4,027 research outputs found
Maternal fluoxetine exposure alters cortical hemodynamic and calcium response of offspring to somatosensory stimuli
Epidemiological studies have found an increased incidence of neurodevelopmental disorders in populations prenatally exposed to selective serotonin reuptake inhibitors (SSRIs). Optical imaging provides a minimally invasive way to determine if perinatal SSRI exposure has long-term effects on cortical function. Herein we probed the functional neuroimaging effects of perinatal SSRI exposure in a fluoxetine (FLX)-exposed mouse model. While resting-state homotopic contralateral functional connectivity was unperturbed, the evoked cortical response to forepaw stimulation was altered in FLX mice. The stimulated cortex showed decreased activity for FLX versus controls, by both hemodynamic responses [oxyhemoglobin (Hb
ISO spectroscopy of circumstellar dust in the Herbig Ae systems AB Aur and HD 163296
Using both the Short- and Long-wavelength Spectrometers on board the Infrared
Space Observatory (ISO), we have obtained infrared spectra of the Herbig Ae
systems AB Aur and HD 163296. In addition, we obtained ground-based N band
images of HD 163296. Our results can be summarized as follows: (1) The main
dust components in AB Aur are amorphous silicates, iron oxide and PAHs; (2) The
circumstellar dust in HD 163296 consists of amorphous silicates, iron oxide,
water ice and a small fraction of crystalline silicates; (3) The infrared
fluxes of HD 163296 are dominated by solid state features; (4) The colour
temperature of the underlying continuum is much cooler in HD 163296 than in AB
Aur, pointing to the existence of a population of very large (mm sized) dust
grains in HD 163296; (5) The composition and degree of crystallization of
circumstellar dust are poorly correlated with the age of the central star. The
processes of crystallization and grain growth are also not necessarily coupled.
This means that either the evolution of circumstellar dust in protoplanetary
disks happens very rapidly (within a few Myr), or that this evolution is
governed by factors other than stellar mass and age.Comment: 6 pages, 2 figures, accepted for publication in Astronomy &
Astrophysic
Structure of a Cyclophane Host Molecule
The cyclophane tetramethyl 3,8,13,18a,2l,26,31,36aoctahydro-
4,6:9,12:22,24:27,30-tetraetheno-l5,18,21:-33,36,39-diethenylylidenedibenzo[k,ɑl][1,8,17,24]tetraoxacyclodotriacontene-1,2,19,20-tetracarboxylate acetonitrile solvate, C_(56)H_(44)O_(12).CH_3C=N, contains a large cavity and forms host-guest complexes in solution with a variety of quaternary nitrogen compounds. Crystallization from an acetonitrile solution that contained damantyltrimethylammonium iodide led, though, to crystals of the uncomplexed cyclophane (but containing one molecule of acetonitrile of crystallization). The cavity, about 7.6
x 4.0 Å and roughly rectangular in cross section, is occupied by ester groupings from two adjacent cyclophanes,
entering from opposite sides. Crystal data: orthorhombic, P2_12_12_1, with a= 11.741 (6), b = 16.155 (5), c = 25.895 (7) Å, v = 4912 Å^3, T = 296 K, Z = 4, M_r= 950.01, D_x = 1.28 g cm^(-3), F(000) = 1992, Mo Kɑ, λ = 0.7107 Å, μ = 0.84 cm^(-1), R = 0.0538 for 2410 independent reflections with I> 0, S = 2.29 for 2610 total reflections
Suite of simple metrics reveals common movement syndromes across vertebrate taxa
ecause empirical studies of animal movement are most-often site- and species-specific, we lack understanding of the level of consistency in movement patterns across diverse taxa, as well as a framework for quantitatively classifying movement patterns. We aim to address this gap by determining the extent to which statistical signatures of animal movement patterns recur across ecological systems. We assessed a suite of movement metrics derived from GPS trajectories of thirteen marine and terrestrial vertebrate species spanning three taxonomic classes, orders of magnitude in body size, and modes of movement (swimming, flying, walking). Using these metrics, we performed a principal components analysis and cluster analysis to determine if individuals organized into statistically distinct clusters. Finally, to identify and interpret commonalities within clusters, we compared them to computer-simulated idealized movement syndromes representing suites of correlated movement traits observed across taxa (migration, nomadism, territoriality, and central place foraging)
Non-thermal high-energy emission from colliding winds of massive stars
Colliding winds of massive star binary systems are considered as potential
sites of non-thermal high-energy photon production. This is motivated merely by
the detection of synchrotron radio emission from the expected colliding wind
location. Here we investigate the properties of high-energy photon production
in colliding winds of long-period WR+OB-systems. We found that in the
dominating leptonic radiation process anisotropy and Klein-Nishina effects may
yield spectral and variability signatures in the gamma-ray domain at or above
the sensitivity of current or upcoming gamma-ray telescopes. Analytical
formulae for the steady-state particle spectra are derived assuming diffusive
particle acceleration out of a pool of thermal wind particles, and taking into
account adiabatic and all relevant radiative losses. For the first time we
include their advection/convection in the wind collision zone, and distinguish
two regions within this extended region: the acceleration region where spatial
diffusion is superior to convective/advective motion, and the convection region
defined by the convection time shorter than the diffusion time scale. The
calculation of the Inverse Compton radiation uses the full Klein-Nishina cross
section, and takes into account the anisotropic nature of the scattering
process. This leads to orbital flux variations by up to several orders of
magnitude which may, however, be blurred by the geometry of the system. The
calculations are applied to the typical WR+OB-systems WR 140 and WR 147 to
yield predictions of their expected spectral and temporal characteristica and
to evaluate chances to detect high-energy emission with the current and
upcoming gamma-ray experiments. (abridged)Comment: 67 pages, 24 figures, submitted to Ap
A Very Large Array 3.6cm continuum survey of Galactic Wolf-Rayet stars
We report the results of a survey of radio continuum emission of Galactic
Wolf-Rayet stars north of declination -46 degrees. The observations were
obtained at 8.46 GHz (3.6cm) using the Very Large Array (VLA), with an angular
resolution of about 6 x 9 arcsec and typical rms noise of 0.04 mJy/beam. Our
survey of 34 WR stars resulted in 15 definite and 5 probable detections, 13 of
these for the first time at radio wavelengths. All detections are unresolved.
Time variations in flux are confirmed in the cases of WR98a, WR104, WR105 and
WR125. WR79a and WR89 are also variable in flux and we suspect they are also
non-thermal emitters. Thus, of our sample 20-30% of the detected stars are
non-thermal emiters. Average mass loss rates determinations obtained excluding
definite and suspected non-thermal cases give similar values for WN (all
subtypes) and WC5-7 stars, while a lower value was obtained for WC8-9 stars.
Uncertainties in stellar distances largely contribute to the observed scatter
in mass loss rates. Upper limits to the mass loss rates were obtained in cases
of undetected sources or for sources which probably show additional non-thermal
emission.Comment: 21 pages, Latex, 21 postscript figures, to be published in The
Astronomical Journal, May 200
Knowledge-based gene expression classification via matrix factorization
Motivation: Modern machine learning methods based on matrix decomposition techniques, like independent component analysis (ICA) or non-negative matrix factorization (NMF), provide new and efficient analysis tools which are currently explored to analyze gene expression profiles. These exploratory feature extraction techniques yield expression modes (ICA) or metagenes (NMF). These extracted features are considered indicative of underlying regulatory processes. They can as well be applied to the classification of gene expression datasets by grouping samples into different categories for diagnostic purposes or group genes into functional categories for further investigation of related metabolic pathways and regulatory networks.
Results: In this study we focus on unsupervised matrix factorization techniques and apply ICA and sparse NMF to microarray datasets. The latter monitor the gene expression levels of human peripheral blood cells during differentiation from monocytes to macrophages. We show that these tools are able to identify relevant signatures in the deduced component matrices and extract informative sets of marker genes from these gene expression profiles. The methods rely on the joint discriminative power of a set of marker genes rather than on single marker genes. With these sets of marker genes, corroborated by leave-one-out or random forest cross-validation, the datasets could easily be classified into related diagnostic categories. The latter correspond to either monocytes versus macrophages or healthy vs Niemann Pick C disease patients.Siemens AG, MunichDFG (Graduate College 638)DAAD (PPP Luso - Alem˜a and PPP Hispano - Alemanas
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