11,987 research outputs found
Design and Performance of the CMS Pixel Detector Readout Chip
The readout chip for the CMS pixel detector has to deal with an enormous data
rate. On-chip zero suppression is inevitable and hit data must be buffered
locally during the latency of the first level trigger. Dead-time must be kept
at a minimum. It is dominated by contributions coming from the readout. To keep
it low an analog readout scheme has been adopted where pixel addresses are
analog coded. We present the architecture of the final CMS pixel detector
readout chip with special emphasis on the analog readout chain. Measurements of
its performance are discussed.Comment: 8 pages, 11 figures. Contribution to the Proceedings of the Pixel2005
Workshop, Bonn, German
Adaptive multilevel-methods for obstacle problems in three space dimensions
We consider the discretization of obstacle problems for second order elliptic differential operators in three space dimensions by piecewise linear finite elements. Linearizing the discrete problems by suitable active set strategies, the resulting linear sub-problems are solved iteratively by preconditioned cg-iterations. We propose a variant of the BPX preconditioner and prove an O(j) estimate for the resulting condition number To allow for local mesh refinement we derive semi-local and local a posteriori error estimates. The theoretical results are illustrated by numerical computations
A Development Environment for Visual Physics Analysis
The Visual Physics Analysis (VISPA) project integrates different aspects of
physics analyses into a graphical development environment. It addresses the
typical development cycle of (re-)designing, executing and verifying an
analysis. The project provides an extendable plug-in mechanism and includes
plug-ins for designing the analysis flow, for running the analysis on batch
systems, and for browsing the data content. The corresponding plug-ins are
based on an object-oriented toolkit for modular data analysis. We introduce the
main concepts of the project, describe the technical realization and
demonstrate the functionality in example applications
Universal deformation rings of modules for algebras of dihedral type of polynomial growth
Let k be an algebraically closed field, and let \Lambda\ be an algebra of
dihedral type of polynomial growth as classified by Erdmann and Skowro\'{n}ski.
We describe all finitely generated \Lambda-modules V whose stable endomorphism
rings are isomorphic to k and determine their universal deformation rings
R(\Lambda,V). We prove that only three isomorphism types occur for
R(\Lambda,V): k, k[[t]]/(t^2) and k[[t]].Comment: 11 pages, 2 figure
Qualification Procedures of the CMS Pixel Barrel Modules
The CMS pixel barrel system will consist of three layers built of about 800
modules. One module contains 66560 readout channels and the full pixel barrel
system about 48 million channels. It is mandatory to test each channel for
functionality, noise level, trimming mechanism, and bump bonding quality.
Different methods to determine the bump bonding yield with electrical
measurements have been developed. Measurements of several operational
parameters are also included in the qualification procedure. Among them are
pixel noise, gains and pedestals. Test and qualification procedures of the
pixel barrel modules are described and some results are presented.Comment: 7 Pages, 7 Figures. Contribution to Pixel 2005, September 5-8, 2005,
Bonn, Germna
Phylogeography of the crown-of-thorns starfish in the Indian Ocean
Background: Understanding the limits and population dynamics of closely related sibling species in the marine realm is particularly relevant in organisms that require management. The crown-of-thorns starfish Acanthaster planci, recently shown to be a species complex of at least four closely related species, is a coral predator infamous for its outbreaks that have devastated reefs throughout much of its Indo-Pacific distribution.
Methodology/Principal Findings: In this first Indian Ocean-wide genetic study of a marine organism we investigated the genetic structure and inferred the paleohistory of the two Indian Ocean sister-species of Acanthaster planci using mitochondrial DNA sequence analyses. We suggest that the first of two main diversification events led to the formation of a Southern and Northern Indian Ocean sister-species in the late Pliocene-early Pleistocene. The second led to the formation of two internal clades within each species around the onset of the last interglacial. The subsequent demographic history of the two lineages strongly differed, the Southern Indian Ocean sister-species showing a signature of recent population expansion and hardly any regional structure, whereas the Northern Indian Ocean sister-species apparently maintained a constant size with highly differentiated regional groupings that were asymmetrically connected by gene flow.
Conclusions/Significance: Past and present surface circulation patterns in conjunction with ocean primary productivity were identified as the processes most likely to have shaped the genetic structure between and within the two Indian Ocean lineages. This knowledge will help to understand the biological or ecological differences of the two sibling species and therefore aid in developing strategies to manage population outbreaks of this coral predator in the Indian Ocean
Application of thermodynamics to driven systems
Application of thermodynamics to driven systems is discussed. As particular
examples, simple traffic flow models are considered. On a microscopic level,
traffic flow is described by Bando's optimal velocity model in terms of
accelerating and decelerating forces. It allows to introduce kinetic,
potential, as well as total energy, which is the internal energy of the car
system in view of thermodynamics. The latter is not conserved, although it has
certain value in any of two possible stationary states corresponding either to
fixed point or to limit cycle in the space of headways and velocities. On a
mesoscopic level of description, the size n of car cluster is considered as a
stochastic variable in master equation. Here n=0 corresponds to the fixed-point
solution of the microscopic model, whereas the limit cycle is represented by
coexistence of a car cluster with n>0 and free flow phase. The detailed balance
holds in a stationary state just like in equilibrium liquid-gas system. It
allows to define free energy of the car system and chemical potentials of the
coexisting phases, as well as a relaxation to a local or global free energy
minimum. In this sense the behaviour of traffic flow can be described by
equilibrium thermodynamics. We find, however, that the chemical potential of
the cluster phase of traffic flow depends on an outer parameter - the density
of cars in the free-flow phase. It allows to distinguish between the traffic
flow as a driven system and purely equilibrium systems.Comment: 9 pages, 6 figures. Eur. Phys. J. B (2007) to be publishe
CYP17A1 deficient XY mice display susceptibility to atherosclerosis, altered lipidomic profile and atypical sex development
CYP17A1 is a cytochrome P450 enzyme with 17-alpha-hydroxylase and C17,20-lyase activities. CYP17A1 genetic variants are associated with coronary artery disease, myocardial infarction and visceral and subcutaneous fat distribution; however, the underlying pathological mechanisms remain unknown. We aimed to investigate the function of CYP17A1 and its impact on atherosclerosis in mice. At 4-6 months, CYP17A1-deficient mice were viable, with a KO:Het:WT ratio approximating the expected Mendelian ratio of 1:2:1. All Cyp17a1 knockout (KO) mice were phenotypically female; however, 58% were Y chromosome-positive, resembling the phenotype of human CYP17A1 deficiency, leading to 46,XY differences/disorders of sex development (DSD). Both male and female homozygous KO mice were infertile, due to abnormal genital organs. Plasma steroid analyses revealed a complete lack of testosterone in XY-KO mice and marked accumulation of progesterone in XX-KO mice. Elevated corticosterone levels were observed in both XY and XX KO mice. In addition, Cyp17a1 heterozygous mice were also backcrossed onto an Apoe KO atherogenic background and fed a western-type diet (WTD) to study the effects of CYP17A1 on atherosclerosis. Cyp17a1 x Apoe double KO XY mice developed more atherosclerotic lesions than Apoe KO male controls, regardless of diet (standard or WTD). Increased atherosclerosis in CYP17A1 XY KO mice lacking testosterone was associated with altered lipid profiles. In mice, CYP17A1 deficiency interferes with sex differentiation. Our data also demonstrate its key role in lipidomic profile, and as a risk factor in the pathogenesis of atherosclerosis
A differential U-module algebra for U=U_q sl(2) at an even root of unity
We show that the full matrix algebra Mat_p(C) is a U-module algebra for U =
U_q sl(2), a 2p^3-dimensional quantum sl(2) group at the 2p-th root of unity.
Mat_p(C) decomposes into a direct sum of projective U-modules P^+_n with all
odd n, 1<=n<=p. In terms of generators and relations, this U-module algebra is
described as the algebra of q-differential operators "in one variable" with the
relations D z = q - q^{-1} + q^{-2} z D and z^p = D^p = 0. These relations
define a "parafermionic" statistics that generalizes the fermionic commutation
relations. By the Kazhdan--Lusztig duality, it is to be realized in a
manifestly quantum-group-symmetric description of (p,1) logarithmic conformal
field models. We extend the Kazhdan--Lusztig duality between U and the (p,1)
logarithmic models by constructing a quantum de Rham complex of the new
U-module algebra.Comment: 29 pages, amsart++, xypics. V3: The differential U-module algebra was
claimed quantum commutative erroneously. This is now corrected, the other
results unaffecte
Universal deformation rings for the symmetric group S_4
Let k be an algebraically closed field of characteristic 2, and let W be the
ring of infinite Witt vectors over k. Let S_4 denote the symmetric group on 4
letters. We determine the universal deformation ring R(S_4,V) for every
kS_4-module V which has stable endomorphism ring k and show that R(S_4,V) is
isomorphic to either k, or W[t]/(t^2,2t), or the group ring W[Z/2]. This gives
a positive answer in this case to a question raised by the first author and
Chinburg whether the universal deformation ring of a representation of a finite
group with stable endomorphism ring k is always isomorphic to a subquotient
ring of the group ring over W of a defect group of the modular block associated
to the representation.Comment: 12 pages, 2 figure
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