10,930 research outputs found
Entropy production and time-asymmetry in the presence of strong interactions
It is known that the equilibrium properties of open classical systems that
are strongly coupled to a heat bath are described by a set of thermodynamic
potentials related to the system's Hamiltonian of mean force. By adapting this
framework to a more general class of non-equilibrium states, we show that the
equilibrium properties of the bath can be well-defined, even when the system is
arbitrarily far from equilibrium and correlated with the bath. These states,
which retain a notion of temperature, take the form of conditional equilibrium
distributions. For out-of-equilibrium processes we show that the average
entropy production quantifies the extent to which the system-bath state is
driven away from the conditional equilibrium distribution. In addition, we show
that the stochastic entropy production satisfies a generalised Crooks relation
and can be used to quantify time-asymmetry of correlated non-equilibrium
processes. These results naturally extend the familiar properties of entropy
production in weakly-coupled systems to the strong coupling regime.
Experimental measurements of the entropy production at strong coupling could be
pursued using optomechanics or trapped ion systems, which allow strong coupling
to be engineered.Comment: 8 pages, 1 figure, comments welcom
Leggett-Garg inequalities for quantum fluctuating work
The Leggett-Garg inequalities serve to test whether or not quantum
correlations in time can be explained within a classical macrorealistic
framework. We apply this test to thermodynamics and derive a set of Leggett-
Garg inequalities for the statistics of fluctuating work done on a quantum
system unitarily driven in time. It is shown that these inequalities can be
violated in a driven two-level system, thereby demonstrating that there exists
no general macrorealistic description of quantum work. These violations are
shown to emerge within the standard Two-Projective-Measurement scheme as well
as for alternative definitions of fluctuating work that are based on weak
measurement. Our results elucidate the influences of temporal correlations on
work extraction in the quantum regime and highlight a key difference between
quantum and classical thermodynamics.Comment: v2, 1 figure, accepted version to appear in Entropy (Special Issue on
"Quantum Thermodynamics II"
Bounds on Localized Modes in the Crystal Impurity Problem
Using general properties of the crystal site representation normal mode
matrix, we provide some very simple bounds on localized modes in simple,
body-centered and face-centered cubic crystals with substitutional point
defects. We derive a trace condition constraint on the net change in crystal
eigenfrequencies caused by the introduction of a defect, with the condition
being a completely general one which holds for any combination of central and
non-central crystal force-constants and for all-neighbor interactions. Using
this condition we show that the sufficient condition for producing localized
modes in an arbitrary cubic crystal by a mass change at the defect site is that
the defect mass be less than one half of that of the host atom mass which it
replaces, and that the sufficient condition for producing localized modes in an
arbitrary cubic crystal by force-constant changes alone is that the defect site
self force-constant be greater than twice that of the pure crystal self
force-constant of the host atom which it replaces.Comment: 25 pages, 3 figures, revtex4. Updated version contains much more
general bounds than original versio
Time-reversal symmetric work distributions for closed quantum dynamics in the histories framework
A central topic in the emerging field of quantum thermodynamics is the
definition of thermodynamic work in the quantum regime. One widely used
solution is to define work for a closed system undergoing non-equilibrium
dynamics according to the two-point energy measurement scheme. However, due to
the invasive nature of measurement the two-point quantum work probability
distribution leads to inconsistencies with two pillars of thermodynamics: it
breaks the first law and the time-reversal symmetry expected for closed
dynamics. We here introduce the quantum histories framework as a method to
characterise the thermodynamic properties of the unmeasured, closed dynamics.
Extending the classical phase space trajectories to continuous power operator
trajectories allows us to derive an alternative quantum work distribution for
closed quantum dynamics that fulfils the first law and is time-reversal
symmetric. We find that the work distribution of the unmeasured dynamics leads
to deviations from the classical Jarzynski equality and can have negative
values highlighting distinctly non-classical features of quantum work.Comment: 18 pages, 2 figures, comments welcom
Quantitative Determination of Enhanced and Suppressed Transmission through Subwavelength Slit Arrays in Silver Films
Measurement of the transmitted intensity from a coherent monomode light
source through a series of subwavelength slit arrays in Ag films, with varying
array pitch and number of slits, demonstrate enhancement (suppression) by as
much as a factor of 6 (9) when normalized to that of an isolated slit.
Pronounced minima in the transmitted intensity were observed at array pitches
corresponding to lambda_SPP, 2lambda_SPP, and 3lambda_SPP where lambda_SPP is
the wavelength of the surface plasmon polariton (SPP). Increasing the number of
slits to more than four does not increase appreciably the per-slit transmission
intensity. These results are consistent with a model for interference between
SPPs and the incident wave that fits well the measured transmitted intensity
profile.Comment: Figure 4 update
Nitric Oxide Bioavailability and Its Potential Relevance to the Variation in Susceptibility to the Renal and Vascular Complications in Patients With Type 2 Diabetes
OBJECTIVEâWe compared the renal and systemic vascular (renovascular) response to a reduction of bioavailable nitric oxide (NO) in type 2 diabetic patients without nephropathy and of African and Caucasian heritage. RESEARCH DESIGN AND METHODSâUnder euglycemic conditions, renal blood flow was determined by a constant infusion of paraminohippurate and changes in blood pressure and renal vascular resistance estimated before and after an infusion of l-Ng-monomethyl-l-arginine. RESULTSâIn the African-heritage group, there was a significant fall in renal blood flow (Îâ46.0 ml/min per 1.73 m(2); P < 0.05) and rise in systolic blood pressure (Î10.0 mmHg [95% CI 2.3â17.9]; P = 0.017), which correlated with an increase in renal vascular resistance (r(2) = 0.77; P = 0.004). CONCLUSIONSâThe renal vasoconstrictive response associated with NO synthase inhibition in this study may be of relevance to the observed vulnerability to renal injury in patients of African heritage
Cracks in rubber under tension exceed the shear wave speed
The shear wave speed is an upper limit for the speed of cracks loaded in
tension in linear elastic solids. We have discovered that in a non-linear
material, cracks in tension (Mode I) exceed this sound speed, and travel in an
intersonic range between shear and longitudinal wave speeds. The experiments
are conducted in highly stretched sheets of rubber; intersonic cracks can be
produced simply by popping a balloon.Comment: 4 pages, 5 eps figure
Seasonal Occurrence of the Sod Webworm Moths (Lepidoptera: Crambidae) of Ohio
While nearly 100 species of sod webworms are known to occur in North America, the species complex and seasonal occurrence of these moths has been documented in relatively few states. For Ohio, there is little published record of the sod webworm species complex, and the seasonal occurrence of only a few economically important species has been documented. Using black light traps, sod web worm adult flight activity was monitored over the course of three to five years at four different locations throughout Ohio. In this paper we report the seasonal occurrence of sod web worms species captured at these locations. These data provide a historical benchmark of sod webÂworm species diversity, local abundance, and seasonal occurrence in Ohio
AN ECONOMIC ANALYSIS OF THE U.S. GENERIC DAIRY ADVERTISING PROGRAM USING AN INDUSTRY MODEL
The market impacts of generic dairy advertising are assessed using an industry model which encompasses supply and demand conditions at the retail, wholesale, and farm levels, and government intervention under the dairy price support program. The estimated model is used to simulate price and quantity values for four advertising scenarios: (1) no advertising, (2) historical fluid advertising, (3) historical manufactured advertising, and (4) historical fluid and manufactured advertising. Compared to previous studies, the dairy-industry model provides additional insights into the way generic dairy advertising influences prices and quantities at the retail, wholesale, and farm levels.Livestock Production/Industries, Marketing,
MODELING THE U.S. DAIRY SECTOR WITH GOVERNMENT INTERVENTION
An econometric framework for estimating a two-regime dairy structural system is presented. Failure to account for switching between regimes due to government price intervention raises the problem of selectivity bias. Further, since a structural system of equations is involved, the problem is not limited to the market associated with the intervention. Rather, bias from a single source can distort all equations in the system. The ramifications of not correcting for the bias in policy analyses are investigated.Agricultural and Food Policy, Industrial Organization,
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