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％。     

Heavy oil exposure induces high moralities in virus carrier Japanese flounder Paralichthys olivaceus

The relationship between chemical exposure and disease outbreak in fish has not been fully defined due to the limitations of experimental systems (model fish and pathogens). Therefore, we constructed a system using the Japanese flounder, Paralichthys olivaceus, and viral haemorrhagic septicemia virus (VHSV), and evaluated it by heavy oil (HO) exposure. The fish were exposed to HO at 0.3, 0.03, 0.003, and 0 g/L following VHSV infection at doses of 10(2.5) or 10(3.5) tissue culture infectious dose (TCID)50/fish. As a result, groups given the dual stressors showed more than 90% mortality. Although VHSV infection at 10(2.5) and 10(3.5) TCID50/fish without HO exposure also induced high mortality, at 68.8% and 81.3%, respectively, HO exposure induced faster and higher mortality in the virus carrier fish, indicating that chemical stressors raise the risk of disease outbreak in fish. The experimental system established in this study could be useful for chemical risk assessment.     

Statistical Analysis of Ground Motions Estimated on the Basis of a Recipe for Strong-motion Prediction: Approach to Quantitative Evaluation of Average and Standard Deviation of Ground Motion Distribution

For seismic hazard assessment, we study the variabilities of predicted ground motion on the basis of a ??recipe for predicting strong ground motion?? and propose approximations to evaluate spatial distributions of the standard deviation for PGV, R1.0, R2.0, and R5.0 in the estimated ground motions. For strong-motion prediction, we use a finite difference method for a long period range (>1.0?s). To estimate variabilities, a Monte Carlo simulation is used and we adopt the Latin Hypercube Sampling (LHS) technique to reduce computations. In this article, we consider only aleatory variabilities in source parameters among all possible variabilities, such as those in the source parameters, the propagation characteristics and site characteristics. Model sources are assumed for dip-slip fault and strike-slip fault, and the variabilities are considered for parameters such as asperity location, rupture starting point, average asperity slip contrast, stress drop and rupture velocity. On the target site, 100 instances of PGV, R1.0, R2.0 and R5.0 data are obtained for 100 sets of parameters and an average and a standard deviation of the log normal distribution, corresponding to the variability for ground motion estimation, are statistically analyzed. For all target sites uniformly distributed in the area around the faults, the average and the standard deviation are statistically analyzed and spread to spatial maps. It is found that the spatial distributions of standard deviation values for both the dip-slip and strike-slip faults are not uniform. Approximations are attempted to develop a quantitative evaluation for spatial distributions of the standard deviation of the log normal distribution for PGV, R1.0, R2.0, and R5.0. The spatial distributions by these approximations are considered to almost reconstruct the characteristics, which are statistically analyzed by the finite difference method.     

Jovian magnetosphere-ionosphere current system characterized by diurnal variation of ionospheric conductance

We developed a new numerical model of the Jovian magnetosphere-ionosphere coupling current system in order to investigate the effects of diurnal variation of ionospheric conductance. The conductance is determined by ion chemical processes that include the generation of hydrogen and hydrocarbon ions by solar EUV radiation and auroral electrons precipitation. The model solves the torque equations for magnetospheric plasma accelerated by the radial currents flowing along the magnetospheric equator. The conductance and magnetospheric plasma then change the field-aligned currents (FACs) and the intensity of the electric field projected onto the ionosphere. Because of the positive feedback of the ionospheric conductance on the FAC, the FAC is the maximum on the dayside and minimum just before sunrise. The power transferred from the planetary rotation is mainly consumed in the upper atmosphere on the dayside, while it is used for magnetospheric plasma acceleration in other local time (LT) sectors. Further, our simulations show that the magnetospheric plasma density and mass flux affect the temporal variation in the peak FAC density. The enhancement of the solar EUV flux by a factor of 2.4 increases the FAC density by 30%. The maximum density of the FAC is determined not only by the relationship between the precipitating electron flux and ionospheric conductance, but also by the system inertia, i.e., the inertia of the magnetospheric plasma. A theoretical analysis and numerical simulations reveal that the FAC density is in proportion to the planetary angular velocity on the dayside and to the square of the planetary angular velocity on the nightside. When the radial current at the outer boundary is fixed at values above 30 MA, as assumed in previous model studies, the peak FAC density determined at latitude 73°-74° is larger than the diurnal variable component. This result suggests large effects of this assumed radial current at the outer boundary on the system.     

Complete fragmentation of the parent bodies of Themis,Eos, and Koronis families

The fragmentation of the parent asteroids of the Themis, Eos, and Koronis families is investigated by considering mutual gravitational effects among the fragmented bodies. The masses of the parent asteroids and the kinetic and gravitational energies of the fragmented bodies are estimated. Comparison of these results and data from the laboratory impact experiments leads to the conclusion that the parent asteroids of the three families were completely fragmented at E_p/M of 10⁸ erg/g or more (E_p, impact energy; M, parent mass). However, since most of the fragments had low relative velocities many reaccumulated through mutual gravitation. The larger members in these families should have the rubble pile structures and hydrostatic equilibrium figures.     

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.     

The Mid-Atlantic Ridge between 29°N and 31°30′N in the last 10 Ma

The segmentation of the Mid-Atlantic Ridge between 29°N and 31°30′ N during the last 10 Ma was studied. Within our survey area the spreading center is segmented at a scale of 25–100 km by non-transform discontinuities and by the 70 km offset Atlantis Transform. The morphology of the spreading center differs north and south of the Atlantis Transform. The spreading axis between 30°30′N and 31°30′N consists of enéchelon volcanic ridges, located within a rift valley with a regional trend of 040°. South of the transform, the spreading center is associated with a well-defined rift valley trending 015°. Magnetic anomalies and the bathymetric traces left by non-transform discontinuities on the flanks of the Mid-Atlantic Ridge provide a record of the evolution of this slow-spreading center over the last 10 Ma. Migration of non-transform offsets was predominantly to the south, except perhaps in the last 2 Ma. The discontinuity traces and the pattern of crustal thickness variations calculated from gravity data suggest that focused mantle upwelling has been maintained for at least 10 Ma south of 30°30′ N. In contrast, north of 30°30′N, the present segmentation configuration and the mantle upwelling centers inferred from gravity data appear to have been established more recently. The orientation of the bathymetric traces suggests that the migration of non-transform offsets is not controlled by the motion of the ridge axis with respect to the mantle. The evolution of the spreading center and the pattern of segmentation is influenced by relative plate motion changes, and by local processes, perhaps related to the amount of melt delivered to spreading segments. Relative plate motion changes over the last 10 Ma in our survey area have included a decrease in spreading rate from 32 mm a⁻¹ to 24 mm a⁻¹, as well as a clockwise change in spreading direction of 13° between anomalies 5 and 4, followed by a counterclockwise change of 4° between anomaly 4 and the present. Interpretation of magnetic anomalies indicates that there are significant variations in spreading asymmetry and rate within and between segments for a given anomaly time. These differences, as well as variations in crustal thickness inferred from gravity data on the flanks of spreading segments, indicate that magmatic and tectonic activity are, in general, not coordinated between adjacent spreading segments.