2,621 research outputs found
High-power test results of a 3 GHz single-cell cavity
Compact, reliable and little consuming accelerators are required for the
treatment of tumours with ions. TERA proposes the "cyclinac", composed of a
high-frequency, fast-cycling linac which boosts the energy of the particles
previously accelerated in a cyclotron. The dimensions of the linac can be
reduced if high gradients are used. TERA initiated a high-gradient test program
to understand the operational limit of such structures. The program foresees
the design, prototyping and high-power test of several high-gradient structures
operating at 3 and 5.7 GHz. The high-power tests of the 3 GHz single-cell
cavity were completed in Winter 2012. The maximum BDR threshold measured for
Emax of 170 MV/m and RF pulses of 2.5 \mu s was 3 x 10-6 bpp/m
Limits on the low energy antinucleon-nucleus annihilations from the Heisenberg principle
We show that the quantum uncertainty principle puts some limits on the
effectiveness of the antinucleon-nucleus annihilation at very low energies.
This is caused by the fact that the realization a very effective short-distance
reaction process implies information on the relative distance of the reacting
particles. Some quantitative predictions are possible on this ground, including
the approximate A-independence of antinucleon-nucleus annihilation rates.Comment: 10 pages, no figure
Dental implants with anti-biofilm properties: A pilot study for developing a new sericin-based coating
Aim: several strategies have been tested in recent years to prevent bacterial colonization of dental implants. Sericin, one of the two main silk proteins, possesses relevant biological activities and also literature reports about its potential antibacterial properties, but results are discordant and not yet definitive. The aim of this study was to evaluate the effectiveness of different experimental protocols in order to obtain a sericin-based coating on medical grade titanium (Ti) able to reduce microbial adhesion to the dental implant surface. Materials and Methods: different strategies for covalent bonding of sericin to Ti were pursued throughout a multi-step procedure on Ti-6Al-4V disks. The surface of grade 5 Ti was initially immersed in NaOH solution to obtain the exposure of functional -OH groups. Two different silanization strategies were then tested using aminopropyltriethoxysilane (APTES). Eventually, the bonding between silanized Ti-6Al-4V and sericin was obtained with two different crosslinking processes: glutaraldehyde (GLU) or carbodiimide/N-Hydroxy-succinimide (EDC/NHS). Micro-morphological and compositional analyses were performed on the samples at each intermediate step to assess the most effective coating strategy able to optimize the silanization and bioconjugation processes. Microbiological tests on the coated Ti-6Al-4V disks were conducted in vitro using a standard biofilm producer strain of Staphylococcus aureus (ATCC 6538) to quantify the inhibition of microbial biofilm formation (anti-biofilm efficacy) at 24 hours. Results: both silanization techniques resulted in a significant increase of silicon (Si) on the Ti-6Al-4V surfaces etched with NaOH. Differences were found between GLU and EDC/NHS bioconjugation strategies in terms of composition, surface micro-morphology and anti-biofilm efficacy. Ti-6Al-4V samples coated with GLU-bound sericin after silanization obtained via vapor phase deposition proved that this technique is the most convenient and effective coating strategy, resulting in a bacterial inhibition of about 53% in respect to the uncoated Ti-6Al-4V disks. Conclusions: The coating with glutaraldehyde-bound sericin after silanization in the vapor phase showed promising bacterial inhibition values with a significant reduction of S. aureus biofilm. Further studies including higher number of replicates and more peri-implant-relevant microorganisms are needed to evaluate the applicability of this experimental protocol to dental implants. View Full-Tex
Three Dimensional Annihilation Imaging of Antiprotons in a Penning Trap
We demonstrate three-dimensional annihilation imaging of antiprotons trapped
in a Penning trap. Exploiting unusual feature of antiparticles, we investigate
a previously unexplored regime in particle transport; the proximity of the trap
wall. Particle loss on the wall, the final step of radial transport, is
observed to be highly non-uniform, both radially and azimuthally. These
observations have considerable implications for the production and detection of
antihydrogen atoms.Comment: Invited Talk at NNP03, Workshop on Non-Neutral Plasmas, 200
First determination of the one-proton induced Non-Mesonic Weak Decay width of p-shell {\Lambda}-Hypernuclei
Previous studies of proton and neutron spectra from Non-Mesonic Weak Decay of
eight Lambda-Hypernuclei (A = 5-16) have been revisited. New values of the
ratio of the two-nucleon and the one-proton induced decay widths,
Gamma_2N/Gamma_p, are obtained from single proton spectra, Gamma_2N/Gamma_p =
0.50 +/- 0.24, and from neutron and proton coincidence spectra,
Gamma_2N/Gamma_p = 0.36 +/- 0.14stat +0.05sys -0.04sys , in full agreement with
previously published ones. With these values, a method is developed to extract
the one-proton induced decay width in units of the free Lambda decay width,
Gamma_p/Gamma_Lambda, without resorting to Intra Nuclear Cascade models but by
exploiting only experimental data, under the assumption of a linear dependence
on A of the Final State Interaction contribution. This is the first systematic
determination ever done and it agrees within the errors with recent theoretical
calculations.Comment: 16 pages, 3 figures, 2 table
A practical guide to the simultaneous determination of protein structure and dynamics using metainference
Accurate protein structural ensembles can be determined with metainference, a
Bayesian inference method that integrates experimental information with prior
knowledge of the system and deals with all sources of uncertainty and errors as
well as with system heterogeneity. Furthermore, metainference can be
implemented using the metadynamics approach, which enables the computational
study of complex biological systems requiring extensive conformational
sampling. In this chapter, we provide a step-by-step guide to perform and
analyse metadynamic metainference simulations using the ISDB module of the
open-source PLUMED library, as well as a series of practical tips to avoid
common mistakes. Specifically, we will guide the reader in the process of
learning how to model the structural ensemble of a small disordered peptide by
combining state-of-the-art molecular mechanics force fields with nuclear
magnetic resonance data, including chemical shifts, scalar couplings and
residual dipolar couplings.Comment: 49 pages, 9 figure
Positron plasma diagnostics and temperature control for antihydrogen production
Production of antihydrogen atoms by mixing antiprotons with a cold, confined,
positron plasma depends critically on parameters such as the plasma density and
temperature. We discuss non-destructive measurements, based on a novel,
real-time analysis of excited, low-order plasma modes, that provide
comprehensive characterization of the positron plasma in the ATHENA
antihydrogen apparatus. The plasma length, radius, density, and total particle
number are obtained. Measurement and control of plasma temperature variations,
and the application to antihydrogen production experiments are discussed.Comment: 5 pages, 4 figures, to be published in Phys. Rev. Let
ATHENA -- First Production of Cold Antihydrogen and Beyond
Atomic systems of antiparticles are the laboratories of choice for tests of
CPT symmetry with antimatter. The ATHENA experiment was the first to report the
production of copious amounts of cold antihydrogen in 2002. This article
reviews some of the insights that have since been gained concerning the
antihydrogen production process as well as the external and internal properties
of the produced anti-atoms. Furthermore, the implications of those results on
future prospects of symmetry tests with antimatter are discussed.Comment: Proc. of the Third Meeting on CPT and Lorentz Symmetry, Bloomington
(Indiana), USA, August 2004, edited by V. A. Kostelecky (World Scientific,
Singapore). 10 pages, 5 figures, 1 table. Author affiliations cor
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