bluuebunny/crossref_metadata_2025 huggingface dataset:
Realizability of the rapid distortion theory spectrum: The mechanism behind the Kelvin–Townsend equations
Authors: Ruiz de Zarate Fabregas A. , Dias N. L. , Alfaro Vigo D. G.
Published: June 2021

In the context of homogeneous turbulence, we prove that the Rapid Distortion Theory (RDT) model for the spectral tensor preserves the symmetry, positive semidefiniteness, and integrability properties required in Cramér’s characterization of the spectral tensor of a continuous homogeneous random process. From this, a statistically valid correlation tensor is obtained that returns a Reynolds stress tensor model that satisfies realizability conditions. The number of hypotheses used is kept to a minimum, which allows a flexible use of the model in the applications. The Kelvin–Townsend equations allow us to construct the solution and prove its properties by means of a factorization approach. Since the RDT spectral tensor model is a system of transport equations plus an algebraic restriction due to incompressibility, we deal with the existence, uniqueness, and persistence of solutions in a specific set of functions by using DiPerna–Lions renormalization techniques.
Cavity quantum electrodynamics design with single photon emitters in hexagonal boron nitride
Authors: Wang Yanan , Lee Jaesung , Berezovsky Jesse , Feng Philip X.-L.
Published: June 2021

Hexagonal boron nitride (h-BN), a prevalent insulating crystal for dielectric and encapsulation layers in two-dimensional (2D) nanoelectronics and a structural material in 2D nanoelectromechanical systems, has also rapidly emerged as a promising platform for quantum photonics with the recent discovery of optically active defect centers and associated spin states. Combined with measured emission characteristics, here we propose and numerically investigate the cavity quantum electrodynamics scheme, incorporating these defect-enabled single photon emitters (SPEs) in h-BN microdisk resonators. The whispering-gallery nature of microdisks can support multiple families of cavity resonances with different radial and azimuthal mode indices simultaneously, overcoming the challenges in coinciding a single point defect with the maximum electric field of an optical mode both spatially and spectrally. The excellent characteristics of h-BN SPEs, including exceptional emission rate, considerably high Debye–Waller factor, and Fourier transform limited linewidth at room temperature, render strong coupling with the ratio of coupling to decay rates g/max(γ, κ) predicated as high as 500. This study not only provides insight into the emitter–cavity interaction, but also contributes toward realizing h-BN photonic components, such as low-threshold microcavity lasers and high-purity single photon sources, critical for linear optics quantum computing and quantum networking applications.
Tunneling based ten attomolar DNA biosensor
Authors: Mardy Z. , Tao Y. L. , Renna L. A. , Ardo S. , Wickramasinghe H. K.
Published: June 2021

Early-stage detection prevents disease progression and complications in treatment procedures, especially for infectious diseases. This requires rapid and accurate sensing technologies and techniques that remove the need for expensive and time-consuming sample preparation and transfer to the labs and the running of multiple experiments. To that end, point-of-care (POC) testing has been introduced for quick disease diagnostics that enables caregivers to start early treatment, leading to improved health outcomes. Here, we introduce a tunneling current bio-sensing technology based on a metal–insulator–electrolyte junction, which is highly sensitive to charge variations at the insulator–electrolyte interface. The charge variations occur as a response of hybridization of complementary DNA sequences to DNA primers immobilized on the insulator surface. This leads to the label-free detection of as little as tens of DNA molecules or, equivalently, samples with 0.01 fM concentrations. Since the sensing is based on a single terminal measurement of current with respect to a reference electrode, our technology can enable the creation of novel compact medical and portable POC devices for real-time disease detection.
Characterizing materials for superconducting radiofrequency applications—A comprehensive overview of the quadrupole resonator design and measurement capabilities
Authors: Keckert S. , Kleindienst R. , Kugeler O. , Tikhonov D. , Knobloch J.
Published: June 2021

Test cavities to characterize superconductor samples are of great interest for the development of materials suitable for superconducting radio frequency (SRF) accelerator systems. They can be used to investigate fundamental SRF loss mechanisms and to study the material limitations for accelerator applications. Worldwide, this research is based on only few systems that differ in operating frequency, sample size and shape, and the accessible parameter space of frequency, temperature, and RF field strength. For useful performance predictions in future accelerators, it is important that the operating parameter range is close to that employed in accelerating systems. Since 2014, the Helmholtz-Zentrum Berlin has operated such a system built around a redesigned Quadrupole Resonator (QPR). It is based on a system originally developed at CERN. Important new design modifications were developed, along with new measurement techniques and insight into their limitations. In the meantime, an increasing number of laboratories are adopting the QPR for their measurement campaigns. This paper provides a comprehensive overview of the state-of-the-art, the wide spectrum of measurement capabilities, and a detailed analysis of measurement uncertainties, as well as the limitations one should be aware of to maximize the effectiveness of the system. In the process, we provide examples of measurements performed with Nb3Sn and bulk niobium.
Atomic coordinates and polarization map around a pair of 12a[011¯] dislocation cores produced by plastic deformation in relaxor ferroelectric PIN–PMN–PT
Authors: Liu Ying , Niu Ran-Ming , Moss Scott D. , Finkel Peter , Liao Xiao-Zhou , Cairney Julie M.
Published: June 2021

The core structures of dislocations are crucial for understanding the plastic deformation mechanisms and the functional properties of materials. Here, we use the scanning transmission electron microscopy imaging techniques of high-resolution high angle annular dark field and integrated differential phase contrast to investigate the atomic structure of a pair of climb-dissociated 12a[011¯] dislocations in a bending-deformed relaxor ferroelectric Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb1/3)O3–PbTiO3 single crystal. Cations at one dislocation core are found to arrange in the same way as the climb-dissociated 12a[011¯] dislocation core in SrTiO3, while the other one is different. Oxygen depletion was observed at both dislocation cores. Geometric phase analysis of the lattice rotation shows opposite signs at both sides of the dislocations, demonstrating the strain gradient, which is known to give rise to flexoelectric polarization. Using the peak finding method, the polarization (a combination of ferroelectric and flexoelectric) around dislocations was mapped at the unit-cell scale. The polarization direction obtained is consistent with that predicted based on the flexoelectric effect in a perovskite oxide with [011] geometry. Head-to-head positively charged and tail-to-tail negatively charged domain walls were revealed based on the polarization map, suggesting a new way to stabilize charged domain walls via dislocations. A distinct dislocation core configuration has been observed, and a unit-cell scale polarization map helps understand the flexoelectric effects (coupling between strain gradient and polarization) around dislocations in a relaxor ferroelectric.
Oscillation in the electrical conductivity of a thick graphene oxide membrane
Authors: Jamilpanah L. , Alihosseini M. , Ghasemi S. , Hassani N. , Peymanirad F. , Mohseni S. M. , Neek-Amal M.
Published: June 2021

Because of their unusual fundamental behavior that arises at the molecular scale, the electrical conductivity of stacked graphene oxide (GO) sheets in the presence of external parameters is not adequately understood. Previous studies concentrated on the DC response of thin GO membranes giving their resistive switching properties. Here, we observe anomalous low-frequency (<1 Hz) oscillations in the electrical conductivity of micrometer size GO, which is repeated in a process over and over in an ongoing feedback loop. Such vibrations and their unique trajectories are not only fundamentally important but also have characteristic frequencies that can be directly linked to the formation and destruction of regions with sp2 hybridization. Also, the reported switching time (of the order of seconds) makes our resistive switching system different than all the previously reported systems and introduces a new class of switching phenomena. The observed phenomena improve our understanding of the electrical conductivity of GO membranes and the corresponding microscopic details that pave the way for the promising application of these new observed low-frequency oscillations.
Schottky contact formation by an insulator: Lithium fluoride on silicon
Authors: Wan Shanshan , Zhang Guohua , Niederhausen Jens , Wu Di , Wang Qi , Sun Baoquan , Song Tao , Duhm Steffen
Published: June 2021

The low work function material lithium fluoride (LiF) facilitates electron-selective contacts to n-type silicon and is frequently used in dopant-free heterocontacts for silicon solar cells. Our photoelectron spectroscopy (PES) data show that LiF deposition on n-Si leads, indeed, to Fermi-level crossing of the conduction band minimum. Furthermore, PES reveals intrinsic surface band bending on hydrogen-terminated p-Si(100). LiF deposition on p-Si leads to a rigid shift of the Si core-levels and the vacuum-level pointing to ideal Schottky contact formation. This is further supported by the open-circuit voltage of Al/LiF/p-Si/Al solar cells, which corresponds to the photoelectron spectroscopy (PES)-measured band bending magnitude.
Multi-instrument Bayesian reconstruction of plasma shape evolution in the C-2W experiment
Authors: Dikovsky M. , Baltz E. A. , Von Behren R. , Geraedts S. , Kast A. , Langmore I. , Madams T. , Norgaard P. , Platt J. C. , Romero J. , Roche T. , Smith R. , Trask E. , Dettrick S. , Gota H. , Titus J. B. , Magee R. M.
Published: June 2021

We determined the time-dependent geometry, including high-frequency oscillations, of the plasma density in TAE's C-2W experiment [Gota et al., Nucl. Fusion 59, 112009 (2019)]. This was done as a joint Bayesian reconstruction from a 14-chord FIR interferometer in the midplane, 32 Mirnov probes at the periphery, and 8 shine-through detectors at the targets of the neutral beams. For each point in time, we recovered, with credibility intervals, the radial density profile of the plasma; bulk plasma displacement; and amplitudes, frequencies, and phases of the azimuthal modes n = 1, …, 4. Also reconstructed were the radial profiles of the deformations associated with each of the azimuthal modes. Bayesian posterior sampling was done via Hamiltonian Monte Carlo with custom preconditioning. This gave us a comprehensive uncertainty quantification of the reconstructed values, including correlations and some understanding of multimodal posteriors.
Algebraic second virial coefficient of the Mie m − 6 intermolecular potential based on perturbation theory
Authors: van Westen Thijs
Published: June 2021

We propose several simple algebraic approximations for the second virial coefficient of fluids whose molecules interact by a generic Mie m − 6 intermolecular pair potential. In line with a perturbation theory, the parametric equations are formulated as the sum of a contribution due to a reference part of the intermolecular potential and a perturbation. Thereby, the equations provide a convenient (low-density) starting point for developing equation-of-state models of fluids or for developing similar approximations for the virial coefficient of (polymeric-)chain fluids. The choice of Barker and Henderson [J. Chem. Phys. 47, 4714 (1967)] and Weeks, Chandler, and Andersen [Phys. Rev. Lett. 25, 149 (1970); J. Chem. Phys. 54, 5237 (1971); and Phys. Rev. A 4, 1597 (1971)] for the reference part of the potential is considered. Our analytic approximations correctly recover the virial coefficient of the inverse-power potential of exponent m in the high-temperature limit and provide accurate estimates of the temperatures for which the virial coefficient equals zero or takes on its maximum value. Our description of the reference contribution to the second virial coefficient follows from an exact mapping onto the second virial coefficient of hard spheres; we propose a simple algebraic equation for the corresponding effective diameter of the hard spheres, which correctly recovers the low- and high-temperature scaling and limits of the reference fluid’s second virial coefficient.
Phase field study on the performance of artificial synapse device based on the motion of domain wall in ferroelectric thin films
Authors: Xiong Weiming , Liu Linjie , Liu Jianyi , Chen Weijin , Zheng Yue
Published: June 2021

Artificial neural networks have gained intensive attention in recent years because of their potential in effectively reducing energy consumption and improving computation performance. Ferroelectric materials are considered to be promising candidates for artificial synapses because of their multiple and nonvolatile polarization states under external stimuli. Despite artificial ferroelectric synapses with multilevel states, long retention and fast switching speed have been reported, and some key fundamental issues, e.g., the influence of domain wall configuration and evolution on the performance of synapse behaviors, also remain unclear. In this work, we study the performance of artificial synapses based on the motion of 180° ferroelectric domain walls of stripe domain and cylinder domain in ferroelectric thin films via a dynamical phase field model. The results demonstrate that artificial synapses based on the stripe domain exhibit high linearity and symmetry in weight update under a weak electric field, compared with the cylinder domain. Based on such artificial synapses, the accuracy of an artificial neural network for the Modified National Institute of Standards and Technology handwritten digit recognition is over 92%. This work provides a domain-wall-based strategy to improve the weight updating linearity and symmetry of artificial synapse devices and the recognition accuracy of artificial neural networks.
How mass disorder affects heat conduction in ternary amorphous alloys
Authors: Ichikawa Tatsuki , Minamitani Emi , Shigesato Yuzo , Kashiwagi Makoto , Shiga Takuma
Published: June 2021

Thermal management is critical in devices that use amorphous semiconductors. Recent studies have revealed how size and mass disorder affect heat conduction, but the effects of more-extreme mass and lattice disorder are also relevant. Here, we report modal analysis of simulated samples of amorphous silicon alloyed with atoms of different-mass silicon to yield a ternary amorphous material. Although we expected the material with high degrees of mass disorder to show dramatic changes in thermal conductivity as the composition of the material changed, the thermal conductivity instead changed monotonically. Thus, we find that no peculiar thermal transport properties appear in ternary amorphous alloys with high degrees of mass disorder. Furthermore, we find that while delocalized propagating modes (propagons) explain nearly 30% of the overall thermal conductivity independent of the composition, the contribution of delocalized non-propagating modes (diffusons) is sensitive to the composition and tends to be the dominant mechanism behind heat conduction in ternary amorphous alloys.
Influence of jet flow on the hydrodynamic and noise performance of propeller
Authors: Guo Hang , Guo Chunyu , Hu Jian , Lin Jianfeng , Zhong Xianghai
Published: June 2021

The non-uniformity of the propeller wake field will lead to noise deterioration and structural strength problems of the underwater vehicles. Therefore, the study of jet flow technology is of great significance for improving the uniformity of the wake field and reducing vibration and noise. In this study, the Reynolds-averaged Navier–Stokes method and Ffowcs Williams and Hawkings acoustic model are used together to ascertain the influence of jet flow on the hydrodynamic and noise performance of the propeller. The accuracy of the numerical simulation method is verified through the convergence analysis of the calculation results. The hydrodynamic performance of the submarine and propeller with jet flows on different parameters is studied. The results show that the triangular jet can significantly improve the non-uniformity of the circumferential distribution of the wake field at the propeller plane and reduce the dynamic bearing force of the propeller blade. Simultaneously, the spectrum analysis of the numerical simulation results of the propeller noise shows that, compared with the no jet condition, the total sound pressure level at the propeller plane in the low-frequency range can be reduced by more than 3 dB using jet flow in front of the propeller. Hence, the low-frequency discrete spectrum noise of the submarine propeller can be better controlled.
Effect of macroscale mesh design of metal nanowire networks on the conductive properties for stretchable electrodes
Authors: Takane Satoshi , Noda Yuki , Toyoshima Naomi , Sekitani Tsuyoshi
Published: June 2021

Elastic, deformable electrodes have attracted substantial interest owing to their applicability in unconventional stretchable devices. In this study, we investigate the effect of tensile strain on the conductive properties of gold nanowire (AuNW) network electrodes with macroscale mesh structures (mesh-shaped AuNW network electrodes) and the mechanism by which the mesh structure affects its conductivity, with the aim of maintaining a stable conductivity as the electrodes are stretched. At 150% elongation, the proposed AuNW macroscale mesh exhibited a relative resistance change (ΔR/R0) of 11, as opposed to 30 for AuNW network electrodes without a mesh structure. Microstructural analysis revealed that resistance changes in the mesh-shaped AuNW network electrodes depend on the electrode stretching direction and the current direction within the network. Our experimental and analytical results provide a basis for optimizing the mesh design for metal nanowire networks used in stretchable electrodes.
Electronic and doping properties of hexagonal silicon carbide with stacking faults induced cubic inclusions
Authors: Li Pei , Yan Xiaolan , Chen Jiabin , Dong Peng , Huang Bing
Published: June 2021

Silicon carbide (SiC) has been considered one of the most important wide bandgap semiconductors for both scientific interest and technological applications. The existence of stacking faults induced inclusions, originated from the “wrong” stacking sequences of Si–C bilayers, is a general feature in SiC. Until now, however, a systematical understanding of the role of cubic inclusions (CIs) in the electronic and doping properties of hexagonal SiC is still lacking, which may prevent further improvement of its electronic performance. In this article, using advanced first-principles calculations, we have systematically studied the stability, electronic structures, and doping properties of hexagonal SiC with CIs. First, we find that the CIs in SiC have rather low formation energies but high kinetic stability. Second, we find that the electronic structures of SiC can be dramatically tuned by the ratio of CIs in SiC. Third, we demonstrate that the CI-induced band offset and the dipole-discontinuity-induced dipole field in the system can give rise to different ground-state doping sites for dopants at their different charge-states, which can consequently result in novel doping-site-dependent charge-state transition levels (CTLs). Meanwhile, the intrinsic dipole field can dramatically enhance the structural relaxation effects during the ionization of the dopants, which can push the CTLs deeper inside the bandgap compared to the case without CIs. Our findings suggest that CIs could play unusual roles in determining the overall electronic and doping properties of SiC and other similar semiconductors.
Numerical study of instabilities of particle-laden fronts in continuously stratified environments
Authors: Cheng Che-Jung , Chou Yi-Ju
Published: June 2021

Numerical simulations are conducted to study instabilities and the associated convective motion of particle-laden layers settling in continuously stratified environments. We show that when the background density stratification is insignificant relative to the bulk excessive density of the particle-laden layer, the unstable motions of the particle-laden interface are mainly driven by Rayleigh–Taylor instability but become double-diffusive convection when the background stratification is relatively significant. Our results agree with theoretical prediction based on linear stability analysis. However, in the Rayleigh–Taylor instability regime, the motion of particle-laden plumes can be further suppressed by the background density stratification while the plumes reach the height of neutral buoyancy. This leads to the second stage of flow development, in which secondary instability occurs at the plumes' tip in the form of double-diffusive convection. Due to the change in the background density gradient within the plumes' head, the occurrence of secondary instability is accompanied by a shift of the dominant mode, which is particularly significant in cases with a high background Prandtl number (i.e., salinity-induced stratification). The theoretical argument on the mode shift is based on previous linear stability analysis for the two-layer structured background density gradient provided. The ratio between the particles' settling velocity and velocity scaling for the developed local density gradient at the plumes' tip then allows us to distinguish and predict whether the final convective motion is driven mainly by double-diffusive or settling-driven buoyancy-dominant convection.
Proposal for energy efficient spin transfer torque-magnetoresistive random access memory device
Authors: Sharma Abhishek , Tulapurkar Ashwin A. , Muralidharan Bhaskaran
Published: June 2021

Utilizing the electronic analogs of optical phenomena such as anti-reflection coating and resonance for spintronic devices, we propose and theoretically analyze the design of a spin transfer torque-magnetoresistive random access memory (STT-MRAM) device. The proposed device consists of a superlattice heterostructure terminated with the anti-reflective regions sandwiched between the fixed and free ferromagnetic layers. Employing Green’s function spin-transport formalism coupled self-consistently with the stochastic Landau–Lifshitz–Gilbert–Slonczewski equation, we design an STT-MRAM based on the anti-reflective superlattice magnetic tunnel junction (AR-SLMTJ) device having an ultrahigh tunnel magnetoresistance (≈3.5×104%) and large spin current. We demonstrate that the STT-MRAM based on the AR-SLMTJ structure owing to the physics of bandpass spin filtering is nearly 1100% more energy efficient than trilayer magnetic tunnel junction (MTJ) based STT-MRAM. We also present detailed probabilistic switching and energy analysis to find out the optimal point of operation of a trilayer MTJ and AR-SLMTJ based STT-MRAM. Our predictions serve as a template to consider the heterostructures for next-generation spintronic device applications.
Numerical simulation and experimental validation of bending and curling behaviors of liquid crystal elastomer beams under thermal actuation
Authors: Potekhina Alissa , Wang Changhai
Published: June 2021

The exceptional actuation properties of liquid crystal elastomers (LCEs) have made these materials highly attractive for various emerging applications such as soft robotics and artificial muscles. The large strain gradients occurring under thermal stimuli induce bending and curling of initially flat LCE films. Due to the complex physics behind the spontaneous deformation in nematic liquid crystal elastomers, there is no single universal finite element-based method for the simulation of the behaviors of LCE actuators. In this work, we developed a simple layered 2D model for modeling and simulation of the bending and curling characteristics of LCE beams based on the gradient of the temperature-dependent equivalent thermal expansion. The appropriate parameters were derived by measuring the radius of curvature of the LCE film aligned unidirectionally at one surface produced on a rubbed Kapton film. It was found that in a large range of thicknesses (12–134 μm) of the LCE beams, the equivalent thermal expansion coefficients tend to approach a similar value. It was demonstrated and experimentally validated that the thermal expansion model is very effective in predicting the nonlinear curling behavior of LCE beams of various thicknesses. Remarkably, the model is also capable of simulating the rolling behavior of LCE beams with tapered thickness variation. The proposed method offers good flexibility in terms of the geometric shape and expansion parameters, computational efficiency, and accuracy.
Computational fluid dynamics investigation on effects of uvulopalatopharyngoplasty on upper airway stability
Authors: Shang Yan , Hu Bin , Yin Guoping , Fu Song , Ye Jingying
Published: June 2021

Uvulopalatopharyngoplasty (UPPP) is a widely accepted surgery to treat patients with obstructive sleep apnea. However, the outcomes of surgery are variable and not satisfactory in many cases. To explore the key factors that influence outcomes of surgery from perspectives of upper airway stability using computational fluid dynamics methods, three-dimensional (3D) upper airway models were reconstructed, and a series of steady-state and unsteady-state simulations were performed based on computerized tomography (CT) scans of five normal subjects and preoperative and postoperative CT scans of ten obstructive sleep apnea (OSA) patients. Aerodynamics in normal subjects, preoperative OSA patients, and postoperative OSA patients was compared, and the outcomes of UPPP were analyzed from perspectives of upper airway resistance and the wall pressure–inspiratory pressure ratio. The negative pressure on the collapsible part of the upper airway was a major contributor to the obstruction. Surgery mitigated the negative pressure by reducing the upper airway resistance as well as the wall pressure–inspiratory pressure ratio. The effect of UPPP was associated with the change in resistance and the wall pressure–inspiratory pressure ratio.
Demonstration of microwave plasmonic-like vortices with tunable topological charges by a single metaparticle
Authors: Su Guangxu , Su Hai , Hu Lumang , Qin Zhaofu , Shen Xiaopeng , Ding Jianping , Liu Fanxin , Lu Minghui , Zhan Peng , Liu Yongmin
Published: June 2021

Light beams with helical wave fronts, also called optical vortices, have attracted great interest in the community of optics and photonics. They provide an additional degree of freedom for light manipulation, leading to wide-ranging potential applications in micro-particle trapping, optical microscopy, and even quantum information processing. Recently, metallic microstructures are introduced to confine the plasmonic vortices into deep subwavelength dimension, which benefits photonic integration on chip. In this Letter, exploiting the excitation of spoof surface plasmon, we experimentally demonstrate the near-field optical vortices with tunable topological charges supported by a single metaparticle in the microwave regime. These microwave plasmonic-like vortices are excited by surface waves with a spatial asymmetric distribution of electromagnetic field, which are launched by a metallic comb-shaped waveguide. Experimental characterization of highly localized and controllable near-field vortices with the nature of deep subwavelength confirms the numerical simulation. In addition, an equivalent physical model based on the coupled mode theory is proposed to understand the generation mechanism of these spoof plasmonic vortices. Our approach offers an efficient way to generate deterministic subwavelength optical vortices, which provides the potential for critical vortex elements on photonic integrated chip.
Numerical investigation of rarefied vortex loop formation due to shock wave diffraction with the use of rorticity
Authors: Cao Ziqu , White Craig , Kontis Konstantinos
Published: June 2021

When compressed gas is ejected from a nozzle into a low-pressure environment, the shock wave diffracts around the nozzle lip and a vortex loop will form. The phenomenon has been widely investigated in the continuum flow regime, but how the shock diffraction and vortex behave under rarefied flow conditions has not received as much attention. It is necessary to understand this transient flow in rarefied environments to improve thrust vector control and avoid potential contamination and erosion of spacecraft surfaces. This work provides numerical results of the vortex loop formation caused by shock wave diffraction around a 90° corner using the direct simulation Monte Carlo method and the compressible Navier–Stokes equations with the appropriate Maxwell velocity slip and the von Smoluchowski temperature jump boundary conditions. The Mach number and rarefaction effects on the formation and evolution of the vortex loop are discussed. A study of the transient structures of vortex loops has been performed using the rorticity concept. A relationship of mutual transformation between the rorticity and shear vectors has been discovered, demonstrating that the application of this concept is useful to understand vortex flow phenomena.
Dynamics of uniaxial-to-biaxial nematics switching in suspensions of hard cuboids
Authors: Mirzad Rafael Effran , Tonti Luca , Corbett Daniel , Cuetos Alejandro , Patti Alessandro
Published: June 2021

Field-induced reorientation of colloidal particles is especially relevant to manipulate the optical properties of a nanomaterial for target applications. We have recently shown that surprisingly feeble external stimuli are able to transform uniaxial nematic liquid crystals (LCs) of cuboidal particles into biaxial nematic LCs. In light of these results, here we apply an external field that forces the reorientation of colloidal cuboids in nematic LCs and sparks a uniaxial-to-biaxial texture switching. By dynamic Monte Carlo simulation, we investigate the unsteady-state reorientation dynamics at the particle scale when the field is applied (uniaxial-to-biaxial switching) and then removed (biaxial-to-uniaxial switching). We detect a strong correlation between the response time, being the time taken for the system to reorient, and particle anisotropy, which spans from rod-like to plate-like geometries. Interestingly, self-dual-shaped cuboids, theoretically considered as the most suitable to promote phase biaxiality for being exactly in between prolate and oblate particles, exhibit surprisingly slow response times, especially if compared to prolate cuboids.
Superposition-state N2+ produced in the intermolecular charge transfer from low-energy Ar+ to N2
Authors: Hu Jie , Xie Jing-Chen , Wu Chun-Xiao , Tian Shan Xi
Published: June 2021

Molecular electronic or vibrational states can be superimposed temporarily in an extremely short laser pulse, and the superposition-state transients formed therein receive much attention, owing to the extensive interest in molecular fundamentals and the potential applications in quantum information processing. Using the crossed-beam ion velocity map imaging technique, we disentangle two distinctly different pathways leading to the forward-scattered N2+ yields in the large impact-parameter charge transfer from low-energy Ar+ to N2. Besides the ground-state (X2Σg+) N2+ produced in the energy-resonant charge transfer, a few slower N2+ ions are proposed to be in the superpositions of the X2Σg+-A2Πu and A2Πu-B2Σu+ states on the basis of the accidental degeneracy or energetic closeness of the vibrational states around the X2Σg+-A2Πu and A2Πu-B2Σu+ crossings in the non-Franck–Condon region. This finding potentially shows a brand-new way to prepare the superposition-state molecular ion.
A time-domain simulation method to predict insertion loss of a dissipative muffler with exhaust flow
Authors: Liu Lianyun , Zheng Xu , Hao Zhiyong , Qiu Yi
Published: June 2021

Insertion loss (IL) is a more useful acoustic index than noise reduction and transmission loss for muffler design, but it is harder to predict because the prediction of IL requires knowing the characteristics of the muffler itself and the acoustic source. A muffler with porous material and complex meanflow makes the prediction even more challenging. Although calculation of noise reduction and transmission loss with the transient computational fluid dynamics (CFD) can naturally solve the flow–acoustic interaction problem, the published CFD methods have not been adopted to evaluate the IL of the dissipative muffler with exhaust flow. In this paper, a time-domain simulation method is developed to predict the IL of a complex engine muffler with porous material. The noise reduction and load impedance of the muffler were first calculated using a three-dimensional CFD model, in which the porous material was simulated by the governing equations modified with the material porosity and flow resistivity. The IL was then predicted from the noise reduction, the load impedance, and the engine source extracted from the measured exhaust noise. This developed method explores the application of the three-dimensional CFD method in calculating noise reduction, load impedance, and insertion loss of complex dissipative mufflers with exhaust flow.
Key computational findings reveal proton transfer as driving the functional cycle in the phosphate transporter PiPT
Authors: Liu Yu , Li Chenghan , Gupta Meghna , Verma Nidhi , Johri Atul Kumar , Stroud Robert M. , Voth Gregory A.
Published: June 2021

Significance

Proton- or sodium-coupled transporters within the major facilitator superfamily are essential for nutrient uptake in all forms of life. We focus on a high-affinity eukaryotic proton-coupled phosphate symporter using extensive classical molecular dynamics (MD) simulations and quantum mechanics/molecular mechanics MD combined with free energy sampling and confirm the role of a key residue, D324, at the molecular level. The results explain the exit direction of the proton once dissociated from D324 and reveal a perspective on proton-coupled transporters, showing that titratable substrates can be involved in the proton transport process as a key aspect of the functional cycle. Mutagenesis and phosphate transport confirm the essential nature of the key D45 residue in the protonation pathway.
À propos de la grammaticalisation/constructionnalisation de la relative attributive en français
Authors: Velinova Malinka
Published: June 2021

In this article, I revisit the origins of the attributive relative clause in French (in Je le vois qui
vient), in order to advance the hypothesis that reanalysis preceding grammaticalization of this construction
originates from a double ambiguity which is situated on two different planes of analysis: (1) on the plane of
(non-)restriction of the referent of the antecedent of qui; (2) on the plane of informational structure of the
sentence; and that the mentioned reanalysis originates from certain semantic and syntactic link between the attributive relative
and the narrative relative clauses, which is best discernible in a kind of mixed relative clause which has relatively high
frequency in Old French. In conclusion, I verify the relevance of the application of the concept of constructionalization to the
evolution of the attributive relative clause.
Developing as a post-PhD researcher: agency and feedback in construction of grant funding success (El desarrollo del investigador posdoctoral: agencia y feedback en la preparación de propuestas de financiación exitosas)
Authors: Yousoubova Larissa , McAlpine Lynn
Published: June 2021

Grant funding is critical to building a sustained research career. Yet in this climate of academic performativity little is known about how individual academics make their contribution to knowledge fundable. This in-depth longitudinal case study explores an approach evolved by an experienced Canadian scientist whose work is recognized for both scholarly and societal impact. We demonstrate how, over ten years, his agentive participation in academic interactions has contributed to continual development of his research and its funding through: his seeking and engaging with feedback; network-wide view of feedback sources; and drawing on feedback to inform his writing and research thinking. The article suggests a developmental view of the process in which, over time, researchers conceive, expand and draw on their feedback networks. Locating funding success within the social dimensions of knowledge and researcher development, the study sheds light on the role of agency and experiential learning in enabling contributions to frontline knowledge. Results suggest a novel, encompassing way for post-PhD researchers to build towards sustained grant funding.
The nature of cell division forces in epithelial monolayers
Authors: Gupta Vivek K. , Nam Sungmin , Yim Donghyun , Camuglia Jaclyn , Martin Judy Lisette , Sanders Erin Nicole , O’Brien Lucy Erin , Martin Adam C. , Kim Taeyoon , Chaudhuri Ovijit
Published: June 2021

Epithelial cells undergo striking morphological changes during division to ensure proper segregation of genetic and cytoplasmic materials. These morphological changes occur despite dividing cells being mechanically restricted by neighboring cells, indicating the need for extracellular force generation. Beyond driving cell division itself, forces associated with division have been implicated in tissue-scale processes, including development, tissue growth, migration, and epidermal stratification. While forces generated by mitotic rounding are well understood, forces generated after rounding remain unknown. Here, we identify two distinct stages of division force generation that follow rounding: (1) Protrusive forces along the division axis that drive division elongation, and (2) outward forces that facilitate postdivision spreading. Cytokinetic ring contraction of the dividing cell, but not activity of neighboring cells, generates extracellular forces that propel division elongation and contribute to chromosome segregation. Forces from division elongation are observed in epithelia across many model organisms. Thus, division elongation forces represent a universal mechanism that powers cell division in confining epithelia.
Nano-scale resolution of native retinal rod disk membranes reveals differences in lipid composition
Authors: Sander Christopher L. , Sears Avery E. , Pinto Antonio F.M. , Choi Elliot H. , Kahremany Shirin , Gao Fangyuan , Salom David , Jin Hui , Pardon Els , Suh Susie , Dong Zhiqian , Steyaert Jan , Saghatelian Alan , Skowronska-Krawczyk Dorota , Kiser Philip D. , Palczewski Krzysztof
Published: June 2021

Photoreceptors rely on distinct membrane compartments to support their specialized function. Unlike protein localization, identification of critical differences in membrane content has not yet been expanded to lipids, due to the difficulty of isolating domain-specific samples. We have overcome this by using SMA to coimmunopurify membrane proteins and their native lipids from two regions of photoreceptor ROS disks. Each sample's copurified lipids were subjected to untargeted lipidomic and fatty acid analysis. Extensive differences between center (rhodopsin) and rim (ABCA4 and PRPH2/ROM1) samples included a lower PC to PE ratio and increased LC- and VLC-PUFAs in the center relative to the rim region, which was enriched in shorter, saturated FAs. The comparatively few differences between the two rim samples likely reflect specific protein–lipid interactions. High-resolution profiling of the ROS disk lipid composition gives new insights into how intricate membrane structure and protein activity are balanced within the ROS, and provides a model for future studies of other complex cellular structures.
Dielectronic recombination along high Rydberg states of Mg+ and Si11+ ions
Authors: Li Yueming
Published: June 2021

In solving the multi-channel equation, I got the analytical expression of the multi-channel wave functions in terms of the solutions of the corresponding homogeneous equations. The homogeneous solutions are described in WKB Wenzel (1926 Z. Phys.
38 518) representation for both open and closed channels, and are calculated numerically using analogous means. By treating the open and closed channels equivalently in the calculation of the multi-channel wave functions, the generalized interaction matrix and generalized scattering matrix can be obtained for all the channels. With the obtained wave functions and generalized scattering matrix, the dielectronic recombination (DR) process can be calculated within the close-coupling framework by employing Bell and Seaton’s analytical deductions. In the method, high Rydberg states can easily be involved in numerical calculations. The method was applied to the calculations of DR of Mg+ and Si11+ ions along their high Rydberg states. The results are compared with those of the published experiments. Excellent agreements have been achieved, except at the extreme high Rydberg states for Si11+ ions, which is discussed in this paper.
Entanglement versus gap, quantum teleportation, and the AKLT model
Authors: Mizel Ari
Published: June 2021

Quantum-mechanical entanglement is notoriously volatile because of its susceptibility to external disturbances. However, entanglement can be stabilized if it is present in the non-degenerate ground state of a gapped, time-independent Hamiltonian. In this paper, we devise a spin-chain Hamiltonian whose ground state contains a Bell pair, with one member of the pair at each end of the chain. We study the Hamiltonian numerically, using full numerical diagonalization and a carefully tailored mean-field theory, to show that it is gapped. Whenever the Hamiltonian is tuned to increase its gap, the fidelity of its Bell pair decreases, manifesting a fundamental contention. The form of the Hamiltonian is motivated by quantum teleportation. Comparing it to the canonical Affleck, Kennedy, Lieb, and Tasaki (AKLT) model, we find that the AKLT model exhibits a sort of ‘failed quantum teleportation’.
Measuring magnetic fields in laser-driven coils with dual-axis proton deflectometry
Authors: Bradford P , Dearling A , Ehret M , Antonelli L , Booth N , Carroll D C , Clarke R J , Glize K , Heathcote R , Khan M , Moody J D , Pikuz S , Pollock B B , Read M P , Ryazantsev S , Spindloe C , Ridgers C P , Santos J J , Tikhonchuk V T , Woolsey N C
Published: June 2021

By driving hot electrons between two metal plates connected by a wire loop, high power lasers can generate multi-tesla, quasi-static magnetic fields in miniature coil targets. Many experiments involving laser-coil targets rely on proton deflectometry directed perpendicular to the coil axis to extract a measurement of the magnetic field. In this paper, we show that quantitative measurements using perpendicular probing are complicated by the presence of GV m−1 electric fields in the target that develop on sub-ns timescales. Probing parallel to the coil axis with fiducial grids is shown to reliably separate the electric and magnetic field measurements, giving current estimates of I ≈ 5 kA in 1 mm- and 2 mm-diameter wire loops. An analytic model of proton deflection in electric and magnetic fields is used to benchmark results from the particle-in-cell code and help deconvolve the magnetic and electric field deflections. Results are used to motivate a new experimental scheme that combines a single-plate target with axial proton probing and direct current measurements. This scheme has several important advantages over the traditional target and diagnostic set-up, enabling the robust measurement of coil magnetic fields and plasma properties, as well as making it easier to validate different theoretical models at a range of laser intensities.
Social bots and mass media manipulated public opinion through dual opinion climate
Authors: Cheng Chun , Luo Yun , Yu Chang-bin , Ding Wei-ping
Published: June 2021

Opinion dynamics models based on the multi-agent method commonly assume that interactions between individuals in a social network result in changes in their opinions. However, formation of public opinion in a social network is a macroscopic statistical result of opinions of all expressive individuals (corresponding to silent individuals). Therefore, public opinion can be manipulated not only by changing individuals’ opinions, but also by changing their states of expression (or silence) which can be interpreted as the phenomenon “spiral of silence” in social psychology. Based on this theory, we establish a “dual opinion climate” model, involving social bots and mass media through a multi-agent method, to describe mechanism for manipulation of public opinion in social networks. We find that both social bots (as local variables) and mass media (as a global variable) can interfere with the formation of public opinion, cause a significant superposition effect when they act in the same direction, and inhibit each other when they act in opposite directions.
KT-E-invexity in E-differentiable vector optimization problems
Authors: Abdulaleem Najeeb
Published: June 2021

In this paper, a new concept of generalized convexity is introduced for E-differentiable vector optimization problems. Namely, the concept of KT-E-invexity is defined for (not necessarily) differentiable vector optimization problems in which the functions involved are E-differentiable. The sufficiency of the so-called E-Karush-Kuhn-Tucker optimality conditions is established for the considered E-differentiable multiobjective programming problem under assumption that is KT-E-invex at an E-Karush-Kuhn-Tucker point. Further, the examples of KT-E-invex optimization problems with E-differentiable functions are constructed to illustrate the aforesaid results. Moreover, the so-called vector Mond-Weir E-dual problem is also derived for the considered E-differentiable vector optimization problem and several E-duality theorems in the sense of Mond-Weir are derived under KT-E-invexity hypotheses.

2020 Mathematics Subject Classification: 90C26, 90C29, 90C30, 90C46.
Numerical solution of the Harry Dym equation using Chebyshev spectral method via Lie group method
Authors: Assabaai M A
Published: June 2021

This study represents the solution of the Harry Dym equation (HDE) that was calculated using the Lie symmetry group method. This method transforms the controlled partial differential equation with boundary and initial conditions to the problem that containing boundary value of ordinary differential equation. The Chebyshev spectral approximation method is used to solve this problem numerically. This approach is performing by using the highest order derivatives of Chebyshev approximations, as starting steps, followed by getting approximations to the derivatives of lower order. Our obtained numerical results were compared with other works is done. It is seen that the proposed method for the Harry Dym equation gives more accurate results comparing with mentioned works.