2,633 research outputs found
Hard x-ray broad band Laue lenses (80 - 600 keV): building methods and performances
We present the status of the laue project devoted to develop a technology for
building a 20 meter long focal length Laue lens for hard x-/soft gamma-ray
astronomy (80 - 600 keV). The Laue lens is composed of bent crystals of Gallium
Arsenide (GaAs, 220) and Germanium (Ge, 111), and, for the first time, the
focusing property of bent crystals has been exploited for this field of
applications. We show the preliminary results concerning the adhesive employed
to fix the crystal tiles over the lens support, the positioning accuracy
obtained and possible further improvements. The Laue lens petal that will be
completed in a few months has a pass band of 80 - 300 keV and is a fraction of
an entire Laue lens capable of focusing X-rays up to 600 keV, possibly
extendable down to 20 - 30 keV with suitable low absorption crystal materials
and focal length. The final goal is to develop a focusing optics that can
improve the sensitivity over current telescopes in this energy band by 2 orders
of magnitude
A focal plane detector design for a wide-band Laue-lens telescope
The energy range above 60 keV is important for the study of many open
problems in high energy astrophysics such as the role of Inverse Compton with
respect to synchrotron or thermal processes in GRBs, non thermal mechanisms in
SNR, the study of the high energy cut-offs in AGN spectra, and the detection of
nuclear and annihilation lines. Recently the development of high energy Laue
lenses with broad energy bandpasses from 60 to 600 keV have been proposed for a
Hard X ray focusing Telescope (HAXTEL) in order to study the X-ray continuum of
celestial sources. The required focal plane detector should have high detection
efficiency over the entire operative range, a spatial resolution of about 1 mm,
an energy resolution of a few keV at 500 keV and a sensitivity to linear
polarization. We describe a possible configuration of the focal plane detector
based on several CdTe/CZT pixelated layers stacked together to achieve the
required detection efficiency at high energy. Each layer can operate both as a
separate position sensitive detector and polarimeter or work with other layers
to increase the overall photopeak efficiency. Each layer has a hexagonal shape
in order to minimize the detector surface required to cover the lens field of
view. The pixels would have the same geometry so as to provide the best
coupling with the lens point spread function and to increase the symmetry for
polarimetric studies.Comment: 10 pages, 9 figure
Exploring the Hard X-/soft gamma-ray Continuum Spectra with Laue Lenses
The history of X-ray astronomy has shown that any advancement in our
knowledge of the X-ray sky is strictly related to an increase in instrument
sensitivity. At energies above 60 keV, there are interesting prospects for
greatly improving the limiting sensitivity of the current generation of direct
viewing telescopes (with or without coded masks), offered by the use of Laue
lenses. We will discuss below the development status of a Hard X-Ray focusing
Telescope (HAXTEL) based on Laue lenses with a broad bandpass (from 60 to 600
keV) for the study of the X-ray continuum of celestial sources. We show two
examplesof multi-lens configurations with expected sensitivity orders of
magnitude better ( photons cm s keV
at 200 keV) than that achieved so far. With this unprecedented sensitivity,
very exciting astrophysical prospects are opened.Comment: 4 pages, 10 figures, to be published in the Proc. of the 39th ESLAB
Symosium, 19-21 April 200
Poster Session II, July 14th 2010 — Abstracts Improvements in the design of a kayak-ergometer using a sliding footrest-seat complex
AbstractAs observed previously in rowing, kayaking an ergometer becomes more and more popular. Nowadays, indoor kayak championships are organized performed on ergometer designed with a fixed footrest-seat complex. The main goal when one designs ergometers is to reproduce as closest as possible the on-water conditions. The reliability with on-water condition is usually assessed using both physiological and kinematics parameters. The previous studies of our research group have shown that the dynamics of the in situ movement has also to be reproduced. In other words, major muscular groups (who generated the joint torque and by the way the contact forces) involved in kayaking should be recruit with the same timing during on-water and ergometer kayaking. At the 7th ISEA conference, our research group presented a method based on numerical optimization to design a kayak ergometer equipped with a sliding footrest-seat complex that reproduces the acceleration generated in flatwater kayak. Based on these preliminary results, we have constructed a new ergometer. Then, the purpose of this study was to present the last developments performed on this ergometer and preliminary 3D kinematics analysis from elite kayakers. The characteristics (stiffness and damping) of the bungee cord linking the back of the frame with the trolley were determined using our previous results. An air brake, composed of a flywheel with a heavy wheel and two freewheel-pulleys on a shaft, simulated the water drag on the blades. However, a magnetic brake was added for specific training sessions. The paddle was linked to the pulleys by two ropes. Each side of the frame is equipped with one slide (1 dof in translation) in order to always keep the directions of the ropes parallel to the long axis of the ergometer whatever the instant of the cycle. First trials performed with elite athlete showed the robustness of all the mechanisms developed. 3D kinematic analysis showed the relevance of the adding slides when compared with on-water paddle trajectories observed during the propulsion phase. An instrumentation (3D force sensors at each contact) coupled with a specific interface that allows real time feedback is under development. This innovative ergometer will be used to collect dynamic and kinematic parameters. They will serve as input data of our simulator in order to carry out intra-athlete comparisons and to still improve the design of kayak ergometers
New frontiers and emerging applications of 3D printing in ENT surgery: A systematic review of the literature
3D printing systems have revolutionised prototyping in the industrial field by lowering production time from days to hours and costs from thousands to just a few dollars. Today, 3D printers are no more confined to prototyping, but are increasingly employed in medical disci- plines with fascinating results, even in many aspects of otorhinolaryngology. All publications on ENT surgery, sourced through updated electronic databases (PubMed, MEDLINE, EMBASE) and published up to March 2017, were examined according to PRISMA guidelines. Overall, 121 studies fulfilled specific inclusion criteria and were included in our systematic review. Studies were classified according to the specific field of application (otologic, rhinologic, head and neck) and area of interest (surgical and preclinical education, customised surgical planning, tissue engineering and implantable prosthesis). Technological aspects, clinical implications and limits of 3D printing processes are discussed focusing on current benefits and future perspectives
Development status of a Laue lens project for gamma-ray astronomy
We report the status of the HAXTEL project, devoted to perform a design study
and the development of a Laue lens prototype. After a summary of the major
results of the design study, the approach adopted to develop a Demonstration
Model of a Laue lens is discussed, the set up described, and some results
presented.Comment: 11 pages, 11 figures, 2007 SPIE Conference on Optics for EUV, X-Ray,
and Gamma-Ray Astronomy II
Insertable cardiac monitoring results in higher rates of atrial fibrillation diagnosis and oral anticoagulation prescription after ischaemic stroke
Aims: After an ischaemic stroke, atrial fibrillation (AF) detection allows for improved secondary prevention strategies. This study aimed to compare AF detection and oral anticoagulant (OAC) initiation in patients with an insertable cardiac monitor (ICM) vs. external cardiac monitor (ECM) after ischaemic stroke. Methods and results: Medicare Fee-for-Service (FFS) insurance claims and Abbott Labs device registration data were used to identify patients hospitalized with an ischaemic stroke in 2017-2019 who received an ICM or ECM within 3 months. Patients with continuous Medicare FFS insurance and prescription drug enrolment in the prior year were included. Patients with prior AF, atrial flutter, cardiac devices, or OAC were excluded. Insertable cardiac monitor and ECM patients were propensity score matched 1:4 on demographics, comorbidities, and stroke hospitalization characteristics. The outcomes of interest were AF detection and OAC initiation evaluated with Kaplan-Meier and Cox proportional hazard regression analyses. A total of 5702 Medicare beneficiaries (ICM, n = 444; ECM, n = 5258) met inclusion criteria. The matched cohort consisted of 2210 Medicare beneficiaries (ICM, n = 442; ECM, n = 1768) with 53% female, mean age 75 years, and mean CHA2DS2-VASc score 4.6 (1.6). Insertable cardiac monitor use was associated with a higher probability of AF detection [(hazard ratio (HR) 2.88, 95% confidence interval (CI) (2.31, 3.59)] and OAC initiation [HR 2.91, CI (2.28, 3.72)] compared to patients monitored only with ECM. Conclusion: Patients with an ischaemic stroke monitored with an ICM were almost three times more likely to be diagnosed with AF and to be prescribed OAC compared to patients who received ECM only
Development and validation of a clinical index to predict survival after cardiac resynchronisation therapy
To develop and validate a prognostic risk index of cardiovascular mortality after cardiac resynchronisation therapy (CRT)
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