226 research outputs found
Effects of rainfall infiltration into fractured and swelling soils on triggering shallow landslides
No full textConnection between spectral features of BK edge XANES of minerals and the local structure
No full textThe potential of XANES spectroscopy for studying the structure of boron-containing compounds is assessed by theoretical modelling of B K edge spectra of minerals. Spectra arising from three-fold coordinated boron sites differ considerably from spectra arising from four-fold coordinated sites. The characteristic shape of the spectra is governed first of all by short range order and, to a lesser extent, by medium range order. Areas of main spectral peaks depend only on the coordination of the photoabsorbing site and can thus be used for quantifying the portion of boron atoms in BO3 and in BO4 units, in minerals as well as in glasses. The width of the main peak of spectrum at a four-fold coordinated boron site generally increases with the the spread of the B-O distances but deviations from this correlation may be substantial. In contrast to spectra of minerals, XANES of BPO4 crystal is governed by long range order and is thus not a suitable model for studying XANES of borate glasses
Structure and base catalysed cyclization of methyl (2,6-disubstituted-4-nitrophenylsulphanyl)ethanoates
No full textThe conformation of side chain –SCH2COOCH3 in title compounds in crystal agrees with the reactivity of these compounds
in base catalysed ring closure in solution. In the 2,4-dinitro derivative, the side chain is oriented towards the unsubstituted
ortho-position of benzene ring, in the case of the 2-methoxycarbonyl derivative towards this substituent
Analysis of rainfall infiltration effects on the stability of pyroclastic soil veneer affected by vertical drying shrinkage fractures
No full textThe paper presents a preliminary, simplified evaluation of the effects of rainfall infiltration on the stability of slopes in layered pyroclastic soils affected by shrinkage vertical fractures. The analysis has been developed with a special reference to a stratigraphic sequence obtained by an in situ survey at Pizzo d'Alvano (Southern Italy). The analysis of rainfall infiltration is performed using an original dual-permeability model. Results show how fractures strongly condition infiltration depending on rainfall intensity. Prolonged low-intensity rainfall may lead to a higher saturation of the surface soil layer than short, intense rainfall when water may flow quickly through fractures into the underlying more permeable soil layers. Calculated distributions of pore pressure are used for the slope stability analysis using the infinite slope approach. Variations of the safety factor as a consequence of infiltration show that prolonged rainfall can induce a more relevant decrease in the safety factor than intense precipitations. © 2013 Springer-Verlag Berlin Heidelberg
Analysis of infiltration processes into fractured and swelling soils as triggering factors of landslides
No full textRainfall infiltration can cause a dramatic decrease of suction in unsaturated soils and, consequently, of shear strength, triggering various instability phenomena, such as the slip of steep surface soil layers. Swelling of cracked soils and capillary barrier effects, induced by fine-grained soils overlying a more permeable material, can also affect water flow through this type of soil systems. In the past, few studies on infiltration and rainfall-induced landslides considered the simultaneous effects of surface cracks, swelling materials, and/or the capillary barrier phenomenon. To this purpose, this paper presents the results obtained by a dual-permeability model, which simulates water flow through a fractured swelling soil overlying a more permeable soil and focusing on the influence of these phenomena on triggering of landslides. Numerical results show that for high-intensity precipitations, flow through fractures quickly reaches significant depths and the capillary barrier is broken, while soil swelling leads to a uniform narrowing of cracks. On the other hand, for low-intensity precipitations, fracture flow and swelling are limited only to the first 30-50 cm of the topsoil, while cracks almost completely closed. Evaluations of the slope stability show that prolonged low-intensity rainfalls might be more dangerous than short high-intensity rains in triggering surface landslides. © 2013 Springer-Verlag Berlin Heidelberg
Improving the estimation of evaporation by the FAO-56 dual crop coefficient approach under subsurface drip irrigation
No full textAbstract not availableV. Phogat, J. Simunek, M.A. Skewes, J.W. Cox, M.G. McCarth
Lateral Water Diffusion in an Artificial Macroporous System: Modeling and Experimental Evidence
No full textLateral Water Diffusion in an Artificial Macroporous System: Modeling and Experimental Evidence
No full textA Three-Dimensional Channel Supramolecular Architecture Based on 3-Amino-2-(4-dimethylaminophenyldiazenyl)-1-phenylbut-2-en-1-one and Aromatic Guests
No full textIf crystallized from aromatic solvents (benzene, toluene, p-xylene, chlorobenzene), 3-amino-2-(4-dimethyl-
aminophenyldiazenyl)-1-phenylbut-2-en-1-one (1) forms a three-dimensional supramolecular H-bonding network with mole-
cular channels of approximately cylindrical shape in which the solvent molecules are placed in a defined manner. The aromatic
molecules are bound with the molecules of the network by means of weak intermolecular interactions of varying nature. The
X-ray structures provide detailed information on the bindingmotifs that consist ofC-H...O and C-H...pi bonds between the
aromatic solvent molecules and the benzoyl moiety of 1. The motifs are identical in all the four inclusion compounds analyzed
showing the robustness of this supramolecular synthon. Accordingly, the crystals adopt isostructural arrangements favored by the mutual orientation of the host molecules of 1 that make identical helical catemers by means of strong N-H...O
intermolecular hydrogen bonds. Thermal stability of the inclusion compounds of compound 1 with benzene, toluene, p-xylene,
and m-xylene has been studied by means of differential scanning calorimetry and thermogravimetric analysis methods
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