Body effects on SAR distributions for microwave exposures in a realistic model of the human head.

The finite-difference time-domain (FDTD) simulations of specific absorption rate (SAR) in a human head exposed to microwaves have, to date, been carried out on models of the head only. This was because it was believed that the body effects on the average SAR of the head could be ignored at high frequencies of around 1 GHz. That opinion, however, was based on inappropriate calculation conditions and is therefore unreliable. In this paper, we have re-examined the body effects on the SAR distributions in a realistic homogeneous model of the adult head exposed to microwaves. We found that the SAR on the eye surface of the head-only model exposed to E-polarized waves was 31% smaller than that of the whole-body model at 900 MHz, and 43% larger at 1.5 GHz. For a size that can practically be considered whole-body, it is necessary to have the top of the head to the belly for 900 MHz and to the chest area for 1.5 GHz. The previously unclear body effects of H-polarized waves were assumed to be less than those of E-polarized waves, suggesting that the chest area would be sufficient for both frequencies.     

Excessive closure of the right eye: a new sign of infarction in the territory of the ipsilateral right middle cerebral artery

In right middle cerebral territory infarction a new sign, excessive closure of the right eye ipsilateral to the lesion and mild closure of the left eye on command, was noted. The excessive ipsilateral eye closure was not observed on spontaneous eye closure.     

Analytical studies of four-inch pipe whip tests under BWR LOCA conditions

The purpose of pipe rupture studies in JAERI is to perform model tests on pipe whip, restraint behavior, jet impingement and jet thrust force, and to establish a computational method for analyzing these phenomena. This report presents the analytical results of 4-inch pipe whip tests under BWR LOCA conditions.Dynamic response analyses were performed using the general-purpose finite element program ADINA. The test pipe was modelled by straight beam elements and the four restraints were modelled by a single truss element. The analytical results were compared with the experimental results. Impact time and maximum total restraint force showed good agreement with experimental results. On the other hand, pipe strain and pipe deflection could not be predicted so well. The reason for this is that the sliding of the restraint during the pipe whip movement cannot be considered in the analyses.     

Novel B-ring modified combretastatin analogues: syntheses and antineoplastic activity

A series of B-ring modified combretastatin analogues were synthesized and their inhibitory activity against microtubule assembly, cytotoxic activity against Colon 26 adenocarcinoma cancer cell line were evaluated. Among these, pyridone derivative (19) showed strong antimitotic activity and cytotoxicity, along with excellent water-solubility.     

High-Strength and High-Fracture-Toughness Ceramics in the Al2O3/LaAl11O18 Systems

Control of microstructure in the Al₂O₃/LaAl₁₁O₁₈ system was performed. Elongated alumina grains were formed by doping with small addition of silica, and 20 vol% lanthana- luminate was formed in situ by the reaction of LaAlO₃- A1₂O₃ in an alumina matrix. Strengths of over 600 MPa and a high fracture toughness (6 MPa.m^1/2) were achieved in the material with both elongated A1₂O₃ grains and LaAl₁₁O₁₈ platelets. Generally antagonistic properties such as strength and fracture toughness have been made compatible in the same ceramic system.     

Fracture Energies of Tape-Cast Silicon Nitride with β-Si3N4 Seed Addition

The fracture energies of the tape-cast silicon nitride with and without 3 wt% rod-like β-Si₃N₄ seed addition were investigated by a chevron-notched-beam technique. The material was doped with Lu₂O₃–SiO₂ as sintering additives for giving rigid grain boundaries and good heat resistance. The seeded and tape-cast silicon nitride has anisotropic microstructure, where the fibrous grains grown from seeds were preferentially aligned parallel to the casting direction. When a stress was applied parallel to the fibrous grain alignment direction, the strength measured at 1500°C was 738 MPa, which was almost the same as room temperature strength 739 MPa. The fracture energy of the tape-cast Si₃N₄ without seed addition was 109 and 454 J/m² at room temperature and 1500°C, respectively. On the contrary, the fracture energy of the seeded and tape-cast Si₃N₄ was 301 and 781 J/m² at room temperature and 1500°C, respectively, when a stress was applied parallel to the fibrous gain alignment. The large fracture energies were attributable primarily to the unidirectional alignment fibrous Si₃N₄ grains.     

Formation and Properties of Ln-Si-O-N Glasses (Ln = Lanthanides or Y)

Homogeneous Y-Si-O-N glasses containing 15 or 20 eq% nitrogen (N) were prepared from compositions with Y/Si ratios in the vicinity of that of the lowest eutectic point on the Y₂O₃–SiO₂ phase diagram. The liquidus on the phase diagram shifted toward lower temperatures by incorporation of N. The density, the elastic moduli, and the glass transition temperature of the Y-Si-O-N glasses increased with incorporation of N. This is due to the closer packing of atoms in the glasses by the substitution of N, which is in three-fold coordination with Si, for O which is in two-fold coordination, and the stronger covalent nature of the Si–N bond compared with the Si–O bond. The coefficient of thermal expansion of the Y-Si-O-N glasses increased with increasing Y content, because the discontinuity of the glass network developed with increasing nonbridging anions by the introduction of Y. In contrast, the glass transition temperature and the elastic moduli increased with Y content due to the high coordination of Y for O, and the relatively high cationic field strength of Y. Furthermore, the effect of cationic field strength on properties of Ln-Si-O-N glasses (Ln = lanthanides or Y) is discussed.     

Processing Strategy for Producing Highly Anisotropic Silicon Nitride

Silicon nitride with a preferred orientation of large elongated grains was obtained by tape casting of raw powder slurry seeded with rodlike β-Si₃N₄ particles, followed by a gas pressure sintering under 1 MPa nitrogen pressure. The large elongated grains developed from seeds lay in planes parallel to the casting direction in a two-dimensional distribution. Increased fracture toughness (11.1 MPa·m^1/2) and bending strength (1100 MPa) were achieved in the direction perpendicular to the grains alignment compared to specimens with a random distribution of elongated grains. Morover, the specimens exhibited a high Weibull modulus of 46 due to the uniform distribution of large grains.     

Mechanical Properties of Textured Alumina Made by High-Temperature Deformation

The mechanical properties of a textured alumina made by high-temperature deformation of normal-purity sintered alumina have been investigated. The textured alumina shows very high bending strength and extremely high fracture toughness. Fracture toughness of more than 10 MPa·m^1/2 was measured by the single-edge precracked beam method, and even using the single-edge V-notched beam method, toughness of over 8 MPa·m^1/2 was obtained. This high fracture toughness was attributed to a large number of aligned small platelike grains of the textured structure enhancing the grain bridging effect.     

Application of the independent molecule model to elucidate the dynamics of structure I methane hydrate: a second report

Two model systems of methane hydrate are constructed. One has a small cage surrounded by 12 large cages. The other has a large cage surrounded by four small cages and ten large cages. Three different H-bonding network patterns between waters are formed, and three random configurations of methane in each cage are chosen. A new method called the surface water fixed model is presented in which the energy minimum conformations for both model systems are preserved close to the X-ray crystallized structure. With normal mode analysis, we calculated frequencies of 2916.6 cm⁻¹ for a small cage at a centre, 2915.9 cm⁻¹ not at a centre, and 2911.7 cm⁻¹ for a large cage at a centre, and 2911.3 cm⁻¹ not at a centre. These frequencies are in moderate agreement with the corresponding Raman spectra, though not adequate. With our new method, however, it should be possible to improve agreement with the Raman spectra, if a model system vastly larger than the present model systems were constructed.