Water in the Neck-Zipper Region of Kinesin

Neck linker （NL） is one of the most important mechanical elements of kinesin motors. The zipping up process of the neck-zipper （NZ） formed by NL and the related secondary structure elements is one of the major parts of kinesin＇s power stroke. All the weak interactions that are responsible for the formation of NZ are sensitive to or dependent on water. To investigate the role of water in the NZ region, a molecular dynamics （MD） model is set up with a crystal structure of kinesin 2KIN surrounded by a 10 A water layer, and minimization is performed to determine the positions of hydrogen atoms and other atoms. It is revealed that water molecules can assist the docking process of NL by forming hydrogen bonds at those positions where direct hydrogen bonding between the two sides of NZ is hindered and then acts as a constructive component of NZ at the docked state of NL. This result may improve the understanding of the mechanism for the docking of NL of kinesin wherein the function of water has not been comprehended sufficiently.     

The Area of Horizons and the Trapped Region

This paper considers some fundamental questions concerning marginally trapped surfaces, or apparent horizons, in Cauchy data sets for the Einstein equation. An area estimate for outermost marginally trapped surfaces is proved. The proof makes use of an existence result for marginal surfaces, in the presence of barriers, curvature estimates, together with a novel surgery construction for marginal surfaces. These results are applied to characterize the boundary of the trapped region. Supported in part by the NSF, under contract no. DMS 0407732 with the University of Miami. Supported in part by a Feodor-Lynen Fellowship of the Humboldt Foundation.     

On Pulsed Modes of the Glowing Corona Region

Russian Physics Journal - A corona discharge is experimentally studied in atmospheric air on a needle electrode with the curvature radius 40 μm. For both electrode voltage polarities, but...     

Heavy-Quark Production in the Target Fragmentation Region

Fixed-target experiments permit the study of hadron production in the target fragmentation region. It is expected that the tagging of specific particles in the target fragments can be employed to introduce a bias in the hard scattering process towards a specific flavour content. The case of hadrons containing a heavy quark is particularly attractive because of the clear experimental signatures and the applicability of perturbative QCD. The standard approach to one-particle inclusive processes based on fragmentation functions is valid in the current fragmentation region and for large transverse momenta p_T in the target fragmentation region, but it fails for particle production at small p_T in the target fragmentation region. A collinear singularity, which cannot be absorbed in the standard way into the phenomenological distribution functions, prohibits the application of this procedure. This situation is remedied by the introduction of a new set of distribution functions, the target fragmentation functions. They describe particle production in the target fragmentation region, and can be viewed as correlated distribution functions in the momentum fractions of the observed particle and of the parton initiating the hard scattering process. It is shown in a next-to-leading-order calculation for the case of deeply inelastic lepton-nucleon scattering that the additional singularity can be consistently absorbed into the renormalized target fragmentation functions on the one-loop level. The formalism is derived in detail and is applied to the production of heavy quarks. The renormalization group equation of the target fragmentation functions for the perturbative contribution is solved numerically, and the results of a case study for deeply inelastic lepton-nucleon scattering at DESY (H1 and ZEUS at HERA), at CERN (NA47) and at Fermilab (E665) are discussed. We also comment briefly on the case of an intrinsic heavy-quark content of the proton.     

用MXAN拟合钩端螺旋体去甲酰化酶XANES谱

钩端螺旋体去甲酰化酶(Leptospira interrogans PDF)是一种重要的含锌金属蛋白酶, 对钩端螺旋体这一广泛存在的致病菌的蛋白合成起着关键的催化作用, 是一个很好的药物设计靶蛋白. 本文测试了LiPDF在pH3.0的溶液状态下的X射线吸收近边结构(XANES: X-Ray Absorption Near-Edge Structure)谱, 利用以从头计算(ab. initio)的多重散射(Multiple Scattering)为基础的MXAN方法确定金属蛋白活性中心的精细结构. 研究发现结合合适的初始结构模型, 可以更好地重现LiPDF蛋白的XANES曲线, 从而能够得到更加准确的结构参数. 活性中心的精细结构为理解LiPDF的pH依赖的催化活性提供了结构基础.     

Smith-Purcell Radiation in the Sub-mm Wavelength Region

Spontaneous Smith-Purcell radiation at wavelengths of 100 and 220m has been observed. The angles of observation were 17° and 28° and the electron beam energies 1.9 and 1.56MeV, respectively. The radiated power was about 320nW at 17° and 92nW at 28°. These values are in reasonable agreement with what is theoretically expected if the emission process is due to the acceleration of image charges induced on the grating surface by the electrons of the beam.     

Stimulated Brillouin Scattering in the Midinfrared Region of the Spectrum

The behavior of opticalmedium parameters governing the efficiency of stimulated Brillouin scattering (SBS) with an increase in the pumpradiation wavelength is studied, and the range of media promising for accomplishing the phase selfconjugation in the course of SBS in the midinfrared region of the spectrum is determined. The SBS effect in the 10m region is realized experimentally in a fiber waveguide made of KRS5. The result obtained is in good agreement with the calculated SBS gain (0.14 cm/MW) and decay time of sound (200 ns) in KRS5. It is noted that the attainment of fairly high efficiencies of SBS reflection and phase selfconjugation for the abovethreshold intensities of excitation are controlled only by the level of technology for fabrication of fiber waveguides from infrared materials, the properties of which can still be much improved.     

Parameters of the Kinetic Layer of Arc-Discharge Cathode Region

The model is presented and the equation system is obtained which describes the nonequilibrium (Knudsen's) region of a cathode jet at the arc discharge burning in vapors of electrode material. The nonequilibrium layer is formed as a result of streaming of cathode-erosion products in the medium with reduced pressure and presents the discontinuity surface of the hydrodynamical region. The equation system was obtained by analyzing the law of conservation of heavy particles in the layer. Calculation results are presented and parameters of a cathode jet in the kinetic layer are discussed. It is shown that this flow is not a free one and its parameters are dependent on energy release in the near-cathode region.     

KCs Molecular Bands in the Visible Region

Optics and Spectroscopy - We measured light absorption of potassium and cesium mixed vapors at temperatures 360–660°C in the visible spectral region 380–780 nm. By comparison with...     

Mechanisms of ZnO Luminescence in the Visible Spectral Region

Existing models of zinc oxide luminescence in the visible spectral region are considered and comparatively analyzed. Experiments are performed with ceramics obtained from initial ZnO powder and ZnO powders annealed in vacuum (ZnO-vac) and in air (ZnO-air). The luminescence characteristics of the ceramics, namely, emission and excitation spectra, kinetics, and temperature stability, are studied. The ZnO-vac ceramics exhibits green luminescence caused by neutral oxygen vacancies. The luminescence of ZnO-air ceramics is shifted to the red and is presumably related to residual lithium impurity. The ceramics differ in the luminescence excitation spectra, time characteristics, and temperature stability.     

The Electronic Spectrum of NiCN in the Visible Region

The electronic spectrum of NiCN in the 500-630 nm region has been observed by laser-induced fluorescence, following the reaction of laser-ablated nickel atoms with cyanogen under free jet expansion conditions. Seven electronic states have been identified. Three of these, X?₁²Δ_5/2, X?₂²Δ_3/2, and W?₁²Π_3/2, are derived from the electron configuration Ni⁺ (3d⁹) CN⁻, and the other four, òΔ_5/2, B?²Π_3/2, C?²Φ_7/2, and D?²Φ_5/2, are derived from the configuration Ni⁺ (3d⁸ 4s) CN⁻. Rotational analysis of bands of NiC¹⁴N and NiC¹⁵N at high resolution has given the bond lengths in the X?₁²Δ_5/2 ground state as r₀ (Ni-C)=1.8292±0.0028 Å; r₀ (C-N)=1.1591±0.0029 Å. The orbital angular momentum splits the bending fundamental of the X?₁²Δ_5/2 state into two vibronic components, which lie at 243.640 cm⁻¹ (²Π_3/2) and 244.964 cm⁻¹ (²Φ_7/2). Exceptionally strong Fermi resonance occurs in the ground state between the Ni-C stretching vibration, ν₃, and the overtone of the bending vibration. Sixty vibrational levels of the ground state with |l|=0 and 1 have been assigned. They could be fitted by least squares to a simple matrix representation of the Fermi resonance that ignores the orbital angular momentum; the interaction matrix element, as a fraction of the bending frequency, turns out to be larger than that in the “prototype” molecule, CO₂. The two low-lying excited electronic states, X?₂²Δ_3/2 at 830 cm⁻¹ and W?₁²Π_3/2 at 2238 cm⁻¹, have very similar properties to the ground state. The energies of the excited states in the visible region bear a remarkable resemblance to those found in NiH (S. A. Kadavathu et al., 1991, J. Mol. Spectrosc.147, 448-470). Again, the effects of Fermi resonance in them are large but those of vibronic coupling are surprisingly small. The most significant vibronic coupling occurs between the òΔ_5/2 and B?²Π_3/2 states, which are separated by 79 cm⁻¹, an interval which is less than half the frequency of the bending vibration that couples them; large numbers of vibronically induced bands appear in the excitation and dispersed emission spectra, but the splitting between the vibronic components of the bending fundamental of the òΔ_5/2 state is only 6.988 cm⁻¹. Rotational perturbations are widespread in the òΔ_5/2 state, particularly in the levels of the ν₃ (Ni-C stretching) progression. Vibrational assignments have been made on the basis of the ⁵⁸Ni-⁶⁰Ni isotope shifts at high resolution and the Franck-Condon patterns in dispersed emission spectra. Various weak unassigned bands, both in the excitation and the dispers ed emission spectra, give evidence for the existence of at least three more excited electronic states which it has not been possible to characterize in detail.     

Nonlinear-Ion-Acoustic-Wave Instability, Threshold, Half Width of Trapped Region and Transition Region

Nonlinear Landau damping of ion acoustic wave (IAW) is one of the most important phenomena in the ionosphere and in space and laboratory plasma as well. The instability growth rate of the IAW with electron drift, the amplitude threshold for exciting the nonlinear effects, the half widths of the trapped region with the trapped electrons are studied experimentally. Under the experimental conditions, it is shown that there is a frequency range of 140--160 kHz, within which the growth rate has the largest value of about 6×10⁴--1.5×10⁵ s^-1. We obtain the transitional region width caused by collisions theoretically and experimentally, for the first time to our knowledge. The experimental results are in good agreement with the theoretical prediction.     

Parametric X Rays in the Region of Anomalous Dispersion

The influence of anomalous dispersion on the intensity of parametric x rays (PXR) is experimentally investigated in the present work. An experiment conducted with an inner electron beam generated by the Tomsk synchrotron with energy E ₀ = 900 MeV is discussed. A Ge monocrystal 0.17 mm thick oriented so that Bragg's angle _B between the electron momentum direction and the (111) plane is 9°30 is used as a target. The experimental data are compared with the results of calculations in the context of the kinematic PXR theory.     

Asymptotic Structure in the Classically Forbidden Region of the Hooke’s Atoms

The two-electron Hooke's atom - a quantum mechanical system with two electrons bound in a harmonic potential - is well known for its exact analytical properties at certain oscillator strengths. The Hooke's atoms with more than two electrons offer more scope for valuable practical applications. In this work, we study the asymptotic structure of these Hooke's atoms in the classically forbidden region. The leading-order term of the long-range expression for the KS exchange-correlation potential v xc (r) is shown to be-1/r. The second and third higher order terms are also exactly obtained. Various components of v xc (r) are also studied. It is shown that the leading term of O(1/r) in vxc (r) is due to the pure Pauli correlation, while the leading contribution of the Coulomb correlation is of O(1/r3 ). Neither of them makes contribution to the term of O(1/r2 ), which is shown to be solely due to the kinetic correlation effect. Results for the two-electron Hooke's atom were obtained before in the literature. Our results reduce to those of the two-electron Hooke's atom as a special case.     

共振Q~2相关的极化结构函数性质的研究

在组分夸克模型基础上，极化质子、中子结构函数随Ｑ~２演化关系得到了研究．同时理论对总的光吸收截面也给出了相应的预言．计算结果与实验数据相一致．     

Study of Strangeness Photoproduction on the Neutron in the Threshold Region

Photoproduction of the neutral kaon on the deuteron has been investigated at the Research Center for Electron Photon Science, Tohoku University. We constructed the Neutral Kaon Spectrometer-2 for the detection of charged particles from the decay of the neutral kaon and the hyperon. We obtained a momentum distribution of K ⁰ with the inclusive measurement. It was consistent with the previous measurement. The total cross section of γ + d → K ⁰ + Λ + p was estimated from the measured integral cross section of γ + d → Λ + X. The total cross section with respect to the photon energy was compared with the theoretical calculations. It favored the Saclay-Lyon A model calculation with the ratio of the neutral to charged coupling constants of the axial-vector meson, K ₁, as ~ ?1.5. The energy dependence and the magnitude of the total cross section were similar to the total cross section of γ + p → K ⁺ Λ.     

Two-Temperature Modeling of the Anode Contraction Region of High-Intensity Arcs

In this paper, an analytical model for a two-temperature plasma (Te > Tg) is established which is suitable for dealing with arcflow interactions induced by the arc itself. This model is applied to the anode contraction region of high-intensity argon arcs taking the interaction of anode and cathode jets close to the anode into account. The complete set of conservation equations describing the mass, charge, momentum, and energy transport of a two-temperature plasma with temperature-dependent transport properties is solved numerically by an interative finite-difference method using appropriate boundary conditions. Results for an atmospheric-pressure argon arc indicate that the temperature discrepancy between electrons and heavy particles is very pronounced in the arc fringes and in the regions close to the anode, while the departure from kinetic equilibrium becomes insignificant in regions in which the temperature exceeds 12 000 K (i.e., in the arc core). The computed temperature fields of the heavy particles in the anode contraction region resemble the observed arc appearance which clearly shows the interaction of anode and cathode jets in front of the anode.     

液滴蒸发对周围气相场的影响域特性分析

液滴在气体中运动蒸发的过程中,两相间会发生相互作用。为了弄清液滴对气相场的影响,基于液滴在气体环境中蒸发过程的现象和机理解释,提出液滴蒸发的影响域的概念,定义了影响域半径,并通过数值计算分析了不同条件下的影响域特性。结果表明,影响域内,由于液滴的存在使得其周围气相场参数变化较为剧烈;其他条件相同时,无量纲影响域半径几乎是一个定值。提出的影响域概念,对于研究气液两相间的相互作用机制具有重要意义。     

SFC的中心区改造

本文描述了SFC中心区的新结构,采用ECRIS后,在中心区安装了螺旋线型静电偏转器,磁极和D电极都作了修改,送入HIRFL的首次束流~(40)Ar~(8+)的流强可大于1.2μA。The new structure of SFC centre region is described. After an ECRIS was used, a spiralinflector had been assembled at the centre of the machine. The magnetic plog and the Dee electrodewere modified. The current of the first beam ~(40)Ar~(8+) sent to HIRFL is more than 1.2μA.     

Observation of Filamentary Structures on the Boundary Region of the LHD Stellarator

Large Helical Device (LHD) high β regime discharges are observed with a fast camera, with 〈β 〉 values up to almost 5%. High frequency sequences (20 µs between shots) of the density fluctuations in the edge region are obtained. Macroscopic coherent scructures, in the shape of “comet”‐like filaments can be seen in these sequences, propagating from the external ergodic region to the wall. These structures are analyzed and their radial and parallel transport is discussed. Strong relation between the generation of low frequency particle ejections and m/n= 2/3 edge mode is found. In the strike point region, “reflected” structures are observed as a response to ejected filaments. These are discussed in terms of plasma wall interaction phenomena (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)