bluuebunny/crossref_metadata_2025 huggingface dataset:
Swelling, softening, and elastocapillary adhesion of cooked pasta
Authors: Hwang Jonghyun , Ha Jonghyun , Siu Ryan , Kim Yun Seong , Tawfick Sameh
Published: April 2022

The diverse chemical and physical reactions encountered during cooking connect us to science every day. Here, we theoretically and experimentally investigate the swelling and softening of pasta due to liquid imbibition as well as the elastic deformation and adhesion of pasta due to capillary force. As water diffuses into the pasta during cooking, it softens gradually from the outside inward as starch swells and relaxes. The softening follows three sequential regimes: regime I, the hard-glassy region, shows a slow decrease in modulus with cooking time; regime II, the glassy to rubbery transition region, or leathery region, is characterized by a very fast, several orders of magnitude drop in elastic modulus and regime III, the rubbery region, has an asymptotic modulus about four orders of magnitude lower than the raw pasta. We present experiments and theory to capture these regimes and relate them to the heterogeneous microstructure changes associated with swelling. Interestingly, we observe a modulus drop of two orders of magnitude within the range of “al dente” cooking duration, and we find the modulus to be extremely sensitive to the amount of salt added to the boiling water. While most chefs can gauge the pasta by tasting its texture, our proposed experiment, which only requires a measurement with a ruler, can precisely provide an optimal cooking time finely tuned for various kinds of pasta shapes.
Progress toward picosecond on-chip magnetic memory
Authors: Polley Debanjan , Pattabi Akshay , Chatterjee Jyotirmoy , Mondal Sucheta , Jhuria Kaushalya , Singh Hanuman , Gorchon Jon , Bokor Jeffrey
Published: April 2022

We offer a perspective on the prospects of ultrafast spintronics and opto-magnetism as a pathway to high-performance, energy-efficient, and non-volatile embedded memory in digital integrated circuit applications. Conventional spintronic devices, such as spin-transfer-torque magnetic-resistive random-access memory (STT-MRAM) and spin–orbit torque MRAM, are promising due to their non-volatility, energy-efficiency, and high endurance. STT-MRAMs are now entering into the commercial market; however, they are limited in write speed to the nanosecond timescale. Improvement in the write speed of spintronic devices can significantly increase their usefulness as viable alternatives to the existing CMOS-based devices. In this article, we discuss recent studies that advance the field of ultrafast spintronics and opto-magnetism. An optimized ferromagnet–ferrimagnet exchange-coupled magnetic stack, which can serve as the free layer of a magnetic tunnel junction (MTJ), can be optically switched in as fast as ∼3 ps. Integration of ultrafast magnetic switching of a similar stack into an MTJ device has enabled electrical readout of the switched state using a relatively larger tunneling magnetoresistance ratio. Purely electronic ultrafast spin–orbit torque induced switching of a ferromagnet has been demonstrated using ∼6 ps long charge current pulses. We conclude our Perspective by discussing some of the challenges that remain to be addressed to accelerate ultrafast spintronics technologies toward practical implementation in high-performance digital information processing systems.
Transition rate theory, spectral analysis, and reactive paths
Authors: Roux Benoît
Published: April 2022

The kinetics of a dynamical system dominated by two metastable states is examined from the perspective of the activated-dynamics reactive flux formalism, Markov state eigenvalue spectral decomposition, and committor-based transition path theory. Analysis shows that the different theoretical formulations are consistent, clarifying the significance of the inherent microscopic lag-times that are implicated, and that the most meaningful one-dimensional reaction coordinate in the region of the transition state is along the gradient of the committor in the multidimensional subspace of collective variables. It is shown that the familiar reactive flux activated dynamics formalism provides an effective route to calculate the transition rate in the case of a narrow sharp barrier but much less so in the case of a broad flat barrier. In this case, the standard reactive flux correlation function decays very slowly to the plateau value that corresponds to the transmission coefficient. Treating the committor function as a reaction coordinate does not alleviate all issues caused by the slow relaxation of the reactive flux correlation function. A more efficient activated dynamics simulation algorithm may be achieved from a modified reactive flux weighted by the committor. Simulation results on simple systems are used to illustrate the various conceptual points.
Quantum oscillations and stacked quantum Hall effect in HfTe5
Authors: Xie Qiyun , Wang Cheng , Yan Sihan , Chen Limin , Zheng Jiajin , Wang Wei
Published: April 2022

We report the magneto-transport measurements on bulk HfTe5 with carrier mobility exceeding 100 000 cm2/(V s). The longitudinal resistance anomaly and the sign change in Hall coefficient with temperature are observed, which may be induced by Lifshitz transition. When the magnetic field is applied along the b-axis and a-axis at low temperature, a series of Shubnikov–de Haas oscillations on the longitudinal transport exhibit, demonstrating a three-dimensional Fermi-surface pocket for HfTe5 rather than two-dimensional (2D). The investigations on Landau level fan diagram confirm the existence of the non-trivial π Berry phase. The cyclotron mass mcyc as around 0.02me and quantum scattering time τ at about 1.76 ps are also estimated with Lifshitz–Kosevich theory. Further detailed analysis suggests that a stacked quantum Hall effect attributed to multi-parallel 2D conduction layers develops in HfTe5.
Numerical study on melting performance improvement with fractal tree-shaped fins
Authors: Ma Ben , Zhang Xiaoying , Wang Lei , He Kun , Li Dinggen
Published: April 2022

In this paper, the melting performance improvement of phase change material (PCM) in latent heat thermal energy storage (LHTES) systems with fractal tree-shaped fins has been discussed via lattice Boltzmann simulation. The abundant melting phenomena are comprehensive results of the heat conduction and convection. Based on the numerical results, it is found that the existence of tree-shaped fins significantly improves the melting performance, compared with the radical-fin LHTES unit. More specifically, the stretched tree-shaped fins uniform the temperature field and make great contributions for heat transfer enhancement at the early stage of melting process and thereby accelerating the generation of convection with the increase in the liquid phase. Moreover, it is observed that the melting efficiency improves with the increase in branch level (k) of tree-shaped fins, and this tendency reverses when k exceeds a critical value. The results also indicate both the length ratio and width ratio of tree-shaped fin have a significant influence on melting performance, and the optimal values for the ratios of length and width are 1.0 and 4/9, respectively. Additionally, different arrangements of tree-shaped fins are also considered to reveal the relationships between heat conduction and convection for melting performance improvement.
Reynolds number dependence of inner peak turbulence intensity in pipe flow
Authors: Ono Marie , Furuichi Noriyuki , Wada Yuki , Kurihara Noboru , Tsuji Yoshiyuki
Published: April 2022

Streamwise turbulence statistics in the range from Reτ = 990 to Reτ = 20 750 at the High Reynolds Number Actual Flow Facility at the National Metrology Institute of Japan are presented, specifically focusing on the Reynolds number dependence of the inner peak turbulence intensity. Velocity measurements are conducted using laser Doppler velocimetry (LDV), taking account of problems specific to this method, with the aim of providing reliable experimental results. The control volume and the fringe pattern of LDV, both of which influence turbulence statistics, are directly measured using a rotary wire device, and they are used to correct the measured turbulence intensity using methods developed in this study. The present results for mean velocity and turbulence intensity profiles agree well with direct numerical simulation data. The inner peak turbulence intensity in this pipe experiment increases with the increasing Reynolds number. It is found that the Reynolds number dependence of the inner peak up to Reτ = 20 750 is very similar to that in a turbulent boundary layer (TBL). The slope of the outer logarithmic region in the turbulence intensity profile is twice the slope obtained from the relation between the inner peak and the Reynolds number. This relation is also consistent with that for TBL flow.
Shock trace prediction by reduced models for a viscous stochastic Burgers equation
Authors: Chen Nan , Liu Honghu , Lu Fei
Published: April 2022

Viscous shocks are a particular type of extreme event in nonlinear multiscale systems, and their representation requires small scales. Model reduction can thus play an essential role in reducing the computational cost for the prediction of shocks. Yet, reduced models typically aim to approximate large-scale dominating dynamics, which do not resolve the small scales by design. To resolve this representation barrier, we introduce a new qualitative characterization of the space–time locations of shocks, named the “shock trace,” via a space–time indicator function based on an empirical resolution-adaptive threshold. Unlike exact shocks, the shock traces can be captured within the representation capacity of the large scales, thus facilitating the forecast of the timing and locations of the shocks utilizing reduced models. Within the context of a viscous stochastic Burgers equation, we show that a data-driven reduced model, in the form of nonlinear autoregression (NAR) time series models, can accurately predict the random shock traces, with relatively low rates of false predictions. Furthermore, the NAR model, which includes nonlinear closure terms to approximate the feedback from the small scales, significantly outperforms the corresponding Galerkin truncated model in the scenario of either noiseless or noisy observations. The results illustrate the importance of the data-driven closure terms in the NAR model, which account for the effects of the unresolved dynamics brought by nonlinear interactions.
Experimental investigation on the alteration of natural frequency of a flexible pipe adjacent to a bottom plane with the consideration of pipe-plane impact
Authors: Zhu Hongjun , Zhao Honglei , Xie Yipu , Zhang Xu
Published: April 2022

The obtainment of natural frequencies of near-wall submarine spanning pipelines is the essential basis of the prediction of vibration response and fatigue life. Nevertheless, published literature has not yet taken into account the pipe–wall impact in free attenuation tests and has not offered a method to identify the impact frequency from natural ones. Therefore, the present work experimentally investigates the free attenuation response of a horizontal flexible pipe positioned adjacent to and parallel to a bottom plane with the consideration of pipe–wall collision, aiming to figure out the influences of wall proximity and wall impact on natural frequencies and to provide a measurement method for attenuation tests of such fluid–flexible-structure–solid interaction issues. The experimental results indicate that setting a horizontal initial displacement is easier than setting a vertical initial displacement to get the vertical natural frequencies of a near-wall flexible pipe. The natural frequency of near-wall flexible pipe is a function of the added mass coefficient, decreasing with the reduction of pipe-to-wall distance. Three main alterations of natural frequencies are introduced in the presence of pipe–wall impact. With the imposition of a horizontal initial displacement, the impact and natural frequencies can be distinguished from the wavelet time-frequency contours because of their participations during different time periods.
Viscous fluid–structure interaction of micro-resonators in the beam–plate transition
Authors: Gesing Andre , Platz Daniel , Schmid Ulrich
Published: April 2022

We numerically investigate the fluid–structure interaction of thin elastic cantilever micro-structures in viscous fluids. The Kirchhoff plate equation describes the dynamics of the structure, and a boundary integral formulation represents the fluid flow. We show how the displacement spectrum of the structures changes as the geometry is altered from a narrow beam to a wide plate in a liquid. For narrow beams, the displacement spectrum exhibits only a few resonance frequencies, which correspond to the vibrational modes described by the Euler–Bernoulli equation (Euler–Bernoulli modes). The spectrum of wide plates exhibits several additional resonance frequencies associated with the plate’s torsional and higher-order vibrational modes. Wide plates in Euler–Bernoulli modes exhibit higher damping coefficients, but due to an increased added-mass effect, also higher Q-factors than slender beams. An investigation into the fluid flow reveals that for the Euler–Bernoulli modes of wider plates, the fluid flow and energy dissipation near the plate’s edges increase, resulting in increased damping coefficients. Concomitantly, a region of minimal viscous dissipation near the plate’s center appears for wider plates, resulting in an increased added-mass effect. Higher-order modes of wider plates exhibit lower Q-factor than the Euler–Bernoulli modes due to a decreased fluid flow at the plate’s edges caused by the appearance of circulation zones on both sides of the plate. This decreased flow at the edge reduces the damping and the added-mass effect, yielding lower Q-factors. We anticipate that the results presented here will play a vital role in conceiving novel MEMS resonators for operation in viscous fluids.
An ion mobility mass spectrometer coupled with a cryogenic ion trap for recording electronic spectra of charged, isomer-selected clusters
Authors: Buntine Jack T. , Carrascosa Eduardo , Bull James N. , Jacovella Ugo , Cotter Mariah I. , Watkins Patrick , Liu Chang , Scholz Michael S. , Adamson Brian D. , Marlton Samuel J. P. , Bieske Evan J.
Published: April 2022

Infrared and electronic spectra are indispensable for understanding the structural and energetic properties of charged molecules and clusters in the gas phase. However, the presence of isomers can potentially complicate the interpretation of spectra, even if the target molecules or clusters are mass-selected beforehand. Here, we describe an instrument for spectroscopically characterizing charged molecular clusters that have been selected according to both their isomeric form and their mass-to-charge ratio. Cluster ions generated by laser ablation of a solid sample are selected according to their collision cross sections with helium buffer gas using a drift tube ion mobility spectrometer and their mass-to-charge ratio using a quadrupole mass filter. The mobility- and mass-selected target ions are introduced into a cryogenically cooled, three-dimensional quadrupole ion trap where they are thermalized through inelastic collisions with an inert buffer gas (He or He/N2 mixture). Spectra of the molecular ions are obtained by tagging them with inert atoms or molecules (Ne and N2), which are dislodged following resonant excitation of an electronic transition, or by photodissociating the cluster itself following absorption of one or more photons. An electronic spectrum is generated by monitoring the charged photofragment yield as a function of wavelength. The capacity of the instrument is illustrated with the resonance-enhanced photodissociation action spectra of carbon clusters (Cn+) and polyacetylene cations (HC2nH+) that have been selected according to the mass-to-charge ratio and collision cross section with He buffer gas and of mass-selected Au2+ and Au2Ag+ clusters.
Unique catalytic mechanisms of methanol dehydrogenation at Pd-doped ceria: A DFT+U study
Authors: Chen Lu , Wu Xin-Ping , Gong Xue-Qing
Published: April 2022

Pd-doped ceria is highly active in promoting oxidative dehydrogenation (ODH) reactions and also a model single atom catalyst (SAC). By performing density functional theory calculations corrected by on-site Coulomb interactions, we systematically studied the physicochemical properties of the Pd-doped CeO2(111) surface and the catalytic methanol to formaldehyde reaction on the surface. Two different configurations were located for the Pd dopant, and the calculated results showed that doping of Pd will make the surface more active with lower oxygen vacancy formation energies than the pristine CeO2(111). Moreover, two different pathways for the dehydrogenation of CH3OH to HCHO on the Pd-doped CeO2(111) were determined, one of which is the conventional two-step process (stepwise pathway) with the O–H bond of CH3OH being broken first followed by the C–H bond cleavage, while the other is a novel one-step process (concerted pathway) involving the two H being dissociated from CH3OH simultaneously even with a lower energy barrier than the stepwise one. With electronic and structural analyses, we showed that the direct reduction of Pd4+ to Pd2+ through the transfer of two electrons can outperform the separated Ce4+ to Ce3+ processes with the help of configurational evolution at the Pd site, which is responsible for the existence of such one-step dehydrogenation process. This novel mechanism may provide an inspiration for constructing ceria-based SAC with unique ODH activities.
Drag reduction in cylindrical wake flow using porous material
Authors: Du Hai , Zhang Qinlin , Li Qixuan , Kong Wenjie , Yang Lejie
Published: April 2022

Due to its unique pore structure, porous materials have the potential to be used in the fields of acoustic noise reduction and flow drag reduction control. In order to study their effects and mechanism of drag reduction on the flow around a circular cylinder, experiments are conducted in a low-speed wind tunnel with low turbulence intensity. The drag forces acting on a circular cylinder model are measured using wind tunnel balance when porous materials with different permeability are applied within different intersection angles on the trailing-edge and leading edge, and the flow fields are visualized with a particle image velocimetry system with high time resolution. The method of dynamic mode decomposition (DMD) is also used for reduced-order analysis of the vorticity field in the wake of the cylinder. The measured drag forces and wake flow fields are then compared with those of a smooth cylinder, and the results show that porous materials laid on the trailing-edge can reduce drag, when a porous material with 20 pores per inch is laid within 270° on the leeward side, the best effect of the drag reduction ratio of 10.21% is reached. The results of flow visualization indicate that after the porous material is applied, the vortex region in the wake of the cylinder is expanded; both the frequency of vortex shedding and the magnitude of vorticity fluctuation decrease; the Reynolds-shear-stress decreases significantly, and both indicate that vorticity is dissipated earlier. The results of DMD analysis show that porous materials can effectively relax the energy of vortices in different modes.
Spreading of a droplet impacting on a smooth flat surface: How liquid viscosity influences the maximum spreading time and spreading ratio
Authors: Aksoy Yunus Tansu , Eneren Pinar , Koos Erin , Vetrano Maria Rosaria
Published: April 2022

Existing energy balance models, which estimate maximum droplet spreading, insufficiently capture the droplet spreading from low to high Weber and Reynolds numbers and contact angles. This is mainly due to the simplified definition of the viscous dissipation term and incomplete modeling of the maximum spreading time. In this particular research, droplet impact onto a smooth sapphire surface is studied for seven glycerol concentrations between 0% and 100%, and 294 data points are acquired using high-speed photography. Fluid properties, such as density, surface tension, and viscosity, are also measured. For the first time according to the authors' knowledge, we incorporate the fluid viscosity in the modeling of the maximum spreading time based on the recorded data. We also estimate the characteristic velocity of the viscous dissipation term in the energy balance equation. These viscosity-based characteristic scales help to formulate a more comprehensive maximum droplet spreading model. Thanks to this improvement, our model successfully fits the data available in the literature for various fluids and surfaces compared to the existing models.
Transient oscillation response characteristics of an electrohydrodynamic settling drop subjected to a uniform electric field
Authors: Zhang Yi-Mo , Su Zheng-Gang , Luo Kang , Yi Hong-Liang
Published: April 2022

The transient oscillation response of an electrohydrodynamic settling drop under a uniform electric field is numerically investigated. The governing equations are solved in the lattice Boltzmann framework through the application of the leaky dielectric model and the pseudopotential model for the multi-phase electrohydrodynamic problem. A viscous drop with inertia is considered for non-density matched settling systems. Numerical simulations are performed over a range of electric capillary numbers CaE, Eotvos numbers Eo, and Ohnesorge numbers Oh. The results indicate that three typical development stages, namely, the electric stress-dominated stage, the force competition stage, and the inertia-dominated stage, are identified in terms of the deformation evolution characteristics. Our study also demonstrates the role of the three dimensionless numbers in the deformation response at each stage. It is found that, at the earlier stage of settling, the maximum achievable deformation is sensitive to CaE and Oh, while the influence of Eo on the first oscillatory peak at the deformation-time curve is approximately neglectable. Moreover, the deformation response time is determined by the interaction of the electric field, the gravitational field, and viscosity. Specifically, the corresponding oscillatory peak time correlates positively with Eo and Oh numbers and exponentially grows with CaE.
High gradient silicon carbide immersion lens ultrafast electron sources
Authors: Leedle Kenneth J. , Niedermayer Uwe , Skär Eric , Urbanek Karel , Miao Yu , Broaddus Payton , Solgaard Olav , Byer Robert L.
Published: April 2022

We present two compact ultrafast electron injector designs with integrated focusing that provide high peak brightness of up to 1.9 × 1012 A/m2 Sr2 with 10’s of electrons per laser pulse using silicon carbide electrodes and silicon nanotip emitters. We demonstrate a few centimeter scale 96 keV immersion lens electron source and a 57 keV immersion lens electron source with a 19 kV/mm average acceleration gradient, nearly double the typical 10 kV/mm used in DC electron sources. The brightness of the electron sources is measured alongside start-to-end simulations including space charge effects. These sources are suitable for dielectric laser accelerator experiments, ultrafast electron diffraction, and other applications, where a compact high brightness electron source is required.
Novel behaviors of coercivity in GdFeCo/Hf/MgO heterostructure
Authors: Hai Ngo Trong , Luong V. S. , Bhatt Ramesh Chandra , Ye Lin-Xiu , Wu Te-ho , Horng Lance , Wu Jong-Ching
Published: April 2022

It is commonly known that the coercivity (Hc) of the rare-earth/transition-metal (RE–TM) compound is tuned based on the varying RE content as compared to the TM component. The drawback of this approach is that the Hc changes are permanent. In this work, we investigate the coercivity behaviors of the GdFeCo/Hf/MgO heterostructure where the heavy metal Hf layer is inserted in the middle not only to convert charge current into spin current but also to prevent the oxygen diffusion effect. A strong geometry dependence of coercivity detected on Hall bar devices is attributed to the intrinsic properties of GdFeCo and elucidates that the oxidation issue from MgO on GdFeCo is prevented. By selecting a proper Gd content, we demonstrate that the coercivity can be altered flexibly in a wide range Hcmax/Hcmin≈200% via electric current. We develop a simple model to simulate the roles of Joule heating and spin–orbit torques in the novel behaviors of coercivity. It is verified that the excellent magnetic characteristics of GdFeCo are still preserved while manipulating coercivity by the electric current. Our findings broaden the new magnetic behaviors of RE–TM alloys, making them attractive for tunable magnetic anisotropy.
Collimated versatile atomic beam source with alkali dispensers
Authors: Wei Bochao , Crawford Alexandra , Andeweg Yorick , Zhuo Linzhao , Li Chao , Raman Chandra
Published: April 2022

Alkali metal dispensers have become an indispensable tool in the production of atomic vapors for magnetometry, alkali vapor cell clocks, and laser cooling experiments. A primary advantage of these dispensers is that they contain alkali metal in an inert form that can be exposed to air without hazard. However, their high temperature of operation (>600 °C) is undesirable for many applications, as it shifts the atomic speed distribution to higher values and presents a radiative heat source that can raise the temperature of its surroundings. For this reason, dispensers are typically not used in line-of-sight applications, such as atomic beam generation. In this work, we present an integrated rubidium dispenser collimating device with a thickness of only 2 mm that produces a beam of atoms traveling primarily in the forward direction. We find that the collimator plate serves to both shield the dispenser's radiation and moderate the velocity of the atomic beam so that the measured longitudinal speed distribution is comparable to that of an ordinary alkali oven at only a slightly elevated temperature of 200 °C. To confirm our theory, we also constructed another compact apparatus consisting of a dispenser and a silicon collimator and the measurements support our conclusion. Our integrated dispenser collimator will particularly be useful in integrated photonics and cavity QED on-chip, where a localized, directed source of Rb vapor in small quantities is needed.
Geometry meta-optimization
Authors: Huang Daniel , Bao Junwei Lucas , Tristan Jean-Baptiste
Published: April 2022

Recent work has demonstrated the promise of using machine-learned surrogates, in particular, Gaussian process (GP) surrogates, in reducing the number of electronic structure calculations (ESCs) needed to perform surrogate model based (SMB) geometry optimization. In this paper, we study geometry meta-optimization with GP surrogates where a SMB optimizer additionally learns from its past “experience” performing geometry optimization. To validate this idea, we start with the simplest setting where a geometry meta-optimizer learns from previous optimizations of the same molecule with different initial-guess geometries. We give empirical evidence that geometry meta-optimization with GP surrogates is effective and requires less tuning compared to SMB optimization with GP surrogates on the ANI-1 dataset of off-equilibrium initial structures of small organic molecules. Unlike SMB optimization where a surrogate should be immediately useful for optimizing a given geometry, a surrogate in geometry meta-optimization has more flexibility because it can distribute its ESC savings across a set of geometries. Indeed, we find that GP surrogates that preserve rotational invariance provide increased marginal ESC savings across geometries. As a more stringent test, we also apply geometry meta-optimization to conformational search on a hand-constructed dataset of hydrocarbons and alcohols. We observe that while SMB optimization and geometry meta-optimization do save on ESCs, they also tend to miss higher energy conformers compared to standard geometry optimization. We believe that further research into characterizing the divergence between GP surrogates and potential energy surfaces is critical not only for advancing geometry meta-optimization but also for exploring the potential of machine-learned surrogates in geometry optimization in general.
Oscillation suppression and chimera states in time-varying networks
Authors: Majhi Soumen , Rakshit Sarbendu , Ghosh Dibakar
Published: April 2022

Complex network theory has offered a powerful platform for the study of several natural dynamic scenarios, based on the synergy between the interaction topology and the dynamics of its constituents. With research in network theory being developed so fast, it has become extremely necessary to move from simple network topologies to more sophisticated and realistic descriptions of the connectivity patterns. In this context, there is a significant amount of recent works that have emerged with enormous evidence establishing the time-varying nature of the connections among the constituents in a large number of physical, biological, and social systems. The recent review article by Ghosh et al. [Phys. Rep. 949, 1–63 (2022)] demonstrates the significance of the analysis of collective dynamics arising in temporal networks. Specifically, the authors put forward a detailed excerpt of results on the origin and stability of synchronization in time-varying networked systems. However, among the complex collective dynamical behaviors, the study of the phenomenon of oscillation suppression and that of other diverse aspects of synchronization are also considered to be central to our perception of the dynamical processes over networks. Through this review, we discuss the principal findings from the research studies dedicated to the exploration of the two collective states, namely, oscillation suppression and chimera on top of time-varying networks of both static and mobile nodes. We delineate how temporality in interactions can suppress oscillation and induce chimeric patterns in networked dynamical systems, from effective analytical approaches to computational aspects, which is described while addressing these two phenomena. We further sketch promising directions for future research on these emerging collective behaviors in time-varying networks.
Hydrodynamic interaction and complex viscosity of multi-bead rods
Authors: Kanso M. A. , Pak Myong Chol , Kim Kwang-Il , Coombs S. J. , Giacomin A. J.
Published: April 2022

One good way to explain the elasticity of a polymeric liquid is to just consider the orientation distribution of the macromolecules. When exploring how macromolecular architecture affects the elasticity of a polymeric liquid, we find the general rigid bead–rod theory to be both versatile and accurate. This theory sculpts macromolecules using beads and rods. Whereas beads represent points of Stokes flow resistances, the rods represent rigid separations. In this way, how the shape of the macromolecule affects its rheological behavior in suspension is determined. Until recently, general rigid bead–rod theory has neglected interferences of the Stokes flow velocity profiles between nearby beads. We call these hydrodynamic interactions, and we here employ our new method for exploring how these interactions affect the complex viscosity of suspensions of multi-bead rods. These multi-bead rods are also called shish-kebabs. We use the center-to-center distance between adjacent beads as the characteristic length. We proceed analytically, beginning with a geometric expression for the shish-kebab bead positions. Our analytical solution for the complex viscosity presents as one for N=3,5,6,7,8,…, one for N=4, and another for the rigid dumbbell, N=2. We find that for shish-kebabs, hydrodynamic interactions (i) increase zero-shear viscosity, (ii) increase zero-shear first normal stress coefficient, (iii) decrease the real part of the dimensionless complex viscosity, and (iv) increase minus the dimensionless imaginary part. We find that the combination of (iii) and (iv) explains crossovers of the parts of the complex viscosity. We further find that for a monodisperse polystyrene solution, the general rigid bead–rod theory with hydrodynamic interaction, for both parts of the complex viscosity, provides stunning improvement over without.
Stable electron beam propagation in a plasma column
Authors: Diederichs S. , Benedetti C. , Esarey E. , Thévenet M. , Osterhoff J. , Schroeder C. B.
Published: April 2022

The stability of plasma-based accelerators against transverse misalignments and asymmetries of the drive beam is crucial for their applicability. Without stabilizing mechanisms, even small initial offsets of the drive beam centroid can couple coherently to the plasma wake, grow, and ultimately lead to emittance degradation or beam loss for a trailing witness beam. In this work, we demonstrate the intrinsic stability of a beam propagating in a plasma column. This result is relevant in the context of plasma-based positron acceleration, where a wakefield suitable for the transport and acceleration of a positron witness beam is generated in a plasma column by means of an electron drive beam. The stable propagation of the drive beam is a necessary condition for the experimental implementation of this scheme. The differences and similarities of stabilizing mechanisms in a plasma column compared to a homogeneous plasma are identified via theory and particle-in-cell simulations. Experimental tolerances are given, demonstrating the experimental feasibility of the scheme.
Contribution of flow topology to the kinetic energy flux in hypersonic turbulent boundary layer
Authors: Xu Dehao , Wang Jianchun , Yu Changping , Li Xinliang , Chen Shiyi
Published: April 2022

The contribution of various flow topologies to the subgrid-scale (SGS) flux of kinetic energy in hypersonic turbulent boundary layer for different Mach numbers and wall temperature ratios is investigated by direct numerical simulation. In the far-wall region (approximately y+=y/δν>50, where y is the wall-normal location and δν is the viscous length scale), the volume fractions of flow topologies unstable focus/compressing (UFC) and stable focus/stretching (SFS) increase with the increase in filter width, resulting in the dominance of UFC and SFS in the inertial range; while in the near-wall region, the volume fractions of flow topologies unstable/saddle/saddle (UN/S/S), stable node/saddle/saddle (SN/S/S), stable focus/compressing (SFC), and unstable focus/stretching (UFS) increase with the increase in filter width, leading to the majority of UN/S/S and SN/S/S in the inertial range. In the inertial range, the SGS flux of kinetic energy is mainly contributed by UFC and SFS far from the wall (approximately y+>50) and is primarily contributed by UN/S/S and SN/S/S near the wall. The wall temperature has a significant effect on the contributions of various flow topologies in the near-wall region. As the wall temperature decreases, the contributions by SN/S/S and SFC to the SGS kinetic energy flux increase in the compression region, and those by UN/S/S and UFS increase in the expansion region. Moreover, the direct transfer of fluctuating kinetic energy from large scales to small scales is mainly characterized by UN/S/S, SFS, and SFC in the compression region, while the reverse transfer of fluctuating kinetic energy is primarily characterized by UFC, SN/S/S, and UFS in the expansion region.
Neutrophil and natural killer cell imbalances prevent muscle stem cell–mediated regeneration following murine volumetric muscle loss
Authors: Larouche Jacqueline A. , Fraczek Paula M. , Kurpiers Sarah J. , Yang Benjamin A. , Davis Carol , Castor-Macias Jesus A. , Sabin Kaitlyn , Anderson Shannon , Harrer Julia , Hall Matthew , Brooks Susan V. , Jang Young C. , Willett Nick , Shea Lonnie D. , Aguilar Carlos A.
Published: April 2022

Significance

Skeletal muscle is one of the largest tissues in the body and can regenerate when damaged through a population of resident muscle stem cells. A type of muscle trauma called volumetric muscle loss overwhelms the regenerative capacity of muscle stem cells and engenders fibrotic supplantation. A comparison of muscle injuries resulting in regeneration or fibrosis revealed that intercellular communication between neutrophils and natural killer cells impacts muscle stem cell-mediated repair. Perturbation of neutrophil–natural killer cell interactions resulted in a variation of healing outcomes and suggested that immunomodulatory interventions can be effective to prevent aberrant healing outcomes.
Proteasome complexes experience profound structural and functional rearrangements throughout mammalian spermatogenesis
Authors: Živković Dušan , Sanchez Dafun Angelique , Menneteau Thomas , Schahl Adrien , Lise Sandrine , Kervarrec Christine , Toste Rêgo Ana , da Fonseca Paula C. A. , Chavent Matthieu , Pineau Charles , Burlet-Schiltz Odile , Marcoux Julien , Bousquet Marie-Pierre
Published: April 2022

Significance

The proteasome is responsible for the homeostasis of intracellular proteins. Here, we describe structural and functional aspects of a poorly characterized proteasome subtype found exclusively in germ cells. The spermatoproteasome was recently shown to be essential for spermatogenesis, a process requiring intense proteolysis. It differs from the constitutive proteasome by only one subunit, α4s, a subunit that replaces its α4 ubiquitous counterpart. In this work, we show how the shift from α4 to α4s regulates proteasome composition, dynamics, interactome, and activity. We reveal a regulation process more complex than previously suggested, which provides the basis for structural and functional studies of the spermatoproteasome.
Nanoparticle targeting of de novo profibrotic macrophages mitigates lung fibrosis
Authors: Singh Abhalaxmi , Chakraborty Sreeparna , Wong Sing Wan , Hefner Nicole A. , Stuart Andrew , Qadir Abdul S. , Mukhopadhyay Amitabha , Bachmaier Kurt , Shin Jae-Won , Rehman Jalees , Malik Asrar B.
Published: April 2022

Significance

Current therapies for pulmonary fibrosis (PF) focus on slowing disease progression and reducing functional decline in patients by dampening the activation of fibroblasts and other implicated cells. There is a need for strategies that target the essential cells and signaling pathways involved in disease pathogenesis. Monocyte-derived macrophages (Mo-Macs) are known to express profibrotic genes and are involved in the pathogenesis of PF. Our results show that engineered mannosylated albumin nanoparticles specifically targeted disease-inducing Mo-Macs, and further, that nanoparticles efficiently delivered small-interfering RNA against profibrotic cytokine tumor growth factor β1 to prevent bleomycin-induced lung fibrosis.
Ionization and electron excitation of C
60
in a carbon nanotube: A variable temperature/voltage transmission electron microscopic study
Authors: Liu Dongxin , Kowashi Satori , Nakamuro Takayuki , Lungerich Dominik , Yamanouchi Kaoru , Harano Koji , Nakamura Eiichi
Published: April 2022

Significance

The destruction of specimen molecules by an electron beam (e-beam) is either beneficial, as in mass spectrometry capitalizing on ion formation, or deleterious, as in electron microscopy. In the latter application, the e-beam not only produces the specimen image, but also causes information loss upon prolonged irradiation. However, the atomistic mechanism of such loss has been unclear. Performing single-molecule kinetic analysis of C
60
dimerization in a carbon nanotube (CNT) under variable-temperature/voltage conditions, we identified three reactive species—that is, radical cation, singlet, and triplet excited states—reacting competitively as the voltage and the properties of the CNT were changed. The key enabler was in situ continuous recording of the whole reaction process, suggesting an upcoming new era of “cinematic chemistry.”
Discharge characteristics in soil under positive pulse voltage superimposed DC component
Authors: Yang Yong , Pi Xiaoqian , Li Chi , Li Chuan , Zhang Haoqin , Chen Huan , Yu Ziheng , Yang Shuai
Published: April 2022

Considerable research efforts have been devoted to the study of the application of atmospheric discharge in soil remediation. Most of them focused on how to improve the degradation efficiency of specific pollutants. In contrast, the generation and development of discharge in soil is less studied, which restricts the widespread application of soil remediation. Pulse voltage is widely used to trigger discharge in soil, but the requirement for the power supply is relatively high. The current paper proposes a new form of discharge voltage, with positive pulse voltage superimposed on DC bias. The results show that the existence of DC component can effectively lower the required pulse voltage and enlarge the active corona volume, in which area most ionization and excitation happens. The characteristics of corona discharge in soil under DC voltage only, pulse voltage only and superimposed voltage with various voltage components are discussed in detail, according to the volt-ampere characteristics and discharge images from a series of experiments. The mechanism behind the experimental phenomenon are also discussed.
Surface plasmonic waveguide and ultra-wideband bandpass filter using double-layered glide symmetric corrugated lines
Authors: Zhang Xuewei , Liu Shaobin , Liao Kun , Lou Jian
Published: April 2022

In this paper, an ultra-wideband high-efficiency bandpass filter based on a surface plasmonic waveguide (SPW) is proposed. The novel SPW consists of double-sided glide symmetric periodic corrugated metal. The dispersion characteristics of the double-layered glide symmetric SPW are analyzed. By using glide symmetry technology, the dispersion curve for the two lowest-order modes of the proposed SPW is a degeneracy at the Brillouin zone boundary, resulting in a higher propagation constant than the traditional symmetric structure with the same geometry. The dispersion relation of the SPW when glide symmetric conditions are broken is also investigated. Based on the proposed double-layered glide symmetric SPW, we design a bandpass filter working in an ultrawide range of frequencies. To realize the high-efficient transmission of the bandpass filter, the matching structure composed of double-layer grooves with gradient variation is designed for the effective mode conversion of quasi-transverse electromagnetic waves and spoof surface plasmonic polariton. The upper cutoff frequency of the passband can be tuned by adjusting the geometric parameters of the corrugated metal unit, and the lower cutoff frequency can be controlled by modifying the coupling distance with the bottom layer. A prototype of an ultra-wideband bandpass filter has been manufactured and measured, showing a reasonable agreement with simulations. The proposed novel UWB bandpass filter with glide symmetry can be widely used in microwave and millimeter wave related communication systems, and may play an important role in the fabrication of advanced plasma functional devices and circuits.
Lattice dynamics of BaFe2Se3
Authors: Weseloh M J , Balédent V , Zheng W , Verseils M , Roy P , Brubach J B , Colson D , Forget A , Foury-Leylekian P , Lepetit M-B
Published: April 2022

This paper presents a study of the lattice dynamics in BaFe2Se3. We combined first-principle calculations, infrared measurements and a thorough symmetry analysis. Our study confirms that Pnma cannot be the space group of BaFe2Se3, even at room temperature. The phonons assignment requires Pm to be the BaFe2Se3 space group, not only in the magnetic phase, but also in the paramagnetic phase at room temperature. This is due to a strong coupling between a short-range spin-order along the ladders, and the lattice degrees of freedom associated with the Fe–Fe bond length. This coupling induces a change in the bond-length pattern from an alternated trapezoidal one (as in Pnma) to an alternated small/large rectangular one. Out of the two patterns, only the latter is fully compatible with the observed block-type magnetic structure. Finally, we propose a complete symmetry analysis of the BaFe2Se3 phase diagram in the 0–600 K range.
Nonconvex regularized sparse representation in a tight frame for gear fault diagnosis
Authors: Huang Weiguo , Zhang Cheng , Wu Shuyou , Shi Juanjuan , Du Guifu , Zhu Zhongkui
Published: April 2022

A gear’s vibration signal consists of multiple components, so it is therefore difficult to accurately extract the transient components of gear faults. Currently, sparse representation is capable of separating fault components from multicomponent noisy vibration signals. However, sparse representation methods still suffer problems with poor computational efficiency and the underestimation of amplitude. To tackle these challenges, this paper proposes a nonconvex regularized sparse representation in a tight frame. The tunable Q-factor wavelet transform (TQWT) is proposed as a sparse dictionary, which can portray the waveform characteristics of the gear’s vibration signal. TQWT satisfies the tight-frame condition, hence it can efficiently reduce the amount of calculations. The minimax concave function is used as the penalty function since it stands out from various penalty functions with the ability to maintain amplitude. The simulation and experimental analysis show that this method has a shorter operation time and a better ability to maintain the amplitude.
The structure of anionic NbH
n

− (n = 2–15) clusters and their maximum hydrogen capacity
Authors: Liao Y H , Zhou W L , Lyon J T , Peng F , Lu C
Published: April 2022

The geometrical structures of the lowest energy states of anionic niobium-doped hydrogen clusters are determined based on Crystal structure AnaLYsis by the Particle Swarm Optimization (CALYPSO) isomer search method. The geometries and relative stabilities are determined by the B3LYP hybrid density functional theory (DFT) method. The calculated results show that a niobium atom can absorb up to twelve hydrogen atoms in the anionic clusters. In exploring the stability, electronic properties, and photoelectron spectra of NbH
n

− clusters, the NbH12
− cluster is found to possesses a relatively high binding energy, high second-order differential energy, and a large HOMO–LUMO gap. The hydrogen storage density of the NbH12
− cluster is calculated as 11.5 wt%. The present findings enrich the database of transition metal doped hydrogen clusters and the insights are important in the pursuit of efficient hydrogen energy storage materials.
Overview of the HERD space mission
Authors: Kyratzis Dimitrios
Published: April 2022

The High Energy cosmic Radiation Detector (HERD) is a prominent space-borne instrument to be installed on-board the Chinese Space Station (CSS) around 2027, resulting from a collaboration among Chinese and European institutions. Primary scientific goals of HERD include: precise measurements of the cosmic ray (CR) energy spectra and mass composition at energies up to few PeV, electron/positron spectra up to tens of TeV, CR anisotropy, gamma ray astronomy and transient studies, along with indirect searches for Dark Matter candidates. The detector is configured to accept incident particles from both its top and four lateral sides. Owing to its pioneering design, more than one order of magnitude increase in geometric acceptance is foreseen, with respect to previous and ongoing experiments. HERD is conceived around a deep (∼55 X
0, 3 λ

I
) 3D cubic calorimeter (CALO), forming an octagonal prism. Fiber Trackers (FiTs) are instrumented on all active sides, with a Plastic Scintillator Detector (PSD) covering the calorimeter and tracker. Ultimately, a Silicon Charge Detector (SCD) envelops the above-stated sub-detectors, while a Transition Radiation Detector (TRD) is instrumented on one of its lateral faces, for energy calibration in the TeV scale. This work illustrates HERD’s latest advancements and scientific objectives along with an overview of upcoming activities.