介观电化学反应的随机热力学

In this work, we discussed the stochastic thermodynamics of mesoscopic electron transfer reactions between ions and electrodes. With a relationship between the reaction rate constant and the electrode potential, we find that the heat dissipation βq equals to the dynamic irreversibility of the reaction system minus an internal entropy change term. The total entropy change Δs_t is defined as the summation of the system entropy change Δs and the heat dissipation βq such that Δs_t=Δs+βq. Even though the heat dissipation depends linearly on the electrode potential, the total entropy change is found to satisfy the fluctuation theorem <(e)^-Δs_t>=1, and hence a second law-like inequality reads <Δs_t>≥0. Our study provides a practical methodology for the stochastic thermodynamics of electrochemical reactions, which may find applications in biochemical and electrochemical reaction systems.     

POSITRON LIFETIME STUDIES OF Y1-xCaxBa2Cu3O7-δ AND Y1-xCaxBa2Cu3-xFexO7-δ

In this paper it is reported that the measurement of the bulk positron lifetime as a function of substitution content x in the temperature range from 70 to 220K was performed in two high-T_c superconducting systems, Y_1-xCa_xBa₂Cu_3-xFe_xO_7-δ and Y_1-xCa_xBa₂Cu₃O_7-δ. It was found that τ_B of both systems decreases significantly with x and the temperature dependence of τ_B is very weak in normal state. In lower temperature region (Tc), a dramatic x-dependent temperature variation of τ_B was observed in the Ca-substituted system: from a decrease of τ_B with decreasing T to an increase of τ_B. With increasing x, the temperature dependence of τ_B remains weak in the Ca- and Fe- substituted systems. Compared with the experimental data of positron lifetime in other substituted systems and the calculation of the positron density distribution, the authors suggest that positron bulk lifetime spectra behaviour can be interpreted by the physical model based on the transfer of electron density between the CuO₂ planes and Cu-O chains. Therefore, the study of positron lifetime spectra provides a useful means to detect the local charge density and to study the correlation between the electronic structure and the high-T_c superconductivity.     

Bipartite entanglement in spin-1/2 Heisenberg model

The bipartite entanglement of the two- and three-spin Heisenberg model was investigated by using the concept of negativity. It is found that for the ground-state entanglement of the two-spin model, the negativity always decreases as B increases if Δ<γ－1, and it may keep a steady value of 0.5 in the region of B2－γ²]^1/2 if Δ>γ－1, while for that of the three-spin model, the negativity exhibits square wave structures if γ=0 or Δ=0. For thermal states, there are two areas showing entanglement, namely, the main region and the sub-region. The main region exists only when Δ>Δ_c (Δ_c=γ－1 and (γ²－1)/2 for the 2- and 3-spin model respectively) and extends in terms of B and T as Δ increases, while the sub-region survives only when γ≠0 and shrinks in terms of B and T as Δ increases.     

Research on total-dose hardening for H-gate PD NMOSFET/SIMOX by ion implanting into buried oxide

In this work, we investigate the back-gate I-V characteristics for two kinds of NMOSFET/ SIMOX transistors with H gate structure fabricated on two different SOI wafers. A transistors are made on the wafer implanted with Si⁺ and then annealed in N₂,and B transistors are made on the wafer without implantation and annealing. It is demonstrated experimentally that A transistors have much less back-gate threshold voltage shift ΔV_th than B transistors under X-ray total dose irradiation. Subthreshold charge separation technique is employed to estimate the build-up of oxide charge and interface traps during irradiation, showing that the reduced ΔV_th for A transistors is mainly due to its less build-up of oxide charge than B transistors. Photoluminescence (PL) research indicates that Si implantation results in the formation of silicon nanocrystalline (nanocluster) whose size increases with the implant dose. This structure can trap electrons to compensate the positive charge build-up in the buried oxide during irradiation, and thus reduce the threshold voltage negative shift.     

一个改进的聚合物结晶生长的相场模型

The irrationality of existing phase field model is analyzed and a modified phase-field model is proposed for polymer crystal growth, in which the parameters are obtained from real materials and very simple to use, and most importantly, no paradoxical parameters appeared in the model. Moreover, it can simulate different microstructure patterns owing to the use of a new different free energy function for the simulation of morphologies of polymer. The new free energy function considers both the cases of T<T_m and T≥T_m, which is more reasonable than that in published literatures that all ignored the T≥T_m case. In order to show the validity of the modified model, the finite difference method is used to solve the model and different crystallization morphologies during the solidification process of isotactic polystyrene are obtained under different conditions. Numerical results show that the growth rate of the initial secondary arms is obviously increased as the anisotropy strength increases. But the anisotropy strength seems to have no apparent effect on the global growth rate. The whole growth process of the dendrite depends mainly upon the latent heat and the latent heat has a direct effect on the tip radius and tip velocity of side branches.     

PHOTOELECTRON SPECTROSCOPIC STUDY OF THE EFFECT OF Cs INTRALAYER ON THE BAND LINEUP OF Ge/InP(100) HETEROJUNCTION

The formation and band lineup of the Ge/InP(100) interface with or without alkali metal Cs intralayer (IL) are studied by means of X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). It is found that the Cs atoms do not react with or diffuse into the subatrate and the Ge overlayer. The thin Cs IL will induce an increase of the valence band offset (ΔE_v) for the Ge/InP(100) heterojunction. The changes of ΔE_v are proportional to the IL thickness and them saturate for IL thickness of about one half of a monolayer of Cs IL. Without the IL, ΔE_v of the Ge/InP(100) heterojunction is equal to 0.70eV, and ΔE_v with one half of monolayer IL is up to 0.90eV. These results show that the interface dipole plays a major role in the band lineup at the heterojunction interface.     

SIZE EFFECT OF INNER RADIUS ON CIRCULARLY SYMMETRIC SOLITON STATES IN ANNULAR JOSEPHSON JUNCTIONS

The effect of the inner radius of an annular Josephson junetion on the excitation 0f circularly symmetric soliton states is explored by direct numerical simulation. In a circularly symmetric annular Josephson junction (CSAJJ hereafter), the phase difference in the order parameters Φ across the junction bar-rier obeys the modified sine-Gordon equation (SGE) in which there is a perturbation term Φ_p/ρ inversely proportional to the radial coordinate ρ. and this term does not appear in the case of a 1D in-line junc-tion. The effect of the Φ_p/ρ term becomes prominent when ρ is small. It turns out that for junctions of grven dissipation and annular width, there is a lower limit of the inner radii for the junctions to support stable soliton motion, while the lower limit depends strongly on the dissipation coefficient α. For example, for a CSAJJ with inner radius 5λ_J, outer radius 10λ_J, no stable soliton states would exist when α=0.01 or α=0.02. However, for 0.06≥α≥0.03, there are ring-shaped solitary wave solutions, presumably because the dissipation suppresses the effect of the Φ_p/ρ term. Finally, the behaviour of the seliton states and the rele-vant I-V characteristics are also disscussed.     

CO分子在肌红蛋白结合口袋的QM/MM动力学模拟

Myoglobin has important biological functions in storing and transporting small diatomic molecules in human body. Two possible orientations of carbon monoxide (CO) in the heme distal pocket (named as B₁ and B₂ states) of myoglobin have been experimentally indicated. In this study, ab initio quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulation of CO in myoglobin was carried out to investigate the two possible B states. Our results demonstrate that the B₁ and B₂ states correspond to Fe…CO (with carbon atom closer to iron center of heme) and Fe…OC (with oxygen atom closer to Fe), by comparing with the experimental infrared spectrum. QM electrostatic polarization effect on CO brought from the protein and solvent environment is the main driving force, which anchors CO in two distinctive orientations and hinders its rotation. The calculated vibrational frequency shift between the state B₁ and B₂ is 13.1 cm^-1, which is in good agreement with experimental value of 11.5 cm^-1. This study also shows that the electric field produced by the solvent plays an important role in assisting protein functions by exerting directional electric field at the active site of the protein. From residue-based electric field decomposition, several residues were found to have most contributions to the total electric field at the CO center, including a few charged residues and three adjacent uncharged polar residues (namely, HIS64, ILE107, and PHE43). This study provides new physical insights on rational design of enzyme with higher electric field at the active site.     

GROUND STATE AND ELEMENTARY EXCITATIONS OF THE PEIERLS-HUBBARD MODEL

The ground state and elementary excitations of the Peierls-Hubbard model are studied by using Gaussian wave functional method. The results show that the charge and spin degrees of freedom couple to each other due to the simultaneous existance of the dimerization and Hubbard repulsions. In the region of β²_s>2π the spin gap m_s is still present. Also the influence of Hubbard repulsions on the dimerization is derived from the critical behavior of ground state energy.     

ANNIHILATION OF VERTICAL-BLOCH-LINE CHAINS IN THE WALLS OF THE SECOND KIND OF DUMBBELL DOMAINS SUBJECTED TO AN IN-PLANE FIELD

An experiment was statistically performed on the annihilation of vertical-Bloch-line (VBL) chains in the walls of the second kind of dumbbell domains (ⅡDs) subjected to an in-plane field H_ip. It was again confirmed that there is a critical in-plane field H′_ip, above which all VBL chains of hard domains in garnet bubble films, including ⅡDa, disappear. Just like ordinary hard bubbles (OHBs), it was also found that there exists a critical range of H_ip, from (H_ip)_ID to H′_ip, for ⅡD softening. Over this range, with the increase of H_ip, more and more ⅡDs are softened, accompanied by the successive appearance of the first kind of dumbbell domains, OHBs and soft bubbles. In addition, for the five samples tested, the ratio, H′_ip/(H_ip)_ID, is obviously greater than 2^1/2.     

Water adsorption on the Be(0001) surface: from monomer to trimer adsorption

In this paper, the density functional theory has been used to perform a comparative theoretical study of water monomer, dimer, trimer, and bilayer adsorptions on the Be(0001) surface. In our calculations, the adsorbed water molecules are energetically favoured adsorbed on the atop sites, and the dimer adsorption is found to be the most stable with a peak adsorption energy of ～437 meV. Further analyses have revealed that the essential bonding interaction between the water monomer and the metal substrate is the hybridization of the water 3a₁-like molecular orbital with the (s, p_z) orbitals of the surface beryllium atoms. While in the case of the water dimer adsorption, the 1b₁-like orbital of the H₂O molecule plays a dominant role.     

Advantages of using gold hollow nanoshells in cancer photothermal therapy

Lots of studies have been conducted on the optical properties of gold nanoparticles in the first region of near infrared(650 nm–950 nm), however new findings show that the second region of near-infrared(1000 nm–1350 nm) penetrates to the deeper tissues of the human body. Therefore, using the above-mentioned region in photo-thermal therapy(PTT) of cancer will be more appropriate. In this paper, absorption efficiency is calculated for gold spherical and rod-shaped nanoshells by the finite element method(FEM). The results show that the surface plasmon frequency of these nanostructures is highly dependent on the dimension and thickness of shell and it can be adjusted to the second region of near-infrared. Thus, due to their optical tunability and their high absorption efficiency the hollow nanoshells are the most appropriate options for eradicating cancer tissues.     

RADIATION-INDUCED DEFECTS IN RADIATION HARD AND SOFT OXIDES

The point defects of P_b and E′ in radiation hard and soft Si-SiO₂ samples were examined using electron spin resonance (ESR). The experimental results showed that these defects were correlated with the ways of oxidation process, the dosage of ⁶⁰Co radiation and the radiation bias field. Besides, the ΔH (peak of peak) of P_b and E′ indicated that P_b is the defect with slow electron spin relaxation time while E′ is the defect with fast electron spin relaxation time. Finally, the experimental results are explained qualitatively.     

CRYSTALLIZATION OF DIELECTRIC SPHERES IN LASER STANDING WAVE FIELD

Experimental study on crystallization of polystyrene spheres and SrTiO₃ particles in laser standing wave field is presented. The diameter of polystyrene, which are able to be trapped, is 7 times smaller than that reported by Burns, the corresponding lattice constant is reduced to 1.5 μm. The crystallization effect of SrTiO₃ particles with a refractive coastant of 2.5 in the visible range is observed for the first time. Based on the results above we believe that it is possible to construct photonic crystal with lattice constant extended to visible wave range by this method.     

MAGNETIC PROPERTIES OF BALL MILLED FexCu1-x (x=0.4, 0.5) ALLOY

The samples Fe_0.4Cu_0.6 and Fe_0.5Cu_0.5 ball milled for 50 h are investigated by X-ray diffraction, M?ssbauer spectra, as well as magnetic measurement. The experiments show that the structure of the samples is fcc, with lattice constant 0.361 nm and there are fcc Fe-rich phase and fcc Cu-rich phase in the samples. Most of Fe atoms (91%) are in the fcc Fe-rich phase, which is a ferromagnetic phase. The M-H curve at 1.5 K shows the saturation magnetization of the samples are 80.5 emu/g and 101.6 emu/g for Fe_0.4Cu_0.6 and Fe_0.5Cu_0.5 respectively. The average magnetic moment of Fe atoms is deduced to be 2.40 μ_B . Compared with theoretical predication, the Fe atoms in the fcc phase are in high spin state.     

Tailoring the microwave permittivity and permeability of composite materials

The microwave permittivity (ɛ_r) and permeability (μ_r) of composite materials are tailored by adding various loading agents to a host plastic and are subsequently modeled using the Maxwell Garnett theory and second order polynomials. With the addition of manganese zinc ferrite, strontium ferrite, nickel zinc ferrite, barium tetratitanate and graphite powders, materials with values of ɛ′, e″, μ′, μ″ as high as 22, 5, 2.5 and 1.7 have been obtained. Permittivity and permeability data are calculated at 2.0245 GHz from reflection and transmission measurements performed in a 7 mm coaxial test line. The Maxwell Garnett (MG) theory successfully models ɛ_r if the filling factor is less than 0.30 and ratio |ɛ₁| (host)/ |ɛ₂| (powder) is greater than 0.04. As this ratio decreases, the MG theory is shown to be independent of ɛ₂ and second order polynomials are used to effectively model the dielectric constant. Polynomials are also used for the ferrite composites because it was determined that the MG theory was unable to model μ_r. This deficiency is attributed to the difference of domain structures that exist in powdered and sintered ferrites.     

CW Nd:YAG THERMO-STABLE RESONATORS OPERATING IN POWER-STEADY STATES

There are two dynamical stable zones in the operation of solid laser containing a thermal lens. In this paper, we point out that in the two stable zones two kinds of dynamical stable states can exist in a laser resonator: mode-steady thermo-stable state and power-steady thermo-stable state. They are different from each other in general. The operating conditions for power-steady thermo-stable state are presented. A cw Nd: YAG thermo-stable resonator operating in power-steady states has been designed, and 40 W TEM₀₀ output power in 1.06μm is obtained experimentally.     

STRUCTURE AND PROPERTIES OF THE La-DOPED Bi-2201 SYSTEM

In this article, the influence of La substitution for Sr on structure and physi-cal properties of the 2201 phase is studied. First, the crystal microstructure of the Bi_2.1Sr_1.9-xLa_xCuO_y (0≤x≤1.0) is characterized by means of X-ray diffraction and electron diffraction analyses, it is discovered that in the La-doped 2201 system with increasing La content the 2201 phase undergoes tetragnoal-orthorhombic-monoclinic structural transition. With this phase transition, the modulation vector of the 2201 phase transforms from incommensurate to commensurate, and the period of the mod- ulation wave decreases. Secondly, the superconductivity of this system is analyzed systematically. The results of the resistivity measurement show that the appropriate amount of La doping can raise the superconducting transition temperature (T_c) of the 2201 phase, with x=0.2, T_c reaches as high as 25K. However the excessive doping of La (x≥0.3) leads the 2201 phase to transit from metal to insulator and the su-perconductivity disappears. The measurement of thermoelectric power (TEP) of this system shows that with increasing La content the TEP value also increases gradu-ally. But the interesting point is that the transition from positive to negative in TEP occurs for x=0.2 sample. In addition, the electronic structure and oxygen content of this system are also studied. Based on these, we analyze the relation between the microstructure, electronic structure of the La-doped 2201 phase and its superconduc-tivity, indicating that the type of element substitution with higher valence, together with the microstructural distortion induced by the substitution affects the electronic states of Cu 3d seriously, that is, changes the degree of coulomb correlation of Cu 3d electrons, thus resulting in the transition of the type of carrier of this system and the decrease of hole carrier concentration, as well as the corresponding variation of the superconductivity of La-doped 2201 phase.     

Stability of Tokamak Equilibrium with Internal Transport Barrier against High-n MHD Ballooning Mode

A new eigen-mode equation for the tokamak high-n （the toroidal mode number） ideal magnetohydrodynamic （MHD） ballooning mode in tokamak plasmas is derived to include the toroidal effects that are significant for stability of configurations with internal transport barriers （ITBs）, Fot tokamak equilibria of shift circular flux surfaces, these toroidal effects basically are the finite inverse aspect ratio and the Shafranov shift. The former yields the averaged favorable curvature stabilization while the latter further strengthens this effect, leading to a low shear stable channel connecting the first and second stability regions, and to the shrinkage of unstable region in the （8,α） diagram. The dependence of the critical shear, below which the plasma is stable, on these effects is given. These results are important for understanding the ITB physics to some regards.     

Feasibility study for the measurement of Bc meson mass and lifetime with the general purpose detector at the LHC

In this paper a feasibility study of the B_c meson to measure its mass and lifetime is described with the general purpose detector at the LHC. The study solely concentrated on the J/ψπ⁺, J/ψ→μ⁺μ^－ decay channel of the B_c and it was concluded that about 120 events can be selected in the first fb^－1 of data. With this data sample, the mass resolution was estimated to be 2.0(stat.)MeV/c² while the cτ resolution was found to be 13.1(stat.)μm, i.e. the lifetime resolution to be 0.044(stat.)ps.