907 research outputs found
Ultra-high brilliance multi-MeV -ray beam from non-linear Thomson scattering
We report on the generation of a narrow divergence (
mrad), multi-MeV ( MeV) and ultra-high brilliance ( photons s mm mrad 0.1\% BW) -ray
beam from the scattering of an ultra-relativistic laser-wakefield accelerated
electron beam in the field of a relativistically intense laser (dimensionless
amplitude ). The spectrum of the generated -ray beam is
measured, with MeV resolution, seamlessly from 6 MeV to 18 MeV, giving clear
evidence of the onset of non-linear Thomson scattering. The photon source has
the highest brilliance in the multi-MeV regime ever reported in the literature
The Ulysses fast latitude scans: COSPIN/KET results
International audienceUlysses, launched in October 1990, began its second out-of-ecliptic orbit in December 1997, and its second fast latitude scan in September 2000. In contrast to the first fast latitude scan in 1994/1995, during the second fast latitude scan solar activity was close to maximum. The solar magnetic field reversed its polarity around July 2000. While the first latitude scan mainly gave a snapshot of the spatial distribution of galactic cosmic rays, the second one is dominated by temporal variations. Solar particle increases are observed at all heliographic latitudes, including events that produce >250 MeV protons and 50 MeV electrons. Using observations from the University of Chicago's instrument on board IMP8 at Earth, we find that most solar particle events are observed at both high and low latitudes, indicating either acceleration of these particles over a broad latitude range or an efficient latitudinal transport. The latter is supported by "quiet time" variations in the MeV electron background, if interpreted as Jovian electrons. No latitudinal gradient was found for >106 MeV galactic cosmic ray protons, during the solar maximum fast latitude scan. The electron to proton ratio remains constant and has practically the same value as in the previous solar maximum. Both results indicate that drift is of minor importance. It was expected that, with the reversal of the solar magnetic field and in the declining phase of the solar cycle, this ratio should increase. This was, however, not observed, probably because the transition to the new magnetic cycle was not completely terminated within the heliosphere, as indicated by the Ulysses magnetic field and solar wind measurements. We argue that the new A<0-solar magnetic modulation epoch will establish itself once both polar coronal holes have developed
An autonomous ground mobile unit for the precision physical weed control.
In this paper the design, the main characteristics and the automation systems of innovative
autonomous ground mobile units (GMU) for physical weed control (PWC) in maize are
described. The machine will be created within the activities of the European Project RHEA
(Robot fleets for Highly Effective Agriculture and forestry management), that aims to produce
different prototypes of autonomous terrestrial and aerial robot able to perform several
activities related to the general crop protection in different agricultural scenarios. The first
autonomous ground unit machine was designed in order to perform a mechanical and
thermal treatment removing weeds from the inter-row crop space and applying in-row
selective and precision flaming by means of two crossed LPG rod burners. By means of
some modifications of the tools it will be possible to realize also an autonomous unit for the
precision broadcast flaming application. In this case the design involves a replacement of the
mechanical tools working in the inter-row space with 50 cm wide burners able to perform
flaming at different intensities according to weed cover detected by the perception system of
the robot. The working width of both the PWC machines will be of 4.5 m, thus covering five
entire maize inter-row spaces of 0.75 m each and 2 half inter-row space of 0.375 m each.
The correct position of the tools (mechanical and thermal) will be guaranteed by an
automatic precision guidance system connected and supervised to an image based row
detection system. Each working elements will be provided by two crossed 0.25 m wide rod
burners, hitting one side of each crop row. The flame should hit the weeds growing in the âinrowâ
space (a 0.25 m wide strip of soil with the maize plant in the middle). Regarding the
control of the weed emerged in the âinter-rowâ space each working unit of the will be provided
with rigid tools (one central foot-goose and two side âLâ shaped sweeps). The mechanical
treatment will be performed, independently from the weed presence, as hoeing is a very
important agronomical practice. On the contrary, broadcast flaming in the inter-row space will
be performed after weed detection, using three different LPG pressures and doses according
to weed cover (no weed cover-no treatment, weed cover between 0 and 25%-flaming at 0.3
MPa, weed cover higher than 25%-flaming at 0.4 MPa). This very innovative application of
precision PWC in maize could represent not only a good opportunity for farmers in term of
herbicide use reduction, but also an environmental friendly and energy saving application of
flaming in organic farming
Thromboembolic risk with IVIg: Incidence and risk factors in inflammatory neuropathy patients
Our objective was to evaluate whether IV immunoglobulin (IVIg) increases the risk of thromboembolic events in neurology outpatients with inflammatory neuropathies, as there is conflicting evidence supporting this hypothesis, mainly from non-neurologic cohorts. We investigated this question over 30 months in our cohort of patients with inflammatory neuropathies receiving regular IVIg anOur objective was to evaluate whether IV immunoglobulin (IVIg) increases the risk of thromboembolic events in neurology outpatients with inflammatory neuropathies, as there is conflicting evidence supporting this hypothesis, mainly from non-neurologic cohorts. We investigated this question over 30 months in our cohort of patients with inflammatory neuropathies receiving regular IVIg and found a greater incidence of arterial and venous thromboembolic events than population-based rates determined by hospital admissions data. Vascular risk factors were more common in the event group but there were no IVIg administration factors that contributed to the risk. This study suggests that IVIg may have a small but contributory role in determining thromboembolic risk in the inflammatory neuropathy cohort and more evidence is required before it is clear whether the current primary prevention guidelines are appropriate in this group of patients.d found a greater incidence of arterial and venous thromboembolic events than population-based rates determined by hospital admissions data. Vascular risk factors were more common in the event group but there were no IVIg administration factors that contributed to the risk. This study suggests that IVIg may have a small but contributory role in determining thromboembolic risk in the inflammatory neuropathy cohort and more evidence is required before it is clear whether the current primary prevention guidelines are appropriate in this group of patients
Development of FTK architecture: a fast hardware track trigger for the ATLAS detector
The Fast Tracker (FTK) is a proposed upgrade to the ATLAS trigger system that
will operate at full Level-1 output rates and provide high quality tracks
reconstructed over the entire detector by the start of processing in Level-2.
FTK solves the combinatorial challenge inherent to tracking by exploiting the
massive parallelism of Associative Memories (AM) that can compare inner
detector hits to millions of pre-calculated patterns simultaneously. The
tracking problem within matched patterns is further simplified by using
pre-computed linearized fitting constants and leveraging fast DSP's in modern
commercial FPGA's. Overall, FTK is able to compute the helix parameters for all
tracks in an event and apply quality cuts in approximately one millisecond. By
employing a pipelined architecture, FTK is able to continuously operate at
Level-1 rates without deadtime. The system design is defined and studied using
ATLAS full simulation. Reconstruction quality is evaluated for single muon
events with zero pileup, as well as WH events at the LHC design luminosity. FTK
results are compared with the tracking capability of an offline algorithm.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C09072
A PMT-Block test bench
The front-end electronics of the ATLAS hadronic calorimeter (Tile Cal) is
housed in a unit, called {\it PMT-Block}. The PMT-Block is a compact instrument
comprising a light mixer, a PMT together with its divider and a {\it 3-in-1}
card, which provides shaping, amplification and integration for the signals.
This instrument needs to be qualified before being assembled on the detector. A
PMT-Block test bench has been developed for this purpose. This test bench is a
system which allows fast, albeit accurate enough, measurements of the main
properties of a complete PMT-Block. The system, both hardware and software, and
the protocol used for the PMT-Blocks characterisation are described in detail
in this report. The results obtained in the test of about 10000 PMT-Blocks
needed for the instrumentation of the ATLAS (LHC-CERN) hadronic Tile
Calorimeter are also reported.Comment: 23 pages, 10 figure
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