bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis and wave tank verification of the performance of point absorber WECs with different configurations
Authors: Li Xiaofan , Martin Dillon , Jiang Boxi , Chen Shuo , Thiagarajan Krish , Parker Robert G. , Zuo Lei
Published: August 2021

Extracting energy from ocean waves has become a heated topic since the energy crisis of the 2000s. Among all the different concepts and designs of Wave Energy Converter (WEC), point absorber is a widely adopted type with great potential, and various configurations and constraints are applicable to it. Here, the point absorber WECs with four different set‐up configurations are explored: single body heaving WEC, two‐body heaving WEC, two‐body WEC with a flat plate (Reference Model 3), and a two‐body WEC with a cylinder‐shaped second body. Dynamic models are established for each case and wave tank tests are conducted for verification. The results show that the power capture of a point absorber can benefit from several aspects: the two‐body WEC with a streamlined shape can double the wave capture width ratio (up to 66.5%) over the single‐body WEC or Reference Model 3, while coupling other motion or mooring dynamics can further improve the capture width ratio by 12% by increasing the relative motion stroke.
Cyano radical emission at small spatial scales towards massive protostars
Authors: Paron S. , Ortega M. E. , Marinelli A. , Areal M. B. , Martinez N. C.
Published: August 2021

Context. The cyano radical (CN), one of the first detected interstellar molecular species, is a key molecule in many astrochemical chains. In particular, it is detected towards molecular cores, the birth places of stars, and it is involved in the rich chemistry that takes place at these sites.

Aims. At present, there are not many studies on the emission of this molecular species at small spatial scales towards massive young stellar objects. We therefore present a high-angular resolution CN study towards a sample of massive protostars, with the aim of unveiling the spatial distribution at the small scale of the emission of this radical in relation to star-forming processes.

Methods. The interstellar CN has a strong emission line at the rest frequency 226 874.764 MHz, thus we searched for observing projects in the Atacama Large Millimeter Array (ALMA) database regarding high-mass star-forming regions observed at Band 6. The used data set was observed in ALMA Cycle 3 with angular and spectral resolutions of 0.′′7 and 1.13 MHz, respectively. A sample of ten high-mass star-forming regions located in the first Galactic quadrant were selected on the basis that they present a clear emission of CN at the mentioned frequency.

Results. We found that the CN traces both molecular condensations and the diffuse and extended gas surrounding them. In general, the molecular condensations traced by the maximums of the CN emission do not spatially coincide with the peaks of the continuum emission at 1.3 mm, which trace the molecular cores where massive stars are born. Based on the presence or lack of near-IR emission associated with such cores, we suggest that our sample is composed of sources at different stages of evolution. The CN is present in all sources, suggesting that this radical may be ubiquitous along the different star formation stages, and hence it may be involved in different chemical reactions occurring during the period of star formation. Additionally, other molecules such as CH3OCHO and CH2CHCN were detected towards the continuum peaks of some of the analysed cores. We found that the missing flux coming from extended spatial scales that are filtered out by the interferometer is an important issue to take into account in the analysis of some spectral features and the spatial distribution of the emission.
Management of Auditory Processing Difficulties Virtually: A Case Study
Authors: Milne Virginia Amy
Published: August 2021

Difficulty hearing in the presence of background noise is a common complaint heard by audiologists. This can be accompanied by additional difficulty in classrooms and other difficult listening situations. This was recently exacerbated by the coronavirus disease 2019 (COVID-19) shutdowns and the accompanying mask usage and virtual meetings. This article describes one such patient seen during the recent shutdown. This patient reported difficulty hearing during her college coursework for her music performance major. She was an established otology patient with an extensive middle ear history including multiple surgeries. During the shutdown, she virtually consulted with the auditory processing disorders clinic at the recommendation of her otologist to discuss her college-related difficulty and pursue educational accommodations. Challenges and solutions for seeing this patient and other, similar patients virtually are discussed as well as a review of how this patient proceeded and how the knowledge gained from this patient could apply to others with similar concerns.
Telehealth Audiology and Virtual Hearing Screenings: A Case Report
Authors: Linkenheimer Erika Sophia
Published: August 2021

Clinic closures across the United States in response to the coronavirus disease 2019 (COVID-19) pandemic meant that many audiology services were reduced to phone calls, video visits, and modified services (e.g., curbside, mail-ins, drop offs). Audiologists and other providers needed a way to manage hearing- and ear-related complaints via telehealth. A simple pure tone air conduction threshold test performed at home was used to determine which patients needed to come into the clinic for an in-person appointment. This case will review a 56-year-old male who was being treated for an idiopathic sudden sensorineural hearing loss prior to clinic closure. He had on file a comprehensive audiogram at first onset of symptoms and was treated with oral steroids. Virtual hearing testing was then utilized for a variety of other patients from teenagers to adults to triage hearing- and ear-related complaints while clinics were closed for in-person visits.
U.S. Policy Considerations for Telehealth Provision in Audiology
Authors: Jilla Anna Marie , Arnold Michelle L. , Miller Erin L.
Published: August 2021

The demand for telehealth services will continue to grow alongside an increased need for audiology services among both children and adults. Insurance coverage policies for audiologic services are specific to each payer and vary widely in the level of coverage provided for both in-person and telehealth-based audiology services. While benefits for children are fairly comprehensive, coverage for audiology services for adults is generally poor. Traditional Medicare does not cover hearing aids or other rehabilitative audiologic services, and other payer policies vary widely. Lack of benefits for hearing and balance services is inconsistent with the evidence base and leaves many beneficiaries without access to meaningful care for hearing and balance disorders, which are highly prevalent among and disproportionately affect Medicare beneficiaries. The purpose of this article is to discuss regulatory and reimbursement considerations for telehealth provision in audiology and elucidate opportunities to influence related health policy at both state and federal levels.
Seeing through transparent materials microfabrication
Authors: Patrick Chris
Published: August 2021

A study of fused silica reveals the controlling factors of material removal in transient and selective laser processing to improve shaping and efficiency.
Temporal shaping of single photons by engineering exciton dynamics in a single quantum dot
Authors: Kim Kyu-Young , Richardson Christopher J. K. , Waks Edo , Kim Je-Hyung
Published: August 2021

The majority of photonic quantum information technologies rely on single photons that have high purity and indistinguishability. Although solid-state quantum emitters can serve such single photons on demand, their asymmetric temporal and spatial mode profiles limit the optimal efficiency and fidelity of quantum interaction. Here, we demonstrate single-photon pulses at a telecom wavelength with a Gaussian-like temporal mode profile from a cavity-coupled single quantum dot. Engineering the exciton dynamics via multi-exciton cascade recombination and cavity detuning enables us to modify the rise and decay dynamics of single excitons. Furthermore, the cascade recombination process temporally retards the single-exciton emission from the background emission, leading to possible purification of single photons at high excitation power. In addition, coupling quantum dots into a low Q cavity mode leads to a Gaussian-like spatial mode profile, which brings a high collection efficiency. This approach paves the way for producing single photons with an optimized temporal and spatial waveform.
A dual-frequency phase-difference method for ultrasonic hydrogen-concentration detection
Authors: Ding Xin , Shi Yunbo , Sun Hui , Ding Xibo
Published: August 2021

Hydrogen has a wide range of energy applications, but hydrogen energy systems can suffer from high-concentration leaks that pose security risks, therefore making the measurement of high-concentration hydrogen very important. Traditional ultrasonic gas-detection methods are based mainly on ultrasonic time-of-flight measurements and can be divided into threshold-detection and phase-difference techniques. Threshold detection suffers from low resolution and a complex structure in gas detection, while the phase-difference technique has high resolution and a simple structure but can only measure the time of flight within one period of the ultrasonic signal. In this study, a dual-frequency phase-difference technique is proposed that solves the problem of multi-period phase detection with the phase-difference technique and can be used to detect high-concentration hydrogen. Simulation analysis and an experiment show that the proposed technique can measure the multi-period phase difference accurately. The maximum hydrogen concentration can reach 50% with an uncertainty of less than 5%, which meets commercial requirements.
Reachability of fractional dynamical systems using ψ-Hilfer pseudo-fractional derivative
Authors: Vanterler da C. Sousa J. , Vellappandi M. , Govindaraj V. , Frederico Gastão S. F.
Published: August 2021

In this paper, we investigate the reachability of linear and non-linear systems in the sense of the ψ-Hilfer pseudo-fractional derivative in g-calculus by means of the Mittag–Leffler functions (one and two parameters). In this sense, two numerical examples are discussed in order to elucidate the investigated results.
A phased approach for the adaptation of telemedicine in arrythmia management
Authors: Bendimerad Abderrahmen , Hadj Slimane Zine-Eddine , Bendimerad Anes
Published: August 2021

Cardiovascular disease is the world’s leading cause of death. People at higher risk of heart disease need early detection to prevent or delay serious disease complications. In this paper, we present a new design of a wireless portable ECG (electrocardiogram). The ECG signal was preprocessed by analog filters and amplifiers before it was converted into digital data via an Arduino board, a highly available device for real-time signal processing. In order to allow communication between Arduino and Android phone, we use a Bluetooth module. The proposed mobile telemedicine technique allows immediate and rapid detection of heart defects followed by an alarm message from the patient to the doctor.
Strong multipolar transition enhancement with graphene nanoislands
Authors: Rosolen Gilles , Maes Bjorn
Published: August 2021

For a long time, the point-dipole model was a central and natural approximation in the field of photonics. This approach assumes that the wavelength is much larger than the size of the emitting atom or molecule so that the emitter can be described as a single or a collection of elementary dipoles. This approximation no longer holds near plasmonic nanostructures, where the effective wavelength can reach the nanometer-scale. In that case, deviations arise and high-order transitions, beyond the dipolar ones, are not forbidden anymore. Typically, this situation requires intensive numerical efforts to compute the photonic response over the spatial extent of the emitter wavefunctions. Here, we develop an efficient and general model for the multipolar transition rates of a quantum emitter in a photonic environment by computing Green’s function through an eigen permittivity modal expansion. A major benefit of this approach is that the position of the emitter and the permittivity of the material can be swept in a rapid way. To illustrate, we apply the method on various forms of graphene nanoislands, and we demonstrate a local breakdown of the selection rules, with quadrupolar transition rates becoming 100 times larger than dipolar ones.
Two-step treatment to obtain single-terminated SrTiO3 substrate and the related difference in both LaAlO3 film growth and electronic property
Authors: Peng J. J. , Hao C. S. , Liu H. Y. , Yan Y.
Published: August 2021

A two-step treatment, first chemical etching then thermal treatment, is proposed to achieve an atomically flat and thermally stable TiO2-terminated SrTiO3 substrate. LaAlO3 films were then grown on those TiO2-terminated and as-received substrates. LaAlO3 films on the TiO2-terminated SrTiO3 substrate maintained the layer-by-layer growth mode with a sharp interface, while films on the as-received substrates easily underwent reconstruction adverse to the sharp interface. Both LaAlO3/SrTiO3 interfaces displayed metallic conductive behavior, while the difference in magnetotransport properties indicated the difference in origin for interface conductivity. Large positive magnetoresistance implied that the LaAlO3/as-received substrate interface was a 3D conductive interface dominated by oxygen vacancies. However, the annealed-LaAlO3/treated-substrate interface preserved intrinsic quasi-2D interface magnetism as evidenced by large negative magnetoresistance.
Chaos control in a multiple delayed phytoplankton–zooplankton model with group defense and predator’s interference
Authors: Sajan  , Dubey Balram
Published: August 2021

Phytoplankton–zooplankton interaction is a topic of high interest among the interrelationships related to marine habitats. In the present manuscript, we attempt to study the dynamics of a three-dimensional system with three types of plankton: non-toxic phytoplankton, toxic producing phytoplankton, and zooplankton. We assume that both non-toxic and toxic phytoplankton are consumed by zooplankton via Beddington–DeAngelis and general Holling type-IV responses, respectively. We also incorporate gestation delay and toxic liberation delay in zooplankton’s interactions with non-toxic and toxic phytoplankton correspondingly. First, we have studied the well-posedness of the system. Then, we analyze all the possible equilibrium points and their local and global asymptotic behavior. Furthermore, we assessed the conditions for the occurrence of Hopf-bifurcation and transcritical bifurcation. Using the normal form method and center manifold theorem, the conditions for stability and direction of Hopf-bifurcation are also studied. Various time-series, phase portraits, and bifurcation diagrams are plotted to confirm our theoretical findings. From the numerical simulation, we observe that a limited increase in inhibitory effect of toxic phytoplankton against zooplankton can support zooplankton’s growth, and rising predator’s interference can also boost zooplankton expansion in contrast to the nature of Holling type IV and Beddington–DeAngelis responses. Next, we notice that on variation of toxic liberation delay, the delayed system switches its stability multiple times and becomes chaotic. Furthermore, we draw the Poincaré section and evaluate the maximum Lyapunov exponent in order to verify the delayed system’s chaotic nature. Results presented in this article might be helpful to interpret biological insights into phytoplankton–zooplankton interactions.
Lagrangian coherent structures and material transport in unsteady flow of vertical-axis turbine wakes
Authors: Wang Kun , Zou Li , Zhang Jiuming , Jiang Yichen , Zhao Peidong
Published: August 2021

In this study, the unsteady phenomena of vertical-axis turbine wake flow were analyzed in two rotational speed conditions from a Lagrangian perspective. The wake flow field was obtained using particle image velocimetry. The spectral proper orthogonal decomposition method was used to decompose the wake modes with different frequencies. The Lagrangian coherent structure theory based on the finite-time Lyapunov exponent was used to study the material transport and mixing in the wake evolution process. The results show that the Lagrangian coherent structures can capture the boundary of the wake vortex. At a low rotation speed, a vorticity–flux window is found, through which the fluid is transported to the rotation-induced structures. At a high rotation speed, the increasing material transport between the separation bubbles and the incoming flow eventually leads to shedding of the large-scale vortex structures, accompanied by a decrease in the length of the separation zone. The material transport and mixing revealed in the unsteady flow of turbine wakes have significance in guiding the study of the flow control mechanism.
Two-photon absorption laser induced fluorescence measurements of absolute neutral deuterium density, temperature, and bulk flow in Proto-MPEX
Authors: Steinberger Thomas E. , McLaughlin Jacob W. , Biewer Theodore M. , Caneses Juan F. , Scime Earl E.
Published: August 2021

Neutral particle control is critical for fusion fueling and confinement. Neutral diagnostics for fusion-relevant plasmas are commonly restricted to line-integrated or ex situ methods. A non-perturbative, two-photon absorption laser induced fluorescence (TALIF) diagnostic is implemented on the Prototype Material Plasma Exposure eXperiment (Proto-MPEX) to probe neutral atomic deuterium in a fusion-relevant plasma at 1 cm intervals along the radius of the vacuum vessel. The diagnostic is situated ∼20 m from the vacuum vessel, and a signal is collected along the laser injection axis, requiring only one line-of-sight. TALIF measurements are absolutely calibrated using xenon and krypton. Absolute atomic densities derived from xenon calibration are compared to absolute atomic densities derived from krypton calibration. Here, preliminary measurements of absolute atomic deuterium density, temperature, and local bulk flow dependence on radial location and input power in Proto-MPEX are presented. Neutral atomic deuterium velocity distribution functions are measured throughout a one-second plasma pulse with a time resolution of 250 ms.
Synchronization of quasiperiodic oscillations in nearly Hamiltonian systems: The degenerate case
Authors: Morozov A. D. , Morozov K. E.
Published: August 2021

Quasiperiodic perturbations of two-dimensional nearly Hamiltonian systems with a limit cycle are considered. The behavior of solutions in a small neighborhood of a degenerate resonance is studied. Special attention is paid to the synchronization problem. Bifurcations of quasiperiodic solutions that arise when the limit cycle passes through the neighborhood of a resonance phase curve are investigated. The study is based on an analysis of an autonomous pendulum-type system, which is obtained by the method of averaging and determines the dynamics in the resonance zone. Two possible topological structures of the unperturbed averaged system are distinguished. For each case, the intervals of a control parameter that correspond to oscillatory synchronization are found. The results are applied to a Duffing–Van der Pol-type equation.
Sol–gel derived barium strontium titanate thin films using a highly diluted precursor solution
Authors: Mansour Claudette , Benwadih Mohammed , Revenant Christine
Published: August 2021

Among lead-free ferroelectric materials, Barium Strontium Titanate (BST) has interesting ferroelectric, pyroelectric, piezoelectric, and energy-harvesting properties. This material can be advantageously solution-deposited. There is a need for homogeneous and dense films with optimized electrical properties. BST thin films are elaborated with a highly diluted precursor solution of less than 0.05 M. The electric properties are correlated with the morphology and structure of the films as a function of precursor solution dilution. The film growth is columnar with a tetragonal perovskite structure. As the dilution increases, the roughness of the top surface and of the columns decreases, facilitating grain coalescence. In addition, the permittivity of the grains and of the grain boundaries decreases. The highest dielectric strength (400 kV/cm) is obtained for the sample elaborated with the most diluted precursor solution of 0.008 M. For a given polarization, the necessary poling electric field decreases by a factor 2.3 as dilution increases by a factor 4. Finally, hysteresis loops are obtained with increasing saturation and remnant polarizations as the dilution increases. The saturation polarization is approximately doubled as the solution dilution is multiplied by four. To conclude, BST films elaborated with highly diluted solutions have enhanced ferroelectric properties.
Supercooled melt structure and dynamics of single-chain nanoparticles: A computer simulation study
Authors: Jia Xiang-Meng , Lin Wen-Feng , Zhao Huan-Yu , Qian Hu-Jun , Lu Zhong-Yuan
Published: August 2021

By using coarse-grained molecular dynamics simulations, we have investigated the structure and dynamics of supercooled single-chain cross-linked nanoparticle (SCNP) melts having a range of cross-linking degrees ϕ. We find a nearly linear increase in glass-transition temperature (Tg) with increasing ϕ. Correspondingly, we have also experimentally synthesized a series of polystyrene-based SCNPs and have found that the measured Tg estimated from differential scanning calorimetry is qualitatively consistent with the trend predicted by our simulation estimates. Experimentally, an increase in Tg as large as ΔTg = 61 K for ϕ = 0.36 is found compared with their linear chain counterparts, indicating that the changes in dynamics with cross-links are quite appreciable. We attribute the increase in Tg to the enlarged effective hard-core volume and the corresponding reduction in the free volume of the polymer segments. Topological constraints evidently frustrate the local packing. In addition, the introduction of intra-molecular cross-linking bonds slows down the structural relaxation and simultaneously enhances the local coupling motion on the length scales within SCNPs. Consequently, a more pronounced dynamical heterogeneity (DH) is observed for larger ϕ, as quantified by measuring the dynamical correlation length through the four-point susceptibility parameter, χ4. The increase in DH is directly related to the enhanced local cooperative motion derived from intra-molecular cross-linking bonds and structural heterogeneity derived from the cross-linking process. These results shed new light on the influence of intra-molecular topological constraints on the segmental dynamics of polymer melts.
Markov state models from hierarchical density-based assignment
Authors: Mitxelena Ion , López Xabier , de Sancho David
Published: August 2021

Markov state models (MSMs) have become one of the preferred methods for the analysis and interpretation of molecular dynamics (MD) simulations of conformational transitions in biopolymers. While there is great variation in terms of implementation, a well-defined workflow involving multiple steps is often adopted. Typically, molecular coordinates are first subjected to dimensionality reduction and then clustered into small “microstates,” which are subsequently lumped into “macrostates” using the information from the slowest eigenmodes. However, the microstate dynamics is often non-Markovian, and long lag times are required to converge the relevant slow dynamics in the MSM. Here, we propose a variation on this typical workflow, taking advantage of hierarchical density-based clustering. When applied to simulation data, this type of clustering separates high population regions of conformational space from others that are rarely visited. In this way, density-based clustering naturally implements assignment of the data based on transitions between metastable states, resulting in a core-set MSM. As a result, the state definition becomes more consistent with the assumption of Markovianity, and the timescales of the slow dynamics of the system are recovered more effectively. We present results of this simplified workflow for a model potential and MD simulations of the alanine dipeptide and the FiP35 WW domain.
Hard vs soft impacts in oscillatory systems' modeling revisited
Authors: Okolewski Andrzej , Blazejczyk-Okolewska Barbara
Published: August 2021

An application of soft and hard impact models to represent vibro-impact systems is reconsidered. The conditions that the two collision models have to satisfy to be equivalent in terms of energy dissipation are discussed and key features of the resulting soft impact models are demonstrated. Then, it is examined what effect will be exerted on the behavior of a vibro-impact system when an additional elastic-damping element and external forcing are used. Both methods are shown to yield the same results for a stiff base with a low rate of energy dissipation; however, when the soft impact model is applied to either the base with low stiffness or even the stiff base with a high rate of energy dissipation, different results are obtained than in the case of the hard impact model.
Porous silicon nanowires phase transformations at high temperatures and pressures
Authors: Rezvani S. J. , Mijiti Y. , Di Cicco A.
Published: August 2021

Porous silicon nanowires (NWs) with homogenous lateral dimensions of 90 nm are investigated by Raman scattering experiments along isothermal pressure cycles in a diamond anvil cell. Experiments were performed at variable temperatures up to 400 °C for maximal pressures of about 30 GPa comparing directly with transformations in bulk Si and porous NWs. Scanning electron microscopy demonstrates the persistence of one-dimensional morphology after high pressure investigation. The diamond phase in porous nanowires persists upon compression up to around 20 GPa at room temperature (25 °C) and to about 14 GPa at 200 °C and 400 °C. However, the β−Sn high pressure phase is seen to coexist with the diamond phase above 12 GPa at 25 °C and above 6 GPa at 200 °C and 400 °C. The coexistence region of the two phases is found to be considerably enlarged as compared with crystal silicon at each temperature. Upon decompression from 30 GPa, nucleation to the β−Sn, followed by formation of amorphous structures, is observed for porous NWs. Returning to ambient pressure and temperature, amorphous silicon is the dominant form with a residual contribution of β−Sn. At higher temperatures, nucleation back to the diamond structure is triggered although coexistence of amorphous and crystalline phases is observed up to 400 °C.
Simulation of multi-species flow and heat transfer using physics-informed neural networks
Authors: Laubscher R.
Published: August 2021

In the present work, single- and segregated-network physics-informed neural network (PINN) architectures are applied to predict momentum, species, and temperature distributions of a dry air humidification problem in a simple two-dimensional (2D) rectangular domain. The created PINN models account for variable fluid properties, species- and heat-diffusion, and convection. Both the mentioned PINN architectures were trained using different hyperparameter settings, such as network width and depth, to find the best-performing configuration. It is shown that the segregated-network PINN approach results in on-average 62% lower losses when compared to the single-network PINN architecture for the given problem. Furthermore, the single-network variant struggled to ensure species mass conservation in different areas of the computational domain, whereas the segregated approach successfully maintained species conservation. The PINN predicted velocity, temperature, and species profiles for a given set of boundary conditions were compared to results generated using OpenFOAM software. Both the single- and segregated-network PINN models produced accurate results for temperature and velocity profiles, with average percentage difference relative to the computational fluid dynamics results of approximately 7.5% for velocity and 8% for temperature. The mean error percentages for the species mass fractions are 9% for the single-network model and 1.5% for the segregated-network approach. To showcase the applicability of PINNs for surrogate modeling of multi-species problems, a parameterized version of the segregated-network PINN is trained that could produce results for different water vapor inlet velocities. The normalized mean absolute percentage errors, relative to the OpenFOAM results, across three predicted cases for velocity and temperature are approximately 7.5% and 2.4% for water vapor mass fraction.
Ligand removal of Au25 nanoclusters by thermal and electrochemical treatments for selective CO2 electroreduction to CO
Authors: Chen Shouping , Li Mufan , Yu Sunmoon , Louisia Sheena , Chuang Wesley , Gao Mengyu , Chen Chubai , Jin Jianbo , Salmeron Miquel B. , Yang Peidong
Published: August 2021

Undercoordinated metal nanoclusters have shown great promise for various catalytic applications. However, their activity is often limited by the covalently bonded ligands, which could block the active surface sites. Here, we investigate the ligand removal process for Au25 nanoclusters using both thermal and electrochemical treatments, as well as its impact on the electroreduction of CO2 to CO. The Au25 nanoclusters are synthesized with 2-phenylethanethiol as the capping agent and anchored on sulfur-doped graphene. The thiolate ligands can be readily removed under either thermal annealing at ≥180°C or electrochemical biasing at ≤−0.5 V vs reversible hydrogen electrode, as evidenced by the Cu underpotential deposition surface area measurement, x-ray photoelectron spectroscopy, and extended x-ray absorption fine structure spectroscopy. However, these ligand-removing treatments also trigger the structural evolution of Au25 nanoclusters concomitantly. The thermally and electrochemically treated Au25 nanoclusters show enhanced activity and selectivity for the electrochemical CO2-to-CO conversion than their pristine counterpart, which is attributed to the exposure of undercoordinated Au sites on the surface after ligand removal. This work provides facile strategies to strip away the staple ligands from metal nanoclusters and highlights its importance in promoting the catalytic performances.
Diameter distribution and formation mechanism of solid-state nanopores prepared by dielectric breakdown
Authors: Liang Shengfa , Zhang Wenchang , Xiang Feibin
Published: August 2021

The diameter distribution and dielectric breakdown mechanism of solid-state nanopores in a liquid environment are discussed based on the experimental results. We discussed the nanopore formation mechanism from the viewpoint of the statistical correlation between the diameter distribution, the charge to breakdown, and the dissipated energy across the nanopore by changing the field stress. We found that high field stress increases the instability of the uniformity of the nanopore diameter. Similar to the mechanism in the solid situation, the diameter of the nanopore can be uniquely correlated to the dissipated energy in the pore formation process.
Simulation of DC surface flashover of epoxy composites in compressed nitrogen
Authors: Li Zhen , Min Daomin , Niu Huan , Li Mingru , Li Shengtao
Published: August 2021

To date, numerical simulation techniques for surface flashover are still under development. In this work, a DC surface flashover numerical simulation model is constructed based on a gas–solid coupling surface flashover theoretical model with a multilayered structure at the gas–solid interface. Considering the effects of solid, gas, and gas–solid interaction on surface flashover, bipolar charge transport in the solid surface layer, collision ionization in the gas phase layer, secondary electron emission, and gas adsorption in the gas surface layer are combined to calculate the surface flashover voltage. By initializing model parameters, surface charge transport dependent dc surface flashover voltages of epoxy composites in compressed nitrogen are calculated. The results indicate that the surface flashover voltage increases with surface deep trap level, deep trap density, shallow trap density, and carrier mobility; however, surface flashover voltage decreases with surface shallow trap level and surface charge density. To further investigate the effects of surface trap on surface flashover, a “U-shaped” curve is constructed to describe the relationship between surface flashover voltage and surface trap level by the simulation method which shows good agreement with experimental results. The simulation indicates surface flashover voltage of epoxy composites is influenced by surface deep and shallow traps in the solid surface layer—shallow traps mainly influence surface charge dissipation, while deep traps mainly influence electron emission on the solid surface. The value of Ptr/Pde is crucial for the dominating surface trap in surface flashover.
Scaling of reaction progress variable variance in highly turbulent reaction waves
Authors: Sabelnikov V. A. , Lipatnikov A. N.
Published: August 2021

Self-propagation of a reaction wave, which consists of an infinitely thin reaction zone (front) and a thick inert mixing layer adjacent to the front, in constant-density statistically stationary, homogeneous isotropic turbulence unaffected by the wave is analytically studied. In the asymptotic case of a high turbulent Reynolds number, high Karlovitz number, and low Damköhler number Da, the scalar variance c′2¯ is shown to be proportional to Da for the statistically stationary stage of the wave evolution. This scaling is supported by newly analyzed Direct Numerical Simulation data discussed in detail by Sabelnikov et al. [“Thin reaction zones in constant-density turbulent flows at low Damköhler numbers: Theory and simulations,” Phys. Fluids 31, 055104 (2019)]. The obtained analytical results also show that, under conditions of the present study, spatial gradients of reactant concentration non-uniformities due to the reaction and spatial gradients of reactant concentration non-uniformities due to the turbulence are of the same order of magnitude. Accordingly, major statistical characteristics of the scalar field c(x,t), such as the mean area of an iso-scalar surface c(x,t)=const, the mean molecular flux through this surface, etc., can be found adopting results known in the theory of inert and passive turbulent mixing. Nevertheless, the reaction indirectly affects these characteristics by controlling the mean thickness of the reaction wave and, consequently, the spatial gradient of the mean reaction progress variable.
Enhancing dropwise condensation on downward-facing surfaces through the synergistic effects of surface structure and mixed wettability
Authors: Tang S. , Li Q. , Yu Y. , Qiu Y.
Published: August 2021

In this paper, the condensation performance and the dynamic behavior of condensed droplets on a downward-facing structured surface with mixed wettability are numerically investigated using a thermal multiphase lattice Boltzmann model, with a focus being placed on exploring the enhancement mechanism of dropwise condensation on downward-facing structured surfaces. The numerical investigation shows that the downward-facing structured surface with mixed wettability exhibits much better condensation performance than those with homogeneous wettability owing to the synergistic effects of surface structure and mixed wettability, which increase the droplet departure frequency and prevent the flooding phenomenon. Furthermore, it is found that the dynamic behavior of condensed droplets on the downward-facing structured surface with mixed wettability can be divided into three stages, i.e., the nucleation-growth stage, the coalescence-slip stage, and the stick-departure stage. Particularly, there exists a competition between the time of the first stage and that of the third stage in terms of the contact angle of the pillar top (θtop). The former reduces but the latter increases with decreasing θtop, because the contact lines are always pinned at the edges of the pillar top during the third stage when θtop is small. An optimal θtop is therefore found, which provides the best droplet dripping rate by achieving a suitable balance between a large droplet departure volume and a relatively short condensation cycle time.
Breakthrough instruments and products RF/Microwave power amplifiers for electromagnetic compatibility testing
Authors: Dayton Pat
Published: August 2021

Electromagnetic compatibility testing presents a challenging environment for an amplifier as the amplifier must operate continuously into load impedances that can vary widely while still meeting its performance ratings. The AR RF/Microwave Instrumentation’s Universal U series is a family of amplifiers designed to withstand these challenges and provide flexibility when used in applications. The U series’ extensive bandwidth is able to provide excellent harmonic suppression performance by minimizing the variation of amplifier gain. This allows usage for a wide range of applications, such as in research and development and general lab use.
Exploring experiences and perceptions of Aboriginal and Torres Strait Islander peoples readmitted to hospital with chronic disease in New South Wales, Australia: a qualitative study
Authors: Jayakody Amanda , Carey Mariko , Bryant Jamie , Ella Stephen , Hussein Paul , Warren Eloise , Bacon Shanell , Field Belinda , Sanson-Fisher Rob
Published: August 2021

Objective This study explored the experiences and perceptions of unplanned hospital readmissions from the perspective of Aboriginal and Torres Strait Islander peoples with chronic disease. Method We conducted semi-structured interviews with Aboriginal and Torres Strait Islander patients readmitted to hospital with chronic disease. Interviews covered perceptions of avoidable readmissions, experiences of health care, medications and carer support. Inductive thematic analysis was used to code and analyse the data. Results Fifteen patients with multiple chronic diseases were interviewed. Several participants believed their readmission was unavoidable due to their poor health, while others considered their readmission was avoidable due to perceived health professional and system failures. Enablers to chronic disease management included the importance of continuity of care and strong family networks, although a few participants struggled with isolation. Four themes emerged as barriers: poor communication from health professionals; low levels of health literacy and adherence to chronic disease management; poor access to community services; and health risk behaviours. Conclusions The participants in our study identified complex and interacting patient-, environmental-, encounter- and organisational-level factors as contributing to chronic disease management and unplanned readmissions. Our findings suggest systemic failures remain in access to basic services and access to culturally appropriate care. Family support and continuity of care were valued by participants. What is known about the topic? Aboriginal and Torres Strait Islander peoples with chronic diseases are more likely to be readmitted to hospital compared with non-Aboriginal people. Unplanned readmissions are associated with high health system costs, as well as poorer quality of life and psychological distress for the patient. What does this paper add? This paper describes the experiences and perceptions of unplanned readmissions by Aboriginal and Torres Strait Islander peoples with chronic disease. Our findings suggest systemic failures exist in access to basic services for a safe and secure living environment, and access to culturally appropriate care that is delivered in a manner which promotes health literacy and self-management capacity. What are the implications for practitioners? Practitioners and policy makers should consider involving family members in discharge planning and other medical care, and funding for Aboriginal and Torres Strait Islander health and community services to enhance transport, care coordination, culturally appropriate disability and housing services, and health promotion.
Bullying in the New Zealand general practitioner workforce
Authors: Wicks Emma , Murton Samantha , Lillis Steven
Published: August 2021

ABSTRACT INTRODUCTION In recent years, there has been growing acknowledgment of problematic unprofessional behaviours such as bullying in the health workforce. AIM The purpose of this research is to investigate how bullying manifests in general practice, responses to bullying and the impact of this behaviour. METHODS Qualitative research using semi-structured interviews or focus groups was conducted. Twenty-four doctors working in the scope of general practice in New Zealand participated: 21 by interview and three by focus group. Participants had been accused of bullying or subject to bullying. RESULTS Results are reported in three categories: people who have experienced being bullied, people accused of bullying, and the cycle of bullying. Participants experienced a range of negative behaviours and had varied responses to bullying, yet the impact of the behaviour was the same. There was considerable overlap in experiences of participants experiencing and accused of bullying, and these categories were not static. DISCUSSION Bullying has a substantial negative impact on the general practice workforce. Responses to bullying often fail to consider the complexities of the behaviour and are premised on simple notions of bully and victim, failing to consider the wider work environment.
Contrasting population structures of freshwater atyid shrimps in Hong Kong and their conservation implications
Authors: Ma Ka Yan , Chow Lai Him , Tsang Ling Ming , De Grave Sammy , Chu Ka Hou
Published: August 2021

Understanding population connectivity is crucial for effective conservation management. Schemes for speculating potential connectivity patterns over large to medium geographic scales using riverscape and life history features have been developed, but whether they are still applicable over fine scales has rarely been examined. Caridina shrimps (Family Atyidae) constitute a major component of freshwater ecosystems. Nonetheless, although over 20% of atyid species are considered Threatened or Near Threatened on the International Union for Conservation of Nature Red List, a general lack of understanding of the population structure of these species, which typically have restricted distributions, significantly hampers conservation management. Here, we examined the fine-scale population structure of five atyid species in Hong Kong, a highly urbanised metropolis, using the mitochondrial cytochrome oxidase subunit I (COI) gene and four to six microsatellite markers. The results reveal species-specific contrasting phylogeographic patterns, ranging from wide-range genetic panmixia to population differentiation at an extremely small scale of <1 km. This pronounced population structuring may be attributed to the freshwater obligates’ limited dispersal ability, high level of inbreeding and marked demographic fluctuations associated with climate changes since the Pleistocene. The results shed new light on the evolution of this widely distributed shrimp genus and bridge the critical knowledge gap in formulating effective conservation plans.
Understanding textual meaning-making in Chinese high school EFL learners’ writing
Authors: Xuan Winfred Wenhui , Zhang Dongbing
Published: August 2021

The present study examines the ways Chinese high school EFL learners organize information in their writing. A class of 50 students at grade 9 from a local high school in Guangzhou, China, were recruited as participants. The students’ writing at grade 9 was collected as a corpus, comprising ten writing tasks from different text types. In order to gain a holistic understanding of the organization of information in student writing, the analytical framework of Theme at three levels – that is, clause, paragraph, and text – from Derewianka and Jones (2010) was adopted. Findings show that the students have varying degrees of control over information organization at different levels. In particular, the students are not proficient in organizing information at the paragraph level. Findings also show that registerial differences affect the organization of information. The study provides relevant pedagogical implications and recommendations for this group of learners.
Not-fragments and negative expansion
Authors: Cappelle Bert
Published: August 2021

This paper focuses on emphatic sentence fragments of the typeNot in a million years!. While such fragments can be partially accounted for by a known type of ellipsis, namely ‘stripping’, it is argued here that this type is best treated as a construction in its own right, with formal, semantic and pragmatic properties specific to it. One useful concept is what could be called ‘negative expansion’. This is a discourse-level construction whereby an already negative clause is followed by one or more negative clause fragments, whose negation is a repetition, rather than cancellation, of the negation in the preceding clause, as inIt will never happen. Not today. Not tomorrow. Not ever.
Semantic polyfunctionality and constructional networks
Authors: Pérez Fernández Sofía , Gras Pedro , Brisard Frank
Published: August 2021

This paper offers an analysis of insubordinate subjunctive complement clauses (ISCs) in Spanish and aims to contribute to the general debate in Construction Grammar on how to deal with a highly pragmatically specified surface form that expresses several meanings. We explore whether the meanings expressed by ISCs are encoded in the construction or can be derived via independently existing principles of pragmatic interpretation. The results of the analysis are represented in a constructional network.
Interference between atomic Rb (5d
5/2–5p
3/2) and (5p
3/2–5s
1/2) coherences: observation of an exceptional point by quantum beating at ∼2.1 THz
Authors: Goldshlag W , Su R , Park S , Reboli T O , Eden J G
Published: August 2021

Coupled oscillators are prevalent in nature and fundamental to fields as disparate as astrophysics, photonics, the mechanical sciences, and geophysics. Theory has identified singularities in the response of coupled oscillators, known as exceptional points (EPs), that are associated with non-Hermitian operators and lie at the transition between weak and strong coupling of the oscillator. Although several EPs have been reported or predicted to exist in nanophotonic resonators and Feshbach resonances, for example, tuning the phase of two interfering atomic or molecular coherences near an EP has not been demonstrated previously. We report the observation of an EP associated with a pair of interfering atomic coherences in Rb, oscillating at 386.3 and 384.2 THz, and confirm the theoretical prediction of an abrupt phase shift of ∼π/4 as the EP is traversed by independently varying two experimental parameters. Pairs (and trios) of coupled coherences in thermal Rb atoms are established among the 7s
1/2, 5d
5/2, 5p
3/2, and 5s
1/2 states in pump–probe experiments with <200 fs laser pulses, and observed directly in the temporal and spectral domains through the ensuing quantum beating in the ∼2–36 THz interval. Interference between the (5d
5/2–5p
3/2) and (5p
3/2–5s
1/2) coherences is mediated by the 5p
3/2 state and detected through quantum beating in the vicinity of the (5d
5/2–5p
3/2)–(5p
3/2–5s
1/2) difference frequency of 2.11 THz which is monitored by a parametric four-wave mixing process. Phase of this composite atomic oscillator is first controlled by varying the mean Rb–Rb nearest neighbor distance (⟨R⟩) in a thermalized vapor. A discontinuous transition of (0.8 ± 0.2) ∼ π/4 radians in the phase of the coupled oscillator occurs when ⟨R⟩ is varied over the ∼80–90 nm interval, a phase shift associated with the transformation of a broadband, dissipative oscillator (characterized by a Fano interference window) into a strongly-coupled system resonant at 2.1 THz.