[en] An analysis of visible/near IF polarimetry of Comet Halley leads to a variation of the complex refractive index m = n - i x k of grain material with wavelength, i.e., a slight decrease of n from 1.39 at lambda = 0.37 micrometer to 1.37 at lambda = 2.2 micrometers, in constrast to an increase of k from 0.024 at lambda = 0.37 micrometer to 0.042 at lambda 2.2 micrometers. The mass distribution of grains reported by Mazets et al. from in situ measurements of Vega 2 was applied in the analysis. Combining these optical constants with those of astronomical silicate proposed by Draine, cometary silicate is presented as a candidate for cometary grains. The complex refractive index of the proposed cometary silicate is shown. Based on Mie theory, an emission coefficiency of each of the grains in computed as well as its temperature, as functions of grain radius and sun comet (grain) distance. It is found that the tentative thermal spectrum from these cometary silicates, where the mass distribution of grains reported by Mazets from Vega 2 was applied, fits very well to the IR spectrum of Comet Halley. This means that cometary silicate can explain not only the phase angle and wavelength dependences of visible/near IF polarization, but also the thermal emission

[en] The competency of the decision about the location of nuclear power plants based on the power police in Brazil is discussed

[en] The authors have applied a multi-pass packed-rolling technique to the production of anisotropic Nd-Fe-B-Cu powders from rapidly quenched ribbons. Analysis of the packed-rolling process shows that densification proceeds from the surface of the packed powder-compact and crystallographic alignment proceeds more rapidly at the center. Rolling to a reduction in ribbon thickness of greater than 80% results in a uniform material with a high (BH)_max of up to 38 MGOe. The present paper discusses the alignment mechanism, taking into consideration the internal stress distribution inside the powder compact under rolling pressure

[en] Using low energy ion data obtained by Akebono satellite, the authors have calculated distribution functions of velocity-dispersed ion beams observed at the poleward edge of the auroral electron precipitation region. The calculated distribution functions can well be fitted by one-dimensional shifted-Maxwellians, whose bulk energy and temperature are several keV and several hundreds of eV, respectively. The bulk energy and temperature show a positive correlation, which may indicate that when the ions are accelerated to higher energy, they are heated to higher temperature simultaneously. A relation has been found between the invariant latitude width of the observed ion beams divided by the square root of the temperature and their bulk velocity, which indicates that the source region of the ion beam is compact. These ion beams are obtained with high occurrence probability, suggesting that they are supplied from a steady X-type neutral line in the earth's magnetotail. 12 refs., 4 figs

[en] The mass loss rate of the zodiacal dust cloud near the Sun has been estimated on the basis of the orbital behaviour of circumsolar dust grains suffering sublimation. It is found that the solar dust ring located at 4 solar radii from the Sun, which consists of grains whose inward spiraling due to the Poynting-Robertson effect is stopped by the influence of sublimation, loses its mass at a rate of between 3.5 and 0.35 tons per second. (Auth.)

[en] Using the data of the rates of spontaneous mutations affecting viability, isozyme mutations, and radiation-induced mutations affecting viability, we have argued that slightly deleterious mutations are induced with irradiation in the region outside the structural genes. The occurrence rates are dependent on the strains; most probably some types of transposons are involved. (orig.)

[en] It is generally accepted that almost all homozygously deleterious mutations are also harmful to the carriers in heterozygous condition in random mating population. The spontaneous polygenic mutations affecting viability are occurring at a high rate on a genome basis, and their main function may be regulatory, and if radiation also induces such polygenic mutations at a high rate, it is most important to consider the effects of these mutant polygenes when the genetic effects of radiation on higher organisms are discussed. Such polygenic mutations have often been called mildly deleterious mutations. Mutations are accumulated with minimum selection pressure on many second chromosomes, all originating from a single stem (ancestral) chromosome with normal homozygous viability. Majority of the mutations induced at the structural loci by chronic γ-ray irradiation are point mutations, and if it is true, radiation also induces point mutations in the region outside the structural loci. It is speculated that this region may be 20 times as large as that of the structural loci in Drosophia melanogaster. It is strongly suggested that radiation induces deleterious mutations including polygenic mutations at a high rate. Most of these occur in the region outside the structural genes, and if their function is of regulatory nature, the effects of most of the mutations in this region may not be manifest in the phenotype, but very important for the estimation of the genetic effects of irradiation on higher organisms. (Yamashita, S.)

[en] Synoptic features of auroral substorm development and relationships between auroral displays and simultaneously precipitating electron fluxes were studied with VUV images from the Kyokko satellite. The existence of both nightside and non-nightside auroral arcs was observed, and electron precipitation with a peaked energy spectra was found to correspond with discrete auroral arcs. An arc was also seen to extend from the dusk- to late evening-region of the auroral oval to the dayside region, with a sharp cut-off of flux at 3 keV. The existence of different mechanisms in the magnetosphere which produce the nightside and non-nightside aurora is suggested, and studies to relate the observations to substorm activities are indicated

[en] Single-photon emission computed tomography (SPECT) for thallium-201 myocardial imaging with a rotating gamma camera was evaluated in comparison with planar imaging and seven-pinhole tomography (7P). Cardiac phantom studies indicated that defects 2 cm in diameter can be visualized by both tomographic methods, but the 7P method showed propagation of the image into nearby planes, with lower image contrast. In a clinical study of 47 patients with myocardial infarction, both sensitivity and specificity for the SPECT system were high (96 and 89%, respectively); the 7P system, on the other hand, showed good sensitivity (93%) but poor specificity (68%), while planar imaging performed conversely (75 against 89%). The overall accuracy was not significantly improved in the 7P method (planar: 81%, 7P: 83%, and SPECT: 94%). Our study indicates that SPECT, which can construct reliable tomographic sections in either the transaxial, frontal, or sagittal planes, will result in a remarkable improvement in the clinical evaluation of ischemic heart disease

[en] Basic and clinical evaluation of thallium single-photon emission computed tomography (SPECT) using a rotating gamma camera with 180 degrees (LPO to RAO) data collection was carried out and compared with the full 360 degrees rotation. No attenuation correction was used. In a phantom study the reconstructed image from the 180 degrees scan revealed better resolution. Although the 180 degrees scan, when compared with the 360 degrees scan, showed great photon attenuation in the deep location of a line source in water, this problem was not significant in the clinical study of six normal hearts. In 11 cases with myocardial infarction, the perfusion defect was more clearly visualized in the 180 degrees scan. The defect-to-normal (D/N) wall-count ratio was lower in the 180 degrees scan (0.48 +/- 0.16; mean +/- s.d.) than in the 360 degrees scan (0.61 +/- 15, p less than 0.05), indicating superior lesion contrast in the former. These results suggest that for myocardial SPECT the 180 degrees collection method is a more effective technique in the clinical evaluation of coronary artery disease