14,604 research outputs found
Aging Dynamics of a Fractal Model Gel
Using molecular dynamics computer simulations we investigate the aging
dynamics of a gel. We start from a fractal structure generated by the DLCA-DEF
algorithm, onto which we then impose an interaction potential consisting of a
short-range attraction as well as a long-range repulsion. After relaxing the
system at T=0, we let it evolve at a fixed finite temperature. Depending on the
temperature T we find different scenarios for the aging behavior. For T>0.2 the
fractal structure is unstable and breaks up into small clusters which relax to
equilibrium. For T<0.2 the structure is stable and the dynamics slows down with
increasing waiting time. At intermediate and low T the mean squared
displacement scales as t^{2/3} and we discuss several mechanisms for this
anomalous time dependence. For intermediate T, the self-intermediate scattering
function is given by a compressed exponential at small wave-vectors and by a
stretched exponential at large wave-vectors. In contrast, for low T it is a
stretched exponential for all wave-vectors. This behavior can be traced back to
a subtle interplay between elastic rearrangements, fluctuations of chain-like
filaments, and heterogeneity.Comment: 30 pages, 25 figure
An atlas of ECMWF analyses (1980-1987). Part 1: First moment quantities
This document is an atlas of the European Center for Medium Range Weather Forecasts (ECMWF) initialized analyses for 1980 to 1987. Various first moment quantities are presented for monthly, seasonal, and annual averages on a global cylindrical projection, as well as, cross section maps of zonal averages. Global maps of winds, temperature, stream function, and velocity potential are presented at 850 and 200 mb. In addition, global maps of the 300 mb height field (total and eddy), the 500 mb vertical velocity, the 850 mb moisture field, and sea level pressure are presented. The average seasonal cycle and anomalies during the 8 year period are presented for selected quantities
Quantum correlations versus Multisimultaneity: an experimental test
Multisimultaneity is a causal model of relativistic quantum physics which
assigns a real time ordering to any set of events, much in the spirit of the
pilot-wave picture. Contrary to standard quantum mechanics, it predicts a
disappearance of the correlations in a Bell-type experiment when both analysers
are in relative motion such that, each one in its own inertial reference frame,
is first to select the output of the photons. We tested this prediction using
acousto-optic modulators as moving beam-splitters and interferometers separated
by 55 m. We didn't observe any disappearance of the correlations, thus refuting
Multisimultaneity.Comment: 4 pages, 3 figures, RevTex 4 versio
Quantum entanglement with acousto-optic modulators: 2-photon beatings and Bell experiments with moving beamsplitters
We present an experiment testing quantum correlations with frequency shifted
photons. We test Bell inequality with 2-photon interferometry where we replace
the beamsplitters by acousto-optic modulators, which are equivalent to moving
beamsplitters. We measure the 2-photon beatings induced by the frequency
shifts, and we propose a cryptographic scheme in relation. Finally, setting the
experiment in a relativistic configuration, we demonstrate that the quantum
correlations are not only independent of the distance but also of the time
ordering between the two single-photon measurements.Comment: 14 pages, 16 figure
Phosphoregulation on mitochondria: Integration of cell and organelle responses
Mitochondria are highly integrated organelles that are crucial to cell adaptation and mitigating adverse physiology. Recent studies demonstrate that fundamental signal transduction pathways incorporate mitochondrial substrates into their biological programs. Reversible phosphorylation is emerging as a useful mechanism to modulate mitochondrial function in accordance with cellular changes. Critical serine/threonine protein kinases, such as the câJun Nâterminal kinase (JNK), protein kinase A (PKA), PTENâinduced kinaseâ1 (PINK1), and AMPâdependent protein kinase (AMPK), readily translocate to the outer mitochondrial membrane (OMM), the interface of mitochondriaâcell communication. OMM protein kinases phosphorylate diverse mitochondrial substrates that have discrete effects on organelle dynamics, protein import, respiratory complex activity, antioxidant capacity, and apoptosis. OMM phosphorylation events can be tempered through the actions of local protein phosphatases, such as mitogenâactivated protein kinase phosphataseâ1 (MKPâ1) and protein phosphatase 2A (PP2A), to regulate the extent and duration of signaling. The central mediators of OMM signal transduction are the scaffold proteins because the relative abundance of these accessory proteins determines the magnitude and duration of a signaling event on the mitochondrial surface, which dictates the biological outcome of a local signal transduction pathway. The concentrations of scaffold proteins, such as Aâkinase anchoring proteins (AKAPs) and Sab (or SH3 binding protein 5âSH3BP5), have been shown to influence neuronal survival and vulnerability, respectively, in models of Parkinson\u27s disease (PD), highlighting the importance of OMM signaling to health and disease. Despite recent progress, much remains to be discovered concerning the mechanisms of OMM signaling. Nonetheless, enhancing beneficial OMM signaling events and inhibiting detrimental proteinâprotein interactions on the mitochondrial surface may represent highly selective approaches to restore mitochondrial health and homeostasis and mitigate organelle dysfunction in conditions such as PD
A review of geological effects and damage distribution of the June 9, 1980 Mexicali Valley Earthquake
The June 9, 1980 earthquake (M_L = 6.1) occurred on the Cerro Prieto fault located in the Mexicali Valley (Figure 8.1). A day and a half after the event, the area was inspected both from the air and on the ground.
The aim of the aerial reconnaissance was to obtain evidence of possible slippage of the Cerro Prieto fault as well as other phenomena related to the earthquake
Le bassin versant du fleuve Santa (Andes du PĂ©rou) : dynamique des Ă©coulements en contexte glacio-pluvio-nival
Au debout des annĂ©es 70 les chercheurs de diffĂ©rents pays ont dĂ©tectĂ© des variations climatiques qu'ils ont appelĂ© « changement climatique », lesquelles se manifestent par des variations des tempĂ©ratures, du cycle de l'eau, du niveau de la mer, un recul accĂ©lĂ©rĂ© des glaciers, etc. Afin d'Ă©valuer ce changement climatique le programme de l'environnement des Nations Unies a crĂ©Ă© pendant l'annĂ©e 1988 le « Intergovernmental Panel on Climate Change » (IPCC en anglais). Cette Institution a Ă©valuĂ© le changement climatique et ses consĂ©quences au niveau planĂ©taire. Le PĂ©rou pays entiĂšrement situĂ© en AmĂ©rique du Sud dans la rĂ©gion intropicale subit directement les effets de cette variation climatique. Le PĂ©rou concentre presque 70% des glaciers tropicaux de la planĂšte. Au nord de la ville de Lima se situe le bassin versant du fleuve Santa qui, avec une surface englacĂ©e de 631 kmÂČ reprĂ©sente presque un tiers de toutes les surfaces englacĂ©es du PĂ©rou. Ce bassin draine une partie de la CordillĂšre Blanche « CordillĂšre Blanca ». Les glaciers de cette CordillĂšre prĂ©sentent un recul qui s'est accĂ©lĂ©rĂ© durant les 30 derniĂšres annĂ©es. Des photos aĂ©riennes de 1970 et les images satellites SPOT 3 et 5 pour les annĂ©es 1991 et 2003 ont permis de quantifier la perte de masse glaciaire de la CordillĂšre Blanche. L'unitĂ© GREAT-ICE de l'Institut de Rechercher pour le DĂ©veloppement (IRD), le Service National de MĂ©tĂ©orologie et hydrologie du PĂ©rou (SENAMHI) et l'Institut des Ressources Naturelles du PĂ©rou (INRENA) ont signĂ© une convention de coopĂ©ration Ă partir de l'annĂ©e 2000 (reconduite en 2004) afin de suivre l'Ă©volution des glaciers et de la ressource en eau qui en dĂ©pend. C'est dans le cadre de cette coopĂ©ration que j'Ă©tudie l'avenir de la ressource en eau de la partie amont (sur les 2000 premiers mĂštres Ă partir des crĂȘtes) des sub - bassins versants englacĂ©s de la cordillĂšre Blanche. Ce travail a permis d'Ă©tablir une modĂ©lisation de la ressource en eau issue de la fusion glaciaire, tenant compte des Ă©coulements liĂ©s de la prĂ©cipitation liquide sur la zone non englacĂ©e. Cette modĂ©lisation travaille suivant 2 scĂ©narios A2 et B2 du changement climatique proposĂ©s pour l'IPCC utilisant diffĂ©rents modĂšles de circulation gĂ©nĂ©ral du couple atmosphĂšre-OcĂ©ans (AOGCM)(RĂ©sumĂ© d'auteur
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