Search results for "STABILITY"
showing 10 items of 3085 documents
Early warning thresholds for partially saturated slopes in volcanic ashes
2013
Rainfall-induced landslides in steep soil slopes of volcanic origin are a major threat to human lives and infrastructure. In the context of constructing early warning systems in regions where extensive data on landslide occurrences and associated rainfall are inexistent, physically-based tools offer the possibility to establish thresholds for measurable field quantities. In this paper, a combined finite element infinite slope model is presented to study the transient hydraulic response of volcanic ash slopes to a series of rainfall events and to estimate seasonal safety factors. Furthermore, analytical considerations of partially saturated infinite slopes are made to define capillary stress…
Hydrothermal alteration can result in pore pressurization and volcano instability
2021
AbstractThe collapse of a volcanic flank can be destructive and deadly. Hydrothermal alteration is common to volcanoes worldwide and is thought to promote volcano instability by decreasing rock strength. However, some laboratory studies have shown that not all alteration reduces rock strength. Our new laboratory data for altered rhyodacites from Chaos Crags (Lassen volcanic center, California, USA) show that pore- and crack-filling mineral precipitation can reduce porosity and permeability and increase strength, Young's modulus, and cohesion. A significant reduction in permeability, by as much as four orders of magnitude, will inhibit fluid circulation and create zones of high pore fluid pr…
Sulle riforme istituzionali: brevi note
2023
It is a contribution to the debate on institutional reforms with reflections on the method and merits of the reforms
Stability and disassembly properties of human naïve Hsp60 and bacterial GroEL chaperonins.
2015
Human Hsp60 chaperonin and its bacterial homolog GroEL, in association with the corresponding co-chaperonins Hsp10 and GroES, constitute important chaperone systems promoting the proper folding of several mitochondrial proteins. Hsp60 is also currently described as a ubiquitous molecule with multiple roles both in health conditions and in several diseases. Naïve Hsp60 bearing the mitochondrial import signal has been recently demonstrated to present different oligomeric organizations with respect to GroEL, suggesting new possible physiological functions. Here we present a combined investigation with circular dichroism and small-angle X-ray scattering of structure, self-organization, and sta…
Analysis of oscillations in discontinuous Lurie systems via LPRS method
2019
We discuss advantages and limitations of the harmonic balance method and the locus of a perturbed relay system (LPRS) method in the problem of finding periodic oscillations. In this paper we present the results of using harmonic balance method and LPRS method while investigating a 3rd order dynamic system in Lurie form. In this system a symmetric periodic oscillation is found, while other two asymmetric periodic motions are not found using both methods. peerReviewed
Interplay of acidity and ionic liquid structure on the outcome of a heterocyclic rearrangement reaction
2021
The study of suitable probe reactions is a powerful tool to investigate the properties of nonconventional solvents such ionic liquids (ILs). In particular, we studied the acid-catalyzed mononuclear rearrangement of heterocycles (MHR) of the Z-phenylhydrazone of 5-amino-3-benzoyl-1,2,4-oxadiazole into the relevant 1,2,3-triazole, in solution of ILs by means of kinetic measurements. We chose as solvents six ILs differing both in the cation and anion, in the presence of five carboxylic and sulfonic acids as catalysts. For a useful comparison, the reaction was also performed in 1,4-dioxane and methanol. In general, the reaction occurs faster in ILs, compared to conventional solvents, according …
Lignin recovery from spent alkaline pulping liquors using acidification, membrane separation, and related processing steps: A Review
2019
The separation of lignin from the black liquor generated during alkaline pulping is reviewed in this article with an emphasis on chemistry. Based on published accounts, the precipitation of lignin from spent pulping liquor by addition of acids can be understood based on dissociation equilibria of weak acid groups, which affects the solubility behavior of lignin-related chemical species. Solubility issues also govern lignin separation technologies based on ultrafiltration membranes; reduction in membrane permeability is often affected by conditions leading to decreased solubility of lignin decomposition products and the presence of colloidal matter. Advances in understanding of such phenomen…
Modeling the hydrological and mechanical effect of roots in shallow landslide analysis
2015
The additional cohesion exercised by vegetation roots (cr) provides an important contribution to the slope stability. This study proposes a methodology for estimating the cr term in a hillslope landslide analysis within a coupled ecohydrological-stability model. The coupled model simulates the spatial distribution and temporal dynamics of the Factor of Safety (FS) as a function of soil moisture dynamics, by taking into account the hydrological effects of vegetation through the root water uptaking. The additional mechanical root cohesion is estimated in a Fiber Bundle Model framework that allows for the evaluation of the root strength as a function of stress-strain relationships of populatio…
Hydrological and mechanical effects of roots in shallow landslide analysis: A physically-based approach
2015
This study provides the first insights of a methodology for estimating the additional cohesion exercised by vegetation roots in a hillslope landslide analysis within a coupled ecohydrological-stability model. The existing coupled system is able to simulate the spatial distribution and temporal dynamics of Factor of Safety (FS) as a function of soil moisture dynamics. The model takes into account the hydrological effects of vegetation which, through the root water uptaking, contributes in reducing the soil water content and, thus, in increasing the slope stability. The additional mechanical root cohesion is estimated in a Fiber Bundle Model (FBM) framework that allows for the evaluation of t…
Photoactivity and Chemical Reactivity in Titanium(IV)-Organic Frameworks
2020
La presente tesis doctoral ha sido realizada como compendio de publicaciones y lleva por título “Fotoactividad y reactividad química en redes metal-orgánicas de titanio(IV)” (Photoactivity and Chemical Reactivity in Titanium(IV)-Organic Frameworks). La tesis se encuentra dividida en cinco capítulos además de un capítulo final de conclusiones y un resumen en castellano. El primer capítulo trata de una introducción acerca de las redes metal-orgánicas (del inglés Metal-Organic Frameworks, MOFs) de titanio(IV) existentes hasta la fecha para dar una visión general de su variedad estructural, así como de las estrategias sintéticas empleadas y las propiedades fotocatalíticas de estos materiales. E…