2,914 research outputs found
Novel Schizophrenia Risk Gene TCF4 Influences Verbal Learning and Memory Functioning in Schizophrenia Patients
Background: Recently, a role of the transcription factor 4 (TCF4) gene in schizophrenia has been reported in a large genome-wide association study. It has been hypothesized that TCF4 affects normal brain development and TCF4 has been related to different forms of neurodevelopmental disorders. Schizophrenia patients exhibit strong impairments of verbal declarative memory (VDM) functions. Thus, we hypothesized that the disease-associated C allele of the rs9960767 polymorphism of the TCF4 gene led to impaired VDM functioning in schizophrenia patients. Method: The TCF4 variant was genotyped in 401 schizophrenia patients. VDM functioning was measured using the Rey Auditory Verbal Learning Test (RAVLT). Results: Carriers of the C allele were less impaired in recognition compared to those carrying the AA genotype (13.76 vs. 13.06; p = 0.049). Moreover, a trend toward higher scores in patients with the risk allele was found for delayed recall (10.24 vs. 9.41; p = 0.088). The TCF4 genotype did not influence intelligence or RAVLT immediate recall or total verbal learning. Conclusion: VDM function is influenced by the TCF4 gene in schizophrenia patients. However, the elevated risk for schizophrenia is not conferred by TCF4-mediated VDM impairment. Copyright (C) 2011 S. Karger AG, Base
The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups
We present a public catalog of galaxy groups constructed from the spectroscopic sample of galaxies in the fourth data release from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Galaxy Redshift Survey, including the Extended Groth Strip (EGS). The catalog contains 1165 groups with two or more members in the EGS over the redshift range 0 0.6 in the rest of DEEP2. Twenty-five percent of EGS galaxies and fourteen percent of high-z DEEP2 galaxies are assigned to galaxy groups. The groups were detected using the Voronoi-Delaunay method (VDM) after it has been optimized on mock DEEP2 catalogs following similar methods to those employed in Gerke et al. In the optimization effort, we have taken particular care to ensure that the mock catalogs resemble the data as closely as possible, and we have fine-tuned our methods separately on mocks constructed for the EGS and the rest of DEEP2. We have also probed the effect of the assumed cosmology on our inferred group-finding efficiency by performing our optimization on three different mock catalogs with different background cosmologies, finding large differences in the group-finding success we can achieve for these different mocks. Using the mock catalog whose background cosmology is most consistent with current data, we estimate that the DEEP2 group catalog is 72% complete and 61% pure (74% and 67% for the EGS) and that the group finder correctly classifies 70% of galaxies that truly belong to groups, with an additional 46% of interloper galaxies contaminating the catalog (66% and 43% for the EGS). We also confirm that the VDM catalog reconstructs the abundance of galaxy groups with velocity dispersions above ~300 km s^(–1) to an accuracy better than the sample variance, and this successful reconstruction is not strongly dependent on cosmology. This makes the DEEP2 group catalog a promising probe of the growth of cosmic structure that can potentially be used for cosmological tests
The zCOSMOS 20k Group Catalog
We present an optical group catalog between 0.1 < z < 1 based on 16,500
high-quality spectroscopic redshifts in the completed zCOSMOS-bright survey.
The catalog published herein contains 1498 groups in total and 192 groups with
more than five observed members. The catalog includes both group properties and
the identification of the member galaxies. Based on mock catalogs, the
completeness and purity of groups with three and more members should be both
about 83% with respect to all groups that should have been detectable within
the survey, and more than 75% of the groups should exhibit a one-to-one
correspondence to the "real" groups. Particularly at high redshift, there are
apparently more galaxies in groups in the COSMOS field than expected from mock
catalogs. We detect clear evidence for the growth of cosmic structure over the
last seven billion years in the sense that the fraction of galaxies that are
found in groups (in volume-limited samples) increases significantly with cosmic
time. In the second part of the paper, we develop a method for associating
galaxies that only have photo-z to our spectroscopically identified groups. We
show that this leads to improved definition of group centers, improved
identification of the most massive galaxies in the groups, and improved
identification of central and satellite galaxies, where we define the former to
be galaxies at the minimum of the gravitational potential wells. Subsamples of
centrals and satellites in the groups can be defined with purities up to 80%,
while a straight binary classification of all group and non-group galaxies into
centrals and satellites achieves purities of 85% and 75%, respectively, for the
spectroscopic sample.Comment: 26 pages, 21 figures, published in ApJ (along with machine-readable
tables
The VIMOS VLT Deep Survey: the group catalogue
[Abridged] We present a homogeneous and complete catalogue of optical groups
identified in the purely flux limited (17.5<=I<=24.0) VIMOS-VLT Deep Survey
(VVDS). We use mock catalogues extracted from the MILLENNIUM simulation, to
correct for potential systematics that might affect the overall distribution as
well as the individual properties of the identified systems. Simulated samples
allow us to forecast the number and properties of groups that can be
potentially found in a survey with VVDS-like selection functions. We use them
to correct for the expected incompleteness and also to asses how well galaxy
redshifts trace the line-of-sight velocity dispersion of the underlying mass
overdensity. In particular, we train on these mock catalogues the adopted
group-finding technique (the Voronoi-Delaunay Method, VDM). The goal is to
fine-tune its free parameters, recover in a robust and unbiased way the
redshift and velocity dispersion distributions of groups and maximize the level
of completeness (C) and purity (P) of the group catalogue. We identify 318 VVDS
groups with at least 2 members within 0.2<=z<=1.0, among which 144 (/30) with
at least 3 (/5) members. The sample has globally C=60% and P=50%. Nearly 45% of
the groups with at least 3 members are still recovered if we run the algorithm
with a parameter set which maximizes P (75%). We exploit the group sample to
study the redshift evolution of the fraction f_b of blue galaxies (U-B<=1)
within 0.2<=z<=1. We find that f_b is significantly lower in groups than in the
whole ensemble of galaxies irrespectively of their environment. These
quantities increase with redshift, with f_b in groups showing a marginally
significant steeper increase. We also confirm that, at any explored redshift,
f_b decreases for increasing group richness, and we extend towards fainter
luminosities the magnitude range over which this result holds.Comment: Submitted to A&A, revised version after referee comments, Table 5
adde
SFI++ II: A New I-band Tully-Fisher Catalog, Derivation of Peculiar Velocities and Dataset Properties
We present the SFI++ dataset, a homogeneously derived catalog of photometric
and rotational properties and the Tully-Fisher distances and peculiar
velocities derived from them. We make use of digital optical images, optical
long-slit spectra, and global HI line profiles to extract parameters of
relevance to disk scaling relations, incorporating several previously published
datasets as well as a new photometric sample of some 2000 objects. According to
the completeness of available redshift samples over the sky area, we exploit
both a modified percolation algorithm and the Voronoi-Delaunay method to assign
individual galaxies to groups as well as clusters, thereby reducing scatter
introduced by local orbital motions. We also provide corrections to the
peculiar velocities for both homogeneous and inhomogeneous Malmquist bias,
making use of the 2MASS Redshift Survey density field to approximate large
scale structure. We summarize the sample selection criteria, corrections made
to raw observational parameters, the grouping techniques, and our procedure for
deriving peculiar velocities. The final SFI++ peculiar velocity catalog of 4861
field and cluster galaxies is large enough to permit the study not just of the
global statistics of large scale flows but also of the {\it details} of the
local velocity field.Comment: 14 pages, 6 figures, 4 external online tables, accepted for
publication in ApJ
Embedding Riemannian Manifolds by the Heat Kernel of the Connection Laplacian
Given a class of closed Riemannian manifolds with prescribed geometric
conditions, we introduce an embedding of the manifolds into based on
the heat kernel of the Connection Laplacian associated with the Levi-Civita
connection on the tangent bundle. As a result, we can construct a distance in
this class which leads to a pre-compactness theorem on the class under
consideration
Tasking Event-B: An Extension to Event-B for Generating Concurrent Code
The Event-B method is a formal approach for modelling systems in safety-, and business-critical, domains. Initially, system specification takes place at a high level of abstraction; detail is added in refinement steps as the development proceeds toward implementation. Our aim has been to develop a novel approach for generating code, for concurrent programs, from Event-B. We formulated the approach so that it integrates well with the existing Event-B methodology and tools. In this paper we introduce a tasking extension for Event-B, with Tasking and Shared Machines. We make use of refinement, decomposition, and the extension, to structure projects for code generation for multitasking implementations. During the modelling phase decomposition is performed; decomposition reduces modelling complexity and makes proof more tractable. The decomposed models are then extended with sufficient information to enable generation of code. A task body describes a task’s behaviour, mainly using imperative, programming-like constructs. Task priority and life-cycle (periodic, triggered, etc.) are also specified, but timing aspects are not modelled formally. We provide tool support in order to validate the practical aspects of the approach
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