1,083 research outputs found
Holography and Stiff-matter on the Brane
Recently, Verlinde noted a surprising similarity between Friedmann equation
governing radiation dominated universe and Cardy's entropy formula in conformal
field theory. In this note, we study a brane-universe filled with radiation and
stiff-matter. We analyze Friedmann equation in this context and compare our
results with Cardy's entropy formula.Comment: 6 pages, Latex, references added to match with published versio
Strength of Mechanical Memories is Maximal at the Yield Point of a Soft Glass
We show experimentally that both single and multiple mechanical memories can
be encoded in an amorphous bubble raft, a prototypical soft glass, subject to
an oscillatory strain. In line with recent numerical results, we find that
multiple memories can be formed sans external noise. By systematically
investigating memory formation for a range of training strain amplitudes
spanning yield, we find clear signatures of memory even beyond yielding. Most
strikingly, the extent to which the system recollects memory is largest for
training amplitudes near the yield strain and is a direct consequence of the
spatial extent over which the system reorganizes during the encoding process.
Our study further suggests that the evolution of force networks on training
plays a decisive role in memory formation in jammed packings.Comment: 13 pages, 4 Figure
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Mechanisms of organelle biogenesis govern stochastic fluctuations in organelle abundance
Fluctuations in organelle abundance can profoundly limit the precision of cell biological processes from secretion to metabolism. We modeled the dynamics of organelle biogenesis and predicted that organelle abundance fluctuations depend strongly on the specific mechanisms that increase or decrease the number of a given organelle. Our model exactly predicts the size of experimentally measured Golgi apparatus and vacuole abundance fluctuations, suggesting that cells tolerate the maximum level of variability generated by the Golgi and vacuole biogenesis pathways. We observe large increases in peroxisome abundance fluctuations when cells are transferred from glucose-rich to fatty acid-rich environments. These increased fluctuations are significantly diminished in mutants lacking peroxisome fission factors, leading us to infer that peroxisome biogenesis switches from de novo synthesis to primarily fission. Our work provides a general framework for exploring stochastic organelle biogenesis and using fluctuations to quantitatively unravel the biophysical pathways that control the abundance of subcellular structures. DOI: http://dx.doi.org/10.7554/eLife.02678.00
Polymer collapse in miscible good solvents is a generic phenomenon driven by preferential adsorption
Water and alcohol, such as methanol or ethanol, are miscible and, individually, good solvents for poly(N-isopropylacrylamide) (PNIPAm), but this polymer precipitates in water–alcohol mixtures. The intriguing behaviour of solvent mixtures that cannot dissolve a given polymer or a given protein, while the same macromolecule dissolves well in each of the cosolvents, is called cononsolvency. It is a widespread phenomenon, relevant for many formulation steps in the physicochemical and pharmaceutical industry, that is usually explained by invoking specific chemical details of the mixtures: as such, it has so far eluded any generic explanation. Here, by using a combination of simulations and theory, we present a simple and universal treatment that requires only the preferential interaction of one of the cosolvents with the polymer. The results show striking quantitative agreement with experiments and chemically specific simulations, opening a new perspective towards an operational understanding of macromolecular solubility
Nonlocality in kinetic roughening
We propose a phenomenological equation to describe kinetic roughening of a
growing surface in presence of long range interactions. The roughness of the
evolving surface depends on the long range feature, and several distinct
scenarios of phase transitions are possible. Experimental implications are
discussed.Comment: Replaced with the published version (Phys. Rev. Lett 79, 2502
(1997)). Eq. 1 written in a symmetrical form, references update
Duality and phase diagram of one dimensional transport
The observation of duality by Mukherji and Mishra in one dimensional
transport problems has been used to develop a general approach to classify and
characterize the steady state phase diagrams. The phase diagrams are determined
by the zeros of a set of coarse-grained functions without the need of detailed
knowledge of microscopic dynamics. In the process, a new class of
nonequilibrium multicritical points has been identified.Comment: 6 pages, 2 figures (4 eps files
Nonequilibrium tricriticality in one dimension
We show the existence of a nonequilibrium tricritical point induced by a
repulsive interaction in one dimensional asymmetric exclusion process. The
tricritical point is associated with the particle-hole symmetry breaking
introduced by the repulsion. The phase diagram and the crossover in the
neighbourhood of the tricritical point for the shock formation at one of the
boundaries are determined.Comment: 6 pages; 4 figure
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