465 research outputs found
Acceleration with Self-Injection for an All-Optical Radiation Source at LNF
We discuss a new compact gamma-ray source aiming at high spectral density, up
to two orders of magnitude higher than currently available bremsstrahlung
sources, and conceptually similar to Compton Sources based on conventional
linear accelerators. This new source exploits electron bunches from
laser-driven electron acceleration in the so-called self-injection scheme and
uses a counter-propagating laser pulse to obtain X and gamma-ray emission via
Thomson/Compton scattering. The proposed experimental configuration inherently
provides a unique test-bed for studies of fundamental open issues of
electrodynamics. In view of this, a preliminary discussion of recent results on
self-injection with the FLAME laser is also given.Comment: 8 pages, 10 figures, 44 references - Channeling 2012 conferenc
The First Results for a New Layout of the Stay Cables for Great Span Bridges
AbstractThe air-elastic vibrations of structures induce fluctuating stresses that lead to fatigue damage accumulation and may determine structural failure without exceeding ultimate strength This paper proposes a new layout of stay cables to be used in the construction or the retrofitting of long span bridges, capable of mitigating the air-elastic problems due to environmental vibrations such as the rain-wind excitations. The structural scheme adopted was derived from the critical conditions in terms of stability obtained by referring to lateral suspension cables stayed bridge with two planes of fan pattern stay cables. The new layout consists in implementing an additional plane of cable stays placed symmetrically just under the deck bridge. The final layout of the cable stays was identified as “duplex”. The numerical investigation was carried out in the frequency domain. The results obtained show a sensible increasing of stiffness, as well as a reduction of the natural period of vibrations. In the analysis the deck was considered as thin and very light. The Duplex layout had, also, permitted to mitigate the wind effects, because the presence of the inferior stay cables simulate the viscous dampers
Frontiers of beam diagnostics in plasma accelerators: measuring the ultra-fast and ultra-cold
Advanced diagnostics are essential tools in the development of plasma-based accelerators. The accurate measurement of the quality of beams at the exit of the plasma channel is crucial to optimize the parameters of the plasma accelerator. 6D electron beam diagnostics will be reviewed with emphasis on emittance measurement, which is particularly complex due to large energy spread and divergence of the emerging beams, and on femtosecond bunch length measurements
Pancreaticoduodenal Artery Aneurysm Ruptured into Duodenum, Associated with Celiac Trunk Stenosis. Case Report and Review of Literature
Pancreaticoduodenal artery (PDA) aneurysm associated with a celiac artery (CA) occlusion or stenosis is an uncommon event. We report the case of a 63-years old man who presented with acute abdominal pain radiating to the back. During the hospital stay, the patient had an episode of severe hematemesis. He had a gastroscopy and then a surgical exploration. However only with arteriography we found a PDA, which had ruptured into duodenum. The aneurysm was associated with a stenosis of the celiac trunk and was supplied by a dense network of collateral vessels from the SMA. The patient was successfully treated with embolization and was discharged on the 64th postoperative day. Short term and mid term follow-up was uneventful. This case shows the difficulty in diagnosing these rare events in time, indicating that angiography is indispensable to establish a diagnosis and enable nonsurgical treatment
Overview of Plasma Lens Experiments and Recent Results at SPARC_LAB
Beam injection and extraction from a plasma module is still one of the
crucial aspects to solve in order to produce high quality electron beams with a
plasma accelerator. Proper matching conditions require to focus the incoming
high brightness beam down to few microns size and to capture a high divergent
beam at the exit without loss of beam quality. Plasma-based lenses have proven
to provide focusing gradients of the order of kT/m with radially symmetric
focusing thus promising compact and affordable alternative to permanent magnets
in the design of transport lines. In this paper an overview of recent
experiments and future perspectives of plasma lenses is reported
Longitudinal phase-space manipulation with beam-driven plasma wakefields
The development of compact accelerator facilities providing high-brightness
beams is one of the most challenging tasks in field of next-generation compact
and cost affordable particle accelerators, to be used in many fields for
industrial, medical and research applications. The ability to shape the beam
longitudinal phase-space, in particular, plays a key role to achieve high-peak
brightness. Here we present a new approach that allows to tune the longitudinal
phase-space of a high-brightness beam by means of a plasma wakefields. The
electron beam passing through the plasma drives large wakefields that are used
to manipulate the time-energy correlation of particles along the beam itself.
We experimentally demonstrate that such solution is highly tunable by simply
adjusting the density of the plasma and can be used to imprint or remove any
correlation onto the beam. This is a fundamental requirement when dealing with
largely time-energy correlated beams coming from future plasma accelerators
Community pharmacists and stress at the counter : Qualitative exploratory initial italian research
Objectives: Community pharmacists are the most accessible healthcare professionals. They interact with a large number of patients who often show emotional concern. Their stressful and complex role is widely acknowledged, nonetheless research on their personal life is practically non-existent. Thus, we set out to qualitatively explore the emotional perceptions of pharmacists. Methods: Twenty experienced pharmacists were interviewed by a psychologist and a pharmacist. Data were analysed using an interpretative phenomenological analysis and coded using NVivo qualitative data analysis software. Key findings: Interviewed pharmacists admitted to different types of difficulties, mostly arising from a series of small, standalone episodes. Their stories describe intrinsic difficulties with their practice, rather than personal experiences. This study reveals the complexity of a community pharmacists' role - divided into health and hygiene advice, counselling and empathic relationships, and entrepreneurship. An important obstacle is the integration and concomitant implementation of these components. Endogenous factors such as personal experiences, personality and academic background, and exogenous factors such as social status of the patient population, legal and administrative issues and location, all affect pharmacists' ability to cope with their role. Conclusions: Improving health care can be obtained by incorporating community pharmacists into the healthcare team. Technical training is important in order to improve relationship skills and personal coping strategies. Further studies are recommended to provide a simple tool for measuring aspects of the personal and emotional aspects (inner life) of a community pharmacist
Design of a plasma discharge circuit for particle wakefield acceleration
Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to
provide very high accelerating fields (10–100 GV m 1), enabling acceleration of electrons to GeV energy
in few centimetres. However, the quality of the electron bunches accelerated with this technique is still
not comparable with that of conventional accelerators; radiofrequency-based accelerators, in fact, are
limited in the accelerating field (10–100 MV m 1) requiring therefore kilometric distances to reach the
GeV energies, but can provide very bright electron bunches. Combining high brightness electron bunches
from conventional accelerators and high accelerating fields reachable with plasmas could be a good
compromise allowing to further accelerate high brightness electron bunches coming from LINAC while
preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train
of short bunches, we have started to study the requirements in terms of plasma for SPARC-LAB [1,2]. In
particular, here we focus on the ionization process; we show a simplified model to study the evolution of
plasma induced by discharge, very useful to design the discharge circuit able to fully ionize the gas and
bring the plasma at the needed temperature and density
Usefulness of the organ culture system in the in vitro diagnosis of coeliac disease: A multicentre study
Objective. Diagnosis of coeliac disease is based on the presence of villous atrophy which recovers following a gluten-free diet. The presence of circulating antiendomysial antibodies as well as their disappearance after a gluten-free diet supports the diagnosis. It has also been demonstrated that antiendomysial antibodies are detectable in supernatants of cultured intestinal biopsies from patients with coeliac disease. The objective of this study was to compare the histology and antiendomysial antibodies in culture supernatants of intestinal biopsies to validate the in vitro organ culture system as a future diagnostic tool for coeliac disease. Material and methods. Seventy-five antiendomysial serum-positive patients on a gluten-containing diet were evaluated. Patients underwent endoscopy with 5 biopsy fragments: 3 for histology, 1 cultured with and the other without gliadin-peptide activator. Antiendomysial antibodies were evaluated in all culture supernatants. Results. Sixty-eight patients had evidence of villous atrophy, while 73 out of 75 were positive to the organ culture system. The agreement rate between organ culture and histology results was 94%. Conclusions. As all the centres participating in the study obtained good agreement between organ culture and histology results, the new system could be considered a reliable tool for the diagnosis of coeliac disease. Nevertheless, it is possible to highlight cases with an organ culture-positive and -negative histology. This feature could be of considerable interest because, as the sensitivity of organ culture seems to be greater than the initial histology, the new system might be useful in uncertain cases where the risk of missing the diagnosis of coeliac disease is high
Focusing of high-brightness electron beams with active-plasma lenses
Plasma-based technology promises a tremendous reduction in size of accelerators used for research, medical, and industrial applications, making it possible to develop tabletop machines accessible for a broader scientific community. By overcoming current limits of conventional accelerators and pushing particles to larger and larger energies, the availability of strong and tunable focusing optics is mandatory also because plasma-accelerated beams usually have large angular divergences. In this regard, active-plasma lenses represent a compact and affordable tool to generate radially symmetric magnetic fields several orders of magnitude larger than conventional quadrupoles and solenoids. However, it has been recently proved that the focusing can be highly nonlinear and induce a dramatic emittance growth. Here, we present experimental results showing how these nonlinearities can be minimized and lensing improved. These achievements represent a major breakthrough toward the miniaturization of next-generation focusing devices
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