126 research outputs found
Isolated noncompaction of the myocardium: an exceedingly rare cardiomyopathy. A case report
No full textIsolated noncompaction of the left ventricular myocardium is a rare cardiac disorder due to an arrest in myocardial morphogenesis. It is characterized by prominent and excessive trabeculation in a ventricular wall segment, with deep intertrabecular spaces perfused from the ventricular cavity. Echocardiographic findings are important clues for the diagnosis. Clinical symptoms include signs of left ventricular systolic dysfunction even to the point of heart failure, ventricular arrhythmias, and embolic events. We describe an adult case in whom the only clinical symptoms were life-threatening ventricular arrhythmias. Transthoracic echocardiography did not contribute to the diagnosis, which was made thanks to left ventricular contrast angiography. Electrophysiological testing induced a fast monomorphic sustained ventricular tachycardia, with hemodynamic impairment, that was refractory to pharmacological treatment, and for this reason a permanent cardioverter-defibrillator was implanted. A subsequently performed transesophageal echocardiographic examination showed a localized, regional increase in left ventricular wall thickness and degree of trabeculation. The causes and electrophysiological mechanisms of arrhythmias in noncompaction are still unknown: grossly irregular branching and connecting of myocardial fascicles in the noncompacted segments, isometric contraction with increased wall stress, and localized coronary perfusion impairment can all induce disorganized or delayed activation and increase the potential for arrhythmias. This is the first reported case of noncompaction in which an implantable defibrillator was used to control life-threatening arrhythmias
A Measurement Method Based on RF Deflector for Particle Bunch Longitudinal Parameters in Linear Accelerators
No full textIn high-brightness electron linear accelerators (LINACs), the particle bunch length is measured by a radio frequency deflector (RFD). The electron bunch is deflected vertically toward a screen and its length can be obtained using vertical spot size measurements after a proper calibration, e.g., measuring the vertical bunch centroid while varying the deflecting voltage phase. The energy parameters of the bunch (the energy chirp and the energy spread) and the correlation between particle positions, divergences, and energies contribute to the bunch vertical dimension at the screen position after the RFD and so far were considered as a source of systematic errors in a bunch length measurement. The measurement theory and production model for bunch length, energy spread and chirp, as well as correlations are described. As usual in particle accelerators physics, the method is validated using numerical simulations of state-of-the-art LINACs with a reference simulation code showing a typical accuracy in the few percent levels
Design and simulations of the cavity BPM readout electronics for the ELI-NP gamma beam system
No full textEnergy chirp measurements by means of an RF deflector: a case study the gamma beam source LINAC at ELI-NP
No full textRF Deflector (RFD) based measurements are widely used in high–brightness electron LINAC around the world in order to measure the ultra–short electron bunch length. The RFD provides a vertical kick to the particles of the electron bunch according to their longitudinal positions. In this paper, a measurement technique for the bunch length and other bunch proprieties, based on the usage of an RFD, is proposed. The basic idea is to obtain information about the bunch length, energy chirp, and energy spread from vertical spot size measurements varying the RFD phase, because they add contributions on this quantity. The case study is the Gamma Beam System (GBS), the Compton Source being built in the Extreme Light Infrastructure–Nuclear Physics (ELI–NP) facility. The ELEctron Generation ANd Tracking (ELEGANT) code is used for tracking the particles from RFD to the measurement screen
Longitudinal phase measurement at the ELI-NP compton gamma source
No full textVirtual bunch length measurement can be carried out by
means of ELEGANT code for tracking the bunch particles
from RF deflector to the screen. The technique relies on
the correlation between the bunch longitudinal coordinate
and transverse coordinates induced through a RF deflector.
Therefore, the bunch length measurement can be carried
out measuring the vertical spot size at the screen, placed
after the RF deflector. The deflecting voltage amplitude
affects the resolution. Adding a dispersive element, e.g. a
magnetic dipole between RF deflector and the screen, the
full longitudinal phase space can be measured. In this paper,
we discuss some issues relevant for the electron linac of
the Compton source at the Extreme Light Infrastructure -
Nuclear Physics (ELI-NP)
S-Band cavity BPM readout electronics for the ELI-NP gamma beam source
No full textThe Extreme Light Infrastructure – Nuclear Physics
Gamma Beam Source (ELI-NP GBS) facility will provide
an high intensity laser and a very intense gamma beam for
various experiments. The gamma beam is generated
through incoherent Compton back-scattering of a laser
light off a high brightness electron beam provided by a
720MeV warm LINAC. The electrons are organized in
compact trains with up to 32 bunches, each separated by
16ns. To optimize the laser-electron interaction and
therefore the generation of the gamma rays, one big
challenge is to precisely monitor the trajectory of each
electron bunch.
To match this requirement, at the interaction point two
S-band cavity beam position monitors will be used, and
the related readout system should perform bunch-bybunch
position measurements with sub-μm resolution.
Using 500MS/s ADC converters and dedicated data
processing, the readout system proposes an alternative
measurement concept. In this paper the architecture of the
system, the implemented signal processing and the results
of the first laboratory tests will be presented
Particle anisotropy and crystalline phase transition in one-pot synthesis of nano-zirconia: A causal relationship
No full textCrystalline phase evolution and morphological changes are strictly correlated phenomena during the growth of zirconia nanoparticles. In this work, the effects of synthetic variables, reaction time (up to 24 hours) and precursor concentration (0.16 and 0.5 M), of a one-step non-hydrolytic sol-gel route to zirconia are investigated. Zirconium tetrachloride (ZrCl4) is chosen as a zirconium oxide precursor to react in benzyl alcohol. At a low precursor concentration and a short reaction time, pseudo-spherical particles of size 2 nm with a narrow size distribution are observed by transmission electron microscopy (TEM). At this stage, mainly the tetragonal phase is detected. By increasing both the zirconium precursor concentration and reaction time, a broadening of size distribution is observed resulting from the growth of anisotropic particles. Concurrently, an increasing amount of the monoclinic is detected by X-ray diffraction and Raman spectroscopy. As a novelty, Rietveld investigations on electron diffraction ring patterns obtained by transmission electron microscopy are performed. This procedure allows the collection of comprehensive information about nanostructured particles in one-step analysis. The results derived from this analysis, together with the high resolution transmission electron microscopy (HR-TEM) data, consistently support the structural transition from pseudo-spherical tetragonal particles to rice-shaped monoclinic particles
Beam diagnostics for charge and position measurements in ELI-NP GBS
No full textThe advanced source of Gamma-ray photons to be built in Bucharest (Romania), as part of the ELI-NP European Research Infrastructure, will generate photons by Compton back-scattering in the collision between a multi-bunch electron beam and a high intensity recirculated laser pulse. An S-Band photoinjector and the following C-band Linac at a maximum energy of 720MeV, under construction by an European consortium (EurogammaS) led by INFN, will operate at 100Hz repetition rate with trains of 32 electron bunches, separated by 16ns and a 250pC nominal charge. The different BPMs and current transformers used to measure transverse beam position and charge along the LINAC are described. Design criteria, production status and bench test results of the charge and position pickups are reported in the paper, together with the related data acquisition systems
Expression of cannabinoid receptor CB2 in the liver from patients with primary biliary cirrhosis. In: Summer Meeting of the British Association of Clinical Anatomists, 16–17 July, 2007, School of Medicine, University of Padova, Italy.
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