Benchmarking GEANT4 nuclear models for hadron therapy with 95 MeV/nucleon carbon ions

In carbon-therapy, the interaction of the incoming beam with human tissues may lead to the production of a large amount of nuclear fragments and secondary light particles. An accurate estimation of the biological dose deposited into the tumor and the surrounding healthy tissues thus requires sophisticated simulation tools based on nuclear reaction models. The validity of such models requires intensive comparisons with as many sets of experimental data as possible. Up to now, a rather limited set of double di erential carbon fragmentation cross sections have been measured in the energy range used in hadrontherapy (up to 400 MeV/A). However, new data have been recently obtained at intermediate energy (95 MeV/A). The aim of this work is to compare the reaction models embedded in the GEANT4 Monte Carlo toolkit with these new data. The strengths and weaknesses of each tested model, i.e. G4BinaryLightIonReaction, G4QMDReaction and INCL++, coupled to two di fferent de-excitation models, i.e. the generalized evaporation model and the Fermi break-up are discussed

Agro-environmental evaluation of vineyard management using organic farming and integrated plant production systems

Organic farming is often considered to be the most environmentally-friendly crop management system, even if integrated production also aims at decreasing the impact of agriculture on the natural environment. In order to establish references for the agro-environmental evaluation of these two production systems in relation to grape growing, INRA carried out an initial study from 2001 to 2004 at the plot scale. This study focused on two grape varieties (Merlot N and Cabernet Sauvignon) in its Couhins vineyard (Graves cru classé), located on two organically-farmed plots and two plots using integrated production, a system based on the implementation of decision rules aimed at limiting the number of pest control treatments. Production means only differed in terms of pest control management (choice of products and application strategy). Each of the parcels covered approximately 0.30 ha. An agro-environmental evaluation of these two systems was made for 2003, using the INDIGO Vigne method at the plot level. Because of their nature, the choice of parameters for the indicators used determines the interpretation of the results. Nevertheless, it appears that the environmental impact of integrated production is more favourable in this case than that of organic farming, particularly in terms of pest control and energy indicators. One of the reasons for this is the high number of applications of pest control treatments in organic farming and, as a result, higher energy consumption, as well as the use of copper that has a major impact on deep waters, the ground and the air. The two systems can decrease their environmental impact by limiting the number of tractor runs for soil maintenance. Flexibility appears to be greater in the case of integrated production since, contrary to organic farming, it can use herbicides under the row. The calculation of the agro-environmental evaluation on the parcel using integrated protection with chemical weeding under the row leads to a clear improvement of the energy indicator, without significantly decreasing the value of the pest control indicator. Natural sodding of the inter-row, when the vigour of the vineyard allows it, provides an effective solution since the decrease in the number of tractor runs leads to an improvement of erosion and organic matter indicators. This type of evaluation should be carried out at the scale of a group of plots or of an entire wine-farm. Ground maintenance is an important factor in decreasing the impact of grape growing on the environment. In this respect, organic farming offers some promising prospects

QSO hosts and environments at z=0.9 to 4.2: JHK images with adaptive optics

We have observed nine QSOs with redshifts 0.85 to 4.16 at near-IR wavelengths with the adaptive optics bonnette of the Canada-France-Hawaii telescope. Exposure times ranged from 1500 to 24000s (mostly near 7000s) in J, H, or K bands, with pixels 0.035 arcsec on the sky. The FWHM of the co-added images at the location of the quasars are typically 0.16 arcsec. Including another QSO published previously, we find associated QSO structure in at least eight of ten objects, including the QSO at z = 4.16. The structures seen in all cases include long faint features which appear to be tidal tails. In four cases we have also resolved the QSO host galaxy, but find them to be smooth and symmetrical: future PSF removal may expand this result. Including one object previously reported, of the nine objects with more extended structure, five are radio-loud, and all but one of these appear to be in a dense small group of compact galaxy companions. The radio-quiet objects do not occupy the same dense environments, as seen in the NIR. In this small sample we do not find any apparent trends of these properties with redshift, over the range 0.8 < z < 2.4. The colors of the host galaxies and companions are consistent with young stellar populations at the QSO redshift. Our observations suggest that adaptive optic observations in the visible region will exhibit luminous signatures of the substantial star-formation activity that must be occurring.Comment: 22 pages including 10 tables, plus 11 figures. To appear in A

Consequences of anisotropy in electrical charge storage: application to the characterization by the mirror method of TiO2 rutile

This article is devoted first to anisotropic distributions of stored electric charges in isotropic materials, second to charge trapping and induced electrostatic potential in anisotropic dielectrics. On the one hand, we examine the case of anisotropic trapped charge distributions in linear homogeneous isotropic (LHI) insulators, obtained after an electron irradiation in a scanning electron microscope. This injection leads to the formation of a mirror image

New approach of fragment charge correlations in 129Xe+(nat)Sn central collisions

A previous analysis of the charge (Z) correlations in the $\Delta Z-$ plane for Xe+Sn central collisions at 32 MeV/u has shown an enhancement in the production of equally sized fragments (low $\Delta Z$) which was interpreted as an evidence for spinodal decomposition. However the signal is weak and rises the question of the estimation of the uncorrelated yield. After a critical analysis of its robustness, we propose in this paper a new technique to build the uncorrelated yield in the charge correlation function. The application of this method to Xe+Sn central collision data at 32, 39, 45 and 50 MeV/u does not show any particular enhancement of the correlation function in any $\Delta Z$ bin.Comment: 23 pages, 9 figures, revised version with an added figure and minor changes. To appear in Nuclear Physics

Composite mirror facets for ground based gamma ray astronomy

Composite mirrors for gamma-ray astronomy have been developed to fulfill the specifications required for the next generation of Cherenkov telescopes represented by CTA (Cherenkov Telescope Array). In addition to the basic requirements on focus and reflection efficiency, the mirrors have to be stiff, lightweight, durable and cost efficient. In this paper, the technology developed to produce such mirrors is described, as well as some tests that have been performed to validate them. It is shown that these mirrors comply with the needs of CTA, making them good candidates for use on a significant part of the array.Comment: 16 pages, 13 figures, accepted to be published on NIM

Computing Aggregate Properties of Preimages for 2D Cellular Automata

Computing properties of the set of precursors of a given configuration is a common problem underlying many important questions about cellular automata. Unfortunately, such computations quickly become intractable in dimension greater than one. This paper presents an algorithm --- incremental aggregation --- that can compute aggregate properties of the set of precursors exponentially faster than na{\"i}ve approaches. The incremental aggregation algorithm is demonstrated on two problems from the two-dimensional binary Game of Life cellular automaton: precursor count distributions and higher-order mean field theory coefficients. In both cases, incremental aggregation allows us to obtain new results that were previously beyond reach