Stochastic simulation of time-series models combined with geostatistics to predict water-table scenarios in a Guarani Aquifer System outcrop area, Brazil   总被引：3，自引：2，他引：1  

Rodrigo L. Manzione  Edson Wendland  Diego H. Tanikawa 《Hydrogeology Journal》2012,20(7):1239-1249

Stochastic methods based on time-series modeling combined with geostatistics can be useful tools to describe the variability of water-table levels in time and space and to account for uncertainty. Monitoring water-level networks can give information about the dynamic of the aquifer domain in both dimensions. Time-series modeling is an elegant way to treat monitoring data without the complexity of physical mechanistic models. Time-series model predictions can be interpolated spatially, with the spatial differences in water-table dynamics determined by the spatial variation in the system properties and the temporal variation driven by the dynamics of the inputs into the system. An integration of stochastic methods is presented, based on time-series modeling and geostatistics as a framework to predict water levels for decision making in groundwater management and land-use planning. The methodology is applied in a case study in a Guarani Aquifer System (GAS) outcrop area located in the southeastern part of Brazil. Communication of results in a clear and understandable form, via simulated scenarios, is discussed as an alternative, when translating scientific knowledge into applications of stochastic hydrogeology in large aquifers with limited monitoring network coverage like the GAS.  相似文献   

The ultraviolet survey of the Gould Belt: general properties of the Taurus star forming region     

Ana I. Gómez de Castro  Javier Lopez-Santiago  Paola Sestito  Victor Rodrigo Gudiel  Fatima López Martínez  Elisa de Castro  Manuel Cornide  Javier Yañez Gestoso 《Astrophysics and Space Science》2011,335(1):97-103

The Gould Belt is the local superassociation of star formation. The age of the Belt is some few 10⁷ yr, henceforth, its population is dominated by luminous young OB associations and low mass pre-main sequence stars. Attempts to unveil the low mass population have been run making use of the ROSAT all-sky survey. The all sky ultraviolet survey run by the GALaxy Evolution eXplorer (GALEX) maps several regions in the Belt. In this contribution, we present the preliminary analysis of the UV stellar population towards the Taurus region, one of the nearest and best studied regions of star formation.  相似文献   

Copper accumulation by bacteria and transfer to scallop larvae     

Miranda CD  Rojas R 《Marine pollution bulletin》2006,52(3):293-300

A bacterial copper-resistant strain was isolated from a hatchery-conditioned adult of the scallop Argopecten purpuratus and was identified as Vibrio sp. according to its physiological characteristics. The lowest concentration of Cu2+ required for its complete inhibition in VNSS medium was 50 microg ml(-1). The Vibrio strain was found to accumulate copper, exhibiting cellular and loosely bound copper levels of 201.14 and 493.21 microg g(-1) dry weight, respectively, after 24 h of incubation in VNSS medium supplemented with 15 microg ml(-1) of Cu2+, with cellular concentration factors of 10.17 and 14.35 after 12 and 24 h of exposure. When a scallop larvae culture was exposed to a concentration of 6.46 x 10(2) CFU ml(-1) of Cu-enriched Vibrio, they accumulated 20.42 +/- 1.12 and 30.96 +/- 1.85 microg Cu2+ g(-1) dry weight after 12 and 24 h, respectively. This study suggests that bacterial copper accumulation could be very active in marine environments increasing the occurrence of copper transfer to marine food chains.  相似文献   

The effects of brine disposal on a subtidal meiofauna community     

Rodrigo Riera  Fernando Tuya  Alicia Sacramento  Eva Ramos  Myriam Rodríguez  Óscar Monterroso 《Estuarine, Coastal and Shelf Science》2011

Desalination plants generate notable (>1,000 s m³) quantities of hypersaline brine which potentially affect the biological communities in the receiving area. We assessed whether proximity to a brine discharge point located off Gran Canaria (Canary Islands, eastern Atlantic) altered patterns in the abundance and assemblage structure of subtidal, soft-bottom, meiofauna. Samples were collected twice (May 2008 and January 2009) at 0, 15 and 30 m away from the brine discharge point, corresponding to a change in salinity from 45 to 36. Proximity to the brine discharge point affected overall meiofaunal abundances: lowest abundances were observed at 0 m (64.55 ± 39.86 ind 10 cm⁻², mean ± SD) than at 15 (210.49 ± 121.01 ind 10 cm⁻²) and 30 m (361.88 ± 102.64 ind 10 cm⁻²) away from the brine discharge point. This pattern was particularly notable for the most conspicuous meiofaunal groups: nematodes and copepods, and meiofaunal assemblage structure also differed with varying proximity to the brine discharge point. Although multivariate techniques identified changes in salinity as a relevant driver of patterns in meiofaunal assemblage structure with varying proximity to the brine outfall, a shift in particle size composition between May 2008 and January 2009 also contributed to explain differences in meiofaunal abundances and assemblage structure with varying proximity to the brine discharge point. Hence, meiofauna can be considered a suitable tool to monitor environmental impacts derived from the discharge of hypersaline effluents on subtidal, soft-bottom, assemblages if potential confounding drivers, i.e. here temporal changes in particle size composition, are accounted for to avoid possible confusing interpretations.  相似文献   

Fluctuations of the Última Esperanza ice lobe (52°S), Chilean Patagonia,during the last glacial maximum and termination 1     

E.A. Sagredo  P.I. Moreno  R. Villa-Martínez  M.R. Kaplan  P.W. Kubik  C.R. Stern 《Geomorphology》2011,125(1):92-108

We present a new record from the Última Esperanza region (51°25’-52°25'S), southwestern Patagonia, to unravel the timing and structure of glacial fluctuations during the Last Glacial Termination (T1). This sector of southern South America represents the only windward-facing continental landmass in the Southern Hemisphere that intersects the core of the Southern Westerly Wind belt.Geomorphic, stratigraphic and geochronological evidence indicate the following stages during and since the Last Glacial Maximum (LGM): (i) deposition of prominent moraine complexes during at least two advances dated between ~ 39 and > 17.5 ka; (ii) development of an ice-dammed proglacial lake (glacial lake Puerto Consuelo) accompanying ice recession; (iii) active deposition of moraine complexes at intermediate positions followed by recession at ≥ 15.2 ka; (iv) lake level drop and subsequent stabilization between 15.2-12.8 ka; (v) a glacial readvance in glacial lake Puerto Consuelo between 14.8-12.8 ka; (vi) ice recession, stabilization, and lake level lowering between 12.8-10.3 ka; and (vii) glacial withdrawal and disappearance of glacial lake Puerto Consuelo prior to 10.3 ka. By comparing our results with the chronologies from neighboring regions we explore whether there was a consistent temporal/geographic pattern of glacial fluctuations during the LGM and T1, and examine their implications at regional, hemispheric, and global scales. The correspondence of these variations with key paleoclimate events recorded in the Southern and the Northern Hemispheres suggest a common forcing that, most likely, propagated through the atmosphere. Regional heterogeneities at millennial timescales probably reflect the influence of processes related to deep ocean circulation, and changes in the position/intensity of the Antarctic Polar Front and Southern Westerly Winds.  相似文献   

Internal heating and thermal emission from old neutron stars     

Andreas Reisenegger  Rodrigo Fernández  Paula Jofré 《Astrophysics and Space Science》2007,308(1-4):413-418

The equilibrium composition of neutron star matter is achieved through weak interactions (direct and inverse beta decays), which proceed on relatively long time scales. If the density of a matter element is perturbed, it will relax to the new chemical equilibrium through non-equilibrium reactions, which produce entropy that is partly released through neutrino emission, while a similar fraction heats the matter and is eventually radiated as thermal photons. We examined two possible mechanisms causing such density perturbations: (1) the reduction in centrifugal force caused by spin-down (particularly in millisecond pulsars), leading to rotochemical heating, and (2) a hypothetical time-variation of the gravitational constant, as predicted by some theories of gravity and current cosmological models, leading to gravitochemical heating. If only slow weak interactions are allowed in the neutron star (modified Urca reactions, with or without Cooper pairing), rotochemical heating can account for the observed ultraviolet emission from the closest millisecond pulsar, PSR J0437-4715, which also provides a constraint on |dG/dt| of the same order as the best available in the literature. This work made use of NASA’s Astrophysics Data System Service, and received financial support from FONDECYT through regular grants 1020840 and 1060644.  相似文献   

Evolution of the Rotational State of Irregular Cometary Nuclei     

Gutiérrez  Pedro J.  Ortiz  José L.  Rodrigo  Rafael  López-Moreno  José J.  Jorda  Laurent 《Earth, Moon, and Planets》2002,90(1-4):239-247

A simplified thermal model has been used to calculate thenon-gravitational forces acting on small irregular nuclei in the orbit ofComet 46P/Wirtanen. The torque of thenon-gravitational force has beencalculated and the Euler equations have been solved in order toinvestigate the rotational evolution of several irregular nuclei duringa single orbital step. Several initial spin axis orientations andactivity patterns on their surfaces have been considered. The nucleiconsidered have a mean radius of 1 km and their inertia moments havebeen calculated assuming a homogeneous bulk density of 500 kg/m³. Inall the simulations, the initial spin period is 6h and the nucleiinitially rotate around their shortest axis. Under these assumptions,significant changes in the angular momentum and in spin period have beenobtained in all the simulations, but the nucleus is found to practicallyremain in its spin state of lowest energy during the entire orbitalperiod.  相似文献   

Grain-size end-members and environmentally sensitive grain-size components: A comparative study in the mud shelf depocenters off southern Brazil     

Michel Michaelovitch de Mahiques  Samara Cazzoli y Goya  Maria Carolina da Silva Nogueira de Matos  Rodrigo Augusto Udenal de Oliveira  Bianca Sung Mi Kim  Paulo Alves de Lima Ferreira  Rubens Cesar Lopes Figueira  Marcia Caruso Bícego 《国际泥沙研究》2021,36(2):317-327

The current study aims to do a comparative analysis of the results obtained with two End-Member(EM)grain-size modeling techniques(AnalySize and BasEMMA)and the Environmental Sensitive Grain-Size(ESGS)modeling for sediment samples collected in the mudbelts of the southern Brazilian shelf.The methods were compared using grain-size data from the south Brazilian shelf,and the results are discussed here.It is the first time that the concept of ESGS,in its present form,is utilized outside China.The results show that despite its relative ease of use,the ESGS is not fully comparable to the EM analyses,and only two grain-size ESGS classes were recognized as analogous to EMs.The comparison of the AnalySize and BasEMMA procedures also revealed significant differences between the techniques.A comparative analysis between the two EM techniques revealed advantages in the BasEMMA,especially in the better correlation of the end-members with the original grain size distribution.The analysis of the geographical distribution of the EM abundances allowed point sources of sandy populations to be recognized as well as the contribution of the Rio de la Plata as a source of silty sediments to be inferred.  相似文献   

Analyzing GNSS data in precise point positioning software   总被引：4，自引：1，他引：3  

Rodrigo F. Leandro  Marcelo C. Santos  Richard B. Langley 《GPS Solutions》2011,15(1):1-13

This work demonstrates that precise point positioning (PPP) can be used not only for positioning, but for a variety of other tasks, such as signal analysis. The fact that the observation model used for accurate error modeling has to take into consideration the several effects present in GPS signals, and that observations are undifferenced, makes PPP a powerful data analysis tool sensitive to a variety of parameters. The PPP application developed at the University of New Brunswick, which is called GAPS (GPS Analysis and Positioning Software), has been designed and built in order to take advantage of available precise products, resulting in a data analysis tool for determining parameters in addition to position, receiver clock error, and neutral atmosphere delay. These other estimated parameters include ionospheric delays, code biases, satellite clock errors, and code multipath among others. In all cases, the procedures were developed in order to be suitable for real-time as well as post-processing applications. One of the main accomplishments in the development described here is the use of very precise satellite products, coupled with a very complete observation error modeling to make possible a variety of analyses based on GPS data. In this paper, several procedures are described, their innovative aspects are pointed out, and their results are analyzed and compared with other sources. The procedures and software are readily adaptable for using data from other global navigation satellite systems.  相似文献   

Singular Elasto-Static Field Near a Fault Kink     

Rodrigo Arias  Raúl Madariaga  Mokhtar Adda-Bedia 《Pure and Applied Geophysics》2011,168(12):2167-2179

We study singular elastic solutions at an angular corner left by a crack that has kinked. We have in mind a geophysical context where the faults on either side of the kink are under compression and are ready to slip, or have already slipped, under the control of Coulomb friction. We find separable static singular solutions that are matched across the sides of the corner by applying appropriate boundary conditions. In our more general solution we assume that one of the sides of the corner is about to slide, i.e. it is just contained by friction, and the other may be less pressured. Our solutions display power law behaviour with real exponents that depend continuously on the angle of the corner, the coefficient of static friction and the difference of shear load on both sides of the corner. When friction is the same on both sides of the kink, the solutions split into a symmetric and an antisymmetric solution. The antisymmetric solution corresponds to the simple shear case; while the symmetric solution appears when the kink is loaded by uniaxial stress along the bisector of the kink. The antisymmetric solution is ruled out under this model with contact since the faults cannot sustain tension. When one side of the corner is less pressured one can also distinguish modes with contact overall from others that must open up on one side. These solutions provide an insight into the stress distributions near fault kinks, they can also be used as tools for improving the numerical calculation of kinks under static or dynamic loads.  相似文献