3,367 research outputs found
Near-optimal protocols in complex nonequilibrium transformations
The development of sophisticated experimental means to control nanoscale
systems has motivated efforts to design driving protocols which minimize the
energy dissipated to the environment. Computational models are a crucial tool
in this practical challenge. We describe a general method for sampling an
ensemble of finite-time, nonequilibrium protocols biased towards a low average
dissipation. We show that this scheme can be carried out very efficiently in
several limiting cases. As an application, we sample the ensemble of
low-dissipation protocols that invert the magnetization of a 2D Ising model and
explore how the diversity of the protocols varies in response to constraints on
the average dissipation. In this example, we find that there is a large set of
protocols with average dissipation close to the optimal value, which we argue
is a general phenomenon.Comment: 6 pages and 3 figures plus 4 pages and 5 figures of supplemental
materia
Classical and Quantum Fluctuation Theorems for Heat Exchange
The statistics of heat exchange between two classical or quantum finite
systems initially prepared at different temperatures are shown to obey a
fluctuation theorem.Comment: 4 pages, 1 included figure, to appear in Phys Rev Let
Coastal Blue Carbon Opportunity Assessment for Snohomish Estuary: The Climate Benefits of Estuary Restoration
This report presents the findings of a groundbreaking study that confirms the climate mitigation benefits of restoring tidal wetland habitat in the Snohomish Estuary, located within the nation's second largest estuary: Puget Sound. The study, the first of its kind, finds major climate mitigation benefits from wetland restoration and provides a much needed approach for assessing carbon fluxes for historic drained and future restored wetlands which can now be transferred and applied to other geographie
Relic Neutrinos and Z-Resonance Mechanism for Highest-Energy Cosmic Rays
The origin of the highest-energy cosmic rays remains elusive. The decay of a
superheavy particle (X) into an ultra-energetic neutrino which scatters from a
relic (anti-)neutrino at the Z-resonance has attractive features. Given the
necessary X mass of GeV, the required lifetime,
y, renders model-building a serious challenge but three logical possibilities
are considered: (i) X is a Higgs scalar in SU(15) belonging to high-rank
representation, leading to {\it power}-enhanced lifetime; (ii) a global X
quantum number has {\it exponentially}-suppressed symmetry-breaking by
instantons; and (iii) with additional space dimension(s) localisation of X
within the real-world brane leads to {\it gaussian} decay suppression, the most
efficient of the suppression mechanisms considered.Comment: 10 page LaTeX and one postscript figure. References adde
Medical Tourism in the Caribbean: A Call for Cooperation
Numerous Caribbean countries have discussed plans for developing medical tourism activities as a means of tourism diversification and economic development. These plans have been encouraged and shaped by outside agencies whose influence might cause a race-to-the-bottom environment between countries competing for the same niche of tourists. This paper provides a call for cooperation between local health officials in the Caribbean region to coordinate plans for the development of a medical tourism industry that enhances regional access to specialized healthcare and facilitates the movement of patients and healthcare resources throughout the region to enhance health equity and health outcomes in the Caribbean
Posterior probability and fluctuation theorem in stochastic processes
A generalization of fluctuation theorems in stochastic processes is proposed.
The new theorem is written in terms of posterior probabilities, which are
introduced via the Bayes theorem. In usual fluctuation theorems, a forward path
and its time reversal play an important role, so that a microscopically
reversible condition is essential. In contrast, the microscopically reversible
condition is not necessary in the new theorem. It is shown that the new theorem
adequately recovers various theorems and relations previously known, such as
the Gallavotti-Cohen-type fluctuation theorem, the Jarzynski equality, and the
Hatano-Sasa relation, when adequate assumptions are employed.Comment: 4 page
Nonequilibrium candidate Monte Carlo: A new tool for efficient equilibrium simulation
Metropolis Monte Carlo simulation is a powerful tool for studying the
equilibrium properties of matter. In complex condensed-phase systems, however,
it is difficult to design Monte Carlo moves with high acceptance probabilities
that also rapidly sample uncorrelated configurations. Here, we introduce a new
class of moves based on nonequilibrium dynamics: candidate configurations are
generated through a finite-time process in which a system is actively driven
out of equilibrium, and accepted with criteria that preserve the equilibrium
distribution. The acceptance rule is similar to the Metropolis acceptance
probability, but related to the nonequilibrium work rather than the
instantaneous energy difference. Our method is applicable to sampling from both
a single thermodynamic state or a mixture of thermodynamic states, and allows
both coordinates and thermodynamic parameters to be driven in nonequilibrium
proposals. While generating finite-time switching trajectories incurs an
additional cost, driving some degrees of freedom while allowing others to
evolve naturally can lead to large enhancements in acceptance probabilities,
greatly reducing structural correlation times. Using nonequilibrium driven
processes vastly expands the repertoire of useful Monte Carlo proposals in
simulations of dense solvated systems
Agreement between blood draw techniques for assessing platelet activation by flow cytometry
It is widely believed that assays of platelet activation are susceptible to preanalytical variables related to blood draw technique. We assessed platelet activation by whole blood flow cytometry and investigated the effects of: (1) drawing blood into vacuum tubes or manually aspirated syringes, and (2) discarding the first drawn blood sample (discard tube). Platelet P-selectin expression and platelet-monocyte complexes were measured by flow cytometry under both basal conditions and following stimulation with 0.1, 1, or 10 µM ADP. Bland-Altman plots demonstrated agreement between results for vacuum tube and syringe-aspirated samples with an a priori-defined clinically relevant agreement limit of 5%. Agreement of results was also observed between discard tube and second draw samples for both vacuum-driven and manually aspirated blood. We conclude that a vacuum tube or a manually-aspirated syringe can be used when assessing platelet activation by flow cytometry and that there is no need for a discard tube
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