5,946 research outputs found
The Chow group of zero-cycles on certain Ch{\^a}telet surfaces over local fields
We compute the Chow group of zero-cycles on certain Ch{\^a}telet surfaces
over local fields.Comment: 14 page
The future of space exploration: the next 50 years
This repository item contains a single issue of Issues in Brief, a series of policy briefs that began publishing in 2008 by the Boston University Frederick S. Pardee Center for the Study of the Longer-Range Future.This policy brief flows from the 2007 Pardee Center conference on The Future of Space and lays out a set fo critical challenges for the next 50 years of space explorations
Study of gain variation as a function of physical parameters of GEM foil
The ALICE experiment at LHC has planned to upgrade the TPC by replacing the
MWPC with GEM based detecting elements to restrict the IBF to a tolerable
value. However the variation of the gain as a function of physical parameters
of industrially produced large size GEM foils is needed to be studied as a part
of the QA procedure for the detector. The size of the electron avalanche and
consequently the gain for GEM based detectors depend on the electric field
distribution inside the holes. Geometry of a hole plays an important role in
defining the electric field inside it. In this work we have studied the
variation of the gain as a function of the hole diameters using Garfield++
simulation package.Comment: 2 pages, 4 figures, Proceedings of 13th. Pisa Meeting on Advanced
Detectors (May 24 - 30, 2015
The stochastic behavior of a molecular switching circuit with feedback
Background: Using a statistical physics approach, we study the stochastic
switching behavior of a model circuit of multisite phosphorylation and
dephosphorylation with feedback. The circuit consists of a kinase and
phosphatase acting on multiple sites of a substrate that, contingent on its
modification state, catalyzes its own phosphorylation and, in a symmetric
scenario, dephosphorylation. The symmetric case is viewed as a cartoon of
conflicting feedback that could result from antagonistic pathways impinging on
the state of a shared component.
Results: Multisite phosphorylation is sufficient for bistable behavior under
feedback even when catalysis is linear in substrate concentration, which is the
case we consider. We compute the phase diagram, fluctuation spectrum and
large-deviation properties related to switch memory within a statistical
mechanics framework. Bistability occurs as either a first-order or second-order
non-equilibrium phase transition, depending on the network symmetries and the
ratio of phosphatase to kinase numbers. In the second-order case, the circuit
never leaves the bistable regime upon increasing the number of substrate
molecules at constant kinase to phosphatase ratio.
Conclusions: The number of substrate molecules is a key parameter controlling
both the onset of the bistable regime, fluctuation intensity, and the residence
time in a switched state. The relevance of the concept of memory depends on the
degree of switch symmetry, as memory presupposes information to be remembered,
which is highest for equal residence times in the switched states.
Reviewers: This article was reviewed by Artem Novozhilov (nominated by Eugene
Koonin), Sergei Maslov, and Ned Wingreen.Comment: Version published in Biology Direct including reviewer comments and
author responses, 28 pages, 7 figure
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