault datasets are applied for experimental verification, and the experimental results show that AIDMM has excellent classification performance in roller bearing fault diagnosis.
Boundary plane-oriented grain boundary model generation
Authors: Hinuma Yoyo , Kohyama Masanori , Tanaka Shingo
Published: February 2022

This study proposes algorithms for building tilt grain boundary (GB) models with a boundary plane-oriented approach that does not rely on existence of a coincidence site lattice (CSL). As conventional GB model generation uses the CSL of superimposed grains as the starting point, our totally different approach allows systematic treatment of diverse grain boundary systems that was previously not possible. Candidates of a pair of GB planes for a selected rotation axis, constituting a symmetrical or asymmetrical tilt GB, are thoroughly obtained by computational search that is applicable to any crystal structure. A GB interface for feasible computational analysis would have two-dimensional (2D) periodicity shared by the 2D lattices of the two GB planes, hence surface-slab supercells (slab-and-vacuum models) with common in-plane basis vectors of the shared 2D lattice are obtained. Finally, a procedure to obtain a GB-model supercell with alternately stacking such slabs is given. Symmetry operations of each slab may be considered such that the iterated interfaces are symmetrically equivalent, which is beneficial in ab initio calculations. The proposed algorithms allow streamlined generation of GB models, both symmetric and asymmetric, with or without an exact 3D-CSL relation.
Self-powered boost-converter for power optimisation and piezo garden lights
Authors: Edla Mahesh , Mikio Deguchi , Izadgoshasb Iman , Mahmud M A Parvez , Kouzani Abbas Z
Published: February 2022

This study gives a thorough model for a small vibration powered piezoelectric device (PD) and analysis modes of operation and control of a self-powered boost converter circuit (SPBC) for the goal of tracking the PD’s finest functioning points. The concept defines the power dependency of the PD on mechanical excitation and frequency, and it aids in the design of load behaviour for power optimisation. With a fundamental control circuit, the electrical nature of the input (i.e. PD) of an SPBC circuit in the discontinuous current mode is found to be in perfect configuration with the studied optimisation requirements. The performance of the proposed SPBC circuit is studied in terms of both simulation and experiment. Firstly, the performance of the SPBC on optimisation of the PD is investigated using a mechanical shaker. Then, the proposed circuit’s ability to charge a battery, which can be used in piezo garden lights with low-frequency applicability, is also investigated. The proposed circuit and control can also be utilised to optimise electromagnetic applications.
On-demand direct printing of tin microdots by a piezoelectric microjet: design, simulation, and experimental evaluation
Authors: Li Kai , Wang Runju , Liu Junkao , Feng Yuming , Liu Yingxiang
Published: February 2022

Metal microdot precision printing is widely applied in flexible circuit manufacturing, ball grid array and additive manufacturing, etc. Compared with indirect metal microdot printing, direct printing can realize high efficiency printing by directly ejecting hot-melt metal droplets. While, due to the compressibility of the driving gas, uniform printed microdots are hardly to be obtained by using the existing direct printing method. In this work, a piezoelectric microjet, which can print tin microdots directly by the drive of piezoelectric actuator without complex pneumatic system, is designed. Optimization analyses of the displacement amplifier are carried out to obtain high amplification efficiency for realizing hot-melt droplet ejection and effective heat insulation. The forming, spreading, and solidification processes of the ejected hot-melt tin droplets are discussed, and the printing mechanism is revealed. Based on experimental research, the influences of the excitation parameters and the target surface characteristics on the morphology and size of the printed tin microdots are studied, and the methods to meet different printing requirements are proposed. Tin microdot diameter of 340 μm can be printed on the surface with temperature of 120 °C when voltage pulse with amplitude of only 16 V is applied on the designed piezoelectric microjet with the nozzle diameter of 200 μm. The feasibility and controllability of the tin microdot printing methods are verified by two-dimensional printing and three-dimensional deposition printing test. This work can provide important reference for on-demand printing of metal microdots.
First principle insight on Mn doped BeTe compound for optoelectronic and spintronic applications
Authors: Ambreen Hina , Aldaghfag Shatha A , Yaseen Muhammad , Zahid Muhammad , Somaily H H
Published: February 2022

The structural, electronic, optical, magnetic and thermoelectric (TE) features of pristine and Mn doped BeTe compound were computed by mean of FP-LAW method. Magnetic stability at various doping concentrations in ferromagnetic (FM) ordering is investigated by minimizing the total ground state energies. A semiconductor behavior is predicated for BeTe and Be1−xMnxTe (X = 6.25, 12.5, 18.75, 25%) because of the fact that spin-up and spin-dn show semiconductor character with direct band gap (Eg). The total and partial density of states of resultant compound have also been calculated. Furthermore, the dilute magnetic semiconductors (DMS) have been considered as the potential candidate to be used in spintronics devices. The magnetic moment of Be1−xMnxTe (X = 6.25, 12.5, 18.75, 25%) has been studied by increasing the concentration of Mn atoms. The contribution of the Mn atoms is significant in the total magnetic moment of resultant alloys, while it is minor in Be and Te. Moreover, the optical features revealed the maximum absorption of light in visible to UV span of electromagnetic spectrum which makes it a potential candidate for optoelectronic applications. Outcome suggest that Mn doped BeTe is an interesting candidates for various technological applications.
Intense laser field effect on the nonlinear optical properties of triple quantum wells consisting of parabolic and inverse-parabolic quantum wells
Authors: Ozturk O , Alaydin B O , Altun D , Ozturk E
Published: February 2022

The nonlinear optical rectification, the second harmonic generation coefficient, and the third harmonic generation coefficient in parabolic-inverse parabolic-parabolic quantum wells (PIPPQWs) and inverse parabolic-parabolic-inverse parabolic quantum wells (IPPIPQWs) are calculated varying the intense laser field (ILF) parameter (

α
0

). The modifications of the dipole moment matrix elements and the energy levels are depending on the potential shape. The results show that the ILF intensity exerts an active influence on the profile, height, and width of the confinement potential of both PIPPQW and IPPIPQW. The potential profile of IPPIPQW has been affected otherwise than PIPPQW for different ILF intensities. The nonlinear optical rectification, the second harmonic generation, and the third harmonic generation coefficients of PIPPQW and IPPIPQW could be altered in the energy range and the size of the resonance peak by rising the ILF intensity. By changing the

α
0

parameter, it is conceivable to organize red or blue shift at the resonance peak positions of the nonlinear optical rectification, the second harmonic generation, and the third harmonic generation coefficients. The shift of the nonlinear optical rectification coefficient occurs when the difference between the ground and the second energy levels changes. According to the parameters used here, while for PIPPQW the spectrum of the resonance peak of the nonlinear optical rectification displays a blue shift with increasing ILF, this spectrum displays a red shift for IPPIPQW. The consequences can be valued in investigating new ways of changing the optical and electronic properties of semiconductor quantum wells.
Influence of Rashba spin-orbit coupling on Josephson effect in triplet superconductor/two-dimensional semiconductor/triplet superconductor junctions
Authors: Du Bin-Hao , Chen Man-Ni , Hu Liang-Bin
Published: February 2022

We study theoretically Josephson effect in a planar ballistic junction between two triplet superconductors with p-wave orbital symmetries and separated by a two-dimensional (2D) semiconductor channel with strong Rashba spin–orbit coupling. In triplet superconductors, three types of orbital symmetries are considered. We use Bogoliubov–de Gennes formalism to describe quasiparticle propagations through the junction and the supercurrents are calculated in terms of Andreev reflection coefficients. The features of the variation of the supercurrents with the change of the strength of Rashba spin–orbit coupling are investigated in some detail. It is found that for the three types of orbital symmetries considered, both the magnitudes of supercurrent and the current-phase relations can be manipulated effectively by tuning the strength of Rashba spin–orbit coupling. The interplay of Rashba spin–orbit coupling and Zeeman magnetic field on supercurrent is also investigated in some detail.
Single-beam leaky-wave antenna with wide scanning angle and high scanning rate based on spoof surface plasmon polariton
Authors: Jiang Huan , Cao Xiang-Yu , Liu Tao , Jidi Liaori , Li Sijia
Published: February 2022

We propose a single-beam leaky-wave antenna (LWA) with a wide-scanning angle and a high-scanning rate based on spoof surface plasmon polariton (SSPP) in this paper. The SSPP transmission line (TL) is etched with periodically arranged circular patches, which converts the slow-wave mode into the fast-wave region for radiation. The proposed LWA is designed, fabricated, and tested. The simulated results imply that the proposed LWA not only achieves a high radiation efficiency of about 81.4%, and a high scanning rate of 12.12, but also has a large scanning angle of 176° over a narrow operation bandwidth of 8.3–9.6 GHz (for |S
11| < –10 dB). In addition, the simulated average gain of the LWA can reach as high as 10.9 dBi. The measured scanning angle range is 175° in the operation band of 8.2–9.6 GHz, and the measured average gain is 10.6 dBi. The experimental results are consistent with the simulation, validating its performance. An antenna with high radiation efficiency, wide scanning angle range, and high scanning rate has great potential for application in radar and wireless communication systems.
Achieving ultracold Bose–Fermi mixture of 87Rb and 40K with dual dark magnetic-optical-trap
Authors: Miao Jie , Bian Guoqi , Shan Biao , Chen Liangchao , Meng Zengming , Wang Pengjun , Huang Lianghui , Zhang Jing
Published: February 2022

We demonstrate that dual dark magnetic-optical-traps (MOTs) have great importance in the two-species 87Rb and 40K mixture compared with dual bright MOTs. The dark MOT has a little improvement in the trapping of single-species 87Rb or 40K gases compared with bright MOT. For the case of loading two-species 87Rb and 40K simultaneously, the improvement of 40K in the dual dark MOTs is mainly from the reduction of light-assisted collision losses. The dual dark MOTs employ a pair of conical lenses to produce the hollow beam for repump laser with high efficiency. The number and density of 87Rb and 40K atoms after evaporative cooling in the hybrid magnetic trap with dark MOT loading are compared with those in bright MOT. The atoms with large number and high density make it easier to realize the quantum degenerate of Bose–Fermi mixture.
Modeling of beam ions loss and slowing down with Coulomb collisions in EAST
Authors: Zheng Yifeng , Xiao Jianyuan , Hao Baolong , Xu Liqing , Wang Yanpeng , Zheng Jiangshan , Zhuang Ge
Published: February 2022

This paper uses the implicit Monte–Carlo full-orbit-following parallel program ISSDE to calculate the prompt loss and slowing down process of neutral beam injection (NBI)-generated fast ions due to Coulomb collisions in the equilibrium configuration of Experimental Advanced Superconducting Tokamak (EAST). This program is based on the weak equivalence of the Fokker–Planck equation under Rosenbluth MacDonald Judd (RMJ) potential and Stratonovich stochastic differential equation (SDE). The prompt loss with the LCFS boundary and the first wall (FW) boundary of the two co-current neutral injection beams are studied. Simulation results indicate that the loss behavior of fast ions using the FW boundary is very different from that of the LCFS boundary, especially for fast ions with a large gyration radius. According to our calculations, about 5.11% of fast ions generated by perpendicular injection drift out of the LCFS and then return inside the LCFS to be captured by the magnetic field. The prompt loss ratio of fast ions and the ratio of orbital types depend on the initial distribution of fast ions in the Pζ
–Λ space. Under the effect of Coulomb collisions, the pitch-angle scattering and stochastic diffusion happens, which will cause more fast ion loss. For short time scales, among the particles lost due to collisions, the fraction of banana ions reaches 92.31% in the perpendicular beam and 58.65% in the tangential beam when the fraction of banana ions in the tangential beam is 3.4% of the total ions, which means that the effect of Coulomb collisions on banana fast ions is more significant. For long time scales, the additional fast ion loss caused by Coulomb collisions of tangential and perpendicular beams accounted for 16.21% and 25.05% of the total particles, respectively. We have also investigated the slowing down process of NBI fast ions.
Dual-function terahertz metasurface based on vanadium dioxide and graphene
Authors: Li Jiu-Sheng , Li Zhe-Wen
Published: February 2022

A dual-function terahertz metasurface based on VO2 and graphene is proposed in this paper. It consists of a gold layer embedded with VO2 patches, a SiO2 spacer layer, a VO2 layer, graphene and a SiO2 spacer substrate. When the bottom VO2 layer is in the metallic state, the designed metasurface can achieve absorption. When the top VO2 patches are in the metallic state, the proposed metasurface can be used as a single-band absorber with terahertz absorptance of 99.7% at 0.736 THz. When the top VO2 patches are in the insulating state, the designed structure behaves as a dual-band absorber with an absorptance of 98.9% at 0.894 THz and 99.9% at 1.408 THz. In addition, the absorber is polarization insensitive and keeps good performance at large angles of incidence. When the bottom VO2 is in an insulating state, the metasurface shows electromagnetically induced transparency. The transparent window can be dynamically regulated by controlling the chemical potential of graphene. The proposed metasurface exhibits the advantages of terahertz absorption, electromagnetically induced transparency and dynamic control, which provides more options for the design of terahertz devices in the future.
Magnetic properties of a mixed spin-3/2 and spin-2 Ising octahedral chain
Authors: Na Xiao-Chen , Si Nan , Zhang Feng-Ge , Jiang Wei
Published: February 2022

Using an effective field theory with correlations, magnetic properties of an octahedral chain described by a mixed spin Ising model are investigated. Unique phenomena such as multiple hysteresis loops, saturation magnetization, and reverse flip of the magnetization plateaus occur when certain typical parameters are applied. These results may be helpful to further investigate the magnetic properties of one-dimensional systems and could potentially be utilized in the design of spin devices.
Robustness of the unidirectional stripe order in the kagome superconductor CsV3Sb5
Authors: Hu Bin , Ye Yuhan , Huang Zihao , Han Xianghe , Zhao Zhen , Yang Haitao , Chen Hui , Gao Hong-Jun
Published: February 2022

V-based kagome materials AV3Sb5 (A = K, Rb, Cs) have attracted much attention due to their novel properties such as unconventional superconductivity, giant anomalous Hall effect, charge density wave (CDW) and pair density wave. Except for the 2a
0 × 2a
0 CDW (charge density wave with in-plane 2 × 2 superlattice modulation) in AV3Sb5, an additional 1 × 4 (4a
0) unidirectional stripe order has been observed at the Sb surface of RbV3Sb5 and CsV3Sb5. However, the stability and electronic nature of the 4a
0 stripe order remain controversial and unclear. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we systematically study the 4a
0 stripe order on the Sb-terminated surface of CsV3Sb5. We find that the 4a
0 stripe order is visible in a large energy range. The STM images with positive and negative bias show contrast inversion, which is the hallmark for the Peierls-type CDW. In addition, below the critical temperature about 60 K, the 4a
0 stripe order keeps unaffected against the topmost Cs atoms, point defects, step edges and magnetic field up to 8 T. Our results provide experimental evidences on the existence of unidirectional CDW in CsV3Sb5.
A study of cavitation nucleation in pure water using molecular dynamics simulation
Authors: Xie Hua , Xu Yuequn , Zhong Cheng
Published: February 2022

To discover the microscopic mechanism responsible for cavitation nucleation in pure water, nucleation processes in pure water are simulated using the molecular dynamics method. Cavitation nucleation is generated by uniformly stretching the system under isothermal conditions, and the formation and development of cavitation nuclei are simulated and discussed at the molecular level. The processes of energy, pressure, and density are analyzed, and the tensile strength of the pure water and the critical volume of the bubble nuclei are investigated. The results show that critical states exist in the process of cavitation nucleation. In the critical state, the energy, density, and pressure of the system change abruptly, and a stable cavitation nucleus is produced if the energy barrier is broken and the critical volume is exceeded. System pressure and water density are the key factors in the generation of cavitation nuclei. When the critical state is surpassed, the liquid is completely ruptured, and the volume of the cavitation nucleus rapidly increases to larger than 100 nm3; at this point, the surface tension of the bubble dominates the cavitation nucleus, instead of intermolecular forces. The negative critical pressure for bubble nucleation is –198.6 MPa, the corresponding critical volume is 13.84 nm3, and the nucleation rate is 2.42 × 1032 m−3⋅s−1 in pure water at 300 K. Temperature has a significant effect on nucleation: as the temperature rises, nucleation thresholds decrease, and cavitation nucleation occurs earlier.
Characteristics of piecewise linear symmetric tri-stable stochastic resonance system and its application under different noises
Authors: Zhang Gang , Zeng Yu-Jie , Jiang Zhong-Jun
Published: February 2022

Weak signal detection has become an important means of mechanical fault detections. In order to solve the problem of poor signal detection performance in classical tristable stochastic resonance system (CTSR), a novel unsaturated piecewise linear symmetric tristable stochastic resonance system (PLSTSR) is proposed. Firstly, by making the analysis and comparison of the output and input relationship between CTSR and PLSTSR, it is verified that the PLSTSR has good unsaturation characteristics. Then, on the basis of adiabatic approximation theory, the Kramers escape rate, the mean first-passage time (MFPT), and output signal-to-noise ratio (SNR) of PLSTSR are deduced, and the influences of different system parameters on them are studied. Combined with the adaptive genetic algorithm to synergistically optimize the system parameters, the PLSTSR and CTSR are used for numerically simulating the verification and detection of low-frequency, high-frequency, and multi-frequency signals. And the results show that the SNR and output amplitude of the PLSTSR are greatly improved compared with those of the CTSR, and the detection effect is better. Finally, the PLSTSR and CTSR are applied to the bearing fault detection under Gaussian white noise and Levy noise. The experimental results also show that the PLSTSR can obtain larger output amplitude and SNR, and can detect fault signals more easily, which proves that the system has better performance than other systems in bearing fault detection, and has good theoretical significance and practical value.
Human activities modulate greening patterns: a case study for southern Xinjiang in China based on long time series analysis
Authors: Zhao Rongtian , Liu Xingcai , Dong Jinwei , Zhao Gang , Manevski Kiril , Andersen Mathias Neumann , Tang Qiuhong
Published: February 2022

Greening of the Earth is observed during the past several decades and both climatic and non-climatic factors drive this process. However, the greening spatio-temporal patterns and the role of human activities such as agricultural intensification in hyper-arid regions remain unclear. This study aimed to (a) reveal the greening pattern in China’s southern Xinjiang using satellite estimations of normalized difference vegetation index and leaf area index data during 1982–2019, and (b) examine the impacts of human activities in terms of land use land cover (LULC) data. Our multi-decadal analysis is ideal to reveal long-term trends and support a better understanding of the anthropogenic effects in this hyper-arid and endorheic region. The results showed that vegetation as a whole increased significantly in southern Xinjiang and the greening rate of cropland was much higher than the other LULC types. Significant greening was found over >90% of cropland, while insignificant changes and browning trends were found over nearly half the area of the other LULCs. The proportion of greening areas was more than 80% within 1 km from human-dominated areas while the proportion decreased to 40% with distances >15 km. The spatial heterogeneity of the greening indicated that, despite widely reported beneficial effects of warmer and wetter climate for a general greening trend, human activities could be the dominant factor modulating the greening rates disproportionately over different LULCs in arid and hyper-arid areas.
Safe drinking water for small low-income communities: the long road from violation to remediation
Authors: Glade Sara , Ray Isha
Published: February 2022

Small, low-income communities in the United States disproportionately lack access to safe drinking water (i.e. water that meets regulated quality standards). At a community level, the literature has broadly claimed that a major barrier to safe drinking water access is low technical, managerial, and financial (TMF) capacity. At a broader structural level, the environmental justice literature has shown that historical neglect of low-income communities of color has resulted in numerous water systems without the financial and political resources to meet water quality standards. This study investigates the contemporary processes by which distributive injustices persist in California’s Central Valley. The study uses key informant interviews with a range of stakeholders, including employees at the state, county and community, non-profit organizations, and engineers, to understand why sustainable water quality solutions for small low-income communities remain such a challenge. The interviews are structured around a decision chain, which builds out the specific steps needed to go from a maximum contaminant level violation to remediation. The resulting decision chain makes visible the multiple steps at multiple stages with multiple actors that are needed to arrive at a solution to substandard water quality. It shows the numerous nodes at which progress can be stalled, and thus functions as a behind-the-scenes look at the (re)production of persistent inequalities. The complexity of the process shows why having the TMF capacity needed to get to a safe water system is not a reasonable expectation for most small community water systems. Inequalities are continually being produced and cemented, often by the very steps aimed towards remediation, thus making persistent disparities in safe drinking water access a de facto state-sanctioned process that compounds a discriminatory historical legacy.
Estimating the impact of shelterbelt structure on corn yield at a large scale using Google Earth and Sentinel 2 data
Authors: Liu Yage , Li Huidong , Yuan Fenghui , Shen Lidu , Wu Minchao , Li Wenliang , Wang Anzhi , Wu Jiabing , Guan Dexin
Published: February 2022

A shelterbelt is an important measure to protect farmland and increase crop yield. However, how a shelterbelt structure affects crop yield is still unclear due to the difficulties accessing sufficient data from traditional field observations. To address this problem, we developed an innovative framework to estimate the shelterbelt structure and crop yield profile at a regional scale based on Google Earth and Sentinel-2 data. Using this method, we quantified the impact of the shelterbelt structure on the corn yield at 302 shelterbelts in the Northeast Plain of China. Generally, the corn yield increased (by 2.41% on average) within a distance of 1.2–15 times the tree height from the shelterbelt. Such an effect was particularly prominent within a distance of two to five times the tree height, where the corn yield was significantly increased by up to 4.63%. The structure of the shelterbelt has a significant effect on the magnitude of increase in yield of the surrounding corn. The increment of corn yields with high-, medium-high-, medium- and low-width-gap grade shelterbelt were 2.01%, 2.21%, 1.99%, and 0.91%, respectively. The medium-high grade shelterbelt achieved the largest yield increase effect. The location of the farmland relative to the shelterbelt also affected the yield, with a yield increase of 2.39% on the leeward side and 1.89% on the windward side, but it did not change the relationship between the yield increase effect and the shelterbelt structure. Our findings highlight the optimal shelterbelt structure for increasing corn yield, providing practical guidance on the design and management of farmland shelterbelts for maximizing yield.
Today’s 100 year droughts in Australia may become the norm by the end of the century
Authors: Araujo Diogo S A , Marra Francesco , Merow Cory , Nikolopoulos Efthymios I
Published: February 2022

Accumulating evidence on the impact of climate change on droughts, highlights the necessity for developing effective adaptation and mitigation strategies. Changes in future drought risk and severity in Australia are quantified by analyzing nine Coupled Model Intercomparison Project Phase 6 climate models. Historic conditions (1981–2014) and projections for mid-century (2015–2050) and end-century (2051–2100) from four shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) are examined. Drought events are identified using both the standardized precipitation index and the standardized precipitation evapotranspiration index. The spatial-temporal evolution of droughts is addressed by quantifying the areal extent of regions under moderate, severe and extreme drought from historic to end-century periods. Drought characteristics derived from the models are used to develop severity–duration–frequency curves using an extreme value analysis method based on ordinary events. Under SSP5-8.5, a tenfold increase in the area subject to extreme droughts is projected by the end of the century, while a twofold increase is projected under SSP1-2.6. Increase in extreme droughts frequency is found to be more pronounced in the southern and western regions of Australia. For example, frequency analysis of 12 month duration droughts for the state of South Australia indicates that, under SSP5-8.5, drought severities currently expected to happen on average only once in 100 years could happen as often as once in 3 years by the end of the century, with a 33 times higher risk (from 1% to 33%), while under SSP1-2.6, the increase is fivefold (1%–5%). The significant difference in the increase of drought risk between the two extreme scenarios highlights the urge to reduce greenhouse gases emission in order to avoid extreme drought conditions to become the norm by the end of the century.
Microwave-assisted synthesis and upconversion luminescence of NaYF4:Yb, Gd, Er and NaYF4:Yb, Gd, Tm nanorods
Authors: Nannuri Shivanand H , Singh Simranjit , Misra Superb K , C Santhosh , George Sajan D
Published: February 2022

Anisotropic rare earth ion (RE3+) doped fluoride upconversion particles are emerging as potential candidate in diverse areas, ranging from biomedical imaging to photonics. Here, we develop a facile strategy to synthesize NaYF4: Yb, Gd, Er, and NaYF4: Yb, Gd, Tm upconversion nanorods via microwave synthesis route by controlling the synthesis time and compared the optical properties similar nanorods prepared via solvothermal technique. With the increase in synthesis time, the phase of the particle found to change from mixed phase to purely hexagonal and morphology of the particles change mixed phase of spherical and rod-shaped particles to completely nanorods for a synthesis time of 60 min. Further, the intrinsically hydrophobic particles changed to hydrophilic by removal of oleic capping via acid treatment and the amine functionalized silica coating. The upconversion luminescence as well as laser power dependent emission properties of the surface modified particles elucidate that surface modification route influence the upconversion luminescence as well as solvent dependent emission properties. Moreover, the laser power dependent studies elucidate that the upconversion process in a multi-photon process.
The effects of micro-texture shape on serrated chip geometry in the hardened steel AISI D2 cutting process
Authors: Fan Lin , Deng Zi-long , He Yan , Zhu Xu-long , Gao Xing-jun , Jin Zhe
Published: February 2022

Five micro-textures were processed on the rake face of PCBN tools: circular pits, elliptical grooves, transverse grooves, composite grooves, and wavy grooves. The effect of different micro-textures on cutting force, the cutting temperature, the micro-morphology of serrated chips, tool wear and surface roughness were investigated utilizing three-dimensional finite element simulation and cutting tests. The results indicates that micro-textured tools can lower cutting force when compared to non-textured tools, while cutting force varies significantly during the cutting process. Micro-texture can decrease the temperature in the adiabatic shear band, changes the temperature distribution of the rake face, reduce the serrated degree, and increase segmentation frequency. However, it is more prone to cracking. The wear resistance and the surface quality of machined surface of the elliptical grooves and wavy grooves micro-texture are better.
The impact of surface slope and calculation resolution on the fractal dimension for fractures of steels after bending-torsion fatigue
Authors: Macek Wojciech
Published: February 2022

The article presents the results of the fractal dimension measurements on the fatigue fracture surfaces of 10HNAP and S355J2 steels specimens after combined bending-torsion fatigue. For smooth and ring-notched specimens, three loading conditions were analyzed: (1) bending; (2) bending-torsion; and (3) torsion fatigue. Post-failure surface topography measurements were carried out on the entire fracture surfaces using an optical profilometer. The fractal dimension was computed with general slope and after removing them by leveling operation, as well as with two different resolutions. The analysis of the fractal dimension delineated by the enclosing boxes method (EBM) allowed to formulate guidelines that, in terms of further estimation of the method of failure, the optimum is extra-fine resolution without leveling.
Analytical covariance estimation for iterative CT reconstruction methods
Authors: Guo Xiaoyue , Zhang Li , Xing Yuxiang
Published: February 2022

Covariance of reconstruction images are useful to analyze the magnitude and correlation of noise in the evaluation of systems and reconstruction algorithms. The covariance estimation requires a big number of image samples that are hard to acquire in reality. A covariance propagation method from projection by a few noisy realizations is studied in this work. Based on the property of convergent points of cost funtions, the proposed method is composed of three steps, (1) construct a relationship between the covariance of projection and corresponding reconstruction from cost functions at its convergent point, (2) simplify the covariance relationship constructed in (1) by introducing an approximate gradient of penalties, and (3) obtain an analytical covariance estimation according to the simplified relationship in (2). Three approximation methods for step (2) are studied: the linear approximation of the gradient of penalties (LAM), the Taylor apprximation (TAM), and the mixture of LAM and TAM (MAM). TV and qGGMRF penalized weighted least square methods are experimented on. Results from statistical methods are used as reference. Under the condition of unstable 2nd derivative of penalties such as TV, the covariance image estimated by LAM accords to reference well but of smaller values, while the covarianc estimation by TAM is quite off. Under the conditon of relatively stable 2nd derivative of penalties such as qGGMRF, TAM performs well and LAM is again with a negative bias in magnitude. MAM gives a best performance under both conditions by combining LAM and TAM. Results also show that only one noise realization is enough to obtain reasonable covariance estimation analytically, which is important for practical usage. This work suggests the necessity and a new way to estimate the covariance for non-quadratically penalized reconstructions. Currently, the proposed method is computationally expensive for large size reconstructions.Computational efficiency is our future work to focus.