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91.
Julio E. Valdivia-Silva Rafael Navarro-González Lauren E. Fletcher Reneé Condori-Apaza 《Geochimica et cosmochimica acta》2011,75(7):1975-1991
The distribution of living organisms, organic matter, and chemical properties in Mars-like environments on Earth can be used as a model to guide the investigation of possible habitable environments on Mars. This work aims to demonstrate that the place known informally as the “Mar de Cuarzo” (Sea of Quartz) in the Pampas de La Joya desert southern Peru (between 16°S and 17°S latitude), contains soils with characteristics similar to those found on the Martian surface. Using a multidisciplinary approach, we studied the environmental data, geology, organic matter content, oxidant activity, and microbiology of this area. Our data show that (1) Mar de Cuarzo is a hyper arid area with a lower concentration of organic matter than those found in the Mars-like soils from Yungay area (Atacama Desert in Chile), while at the same time having, comparable extreme environmental conditions, and very low levels of microorganisms. (2) The detrital components of the soils come essentially from the Andean volcanic chain and local outcrops of Precambrian gneisses and Cretaceous granitic batholiths. (3) The presence of microclimates, geomorphological features, and the high influence of the “El Niño Southern Oscillation (ENSO)” allowed the formation of exotic and heterogeneous chemical deposits in these soils, including iron oxides, sulfates, and other evaporites. (4) Thermal volatilization in these soils (using methods similar to the Viking and Phoenix instruments) shows high oxidant activity. (5) Labeled release experiment (similar to the Viking instrument) shows high degradation of nutrients added in these soils.Altogether, the Mar de Cuarzo area in the Pampas de La Joya is an interesting place for astrobiological studies as a new analog to Mars, and for comparative analyses with other hyperarid analogs as Yungay. 相似文献
92.
Gertrude Friedl Rob A. Cooke Friedrich Finger Neal J. McNaughton Ian R. Fletcher 《Mineralogy and Petrology》2011,102(1-4):63-75
In an attempt to better constrain the timing of Variscan HP-HT metamorphism in the SE Bohemian Massif we have dated zoned zircons from a garnet-kyanite granulite of granitic composition from the Dunkelsteiner Wald Massif, Lower Austria, by means of sensitive high-resolution ion microprobe (SHRIMP) technique. In order to combine isotopic information with crystal growth textures, CL and BSE images were systematically taken from the dated zircons. A characteristic threefold concentric zoning was found in many zircons. This involves pre-Variscan protolithic cores followed by two distinct metamorphic/anatectic overgrowth shells of Variscan age. The inner overgrowth shell is characterized by a weak CL but bright BSE signal, and yields high contents of uranium (0.1 to 0.2 wt.%). A pooled U-Pb Concordia age for this zone is 342.0?±?3.0?Ma (n?=?11, MSWD?=?0.12). The second, outer, overgrowth shell is always bright in the CL image, dark in the BSE image, and has generally low uranium contents (mostly <500?ppm). A pooled U-Pb Concordia age for this zone is 337.1?±?2.7?Ma (n?=?11, MSWD?=?0.22). These results imply that the Variscan HT crystallisation history of the Moldanubian granulites took place over a period of a few million years and was not an extremely rapid subduction-exhumation process. SHRIMP measurements in the protolithic cores yield a cluster of (sub)concordant ages between ??390 and 460?Ma and a few outliers at higher ages mostly represented by cores in cores. Core domains, which are large, homogeneous and with undisturbed igneous oscillatory zoning, yielded preferentially ages between 430 and 460?Ma. We therefore consider that granitic protolith formation took place at that time. The still older inner cores are interpreted as inherited into the granitic melt. 相似文献
93.
Maochen Ge H. Reginald HardyJr Hongliang Wang Jin Wang 《Geotechnical and Geological Engineering》2011,29(1):137-142
A Simple Mechanical Impact System (SMIS) was developed recently as a non-explosive seismic source. The SMIS consists of an
impact head, a steel rod with extensions, and an anchoring system. The system is small and simple, and can be conveniently
installed in a shallow borehole oriented in any direction. The SMIS was developed to address two problems commonly associated
with non-explosive seismic sources: insufficient seismic strength and lack of repeatability. Field tests have shown that it
is possible to produce clear and repeatable signals with this system even when the SMIS is installed in a coal seam. 相似文献
94.
S. T. Fletcher W. J. Chaplin Y. Elsworth 《Monthly notices of the Royal Astronomical Society》2003,346(3):825-832
We present a comparative study of genetic and standard fitting routines applied to the task of extracting reliable estimates of the rotational splitting of full-disc, low-angular-degree (low- l ) solar p-mode data at high frequencies. 100 artificial proxies of a 10-yr data base of observations made by the Birmingham Solar-Oscillations Network (BiSON) were used to test the two approaches. All sets were analysed over the frequency range from 3000 to 4000 μHz.
Previous work, based on non-linear 'hill-climbing' fitting techniques, has demonstrated the unfortunate tendency for full-disc estimates of the splitting to overestimate the true, underlying values at high frequencies. Here, we show that the resulting bias is less severe when a genetic-fitting approach is adopted. This is largely the result of the number of erroneous 'null-valued' estimates of the splitting being considerably reduced: these estimates are, in effect, re-introduced into the expected normal distribution of fitted splittings. We also illustrate the diverse control one has when using a genetic algorithm as a fitting routine; this diversity is shown to allow further refinement in the estimate of the rotational splitting.
Finally, we address the issue of the reliability of the formal splitting uncertainties returned by the mode fitting, and find that complications arising from the strong anticorrelation between the splittings and their error estimates are not alleviated by the use of the genetic technique. 相似文献
Previous work, based on non-linear 'hill-climbing' fitting techniques, has demonstrated the unfortunate tendency for full-disc estimates of the splitting to overestimate the true, underlying values at high frequencies. Here, we show that the resulting bias is less severe when a genetic-fitting approach is adopted. This is largely the result of the number of erroneous 'null-valued' estimates of the splitting being considerably reduced: these estimates are, in effect, re-introduced into the expected normal distribution of fitted splittings. We also illustrate the diverse control one has when using a genetic algorithm as a fitting routine; this diversity is shown to allow further refinement in the estimate of the rotational splitting.
Finally, we address the issue of the reliability of the formal splitting uncertainties returned by the mode fitting, and find that complications arising from the strong anticorrelation between the splittings and their error estimates are not alleviated by the use of the genetic technique. 相似文献
95.
K. Petrovay J. C. Brown L. van Driel-Gesztelyi L. Fletcher M. Marik G. Stewart 《Solar physics》1990,127(1):51-64
We propose that magnetic flux loops in the subphotospheric layers of the Sun are seriously asymmetrical as a consequence of the drag force exerted on them because of the different rotational rate of the surrounding plasma. In numerical models of stationary slender flux loops in the plane parallel approximation we show that a serious tilt is both possible and probable. Observational facts (see van Driel-Gesztelyi and Petrovay, 1989; Paper I) strongly support the case for high asymmetry. The different stability of p and f spots may also be related to such an asymmetry.The tilts are very sensitive to the rotational profile and to the magnetic field structure. Nevertheless the characteristic maximal tilts can be tentatively estimated to be 20° for thin flux tubes and 5° for thick tubes.For two of the five observational consequences of such a tilt (described in detail in Paper I) order-of-magnitude estimates of the effects are given. The estimates are in reasonable accord with observations.We also explore the possibilities of an inverse treatment of the problem whereby subphotospheric rotation and/or flux tube shapes can be inferred from observations of velocities of photospheric spot motions. In particular we demonstrate how analytic inverse solutions can be obtained in special cases. 相似文献
96.
S.J. Collander-Brown A. Fitzsimmons E. Fletcher M.J. Irwin I.P. Williams 《Monthly notices of the Royal Astronomical Society》2001,325(3):972-978
On 1998 December 12 a new trans-Neptunian object, 1998 XY95, was discovered as part of a deep search. Recent observations of this object have placed it amongst the class of objects known as the scattered trans-Neptunian objects (TNOs). A total of 39 CCD images of 1998 XY95 were taken over two nights, and these were used to search for a light curve, but no significant periodicity was found. An examination of the possible orbital evolution gives no indication of how it may have arrived on its present orbit. The current best-fitting orbit is unstable, but remains within a band of semi-major axis approximately 2 au wide. The bottom of this band is due to 3:1 mean motion resonance with Neptune, while the reason for the top of the band remains unclear. 相似文献
97.
Potassium chlorate—hydrochloric acid is compared to ascorbic acid—hydrogen peroxide, aqua regia, and nitric—perchloric as a sulphide-selective leach for bedrock geochemistry. Results obtained on granodiorite samples containing copper sulphides indicate that the procedure is probably more selective than the other leaches and has the advantages of rapidity and simplicity. 相似文献
98.
Lal C. Ram Nishant K. Srivastava Ramesh C. Tripathi Sanjay K. Thakur Awadhesh K. Sinha Sangeet K. Jha Reginald E. Masto Swapan Mitra 《Environmental Geology》2007,51(7):1119-1132
The maximum concentration of the majority of the trace metals in the leachates from shake and column test of lignite fly ash
(LFA) was within the prescribed limits; however, total dissolved solids, total hardness, cations and anions (except K+), being above the prescribed limits, may lead to the increase in the hardness and salinity in the soil on the disposal of
LFA. Present generation of huge amount of fly ash from thermal power plants (TPPs) is a big challenge concerning contamination
of soil, crop produce and surface and ground water bodies due to the presence of some of the toxic trace metals in it. The
leaching behavior of alkaline LFA (pH, 10.94), from TPP of Neyveli Lignite Corporation (NLC), India, was investigated by shake
and column tests using water and sodium acetate buffer. The leaching of trace metals from LFA was governed by their concentrations,
association with the ash particles, leaching duration and pH of the leachate (most influencing parameter). The leaching of
metals followed the order: buffer column > aqueous column > aqueous shake > buffer shake test. 相似文献
99.
B. Christophe L. J. Spilker J. D. Anderson N. André S. W. Asmar J. Aurnou D. Banfield A. Barucci O. Bertolami R. Bingham P. Brown B. Cecconi J. -M. Courty H. Dittus L. N. Fletcher B. Foulon F. Francisco P. J. S. Gil K. H. Glassmeier W. Grundy C. Hansen J. Helbert R. Helled H. Hussmann B. Lamine C. L?mmerzahl L. Lamy R. Lehoucq B. Lenoir A. Levy G. Orton J. Páramos J. Poncy F. Postberg S. V. Progrebenko K. R. Reh S. Reynaud C. Robert E. Samain J. Saur K. M. Sayanagi N. Schmitz H. Selig F. Sohl T. R. Spilker R. Srama K. Stephan P. Touboul P. Wolf 《Experimental Astronomy》2012,34(2):203-242
100.
This paper describes an effort to map the habitat for the Eastern Tehama Deer Herd located in Northern California. The range of this herd encompasses almost 600,000 hectares (1.5 million acres). Knowledge of the spatial distribution of suitable habitat is prerequisite to managing the deer herd. Remote sensing and GIS are appropriate tools for such an assessment. Remotely sensed data were used to map vegetation/land cover. These data along with elevation, aspect, slope, juxtaposition, and various buffer zones were input into a GIS and a model was used to produce a map of habitat suitability. The accuracy of the vegetation/land cover map was assessed and methods for validating the habitat suitability map are presented. 相似文献