753 research outputs found
Linac modeling for external beam radiotherapy quality assurance using a dedicated 2D pixelated detector
International audienceQuality assurance is a key issue in intensity modulated radiotherapy. Errors can occur in the dose delivery process induces significant differences between the planned treatment and the delivered one. In this context, the Medical Application Physics group of the LPSC is developing TraDeRa (Transparent Detector for Radiotherapy), a 2D pixelated matrix of ionization chambers located upstream to the patient. The signal map obtained with TraDeRa has to be processed to provide medical observables to quantify the quality of the treatment delivery. This relies on accurate Monte Carlo simulations benchmarked with measurements performed under a linear accelerator (Linac).The work described in this paper lies in the optimization of the Linac head simulation and the development of an innovative Monte Carlo/measurements comparison method to perform an accurate enough model of the X-ray production device. An optimized parametrization of the particles transport allowed an increase of the simulation efficiency by a factor 3. The characteristics of an electron beam of a reference Linac were matched with the simulation results by using dose deposition of the created X-ray beam in a water tank. Two parameters are particularly critical: the nominal energy of the electrons and the radial distribution of impact on the target. The innovative method was able to provide within minutes those two parameters for any Linac, achieving, for example, a 10 keV precision on the energy determination for a 6 MV operating Linac
Experimental study of a liquid Xenon PET prototype module
A detector using liquid Xenon in the scintillation mode is studied for
Positron Emission Tomography (PET). The specific design aims at taking full
advantage of the liquid Xenon properties. It does feature a promising
insensitive to any parallax effect. This work reports on the performances of
the first LXe prototype module, equipped with a position sensitive PMT
operating in the VUV range (178 nm).Comment: Proc. of the 7th International Workshops on Radiation Imaging
Detectors (IWORID-7), Grenoble, France 4-7 July 200
Global unions: chasing the dream or building the reality?
This article takes as its theme the global restructuring of capital and its impact on worker organization. It argues for a reassertion of class in any analysis of global solidarity, and assesses the opportunities and barriers to effective global unionization. Rooted in the UK experience, the article analyzes the impact of the European social dimension on trade unions, before taking the discussion into a global dimension. It concludes by suggesting that there are reasons for cautious optimism in terms of solidarity building, despite difficult historical legacies and the common replacement of action with rhetoric
Constructing transnational solidarity: the role of campaign governance
Our inductive study of two transnational labour solidarity efforts focuses on the role of campaign governance. Specifically, we study contrasting campaign strategies, tactics and coalition structures in campaigns by two global union federations, UNI Global Union and the IUF, contextualized in terms of how these campaigns unfolded in India. Our contribution consists of two arguments. The first is that a degree of internal consistency amongst different campaign elements is important for success, and the second is that a mode of articulation that allows for local concerns in affiliate countries to find voice in global campaigns is more likely to result in concrete gains at the local level
Economic precariousness: A new channel in the housing market cycle
Abstract: Demographic and institutional elements, as important drivers of the housing market, should not be neglected since it is not only financial and monetary elements that matter in the case of the housing market. In this context, one relationship, which still remains unclear, is the relationship between the housing and the labour markets. Some research has been undertaken to support the hypothesis that high rates of
homeownership lead to high unemployment via increases in the reservation wage. However, further research is needed to address the possible implications of the institutional settings of the labour market in the dynamics of the housing market. The aim of this paper is to bring some light on the link between both markets. In particular, this contribution explains how the housing cycle could be âamplifiedâ via a new
channel, i.e. economic precariousness, which is closely related to job insecurity. Subsequently, we provide evidence in the case of five developed economies, Ireland, the Netherlands, Spain, the United Kingdom and the United States, over the period 1985-2013.Not appicabl
The Ring Imaging Cherenkov detector (RICH) of the AMS experiment
The Alpha Magnetic Spectrometer (AMS) experiment to be installed on the
International Space Station (ISS) will be equipped with a proximity focusing
Ring Imaging Cherenkov (RICH) detector for measuring the electric charge and
velocity of the charged cosmic particles. A RICH prototype consisting of 96
photomultiplier units, including a piece of the conical reflector, was built
and its performance evaluated with ion beam data. Preliminary results of the
in-beam tests performed with ion fragments resulting from collisions of a 158
GeV/c/nuc primary beam of Indium ions (CERN SPS) on a Pb target are reported.
The collected data included tests to the final front-end electronics and to
different aerogel radiators. Cherenkov rings for a large range of charged
nuclei and with reflected photons were observed. The data analysis confirms the
design goals. Charge separation up to Fe and velocity resolution of the order
of 0.1% for singly charged particles are obtained.Comment: 29th International Conference on Cosmic Rays (Pune, India
Conflict in pedestrian networks
Encouraging pedestrian activity is increasingly recognised as beneïŹcial for public health, the environment and the economy. As our cities become more crowded, there is a need for urban planners to take into account more explicitly pedestrian needs. The term that is now in use is that a city should be âwalkableâ. For route planning, whereas much attention has been given to shortest path, in distance or time, much less attention has been paid to ïŹow levels and the diïŹculties they pose on the route. This paper considers problems posed by conïŹicting paths, for example cross-traïŹc. We use network centrality measures to make a ïŹrst estimate of diïŹering levels of conïŹict posed at the network nodes. We take special note of the role of collective motion in determining network usage. A small case study illustrates the method
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