Effects of Precursors with Fine BaZrO3 Inclusions on the Growth and Microstructure of Textured YBCO

We prepared precursors with fine BaZrO₃ inclusions for melt-texture growth of high-temperature superconductors with nominal composition of Y_1.5Ba₂Cu₃O _y + x BaZrO₃ (x = 0, 0.04, 0.08, and 0.1), by the process of liquid-phase powder melt-texture growth (LPMG). We then investigated the effects of the precursors on the texture growth and the microstructure of composite YBa₂Cu₃O_7-/Y₂BaCuO₅ (YBCO). The BaZrO₃ particles were about 100 nm in size in the textured YBa₂Cu₃O_7- (Y123), observed by the scanning electron microscopy (SEM). Owing to the pushing effects of growing fronts, fine particles were pushed out of and thus gathered in front of the growing fronts or between Y123 grains. The gathered particles in turn blocked the further growth of the Y123 grains. However, BaZrO₃ particles seeded Y123 grains, giving rise to multigrain growths. These negative effects of BaZrO₃ fine particles exclude themselves as effective flux pinning centers in the textured YBCO.     

Substitution Effect of Sn for Cu in the Bi2Sr2CaCu2?xSnxO8+δ System

The Bi₂Sr₂CaCu₂O₈₊ system samples doped with Sn on Cu sites were synthesized. Resistivity temperature dependence, X-ray powder diffraction and photoemission experiments have been performed. Suppression of superconductivity in the Sn-doped Bi₂Sr₂CaCu₂O₈₊ system has been observed. X-ray photoemission measurements show that Sn ion enters the lattice. Our results reveal that Sn ions are mostly in bivalent states.     

Comparison of Superconductivity and Structure for YBa2Cu3Oy with Potassium and Sodium Doping

The nominal composition of YBa_2–x M _x Cu₃O _y (M = K, Na) cuprates with x 0.30 were synthesized by the standard solid-state reaction technique. X-ray diffraction (XRD) and the resistivity measurements were used to characterize the structure and the superconductivity of the doped cuprates. There was no impurity phase detected within the whole doping range. The structure of the main phase (123) has the orthorhombic with P _mmm symmetry. With increasing the content of dopants, the lattice constants and some other structural parameters are almost unchanged for M = K, whereas they changed for M = Na. The refined contents of dopants are consistent with that of the nominal ones. The zero resistance temperature T _c0 decreases sharply with the increase of the content of potassium in potassium-doped samples as x 0.20. For sodium-doped YBa_2–z Na _x Cu₃O _y cuprates, T _c0 varies very little. The difference in superconductivity depression may result from the shift oxygen, which transfers conducting carriers from Cu-O chains to Cu-O₂ sheets or the structural stress effect.     

Influence of unparallel grating planes in talbot interferometry with cross gratings of different spatial frequencies in two directions

The effects of an arbitrary small inclination between two cross gratings on the moiré fringes in Talbot interferometry are discussed when the frequencies of the grating differ in two perpendicular directions. We show that the small angles, alpha and beta, by which the beam-splitter cross grating is rotated around the two axes parallel to the two perpendicular line directions of the cross grating, have a greater influence on the moiré fringes with cross gratings than that with one-dimensional gratings. A simple and practical detection method for the angles between the two unparallel grating planes in Talbot interferometry is also proposed. The theoretical analyses are proved by experimental results.     

Vacuum deposition of chiral sculptured thin films with high optical activity

We present the technique of bideposition to realize thin-film helicoidal bianisotropic mediums (TFHBM's) that exhibit high optical activity. We show, by experiment as well as by simulation, that the optical rotation produced by these chiral sculptured thin films is roughly proportional to the square of the local linear birefringence. Experimental measurements on bideposited TFHBM's of titanium oxide yield a typical value of 5 degrees /mum for the effective specific rotation in the short-wavelength regime; the corresponding value determined for the standard unideposited TFHBM's is 1 degrees /mum. Both types of TFHBM's are highly optically active in comparison with quartz, fluorite films, and cholesteric liquid crystals. Bideposited TFHBM's will lend themselves to many different types of optical devices.     

Light Scattering from Deformed Droplets and Droplets with Inclusions. II. Theoretical Treatment

We provide theoretical results from the scattering of light by deformed liquid droplets and droplets with inclusions. With improved instrumentation and computer technologies available, researchers are able to employ two-dimensional angular optical scattering as a tool for analyzing such particle systems and which then could be applied in industrial, occupational, and military aerosol measurement. We present numerically calculated spatial light-scattering data from various droplet morphologies. We describe characteristic features of the theoretical data and compare these with the experimental results.     

Polar cap mesosphere wind observations: comparisons of simultaneous measurements with a Fabry-Perot interferometer and a field-widened Michelson interferometer

Polar cap mesospheric winds observed with a Fabry-Perot interferometer with a circle-to-line interferometer optical (FPI/CLIO) system have been compared with measurements from a field-widened Michelson interferometer optimized for E-region winds (ERWIN). Both instruments observed the Meinel OH emission emanating from the mesopause region (~86 km) at Resolute Bay, Canada (74.9 degrees N, 94.9 degrees W). This is the first time, to our knowledge, that winds measured simultaneously from a ground-based Fabry-Perot interferometer and a ground-based Michelson interferometer have been compared at the same location. The FPI/CLIO and ERWIN instruments both have a capability for high temporal resolution (less than 10 min for a full scan in the four cardinal directions and the zenith). Statistical comparisons of hourly mean winds for both instruments by scatterplots show excellent agreement, indicating that the two optical techniques provide equivalent observations of mesopause winds. Small deviations in the measured wind can be ascribed to the different zenith angles used by the two instruments. The combined measurements illustrate the dominance of the 12-h wave in the mesopause winds at Resolute Bay, with additional evidence for strong gravity wave activity with much shorter periods (tens of minutes). Future operations of the two instruments will focus on observation of complementary emissions, providing a unique passive optical capability for the determination of neutral winds in the geomagnetic polar cap at various altitudes near the mesopause.     

Characterization of chicken antisera raised against Aspergillus spp. by enzyme linked immunosorbent assay

Enzyme linked immunosorbent assays of three Aspergillus species have been developed. Laying hens were immunized with the exoantigens from Asp. flavus, Asp. ochreaus and Asp. versicolor. All test chickens except for one produced antisera raised against the exoantigens. The antisera production process and ELISA titer were analysed. Fourteen days after the first injection, the antisera began to produce largely, on the 35th day reached to the peak, and maintained a stable level until the 42nd day. The maximum ELISA titer of the antisera to the exoantigens from Asp. flavus, Asp. ochreaus and Asp. versicolor was 1:8,000, 1:10,000 and 1:10,000, respectively. The cross-reactivities of antisera were determined with seventeen species of Aspergillus, ten species of fungi from other genera and the buffer-extracts of grain. The antisera did not cross-react with the exoantigens from other genera and the buffer-extracts of grain. The antiserum to exoantigen from Asp. ochreaus was species-specific, whereas the antisera against Asp. flavus and Asp. versicolor tended to cross-react with other Aspergillus species to varying degrees. The results suggest that exoantigens immunoassays can be developed to indentify and detect Aspergillus genus in grains.     

A multiscale dynamic programming procedure for boundary detection in ultrasonic artery images

Ultrasonic measurements of human carotid and femoral artery walls are conventionally obtained by manually tracing interfaces between tissue layers. The drawbacks of this method are the interobserver variability and inefficiency. In this paper, we present a new automated method which reduces these problems. By applying a multiscale dynamic programming (DP) algorithm, approximate vessel wall positions are first estimated in a coarse-scale image, which then guide the detection of the boundaries in a fine-scale image. In both cases, DP is used for finding a global optimum for a cost function. The cost function is a weighted sum of terms, in fuzzy expression forms, representing image features and geometrical characteristics of the vessel interfaces. The weights are adjusted by a training procedure using human expert tracings. Operator interventions, if needed, also take effect under the framework of global optimality. This reduces the amount of human intervention and, hence, variability due to subjectiveness. By incorporating human knowledge and experience, the algorithm becomes more robust. A thorough evaluation of the method in the clinical environment shows that interobserver variability is evidently decreased and so is the overall analysis time. We conclude that the automated procedure can replace the manual procedure and leads to an improved performance.