Toroidal,compression, and vortical dipole strengths in 144-154Sm: Skyrme-RPA exploration of the deformation effect

All transfer reactions and radiative capture nuclear-astrophysical reactions at low energies measured so far are analysed using a reaction theory that contains overlap functions between the wave functions of the target and residual nuclei. These overlaps are assumed to have an asymptotic form determined by the separation energy of the transferred (or radiative captured) cluster and such an assumption is incorporated into all reaction codes. We point out that although this asymptotic form is dominant for the majority of the transfer reactions and the nuclear-astrophysical radiative capture reactions, for some cases the overlap function has anomalous asymptotic behavior. This behavior originates from virtual decays of the complex nucleus into intermediate channels and, mathematically, is generated by contributions from the singularities of the triangle Feynman diagram and the generalised triangle diagram containing a loop. In the present work, these contributions are investigated in detail and expressions are derived for the strengths of the anomalous terms taking spin variables and the Coulomb effects into account. We present specific examples of nuclear vertices with anomalous asymptotics and discuss their application for peripheral nuclear processes.     

Giant-dipole resonance and the deformation of hot,rotating nuclei

The development of nuclear shapes under the extreme conditions of high angular momentum and/or temperature is examined. Scaling properties are used to demonstrate universal properties of both thermal expectation values of nuclear shapes as well as the minima of the free energy, which can be used to understand the Jacobi transition. A universal correlation between the width of the giant-dipole resonance and quadrupole deformation is found, providing a novel probe to measure the nuclear deformation in hot nuclei.     

Ceria: Relation among thermodynamic,electronic hole and proton properties

The proton solubility and the hole conductivity of the rare earth doped ceria have been examined in their relations to the thermodynamic properties of doped ceria under the assumption that the hypothetical species, LnOOH and LnOO (Ln = Rare earth), can be regarded as constituents for representing protons and holes in the fluorite lattice. Focus is made on the dopant dependence, the host dependence and the temperature dependence in the rare earth doped zirconia(or ceria) fluorite lattice. The chemical potentials of the rare earth dopant are less stabilized in the ceria-based oxides than in the zirconia-based ones. The proton solubility in the ceria-based, zirconia-based, and ceria–zirconia solid solutions has been well interpreted in terms mainly of the hydroxidation energy and the stabilization energy of LnO_1.5 in the fluorite lattice. Since the dopant dependence of the stabilization energy of LnO_1.5 is stronger than the hydroxidation energy, the proton solubility becomes high in the smaller dopants. To account for less dopant-dependent behavior in the hole conduction, the peroxidation energy is assumed to have about the same dopant dependence as the stabilization energy. The calculated temperature dependences of proton solubility and hole concentration were compared with available experimental data; it has been suggested that holes and protons in ceria reach to saturation levels with lowering temperature. Some discussions are made on the possible explanation on recently observed anomalous hole conductivity in nano-size Ce_0.8Gd_0.2O_1.9 in terms of plausible effects of miscibility gap, associated Gd enrichment, and simultaneous formation of Ce³⁺ and holes.     

Spin-reorientation phase transition: Magnetic resonance, acoustic and optic properties

The problem dealt within this paper is the study of soft modes near the spin-reorientation phase transition (SRPT) in ferromagnets (and partly in antiferromagnets) when the magnetoelastic interaction is taken into account. A detailed discussion is given for the long wavelength magnetoacoustic modes (MAM) and their influence on various physical properties. The results are: the conditions for linear and nonlinear (parametric) excitations of MAM by an ac magnetic field; MAM contributions to the local magnetic susceptibility, nuclear magnetic and magnetoacoustic resonances; the modulation of the sound velocity by an ac magnetic field; and the magnetic birefrigence of light by sound waves. All these phenomena manifest a sharp increase near the SRPT.     

Large-area aligned CuO nanowires arrays: Synthesis,anomalous ferromagnetic and CO gas sensing properties

Thermal evaporation was carried out in a horizontal quartz tube under an oxygen flow of about 50 ml/min and the influence of reaction time and temperature on the microstructure of the CuO nanowires (CNWs) is examined. The magnetic susceptibilities of the as-synthesized CNWs in the 5–300 K range were studied. It is interesting to note that the CNWs with a much larger diameter than 10 nm exhibit anomalous ferromagnetic behavior which has never been reported previously, demonstrating the effect of their peculiar morphology. The saturation magnetization (MS) and coercive field (Hc) of CNWs grown at 700 °C are 2.39 × 10^?4 emu and 48 Oe, respectively. We fabricated gas sensors based on p-type single CNWs and demonstrate that CuO nanowires could be a promising candidate for a gas sensor with good performance. The reaction between the reducing gas and O^? leads to a decrease of the hole density in the surface charge layer and an increase of the CuO resistance.     

Structure,unelastic properties,and deformation behavior of ultrafine-grained titanium

The results of investigations into the structure, unelastic properties, deformation behavior, strength, and plasticity of ultrafine-grained titanium produced by equichannel angular pressing are discussed. Particlular emphasis has been placed on the grain-boundary unelasticity and the effects of external thermal and thermal-force actions on the deformation behavior and plastic deformation localization at the meso- and macroscale levels. The influence of cold plastic deformation of ultrafine-grained titanium on the grain-boundary unelasticity and temperature dependence of the mechanical properties is considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 33–43, September, 2004.     

Ordering potential: the anomalous structure and properties of liquid KPb alloy

The anomalous structure and related properties of liquid KPb alloy are presented through an ab initio evaluated ordering potential as a function of concentration. It appears that considerable ordering occurs and it maximizes at the stoichiometric composition (c_k∼0.5). We then use the model to obtain the Bhatia-Thornton(BT) structure factors at different compositions (c_k=0.1,0.3,0.5 and 0.8). The calculations of concentration fluctuation and other related thermodynamic properties show that this ordering potential approach works reasonably for this compound forming liquid alloy.     

Bistability,autowaves and dissipative structures in semiconductor fibers with anomalous resistivity properties

This work provides a discussion of bistability conditions, switching autowave properties and emergence of dissipative structures in semiconducting fibers with anomalous positive dependence of electrical resistivity on temperature of sigmoid type, (1?+?e ^?T )^?1. An open system thermodynamics approach is utilized for the analysis of this dissipative solid-state system. The approach aims to represent the structure of the solution space of its governing equation in the form of physical phase diagrams, known as non-equilibrium phase diagrams, and two specific binary diagrams have been obtained here. One of the diagrams, where the electrical power density and ambient temperature represent external parameters, shows a wide region with dissipative structures as non-uniform steady-state temperature profiles on the fiber. The possibility of efficient external control over the dissipative structure geometry is also demonstrated.     

Optomechanical coupling between two optical cavities: Cooling of a micro-mirror and parametric normal mode splitting

We propose a technique aimed at cooling a harmonically oscillating mirror mechanically coupled to another vibrating mirror to its quantum mechanical ground state. Our method involves optomechanical coupling between two optical cavities. We show that the cooling can be controlled by the mechanical coupling strength between the two movable mirrors, the phase difference between the mechanical modes of the two oscillating mirrors and the photon number in each cavity. We also show that both mechanical and optical cooling can be achieved by transferring energy from one cavity to the other. We also analyze the occurrence of normal-mode splitting (NMS). We find that a hybridization of the two oscillating mirrors with the fluctuations of the two driving optical fields occurs and leads to a splitting of the mechanical and optical fluctuation spectra.     

BaSnF4 fast ion conductor: Variations versus the method of preparation and anomalous temperature variation of the quadrupole splitting

A new method of preparation of high performance fluoride ion conductor, BaSnF₄, by water leaching of newly discovered barium tin(II) chloride fluorides, has been designed, and the materials have been studied and compared to the solid prepared by the usual dry method. The unit-cell parameters and crystallite dimensions were found to vary with the method of preparation. In addition, the crystallite dimensions were found to be highly anisotropic for the samples obtained by the wet method. The Mössbauer spectrum is made of a large tin(II) quadrupole doublet, and a broad tin(IV) oxide peak due to surface oxidation. The tin(II) spectrum is in agreement with covalently bonded tin(II) having a strongly stereoactive lone pair. An unusually high dependence of the quadrupole splitting at low temperatures was observed (5.8 times larger than for α-SnF₂).     

Autoparametric resonance in a structure containing a liquid,Part II: Three mode interaction

Autoparametric coupling of the first antisymmetric liquid sloshing mode with two orthogonal structure freedoms in a simple structure containing a liquid is investigated theoretically and experimentally. Asymptotic approximation up to the first order shows four possible conditions of internal resonance. The response of the system is obtained analytically and numerically in the neighbourhood of the internal resonance conditions. Under the principal internal resonance (i.e., when one of the normal mode frequencies is twice one of the other mode frequencies) the system possesses a steady-state response. Under the summed or differenced internal resonance (i.e., when one of the normal mode frequencies equals the sum or difference of two other natural mode frequencies) the system does not achieve a constant amplitude steady-state response.Experimental investigations confirm the possible existence of most of the internal resonance conditions considered in the analytical study; however, theoretical amplitude-frequency response curves are rather higher than the experimental results. Experimental observations showed that other kinds of instabilities occur when the liquid free surface exhibits rotational flow at a forcing frequency just above twice the liquid sloshing frequency.     

Autoparametric resonance in a structure containing a liquid,Part I: Two mode interaction

An elastic structure carrying a rigid circular cylindrical tank containing a liquid with a free surface is considered. Autoparametric coupling between a single structural freedom and the first antisymmetric sloshing mode is investigated theoretically and experimentally. Under the condition of principal internal resonance (i.e., when the structure natural frequency equals twice the liquid sloshing frequency) the response of the system is obtained by an asymptotic approximation taken to the second order. Both theoretical and experimental results show that the coupling between liquid sloshing and vertical structure vibration is rather weak.     

The symmetry properties and collinearity of the magnetogyric,hyperfine splitting and magnetic susceptibility tensors

The symmetry properties of g and A cannot be elicited using invariance properties, due to their special nature, and are found using the properties of a Kramers doublet. It is shown that the collinearity of g and A depends on the molecule having at least C ₂ with σ _v or C ₂′ symmetry elements. The symmetry properties of x are found from those of g. The conditions for collinearity of the tensors and the consequences of non-collinearity are discussed, with examples.     

Modeling of the muscle-like actuation in soft dielectrics: deformation mode and electromechanical stability

Soft dielectric elastomer is able to generate an electromechanical response in terms of reversible shape changing, which is a muscle-like behavior. The deformation and electromechanical stability of dielectric elastomers, classified by their deformation modes, uniaxial extension, equal biaxial expansion and pure shear, are investigated. Pull-in instability occurs in equal biaxial and uniaxial modes at a small stretch ratio, while the pure shear mode features wrinkling instability after a large stable deformation. The coupled stiffness of the voltage-activated material is established and studied for achieving the goal of high performance stretchable dielectric actuators.     

Introduction to focus issue: mixed mode oscillations: experiment, computation, and analysis

Mixed mode oscillations (MMOs) occur when a dynamical system switches between fast and slow motion and small and large amplitude. MMOs appear in a variety of systems in nature, and may be simple or complex. This focus issue presents a series of articles on theoretical, numerical, and experimental aspects of MMOs. The applications cover physical, chemical, and biological systems.     

Effective material parameters,resonance, and polarization properties of a magnetophotonic crystal

For mutually perpendicular orientations of the periodicity axis, the wavevector, and the magnetic bias, the expressions for the effective material parameters of the magnet-dielectric periodic structure are obtained in the fine-layered medium approximation. The allowance for corrections proportional to (L/λ)² leads to the dependence of the effective permittivity and permeability on the permittivity and permeability of the layers. The resonance and polarization properties, as well as the conductance of the magnetophotonic structure under consideration, are investigated.