70 research outputs found
Simulating the Formation of the Local Galaxy Population
We simulate the formation and evolution of the local galaxy population
starting from initial conditions with a smoothed linear density field which
matches that derived from the IRAS 1.2 Jy galaxy survey. Our simulations track
the formation and evolution of all dark matter haloes more massive than 10e+11
solar masses out to a distance of 8000 km/s from the Milky Way. We implement
prescriptions similar to those of Kauffmann et al. (1999) to follow the
assembly and evolution of the galaxies within these haloes. We focus on two
variants of the CDM cosmology: an LCDM and a tCDM model. Galaxy formation in
each is adjusted to reproduce the I-band Tully-Fisher relation of Giovanelli et
al. (1997). We compare the present-day luminosity functions, colours,
morphology and spatial distribution of our simulated galaxies with those of the
real local population, in particular with the Updated Zwicky Catalog, with the
IRAS PSCz redshift survey, and with individual local clusters such as Coma,
Virgo and Perseus. We also use the simulations to study the clustering bias
between the dark matter and galaxies of differing type. Although some
significant discrepancies remain, our simulations recover the observed
intrinsic properties and the observed spatial distribution of local galaxies
reasonably well. They can thus be used to calibrate methods which use the
observed local galaxy population to estimate the cosmic density parameter or to
draw conclusions about the mechanisms of galaxy formation. To facilitate such
work, we publically release our z=0 galaxy catalogues, together with the
underlying mass distribution.Comment: 25 pages, 20 figures, submitted to MNRAS. High resolution copies of
figures 1 and 3, halo and galaxy catalogues can be found at
http://www.mpa-garching.mpg.de/NumCos/CR/index.htm
Bayesian power-spectrum inference for Large Scale Structure data
We describe an exact, flexible, and computationally efficient algorithm for a
joint estimation of the large-scale structure and its power-spectrum, building
on a Gibbs sampling framework and present its implementation ARES (Algorithm
for REconstruction and Sampling). ARES is designed to reconstruct the 3D
power-spectrum together with the underlying dark matter density field in a
Bayesian framework, under the reasonable assumption that the long wavelength
Fourier components are Gaussian distributed. As a result ARES does not only
provide a single estimate but samples from the joint posterior of the
power-spectrum and density field conditional on a set of observations. This
enables us to calculate any desired statistical summary, in particular we are
able to provide joint uncertainty estimates. We apply our method to mock
catalogs, with highly structured observational masks and selection functions,
in order to demonstrate its ability to reconstruct the power-spectrum from real
data sets, while fully accounting for any mask induced mode coupling.Comment: 25 pages, 15 figure
Bayesian reconstruction of the cosmological large-scale structure: methodology, inverse algorithms and numerical optimization
We address the inverse problem of cosmic large-scale structure reconstruction
from a Bayesian perspective. For a linear data model, a number of known and
novel reconstruction schemes, which differ in terms of the underlying signal
prior, data likelihood, and numerical inverse extra-regularization schemes are
derived and classified. The Bayesian methodology presented in this paper tries
to unify and extend the following methods: Wiener-filtering, Tikhonov
regularization, Ridge regression, Maximum Entropy, and inverse regularization
techniques. The inverse techniques considered here are the asymptotic
regularization, the Jacobi, Steepest Descent, Newton-Raphson,
Landweber-Fridman, and both linear and non-linear Krylov methods based on
Fletcher-Reeves, Polak-Ribiere, and Hestenes-Stiefel Conjugate Gradients. The
structures of the up-to-date highest-performing algorithms are presented, based
on an operator scheme, which permits one to exploit the power of fast Fourier
transforms. Using such an implementation of the generalized Wiener-filter in
the novel ARGO-software package, the different numerical schemes are
benchmarked with 1-, 2-, and 3-dimensional problems including structured white
and Poissonian noise, data windowing and blurring effects. A novel numerical
Krylov scheme is shown to be superior in terms of performance and fidelity.
These fast inverse methods ultimately will enable the application of sampling
techniques to explore complex joint posterior distributions. We outline how the
space of the dark-matter density field, the peculiar velocity field, and the
power spectrum can jointly be investigated by a Gibbs-sampling process. Such a
method can be applied for the redshift distortions correction of the observed
galaxies and for time-reversal reconstructions of the initial density field.Comment: 40 pages, 11 figure
Stress Hormones Receptors in the Amygdala Mediate the Effects of Stress on the Consolidation, but Not the Retrieval, of a Non Aversive Spatial Task
This study examined the effects of the arousal level of the rat and exposure to a behavioral stressor on acquisition, consolidation and retrieval of a non-aversive hippocampal-dependent learning paradigm, the object location task. Learning was tested under two arousal conditions: no previous habituation to the experimental context (high novelty stress/arousal level) or extensive prior habituation (reduced novelty stress/arousal level). Results indicated that in the habituated rats, exposure to an out-of-context stressor (i.e, elevated platform stress) impaired consolidation and retrieval, but not acquisition, of the task. Non-habituated animals under both stressed and control conditions did not show retention of the task. In habituated rats, RU-486 (10 ng/side), a glucocorticoid receptor (GR) antagonist, or propranolol (0.75 µg/side), a beta-adrenergic antagonist, injected into the basolateral amygdala (BLA), prevented the impairing effects of the stressor on consolidation, but not on retrieval. The CB1/CB2 receptor agonist WIN55,212-2 (WIN, 5 µg/side) microinjected into the BLA did not prevent the effects of stress on either consolidation or retrieval. Taken together the results suggest that: (i) GR and β-adrenergic receptors in the BLA mediate the impairing effects of stress on the consolidation, but not the retrieval, of a neutral, non-aversive hippocampal-dependent task, (ii) the impairing effects of stress on hippocampal consolidation and retrieval are mediated by different neural mechanisms (i.e., different neurotransmitters or different brain areas), and (iii) the effects of stress on memory depend on the interaction between several main factors such as the stage of memory processing under investigation, the animal's level of arousal and the nature of the task (neutral or aversive)
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The feud of love: A cycle of love/hate scenes from Shakespeare for chamber ensemble, soprano, and baritone
The Feud of Love is a cycle of love/hate scenes between feuding couples from three Shakespeare plays, Richard III, Troilus and Cressida, and The Taming of the Shrew. The work is written in a tonal idiom and makes extensive use of motives. Within the scenes, recitative sections alternate with lyrical passages. The work is scored for two singers (soprano and baritone) and a chamber ensemble consisting of flute/piccolo, oboe, Bb clarinet, bassoon, horn in F, percussion (timpani and tubular bells), harp, two violins, viola, cello, and contrabass. It has an approximate duration of 50 minutes
Loss of function of NaPiIIa causes nephrocalcinosis and possibly kidney insufficiency
BACKGROUND Inherited metabolic disorders associated with nephrocalcinosis are rare conditions. The aim of this study was to identify the genetic cause of an Israeli-Arab boy from a consanguineous family with severe nephrocalcinosis and kidney insufficiency. METHODS Clinical and biochemical data of the proband and family members were obtained from both previous and recent medical charts. Genomic DNA was isolated from peripheral blood cells. The coding sequence and splice sites of candidate genes (CYP24A1, CYP27B1, FGF23, KLOTHO, SLC34A3 and SLC34A1) were sequenced directly. Functional studies were performed in Xenopus laevis oocytes and in transfected opossum kidney (OK) cells. RESULTS Our patient was identified as having nephrocalcinosis in utero, and at the age of 16.5 years, he had kidney insufficiency but no bone disease. Genetic analysis revealed a novel homozygous missense mutation, Arg215Gln, in SLC34A1, which encodes the renal sodium phosphate cotransporter NaPiIIa. Functional studies of the Arg215Gln mutant revealed reduced transport activity in Xenopus laevis oocytes and increased intracellular cytoplasmic accumulation in OK cells. CONCLUSIONS Our findings show that dysfunction of the human NaPiIIa causes severe renal calcification that may eventually lead to reduced kidney function, rather than complications of phosphate loss
Chinese and Filipino market interaction: An experimental approach on social capital measurement
Cannabinoids and Glucocorticoids in the Basolateral Amygdala Modulate Hippocampal–Accumbens Plasticity After Stress
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