18,426 research outputs found
Transition from single-file to two-dimensional diffusion of interacting particles in a quasi-one-dimensional channel
Diffusive properties of a monodisperse system of interacting particles
confined to a \textit{quasi}-one-dimensional (Q1D) channel are studied using
molecular dynamics (MD) simulations. We calculate numerically the mean-squared
displacement (MSD) and investigate the influence of the width of the channel
(or the strength of the confinement potential) on diffusion in finite-size
channels of different shapes (i.e., straight and circular). The transition from
single-file diffusion (SFD) to the two-dimensional diffusion regime is
investigated. This transition (regarding the calculation of the scaling
exponent () of the MSD ) as a
function of the width of the channel, is shown to change depending on the
channel's confinement profile. In particular the transition can be either
smooth (i.e., for a parabolic confinement potential) or rather sharp/stepwise
(i.e., for a hard-wall potential), as distinct from infinite channels where
this transition is abrupt. This result can be explained by qualitatively
different distributions of the particle density for the different confinement
potentials.Comment: 13 pages, 11 figure
Periodicity Manifestations in the Turbulent Regime of Globally Coupled Map Lattice
We revisit the globally coupled map lattice (GCML). We show that in the so
called turbulent regime various periodic cluster attractor states are formed
even though the coupling between the maps are very small relative to the
non-linearity in the element maps.
Most outstanding is a maximally symmetric three cluster attractor in period
three motion (MSCA) due to the foliation of the period three window of the
element logistic maps. An analytic approach is proposed which explains
successfully the systematics of various periodicity manifestations in the
turbulent regime. The linear stability of the period three cluster attractors
is investigated.Comment: 34 pages, 8 Postscript figures, all in GCML-MSCA.Zi
Effect of nonlinearity on the dynamics of a particle in dc field-induced systems
Dynamics of a particle in a perfect chain with one nonlinear impurity and in
a perfect nonlinear chain under the action of dc field is studied numerically.
The nonlinearity appears due to the coupling of the electronic motion to
optical oscillators which are treated in adiabatic approximation.
We study for both the low and high values of field strength. Three different
range of nonlinearity is obtained where the dynamics is different. In low and
intermediate range of nonlinearity, it reduces the localization. In fact in the
intermediate range subdiffusive behavior in the perfect nonlinear chain is
obtained for a long time. In all the cases a critical value of nonlinear
strength exists where self-trapping transition takes place. This critical value
depends on the system and the field strength. Beyond the self-trapping
transition nonlinearity enhances the localization.Comment: 9 pages, Revtex, 6 ps figures include
Transport and fluctuation-dissipation relations in asymptotic and pre-asymptotic diffusion across channels with variable section
We study the asymptotic and pre-asymptotic diffusive properties of Brownian
particles in channels whose section varies periodically in space. The effective
diffusion coefficient is numerically determined by the
asymptotic behavior of the root mean square displacement in different
geometries, considering even cases of steep variations of the channel
boundaries. Moreover, we compared the numerical results to the predictions from
the various corrections proposed in the literature to the well known
Fick-Jacobs approximation. Building an effective one dimensional equation for
the longitudinal diffusion, we obtain an approximation for the effective
diffusion coefficient. Such a result goes beyond a perturbation approach, and
it is in good agreement with the actual values obtained by the numerical
simulations. We discuss also the pre-asymptotic diffusion which is observed up
to a crossover time whose value, in the presence of strong spatial variation of
the channel cross section, can be very large. In addition, we show how the
Einstein's relation between the mean drift induced by a small external field
and the mean square displacement of the unperturbed system is valid in both
asymptotic and pre-asymptotic regimes.Comment: RevTeX 4-1, 11 Pages, 11 pdf figure
Time evolution of models described by one-dimensional discrete nonlinear Schr\"odinger equation
The dynamics of models described by a one-dimensional discrete nonlinear
Schr\"odinger equation is studied. The nonlinearity in these models appears due
to the coupling of the electronic motion to optical oscillators which are
treated in adiabatic approximation. First, various sizes of nonlinear cluster
embedded in an infinite linear chain are considered. The initial excitation is
applied either at the end-site or at the middle-site of the cluster. In both
the cases we obtain two kinds of transition: (i) a cluster-trapping transition
and (ii) a self-trapping transition. The dynamics of the quasiparticle with the
end-site initial excitation are found to exhibit, (i) a sharp self-trapping
transition, (ii) an amplitude-transition in the site-probabilities and (iii)
propagating soliton-like waves in large clusters. Ballistic propagation is
observed in random nonlinear systems. The effect of nonlinear impurities on the
superdiffusive behavior of random-dimer model is also studied.Comment: 16 pages, REVTEX, 9 figures available upon request, To appear in
Physical Review
Antitumour activity of pembrolizumab in advanced mucosal melanoma: a post-hoc analysis of KEYNOTE-001, 002, 006.
BackgroundMucosal melanoma is an aggressive melanoma with poor prognosis. We assessed efficacy of pembrolizumab in patients with advanced mucosal melanoma in KEYNOTE-001 (NCT01295827), -002 (NCT01704287), and -006 (NCT01866319).MethodsPatients received pembrolizumab 2 mg/kg every 3 weeks (Q3W) or 10 mg/kg Q2W or Q3W. Response was assessed by independent central review per RECIST v1.1.Results1567 patients were treated and 84 (5%) had mucosal melanoma. Fifty-one of 84 were ipilimumab-naive. In patients with mucosal melanoma, the objective response rate (ORR) was 19% (95% CI 11-29%), with median duration of response (DOR) of 27.6 months (range 1.1 + to 27.6). Median progression-free survival (PFS) was 2.8 months (95% CI 2.7-2.8), with median overall survival (OS) of 11.3 months (7.7-16.6). ORR was 22% (95% CI 11-35%) and 15% (95% CI 5-32%) in ipilimumab-naive and ipilimumab-treated patients.ConclusionPembrolizumab provides durable antitumour activity in patients with advanced mucosal melanoma regardless of prior ipilimumab
Non-Equilibrium relation between mobility and diffusivity of interacting Brownian particles under shear
We investigate the relation between mobility and diffusivity for Brownian
particles under steady shear near the glass transition, using mode coupling
approximations. For the two directions perpendicular to the shear direction,
the particle motion is diffusive at long times and the mobility reaches a
finite constant. Nevertheless, the Einstein relation holds only for the
short-time in-cage motion and is violated for long times. In order to get the
relation between diffusivity and mobility, we perform the limit of small
wavevector for the relations derived previously [Phys. Rev. Lett. 102 (2009),
135701], without further approximation. We find good agreement to simulation
results. Furthermore, we split the extra term in the mobility in an exact way
into three terms. Two of them are expressed in terms of mean squared
displacements. The third is given in terms of the (less handy) force-force
correlation function.Comment: 14 pages, 4 figures, accepted for Prog. Theor. Phys. Suppl., issue
for the workshop "Frontiers in Nonequilibrium Physics", Kyoto, 200
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