15,851 research outputs found
Modelling cytoskeletal traffic: an interplay between passive diffusion and active transport
We introduce the totally asymmetric exclusion process with Langmuir kinetics
(TASEP-LK) on a network as a microscopic model for active motor protein
transport on the cytoskeleton, immersed in the diffusive cytoplasm. We discuss
how the interplay between active transport along a network and infinite
diffusion in a bulk reservoir leads to a heterogeneous matter distribution on
various scales. We find three regimes for steady state transport, corresponding
to the scale of the network, of individual segments or local to sites. At low
exchange rates strong density heterogeneities develop between different
segments in the network. In this regime one has to consider the topological
complexity of the whole network to describe transport. In contrast, at moderate
exchange rates the transport through the network decouples, and the physics is
determined by single segments and the local topology. At last, for very high
exchange rates the homogeneous Langmuir process dominates the stationary state.
We introduce effective rate diagrams for the network to identify these
different regimes. Based on this method we develop an intuitive but generic
picture of how the stationary state of excluded volume processes on complex
networks can be understood in terms of the single-segment phase diagram.Comment: 5 pages, 7 figure
Bertrand-Edgeworth competition in an almost symmetric oligopoly
We analyze a Bertrand-Edgeworth game in homogeneous product industry, under effcient rationing, constant marginal cost until full capacity utilization, and identical technology across firms. We solve for the equilibrium and establish its uniqueness for capacity configurations in the mixed strategy region of the capacity space such that the capacities of the largest and smallest firm are sufficiently close.Bertrand-Edgeworth competition; mixed strategy equilibrium; almost symmetric oligopoly; Mixed strategy equilibrium
Bertrand-Edgeworth games under oligopoly with a complete characterization for the triopoly
The paper extends the analysis of price competition among capacity-constrained sellers beyond the cases of duopoly and symmetric oligopoly. We first provide some general results for the oligopoly and then focus on the triopoly, providing a complete characterization of the mixed strategy equilibrium of the price game. The region of the capacity space where the equilibrium is mixed is partitioned according to the features of the mixed strategy equilibrium arising in each subregion. Then computing the mixed strategy equilibrium becomes a quite simple task. The analysis reveals features of the mixed strategy equilibrium which do not arise in the duopoly (some of them have also been discovered by Hirata (2008)).Bertrand-Edgeworth; Price game; Oligopoly; Triopoly; Mixed strategy equilibrium
Precision radiative corrections to the Dalitz plot of baryon semileptonic decays including the spin-momentum correlation of the decaying baryon and the emitted charged lepton
We calculate the radiative corrections to the angular correlation between the
polarization of the decaying baryon and the direction of the emitted charged
lepton in the semileptonic decays of spin one-half baryons to order
(\alpha/\pi)(q/M_1). The final results are presented, first, with the triple
integration of the bremsstrahlung photon ready to be performed numerically and,
second, in an analytical form. A third presentation of our results in the form
of numerical arrays of coefficients to be multiplied on the quadratic products
of form factors is discussed. This latter may be the most practical one to use
in Monte Carlo simulations. A series of crosschecks is performed. The results
are useful in the analysis of the Dalitz plot of precision experiments
involving light and heavy quarks and is not compromised to fixing the form
factors at predetermined values. It is assumed that the real photons are
kinematically discriminated. Otherwise, our results have a general
model-independent applicability.Comment: 8 pages, RevTex4, 5 tables, no figures. Shortened version; results
and conclusions remain unchange
Precision radiative corrections to the semileptonic Dalitz plot with angular correlation between polarized decaying and emitted baryons: Effects of the four-body region
Analytical radiative corrections of order (\alpha/\pi)(q/M_1) are calculated
for the four-body region of the Dalitz plot of baryon semileptonic decays when
the s_1 \cdot p_2 correlation is present. Once the final result is available,
it is possible to exhibit it in terms of the corresponding final result of the
three-body region following a set of simple changes in the latter. We cover two
cases, a charged and a neutral polarized decaying baryon.Comment: Revtex4, 7 pages, no figure
Motor proteins traffic regulation by supply-demand balance of resources
In cells and in vitro assays the number of motor proteins involved in
biological transport processes is far from being unlimited. The cytoskeletal
binding sites are in contact with the same finite reservoir of motors (either
the cytosol or the flow chamber) and hence compete for recruiting the available
motors, potentially depleting the reservoir and affecting cytoskeletal
transport. In this work we provide a theoretical framework to study,
analytically and numerically, how motor density profiles and crowding along
cytoskeletal filaments depend on the competition of motors for their binding
sites. We propose two models in which finite processive motor proteins actively
advance along cytoskeletal filaments and are continuously exchanged with the
motor pool. We first look at homogeneous reservoirs and then examine the
effects of free motor diffusion in the surrounding medium. We consider as a
reference situation recent in vitro experimental setups of kinesin-8 motors
binding and moving along microtubule filaments in a flow chamber. We
investigate how the crowding of linear motor proteins moving on a filament can
be regulated by the balance between supply (concentration of motor proteins in
the flow chamber) and demand (total number of polymerised tubulin
heterodimers). We present analytical results for the density profiles of bound
motors, the reservoir depletion, and propose novel phase diagrams that present
the formation of jams of motor proteins on the filament as a function of two
tuneable experimental parameters: the motor protein concentration and the
concentration of tubulins polymerized into cytoskeletal filaments. Extensive
numerical simulations corroborate the analytical results for parameters in the
experimental range and also address the effects of diffusion of motor proteins
in the reservoir.Comment: 31 pages, 10 figure
Radiative corrections to the three-body region of the Dalitz plot of baryon semileptonic decays with angular correlation between polarized emitted baryons and charged leptons: The initial-baryon rest frame case
We complement the results for the radiative corrections to the s2.l angular
correlation of baryon semileptonic decays of Ref. [1] with the final results in
the rest frame of the decaying baryon.Comment: 7 pages, Revtex4, no figure
Of Mongrels and Men: The Shared Ideology of Anti-Miscegenation Law, Chinese Exclusion, and Contemporary American Neo-Nativism
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