314 research outputs found
Zeroth and Second Laws of Thermodynamics Simultaneously Questioned in the Quantum Microworld
Several models of quantum open systems are known at present to violate,
according to principles of the standard quantum theory of open systems, the
second law of thermodynamics. Here, a new and rather trivial model of another
type is suggested describing mechanism that violates, according to the same
principles, the zeroth and the second laws of thermodynamics simultaneously. Up
to a technically minor modification, the model resembles some models already
known, solved by standard means, and properly understood. Universal validity of
two basic principles of thermodynamics in strictly quantum situations is thus
simultaneously called in question.Comment: Extended reference list and acknowledgement
On apparent breaking the second law of thermodynamics in quantum transport studies
We consider a model for stationary electronic transport through a
one-dimensional chain of two leads attached to a perturbed central region
(quantum dot) in the regime where the theory proposed recently by Capek for a
similar model of phonon transport predicts the striking phenomenon of a
permanent current between the leads. This result based on a rigorous but
asymptotic Davies theory is at variance with the zero current yielded by direct
transport calculations which can be carried out in the present model. We find
the permanent current to be within the error of the asymptotic expansion for
finite couplings, and identify cancelling terms of the same order.Comment: 5 pages, 3 figure
Does the Third Law of Thermodynamics hold in the Quantum Regime?
The first in a long series of papers by John T. Lewis,
G. W. Ford and the present author, considered the problem of the most general
coupling of a quantum particle to a linear passive heat bath, in the course of
which they derived an exact formula for the free energy of an oscillator
coupled to a heat bath in thermal equilibrium at temperature T. This formula,
and its later extension to three dimensions to incorporate a magnetic field,
has proved to be invaluable in analyzing problems in quantum thermodynamics.
Here, we address the question raised in our title viz. Nernst's third law of
thermodynamics
Neural Networks Supporting Phoneme Monitoring Are Modulated by Phonology but Not Lexicality or Iconicity: Evidence From British and Swedish Sign Language
Sign languages are natural languages in the visual domain. Because they lack a written
form, they provide a sharper tool than spoken languages for investigating lexicality effects
which may be confounded by orthographic processing. In a previous study, we showed
that the neural networks supporting phoneme monitoring in deaf British Sign Language
(BSL) users are modulated by phonology but not lexicality or iconicity. In the present
study, we investigated whether this pattern generalizes to deaf Swedish Sign Language
(SSL) users. British and SSLs have a largely overlapping phoneme inventory but are
mutually unintelligible because lexical overlap is small. This is important because it means
that even when signs lexicalized in BSL are unintelligible to users of SSL they are usually
still phonologically acceptable. During fMRI scanning, deaf users of the two different sign
languages monitored signs that were lexicalized in either one or both of those languages
for phonologically contrastive elements. Neural activation patterns relating to different
linguistic levels of processing were similar across SLs; in particular, we found no effect of
lexicality, supporting the notion that apparent lexicality effects on sublexical processing
of speech may be driven by orthographic strategies. As expected, we found an effect of
phonology but not iconicity. Further, there was a difference in neural activation between
the two groups in a motion-processing region of the left occipital cortex, possibly driven
by cultural differences, such as education. Importantly, this difference was not modulated
by the linguistic characteristics of the material, underscoring the robustness of the neural
activation patterns relating to different linguistic levels of processing
Mimicry cannot explain rejection type in a hostâbrood parasite system
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordOne of the most effective defensive strategies of hosts against brood parasites is rejection, commonly achieved by ejection of the parasitic egg or desertion of the parasitized nest. Nest desertion should be a costlier strategy than egg ejection, because birds must thesn spend additional time and energy renesting, and therefore we still cannot explain why some individuals desert their nests rather than eject parasitic eggs and continue a given breeding attempt. The great reed warbler, Acrocephalus arundinaceus, is a frequent host of the common cuckoo, Cuculus canorus, and is known to use both types of rejection response. By measuring cuckoo egg mimicry, we investigated the hypothesis that the hosts desert if they cannot reliably recognize the cuckoo egg in their nest. We predicted that we would find better mimicry when hosts deserted rather than ejected. However, we did not find a difference in mimicry between these two groups of nests, implying that host females do not desert because they cannot reliably recognize the parasitic egg. We also showed that neither the date in the season nor the age of the host females influenced the type of rejection. Other factors potentially eliciting nest desertion, including host personality, host, inability to eject, excessive clutch reduction and visibility of the cuckoo female at the host nest, are discussed. Finally, we suggest that desertion may persist as a host defensive strategy against brood parasitism because it is not as costly as previously assumed and/or it is beneficial for host females in good physical condition.Czech Science FoundationCzech Academy of SciencesNatural Environment Research Council (NERC
Impact of the tip radius on the lateral resolution in piezoresponse force microscopy
We present a quantitative investigation of the impact of tip radius as well
as sample type and thickness on the lateral resolution in piezoresponse force
microscopy (PFM) investigating bulk single crystals. The observed linear
dependence of the width of the domain wall on the tip radius as well as the
independence of the lateral resolution on the specific crystal-type are
validated by a simple theoretical model. Using a Ti-Pt-coated tip with a
nominal radius of 15 nm the so far highest lateral resolution in bulk crystals
of only 17 nm was obtained
Quantum thermodynamics of a charged magneto-oscillator coupled to a heat bath
Explicit results for various quantum thermodynamic function (QTF) of a
charged magneto-oscillator coupled to a heat bath at arbitrary temperature are
demonstrated in this paper. Discernible expressions for different QTF in the
two limits of very low and very high temperatures are presented for three
popular heat bath models : Ohmic, single relaxation time and blackbody
radiation. The central result is that the effect of magnetic field turns out to
be important at low temperatures yet crucial at high temperatures. It is
observed that the dissipation parameter, , and the cyclotron frequency,
, affect the decaying or rising behaviour of various QTF in just the
opposite way to each other at low temperatures. In the high temperature regime,
the effect of is much pronounced than that of .Comment: 26 Pages, 18 Figure
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