bluuebunny/crossref_metadata_2025 huggingface dataset:
An improved method for bandgap calculation of a locally resonant plate with multi-periodic of multiple degree-of-freedom resonators
Authors: Li Qiaojiao , Sheng Meiping
Published: June 2021

An improved plane wave expansion (PWE) method is developed based on the governing equations of a lattice unit cell, providing support for calculating the band structures of a locally resonant (LR) plate with multiple arrays of multiple degree-of-freedom resonators. The extended plane wave expansion (EPWE) method is correspondingly presented to obtain the complex band structures of the LR plate. Then the bandgap properties of LR plate systems with single/multiple arrays of single/multiple degree-of-freedom resonators are analyzed, which present a good agreement with the results calculated by the classical theory or finite element method. Compared with the classical theory, the improved PWE and EPWE methods have excellent efficiency and broad applicability for LR plate systems with complex attachments. Furthermore, when the damping of resonators is taken into account, the merging of the multiple bandgaps can be observed using the EPWE method adopted in this paper, which gives a useful tool to analyze the band structures of an LR plate with merged bandgaps for broadband vibration suppression.
Evanescent surface acoustic waves in 1D viscoelastic phononic crystals
Authors: Zhang Shu-Yan , Wang Yan-Feng , Wang Yue-Sheng
Published: June 2021

In this paper, evanescent surface waves propagating in a one-dimensional surface phononic crystal are investigated. The phononic crystal consists of elastic pillars periodically arranged on a viscoelastic substrate. By using the finite element method, the complex band structures and transmission spectra of surface waves are calculated. It is found that the evanescent wave with π phase change of the real part lies inside the resonant bandgap, and no cusp is observed for the minimum imaginary part. With the increase of frequency, the surface waves can be gradually converted to bulk waves. When the pillar height is increased, the generation mechanism of the first bandgap gradually varies from Bragg scattering to local resonance, and the evanescent waves above the sound line can be reconstructed and shifted below the sound line. When the viscosity is introduced, the minimum imaginary part inside the bandgap decreases. However, the corresponding attenuation is strengthened because the contribution of the bulk wave to the transmission gets weak. The work in this paper is relevant to the practical application of surface waves.
In situ heteroepitaxial construction and transport properties of lattice-matched
α
-Ir2O3/
α
-Ga2O3 p-n heterojunction
Authors: Hao J. G. , Gong H. H. , Chen X. H. , Xu Y. , Ren F.-F. , Gu S. L. , Zhang R. , Zheng Y. D. , Ye J. D.
Published: June 2021

The construction of Ga2O3-based p-n heterojunction offers an alternative strategy to realize bipolar power devices; however, lattice mismatch usually leads to undesirable device performance and makes interface engineering more challenging. In this work, we demonstrated the construction of lattice-matched p-n heterojunctions by the in situ hetero-epitaxy of p-type α-Ir2O3 on n-type Si-doped α-Ga2O3 using the mist-chemical vapor deposition technique. The α-Ga2O3/α-Ir2O3 p-n heterojunction shows single-crystalline corundum structures and well-defined rectifying characteristics. The transport mechanism has been identified to be space-charge-limited current conduction, which is induced by interfacial traps in an ultrathin disordered layer at the α-Ga2O3/α-Ir2O3 interface. Through thermal treatment in oxygen ambient, interfacial trapping states are suppressed, and more shallow acceptors of Ir vacancies are activated, both of which lead to the profound reduction of reverse leakage current, thus the improved current rectification ratio. The p-type α-Ir2O3 with advantages of lattice matching to α-Ga2O3 provides a promising strategy to realize high-performance bipolar power devices.
Single-shot phase-shifting radial-shearing digital holography with Fibonacci-sieve array irrespective of initial phases
Authors: Li You , Zhang Simin , Zhang Junyong , Zhang Yanli , Liu Dean
Published: June 2021

We present a kind of single-shot common-path phase-shifting digital holography realized by both a holographic grating and a Fibonacci-sieve array. A test object wave is first split into multiple image copies by the holographic grating placed at the Fourier plane in a Kepler telescope. Then, the image copies are directed onto their own sieves, which can generate a pair of axial foci with customized phase shifts. This way, three phase-shifting sub-holograms are captured by a single exposure and extracted to reconstruct the original complex amplitude of the test object. The proposed method is free of pre-calibration and mechanical movement during the measuring process, so the imaging speed and robustness are significantly improved. The common path is less sensitive to external interference than an in-line system. A measurement of a USAF1951 test target is presented, and the results show the high resolution and stability over 24 h at least, which gives it potential in application to high-resolution dynamic measurements, such as biological microscopy.
Crystal nucleation in colloidal rod suspensions: The effect of depletant size
Authors: Wood Jared A. , Liu Yawei , Widmer-Cooper Asaph
Published: June 2021

In order to better control the assembly of nanorods, knowledge of the pathways by which they form ordered structures is desirable. In this paper, we characterize crystal nucleation in suspensions of spherocylindrical rods with aspect ratio L/D = 2.3 in the presence of both small and large polymer depletants. Using a combination of Langevin dynamics and Monte Carlo simulations, together with biased sampling techniques, we show that the preferred pathway always involves the formation of monolayer assemblies irrespective of the volume fraction of the initial isotropic phase and the diameter of the depletants. This includes the previously neglected case of nucleation from the colloidal liquid phase and shows that the presence of depletion attraction can alter nucleation pathways even when the initial phase is dense.
Flow, mixing, and flame stabilization in bluff-body burner with decreased central jet velocity
Authors: Wei Jieli , Xie Qing , Zhang Jian , Ren Zhuyin
Published: June 2021

The flame stabilization is a complex problem, especially when reducing the fuel supply, as it involves complicated interactions of turbulence, mixing, and chemistry. In this study, the flamelet progress variable combined with large eddy simulation has been used to simulate a bluff-body non-premixed flame to reveal the mechanisms of flow, mixing, and flame stabilization during the central fuel jet velocity reduction. The two flow patterns of jet dominant and coflow dominant are first analyzed by the concept of persistence of decay similarity of jet. The results show that this concept is informative to interpret whether and where the flow is jet dominant and understand the competition between two flows in detail, not only for flow but also for mixing. The results further show that the jet–coflow interaction, which has a pronounced impact on flame topology, has a minimal impact on flame stabilization for the bluff-body stabilized non-premixed flames over a wide range of fuel jet velocities, because of approximately close ignition delay time and flow convection velocities. In addition, it is observed that a ribbon-like structure of formaldehyde forms upstream of the hydroxyl. This phenomenon is caused by autoignition which is favored by high temperature in the recirculation zone and takes place far upstream of the flame. That would particularly facilitate flame stabilization in bluff-body burners.
Damping of piston mode resonance between two fixed boxes
Authors: Tan Lei , Cheng Liang , Ikoma Tomoki
Published: June 2021

In this paper, the damping of wave-induced resonant oscillations of water column in the gap between two fixed boxes is investigated through physical model testing. A pair of rectangular fins with different geometries is attached to the sidewalls of the gap to suppress the resonant response. This study is an extension to Tan et al. [“A viscous damping model for piston mode resonance,” J. Fluid Mech. 871, 510–533 (2019)], where the damping of wave resonance in a plain gap without fins was investigated. We found that (1) the resonant wave height in the gap decreased substantially with the increasing fin thickness, but was not very sensitive to the variation of the fin height. This observation suggests that the fin thickness has a more significant influence on the damping of oscillations than the fin height; (2) the resonant frequency decreased as the thickness of the fins was enlarged, which is primarily attributable to the decrease in the natural frequency (due to increasing added mass) and partly ascribed to the increase in viscous damping. The viscous dissipation was found to be approximately 3–10 times larger than the radiation energy and explains the well-known over-estimations of inviscid potential solution in resonant amplitude. A modified potential flow model with a damping mechanism was employed to predict the wave response in the gap, wave reflections, and transmissions. Reasonable agreements were obtained between the experimental results and the modified potential flow solutions with respect to amplitude, whereas a difference of 6%–14% in resonant frequency was observed. This difference is ascribed to the effects of flow separation on the added mass of fins, which cannot be fully captured by modified potential flow models. In addition to the present geometries, the local loss coefficients for other appendage configurations were also calibrated based on the available experimental and computational fluid dynamics data in the literature.
Oscillatory square cavity flows of binary gas mixtures
Authors: Zhang Yue , Wang Peng , Guo Zhaoli
Published: June 2021

The linear oscillation of rarefied binary gas mixtures inside a two-dimensional square cavity is studied based on the McCormack model. The discrete unified gas kinetic scheme is applied to solving this problem over wide ranges of the Knudsen number and the oscillation frequency. Two typical groups of binary mixtures, i.e., the Neon–Argon (Ne–Ar) mixture with comparable molecular masses and the Helium–Xenon (He–Xe) with significant different masses are considered. The dependence of the flow characteristics and damping force on the mass ratio and the molar concentration is also investigated in detail. It is found that results of the Ne–Ar mixture with a small mass ratio have similar tendencies to those of a single gas as expected. However, the damping force of the He–Xe mixture is qualitatively different from that of a single gas. In the free-molecular and transition regimes, the molar concentration of the He–Xe mixture shows significant influence on the anti-resonant frequency. Furthermore, the anti-resonance appearing in a single gas can no longer be observed in the He–Xe mixture as the molar concentration of the light species is large in the near-continuum regime, which is helpful to avoid the damping damage for the micro-electro-mechanical devices.
Tuning of subwavelength topological interface states in locally resonant metastructures with shunted piezoelectric patches
Authors: Liu Yijie , Fang Wenbo , Liang Yingjing , Liu Dianzi , Han Qiang
Published: June 2021

We investigate the propagation behavior of the low-frequency topological interface state of the flexural wave in the locally resonant metastructure and analyze the tunability of the sub-wavelength interface states by the piezoelectric shunting circuit. One homogeneous thin beam is periodically attached with local resonant beams, which connect shunted piezoelectric actuators. The folding band obtained by merging two primitive unit cells into one new element can generate a Dirac point below the low-frequency locally resonant bandgap. This folding point is opened to develop one new bandgap originated from the Bragg scattering effect by breaking the mirror symmetry. Then, topological transitions are demonstrated during the distance variation between two adjacent resonances. The interface state’s existence is further confirmed by using steady and transient analysis of the heterostructure composed of two media with different topological properties. Finally, we show the relationship between the interface frequency and the capacitance ratio and research the influence of the distance parameter on the topological interface state. Because of the tunability of elastic waves by the piezoelectric shunting circuit, our design has potential for applications such as energy harvesters, filters, and physical switches.
An efficient adaptive variational quantum solver of the Schrödinger equation based on reduced density matrices
Authors: Liu Jie , Li Zhenyu , Yang Jinlong
Published: June 2021

Recently, adaptive variational quantum algorithms, e.g., Adaptive Derivative-Assembled Pseudo-Trotter-Variational Quantum Eigensolver (ADAPT-VQE) and Iterative Qubit-Excitation Based-Variational Quantum Eigensolver (IQEB-VQE), have been proposed to optimize the circuit depth, while a huge number of additional measurements make these algorithms highly inefficient. In this work, we reformulate the ADAPT-VQE with reduced density matrices (RDMs) to avoid additional measurement overhead. With Valdemoro’s reconstruction of the three-electron RDM, we present a revised ADAPT-VQE algorithm, termed ADAPT-V, without any additional measurements but at the cost of increasing variational parameters compared to the ADAPT-VQE. Furthermore, we present an ADAPT-Vx algorithm by prescreening the anti-Hermitian operator pool with this RDM-based scheme. ADAPT-Vx requires almost the same variational parameters as ADAPT-VQE but a significantly reduced number of gradient evaluations. Numerical benchmark calculations for small molecules demonstrate that ADAPT-V and ADAPT-Vx provide an accurate description of the ground- and excited-state potential energy curves. In addition, to minimize the quantum resource demand, we generalize this RDM-based scheme to circuit-efficient IQEB-VQE algorithm and achieve significant measurement reduction.
In situ surface acoustic wave field probing in microfluidic structures using optical transmission interferometry
Authors: Weser R. , Schmidt H.
Published: June 2021

The generation of mechanical driving forces in fluids at the microscale can be efficiently realized using acoustic actuators. For this purpose, bulk or surface acoustic waves (SAWs) are typically excited by an electroacoustic transducer, and the acoustic energy is subsequently coupled to the fluid. The resultant acoustic pressure field in the fluid allows for precise manipulation of immersed objects and also for the agitation of the fluid itself. In general, the fluidic actuation capability is mainly determined by the mechanical displacement amplitude at the interface between the fluid and the acoustically active surface. In the case of SAW-based actuators, the fluid most often is directly attached to the substrate surface along which the surface waves propagate. Hence, the lateral distribution of surface displacement amplitude, i.e., the surface acoustic wave field, at the fluid–substrate interface is of particular interest in order to achieve full control of the fluidic actuation. Here, we present a reliable experimental method for the in situ determination of the SAW field on fluid loaded substrate surfaces based on laser interferometry. The optical accessibility of the fluid–substrate interface is realized via transmission through the anisotropic, piezoelectric substrate material requiring only an additional calibration procedure in order to compensate the parasitic influence of effects based on different indices of refraction as well as on complex acousto-optic effects. Finally, the proposed method is demonstrated to yield reliable results of displacement amplitude on the fluid loaded surface and thus, to provide a valuable insight into acoustofluidic coupling that was not available so far.
A numerical study on the drag law of a gas bubble using dynamic body force method
Authors: Zhang Lingxin , Zhou Zecai , Deng Jian , Shao Xueming
Published: June 2021

For a gas bubble rising in quiescent liquid, most previous drag force models correlate the drag coefficient Cd to dimensionless parameters such as the Reynolds number Re, the Eötvös number Eo, and the Morton number Mo. However, it is still an open question if the current models can be applied to non-buoyancy-driven bubbles in a wide range of parameters. In the present study, we investigate the effects of Reynolds number Re and Weber number We on the drag force coefficient Cd of bubbly flows. To obtain a converged drag force, a dynamic body force model is developed, which constraints the bubble at a fixed position. A large number of numerical simulations are carried out, spanning in the (We, Re) parametric space. The correlations of Cd to We and Re are studied, respectively. We find that for low We, as the bubble keeps spherical, its drag coefficients can be well predicted by the previous spherical bubble models. For medium–high We, when Re is low, the viscous force contributes most, and therefore, the bubble deformation or We plays an insignificant role on the drag. In contrast, when Re is high, the pressure force or shape drag becomes dominant, which is strongly dependent of We. Therefore, we can identify three different regions, spherical, We-dependent, and We-independent, in the parametric space. Finally, a new empirical drag force model for a non-buoyancy-driven bubble is proposed based on the Cd-Re and Cd-We correlations obtained by our numerical simulations. The current model is superior to the previous drag models, with predicting errors within 20%, by compared to the direct numerical simulation and experimental data. More profoundly, the current model can apply to a wider range of parameters, that is, 1≤Re≤1000 and 0≤We≤20, particularly for high We, when the bubble deformation cannot be neglected.
Structural, electrical, and thermal features of polyimide composites filled with semiconductive MXene sheets
Authors: Feng Qi-Kun , Pei Jia-Yao , Dong Qi , Zhong Shao-Long , Lu Wei-Wei , Zhang Dong-Li , Liu Chang , Dang Zhi-Min
Published: June 2021

Polymer-based dielectrics are widely applied in the fields of electronics and electrical power systems due to the high breakdown strength, excellent flexibility, and unique self-healing capability. However, the low stored energy density and unsatisfactory heat management of polymer dielectrics hinder the development of polymer-based film capacitors. In this research, artificial composites with improved capacitive energy storage and thermal conductivity are fabricated by blending the two-dimensional semiconductive MXene sheets with a polyimide (PI) matrix. Remarkably, a PI based composite with 1 wt. % MXene sheets increases its dielectric permittivity from ≈3.27 to ≈3.53 and enhances its discharged energy density from ≈1.93 to ≈2.38 J/cm3 while maintaining its low dielectric loss of <0.02 and relatively high charge–discharge efficiency of >80%. Meanwhile, a high in-plane thermal conductivity of 0.418 W m−1 K−1 is achieved for PI/MXene composites with 5 wt. % MXene. In addition, the distribution of temperature field inside the composites has been investigated by a finite element method. These results represent a strategy in polymer dielectrics to achieve simultaneous high energy density and thermal conductivity, which may also have potential for applications in high temperature environments.
Time-resolved broadband impulsive stimulated Brillouin scattering in single crystal hematite
Authors: Gicala Patrick , Cheng Meixin , Lott Tyler S. , Du Kai , Cheong Sang-Wook , Petruk Ariel A. , Pichugin Kostyantyn , Sciaini German
Published: June 2021

Impulsive stimulated Brillouin scattering (ISBS) has emerged as a noninvasive means to determine the elastic properties of transparent materials. Here, we report on time-resolved broadband ISBS reflectivity measurements in single crystal hematite, α-Fe2O3. We found that the observed transient reflectivity changes are best described by the known strain propagation model (SPM) and introduced a simple derivation of the ISBS-SPM formula based on ray tracing, which accounts for the presence of the interface. Measurements at different incident probe beam angles illustrate a plausible approach toward determining the speed of sound in transparent media without any prior knowledge of their dielectric properties and vice versa.
Aerobic bacterial methane synthesis
Authors: Wang Qian , Alowaifeer Abdullah , Kerner Patricia , Balasubramanian Narayanaganesh , Patterson Angela , Christian William , Tarver Angela , Dore John E. , Hatzenpichler Roland , Bothner Brian , McDermott Timothy R.
Published: June 2021

Significance

Observations summarized herein contribute to an ongoing paradigm shift in microbial ecology, documenting an emergent property of ecosystem function that further challenges the perception that biogenic methane (CH
4
) production is strictly an anaerobic process. Relevant metabolites, a model bacterial isolate, gene, and enzyme are identified, and we show how this property can conceivably be broadly distributed in the biosphere and contribute to global CH
4
emissions. Scientifically, this study will enable lines of investigation that will expand our understanding of CH
4
synthesis and emission in nature and illustrates how CH
4
synthesis may actually serve as a nexus for the C and N cycles in nature.
Connecting structure and function from organisms to molecules in small-animal symbioses through chemo-histo-tomography
Authors: Geier Benedikt , Oetjen Janina , Ruthensteiner Bernhard , Polikarpov Maxim , Gruber-Vodicka Harald R. , Liebeke Manuel
Published: June 2021

Significance

Metabolites mediate the establishment and persistence of most interkingdom symbioses. Still, to pinpoint the metabolites each partner displays upon interaction remains the biggest challenge in studying multiorganismal assemblages. Addressing this challenge, we developed a correlative imaging workflow to connect the in situ production of metabolites with the organ-scale and cellular three-dimensional distributions of mutualistic and pathogenic (micro)organisms in the same host animal. Combining mass spectrometry imaging and micro-computed X-ray tomography provided a culture-independent approach, which is essential to include the full spectrum of naturally occurring interactions. To introduce the potential of combining high-resolution tomography with metabolite imaging, we resolved the metabolic interactions between an invertebrate host, its symbiotic bacteria, and tissue parasites at unprecedented detail for model and nonmodel symbioses.
Aerodynamic integration produces a vehicle shape with a negative drag coefficient
Authors: Salari Kambiz , Ortega Jason M.
Published: June 2021

Negative drag coefficients are normally associated with a vessel outfitted with a sail to extract energy from the wind and propel the vehicle forward. Therefore, the notion of a heavy vehicle, that is, a semi truck, that generates negative aerodynamic drag without a sail or any external appendages may seem implausible, especially given the fact that these vehicles have some of the largest drag coefficients on the road today. However, using both wind tunnel measurements and computational fluid dynamics simulations, we demonstrate aerodynamically integrated vehicle shapes that generate negative body-axis drag in a crosswind as a result of large negative frontal pressures that effectively “pull” the vehicle forward against the wind, much like a sailboat. While negative body-axis drag exists only for wind yaw angles above a certain analytical threshold, the negative frontal pressures exist at smaller yaw angles and subsequently produce body-axis drag coefficients that are significantly less than those of modern heavy vehicles. The application of this aerodynamic phenomenon to the heavy vehicle industry would produce sizable reductions in petroleum use throughout the United States.
Pollination interactions promoting plant invasions.
Authors:   School of Environmental Sciences,University of Guelph,Guelph,Canada., Montero-Castaño Ana , Traveset Anna ,   Mediterranean Institute of Advanced Studies (IMEDEA-CSIC),Esporles,Mallorca,Spain.
Published: June 2021

Most plant species rely on, or benefit from, animal pollination. Therefore, pollination interactions are expected to play a key role in the reproduction and invasion success of non-native plants in their new areas. Understanding this role will allow us to better predict certain plant invasions. Also, it will allow us to explore the potential of invasion management measures based on disrupting or avoiding pollination interactions. In this chapter we review the available information on reproductive systems and their degree of dependence on animal-mediated pollination of non-native plant species. We review the characteristics of resident pollinators feeding on non-native plants and the different environmental setups that allow or impede non-native plants to reproduce in their new areas. Finally, we explore the scarce literature on invasion management measures based on disrupting pollination interactions and discuss their potentiality. Evidence so far shows that animal pollination does not usually act as an effective barrier to invasion. Most introduced plants are able to receive suitable pollination service from resident pollinators, while others are able to minimize their reliance on pollinators through different mechanisms (e.g. selfing or asexual reproduction). The environmental settings where the introduction occurs (for instance, the presence of neighbours with similar or dissimilar flower morphologies), can play an important role on the success or failure of non-native plants overcoming reproductive barriers. Although it seems that most introduced plants do not face pollination barriers, we consider that, for certain species, the disruption or avoidance of pollination interactions as control or prevention measures deserve further exploration.
The role of plant-plant facilitation in non-native plant invasions.
Authors:   Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile., Cavieres Lohegrin A. ,   Instituto de Ecología y Biodiversidad (IEB), Santiago, Chile
Published: June 2021

Biological invasions are one the most important drivers of the current environmental changes generating important biodiversity losses. Although several hypotheses have been proposed to understand the mechanisms underpinning biological invasions, most of them relate to negative interactions among native and invasive species, where the capacity for many invasive species to reduce diversity is often attributed to a greater competitiveness. However, neighbouring species can also show facilitative interactions, where the presence of one species can facilitate another directly by improving environmental conditions or indirectly through negative effects on a third party species. This chapter reviews the scientific literature on plant invasion, seeking examples of where facilitative interactions either among native and non-native plant species or among non-native species were demonstrated. There are several examples of native species that directly facilitate a non-native species, while examples of native species having a negative effect either on a native or a non-native species that compete with a target non-native, generating a net indirect facilitative effect of the native on the target non-native, are less numerous. Direct facilitation among non-native species has been reported as part of the 'invasional meltdown' phenomenon (Chapter 8, this volume). There are cases where non-native species can have a negative effect on a native species that competes with a target non-native, generating a net indirect facilitative effect among the non-natives. Finally, a non-native species can have a direct facilitative effect on native species, which might have important implications in restoration.
Biotic resistance to plant invasions.
Authors:   Smithsonian Environmental Research Center,Edgewater,Maryland,USA., Parker John D. , Devaney John L. ,   Smithsonian Environmental Research Center,Edgewater,Maryland,USA.,   Department of Biology,Maynooth University,Maynooth,Co. Kildare,Irish Republic., Lemoine Nathan P.
Published: June 2021

Biotic resistance to plant invasions takes many forms: consumption by native herbivores, competition with native plants and infection by native pathogens. But how often does biotic resistance prevent the damaging monocultures that typify the most problematic plant invaders, and how often is biotic resistance overwhelmed by the direct and indirect impacts of human activities? This chapter attempts to answer these questions, drawing on the long history of research into biotic resistance. We first briefly describe the major forms of biotic resistance to exotic plant invasions as an antecedent to other, more detailed chapters on competition, herbivory and pathogens. We then describe a new neutral model where variance in disturbance promotes invasions over the short term, but over longer timescales only propagule pressure drives invasions. These findings are a cautionary tale; pending increases in global trade and travel, particularly to the tropics, may provide the prerequisite disturbance and propagule pressure needed to ultimately stoke further invasions. Finally, we highlight case studies where invasions have been mitigated by restoration of biotic resistance from native herbivores and competitors. These studies provide strong empirical support that conservation of native biodiversity can be a nature-based solution to some invasions, although it remains to be seen if climate change will alter these effects over longer timescales.
How can progress in the understanding of antagonistic interactions be applied to improve biological control of plant invasions?
Authors:   Centre for Biological Control,Department of Zoology and Entomology,Rhodes University,Grahamstown,6140,South Africa., Hill Martin P. , Coetzee Julie E. ,   Centre for Biological Control,Botany Department,Rhodes University,Grahamstown,6140,South Africa.
Published: June 2021

Classical biological control has been used as a management tool for invasive non-native plant species globally for over 200 years. There have been some very successful programmes, most notably on waterweeds, cacti and seed reduction in perennial trees. Seventy per cent of agents released have established in at least one instance, and 66% of the targeted invasive species have showed some level of control. However, some programmes have failed to meet expectations, for example on Lantana camara. The most commonly cited reasons for the failure of establishment or limited efficacy of biological control agents are unsuitable climatic conditions and genotype incompatibility. We propose that antagonistic biotic interactions play a significant role in the outcomes of weed biological control programmes. Induced plant defences (physical and chemical) that can be mounted rapidly by the invasive non-native plants can result in the reduction in agent populations after initial attack. Rapid induction of plant defences have been implicated in the lack of long-term establishment of the agent Falconia intermedia that showed great initial promise against the widespread invasive shrub L. camara. Host range expansion by native natural enemies onto biological control agents have also been shown to reduce population growth of agents. Finally, competition from indigenous plant species aids invasive alien plant population reduction in the presence of herbivory. All three factors have been poorly studied and further work is needed to better explain the outcomes of weed biological control programmes.
The fast-track land reform programme in Zimbabwe: implications for land restitution
Authors: Rusenga Clemence , Ncube Senzeni
Published: June 2021

This study explores implications of the failure to accommodate formal land restitution in the Zimbabwean Fast-Track Land Reform Programme (FTLRP), resulting in neglect of local communities’ autochthonous connections to land especially where their interests clash with those of political elites. It makes the point that this opened land reform to abuse by political elites and marginalized competing local community interests in prime land and valuable agricultural properties. In the absence of a formal policy for restitution, elites mobilized political and state power to enforce their commercial interests over those of neighbouring communities. Drawing from international experiences, the study argues that a formal policy of land restitution would enable local communities, including ethnic minorities, to legally reclaim lost ancestral land and limit elite capture of valuable agricultural properties.
Getting There: Strategies To Improve Gender Equality In Pharmaceuticals And Healthcare
Authors: Sandle Tim
Published: June 2021

Women make up the majority of the workforce in pharmaceuticals and healthcare globally, yet the distribution of pay, other benefits, scientific standing, representation in leadership positions, and access to certain occupations, is highly disproportionate. Some progress is being made, especially with more women occupying higher positions within...
Shining (Invisible) Light On Viral Pathogens: Virucidal Contamination Control Strategies Using UV-C Light
Authors: Sandle Tim
Published: June 2021

Respiratory droplets are coronaviruses primary transmission mode and thus the majority of coronavirus risk mitigation strategies focus on the control of air. However, surface contact remains an alternative infection route. Hence, it remains a concern that the SARS CoV-2 virus can remain viable on surfaces for several hours.
Cardiac mechanical efficiency is preserved in primary cardiac hypertrophy despite impaired mechanical function
Authors: Han June-Chiew , Tran Kenneth , Crossman David J. , Curl Claire L. , Koutsifeli Parisa , Neale Joshua P.H. , Li Xun , Harrap Stephen B. , Taberner Andrew J. , Delbridge Lea M.D. , Loiselle Denis S. , Mellor Kimberley M.
Published: June 2021

Increased heart size is a major risk factor for heart failure and premature mortality. Although abnormal heart growth subsequent to hypertension often accompanies disturbances in mechano-energetics and cardiac efficiency, it remains uncertain whether hypertrophy is their primary driver. In this study, we aimed to investigate the direct association between cardiac hypertrophy and cardiac mechano-energetics using isolated left-ventricular trabeculae from a rat model of primary cardiac hypertrophy and its control. We evaluated energy expenditure (heat output) and mechanical performance (force length work production) simultaneously at a range of preloads and afterloads in a microcalorimeter, we determined energy expenditure related to cross-bridge cycling and Ca2+ cycling (activation heat), and we quantified energy efficiency. Rats with cardiac hypertrophy exhibited increased cardiomyocyte length and width. Their trabeculae showed mechanical impairment, evidenced by lower force production, extent and kinetics of shortening, and work output. Lower force was associated with lower energy expenditure related to Ca2+ cycling and to cross-bridge cycling. However, despite these changes, both mechanical and cross-bridge energy efficiency were unchanged. Our results show that cardiac hypertrophy is associated with impaired contractile performance and with preservation of energy efficiency. These findings provide direction for future investigations targeting metabolic and Ca2+ disturbances underlying cardiac mechanical and energetic impairment in primary cardiac hypertrophy.
Is there really a Hubble tension?
Authors: Rameez Mohamed , Sarkar Subir
Published: June 2021

The heliocentric redshifts (z
hel) reported for 150 type Ia supernovae in the Pantheon compilation are significantly discrepant from their corresponding values in the JLA compilation. Both catalogues include corrections to the redshifts and magnitudes of the supernovae to account for the motion of the heliocentric frame relative to the ‘CMB rest frame’, as well as corrections for the directionally coherent bulk motion of local galaxies with respect to this frame. The latter is done employing modelling of peculiar velocities which assume the ΛCDM cosmological model but nevertheless provide evidence for residual bulk flows which are discordant with this model (implying that the observed Universe is in fact anisotropic). Until recently such peculiar velocity corrections in the Pantheon catalogue were made at redshifts exceeding 0.2 although there is no data on which to base such corrections. We study the impact of these vexed issues on the 4.4σ discrepancy between the Hubble constant of H
0 = 67.4 ± 0.5 km s−1 Mpc−1 inferred from observations of CMB anisotropies by Planck assuming ΛCDM, and the measurement of H
0 = 73.5 ± 1.4 km s−1 Mpc−1 by the SH0ES project which extended the local distance ladder using type Ia supernovae. Using the same methodology as the latter study we find that for supernovae whose redshifts are discrepant between Pantheon and JLA with Δz
hel > 0.0025, the Pantheon redshifts favour H
0 ≃ 72 km s−1 Mpc−1, while the JLA redshifts favour H
0 ≃ 68 km s−1 Mpc−1. Thus the discrepancies between SNe Ia datasets are sufficient to undermine the claimed ‘Hubble tension’. We further note the systematic variation of H
0 by ∼6–9 km s−1 Mpc−1 across the sky seen in multiple datasets, implying that it cannot be measured locally to better than ∼10% in a model-independent manner.
On the elliptic sinh–Gordon equation with integrable boundary conditions
*
Authors: Kilian M , Smith G
Published: June 2021

We adapt Sklyanin’s K-matrix formalism to the sinh–Gordon equation, and prove that all free boundary constant mean curvature annuli in the unit ball in

R

3

are of finite type.
Quantifying entropy production in active fluctuations of the hair-cell bundle from time irreversibility and uncertainty relations
Authors: Roldán Édgar , Barral Jérémie , Martin Pascal , Parrondo Juan M R , Jülicher Frank
Published: June 2021

We introduce lower bounds for the rate of entropy production of an active stochastic process by quantifying the irreversibility of stochastic traces obtained from mesoscopic degrees of freedom. Our measures of irreversibility reveal signatures of time’s arrow and provide bounds for entropy production even in the case of active fluctuations that have no drift. We apply these irreversibility measures to experimental recordings of spontaneous hair-bundle oscillations in mechanosensory hair cells from the ear of the bullfrog. By analyzing the fluctuations of only the tip position of hair bundles, we reveal irreversibility in active oscillations and estimate an associated rate of entropy production of at least ∼3k
B/s, on average. Applying thermodynamic uncertainty relations, we predict that measuring both the tip position of the hair bundle and the mechano-electrical transduction current that enters the hair cell leads to tighter lower bounds for the rate of entropy production, up to ∼103
k
B/s in the oscillatory regime.
Robust H
∞ state estimation for a class of complex networks with dynamic event-triggered scheme against hybrid attacks
Authors: Deng Yahan , Mo Zhongkai , Lu Hongqian
Published: June 2021

We investigate the dynamic event-triggered state estimation for uncertain complex networks with hybrid delays suffering from both deception attacks and denial-of-service attacks. Firstly, the effects of time-varying delays and finite-distributed delays are considered during data transmission between nodes. Secondly, a dynamic event-triggered scheme (ETS) is introduced to reduce the frequency of data transmission between sensors and estimators. Thirdly, by considering the discussed plant, dynamic ETS, state estimator, and hybrid attacks into a unified framework, this framework is transferred into a novel dynamical model. Furthermore, with the help of Lyapunov stability theory and linear matrix inequality techniques, sufficient condition to ensure that the system is exponentially stable and satisfies H
∞ performance constraints is obtained, and the design algorithm for estimator gains is given. Finally, two numerical examples verify the effectiveness of the proposed method.
Collective behavior of cortico-thalamic circuits: Logic gates as the thalamus and a dynamical neuronal network as the cortex
Authors: Bahramian Alireza , Jamal Sajjad Shaukat , Parastesh Fatemeh , Rajagopal Kartikeyan , Jafari Sajad
Published: June 2021

This paper introduces a two-layer network to investigate the effects of cortico-thalamic circuits on the cortexʼs collective behavior. In the brain, different parts of the cortex collaborate to process information. One of the main parts, which is the path of different cortex contacts, is the thalamus whose circuit is referred to as the “vertical” cortico-thalamic connectivity. Thalamus subnuclei can participate in the processing of the information that passes through them. It has been shown that they play the functional role of logic gates (AND, OR and XOR). To study how these thalamus circuits affect the cortical neuron behavior, a two-layer network is proposed wherein the cortex layer is composed of Hindmarsh–Rose models and the thalamus layer is constructed with logic gates. Results show that considering these logic gates can lead the network towards different synchronization, asynchronization, chimera and solitary patterns. It is revealed that for AND-gate and OR-gate, increasing the number of gates or their outputs can increase and decrease the networkʼs coherency in excitatory and inhibitory cases, respectively. However, considering XOR-gates always results in the chimera state.
An extended smart driver model considering electronic throttle angle changes with memory
Authors: Wu Congzhi , Ge Hongxia , Cheng Rongjun
Published: June 2021

Based on the fact that the electronic throttle angle effect performs well in the traditional car following model, this paper attempts to introduce the electronic throttle angle into the smart driver model (SDM) as an acceleration feedback control term, and establish an extended smart driver model considering electronic throttle angle changes with memory (ETSDM). In order to show the practicability of the extended model, the next generation simulation (NGSIM) data was used to calibrate and evaluate the extended model and the smart driver model. The calibration results show that, compared with SDM, the simulation value based on the ETSDM is better fitted with the measured data, that is, the extended model can describe the actual traffic situation more accurately. Then, the linear stability analysis of ETSDM was carried out theoretically, and the stability condition was derived. In addition, numerical simulations were explored to show the influence of the electronic throttle angle changes with memory and the driver sensitivity on the stability of traffic flow. The numerical results show that the feedback control term of electronic throttle angle changes with memory can enhance the stability of traffic flow, which shows the feasibility and superiority of the proposed model to a certain extent.
Color halo scenario of charmonium-like hybrids *
Authors: Ma Yunheng , Sun Wei , Chen Ying , Gong Ming , Liu Zhaofeng
Published: June 2021

The internal structures of

charmonium-like hybrids are investigated under lattice QCD in the quenched approximation. We define the Bethe-Salpeter wave function (

) in the Coulomb gauge as the matrix element of a spatially extended hybrid-like operator (

) between the vacuum and n-th state for each

, with r being the spatial separation between a localized

component and the chromomagnetic strength tensor. These wave functions exhibit some similarities for states with the aforementioned different quantum numbers, and their r-behaviors (no node for the ground states and one node for the first excited states) imply that r can be a meaningful dynamical variable for these states. Additionally, the mass splittings of the ground states and first excited states of charmonium-like hybrids in these channels are obtained for the first time to be approximately 1.2-1.4 GeV. These results do not support the flux-tube description of heavy-quarkonium-like hybrids in the Born-Oppenheimer approximation. In contrast, a charmonium-like hybrid can be viewed as a “color halo” charmonium for which a relatively localized color octet

is surrounded by gluonic degrees of freedom, which can readily decay into a charmonium state along with one or more light hadrons. The color halo picture is compatible with the decay properties of

and suggests LHCb and BelleII to search for

charmonium-like hybrids in

and

final states.
The entrance channel effect on the synthesis of a superheavy element 296119
Authors: Naderi D. , Sharifi B.
Published: June 2021

In this study, we investigated the entrance channel effect on the evaporation residue cross section of a superheavy element 296119. Using 29 projectile-target combinations, we investigated the role of the entrance channel on the 3n and 4n evaporation channels in hot combinations. This effect can be evaluated based on the entrance channel asymmetry and Q value of complete fusion. We calculated the variation of the maximum evaporation residue cross sections (

and

) with

for the reactions

,

,

, and

. With an increase in

,

and

increase. In addition, we studied the role of asymmetry and mean fissility parameters in the synthesis of the superheavy element. The obtained results in this study can be utilized in future studies.
An Artificial Intelligence Security Framework
Authors: Jing Huiyun , Wei Wei , Zhou Chuan , He Xin
Published: June 2021

With the overall acceleration of the scale construction and application of artificial intelligence worldwide, the security risks of artificial intelligence infrastructure, design and development, and integration applications are becoming increasingly prominent. Major countries have developed AI security governance by formulating AI ethical norms and improving laws and regulations and industry management. Artificial intelligence security technology system is an essential part of artificial intelligence security governance, critical support for implementing artificial intelligence ethical norms, meeting legal and regulatory requirements. It is also an important guarantee for the artificial intelligence industry’s healthy and orderly development. This article in view of the problem of lacking artificial intelligence security framework worldwide, focusing on the current artificial intelligence prominent security risks, proposes an AI security framework that covers AI security goals, graded capabilities of AI security, and AI security technologies and management systems. We look forward to providing useful references for the community to improve the safety and protection capabilities of artificial intelligence.
The optimization of machining cutting zone based on improved genetic algorithm
Authors: Ji S C , Lu D X , Deng L
Published: June 2021

The processing accuracy in the machining cutting zone is uneven. The condition of processing parts is most sharply worsened, when the guides junction occurs opening (the graph of pressure in the guides’ surfaces is not distributed over their entire length). The aim of this paper is optimization of the effective cutting zone (ECZ) of machining tool, in which graph of the guides pressure is always distributed on all surfaces. The layout of machining tools must ensure the largest zone of ECZ. The optimization of the objective function could change these parameters of layout, such as the vector of cutting forces, the weighting centre of the support, the coordinates of applied force from driving system, the width and length of guides. The task of optimization is a nonlinear extreme. According to the structural parameters of the machine tool, the pressure equation of the guide rail is established. For finding the optimal value, the method for determining extremum of the objective function used improving genetic algorithm (GA). Application of the method GA has allowed approximately ten times to raising the speed of determining of the layout parameters that ensure the largest ECZ.