Spectra of spin-wave excitations of a 71° domain boundary in a cubic ferromagnet

Features of the long-wavelength part of the spectrum of spin waves localized on a 71° domain boundary of a cubic ferromagnet are examined on the basis of a qualitative analysis and simultaneous numerical solution of the Landau-Lifshitz equations and the equation of magnetostatics. Fiz. Tverd. Tela (St. Petersburg) 41, 2183–2186 (December 1999)     

Hadrons as collective excitations of a superfluid coloured — Quark liquid

We investigate the excitation spectrum of a non-relativistic many-body system of coloured quarks in the presence of various Cooper-pair condensate fields. While the spin zeroqq colourless condensate within QCD is known to be responsible for the existence of pions, we argue non-relativistically that the spin — 1qq colourless condensate implies the existence of mesons, and the colour-tripletqq condensate implies the existence of baryons.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 7–June 1, 1985.     

Dynamic stability of a slender beam under horizontal–vertical excitations

The dynamic stability of a vertically standing cantilevered beam simultaneously excited in both horizontal and vertical directions at its base is studied theoretically. The beam is assumed to be an inextensible Euler–Bernoulli beam. The governing equation of motion is derived using Hamilton's principle and has a nonlinear elastic term and a nonlinear inertia term. A forced horizontal external term is added to the parametrically excited system. Applying Galerkin's method for the first bending mode, the forced Mathieu–Duffing equation is derived. The frequency response is obtained by the harmonic balance method, and its stability is investigated using the phase plane method. Excitation frequencies in the horizontal and vertical directions are taken as 1:2, from which we can investigate the influence of the forced response under horizontal excitation on the parametric instability region under vertical excitation. Three criteria for the instability boundary are proposed. The influences of nonlinearities and damping of the beam on the frequency response and parametric instability region are also investigated. The present analytical results for instability boundaries are compared with those of experiments carried out by one of the authors.     

Announcing a new journal——PHOTONICS Research

Editor-in-Chief:Prof.Zhiping(James)Zhou,Peking University Photonics Research(PR)is an English-language,peer-reviewed open access journal serving as an international platform for optics researchers to share theoretical and applied research progress in optics and photonics.PR is co-published by Chinese Laser Press(CLP)and OSA.The scope of PR includes the following topics:     

P2—a new measurement of the weak charge of the proton

After ten years of experience with parity-violating electron-proton-scattering, the preparatory work on a new high precision parity-violation experiment in Mainz has begun. Project P2 is bound to measure the weak charge of the proton to a relative uncertainty of 1.9 %, which corresponds to a relative uncertainty of 0.15 % for $\sin^2{\theta_{W}}$ . This can be achieved by measuring the parity-violating asymmetry in elastic electron-proton-scattering to a relative precision of 1.7 % at E _beam~200 MeV and Q ²~0.005 GeV². In this proceeding, we will discuss the achievable precision within project P2 as well as the experimental concept and present first results of studies involving Monte Carlo methods.     

Biotrophic interaction of Sporisorium scitamineum on a new host—Saccharum spontaneum

Sporisorium scitamineum is a biotrophic smut fungus harbored inside the smut gall on the top internodal region of Saccharum spontaneum, a wild relative of sugarcane (Saccharum officinarum). The interactions of spined conidia of S. scitamineum with S. spontaneum were examined during the different stages of plant growth starting from the bud stage to the decaying stage. The spores in the soil from the polyetic inocula grew into confined epidermal cells of the buds and finally sporulated in the topmost internodal region. Hyphae invasion of the plant tissues were restricted to the point of infection. Culms of infected plants in late October sporulated, notably; hyphal sporulation produced shorter hyphal stolons. Remarkably, the nodal regions of infected plants had no spores and fragmented hyphae. On the basis of microscopic analyses, hyphae and spores were absent in all internodes above the ground till the topmost smut gall region. This result indicated that, S. scitamineum undergoes tissue-confined invasion of S. spontaneum. By associating culture medium method with polymerase chain reaction (PCR) on plant portions void of smut gall, S. scitamineum was not detected, indicating that colonization was not systemic. It was observed that the biotrophic interaction resulted in structural reorganization in the restricted region of infection forming erect cylindrical structure, in which the fungus was sandwiched between the central stalk and sheath, and possibly played a key role in preventing inflorescence. Comparatively, a significant difference in the rate of teliospores germination between reference Ustilago esculenta (26.6%, P < 0.05) and S. scitamineum (62.9%, P < 0.05) at 20° C was observed. This study also provides insights on the effect of different temperature regimes on the germination of S. scitamineum teliospores in vitro.     

Robust estimation of excitations in mechanical systems using M-estimators—Experimental applications

This second part of the study presents some experimental applications to mechanical systems in which the results of excitation estimation, obtained using traditional least squares and M-estimate, are compared.The first case presented is a single input–multiple outputs system: a simple test-rig for the study of the vibrations of a two-degrees of freedom system is employed to identify the constraint displacement that causes the measured mass vibrations in presence of heavy noise.The second case is a multiple inputs–multiple outputs system: a rotor test-rig is used to identify the positions, the amplitudes and the phases of two unbalances using the vibrations measured in the bearings. In this case, also an additional theoretical part is introduced about the basics of model-based identification in the frequency domain applied to rotor dynamics.The last case is again a single input–multiple outputs system, but in an industrial application: experimental vibrations of a 320 MW steam turbo-generator are used to identify position and amount of a known balancing mass in an on-field real case.Moreover, whilst in the numerical examples presented in the first part the knowledge of the system was perfect, in these cases some uncertainties are present also in the system model.Finally, the paper introduces the use of the M-estimate technique to evaluate the adequacy the model of the system, by means of the analysis of the weights attributed to the measures as a function of the frequency of the excitation.     

Specific features of excitations of “flow”-type self-oscillations in a two-component active medium of a fast-flow gas laser

The mechanism of “flow”-type self-oscillations in a two-component active medium of a flow laser with an unstable resonator is studied. It is shown that this mechanism is associated with the excitation of edge self-oscillatory in-phase perturbations of the medium components. These flow perturbations with low damping reach the optical axis of the resonator and result in an instability.     

Bose–Einstein condensation of magnons in ferromagnetic thin films

Experimental evidence for Bose–Einstein condensation (BEC) of magnons at room temperature in a thin film of yttrium iron garnet (YIG) excited by parallel pumping is already available and different features of the experimental results have been explained qualitatively [Nature 443, 430 (2006)]. In the present work, we explain quantitatively different aspects of this experimental observation through spin wave treatment. In the case of parallel pumping field, we have developed a formula for the time required for the formation of magnon BEC in a thin film of ferromagnetic material. This relation is found to be in good agreement with known experimental results. In a similar treatment we predict the condition for the formation of BEC of magnons in the case of perpendicular pumping.     

FLASH—A superluminal communicator based upon a new kind of quantum measurement

The FLASH communicator consists of an apparatus which can distinguish between plane unpolarized (PUP) and circularly unpolarized (CUP) light plus a simple EPR arrangement. FLASH exploits the peculiar properties of measurements of the Third Kind. One purpose of this article is to focus attention on the operation of idealized laser gain tubes at the one-photon limit.FLASH: acronym for First Laser-Amplified Superluminal Hookup.     

Dark-state mechanism for the long-time transfer of excitations in a donor–acceptor system

The excitation energy transfer between a donor–acceptor pair with fixed distance apart through energy exchanging with environment is investigated. The total system is modeled as two two-level systems (TLSs) interacting with many harmonic oscillators. The pair behaves coherently or incoherently, depending on whether the dipolar coupling is stronger or weaker than the TLS–environment coupling. The environmental linear dispersion relation gives an analytical solution to the pair?s probability involving all the retardation times. We found that the long-time trapping of energy within the pair is caused by the inhibiting dark-state radiative decay when two TLSs are at half a resonant wavelength.     

Band structure of SrFeAsF and CaFeAsF—the base phases of a new group of oxygen-free FeAs superconductors

The results of ab initio FLAPW-GGA calculations of the band structure of the recently synthesized four-component fluorine arsenides SrFeAsF and CaFeAsF, which are the base phases of a new group of oxygen-free FeAs superconductors, are presented. The energy bands, electron state density distributions, effective atomic charges, Fermi surface topology, low-temperature electronic specific heat, and molar Pauli paramagnetic susceptibility have been determined for SrFeAsF and CaFeAsF and are compared to similar data for oxyarsenide LaFeAsO, which is the base phase of the family of the recently discovered high-temperature (T _c ～ 26–56 K) FeAs oxygen-containing superconductors.     

New localized excitations in a (2+1)-dimensional Broer—Kaup system

Starting with the extended homogeneous balance method and a variable separation approach, a general variable separation solution of the Broer—Kaup system is derived. In addition to the usual localized coherent soliton excitations like dromions, lumps, rings, breathers, instantons, oscillating soliton excitations, peakon and fractal localized solutions, some new types of localized excitations, such as compacton and folded excitations, are obtained by introducing appropriate lower-dimensional piecewise smooth functions and multiple-valued functions, and some interesting novel features of these structures are revealed.     

Bogoliubov excitations in a Bose–Hubbard model on a hyperhoneycomb lattice

We study the topological properties of Bogoliubov excitation modes in a Bose–Hubbard model of three-dimensional(3 D) hyperhoneycomb lattices. For the non-interacting case, there exist nodal loop excitations in the Bloch bands. As the on-site repulsive interaction increases, the system is first driven into the superfluid phase and then into the Mott-insulator phase. In both phases, the excitation bands exhibit robust nodal-loop structures and bosonic surface states. From a topology point of view, these nodal-loop excitation modes may be viewed as a permanent fingerprint left in the Bloch bands.     

Cavitation field from a horn—A new model

The cavitation field from a horn-type transducer is experimentally probed by the optical method.Based on these observations,we propose a model of the field which hypothesizes that most violent caviation bubbles originate from the vibrating surface and there-from fast drift to the near liquid region.These bubbles are chiefly responsible for the practical applications of cavitation for a large power input to the transducer.During migration they become weakened.Cavitation bubbles are also produced in the liqui...     

Solid-state quantum computation—a new direction for nanotechnology

We review current proposals for six types of solid-state quantum computers. We discuss the general requirements for solid-state quantum computers and describe proposals which employ superconducting junctions, electron orbitals in quantum dots, electron spin resonance, nuclear spins of impurity atoms, and nuclear spins in a crystal lattice. We also describe our proposed nuclear spin quantum computer based on magnetic resonance force microscopy. Finally, we describe our numerical method for modeling quantum transformations with a large number (up to 1000) of qubits.     

Light intensity distribution of a new type of contact laser scalpel

The emergent light distribution of a new type of contact laser scalpel is measured in three different states using a light sensor.The relationship between the angle and the light intensity is analyzed.The results show that the strongest light is emitted from two sides and the front of the scalpel.The light from the front mainly plays a role of cutting.The light from two sides contributes to stanch the wound so as to remain a clear visual field during the surgery.It also helps to increase the cutting efficiency.