Localized waves of the coupled cubic-quintic nonlinear Schrödinger equations in nonlinear optics
Temperature dependence of migration features of self-interstitials in zirconium
Analytical and numerical investigations of displaced thermal state evolutions in a laser process
Decoy-state reference-frame-independent quantum key distribution with both source errors and statistical fluctuations
Monogamy relations of quantum entanglement for partially coherently superposed states
Topological superfluid in a two-dimensional polarized Fermi gas with spin-orbit coupling and adiabatic rotation
Linear synchronization and circuit implementation of chaotic system with complete amplitude control
Parameter analysis of chaotic superlattice true random number source
Asymmetric W-shaped and M-shaped soliton pulse generated from a weak modulation in an exponential dispersion decreasing fiber
A novel image encryption scheme based on Kepler's third law and random Hadamard transform
Role of entropy generation minimization in thermal optimization
Constant evacuation time gap:Experimental study and modeling
Signal-to-noise ratio comparison of angular signal radiography and phase stepping method
Investigation on the dynamic behaviors of the coupled memcapacitor-based circuits
A dual-axis, high-sensitivity atomic magnetometer
Improvement of the thermoelectric efficiency of pyrene-based molecular junction with doping engineering
CN bond orientation in metal carbonitride endofullerenes:A density functional theory study
The geometric and electronic structures of scandium carbonitride endofullerene Sc3CN@C2n (2n=68, 78, 80, 82, and 84) and Sc(Y)NC@C76 have been systematically investigated to identify the preferred position of internal C and N atoms by density functional theory (DFT) calculations combined with statistical mechanics treatments. The CN bond orientation can generally be inferred from the molecule stability and electronic configuration. It is found that Sc3CN@C2n molecules have the most stable structure with C atom locating at the center of Sc3CN cluster. The CN bond has trivalent form of[CN]3- and connects with adjacent three Sc atoms tightly. However, in Sc(Y)NC@C76 with[NC]-, the N atom always resides in the center of the whole molecule. In addition, the stability of Sc3CN@C2n has been further compared in terms of the organization of the corresponding molecular energy level. The structural differences between Sc3CN@C2n and Sc3NC@C2n are highlighted by their respected infrared spectra.
Effects of temperature and pressure on thermodynamic properties of Cd0.25Zn0.75 alloy
Anisotropic self-diffusion of fluorinated poly(methacrylate) in metal-organic frameworks assessed with molecular dynamics simulation
Enhancement of signal-to-noise ratio of ultracold polar NaCs molecular spectra by phase locking detection
We report a method of high-sensitively detecting the weak signal in photoassociation (PA) spectra of ultracold NaCs molecules by phase sensitive-demodulated trap-loss spectra of Na atoms from a photomultiplier tube. We find that the signal-to-noise ratio (SNR) of the PA spectra is strongly dependent on the integration time and the sensitivity of the lock-in amplifier, and our results show reasonable agreement with the theoretical analyses of the SNR with the demodulation parameters. Meanwhile, we investigate the effect of the interaction time of the PA laser with the colliding Na-Cs atom pairs on the SNR of the PA spectra. The atom loss rate is dependent on both the PA-induced atom loss and the loading of the MOT. The high-sensitive detection of the excited ultracold NaCs molecules lays a solid foundation for further study of the formation and application of ultracold NaCs molecules.
Highly sensitive photoassociation spectroscopy of ultracold 23Na133Cs molecular long-range states below the 3S1/2+6P3/2 limit
We present high resolution photoassociation spectroscopy of ultracold 23Na133Cs molecules in a long-range c3∑+ state below the (3S1/2 + 6P3/2) asymptote. We perform photoassociation spectroscopy in a dual-species magneto-optical trap (MOT) and detect the photoassociation resonances using trap-loss spectroscopy. By fitting the experimental data with the semi-classical LeRoy-Bernstein formula, we deduce the long-range molecular coefficient C6 and derive the empirical potential energy curve in the long-range region.
Studies on convergence and scaling law of Thomson backscattering spectra in strong fields
Error analysis and Stokes parameter measurement of rotating quarter-wave plate polarimeter
(3+1)-dimensional localized self-accelerating Airy elegant Ince-Gaussian wave packets and their radiation forces in free space
We construct analytically linear self-accelerating Airy elegant Ince-Gaussian wave packet solutions from (3+1)-dimensional potential-free Schrödinger equation. These wave packets have elliptical geometry and show different characteristics when the parameters (p, m) and ellipticity ε are adjusted. We investigate these characteristics both analytically and numerically and give the 3-dimensional intensity and phase distribution of these wave packets. Lastly, we analyze the radiation forces on a Rayleigh dielectric particle. In addition, we also find an interesting phenomenon that if the energy distribution between every part of wave packets is uneven at the input plane, the energy will be transferred between every part in the process of transmission.
High efficiency terahertz diffraction grating with trapezoidal elements
Reconfigurable dynamic all-optical chaotic logic operations in an optically injected VCSEL
In a chaotic system of vertical cavity surface emitting laser (VCSEL) with external optical-injection, we propose a novel implementation scheme for reconfigurable dynamic all-optical chaotic logic operations (AOCLOs). Under different key parameters, such as the bias current, the injection strength and the frequency detuning of the injected light field and the VCSEL, we also explore the evolutions of the polarization-bistability with the amplitude of the injected light field when the output of VCSEL is chaotic wave. According to the dynamic evolutions, we find out the optimal value of the frequency detuning that is considered as a control logic signal, and further implement different AOCLOs, such as AND, NAND, OR, NOR, XOR, and XNOR, by controlling the logic operation of the control logic signal between two logic inputs. Moreover, the ability to reconstruct these logic operations is demonstrated under relatively low noise strength of the spontaneous emission.
Parallel generation of 31 tripartite entangled states based on optical frequency combs
Quantum entangled states, especially those having particular properties, are key resources for quantum information and quantum computation. In this paper, we put forward a new scheme to produce 31 continuous-variable (CV) tripartite entanglement fields based on three optical frequency combs via cascade nonlinear processes in an optical parametric cavity, and investigate the spectral characteristics of three frequency combs. The center wavelengths of the three combs are designed as 852 nm, 780 nm (atomic transition lines), and 1550 nm (fiber communication wavelength). The positivity under partial transposition (PPT) criterion, which is sufficient and necessary, is used to evaluate the entanglement in each group of comb lines. This scheme is experimentally feasible and valuable for constructing quantum information networks in future.
Generation of squeezed vacuum on cesium D2 line down to kilohertz range
We report the experimental generation of a squeezed vacuum at frequencies ranging from 2.5 kHz to 200 kHz that is resonant on the cesium D2 line by using a below-threshold optical parametric oscillator (OPO). The OPO is based on a periodically-poled KTiOPO4 (PPKTP) crystal that is pumped using a bow-tie four-mirror ring frequency doubler. The phase of the squeezed light is controlled using a quantum noise locking technique. At a pump power of 115 mW, maximum quadrature phase squeezing of 3.5 dB and anti-squeezing of 7.5 dB are detected using a home-made balanced homodyne detector. This squeezed vacuum at an atomic transition in the kilohertz range is an ideal quantum source for quantum metrology of enhancing measurement precision, especially for ultra-sensitive measurement of weak magnetic fields when using a Cs atomic magnetometer in the audio frequency range.
Broadrange tunable slow and fast light in quantum dot photonic crystal structure
Time-resolved spectroscopy for 5s'4D7/2 state transitions undergoing electron-ion recombination in femtosecond laser-produced copper plasma
Coherently induced grating in refractive index enhanced medium
Output light power of InGaN-based violet laser diodes improved by using a u-InGaN/GaN/AlGaN multiple upper waveguide Hot!
The upper waveguide (UWG) has direct influences on the optical and electrical characteristics of the violet laser diode (LD) by changing the optical field distribution or barrier of the electron blocking layer (EBL). In this study, a series of InGaN-based violet LDs with different UWGs are investigated systematically with LASTIP software. It is found that the output light power (OLP) under an injecting current of 120 mA or the threshold current (Ith) is deteriorated when the UWG is u-In0.02Ga0.98N/GaN or u-In0.02Ga0.98N/AlxGa1-xN (0 ≤ x ≤ 0.1), which should be attributed to small optical confinement factor (OCF) or severe electron leakage. Therefore, a new violet LD structure with u-In0.02Ga0.98N/GaN/Al0.05Ga0.95N multiple layer UWG is proposed to reduce the optical loss and increase the barrier of EBL. Finally, the output light power under an injecting current of 120 mA is improved to 176.4 mW.
Optical properties of a three-dimensional chiral metamaterial
Plasmonically induced reflection in metal-insulator-metal waveguides with two silver baffles coupled square ring resonator
Performance analysis of surface plasmon resonance sensor with high-order absentee layer
Geometrical representation of coherent tunneling process in two-waveguide and three-waveguide coupler
All polymer asymmetric Mach-Zehnder interferometer waveguide sensor by imprinting bonding and laser polishing
Ultra-broadband polarization splitter based on graphene layer-filled dual-core photonic crystal fiber
Seismoelectric wave propagation modeling in a borehole in water-saturated porous medium having an electrochemical interface
Water-saturated porous media often exhibit a seismoelectric effect due to the existence of an electrical double layer and a relative flow of pore fluid. Here we consider the seismoelectric waves in an open borehole surrounded by water-saturated porous formation which exhibits discontinuity of electrochemical properties at a cylindrical interface. We carefully analyze the seismoelectric interface response since these signals show sensitivity to contrasts in electrochemical properties across an interface. Both coupled and approximate methods are used to compute borehole seismoelectric fields. The simulation results show that the radiated electromagnetic wave from the electrochemical interface is generated due to the change of salinity in pore fluid in the porous formation. However, the elastic properties of the formation remain unchanged across such an electrochemical interface. As a result it is difficult to recognize such a change in electrochemical properties using only elastic waves. Therefore, the seismoelectric interface response is potentially used to detect the changes of the electrochemical properties in the formation.
Lorentz force electrical impedance tomography using pulse compression technique
Lorentz force electrical impedance tomography (LFEIT) combines ultrasound stimulation and electromagnetic field detection with the goal of creating a high contrast and high resolution hybrid imaging modality. In this study, pulse compression working together with a linearly frequency modulated ultrasound pulse was investigated in LFEIT. Experiments were done on agar phantoms having the same level of electrical conductivity as soft biological tissues. The results showed that:(i) LFEIT using pulse compression could detect the location of the electrical conductivity variations precisely; (ii) LFEIT using pulse compression could get the same performance of detecting electrical conductivity variations as the traditional LFEIT using high voltage narrow pulse but reduce the peak stimulating power to the transducer by 25.5 dB; (iii) axial resolution of 1 mm could be obtained using modulation frequency bandwidth 2 MHz.
Effects of gas pressure on plasma characteristics in dual frequency argon capacitive glow discharges at low pressure by a self-consistent fluid model
Rayleigh-Taylor instability of multi-fluid layers in cylindrical geometry
Structural and size evolution of indium nanoparticles embedded in aluminum synthesized by ion implantation
Finite element analysis of ionic liquid gel soft actuator Hot!
A new type of soft actuator material-ionic liquid gel (ILG), which consists of HEMA, BMIMBF4, and TiO2, can be transformed into gel state under the irradiation of ultraviolet (UV) light. In this paper, Mooney-Rivlin hyperelastic model of finite element method is proposed for the first time to study the properties of the ILG. It has been proved that the content of TiO2 has a great influence on the properties of the gel, and Young's modulus of the gel increases with the increase of its content, despite of reduced tensile deformation. The results in this work show that when the TiO2 content is 1.0 wt%, a large tensile deformation and a strong Young's modulus can be obtained to be 325% and 7.8 kPa, respectively. The material parameters of ILG with TiO2 content values of 0.2 wt%, 0.5 wt%, 1.0 wt%, and 1.5 wt% are obtained, respectively, through uniaxial tensile tests, including C10, C01, C20, C11, C02, C30, C21, C12, and C03 elements. In this paper, the large-scaled general finite element software ANSYS is used to simulate and analyze the ILG, which is based on SOLID186 element and nonlinear hyperelastic Mooney-Rivlin model. The finite element simulation analysis based stress-strain curves are almost consistent with the experimental stress-strain curves, and hence the finite element analysis of ILG is feasible and credible. This work presents a new direction for studying the performance of soft actuator for the ILG, and also contributes to the design of soft robot actuator.
First-principles calculations of structure and elasticity of hydrous fayalite under high pressure
Zn-Cu-codoped SnO2 nanoparticles:Structural, optical, and ferromagnetic behaviors
Mechanical, elastic, anisotropy, and electronic properties of monoclinic phase of m-SixGe3-xN4
Negative linear compressibility of generic rotating rigid triangles
Effects of alloying element on stabilities, electronic structures, and mechanical properties of Pd-based superalloys
Variations in defect substructure and fracture surface of commercially pure aluminum under creep in weak magnetic field
A diffusion model for solute atoms diffusing and aggregating in nuclear structural materials
Segregations and desorptions of Ge atoms in nanocomposite Si1-xGex films during high-temperature annealing
Molecular dynamics study of plastic deformation mechanism in Cu/Ag multilayers
Tuning electronic properties of the S2/graphene heterojunction by strains from density functional theory
Effects of post-annealed floating gate on the performance of AlGaN/GaN heterostructure field-effect transistors
Characteristics and mechanism analysis of Fano resonances in Π-shaped gold nano-trimer
Capacitance extraction method for a gate-induced quantum dot in silicon nanowire metal-oxide-semiconductor field-effect transistors
Spin-valley-dependent transport and giant tunneling magnetoresistance in silicene with periodic electromagnetic modulations
The transport property of electrons tunneling through arrays of magnetic and electric barriers is studied in silicene. In the tunneling transmission spectrum, the spin-valley-dependent filtered states can be achieved in an incident energy range which can be controlled by the electric gate voltage. For the parallel magnetization configuration, the transmission is asymmetric with respect to the incident angle θ, and electrons with a very large negative incident angle can always transmit in propagating modes for one of the spin-valley filtered states under a certain electromagnetic condition. But for the antiparallel configuration, the transmission is symmetric about θ and there is no such transmission channel. The difference of the transmission between the two configurations leads to a giant tunneling magnetoresistance (TMR) effect. The TMR can reach to 100% in a certain Fermi energy interval around the electrostatic potential. This energy interval can be adjusted significantly by the magnetic field and/or electric gate voltage. The results obtained may be useful for future valleytronic and spintronic applications, as well as magnetoresistance device based on silicene.
Quantum spin Hall and quantum valley Hall effects in trilayer graphene and their topological structures
The present study pertains to the trilayer graphene in the presence of spin orbit coupling to probe the quantum spin/valley Hall effect. The spin Chern-number Cs for energy-bands of trilayer graphene having the essence of intrinsic spin-orbit coupling is analytically calculated. We find that for each valley and spin, Cs is three times larger in trilayer graphene as compared to single layer graphene. Since the spin Chern-number corresponds to the number of edge states, consequently the trilayer graphene has edge states, three times more in comparison to single layer graphene. We also study the trilayer graphene in the presence of both electric-field and intrinsic spin-orbit coupling and investigate that the trilayer graphene goes through a phase transition from a quantum spin Hall state to a quantum valley Hall state when the strength of the electric field exceeds the intrinsic spin coupling strength. The robustness of the associated topological bulk-state of the trilayer graphene is evaluated by adding various perturbations such as Rashba spin-orbit (RSO) interaction αR, and exchange-magnetization M. In addition, we consider a theoretical model, where only one of the outer layers in trilayer graphene has the essence of intrinsic spin-orbit coupling, while the other two layers have zero intrinsic spin-orbit coupling. Although the first Chern number is non-zero for individual valleys of trilayer graphene in this model, however, we find that the system cannot be regarded as a topological insulator because the system as a whole is not gaped.
Effects of rapid thermal annealing on crystallinity and Sn surface segregation of Ge1-xSnx films on Si (100) and Si (111)
Macro-performance of multilayered thermoelectric medium
Dynamic localization of two electrons in AC-driven triple quantum dots and quantum dot shuttles
Evaluation of threading dislocation density of strained Ge epitaxial layer by high resolution x-ray diffraction
One-dimensional method of investigating the localized states in armchair graphene-like nanoribbons with defects
Comparison of band structure and superconductivity in FeSe0.5Te0.5 and FeS
A hybrid functional first-principles study on the band structure of non-strained Ge1-xSnx alloys
Random crystal field effect on hysteresis loops and compensation behavior of mixed spin-(1,3/2) Ising system
Magnetic hysteresis and compensation behavior of a mixed spin-(1, 3/2) Ising model on a square lattice are investigated in the framework of effective field theory based on a probability distribution technique. The effect of random crystal field, ferromagnetic and ferrimagnetic exchange interaction on hysteresis loops and compensation phenomenon are discussed. A number of characteristic phenomena have been reported such as the observation of triple hysteresis loops at low temperatures and for negative values of random crystal field. Critical and double compensation temperatures have been also found. The obtained results are also compared to some previous works.
Low temperature magnetic and magnetostrictive properties in Pr(Fe1-xCox)1.9 cubic Laves alloys
The structures, spin reorientations, magnetic, and magnetostrictive properties of the polycrystalline Pr(Fe1-xCox)1.9 (x=0-1.0) cubic laves phase alloys between 5 K and 300 K are investigated. Large low-field magnetostrictions are observed at 5 K in the alloys with x=0.2 and 0.4 due to the low magnetic anisotropies of these two alloys. A large negative magnetostriction of about-1130 ppm is found in PrCo1.9 alloy at 5 K. The magnetizations of the alloys with 0 ≤ x ≤ 0.6 decrease abnormally at the spin reorientation temperature Tsr, and an abnormity is detected in the alloy with x=1.0 at its Curie temperature Tc (45 K). The substitution of Fe by Co increases the value of Tsr in the alloy with x value increasing from 0.0 to 0.4, and then reduces the value of Tsr with x value further increasing to 0.6.
Modeling of LiFePO4 battery open circuit voltage hysteresis based on recursive discrete Preisach model
Near-interface oxide traps in 4H-SiC MOS structures fabricated with and without annealing in NO
Singular variation property of elastic constants of piezoelectric ceramics shunted to negative capacitance
Piezoelectric shunt damping has been widely used in vibration suppression, sound absorption, noise elimination, etc. In such applications, the variant elastic constants of piezoelectric materials are the essential parameters that determine the performances of the systems, when piezoelectric materials are shunted to normal electrical elements, i.e., resistance, inductance and capacitance, as well as their combinations. In recent years, many researches have demonstrated that the wideband sound absorption or vibration suppression can be realized with piezoelectric materials shunted to negative capacitance. However, most systems using the negative-capacitance shunt circuits show their instabilities in the optimal condition, which are essentially caused by the singular variation properties of elastic constants of piezoelectric materials when shunted to negative capacitance. This paper aims at investigating the effects of negative-capacitance shunt circuits on elastic constants of a piezoelectric ceramic plate through theoretical analyses and experiments, which gives an rational explanation for why negative capacitance shunt circuit is prone to make structure instable. First, the relationships between the elastic constants c11, c33, c55 of the piezoelectric ceramic and the shunt negative capacitance are derived with the piezoelectric constitutive law theoretically. Then, an experimental setup is established to verify the theoretical results through observing the change of elastic constant c55 of the shunted piezoelectric plate with the variation of negative capacitance. The experimental results are in good agreement with the theoretical analyses, which reveals that the instability of the shunt damping system is essentially caused by the singular variation property of the elastic constants of piezoelectric material shunted to negative capacitance.
Design and theoretical study of a polarization-insensitive multiband terahertz metamaterial bandpass filter
Modeling for multi-resonant behavior of broadband metamaterial absorber with geometrical substrate
Positive gate bias stress-induced hump-effect in elevated-metal metal-oxide thin film transistors
Nucleation mechanism and morphology evolution of MoS2 flakes grown by chemical vapor deposition
We study the nucleation mechanism and morphology evolution of MoS2 flakes grown by chemical vapor deposition (CVD) on SiO2/Si substrates with using S and MoO3 powders. The MoS2 flake is of monolayer with triangular nucleation, which might arise from the initial MoO3-x that is deposited on the substrate, and then bonded with S to form MoS2 flake. The ratio of Mo and S is higher than 1:2 at the beginning with Mo terminated triangular nucleation formed. After that, the morphology of MoS2 flake evolves from triangle to similar hexagon, then to truncated triangle which is determined by the faster growth speed of Mo termination than that of S termination under the S rich environment. The nucleation density does not increase linearly with the increase of reactant concentration, which could be explained by the two-dimensional nucleation theory.
Optical properties of wavelength-tunable green-emitting color conversion glass ceramics
Color conversion glass ceramics are prepared by cosintering borosilicate glass frits and green 0.06Ce:Y2.94(Al1-xGax)5O12 phosphors. The crystal structures, the influence of Ga concentration on the photoluminescence (PL), and reliability properties of the color conversion glass ceramics are investigated. The PL emission wavelengths of 0.06Ce:Y2.94(Al1-xGax)5O12 glass ceramics show blue shift from 545 nm to 525 nm with increasing Ga content (x value) under excited at 460 nm. Reliability test results show that the quantum yield (QY) of 0.06Ce:Y2.94(Al1-xGax)5O12 glass ceramics decreases from 70.60% to 59.06% with x value increasing from 0.15 to 0.35 under the ambient condition of 85℃/RH85% for the exposure time of 168 h. And the quantum yield (QY) of 0.06Ce:Y2.94(Al1-xGax)5O12 glass ceramics decreases from 65.13% to 52.23% after being soaked into boiled water for 4 h. The finding reveals that the addition of Ga can deteriorate the reliability of the color conversion glass ceramics.
Effect of elastic strain energy on grain growth and texture in AZ31 magnesium alloy by phase-field simulation
Bursting oscillations in a hydro-turbine governing system with two time scales
Compact superconducting single-and dual-band filter design using multimode stepped-impedance resonator
Electrically controlled optical switch in the hybrid opto-electromechanical system
Importance of PbI2 morphology in two-step deposition of CH3NH3PbI3 for high-performance perovskite solar cells
A uniform framework of projection and community detection for one-mode network in bipartite networks
Anisotropic formation mechanism and nanomechanics for the self-assembly process of cross-β peptides
Nanostructures self-assembled by cross-β peptides with ordered structures and advantageous mechanical properties have many potential applications in biomaterials and nanotechnologies. Quantifying the intra-and inter-molecular driving forces for peptide self-assembly at the atomistic level is essential for understanding the formation mechanism and nanomechanics of various morphologies of self-assembled peptides. We investigate the thermodynamics of the intra-and inter-sheet structure formations in the self-assembly process of cross-β peptide KⅢIK by means of steered molecular dynamics simulation combined with umbrella sampling. It is found that the mechanical properties of the intra-and inter-sheet structures are highly anisotropic with their intermolecular bond stiffness at the temperature of 300 K being 5.58 N/m and 0.32 N/m, respectively. This mechanical anisotropy comes from the fact that the intra-sheet structure is stabilized by enthalpy but the inter-sheet structure is stabilized by entropy. Moreover, the formation process of KⅢIK intra-sheet structure is cooperatively driven by the van der Waals (VDW) interaction between the hydrophobic side chains and the electrostatic interaction between the hydrophilic backbones, but that of the inter-sheet structure is primarily driven by the VDW interaction between the hydrophobic side chains. Although only peptide KⅢIK is studied, the qualitative conclusions on the formation mechanism should also apply to other cross-β peptides.
Computational study of non-catalytic T-loop pocket on CDK proteins for drug development
Cyclin-dependent kinases (CDKs) are critical to the cell cycle and many other biological processes, and as such, are considered as one of the promising targets for therapy against cancer and other diseases. Most pan-CDK inhibitors bind to the highly conserved catalytic ATP-binding pocket and therefore lack the specificity to prevent side effects. It is desirable to develop drugs targeting non-catalytic pockets for specificity towards individual CDKs. Here we performed a systematic analysis of non-catalytic pockets on CDKs and identified a region underneath the T-loop, which we term TL pocket, for potential inhibitor development. Specifically, we compared the TL pockets of human CDK2 and CDK7-homolog Pfmrk of Plasmodium falciparum, a malaria-causing parasite. Molecular dynamics simulations of several short peptides revealed that this less conserved TL pocket could be used to design potentially specific inhibitors against malaria disease.
Biexponential distribution of open times of a toy channel model
The biexponential distributions of open times are observed in various types of ion channels. In this paper, by discussing a simple channel model, we show that there are two different schemes to understand the biexponential distribution of open times. One scheme is mathematically strict based on generator matrix theory, while the other one has a clear physical explanation according to an approximation process with numerical simulation of Markovian channel dynamics. Our comparison results suggest that even for biologically complex channels, in addition to carrying out a stochastic simulation, the strict theoretical analysis should be considered to understand the multiple exponential distributions of open times.
Enhanced effect of dimension of receptor-ligand complex and depletion effect on receptor-mediated endocytosis of nanoparticles
We present an extended analytical model including the depletion effect and the dimension of ligand-receptor complex, aiming to elucidate their influences on endocytosis of spherocylindrical nanoparticles (NPs). It is found that the dimension of ligand-receptor complex (δ) and the depletion effect interrelatedly govern the optimal conditions of NP endocytosis. The endocytosis phase diagram constructed in the space of NP radius and relative aspect ratio indicates that the endocytosis of NP is enhanced evidently by reducing the optimal radius and the threshold radius of endocytosed NP. Meanwhile, through thermodynamic and kinetic analysis of the diffusion of receptors, the dependence of diffusion length on depletion effect and the dimension of ligand-receptor complex can be identified in great detail. For small aspect ratio, diffusion length decreases with increasing concentration c of small bioparticles in cellular environment. Endocytosis speed corresponding to large radius R and high concentration c of small bioparticles strongly depends on the increasing (2r-δ). These results may show some highlights into the conscious design of NPs for diagnostic agents and therapeutic drug delivery applications.
Derivation of persistent time for anisotropic migration of cells
Cell migration plays an essential role in a wide variety of physiological and pathological processes. In this paper we numerically discuss the properties of an anisotropic persistent random walk (APRW) model, in which two different and independent persistent times are assumed for cell migrations in the x-and y-axis directions. An intrinsic orthogonal coordinates with the primary and non-primary directions can be defined for each migration trajectory based on the singular vector decomposition method. Our simulation results show that the decay time of single exponential distribution of velocity auto-correlation function (VACF) in the primary direction is actually the large persistent time of the APRW model, and the small decay time of double exponential VACF in the non-primary direction equals the small persistent time of the APRW model. Thus, we propose that the two persistent times of anisotropic migration of cells can be properly estimated by discussing the VACFs of trajectory projected to the primary and non-primary directions.
Protein-membrane interactions investigated with surface-induced fluorescence attenuation
Research on protein-membrane interactions has been undeveloped due to the lack of proper techniques to detect the position of proteins at membranes because membranes are usually only about 4-nm thick. We have recently developed a new method named surface-induced fluorescence attenuation (SIFA) to track both vertical and lateral kinetics of a single labelling dye in supported lipid bilayers. It takes advantage of strong interaction between a light-emitting dye and a partially reflecting surface. By applying the technique to membrane proteins being fluorescently labelled at different residues, here we show that SIFA can measure not only the insertion depth of a dye inside a lipid bilayer, but also the position of a dye in solution near the surface. SIFA can therefore be used to study membrane proteins of various types.
The birhythmicity increases the diversity of p53 oscillation induced by DNA damage
The tumor suppressor p53 mediates the cellular response to various stresses. It was experimentally shown that the concentration of p53 can show oscillations with short or long periods upon DNA damage. The underlying mechanism for this phenomenon is still not fully understood. Here, we construct a network model comprising the ATM-p53-Wip1 and p53-Mdm2 negative feedback loops and ATM autoactivation. We recapitulate the typical features of p53 oscillations including p53 birhythmicity. We show the dependence of p53 birhythmicity on various factors such as the phosphorylation status of ATM. We also perform stochastic simulation and find the noise-induced transitions between two modes of p53 oscillation, which increases the p53 variability in both the amplitude and period. These results suggest that p53 birhythmicity enhances the responsiveness of p53 network, which may facilitate its tumor suppressive function.