5,143 research outputs found
Dominance of extreme statistics in a prototype many-body Brownian ratchet
Many forms of cell motility rely on Brownian ratchet mechanisms that involve
multiple stochastic processes. We present a computational and theoretical study
of the nonequilibrium statistical dynamics of such a many-body ratchet, in the
specific form of a growing polymer gel that pushes a diffusing obstacle. We
find that oft-neglected correlations among constituent filaments impact
steady-state kinetics and significantly deplete the gel's density within
molecular distances of its leading edge. These behaviors are captured
quantitatively by a self-consistent theory for extreme fluctuations in
filaments' spatial distribution.Comment: 5 pages with 3 figures + 20 pages of Supplementary Material with 2
figures. Updated to agree with published version; published as a
Communication in J. Chem. Phy
Current-Induced Motion of Narrow Domain Walls and Dissipation in Ferromagnetic Metals
Spin transport equations in a non-homogeneous ferromagnet are derived in the
limit where the sd exchange coupling between the electrons in the conduction
band and those in the d band is dominant. It is shown that spin diffusion in
ferromagnets assumes a tensor form. The diagonal terms are renormalized with
respect to that in normal metals and enhances the dissipation in the magnetic
system while the off-diagonal terms renormalize the precessional frequency of
the conduction electrons and enhances the non-adiabatic spin torque. To
demonstrate the new physics in our theory, we show that self-consistent
solutions of the spin diffusion equations and the Landau-Lifshitz equations in
the presence of a current lead to a an increase in the terminal velocity of a
domain wall which becomes strongly dependent on its width. We also provide a
simplified equation that predicts damping due to the conduction electrons
A First Look at QUIC in the Wild
For the first time since the establishment of TCP and UDP, the Internet
transport layer is subject to a major change by the introduction of QUIC.
Initiated by Google in 2012, QUIC provides a reliable, connection-oriented
low-latency and fully encrypted transport. In this paper, we provide the first
broad assessment of QUIC usage in the wild. We monitor the entire IPv4 address
space since August 2016 and about 46% of the DNS namespace to detected
QUIC-capable infrastructures. Our scans show that the number of QUIC-capable
IPs has more than tripled since then to over 617.59 K. We find around 161K
domains hosted on QUIC-enabled infrastructure, but only 15K of them present
valid certificates over QUIC. Second, we analyze one year of traffic traces
provided by MAWI, one day of a major European tier-1 ISP and from a large IXP
to understand the dominance of QUIC in the Internet traffic mix. We find QUIC
to account for 2.6% to 9.1% of the current Internet traffic, depending on the
vantage point. This share is dominated by Google pushing up to 42.1% of its
traffic via QUIC
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