358 research outputs found
Synchrotron oscillation damping due to beam-beam collisions
In DA{\Phi}NE, the Frascati e+/e- collider, the crab waist collision scheme
has been successfully implemented in 2008 and 2009. During the collision
operations for Siddharta experiment, an unusual synchrotron damping effect has
been observed. Indeed, with the longitudinal feedback switched off, the
positron beam becomes unstable with beam currents in the order of 200-300 mA.
The longitudinal instability is damped by bringing the positron beam in
collision with a high current electron beam (~2A). Besides, we have observed a
shift of \approx 600Hz in the residual synchrotron sidebands. Precise
measurements have been performed by using both a commercial spectrum analyzer
and the diagnostics capabilities of the DA{\Phi}NE longitudinal bunch-by-bunch
feedback. This damping effect has been observed in DA{\Phi}NE for the first
time during collisions with the crab waist scheme. Our explanation is that beam
collisions with a large crossing angle produce a longitudinal tune shift and a
longitudinal tune spread, providing Landau damping of synchrotron oscillations.Comment: 3 pages, 5 figures, talk presented to IPAC'10 - Kyoto - May 24-28
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Imaging of temporomandibular joint: Approach by direct volume rendering
Materials and Methods: We have studied the temporom-andibular joint anatomy, directly on the living, from 3D images obtained by medical imaging Computed Tomography and Nuclear Magnetic Resonance acquisition, and subsequent re-engineering techniques 3D Surface Rendering and Volume Rendering. Data were analysed with the goal of being able to isolate, identify and distinguish the anatomical structures of the joint, and get the largest possible number of information utilizing software for post-processing work.Results: It was possible to reproduce anatomy of the skeletal structures, as well as through acquisitions of Magnetic Resonance Imaging; it was also possible to visualize the vascular, muscular, ligamentous and tendinous components of the articular complex, and also the capsule and the fibrous cartilaginous disc. We managed the Surface Rendering and Volume Rendering, not only to obtain three-dimensional images for colour and for resolution comparable to the usual anatomical preparations, but also a considerable number of anatomical, minuter details, zooming, rotating and cutting the same images with linking, graduating the colour, transparency and opacity from time to time.Conclusion: These results are encouraging to stimulate further studies in other anatomical districts.Background: The purpose of this study was to conduct a morphological analysis of the temporomandibular joint, a highly specialized synovial joint that permits movement and function of the mandible
Aplication of Frequency Map Analysis to Beam-Beam Effects Study in Crab Waist Collision Scheme
We applied Frequency Map Analysis (FMA) - a method that is widely used to
explore dynamics of Hamiltonian systems - to beam-beam effects study. The
method turned out to be rather informative and illustrative in the case of a
novel Crab Waist collision approach, when "crab" focusing of colliding beams
results in significant suppression of betatron coupling resonances. Application
of FMA provides visible information about all working resonances, their widths
and locations in the planes of betatron tunes and betatron amplitudes, so the
process of resonances suppression due to the beams crabbing is clearly seen.Comment: 11 pages, 10 figure
Da\phi ne gamma-rays factory
Gamma sources with high flux and spectral densities are the main requirements
for new nuclear physics experiments to be performed in several worldwide
laboratories and envisaged in the ELI-NP (Extreme Light Infrastructure-Nuclear
Physics) project or in the IRIDE (Interdisciplinary Research Infrastructure
with Dual Electron Linacs) proposals. The paper is focalized on an experiment
of gamma photons production using Compton collisions between the DA\Phi NE
electron beam and a high average power laser pulse, amplified in a
Fabry-P\'erot optical resonator. The calculations show that the resulting gamma
beam source has extremely interesting properties in terms of spectral density,
energy spread and gamma flux comparable (and even better) with the last
generation gamma sources. The energy of the gamma beam depends on the adopted
laser wavelength and can be tuned changing the energy of the electron ring. In
particular we have analyzed the case of a gamma factory tunable in the 2-9 MeV
range. The main parameters of this new facility are presented and the
perturbation on the transverse and longitudinal electron beam dynamics is
discussed. A preliminary accelerator layout to allow experiments with the gamma
beam is presented with a first design of the accelerator optics.Comment: 26 pages, 15 figure
Cationic porphyrins are reversible proteasome inhibitors
The aim of this study is to verify if watersoluble porphyrins can be used as proteasome inhibitors. We have found that cationic porphyrins inhibit proteasome peptidase activities much more effectively than the corresponding anionic derivatives. The relevance of electrostatics in driving porphyin−proteasome interactions has been confirmed by the observation that the inhibitory efficiency of the cationic macrocycles decreases with the number of positive substituents. We have also investigated various metalloporphyrins, which differ due to the different propension of the central metal ion toward axial coordination. Our experimental results indicate that the naked cationic porphyrins are the most active in reversibly inhibiting the three main protease activities of the proteasome in the micromolar range. A spectroscopic characterization of porphyrin−proteasome interactions by UV−vis spectra parallels the results of inhibition assays: the higher the inhibitory effect the stronger the spectroscopic variations are. To interpret the action of porphyrins at a molecular level, we have performed calculations evidencing that cationic porphyrins may hinder the access to the canonical proteolytic site on the proteasome β5 subunit. In particular, an inspection of the top-scoring docking modes shows that the tetracationic porphyrin blocks the catalytic pocket, close to the N termini of the β5 proteasome subunit, more efficiently than its anionic counterpart. Proteasome inhibition activity of porphyrins unites their known anticancer properties making them suitable as a scaffold for the design of novel multitargeted molecules
New insights into cortico-basal-cerebellar connectome: clinical and physiological considerations
The current model of the basal ganglia system based on the 'direct', 'indirect' and 'hyperdirect' pathways provides striking predictions about basal ganglia function that have been used to develop deep brain stimulation approaches for Parkinson's disease and dystonia. The aim of this review is to challenge this scheme in light of new tract tracing information that has recently become available from the human brain using MRI-based tractography, thus providing a novel perspective on the basal ganglia system. We also explore the implications of additional direct pathways running from cortex to basal ganglia and between basal ganglia and cerebellum in the pathophysiology of movement disorders
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