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[en] Structures of some bisphosphonates (clodronate, etidronate, pamidronate, alendronate, risedronate, zoledronate) were relaxed and analyzed by DFT method. By comparing their adsorption energies onto hydroxyapatite (001) surface with and without solvation effect and analyzing HOMOs (highest occupied molecular orbitals), LUMOs (lowest unoccupied molecular orbitals), and DOS (density of states) of bisphosphonates and hydroxyapatite (001) surface, it can be shown that the binding affinity of alkyl N-BPs (bisphosphonates containing nitrogen atom in an alkyl chain) is the highest among bisphosphonates, and the adsorption energy of bisphosphonates onto hydroxyapatite (001) surface is the main factor to determine the binding affinity of bisphosphoates with bone material.
[en] Properties of electrons in non-crystalline (alias disordered) systems has been a very active research topic for over half a century, since Anderson’s ground breaking paper on localization. In strongly disordered systems electrons become Anderson and Mott localized. Interactions become important because screening by localized electrons is ineffective. Dynamical theories for such systems have long been controversial. Nevertheless one theory came to prominence in the literature and is often invoked and/or used. It is shown here that that theory is unsatisfactory in several aspects. It is based on the one-particle density of states, which turns out to be irrelevant to the problem it addresses. Another shortcoming is an implicit conjecture that interacting electrons move independently of each other. The theory is also in questionable agreement with experiment. It is shown that two other theories are free of those problems. They are useful for different types of studies, are compatible with each other and in agreement with experiment. (paper)
[en] Here in this paper, a full-spectrum responsive vacancy-rich monolayer BiO2-x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO2-x is responsible for the enhanced photon response and photo-absorption, which were confirmed by UV/Vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO2-x, monolayer BiO2-x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near-infrared light (NIR) irradiation, which can be attributed to the vacancy VBi-O' as confirmed by the positron annihilation spectra. The presence of VBi-O' defects in monolayer BiO2-x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts.
[en] The lateral density distributions (LDD) of inclined cosmic-ray (CR) air showers are asymmetric. The iso-density contours of an EAS are of increasing eccentric ellipses with shower zeniths. These asymmetries introduce a significant shift of the shower core, which is quantitatively expressed by a linear shift (LS) between the shower core and the center of the modified density pattern consisting of several equi-density ellipses. A polar angle (βg) dependent modified elliptic lateral density function (E-LDF) of the LDD has been derived analytically by considering the effect of attenuation of EAS electrons in the atmosphere. The LS shows sensitivity to the CR mass composition. In this work a modelling of the atmospheric attenuation effect on the LDD of electrons is made considering the conical shower profile. The magnitude of the LS which determines the attenuation power of shower particles for a non-vertical EAS, possesses a clear primary cosmic ray mass dependence. The ELDF has been used to the simulated electron densities to estimate the LAP, which manifests different radial variation
[en] Here, it is of interest to determine the exit angle of a vortex from a superconductor surface, since this affects the intervortex interactions and their consequences. Two ways to determine this angle are to image the vortex magnetic fields above the surface, or the vortex core shape at the surface. In this work we evaluate the field h(x,y,z) above a flat superconducting surface x,y and the currents J(x,y) at that surface for a straight vortex tilted relative to the normal to the surface, for both the isotropic and anisotropic cases. In principle, these results can be used to determine the vortex exit tilt angle from analyses of magnetic field imaging or density of states data.
[en] In lattice calculations, the approach to the continuum limit is hindered by the severe freezing of the topological charge, which prevents ergodic sampling in configuration space. In order to significantly reduce the autocorrelation time of the topological charge, we develop a density of states approach with a smooth constraint and use it to study SU(3) pure Yang Mills gauge theory near the continuum limit. Our algorithm relies on simulated tempering across a range of couplings, which guarantees the decorrelation of the topological charge and ergodic sampling of topological sectors. Particular emphasis is placed on testing the accuracy, efficiency and scaling properties of the method. In their most conservative interpretation, our results provide firm evidence of a sizeable reduction of the exponent z related to the growth of the autocorrelation time as a function of the inverse lattice spacing.
[en] The electronic and mechanical properties of AlGaN and InGaN were analyzed in the pressure range of 0 GPa to 50 GPa by the first-principles study. Moreover, the energy band structure gets modified upon increasing pressure. The density of states (DOS) spectrum of AlGaN and InGaN shows the shift in the peaks upon increase in the pressure. The elastic constants for rhombohedral AlGaN and InGaN were established. By estimating the Young’s, bulk and shear moduli, an upsurge in the magnitude was observed with the intensifying pressure. The ductility of AlGaN and InGaN were demonstrated by examining the Poisson’s ratio, Cauchy’s pressure and Pugh’s criterion under increasing the pressure. We observed increase in the ductility of AlGaN and InGaN upon applied pressure. Thus, the findings suggest that the band gap of AlGaN and InGaN can be fine-tuned on applying the pressure, which is suitable to fabricate new optoelectronic devices. (paper)
[en] A model consisting of two quantum XX spin chains, one homogeneous and the second with random couplings drawn from a binary distribution, is considered. The two chains are coupled to two different non-local thermal baths and their dynamics is governed by a Lindblad equation. In the steady state, a current J is induced between the two chains by coupling them together by their edges and imposing different chemical potentials μ to the two baths. While a regime of linear characteristics J versus is observed in the absence of randomness, a gap opens as the disorder strength is increased. In the infinite-randomness limit, this behavior is related to the density of states of the localized states contributing to the current. The conductance is shown to diverge in this limit. (paper: disordered systems, classical and quantum)
[en] We study the eigenvalues and the eigenvectors of structured random matrices of the form with diagonal matrices D and W and from the Gaussian Unitary Ensemble. Using the supersymmetry technique we derive general asymptotic expressions for the density of states and the moments of the eigenvectors. We find that the eigenvectors remain ergodic under very general assumptions, but a degree of their ergodicity depends strongly on a particular choice of W and D. For a special case of D = 0 and random W, we show that the eigenvectors can become critical and are characterized by non-trivial fractal dimensions. (paper)
[en] ZrSiS was recently shown to be a new material with topologically non-trivial band structure that exhibits multiple Dirac nodes and a robust linear band dispersion up to an unusually high energy of 2 eV. Such a robust linear dispersion makes the topological properties of ZrSiS insensitive to perturbations like carrier doping or lattice distortion. Here, we show that a novel superconducting phase with a remarkably high of 7.5 K can be induced in single crystals of ZrSiS by a non-superconducting metallic tip of Ag. From first-principles calculations, we show that the observed superconducting phase might originate from a dramatic enhancement of density of states due to the presence of a metallic tip on ZrSiS. Our calculations also show that the emerging tip-induced superconducting phase co-exists with the well preserved topological properties of ZrSiS. (paper)