1,913 research outputs found
Looks Can Be Deceiving: Reconsidering the Evidence for Gliotransmission
Gliotransmission, a process involving active vesicular release of glutamate and other neurotransmitters by astrocytes, is thought to play a critical role in many brain functions. A new paper by Nedergaard et al. (2014) identifies an experimental flaw in these previous studies suggesting that astrocytes may not perform active vesicular release after all
LATTES: a novel detector concept for a gamma-ray experiment in the Southern hemisphere
The Large Array Telescope for Tracking Energetic Sources (LATTES), is a novel
concept for an array of hybrid EAS array detectors, composed of a Resistive
Plate Counter array coupled to a Water Cherenkov Detector, planned to cover
gamma rays from less than 100 GeV up to 100 TeVs. This experiment, to be
installed at high altitude in South America, could cover the existing gap in
sensitivity between satellite and ground arrays.
The low energy threshold, large duty cycle and wide field of view of LATTES
makes it a powerful tool to detect transient phenomena and perform long term
observations of variable sources. Moreover, given its characteristics, it would
be fully complementary to the planned Cherenkov Telescope Array (CTA) as it
would be able to issue alerts.
In this talk, a description of its main features and capabilities, as well as
results on its expected performance, and sensitivity, will be presented.Comment: Proceedings of the 35th International Cosmic Ray Conference
(ICRC2017), Busan, South Korea. Presented by R. Concei\c{c}\~{a}o. 8 pages;
v2: correct affiliation + journal referenc
GRB 170817A-GW170817-AT 2017gfo and the observations of NS-NS, NS-WD and WD-WD mergers
The LIGO-Virgo Collaboration has announced the detection of GW170817 and has
associated it with GRB 170817A. These signals have been followed after 11 hours
by the optical and infrared emission of AT 2017gfo. The origin of this complex
phenomenon has been attributed to a neutron star-neutron star (NS-NS) merger.
In order to probe this association we confront our current understanding of the
gravitational waves and associated electromagnetic radiation with four observed
GRBs originating in binaries composed of different combinations NSs and white
dwarfs (WDs). We consider 1) GRB 090510 the prototype of NS-NS merger leading
to a black hole (BH); 2) GRB 130603B the prototype of a NS-NS merger leading to
massive NS (MNS) with an associated kilonova; 3) GRB 060614 the prototype of a
NS-WD merger leading to a MNS with an associated kilonova candidate; 4) GRB
170817A the prototype of a WD-WD merger leading to massive WD with an
associated AT 2017gfo-like emission. None of these systems support the above
mentioned association. The clear association between GRB 170817A and AT 2017gfo
has led to introduce a new model based on on a new subfamily of GRBs
originating from WD-WD mergers. We show how this novel model is in agreement
with the exceptional observations in the optical, infrared, X- and gamma-rays
of GRB 170817A-AT 2017gfo.Comment: version accepted for publication in JCAP. Missing references adde
Contamination of green bay water with lead and cadmium by a 37-m long, 2-m draft research vessel
During late April 1989, Green Bay, Lake Michigan water was sampled for dissolved concentrations of lead and cadmium. Samples used to document horizontal contamination of the water by a research vessel were collected using a rubber boat rowed 2, 50, 100, and 200 m upwind of the anchored mother ship. Samples used to document vertical contamination of the water column by the research vessel were collected from the vessel at water depths of 0.2, 2, 5, 10, and 20 m. Both lead and cadmium blanks were < 0.5 ng/l and below their limits of detection at the 95% level of confidence of 3.5 and 0.98 ng/l, respectively. Concentrations of lead in the horizontal direction varied between 3.5 ng/l at 200 m from the ship and 7.7 ng/l at 2 m from the ship. Cadmium concentrations varied from 2.8 ng/l at 2 m from the ship to 1.5 ng/l at 200 m from the ship. Lead concentrations in the vertical direction varied between 8.4 ng/k at a depth of 0.2 m and 3.3 ng/l at 5 m. Cadmium concentrations ranged between 4.5 ng/l at 2 m and 2.2 ng/l at 20 m. The vertical studies were inconclusive and appeared to be influenced by resuspension of bottom sediments. Uncontaminated samples can be collected as close as 100 m to the research vessel.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29851/1/0000198.pd
LATTES: A new gamma-ray detector concept for South America
Currently the detection of Very High Energy gamma-rays for astrophysics rely on the measurement of the Extensive Air Showers (EAS) either using Cherenkov detectors or EAS arrays with larger field of views but also larger energy thresholds. In this talk we present a novel hybrid detector concept for a EAS array with an improved sensitivity in the lower energies (~ 100 GeV). We discuss its main features, capabilities and present preliminary results on its expected perfomances and sensitivities.This wide field of view experiment is planned to be installed at high altitude in South America making it a complementary project to the planned Cherenkov telescope experiments and a powerful tool to trigger further observations of variable sources and to detect transients phenomena
The Optical System for the Large Size Telescope of the Cherenkov Telescope Array
The Large Size Telescope (LST) of the Cherenkov Telescope Array (CTA) is
designed to achieve a threshold energy of 20 GeV. The LST optics is composed of
one parabolic primary mirror 23 m in diameter and 28 m focal length. The
reflector dish is segmented in 198 hexagonal, 1.51 m flat to flat mirrors. The
total effective reflective area, taking into account the shadow of the
mechanical structure, is about 368 m. The mirrors have a sandwich structure
consisting of a glass sheet of 2.7 mm thickness, aluminum honeycomb of 60 mm
thickness, and another glass sheet on the rear, and have a total weight about
47 kg. The mirror surface is produced using a sputtering deposition technique
to apply a 5-layer coating, and the mirrors reach a reflectivity of 94%
at peak. The mirror facets are actively aligned during operations by an active
mirror control system, using actuators, CMOS cameras and a reference laser.
Each mirror facet carries a CMOS camera, which measures the position of the
light spot of the optical axis reference laser on the target of the telescope
camera. The two actuators and the universal joint of each mirror facet are
respectively fixed to three neighboring joints of the dish space frame, via
specially designed interface plate.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
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