TV Observation of the Daytime Meteor Shower; The Arietids

We have carried out multi-station TV observations since 1994 in order to determine the orbit of the Arietid daytime meteor stream. In 1999, one possible Arietid meteor was recorded by our simultaneous observations and its orbit was determined. In 2003, two Arietid meteors were observed from two stations of our observing site, those orbits were determined precisely, the orbital elements were in good agreement with each other. This is the first time that determination of the precise orbit of the Arietids has been made from optical observations. The orbit of these Arietid meteors, and comparison with the orbit obtained from radar observations are discussed.     

Effects of heavy oil in the developing spotted halibut, Verasper variegatus

It is well known that heavy oil (HO) on the sea surface causes serious problems in the aquatic environment. In particular, some species of teleosts which develop on the sea surface are thought to be affected by the HO which flows out from tankers or coastal industry. However, the toxicological effects of HO are not fully understood. We performed exposure experiments using the Pleuronectiformean fish, spotted halibut (Verasper variegatus), which is an important fishery resource in Japan. In course of the development, HO-exposed embryos showed remarkable delay in developmental processes including somite formation. We further observed abnormal development of the head morphology. Notably, treated embryos had relatively small eyes and craniofacial structures. These findings strongly suggest that HO seriously affects the cell proliferation and differentiation of the embryo. In addition, HO-exposed embryos showed abnormal neuronal development. We also performed the exposure in the larval stage. Treatment of post-hatching larvae with HO resulted in significantly greater mortality compared with controls. Through these observations, we finally conclude that HO is strongly toxic to halibut in their early life stages.     

Effects of deposit feeder Stichopus japonicus on algal bloom and organic matter contents of bottom sediments of the enclosed sea

Algae growing in an enclosed sea may inhibit eutrophication because they absorb nutrients in the water. However, dead algae often cause anaerobic conditions in the water just above and on sediment after they are deposited on the bottom. We found that Stichopus japonicus inhibited the anaerobic processes coupling water sulfite production in sediment. The present study investigates whether S. japonicus inhibits algal flourish and influences sediment properties such as organic matter contents. Aquarium experiments were carried out at Komatsushima port in Tokushima Prefecture, western Japan. The aquaria used in the experiments were supplied with water directly from the adjacent sea (6 L/min), laid with sand of 10 cm depths, and lighted at 12 h intervals. Six aquaria each containing a sea cucumber from Komatsushima port and six aquaria without any were used in the experiments. Water temperature ranged between 9 and 15 degrees C during December 2000 and April 2001. Salinity ranged between 32 per thousand and 34 per thousand. Algae began to cover the bottom of the aquaria without S. japonicus after 2 weeks, whereas no growth was evident in the aquaria containing sea cucumbers. Chlorophyll a concentration in the surface sediment of the aquaria with S. japonicus (6.1+/-3.6 microg/g, mean S.D.+/-standard deviation) was significantly lower than that without it (60+/-17 microg/g, U-test, p<0.05). Phaeophytin concentration in the surface sediment of the aquaria with S. japonicus (0.9+/-0.09 microg/g) was also significantly lower than that without it (4.5+/-1.0 microg/g, U-test, p<0.05). TOC concentration in the surface sediment of the aquaria with S. japonicus (2.6+/-1.3 microg/g) was slightly lower than that without it (4.0+/-1.2 microg/g). These results showed that algal biomass and organic matter concentration of the bottom were decreased in the presence of S. japonicus. Therefore, S. japonicus inhibits algal bloom and decrease the contents of organic matter deposited on the bottom of enclosed sea areas.     

The origin and formation of cuspy density profiles through violent relaxation of stellar systems

It is shown that the cuspy density distributions observed in the cores of elliptical galaxies can be realized by dissipationless gravitational collapse. The initial models consist of power-law density spheres such as ρ ∝ r ⁻¹ with anisotropic velocity dispersions. Collapse simulations are carried out by integrating the collisionless Boltzmann equation directly, on the assumption of spherical symmetry. From the results obtained, the extent of constant density cores, formed through violent relaxation, decreases as the velocity anisotropy increases radially, and practically disappears for extremely radially anisotropic models. As a result, the relaxed density distributions become more cuspy with increasing radial velocity anisotropy. It is thus concluded that the velocity anisotropy could be a key ingredient for the formation of density cusps in a dissipationless collapse picture. The velocity dispersions increase with radius in the cores according to the nearly power-law density distributions. The power-law index, n , of the density profiles, defined as ρ ∝ r ^{− n} , changes from n ≈2.1 at intermediate radii to a shallower power than n ≈2.1 toward the centre. This density bend can be explained from our postulated local phase-space constraint that the phase-space density accessible to the relaxed state is determined at each radius by the maximum phase-space density of the initial state.     

Global instability of thin stellar discs

We have determined the dominant global modes of stellar discs by integrating the linearized collisionless Boltzmann equation. The models examined are the Kuzmin discs with two types of the distribution function. It is found that the growth rate correlates well with the central value ofQ.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Late Paleozoic faults of the Altai region, Central Asia: tectonic pattern and model of formation

The present kinematic and dynamic analysis of large-scale strike-slip faults, which enabled the formation of a collage of Altai terranes as a result of two collisional events. The Late Devonian–Early Carboniferous collision of the Gondwana-derived Altai-Mongolian terrane and the Siberian continent resulted in the formation of the Charysh–Terekta system of dextral strike-slip faults and later the Kurai and Kuznetsk–Teletsk–Bashkauss sinistral strike-slip faults. The Late Carboniferous–Permian collision of the Siberian and Kazakhstan continents resulted in the formation of the Chara, Irtysh and North-East sinistral strike-slip zones. The age of deformation of both collisional events becomes younger toward the inner areas of the Siberian continent. In the same direction the amount of displacement of strike-slip faulting decreases from several thousand to several hundred kilometers. The width of the Late Paleozoic zone of deformation reaches 1500 km. These events deformed the accretion-collision continental margins and their primary paleogeographic pattern.     

Morphology and tectonics of the Yap Trench

We conducted swath bathymetry and gravity surveys the whole-length of the Yap Trench, lying on the southeastern boundary of the Philippine Sea Plate. These surveys provided a detailed morphology and substantial insight into the tectonics of this area subsequent the Caroline Ridge colliding with this trench. Horst and graben structures and other indications of normal faulting were observed in the sea-ward trench seafloor, suggesting bending of the subducting oceanic plate. Major two slope breaks were commonly observed in the arc-ward trench slope. The origin of these slope breaks is thought to be thrust faults and lithological boundaries. No flat lying layered sediments were found in the trench axis. These morphological characteristics suggest that the trench is tectonically active and that subduction is presently occurring. Negative peaks of Bouguer anomalies were observed over the arc-ward trench slope. This indicates that the crust is thickest beneath the arc-ward trench slope because the crustal layers on the convergent two plates overlap. Bouguer gravity anomalies over the northern portion of the Yap Arc are positive. These gravity signals show that the Yap Arc is uplifted by dynamic force, even though dense crustal layers underlie the arc. This overlying high density arc possibly forces the trench to have great water depths of nearly 9000 m. We propose a tectonic evolution of the trench. Subduction along the Yap Trench has continued with very slow rates of convergence, although the cessation of volcanism at the Yap Arc was contemporaneous with collision of the Caroline Ridge. The Yap Trench migrated westward with respect to the Philippine Sea Plate after collision, then consumption of the volcanic arc crust occurred, caused by tectonic erosion, and the distance between the arc and the trench consequently narrowed. Lower crustal sections of the Philippine Sea Plate were exposed on the arc-ward trench slope by overthrusting. Intense shearing caused deformation of the accumulated rocks, resulting in their metamorphism in the Yap Arc.     

银离子和含银不锈钢的抗菌性研究

基于银因其具有良好的广谱抗茵活性和低毒性而在医学方面有着较为广泛的应用,对银离子(硝酸银)和含银不锈钢的抗茵活性进行了初步研究。实验结果表明,在10^6CFu／mL的初始接种浓度下,银离子对枯草杆菌、大肠杆菌和假单胞茵的最小抑茵质量浓度和最小杀菌质量浓度分别为2,6,8mg／L和2,8,10mg／L。大肠杆菌经8mg／L的银离子处理2h后,有99．9％以上的细菌被破坏。含银不锈钢也表现了较强的抗菌性能。在普通的、银合金和银涂层的sus304不锈钢表面附着的单层生物膜浸泡在PBS溶液中3d后,经CFDA-DAPI双染色和荧光显微镜观察计数获得的假单胞菌的平均存活率为98．0％,38．5％和15．1％。