Volume 10, Issue 1

We argue that both the positron fraction measured by PAMELA and the peculiar spectral features reported in the total electron-positron flux measured by ATIC have a very natural explanation in electron-positron pairs produced by nearby pulsars. While this possibility was pointed out a long time ago, the greatly improved quality of current data potentially allow to reverse-engineer the problem: given the regions of pulsar parameter space favored by PAMELA and by ATIC, are there known pulsars that explain the data with reasonable assumptions on the injected electron-positron pairs? In the context of simple benchmark models for estimating the electron-positron output, we consider all known pulsars, as listed in the most complete available catalogue. We find that it is unlikely that a single pulsar be responsible for both the PAMELA positron fraction anomaly and for the ATIC excess, although two single sources are in principle enough to explain both experimental results. The PAMELA excess positrons likely come from a set of mature pulsars (age ∼ × 106 yr), with a distance of 0.8–1 kpc, or from a single, younger and closer source like Geminga. The ATIC data require a larger (and less plausible) energy output, and favor an origin associated to powerful, more distant (1–2 kpc) and younger (age ∼ × 5 × 105 yr) pulsars. We list several candidate pulsars that can individually or coherently contribute to explain the PAMELA and ATIC data. Although generally suppressed, we find that the contribution of pulsars more distant than 1–2 kpc could contribute for the ATIC excess. Finally, we stress the multi-faceted and decisive role that Fermi-LAT will play in the very near future by (1) providing us with an exquisite measurement of the electron-positron flux, (2) unveiling the existence of as yet undetected gamma-ray pulsars, and (3) searching for anisotropies in the arrival direction of high-energy electrons and positrons.

A classical and a relativistic law of motion for an advancing shell are deduced applying the thin layer approximation. A new parameter connected with the quantity of absorbed matter in the expansion is introduced; this allows the matching of theory with observation.

We calculated the quasinormalmodes ofmassive scalar field of a black hole in the deformed Hořava-Lifshitz gravity with coupling constant λ = 1, using the third-order WKB approximation. Our results show that when the scalar field mass increases, the oscillation frequency increases while the damping decreases. And we find that the imaginary parts are almost linearly related to the real parts, the behaviors are very similar to that in the Reissner-Nordström black hole spacetime. These information will help us understand more about the Hořava-Lifshitz gravity.

In this paper, we have considered the g-essence and its particular cases, k-essence and f-essence, within the framework of the Einstein-Cartan theory. We have shown that a single fermionic field can give rise to the accelerated expansion within the Einstein-Cartan theory. The exact analytical solution of the Einstein-Cartan-Dirac equations is found. This solution describes the accelerated expansion of the Universe with the equation of state parameter w = −1 as in the case of ΛCDM model.

We discuss the evolution of a quantum wave packet in the expanding de Sitter spacetime using the plane wave solutions of the Dirac equation. We concentrate on the case of large negative times when the packet approaches the event horizon and confirm that the evolution accords with that expected from the classical trajectories. We point out that in certain conditions the packet can split into two components that become localized at different parts of the horizon and that this effect can be seen, in an idealized sense, as a measuring process for the momentum of the particle, in direct analogy with the measurement of spin in a Stern-Gerlach experiment.

We give an explicit formula for the Becchi-Rouet-Stora-Tyutin (BRST) charge associated with Poisson superalgebras. To this end, we split the master equation for the BRST charge into a pair of equations such that one of themis equivalent to the original one and find a solution to this equation. The solution possesses a graphical representation in terms of diagrams.

The work presents geometric phase decomposition for analytical signals using Hermite-Gaussian functions. The decomposition is based on the time-frequency distribution with reassigned and multi-tapered spectrogram resulting in increased phase estimation resolution. Numerical analysis is applied to a number of SU(2) evolutions, such as spin-1/2 particle in a static and rotating magnetic field, as well as polarization rotation of a plane wave in optically active medium. Geometric phase decomposition results are provided also for quantum harmonic oscillator and a radiation field of an electric dipole exited by a short pulse.

The variational iteration method (VIM) proposed by Ji-Huan He is a new analytical method for solving linear and nonlinear equations. In this paper, the variational iteration method has been applied in solving nth-order fuzzy linear differential equations with fuzzy initial conditions. This method is illustrated by solving several examples.

Metal hydrides are solutions of hydrogen in a metal, where phase transitions may occur depending on temperature, pressure etc. We apply Le Chatelier’s principle of thermodynamics to a particular phase transition in TiHx, which can approximately be described as a second-order phase transition. We show that the fluctuations of the order parameter correspond to fluctuations both of the density of H+ ions and of the distance between adjacent H+ ions. Moreover, as the system approaches the transition and the correlation radius increases, we show -with the help of statistical mechanics-that the statistical weight of modes involving a large number of H+ ions (‘collective modes’) increases sharply, in spite of the fact that the Boltzmann factor of each collective mode is exponentially small. As a result, the interaction of the H+ ions with collective modes makes a tiny suprathermal fraction of the H+ population appear. Our results hold for similar transitions in metal deuterides, too. A violation of an -insofar undisputed-upper bound on hydrogen loading follows.

We present an accurate calculation of the energies of the bound states of the quantumdipole problemin two dimensions using a Rayleigh-Ritz approach. We obtain an upper bound for the energy of the ground state, which is by far the most precise in the literature for this problem. We also obtain an alternative estimate of the fundamental energy of the model performing an extrapolation of the results corresponding to different subspaces. Finally, our calculation of the energies of the first 500 states shows a perfect agreement with the expected asymptotic behavior.

We analyze the convergence properties of the connected moments expansion (CMX) for the Rabi Hamiltonian. To this end we calculate the moments and connected moments of the Hamiltonian operator to a sufficiently large order. Our large-order results suggest that the CMX is not reliable for most practical purposes because the expansion exhibits considerable oscillations.

We present the elastic scattering of the 6He+208Pb and the 6He+197Au systems at the laboratory energy of E lab=27 MeV within the framework of the McIntyre parametrization, and systematically investigate χ 2/N analysis of both systems to obtain an excellent agreement between the theoretical results and the experimental data. We find large diffusivity parameters indicating long range absorption mechanisms. We also show that both systems lack both the nuclear and the Coulomb rainbow scattering for obtained S-matrix parameters.

The relationship between electronic spectral shifts and hydrogen-bonding dynamics in electronically excited states of the hydrogen-bonded complex is put forward. Hydrogen bond strengthening will induce a redshift of the corresponding electronic spectra, while hydrogen bond weakening will cause a blueshift. Time-dependent density function theory (TDDFT) was used to study the excitation energies in both singlet and triplet electronically excited states of Benzonitrile (BN), 4-aminobenzonitrile (ABN), and 4-dimethylaminobenzonitrile (DMABN) in methanol solvents. Only the intermolecular hydrogen bond C≡N...H-O was involved in our system. A fairly accurate forecast of the hydrogen bond changes in lowlying electronically excited states were presented in light of a very thorough consideration of their related electronic spectra. The deduction we used to depict the trend of the hydrogen bond changes in excited states could help others understand hydrogen-bonding dynamics more effectively.

Using the relativistic Hartree-Fock (HFR) method developed by Cowan, we calculated the energy levels, Landé g-factors, and lifetimes for nd (n = 5–25), ns (n = 6–24), ng (n = 5–25), nf (n = 4–22), and np (n = 6–25) excited levels of doubly ionized lanthanum (La III, Z = 57). We compared the results with previously reported calculations and experiments.

In this paper, we investigate the dynamics of two coupled quantum degenerate atomic fields (BEC) interacting with two classical optical fields in the nonlinear atom optics regime. Two-photon interaction produces entangled atom-atom pairs which exhibit nonclassical correlations. Since the system involves the creation of two correlated atom pairs, we call it the nondegenerate dual atomic parametric amplifier.

Based on the method of transformation optics, we show the miniaturization of a resonant cavity filled with metamaterials. Because the electromagnetic behavior in the transformation space is invariant in the original space, the quality factor Q and the resonant modes of a miniaturized resonant cavity filled with metamaterial are the same as for those in the original space. Theoretical analysis and numerical simulation confirms that the miniaturization of resonant cavities is effective.

Considering a double JC model, this paper investigates the quantum discord dynamics of two isolated moving two-level atoms each interacting with a single-mode thermal cavity field, and studies the effect of the atomic motion and the field-mode structure on quantumdiscord. The results show that, on the one hand the quantum discord evolves periodically with time and the periods are affected by the atomic motion and the field-mode structure; on the other hand, the quantum discord still can capture the quantum correlation between the two atoms when the entanglement is zero. It is interesting to note that the quantum discord can be effectively preserved by controlling the field-mode structure parameter

The nonlinear interaction of acoustic and entropy modes in a bubbly liquid is considered. The reasons for interaction are both nonlinearity and dispersion. In the field of intense sound, a decrease in the mixture density is predicted. That corresponds to the well-established growth of bubbles volumes due to rectified diffusion. The nonlinear interaction of modes as a reason for a bubble to grow due to sound, is discovered. The example considers variation in the mixture density and bubbles radii caused by acoustic soliton.

We observe time dependent variations in the light intensity transmitted through an aqueous suspension of Fe3O4 nanoparticles caused by applied DC magnetic field. Two types of variations can be distinguished. Fast response takes less than 1ms while slow variations occur at the time interval fromseconds to hundreds of minutes. Possible mechanisms of these variations are discussed. Formation of chain-like structures consisted from iron oxide nanoparticles is responsible for the slow variations. It is also accompanied by a diffraction pattern when the magnetic field is orthogonal to the light beam. Fast variations are due to particle rotation and reorientation of the magnetic moment inside a nanoparticle.

Solids containing an extended network of free radicals have been prepared and studied by magnetic resonance techniques in the 4–290 K temperature range. One solid contained additionally a small amount of magnetic γ-Fe2O3 in the form of nanoparticle agglomerates. The solid without agglomerates displayed only a narrow, single resonance line centered at g eff = 2.0043. The magnetic resonance measurements of the solid with γ-Fe2O3 agglomerates gave a spectrum composed of two lines attributed to two different magnetic centers: a narrow line due to free radicals and a broad line arising from magnetic iron oxide agglomerates. In the high temperature range the integrated intensities of both lines decreased with decreasing temperature. The resonance field of the broad line shifted to lower magnetic fields upon lowering the temperature with the gradient ΔH r/ΔT = 2.3 G/K, while the narrow line shifted towards higher magnetic fields. The linewidth of the broader line increased with decreasing temperature while for the narrow lines in both samples this change was small. The magnetic iron oxide clusters produce a magnetic field which acts on the free radicals network and its strength depends essentially on the concentration of clusters. The reorientation process in the free radicals network is more intense in the sample without magnetic clusters.

We investigate the energy-loss function for a previously developed model of quasi-one-dimensional metals with two one-dimensional electron bands per donor and acceptor chains and the three-dimensional long-range Coulomb electron-electron interaction within the random phase approximation. It is essentially influenced by two hybridized collective modes which result from the strong coupling of the intraband plasmon and the interband dipolar modes. Our calculations show that the spectral weights of the renormalized plasmon and the dipolar mode dominate within the long wavelength limit, while for large longitudinal wave vectors the intraband electron-hole quasi-continuumgains some experimentally observable spectral weight as the second mode approaches it. The function obtained is brought into correspondence with the data of the quasi-one-dimensional organic conductor tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) obtained from electron energy-loss spectroscopy (EELS) measurements.

In this article, we review special features of Gwyddion—a modular, multiplatform, open-source software for scanning probe microscopy data processing, which is available at http://gwyddion.net/. We describe its architecture with emphasis on modularity and easy integration of the provided algorithms into other software. Special functionalities, such as data processing from non-rectangular areas, grain and particle analysis, and metrology support are discussed as well. It is shown that on the basis of open-source software development, a fully functional software package can be created that covers the needs of a large part of the scanning probe microscopy user community.

Compounds with the general formula Mg1−x AlxB2 were obtained by two-step ceramic synthesis. All compounds were characterized by X-ray diffraction, NMR spectroscopy, and by four point probe resistivity measurements in various magnetic fields method. The diborides unit cell parameters were determined as a function of the Al mole fraction. With the vaues of x up to 0.40 (where x is the composition of the stock prepared for sintering), the unit cell parameters of Mg1−x AlxB2 are similar to those of pure MgB2 and the superconducting transition temperature was lowered. For stock compositions of 0:25 ≤ x ≤ 0:60, the products contain a superstructure, also superconducting phase, which becomes the only product at x = 0:50, and at x > 0:60 this phase is replaced by AlB2-based solid solutions.

The structural, elastic and thermodynamic characteristics of CeGa2 compound in the AlB2 (space group: P6/mmm) and the omega trigonal (space group: P-3m1) type structures are investigated using the methods of density functional theory within the generalized gradient approximation (GGA). The thermodynamic properties of the considered structures are obtained through the quasi-harmonic Debye model. The results on the basic physical parameters, such as the lattice constant, the bulk modulus, the pressure derivative of bulk modulus, the phase-transition pressure (P t) from P6/mmm to P-3m1 structure, the second-order elastic constants, Zener anisotropy factor, Poisson’s ratio, Young’s modulus, and the isotropic shear modulus are presented. In order to gain further information, the pressure and temperature-dependent behavior of the volume, the bulk modulus, the thermal expansion coefficient, the heat capacity, the entropy, Debye temperature and Grüneisen parameter are also evaluated over a pressure range of 0–6 GPa and a wide temperature range of 0–1800 K. The obtained results are in agreement with the available experimental and the other theoretical values.

Structural studies of (Ag3AsS3)x (As2S3)1−x chalcogenide superionic glasses in the compositional range x = 0.3–0.9 were performed by scanning electron microscopy. Temperature and compositional dependences of transmission coefficient, electrical conductivity, and activation energy were investigated

The quality of the interface region in a semiconductor device and the density of interface states (DOS) play important roles and become critical for the quality of the whole device containing ultrathin oxide films. In the present study the metal-oxide-semiconductor (MOS) structures with ultrathin SiO2 layer were prepared on Si(100) substrates by using a low temperature nitric acid oxidation of silicon (NAOS) method. Carrier confinement in the structure produces the space quantization effect important for localization of carriers in the structure and determination of the capacitance. We determined the DOS by using the theoretical capacitance of the MOS structure computed by the quantum mechanical approach. The development of the density of SiO2/Si interface states was analyzed by theoretical modeling of the C-V curves, based on the superposition of theoretical capacitance without interface states and additional capacitance corresponding to the charges trapped by the interface states. The development of the DOS distribution with the passivation procedures can be determined by this method.

In this study we have investigated diamond nucleation on Si substrates by ultrasonic seeding with different liquid solutions of Ultradispersed Detonation Diamond (UDD) powder in a mixture of metal nano- or microparticles (Ni, Co, Y). The influence of different solutions on nucleation efficiency was investigated. For highlighting nucleation centers and better evaluation of the nucleation process the nucleated samples were moved into a Microwave Plasma Enhanced Chemical Vapor Deposition (MW CVD) reactor and a ”short-time” (10 min), then followed by a ”long-time” (+1 hour), diamond deposition was performed. The morphology of samples was characterized by Scanning Electron Microscopy (SEM) and the chemical composition of grown diamond layer was investigated by Raman Spectroscopy. From the measurements we found out that microsized metal particles positively influenced nucleation and the uniformity of the deposited diamond thin film. The lowest surface roughness was achieved in the case of nanodiamond powder mixed with Co and Y metal powder. The influence of Ni, Co and Y to the nucleation and early growth stage are discussed.

We present an overview of design approaches for nanometrology measuring setups with a focus on interferometry techniques and associated problems. The design and development of a positioning system with interferometric multiaxis monitoring and control is presented. The system is intended to operate as a national nanometrology standard combining local probe microscopy techniques and sample position control with traceability to the primary standard of length.

Adsorption of human plasma fibrinogen, osteoblasts, and fibroblasts on differently treated titanium samples as implants were examined in this study. Titanium samples were mechanically polished, chemically etched (with and without surface material loss), and grinded. The main goal of this study is to find the best surface treatment of titanium for its possible use as implants. Atomic force microscopy was used to evaluate the adsorption of human plasma fibrinogen onto the titanium samples. Cell counting was used to determine the adherability of osteoblasts and fibroblasts on the titanium samples. Our preliminary results show that the etched titanium surface with surface material loss is the best surface treatment used in our experiments.

The nonlinear optical properties of some ABO3 materials (BaTiO3, KNbO3, LiTaO3 and LiNbO3) are studied by density functional theory (DFT) in the local density approximation (LDA) expressions based on first-principle calculations. Our goals are to give the details of the calculations for linear and nonlinear optical properties, including the linear electro-optic (EO) tensor for some ABO3 structures with oxygen octahedral structures using first-principles methods. These results can then be used in the study of the physics of ferroelectrics, specifically, we present calculations of the second harmonic generation response coefficient X ijk(2) (−2ω, ω, ω) over a large frequency range for ABO3 crystals. The electronic linear EO susceptibility X ijk(2) (−ω, ω,0) is also evaluated below the band gap. These results are based on a series of the LDA calculations using DFT. Results for X ijk(2) (−ω, ω,0) are in agreement with experiments below the band gap. The results are compared with the theoretical calculations and the available experimental data.