Development of the Emulsion Chamber Detector for Space Observations

The emulsion chamber detector on board the “ShiJian-8” satellite is the first one in China designed especially for observing in space the highenergy electrons and γ-rays. In this paper, the principle of the detector design, the method of data processing and the preliminary results of observations are introduced. The design lifetime of the detector is 15 days on the orbit, and the energy range of detectable particles is 100GeV∼5TeV.     

Some regular patterns in the distribution of sediment contamination in the coastal waters along Japan

Observations of sediment contamination along the coast of Japan were analyzed. When the pollutant concentration is divided by the fine particle fraction in the sediment, a regular pattern is observed in the quantitative relationship among the degree and the area of contamination and the discharge rate of pollutant released continuously into the water along the coast. This regularity was observed with respect to COD,n-hexane soluble substances and heavy metals, and could be expressed by a formula.Polluted particles were supposed to disperse through suspension in the bottom water layer, and thus their distribution in the surface sediment is expected to become similar to effluent dispersion in the surface water.     

近岸波生流数值计算的一种新方法

运用Hardy-Cross法的基本原理建立了一种波生流计算的数值模型.本方法在维持计算稳定性方面表现出色,解决了以往的计算方法所存在的计算不稳定的根本缺陷,但是运用这一方法进行实际问题计算时还明显存在计算收敛缓慢的现象,对此,在探讨计算收敛原因的基础上,提出了同心矩形回路补正、粗网格计算初始值等对策.运用这些对策成功地提高了计算的效率和精度.最后通过计算例验证表明,运用本方法既能有效地维持计算的稳定,又能有效地解决局部缓和法所固有的计算效率低的问题,从而为研究和预测海岸工程对地形及环境变化影响问题提供了合理、实用的方法.     

Distributions of Water Masses and Currents in Tachibana Bay, West of Ari-ake Sound, Kyushu, Japan

We have investigated the water mass distribution and circulation in Tachibana Bay, which is located in the junction area between Ari-ake Sound and Amakusa-Nada in western Kyushu, Japan. This was done to clarify the mechanism by which ghost shrimp larvae, originating from a sandflat of Amakusa-Shimoshima Island, are transported. Temperature and salinity data repeatedly obtained over the area of Tachibana Bay show that relatively low salinity water lies over northern part of the bay, while high salinity water lies over southern part of the bay. The location of the low salinity water margin tends to depend on the amount of rainfall several days before the observation. A large amount of rainfall makes a clear boundary between low and high salinity waters. Current velocity data indicate an eastward mean flow just north of Tomioka, northern tip of Amakusa-Shimoshima Island, and a clockwise mean flow approaching the Tomioka Bay sandflat, which should be suitable for the on-shore transport of the ghost shrimp postlarvae. Current measurements with shipboard ADCP just west of Hayasaki Strait, at the entrance of Ari-ake Sound, show that a westward tidal residual current tends to incline to the north, with evidence of a density current in the northern part of the western Hayasaki Strait.     

Hypernovae and Gamma-Ray Bursts

The nature of very energetic supernovae (hypernovae) is discussed. They are the explosive death of stars more massive than ~20–25M _⊙, probably linked to the enigmatic Gamma-Ray Bursts. The optical properties of hypernovae indicate that they are significantly aspherical. Synthetic light curves and late-phase spectra of aspherical supernova/hypernova models are presented. These models can account for the optical observations of SNe 1998bw and 2002ap. The abundance patterns of hypernovae are characterized by large ratios (Zn, Co)/Fe and small ratios (Mn, Cr)/Fe, indicating a significant contribution of hypernovae to the early Galactic chemical evolution.     

Mercury concentration in the ocean

Seventy percent of 342 seawater samples collected in the Bering Sea, North and South Pacific, Japan Sea, East and South China Seas, and Indian Ocean had concentrations of “total” mercury ranging from 3 to 6 ng Hg l^?1 with an arithmetic mean of 5.3 ng l^?1 and a geometric mean of 5.0 ng l^?1. In some cases, a higher concentration was observed at the surface, at the halocline or thermocline, or in the bottom water. But in general, there was no consistent correlation between mercury concentration and depth, except for a statistical tendency for mercury concentration to be slightly higher in the surface water. This tendency suggests that mercury in the ocean is supplied from the atmosphere by rain washout. The latitudinal variation of surface mercury concentrations showed that the maximum concentration at each latitude decreased from 40°N to 30°S. This variation provides evidence that atmospheric mercury is emitted mainly from continental areas naturally or anthropogenically.     

Submersible observations of manganese nodule and crust deposits on the Tenpo Seamount,Northwestern Pacific

Pavements of manganese nodules and crusts and outcrops of Miocene limestones were observed on the flanks and flat top of the Tenpo Seamount during three Shinkai 2000 dives. The pre‐Miocene volcano supplied nuclei of volcanic rocks and hydrothermal manganese deposits, and subsequent slow or no sedimentation promoted deposition of abundant hydrogenetic nodules and crusts, mainly on the upper flank of the seamount. Nodule pavements generally cover calcareous sand surface sediments, while crusts cover hard outcrops composed probably of volcanic rocks. The fields of crusts and nodules are sparsely distributed with each other on scales of meters to tens of meters. The on‐site observation suggests the deposits have encountered tectonic and/or mass movements that resulted in unusual occurrences of densely stacked nodules and occasionally the nodules resting directly on crusts or hard substrates. Mineralogical and chemical compositions reveal that for nodules and crusts the encrusting manganese layers of around 1 cm thickness are composed of hydrogenetic vernadite, and diagenetic influence is negligible.     

Volcanic and Seismic Swarm Events on the Reykjanes Ridge and Their Similarities to Events on Iceland: Results of a Rapid Response Mission

On 21 May 1989, a major earthquake swarm on the Reykjanes Ridge at59°44 N, 29°32 W at a water depth of about 1000 m andabout 500 km southwest of Iceland was detected on both the WorldwideStandard Seismic Network (WWSSN) and Icelandic seismic networks. As part ofa multi-institutional response to this swarm, the Naval ResearchLaboratory arranged for a P3 Orion Aircraft to deploy sonobuoys and AXBTs inthe immediate vicinity of the swarm activity. The detection of the swarmmotivated a survey of the region in 1990, using the towed SeaMARC IIside-looking sonar system. In 1990–1991 the Russian ShirshovInstitute of Oceanology offered the use of its MIR deep-divingsubmersibles to investigate the rise axis for recent volcanism. During 1992,a scientific team comprised of five US and ten Russian scientists mobilizedthe twin, deep diving Russian submersibles to study the spreading axis ofthe Reykjanes Ridge. The resulting data analyses allows us to conclude thatthe 1989 seismic swarm event occurred adjacent to and east of the largeaxial high in the center of our survey area. The length, width and depthrange of the earthquakes were very similar to major seismic swarm eventsconfined to fissure systems in the Krafla region of Iceland. It is likelythat the earthquake swarm was located on a fresh, well-defined systemof fissures and faults extending south of the northernmost axial highstudied. The earthquake swarm was probably associated with an emanation oflava creating a region of high backscatter, located just to the east of thecentral axial high. In addition, the region of high-backscatterremains unsampled because it lay underneath the nadir of the processedSeaMARC tracks used to plan the submersible survey. However many sampleswere taken and structural studies of the evolving Reykjanes Ridge werecarried out.