Search results for "instability"
showing 10 items of 724 documents
Achievement perceived, parenting, internet use and adolescent behavior
2019
espanolResumen El uso intensivo de internet puede contribuir a desarrollar disfunciones psicosociales graves en la adolescencia. El objetivo de esta investigacion es analizar las relaciones de la percepcion de eficacia academica con el uso de internet para ocio, los estilos de crianza y los problemas exteriorizados e interiorizados en la adolescencia (agresividad proactiva, reactiva, fisica y verbal, afiliacion a pares rebeldes e inestabilidad emocional). Han participado 762 adolescentes de 12 a 17 anos (M = 13.69; DT = 1.40; varones 52.8%). Utilizan internet en tiempo de ocio entre cero y 98 horas semanales, de ahi que la poblacion se haya distribuido en cuartiles. Las variables se han obt…
Talking about emotions with children at risk of social exclusion: a preliminary study
2016
Resumen Este trabajo tiene como objetivo principal probar de forma preliminar el funcionamiento de un programa de intervención para mejorar las competencias emocionales en niños de entre 9 y 10 años en situación de riesgo de exclusión social. El programa se centra en la mejora de algunos componentes del conocimiento y la regulación emocional. Para ello, se utilizó un diseño pre-experimental de un solo grupo con pretest y postest (N = 14). Los niños asistieron a las sesiones una vez por semana durante cuatro meses. Los resultados mostraron una mejora estadísticamente significativa en manejo de emociones, adaptabilidad e inestabilidad emocional, además de una utilización más efectiva de estra…
Mechanics of invagination and folding: Hybridized instabilities when one soft tissue grows on another
2015
We address the folding induced by differential growth in soft layered solids via an elementary model that consists of a soft growing neo-Hookean elastic layer adhered to a deep elastic substrate. As the layer/substrate modulus ratio is varied from above unity towards zero we find a first transition from supercritical smooth folding followed by cusping of the valleys to direct subcritical cusped folding, then another to supercritical cusped folding. Beyond threshold the high amplitude fold spacing converges to about four layer thicknesses for many modulus ratios. In three dimensions the instability gives rise to a wide variety of morphologies, including almost degenerate zigzag and triple-ju…
Arsenite-induced aneuploidy following short and long-term exposure in mammalian cells
2009
We studied the long-term progression of chromosomal instability in V79 cells treated acutely with arsenite (10mM, 24 hr) followed by growth in arsenic-free medium for 120 cell generations. Indirect immunostaining using anti-ß-tubulin antibody showed severe alterations in spindle morphology after only 6 h treatment and cytogenetic investigations carried out at the end of treatment revealed that the percentage of cells with 21 chromosomes (modal number of the cell line) decreased, making way for aneuploid cells. The acquired instability remained and propagated within the cell population. Moreover, we treated V79-derived G12 cells with sub-lethal doses (0.1-1.0 μM) of arsenite for 10 days foll…
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…
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…
Optimality of Increasing Stability for an Inverse Boundary Value Problem
2021
In this work we study the optimality of increasing stability of the inverse boundary value problem (IBVP) for the Schrödinger equation. The rigorous justification of increasing stability for the IBVP for the Schrödinger equation were established by Isakov [Discrete Contin. Dyn. Syst. Ser. S, 4 (2011), pp. 631--640] and by Isakov et al. [Inverse Problems and Applications, Contemp. Math. 615, American Math Society, Providence, RI, 2014, pp. 131--141]. In [Discrete Contin. Dyn. Syst. Ser. S, 4 (2011), pp. 631--640] and [Inverse Problems and Applications, Contemp. Math. 615, American Math Society, Providence, RI, 2014, pp. 131--141], the authors showed that the stability of this IBVP increases …
Endogenous firm asymmetry and cooperative R&D in linear duopoly with spillovers
2005
In a linear model ofcost reducing R&D/Cournot competition, firm asymmetry is shown to be sustainable as subgame perfect Nash equilibrium with R&D competition only ifthe productivity of research is sufficiently large relative to the benefits from imitation. In such a case, industry-wide cost reduction and firms asymmetry are increasing and decreasing functions of the spillover rate, respectively. In the absence of spillovers, a symmetric joint lab generates higher consumer surplus and social welfare than a pair ofasymmetric competitors. If spillovers are not too small, asymmetric R&D competition is advantageous toconsumers, but not to firms.
Analytical approach for the problems of dynamics and stability of a moving web
2015
Problems of dynamics and stability of a moving web, modelled as an elastic rod or string, and axially travelling between rollers (supports) at a constant velocity, are studied using analytical approaches. Transverse, longitudinal and torsional vibrations of the moving web are described by a hyperbolic second-order partial differential equation, corresponding to the string and rod models. It is shown that in the framework of a quasi-static eigenvalue analysis, for these models, the critical point cannot be unstable. The critical velocities of one-dimensional webs, and the arising non-trivial solution of free vibrations, are studied analytically. The dynamical analysis is then extended into t…