A molecular face-on view of the Galactic Centre region   总被引：1，自引：0，他引：1  

Tsuyoshi Sawada  Tetsuo Hasegawa  Toshihiro Handa  R. J. Cohen 《Monthly notices of the Royal Astronomical Society》2004,349(4):1167-1178

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Melt inclusion analysis of the Unzen 1991–1995 dacite: implications for crystallization processes of dacite magma     

Koshi Nishimura  Tatsuhiko Kawamoto  Tetsuo Kobayashi  Takeshi Sugimoto  Shigeru Yamashita 《Bulletin of Volcanology》2005,67(7):648-662

Dacitic magma, a mixture of high-temperature (T) aphyric magma and low-T crystal-rich magma, was erupted during the 1991–1995 Mount Unzen eruptive cycle. Here, the crystallization processes of the low-T magma were examined on the basis of melt inclusion analysis and phase relationships. Variation in water content of the melt inclusions (5.1–7.2 wt% H₂O) reflected the degassing history of the low-T magma ascending from deeper levels (250 MPa) to a shallow magma chamber (140 MPa). The ascent rate of the low-T magma decreased markedly towards the emplacement level as crystal content increased. Cooling of magma as well as degassing-induced undercooling drove crystallization. With the decreasing ascent rate, degassing-induced undercooling decreased in importance, and cooling became more instrumental in crystallization, causing local and rapid crystallization along the margin of the magma body. Some crystals contain scores of melt inclusions, whereas there are some crystals without any inclusions. This heterogeneous distribution suggests the variation in the crystallization rate within the magma body; it also suggests that cooling was dominant cause for melt entrapment. Numerical calculations of the cooling magma body suggest that cooling caused rapid crystal growth and enhanced melt entrapment once the magma became a crystal-rich mush with evolved interstitial melt. The rhyolitic composition of melt inclusions is consistent with this model.Editorial responsibility: H Shinohara  相似文献   

A search for millimeter wave spectral lines from comet Sugano-Saigusa-Fujikawa (1983e)     

Tetsuo Hasegawa  Masatoshi Ohishi  Masaki Morimoto  Hiroko Suzuki  Norio Kaifu 《Icarus》1984,60(1):211-214

The search for radio spectral lines from Comet Sugano-Saigusa-Fujikawa (1983e) was conducted using the 45-m telescope of Nobeyama Radio Observatory. The frequency ranges of 44.0–46.0 and 47.5–49.5 GHz were surveyed down to $\text{ΔT}{}_{\mathrm{<mtext>A</mtext>}}{}^1\text{(}\text{rms}\text{) = 20–30}\text{mK}$, with a beam size of ～35 arc sec. Upper limits have been established for spectral lines of atomic hydrogen, CS, OCS, SO₂, H₂CO, CH₃OH, HCCCCCN, HCOOCH₃, CH₃OCH₃, and CH₃CH₂CN. The J = 5?4 line from HCCCN in the vibrational ground state possibly has been detected but not confirmed. The suggested total amount of HCCCN in the coma is consistent with the possible picture that HCCCN is the main parent molecule of CN.  相似文献   

A model with rigid rotations and slip deficits for the GPS-derived velocity field in Southwest Japan     

Sou Nishimura  Manabu Hashimoto   《Tectonophysics》2006,421(3-4):187-207

We interpret the GPS-derived velocity field in southwest Japan by a superposition of the elastic deformation caused by fault interactions (slips or slip deficits) on the rigid motion of tectonic blocks (or plates). Based on the strain rate field and crustal seismicity, we apply a model with three blocks (Inner Arc, Outer Arc, and the northern Ryukyu block) and slip deficits along the block boundaries.Several characteristics of the synthesized contributions are found:

(1) Westward motion of the outer arc relative to the Amurian plate and the inner arc,

(2) southeastward motion of the northern Ryukyu block relative to the Amurian plate,

(3) 2−4 mm/yr deficits of left lateral slip rates along the boundary at 32°N in southern Kyushu,

(4) 0−8 mm/yr deficits of right lateral slip rates along the Median Tectonic Line and the Beppu-Shimabara Graben,

(5) slip deficit rates on the plate interface smaller than those in the case without any consideration for rigid block motions,

(6) clockwise deflection of slip deficit rate vector on the plate interface from that estimated when not taking rigid block motions into consideration.

Analysis of primary production in the Seto Inland Sea, Japan, using a simple ecosystem model     

Toshiya Hashimoto  Hidetaka Takeoka 《Journal of Oceanography》1998,54(2):123-132

A simple model of lower trophic level ecosystem has been created to analyze possible environmental control of primary production in eight sub-areas of the Seto Inland Sea. The primary production rates observed by Hashimotoet al. (1997a) in these sub-areas are well reproduced by the model, including horizontal processes such as horizontal transport of nutrients and vertical processes such as vertical mixing, light intensity and sinking of particulate matter. Without taking account of horizontal processes the model also successfully reproduces the observed primary production rates in some areas, but if fails to reproduce those in the others. This shows that the relative importance of the horizontal transport on the primary production differs are by area. Two time scales,T _z andT _H, are introduced to explain this difference.T _z is a vertical cycling time of material, which is defined as the time during which the stock of the material in the water column is utilized for primary production;T _H is the horizontal transit time of the material. The relative importance of the horizontal process is well explained by theT _H/T _z ratio; that is, the horizontal transport process is important in the areas where this ratio is small. Further the possible mechanisms of nutrient supply for the primary production in each sub-area are investigated using this model.  相似文献   

Variations in snowmelt energy and energy balance characteristics with larch forest density on Mt Iwate,Japan: observations and energy balance analyses     

Kazuyoshi Suzuki  Takeshi Ohta  Atsushi Kojima  Tetsu Hashimoto 《水文研究》1999,13(17):2675-2688

The variation in snowmelt energy and energy components were evaluated with respect to forest density. Surface snowmelt rates, surface evaporation from snow cover and meteorological elements were measured in the open and under sparse (411 trees/ha) and dense (1433 trees/ha) larch canopies. The surface snowmelt rate decreased as the forest density increased. Based on the observations and energy balance analyses, we concluded the following. (1) Albedo decreased while the bulk coefficient for latent heat increased with forest density. (2) The duration of snowmelt increased with forest density because the energy for nocturnal cooling of the snow cover decreased. (3) When comparing the open and forested sites, the changes in snowmelt energy with forest density were caused by sensible heat flux. However, the contribution of net radiation was highest in the forested sites. Therefore, the effects of forest cover on the snowmelt energy were different when comparing both the open and forested sites and the sparse and densely forested sites. (4) The ratio of net radiation to snowmelt energy increased with forest density; although both snowmelt energy and net radiation decreased with increased forest density, the snowmelt energy decreased more rapidly. Sensible heat also decreased as forest density increased. Both albedo and downward long‐wave radiation influenced net radiation. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Holocene paleolimnological changes in Lake Skallen Oike in the Syowa Station area of Antarctica inferred from organic components in a sediment core (Sk4C-02)     

Genki I. Matsumoto  Yukinori Tani  Koji Seto  Tomoko Tazawa  Masumi Yamamuro  Takahiro Watanabe  Toshio Nakamura  Tetsuo Takemura  Satoshi Imura  Hiroshi Kanda 《Journal of Paleolimnology》2010,44(2):677-693

Antarctic climate changes influence environmental changes at both regional and local scales. Here we report Holocene paleolimnological changes in lake sediment core Sk4C-02 (length 378.0 cm) from Lake Skallen Oike in the Soya Kaigan region of East Antarctica inferred from analyses of sedimentary facies, a range of organic components, isotope ratios of organic carbon and nitrogen, and carbon-14 dating by Tandetron accelerator mass spectrometry. The sediment core was composed of clayish mud (378.0–152.5 cm) overlain by organic sediments (152.5 cm-surface). The age of the surface and the core bottom were 150 (AD1950-1640) and ca. 7,030 ± 73 calibrated years before present (cal BP), respectively, and the mean sedimentation rate was estimated to be 0.55 mm/year. Multi-proxy analyses revealed that the principal environmental change in the core is a transition from marine to lacustrine environments which occurred at a depth of 152.5 cm (ca. 3,590 cal BP). This was caused by relative sea level change brought about by ongoing retreat of glaciers during the mid-Holocene warming of Antarctica, and ongoing isostatic uplift which outpaced changes in global (eustatic) sea level. The mean isostatic uplift rate was calculated to be 2.8 mm/year. The coastal marine period (378.0–152.5 cm, ca. 7,030–3,590 cal BP) was characterized by low biological production with the predominance of diatoms. During the transition period from marine to freshwater conditions (152.5-approximately 135 cm, ca. 3,590–3,290 cal BP) the lake was stratified with marine water overlain by freshwater, with a chemocline and an anoxic (sulfidic) layer in the bottom of the photic zone. Green sulfur bacteria and Cryptophyta were the major photosynthetic organisms. The Cryptophyta appeared to be tolerant of the moderate salinity and stratified water conditions. The lacustrine period (approximately 135 cm-surface, ca. 3,290 cal BP-present) was characterized by high biological production by green algae (e.g. Comarium clepsydra and Oedegonium spp.) with some contributions from cyanobacteria and diatoms. Biological production during this period was 8.7 times higher than during the coastal marine period.  相似文献   

Anomalous change in atmospheric radon concentration sourced from broad crustal deformation: A case study of the 1995 Kobe earthquake     

Yumi Yasuoka  Yusuke Kawada  Yasutaka Omori  Hiroyuki Nagahama  Tetsuo Ishikawa  Shinji Tokonami  Masahiro Hosoda  Tetsuo Hashimoto  Masaki Shinogi 《Applied Geochemistry》2012

Before the Kobe earthquake, an anomalous increase in atmospheric Rn concentration was observed. By separating the measured concentration of atmospheric Rn into three components according to the distance from the monitoring station, the variation of Rn exhalation rate can be estimated for the respective area using the daily minimum and maximum concentrations. The mean rate of Rn exhalation gradually increased in an area of 20 km around the monitoring station, becoming five times higher than normal in the period between October 1994 and the date of the earthquake. This area had a large co-seismic displacement of up to 30 cm, which roughly corresponds to the crustal strain of 10⁻⁶-order, and it is considered the main source for the atmospheric Rn prior to the Kobe earthquake. Analyses revealed that the pre-seismic change in the atmospheric Rn concentration exhibited an anomalous pattern which would yield information on the spatial distribution of the mechanical response of the ground.  相似文献   

Thermal equation of state of Mg3Al2Si3O12 pyrope garnet up to 19?GPa and 1,700?K     

Yongtao Zou  Steeve Gréaux  Tetsuo Irifune  Matthew L. Whitaker  Toru Shinmei  Yuji Higo 《Physics and Chemistry of Minerals》2012,39(7):589-598

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Analytical methods for error propagation in planar space–time prisms     

Tetsuo Kobayashi  Harvey J. Miller  Walied Othman 《Journal of Geographical Systems》2011,13(4):327-354

The space–time prism demarcates all locations in space–time that a mobile object or person can occupy during an episode of potential or unobserved movement. The prism is central to time geography as a measure of potential mobility and to mobile object databases as a measure of location possibilities given sampling error. This paper develops an analytical approach to assessing error propagation in space–time prisms and prism–prism intersections. We analyze the geometry of the prisms to derive a core set of geometric problems involving the intersection of circles and ellipses. Analytical error propagation techniques such as the Taylor linearization method based on the first-order partial derivatives are not available since explicit functions describing the intersections and their derivatives are unwieldy. However, since we have implicit functions describing prism geometry, we modify this approach using an implicit function theorem that provides the required first-order partials without the explicit expressions. We describe the general method as well as details for the two spatial dimensions case and provide example calculations.  相似文献