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171.
Modern digital conductivity meters are readily portable, robust, cheap, and give precisely reproducible values of specific electrical conductivity (SpC, in µS cm?1). Here we investigate the accuracy of their estimates of the amounts of gypsum dissolved in waters collected in gypsum karst terrains, expressed as total hardness (TH) in mg L?1 of CaSO4·2H2O (GYP). Total dissolved solid concentrations (TDS) are also considered. Curves obtained with the program PHREEQC, for the dissolution of pure gypsum in water at 25 C, are compared with 574 comprehensive water chemical analyses selected from gypsum karst studies in Europe and the Americas. Principal common and foreign ions encountered are the BNC group (bicarbonates, nitrates, chlorides). It is found that GYP = 1·12·SpC + 62 where BNC < 33% (Cl? < 5%), with one standard error <5% for waters with SpC > 2400 µS cm?1; GYP = 0·74·SpC + 777 where BNC < 33% (5% ≤ Cl? < 15%), with one standard error <10% for waters with SpC > 3100 µS cm?1; GYP = 0·97·SpC ? 209 where BNC < 33% and Cl? ≥ 15%, with one standard error <10% for samples with SpC > 4300 µS cm?1. There are similar results for the more complex waters found in gypsum karsts where much carbonate rock or salt is also present, to the limit of BNC < 50% for what may reasonably be defined as ‘gypsum waters’. Values of R2 for linear correlations of different subsets of the water samples range from 0·69 to 0·96, the majority being >0·8. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
172.
Mark Clampin Marco Sirianni George F. Hartig Holland C. Ford Garth D. Illingworth Bill Burmester William Koldewynd Andre R. Martel Adam Riess Ronald J. Schrein Pamela C. Sullivan 《Experimental Astronomy》2002,14(2):107-115
The Advanced Camera for Surveys (ACS), installed in the Hubble Space telescope in March 2002, will significantly extend HST's
deep, survey imaging capabilities. ACS has met, or exceeded, all of its key performance specifications. In this paper we briefly
review the in-flight performance of the instrument's CCD detectors and preview early ACS science observations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
173.
Michele Spizzico 《Hydrogeology Journal》2005,13(3):493-505
High concentrations of 222Rn have been found throughout the waters of the coastal carbonate-rock Mesozoic aquifer located in the region of Apulia in southern Italy. Studies undertaken have determined that such concentrations are due to the radioisotopic features of terra rossa, a type of paleosol that is generated as a residual byproduct of carbonate dissolution and is found to be widespread throughout the aquifers fissures and karst cavities.These special types of soil feature a rather high clay content (80–95%) and, although variable, their specific 226Ra activity (70–147 Bq/kg) is nonetheless considerably greater than that of limestone (~50 Bq/kg). In fact, there are substantial differences in 222Rn concentrations found in waters that come into contact with this type of rock and paleosol.The partial dissolution of some carbonate rock samples in the laboratory confirmed that the 226Ra released by the dissolved rock primarily accumulates in the residual soil deposits, especially in ones containing finer granules. This has also been the result of experiments conducted on 15 terra rossa samples collected from the region, which indicates that there is a close correlation between the specific 226Ra activity and the clay content of such paleosols, which varies with the stage of weathering.It has been found that the 222Rn concentrations in the regions waters, depend on the specific terra rossa 226Ra activity rather than on the quantity of terra rossa.Field checks have confirmed the possibility of using 226Ra and 222Rn as natural tracers in order to define hydrogeological problems in special environments such as karst. They can be used to distinguish the different water bearing zones in the carbonate-rock aquifer; analyze the influence of tides on coastal springs; determine the flow direction in the proximity of a well; recognize, recharge and the progressive decline of the groundwater level; derive indications of underground flow paths; and the occurrence of fissures and karstic cavities in the carbonate-rock aquifer.
相似文献
Michele SpizzicoEmail: Phone: +39-080-5963676Fax: +39-080-5963675 |
174.
Andrea?Tallarico Stefano?SantiniEmail author Michele?Dragoni 《Pure and Applied Geophysics》2005,162(12):2273-2298
The Central Apennines, Italy, are characterized by moderate seismic activity on normal faults, oriented in directions parallel
to the Apenninic chain. The subject of this study is the Umbria-Marche Apennines, a segment approximately 200-km long, where
three main seismic events occurred in the last three decades. The 1979 Norcia earthquake was a Mw = 5.8 event, taking place at the south end of the considered segment. The 1984 Gubbio earthquake was a Mw = 5.6 event which took place at the north end. The 1997-1998 Colfiorito sequence constituted 8 main shocks with magnitudes
Mw between 5 and 6 and epicenters located between the Gubbio and the Norcia earthquake areas. A model made of an elastic half-space
is considered, in which the seismic sources are represented by rectangular dislocations which have the appropriate values
of source parameters, and in which the static stress field produced by each event is calculated. The analysis of the Coulomb
stress change (ΔC) as a function of time shows that the coseismic stress transfer and fault interaction played an important role in the region
during the past three decades: 7 earthquakes of the 9 considered took place where ΔC>0. Such an interaction has been confirmed by the analysis of the aftershocks in the Colfiorito zone post September 26, 1997:
about the 61% of the aftershocks considered took place where ΔC>0. The comparison between the ΔCs due to the coseismic stress transfer and the rate ΔĊt due to the tectonic stress allows us to quantify the time advance of the earthquakes. The ΔCs pattern shows positive values in two areas that can be regarded as historical seismic gaps. 相似文献
175.
Michele Caputo 《Geophysical Journal International》1979,59(1):227-230
Summary. The effect of anelasticity on the periods of the Earth's free oscillation (toroidal modes) is examined in the light of several different studies leading to different results. The possibility of discrimination between the different analytic models for the anelasticity of the Earth's interior is discussed. A splitting of the spectral lines caused by Q is also suggested. 相似文献
176.
177.
Michele Caputo 《Geophysical Journal International》1967,13(5):529-539
178.
179.
Tamara T. Helfer Michael W. Regan Michele D. Thornley Tony Wong Kartik Sheth Stuart N. Vogel Douglas C.-J. Bock LEO Blitz Andy Harris 《Astrophysics and Space Science》2001,276(2-4):1131-1139
BIMA SONG is a systematic imaging study of the 3 mm CO J = 1 → 0molecular emission within the centres and discs of 44 nearby spiral galaxies on size scales of a few hundred parsecs
(6-9"). The overall goal of the survey is to study the role of molecular gas in the evolution of spiral galaxies. To this
end, BIMA SONG addresses 1) the distribution and physical conditions of the molecular gas in galactic discs and its relation
to star formation, 2) the effects of a stellar bar on the kinematics of molecular gas, including the possible inflow of gas
along a bar, and 3) the distribution and role of molecular gas in the central few hundred parsecs of active and quiescent
galaxies. The source list includes all (except M33and M31) 44 galaxies of Hubble types Sa–Sd, with declinations δ >−20°, visual magnitudes B < 11.0, velocities v
hel <2000 km s-1, and inclinations i < 70°. Beyond the specific scientific questions we will address, this survey will provide a unique database for astronomers who
study galaxies at all wavelengths.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
180.
The Discovery of a Second Field Methane Brown Dwarf from Sloan Digital Sky Survey Commissioning Data
Tsvetanov ZI Golimowski DA Zheng W Geballe TR Leggett SK Ford HC Davidsen AF Uomoto A Fan X Knapp GR Strauss MA Brinkmann J Lamb DQ Newberg HJ Rechenmacher R Schneider DP York DG Lupton RH Pier JR Annis J Csabai I Hindsley RB Ivesic Z Munn JA Thakar AR Waddell P 《The Astrophysical journal》2000,531(1):L61-L65
We report the discovery of a second field methane brown dwarf from the commissioning data of the Sloan Digital Sky Survey (SDSS). The object, SDSS J134646.45-003150.4 (hereafter SDSS 1346-00), was selected because of its very red color and stellar appearance. Its spectrum between 0.8 and 2.5 μm is dominated by strong absorption bands of H2O and CH4 and closely mimics those of Gliese 229B and SDSS 162414.37+002915.6 (hereafter SDSS 1624+00), two other known methane brown dwarfs. SDSS 1346-00 is approximately 1.5 mag fainter than Gliese 229B, suggesting that it lies about 11 pc from the Sun. The ratio of flux at 2.1 μm to that at 1.27 μm is larger for SDSS 1346-00 than for Gliese 229B and SDSS 1624+00, which suggests that SDSS 1346-00 has a slightly higher effective temperature than the others. Based on a search area of 130 deg2 and a detection limit of z*=19.8, we estimate a space density of 0.05 pc-3 for methane brown dwarfs with Teff approximately 1000 K in the 40 pc3 volume of our search. This estimate is based on small-sample statistics and should be treated with appropriate caution. 相似文献