7,880 research outputs found
Towards a Full Census of the Obscure(d) Vela Supercluster using MeerKAT
Recent spectroscopic observations of a few thousand partially obscured
galaxies in the Vela constellation revealed a massive overdensity on
supercluster scales straddling the Galactic Equator (l 272.5deg) at km/s. It remained unrecognised because it is located just beyond the
boundaries and volumes of systematic whole-sky redshift and peculiar velocity
surveys - and is obscured by the Milky Way. The structure lies close to the
apex where residual bulkflows suggest considerable mass excess. The uncovered
Vela Supercluster (VSCL) conforms of a confluence of merging walls, but its
core remains uncharted. At the thickest foreground dust column densities (|b| <
6 deg) galaxies are not visible and optical spectroscopy is not effective. This
precludes a reliable estimate of the mass of VSCL, hence its effect on the
cosmic flow field and the peculiar velocity of the Local Group. Only systematic
HI-surveys can bridge that gap. We have run simulations and will present
early-science observing scenarios with MeerKAT 32 (M32) to complete the census
of this dynamically and cosmologically relevant supercluster. M32 has been put
forward because this pilot project will also serve as precursor project for HI
MeerKAT Large Survey Projects, like Fornax and Laduma. Our calculations have
shown that a survey area of the fully obscured part of the supercluster, where
the two walls cross and the potential core of the supercluster resides, can be
achieved on reasonable time-scales (200 hrs) with M32.Comment: 10 pages, 3 figures, accepted for publication, Proceedings of
Science, workshop on "MeerKAT Science: On the Pathway to the SKA", held in
Stellenbosch 25-27 May 201
Nonclassical correlation in NMR quadrupolar systems
The existence of quantum correlation (as revealed by quantum discord), other
than entanglement and its role in quantum-information processing (QIP), is a
current subject for discussion. In particular, it has been suggested that this
nonclassical correlation may provide computational speedup for some quantum
algorithms. In this regard, bulk nuclear magnetic resonance (NMR) has been
successfully used as a test bench for many QIP implementations, although it has
also been continuously criticized for not presenting entanglement in most of
the systems used so far. In this paper, we report a theoretical and
experimental study on the dynamics of quantum and classical correlations in an
NMR quadrupolar system. We present a method for computing the correlations from
experimental NMR deviation-density matrices and show that, given the action of
the nuclear-spin environment, the relaxation produces a monotonic time decay in
the correlations. Although the experimental realizations were performed in a
specific quadrupolar system, the main results presented here can be applied to
whichever system uses a deviation-density matrix formalism.Comment: Published versio
DOPAL derived alpha-synuclein oligomers impair synaptic vesicles physiological function
Parkinson's disease is a neurodegenerative disorder characterized by the death of dopaminergic neurons and by accumulation of alpha-synuclein (aS) aggregates in the surviving neurons. The dopamine catabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) is a highly reactive and toxic molecule that leads to aS oligomerization by covalent modifications to lysine residues. Here we show that DOPAL-induced aS oligomer formation in neurons is associated with damage of synaptic vesicles, and with alterations in the synaptic vesicles pools. To investigate the molecular mechanism that leads to synaptic impairment, we first aimed to characterize the biochemical and biophysical properties of the aS-DOPAL oligomers; heterogeneous ensembles of macromolecules able to permeabilise cholesterol-containing lipid membranes. aS-DOPAL oligomers can induce dopamine leak in an in vitro model of synaptic vesicles and in cellular models. The dopamine released, after conversion to DOPAL in the cytoplasm, could trigger a noxious cycle that further fuels the formation of aS-DOPAL oligomers, inducing neurodegeneration
ESO 381-47, an early-type galaxy with extended HI and a star forming ring
ESO 381-47 is an early type galaxy with an extended HI disk. GALEX and very
deep optical images reveal a distinct stellar ring far outside the optical body
with a diameter of ~30 kpc, which has undergone recent star formation at 1.8 x
10^-4 Msun/yr/kpc^-2, consistent with other new results which detect low level
star formation below the traditional Kennicutt relation in the outer parts of
spiral galaxies. The morphology of this galaxy resembles the recently
identified class of ultraviolet objects called extended ultraviolet disks, or
XUV-disks. New HI observations of this galaxy taken at the ATCA and in the CnB
array at the VLA show that the cold gas lies in an extended (diameter ~90 kpc)
ring around the central S0 galaxy. The HI data cube can be well modeled by a
warped ring. The faint ionized gas in the inner parts of the galaxy is
kinematically decoupled from the stars and instead appears to exhibit
velocities consistent with the rotation of the HI ring at larger radius. The
peak of the stellar ring, as seen in the optical and UV, is slightly displaced
to the inside relative to the peak of the HI ring. We discuss the manner in
which this offset could be caused by the propagation of a radial density wave
through an existing stellar disk, perhaps triggered by a galaxy collision at
the center of the disk, or possibly due to a spiral density wave set up at
early times in a disk too hot to form a stellar bar. Gas accretion and
resonance effects due to a bar which has since dissolved are also considered to
explain the presence of the star forming ring seen in the GALEX and deep
optical data.Comment: 48 pages, 16 figures, 4 tables. Accepted for publication in the
Astronomical Journa
Sudden change in quantum and classical correlations and the Unruh effect
We use the Unruh effect to analyze the dynamics of classical and quantum
correlations for a two-qubit system when one of them is uniformly accelerated
for a finite amount of proper time. We show that the quantum correlation is
completely destroyed in the limit of infinite acceleration, while the classical
one remains nonzero. In particular, we show that such correlations exhibit the
so-called sudden-change behavior as a function of acceleration. Eventually, we
discuss how our results can be interpreted when the system lies in the vicinity
of the event horizon of a Schwarzschild black hole.Comment: Published versio
Apparent digestibility of insect protein meals for rainbow trout
Insect meals are considered to be promising future ingredients for aquaculture feeds. In past feeding trials in rainbow trout, insect meals were included in diets only on the basis of their nutrients content and energy density without taking into account their biological availability due to the lack of their digestible values. Apparent digestibility (ADC) provides good indication of the bioavailability of nutrients and energy thus providing rational basis for the correct inclusion of feedstuffs. The aim of this research was to assess, in an in vivo trial on rainbow trout, the ADC of five full fat insect meals: one Tenebrio molitor (TM), two Hermetia illucens obtained through two different process (HI1 and HI2), one Musca domestica (MD), and one Alphitobius diaperinus (AD). Fish were fed a high-quality reference diet (R) and test diets obtained mixing the R diet with each of the test ingredients at a ratio of 70:30. Diets contained 1% celite as inert marker. Fish were fed to visual satiety twice a day and faecal samples collected using a continuous automatic device. Faeces were freeze dried and frozen (-20 \ub0C) until analyses. The ADC of dry matter, crude protein and ether extract of each insect meal diet were calculated. ADC for dry matter varied between 70.07 (HI1) and 80.85 (TM). ADC for protein was above 84% in all treatments and resulted the highest in MD, TM and AD treatments. Ether extract apparent digestibility significantly differed among diets with the highest value reported for TM treatment. All treatments reported values higher than 96%. Observed differences could be due to the insect species and meal treatment but in general, tested insect meals were highly digestible for rainbow trout. The results from this research could be useful to optimize the diet formulation
EFSUMB Recommendations and Guidelines for Gastrointestinal Ultrasound - Part 1: Examination Techniques and Normal Findings (Short version)
Abstract
â–¼
In October 2014 the European Federation of Societies
for Ultrasound in Medicine and Biology formed
a Gastrointestinal Ultrasound (GIUS) task force
group to promote the use of GIUS in a clinical setting.
One of the main objectives of the task force
group was to develop clinical recommendations
and guidelines for the use of GIUS under the auspices
of EFSUMB. The first part, gives an overview of
the examination techniques for GIUS recommended
by experts in the field. It also presents the
current evidence for the interpretation of normal
sonoanatomical and physiological features as examined
with different ultrasound modalities
EFSUMB Recommendations and Guidelines for Gastrointestinal Ultrasound - Part 1: Examination Techniques and Normal Findings (Long version).
Abstract
â–¼
In October 2014 the European Federation of Societies
for Ultrasound in Medicine and Biology formed
a Gastrointestinal Ultrasound (GIUS) task force
group to promote the use of GIUS in a clinical setting.
One of the main objectives of the task force
group was to develop clinical recommendations
and guidelines for the use of GIUS under the auspices
of EFSUMB. The first part, gives an overview of
the examination techniques for GIUS recommended
by experts in the field. It also presents the
current evidence for the interpretation of normal
sonoanatomical and physiological features as examined
with different ultrasound modalities
Magnetoplasmons in quantum rings
We have studied the structure and dipole charge density response of nanorings
as a function of the magnetic field using local-spin density functional theory.
Two small rings consisting of 12 and 22 electrons confined by a positively
charged background are used to represent the cases of a narrow and a wide ring.
The results are qualitatively compared with experimental data existing on
microrings and on antidots. A smaller ring containing 5 electrons is also
analyzed to allow for a closer comparison with a recent experiment on a two
electron quantum ring.Comment: Typeset using Revtex, 13 pages and 11 Postscript figure
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