Characteristics of cell motility during cell collision

Quantitative examination of cellular motion and intercellullar interactions possesses substantial relevance for both biology and medicine.However,the effects of intercellular interactions during cellular locomotion remain under-explored in experimental research.As such,this study seeks to bridge this research gap,adopting Dictyostelium discoideum(Dicty)cells as a paradigm to investigate variations in cellular motion during reciprocal collisions.We aim to attain a comprehensive understanding of how cell interactions influence cell motion.By observing and processing the motion trajectories of colliding cells under diverse chemical environments,we calculated the diffusion coefficient(D)and the persistence time(τ),using mean square displacement.Our analysis of the relationship dynamics between D andτprior to the collisions reveals intricate and non-monotonic alterations in cell movements during collisions.By quantitatively scrutinizing theτtrend,we were able to categorize the cellular responses to interactions under different conditions.Importantly,we ascertained that the effect of cell interactions during collisions in Dicty cells emulates a classical sigmoid function.This discovery suggests that cellular responses might comply with a pattern akin to the Weber–Fechner law.

Orbital-Ordering Driven Simultaneous Tunability of Magnetism and Electric Polarization in Strained Monolayer VCl_(3)

Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally verified.We theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground state.Utilizing first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are occupied.The atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase transitions.Introducing doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane polarizations.This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain.The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3).

Microscopic Magnetism of Nickel-Based Infinite-Layer Superconducting Parent Compounds RNiO_(2)(R=La,Nd):A μSR Study

By using muon spin relaxation(μSR)measurements,we perform a comparative study of the microscopic magnetism in the parent compounds of infinite-layer nickelate superconductors RNiO_(2)(R=La,Nd).In either compound,the zero-fieldμSR spectra down to the lowest measured temperature reveal no long-range magnetic order.In LaNiO_(2),short-range spin correlations appear below T=150 K,and spins fully freeze below T∼10 K.NdNiO_(2)exhibits a more complex spin dynamics driven by the Nd 4f and Ni3d electron spin fluctuations.Further,it shows features suggesting the proximity to a spin-glass state occurring below T=5 K.In both compounds,the spin behavior with temperature is further confirmed by longitudinal-field μSR measurements.These results provide new insight into the magnetism of the parent compounds of the superconducting nickelates,crucial to understanding the microscopic origin of their superconductivity.

Statistical physics of human beings in games:Controlled experiments

It is important to know whether the laws or phenomena in statistical physics for natural systems with non-adaptive agents still hold for social human systems with adaptive agents, because this implies whether it is possible to study or understand social human systems by using statistical physics originating from natural systems. For this purpose, we review the role of human adaptability in four kinds of specific human behaviors, namely, normal behavior, herd behavior, contrarian behavior, and hedge behavior. The approach is based on controlled experiments in the framework of market-directed resource-allocation games. The role of the controlled experiments could be at least two-fold： adopting the real human decision-making process so that the system under consideration could reflect the performance of genuine human beings; making it possible to obtain macroscopic physical properties of a human system by tuning a particular factor of the system, thus directly revealing cause and effect. As a result, both computer simulations and theoretical analyses help to show a few counterparts of some laws or phenomena in statistical physics for social human systems： two-phase phenomena or phase transitions, entropy-related phenomena, and a non-equilibrium steady state. This review highlights the role of human adaptability in these counterparts, and makes it possible to study or understand some particular social human systems by means of statistical physics coming from natural systems.

Impurity effect on surface states of Bi(111) ultrathin films

The surface impurity effect on the surface-state conductivity and weak antilocalization（WAL） effect has been investigated in epitaxial Bi（111） films by magnetotransport measurements at low temperatures. The surface-state conductivity is significantly reduced by the surface impurities of Cu, Fe, and Co. The magnetotransport data demonstrate that the observed WAL is robust against deposition of nonmagnetic impurities, but it is quenched by the deposition of magnetic impurities which break the time reversal symmetry. Our results help to shed light on the effect of surface impurities on the electron and spin transport properties of a 2D surface electron systems.

Effects of Hydrogen Ion Bombardment on Carbon Terminated Si (111) Surface Studied by LEED and AES

Etching effects of hydrogen ions on the Si(111)-(1×1)C surface have been studied by LEED(low-energy electron diffraction)and AES(Auger electron spectroscopy).It has been found that hydrogen ions,can break the carbon-silicon covalent bonds and cause a phase transition of Si(111)-(1×1)C to the reconstructed Si(111)-(7×7)structure.

Reaction Processes at the Initial Stage of Diamond Nucleation on the Surface of Si(111)

The thermal behavior of CHx(x=2,3)radicals and H atoms adsorbed on Si(111)surface was investigated by high-resolution electron-energy-loss spectroscopy,quadrupole mass spectrometry,and low-energy electron diffraction.Based on the analysis of thermal desorption mass spectrometry,the initial stage of diamond nucleation on Si is speculated.Compared with the result reported by Lee for diamond,it is concluded that low stability of hydrocarbon species on Si is the basic reason which results in the difficulty of diamond nucleation on perfect Si surface.

Analytical study of surface states caused by the edge decoration

Analytical studies of the effect of edge decoration on the energy spectrum of semi-infinite one-dimensional （1D） model and zigzag edged graphene （ZEG） are presented by means of transfer matrix method, in the frame of which the conditions for the existence of edge states are determined. For 1D model, the zero-energy surface state occurs regardless of whether the decorations exist or not, while the non-zero-energy surface states can be induced and manipulated through adjusting the edge decoration. On the other hand, the case for the semi-infinite ZEG model with nearestneighbour interaction is discussed in the analogous way. The non-zero-energy surface states can be induced by the edge decoration and moreover, the ratio between the edge hopping and the bulk hopping amplitudes should be within a certain threshold.

Surface-Induced Enhancement of Piezoelectricity in ZnO Nanowires

Piezoelectric nanowires are promising building blocks in various micro-electromechanical systems. Using firstprinciples calculations, we systematically investigate the influence of surface and volume changes on piezoelectric coefficients in [001]-oriented ZnO nanowires and hollow nanowires. We find that the increased non-axial ion displacements under strain near the {100} surface cause a notable enhancement in piezoelectric coefficients for these nanowires. Furthermore, by introducing the obtained surface modifications, we break through the limitation of simulation size and obtain the piezoelectric coefficients at the experimental size. Our findings are of importance to expand simulations and guide experimental explorations.

Suppressing Effects of Ag Wetting Layer on Surface Conduction of Er Silicide/Si(001) Nanocontacts

Current-voltage electrical characteristics of Er silicide/Si（001） nanocontacts are measured in situ in a scanning tunneling microscopy system. Introduced as a new technique to suppress surface leakage conduction on Si（001）,a silver wetting layer is evaporated onto the substrate surface kept at room temperature with Er Si2 nanoislands already existing. The effects of the silver layer on the current-voltage characteristics of nanocontacts are discussed.Our experimental results reveal that the silver layer at coverage of 0.4–0.7 monolayer can suppress effectively the current contribution from the surface conduction path. After the surface leakage path of nanocontacts is obstructed, the ideality factor and the Schottky barrier height are determined using the thermionic emission theory, about 2 and 0.5 eV, respectively. The approach adopted here could shed light on the intrinsic transport properties of metal-semiconductor nanocontacts.

Anisotropic Diffusion Evolution of Vacancies Created by Oxygen Etching on a Si Surface

We report the diffusion behavior of dimer vacancies on a Si(100)-(2×1)surface by using ultrahigh−vacuum scanning tunneling microscopy.The dimer vacancies are created by oxygen etching of Si atoms at elevated temperatures.By annealing the sample at 600–750°C,the dimer vacancies uniformly distribute on the terrace nucleate to form larger elongated voids of one atomic layer deep.The long axis of these voids is parallel to the Si dimer rows.During annealing,the surface morphology evolves in a way dominantly caused by the anisotropic diffusion of the dimer vacancies.A difference of diffusion barriers of 0.17±0.09 eV is obtained between the[110]and[110]directions.

Effect of Surface Hydrogen Coverage on Field Emission Properties of DiamondFilms Investigated by High-Resolution Electron Energy Loss Spectroscopy

The influence of surface hydrogen coverage on the electron field emission of diamond films was investigated by high-resolution electron energy loss spectroscopy.It was found that hydrogen plasma treatment increased the surface hydrogen coverage while annealing caused hydrogen desorption and induced surface reconstruction.Field electron emission measurements manifested that increase of surface hydrogen coverage could improve the field emission properties,due to the decrease of electron affinity of the diamond.surface hy hvdrogen adsorption.

Thermal Stability and Growth Behavior of Erbium Silicide Nanowires Self-Assembled on a Vicinal Si(001) Surface

Erbium silicide nanowires are self-assembled on vicinal Si(001)substrates after electron beam evaporation and post annealing at 630°C In−situ scanning tunneling microscopy investigations manifest that the nanowires will successively shrink and transform into a nanoisland with annealing prolonged.Meanwhile,a structural transition from hexagonal AlB2 phase to tetragonal ThSi2 phase is revealed with high-resolution transmission electron microscopy.It is also found that the nanowires gradually expand to embed into the substrates during the growth process,which has much influence on the shape instability of nanowires.Additionally,a multiple deposition-annealing treatment is given as a novel growth method to strengthen the controlled fabrication of nanowires.

Enhanced Anomalous Hall Effect of Pt on an Antiferromagnetic Insulator with Fully Compensated Surface

We report a significantly enhanced anomalous Hall effect(AHE)of Pt on antiferromagnetic insulator thin film(3-unit-cell La_(0.7)Sr_(0.3)MnO_(3),abbreviated as LSMO),which is one order of magnitude larger than that of Pt on other ferromagnetic(e.g.Y_(3)Fe_(5)O_(12))and antiferromagnetic(e.g.Cr_(2)O_(3))insulator thin films.Our experiments demonstrate that the antiferromagnetic La_(0.7)Sr_(0.3)MnO_(3)with fully compensated surface suppresses the positive anomalous Hall resistivity induced by the magnetic proximity effect and facilitates the negative anomalous Hall resistivity induced by the spin Hall effect.By changing the substrate’s temperature during Pt deposition,we observed that the diffusion of Mn atoms into Pt layer can further enhance the AHE.The anomalous Hall resistivity increases with increasing temperature and persists even well above the Neel temperature(T_(N))of LSMO.The Monte Carlo simulations manifest that the unusual rise of anomalous Hall resistivity above T_(N)originates from the thermal induced magnetization in the antiferromagnetic insulator.

Surface Tension and Electrostriction in a Suspended Bridge of Dielectric Liquid

The mechanism of the formation of a surprisingly long suspended liquid bridge subjected to a dc electric field has been intensively studied in the past few decades. However, the role of electrostriction and quantitative evaluation of surface tension in the bridge have not been evaluated. We present combined theoretical and experimental studies on this issue. Electrostriction is pointed out to be the driving force that pushes liquid upward against gravity and into the gap between two containers and forms the suspended bridge, which is within the framework of the Maxwell pressure tensor. Through a comparison between experiment and theory, the surface tension is found to play an important role in holding the long suspended bridge. Ignorance of the surface tension leads to much smaller bridge length than the experimental values. The dynamic stability of the bridge with respect to its diameter, length and conductance is also discussed.

Er intercalation and its impact on transport properties of epitaxial graphene

Intercalation of atomic species is a practicable method for epitaxial graphene to adjust the electronic band structure and to tune the coupling between graphene and Si C substrate. In this work, atomically flat epitaxial graphene is prepared on 4H-SiC(0001) using the flash heating method in an ultrahigh vacuum system. Scanning tunneling microscopy, Raman spectroscopy and electrical transport measurements are utilized to investigate surface morphological structures and transport properties of pristine and Er-intercalated epitaxial graphene. It is found that Er atoms are intercalated underneath the graphene layer after annealing at 900℃, and the intercalation sites of Er atoms are located mainly at the bufferlayer/monolayer-graphene interface in monolayer domains. We also report the different behaviors of Er intercalation in monolayer and bilayer regions, and the experimental results show that the diffusion barrier for Er intercalated atoms in the buffer-layer/monolayer interface is at least 0.2 eV higher than that in the first/second graphene-layer interface. The appearance of Er atoms is found to have distinct impacts on the electronic transports of epitaxial graphene on SiC(0001).

Characteristics of Speed–Acceleration Phase Diagram of Migrating Cells

Cell movement behavior is one of the most interesting biological problems in physics, biology, and medicine.We experimentally investigate the characteristics of random cell motion during migration. Observing cell motion trajectories under a microscope, we employ a nonlinear dynamics method to construct a speed–acceleration phase diagram. Our analysis reveals the presence of a fixed point in this phase diagram, which suggests that migrating cells possess a stable state. Cells that deviate from this stable state display a tendency to return to it, following the streamline trends of an attractor structure in the phase diagram. We derive a set of characteristic values describing cell motion, encompassing inherent speed, inherent acceleration, characteristic time for speed change,and characteristic time for acceleration change. We develop a differential equation model based on experimental data and conduct numerical calculations. The computational results align with the findings obtained from experiments. Our research suggests that the asymmetrical characteristics observed in cell motion near an inherent speed primarily arise from properties of inherent acceleration of cells.

Propagation of light near the band edge in one-dimensional multilayers

Optical systems offer rich modulation in light propagation, but sufficient quantitative descriptions lack when highly complex structures are considered since practical structures contain defects or imperfections. Here, we utilize a method combining a data-fitting method and a time-resolved system to describe light propagation near the band edges in onedimensional structures. Calculations after optimization of the method show little deviation to the measurements.

Highly specific characterization and discrimination of monosodium urate crystals in gouty arthritis based on aggregation-induced emission luminogens

Existing technologies used to detect monosodium urate(MSU)crystals for gout diagnosis are not ideal due to their low sensitivity and complexity of operation.The purpose of this study was to explore whether aggregation-induced emission luminogens(AIEgens)can be used for highly specific imaging of MSU crystals to assist in the diagnosis of gout.First,we developed a series of luminogens(i.e.,tetraphenyl ethylene(TPE)-NH_(2),TPE-2NH_(2),TPE-4NH_(2),TPE-COOH,TPE-2COOH,TPE-4COOH,and TPE-Ketoalkyne),each of which was then evenly mixed with MSU crystals.Next,optimal fluorescence imaging of each of the luminogens was characterized by a confocal laser scanning microscope(CLSM).This approach was used for imaging standard samples of MSU,hydroxyapatite(HAP)crystals,and mixed samples with 1:1 mass ratio of MSU/HAP.We also imaged samples from mouse models of acute gouty arthritis,HAP deposition disease,and comorbidities of interest.Subsequently,CLSM imaging results were compared with those of compensated polarized light microscopy,and we assessed the biosafety of TPE-Ketoalkyne in the RAW264.7 cell line.Finally,CLSM time series and three-dimensional imaging were performed on MSU crystal samples from human gouty synovial fluid and tophi.As a promising candidate for MSU crystal labeling,TPE-Ketoalkyne was found to detect MSU crystals accurately and rapidly in standard samples,animal samples,and human samples,and could precisely distinguish gout from HAP deposition disease.This work demonstrates that TPE-Ketoalkyne is suitable for highly specific and timely imaging of MSU crystals in gouty arthritis and may facilitate future research on MSU crystal-related diseases.

Coupled model analysis of the ablative Rayleigh–Taylor instability

The weakly nonlinear stage of the ablative Rayleigh–Taylor instability(ARTI)is investigated by expanded hydrodynamic equations in which the third-order corrections of the two-mode perturbations are considered.In the present coupling model,two linear perturbations are simultaneously added near the ablation front at the initial moment,and we have derived the first three coupling harmonics.Furthermore,the coupling model analysis is studied via direct numerical simulation as well.When the original two fundamental modes are always dominant over other modes,the time evolution of the density amplitudes for these modes agrees well with the results of direct numerical simulation.It is found that the harmonics are stabilized by the mode coupling effects,and the long wavelength mode of the fundamental modes tends to dominate the growth of the ARTI.Two-mode coupling is one of the restriction factors for the realization of controlled inertial confinement fusion.Therefore,the coupling harmonics excited by two-mode perturbations have good application potential and are worth further study.