bluuebunny/crossref_metadata_2025 huggingface dataset:
Synergistic therapeutic efficacy of ebselen and silver ions against multidrug-resistant Acinetobacter baumannii-induced urinary tract infections
Authors: Dong Chuanjiang , Wang Jun , Chen Huan , Wang Peng , Zhou Jingxuan , Zhao Ying , Zou Lili
Published: May 2020

Ebselen (EbSe), an organo-selenium compound with well-characterized toxicology and pharmacology, exhibited potent antibacterial activity against glutathione (GSH)-positive bacteria when combined with silver ions (Ag+). In this paper, the strong bactericidal activity of EbSe–Ag+ against multidrug-resistant (MDR) Acinetobacter baumannii has been confirmed, and its efficacy was mainly based on the inhibition of thioredoxin reductase (TrxR) activity and the depletion of the total GSH amount. Moreover, the therapeutic effect of EbSe–Ag+ on urinary tract infection was assessed in a mouse model induced with A. baumannii 0361# strain. The treatment with EbSe–Ag+ significantly reduced the bacterial load and expression levels of the pro-inflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) in bladder lesions; meanwhile, the pathological experiment showed that A. baumannii-induced changes in EbSe–Ag+ treated mice were much attenuated than that in the control group. Thus, all the results obtained here may lay the foundation for further analysis and development of EbSe–Ag+ as potential antibacterial agents for MDR A. baumannii-induced urinary tract infection treatment.
Facile fabrication of superhydrophobic zinc coatings with corrosion resistance via an electrodeposition process
Authors: Hu Chuanbo , Xie Xinying , Zheng Hui , Qing Yongquan , Ren Kangning
Published: May 2020

In this investigation, we demonstrated a controlled electrodeposition method by varying the current density to generate hierarchical structures of zinc (Zn) on a carbon steel surface, which serves as a hydrophobic and anticorrosion coating when further modified by stearic acid to form a covalently bonded layer that offers low surface energy.
Computational characterization of N-type characteristics and optoelectronic properties in air-stable pyromellitic diimide derivatives
Authors: Khatua Rudranarayan , Debata Suryakanti , Sahu Sridhar
Published: May 2020

Theoretical investigation of charge transport and optoelectronic properties of the pyromellitic diimide derivatives; BPyDI, BPyDI1, BPIT, BPPIT, and BPPyDI using DFT methodology.
Thiophene backbone-based polymers with electron-withdrawing pendant groups for application in organic thin-film transistors
Authors: Jeong Moon-Ki , Lee Kyumin , Kang Jinhyeon , Jang Jaeyoung , Jung In Hwan
Published: May 2020

The suboptimal molecular ordering of by PF2-BDD quick freezing during hot-solution spin-coating hindered an efficient hole transport, whereas the more crystalline structure of PT2-BDD resulted in higher hole mobility in the corresponding OTFT.
A study on the photocatalytic sterilization performance and mechanism of Fe-SnO2/g-C3N4 heterojunction materials
Authors: Chen Xin , Wang Qing , Tian Jing , Liu Yuanyuan , Wang Yiding , Yang Chun
Published: May 2020

From the perspective of the biochemical reaction energy and chemical bond energy, the Z-scheme charge sterilization mechanism was enriched and perfected.
Chiral liquid chromatography-mass spectrometry (LC-MS/MS) method development with β-cyclodextrin (β-CD) derivatized chiral stationary phase for the enhanced separation and determination of flurbiprofen enantiomers: application to a stereoselective pharmacokinetic study
Authors: Sun Jiayi , Liu Beibei , Cai Liangzhao , Yu Jia , Guo Xingjie
Published: May 2020

Home-made chiral stationary phase for enhanced enantioselective separation and determination of flurbiprofen by liquid chromatography-mass spectrometry (LC-MS/MS) for the first time.
Tuning the ORR activity of Pt-based Ti2CO2 MXenes by varying the atomic cluster size and doping with metals
Authors: Zhang Xilin , Zhang Yiying , Cheng Cheng , Yang Zongxian , Hermansson Kersti
Published: May 2020

The introduction of Au that possesses high electronegativity and many d electrons greatly improved the ORR activity of Ptn/v-Ti2CO2.
Two-dimensional nanocoating-enabled orthopedic implants for bimodal therapeutic applications
Authors: Wang Song , Duan Chunyan , Yang Weizhong , Gao Xiangyu , Shi Jiacheng , Kang Jianping , Deng Yi , Shi Xiao-Lei , Chen Zhi-Gang
Published: May 2020

A multifunctional two-dimensional nanocoating consists of graphene oxide nanosheets, polydopamine nanofilm, and oligopeptide constructed on porous sulfonated polyetheretherketone for the purpose of bone infection treatment.
Recent advances in engineering active sites for photocatalytic CO2 reduction
Authors: Bo Yanan , Gao Chao , Xiong Yujie
Published: May 2020

This review highlights recent advances in the strategies for engineering active sites on surfaces and in open frameworks toward photocatalytic CO2 reduction.
Precisely targeted gene delivery in human skin using supramolecular cationic glycopolymers
Authors: Blakney Anna K. , Liu Renjie , Yilmaz Gokhan , Abdouni Yamin , McKay Paul F. , Bouton Clément R. , Shattock Robin J. , Becer C. Remzi
Published: May 2020

Gene delivery has become the focus of clinical treatments, thus motivating delivery strategies that are capable of targeting certain cell types in the context of both vaccines and therapeutics.
Superacid-catalyzed Friedel–Crafts polyhydroxyalkylation: a straightforward method to construct sky-blue thermally activated delayed fluorescence polymers
Authors: Zhou Xiang , Huang Manli , Zeng Xuan , Zhong Cheng , Xie Guohua , Cao Xiaosong , Yang Changan , Yang Chuluo
Published: May 2020

A series of sky-blue TADF polymers were developed by Friedel–Crafts polyhydroxyalkylation for efficient solution processed OLEDs.
The corrosion resistance, cytotoxicity, and antibacterial properties of lysozyme coatings on orthodontic composite arch wires
Authors: He Longwen , Cui Ye , Zhang Chao
Published: May 2020

The corrosion resistance of new orthodontic composite arch wires (CAWs), which have excellent mechanical properties in a simulated oral environment, must be improved.
Modular bioengineered kinase sensorsviascaffold protein-mediated split-luciferase complementation
Authors: Xu Xiaolu , Lemmens Lenne J. M. , den Hamer Anniek , Merkx Maarten , Ottmann Christian , Brunsveld Luc
Published: May 2020

Phosphorylation is a key regulation event in cellular signaling. To sense the underlying kinase activity, we engineered modular and easy adaptable serine kinase sensors for the exemplary kinases PKA, PKB and CHK1.
Raman spectrum feature extraction and diagnosis of oil–paper insulation ageing based on kernel principal component analysis
Authors: Yang Dingkun , Weigen Chen , Haiyang Shi , Fu Wan , Yongkuo Zhou
Published: May 2020

Raman spectroscopy, with its specific ability to generate a unique fingerprint‐like spectrum of certain substances, has attracted much attention in diagnosing the ageing degree of oil–paper insulation. In this study, the feature extraction and ageing diagnosis methods of oil–paper insulation Raman spectroscopy data are further studied. Based on the non‐linear analysis of Raman spectra of different ageing samples, kernel principal component analysis was applied to extract the spectral features, and the back‐propagation neural network was used to build a diagnosis model with high diagnostic accuracy. The results show that Raman spectroscopy combined with kernel principal component analysis and the back‐propagation neural network can diagnose the ageing state of oil–paper insulation, with a diagnostic accuracy of 91.43% (64/70). The proposed method provides an effective and feasible method for the ageing assessment of oil‐immersed electrical equipment.
Modelling and simulation frameworks for wireless sensor networks: a comparative study
Authors: Sharma Richa , Vashisht Vasudha , Singh Umang
Published: May 2020

In real‐time scenarios, wireless sensor network (WSN) suffers from severe constraints such as restricted power supply, short communication range, less bandwidth availability, and small memory storage. Owing to these severe constraints, the time complexity, space complexity, and cost complexity of these networks are very high. Hence, deploying a real sensor network environment for the testing of a newly designed protocol is a Herculean task. To overcome this issue, instead of doing live implementation of such networks, simulation modelling is accepted as an alternative approach. This study provides a comprehensive study about existing network simulators along with their advantages and weaknesses. This study also presented a case study for a preferable simulation methodology, i.e. MATLAB/Simulink. Firstly, this case study highlights prominent features of MATLAB/Simulink. Secondly, simulation results of implementing AODV (Adhoc on Demand Vector Protocol) in terms of simulation runtime using four simulators net simulator‐2 (NS‐2), NS‐3, OMNet++, and MATLAB is presented. Thirdly, survey of few very well‐known clustering protocols in WSNs is done. This study will prove to be beneficial for researchers of this domain as it surveys the literature over the period 2008–2020 focusing on simulation tools and simulation metrics used by researchers to simulate WSNs.
Decentralised federated learning with adaptive partial gradient aggregation
Authors: Jiang Jingyan , Hu Liang
Published: May 2020

Federated learning aims to collaboratively train a machine learning model with possibly geo‐distributed workers, which is inherently communication constrained. To achieve communication efficiency, the conventional federated learning algorithms allow the worker to decrease the communication frequency by training the model locally for multiple times. Conventional federated learning architecture, inherited from the parameter server design, relies on highly centralised topologies and large nodes‐to‐server bandwidths, and convergence property relies on the stochastic gradient descent training in local, which usually causes the large end‐to‐end training latency in real‐world federated learning scenarios. Thus, in this study, the authors propose the adaptive partial gradient aggregation method, a gradient partial level decentralised federated learning, to tackle this problem. In FedPGA, they propose a partial gradient exchange mechanism that makes full use of node‐to‐node bandwidth for speeding up the communication time. Besides, an adaptive model updating method further reduces the convergence rate by adaptive increasing the step size of the stable direction of gradient descent. The experimental results on various datasets demonstrate that the training time is reduced up to compared to baselines without accuracy degrade.
Plasma characterization at comet 67P between 2 and 4 AU from the Sun with the RPC-MIP instrument
Authors: Wattieaux Gaëtan , Henri Pierre , Gilet Nicolas , Vallières Xavier , Deca Jan
Published: May 2020

The plasma of comet 67P/Churyumov-Gerasimenko is analyzed based on the RPC-MIP mutual impedance probe data of the Rosetta mission. Numerical simulations of the RPC-MIP instrumental response considering two populations of electrons were fit on experimental responses acquired from January to September 2016 to extract the electron densities and temperatures. A time-tracking of the plasma parameters was performed, leading to the identification of a cold and a warm population of electrons during the period of interest. The respective densities and temperatures lie in the ranges [100; 1000] cm−3 and [0.05; 0.3] eV for the cold electrons and in the ranges [50; 500] cm−3 and [2; 10] eV for the warm electrons. Warm electrons most of the time made up between 10 and 30% of the whole population, while the temperature ratio between warm and cold electrons lay mostly between 30 and 70 during the period we studied. The fluctuation range of the plasma parameters, that is, the electron densities and temperatures, appears to have remained rather constant during the last nine months of the mission. We take the limitations of the instrument that are due to the experimental noise into account in our discussion of the results.
Stimulated Brillouin gain spectroscopy in a confined spatio-temporal domain (30 μm, 170 ns)
Authors: Djadaojee Lionel , Douillet Albane , Grucker Jules
Published: May 2020

The Brillouin gain spectrum of a test sample (liquid acetone at room temperature) on scales simultaneously confined in space (~30 μm) and time (~170 ns) is reported. This is done using a pulsed stimulated Brillouin scattering gain spectrometer in a θ ≈ 90° crossing beam configuration. After having identified and corrected for different sources of background signals, we obtained a Brillouin gain spectrum allowing an accurate measurement (MHz range) of the Brillouin frequency (few GHz). This is of interest for probing acoustic properties of transparent media subjected to repetitive fast transient phenomena on small length scales.
Analysis of Flight Energy Variation of Small Solar UAVs Using Dynamic Soaring Technology
Authors: LIU Siqi , Bai Junqiang
Published: May 2020

Limited by its low energy capacity, small UAVs have short flight time. Therefore, it is of great significance to improve the endurance performance of small UAVs by applying solar energy technology and dynamic soaring technology which can obtain external energy. This paper analyzes the energy exchange principle of small UAVs using solar energy technology and dynamic soaring technology, and works out the strategy of maximum energy gain. Small UAV flight dynamics model combined with solar power-energy system was built, choosing surround flight path at twilight moment for simulation validation. The advantages of small solar UAV using dynamic soaring technology in energy acquisition in hovering flight and pure dynamic gliding flight are verified, compared with traditional solar vehicle. The significance of combining the two energy acquisition technologies to improve the endurance of small UAV is proved, which provides a basis for further study of all-weather uninterrupted flight in the future.
Guidance Strategy for UAV Tracking Target Based on Reference Point Guidance Method
Authors: Tan Yanying , Tang Weixian
Published: May 2020

When the target is tracked based on the current traditional reference point guidance method by standoff mode, if the angle between the relative speed of the UAV and the target and the tangential direction of the corresponding point on the circular expected flight path of UAV is close to 90 degrees, and UAV is close to the desired path, the efficiency of the UAV converging to the circular desired path is not high enough. In this paper, the small angle hypothesis for reference point guidance method tracking desired circular path is studied. According to this, we designed a maneuvering entry guiding strategy for UAV standoff tracking fixed/moving target based on reference point guidance method. Simulation results show effectiveness of the guidance strategy. UAV might quickly converge to the circular desired path.
Obstacle Avoidance Path Planning of Space Redundant Manipulator Based on a Collision Detection Algorithm
Authors: Zhu Zhanxia , Jing Sa , Zhong Jianfei , Wang Mingming
Published: May 2020

This paper focuses on the path planning of free-floating space redundant manipulator in an environment with obstacles. Firstly, based on the idea of spherical bounding volume and spatial superposition, the spatial occupying relationship between obstacles and manipulators is described in a simpler way. Then the relative position relationship between straight line segment and sphere is used to judge whether a collision between the manipulator and the obstacle. With the principle of forward kinematics, we use the joint parameterization method to transform the path planning problem into a parameter optimization problem with constraints. In this optimization problem, the objective function is a weighted optimization objective function, which includes two terms, the first term describes the base attitude disturbance and the second one is established according to the requirement of avoidance collision. The motion trajectories of the manipulator joints can be obtained by solving the optimization problem using the particle swarm optimization algorithm. We choose a 7-DOF space redundant manipulator for simulation study, and simulation results show the effectiveness of the proposed method, there is no collision between the manipulator and obstacles, and there is no disturbance on the base attitude. What's more, the trajectory of the joint is smooth, which can make the end-effector reach the desired pose with a high accuracy.
A Neighbor Discovery Algorithm for UAV Networking Based on Directional Antennas
Authors: Hong Liang , Luo Pengtao , Yan Xiong , Chen Wu
Published: May 2020

Using directional antennas in Unmanned Aerial Vehicle (UAV) swarm has many advantages, such as longer transmission range, spatial reuse, anti-jamming and low probability of intercept. Neighbor discovery is a crucial step in the initialization of UAV networking. We introduce a neighbor discovery algorithm based on iterative common neighbors (ICN-ND), which can reduce the time of neighbor discovery process and the networking delay. To avoid the huge exchange-data quantity, we use the orientation and distance to represent the neighbor's location instead of latitude and longitude. Compared with the scan-based algorithm, the ICN-ND has better performance on the time to complete the neighbor discovery process and the convergence speed, which is validated the practicality by QualNet simulations.
Kinesiotaping Diminishes Delayed Muscle Soreness but does not Improve Muscular Performance
Authors: Camacho Maria Alejandra , Herrera Esperanza , Barela Jose Angelo , Delgado-Diaz Diana Carolina
Published: May 2020

This study aimed at determining the effect of kinesio-taping (KT) on muscle performance and delayed onset muscle soreness (DOMS) after exercise induced muscle damaged. Sixty-six healthy men volunteered to participate (age:18–25 y/o), who performed 200 isokinetic lengthening contractions of the dominant quadriceps. Then subjects were randomized to either control (no treatment), sham (no tape tension), or KT (10% tape tension) groups. Muscle performance was assessed by peak torque and muscular work during maximal isometric and concentric isokinetic contractions. DOMS intensity was assessed using a visual analog scale. Measurements were taken pre-exercise (Pre), 48 h and 96 h post-exercise. Repeated measures ANOVA was used for comparisons within group, and ANCOVA for comparisons among groups. Muscle damage was confirmed in all participants by an increase in CK activity level (p<0.01). Decrease in isometric and isokinetic peak torque was detected at 48 h in the control and sham groups (p<0.01). Muscular work decreased in all groups at 48 h (p<0.01). No differences between groups were detected in muscular performance variables. Increase in DOMS intensity was determined in all groups at 48 h. Comparisons between groups showed lower DOMS intensity in the KT group at 48 h. KT decreased DOMS intensity perception after exercise-induced muscle damage; however, it did not impact muscular performance.
Evolution of Functional Recovery using Hop Test Assessment after ACL Reconstruction
Authors: Rambaud Alexandre J.M. , Rossi Jérémy , Neri Thomas , Samozino Pierre , Edouard Pascal
Published: May 2020

The purpose of this study was to evaluate improvements in functional performance through the use of the Limb Symmetry Index of Single and Triple Hop tests between 12 and 52 weeks after anterior cruciate ligament reconstruction, and to compare these values with usual time-based and performance-based criteria used during the return to sport continuum. Repeated functional assessments using Single and Triple Hop Tests at 12, 16, 22, 26, 39 and 52 postoperative weeks were evaluated. At each session, the median and interquartile range of Limb Symmetry Index of tests were calculated and compared with the usual criteria: return to participation:≥85%, between 12–16 w; return to play:≥90%, between 26–39 w. The results indicate that the median increased over time to 39 postoperative weeks and then stabilized. For Single Hop Test, wide variability was seen at 12 and 16 weeks (interquartile range=20%); this was lower from 22 to 52 weeks (interquartile range=8–6%). At 12 weeks for Single Hop Test, the median was 83.6% and did not meet>85% criteria for return to participation. Hop tests could be interesting functional tests to follow the functional recovery and help decision-making regarding return to participation and return to play.
Low-Field Magnetic Resonance Imaging
Authors: Klein Hans-Martin
Published: May 2020

Background For more than two decades, the focus of technological progress in MRI was restricted to systems with a field strength of 1.5 T and higher. Low- and mid-field MRI systems, which offer some specific advantages, are vanishing from the market. This article is intended to initiate a re-evaluation of the factor ‘field strength’ in MR imaging.

Method Literature review was carried out using MEDLINE database (via Pubmed) over a time span from 1980 to 2019 using free-text and Medical Subject headings (MeSH). Article selection was based on relevance and evidence.

Results and Conclusion Low-field MR systems are meanwhile rare in clinical imaging. MRI systems with a lower field strength provide a reduced signal-noise ratio (SNR) and spectral differentiation. However, these systems offer a variety of advantages: Shorter T1 relaxation, better T1 contrast, fewer metal artifacts, reduced susceptibility and chemical shift artifacts, fewer dielectric effects, better tissue penetration, less RF-power deposition, fewer ‘missile effects’, reduced effect on biomedical implants such as shunt valves, less energy and helium consumption. If we free ourselves from the constraints of high-field strength, we are able to offer multiple medical, economic and ecologic advantages to our patients. The development of high-quality low-field MRI is possible and necessary.

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Citation Format
Periodontal Ligament Cell Sheets and RGD-Modified Chitosan Improved Regeneration in the Horizontal Periodontal Defect Model
Authors: Amir Lisa R. , Soeroso Yuniarti , Fatma Dewi , Sunarto Hari , Sulijaya Benso , Idrus Erik , Rahdewati Herlis , Tjokrovonco Angelia M. , Izumi Kenji , Abbas Basril , Latief Fourier D. E.
Published: May 2020

Objective The aim of this study was to examine the potential of periodontal ligament (PDL) cells sheet and arginine-glycyl-aspartic acid (RGD)-modified chitosan scaffold for periodontal tissue regeneration in horizontal periodontal defect model.

Materials and Methods PDL cell cytotoxicity was tested with 3–[4,5- dimethylthiazol-2yl]–2,5-diphenyl-2H-tetrazolium bromide assay. Cell migration toward the chitosan-based materials was analyzed with trans-well migration assay. Horizontal periodontal defect model was created in four maxillary and mandibular lateral incisors of Macaque nemestrina. Following periodontal therapy, the sites were transplanted with various regenerative materials: (1) chitosan, (2) RGD-modified chitosan, (3) PDL cell sheet with chitosan, (4) PDL cell sheet with RGD-modified chitosan. The periodontal tissue regeneration was evaluated clinically and radiographically. Gingival crevicular fluids were collected each week to evaluate cementum protein-1 (CEMP-1) expression with enzyme-linked immunosorbent assay, while the biopsies were retrieved after 4 weeks for histological and microcomputed tomography evaluation.

Statistical Analysis Data was statistically analyzed using GraphPad Prism 6 for MacOS X. Normality was tested using the Shapiro–Wilk normality test. The Kruskal–Wallis test was used to compare the groups. Significance was accepted when p < 0.05.

Results Clinical examination revealed more epithelial attachment was formed in the group with PDL cell sheet with RGD-modified chitosan. Similarly, digital subtraction radiography analysis showed higher gray scale, an indication of higher alveolar bone density surrounded the transplanted area, as well as higher CEMP-1 protein expression in this group. The incorporation of RGD peptide to chitosan scaffold in the group with or without PDL cells sheet reduced the distance of cement–enamel junction to the alveolar bone crest; hence, more periodontal tissue formed.

Conclusions Horizontal periodontal defect model could be successfully created in M. nemestrina model. Combination of PDL cell sheet and RGD-modified chitosan resulted in the higher potential for periodontal tissue regeneration. The results of this study highlight the PDL cell sheet and RGD-modified chitosan as a promising approach for future clinical use in periodontal regeneration.
Relationship of Peak Expiratory Flow Rate with Waist Circumference, Hip Circumference, and Waist-to-Hip Ratio in Young Adults
Authors: Rai Richa Hirendra , Gupta Shailly , Mohd Asif
Published: May 2020

Introduction It has been observed that respiratory problems and the consequent pulmonary dysfunction are associated with an increase in waist circumference (WC), a measure of obesity. Both comorbidities result in changes in the overall health, quality of life, and life span. The literature shows that body fat distribution can affect pulmonary function. Pulmonary function test (PFT) is a basic and essential tool for the diagnosis and assessment of pulmonary dysfunction, lung diseases, and treatment effects. However, the facilities to measure PFT are not readily available for individual use. Peak expiratory flow rate (PEFR) is a simple and important biomarker that can measure the pulmonary function and can help monitor lung function to initiate early preventive measure. PEFR can be measured by a portable device, which can be carried anytime anywhere. Using this portable instrument, this study was undertaken to investigate whether there is any relationship of PEFR with the biomarkers of obesity, such as WC, hip circumference (HC), and waist-to-hip ratio (WHR) in young adults.

Materials and Methods A total of 84 participants of either sex (38 males and 46 females) aged 20 to 26 years were recruited from a college of South Delhi. Demographic and anthropometric data regarding WC, HC, and WHR were recorded. For PEFR, three consecutive measurements were taken at about 2-minute intervals, and the maximum of the three values was taken into account.

Results Though not statistically significant, but a tendency of negative correlation was observed between PEFR and WC (r = –0.43) and between PEFR and WHR (r = –0.48) in males. However, no significant correlation of PEFR with any of the obesity markers was found in females. No correlation was observed between PEFR and HC in the participants of either sex.

Conclusion PEFR may be adversely affected with increase in WC and WHR, as seen in males. However, no association was observed between PEFR and HC in participants of either sex.
On the illposedness and stability of the relativistic heat equation
Authors: García-Perciante A. L. , Reula O.
Published: May 2020

In this article, we analyze, in terms of a simple example, the incompatibility of parabolic evolution and general covariance. For this, we introduce a unit time-like four-vector and study the simplest heat flux equation with respect to it. In cases where this vector field is surface forming, then the local high wave number limit shows well posedness, but as soon as that property is lost, the Cauchy problem becomes ill-posed. We also discuss how the Maxwell–Cattaneo type modification of the system renders it well posed and link the amplitude of the modification, which is related to the so-called second wave speed of the system, to the size of the failure of surface orthogonality.
Generation of energetic ring-shaped ion beam from relativistic Laguerre–Gaussian laser pulse interacting with micro-structure targets
Authors: Zhang H. , Zhang G. B. , Zou D. B. , Hu L. X. , Zhou H. Y. , Wang W. Q. , Xu X. R. , Liu K. , Yin Y. , Zhuo H. B. , Shao F. Q. , Yu T. P.
Published: May 2020

By using three-dimensional particle-in-cell simulations, we demonstrate that an energetic ring-shaped ion beam can be generated by an ultra-intense circularly polarized Laguerre–Gaussian laser pulse interacting with micro-structure targets. The electron and ion dynamics of three different targets including a sleeve–wire target, wire target, and common planar target are investigated. It is found that an optimized sleeve–wire target can provide a remarkable increase in the maximum ion energy and laser-to-ion energy conversion efficiency. The reason can be attributed to the matched transverse profiles between the electric-field distribution of Laguerre–Gaussian laser and sleeve–wire structure, resulting in efficient laser-target energy coupling. In fact, using a laser pulse of intensity 2.74 ×1020 W/cm2, duration 66.7 fs, and energy ∼1 J, one can obtain ∼35 MeV protons, ∼5.8 MeV/u carbon ions, and ∼15% laser-to-ion energy conversion.
Effect of interparticle electrostatic interactions on the dielectric response of 0–3 connectivity particle/polymer composites for high energy density storage
Authors: Zhong Shao-Long , Cai Ziming , Zha Jun-Wei , Zhao Yu , Dang Zhi-Min
Published: May 2020

Polymer composites with high energy density have been of great interest to scientists for a long time, and this accounts for a great wealth of experimental data that are available for interpretation. One of the important phenomena is the variation rate of the permittivity of composites, which always deviates from the linear increase and rises steeply toward the high concentration. Interestingly, the critical transition concentration is always located in the range of 20 vol. %–25 vol. %, but still far less than the common percolation threshold of composites. Through the analysis of the local electric field distribution and surface polarized charges distribution, the phenomenon is successfully interpreted as the effect of the electrostatic interactions between the adjacent polarized particles. Two specified composite configurations (BCC and FCC) are designed, and their dielectric properties have been systematically studied with the help of the finite element method and the phase field method. The simulation results indicate that the strength of the particles’ interaction is short-range effective and depends closely on the gap distance between adjacent particles. When the gap distance is smaller than 0.8 times the radius of the particles, which is tantamount to the concentration larger than 20 vol. % and 25 vol. % for BCC and FCC, respectively, the electrostatic interaction of the particles is rather significant, resulting in an additional contribution on the variation of the dielectric properties of composites and vice versa. The synchronous variation tendency between the simulation results and experimental measurements demonstrates the effect of electrostatic interaction on the dielectric properties of composites.
Entropy production and fluctuation theorems on complex networks
Authors: Jung Jaewoo , Um Jaegon , Lee Deokjae , Kim Yong W. , Lee D. Y. , Pak H. K. , Kahng B.
Published: May 2020

Entropy production (EP) is a fundamental quantity useful for understanding irreversible process. In stochastic thermodynamics, EP is more evident in probability density functions of trajectories of a particle in the state space. Here, inspired by a previous result that complex networks can serve as state spaces, we consider a data packet transport problem on complex networks. EP is generated owing to the complexity of pathways as the packet travels back and forth between two nodes along the same pathway. The total EPs are exactly enumerated along all possible shortest paths between every pair of nodes, and the functional form of the EP distribution is proposed based on our numerical results. We confirm that the EP distribution satisfies the detailed and integral fluctuation theorems. Our results should be pedagogically helpful for understanding trajectory-dependent EP in stochastic processes and exploring nonequilibrium fluctuations associated with the entanglement of dividing and merging among the shortest pathways in complex networks.
Improvements in fluorescence techniques enhance studies of cell membranes
Authors: Bandari Anashe
Published: May 2020

Cell membrane structures and dynamics remain only partially understood, but combining various fluorescence techniques will help characterize different properties and their correlations.
Highly sensitive resonant sensor using quartz resonator cluster for inclination measurement
Authors: Chen Fubin , Tian Wenjie , Wei Ying
Published: May 2020

Quartz crystal resonators are suitable for digital output sensors due to their sensitivity to force. This paper presents a highly sensitive inclinometer sensor with a quartz resonator cluster. The force sensitive resonator cluster is designed on the quartz substrate to eliminate common-mode disturbances, such as temperature, as well as to improve sensitivity to force. The inclinometer sensor comprises two quartz resonator clusters that form a push–pull structure. The difference in inclination causes gravitational acceleration to produce an axial force along the input axis, with the resonance frequency shifting in proportion to the axial force. A signal processing and fusion scheme for the inclinometer sensor is presented and then tested. The results show that the scale factor of the sensor prototype is 3.5102 Hz/1′ and that nonlinearity is 1.040% full scale in the range of −2°–+2°. The resolution of the inclinometer sensor is better than 0.0055°, making these devices a potentially attractive option for numerous precision inclination measurement applications.
Toward the laser control of electronic decoherence
Authors: Hu Wenxiang , Gu Bing , Franco Ignacio
Published: May 2020

Controlling electronic decoherence in molecules is an outstanding challenge in chemistry. Recent advances in the theory of electronic decoherence [B. Gu and I. Franco, J. Phys. Chem. Lett. 9, 773 (2018)] have demonstrated that it is possible to manipulate the rate of electronic coherence loss via control of the relative phase in the initial electronic superposition state. This control emerges when there are both relaxation and pure-dephasing channels for decoherence and applies to initially separable electron–nuclear states. In this paper, we demonstrate that (1) such an initial superposition state and the subsequent quantum control of electronic decoherence can be created via weak-field one-photon photoexcitation with few-cycle laser pulses of definite carrier envelope phase (CEP), provided the system is initially prepared in a separable electron–nuclear state. However, we also demonstrate that (2) when stationary molecular states (which are generally not separable) are considered, such one-photon laser control disappears. Remarkably, this happens even in situations in which the initially factorizable state is an excellent approximation to the stationary state with fidelity above 98.5%. The laser control that emerges for initially separable states is shown to arise because these states are superpositions of molecular eigenstates that open up CEP-controllable interference routes at the one-photon limit. Using these insights, we demonstrate that (3) the laser control of electronic decoherence from stationary states can be recovered by using a two-pulse control scheme, with the first pulse creating a vibronic superposition state and the second one inducing interference. This contribution advances a viable scheme for the laser control of electronic decoherence and exposes a surprising artifact that is introduced by widely used initially factorizable system-bath states in the field of open quantum systems.
Magnetocaloric effect in exchange-coupled strong/weak/strong ferromagnet stacks
Authors: Kuznetsov M. A. , Pashenkin I. Y. , Polushkin N. I. , Sapozhnikov M. V. , Fraerman A. A.
Published: May 2020

We study the magnetocaloric effect in layered systems composed of a ferromagnet with a relatively low Curie temperature (TC), which is sandwiched by stronger ferromagnets and exchange coupled to them across the interfaces. Switching of magnetization in the softer ferromagnetic surrounding in an applied magnetic field (H) of the strength in several tens of oersteds provides the isothermal magnetic entropy change (Δs) in the system because of magnetization redistribution in the spacer. Our simulations of these effects we present here reveal the maximal value of Δs, obtained at a realistic interfacial exchange constant, which is in quantitative agreement with this quantity observed experimentally in different heterosystems based on the NixCu100 − x (x ∼ 70 at. %) spacer.
Magnetic properties of rare-earth and transition metal based perovskite type high entropy oxides
Authors: Witte Ralf , Sarkar Abhishek , Velasco Leonardo , Kruk Robert , Brand Richard A. , Eggert Benedikt , Ollefs Katharina , Weschke Eugen , Wende Heiko , Hahn Horst
Published: May 2020

High entropy oxides (HEOs) are a recently introduced class of oxide materials, which are characterized by a large number of elements (i.e., five or more) sharing one lattice site, which crystallize in a single phase structure. One complex example of the rather young HEO family is the rare-earth transition metal perovskite high entropy oxides. In this comprehensive study, we provide an overview of the magnetic properties of three perovskite type high entropy oxides. The compounds have a rare-earth site that is occupied by five different rare-earth elements, while the transition metal site is occupied by a single transition metal. In this way, a comparison to the parent binary oxides, namely, the orthocobaltites, -chromites, and -ferrites, is possible. X-ray absorption near edge spectroscopy, magnetometry, and Mössbauer spectroscopy are employed to characterize these complex materials. In general, we find surprising similarities to the magnetic properties of the binary oxides despite the chemical disorder on the rare-earth site. However, distinct differences and interesting magnetic properties are also observed such as noncollinearity, spin reorientation transitions, and large coercive fields of up to 2 T at ambient temperature. Both the chemical disorder on the rare-earth A-site and the nature of the transitional metal on the B-site play an important role in the physical properties of these high entropy oxides.
Transition to chaos for buoyant flows in a groove heated from below
Authors: Qiao Manman , Tian Zhao Feng , Yang Qingshan , Xu Feng
Published: May 2020

In this paper, the transition to chaos for buoyant flows in a groove heated from below is analyzed using a three-dimensional numerical model. With a Prandtl number of 0.71 and an aspect ratio of 0.5, numerical simulations are performed for Rayleigh number Ra from 100 to 105. This wide range covers the transition process to chaos, the first change being the instability of the primary steady symmetric flow in the form of a symmetry-breaking pitchfork bifurcation between Ra = 1.5 × 103 and 1.6 × 103 that tilts the buoyant flow toward one or the other sidewall of the groove. A second pitchfork bifurcation to the three-dimensional flow occurs between Ra = 5.3 × 103 and 5.4 × 103. A Hopf bifurcation is observed between Ra = 5.6 × 103 and 5.7 × 103 at which the buoyant flow in the groove becomes temporally periodic; this is followed by a sequence of further bifurcations including period-doubling and quasi-periodic bifurcations. Finally, the buoyant flow becomes chaotic when bulge motion appears along the groove between Ra = 6.5 × 103 and 6.6 × 103. Limit points, limit cycles, attractors, maximum Lyapunov exponents, and power spectral density are presented to analyze typical buoyant flows in the transition to chaos. Additionally, the heat and mass transfer is quantified for the different regimes.
A novel stick-slip piezoelectric actuator based on two-stage flexible hinge structure
Authors: Li Zheng , Zhao Liang , Yu Xuze
Published: May 2020

The traditional stick-slip piezoelectric actuator uses a single flexible hinge structure, and the output force of the piezoelectric stack is greater than the clamping force between the driving foot and the slider, resulting in a small working stroke, slow speed, and poor load capacity. A new piezoelectric actuator based on a two-stage flexible hinge structure is proposed. The piezoelectric actuator uses a combination of a lever flexible hinge and a triangular flexible hinge. The working stroke and speed of the actuator are enlarged by the lever flexible hinge, and the output force of the piezoelectric stack is perpendicular to and greater than the clamping force between the driving foot and the slider through the triangular flexible hinge, which enhances the load capacity of the actuator. First, the structure and working principle of the piezoelectric actuator are presented. The lateral output displacement of the piezoelectric ceramic stack is amplified by the lever amplification structure so that the triangular flexible hinge structure is then used to convert the lateral displacement into a coupled motion composed of longitudinal and lateral displacement to drive the slide rail to generate total displacement. Then, the superiority of the piezoelectric actuator was verified through the analysis of displacement amplification and clamping force and finite element analysis. Finally, the performance of the piezoelectric actuator is studied. It can produce an output speed of 354.55 mm/s under a driving voltage of 4.7 kHz and 150 V, and the maximum load can reach 3 kg. This article provides a new design idea for stick-slip piezoelectric actuators.
Three-dimensional simulation of wind tunnel diffuser to study the effects of different divergence angles on speed uniform distribution, pressure in outlet, and eddy flows formation in the corners
Authors: Li Zhixiong , Moradi Iman , Nguyen Quyen , Karimipour Arash , Afrand Masoud , Tlili Iskander , Incecik Atilla
Published: May 2020

Despite the widespread use of diffusers in various industries, there is no comprehensive research so far. This is expressive on how the flow diffuses throughout the diffuser geometry, the amount of non-uniformity of speed distribution at the outlet, and the rate of eddy flows at the corners. The present study simulated a three-dimensional diffuser with a square geometry at different divergence angles in order to obtain a better understanding of the flow diffusion across the geometry, velocity distribution at the outlet, and reverse flow. Moreover, the aspect ratio and the Reynolds number were considered constant in all cases. The turbulence model was used along with a high-resolution discretization and a root-mean-square convergence criterion to solve this problem. The speed was substantially reduced to nearly zero at corners of the diffuser with a square cross section. Reverse flow and eddy currents were also observed in the same regions. By increasing the divergence angle, this effect was further intensified, and in addition to the corners, flow separation and eddy currents were formed in the regions close to the wall due to the adverse pressure gradient. The maximum velocity and flow distribution at the outlet cross section was located in the central region, which was intensified by increasing the divergence angle. The deviation of the average velocity at the diffuser outlet with a divergence angle of 5°, with a completely uniform velocity distribution at the outlet, was observed to be 15.3%. This deviation grew with an increase in divergence angle and reached 128.9% at a divergence angle of 30°.
Highly tunable thermal conductivity of C3N under tensile strain: A first-principles study
Authors: Taheri Armin , Da Silva Carlos , Amon Cristina H.
Published: May 2020

In this study, the phonon thermal transport in monolayer C3N under biaxial strains ranging from 0% to 10% has been investigated using first-principles calculations based on the Boltzmann transport equation. It is found that the thermal conductivity κ of C3N shows a nonmonotonic up-and-down behavior in response to tensile strain, and the maximum κ occurs at a strain of 6%. Interestingly, the thermal conductivity of monolayer C3N shows a remarkable high strain tunability, as its value at 6% strain is about 13.2 times higher than the value of κ in an unstrained monolayer. A mode-by-mode phonon level analysis shows that a competition between different phonon properties is responsible for such variations in the thermal conductivity. We found that the decrease in group velocity of the transverse acoustic, longitudinal acoustic, and optical modes as well as the increase in the three-phonon phase space of all the acoustic modes tend to reduce the thermal conductivity with strain. However, the group velocity of the z-direction acoustic mode and the Grüneisen parameter of all acoustic modes change in the direction of increasing the phonon lifetime and the thermal conductivity with increasing strain. Upon stretching, the change in the Grüneisen parameter and the phonon lifetime of the acoustic modes is found to be drastically higher than the change in other properties. The competition between these opposite effects leads to the up-and-down behavior of the thermal conductivity in C3N.
Structure functions and invariants of the anisotropic Reynolds stress tensor in turbulent flows on water-worked gravel beds
Authors: Penna Nadia , Padhi Ellora , Dey Subhasish , Gaudio Roberto
Published: May 2020

In this paper, a statistical description of turbulence in flow on a water-worked gravel-bed is presented by applying the laws of turbulence in conjunction with the double-averaging methodology. To this end, a laboratory experiment was performed, in which the gravel-bed was worked by flowing water. From the Taylor frozen-in approximation, the energy spectra of streamwise velocity fluctuation reveal the existence of the inertial subrange (lying between the energy containing and the dissipation ranges), where the turbulent kinetic energy (TKE) dissipation rate is constant. It is revealed that, in this range, Kolmogorov’s 4/5-law for the spatial increments of streamwise velocity is valid, thus allowing an accurate estimation of the TKE dissipation rate. Although Monin–Yaglom’s 4/3-law for the third-order mixed structure function provides a behavior similar to that of Kolmogorov’s 4/5-law, the estimation of the TKE dissipation rate by Monin–Yaglom’s 4/3-law is not quite accurate, owing to the departure from the isotropic turbulence at large scales. Therefore, the present study demonstrates the validity of this statistical approach (Kolmogorov’s 4/5-law) to investigate the turbulence at small scales. Besides, the data plots for an anisotropy invariant map suggest that near-bed anisotropic turbulence tends to reduce to the three-dimensional isotropic turbulence with an increase in the vertical distance, indicating a relaxation of the effects of bed roughness on anisotropic turbulence toward the free surface.
Self-reproducing chaos and bursting oscillation analysis in a meminductor-based conservative system
Authors: Yuan Fang , Jin Yuan , Li Yuxia
Published: May 2020

In this paper, a new meminductor model with sine function is presented. Based on this meminductor and a capacitor, a simple conservative chaotic system is designed. The proposed system has rich dynamic characteristics, including zero divergence, self-reproducing chaos, bursting oscillations, and symmetric Lyapunov exponent spectra. The corresponding mechanisms of these dynamic behaviors are analyzed theoretically. Furthermore, Multisim simulations and experimental circuit are performed to verify the numerical results.