1,511 research outputs found
Efficiency of molecular machines with continuous phase space
We consider a molecular machine described as a Brownian particle diffusing in
a tilted periodic potential. We evaluate the absorbed and released power of the
machine as a function of the applied molecular and chemical forces, by using
the fact that the times for completing a cycle in the forward and the backward
direction have the same distribution, and that the ratio of the corresponding
splitting probabilities can be simply expressed as a function of the applied
force. We explicitly evaluate the efficiency at maximum power for a simple
sawtooth potential. We also obtain the efficiency at maximum power for a broad
class of 2-D models of a Brownian machine and find that loosely coupled
machines operate with a smaller efficiency at maximum power than their strongly
coupled counterparts.Comment: To appear in EP
Efficiency at maximum power of interacting molecular machines
We investigate the efficiency of systems of molecular motors operating at
maximum power. We consider two models of kinesin motors on a microtubule: for
both the simplified and the detailed model, we find that the many-body
exclusion effect enhances the efficiency at maximum power of the many-motor
system, with respect to the single motor case. Remarkably, we find that this
effect occurs in a limited region of the system parameters, compatible with the
biologically relevant range.Comment: To appear in Phys. Rev. Let
Probing the interactions of charmed mesons with nuclei in induced reactions
We study the perspectives of resonant and nonresonant charmed meson
production in reactions within the Multiple Scattering Monte
Carlo (MSMC) approach. We calculate the production of the resonances
and on various nuclei, their propagation
and decay to in the medium and
vacuum, respectively. The modifications of the open charm vector mesons in the
nuclear medium are found to be rather moderate or even small such that dilepton
spectroscopy will require an invariant mass resolution of a few MeV.
Furthermore, the elastic and inelastic interactions of the open charm mesons in
the medium are taken into account, which can be related to -, - or
-quark exchange with nucleons. It is found that by studying the
ratio for low momenta in the laboratory ( GeV/c) as a function of
target mass stringent constraints on the -quark exchange cross section
can be obtained. On the other hand, the ratios
as well as and at low momenta as a function
of will permit to fix independently the strength of the -quark exchange
reaction in scattering.Comment: 9 pages, LaTeX, including 9 postscript figures, submitted to Eur.
Phys. J.
Medium effects in the production and decay of vector mesons in pion-nucleus reactions
The -, - and -resonance production and their dileptonic
decay in reactions at 1.1 - 1.7 GeV/c are calculated within the
intranuclear cascade (INC) approach. The invariant mass distribution of the
dilepton pair for each resonance can be decomposed in two components which
correspond to their decay 'inside' the target nucleus and in the vacuum,
respectively. The first components are strongly distorted by the nuclear medium
due to resonance-nucleon scattering and a possible mass shift at finite baryon
density. These medium modifications are compared to background sources in the
dilepton spectrum from bremsstrahlung as well as the Dalitz decays of
and mesons produced in the reaction. Detailed predictions for
reactions at 1.3 and 1.7 GeV/c are made within several momentum bins
for the lepton pair.Comment: 29 pages, LaTeX, including 12 postscript figures, UGI-97-07, Nucl.
Phys. A., in pres
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