1,003 research outputs found
Results from the commissioning of the ALICE Inner Tracking System with cosmics
The Inner Tracking System (ITS) is the detector of the ALICE central barrel
located closest to the beam axis and it is therefore a key detector for
tracking and vertexing performance. Here, the main results from the ITS
commissioning with atmospheric muons in 2008 are presented, focusing in
particular on the detector operation and calibration and on the methods
developed for the alignment of the ITS detectors using reconstructed tracks.Comment: 4 pages, 1 figure with 3 panels (=3 separate eps files) To appear in
the conference proceedings for Quark Matter 2009, March 30 - April 4,
Knoxville, Tennesse
Locomotive and reptation motion induced by internal force and friction
We propose a simple mechanical model of locomotion induced by internal force
and friction. We first construct a system of two elements as an analog of the
bipedal motion. The internal force does not induce a directional motion by
itself because of the action-reaction law, but a directional motion becomes
possible by the control of the frictional force. The efficiency of these model
systems is studied using an analogy to the heat engine. As a modified version
of the two-elements model, we construct a model which exhibits a bipedal motion
similar to kinesin's motion of molecular motor. Next, we propose a linear chain
model and a ladder model as an extension of the original two-element model,. We
find a transition from a straight to a snake-like motion in a ladder model by
changing the strength of the internal force.Comment: 10 pages, 7 figur
Influence of the Leakage Current on the Performance of Large Area Silicon Drift Detectors
In this paper we investigate the influence of the leakage current on the performance of Silicon Drift Detectors. First, analytical considerations are given in order to highlight the problems, specific for this type of detector, that emerge with leakage current. Then the obtained results are compared with the data of laboratory measurements. Aiming at a mass production of SDDs for the Inner Tracking System of the ALICE experiment at LHC we propose a simple and fast measurement for a preliminary selection before passing to a detailed acceptance test
Synthetic Turing protocells: vesicle self-reproduction through symmetry-breaking instabilities
The reproduction of a living cell requires a repeatable set of chemical
events to be properly coordinated. Such events define a replication cycle,
coupling the growth and shape change of the cell membrane with internal
metabolic reactions. Although the logic of such process is determined by
potentially simple physico-chemical laws, the modeling of a full,
self-maintained cell cycle is not trivial. Here we present a novel approach to
the problem which makes use of so called symmetry breaking instabilities as the
engine of cell growth and division. It is shown that the process occurs as a
consequence of the breaking of spatial symmetry and provides a reliable
mechanism of vesicle growth and reproduction. Our model opens the possibility
of a synthetic protocell lacking information but displaying self-reproduction
under a very simple set of chemical reactions
Dynamics of Internal Models in Game Players
A new approach for the study of social games and communications is proposed.
Games are simulated between cognitive players who build the opponent's internal
model and decide their next strategy from predictions based on the model. In
this paper, internal models are constructed by the recurrent neural network
(RNN), and the iterated prisoner's dilemma game is performed. The RNN allows us
to express the internal model in a geometrical shape. The complicated
transients of actions are observed before the stable mutually defecting
equilibrium is reached. During the transients, the model shape also becomes
complicated and often experiences chaotic changes. These new chaotic dynamics
of internal models reflect the dynamical and high-dimensional rugged landscape
of the internal model space.Comment: 19 pages, 6 figure
Geometric Hardy inequalities for the sub-elliptic Laplacian on convex domains in the Heisenberg group
We prove geometric versions of Hardy's inequality for the sub-elliptic
Laplacian on convex domains in the Heisenberg group ,
where convex is meant in the Euclidean sense. When and is the
half-space given by this generalizes an
inequality previously obtained by Luan and Yang. For such and the
inequality is sharp and takes the form \begin{equation}
\int_\Omega |\nabla_{\mathbb{H}^n}u|^2 \, d\xi \geq \frac{1}{4}\int_{\Omega}
\sum_{i=1}^n\frac{\langle X_i(\xi), \nu\rangle^2+\langle Y_i(\xi),
\nu\rangle^2}{\textrm{dist}(\xi, \partial \Omega)^2}|u|^2\, d\xi,
\end{equation} where denotes the
Euclidean distance from .Comment: 14 page
Beam test results of the irradiated Silicon Drift Detector for ALICE
The Silicon Drift Detectors will equip two of the six cylindrical layers of
high precision position sensitive detectors in the ITS of the ALICE experiment
at LHC. In this paper we report the beam test results of a SDD irradiated with
1 GeV electrons. The aim of this test was to verify the radiation tolerance of
the device under an electron fluence equivalent to twice particle fluence
expected during 10 years of ALICE operation.Comment: 6 pages,6 figures, to appear in the proceedings of International
Workshop In high Multiplicity Environments (TIME'05), 3-7 October 2005,
Zurich,Switzerlan
Mass Transportation on Sub-Riemannian Manifolds
We study the optimal transport problem in sub-Riemannian manifolds where the
cost function is given by the square of the sub-Riemannian distance. Under
appropriate assumptions, we generalize Brenier-McCann's Theorem proving
existence and uniqueness of the optimal transport map. We show the absolute
continuity property of Wassertein geodesics, and we address the regularity
issue of the optimal map. In particular, we are able to show its approximate
differentiability a.e. in the Heisenberg group (and under some weak assumptions
on the measures the differentiability a.e.), which allows to write a weak form
of the Monge-Amp\`ere equation
On the Hausdorff volume in sub-Riemannian geometry
For a regular sub-Riemannian manifold we study the Radon-Nikodym derivative
of the spherical Hausdorff measure with respect to a smooth volume. We prove
that this is the volume of the unit ball in the nilpotent approximation and it
is always a continuous function. We then prove that up to dimension 4 it is
smooth, while starting from dimension 5, in corank 1 case, it is C^3 (and C^4
on every smooth curve) but in general not C^5. These results answer to a
question addressed by Montgomery about the relation between two intrinsic
volumes that can be defined in a sub-Riemannian manifold, namely the Popp and
the Hausdorff volume. If the nilpotent approximation depends on the point (that
may happen starting from dimension 5), then they are not proportional, in
general.Comment: Accepted on Calculus and Variations and PD
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