Theoretical approach based on Monte-Carlo simulations to predict the cell survival following BNCT

International audienceWe present here a very preliminary work on BNCT Dosimetry. The approach is as follows:A full Monte Carlo calculation is used to separate all dose components and determine the corresponding physical dose fractions with a realistic clinical model.These dose fractions are then used as mixed fields to predict cell-survivals and RBE values for a specific cell-line, thanks to the radiobiological model NanOxTM

2012 Activity Report of the Regional Research Programme on Hadrontherapy for the ETOILE Center

2012 is the penultimate year of financial support by the CPER 2007-2013 for ETOILE's research program, sustained by the PRRH at the University Claude Bernard. As with each edition we make the annual review of the research in this group, so active for over 12 years now. Over the difficulties in the decision-making process for the implementation of the ETOILE Center, towards which all our efforts are focussed, some "themes" (work packages) were strengthened, others have progressed, or have been dropped. This is the case of the eighth theme (technological developments), centered around the technology for rotative beam distribution heads (gantries) and, after being synchronized with the developments of ULICE's WP6, remained so by ceasing its activities, coinciding also with the retirement of its historic leader at IPNL, Marcel Bajard. Topic number 5 ("In silico simulations") has suffered the departure of its leader, Benjamin Ribba, although the work has still been provided by Branka Bernard, a former postdoctoral fellow in Lyon Sud, and now back home in Croatia, still in contract with UCBL for the ULICE project. Aside from these two issues (and the fact that the theme "Medico-economical simulations" is now directly linked to the first one ("Medical Project"), the rest of the teams are growing, as evidenced by the publication statistics at the beginning of this report. This is obviously due to the financial support of our always faithful regional institutions, but also to the synergy that the previous years, the European projects, the arrival of the PRIMES LabEx, and the national France Hadron infrastructure have managed to impulse. The Rhone-Alpes hadron team, which naturally includes the researchers of LPC at Clermont, should also see its influence result in a strong presence in France Hadron's regional node, which is being organized. The future of this regional research is not yet fully guaranteed, especially in the still uncertain context of ETOILE, but the tracks are beginning to emerge to allow past and present efforts translate into a long future that we all want to see established. Each of the researchers in PRRH is aware that 2013 will be (and already is) the year of great challenge : for ETOILE, for the PRRH, for hadron therapy in France, for French hadrontherapy in Europe (after the opening and beginning of treatments in the German [HIT Heidelberg, Marburg], Italian [CNAO, Pavia] and Austrian [MedAustron, Wien Neuerstadt]) centers. Let us meet again in early 2014 for a comprehensive review of the past and a perspective for the future ..

Influence of the spatial and temporal structure of the deposited-energy distribution in swift-ion-induced sputtering

International audienceThe sputter processes occurring under swift-ion bombardment in the electronic-stopping regime are investigated by molecular-dynamics simulations performed for a Lennard-Jones solid (Ar). Two aspects of the dynamics of the excited electronic subsystem are included in the simulation and their influence on the sputter yield is studied. First, we assume the energy transfer from the electronic to the atomic system not to be instantaneous, but to last for a period of time τ. For τ≳1ps, we find the sputter yield Y to become strongly nonlinear as a function of the stopping power dE/dx. Second, we test the influence of a nonhomogeneous spatial distribution of the electronic excitations. It is shown that such a spatial distribution also leads to a strongly nonlinear dependence of Y on dE/dx.

Theoretical investigation on the cylinder-shaped N66 cage

Recent theoretical studies suggested that the stabilizing factors for large nitrogen cages tend to favor more five-membered rings, more three-membered rings and cylinder-shaped structure with large numbers of layers. Our present studies on the relative stability of all-nitrogen cages suggest that the stabilizing factors originate from the dispersion interactions. The cylinder-shaped of N66 (with D3h symmetry) has been studied in detail. The structure and energies are examined at the B3LYP/cc-pVDZ level. In addition, single-point energy calculations at the MP2/cc-pVDZ and the B3LYP/cc-pVTZ levels are carried out in order to determine whether or not dispersion interactions exist in N66. To fully understand the bonding in this cage molecule, NBO and AIM analyses are performed. The results show that the dispersion interactions contribute to the stability of the cylinder-shaped N66. Meanwhile, electrostatic potential analysis shows that N66 has negative electrostatic potential on the outside and positive electrostatic potential inside the tube. As the eleventh member of the series (N6)n (n = 1-30, with D3h or D3d symmetry alternatively), cylinder-shaped N66 may also be a novel beeline nanotube which is environmentally friendly. This work is expected to impact a wide range of applications

Putative role of γ -aminobutyric acid (GABA) as a long-distance signal in up-regulation of nitrate uptake in Brassica napus L.

The relationship between nitrate influx, BnNrt2 nitrate transporter gene expression and amino acid composition of phloem exudate was investigated during N-deprivation (short-term experiment) and over a growth cycle (long-term experiment) in Brassica napus L. The data showed a positive correlation between γ-aminobutyric acid (GABA) in phloem exudate and nitrate uptake in the short- and the long-term experiments. The hypothesis that this non-protein amino acid could up-regulate nitrate uptake via a long-distance signalling pathway was tested by providing an exogenous GABA supply to the roots. The effect of GABA was compared with the effects of Gln, Glu and Asn, each known to be inhibitors of nitrate uptake. The results showed that GABA treatment induced a significant increase of BnNrt2 mRNA expression, but had less effect on nitrate influx. By contrast, Gln, Glu and Asn significantly reduced nitrate influx and BnNrt2 mRNA expression compared with the control plants. This study provides the first evidence that GABA may act as a putative long-distance inter-organ signal molecule in plants in conjunction with negative control exerted by Gln. The up-regulation effect of GABA on nitrate uptake is discussed in the context of its role in N metabolism, nutritional stress and the recent discovery of a putative role of GABA as a signal molecule in plant development.Peer reviewe

Neutral atom sputtering yields from Gd3Ga5O12 and Y3Fe5O12 garnets: Observation of a velocity effect

International audienceThe effects of swift heavy ions in insulators, leading e.g. to the appearance of latent tracks, have been extensively studied. In particular, it has been shown that at a fixed value of electronic stopping power the damage cross-section in the yttrium iron garnet (Y3Fe5O12) is larger for low energy ions than for high energy ions. This is the so-called ''velocity effect'' in the damage creation in the electronic stopping power regime. In order to verify if such a velocity effect also exists for atoms sputtering, the total sputtering yields of yttrium iron garnet (Y3Fe5O12) and gadolinium gallium garnet (Gd3Ga5O12) irradiated at high energy with a lead beam of 19.3 MeV/u, were measured using the catcher technique. The sputtered particles, were collected upon an aluminum foil placed in front of the target and the impurities deposited on the collectors were analysed by Rutherford backscattering. By comparison with previous measurements of the sputtering yield for the same electronic energy loss value at lower velocity, we clearly observed an important velocity effect: the sputtering yield is higher at low velocity than at high velocity