2,562 research outputs found
Thermodynamic Cross-Effects from Dynamical Systems
We give a thermodynamically consistent description of simultaneous heat and
particle transport, as well as of the associated cross-effects, in the
framework of a chaotic dynamical system, a generalized multibaker map. Besides
the density, a second field with appropriate source terms is included in order
to mimic, after coarse graining, a spatial temperature distribution and its
time evolution. A new expression is derived for the irreversible entropy
production in a steady state, as the average of the growth rate of the relative
density, a unique combination of the two fields.Comment: 4 pages, 2 postscript figure
A MultiBaker Map for Thermodynamic Cross-Effects in Dynamical Systems
A consistent description of simultaneous heat and particle transport,
including cross effects, and the associated entropy balance is given in the
framework of a deterministic dynamical system. This is achieved by a multibaker
map where, besides the phase-space density of the multibaker, a second field
with appropriate source terms is included in order to mimic a spatial
temperature distribution and its time evolution. Conditions are given to ensure
consistency in an appropriately defined continuum limit with the thermodynamic
entropy balance. They leave as the only free parameter of the model the entropy
flux let directly into a surroundings. If it vanishes in the bulk, the
transport properties of the model are described by the thermodynamic transport
equations. Another choice leads to a uniform temperature distribution. It
represents transport problems treated by means of a thermostatting algorithm,
similar to the one considered in non-equilibrium molecular dynamics.Comment: 18 pages, 3 postscript figure
Escape-rate formalism, decay to steady states, and divergences in the entropy-production rate
In summer 1997 we were sitting with Bob Dorfman and a few other friends
interested in chaotic systems and transport theory on a terrace close to
Oktogon in Budapest. While taking our (decaf) coffee after a very nice Italian
meal, we discussed about logarithmic divergences in the entropy production of
systems with absorbing boundary conditions and their consequences for the
escape-rate formalism. It was guessed at that time that the problem could be
resolved by a careful discussion of the physical content of the absorbing
boundary conditions. To our knowledge a thorough analysis of this long-standing
question is still missing. We dedicate it hereby to Bob on occasion of his 65th
birthday.Comment: 16 pages; RevTex 4 with graphicx package; eps-figure
Termination Detection of Local Computations
Contrary to the sequential world, the processes involved in a distributed
system do not necessarily know when a computation is globally finished. This
paper investigates the problem of the detection of the termination of local
computations. We define four types of termination detection: no detection,
detection of the local termination, detection by a distributed observer,
detection of the global termination. We give a complete characterisation
(except in the local termination detection case where a partial one is given)
for each of this termination detection and show that they define a strict
hierarchy. These results emphasise the difference between computability of a
distributed task and termination detection. Furthermore, these
characterisations encompass all standard criteria that are usually formulated :
topological restriction (tree, rings, or triangu- lated networks ...),
topological knowledge (size, diameter ...), and local knowledge to distinguish
nodes (identities, sense of direction). These results are now presented as
corollaries of generalising theorems. As a very special and important case, the
techniques are also applied to the election problem. Though given in the model
of local computations, these results can give qualitative insight for similar
results in other standard models. The necessary conditions involve graphs
covering and quasi-covering; the sufficient conditions (constructive local
computations) are based upon an enumeration algorithm of Mazurkiewicz and a
stable properties detection algorithm of Szymanski, Shi and Prywes
Adware, Shareware, and Consumer Privacy
Programmers can distribute new software to online users either for a fee
as shareware or bundle it with advertising banners and distribute it for
free as adware. In this paper we study the programmers' choice between
these two modes of distribution in the context of a model that take
explicit account of the strategic interaction between programmers who
develop software, firms that advertise their products through ad
banners, and consumers who buy software and consumer products. Adware
allows advertisers to send targeted information to specific consumers
and may therefore improve their purchasing decisions. At the same time,
adware also raises privacy concerns. We study the effect of programmers'
choice between shareware and adware on consumers' welfare through its
effect on the beneficial information that consumers receive about
consumers products on the one hand and their loss of privacy on the
other hand. We also examine the implications of improvements in the
technology of ad banners and the desirability of bans on the use of adware
Non-leaching antimicrobial surfaces through polydopamine bio-inspired coating of quaternary ammonium salts or an ultrashort antimicrobial lipopeptide.
Bacterial fouling on surfaces significantly increases the resistance of bacteria toward antibiotics, which leads to medical complications and a corresponding financial burden. Here, we report on a general and robust technique for facile modification of various surfaces with different antibacterial agents. Our approach in this study was inspired by the strong adhesion of mussel adhesion proteins (MAPs) to many types of surfaces, including metals, polymers, and inorganic materials. Thus, glass and polymeric slides were dip-coated with dopamine, as a MAP mimic, and the resulting surfaces were characterized. The reactivity of dopamine-coated surfaces toward nucleophilic addition was then confirmed by reacting them with fluorescent probes containing either a free amino or a free thiol group. Laser scanning confocal microscopy (LSCM), X-ray photoelectron spectroscopy (XPS), confocal Raman microscopy, matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectroscopy, and cyclic voltammetry studies collectively suggested that the probes had covalently attached to the surfaces. Fabrication of dopamine-coated surfaces with an antibacterial quaternary amine or an ultrashort lipopeptide analog generated surfaces that effectively kill Escherichia coli and Staphylococcus aureuscells on contact. Moreover, minimal leaching of the fabricated agent was detected after prolonged incubation. This technique could be further developed to a "paint-like" or self-assembling monolayer-like procedure for the preparation of antibacterial surfaces on various materials
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