The influence of the composition of eight-atom Pt–Ir clusters on the magnetic properties

The energetic stability, electronic structure and magnetic properties of Pt_8–nIr_n clusters have been investigated by employing the spin-polarised generalised gradient approximation. The cubic structure is expected to be the effective building block in Ir-rich clusters after optimisation extensively. The average binding energy of all the clusters presents the linear increment trend with iridium atoms, due to the stronger interaction between Ir atoms than Pt atoms. Bader charge analysis shows how tiny charge transfers from iridium to platinum. The atomic moments of Ir are larger than that of Pt, and the Ir-rich clusters show greater moments than the Pt-rich cluster, with the exception of Ir₈ and Ir₇Pt. A unique magnetic property is found in the Pt₄Ir₄ cluster, where two Pt atoms show antiferromagnetic alignment and the other atoms are found to be aligned ferromagnetically.     

The Influence of Temperature on the Spectral Dependences of Aluminum’s Optical Properties

Data in the literature on the optical properties of aluminum in the range of 198–1173 K are analyzed. Analytical expressions describing the dependences of aluminum permittivity on photon energy and temperature are proposed and tested. The spectral dependences of the aluminum absorption coefficient and specular reflectance at normal incidence, as well as of the absorption-efficiency coefficients of aluminum nanoparticles in a lithium-fluoride matrix, are calculated at different temperatures. The results obtained indicate the appearance of unusual nonlinear absorption effects in nanocomposites containing aluminum nanoparticles, which manifest themselves in a decrease in the absorption efficiency with increasing temperature at photon energies exceeding 1.40 eV.     

The influence of defects on the effective Young’s modulus of a defective solid

It is difficult to establish structure-property relationships in a defective solid because of its inhomogeneous-geometry microstructure caused by defects. In the present research, the effects of pores and cracks on the Young’s modulus of a defective solid are studied. Based on the law of the conservation of energy, mathematical formulations are proposed to indicate how the shape, size, and distribution of defects affect the effective Young’s modulus. In this approach, detailed equations are illustrated to represent the shape and size of defects on the effective Young’s modulus. Different from the results obtained from the traditional empirical analyses, mixture law or statistical method, for the first time, our results from the finite element method (FEM) and strict analytical calculation show that the influence of pore radius and crack length on the effective Young’s modulus can be quantified. It is found that the longest crack in a typical microstructure of ceramic coating dominates the contribution of the effective Young’s modulus in the vertical direction of the crack.     

Wahlquist’s metric versus an approximate solution with the same equation of state

We compare an approximation of the singularity-free Wahlquist exact solution with a stationary and axisymmetric metric for a rigidly rotating perfect fluid with the equation of state $\mu +3p=\mu _0$ , a sub-case of a global approximate metric obtained recently by some of us. We see that to have a fluid with vanishing twist vector everywhere in Wahlquist’s metric the only option is to let its parameter $r_0\rightarrow 0$ and using this in the comparison allows us in particular to determine the approximate relation between the angular velocity of the fluid in a set of harmonic coordinates and $r_0$ . Through some coordinate changes we manage to make every component of both approximate metrics equal. In this situation, the free constants of our metric take values that happen to be those needed for it to be of Petrov type D, the last condition that this fluid must verify to give rise to the Wahlquist solution.     

The Optical Characteristics of the Acousto-optic Tunable Filter with the Equivalent Point

In this paper, the interaction curves of acoustic and optical waves in a non-collinear AOTF (acousto-optic tunable filter) cell under the parallel-tangent momentum matching condition are analyzed systematically. A new theory of equivalent point for AOTF design is put forward. The wavelength characteristics and the wavelength resolution of two diffraction beams with equivalent point design in AOTF are emphatically analyzed. The optical characteristics at δ = 0 (ideal case) and δ≠0 (real case) are also discussed. The advantages of the AOTF with equivalent point design include high wavelength resolution, more quantitative energy and larger incident angle aperture.     

The main properties and peculiarities of the Earth’s motion relative to the center of mass

The methods of theoretical and celestial mechanics and mathematical statistics have been used to prove that the Earth’s motion relative to the center of mass, the polar wobble, in the principal approximation is a combination of two circumferences with a slow trend in the mean position corresponding to the annual and Chandler components. It has been established that the parameters (amplitude and phase shift) of the annual wobble are stable, while those of the Chandler component are less stable and undergo significant variations over the observed time intervals. It has been proven that the behavior of these polar motion parameters is attributable to the gravitational-tidal mechanisms of their excitation.     

Optical properties change of oxide film — metal system during the film growth: computer simulation

Results of computer simulation of reflective properties of the oxide film-metal system in the process of oxidation in the air environment are presented. The complex refractive indices for oxide film and metal were used as the initial data. Thin films (the thickness is comparable with the wavelength of incident radiation) and thick films (thickness is much larger than the wavelength of incident radiation) are considered. The parameter characterizing the cyclic character of system reflectivity during the growth of film thickness was derived for the thin film. It is shown that the cyclic parameter does not depend on optical properties of a metal substrate. In the air environment, this parameter is determined by a complex refractive index of the film, its thickness, and direction of incident radiation. Relationships for the estimate of system reflectivity in the process of oxide film growth are presented for the thick film.     

Four-Dimensional Geometric Quantities versus the Usual Three-Dimensional Quantities: The Resolution of Jackson’s Paradox

In this paper we present definitions of different four-dimensional (4D) geometric quantities (Clifford multivectors). New decompositions of the torque N and the angular momentum M (bivectors) into 1-vectors N_s, N_t and M_s, M_t, respectively, are given. The torques N_s, N_t (the angular momentums M_s, M_t), taken together, contain the same physical information as the bivector N (the bivector M). The usual approaches that deal with the 3D quantities etc. and their transformations are objected from the viewpoint of the invariant special relativity (ISR). In the ISR, it is considered that 4D geometric quantities are well-defined both theoretically and experimentally in the 4D spacetime. This is not the case with the usual 3D quantities. It is shown that there is no apparent electrodynamic paradox with the torque, and that the principle of relativity is naturally satisfied, when the 4D geometric quantities are used instead of the 3D quantities.     

The influence of the acetate group in the polyvinyl alcohol structure on the direct blackening photostimulated processes in the polymer–zinc oxide–salt of metal photosensitive composition

In this presented paper, we will investigate the photographic characteristics of photosensitive compositions which consist of a polymer, zinc oxide and salt of metal using the examples of PVA–ZnO–BiCl₃ and PVA–ZnO–Pb(CH₃COO)₂ compositions. An experimental result of the dependence between the photographic characteristics of a similar system and the content of the acetate groups in the polymer structure, and its explanation are presented here.     

On wave and rheidity properties of the Earth’s crust

The properties of the Earth’s solid crust have been studied on the assumption that this crust has a block structure. According to the rotation model, the motion of such a medium (geomedium) follows the angular momentum conservation law and can be described in the scope of the classical elasticity theory with a symmetric stress tensor. A geomedium motion is characterized by two types of rotation waves with shortand long-range actions. The first type includes slow solitons with velocities of 0 ≤ V_sol ≤ c0, max = 1–10 cm s^–1; the second type, fast excitons with V₀ ≤ V_ex ≤ V_S–V_P. The exciton minimal velocity (V₀ = 0) depends on the energy of the collective excitation of all seismically active belt blocks proportional to the Earth’s pole vibration frequency (the Chandler vibration frequency). The exciton maximal velocity depends on the velocities of S (V_S ≈ 4 km s^–1) and/or P (V_P ≈ 8 km s^–1) seismic (acoustic) waves. According to the rotation model, a geomedium is characterized by the property physically close to the corpuscular–wave interaction between blocks that compose this medium. The possible collective wave motion of geomedium blocks can be responsible for the geomedium rheidity property, i.e., a superplastic volume flow. A superplastic motion of a quantum fluid can be the physical analog of the geomedium rheid motion.     

Phenomenological theory of multicritical points splitting in the phase diagrams. The case of Landau’s potentials with ℒ = 3m

A general technique of exact calculation of any correlation functions for the special class of one-dimensional spin models containing small clusters of quantum spins assembled to a chain by alternating with the single Ising spins is proposed. The technique is a natural generalization of that in the models solved by a classical transfer matrix. The general expressions for corresponding matrix operators which are the key components of the technique are obtained. As it is clear from the general principles, the decay of the correlation functions of various types is explicitly shown to be governed by a single correlation length. The technique is illustrated by two examples: symmetric diamond chain and asymmetric sawtooth chain.     

Optical properties of the Au–Ag alloy nanowire coated with an anisotropic shell

The optical properties of the Au–Ag alloy nanowire coated with a cylindrical shell with radial dielectric anisotropy are investigated based on quasistatic theory. Numerical results show that the surface plasmon resonance (SPR) peak is redshifted with increasing the component ratio of Au in the alloy, while the intensity of extinction section at the SPR increases with increasing the component ratio of Ag in the alloy. In addition, as the extent of anisotropy of the shell increases, the extinction section at SPR wavelength decreases and the SPR wavelength is redshifted, but compared with the isotropic shell consisting of comparable dielectric constant materials, the SPR has a distinct blueshift for anisotropic shell. We also find that the field enhancement can be completely concentrated inside the anisotropic shell and the electromagnetic transparency can be exhibited.     

The influence of growth patterns on the transmission properties of nonabrupt GaAs/AlxGa1−xAs heterojunctions

The influence of growth patterns in the transmission properties of nonabrupt GaAs/Al_xGa_1−xAs heterojunctions is investigated. Five interfacial growth patterns, representative of interfacial alloy variations generated by different growth techniques, are used. It is shown that carrier transmission depends on the type of the aluminum molar fraction variation through the interface. A study of the role of the interface width in carrier transmission is done for each compositional growth profile.     

Random versus holographic fluctuations of the background metric. I. (Cosmological) running of space–time dimension

A profound quantum-gravitational effect of space–time dimension running with respect to the size of space–time region has been discovered a few years ago through the numerical simulations of lattice quantum gravity in the framework of causal dynamical triangulation [hep-th/0505113] as well as in renormalization group approach to quantum gravity [hep-th/0508202]. Unfortunately, along these approaches the interpretation and the physical meaning of the effective change of dimension at shorter scales is not clear. The aim of this Letter is twofold. First, we find that box-counting dimension in face of finite resolution of space–time (generally implied by quantum gravity) shows a simple way how both the qualitative and the quantitative features of this effect can be understood. Second, considering two most interesting cases of random and holographic fluctuations of the background space, we find that it is random fluctuations that gives running dimension resulting in modification of Newton's inverse square law in a perfect agreement with the modification coming from one-loop gravitational radiative corrections.     

The phosphor’s optical properties—chromaticity coordinate relationship of phosphor converted white LEDs

Based on optical ray-tracing simulations we discuss the effect of the extinction coefficient and the quantum efficiency of the phosphors on the angular homogeneity of the white light emitted from phosphor converted light-emitting diodes. In particular variations of the extinction coefficient are prone to affect diverse CIE chromaticity coordinates for different viewing angles. Contrarily, the impact of the quantum efficiency on angle dependent variations of the chromaticity coordinates turns out to be of minor importance.     

Solution of A. Einstein’s Problem on the Density of Matter in the Universe

Russian Physics Journal - On the basis of the special theory of relativity and a solution of the Schwarzschild equations of general relativity, a generalized equation of...     

Phenomenological theory of phase diagrams. The case of Landau’s potentials with \mathcal{L} = 43m

Diversity-induced resonance, the emergence of coherent spatiotemporal patterns at intermediate parameter disorder, is a well-known phenomenon in lattices of excitable elements. Here we study the pattern events behind diversity-induced resonance in a lattice of coupled FitzHugh-Nagumo oscillators. Starting out with the observation that maximal spiral wave counts occur at intermediate values of parameter diversity, we analyze the competition between spiral and target wave patterns in the asymptotic collective state. We devise stylized numerical “in silico” competition experiments of (individual) patterns to understand the regulating parameters of the competing pattern events occurring stochastically in the full (“in vivo”) numerical simulation. Our analysis shows that pattern competition is a principal driving mechanism behind this form of diversity-induced resonance and that different types of competition take place: some follow the frequency composition of target and spiral waves, others are dictated by the statistics of parameter distributions. In particular, the increase and decrease of spiral wave counts with increasing diversity are statistically regulated by the number of oscillatory elements in the lattice, rather than by the frequency differences between target and spiral waves.