Publications

2012

• Coherent phonon coupling to individual Bloch states in photoexcited bismuth.
  
  • Papalazarou Evangelos
  • Faure Jérôme
  • Mauchain Julien
  • Marsi Marino
  • Taleb-Ibrahimi Amina
  • Reshetnyak Igor
  • van Roekeghem Ambroise
  • Timrov Iurii
  • Vast Nathalie
  • Arnaud B.
  • Perfetti Luca
  Physical Review Letters, American Physical Society, 2012, 108 (25), pp.256808. We investigate the temporal evolution of the electronic states at the bismuth (111) surface by means of time- and angle-resolved photoelectron spectroscopy. The binding energy of bulklike bands oscillates with the frequency of the A(1g) phonon mode, whereas surface states are insensitive to the coherent displacement of the lattice. A strong dependence of the oscillation amplitude on the electronic wave vector is correctly reproduced by ab initio calculations of electron-phonon coupling. Besides these oscillations, all the electronic states also display a photoinduced shift towards higher binding energy whose dynamics follows the evolution of the electronic temperature. (10.1103/PhysRevLett.108.256808)
  DOI : 10.1103/PhysRevLett.108.256808
• Size-dependent infrared properties of MgO nanoparticles with evidence of screening effect
  
  • Chalopin Y.
  • Dammak H.
  • Hayoun M.
  • Besbes Mondher
  • Greffet Jean-Jacques
  Applied Physics Letters, American Institute of Physics, 2012, 100, pp.241904. We have investigated the infrared (IR) absorption properties of MgO nanoparticles (NPs) with the means of molecular dynamics simulations. Several size effects have been observed. We show in particular that the absorption of IR radiation does not occur predominantly through the polariton mode but preferentially through surface modes. This enhanced surface absorption is found to result from the absence of dielectric screening of the first atomic layer of the NPs. We demonstrate concomitantly that a macroscopic description of electrodynamics is inadequate to capture these unusual IR properties. (10.1063/1.4729384)
  DOI : 10.1063/1.4729384
• Probability- and spin-current operators for effective Hamiltonians
  
  • Bottegoni Federico
  • Drouhin H. -J.
  • Fishman Guy
  • Wegrowe J. -E.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2012, 85, pp.235313. We present a systematic construction of the probability-and spin-current operators, based on a momentum power expansion of effective Hamiltonians. These operators play an essential role in transport problems related to semiconductor heterostructures, in particular when spin-orbit interaction is taken into account. The result, valid whatever the momentum power and including the linear (Bychkov-Rashba) term as well as the cubic (Dresselhaus or D'yakonov-Perel) term, is of special importance for spintronics. (10.1103/PhysRevB.85.235313)
  DOI : 10.1103/PhysRevB.85.235313
• Extrudable Reactive Powder Concretes Hydration, shrinkage and transfer properties
  
  • Mounanga Pierre
  • Cherkaoui Khalid
  • Khelidj Abdelhafid
  • Courtial Mireille
  • de Noirfontaine Marie-Noëlle
  • Dunstetter Frederic
  European Journal of Environmental and Civil Engineering, Taylor & Francis, 2012, 16 (Suppl. 1), pp.s99-s114. The behavior of five reactive powder concretes (RPC), with four of them being extrudable, has been studied since the first minutes up to more than 90 days. The extrusion force, hydration rate, free autogenous shrinkage at early age, mechanical properties and durability parameters were measured. The performance analysis showed the benefits of a partial substitution of silica fume with crushed quartz on the RPC properties. The cost/performances analysis highlighted that the main advantage of using RPC lies in their potential of durability, which is 10 to 100 times higher than that of ordinary or high-performance concretes, according to the property considered. (10.1080/19648189.2012.681961)
  DOI : 10.1080/19648189.2012.681961
• Ultrafast Surface Carrier Dynamics in the Topological Insulator Bi2Te3
  
  • Hajlaoui Mahdi
  • Papalazarou E.
  • Mauchain Julien
  • Lantz G.
  • Moisan N.
  • Boschetto Davide
  • Jiang Z.
  • Miotkowski I.
  • Chen Y. P.
  • Taleb-Ibrahimi Amina
  • Perfetti Luca
  • Marsi M.
  Nano Letters, American Chemical Society, 2012, 12 (7), pp.3532-3536. We discuss the ultrafast evolution of the surface electronic structure of the topological insulator Bi2Te3 following a femtosecond laser excitation. Using time and angle-resolved photoelectron spectroscopy, we provide a direct real-time visualization of the transient carrier population of both the surface states and the bulk conduction band. We find that the thermalization of the surface states is initially determined by interband scattering from the bulk conduction band, lasting for about 0.5 ps; subsequently, few picoseconds are necessary for the Dirac cone non-equilibrium electrons to recover a Fermi-Dirac distribution, while their relaxation extends over more than 10 ps. The surface sensitivity of our measurements makes it possible to estimate the range of the bulk-surface interband scattering channel, indicating that the process is effective over a distance of 5 nm or less. This establishes a correlation between the nanoscale thickness of the bulk charge reservoir and the evolution of the ultrafast carrier dynamics in the surface Dirac cone. (10.1021/nl301035x)
  DOI : 10.1021/nl301035x
• Novel Structural Motifs in Low Energy Phases of LiAlH4
  
  • Amsler Maximilian
  • Flores-Livas Jose A.
  • Doan Huan Tran
  • Botti Silvana
  • Marques Miguel A. L.
  • Goedecker Stefan
  Physical Review Letters, American Physical Society, 2012, 108, pp.205505. (10.1103/PhysRevLett.108.205505)
  DOI : 10.1103/PhysRevLett.108.205505
• Beyond Ferromagnetic Resonance: The Inertial Regime of the Magnetization
  
  • Olive Enrick
  • Lansac Yves
  • Wegrowe J.-E.
  Applied Physics Letters, American Institute of Physics, 2012, 100 (19), pp.192407. [No abstract] (10.1063/1.4712056)
  DOI : 10.1063/1.4712056
• Beyond the GW approximation: combining correlation channels
  
  • Romaniello Pina
  • Bechstedt Friedhelm
  • Reining Lucia
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2012, 85 (15), pp.155131. In many-body perturbation theory (MBPT) the self-energy $\Sigma=iGW\Gamma$ plays the key role since it contains all the many body effects of the system. The exact self-energy is not known; as first approximation one can set the vertex function $\Gamma$ to unity which leads to the GW approximation. The latter properly describes the high-density regime, where screening is important; in the low-density regime, instead, other approximations are proposed, such as the T matrix, which describes multiple scattering between two particles. Here we combine the two approaches. Starting from the fundamental equations of MBPT we show how one can derive the T-matrix approximation to the self-energy in a common framework with GW. This allows us to elucidate several aspects of this formulation, including the origin of, and link between, the electron-hole and the particle-particle T matrix, the derivation of a screened T matrix, and the conversion of the T matrix into a vertex correction. The exactly solvable Hubbard molecule is used for illustration. (10.1103/PhysRevB.85.155131)
  DOI : 10.1103/PhysRevB.85.155131
• Electromagnetic modeling of plasmonic properties of gold nanoparticles embedded within a dielectric matrix deformed by swift heavy ions
  
  • Cardin Julien
  • Fafin Alexandre
  • Gourbilleau Fabrice
  • Coulon Pierre-Eugène
  • Rizza Giancarlo
  • Dufour Christian
  , 2012. The growing number of fields in which are studied the localized plasmon surface resonance such as light management for energy, enhanced field spectroscopy, or for integrated optical telecommunications bellow the diffraction limit is driving the development of modeling methods of these systems. In this paper, the electromagnetic properties of ion-deformed gold, sphere, prolate, nanorods and nanowires embedded within a dielectric matrix are simulated in a spectral range from visible to infra-red by means of Auxiliary Differential Equations (ADE) coupled to a Finite Difference Time Domain (FDTD) method. The electromagnetic field distribution is investigated in gold nanostructures in order to evidence the local field enhancement effect characteristic of the Localized Surface Plasmon Resonance (LPSR).
• Microwave heating-induced DC magnetic flux penetration in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ superconducting thin films
  
  • Kermorvant Julien
  • Mage Jean-Claude
  • Marcilhac Bruno
  • Lemaître Yves
  • Bobo Jean-François
  • van Der Beek Cornelis Jacominus
  , 2012. The magneto-optical imaging technique is used to visualize the penetration of the magnetic induction in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films during surface resistance measurements. The in-situ surface resistance measurements were performed at 7 GHz using the dielectric resonator method. When only the microwave magnetic field $H_{rf}$ is applied to the superconductor, no $H_{rf}$-induced vortex penetration is observed, even at high rf power. In contrast, in the presence of a constant magnetic field superimposed on $H_{rf}$ we observe a progression of the flux front as $H_{rf}$ is increased. A local thermometry method based on the measurement of the resonant frequency of the dielectric resonator placed on the YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin film shows that the $H_{rf}$--induced flux penetration is due to the increase of the film temperature.
• Full characterization and optimization of a femtosecond ultraviolet laser source for time and angle-resolved photoemission on solid surfaces
  
  • Faure Jérôme
  • Mauchain Julien
  • Papalazarou E.
  • Yan W.
  • Pinon J.
  • Marsi M.
  • Perfetti Luca
  Review of Scientific Instruments, American Institute of Physics, 2012, 83, pp.043109. A novel experimental apparatus for time and angle-resolved photoemission on solid surfaces is presented. A 6.28 eV laser source operating at 250 kHz repetition rate is obtained by frequency mixing in nonlinear beta barium borate crystals. This UV light source has a high photon flux of 10(13) photons/s with relatively low number of photons/pulse so that Fermi surface mapping over a wide region of the Brillouin zone is possible while mitigating space charge effects. The UV source has been fully characterized spatially, spectrally, and temporally. Its potential for time and angle-resolved photoemission is demonstrated through Fermi surface mapping and photoexcited electron dynamics in Bismuth. True femtosecond time resolution <65 fs is obtained while the energy resolution of 70 meV appears to be mainly limited by the laser bandwidth. (C) 2012 American Institute of Physics. (10.1063/1.3700190)
  DOI : 10.1063/1.3700190
• Élaboration et étude des propriétés électriques d'un matériau composite nanotubes de carbone alignés - époxy
  
  • Roussel Florent
  , 2012. (NTC) multi-feuillets (MWNTs) synthétisés par CCVD (Catalytic Chemical Vapour Deposition) d'aérosol en tapis de nanotubes continus et verticalement alignés, et d'un matrice polymère époxy. En second lieu, sur la caractérisation de la structure et de la surface de ce matériau. En dernier lieu, sur l'étude de ses propriétés de transport électrique. La conduction électrique à température ambiante est mesurée. D'une part, ceci est fait localement par CS-AFM (Current-Sensing AFM) afin de caractériser les NTCs à l'échelle individuelle. D'autre part à l'échelle macroscopique, pour caractériser les propriétés du matériau à une structure de dimensions exploitables. Cette étude montre un matériau avec une résistivité faible et anisotrope. Des fluctuations importantes (environ facteur 10) de la résistance macroscopique sont observées d'une mesure sur l'autre. La nature de ces fluctuations est discutée. La conduction électrique à basse température (entre 4 et 50◦K) montre la persistance à l'échelle macroscopique d'effets mésoscopiques tels qu'observés sur des NTCs individuels. Notamment une loi d'échelle de la conductance en fonction de la température et de la tension (" anomalie à faible tension ") apparaît, ainsi qu'une loi de localisation faible de la conductance. De plus, la mesure de la distribution de la conductance sur la surface par le CS-AFM a permis de démontrer l'origine de cette persistance par un modèle simple et réaliste.
• Dielectric characteristic of nanocrystalline Na0.5K0.5NbO3 ceramic green body
  
  • Liu Laijun
  • Fang Huiqing
  • Fang Liang
  • Dammak Hichem
  • Pham-Thi Maï
  Journal of Electroceramics, Springer Verlag, 2012, 28, pp.144-148. Dielectric spectroscopy was applied to porous nanocrystalline Na0.5K0.5NbO3 (NKN) ceramic green body, wherein influences of percolation effect and water adsorption at pore surface of the ceramic green body on dielectric response were examined over wide temperature (150 to 450 K) and frequency (100 Hz to 1 MHz) ranges. Dielectric permittivity of the ceramic green body is about 2-3 orders of magnitude higher than that of pure NKN powder or NKN ceramic. Furthermore, the high dielectric permittivity and high humidity sensitivity of the ceramic green body can appear again with aging a period of time in air. The data from this investigation make potential applications for NKN as a giant dielectric material or a humidity sensing material. (10.1007/s10832-012-9695-6)
  DOI : 10.1007/s10832-012-9695-6
• Efficient GW calculations for SnO2, ZnO, and rubrene: The effective-energy technique
  
  • Berger Arjan
  • Reining Lucia
  • Sottile Francesco
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2012, 85 (8), pp.085126. In a recent Rapid Communication [ J. A. Berger, L. Reining and F. Sottile Phys. Rev. B 82 041103 (2010)], we presented the effective-energy technique to evaluate, in an accurate and numerically efficient manner, electronic excitations by reformulating spectral sum-over-states expressions such that only occupied states appear. In our approach all the empty states are accounted for by a single effective energy that can be obtained from first principles. In this work we provide further details of the effective-energy technique, in particular, when combined with the GW method, in which a huge summation over empty states appears in the calculation of both the screened Coulomb interaction and the self-energy. We also give further evidence of the numerical accuracy of the effective-energy technique by applying it to the technological important materials SnO2 and ZnO. Finally, we use this technique to predict the band gap of bulk rubrene, an organic molecular crystal with a 140-atom unit cell. (10.1103/PhysRevB.85.085126)
  DOI : 10.1103/PhysRevB.85.085126
• Crystal Structure of Cold Compressed Graphite
  
  • Amsler Maximilian
  • Flores-Livas Jose A.
  • Lehtovaara Lauri
  • Balima Félix
  • Alireza Ghasemi S.
  • Machon Denis
  • Pailhes Stephane
  • Willand Alexander
  • Caliste Damien
  • Botti Silvana
  • San Miguel Alfonso
  • Goedecker Stefan
  • Marques Miguel A. L.
  Physical Review Letters, American Physical Society, 2012, 108, pp.065501. (10.1103/PhysRevLett.108.065501)
  DOI : 10.1103/PhysRevLett.108.065501
• Tricalcium silicate Ca3SiO5 superstructure analysis: a route towards the structure of the M1 polymorph
  
  • de Noirfontaine Marie-Noëlle
  • Courtial Mireille
  • Dunstetter Frederic
  • Gasecki Gilles
  • Signes-Frehel Marcel
  Zeitschrift für Kristallographie, De Gruyter, 2012, 227 (2), pp.102-112. In this paper, we present a structural model for the M1 polymorph of tricalcium silicate Ca3SiO5 from Powder X-Ray Diffraction (XRD) data, including weak intensity superstructure Bragg lines. As no single crystal is available, this structural model has been deduced using the structural relationships found between the previously known triclinic and monoclinic M3 polymorphs. We find that the better starting set of atomic positions for Rietveld refinement is the triclinic set and not the monoclinic set. A key observation is that the monoclinic M1 structure is closer to the low temperature triclinic T3 structure (within the Golovastikov model) than to the higher temperature monoclinic M3 structure. The unit cell and the set of atomic positions of the two best models, called 3Pc and 3Pn models, are provided. We prefer the 3Pc model for it better reproduces the weak characteristic Bragg lines of the superstructure. (10.1524/zkri.2011.1425)
  DOI : 10.1524/zkri.2011.1425
• Evolutions structurales et microstructurales dans les matériaux du nucléaire.
  
  • Baldinozzi Gianguido
  • Simeone David
  • Gosset Dominique
  • Lunéville Laurence
  • Gorse-Pomonti D.
  • Desgranges Lionel
  • Garcia Philippe
  • Bouffard Serge
  • Monnet Isabelle
  • Zhang Yanwen
  , 2012. The study of nanostructured and conventional materials for nuclear applications can be performed using laboratory diffraction in conjunction with neutron and synchrotron experiments. A selection of results obtained on several classes of materials of nuclear interest is displayed in the panels of this poster, illustrating how accurate and quantitative information can be extracted about symmetry, lattice strain, atomic positions, crystallite size and microstrain. Our investigations at the LRC Carmen are focused at tracking the structural and microstructural changes produced by irradiation.
• CALPHAD formalism for Portland clinker: thermodynamic models and databases
  
  • de Noirfontaine Marie-Noëlle
  • Tusseau-Nenez Sandrine
  • Girod-Labianca Caroline
  • Pontikis V.
  Journal of Materials Science, Springer Verlag, 2012, 47 (3), pp.1471-1479. The so-called CALPHAD method is widely used in metallurgy to predict phase diagrams of multi-component systems. The application of the method to oxide systems is much more recent, because of the difficulty of modelling the ionic liquid phase. Since the 1980s, several models have been proposed by various communities. Thermodynamic databases for oxides are available and still under development. The purpose of this article is to discuss the distinct approaches of the method for the calculation of multi-component systems for Portland cement elaboration. The article gives a state of the art of the most recent experimental data and the various calculations for the CaO-Al2O3-SiO2 phase diagram. A literature review of the three binary sub-systems leads to main conclusions: (i) discrepancies are found in the literature for the selected experimental data, (ii) the phase diagram data in the reference books are not complete and up to date and (iii) the two-sublattices model and the modified quasichemical model can be equally used for the modelling of the aluminates liquid. The predictive feature of the CALPHAD method is illustrated using the CaO-Al2O3-SiO2 system with the two-sublattices model: extrapolated (predicted) and fully-assessed phase diagrams are compared in the clinkering zone of interest. The recent application of the predictive method for the calculations of high-order systems (taking into account Fe2O3, SO3, CaF2, P2O5) shows that the databases developed with the two-sublattices model and the modified quasichemical model are no longer equivalent. (10.1007/s10853-011-5932-7)
  DOI : 10.1007/s10853-011-5932-7
• Approximations for many-body Green's functions: insights from the fundamental equations
  
  • Lani Giovanna
  • Romaniello Pina
  • Reining Lucia
  New Journal of Physics, Institute of Physics: Open Access Journals, 2012, 14, pp.013056. Several widely used methods for the calculation of band structures and photo emission spectra, such as the GW approximation, rely on Many-Body Perturbation Theory. They can be obtained by iterating a set of functional differential equations relating the one-particle Green's function to its functional derivative with respect to an external perturbing potential. In the present work we apply a linear response expansion in order to obtain insights in various approximations for Green's functions calculations. The expansion leads to an effective screening, while keeping the effects of the interaction to all orders. In order to study various aspects of the resulting equations we discretize them, and retain only one point in space, spin, and time for all variables. Within this one-point model we obtain an explicit solution for the Green's function, which allows us to explore the structure of the general family of solutions, and to determine the specific solution that corresponds to the physical one. Moreover we analyze the performances of established approaches like $GW$ over the whole range of interaction strength, and we explore alternative approximations. Finally we link certain approximations for the exact solution to the corresponding manipulations for the differential equation which produce them. This link is crucial in view of a generalization of our findings to the real (multidimensional functional) case where only the differential equation is known. (10.1088/1367-2630/14/1/013056)
  DOI : 10.1088/1367-2630/14/1/013056
• Point defect stability in gamma irradiated aluminoborosilicate glasses: Influence of Yb3+ doping ions
  
  • Ollier N.
  • Pukhkaya V.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2012, 277, pp.121. Yb-doped aluminoborosilicate were irradiated with gamma rays at 10(4), 10(5), 10(6) and 10(7) Gy. The thermal stability as well as the recovery at room temperature of paramagnetic point defects such as Boron Oxygen Hole Center (BOHC), peroxy radicals and E' center were studied. At first, doping with Yb induced a saturation of the E' defect production and more importantly, the E' center recovering temperature was decreased by 50 degrees C. E' and BOHC defects both showed a limited stability at room temperature. By doping with Yb the glasses, the fading time of defects and in particular the BOHC defect recovery was modified. The BOHC defect showed moreover a larger sensitivity to photobleaching compared to the E' centers. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved. (10.1016/j.nimb.2011.12.053)
  DOI : 10.1016/j.nimb.2011.12.053
• Ion-matter interaction: the three-dimensional version of the thermal spike model. Application to nanoparticle irradiation with swift heavy ions NA
  
  • Dufour Ch
  • Khomenkov V.
  • Rizza G.
  • Toulemonde M.
  Journal of Physics D: Applied Physics, IOP Publishing, 2012, 45 (6), pp.NA. In the framework of swift heavy ion-matter interaction, the thermal spike has proved its worth for nearly two decades. This paper deals with the necessary refinement of the computation due to the kind of materials of interest, i.e. nanomaterials such as multilayered systems or composite films constituted of nanocylinders or nanospheres embedded in an insulating matrix. The three-dimensional computation of the thermal spike model is applied for the first time in the case of ions striking layers containing spherical nanoparticles embedded in a silica matrix. The temperature profiles calculated at each point (x, y, z) of the target for a total duration up to 10(-10) s and different values of ion impact parameter allow a possible explanation of the particle shape change under irradiation with swift heavy ions having an energy of several MeVamu(-1) (10.1088/0022-3727/45/6/065302)
  DOI : 10.1088/0022-3727/45/6/065302
• Microstructure of Powellite-Rich Glass-Ceramics: A Model System for High Level Waste Immobilization
  
  • Taurines T
  • Boizot B
  Journal of the American Ceramic Society, Wiley, 2012, 95 (3), pp.1-7. In this study, we synthesized glass-ceramics from glasses in the system SiO 2-B 2 O 3-Na 2 O-CaO-Al 2 O 3-MoO 3-Gd 2 O 3 by various heat treatments. Glass-ceramics contain only one crystalline phase in the bulk: powellite (namely CaMoO 4). The influence of molybdenum and rare earth contents was studied by SEM and XRD. Heat treatments were optimized to lead to a wide range in size and concentration of powellite. Moreover, the molybdenum content left in residual glasses, calculated by XRD quantification, showed that the residual glasses have a similar composition for a given Gd 2 O 3 content after heat treatments. This work has permitted to synthesize two phase glass-ceramics with constant borosilicate glass matrices and powellite crystals with controlled sizes and concentrations. (10.1111/j.1551-2916.2011.05015.x)
  DOI : 10.1111/j.1551-2916.2011.05015.x
• p Doping in Expanded Phases of ZnO: An Ab Initio Study
  
  • Hapiuk D.
  • Marques Miguel A. L.
  • Melinon P.
  • Flores-Livas Jose A.
  • Botti Silvana
  • Masenelli Bruno
  Physical Review Letters, American Physical Society, 2012, 108 (11), pp.NA. The issue of p doping in nanostructured cagelike ZnO is investigated by state-of-the-art calculations. Our study is focused on one prototypical structure, namely, sodalite, for which we show that p-type doping is possible for elements of the V, VI, and VII columns of the periodic table. However, some dopants tend to form dimers, thus impairing the stability of this kind of doping. This difference of behavior is discussed, and two criteria are proposed to ensure stable p doping. (10.1103/PhysRevLett.108.115903)
  DOI : 10.1103/PhysRevLett.108.115903
• Sodium selenide toxicity is mediated by O2-dependent DNA breaks.
  
  • Peyroche Gerald
  • Saveanu Cosmin
  • Dauplais Marc
  • Lazard Myriam
  • Beuneu Francois
  • Decourty Laurence
  • Malabat Christophe
  • Jacquier Alain
  • Blanquet Sylvain
  • Plateau Pierre
  PLoS ONE, Public Library of Science, 2012, 7 (5), pp.e36343. Hydrogen selenide is a recurrent metabolite of selenium compounds. However, few experiments studied the direct link between this toxic agent and cell death. To address this question, we first screened a systematic collection of Saccharomyces cerevisiae haploid knockout strains for sensitivity to sodium selenide, a donor for hydrogen selenide (H(2)Se/HSe(-/)Se(2-)). Among the genes whose deletion caused hypersensitivity, homologous recombination and DNA damage checkpoint genes were over-represented, suggesting that DNA double-strand breaks are a dominant cause of hydrogen selenide toxicity. Consistent with this hypothesis, treatment of S. cerevisiae cells with sodium selenide triggered G2/M checkpoint activation and induced in vivo chromosome fragmentation. In vitro, sodium selenide directly induced DNA phosphodiester-bond breaks via an O(2)-dependent reaction. The reaction was inhibited by mannitol, a hydroxyl radical quencher, but not by superoxide dismutase or catalase, strongly suggesting the involvement of hydroxyl radicals and ruling out participations of superoxide anions or hydrogen peroxide. The (*)OH signature could indeed be detected by electron spin resonance upon exposure of a solution of sodium selenide to O(2). Finally we showed that, in vivo, toxicity strictly depended on the presence of O(2). Therefore, by combining genome-wide and biochemical approaches, we demonstrated that, in yeast cells, hydrogen selenide induces toxic DNA breaks through an O(2)-dependent radical-based mechanism. (10.1371/journal.pone.0036343)
  DOI : 10.1371/journal.pone.0036343
• Kinetic Monte-Carlo simulation of the homoepitaxial growth of MgO\001\ thin films by molecular deposition
  
  • Antoshchenkova Ekaterina
  • Hayoun Marc
  • Finocchi Fabio
  • Geneste Grégory
  Surface Science : A Journal Devoted to the Physics and Chemistry of Interfaces, Elsevier, 2012, 606 (5-6), pp.605-614. A lattice-based kinetic Monte-Carlo (KMC) code has been developed to investigate the MgO\001\ crystal growth from deposition of MgO molecules, as a prototypical case of the growth of oxide thin films. The KMC approach has been designed on the basis of an extensive database including all possible diffusion mechanisms. The corresponding activation energies have been computed through first-principles calculations at zero temperature or from Arrhenius plots of the frequencies obtained by molecular dynamics simulations with empirical potentials. Crystal growth occurs layer by layer, as experimentally observed, and the diffusion of admolecules leads to a high capacity of nucleation, which is enhanced by vacancy diffusion. We have characterized the growth through surface roughness, size distribution and density of the islands, and filling ratios of the growing layers. Moreover, we have analysed the influence of each elementary mechanism on the growth. The best quality of the deposited layers is reached for temperatures larger than 700 K and for pressures smaller than 0.1 Torr. For these conditions, the simulated surface roughness is fully consistent with available experimental results. (C) 2011 Elsevier B.V. All rights reserved. (10.1016/j.susc.2011.11.026)
  DOI : 10.1016/j.susc.2011.11.026