bluuebunny/crossref_metadata_2025 huggingface dataset:
Separation of a binary gas mixture outflowing into vacuum through a micronozzle
Authors: Kosyanchuk Vasily , Yakunchikov Artem
Published: August 2021

The present paper studies the separation phenomenon for argon–helium mixture outflowing through a convergent–divergent micronozzle into a vacuum. We numerically investigate the effect of the geometrical parameters of the micronozzle and gas rarefaction (Knudsen number is varied in range ≈0.01−100). Simulations were performed using the event-driven molecular dynamics method. Performed analysis revealed several interesting and important features of the separation process. First, it was shown that separation in the present problem results mainly from a lateral component, which appears when significant curvature of gas streamlines is present. Second, it was demonstrated how the fine-tuning of micronozzle geometry can enhance separation efficiency. At the same time, the simplest microslit arrangement (a microchannel without converging and diverging parts) was shown to provide results comparable to micronozzles and may be preferable due to its manufacturing simplicity. Then, it was shown that the position of the product gas selector is crucial for effective separation and its proper placement brings more influence than the geometry of the micronozzle itself. Finally, it was shown that maximal purity of product gas can be obtained in a peripheral area in transitional and slip flow regimes inside the micronozzle. Therefore, for effective separation, there is no need to achieve high rarefaction levels inside the micronozzle.
Multifunctionality in (K,Na)NbO3-based ceramic near polymorphic phase boundary
Authors: Wang Xiangjian , Lou Xiaojie , Geng Wenping , Yao Yingbang , Tao Tao , Liang Bo , Lu Sheng-Guo
Published: August 2021

The 0.95K0.42Na0.58Nb0.96Sb0.04O3–0.02BaZrO3–0.03Bi0.5K0.5HfO3 ceramic was fabricated via a conventional solid-state reaction. This ceramic exhibits the diffuse polymorphic phase boundary (PPB) near room temperature. The dielectric, ferroelectric, electromechanical, electrocaloric, and dielectric energy storage properties were studied systemically. The normalized large signal d33* values are approximately 400–600 pm/V at measured temperatures and electric fields, which are larger than or comparable with the values reported in other lead-free compositions. The electrocaloric strength is enhanced at the broad region of PPB provided by the indirect and direct measurements. At low field of 30 kV/cm, the dielectric energy storage is ∼0.12–018 J/cm3 at relative broad temperature range due to the diffuse nature of polymorphic phase boundary. Theoretical simulations reveal that multi-element dopants, such as Sb5+, Hf4+, Zr4+, and Bi3+ ions, could induce the breaking of local structure symmetry in the orthorhombic phase to form the PPB. In addition, the charge distribution may also break the long-range ferroelectric order through the analysis of Bader charge. Our study suggests that the K0.5Na0.5NbO3-based ceramic exhibits improved performance and good thermal stability in piezoelectric, electrocaloric, and dielectric energy storage characteristics in terms of the design of multi-element dopants to form the PPB and it will benefit the promising applications in electronic devices.
Superconductivity in infinite layer nickelates
Authors: Ji Yaoyao , Liu Junhua , Li Lin , Liao Zhaoliang
Published: August 2021

The discovery of an infinite layer nickelate superconductor in 2019 provided a perfect ending to the long race of searching nearly 30 years for a cuprate analog and at the same time marks a new era of nickel-based superconductivity. The similarities and differences between nickelates and cuprates provide great opportunities for us to reveal the origin of high-Tc superconductivity. Therefore, the observation of nickelate superconductivity is now motivating tremendous efforts to look into this new superconducting family from both aspects of experiment and theory. Here, we give an early perspective on the superconductivity in nickelates, including (1) the theoretical explorations and main conclusions in the past; (2) the newly discovered superconductor R1−xSrxNiO2, in terms of its synthesis, electronic structure, and comparison with cuprates; and (3) the future perspectives of nickelate superconductivity.
Water on hydroxylated silica surfaces: Work of adhesion, interfacial entropy, and droplet wetting
Authors: Bistafa Carlos , Surblys Donatas , Kusudo Hiroki , Yamaguchi Yasutaka
Published: August 2021

In the last few years, much attention has been devoted to the control of the wettability properties of surfaces modified with functional groups. Molecular dynamics (MD) simulation is one of the powerful tools for microscopic analysis providing visual images and mean geometrical shapes of the contact line, e.g., of nanoscale droplets on solid surfaces, while profound understanding of wetting demands quantitative evaluation of the solid–liquid (SL) interfacial tension. In the present work, we examined the wetting of water on neutral and regular hydroxylated silica surfaces with five different area densities of OH groups ρAOH, ranging from a non-hydroxylated surface to a fully hydroxylated one through two theoretical methods: thermodynamic integration (TI) and MD simulations of quasi-two-dimensional equilibrium droplets. For the former, the work of adhesion needed to quasi-statically strip the water film off the solid surface was computed by the phantom wall TI scheme to evaluate the SL interfacial free energy, whereas for the latter, the apparent contact angle θapp was calculated from the droplet density distribution. The theoretical contact angle θYD and the apparent one θapp, both indicating the enhancement of wettability by an increase in ρAOH, presented good quantitative agreement, especially for non-hydroxylated and highly hydroxylated surfaces. On partially hydroxylated surfaces, in which θYD and θapp slightly deviated, the Brownian motion of the droplet was suppressed, possibly due to the pinning of the contact line around the hydroxyl groups. Relations between work of adhesion, interfacial energy, and entropy loss were also analyzed, and their influence on the wettability was discussed.
Source-like patterns of flow past a circular cylinder of finite span at low Reynolds numbers
Authors: Chang Yuan-Shuo , Chen Yi-Ju , Qiu Yu-Hau , Chang Chien C. , Chu Chin-Chou , Lee Fang-Shou
Published: August 2021

This article is to report results of a joint numerical and experimental investigation of vortex structures of flow past a circular cylinder of diameter D and finite span L in a range of low Reynolds numbers. The aspect ratio (AR) (= L/D) of the cylinder varies from 1.5 to 5, and the Reynolds number Re varies from 10 to 150. Given Re = 80, we study the various cases of AR, and given AR = 5, we study the various cases of Reynolds numbers Re. In a regime of parameters, the flow is found to be steady, separated, and doubly symmetric. Beyond this regime, the present study also covers a range of unsteady flow with vortex shedding in the wake behind the cylinder. This study is focused on the streamline patterns on the two planes of symmetry: the middle cross section plane (MCP) of the circular cylinder as well as on the bisectional cross section plane (BCP) on the circular cylinder. The exclusive phenomenon discovered is the occurrence, in a range of flow conditions, of a point-like or line-like source pattern of streamlines in the wake on the MCP. The center of the singular source is denoted by the center of the source (CS). In the cases of steady flow, there is always a pair of recirculating eddies on the BCP, which forms a saddle point (SP) structure at their far end from the cylinder. At the occurrence of source-like flow patterns, CS coincides with SP, signifying that the source-like points concentrate in a small neighborhood of CS (or SP). The SP is characterized by normalizing the location of the source Ds from the cylinder center. It is given a definition of the strength of the source (SS), determined by normalizing the two-dimensional divergence ∇2·v on the MCP. Moreover, the flow patterns with or without a singular source are classified into four categories on the Re–AR parameter plane. In particular, a criterion on SS is found for the occurrence of a source-like pattern. The formation of the source-like wake flow and variations of the source locations and the source strength with Re and AR are given full physical explanations. The interesting trends of the drag coefficients with AR are explained on the relative importance of the surface friction and the pressure (form) drag.
An all-dielectric metasurface absorber based on surface wave conversion effect
Authors: Wen Jingda , Ren Qiang , Peng Ruiguang , Zhao Qian
Published: August 2021

The high-absorption ultra-thin metasurface absorber has important applications in EM radiation prevention and stealth design. In this paper, the proposed metasurface absorber composed of one-dimensional phase gradient supercell and uniform resonant supercell can reach perfect absorption at 10 GHz by reducing the scattering of the surface wave. Furthermore, the two-dimensional phase gradient metasurface absorber has better absorption of waves with different polarization angles and a wider range of incident angles. Our work provides a promising method to achieve high absorption, which is simpler and more robust than adjusting the effective EM parameters of metasurface absorber.
Numerical investigation of sheath characteristics for electronegative magnetized plasma and dust charging
Authors: Basnet Suresh , Maskey Anish , Deuja Atit , Khanal Raju
Published: August 2021

We have studied the effects of the magnetic field on the active electronegative plasma sheath properties and dust charging process in the sheath region for two different collisional models: constant ion mean free path and constant ion mobility using 1d3v fluid hydrodynamics model. It is found that the magnetic field strength and choice of collisional models have a significant effect on the active plasma sheath characteristics and charging of an isolated dust grain. The sheath criterion for an active electronegative magnetized plasma for both collisional models has been extended, and the effects of neutral gas pressure, source frequency, obliqueness of magnetic field, and initial electric field at sheath edge are graphically illustrated. There are two distinct regions observed in the sheath region: magnetic field and electric field dominant regions. The spatial distribution of plasma sheath parameters is systematically presented. It is found that the evolution of dust surface potential is affected by the magnitude of the magnetic field and collisional models. The stable levitation of dust grains in the sheath region is close to the sheath entrance. Moreover, the total force experienced by an isolated dust grain in the sheath region rapidly increases close to the material surface, and the magnitude of force is higher for larger dust grain.
Blast in the one-dimensional cold gas: Comparison of microscopic simulations with hydrodynamic predictions
Authors: Ganapa Santhosh , Chakraborti Subhadip , Krapivsky P. L. , Dhar Abhishek
Published: August 2021

We study the response of an infinite system of point particles on the line initially at rest to the instantaneous release of energy in a localized region. The blast generates shock waves, and we make a detailed comparison of the density, velocity, and temperature in the growing region between the shock waves predicted by Euler equations for the ideal nondissipative compressible gas and the results of direct microscopic simulations. At long times, the hydrodynamic variables acquire self-similar forms with scaling functions predicted by the Taylor–von Neumann–Sedov (TvNS) blast-wave solution. The scaling functions obtained from the microscopic dynamics show a remarkable agreement with the TvNS predictions, except at the blast core, where the TvNS solution predicts a diverging temperature, which is not observed in simulations. We show that the effect of heat conduction becomes important and present results from a numerical solution of the Navier–Stokes–Fourier equations. A different scaling form is observed in the blast core. Our microscopic model is the one-dimensional hard-point gas with binary mass distribution and alternating masses. This infinitely dilute gas has the ideal gas equation of state and is nonintegrable and known to display fast equilibration.
A microwave sensor for measuring multi-frequency full characteristics of magneto-dielectric materials
Authors: Shen Haitao , Zhang Yifan , Niu Tiaoming , Mei Zhonglei
Published: August 2021

In this paper, a microwave sensor based on a complementary split resonance ring structure is proposed to measure the full characteristics of magneto-dielectric materials at multiple frequencies. The sensor is generally an upside down microstrip line structure. Circular and semicircular grooves are engraved at the top ground side to probe the material, and a voltage-controlled variable capacitance diode is added to play the role of frequency tuning. The proposed design provides two separate areas for permittivity and permeability sensing, with higher-strength electric and magnetic fields in each area. By analyzing the measured resonant frequency and quality factor of the microstrip line, the real and imaginary parts of the permittivity and permeability of the material can be determined. Different from other sensors, the proposed sensor can measure permittivity and permeability with two separate measurements using only one sample, and it can measure the permittivity and permeability at multiple frequencies. Numerical calculations and experimental data are given, which clearly support our design.
Acoustics of oscillating bubbles when a drop hits the water surface
Authors: Prokhorov V. E.
Published: August 2021

In experiments on a collision of a drop with the water surface, video recording of gas bubbles detached from underwater cavities was accompanied by simultaneous measurement of acoustic radiation. In each experiment, a number of video frames, in which the bubbles exhibit a rotational symmetry, were extracted and processed. The curvatures and volumes of the bubbles were derived, from which time series of volumetric oscillations and an external pressure component introduced by surface tension were calculated. The frequencies found from the spectra of volumetric and acoustic oscillations match well with both each other and the natural frequency defined by the bubble size at rest. An eventual mechanism of the bubble oscillations is an abrupt fall of an external pressure caused by a loss of the curvature during detachment of the bubble. The pressure fall leads to an expansion of gas inside the bubble, triggering the volumetric oscillations and accompanying acoustic radiation, which starts with a positive half-wave.
The effect of gravity on turbulence modulation in particle-laden horizontal open channel flow
Authors: Wang Ping , Li Jinchi , Zheng Xiaojing
Published: August 2021

Two-way coupled direct numerical simulation of turbulence in a horizontal open channel with Lagrangian tracking of heavy particles is performed to study the joint influence of particle inertia and wall-normal gravity on turbulence modulation. The Stokes numbers based on the wall units considered in the study are St+= 1 (low inertia), 31 (moderate inertia), and 202 (high inertia) and the gravitational accelerations are g+= 0, 0.0068, 0.068, and 0.2221, varying from case to case. It is found that heavy particles (gravity involved in simulation) with low inertia subtly increase or have little significant influence on turbulence modulation, regardless of gravitational acceleration. Particles with high inertia and large gravitational acceleration significantly reduce the mean streamwise fluid velocity and the scales of turbulence structure near the wall, and vice versa in the outer layer. In this case, turbulence fluctuations are notably suppressed and the turbulence structures tend to be two-dimensional and laminar due to the strong rebound and trajectory-crossing effect. Moderate-inertia particles probably cause anisotropic turbulence modulation due to the competition between particle inertia and gravity settling. In the parameter range studied in this work, particles have indistinctive modification on turbulence when τp+g+ (=St+g+)<0.2 but suppress turbulence when τp+g+>0.2.
Efimov-DNA phase diagram: Three stranded DNA on a cubic lattice
Authors: Bhattacharjee Somendra M. , Foster Damien Paul
Published: August 2021

We define a generalized model for three-stranded DNA consisting of two chains of one type and a third chain of a different type. The DNA strands are modeled by random walks on the three-dimensional cubic lattice with different interactions between two chains of the same type and two chains of different types. This model may be thought of as a classical analog of the quantum three-body problem. In the quantum situation, it is known that three identical quantum particles will form a triplet with an infinite tower of bound states at the point where any pair of particles would have zero binding energy. The phase diagram is mapped out, and the different phase transitions are examined using finite-size scaling. We look particularly at the scaling of the DNA model at the equivalent Efimov point for chains up to 10 000 steps in length. We find clear evidence of several bound states in the finite-size scaling. We compare these states with the expected Efimov behavior.
Thermoelectric characterization of the clathrate-I solid solution Ba8−
δ
AuxGe46−x
Authors: Baitinger Michael , Nguyen Hong Duong , Candolfi Christophe , Antonyshyn Iryna , Meier-Kirchner Katrin , Veremchuk Igor , Razinkov Valeriy , Havryluk Mykola , Cardoso-Gil Raul , Burkhardt Ulrich , Böhme Bodo , Anatychuk Lukyan , Grin Yuri
Published: August 2021

Clathrate-I-based materials are promising for waste-heat recovering applications via thermoelectric (TE) effects. However, the lack of highly efficient p-type materials hampers the development of clathrate-based TE devices. In this work, the synthesis of the p-type semiconductor Ba7.8Au5.33Ge40.67 with clathrate-I structure is up-scaled by steel-quenching and spark plasma sintering treatment at 1073 K. A thermoelectric figure of merit ZT ≈ 0.9 at 670 K is reproducibly obtained, and 40 chemically homogeneous module legs of 5 × 5 × 7 mm3 are fabricated. By using a carbon layer as a diffusion barrier, electrical contacts are sustainable at elevated application temperatures. Eight couples with the clathrate-I compounds Ba7.8Au5.33Ge40.67 as p-type and Ba8Ga16Ge30 as n-type materials are integrated into a TE module with an output power of 0.2 W achieved under a temperature difference ΔT = 380 K (T1 = 673 K and T2 = 293 K). The thermoelectric performance of Ba7.8Au5.33Ge40.67 demonstrates the potential of type-I clathrates for waste heat recycling.
Dynamic magnetic response of ferrofluids under a static electric field
Authors: Rajnak Michal , Dolnik Bystrik , Hodermarsky Patrik , Paulovicova Katarina , Cimbala Roman , Timko Milan , Kopcansky Peter
Published: August 2021

Magnetic nanoparticles in a non-polar ferrofluid can reassemble in external electric fields. The resulting electric field-driven structural changes in ferrofluids are expected to influence the magnetic response of ferrofluids to an alternating magnetic field. Hence, it should be possible to control the magnetic susceptibility of ferrofluids by electric forces. To address the problem of a possible electro-magnetic coupling, a low-frequency alternating current magnetic susceptibility of a ferrofluid based on insulating oil and iron oxide nanoparticles is measured under a static electric field. The electric field is generated by applying a voltage on a pair of electrodes embracing the ferrofluid and acts parallel and perpendicular to the probing alternating magnetic field. The susceptibility is measured simultaneously with the ferrofluid's temperature and a leakage current. A noticeable susceptibility decrease with increasing voltage is found. The susceptibility decrease is partially caused by the temperature increase. Based on theoretical calculations, it is found that the detected temperature increase cannot be the only reason for the measured susceptibility decrease. Other mechanisms resulting from magnetic nanoparticle interactions with the electric field (nanoparticle trapping due to dielectrophoresis, electric field-induced nanoparticle aggregation) must contribute to the susceptibility drop in a static electric field.
Effective potentials induced by mixtures of patchy and hard co-solutes
Authors: Handle Philip H. , Zaccarelli Emanuela , Gnan Nicoletta
Published: August 2021

The addition of co-solutes to colloidal suspensions is often employed to induce tunable depletion interactions. In this work, we investigate effective colloidal interactions arising from binary co-solute mixtures of hard spheres and patchy particles. By changing the relative concentration of the two species, we show that the resulting effective potential Veff continuously changes from the one obtained for a single-component hard sphere co-solute to that mediated by the single-component patchy particle co-solute. Interestingly, we find that, independent of the relative concentration of the two components, the resulting Veff is additive, i.e., it is well-described by the linear combination of the effective interactions mediated by respective pure co-solutes. However, a breakdown of the additivity occurs when the co-solute mixture is close to the onset of a demixing transition. These results represent a step forward in understanding and predicting colloidal behavior in complex and crowded environments and for exploiting this knowledge to design targeted colloidal superstructures.
Quantum efficiency of photoemission from biased metal surfaces with laser wavelengths from UV to NIR
Authors: Zhou Yang , Zhang Peng
Published: August 2021

This paper studies photoelectron emission from metal surfaces with laser wavelengths from 200 to 1200 nm (i.e., ultraviolet to near-infrared), using a recent quantum model based on the exact solution of time-dependent Schrödinger equation. The dominant electron emission mechanism varies from different multiphoton emission processes to dc or optical field emission, depending on the laser intensity, wavelength, and dc bias field. The parametric dependence of the quantum efficiency (QE) is analyzed in detail. It is found that QE can be increased nonlinearly by the non-equilibrium electron heating produced by intense sub-picosecond laser pulses. This increase of QE due to laser heating is the strongest near laser wavelengths where the cathode work function is an integer multiple of the corresponding laser photon energy. The quantum model, with laser heating effects included, reproduces previous experimental results, which further validates our quantum model and the importance of laser heating.
Coupling mechanism between photogenerated carriers and triboelectric charges and photoinduced reinforcement of a triboelectric nanogenerator
Authors: Li Mingqing , Yang Liya , Wang Hao , Qin Chaochao , Song Jinsheng , Zhang Yunchen , Wang Weichao , Wu Yonghui , Zhang Xinan , Zheng Haiwu
Published: August 2021

It has been reported that the output performance of a triboelectric nanogenerator (TENG) can be enhanced by applying light; however, the coupling mechanism between photogenerated carriers and triboelectric charges is still not well explained. Here, we propose a light-enhanced TENG based on a P3HT:PC61BM active blend layer, which processes dual functions of the photoelectric effect and the triboelectric effect. The open-circuit voltage, short circuit current, and amount of transferred charges for the TENG were enhanced by 63%, 76%, and 127%, respectively, after illumination under the white light condition. Moreover, we have investigated the interaction between the triboelectric charges and the photogenerated carriers to further explore the coupling mechanism between the triboelectric and photoelectric effects. Both Kelvin probe force microscopy and conductive atomic force microscopy demonstrate that the photogenerated carriers produced by the P3HT:PC61BM active blend layer can improve the surface triboelectric charge density. More interestingly, the transient absorption spectrum indicates that the electrostatic field induced by triboelectric charges contributes to the dissociation of excitons. In other words, there exists a beneficial promoting effect between the triboelectric charges and the photogenerated carriers during the operation of the light-enhanced TENG. This work provides an important guideline for the design and performance improvement of the hybrid TENG that captures both mechanical energy and light energy simultaneously.
Three-dimensional simulation of clouds of multi-disperse evaporating saliva droplets in a train cabin
Authors: Visone M. , Lanzetta M. , Lappa M. , Lanzaro C. , Polizio L.
Published: August 2021

In line with recent ongoing efforts to collect crucial information about the mechanisms of virus diffusion and put them in relation to the effective complexity of the several natural or artificial environments where human beings leave and operate, the present study deals with the dispersion of evaporating saliva droplets in the cabin of an interregional train. A relevant physical model is constructed taking into account the state of the art in terms of existing paradigms and their ability to represent some fundamental aspects related to the evolution in time of a cloud of multi-disperse droplets. Conveniently, such a theoretical framework is turned into a computational one that relies on low Mach-number asymptotics and can therefore take advantage of the typical benefits (relatively low computational cost) associated with pressure-based methods. Numerical simulations are used to predict the flow established in the cabin as a result of the ventilation systems and related settings dictated by considerations on passenger comfort. The solution of two-way coupled Lagrangian evolution equations is used to capture the associated dynamics of the dispersed phase and predict its transport in conjunction with the peculiar topology of the considered flow and morphology of solid surfaces, which bound it (including the human beings). Typical physiological processes such as talking or coughing are considered. An analysis on the impact of the multiplicity of droplet sources is also conducted, thereby providing some indications in terms of potential risks for the cabin occupants.
Emission and absorption coefficients of diatomic gases in air plasmas produced by Earth entry
Authors: Liang Rihui , Liu Yanming , Li Fangyan
Published: August 2021

Accurate radiative properties data are required for the further calculations of radiative transfer in thermodynamic nonequilibrium plasmas produced by Earth entry. However, most of the published radiative properties were determined using the outdated spectroscopic constants, transition probabilities, and partition functions, some of which are less accurate and may deviate from the experimental results. In this paper, the spectral emission and absorption coefficients of diatomic molecules in air plasmas are thoroughly calculated based upon the exact line by line approach. In this scheme, the accurate spectroscopic constants and Franck–Condon factors were selected from the recent publications to reconstruct the rotational structure of spectral lines. Moreover, the level populations were determined by means of our newly reported two-temperature partition functions. The required thermodynamic parameters of each species were obtained by simulating a hypersonic flow field of the RAMC II vehicle. The calculated radiative properties were verified by the experimental and numerical equilibrium radiative source strength and the results show good consistency with measured and theoretical values in the available literature. Based upon the obtained flow field parameters, we finally predicted the distributions of nonequilibrium source strength along the stagnation line. Estimates and analysis were also made for the contributions of each transition system of the diatomic molecule to the total source strength.
Strategy toward white LEDs based on vertically integrated rare earth doped Ga2O3 films
Authors: Huang Yafei , Saito Katsuhiko , Tanaka Tooru , Guo Qixin
Published: August 2021

Monolithic and phosphor-free light-emitting diodes (LEDs) have been fabricated based on vertically integrated Ga2O3:Tm, Ga2O3:Eu, and Ga2O3:Er films by alternate-target pulsed laser deposition. Direct white light emission with superior CIE chromaticity coordinates of (0.3329, 0.3335) and correlated color temperature of 5479 K has been achieved from LEDs. Electroluminescence spectra demonstrate that the white emission was a consequence of the combination of dominant blue emissions at 461 and 475 nm from Tm3+ ions, green emissions at 529 and 550 nm from Er3+ ions, and red emissions at 590 and 615 nm from Eu3+ ions. The Ga2O3:(Tm+Eu+Er)-based LED exhibits current-controlled color tunability, which endows it with the capability of affording both “warm” and “cold” white light by controlling the operating current. Moreover, this strategy for LEDs shows the full color tunability by intentionally modifying the thickness ratios of Ga2O3:Tm, Ga2O3:Eu, and Ga2O3:Er monolayers. We anticipate that this study will pave the way toward full-color displays and solid-state lighting technology using rare-earth doped Ga2O3.
Dynamical attributes of nanocatalyzed self-oscillating reactions via bifurcation analyses
Authors: Rajput Vandana , Dayal Pratyush
Published: August 2021

Self-oscillating chemical reactions that undergo reaction–diffusion (RD) phenomena have shown great potential for designing stimuli-responsive materials. Belousov–Zhabotinsky (BZ) reactions are one such class of reactions that exhibit nonlinear chemical oscillations due to redox cycles of the metal-ion catalyst by virtue of Hopf bifurcation. Using bifurcation analyses, here we investigate the BZ reactions, catalyzed by 0D–2D catalytic nanomats and bare nanosheets, which are known to exhibit enhanced dynamic response due to catalysts’ heterogeneity. Specifically, we incorporate the nanocatalysts’ activity in the kinetic model of the BZ reactions and, subsequently, use catalysts’ activity as the bifurcation parameter for analyses. By computing higher-order Lyapunov and frequency coefficients, we have revealed new oscillatory regimes in the bifurcation diagram, including re-entrant regions where sustained oscillations are unexpectedly suppressed, even with high catalytic activity. In addition, we also calculate the amplitude and frequency of BZ oscillations in each of these regions as a function of nanocatalysts’ activity. We believe that our current findings can be used to harness the nonlinearity of RD-based dynamical systems to provide unique functionalities to active stimuli-response systems.
Rheological modeling of thermoplastic vulcanizates (TPVs) using the Kaye–Bernstein, Kearsley, Zapas (K–BKZ) constitutive law
Authors: Ghahramani Nikoo , Iyer Krishnan A. , Doufas Antonios K. , Hatzikiriakos Savvas G.
Published: August 2021

Thermoplastic vulcanizates (TPVs) comprise a thermoplastic polypropylene (PP) matrix and a dynamically vulcanized ethylene propylene diene monomer (EPDM) rubber. Several model TPVs of known composition were studied rheologically in both shear and elongation to understand and model their response using the Kaye–Bernstein, Kearsley, Zapas (K–BKZ) rheological law. A new technique is proposed to capture the effects of yielding and wall slip using the K–BKZ model. Moreover, the linear viscoelastic behavior of the TPVs was investigated, and it was found that all the TPVs exhibit a universal relaxation modulus (power-law with added yield). All TPVs exhibited a yield stress due to the presence of curing at the PP/EPDM interface evident from simple shear and uniaxial extensional experiments. The damping function was also determined, and it was shown to follow the universal Zapas relation. Finally, due to their elastomeric nature, TPVs slip significantly. Overall, it is shown that the use of the K–BKZ with yield stress and slip can capture well their rheological response.
Reaction front development from ignition spots in n-heptane/air mixtures: Low-temperature chemistry effects induced by ultrafine water droplet evaporation
Authors: Yu Zhou , Zhang Huangwei
Published: August 2021

Effects of low-temperature chemistry induced by ultrafine water droplet evaporation on reaction front development from an ignition spot with temperature gradient are studied in this work. The Eulerian–Eulerian method is used to simulate the gas–liquid two-phase reactive flows, and the physical model is one-dimensional spherical reactor with stoichiometric gaseous n-heptane/air mixture and ultrafine monodisperse water droplets (initial diameter 5 μm). Homogeneous ignitions of two-phase mixtures are first simulated. The water droplets can completely evaporate in the reactor prior to ignition, and hence pronouncedly reduce gas temperature, which may induce the low-chemistry reactions. It is found that the turnover temperature for negative temperature coefficient range increases with droplet volume fraction. Three-stage ignitions are present when the volume fraction is beyond a critical value, that is, low-temperature, intermediate-temperature, and high-temperature ignitions. The chemical explosive mode analysis also confirms the low-chemistry reactions induced by the evaporation of ultrafine water droplets. Then, reaction front development from an ignition spot with temperature gradient in two-phase mixtures is analyzed based on one-dimensional simulations. Different modes for reaction front origin in the spot are identified, based on the initial gas temperature and lower turnover temperature. Specifically, the reaction front can be initiated at the left and right ends of the ignition spot, and inside it. Detailed reaction front developments corresponding to the above three modes are discussed. In addition, the pressure wave from high-temperature ignition is important, compared to those from low and intermediate chemistries. The reaction front propagation speed and thermal states of fluid particles corresponding to different reaction front initiation modes are analyzed. Moreover, autoignition modes are summarized in the diagrams of normalized temperature gradient vs normal acoustic time and droplet volume fraction. The detonation limits of two-phase mixtures highly depend on the droplet volume fraction and are not regularly peninsular-shaped, like those for purely gaseous mixtures.
Bidirectional negative differential resistance in AlN/GaN resonant tunneling diodes grown on freestanding GaN
Authors: Qiu Haibing , Zhou Xiangpeng , Yang Wenxian , Zhang Xue , Jin Shan , Lu Shulong , Qin Hua , Bian Lifeng
Published: August 2021

In this paper, we report bidirectional negative differential resistance (NDR) in Al(Ga)N/GaN/AlN resonant tunneling diodes grown on free-standing GaN substrates by RF-plasma assisted molecular beam epitaxy. Bidirectional NDR has exhibited a current–voltage (I–V) characteristic in both forward and reverse biases at room temperature. The positive peak current density is 160 kA/cm2 with a peak to valley current ratio (PVCR) of 1.34, and the negative peak current density is 112 kA/cm2 with a high PVCR of 1.56. The bidirectional NDR is attributed to the change in the polarization field in the active region, which is caused by the asymmetric barrier component.
A survey of cetaceans in New Britain, Papua New Guinea
Authors: Mavea Wilma B. , Belonovich Olga , Nagombi Elizah , Boslogo Tracey , Gwynn Lisle , Russ Rodney , Bird Jeremy P.
Published: August 2021

A recent assessment of spatial conservation priorities in mega-diverse Papua New Guinea noted a lack of marine data. We surveyed cetaceans in inshore and pelagic waters along the south coast of New Britain island. The total number of cetaceans encountered was 397, attributed to at least 6 species, with spinner dolphins and pantropical spotted dolphins both the most frequently sighted and abundant species. Although diversity and abundance were lower than expected, we hope that by contributing to a national cetacean sightings database this survey will support a growing understanding of marine mammal diversity and distribution within the region.
Formation of marine secondary aerosols in the Southern Ocean, Antarctica
Authors: Wang Shanshan , Yan Jinpei , Lin Qi , Zhang Miming , Xu Suqing , Zhao Shuhui , Ruan Meina
Published: August 2021

Environmental context Water soluble ions (WSIs) in aerosols, especially in marine secondary aerosols, can participate in the formation of cloud condensation nuclei (CCN) in the marine boundary layer, which can affect global climate. In our study, in-situ gas and aerosol compositions were analysed to explore the formation paths and forms of secondary aerosols in the Southern Ocean (SO) in summer. Our study provided novel data on these formation mechanisms of secondary aerosols in the SO, with potential impacts on our understanding of global climate change. Abstract Water-soluble ions (WSIs) in aerosols, especially marine secondary aerosols, may participate in the formation of cloud condensation nuclei (CCN) in the marine boundary layer and affect the global climate. However, there is still a lack of studies on the background concentrations and the formation mechanisms of marine secondary aerosols in polar areas. High time resolution concentrations of WSIs in aerosols were analysed by an in situ gas and aerosol composition monitoring system in the Southern Ocean (SO) to identify the formation of marine secondary aerosols including methanesulfonic acid (MSA), SO42− and NO3−. The average hourly mass concentration of WSIs was 663 ng m−3 and secondary aerosols accounted for 49.8 ± 20.2 % of the WSIs. SO42− and NO3− were mainly formed by homogeneous reaction, whereas homogeneous and heterogeneous reactions together contributed to the formation of MSA− in aerosols in the SO. The melting of sea ice and the increase of chlorophyll-a (Chl-a) concentration contributed to the formation of MSA−. MSA-Na, MSA-NH4+, MSA-SO42−, MSA-Mg, MSA-K and MSA-Cl existed in marine aerosols. Secondary inorganic aerosols existed mainly in the forms of NH4NO3, (NH4)2SO4, Na2SO4 and MgSO4. The results enrich the data of WSI concentrations and formation mechanisms of secondary aerosols in the SO.
Shared understanding of color among sighted and blind adults
Authors: Kim Judy Sein , Aheimer Brianna , Montané Manrara Verónica , Bedny Marina
Published: August 2021

Significance

We learn in a variety of ways: through direct sensory experience, by talking with others, and by thinking. Disentangling how these sources contribute to what we know is challenging. A wedge into this puzzle was suggested by empiricist philosophers, who hypothesized that people born blind would lack deep knowledge of “visual” phenomena such as color. We find that, contrary to this prediction, congenitally blind and sighted individuals share in-depth understanding of object color. Blind and sighted people share similar intuitions about which objects will have consistent colors, make similar predictions for novel objects, and give similar explanations. Living among people who talk about color is sufficient for color understanding, highlighting the efficiency of linguistic communication as a source of knowledge.
Hexokinases inhibit death receptor–dependent apoptosis on the mitochondria
Authors: Lauterwasser Joachim , Fimm-Todt Franziska , Oelgeklaus Aline , Schreiner Annabell , Funk Kathrin , Falquez-Medina Hugo , Klesse Ramona , Jahreis Günther , Zerbes Ralf M. , O'Neill Katelyn , van der Laan Martin , Luo Xu , Edlich Frank
Published: August 2021

Significance

Receptor–ligand interactions on the cell surface or intrinsic stress signals can commit mammalian cells to apoptosis. In this study, we discover how hexokinases confer resistance to receptor-mediated apoptosis through specific inhibition of B-cell lymphoma 2 (BCL-2) proteins. Hexokinases retrotranslocate activator and effector BCL-2 proteins from the mitochondria into the cytosol. Hexokinase-dependent BCL-2 protein retrotranslocation can protect cells from apoptosis despite death receptor signaling.
Nonrandom segregation of sister chromosomes by
Escherichia coli
MukBEF
Authors: Mäkelä Jarno , Uphoff Stephan , Sherratt David J.
Published: August 2021

Significance

Circular chromosomes in rod-shaped bacteria exist inside a cell in two distinct configurations, “transverse” and “longitudinal,” relative to the long cell axis, with chromosomal loci occupying specific cellular locations in both cases. Bacteria with longitudinal chromosome organization (e.g.,
Caulobacter crescentus
) typically tether their origins of replication to the cell membrane and do not undergo overlapping rounds of replication. In contrast, bacteria with transverse organization (e.g.,
Escherichia coli
) orient their chromosomes by an unknown mechanism and have lifestyles compatible with overlapping rounds of replication. Here, we address the relative roles of two major players in chromosome organization–segregation and propose a model of how
E. coli
maintains chromosome conformation and orientation inside cells and how this organization is propagated over generations.
Biochemical insights into Paf1 complex–induced stimulation of Rad6/Bre1-mediated H2B monoubiquitination
Authors: Chen Feilong , Liu Beibei , Guo Lu , Ge Xuan , Feng Wei , Li De-Feng , Zhou Hao , Long Jiafu
Published: August 2021

Significance

PAF1C is a highly conserved multiprotein complex composed of five core subunits (Paf1, Leo1, Ctr9, Cdc73, and Rtf1) and is required for Rad6/Bre1-mediated H2B monoubiquitination (H2Bub). This study involves a mechanistic analysis of the contributions of the PAF1C subunits to H2Bub. The results from an established in vitro ubiquitination assay clearly suggest that PAF1C might stimulate H2Bub through multivalent interactions with Rad6 and nucleosomal substrates to facilitate ubiquitin transfer and indicate that intact PAF1C is required to efficiently stimulate Rad6/Bre1-mediated H2Bub.
Structure of autoinhibited Akt1 reveals mechanism of PIP3-mediated activation
Authors: Truebestein Linda , Hornegger Harald , Anrather Dorothea , Hartl Markus , Fleming Kaelin D. , Stariha Jordan T. B. , Pardon Els , Steyaert Jan , Burke John E. , Leonard Thomas A.
Published: August 2021

Significance

Akt is an essential protein kinase that controls cell growth, survival, and metabolism. Akt is activated by the lipid second messengers PIP3and PI(3,4)P2and by phosphorylation. However, the relative contributions of lipid binding and phosphorylation to Akt activity in the cell are controversial. Here, we have determined the structure of autoinhibited Akt1, which reveals how the lipid-binding PH domain maintains the kinase domain in an inactive conformation in the absence of PIP3. Despite stoichiometric phosphorylation, Akt adopts an autoinhibited conformation with low basal activity in the absence of PIP3. Our work reveals the mechanistic basis of Akt hyperactivation in cancer and overgrowth diseases and unambiguously establishes that Akt depends on lipids for activity in the cell.
Microbial population dynamics and evolutionary outcomes under extreme energy limitation
Authors: Shoemaker William R. , Jones Stuart E. , Muscarella Mario E. , Behringer Megan G. , Lehmkuhl Brent K. , Lennon Jay T.
Published: August 2021

Significance

Energy limitation is a widespread phenomenon that governs microbial processes ranging from the metabolism of individual cells to the functioning of the biosphere. By tracking the population dynamics of diverse bacterial taxa under prolonged starvation, we identified common strategies that sustain life. Although bacteria have the capacity to reproduce on timescales of minutes to hours, we predict that populations can persist for hundreds to thousands of years, placing upper bounds on microbial lifespans. While the dynamics observed in our long-term experiment were driven by a reduction in death rates, cryptic birth events generated mutations that fueled evolution. Our findings shed light on cellular longevity with implications for biodiversity in extreme environments that dominate vast expanses of Earth.
The Sw5a gene confers resistance to ToLCNDV and triggers an HR response after direct AC4 effector recognition
Authors: Sharma Namisha , Sahu Pranav Pankaj , Prasad Ashish , Muthamilarasan Mehanathan , Waseem Mohd , Khan Yusuf , Thakur Jitendra Kumar , Chakraborty Supriya , Prasad Manoj
Published: August 2021

Significance

Tomato leaf curl New Delhi virus(ToLCNDV) infection causes severe losses in tomato yield worldwide. Lack of information on resistance (R) genes against ToLCNDV has considerably retarded the pace of crop improvement against this rapidly spreading pathogen. Here, we report an effective defense strategy deployed by a resistant tomato cultivar against ToLCNDV. It employs Sw5a (R gene) that recognizes AC4 protein (viral effector) of ToLCNDV to restrict virus spread. At the transcriptional level, the sly-miR159-SlMyb33 module has been identified as governing gene expression of Sw5a. Thus, we provide a mechanistic insight into sly-miR159-SlMyb33–controlled Sw5a-mediated defense response in tomato against ToLCNDV. These findings could be translated into development of resistance in susceptible cultivars of tomato through modern breeding or molecular approaches.
Nucleocytoplasmic trafficking and turnover mechanisms of BRASSINAZOLE RESISTANT1 in
Arabidopsis thaliana
Authors: Wang Ruiju , Wang Ruixuan , Liu Mengmeng , Yuan Weiwei , Zhao Zhiying , Liu Xiaoqian , Peng Yameng , Yang Xiaorui , Sun Yu , Tang Wenqiang
Published: August 2021

Significance

Upon brassinosteroid (BR) treatment, BRASSINAZOLE RESISTANT1 (BZR1) is dephosphorylated and accumulate in the nucleus. However, it was unclear whether these two processes are interdependent. Here, we show that BR signaling first recruits phosphorylated BZR1 to the nucleus where it is dephosphorylated by protein phosphatase 2A (PP2A). BZR1 is constitutively degraded via a BR- and 26S proteosome–independent mechanism; however, BR treatment activates a different 26S proteosome–dependent pathway and increases BZR1 turnover rate. These results help to untangle the intertwined mechanisms governing BZR1 phosphorylation/dephosphorylation, nucleocytoplasmic trafficking, and protein turnover during BR signaling and clarify the role of PP2A in the BR signaling pathway. Our results will inspire new studies on BR signaling and in other fields of plant research.
Regulation of beta-amyloid production in neurons by astrocyte-derived cholesterol
Authors: Wang Hao , Kulas Joshua A. , Wang Chao , Holtzman David M. , Ferris Heather A. , Hansen Scott B.
Published: August 2021

Significance

The accumulation of amyloid β (Aβ) in the brain appears to be a necessary event in the pathogenesis of Alzheimer’s disease (AD). However, processes linked to the endogenous regulation of Aβ production are still not completely understood. Here, the authors show that Aβ accumulation in neurons is tightly regulated by cholesterol synthesis and apoE transport from astrocytes. The study provides a molecular context for understanding the endogenous regulation of Aβ accumulation and why it correlates with AD. The tight regulation suggests that Aβ may perform an important cellular function. A complete understanding of the mechanism is likely necessary to predict whether the selective removal of Aβ has potential for a therapeutic benefit.
The attention schema theory in a neural network agent: Controlling visuospatial attention using a descriptive model of attention
Authors: Wilterson Andrew I. , Graziano Michael S. A.
Published: August 2021

Significance

Attention, the deep processing of select items, is one of the most important cognitive operations in the brain. But how does the brain control its attention? One proposed part of the mechanism is that the brain builds a model, or attention schema, that helps monitor and predict the changing state of attention. Here, we show that an artificial neural network agent can be trained to control visual attention when it is given an attention schema, but its performance is greatly reduced when the schema is not available. We suggest that the brain may have evolved a model of attention because of the profound practical benefit for the control of attention.