Asymptotics of Block Toeplitz Determinants and the Classical Dimer Model

We compute the asymptotics of a block Toeplitz determinant which arises in the classical dimer model for the triangular lattice when considering the monomer-monomer correlation function. The model depends on a parameter interpolating between the square lattice (t = 0) and the triangular lattice (t = 1), and we obtain the asymptotics for 0 < t ≤ 1. For 0 < t < 1 we apply the Szegö Limit Theorem for block Toeplitz determinants. The main difficulty is to evaluate the constant term in the asymptotics, which is generally given only in a rather abstract form.     

Validity of retinal oxygen saturation analysis: Hyperspectral imaging in visible wavelength with fundus camera and liquid crystal wavelength tunable filter

The purpose of this paper was to investigate the feasibility of a newly developed hyperspectral fundus imaging camera with a liquid crystal tunable filter. The intensities of different wavelengths of light transmitted through an artery, vein, and the area surrounding these vessels and reflected out were measured, and the differential spectral absorptions were analyzed. Measurements were made from 16 normal eyes and from two artificial capillaries. The ratios of absorption (ROA) of arteries to veins from 500 to 580 nm (range 1) and from 600 to 720 nm (range 2) were calculated. For all eyes, the ROA_range1 was larger than ROA_range2. The ROA obtained from the artificial capillary filled with blood saturated with oxygen or nitrogen was similar to that of simulated data of oxy- and deoxyhemoglobin extinction rate. Most ROAs of human eyes were lower than those of the simulated data and the artificial capillaries. Oxygen saturation analysis by hyperspectral fundus imaging of retinal vessels were qualitatively in agreement with thein vitro analysis or simulated values. However, further improvements are necessary to evaluate the oxygen saturation quantitatively in the retinal blood vessels.     

False Vacuum Decay with Gravity in a Critical Case

The vacuum decay in a de Sitter universe is studied for the class of effective inflaton potentials that curvature at the top is less than as well as greater than a critical value determined previously. By comparing the actions of the Hawking - Moss instanton and the Coleman - de Luccia instanton(s) the mode of vacuum decay is determined in this critical situation.     

Spin physics with COMPASS

COMPASS is a fixed target experiment at CERN studying nucleon spin structure in polarised deep inelastic muon nucleon scattering and hadron spectroscopy using hadron beams. The main goal of the COMPASS spin physics program is the measurement of the helicity contribution of the gluons to the nucleon spin, ΔG. This quantity is accessible via the photon-gluon-fusion process which can be selected by open charm production or production of hadron pairs with large transverse momenta. The spin physics program of COMPASS includes also measurements with a transversely polarised target. These allow to measure the transverse structure function.COMPASS has up to now successfully finished three runs with a muon beam of 160 GeV and a longitudinally polarized⁶LiD target in the years 2002, 2003 and 2004. An overview of the physics addressed by the muon program, with an emphasis on the ΔG/G measurement will be presented. The status of the analysis of the highpt hadron pairs, open charm, longitudinal and transverse asymmetries will be reviewed.     

Synthesis,formation mechanism and electric property of hollow InP nanospheres

The present work reports on novel four-layer thermally driven piezoresistive cantilevers implemented in one- and two-dimensional arrays for parallel proximity scanning. There, the heater (metallic meander), the piezoresistive deflection sensor, and the metal actuation film with significantly higher thermal expansion coefficient make up separate layers. Actuation efficiency and cross-talk of the novel cantilever design are studied and compared with two recent designs: thin metallic film and ion-implanted heater. The novel actuator, integrated on a 240 μm long and 3 μm thick silicon cantilever and supplied by V _dc=1 V enables deflections up to 5 μm of the AFM-tip with an actuation efficiency of about 170 nm/mW and suppressed cross-talk between actuator and sensor.     

Controlled growth of uniform nanoflakes-built pyrite FeS<Subscript>2</Subscript> microspheres and their electrochemical properties

Nanoflakes-built pyrite FeS₂ microspheres were synthesized through a simple solvothermal process in mixed solvents of N, N-dimethytformamide and ethylene glycol without using any surfactant. Both the composition of the solvents and urea were key factors for the formation of the uniform products. It was found that the flake-like intermediate products transformed into FeS₂ nanoflakes in situ in the early stage and Ostwald ripening growth mechanism would contribute to the uniformity of the final products. Electrochemical studies revealed that the nanoflakes-built pyrite FeS₂ microspheres exhibited large lithium storage capacities. This method can be easily controlled and is expected to be extendable to the fabrication of other metal chalcogenides with controlled shape and structure.     

Morphology of a silver/polyacrylonitrile nanocomposite

Silver/polyacrylonitrile (Ag/PAN) nanocomposites are synthesized at the stage of simultaneous acrylonitrile polymerization and the reduction of silver ions from a mixture of silver nitrate AgNO₃, acrylonitrile, and a photoinitiator. The synthesized films are transparent in the visible region and are characterized by a uniform dispersion of silver nanoparticles in a PAN matrix without any macroscopic agglomeration. The effects of the metal salt and photoinitiator concentrations on the size and density of metal nanoparticles in a composite are revealed.     

An optimum design and fabrication of lens on luminous uniformity and light extraction of high-power light-emitting diode

The effect of lens inner structure on radiation pattern and light extraction efficiency of light-emitting diode (LED) and the application to artificial light in compact greenhouse is demonstrated. A commercial software package of Trace Pro and one-factor at-a-time (OFAT) method are used to simulate the lens with different inner structure. The optimum parameters of lens inner structure design for the maximum light extraction efficiency and the best uniform luminous are described by the corner radius of curvature, lens width, and lens height, respectively. For a real single LED module, base on the optimum parameters of lens inner structure, the corresponding best luminous uniformity is 62% and corresponding output extraction is 14.11 lm. The maximum uniformity of illumination for LED matrix assembled by LED modules with optimum lens is 88% and corresponding light extraction 1141 lm. In comparison with a commercial artificial light of LED matrix used in agriculture, the high-power LED module with proposed lens inner structure exhibit good improvement in uniformity of illumination and light extraction. This study may provide a practical guideline for design and fabrication of a high-performance lens used in various compact agricultural applications.     

Tomographic implementation of astronomical speckle imaging from bispectra

A bispectral method for astronomical speckle imaging utilizes an average speckle bispectrum of an object to derive its Fourier phase. There has been, however, a problem in conventional bispectral algorithm owing to difficulty in processing bispectral data in a four-dimensional (4D) space. In this paper, we propose an implementation to overcome this problem, where a one-dimensional (1D) object projection is reconstructed from a two-dimensional (2D) average bispectrum of speckle projections, and object projections so obtained at various angles are then tomographically combined into a 2D object image. In this tomographic approach, processes are separable into those for individual projection angles, implying that bispectral data required to be stored at a time are from 4D to 2D and computation time can be substantially reduced by parallelizing angle-by-angle processes. We have performed experiments using simulated and observed data, and have demonstrated the feasibility of the present approach with an achievable accuracy comparable to that of a conventional approach.