Cloud optical thickness and effective particle radius derived from transmitted solar radiation measurements : Comparison with cloud radar observations

A method is presented for determining the optical thickness and effective particle radius of stratiform clouds containing liquid water drops in the absence of drizzle from transmitted solar radiation measurements. The procedure compares measurements of the cloud transmittance from the ground at water-absorbing and nonabsorbing wavelengths with lookup tables of the transmittance precomputed for plane-parallel, vertically homogeneous clouds. The optical thickness derived from the cloud transmittance may be used to retrieve vertical profiles of cloud microphysics in combination with the radar reflectivity factor. To do this, we also present an algorithm for solving the radar equation with a constraint of the optical thickness at the visible wavelength. Observations of clouds were made in August and September 2003 at Koganei, Tokyo, Japan, using a PREDE i-skyradiometer and a 95-GHz cloud radar Super Polarimetric Ice Crystal Detection and Explication Radar (SPIDER). The optical thickness and effective radius of water clouds were derived from the i-skyradiometer. Then, the vertical profile of the effective radius was retrieved from SPIDER, using the optical thickness determined from the i-skyradiometer. We found that the effective radii derived by using these two instruments were in good agreement

X-ray diffractometry for the structure determination of a submicrometre single powder grain

A high-precision diffractometer with a synchrotron radiation microfocusing technique has been developed to investigate the crystal structure of a submicrometre-scale single grain of powder sample. The structure of a BaTiO3 single powder grain, of dimensions ∼600 × 600 × 300 nm, was determined

Piezoelectric properties of high Curie temperature barium titanate-bismuth perovskite-type oxide system ceramics

Barium titanate (BaTiO3, BT)-bismuth magnesium titanium oxide [Bi(Mg0.5Ti0.5)O-3, BMT] system ceramics were prepared in an ambient atmosphere in order to increase the Curie temperature (T-c) of BT above 132 degrees C. A single perovskite phase was observed for BT-BMT ceramics with BMT compositions less than 50 mol %, and their relative densities were greater than 94%. Synchrotron measured x-ray diffraction patterns revealed that all the cations in the ceramics were homogeneously distributed. The temperature dependence of the dielectric properties revealed that the BT-BMT system ceramics exhibited relaxorlike characteristics with a dielectric maximum temperature as high as 360 degrees C for the 0.5BT-0.5BMT ceramic. The apparent piezoelectric constant (d*) was 60 pC/N for the 0.4BT-0.6BMT ceramic. Based upon these results, the BT-BMT system shows potential as a new type of lead-free material for high T-c piezoelectric applications

Choroidal Structure of CSC on OCT Image

Purpose To determine the structural changes of the choroid in eyes with central serous chorioretinopathy (CSC) by enhanced depth imaging optical coherence tomography (EDI-OCT). Methods A retrospective comparative study was performed at two academic institutions. Forty eyes with CSC, their fellow eyes, and 40 eyes of age-matched controls were studied. Subfoveal cross sectional EDI-OCT images were recorded, and the hypo reflective and hyperreflective areas of the inner and outer choroid in the EDI-OCT images were separately measured. The images were analyzed by a binarization method to determine the sizes of the hyporeflective and hyperreflective areas. Results In the inner choroid, the hyperreflective area was significantly larger in the CSC eyes (35,640±10,229 μm2) than the fellow eyes (22,908±8,522 μm2) and the control eyes (20,630±8,128 μm2; P<0.01 vs control for both, Wilcoxon signed-rank test). In the outer choroid, the hyporeflective area was significantly larger in the CSC eyes (446,549 ±121,214 μm2) than the control eyes (235,680±97,352 μm2, P<0.01). The average ratio of the hyporeflective area to the total choroidal area was smaller in the CSC eyes (67.0%) than the fellow eyes (76.5%) and the control eyes (76.7%) in the inner choroid (P<0.01, both). However, the ratio was larger in the CSC eyes (75.2%) and fellow eyes (71.7%) than in the control eyes (64.7%) in the outer choroid (P<0.01, both). Conclusions The larger hyperreflective area in the inner choroid is related to the inflammation and edema of the stroma of the choroid in the acute stage of CSC. The larger hyporeflective areas in the outer choroid is due to a dilatation of the vascular lumens of the larger blood vessels. These are the essential characteristics of eyes with CSC regardless of the onset

Enhanced piezoelectric response of BaTiO3–KNbO3 composites

The piezoelectric response of solvothermally synthesized BaTiO3 (BT)–KNbO3 (KN) composites (the nominal BT/KN ratio was 1) with distinct interfaces was investigated. The x-ray diffraction pattern showed two distinct peaks began to merge into a singular broad peak at a two-theta position between (200) and (002) tetragonal-related peaks of BT. The transmission electron microscopy observation showed a heteroepitaxial interface region between BT single-crystal particles and deposited KN crystals. The large-field piezoelectric constant was 136 pC/N, which was three times larger than that of a sintered 0.5BT–0.5KN composite. The enhanced piezoelectric response was attributed to the strained epitaxial interface region

Octahedral and trigonal-prismatic coordination preferences in Nb-, Mo-, Ta-, and W-based ABX2 layered oxides, oxynitrides, and nitrides

Crystallographic and electronic structures of Nb-, Mo-, Ta-, and W-based layered oxides, oxynitrides, and nitrides were analyzed to elucidate the structural relationship between layered oxides and nitrides consisting of octahedral and trigonal-prismatic layers. The electron density, as derived by synchrotron X-ray analysis of LiNbO2 and Ta5−x(O,N)6, showed orbital overlaps between Nb–Nb and Ta–Ta metals in the trigonal layers. Computational calculations based on DFT exhibited that these overlaps stabilized these structures by lowering the hybridization states composed of the dxydxy, dx2−y2dx2−y2, and dz2dz2 orbitals below the Fermi level. Crystal structures and formation energies suggest that tuning the Fermi level through the substitutions and vacancies of the cation/anion sites determines the structural preferences of the coordination. The properties and syntheses of these compounds are briefly described. This study enhances the understanding of layered oxides, oxynitrides, and nitrides to further the development of new synthetic approaches, compounds, and applications

Structural Difference in Superconductive and Nonsuperconductive Bi–S Planes within Bi4O4Bi2S4Blocks

The relationship between the structure and superconductivity of Bi4O4S3 powders synthesized by heating under ambient and high pressures was investigated using synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy (TEM) observation. The Bi4O4S3 powders synthesized under ambient pressure exhibited a strong superconductivity (diamagnetic) signal and zero resistivity below ∼4.5 K, while the Bi4O4S3 powder synthesized by the high-pressure method exhibited a low-intensity signal down to 2 K. Further annealing of the latter Bi4O4S3 powder under ambient pressure led to the development of a strong signal and zero resistivity. The crystal structures of all Bi4O4S3 phases consisted of Bi4O4Bi2S4 blocks including a Bi–S layer and anion(s) sandwiched between Bi4O4Bi2S4 blocks, but minor structural differences were detected. A comparison of the structures of the superconductive and nonsuperconductive Bi4O4S3 samples suggested that the superconductive Bi4O4S3 phases had slightly smaller lattice parameters. The average structures of the superconductive Bi4O4S3 phases were characterized by a slightly shorter and less bent Bi–S plane. Raman spectroscopy detected vibration of the S–O bonds, which can be attributed to sandwiched anion(s) such as SO42–. TEM observation showed stacking faults in the superconductive Bi4O4S3 phases, which indicated local fluctuation of the average structures. The observed superconductivity of Bi4O4S3 was discussed based on impurity phases, enhanced hybridization of the px and py orbitals of the Bi–S plane within Bi4O4Bi2S4 blocks, local fluctuation of the average structures, compositional deviation related to suspicious anion(s) sandwiched between Bi4O4Bi2S4 blocks, and the possibility of suppression of the charge-density-wave state by enriched carrier concentrations