820 research outputs found
The spin-echo system reconsidered
Simple models have played an important role in the discussion of foundational
issues in statistical mechanics. Among them the spin--echo system is of
particular interest since it can be realized experimentally. This has led to
inferences being drawn about approaches to the foundations of statistical
mechanics, particularly with respect to the use of coarse-graining. We examine
these claims with the help of computer simulations
SUPPORT Tools for evidence-informed health Policymaking (STP) 13: Preparing and using policy briefs to support evidence-informed policymaking
This article is part of a series written for people responsible for making decisions about health policies and programmes and for those who support these decision makers
SUPPORT Tools for evidence-informed health Policymaking (STP)
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SUPPORT Tools for evidence-informed health Policymaking (STP) 7: Finding systematic reviews
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SUPPORT Tools for evidence-informed health Policymaking (STP) 14: Organising and using policy dialogues to support evidence-informed policymaking
This article is part of a series written for people responsible for making decisions about health policies and programmes and for those who support these decision makers
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Robust model-based analysis of single-particle tracking experiments with Spot-On.
Single-particle tracking (SPT) has become an important method to bridge biochemistry and cell biology since it allows direct observation of protein binding and diffusion dynamics in live cells. However, accurately inferring information from SPT studies is challenging due to biases in both data analysis and experimental design. To address analysis bias, we introduce 'Spot-On', an intuitive web-interface. Spot-On implements a kinetic modeling framework that accounts for known biases, including molecules moving out-of-focus, and robustly infers diffusion constants and subpopulations from pooled single-molecule trajectories. To minimize inherent experimental biases, we implement and validate stroboscopic photo-activation SPT (spaSPT), which minimizes motion-blur bias and tracking errors. We validate Spot-On using experimentally realistic simulations and show that Spot-On outperforms other methods. We then apply Spot-On to spaSPT data from live mammalian cells spanning a wide range of nuclear dynamics and demonstrate that Spot-On consistently and robustly infers subpopulation fractions and diffusion constants
Anomalous latent heat in non-equilibrium phase transitions
We study first-order phase transitions in a two-temperature system, where due
to the time-scale separation all the basic thermodynamical quantities (free
energy, entropy, etc) are well-defined. The sign of the latent heat is found to
be counterintuitive: it is positive when going from the phase where the
temperatures and the entropy are higher to the one where these quantities are
lower. The effect exists only out of equilibrium and requires conflicting
interactions. It is displayed on a lattice gas model of ferromagnetically
interacting spin-1/2 particles.Comment: 4 pages, 2 figure
SUPPORT Tools for evidence-informed health Policymaking (STP) 4: Using research evidence to clarify a problem
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Exactly Solvable Model of Monomer-Monomer Reactions on a Two-Dimensional Random Catalytic Substrate
We present an \textit{exactly solvable} model of a monomer-monomer reaction on a 2D inhomogeneous, catalytic substrate and study the
equilibrium properties of the two-species adsorbate. The substrate contains
randomly placed catalytic bonds of mean density which connect neighboring
adsorption sites. The interacting and (monomer) species undergo
continuous exchanges with corresponding adjacent gaseous reservoirs. A reaction
takes place instantaneously if and particles
occupy adsorption sites connected by a catalytic bond. We find that for the
case of \textit{annealed} disorder in the placement of the catalytic bonds the
reaction model under study can be mapped onto the general spin (GS1)
model. Here we concentrate on a particular case in which the model reduces to
an exactly solvable Blume-Emery-Griffiths (BEG) model (T. Horiguchi, Phys.
Lett. A {\bf 113}, 425 (1986); F.Y. Wu, Phys. Lett. A, {\bf 116}, 245 (1986))
and derive an exact expression for the disorder-averaged equilibrium pressure
of the two-species adsorbate. We show that at equal partial vapor pressures of
the and species this system exhibits a second-order phase transition
which reflects a spontaneous symmetry breaking with large fluctuations and
progressive coverage of the entire substrate by either one of the species.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
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