4,452 research outputs found
Mechanical response of a self avoiding membrane: fold collisions and the birth of conical singularities
An elastic membrane that is forced to reside in a container smaller than its
natural size will deform and, upon further volume reduction, eventually
crumple. The crumpled state is characterized by the localization of energy in a
complex network of highly deformed crescent-like regions joined by line ridges.
Previous studies have focused on the onset of the crumpled state by analyzing
the mechanical response and stability of a conical dislocation, while others
have simulated the highly packed regime neglecting the importance of the
connectivity of the membrane. Here we show, through a combination of
experiments, numerical simulations, and analytic approach, that the emergence
of new regions of high stretching is a generic outcome when a self avoiding
membrane is subject to a severe geometrical constraint. We demonstrate that, at
moderate packing fraction, interlayer interactions produce a response
equivalent to the one of a thicker membrane that has the shape of the deformed
one. Evidence is found that friction plays a key role stabilizing the folded
structures.Comment: 10 page
La reforma de la negociación colectiva en la ley 3/2012
En el presente estudio se analizan las reformas en el régimen jurídico de la negociación colectiva mediante la Ley 3/2012 (precedida por el RDL 3/2012) y el RDL 20/2012, que han perjudicado y dificultado algunas de las funciones esenciales de la negociación colectiva para la evitación de vacíos de regulación, progreso en las condiciones de trabajo y freno a la individualización, y que han hecho girar el eje de la negociación hacia la empresa, solución poco realista en un marco productivo dominado por la microempresa y que otorga más poder al empleador. Las reformas han afectado sobre todo a la situación del convenio una vez finalizada su vigencia pactada (régimen de prórroga), a la estructura de la negociación (prevalencia del convenio de empresa), a los procedimientos de inaplicación, suspensión y modificaciones de las condiciones pactadas en los convenios y al contenido de estos
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The contextualization of the watchdog and civic journalistic roles: Reevaluating journalistic role performance in U.S. newspapers
This study examines the two dominant U.S. journalism models-the watchdog and civic-oriented professional performance-in the aftermath of the economic crises. The study, based on a content analysis of 1,421 news stories published by five national U.S. dailies, measures journalists' role conception through a content analysis of newspaper articles, examining the concept of journalistic role performance. The findings indicate different contextualizations of the two roles: The civic journalism performance was mostly found in stories dealing with issues such as human rights, demonstrations, and religion. The watchdog model was found in stories dealing with religion as well, but was found more frequently than the civic model in stories covering the government, police and crime. While the overall results indicate shifting roles of journalists toward a more civic approach, the traditional watchdog role remains important in covering politics. The roles journalists perform and their implications for U.S. news coverage are discussed
Wrinkling of a bilayer membrane
The buckling of elastic bodies is a common phenomenon in the mechanics of
solids. Wrinkling of membranes can often be interpreted as buckling under
constraints that prohibit large amplitude deformation. We present a combination
of analytic calculations, experiments, and simulations to understand wrinkling
patterns generated in a bilayer membrane. The model membrane is composed of a
flexible spherical shell that is under tension and that is circumscribed by a
stiff, essentially incompressible strip with bending modulus B. When the
tension is reduced sufficiently to a value \sigma, the strip forms wrinkles
with a uniform wavelength found theoretically and experimentally to be \lambda
= 2\pi(B/\sigma)^{1/3}. Defects in this pattern appear for rapid changes in
tension. Comparison between experiment and simulation further shows that, with
larger reduction of tension, a second generation of wrinkles with longer
wavelength appears only when B is sufficiently small.Comment: 9 pages, 5 color figure
Classical Topological Order in Kagome Ice
We examine the onset of classical topological order in a nearest-neighbor
kagome ice model. Using Monte Carlo simulations, we characterize the
topological sectors of the groundstate using a non-local cut measure which
circumscribes the toroidal geometry of the simulation cell. We demonstrate that
simulations which employ global loop updates that are allowed to wind around
the periodic boundaries cause the topological sector to fluctuate, while
restricted local loop updates freeze the simulation into one topological
sector. The freezing into one topological sector can also be observed in the
susceptibility of the real magnetic spin vectors projected onto the kagome
plane. The ability of the susceptibility to distinguish between fluctuating and
non-fluctuating topological sectors should motivate its use as a local probe of
topological order in a variety of related model and experimental systems.Comment: 17 pages, 9 figure
Probing the role of point mutations in the cyp51A gene from Aspergillus fumigatus in the model yeast Saccharomyces cerevisiae
Azole-resistant strains of Aspergillus fumigatus have been detected and the underlying molecular mechanisms of resistance characterized. Point mutations in the cyp51A gene have been proved to be related to azole resistance in A. fumigatus clinical strains and with different resistance profiles depending on the amino acid change (G54E, G54V, G54R, G54W, M220V, M220K, M220T, M220I). The aim of this work was to express A. fumigatus cyp51A genes in the yeast Saccharomyces cerevisiae in order to better assess the contribution of each independent amino acid substitution to resistance. A tetracycline regulatable system allowing repression of the endogenous essential ERG11 gene was used. The expression of Aspergillus cyp51A alleles could efficiently restore the absence of ERG11 in S. cerevisiae. In general, S. cerevisiae clones expressing. A. fumigatus cyp51A alleles from azole-resistant isolates showed higher MICs to all azoles tested than those expressing alleles from susceptible isolates. The azole susceptibility profiles obtained in S. cerevisiae upon expression of specific cyp51A alleles recapitulated susceptibility profiles observed from their A. fumigatus origins. In conclusion this work supports the concept that characteristics of specific A. fumigatus cyp51A alleles could be investigated in the heterologous host S. cerevisia
A comparative study of the electrochemical properties of vitamin B-6 related compounds at physiological pH
A comparative study of vitamin B6 group and related compounds in buffered solutions using electrochemical techniques has been performed at neutral pH. Irreversible bi- or tetra-electronic processes are observed for these substances, and the electron transfer coefficient (αn) calculated. It was concluded that either the first or second electron transfer were the rate determining step of the electrode process. The diffusion coefficient of these substances was calculated and the values given follow an inverse tendency to the molecular size. For aldehydes the values obtained were corrected of the hydration reaction.
It is important to remark that catalytic waves were reported for the first time for these compounds. Using a model involving the nitrogen of the basic structure the kinetic constants were calculated for most of them
A Method to Estimate the Boson Mass and to Optimise Sensitivity to Helicity Correlations of tau+tau- Final States
In proton-proton collisions at LHC energies, Z and low mass Higgs bosons
would be produced with high and predominantly longitudinal boost with respect
to the beam axis. This note describes a new analysis tool devised to handle
this situation in cases when such bosons decay to a pair of tau-leptons. The
tool reconstructs the rest frame of the tau+tau- pair by finding the boost that
minimises the acollinearity between the visible tau decay products. In most
cases this gives a reasonable approximation to the rest frame of the decaying
boson. It is shown how the reconstructed rest frame allows for a new method of
mass estimation. Also a considerable gain in sensitivity to helicity
correlations is obtained by analysing the tau-jets in the reconstructed frame
instead of using the laboratory momenta and energies, particularly when both
tau-leptons decay hadronically.Comment: 13 pages, method extended with 3D boost finde
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