571 research outputs found
Use of and irradiation from plain lumbar spine radiography in Switzerland.
Plain lumbar spine radiographic examination (LSRE) is frequently used in medical practice and delivers a high dose of ionising radiation. The objectives of the study were to determine the annual frequency of LSRE in Switzerland and its distribution according to practitioners' and patients' characteristics, as well as the related population dose of ionising radiation.
Data were extrapolated from a nationwide questionnaire survey on radiation exposure resulting from medical imaging in 1998, involving physicians and other healthcare providers performing radiological examinations in Switzerland.
An estimated number of 273,000 LSRE are performed annually in Switzerland (39 LSRE per 1000 inhabitants per year). The collective dose to the population due to LSRE was 1130 Sv (0.16 mSv per person per year). 50-60% of these procedures were performed to confirm or rule out a diagnosis, the majority (85%) in the context of an illness.
LSRE is the third most frequent radiographic procedure performed and delivers the highest population dose of ionising radiation of any radiodiagnostic procedure. Efforts to reduce the frequency and the radiation dose of this procedure must be kept up, technically by optimising the equipment and radioprotection measures, and clinically by implementing evidence-based approaches to appropriate indications for this imaging technique
Anisotropic Pair Correlations and Structure Factors of Confined Hard-Sphere Fluids: An Experimental and Theoretical Study
We address the fundamental question: how are pair correlations and structure factors of hard-sphere fluids affected by confinement between hard planar walls at close distance? For this purpose, we combine x-ray scattering from colloid-filled nanofluidic channel arrays and first-principles inhomogeneous liquid-state theory within the anisotropic Percus-Yevick approximation. The experimental and theoretical data are in remarkable agreement at the pair-correlation level, providing the first quantitative experimental verification of the theoretically predicted confinement-induced anisotropy of the pair-correlation functions for the fluid. The description of confined fluids at this level provides, in the general case, important insights into the mechanisms of particle-particle interactions in dense fluids under confinement
A new access control unit for GANIL and SPIRAL 2
International audienceFor the GANIL safety revaluation and the new project of accelerator SPIRAL 2, it was decided to replace theexisting access control system for radiological controlled areas. These areas are all cyclotron rooms and experimental areas. The existing system is centralized around VME cards. Updating is becoming very problematic. The new UGA (access control unit) will becomposed of a pair of PLC to ensure the safety of each room. It will be supplemented by a system UGB (radiological control unit) that will assure the radiological monitoring of the area concerned
Search for supersymmetry with a dominant R-parity violating LQDbar couplings in e+e- collisions at centre-of-mass energies of 130GeV to 172 GeV
A search for pair-production of supersymmetric particles under the assumption
that R-parity is violated via a dominant LQDbar coupling has been performed
using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV.
The observed candidate events in the data are in agreement with the Standard
Model expectation. This result is translated into lower limits on the masses of
charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for
m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81
GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the
95% confidence level for any generation structure of the LQDbar coupling.Comment: 32 pages, 30 figure
flavour tagging using charm decays at the LHCb experiment
An algorithm is described for tagging the flavour content at production of
neutral mesons in the LHCb experiment. The algorithm exploits the
correlation of the flavour of a meson with the charge of a reconstructed
secondary charm hadron from the decay of the other hadron produced in the
proton-proton collision. Charm hadron candidates are identified in a number of
fully or partially reconstructed Cabibbo-favoured decay modes. The algorithm is
calibrated on the self-tagged decay modes and using of data collected by the LHCb
experiment at centre-of-mass energies of and
. Its tagging power on these samples of
decays is .Comment: All figures and tables, along with any supplementary material and
additional information, are available at
http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-027.htm
Determination of gamma and -2beta_s from charmless two-body decays of beauty mesons
See paper for full list of authorsInternational audienceUsing the latest LHCb measurements of time-dependent CP violation in the B^0_s -> K^+K^- decay, a U-spin relation between the decay amplitudes of B^0_s -> K^+K^- and B^0 -> \pi^+\pi^- decay processes allows constraints to be placed on the angle gamma of the unitarity triangle and on the B^0_s mixing phase -2\beta_s. Results from an extended approach, which uses additional inputs on B^0 -> \pi^0\pi^0 and B^+ -> \pi^+\pi^0 decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value \gamma = ( 63.5 +7.2 -6.7 ) degrees modulo 180 degrees is determined. In an alternative analysis, the value -2\beta_s = -0.12 +0.14 -0.16 rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included
Measurement of the CP-violating phase ÎČ in B0âJ/ÏÏ+Ïâ decays and limits on penguin effects
18 pages, 6 figures - See paper for full list of authorsInternational audienceTime-dependent CP violation is measured in the B0âJ/ÏÏ+Ïâ channel for each Ï+Ïâ resonant final state using data collected with an integrated luminosity of 3.0 fbâ1 in pp collisions using the LHCb detector. The final state with the largest rate, J/ÏÏ0(770), is used to measure the CP-violating angle 2ÎČeff to be (41.7±9.6+2.8â6.3)â. This result can be used to limit the size of penguin amplitude contributions to CP violation measurements in, for example, B0sâJ/ÏÏ decays. Assuming approximate SU(3) flavour symmetry and neglecting higher order diagrams, the shift in the CP-violating phase Ïs is limited to be within the interval [â1.05â, +1.18â] at 95% confidence level. Changes to the limit due to SU(3) symmetry breaking effects are also discussed
Measurement of the lifetime of the B+c meson using the B+câJ/ÏÏ+ decay mode
See paper for full list of authors - 19 pages, 3 figuresInternational audienceThe difference in total widths between the B+c and B+ mesons is measured using 3.0fbâ1 of data collected by the LHCb experiment in 7 and 8 TeV centre-of-mass energy proton-proton collisions at the LHC. Through the study of the time evolution of B+câJ/ÏÏ+ and B+âJ/ÏK+ decays, the width difference is measured to beÎÎâĄÎB+câÎB+=4.46±0.14±0.07mmâ1c,where the first uncertainty is statistical and the second systematic. The known lifetime of the B+ meson is used to convert this to a precise measurement of the B+c lifetime,ÏB+c=513.4±11.0±5.7fs,where the first uncertainty is statistical and the second systematic
Study of the rare B0s and B0 decays into the Ï+ÏâÎŒ+ÎŒâ final state
See paper for full list of authors - Submitted to Phys. Lett. BInternational audienceA search for the rare decays B0sâÏ+ÏâÎŒ+ÎŒâ and B0âÏ+ÏâÎŒ+ÎŒâ is performed in a data set corresponding to an integrated luminosity of 3.0 fbâ1 collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay B0sâÏ+ÏâÎŒ+ÎŒâ and the first evidence of the decay B0âÏ+ÏâÎŒ+ÎŒâ are obtained and the branching fractions are measured to be B(B0sâÏ+ÏâÎŒ+ÎŒâ)=(8.6±1.5(stat)±0.7(syst)±0.7(norm))Ă10â8 and B(B0âÏ+ÏâÎŒ+ÎŒâ)=(2.11±0.51(stat)±0.15(syst)±0.16(norm))Ă10â8, where the third uncertainty is due to the branching fraction of the decay B0âJ/Ï(âÎŒ+ÎŒâ)Kâ(890)0(âK+Ïâ), used as a normalisation
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