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Research Interests: Materials Science and De
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... the time-dependence of the kinetics of high LET tracks (for a large LET range between 1 and 10 5 eV/nm) (Pimblott and LaVerne, 1994) or ... 5 OH+NaNO 3 (Draganic and Draganic, 1969); (□) C 2 H 5 OH+C 3 H 6 O (Draganic and Draganic,... more
... the time-dependence of the kinetics of high LET tracks (for a large LET range between 1 and 10 5 eV/nm) (Pimblott and LaVerne, 1994) or ... 5 OH+NaNO 3 (Draganic and Draganic, 1969); (□) C 2 H 5 OH+C 3 H 6 O (Draganic and Draganic, 1969); (▾) acrylamide (Armstrong et al ...
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ABSTRACT We have studied the effects of dense electronic excitations on the physico-chemical modifications of polymers by performing heavy ion irradiations in the energy range of some MeV amu-1. The effects induced by swift heavy ion... more
ABSTRACT We have studied the effects of dense electronic excitations on the physico-chemical modifications of polymers by performing heavy ion irradiations in the energy range of some MeV amu-1. The effects induced by swift heavy ion irradiations were compared to those induced by MeV electron irradiations performed in similar experimental conditions in polyethylene and poly(vinylidene difluoride) films. The irradiated samples were analysed ex situ by means of Fourier transform infrared spectroscopy in the transmission mode. High electronic stopping power, (dE/dx)e, irradiations are characterised by a significant increase of the yield of chain scission. Vinyl terminal unsaturations are recorded with radiochemical yields increasing markedly as (dE/dx)e increases. Moreover, characteristic bands of alkyne terminal groups were observed only above a threshold of (dE/dx)e. The overall set of results is analysed taking into account the radial dose deposition predicted by numerical calculations and the defect creation measured after electron irradiations. This allows us to elucidate the kind of chemical modifications influenced by the local dose rate; i.e. for which a specific effect due to a dense electronic excitation appears.
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ABSTRACT We present the results of simultaneous in situ luminescence and optical absorption studies of alkali-halides, submitted to very dense electronic excitations induced by swift heavy ion irradiations at low temperatures (15-200 K).... more
ABSTRACT We present the results of simultaneous in situ luminescence and optical absorption studies of alkali-halides, submitted to very dense electronic excitations induced by swift heavy ion irradiations at low temperatures (15-200 K). X-ray irradiations performed in the same experimental conditions permit the necessary comparison with ion irradiations. The luminescence of the self-trapped excitons is only slightly modified by increasing the electronic stopping power, while new features appear for the point defect creation. For instance, in NaCl at 15 K, F centres are efficiently created by Ne, Zn and Xe irradiations and F2 centres only by Zn and Xe irradiations. We discuss the evolution of the yields of defect creation as a function of the temperature and of the electronic stopping power.
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The chromosomal protein MC1 is a monomeric protein of 93 amino acids that is able to bind any DNA but has a slight preferential affinity for some sequences and structures, like cruciform and minicircles. The protein has been irradiated... more
The chromosomal protein MC1 is a monomeric protein of 93 amino acids that is able to bind any DNA but has a slight preferential affinity for some sequences and structures, like cruciform and minicircles. The protein has been irradiated with 36Ar18+ ions of 95 MeV/nucleon. The LET of these particles in water is close to 270 keV/microm. We tested the activity of the protein by measuring its ability to form complexes with DNA. We tested the integrity of the protein by measuring the molecular weight of the species formed. Compared with gamma radiation, we observed for the same dose a less efficient inactivation of the protein, a greater protection of the protein by the bound DNA, a lower induction of chain breakage, and a greater production of protein-protein and DNA-protein crosslinks. The results are discussed in terms of the quantitative and the qualitative differences between the two types of radiation: The global radical yield is slightly higher with gamma rays, whereas the density of radicals produced along the particle track is considerably higher with argon ions.
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... This is attributed to spatially localized atomic motions in the initial spinel structure followed by a rapid quench and recrystallisation in the same structure, but with some random orientation. No amorphous phase was detected. ...
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... 43 (1990), p. 229. Abstract | PDF (3109 K) | View Record in Scopus | Cited By in Scopus (176). [5]. H. Iskef, JW Cunningham and DE Watt. Phys. Med. Biol. ... Article | PDF (710 K) | View Record in Scopus | Cited By in Scopus (21).... more
... 43 (1990), p. 229. Abstract | PDF (3109 K) | View Record in Scopus | Cited By in Scopus (176). [5]. H. Iskef, JW Cunningham and DE Watt. Phys. Med. Biol. ... Article | PDF (710 K) | View Record in Scopus | Cited By in Scopus (21). [10]. B. Gervais and S. Bouffard. Nucl. Instr. ...
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ABSTRACT Samples of monosilicated sintered fluorapatite (Ca9Nd(PO4)5(SiO4)F2, britholite) and full-phosphated Durango fluorapatite were irradiated using different heavy ions with incident energies in the range of several hundred MeV,... more
ABSTRACT Samples of monosilicated sintered fluorapatite (Ca9Nd(PO4)5(SiO4)F2, britholite) and full-phosphated Durango fluorapatite were irradiated using different heavy ions with incident energies in the range of several hundred MeV, corresponding to the electronic stopping power regime. The induced damage was characterized by means of X-ray diffraction for the monosilicated fluorapatites and Rutherford backscattering spectrometry associated with channeling technique (CRBS) for the Durango fluorapatites. Characterizing the amorphization of the monosilicated fluorapatites revealed two main features. First, the evolution of the damaged fraction with the ion fluence and the ion species shows that amorphization is mainly dependent on the electronic energy loss (Se) value. Second, we suggest that a percolation of defects only occurs when Se is above a threshold near 5 keV nm−1. This can be related to the limit of a fragmentation zone defined from microscopic observations. We have quantified damage in monosilicated fluorapatites by calculating amorphization effective radii (Re). By plotting these results versus Se, we found that they are in good agreement with those obtained from the irradiated single crystals of Durango fluorapatite.
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We have investigated in a very direct way the effect of irradiation with 1.66 GeV argon ions, on the viscosity of the B2O3 glass. Up to a threshold temperature, a very drastic decrease of the viscosity is observed under irradiation. On a... more
We have investigated in a very direct way the effect of irradiation with 1.66 GeV argon ions, on the viscosity of the B2O3 glass. Up to a threshold temperature, a very drastic decrease of the viscosity is observed under irradiation. On a large range of temperature a quasi-athermal behavior appears. This effect is discussed in the framework of two models. The first one is based on an analogy with the diffusion in crystals under irradiation and the second takes into account the deformation of a cylinder of matter which becomes very fluid during a very short time along the ion range.
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We studied the Hall effect in the mixed state of a Tl2Ba2CaCu2O8 superconducting film and of a YBa2Cu3O7 single crystal before and after irradiation with high energy Pb ions. The irradiation decreased the magnitude of the mixed state... more
We studied the Hall effect in the mixed state of a Tl2Ba2CaCu2O8 superconducting film and of a YBa2Cu3O7 single crystal before and after irradiation with high energy Pb ions. The irradiation decreased the magnitude of the mixed state longitudinal and Hall resistivities, but the Hall conductivity remained unchanged, within experimental accuracy, after changing the pinning strength, in agreement with theory.
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The irradiation induced defects act as strong pinning centers at very low defect concentration. The threshold field increases linearly with the defect concentration. The metastable properties are governed by the presence of such defects :... more
The irradiation induced defects act as strong pinning centers at very low defect concentration. The threshold field increases linearly with the defect concentration. The metastable properties are governed by the presence of such defects : a smooth threshold of non linearity becomes a switch associated with large hysteresis. The results suggest that deformable COW are arranged in domains and trapped
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The radiolysis of water with heavy ions of high linear energy transfer (LET) (-dE/dx) is characterized, in deaerated medium, by the production of superoxide anions, the radiolytic yields of which increase with the LET. Radiobiological... more
The radiolysis of water with heavy ions of high linear energy transfer (LET) (-dE/dx) is characterized, in deaerated medium, by the production of superoxide anions, the radiolytic yields of which increase with the LET. Radiobiological interest in such radical species comes from the oxidative stress which may be generated by their dismutation in O2 and H2O2 in anoxic medium (radiotherapy with heavy ions). A brief review of the measurements of superoxide free radicals in aqueous solution by indirect or direct methods is presented. Moreover, some experimental results obtained by pulse radiolysis with Ar18+ ions (TEL = 290 keV x microm(-1)), are described. The interpretation of the kinetics takes into account the superoxide absorbance and that of hydrogen peroxide, which is present at the millisecond time scale.
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ABSTRACT The organic metals are interesting systems for the irradiation of molecular compounds: they behave similarly, from the point of view of defect production, to conventional molecular crystals and their quasi-one-dimensionality... more
ABSTRACT The organic metals are interesting systems for the irradiation of molecular compounds: they behave similarly, from the point of view of defect production, to conventional molecular crystals and their quasi-one-dimensionality allows a direct determination, by electrical conductivity measurement of the defect concentration. The irradiations with highly energetic heavy ions **** Experiments performed at Grand Accélérateur National d'Ions Lourds GANIL, Caen, France. show an increase of the damage production rate when the energy released by the ions in electronic excitation increases; this enhancement is interpreted as a reduction of the probability of deexcitation without defect production.
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ABSTRACT Transmission electron microscopy (TEM) characterizations were carried out on a set of UO2 thin foils previously implanted at room temperature with 400 keV Xe2+ and 250 keV Kr2+ ions at the fluence 7.1015 at.cm-2 (equivalent to 1... more
ABSTRACT Transmission electron microscopy (TEM) characterizations were carried out on a set of UO2 thin foils previously implanted at room temperature with 400 keV Xe2+ and 250 keV Kr2+ ions at the fluence 7.1015 at.cm-2 (equivalent to 1 at.%/at. UO2). The experiment was devoted to the study of the evolution of the fission gases bubbles populations with increasing temperature. Annealings were performed in the laboratory furnace at 600°C, 800°C, 1000°C for 12h, 1400°C for 4h and 1500°C for 2h under Ar-5%H2 atmosphere. For each annealing condition and for as-implanted specimens the bubble population has been characterized in size and number density. A comparison between Xe and Kr has been done that showed a similar behaviour. Globally, from the as-implanted sample to the 1500°C annealed, the bubbles growth phenomenon and the microstructure evolution with temperature was put in relieve.
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Tracks of various heavy ions with energies up to 13 MeV/u were studied using the technique of selective chemical etching. It was found that for homogeneous track etching the energy loss of the ions has to surpass a threshold of about 450... more
Tracks of various heavy ions with energies up to 13 MeV/u were studied using the technique of selective chemical etching. It was found that for homogeneous track etching the energy loss of the ions has to surpass a threshold of about 450 eV/Å. In a transition regime between 180 and 450 eV/Å etching was possible but the mean diameter of
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... References. 1. S. Klaumünzer, G. Schumacher, S. Rentzsch, G. Vogl, L. Söldner and H. Bieger. Acta Metall. 30 (1982), p. 1493. Abstract | PDF (1129 K) | View Record in Scopus | Cited By in Scopus (25). 2. A. Audouard, E. Balanzat ...
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ABSTRACTThe resistivity measurements of bulk super-conducting oxides La2−xSrxCuO4−x/2+ 〈0.15〈x〈0.2) irradiated by 2.5 Mev-electrons and YBa2Cu3O7-δ 〈0〈δ〈0.15) irradiated by 2.9 GeU-krypton ions have shown a regular and constant decrease... more
ABSTRACTThe resistivity measurements of bulk super-conducting oxides La2−xSrxCuO4−x/2+ 〈0.15〈x〈0.2) irradiated by 2.5 Mev-electrons and YBa2Cu3O7-δ 〈0〈δ〈0.15) irradiated by 2.9 GeU-krypton ions have shown a regular and constant decrease of the critical temperature Tc as a function of the fluence.On the contrary, an increase of Tc has been observed durino irradiation of super-conduct ino La2CuO4 compound by 2.9 GeV-krypton ions, which saturates at Tc/Tco = 0.1 for fluences hioher than 3.1012 Kr.cm−. The evolution of the R(T) curves during irradiation is very similar to the one observed under Dressure.A comparison of the variations of Tc as a function of the number of di solacements oer atom for various particles (n. e−. He+. O. Kr) suggests that the hijjh electronic stoppino power of the heavy ions could be the main factor of damage.
Experimental results concerning the transport properties of irradiated 1-D conductors are surveyed. The mechanisms which account for the changes in the dc conductivity either at high or low temperatures are considered. These mechanisms... more
Experimental results concerning the transport properties of irradiated 1-D conductors are surveyed. The mechanisms which account for the changes in the dc conductivity either at high or low temperatures are considered. These mechanisms are: the 1-D blocking effects of defects and subsequent transverse fixed range phonon activated hopping of single electrons in the metallic regime, and the charge density waves pinning either in the metallic or the insulating regime. The difficulty between disordered systems and intrinsic or so-called pure ones is demonstrated.
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... This method has been used by LaVerne for the study of heavy-ion radiolysis of benzene, with a single-photon-counting technique. ... Formic acid was used by Burns et al., 3 La Verne, 12 and Baldacchino et al. 9 to measure the hydroxyl... more
... This method has been used by LaVerne for the study of heavy-ion radiolysis of benzene, with a single-photon-counting technique. ... Formic acid was used by Burns et al., 3 La Verne, 12 and Baldacchino et al. 9 to measure the hydroxyl primary yield. ...