Leaching and dilution of fertilizers in the Yucatan karstic aquifer     

Roger Gonzalez-Herrera  Eden Martinez-Santibañez  Julia Pacheco-Avila  Armando Cabrera-Sansores 《Environmental Earth Sciences》2014,72(8):2879-2886

The application of agrochemicals in crops can cause pollution of aquifers, especially those with a shallow water table and covered by thin soils; such is the case of Yucatan, Mexico. Information about the requirements and application of fertilizers to major irrigation and rainfed crops as well as the volume of water consumed in growing were used to determine the potential amount of nitrate delivered to groundwater. The research reported in this paper was conducted in the metropolitan area of the city of Merida, in Yucatán, Mexico, where groundwater plays an important role since it is the main source of supply, due to the lack of surface water in the region. In addition, the vulnerability of this aquifer is threatened by the various activities taking place in the municipalities, which emphasize agriculture, located within the groundwater basin. This activity is analyzed as a source of contamination given the concentration of NO₃ ^? present in groundwater intended for human consumption. The results show that the contribution of farming that enriches the presence of nitrates in the aquifer is different for each municipality in the study area. For the ZMM, the average nutrient leaching is 44 % of the original mass applied; it could be diluted approximately 12 times, in the groundwater.  相似文献   

The role of infiltration processes in steep slope stability of pyroclastic granular soils: laboratory and numerical investigation   总被引：1，自引：0，他引：1  

Emilia Damiano  Lucio Olivares 《Natural Hazards》2010,52(2):329-350

Rainfall-induced landslides on steep slopes are a common feature in much of Italy’s mountain areas covered by shallow-pyroclastic deposits. Generally, these deposits are unsaturated and have a slope angle higher than 40°–50°; hence their stability is due to the positive effect of matric suction on soil shear strength. During rainfall, rainwater infiltration causes a decrease in suction, which in turn causes changes in soil mechanical and hydraulic properties, leading towards an instability process. However, the response of pyroclastic soil slopes to rainwater infiltration is not fully understood. The aim of this study is to link slope instability to the infiltration process on the basis of advanced geotechnical characterization, in situ monitoring and numerical analysis calibrated through a back-analysis of well-instrumented flume tests.  相似文献   

Gravitational instability in binary protoplanetary discs: new constraints on giant planet formation     

Lucio Mayer  James Wadsley  Thomas Quinn  Joachim Stadel 《Monthly notices of the Royal Astronomical Society》2005,363(2):641-648

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COMPASS: an instrument for measuring the polarization of the CMB on intermediate angular scales     

Philip C. Farese  Giorgio Dall&#x;Oglio  Josh Gundersen  Brian Keating  Slade Klawikowski  Lloyd Knox  Alan Levy  Chris O&#x;Dell  Alan Peel  Lucio Piccirillo  John Ruhl  Peter Timbie 《New Astronomy Reviews》2003,47(11-12):1033

COMPASS is an on-axis 2.6-m telescope coupled to a correlation polarimeter. The entire instrument was built specifically for CMB polarization studies. Careful attention was given to receiver and optics design, stability of the pointing platform, avoidance of systematic offsets, and development of data analysis techniques. Here we describe the experiment, its strengths and weaknesses, and the various things we have learned that may benefit future efforts to measure the polarization of the CMB.  相似文献   

Fundamental differences between SPH and grid methods   总被引：1，自引：0，他引：1  

Oscar Agertz  Ben Moore  Joachim Stadel  Doug Potter  Francesco Miniati  Justin Read  Lucio Mayer  Artur Gawryszczak  rey Kravtsov  Åke Nordlund  Frazer Pearce  Vicent Quilis  Douglas Rudd  Volker Springel  James Stone  Elizabeth Tasker  Romain Teyssier  James Wadsley  Rolf Walder 《Monthly notices of the Royal Astronomical Society》2007,380(3):963-978

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Titan: Preliminary results on surface properties and photometry from VIMS observations of the early flybys     

B.J. Buratti  C. Sotin  M.D. Hicks  J.A. Mosher  R. Jaumann  P.D. Nicholson  D.P. Simonelli 《Planetary and Space Science》2006,54(15):1498-1509

Cassini observations of the surface of Titan offer unprecedented views of its surface through atmospheric windows in the 1-5 μm region. Images obtained in windows for which the haze opacity is low can be used to derive quantitative photometric parameters such as albedo and albedo distribution, and physical properties such as roughness and particle characteristics. Images from the early Titan flybys, particularly T0, Ta, and T5 have been analyzed to create albedo maps in the 2.01 and 2.73 μm windows. We find the average normal reflectance at these two wavelengths to be 0.15±0.02 and 0.035±0.003, respectively. Titan's surface is bifurcated into two albedo regimes, particularly at 2.01 μm. Analysis of these two regimes to understand the physical character of the surface was accomplished with a macroscopic roughness model. We find that the two types of surface have substantially different roughness, with the low-albedo surface exhibiting mean slope angles of ∼18°, and the high-albedo terrain having a much more substantial roughness with a mean slope angle of ∼34°. A single-scattering phase function approximated by a one-term Henyey-Greenstein equation was also fit to each unit. Titan's surface is back-scattering (g∼0.3-0.4), and does not exhibit substantially different backscattering behavior between the two terrains. Our results suggest that two distinct geophysical domains exist on Titan: a bright region cut by deep drainage channels and a relatively smooth surface. The two terrains are covered by a film or a coating of particles perhaps precipitated from the satellite's haze layer and transported by eolian processes. Our results are preliminary: more accurate values for the surface albedo and physical parameters will be derived as more data is gathered by the Cassini spacecraft and as a more complete radiative transfer model is developed from both Cassini orbiter and Huygens Lander measurements.  相似文献   

Simultaneous ram pressure and tidal stripping; how dwarf spheroidals lost their gas     

Lucio Mayer  Chiara Mastropietro  James Wadsley  Joachim Stadel  Ben Moore 《Monthly notices of the Royal Astronomical Society》2006,369(3):1021-1038

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Cooling flows within galactic haloes: the kinematics and properties of infalling multiphase gas   总被引：1，自引：0，他引：1  

Tobias Kaufmann  Lucio Mayer  James Wadsley  Joachim Stadel  Ben Moore 《Monthly notices of the Royal Astronomical Society》2006,370(4):1612-1622

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HD 172189, a Cluster Member Binary System with a δ Scuti Component in the Field of View of COROT     

Pedro J. Amado  Susana Martín-Ruíz  Juan Carlos Suárez  Armando Arellano Ferro  Andrés Moya  Ignasi Ribas  Ennio Poretti 《Astrophysics and Space Science》2006,304(1-4):173-175

Photometric and spectroscopic results for the star HD 172189, member of the open cluster IC 4756 in the summer field of the space mission COROT, are presented. From photometric observations in the Strömgren system carried out at various epochs, its binary nature as well as the presence of a δ Scuti-type pulsating component have been discovered. The frequency analysis of the whole dataset confirms a dominant frequency of 19.5974 c d^?1 with a maximum amplitude near 0.02 mag plus other frequencies in the range 18–20 c d^?1. A preliminary orbital solution from the light curve and from four FEROS spectra reveals two similar components of around 1.5 M _⊙ orbiting with a period of 5.702 d.  相似文献   

Transient kinematic pile bending in two-layer soil     

Stefania Sica  George Mylonakis  Armando Lucio Simonelli 《Soil Dynamics and Earthquake Engineering》2011

The dynamic response of piles to seismic loading is explored by means of an extensive parametric study based on a properly calibrated Beam-on-Dynamic-Winkler-Foundation (BDWF) model. The investigated problem consists of a single vertical cylindrical pile, modelled as an Euler–Bernoulli beam, embedded in a subsoil consisting of two homogeneous viscoelastic layers of sharply different stiffness resting on a rigid stratum. The system is subjected to vertically propagating seismic S waves, in the form of a transient motion imposed on rock outcrop. Several accelerograms recorded in Italy are employed as input motions in the numerical analyses. The paper highlights the severity of kinematic pile bending in the vicinity of the interface separating the two soil layers. In addition to factors already investigated such as layer stiffness contrast, relative soil–pile stiffness, interface depth and intensity of ground excitation, the paper focuses on additional important factors, notably soil material damping, stiffness of Winkler springs and frequency content of earthquake excitation. Existing predictive equations for assessing kinematic pile bending at soil layer interfaces are revisited and new regression analyses are performed. A synthesis of findings in terms of a set of simple equations is provided. The use of these equations is discussed through examples.  相似文献