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1.
J. Rajchl J. Bočcek D. Očenáš J. Škvarka P. Zimnikoval H. Murayama K. Ohtsuka 《Earth, Moon, and Planets》1995,68(1-3):479-486
Some results following from two contemporary photographical programs (Slovakia and Japan) for persistent meteor train spectra are compared. It shows that even though both programs are not too different according to their lenses and films used, the spectral interval detected is very different. In this respect prism as a dispersion element is more favourable than the grating with blaze wavelength near 610 nm. However, some results previously assumed as typicai for presented persistent trains-e.g. the forbidden Herzberg O2 emission, the NO2 continuum and OH red emissions-seem to be substanciated especially due to higher and linear dispersion of those grating spectra. 相似文献
2.
Sea‐surface temperature and salinity changes in the northwest Pacific since the Last Glacial Maximum
The oxygen isotope records of both benthic and planktonic Foraminifera in five piston cores, collected from the region between the Oyashio and Kuroshio Currents near Japan, clearly show the marked latitudinal shifts of these two currents during the past 25 kyr. Under the present hydrographic condition, a clear relationship between the sea‐surface temperature (SST) and oxygen isotope differences from benthic to planktonic Foraminifera is observed in this region. Using this relationship, we find decreased SSTs of 12–13°C (maximum 15°C) in the southernmost core site at the Last Glacial Maximum (LGM), indicating the Oyashio Current shifted southward. The SSTs at the southern two core sites abruptly increased more than 10°C at 10–11 ka, suggesting the Kuroshio Current shifted northward over these sites at 10–11 ka. In contrast, the northern two core sites have remained under the influence of the cold Oyashio Current for the past 25 kyr. With the reasonable estimate of bottom‐water temperature decrease of 2.5°C at the LGM, the SSTs estimated by this new method give exactly the same SST values calculated from Mg/Ca ratio of planktonic Foraminifera, allowing palaeosea‐surface salinities to be reconstructed. The result suggests that the ice volume effect was 1.0 ± 0.1‰ at the LGM. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
3.
4.
A comparative study of blue and green beryl crystals (from the region of Governador Valadares, Minas Gerais, Brazil) using electron paramagnetic resonance (EPR) and optical absorption (OA) spectroscopy is reported. The EPR spectra show that Fe3+ in blue beryl occupies a substitutional Al3+ site and in green beryl is localized in the structural channels between two O6 planes. On the other hand the infrared spectra show that the alkali content in the blue beryl is mostly at substitutional and/or interstitial sites and in green beryl is mostly in the structural channels. The OA spectra show two types of Fe2+. Thermal treatments above 200° C in green beryl cause the reduction of Fe3+ into Fe2+ accompanied by a change of color to blue. The blue beryl color does not change on heating. The kinetics of the thermal conversion of Fe3+ into Fe2+ is composed of two first order processes; the first one has an activation energy ΔE 1=0.30 eV and the second one has an activation energy ΔE 2=0.46 eV. 相似文献
5.
This paper discusses the situation of sea navigation in south East Asia focusing on the Strait of Malacca. The strait links
the Indian and Pacific oceans, which is considered one of the busiest in several narrow channels around the world. The paper
highlights the significance of the strait to global maritime trade, volume of traffic, and rising environmental and social
consequences in the strait. A feasibility study of constructing a new shipping canal in the South Thai Kra Isthmus as an alternative
option of Malacca route had been studied since 19th century. The paper explores suitable sites for a potential shipping canal
in the Kra Isthmus using physiographic spatial data i.e., elevation, sea charts, geology, soils and river systems. Each spatial
data was considered as a separate decision variable for site evaluation. Separate evaluation criterions were prepared for
each variable based on shipping canal requirements. Overlaying the maps in GIS environment, the variables were carefully evaluated,
and five geographic sites for the canal were derived. The length of the shipping canal over sea and land was computed for
each site. Site B located in south of Ranong and Chumphon provinces, was the shortest one, whereas site C in Surat Thani,
Pangnna and Krabi provinces was the longest. However, each site consisted of benefits and constraints. 相似文献
6.
Hitoshi Chiba Minoru Kusakabe Shin-Ichi Hirano Sadao Matsuo Shigeyuki Somiya 《Earth and Planetary Science Letters》1981,53(1):55-62
Oxygen isotope exchange between anhydrite and water was studied from 100 to 550°C, using the partial equilibrium method. The exchange rate was extremely low in NaCl solution. In the lower-temperature range, acid solutions were used to produce sufficient reaction to determine the oxygen isotope fractionation factors. The fractionation factors obtained in the present study are definitely different from those given by Lloyd [8]. They are similar to those for the HSO4?-water system studied by Mizutani and Rafter [19], and are consistently 2‰ higher than those of the barite-water system by Kusakabe and Robinson [5]. The temperature dependence of the oxygen isotope fractionation factors was calculated by the least squares method in which the weight was taken to be inversely proportional to the experimental error. The fractionation is given by:103lnαanhydrite-water=3.21×(103/T)2?4.72Available δ18O values of natural anhydrite were used to test the validity of this expression. It is shown that this newly revised geothermometer can be successfully applied to natural hydrothermal anhydrite. 相似文献
7.
8.
Shinsuke Abe Noboru Ebizuka Hideyuki Murayama Katsuhito Ohtsuka Satoru Sugimoto Masa-yuki Yamamoto Hajime Yano Jun-ichi Watanabe Jiří Borovička 《Earth, Moon, and Planets》2004,95(1-4):265-277
Spectra of persistent meteor trains were observed at wavelength between 300 and 930 nm. Two obtained train spectra during
the 1998 and 2001 Leonid meteor showers are reported here. During the 1998 Leonids, one train was detected by a photographic
camera with a spectrograph covering 370–640 nm region. On the other hand, during the 2001 Leonids, video observations were
carried out using image intensified cameras in ultraviolet (UV), visible and near infrared (near-IR) wavelengths. Temperatures
in persistent trains have been measured by atmospheric O2 A(0,1) band at the wavelength near 864.5 nm. From a video spectrum obtained just 7 s after parent fireball’s flare, a rotational
temperature of 250 K at altitude of 88.0±0.5 km was estimated. We can say that the cooling time scale of train strongly depends
on the initial mass of its fireball at least for Leonids. Based on cooling constant calculated from our results, we estimated
a temperature of ∼
∼130 K as a final exothermic temperature at early stage of persistent trains. 相似文献
9.
In April 1969, the chondrite was accidentally found in the side wall of the vegetable storage excavated at Shibayama-machi, Sanbu-gun, Chiba-ken, Japan, by Mr. A. Ishii and his grandson, Mr. S. Ito. The chondrite named Shibayama has been weathered thoroughly for a long period of burial underground. The bulk chemical composition, especially total Fe (21.41%) and ratios of Fetotal/SiO2(0.557), SiO2/MgO (1.59) and molar composition of olivine (Fa23) and pyroxene (Fs22) as well as mineral composition, indicate that Shibayama is a typical olivine-hypersthene chondrite. If the oxidized Fe is assumed only from metallic Fe, the original metallic Fe (7.75%) and Femetal/Fetotal(0.361) also support the above conclusion. From the well-recrystallized texture, indistinct and obliterated chondrule-matrix boundary, homogeneous composition of olivine and pyroxene, absence of igneous glass, and interstitial and well-developed plagioclase, this chondrite could be classified in petrologic type 6. Mosaic texture, kink bands, undulatory extinction of silicate grains and maskelynitization of plagioclase indicate that Shibayama suffered from a heavy shock effect, as is seen in other L-6 group chondrites. 相似文献
10.
Summary. Palaeomagnetic studies require a theory of magnetization mechanism of sediments and a method of estimating magnetic field intensity from their remanences. This paper establishes a physical basis for the generation of the remanence in deep-sea and lake sediments experimentally.
Redeposition experiments have been carried out under centrifugal force in weak magnetic fields. The centrifuging method produces post-depositional remanent magnetization (post-DRM) in the compacted sediment, and its remanence and susceptibility are compatible with those of natural sediments and reconstituted materials of other redepositional experiments. Three properties of the post-DRM have been deduced from the experiments: (1) the efficiency of acquisition of post-DRM decreases with increase in density during the compaction process, (2) the total post-DRM is equal to the sum of the partial post-DRM (addition law), and (3) time is not a substantial factor for alignment of the magnetic particles. These results lead to the conclusions that the magnetic particles do not rotate steadily but in a series of steps, and that the density change is the crucial factor giving rise to the post-DRM.
A mathematical formula representing the remanence record in sediments is proposed on the basis of the experimental results and the model. The principal equation is expressed as an integral of the product of three parameters over time when sediments have been compacted; the field intensity variation, characteristic function of the sediment and the time derivative of the density change. 相似文献
Redeposition experiments have been carried out under centrifugal force in weak magnetic fields. The centrifuging method produces post-depositional remanent magnetization (post-DRM) in the compacted sediment, and its remanence and susceptibility are compatible with those of natural sediments and reconstituted materials of other redepositional experiments. Three properties of the post-DRM have been deduced from the experiments: (1) the efficiency of acquisition of post-DRM decreases with increase in density during the compaction process, (2) the total post-DRM is equal to the sum of the partial post-DRM (addition law), and (3) time is not a substantial factor for alignment of the magnetic particles. These results lead to the conclusions that the magnetic particles do not rotate steadily but in a series of steps, and that the density change is the crucial factor giving rise to the post-DRM.
A mathematical formula representing the remanence record in sediments is proposed on the basis of the experimental results and the model. The principal equation is expressed as an integral of the product of three parameters over time when sediments have been compacted; the field intensity variation, characteristic function of the sediment and the time derivative of the density change. 相似文献