3,155 research outputs found
Non-equilibrium Relations for Spin Glasses with Gauge Symmetry
We study the applications of non-equilibrium relations such as the Jarzynski
equality and fluctuation theorem to spin glasses with gauge symmetry. It is
shown that the exponentiated free-energy difference appearing in the Jarzynski
equality reduces to a simple analytic function written explicitly in terms of
the initial and final temperatures if the temperature satisfies a certain
condition related to gauge symmetry. This result is used to derive a lower
bound on the work done during the non-equilibrium process of temperature
change. We also prove identities relating equilibrium and non-equilibrium
quantities. These identities suggest a method to evaluate equilibrium
quantities from non-equilibrium computations, which may be useful to avoid the
problem of slow relaxation in spin glasses.Comment: 8 pages, 2 figures, submitted to JPS
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
Quantum Operation Time Reversal
The dynamics of an open quantum system can be described by a quantum
operation, a linear, complete positive map of operators. Here, I exhibit a
compact expression for the time reversal of a quantum operation, which is
closely analogous to the time reversal of a classical Markov transition matrix.
Since open quantum dynamics are stochastic, and not, in general, deterministic,
the time reversal is not, in general, an inversion of the dynamics. Rather, the
system relaxes towards equilibrium in both the forward and reverse time
directions. The probability of a quantum trajectory and the conjugate, time
reversed trajectory are related by the heat exchanged with the environment.Comment: 4 page
Regionalisation of climate impacts on flood flows to support the development of climate change guidance for Flood Management
Current Defra / Environment Agency guidance (FCDPAG3 supplementary note: http://www.defra.gov.uk/environ/fcd/pubs/pagn/climatechangeupdate.pdf) requires all flood management plans to allow for climate change by incorporating, within a sensitivity analysis, an increase in river flows of up 20% over the next 50 years, and beyond. This guidance is the same for all of England and Wales, making no allowance for regional variation in climate change or catchment type. This reflects the lack of scientific evidence to resolve the spatial distribution of potential impacts on flood flows with enough confidence to set such policy regionally. The 20% allowance was first raised in 1999 for MAFF and subsequently reviewed following the release of the UKCIP02 scenarios. Although the 20% figure is a memorable precautionary target, there is the risk that it leads to a significant under- or over-estimation of future flood risk in individual catchments.
Defra and the Environment Agency procured project FD2020 (Regionalisation of climate change impacts on flood flows) to provide a more rigorous science base for refreshing the FCDPAG3: supplementary note guidance. The FD2020 approach is exploring the relationships between catchment characteristics and climate change impacts on peak flows in a “scenario neutral” way. This is done by defining a regular set of changes in climate that encompass all the current knowledge from the new scenarios available from the IPCC Fourth Assessment Report. For each of the 155 catchments included in the research, this broad approach will provide multiple scenarios to produce a “vulnerability surface” for change in the metrics of peak flows (e.g. the 20-year flood flow). Some of the UKCP09 products have also been used to understand what these projections may mean for changes to peak flow. The catchment-based analysis will be used to generalise to other gauged sites across Britain, using relationships with catchment characteristics, providing the scientific evidence for the development of regional guidance on climate change allowances.
Specifically the project is:
Investigating the impact of climate change on peak river flows in over 150 catchments across Britain to assess the suitability of the FCDPAG3 20% climate change allowance.
Investigating catchment response to climate change to identify potential similarities such that the FCDPAG3 nationwide allowance could be regionalised.
Investigating the uncertainty in changes to future peak river flows from climate change.
Developing an approach that has longevity beyond the project timeframe and the lifetime of the latest generation of climate model results
Nonequilibrium work on spin glasses in longitudinal and transverse fields
We derive a number of exact relations between equilibrium and nonequilibrium
quantities for spin glasses in external fields using the Jarzynski equality and
gauge symmetry. For randomly-distributed longitudinal fields, a lower bound is
established for the work done on the system in nonequilibrium processes, and
identities are proven to relate equilibrium and nonequilibrium quantities. In
the case of uniform transverse fields, identities are proven between physical
quantities and exponentiated work done to the system at different parts of the
phase diagram with the context of quantum annealing in mind. Additional
relations are given, which relate the exponentiated work in quantum and
simulated (classical) annealing. It is also suggested that the Jarzynski
equality may serve as a guide to develop a method to perform quantum annealing
under non-adiabatic conditions.Comment: 17 pages, 5 figures, submitted to JPS
Medical Tourism in Barbados: Negotiating Inherent Tensions
This chapter draws on our long term-research program examining medical tourism in Barbados and the wider Anglophone Caribbean. Since 2011 we have undertaken 69 semi-structured interviews and three focus groups with a wide range of health system and tourism sector stakeholders in Barbados, compiled a comprehensive collection of state and media reports discussing medical tourism, and collectively spent over a year conducting on-site ethnographic fieldwork that has included many informal conversations with users of the Barbadian health system from a wide range of backgrounds. Together, these datasets and experiences provide a rich understanding of the potential considerations and hopes arising from the ongoing discussion about medical tourism development in a small island setting. Exploring these considerations and hopes suggests ways in which Barbados and other small island states seeking to develop their medical tourism sectors can negotiate a structure for medical tourism that can best meet their development goals
Jarzynski equality for the transitions between nonequilibrium steady states
Jarzynski equality [Phys. Rev. E {\bf 56}, 5018 (1997)] is found to be valid
with slight modefication for the transitions between nonequilibrium stationary
states, as well as the one between equilibrium states. Also numerical results
confirm its validity. Its relevance for nonequilibrium thermodynamics of the
operational formalism is discussed.Comment: 5 pages, 2 figures, revte
Compounds of Use in the Treatment of Epilepsy, Seizure, and Electroconvulsive Disorders
The present invention provides pharmaceutical preparations and the uses thereof for preventing and/or treating seizures and other electroconvulsive disorders by administering a pharmaceutically effective amount of a therapeutic compound . . .
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Membraneless seawater desalination
Disclosed are microfluidic devices and systems for the desalination of water. The devices and systems can include an electrode configured to generate an electric field gradient in proximity to an intersection formed by the divergence of two microfluidic channels from an inlet channel. Under an applied bias and in the presence of a pressure driven flow of saltwater, the electric field gradient can preferentially direct ions in saltwater into one of the diverging microfluidic channels, while desalted water flows into second diverging channel. Also provided are methods of using the devices and systems described herein to decrease the salinity of water.Board of Regents, University of Texas Syste
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