基于声学摄像仪的溯河洄游幼香鱼计数

至今主要靠目视计数来掌握香鱼(Plecoglossus altivelis)的资源量,这种方法很耗劳动力且精度低.由华盛顿大学研发的声学摄像仪DIDSON(Dual-frequency IDentification SONar)可在浑浊不清的水中摄取接近光学视频画质的图像.其附带软件虽可对体长为几十厘米的大个体鱼计数,但对于体长6 cm以下的小个体鱼,由于其回波信号弱,计数显得非常困难.本文提供了一种基于DIDSON的溯河洄游幼香鱼计数的新方法.首先从声学图像中消除静止的背景,提取出运动目标并除去噪音像素,然后用卡尔曼滤波器对剩下的目标进行跟踪,根据目标移动的特性把目标分为香鱼和垃圾2大类,在除去向下游移动的垃圾之后,可正确地计算向上游移动香鱼的数量.通过现场实测验证了上述声学计数方法的实用性和高效性.     

A time-series data analysis to examine effects of subsidies to fishery productions in Japan

A cointegration analysis is conducted to examine the effect of fishery subsidies on fisheries production using data compiled over more than 30 years in Japan. The results illustrate that one fishery production indicator (production value per fishermen) shows a positive relationship with one particular group of government financial transfer (GFT) (that is, government general service expenditures including cost for fishery managements, scientific researches, and other administrative activities). No other tested results between GFTs and fishery indicators showed a real relationship. Although further scrutiny is awaited, this study could provide an empirical basis for an argument that, under an effective fishing management system, fisheries subsidies do not necessarily cause production increases or negative impact on fishing stocks.     

Amorphous clay materials of towada ando soils

Towada Ando soils consisted of five soils—Towada-a (1,000 years old), Towada-b (2,000 years old), Chuseri (4,000 years old), Nanbu (8,600 years old), and Ninokura soils (10,000 years Amorphous clay materials of these soils taken at different localities were studied by the combined use of selective dissolution and differential infrared spectroscopy, X-ray analysis, electron microscopy, etc.

The main clay minerals of Towada-a soils, present-day soils, were montmorillonite-vermic-ulite chloritic intergrades and opaline silica, or these minerals and allophane in the humus horizons, and allophane in the non-humus ones. Towada-b soils overlain by the Towada-a soils showed the clay mineralogical constituents similar to those of Towada-a soils. However, allophane was one of the main clay minerals in all the humus horizons as well as non-humus ones. The main clay minerals of Chuseri soils were allophane and layer silicates consisting chiefly of chloritic intergrades and chlorite in the humus horizons, and allophane in the non-humus ones. Opaline silica was present in minor amounts in the humus horizons of Chuseri soils, but nearly absent in Nanbu and Ninokura soils.

There were remarkable differences in the clay mineralogical composition of Nanbu and Ninokura soils with differences of their environmental conditions. Allophane and imogolite Were dominant in the clay fractions of both humus and non-humus horizons of very shallowly buried Nanbu soil which was subjected to the strong leaching process. Allophane was the main clay mineral of deeply buried Nanbu and Ninokura soils which showed the absence of notable accumulation of bases and silica. On the contrary, halloysite with a small amount of siliceous amorphous material appeared in very deeply buried Nanbu and Ninokura soils where bases and silica were distinctly accumulated. The amounts of halloysite in the clay fractions were larger in the humus horizons than non-humus ones, and in Ninokura soil than Nanbu soil.

Soil age, soil organic matter, and depositional overburden of tephras were observed to be conspicuous among various factors relating to the weathering of amorphous clay materials in Towada Ando soils.     

Sites and processes of nutrient accumulation in the subsoil through water percolation from the plow layer in a submerged paddy soil microcosm

The leaching of nutrients from the plow layer by water percolation and their accumulation in the subsoil observed in a Japanese paddy field (Katoh et al. 2004: Soil Sci. Plant Nutr., 50, 721-729) were determined semi-quantitatively in a soil column experiment. Ca²⁺, Mg²⁺, K⁺, Mn²⁺, Fe²⁺, and phosphate in percolating water from the plow layer soil column were retained in the subsoil columns that were connected to the plow layer soil column. Fe²⁺, K⁺, and phosphate accumulated in the uppermost part of the subsoil. Accumulation of Fe²⁺ in the uppermost part of the subsoil was presmnably due to the cation exchange process with concomitant desorption of Ca²⁺. In contrast, Ca²⁺ and Mg²⁺ in percolating water from the plow layer soil colmnn accumulated once in the subsoil, and translocated downwards slowly with successive water percolation. Considerable amounts of inorganic carbon (IC) and dissolved organic carbon (DOC) in percolating water from the plow layer soil column were also retained in the subsoil columns. IC did not accumulate a gaseous form.     

A Spontaneous Oligodendroglioma in the Lumbar Portion of the Spinal Cord in a Young BrlHan:WIST@Jcl (GALAS) Rat

Oligodendroglioma is a rare tumor originating from oligodendrocytes found mainly in the cerebrum in aged rats. Only a few reports have shown spontaneous occurrence of this tumor in the spinal cord, and no report has mentioned its occurrence in young rats. We encountered a case of spontaneous oligodendroglioma in the lumbar portion of the spinal cord in a young (9 weeks old) female BrlHan:WIST@Jcl (GALAS) rat. Here we report the detailed histopathological and immunohistochemical characteristics of this case. No clinical signs, no gross lesions at necropsy, and no specific changes in hematology or blood biochemistry were observed. The tumor was located in the dorsal funiculus in the lumbar portion of the spinal cord and widely spread to the dorsal root nerve. The neoplastic cells showed a sheet-like growth pattern and had small round nuclei, clear cytoplasm and distinct cell borders that resulted in a honeycomb pattern. No mitotic figures or other histological lesions were observed. The neoplastic cells were positively stained for Olig2 and PCNA. The present case was considered to be a low-grade oligodendroglioma based on the histological and immunohistochemical features. To our knowledge, our case is considered to be extremely rare and the first report in a young rat.     

Itokawa dust particles: a direct link between S-type asteroids and ordinary chondrites

The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission and scanning electron microscope analyses indicate that the mineralogy and mineral chemistry of the Itokawa dust particles are identical to those of thermally metamorphosed LL chondrites, consistent with spectroscopic observations made from Earth and by the Hayabusa spacecraft. Our results directly demonstrate that ordinary chondrites, the most abundant meteorites found on Earth, come from S-type asteroids. Mineral chemistry indicates that the majority of regolith surface particles suffered long-term thermal annealing and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid.     

Mechanism of self-sterility in a hermaphroditic chordate

Hermaphroditic organisms avoid inbreeding by a system of self-incompatibility (SI). A primitive chordate (ascidian) Ciona intestinalis is an example of such an organism, but the molecular mechanism underlying its SI system is not known. Here, we show that the SI system is governed by two gene loci that act cooperatively. Each locus contains a tightly linked pair of polycystin 1-related receptor (s-Themis) and fibrinogen-like ligand (v-Themis) genes, the latter of which is located in the first intron of s-Themis but transcribed in the opposite direction. These genes may encode male- and female-side self-recognition molecules. The SI system of C. intestinalis has a similar framework to that of flowering plants but utilizing different molecules.