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81.
Abdelrahman Mohamed Abdelgawad Kunio Watanabe Mebruk Mohammed Shinji Takeuchi 《Environmental Earth Sciences》2010,60(3):449-462
High levels of fluoride concentration were observed in deep groundwater of the Mizunami area in Central Japan. Fluoride occurs
mainly due to the reaction between granitic basement rock and groundwater. Granites were collected, crushed to powder, and
then allowed to react with purified water for 80 days. Water–rock interaction results showed that the major factor affecting
fluoride concentration is the residence time of the groundwater. Coexisting ions have also some contribution toward fluoride
concentration. The groundwater residence time in the Mizunami area was estimated by applying results of water–rock interaction
to correspond with field data. A regression model relating fluoride concentration, residence time, and coexisting ions was
developed. The parameters of the regression model were determined using the genetic algorithms technique. Residence time was
estimated by extrapolating experimental data to correspond with filed data. Near the recharge area, residence times in the
potential fluoride source rock varied between 1 and 2,000 years, whereas near the discharge area residence times were in excess
of tens of thousands of years. The groundwater residence time was also estimated by the groundwater particle-tracking-flow
model. The estimates of groundwater residence time based on geochemical regression model were often larger than estimates
of groundwater residence time developed by particle-tracking analysis using a groundwater flow model. There were large uncertainties—on
the order of 10–10,000 years—in the estimates based on geochemical data. 相似文献
82.
Tsuneomi Kawasaki Yusuke Fujii Kenso Soai Sandra Pizzarello 《Geochimica et cosmochimica acta》2006,70(21):5395-5402
We separated and analyzed several organic and inorganic phases of the carbonaceous chondrite matrix to determine whether they contained any inherent asymmetry. Our intent was to determine any possible foci of asymmetry besides the one determined for meteoritic amino acids. As a probe, we employed a very sensitive asymmetric autocatalytic reaction. We were able to determine that asymmetry still resides in powders after extraction with water and solvents as well as in the insoluble organic material (IOM) obtained after demineralization. Asymmetry is not found any longer in the IOM after hydrothermal treatment and in meteorite powders from which all organics had been removed by O2 plasma at low temperature. The data are interpreted to indicate a diverse molecular asymmetry residing in yet unknown meteorite organics; these organics might have had an inductive effect on organic molecular evolution upon exogenous delivery to the early Earth. 相似文献
83.
Temporal change in permeability of the Nojima fault zone by repeated water injection experiments 总被引:8,自引:1,他引:8
Three boreholes were drilled near the Nojima fault, which the 1995 Hyogoken–Nanbu earthquake occurred on. In order to research the properties and the healing process of the fault, water injection experiments were conducted every 3 years. In this report, we researched the permeability of the fault as a measurement of crack density or porosity of the fault zone. Pore water pressure changes in rock due to the water injections at one borehole were observed as discharge changes or groundwater level changes at the other borehole. Using numerical calculations, the permeability of the fault fracture zone was estimated for each experiment. The permeability has been decreasing as time passed, which is thought to show the fault healing process of the Nojima fault after the 1995 Hyogoken–Nanbu earthquake. 相似文献
84.
Oceanic crust production and climate during the last 100 Myr 总被引:2,自引:0,他引:2
In order to evaluate the possible influence of oceanic crust production on climatic changes during the past 100Myr variations in total oceanic crust for this period including production at mid-ocean ridges, oceanic plateaus, and back-arc basins were calculated using the most recent and accurate time-scales. The rates presented here differ from those of Larson (1991a, b) on Cenozoic fluctuations and show that (1) maximum production values occurred during the Cenomanian, Palaeocene, and late Oligocene-early Miocene and (2) minimum values occurred in Campanian-Maastrichtian, late Eocene, and middle Miocene. Significantly, variations of oceanic crust production correspond with variations in the δ18 O of deep-water benthic foraminifera: maximum values of oceanic crust production correspond with minimum values of δ18 O, and minimum production values with maximum values of δ18 O. This latter synchronism suggests that changes in land-sea relationships and atmospheric CO2 related to major fluctuations in oceanic crust production were the main cause of mid-Cretaceous warming and Late Cretaceous cooling, and of climatic quasi-cycles having a periodicity of 33–38 million years over the last 100 Myr. This is the first report showing variations of ocean crust production synchronized with the Cenozoic climate changes. 相似文献
85.
On moderately disturbed days when substorms occur frequently, the quiet day daily variation in the polar region (Sqp) is enhanced. On such days, however, the quiet day variation along the dip equator appears to be suppressed, as well as being superposed with ‘fluctuations’.It is suggested that the enhancement of Sqp is related to a partial suppression of the equatorial electrojet. The asymmetric ring current also causes an apparent suppression of the electrojet.On the other hand, the substorm-associated electric field which drives the eastward current in the auroral and subauroral zone (causing positive bays) in the afternoon sector appears to enhance the equatorial electrojet.Thus, magnetic variations along the dip equator are influenced by a number of processes in the magnetosphere. 相似文献
86.
Motoaki Kishino Takashi Ishimaru Ken Furuya Tomohiko Oishi Kiyoshi Kawasaki 《Journal of Oceanography》1998,54(5):431-436
In-water algorithms for OCTS standard products were developed using in situ data and installed for operationally processing
at NASDA/EOC. This paper describes the in-water algorithms Version 1.0 for chlorophylla concentration, pigment concentration, and attenuation coefficient at a wavelength of 490 nm. The selected OCTS standard algorithms
(Ver. 1.0) are as follows:
相似文献
87.
Ryuichiro Inoue Jiro Yoshida Yutaka Hiroe Kousei Komatsu Kiyoshi Kawasaki Ichiro Yasuda 《Journal of Oceanography》2003,59(2):211-224
The mixing processes in the Mixed Water Region (MWR) that lead to changes in the properties of North Pacific Intermediate
Water (NPIW) have been studied using observational data sets obtained in May–June 1998. Neutral surfaces, the equation of
water mass conversion rate on neutral surfaces and the equation of vertical velocity across neutral surfaces have been used
to distinguish dominant processes by assuming the horizontal scale to be the streamer scale (under 100 km). The possibility
of double diffusive convection is also discussed in relation to the density ratio. These results may be summarized as follows:
(1) the difference between the potential density surface and the neutral surface may rise to −0.04 kg/m3 around the source water of NPIW; (2) horizontal diffusion causes strong modifications of the source water of NPIW; (3) the
density range within which strong modification of the source water of NPIW occurs becomes dense from the northern part of
MWR near the Oyashio Front to the southern part near the Kuroshio Front, and to the eastern part. Our modeling of these processes
shows that cabbeling has effects on the density increment of the source water of NPIW in the northern and southern part of
MWR. Double diffusive convection has effects on the density increment of the source water of NPIW, mainly in the northern
part of MWR. The possible density increment due to cabbeling in these areas is estimated to be 0.01≈0.03 kg/m3. The possible density increment due to double diffusive convection is 0.01≈0.03 kg/m3. The total density increment due to cabbeling and double diffusive convection amounts to 0.06 kg/m3.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
It is shown that Mie theory predictions of extinction for pure water-ice with the optical constant measured at 100 K do not fit in detail the observed ice absorption feature in infrared objects, although we attempt to explain the observations by considering size distribution and shape of the grains.In addition, based on a similarity between the ice band and the absorption band found in carbon stars, we feel it is questionable whether or not the ice band can really be attributed to the interstellar water-ice. 相似文献
89.
During Tropical Ocean and Global Atmosphere (TOGA)/Coupled Ocean and Atmosphere Research Experiment (COARE) Intensive Observing Period (IOP), upward-looking acoustic Doppler current profilers (ADCP) and current meters were moored at two equatorial sites (147°E and 154°E) and two off-equatorial sites (2°N and 2°S, 156°E) in the warm pool region of the western equatorial Pacific. Using current data obtained by these moorings, we have shown that there is a dominant signal with a period of about 2 days from the end of November to the middle of December in 1992, except at the equatorial site on 147°E (Ueki et al., 1998). The energy of this quasi-2-day signal for the meridional current is larger than that for the zonal one and the signal has a high coherence between two off-equatorial sites. In this paper, using band-passed time series of the meridional curerent, we investigated characters of the quasi-2-day signal and attempted to interpret this signal as an equatorially trapped wave. Complex empirical orthogonal function (CEOF) analysis reveals two different phase propagating features between the equatorial and off-equatorial site. One is an upward propagating signal, which is dominant near the surface at two off-equatorial sites, and the other is a downward propagating signal, which is dominant near 200 m at the equatorial site. If one interprets the quasi-2-day signal as an equatorially trapped wave, it is suggested that it cannot be explained as a single wave but can be described as the superimposition of several wave signals. The main part of these signals consists of two signals, one caused by a meteorological forcing and another by another factor in the ocean field. 相似文献
90.
S. M. White K. Iwai N. M. Phillips R. E. Hills A. Hirota P. Yagoubov G. Siringo M. Shimojo T. S. Bastian A. S. Hales T. Sawada S. Asayama M. Sugimoto R. G. Marson W. Kawasaki E. Muller T. Nakazato K. Sugimoto R. Brajša I. Skokić M. Bárta S. Kim A. J. Remijan I. de Gregorio S. A. Corder H. S. Hudson M. Loukitcheva B. Chen B. De Pontieu G. D. Fleishmann D. E. Gary A. Kobelski S. Wedemeyer Y. Yan 《Solar physics》2017,292(7):88
The Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12 m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that uses the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions, we derive quiet-Sun values at disk center of 7300 K at \(\lambda = 3~\mbox{mm}\) and 5900 K at \(\lambda = 1.3~\mbox{mm}\). These values have statistical uncertainties of about 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of about \(25''\), the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range. Active regions and plages are among the hotter features, while a large sunspot umbra shows up as a depression, and filament channels are relatively cool. Prominences above the solar limb are a common feature of the single-dish images. 相似文献