Erratum: Oxidation and emission of methane in a monomictic lake (Rotsee,Switzerland)     

C. J. Schubert  F. S. Lucas  E. Durisch-Kaiser  R. Stierli  T. Diem  O. Scheidegger  F. Vazquez  B. Müller 《Aquatic Sciences - Research Across Boundaries》2011,73(1):183-183

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Statistical approach of the influence of petrography in mechanical properties and durability of granitic stones     

P. Vazquez  N. Sánchez-Delgado  L. Carrizo  C. Thomachot-Schneider  F. J. Alonso 《Environmental Earth Sciences》2018,77(7):287

The influence of petrographic features on the strength of granitic stones is a wide studied topic which finds different correlations depending on the research and the granite type. The aim of this article was to provide an accurate statistical analysis in which the amount of analysed data did not imply any doubt about the representativity of the samples and the accuracy of the results. The focused principal component analysis was used because it allows to explain a determinate property in relation to several variables. In addition, the expression of the results was done as a simple and graphical representation that allowed to interpret the results in a global way. Data of texture, mineralogy and strength of 12 granites were obtained in this study and were completed by those of more than 100 granites obtained from the literature. The durability of the twelve granite characterized was also assessed. A thermal fatigue test was carried out in 5?×?5?×?5 cm cubes revealing that the thermal expansion experimented by the different minerals was enough to produce variations in the crack network even if temperature was lower than the microfissuration threshold.  相似文献   

Linking soil water balance with flood spatial arrangement in an extremely flat landscape     

Natalia Vercelli  Marcelo Varni  Bruno Lara  Ilda Entraigas  María Guadalupe Ares 《水文研究》2020,34(1):21-32

In areas with very mild relief, water drains in a disordered way due to the lack of a developed drainage network, as it occurs in extremely flat sedimentary regions like the Argentine Pampas. The study analysed the flood spatial arrangements in 2014 by calculating landscape metrics and relating them to soil water balance. The study area is located at Del Azul creek lower basin (Pampa Ecoregion, Argentina). Daily soil water balances were obtained, and seven landscape metrics were calculated in 15 windows in five LandSat images, all along 2014, to explore the relationship between hydrological scenarios and spatial pattern summarized with principal component analysis. Water excess concentrated in winter (June and August); deficits were in late spring and summer (January and November), whereas the beginning of autumn (March) was an intermediate situation. Principal component 1 (44.7%) reflected area and shape metrics and correlated positively with water table level; principal component 2 (32.3%) summarized aggregation ones and was negatively associated with accumulated water excesses or deficits in previous 30 days and useful reserve. Both exhibited possible threshold-driven behaviour. Internal heterogeneity between NW and SE zones within the study area coincided with the existence of ancient alluvial fans. The results highlight the peculiarities of the flood spatial patterns in regions with very mild relief, where landforms usually determine water flows.  相似文献   

Intrinsic aquifer vulnerability assessment: validation by environmental tracers in San Miguel de Allende, Mexico   总被引：1，自引：0，他引：1  

Jürgen Mahlknecht  Ma. Guadalupe Medina-Mejía  Jaime Gárfias-Solis  Irene Cano-Aguilera 《Environmental Geology》2006,51(3):477-491

Vulnerability maps are important tools for water decision makers and land-use planners for protection of aquifers against contamination. The vulnerability map, according to the parametric method SINTACX for assessing intrinsic aquifer vulnerability, was validated in a case study with chlorofluorocarbon tracer technologies (CFC-11, CFC-12, and CFC-113) of groundwater. The tested area was the 1,295 km² volcano-sedimentary area of San Miguel de Allende (SMA), Mexico. From the results of this area, it appears that the vulnerability map is in parts inconsistent with the underlying groundwater flow system. Thus, the vulnerability map was corrected with tracer information. The validated vulnerability map indicates that the degree of vulnerability varies from low to moderate-high. Low vulnerability values are found in the graben extending from north to south along the SMA fault system and high values in recharge areas southeast and northwest of the study area. The investigation is a demonstration that the scientific reliability of results of the parametric method can be improved by validation with tracer techniques representing the groundwater dynamics. The flexible structure of SINTACX allows revising and adjusting scores and weights of the parameter maps to rebuild a new vulnerability map consistent with the hydrological system.  相似文献   

Surface organic geochemical prospecting for hydrocarbons: multivariate analysis     

Guadalupe Saenz  Nicholas E. Pingitore Jr. 《Journal of Geochemical Exploration》1989,34(3)

A database of analyses of C₁ and C₇ hydrocarbons from an oil and gas producing region in Mexico has been assembled from gas samples collected at depths of 3, 15 and 30 meters from surficial holes drilled in traverses over producing and barren structures. The surface consisted of subtropical swamps; depth to structure was 3500 to 5800 meters.Hydrocarbon analysis from six structures (three producing and three barren) selected from the database were subjected to multiple discriminant function analysis to produce a retrospective statistical test of the ability of geochemical prospecting to distinguish producing from non-producing structures. The hydrocarbon spectra from 3 meters depth yielded ambiguous results; those from 30 meters produced clear distinction between barren and producing structures. Further, the discriminant functions established a base of geochemical characteristics, founded on known areas (retrospective), to which additional unknown areas (prospective) may be compared for classification. This suggests a bootstrapping approach to exploration in which an increasing number of “known” results can be used to continually update and refine the predictive power of the discriminant function.This indicates the practical ability of a combined geochemical-multivariate statistical prospecting approach as an exploration tool, particularly within a single geochemical/geological province. Geochemical prospecting, perhaps with relatively deep (30 m) penetration, combined with multivariate data analysis is a rapid, potent and relatively inexpensive additional tool for petroleum exploration.  相似文献   

The age decay of stellar magnetic activity in MS field solar-type stars     

J. Cabestany  M. Vazquez 《Astrophysics and Space Science》1983,97(1):151-156

The age decay of two indicators of the stellar magnetic activity (λ 2800 Mgii emission flux and λ 10830 Hei equivalent width) have been studied for field solar-type stars. The Li abundance has been used, in most of the cases, as a stellar age indicator. A calibrated decay law for Mgii has been determined and compared with a similar one, recently published, for the Caii K emission. The greater scatter in the Hei results is atributed to the different rotation rates.  相似文献   

Effect of isolation temperature on the characteristics of extracellular proteases produced by Antarctic bacteria   总被引：1，自引：0，他引：1  

Susana C. Vazquez  Walter P. Mac Cormack 《Polar research》2002,21(1):63-71

Protease-producing psychrotolerant bacteria were isolated from Antarctic biotopes on casein agar plates using different incubation temperatures. Most of the isolates were non-spore-forming Gram-negative motile rods with catalase activity, 30% were pigmented and none of them were glucose fermenters. All the strains were grown in liquid cultures at 20°C and protease secretion was tested using the azocasein method. Despite their capacity for production of a clear zone of hydrolysis in agar plates, some strains did not produce detectable levels of proteolytic activity in liquid cultures. The lowest apparent optimum temperature for protease activity found in culture supernatants was 40°C. Almost all the strains showed activation energy values about 10-20 kJ-mol⁻¹ lower than that observed for a mesophilic Subtilisin. Most of the proteases showed optimal activity at neutral or alkaline pH values and developed a multiple-band profile on gelatine-SDS-PAGE. It was observed that the lower the strain isolation temperature was, the more stongly cold-adapted–in terms of optimal temperature and activation energy–were the proteases produced by them. This dependence of the characteristics of the proteases on the isolation temperature is an important factor to take into account in the design of screening programmes directed towards the isolation of psychrotolerant bacteria able to produce proteases strongly or weakly adapted to work in the cold. The Antarctic area explored proved to be a promising source of proteolytic bacteria with potential use in industrial processes to be carried out at low or moderate temperatures.  相似文献   

Rotating Stratified Heterogeneous Oblate Spheroid in Newtonian Physics     

E.P. Esteban  S. Vazquez 《Celestial Mechanics and Dynamical Astronomy》2001,81(4):299-312

By solving the Euler hydrodynamical equations we have obtained closed form solutions for the angular velocities and pressures of a three stratified non-confocal heterogeneous oblate spheroid. Limiting and particular solutions cases, such as a spheroid with N layers, a stratified spheroid with the same eccentricities, as well as confocal layered spheroids are also explicitly written down. As an application, we have numerically estimated planet Earth's outer and inner cores' ellipticities to be _o=1/413.318 and _i=1/424.616, respectively. These Earth's ellipticities values are in good agreement with those found in the literature.  相似文献   

Zircon-scale insights into the history of a Supervolcano,Bishop Tuff,Long Valley,California, with implications for the Ti-in-zircon geothermometer   总被引：7，自引：6，他引：1  

Mary R. Reid  Jorge A. Vazquez  Axel K. Schmitt 《Contributions to Mineralogy and Petrology》2011,161(2):293-311

Zircon has the outstanding capacity to record chronological, thermal, and chemical information, including the storage history of zoned silicic magma reservoirs like the one responsible for the Bishop Tuff of eastern California, USA. Our novel ion microprobe approach reveals that Bishop zircon rims with diverse chemical characteristics surround intermediate domains with broadly similar compositions. The highest Y, REE, U, and Th concentrations tend to accompany the largest excesses in Y + REE³⁺:P beyond what can be explained by xenotime substitution in zircon. Apparent Ti-in-zircon temperatures of <720°C for zircon rims are distinctly lower than most of the range in eruption temperatures, as estimated from FeTi-oxide equilibria and zircon solubility at quench. While permissive of crystallization of zircon at near-solidus conditions, the low Ti-in-zircon temperatures are probably better explained by sources of inaccuracy in the temperature estimates. After apparently nucleating from different melts, zircons from across the Bishop Tuff compositional spectrum may have evolved to broadly similar chemical and thermal conditions and therefore it is possible that there was no significant thermal gradient in the magma reservoir at some stage in its evolution. There is also no compelling evidence for punctuated heat ± chemical influxes during the intermediate stages of zircon growth. Judging by the zircon record, the main volume of the erupted magma evolved normally by secular cooling but the latest erupted portion is characterized by a reversal in chemistry that appears to indicate perfusion of the magma reservoir by—or zircon entrainment in—a less evolved melt from the one in which the zircons had previously resided.  相似文献   

Preface     

F. Sanchez  M. Vazquez 《Astrophysics and Space Science》1990,169(1-2):ix-ix

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