Search results for "Instability"

Actividad de los músculos paravertebrales durante ejercicios que requieran estabilidad raquídea

2011

CONTEXTO: El entrenamiento aplicando elementos de inestabilidad está siendo ampliamente utilizado en el campo del entrenamiento como una herramienta novedosa y eficaz. No obstante, recientes hallazgos aportan datos contrarios a esta creencia y sugieren que la ejecución de ejercicios tradicionales sobre superficies inestables o ejercicios calisténicos específicos para el fortalecimiento estabilizador pueden no resultar estímulo suficiente para personas con un nivel de entrenamiento elevado llegando incluso a interferencia en el rendimiento final por la reducción de la capacidad de fuerza y la carencia de especificidad del entrenamiento. OBJETIVO: Cuantificar y comparar la actividad muscular …

How to untie G-quadruplex knots and why?

2021

International audience; For over two decades, the prime objective of the chemical biology community studying G-quadruplexes (G4s) has been to use chemicals to interact with and stabilize G4s in cells to obtain mechanistic interpretations. This strategy has been undoubtedly successful, as demonstrated by recent advances. However, these insights have also led to a fundamental rethinking of G4-targeting strategies: due to the prevalence of G4s in the human genome, transcriptome, and ncRNAome (collectively referred to as the G4ome), and their involvement in human diseases, should we continue developing G4-stabilizing ligands or should we invest in designing molecular tools to unfold G4s? Here, …

Genome Instability in DNA Viruses

2016

Genome instability generally refers to the appearance of a high frequency of mutations in a single genome, including point mutations, insertions/deletions, or major rearrangements. DNA viruses usually show greater genome stability than RNA viruses. However, recent genome-wide molecular evolution and experimental studies have shown that DNA viruses can exhibit rapid sequence changes that are often found in loci involved in dynamic host–virus interactions. In fact, DNA viruses are capable of promoting genome instability specifically at certain genes, thus boosting diversity wherein needed. We review some of the molecular mechanisms underlying genomic instability in prokaryotic and eukaryotic …

A sufficient condition for the instability of theq-d algorithm

1959

The rate of multiplicity of the roots of nonlinear equations and its application to iterative methods

2015

Nonsimple roots of nonlinear equations present some challenges for classic iterative methods, such as instability or slow, if any, convergence. As a consequence, they require a greater computational cost, depending on the knowledge of the order of multiplicity of the roots. In this paper, we introduce dimensionless function, called rate of multiplicity, which estimates the order of multiplicity of the roots, as a dynamic global concept, in order to accelerate iterative processes. This rate works not only with integer but also fractional order of multiplicity and even with poles (negative order of multiplicity).

Optical Fibers Enter a New Space-Time Era

2016

We show experimentally a new type of parametric instability associated with the original phenomenon of beam self-cleaning in multimode fibers. Our experimental results are in good agreement with numerical solutions of the Gross-Pitaevskii equation.

Scaling Behavior in Non-Hookean Compression of Thin-Walled Structures

2010

The mechanics and stability of thin-walled structures is a challenging and important branch in structural mechanics. Under vertical compression the deformation of a thin-walled box differs from that of, e.g., a cylindrical shell. It is demonstrated here that compression of a box can be described by a set of generic scaling laws representing three successive regimes: a linear, wrinkled, and collapsed regime. The linear Hookean regime represents the normal behavior before any instability sets in, while the following wrinkled regime is shown to be analogous to compression of thin-film blisters. The compression force reaches its maximum at the onset of the final collapsed regime that has all th…

Re-entrance phase formation of CeSb thin films

2001

Abstract We report the epitaxial growth of (1 0 0)- and (1 1 1)-oriented CeSb thin films on Al 2 O 3 (1 1 2 0) and (0 0 0 1) substrates by means of molecular beam epitaxy. Depending on the overall Sb-to-Ce flux ratio and the molecular state of Sb x , we observe a re-entrance behavior in the phase formation and orientation of CeSb on Al 2 O 3 (1 1 2 0) . This behavior is shown to exhibit, in some respect, similarities to III–V compound growth, but also more complexities due to the instability of the rare earth component against oxidation. A geometric orientation selection model is suggested which reproduces the observed re-entrance behavior as well as the overall CeSb growth rate.

Instability of the melt flow in VGF growth with a traveling magnetic field

2009

The linear instability of a thermally stratified melt flow in the VGF configuration driven by a traveling magnetic field (TMF) is considered numerically and experimentally. The dependency of the instability threshold on the governing parameters is found for several cuts through the parameter space covering a wide range of possible applications. In a first approximation the linear instability occurs when the dimensionless TMF forcing parameter reaches the magnitude of the Grashof number. This is particularly true in a medium-sized crucible where the first instability is axisymmetric and sub-critical. As the Grashof number increases the flow develops self-similar boundary layers and the insta…

Gravity effects on mixing with magnetic micro-convection in microfluidics.

2018

Mixing remains an important problem for development of successful microfluidic and lab-on-a-chip devices, where simple and predictable systems are particularly interesting. One is magnetic micro-convection, an instability happening on the interface of miscible magnetic and non-magnetic fluids in a Hele-Shaw cell under applied field. Previous work proved that Brinkman model quantitatively explains the experiments. However, a gravity caused convective motion complicated the tests. Here we first improve the experimental system to exclude the gravitational convective motion. Afterwards, we observe and quantify how gravity and laminar flow play an important role in stabilizing the perturbations …