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311.
Attachment and feeding of pelagic copepods on larvacean houses 总被引:3,自引:0,他引:3
The attachment and feeding of pelagic copepods on discarded and occupied oikopleurid larvacean houses were investigated from May 1989 to August 1991 at an offshore station in the Nansei Islands, which is strongly influenced by the Kuroshio Current, and an inshore station in the central Seto Inland Sea.Oncaea spp.,Microsetella norvegica, and other calanoid and cyclopoid copepods were found attached onto discarded and occupied houses throughout the year at the offshore station, whereas neither discarded nor occupied houses, carried copepods at the inshore station at any time. The feeding behavior ofOncaea sp. in a discarded house was observed with a video tape recorder system. 相似文献
312.
Mid-pacific mountains revisited 总被引:1,自引:0,他引:1
The Mid-Pacific Mountains are guyots whose volcanic pedestals have been constructed on a broad basement plateau, the flanks of which are downfaulted. Edifice construction may have been controlled by an orthogonal system of intersecting faults trending roughly ENE and NNW. Low amplitude gravity anomalies observed over the Mid-Pacific Mountains indicate complete Airy-Heiskanen isostatic compensation, crustal thickening, and eruption on thin elastic lithosphere. Tholeiites of the Mid-Pacific Mountains resemble lavas of Iceland and the Galapagos Islands. The orthogonal fault system, low gravity anomalies, and lava chemistry of the Mid-Pacific Mountains can be explained by eruption on or near a great ENE-trending rift system. 相似文献
313.
Yoshiaki Toba Masayuki Tokuda Kuniaki Okuda Sanshiro Kawai 《Journal of Oceanography》1975,31(5):192-198
Wind-wave tunnel experiments reveal, by use of techniques of the flow visualization, that wind waves are accompanied by the wind drift surface current with large velocity shear and with horizontal variation of velocity relative to the wave profile. The surface current converges from the crest to a little leeward face of the crest, making a downward flow there, even though the wave is not breaking. Namely, wind waves are accompanied by forced convections relative to the crests of the waves. Since the location of the convergence and the downward flow travels on the water surface as the crest of the wave propagates, the motion as a whole is characterized by turbulent structure as well as by the nature of water-surface waves. In this meaning, the term of real wind waves is proposed in contrast with ordinary water waves. The study of real wind waves will be essential in future development of the study of wind waves. 相似文献
314.
A high-resolution downward surface solar radiation (DSSR) dataset has been produced using geostationary meteorological satellite
measurements. Its validation with in situ observations shows that the daily satellite DSSRs are highly accurate. Comparing
the satellite DSSRs with reanalysis DSSR datasets, the former has higher probability density in a low value range, and lower
density in a high value range. Overestimations of the reanalysis DSSR are significant in the low range. Correlations between
the reanalysis DSSRs and the satellite DSSR are relatively low in the tropics. It is suggested that the satellite DSSRs have
good potential to capture cloud behavior in the tropics. 相似文献
315.
316.
Observational data on air-sea boundary processes at the Shirahama Oceanographic Tower Station, Kyoto University, obtained in November, 1969, was analyzed and presented as an example representing the structure of growing wind-wave field. The condition was an ideal onshore wind, and the data contained continuous records of the wind speed at four heights, the wind direction, the air and water temperatures, the tides, and the growing wind waves, for more than six hours. The main results are as follows. Firstly, in both of the wind speed and the sea surface wind stress, rather conspicuous variations of about six-minute period were appreciable. Secondly, the three-seconds power law and its lemma expressed byH
*=BT
*3/2 and=2BT
*–1/2, respectively, are very well supported by the data, whereH
*(gH/u
*
2) andT
*(gT/u
*) are the dimensionless significant wave height and period, respectively, the wave steepness,u
* the friction velocity of air,g the acceleration of gravity, andB=0.062 is a universal constant. Thirdly, the spectral form for the high-frequency side of the spectral maximum is well expressed by the form of()=
sgu*–4, where is the angular frequency and() the spectral density. The value of
s is determined as 0.062±0.010 from the observational data. There is a conspicuous discrepancy between the spectral shape of wind waves obtained in wind-wave tunnels and those in the sea, the former containing well-defined higher harmonics of the spectral peak, and consequently there is an apparent difference in the values of
s also. However, it is shown that the discrepancy of
s may be eliminated by evaluating properly the energy level of the spectral form containing higher harmonics. 相似文献
317.
Masashi Taguchi Kenji Yasuda Shozo Toda Makoto Shimizu 《Marine environmental research》1979,2(3):239-249
Concentrations of Hg, Zn, Fe, Cd and Cu in the muscle tissues of a dogfish, Squalus mitsukurii, were determined by atomic absorption spectrometry and found to be in the ranges of f0·019–2·13, 1·8–3·6, 1·5–5·7, 0·001–0·018 and 0·12–0·70 μg/g wet weight, respectively. The frequency distributions of concentrations, with the exception of mercury, were found to be log-normal. The correlation coefficient between mercury content and total length was positive and large and statistically highly significant. For other metals negative correlations were observed. Mercury concentration in the muscle was found to increase in proportion to the total length cubed. Regression of mercury concentration on age of sharks was shown to be linear. Analysis of covariance showed that the difference between sexes was not statistically significant, either in slope or in height. The concentration of mercury in the muscle tissues of embryos was considerably lower, Cd roughly the same and Zn and Fe higher than those of mothers. The concentrations of Zn, Fe and Cu are higher in the embryonic stage and immediately after birth than in later stages of growth. 相似文献
318.
M. A. Kashem Ph.D. B. R. Singh Ph.D. T. Kondo M.Sc. S. M. Imamul Huq Ph.D. S. Kawai Ph.D. 《International Journal of Environmental Science and Technology》2007,4(2):169-176
Various extraction procedures were employed for measuring extractable concentrations of potential toxic elements in soil. The extractability of Cd, Cu, Pb and Zn in four contaminated and four non-contaminated soils of Japan, was compared by single extraction (CaCl2, DTPA, NH4Cl, 0.1 M HCl and 1 M HCl ) and sequential extraction procedures [(six operationally defined chemical phases, viz. water soluble (Fl), exchangeable (F2), carbonate (F3), oxide (F4), organic (F5) and residual (F6) fractions)]. Extractability of metals from soils samples varied depending on metals and/or extradants used. Among the extradants, 1 M HCl extracted the largest proportion of Cd (79 to 96% of total), Cu (61 to 83%), Pb (51 to 99%) and Zn (23 to 52%) from soils followed by 0.1 M HCl, NH4Cl, DTPA and CaCl2. In all the extradants, the proportion of extractability of metals was higher in the contaminated soils than the non-contaminated soils. Regardless of soils and extradants, relative extractability was higher for Cd as compared to other three metals. The use of 1 M HCl may be recommended for first-level screening of soil contamination with heavy metals. The other four weak extradants are believed to provide a better assessment of bioavailable/mobile metals content in soils than 1 M HCl extradant. However, 0.1 M HCl mobilized all four metals irrespective of soil types, therefore, might be the best choice if only one extradant is to be used. The sequential extraction procedures showed 22 to 64% of total Cd was in the mobile fraction (sum of Fl to F3), while the corresponding values for Cu, Pb and Zn in this fractions were 2 to 23% suggesting higher mobility of Cd than other three metals. The single extraction procedures are simple and easy to perform and obtained results are comparable with sequential extraction procedure. 相似文献
319.
Koji Nishiyama Shinichi Endo Kenji Jinno Cintia Bertacchi Uvo Jonas Olsson Ronny Berndtsson 《Atmospheric Research》2007,83(2-4):185-200
In order to systematically and visually understand well-known but qualitative and complex relationships between synoptic fields and heavy rainfall events in Kyushu Islands, southwestern Japan, during the BAIU season, these synoptic fields were classified using the Self-Organizing Map (SOM), which can convert complex non-linear features into simple two-dimensional relationships. It was assumed that the synoptic field patterns could be simply expressed by the spatial distribution of (1) wind components at the 850 hPa level and (2) precipitable water (PW) defined by the water vapor amount contained in a vertical column of the atmosphere. By the SOM algorithm and the clustering techniques of the U-matrix and the K-means, the synoptic fields could be divided into eight kinds of patterns (clusters). One of the clusters has the notable spatial features represented by a large PW content accompanied by strong wind components known as low-level jet (LLJ). The features of this cluster indicate a typical synoptic field pattern that frequently causes heavy rainfall in Kyushu during the rainy season.In addition, an independent data set was used for validating the performance of the trained SOM. The results indicated that the SOM could successfully extract heavy rainfall events related to typical synoptic field patterns of the BAIU season. Interestingly, one specific SOM unit was closely related to the occurrence of disastrous heavy rainfall events observed during both training and validation periods. From these results, the trained SOM showed good performance for identifying synoptic fields causing heavy rainfall also in the validation period. We conclude that the SOM technique may be an effective tool for classifying complicated non-linear synoptic fields and identifying heavy rainfall events to some degree. 相似文献
320.
Biological and environmental changes in Lake Baikal during the late Quaternary inferred from carbon, nitrogen and sulfur isotopes 总被引:1,自引:0,他引:1
An 8-m continuous sediment core, approximately 250-ky-old at the bottom, from Academician Ridge in Lake Baikal, has been analyzed for the stable isotopes of carbon, nitrogen and sulfur, in order to study the paleoclimatic and paleobiological changes that occurred in the Eurasian continental interior. These isotopic changes are closely related to changes in vertical lake-water circulation between glacial and interglacial periods. Sedimentary organic carbon in cool periods is more enriched in 13C (−23.8‰ on average) than that in warm periods (−27.0‰ on average). The 13C-enrichment of organic carbon suggests a decrease of land-derived organic matter influx to the lake, less precipitation, and loss of terrestrial vegetation around Lake Baikal in cool periods. Pyrite in high total sulfur/total organic carbon (TS/TOC) layers shows strong depletion in 34S (−20.8‰ to −32.4‰) during climate transitions from glacial to interglacial periods at the beginning of oxygen isotope stages (OIS) 1, 5 and 7. The 34S-depleted pyrite indicates augmentation of dissimilatory sulfate reduction by sulfate reducing bacteria (SRB) at the sediment-water interface. Enhancement of aqueous sulfate concentrations and limitation of oxygen circulation to the surface sediments might also occur in the climate transition periods. The δ15N values of total nitrogen increase abruptly by ∼2‰ just after the δ34S negative peaks, which may result from low nutrient concentrations in the euphotic zone associated with water circulation changes in Lake Baikal. 相似文献