5,126 research outputs found
Computer program simplifies design of rotating components of turbomachinery
Digital computer program performs stress analysis and burst speed calculations on rotating axisymmetric turbomachinery components. The computer printout contains the displacement of each nodal point, the stress at the center of each element, the average tangential stress within the component, and the burst speed
Status of the ILC Main Linac BPM R&D
An introduction and the status of R&D activities for a high-resolution,
"cold" beam position monitor (BPM) and the related read-out electronics are
discussed. Two different BPM detector concepts, to be attached to the SC
quadrupole and located inside the ILC cryomodule, are currently under
investigation: A resonant dipole-mode cavity-style BPM pickup, developed at
Fermilab, and a re-entrant resonant coaxial waveguide BPM, designed by
CEA-Saclay. While the 1.5 GHz dipole-mode cavity BPM is still in the R&D phase,
the re-entrant BPM has already passed first beam tests, including its read-out
system. Furthermore, the LAPP group is developing radiation tolerant digital
read-out systems, which are tested at the CLIC test facility (CTF).Comment: LCWS / ILC08 conference contribution, 6 pages, 6 figure
Integrating Grounding in the Search Process for Answer Set Computing
Answer Set Programming (ASP) is a very convenient paradigmto represent knowledge in Artificial Intelligence and to encode Constraint Satisfaction Problems. For that, the natural way to use ASP is to elaborate a first order logic program with default negation encoding the problem to solve. In a preliminary step this program is translated in an equivalent propositional one by a first tool: the grounder. Then, the propositional program is given to a second tool: the solver. This last one computes (if they exist) one or many answer sets (models) of the program, each answer set encoding one solution of the initial problem. Today, we can say that almost all ASP solvers follow this approach of two steps computation. In this work, we begin by putting in evidence that sometimes the preliminary grounding phase is the only bottleneck for the answer set computation. We show that a lot of useless and counterintuitive work is done in some situations. But, our major contribution is to introduce a new approach of answer set computing that escapes the preliminary phase of rule instantiation by integrating it in the search process. Furthermore, we describe the main lines of the first implementation of our new ASP solver ASPeRiX developed following the introduced methodology
SigTree: A Microbial Community Analysis Tool to Identify and Visualize Significantly Responsive Branches in a Phylogenetic Tree.
Microbial community analysis experiments to assess the effect of a treatment intervention (or environmental change) on the relative abundance levels of multiple related microbial species (or operational taxonomic units) simultaneously using high throughput genomics are becoming increasingly common. Within the framework of the evolutionary phylogeny of all species considered in the experiment, this translates to a statistical need to identify the phylogenetic branches that exhibit a significant consensus response (in terms of operational taxonomic unit abundance) to the intervention. We present the R software package SigTree, a collection of flexible tools that make use of meta-analysis methods and regular expressions to identify and visualize significantly responsive branches in a phylogenetic tree, while appropriately adjusting for multiple comparisons
Unveiling hidden structures in the Coma cluster
We have assembled a large data-set of 613 galaxy redshifts in the Coma
cluster, the largest presently available for a cluster of galaxies. We have
defined a sample of cluster members complete to b, using a
membership criterion based on the galaxy velocity, when available, or on the
galaxy magnitude and colour, otherwise. Such a data set allows us to define
nearly complete samples within a region of 1~\Mpc\ radius, with a sufficient
number of galaxies per sample to make statistical analyses possible. Using this
sample and the {\em ROSAT} PSPC X--ray image of the cluster, we have
re-analyzed the structure and kinematics of Coma, by applying the wavelet and
adaptive kernel techniques. A striking coincidence of features is found in the
distributions of galaxies and hot intracluster gas. The two central dominant
galaxies, NGC4874 and NGC4889, are surrounded by two galaxy groups, mostly
populated with galaxies brighter than b and well separated in
velocity space. On the contrary, the fainter galaxies tend to form a single
smooth structure with a central peak coinciding in position with a secondary
peak detected in X--rays, and located between the two dominant galaxies; we
suggest to identify this structure with the main body of the Coma cluster. A
continuous velocity gradient is found in the central distribution of these
faint galaxies, a probable signature of tidal interactions rather than
rotation. There is evidence for a bound population of bright galaxies around
other brightest cluster members. Altogether, the Coma cluster structure seems
to be better traced by the faint galaxy population, the bright galaxies being
located in subclusters. We discuss this evidence in terms of an ongoing
accretion of groups onto the cluster.Comment: to appear in A&A, 19 pages, uuencoded gzipped postscript fil
The replacement histone H2A.Z in a hyperacetylated form is a feature of active genes in the chicken
The replacement histone H2A.Z is variously reported
as being linked to gene expression and preventing the
spread of heterochromatin in yeast, or concentrated
at heterochromatin in mammals. To resolve this
apparent dichotomy, affinity-purified antibodies
against the N-terminal region of H2A.Z, in both a triacetylatedandnon-
acetylatedstate, areusedin native
chromatin immmuno-precipitation experiments with
mononucleosomes from three chicken cell types. The
hyperacetylated species concentrates at the 50 end of
active genes, both tissue specific and housekeeping
but is absent from inactive genes, while the
unacetylated form is absent from both active and
inactive genes. A concentration of H2A.Z is also
found at insulators under circumstances implying a
link to barrier activity but not to enhancer blocking.
Although acetylated H2A.Z is widespread throughout
the interphase genome, at mitosis its acetylation is
erased, the unmodified form remaining. Thus,
although H2A.Z may operate as an epigenetic marker
for active genes, its N-terminal acetylation does not
The replacement histone H2A.Z in a hyperacetylated form is a feature of active genes in the chicken
The replacement histone H2A.Z is variously reported
as being linked to gene expression and preventing the
spread of heterochromatin in yeast, or concentrated
at heterochromatin in mammals. To resolve this
apparent dichotomy, affinity-purified antibodies
against the N-terminal region of H2A.Z, in both a triacetylatedandnon-
acetylatedstate, areusedin native
chromatin immmuno-precipitation experiments with
mononucleosomes from three chicken cell types. The
hyperacetylated species concentrates at the 50 end of
active genes, both tissue specific and housekeeping
but is absent from inactive genes, while the
unacetylated form is absent from both active and
inactive genes. A concentration of H2A.Z is also
found at insulators under circumstances implying a
link to barrier activity but not to enhancer blocking.
Although acetylated H2A.Z is widespread throughout
the interphase genome, at mitosis its acetylation is
erased, the unmodified form remaining. Thus,
although H2A.Z may operate as an epigenetic marker
for active genes, its N-terminal acetylation does not
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