bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulent scalar fluxes from a generalized Langevin model: Implications on mean scalar mixing and tracer particle dispersion
Authors: Naud Bertrand , Roekaerts Dirk
Published: March 2021

A Generalized Langevin Model (GLM) formulation to be used in transported joint velocity-scalar probability density function methods is recalled in order to imply a turbulent scalar-flux model where the pressure-scrambling term is in correspondence with standard Monin's return-to-isotropy term. The proposed non-constant C0 formulation is extended to seen-velocity models for particle dispersion modeling in dispersed two-phase flows. This allows us to correct the wrong turbulent scalar-flux modeling in the limit of tracer particles. Moreover, this allows us to have a more general formulation in order to consider advanced Reynolds-stress models. The cubic model of Fu, Launder, and Tselepidakis is considered, together with the model of Merci and Dick for turbulent dissipation. Results are presented for different swirling and recirculating single-phase and two-phase flows, showing the capabilities of the proposed non-constant C0 GLM formulations compared to the standard GLM.
Engineering Schottky-to-Ohmic contact transition for 2D metal–semiconductor junctions
Authors: Ding Xiang , Zhao Yang , Xiao Haiyan , Qiao Liang
Published: March 2021

An Ohmic contact is critical for achieving 2D material-based high performance electronic devices. Unfortunately, the formation of an intrinsic Ohmic contact for 2D materials is difficult; thus, current studies mostly stay in the Schottky regime. In this work, density functional calculations are performed for work function engineering for metal–semiconductor junctions involving 2D H-WSe2 and 2D metals of MX2 (M = Ti, V, Nb, Ta, Mo, and W and X = S and Se). We unambiguously identify a Schottky-to-Ohmic contact transition boundary, beyond which p-type Ohmic contacts are demonstrated to be stable. We show that the Fermi level pinning effect is relatively weak in the Schottky region, while similar pinning-like behavior is strong in the Ohmic region, creating a discontinuity near the contact transition boundary. The observed deviation from the ideal Schottky–Mott limit is directly related to the charge redistribution and interface dipole-induced potential step, reflected by metal work function modification due to contact formation. Our work not only provides a strategy to identify effective Ohmic contacts but also offers insights for prospection into the fundamental electronic properties of van der Waals-based heterojunctions.
Mechanical strain mapping of GaAs based VCSELs
Authors: Mokhtari Merwan , Pagnod-Rossiaux Philippe , Levallois Christophe , Laruelle François , Cassidy Daniel T. , Bettiati Mauro , Landesman Jean-Pierre
Published: March 2021

We report an investigation of the strain field in mesa structures for oxide-confined vertical-cavity surface-emitting lasers (VCSELs) using the polarization-resolved micro-photoluminescence (PL) measurement of the degree of polarization (DOP) at room temperature. The DOP of the PL is correlated with the spatial distribution of the embedded anisotropic strain in a VCSEL structure. Measurements normal to (100) surfaces of the samples and from (110) cross-sectional planes were performed. The effect of two processes required in the fabrication of GaAs-based VCSELs was studied: the plasma etching of the P-doped distributed Bragg reflector and the wet oxidation process used to control current flow and lateral optical confinement. The DOP method allows very sensitive measurements of the mechanical strain (on the order of 10−5) accumulated in VCSEL devices even during different steps of the fabrication process.
Electronic transport in molecular junctions: The generalized Kadanoff–Baym ansatz with initial contact and correlations
Authors: Tuovinen Riku , van Leeuwen Robert , Perfetto Enrico , Stefanucci Gianluca
Published: March 2021

The generalized Kadanoff–Baym ansatz (GKBA) offers a computationally inexpensive approach to simulate out-of-equilibrium quantum systems within the framework of nonequilibrium Green’s functions. For finite systems, the limitation of neglecting initial correlations in the conventional GKBA approach has recently been overcome [Karlsson et al., Phys. Rev. B 98, 115148 (2018)]. However, in the context of quantum transport, the contacted nature of the initial state, i.e., a junction connected to bulk leads, requires a further extension of the GKBA approach. In this work, we lay down a GKBA scheme that includes initial correlations in a partition-free setting. In practice, this means that the equilibration of the initially correlated and contacted molecular junction can be separated from the real-time evolution. The information about the contacted initial state is included in the out-of-equilibrium calculation via explicit evaluation of the memory integral for the embedding self-energy, which can be performed without affecting the computational scaling with the simulation time and system size. We demonstrate the developed method in carbon-based molecular junctions, where we study the role of electron correlations in transient current signatures.
Spin wave propagation in corrugated waveguides
Authors: Turčan Igor , Flajšman Lukáš , Wojewoda Ondřej , Roučka Václav , Man Ondřej , Urbánek Michal
Published: March 2021

Curvature-induced effects allow us to tailor the static and dynamic response of a magnetic system with a high degree of freedom. We study corrugated magnonic waveguides deposited on a sinusoidally modulated substrate prepared by focused electron beam-induced deposition. The curvature of the waveguides with thicknesses comparable to the amplitude of modulation modifies the contributions of dipolar and exchange energies and results in an effective anisotropy term, which is strong enough to overcome the shape anisotropy. At zero external magnetic field, the magnetization of the waveguide then points perpendicular to its long axis in a geometry, which is best-suited to spin-wave propagation. We show, by Brillouin light scattering microscopy, that without the presence of the external magnetic field, spin waves propagate over a distance 10×larger in the corrugated waveguide than in the planar waveguide. We further analyze the influence of the modulation amplitude on the spin-wave propagation length and conclude that for moderate modulation amplitudes, the spin-wave decay length is not affected. For larger amplitudes, the decay length decreases linearly with increasing modulation. The presented approach opens many possibilities for the design of complex 2D magnonic circuits where the waveguides can be oriented in any direction and placed anywhere on the sample while still allowing spin-wave propagation with the same efficiency.
Effect of disruption of anode potential symmetrical supply on Hall thruster discharge
Authors: Ding Minghao , Li Hong , Ding Yongjie , Wei Liqiu , Mao Wei , Han Liang , Yu Daren
Published: March 2021

During a long-term discharge of a Hall thruster, local overheating on the anode surface occurs and its location shifts randomly. The asymmetrical supply of anode potential is thought to be the cause. To investigate their relationship, a bias voltage is applied on one piece of a quartered anode to realize the asymmetrical supply of anode potential. Variations of both the current and temperature of each anode piece are measured and analyzed. The results indicate that the disruption of the anode potential symmetrical supply does not affect the total anode current; however, it enhances the current oscillation. As the bias voltage increases, the current concentrates gradually on the high-potential part of the anode, accompanied by an increase in the local temperature. Changes in the Ez × Br drift direction, magnetic field strength, discharge voltage, and anode flow rate do not affect the above-mentioned laws. Preliminary analysis shows that the formation of a local electric field near the anode and the generation of an extra Eθ × Br drift are the main causes, which can affect the movement of electrons in the near-anode region greatly.
Wetting transition and phase separation on flat substrates and in porous structures
Authors: Wang Fei , Nestler Britta
Published: March 2021

In contrast to the wetting phenomenon of pure substance phase, we here concentrate on the wetting behavior of immiscible fluids with two components via numerical simulations. We investigate the energetic contribution, the wall energy and the surface excess energy, to the wetting behavior of liquid solutions varying with temperature. This investigation is in accordance with Cahn’s wetting transition theory, where the surface composition plays a vital role. By analyzing the energetic contributions, we reveal two different physical mechanisms of complete wetting: (i) surface tension driven complete wetting, where the wetting microstructure is achieved via the outward spreading of the triple junction, and (ii) diffusion induced complete wetting, where the wetting film is achieved through a direct deposition of the solute on the substrate. The former one is consistent with the classic theory of Young’s law, and the latter one is an alternative mechanism. To indicate the broad multiplicity of the microstructural arrangements, we take porous structures to exemplarily elucidate the formation of alternative perfect wetting structures. Differing from the wetting on a flat substrate, we show that the surface composition varying with temperature leads to a distinct wetting phenomenon in porous structures. The present findings provide an alternative interpretation for complete wetting and are expected to be exploited for designing more effectively and efficiently superhydrophilic structures.
Selective constraints on global plankton dispersal
Authors: Ward Ben A. , Cael B. B. , Collins Sinead , Young C. Robert
Published: March 2021

Significance

Microscopic plankton form the ecological and biogeochemical foundation of almost all marine ecosystems. In the fluid ocean environment, biodiversity and community structure are determined by the poorly constrained balance of local selection and global dispersal. While ocean currents have the capacity to rapidly connect distant locations, we use numerical simulations to show that extremely high rates of adaptation are required for populations to traverse large-scale gradients in environmental variables such as temperature. Changing the assumed balance of selection, adaptation, and dispersal in our simulations has pronounced effects on the simulated community structure, accounting for emergent patterns in the global ocean microbiome and emphasizing the importance of evolutionary history in global marine biodiversity and biogeography.
Nonthermal and reversible control of neuronal signaling and behavior by midinfrared stimulation
Authors: Liu Xi , Qiao Zhi , Chai Yuming , Zhu Zhi , Wu Kaijie , Ji Wenliang , Li Daguang , Xiao Yujie , Mao Lanqun , Chang Chao , Wen Quan , Song Bo , Shu Yousheng
Published: March 2021

Significance

Infrared neural stimulation (INS) is an emerging technology for neuromodulation and holds promise for clinical application. While most INS studies have been conducted at near-infrared wavelengths, whether midinfrared light with frequencies matching the chemical bond vibration of biomolecules can influence neuronal function remains unknown. We found that midinfrared light with low water absorption provides nonthermal and reversible modulation of neuronal spiking activity and sensorimotor behavior. Nonlinear resonance between light and chemical bond vibration at the selectivity sieve of the K
+
channel directly enhances ion conductivity and thus regulates AP waveform and spiking activity. Together, our results reveal nonthermal effects of MIRS on functional biomolecules, neuronal signaling, and behavior state. Therefore, MIRS could serve as a form of physical neuromodulation.
Comparative parallel analysis of RNA ends identifies mRNA substrates of a tRNA splicing endonuclease-initiated mRNA decay pathway
Authors: Hurtig Jennifer E. , Steiger Michelle A. , Nagarajan Vinay K. , Li Tao , Chao Ti-Chun , Tsai Kuang-Lei , van Hoof Ambro
Published: March 2021

Significance

The transfer RNA (tRNA) splicing endonuclease (TSEN) has a well-known role in cleaving pre-tRNAs to remove introns, but has other uncharacterized functions. Here we show that yeast TSEN cleaves several mRNAs that encode mitochondrial proteins, and that the cleavage sites are in part determined by their sequence. This provides an explanation for the counterintuitive mitochondrial localization of yeast TSEN. Human patients that inherit mutations in TSEN are born with pontocerebellar hypoplasia, which may be because of a defect in the mRNA cleavage functions of TSEN. The similarity of this TSEN-initiated decay pathway to other mRNA decay pathways suggests that mRNA specificity by colocalization may be an important determinant for the degradation of localized mRNAs in a variety of eukaryotic cells.
Structural basis for IFN antagonism by human respiratory syncytial virus nonstructural protein 2
Authors: Pei Jingjing , Wagner Nicole D. , Zou Angela J. , Chatterjee Srirupa , Borek Dominika , Cole Aidan R. , Kim Preston J. , Basler Christopher F. , Otwinowski Zbyszek , Gross Michael L. , Amarasinghe Gaya K. , Leung Daisy W.
Published: March 2021

Significance

The human respiratory syncytial virus (RSV) is a significant cause of lower respiratory tract infections in the young and the elderly and a substantial burden to global human health. Currently, there are no specific and effective treatments for RSV infections. Here we report the first X-ray crystal structure of RSV nonstructural protein 2 (NS2), which revealed a unique fold. The combined biochemical and structural analyses of the NS2 structure identified a region that binds to and inhibits ubiquitination of an inactive form of RIG-I and MDA5, preventing downstream signaling and type I interferon production. Our study provides structural insight into the mechanism of how NS2 antagonizes IFN response to RSV infection and defines a target for antiviral development.
Posttranslational regulation of multiple clock-related transcription factors triggers cold-inducible gene expression in
Arabidopsis
Authors: Kidokoro Satoshi , Hayashi Kentaro , Haraguchi Hiroki , Ishikawa Tomona , Soma Fumiyuki , Konoura Izumi , Toda Satomi , Mizoi Junya , Suzuki Takamasa , Shinozaki Kazuo , Yamaguchi-Shinozaki Kazuko
Published: March 2021

Significance

The DREB1/CBF transcription factors function as master switches for cold stress adaptation in
Arabidopsis
. Cold stress strongly induced the
DREB1
genes, and elucidation of the mechanisms of
DREB1
induction is important to clarify the cold stress responses in plants. We revealed that the clock-related MYB proteins RVE4 and RVE8 were quickly transferred from the cytoplasm to the nucleus in response to cold stress and functioned as direct transcriptional activators of
DREB1
expression. The other clock-related MYB proteins, CCA1 and LHY, suppressed
DREB1
expression under unstressed conditions and were rapidly degraded under cold stress, which suggests that these factors indirectly regulate cold-inducible
DREB1
expression. We concluded that posttranslational regulation of the clock-related transcription factors triggered cold-inducible gene expression.
Chemically controlled pattern formation in self-oscillating elastic shells
Authors: Li Siyu , Matoz-Fernandez Daniel A. , Aggarwal Aaveg , Olvera de la Cruz Monica
Published: March 2021

Significance

Mechanochemical processes drive various biological functions including morphogenesis and morphological changes in responsive synthetic hydrogels. By allowing reactive components to function in an elastic closed shell, autonomous chemical reactions generate microcompartments capable of expanding or contracting or induce buckled patterns. This capability can drive specific functions such as enhancing the rate of diffusion of compartmentalized chemicals or releasing cargos at specific rates. Here, we demonstrate the coupling of mechanical response to autonomous chemical reactions in elastic shells which swell and deswell to generate specific dynamic patterns and morphologies. The reverse feedback from the mechanical input triggers the chemical reaction. Our work inspires the design of responsive shells to enhance the functionality of microcompartments and nanoreactors.
Even Americans pre-aspirate
Authors: Hejná Míša , Kaźmierski Kamil , Guo Wenyu
Published: March 2021

This paper focuses on a phenomenon known as pre-aspiration, defined as a period of glottal friction found in the sequences of sonorants and phonetically voiceless obstruents, as inhit[hɪht],hat[hæht],hiss[hɪhs], andcash[kæhʃ]. Pre-aspiration has been reported in North American English (Clayards and Knowles 2015); however, there are no systematic studies of pre-aspiration in this part of the English-speaking world. Our study therefore considers the following main questions. 1. Is pre-aspiration present in American English and how frequent is it? 2. Does it vary by region? We also map variation related to speaking task, sex, and a range of language-internal factors. Our analyses of data from the Nationwide Speech Project Corpus (Clopper and Pisoni 2006) confirm that pre-aspiration is a feature of American English, with rates of application reaching between 0–20 percent, depending on the region and the task. Furthermore, the more formal the task, the higher the rate of pre-aspiration application.
Introduction
Authors: Betz Emma , Sorjonen Marja-Leena
Published: March 2021

This chapter sets the context for the articles in the
volume – explorations in the use of OKAY in a diverse set of languages,
including American English, Brazilian Portuguese, Danish, Estonian, Finnish,
French, German, Italian, Japanese, Korean, Mandarin, Polish, and Swedish. We
first outline the origins of OKAY in American English and its spread to
other languages as a loanword, motivating this study of OKAY. We then review
the state of the art in research on OKAY in spoken interaction in a variety
of settings. Since this volume makes a case for investigating OKAY
empirically as it is actually used in particular occasions of spoken and
embodied interaction, the review of existing work on OKAY will be connected
to relevant developments in Conversation Analysis (Sidnell 2010; Clift 2016) and Interactional Linguistics (Couper-Kuhlen and Selting 2018). We
close with a discussion of overarching themes and promising new research
directions that emerge from existing work.
Data and methods used in the study of OKAY across languages
Authors: Deppermann Arnulf , Mondada Lorenza
Published: March 2021

In this chapter, we overview the specificity of
comparisons made within the perspective of Conversation Analysis (CA), and
we position them in relation to other fields. We introduce the analytical
mentality, methodology, and procedures of CA, and we show how we used it for
the analysis of OKAY in this volume.
A resource for action transition
Authors: De Stefani Elwys , Mondada Lorenza
Published: March 2021

This chapter examines French
oké and Italian occhei
as resources with which interactants manage transitions from
one course of action to another. It analyzes different kinds of
institutional interactions, such as work meetings, political
assemblies, and guided visits in French and Italian. In these
settings, participants use OKAY within extended “transition phases”,
situated in specific multimodal, material and spatial environments.
This chapter shows that the sequential positions of OKAY are
sensitive to co-occurring embodied conduct, giving rise to complex
multimodal arrangements. Transitions from one course of action to
another are multimodally accomplished within the local ecology of
the interaction: the use of OKAY plays a crucial part in this
accomplishment.
OKAY projecting embodied compliance to directives
Authors: Keevallik Leelo , Weidner Matylda
Published: March 2021

This chapter on Estonian and Polish OKAY focuses
on complying responses to high entitlement directives. The responses
are built of two parts, the verbal OKAY that completes the adjacency
pair and an embodied compliance that ensues. The OKAY provides an
immediate verbal notification and acceptance of the suggested action
trajectory, which is relevant for the co-participants’ continuing
coordination of activities in progress, while the projected embodied
compliance is necessarily deferred. By looking at two genetically
and historically unrelated languages and showing a similar response
pattern in them, we hope to illustrate the general interactional
potential of the particle OKAY, and perhaps begin to understand some
of its cross-linguistic allure.
Data-free likelihood-informed dimension reduction of Bayesian inverse problems
Authors: Cui Tiangang , Zahm Olivier
Published: March 2021

Identifying a low-dimensional informed parameter subspace offers a viable path to alleviating the dimensionality challenge in the sampled-based solution to large-scale Bayesian inverse problems. This paper introduces a novel gradient-based dimension reduction method in which the informed subspace does not depend on the data. This permits online–offline computational strategy where the expensive low-dimensional structure of the problem is detected in an offline phase, meaning before observing the data. This strategy is particularly relevant for multiple inversion problems as the same informed subspace can be reused. The proposed approach allows to control the approximation error (in expectation over the data) of the posterior distribution. We also present sampling strategies which exploit the informed subspace to draw efficiently samples from the exact posterior distribution. The method is successfully illustrated on two numerical examples: a PDE-based inverse problem with a Gaussian process prior and a tomography problem with Poisson data and a Besov-

B

11

2

prior.
Tuning Jahn–Teller distortion and electron localization of LaMnO3 epitaxial films via substrate temperature
Authors: Chen Xin , Wang Baohua , Chen Yang , Wei Haoming , Cao Bingqiang
Published: March 2021

High-quality epitaxial LaMnO3 films have been grown on (001)-oriented LaAlO3 substrates at different substrate temperatures by pulsed laser deposition. The layer-by-layer growth is indicated by oscillations of reflection high-energy electron diffraction. Raman spectra together with in-plane resistivity measurements reveal that the degree of Jahn–Teller (JT) distortion can be well controlled by the substrate temperature during film deposition. The JT distortion-related/induced electron localization is studied by fitting temperature-dependent resistivity with a three-dimensional variable range hopping model. It is found that the larger JT distortion leads to a stronger localization of electrons. This study might pave the way for further study of JT interaction and highly correlated electronic states in perovskites.
Differentiation of mesenchymal stem cells using metal oxide thin films
Authors: Khokhlova M , Hammad M , Lhuissier E , Retoux R , Goux D , Fouchet A , David A , Lüders U , Boumediene K , Prellier W
Published: March 2021

While metal oxides synthesized as thin films have attracted much attention due to their electronic applications, we show here that they can also be used as bio-surfaces for the growth of stem cells, a field of research which has not been much explored. To demonstrate this, thin films (150–200 Å) of titanium oxide (TiO2) and aluminum oxide (Al2O3) were deposited on glass using the pulsed laser deposition technique and mesenchymal stem cells were grown on these layers. Cell behavior was evaluated with respect to various key parameters, such as the composition, wettability, morphology and thickness of the films. Our results indicate that thin films of TiO2 and Al2O3 can not only support stem cell adhesion and growth, but can be used to influence the osteogenic and chondrogenic differentiation paths, which opens the route for a variety of novel biocompatible materials.
Hard x-ray photoelectron spectroscopy: a snapshot of the state-of-the-art in 2020
Authors: Kalha Curran , Fernando Nathalie K , Bhatt Prajna , Johansson Fredrik O L , Lindblad Andreas , Rensmo Håkan , Medina León Zendejas , Lindblad Rebecka , Siol Sebastian , Jeurgens Lars P H , Cancellieri Claudia , Rossnagel Kai , Medjanik Katerina , Schönhense Gerd , Simon Marc , Gray Alexander X , Nemšák Slavomír , Lömker Patrick , Schlueter Christoph , Regoutz Anna
Published: March 2021

Hard x-ray photoelectron spectroscopy (HAXPES) is establishing itself as an essential technique for the characterisation of materials. The number of specialised photoelectron spectroscopy techniques making use of hard x-rays is steadily increasing and ever more complex experimental designs enable truly transformative insights into the chemical, electronic, magnetic, and structural nature of materials. This paper begins with a short historic perspective of HAXPES and spans from developments in the early days of photoelectron spectroscopy to provide an understanding of the origin and initial development of the technique to state-of-the-art instrumentation and experimental capabilities. The main motivation for and focus of this paper is to provide a picture of the technique in 2020, including a detailed overview of available experimental systems worldwide and insights into a range of specific measurement modi and approaches. We also aim to provide a glimpse into the future of the technique including possible developments and opportunities.
CLIMAR: classified linear interpolation based metal artifact reduction for severe metal artifact reduction in x-ray CT imaging
Authors: Yoon Huisu , Lee Kyoung-Yong , Bechwati Ibrahim
Published: March 2021

In x-ray CT imaging, the existence of metal in the imaging field of view deteriorates the quality of the reconstructed image. This is because rays penetrating dense metal implants are highly corrupted, causing huge inconsistency between projection data. The result appears as strong artifacts such as black and white streaks on the reconstructed image disturbing correct diagnosis. For several decades, there have been various trials to reduce metal artifacts for better image quality. As the computing power of computer processors became more powerful, more complex algorithms with improved performance have been introduced. For instance, the initially developed metal artifact reduction (MAR) algorithms based on simple sinogram interpolation were combined with computationally expensive iterative reconstruction techniques to pursue better image quality. Recently, even machine learning based techniques have been introduced, which require huge amounts of computations for training. In this paper, we introduce an image based novel MAR algorithm in which severe metal artifacts such as black shadings are detected by the proposed method in a straightforward manner based on a linear interpolation. To do that, a new concept of metal artifact classification is devised using linear interpolation in the virtual projection domain. The proposed method reduces severe artifacts very quickly and effectively and has good performance to keep the detailed body structure preserved. Results of qualitative and quantitative comparisons with other representative algorithms such as LIMAR and NMAR support the excellence of the proposed algorithm. Thanks to the nature of reducing artifacts in the image itself and its low computational cost, the proposed algorithm can function as an initial image generator for other MAR algorithms, as well as being integrated in the modalities under limited computation power such as mobile CT scanners.
Cuffless blood pressure estimation methods: physiological model parameters versus machine-learned features
Authors: Esmaelpoor Jamal , Moradi Mohammad Hassan , Kadkhodamohammadi Abdolrahim
Published: March 2021

Objective. For the first time in the literature, this paper investigates some crucial aspects of blood pressure (BP) monitoring using photoplethysmogram (PPG) and electrocardiogram (ECG). In general, the proposed approaches utilize two types of features: parameters extracted from physiological models or machine-learned features. To provide an overview of the different feature extraction methods, we assess the performance of these features and their combinations. We also explore the importance of the ECG waveform. Although ECG contains critical information, most models merely use it as a time reference. To take this one step further, we investigate the effect of its waveform on the performance. Approach. We extracted 27 commonly used physiological parameters in the literature. In addition, convolutional neural networks (CNNs) were deployed to define deep-learned representations. We applied the CNNs to extract two different feature sets from the PPG segments alone and alongside corresponding ECG segments. Then, the extracted feature vectors and their combinations were fed into various regression models to evaluate our hypotheses. Main results. We performed our evaluations using data collected from 200 subjects. The results were analyzed by the mean difference t-test and graphical methods. Our results confirm that the ECG waveform contains important information and helps us to improve accuracy. The comparison of the physiological parameters and machine-learned features also reveals the superiority of machine-learned representations. Moreover, our results highlight that the combination of these feature sets does not provide any additional information. Significance. We conclude that CNN feature extractors provide us with concise and precise representations of ECG and PPG for BP monitoring.
Remotely triggered morphing behavior of additively manufactured thermoset polymer-magnetic nanoparticle composite structures
Authors: Cohn Daniel , Zarek Matt , Elyashiv Ariel , Sbitan Mostafa Abu , Sharma Vinay , Ramanujan R V
Published: March 2021

Shape memory polymers (SMPs) based systems find technological applications in diverse areas such as soft robotics, biomedical devices and aerospace structures. The shape memory (SM) response of a custom-made, additively manufactured (AM) SMP structure can be triggered by a remote, contactless AC magnetic field, resulting in morphing of the structure. We developed AM architectures based on SM thermoset polymers loaded with magnetic nanoparticles (MNPs). Composite structures were prepared from a crosslinkable polycaprolactone dimethacrylate SMP matrix and iron oxide MNP filler. Additive manufacturing of these structures was carried out using these polymers loaded with MNP. Triggered morphing of these structures is achieved by an external alternating magnetic field; the MNP heat up, triggering the SM shape change of the polymer matrix. A variety of structures were AM by a careful choice of materials and process parameters and morphing behavior was demonstrated. This convergence of additive manufacturing technologies and structures prepared from SM thermoset polymers loaded with MNP demonstrates the feasibility of personalized, remotely triggered morphing components for advanced applications, e.g. soft robotics, biomedical devices and smart structural components in buildings.
Time-resolved radial uniformity of pulse-modulated inductively coupled O2/Ar plasmas*
Authors: Liu Wei , Xue Chan , Gao Fei , Liu Yong-Xin , Wang You-Nian , Zhao Yong-Tao
Published: March 2021

Time-resolved radial uniformity of pulse-modulated inductively coupled O2/Ar plasma has been investigated by means of a Langmuir probe as well as an optical probe in this paper. The radial uniformity of plasma has been discussed through analyzing the nonuniformity factor β (calculated by the measured n
e, lower β means higher plasma radial uniformity). The results show that during the active-glow period, the radial distribution of n
e exhibits an almost flat profile at the beginning phase, but it converts into a parabola-like profile during the steady state. The consequent evolution for β is that when the power is turned on, it declines to a minimum at first, and then it increases to a maximum, after that, it decays until it keeps constant. This phenomenon can be explained by the fact that the ionization gradually becomes stronger at the plasma center and meanwhile the rebuilt electric field (plasma potential and ambipolar potential) will confine the electrons at the plasma center as well. Besides, the mean electron energy (〈 ε 〉on) at the pulse beginning decreases with the increasing duty cycle. This will postpone the plasma ignition after the power is turned on. This phenomenon has been verified by the emission intensity of Ar (; = 750.4 nm). During the after-glow period, it is interesting to find that the electrons have a large depletion rate at the plasma center. Consequently, n
e forms a hollow distribution in the radial direction at the late stage of after-glow. Therefore, β exhibits a maximum at the same time. This can be attributed to the formation of negative oxygen ion (O−) at the plasma center when the power has been turned off.
Transition parameters of Li-like ions (Z = 7 – 11) in dense plasmas*
Authors: Li Xiang-Fu , Jia Li-Ping , Wang Hong-Bin , Jiang Gang
Published: March 2021

The energy levels, transition energies, transition probabilities, weighted oscillator strengths, and line strengths of Li-like ions (Z = 7–11) in dense plasmas are investigated in this work. The relativistic effects and electron correlation effects are described by the MCDHF method. The ion sphere model is applied to include the dense plasma screening effect. The ground configuration 1s22s and the excited 1s22p, 1s23l (l = 0–2) are considered. The configuration sets are enlarged until n = 7 where the calculated energy levels have converged. The critical free electron densities of 1s23d states are estimated. Except for 1s23s–1s23p transitions, the transition energies for Δ n = 0 increase, and for Δ n ≠ 0 decrease with increasing free electron densities. For 1s23s–1s23p transitions, the spectra show blue-shift at lower free electron densities and red-shift at higher free electron densities, and the energy level crossing phenomens are observed at higher free electron densities.
Computational model investigating the effect of magnetic field on neural–astrocyte microcircuit*
Authors: Li Li-Cong , Zhou Jin , Sun Hong-Ji , Xiong Peng , Wang Hong-Rui , Liu Xiu-Ling , Wang Chang-Yong
Published: March 2021

Extremely low-frequency magnetic field is widely used as a noninvasive stimulation method in clinical practice and basic research. Electrical field induced from magnetic pulse can decrease or increase neuronal electrical activity. However, the cellular mechanism underlying the effects of magnetic field is not clear from experimental data. Recent studies have demonstrated that “non-neuronal” cells, especially astrocytes, may be the potential effector for transcranial magnetic stimulation (TMS). In the present study, we implemented a neural–astrocyte microcircuit computational model based on hippocampal architecture to investigate the biological effects of different magnetic field frequencies on cells. The purpose of the present study is to elucidate the main influencing factors of MS to allow a better understanding of its mechanisms. Our model reproduced the basic characteristics of the neuron and astrocyte response to different magnetic stimulation. The results predict that interneurons with lower firing thresholds were more active in magnetic fields by contrast to pyramidal neurons. And the synaptic coupling strength between the connected neurons may be one of the critical factor to affect the effect of magnetic field on cells. In addition, the simulations show that astrocytes can decrease or increase slow inward currents (SICs) to finely tune neuronal excitation, which suggests their key role in excitatory–inhibitory balance. The interaction between neurons and astrocytes may represent a novel target for effective therapeutic strategies involving magnetic stimulation.
Nonlinear vibration of iced cable under wind excitation using three-degree-of-freedom model*
Authors: Zhang Wei , Li Ming-Yuan , Wu Qi-Liang , Xi An
Published: March 2021

High-voltage transmission line possesses a typical suspended cable structure that produces ice in harsh weather. Moreover, transversely galloping will be excited due to the irregular structure resulting from the alternation of lift force and drag force. In this paper, the nonlinear dynamics and internal resonance of an iced cable under wind excitation are investigated. Considering the excitation caused by pulsed wind and the movement of the support, the nonlinear governing equations of motion of the iced cable are established using a three-degree-of-freedom model based on Hamilton’s principle. By the Galerkin method, the partial differential equations are then discretized into ordinary differential equations. The method of multiple scales is then used to obtain the averaged equations of the iced cable, and the principal parametric resonance-1/2 subharmonic resonance and the 2:1 internal resonance are considered. The numerical simulations are performed to investigate the dynamic response of the iced cable. It is found that there exist periodic, multi-periodic, and chaotic motions of the iced cable subjected to wind excitation.
Fang–Howard wave function modelling of electron mobility in AlInGaN/AlN/InGaN/GaN double heterostructures*
Authors: Li Yao , Pu Hong-Bin
Published: March 2021

To study the electron transport properties in InGaN channel-based heterostructures, a revised Fang-Howard wave function is proposed by combining the effect of GaN back barrier. Various scattering mechanisms, such as dislocation impurity (DIS) scattering, polar optical phonon (POP) scattering, piezoelectric field (PE) scattering, interface roughness (IFR) scattering, deformation potential (DP) scattering, alloy disorder (ADO) scattering from InGaN channel layer, and temperature-dependent energy bandgaps are considered in the calculation model. A contrast of AlInGaN/AlN/InGaN/GaN double heterostructure (DH) to the theoretical AlInGaN/AlN/InGaN single heterostructure (SH) is made and analyzed with a full range of barrier alloy composition. The effect of channel alloy composition on InGaN channel-based DH with technologically important Al(In,Ga)N barrier is estimated and optimal indium mole fraction is 0.04 for higher mobility in DH with Al0.4In0.07Ga0.53N barrier. Finally, the temperature-dependent two-dimensional electron gas (2DEG) density and mobility in InGaN channel-based DH with Al0.83In0.13Ga0.04N and Al0.4In0.07Ga0.53N barrier are investigated. Our results are expected to conduce to the practical application of InGaN channel-based heterostructures.
Role of graphene in improving catalytic behaviors of AuNPs/MoS2/Gr/Ni-F structure in hydrogen evolution reaction*
Authors: Xiu Xian-Wu , Zhang Wen-Cheng , Hou Shu-Ting , Li Zhen , Lei Feng-Cai , Xu Shi-Cai , Li Chong-Hui , Man Bao-Yuan , Yu Jing , Zhang Chao
Published: March 2021

The efficient production of hydrogen through electrocatalytic decomposition of water has broad prospects in modern energy equipment. However, the catalytic efficiency and durability of hydrogen evolution catalyst are still very deficient, which need to be further explored. Here in this work, we prove that introducing a graphene layer (Gr) between the molybdenum disulfide and nickel foam (Ni–F) substrate can greatly improve the catalytic performance of the hybrid. Owing to the excitation of local surface plasmon resonance (LSPR) of gold nanoparticles (NPs), the electrocatalytic hydrogen releasing activity of the MoS2/Gr/Ni–F heterostructure is greatly improved. This results in a significant increase in the current density of AuNPs/MoS2/Gr/Ni–F composite material under light irradiation and in the dark at 0.2 V (versus reversible hydrogen electrode (RHE)), which is much better than in MoS2/Gr/Ni–F composite materials. The enhancement of hydrogen release can be attributed to the injection of hot electrons into MoS2/Gr/Ni–F by AuNPs, which will improve the electron density of MoS2/Gr/Ni–F, promote the reduction of H2O, and further reduce the activation energy of the electrocatalyst hydrogen evolution reaction (HER). We also prove that the introduction of graphene can improve its stability in acidic catalytic environments. This work provides a new way of designing efficient water splitting system.
Broadband topological valley-projected edge-states transport in composite structure phononic crystal*
Authors: Mao Hong-Yong , Chen Fu-Jia , Guo Kai , Guo Zhong-Yi
Published: March 2021

The topological valley transport, realized in phononic crystals, has aroused tremendous interest in these years. Many previous researches have further promoted the development of this transport phenomenon. Crucially, the bandwidth of the valley-projected edge mode has been an essential research topic. As is well known, the broadband will improve the adaptability of the acoustic edge-states, which will be more conducive to the transmission of information. Therefore, in this paper, we present a composite structure, composed of the atoms with different shapes forming a hexagonal lattice, which can achieve larger bandwidth than a single structure. Meanwhile, the results demonstrate that the topological protected edge states are also observed in our structure. Furthermore, the backscattering suppressions from associated valley-protected edge states under certain perturbations have also been investigated and demonstrated. Our work can provide a new idea for designing acoustic devices based on valley degree of freedom.
Achieving high-performance multilayer MoSe2 photodetectors by defect engineering*
Authors: Hong Jintao , Zhang Fengyuan , Liu Zheng , Jiang Jie , Wu Zhangting , Zheng Peng , Zheng Hui , Zheng Liang , Huo Dexuan , Ni Zhenhua , Zhang Yang
Published: March 2021

Optoelectronic properties of MoSe2 are modulated by controlled annealing in air. Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects. Considerable increase in electron and hole mobilities reveals the highly improved electron and hole transport. Furthermore, the photocurrent is enhanced by nearly four orders of magnitudes under 7 nW laser exposure after annealing. The remarkable enhancement in the photoresponse is attributed to an increase in hole trapping centers and a reduction in resistance. Furthermore, the annealed photodetector shows a fast time response on the order of 10 ms and responsivity of 3 × 104 A/W.
Quantum plasmon enhanced nonlinear wave mixing in graphene nanoflakes*
Authors: Deng Hanying , Huang Changming , He Yingji , Ye Fangwei
Published: March 2021

A distant-neighbor quantum-mechanical method is used to study the nonlinear optical wave mixing in graphene nanoflakes (GNFs), including sum- and difference-frequency generation, as well as four-wave mixing. Our analysis shows that molecular-scale GNFs support quantum plasmons in the visible spectrum region, and significant enhancement of nonlinear optical wave mixing is achieved. Specifically, the second- and third-order wave-mixing polarizabilities of GNFs are dramatically enhanced, provided that one (or more) of the input or output frequencies coincide with a quantum plasmon resonance. Moreover, by embedding a cavity into hexagonal GNFs, we show that one can break the structural inversion symmetry and enable otherwise forbidden second-order wave mixing, which is found to be enhanced by the quantum plasmon resonance too. This study reveals that the molecular-sized graphene could be used in the quantum regime for nanoscale nonlinear optical devices and ultrasensitive molecular sensors.
Charge disturbance/excitation in the Raman virtual state revealed by ROA signal: A case study of pinane*
Authors: Zhu Ziqi , Wang Peijie , Wu Guozhen
Published: March 2021

The Raman mode intensities are used to extract the bond polarizabilities which are the indication of the charge disturbance/excitation of the Raman virtual state. A classical formula based on the electric and magnetic dipolar coupling among the charges on the atoms is developed which relates the charges and vibrational amplitudes of the atoms in a normal mode to the Raman optical activity (ROA) mode signatures. By fitting with the experimental ROA signatures, we are able to elucidate the scaling parameter which relates the bond polarizability to the electric charge. The result shows that around 40% of the charges in pinane are involved in the Raman process under 532 nm laser excitation.
Dynamic modeling and aperiodically intermittent strategy for adaptive finite-time synchronization control of the multi-weighted complex transportation networks with multiple delays*
Authors: Li Ning , Sun Haiyi , Jing Xin , Chen Zhongtang
Published: March 2021

The idea of network splitting according to time delay and weight is introduced. Based on the cyber physical systems (CPS), a class of multi-weighted complex transportation networks with multiple delays is modeled. The finite-time synchronization of the proposed complex transportation networks model is studied systematically. On the basis of the theory of stability, the technique of adaptive control, aperiodically intermittent control and finite-time control, the aperiodically intermittent adaptive finite-time synchronization controller is designed. The controller designed in this paper is beneficial for understanding the synchronization in multi-weighted complex transportation networks with multiple delays. In addition, the conditions for the existence of finite time synchronization have been discussed in detail. And the specific value of the settling finite time for synchronization is obtained. Moreover, the outer coupling configuration matrices are not required to be irreducible or symmetric. Finally, simulation results of the finite-time synchronization problem are given to illustrate the correctness of the results obtained.
Controlled quantum teleportation of an unknown single-qutrit state in noisy channels with memory*
Authors: Jiang Shexiang , Zhao Bao , Liang Xingzhu
Published: March 2021

This paper proposes a three-dimensional (3D) controlled quantum teleportation scheme for an unknown single-qutrit state. The scheme is first introduced in an ideal environment, and its detailed implementation is described via the transformation of the quantum system. Four types of 3D-Pauli-like noise corresponding to Weyl operators are created by Kraus operators: trit-flip, t-phase-flip, trit-phase-flip, and t-depolarizing. Then, this scheme is analyzed in terms of four types of noisy channel with memory. For each type of noise, the average fidelity is calculated as a function of memory and noise parameters, which is afterwards compared with classical fidelity. The results demonstrate that for trit-flip and t-depolarizing noises, memory will increase the average fidelity regardless of the noise parameter. However, for t-phase-flip and trit-phase-flip noises, memory may become ineffective in increasing the average fidelity above a certain noise threshold.
Epitaxial growth and transport properties of compressively-strained Ba2IrO4 films*
Authors: Zhao Yun-Qi , Zhang Heng , Cai Xiang-Bin , Guo Wei , Ji Dian-Xiang , Zhang Ting-Ting , Gu Zheng-Bin , Zhou Jian , Zhu Ye , Nie Yue-Feng
Published: March 2021

Ba2IrO4 is a sister compound of the widely investigated Sr2IrO4 and has no IrO6 octahedral rotation nor net canted antiferromagnetic moment, thus it acts as a system more similar to the high-T
c cuprate. In this work, we synthesize the Ba2IrO4 epitaxial films by reactive molecular beam epitaxy and study their crystalline structure and transport properties under biaxial compressive strain. High resolution scanning transmission electron microscopy and x-ray diffraction confirm the high quality of films with partial strain relaxation. Under compressive epitaxial strain, the Ba2IrO4 exhibits the strain-driven enhancement of the conductivity, consistent with the band gap narrowing and the stronger hybridization of Ir-t2g and O-2p orbitals predicted in the first-principles calculations.