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  1. Radiative energy loss in the absorptive QGP: taming the long formation lengths in coherent emission
    Erschienen: 2012
    Verlag:  HAL CCSD

    contribution to the International Meeting "Excited QCD", Peniche, Portugal, 06 - 12 May 2012 ; In an absorptive plasma, damping of radiation mechanisms can influence the bremsstrahlung formation in case of large radiation formation lengths. We study... mehr

     

    contribution to the International Meeting "Excited QCD", Peniche, Portugal, 06 - 12 May 2012 ; In an absorptive plasma, damping of radiation mechanisms can influence the bremsstrahlung formation in case of large radiation formation lengths. We study qualitatively the influence of this effect on the gluon bremsstrahlung spectrum off heavy quarks in the quark-gluon plasma. Independent of the heavy-quark mass, the spectrum is found to be strongly suppressed in an intermediate gluon energy region which grows with increasing gluon damping rate and increasing energy of the heavy quark. Thus, just as polarization effects in the plasma render the bremsstrahlung spectra independent of the quark mass in the soft gluon regime, damping effects tend to have a similar impact for larger gluon energies.

     

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    Übergeordneter Titel: Excited QCD 2012 ; http://hal.in2p3.fr/in2p3-00730449 ; Excited QCD 2012, May 2012, Peniche, Portugal
    Schlagworte: [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph]; [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th]
  2. J/psi elliptic flow measurement in Pb-Pb collisions at \sqrt{s_{NN}} = 2.76 TeV at forward rapidity with the ALICE experiment
    Autor*in: Massacrier, L.
    Erschienen: 2012
    Verlag:  HAL CCSD

    proceeding of Hard Probes 2012 conference ; J/psi suppression induced by color screening of its constituent quarks was proposed 26 years ago as a signature of the formation of a quark gluon plasma in heavy-ion collisions. Recent results from ALICE in... mehr

     

    proceeding of Hard Probes 2012 conference ; J/psi suppression induced by color screening of its constituent quarks was proposed 26 years ago as a signature of the formation of a quark gluon plasma in heavy-ion collisions. Recent results from ALICE in Pb-Pb collisions exhibit a smaller suppression with respect to previous measurements at the SPS and RHIC. The study of azimuthal anisotropy in particle production gives information on the collective hydrodynamic expansion at the early stage of the fireball, where the matter created in high-energy nuclear collisions is expected to be in a deconfined state. In particular, J/psi elliptic flow v2 is important to test the degree of thermalization of heavy quarks. Together with the production yields, the elliptic flow is a powerful observable to address the question of suppression and regeneration of J/psi in QGP. We present the first inclusive J/psi elliptic flow measurement performed with the muon spectrometer of ALICE, in Pb-Pb collisions, at forward rapidity. Integrated and pT-differential v2 results are presented and a comparison with recent STAR results and with a parton transport model is also performed.

     

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    Übergeordneter Titel: Hard Probes 2012 ; http://hal.in2p3.fr/in2p3-00730928 ; Hard Probes 2012, May 2012, Cagliari, Italy
    Schlagworte: [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
  3. Molecular modeling of the swelling properties and interlayer structure of Cs, Na, K-Montmorillonite: Effects of charge distribution in the clay layers
    Erschienen: 2012
    Verlag:  HAL CCSD

    Safe and sustainable management of nuclear waste poses major scientific challenges to make the environmental footprint of nuclear energy as small as possible for very long periods of time. As many other countries, France is considering the deep... mehr

     

    Safe and sustainable management of nuclear waste poses major scientific challenges to make the environmental footprint of nuclear energy as small as possible for very long periods of time. As many other countries, France is considering the deep geological disposal (in the Callovo-Oxfordian (COx) argillite formations of the Paris basin) as a reliable way of storing high-level radioactive waste in order to provide adequate protection for humans and the environment. In addition to being proven geologically stable for million years, the natural and engineered clay barriers can benefit from many favorable properties, such as low permeability, high sorption capacity, etc. The mineralogical composition of the Callovo-Oxfordian argillite shows about 41% of clay minerals (23% of interstratified illite/smectite, 14% of illite-type minerals, 2% kaolinite and 2% chlorite) [1,2]. A non-negligible amount of organic matter is also present (~1%) [3], and it is known that the interaction of natural organic matter (NOM) with radionuclides and clays can affect the solubility and toxicity of trace elements in natural aqueous environments [4,5]. Reliable prediction of the behaviour of radionuclides and their transport and retention in clayey formations at nuclear waste repositories requires detailed molecular scale understanding of these complex multicomponent systems. Computational molecular modelling has already become an important tool in the study of thermodynamic, structural and transport properties of hydrated clays (e.g., [6-8]). As the first step in our study of the effects of organic molecules on the adsorption and transport of radionuclides in hydrated clay systems we have investigated the effects of the ordering in charge distributions on the swelling behavior of simulated clays. Montmorillonite was chosen as a model of smectite clay. Montmorillonite structure consists of aluminum-oxygen octahedral sheet sandwiched between two opposing silicon-oxygen tetrahedral sheets giving rise to a 2:1 clay mineral. Isomorphic substitutions in the tetrahedral and octahedral sheets are responsible of the negative layer charge of montmorillonite clay minerals having the chemical composition (Si8-xXx)(Al4-yYy)O20(OH)4 where X = Al, Y = Mg, Fe.[9]. The montmorillonite models for our study are based on a pyrophillite unit cell structure (5.16Å×8.966Å×9.347Å) obtained from the crystallographic data of Lee et al. [10]. The 4×4×2 simulation supercells were built and substitutions were made in the pyrophillite structure in order to approximate as close as possible the chemical composition of Wyoming montmorillonite M24(Si248Al8)(Al112Mg16)O640(OH)128, where M is either Cs+, Na+, or K+ [9]. We explored three different models of substitution distributions. In the first model, the substitutions were uniformly and orderly distributed within the tetrahedral and octahedral sheets. In the second model, the substituted positions were kept ordered in the octahedral sheets but made disordered in the tetrahedral one. In the third model, the substituted positions of the octahedral sites were additionally made disordered. In order to study the swelling behavior of these montmorillonites, molecular dynamics (MD) simulations were run in the NPzT statistical ensemble (T = 298 K, Pz = 1 bar) for each of the three different substitution models and with 22 different hydration states ranging from 0 to 700 mgwater/gclay (from 0 to 42 H2O molecules per one monovalent cation). All MD runs were performed for a total of 2 ns using the CLAYFF force field [11]. At the beginning of the simulations, the cations were placed at the midplane of the clay interlayer space and water molecules were added randomly. After the system reached equilibrium, the last 1ns of each MD trajectory was used to compute the clay basal spacing and the swelling thermodynamic properties: hydration energy, immersion energy, isosteric heat of adsorption. The MD simulation results indicate that in addition to the commonly observed 1-layer and 2-layer hydrates, stable hydration states corresponding to 3-layer and 4-layer hydrates can also be distinguished. The stable states corresponding to the minima of hydration energy were then selected to run further 500 ps NVT-ensemble MD simulations at the same temperature and with the volume fixed at the average value resulting from the corresponding previous NPzT simulation. The equilibrium parts of these NVT-simulated trajectories were then used to calculate the structural (radial distribution functions, atomic density profiles) and dynamical (diffusion coefficient) properties of the hydrated montmorillonite. References [1] ERM (1997) Echantillons d'argiles du forage EST104 : Etude minéralogique approfondie. Rapport ANDRA n° D.RP.0ERM.97.008 [2] ERM (1996b) Caractérisation d'échantillons d'argiles du forage EST103. Rapport ANDRA n° B.RP.0ERM.96.003 [3] ANDRA (2005) Dossier 2005 Argile, Référentiel du site de Meuse Haute Marne. C.R.P.ADS.04.0022 Andra : Paris [4] Buffle, J. (1988) Complexation Reactions in Aquatic Systems: An Analytical Approach; Ellis Horwood Ltd.:Chichester, p 692. [5] Tipping, E. (2002) Cation Binding by Humic Substances, Cambridge University Press: Cambridge, p 434. [6] Smith, D.E., Langmuir, 14, 5959-5967 (1998). [7] Rotenberg, B., Marry, V., Vuilleumier, R., Malikova, N., Simon, C., Turq, P., Geochim. Cosmochim. Acta, 71, 5089-5101 (2007). [8] Liu, X.D., Lu, X.C., Wang, R.C., Zhou, H.Q. Geochim. Cosmochim. Acta, 72, 1837-1847 (2008). [9] Tsipursky, S.I., Drits, V.A. Clay Minerals, 19, 177-193 (1984). [10] Lee, J.H. and Guggenheim, S. American Mineralogist, 66, 350-357 (1981). [11] Cygan, R.T., Liang, J.J., Kalinichev, A.G. Journal of Physical Chemistry B, 108, 1255-1266 (2004).

     

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    Übergeordneter Titel: 5th International meeting "Clays in Natural and Engineered Barriers for Radioactive Waste Confinement" ; http://hal.in2p3.fr/in2p3-00769152 ; 5th International meeting "Clays in Natural and Engineered Barriers for Radioactive Waste Confinement", Oct 2012, Montpellier, France
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  4. Effects of surface cations on the structure and dynamics of the hydrogen-bonding network at the illite-water interface: A molecular dynamics simulation study
    Erschienen: 2012
    Verlag:  HAL CCSD

    Safe and sustainable management of nuclear energy poses major scientific and engineering challenges, one of which is the necessity to make the environmental impacts of the long-term nuclear waste storage as small as possible. This requires detailed... mehr

     

    Safe and sustainable management of nuclear energy poses major scientific and engineering challenges, one of which is the necessity to make the environmental impacts of the long-term nuclear waste storage as small as possible. This requires detailed understanding and prediction of the behaviour of radionuclides and their migration and retention properties in the geological formations of nuclear waste repositories. The Callovo-Oxfordien rock formation of the French nuclear repository site is mainly composed of clay minerals (illite, smectite and interstratified illite/smectite), quartz, calcite, with some non-negligible amount of organic matter. The adsorption of water can change the properties of mineral surfaces, including protonation state, surface charge, structure, and reactivity [1]. Similarly, the properties of interfacial water are strongly affected by the mineral substrate structure and composition. Recent advances in experimental techniques such as FTIR [2], ellipsometry [3], synchrotron X-ray scattering [4], sum-frequency vibrational spectroscopy [5] are capable of probing the properties of mineral-water interfaces at different levels of hydration. However, the surface-specific results of these experiments are often difficult to quantitatively interpret without having a reliable molecular scale picture of the underlying physical and chemical processes. Molecular computer simulations have become one of the most important tools in the study of such interfacial systems and phenomena by providing invaluable atomistic information on the underlying chemical and physical processes. The present study is aimed at investigating the structural and dynamics effects of three different cations (K+, NH4+, and H3O+) exchanged at the hydrated surface of muscovite mica, which is taken here as a model illite. Molecular dynamics computer simulations were performed using the CLAYFF force field [6] to investigate the important differences of the H-bonding configurations formed by the sorbed species, including H2O, H3O+, and NH4+, in contrast to the behavior of spherical metal ions, such as K+. At the muscovite (001) surface, H2O can donate 2 H-bonds (to other H2O and/or to the surface O atoms) and accept 2 H-bonds (from other H2O), but it can also partially replace surface K+, because the hydrogens of H2O bear some positive charge. This behavior was observed in previous MD simulations of the mica surface [7]. Such surface-adsorbed H2O molecules have their negatively charged oxygen atoms exposed to the fluid phase and accessible for either H-bond acceptance from other H2Os or hydration of metal cations in outer-sphere coordination. For surface H3O+, the charges on the hydrogens are slightly higher than those of H2O, but the oxygen atom of hydronium is now almost hydrophobic, and cannot participate in a H-bond network (e.g., [8]). In contrast, NH4+ can equally well donate H-bonds to the surface O atoms and to the neighboring H2O molecules, but it cannot participate in the hydration shell of a displaced metal cation. Thus, three similar species (H2O - two HB donors and 2 HB acceptors; H3O+ - 3 HB donors and no acceptors; NH4+ - 4 HB donors, no acceptors) can provide for three greatly different structural, energetic, and dynamical situations at the muscovite-water interface. Since the hydrogen-bonding network in any aqueous media provides a natural mechanism of forming low-barrier reaction paths for proton transfer in such systems, it is also an important phenomenon controlling the surface reactivity under various pH conditions. In addition, a detailed study of the structural characteristics of surface-adsorbed NH4+ provides a way for better understanding of the mechanisms of adsorption for organic molecules having amino-groups in their structure, which is quite common for natural organic matter (e.g., [9]). Each of the three systems was simulated at 7 different hydration states providing information on the structure and dynamics of the adsorbed water film in a wide range of relative humidity conditions. The atomic density profiles of water show significant layering at all hydration levels and the layering strongly depends upon the nature of the ionic species present on the surface. Our studies support the fact that the H3O+ ion is less strongly bound when compared to K+ on the muscovite surface as observed in earlier studies [7]. At muscovite surfaces, both NH4+ and H3O+ cations establish strong hydrogen bonds with the surface bridging oxygen atoms and also with the neighbouring H2O molecules at all hydration levels. However, we observed that the interactions are different for both species at low hydration levels (<< molecular monolayer). At low hydration levels, H3O+ prefers to strongly bind as 3-cordinated species to the surface than with the neighbouring waters molecules. However, as the hydration levels increase, H3O+ binds as 2-cordinated species with the surface as is indicated by hydrogen bonding analysis (Figure 1). In contrast, irrespective of the hydration levels, NH4+ ion strongly interacts with the surface as 3-cordinated species because of its tetrahedral geometry. At the same time, we observe from hydrogen bond analysis that the hydrogen bonding network of water has been strongly influenced by the nature of the surface cations present at the mineral-water interface. The dynamics of water molecules were examined by self-diffusion coefficients from the mean square displacement of water oxygen. The diffusion mechanism is similar for K+ and NH4+ but was different for H3O+, in particular at the low hydration states. Furthermore, the spatial and orientation distributions of H2O and ions at the muscovite-water surface are analyzed in quantitative detail. All the simulation results are compared with available experimental data and the results of previous molecular simulations to provide reliable molecular view of the ions and water at the muscovite surface. References [1] Henderson, M. A. Surf. Sci. Rep. 2002, 46, 5-308. [2] Cantrell and G. E. Ewing. J. Phys. Chem. B, 2001, 105, 5434-5439. [3] Beaglehole, D and Christenson, H. K. J. Phys. Chem, 1992, 96, 3395-3403. [4] Fenter, P. and Sturchio, N. C. Progress in Surface Science, 2004, 77, 171-258. [5] Shen, Y. R. and Ostroverkhov, V. Chem. Rev., 2006, 106, 1140-1154. [6] Cygan, R.T., Liang, J.J., and Kalinichev, A.G. J. Phys. Chem. B, 2004, 108, 1255-1266. [7] Wang, J., Kalinichev, A., Kirkpatrick, R., Cygan, R. J. Phys. Chem B., 2005, 109, 15893-15905. [8] Petersen, P.B. and Saykally, R.J. J. Phys. Chem. B, 2005, 109, 7976-7980. [9] Leenheer, J.A. Annals of Environmental Science, 2009, 3, 1-130.

     

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    Übergeordneter Titel: 5th International meeting "Clays in Natural and Engineered Barriers for Radioactive Waste Confinement" ; http://hal.in2p3.fr/in2p3-00769153 ; 5th International meeting "Clays in Natural and Engineered Barriers for Radioactive Waste Confinement", Oct 2012, Montpellier, France
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  5. Ethylene glycol intercalation in smectites. Molecular dynamics simulation studies
    Erschienen: 2012
    Verlag:  HAL CCSD

    Intercalation of ethylene glycol in smectites (glycolation) is widely used to discriminate smectites and vermiculites from other clays and among themselves. During this process, ethylene glycol molecules enter into the interlayer spaces of the... mehr

     

    Intercalation of ethylene glycol in smectites (glycolation) is widely used to discriminate smectites and vermiculites from other clays and among themselves. During this process, ethylene glycol molecules enter into the interlayer spaces of the swelling clays, leading to the formation of two-layer structure (~17 Å) in the case of smectites, or one-layer structure (~14 Å) in the case of vermiculites. In spite of the relatively broad literature on the understanding/characterization of ethylene glycol/water-clays complexes, the simplified structure of this complex presented by Reynolds (1965) is still used in the contemporary X-ray diffraction computer programs, which simulate structures of smectite and illite-smectite. The monolayer structure is only approximated using the assumption of the interlayer cation and ethylene glycol molecules lying in the middle of interlayer spaces. This study was therefore undertaken to investigate the structure of ethylene glycol/water-clays complex in more detail using molecular dynamics simulation. The structural models of smectites were built on the basis of pyrophyllite crystal structure (Lee and Guggenheim, 1981), with substitution of particular atoms. In most of simulations, the structural model assumed the following composition, considered as the most common in the mixed layer illite-smectites (Środoń et al. 2009): EXCH0.4(Si3.96Al0.04)(Al1.46Fe0.17Mg0.37)O10(OH)2 Atoms of the smectites were described with CLAYFF force field (Cygan et al., 2004), while atoms of water and ethylene glycol with flexible SPC (Berendsen et al., 1981) and OPLS (Jorgensen et al., 1996) force fields, respectively. Ewald summation was used to calculate long range Coulombic interactions and the cutoff was set at 8.5 Å. Results of the simulations show that in the two-layer glycolate the content of water is relatively small: up to 0.8 H2O per half of the smectite unit cell (thereafter phuc). Clear thermodynamic preference of mono- or two-layer structure of the complex is observed for typical smectite. Based on the calculated radial distribution functions, it was confirmed that water and ethylene glycol molecules compete for the coordination sites of the calcium ions in the clay interlayers. It was also found that the differences in the smectite layer charge, charge location, and the type of the interlayer cation affect the ethylene glycol and water packing in the interlayer space and as result have strong influence on the basal spacing and on the structure of complex. Varying amounts and ratio of both ethylene glycol and water are, however, the most important factor influencing the extent of the smectite expansion. Comparison of two-layer structure obtained from molecular dynamics simulations with previous models leads to the conclusion that the arrangement of ethylene glycol molecules in the interlayers, used in simulations of X-ray diffractograms of clays, should be modified. In contrast to the Reynolds (1965) model, the main difference is that, for different location of the clay charge, interlayer ions tend to change their positions. In the case of montmorillonite, calcium ions are located in the middle of the interlayer space, while for beidellite they are located much closer to the clay surface. Water in these structures does not form distinct layers but is distributed rather broadly with a tendency to be concentrated close to the smectite surface. One-layer structure of ethylene glycol/water-smectite complex, characteristic of vermiculite was also proposed. References Berendsen, H.J.C., Postma, J.P.M., van Gunsteren, W.F., Hermans, J. (1981) Interaction models for water in relation to protein hydration. In Intermolecular Forces; Pullman, B., Ed.; D. Reidel: Amsterdam, pp 331. Cygan, R. T., Liang, J. J., and Kalinichev, A. G. (2004) Molecular models of hydroxide, oxyhydroxide, and clay phases and the development of a general force field. Journal of Physical Chemistry B, 108, 1255-1266. Jorgensen,W.L., Maxwell, D.S., Tirado-Rives, J. (1996) Development and testing of the OPLS all-atom force field on conformational energetics and properties of organic liquids. J. Am. Chem. Soc., 118, 11225-11236. Lee J.H., Guggenheim S. (1981) Single crystal X-ray refinement of pyrophyllite-1Tc. American Mineralogist, 66, 350-357 Reynolds R. C. (1965) An X-ray study of an ethylene glycol-montmorillonite complex. American Mineralogist, 50, 990-1001 Środoń J., Zeelmaekers E., Derkowski A. (2009) The charge of component layers of illite-smectite in bentonites and the nature of end-member illite. Clays and Clay Minerals, 57, 650-672

     

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    Übergeordneter Titel: 5th International meeting "Clays in Natural and Engineered Barriers for Radioactive Waste Confinement" ; http://hal.in2p3.fr/in2p3-00769154 ; 5th International meeting "Clays in Natural and Engineered Barriers for Radioactive Waste Confinement", Dec 2012, Montpellier, France
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  6. Molecular Modeling of the Swelling Properties and Interlayer Structure of Cs, and K-Montmorillonites: Effects of Charge Distribution in the Clay Layers
    Erschienen: 2012
    Verlag:  HAL CCSD

    Reliable prediction of the behaviour of radionuclides and their transport and retention in clayey formations at nuclear waste repositories requires detailed molecular scale understanding of these complex multicomponent systems. As the first step in... mehr

     

    Reliable prediction of the behaviour of radionuclides and their transport and retention in clayey formations at nuclear waste repositories requires detailed molecular scale understanding of these complex multicomponent systems. As the first step in our study of the effects of organic molecules on the adsorption and transport of radionuclides in hydrated clay systems we have investigated the effects of the ordering in charge distributions on the swelling behavior of montmorillonite (a smectite clay). Montmorillonite layered structure consists of aluminum-oxygen octahedral sheet sandwiched between two opposing silicon-oxygen tetrahedral sheets giving rise to a 2:1 clay mineral. Isomorphic substitutions in the tetrahedral and octahedral sheets are responsible of the negative layer charge of montmorillonite clay minerals having the chemical composition (Si8-xXx)(Al4-yYy)O20(OH)4 where X = Al3+, Y = Mg2+, Fe2+.[1]. The montmorillonite models for our study are based on a pyrophillite unit cell structure (5.16Å×8.966Å×9.347Å) obtained from the crystallographic data of Lee et al. [2]. The 4×4×2 simulation supercells were built and substitutions were made in the pyrophillite structure in order to approximate as close as possible the chemical composition of Wyoming montmorillonite [1] M24(Si248Al8)(Al112Mg16)O640(OH)128, where M is either Cs+, or K+. We have explored three different models of the substitution distributions. In the first model, the substitutions were uniformly and orderly distributed within the tetrahedral and octahedral sheets. In the second model, the substituted positions were kept ordered in the octahedral sheets but made disordered in the tetrahedral one. In the third model, the substituted positions of the octahedral sites were additionally made disordered. In order to study the swelling behavior of these montmorillonites, NPT-ensemble molecular dynamics (MD) simulations were run at T = 298 K and P = 1 bar for each of the three different substitution models and with 23 different hydration states ranging from 0 to 700 mgwater/gclay (from 0 to 42 H2O molecules per one monovalent cation). All MD runs were performed for a total of 2 ns using the CLAYFF force field [3]. After the system reached equilibrium, the last 1ns of each MD trajectory was used to compute the clay basal spacing and the swelling thermodynamic properties: hydration energy, immersion energy, isosteric heat of adsorption. These calculations indicate that in addition to the commonly observed 1-layer and 2-layer hydrates, stable hydration states corresponding to 3-layer and 4-layer hydrates can also be distinguished. These stable states (minima of hydration and immersion energies) were then selected to run further 500 ps NVT-ensemble MD simulations at the same temperature. The equilibrium parts of these NVT-simulated trajectories were then used to calculate radial distribution functions and atomic density profiles of the interlayer species in hydrated montmorillonites. References [1] Tsipursky, S.I., Drits, V.A. Clay Minerals, 19, 177-193 (1984). [2] Lee, J.H. and Guggenheim, S. American Mineralogist, 66, 350-357 (1981). [3] Cygan, R.T., Liang, J.J., Kalinichev, A.G. Journal of Physical Chemistry B, 108, 1255-1266 (2004).

     

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    Übergeordneter Titel: XIIIe journées nationale de radiochimie et de chimie nucléaire ; http://hal.in2p3.fr/in2p3-00769157 ; XIIIe journées nationale de radiochimie et de chimie nucléaire, Oct 2012, Nantes, France
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  7. Molecular Dynamics Simuation of Cs+ on the Hydrated Muscovite Surface: Local Structural Environment and Dynamics
    Erschienen: 2012
    Verlag:  HAL CCSD

    Adsorption of metal cations on mineral surfaces often controls their distribution in both natural and technological environments. The Callovo-Oxfordian (COx) formation, consisting largely of clay minerals like illite and smectite, is the location... mehr

     

    Adsorption of metal cations on mineral surfaces often controls their distribution in both natural and technological environments. The Callovo-Oxfordian (COx) formation, consisting largely of clay minerals like illite and smectite, is the location investigated in France as a site for geological nuclear waste disposal and storage. The uptake of radionuclides by layered clay minerals is the principal retention process for their diffusion. Hence, detailed molecular-scale understanding of the adsorption mechanisms of radionuclides on silicate minerals is essential, because it can significantly influence their mobility under the conditions of nuclear waste repositories. Cs+ ion is one of the important components of nuclear waste that is highly soluble in water and migrates easily in surface and sub-surface environments. The atomically smooth surface of muscovite mica, KAl2(Si3Al)O10(OH)2 is often used as an accurate model of illite clay. Experimental studies suggest that Cs+ ion adsorbs directly at the muscovite surface as an "inner sphere complex" [1]. We have investigated the structure and dynamics of Cs+ (exchanged for K+) and H2O molecules at the surface of muscovite at two different hydration levels by molecular dynamics (MD) computer simulations using fully flexible CLAYFF force field [2]. At the muscovite (001) surface, water molecules can donate 2 hydrogen bonds (to other H2O and/or to the surface O atoms) and accept 2 H-bonds (from other H2O). Water molecules can also partially replace surface cations, because their hydrogens bear some positive charge. Such surface-adsorbed H2O molecules have their negatively charged oxygen atoms exposed to the fluid phase and accessible for either H-bond acceptance from other H2Os or for their coordination of surface cations in the inner-sphere or outer-sphere configuration. Atomic density profiles of the surface species evidently support the presence of Cs+ as inner sphere complexes at the muscovite interface. Angular distributions of H2O molecular orientations with respect to the muscovite surface have also been studied, as well as the dynamical behaviour of surface species in terms of their self-diffusion coefficients, H-bonding time correlation functions, and residence times. The comparison of the surface behaviour at two different hydration states and the topological details of the interfacial H-bonding network provide new insight into the structure and dynamics of hydrated Cs+ at confined geometries. The MD simulation results are compared with available experimental data and the results of previous molecular simulations [3] to provide reliable molecular view of the hydrated Cs+ ions at the surface of illite. References [1] Kim, Y., Kirkpatrick, J.R., Cygan, R.T. Geochim. Cosmochim Acta, 60, 4059-4074 (1996). [2] Cygan, R.T., Liang, J.J., Kalinichev, A.G. J. Phys. Chem. B, 108, 1255-1266 (2004). [3] Wang, J.W., Kalinichev, A.G., Kirkpatrick, R.J., Cygan, R.T. J. Phys. Chem. B, 109, 15893-15905 (2005).

     

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    Medientyp: Konferenzveröffentlichung; Weitere
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    Übergeordneter Titel: XIIIe journées nationale de radiochimie et de chimie nucléaire ; http://hal.in2p3.fr/in2p3-00769158 ; XIIIe journées nationale de radiochimie et de chimie nucléaire, Oct 2012, Nantes, France
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  8. Slow diffusional dynamics of water in cement nanopores: Multiscale challenges for atomistic modeling (topic leader)
    Erschienen: 2012
    Verlag:  HAL CCSD

    Molecular modeling of the properties of aqueous solutions confined in the nanopores and at the interfaces of cementitious materials is complicated by the significant structural and compositional heterogeneity of these phases and also by the fact that... mehr

     

    Molecular modeling of the properties of aqueous solutions confined in the nanopores and at the interfaces of cementitious materials is complicated by the significant structural and compositional heterogeneity of these phases and also by the fact that many of the important processes span several orders of magnitude both in time and in length. Here we present an attempt to quantify the diffusional dynamics of 0.25 M KCl aqueous solution in contact with a model C-S-H binding phase (tobermorite) on the basis of molecular dynamics computer simulations. At the (001) surface of tobermorite, two types of H2O molecules can be effectively distinguished: the ones that spend most of their time within channels between the drierketten chains of silica on the tobermorite surface, and the more mobile adsorbed molecules that reside right above the interface. Within the channels, H2O molecules donate H-bonds to both the bridging and non-bridging oxygens of the Si-tetrahedra as well as to other H2O. Some of these molecules form particularly strong H-bonds persisting well over 100 ps, but many others undergo frequent librational motions and occasional diffusional jumps from one surface site to another. The average diffusion coefficients of the surface-associated H2O molecules that spend most of their time in the channels and those that lie above the nominal interface differ by about one order of magnitude (DH2O[internal]=5.0×10−11 m2/s and DH2O[external]=6.0×10−10 m2/s, respectively). The average diffusion coefficient for all surface-associated H2O molecules is about 1.0×10−10 m2/s. All of these values are significantly less than the value of 2.3×10−9 m2/s, characteristic of H2O self-diffusion in bulk liquid water. The MD simulations provided an opportunity to further quantify these relatively slow diffusional motions of H2O at the tobermorite interface on the longer time- and length- scale in terms of the Van Hove self-correlation function (VHSCF). The emerging picture is in surprisingly good agreement with available experimental data on the dynamics of surface-associated water in similar cement materials obtained by 1H NMR [1,2]. 1. Korb J.P., Monteilhet L., McDonald P.J., Mitchell J., Microstructure and texture of hydrated cement-based materials: A proton field cycling relaxometry approach. Cement and Concrete Research, 37, 2007, 295-302. 2. Korb J.P., NMR and nuclear spin relaxation of cement and concrete materialsCurrent Opinion in Colloid & Interface Science, 14, 2009, 192-202.

     

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    Übergeordneter Titel: International US-Poland Workshop "Multiscale Computational Modeling of Cementitious Materials" ; http://hal.in2p3.fr/in2p3-00769185 ; International US-Poland Workshop "Multiscale Computational Modeling of Cementitious Materials", Oct 2012, Kraków, Poland
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  9. Structure and Energetics of Smectite Interlayer Hydration: Molecular Dynamics Investigations of Na- and Ca Hectorite

    Molecular-scale interactions present at mineral-water interfaces and in clay interlayer galleries control numerous environmental processes, including chemical interactions in soils and transport of nutrients and pollutants through them.[1-4]... mehr

     

    Molecular-scale interactions present at mineral-water interfaces and in clay interlayer galleries control numerous environmental processes, including chemical interactions in soils and transport of nutrients and pollutants through them.[1-4] Understanding these processes requires accurate knowledge of the structure, energetics, and dynamics of the interaction among the mineral substrate, ions, and water molecules.[5, 6] Challenges to this objective include experimental difficulties in probing these interfaces and interlayers at the molecular scale; fully characterizing the mineral substrate; and identifying how the mineral surface, ions, and water molecules each contribute to the overall structure, energetics, and dynamics of these systems.[6] Linked computational molecular dynamics (MD) simulations and experimental nuclear magnetic resonance (NMR) studies are particularly effective in addressing these issues.[7-9] Here we focus on MD studies of Na- and Ca-smectite (hectorite) interlayer galleries to provide a molecular-scale picture of the structure and dynamics of their hydration[9, 10] and to complement our earlier NMR investigations of these systems.[7-9] Classical MD simulations were undertaken in the NPT and NVT ensembles to determine the structural and energetic changes with increasing hydration with focus on the single- and double-layer hydrates. The results show substantial changes in the hydration of the interlayer cations, the orientations of the water molecules, the hydrogen bond network involving the water molecules and basal oxygen atoms, and the resulting potential energies as the interlayer gallery expands. [1] Scheidegger et al. (1996) Soil Science 161 813-831. [2] Stumm (1997) Colloids and Surfaces A-Physicochemical and Engineering Aspects 120 143-166. [3] O'Day (1999) Reviews of Geophysics 37 249-274. [4] Koretsky (2000) Journal of Hydrology 230 127-171. [5] Wang et al. (2001) Chemistry of Materials 13 145-150. [6] Wang et al. (2006) Geochimica et Cosmochimica Acta 70 562-582. [7] Bowers et al. (2008) Journal of Physical Chemistry C 112 6430-6438. [8] Bowers et al. (2011) Journal of Physical Chemistry C 115 23395-23407. [9] Bowers et al. (2012), unpublished. [10] Morrow et al. (2012) Journal of Physical Chemistry C, submitted.

     

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    Format: Online
    Übergeordneter Titel: Symposium 8g: Structure and dynamics of ions and water at mineral-water interfaces: insights from experimental and computational studies, 2012 Goldschmidt Conference ; http://hal.in2p3.fr/in2p3-00769208 ; Symposium 8g: Structure and dynamics of ions and water at mineral-water interfaces: insights from experimental and computational studies, 2012 Goldschmidt Conference, Jun 2012, Montreal, Canada
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  10. Molecular structure and dynamics of nano-confined aqueous solutions: Computer simulations of clay, cement, and polymer membranes
    Erschienen: 2012
    Verlag:  HAL CCSD

    Molecular-scale knowledge of the thermodynamic, structural, and transport properties of water confined by interfaces and nano-pores of various materials is crucial for quantitative understanding and prediction of many natural and technological... mehr

     

    Molecular-scale knowledge of the thermodynamic, structural, and transport properties of water confined by interfaces and nano-pores of various materials is crucial for quantitative understanding and prediction of many natural and technological processes, including carbon sequestration, water desalination, nuclear waste storage, cement chemistry, fuel cell technology, etc. Experimental nanoscale studies of such systems are not always feasible, and their results often require considerable interpretation in the efforts to extract surface- and confinement-specific quantitative information from the measurements. Computational molecular modeling significantly complements such efforts and provides invaluable molecular-scale background for better understanding of the specific effects of the substrate structure and composition on the structure, dynamics and reactivity of interfacial and nano-confined aqueous solutions. Based on the successful development and implementation of the CLAYFF force field (Cygan et al., 2004), we have recently performed a series of molecular dynamics simulations of aqueous interfaces with several representative inorganic and organic nanoporous materials (Ahn et al., 2008; Kalinichev et al., 2007, 2010; Wang et al., 2006, 2009) in order to better understand and quantify the effects of the substrate composition and structure on the properties of interfacial and nano-confined aqueous solutions. Individual H2O molecules and hydrated ions at interfaces simultaneously participate in several dynamic processes, which can be characterized by different, but equally important time- and length- scales. The first molecular layer of interfacial water at all substrates is often highly ordered, indicating reduced translational and orientational mobility of the H2O molecules. However, this ordering can not be simply described as "ice-like", but rather resembles the behavior of supercooled water or amorphous ice, although with significant substrate-specific variations. These results help to interpret experimental NMR, IR, X-ray, and neutron scattering measurements performed for the same systems. Ahn, W.-Y., Kalinichev, A.G., Clark, M.M. (2008) Effects of background cations on the fouling of polyethersulfone membranes by natural organic matter: Experimental and molecular modeling study. J.Membr.Sci., 309,128-140. Cygan R.T., Liang J.-J., Kalinichev A.G. (2004) Molecular models of hydroxide, oxyhydroxide, and clay phases and the development of a general force field. Journal of Physical Chemistry B, 108, 1255-1266. Kalinichev A.G., Wang, J., Kirkpatrick R. J. (2007) Molecular dynamics modeling of the structure, dynamics and energetics of mineral-water interfaces: Application to cement materials. Cement and Concrete Res., 37, 337-347. Kalinichev, A.G., Kumar, P., Kirkpatrick, R.J. (2010) Effects of hydrogen bonding on the properties of layered double hydroxides intercalated with organic acids: MDF computer simulations. Philos. Mag., 90, 2475-2488. Wang J., Kalinichev A.G., Kirkpatrick R.J. (2006) Effects of substrate structure and composition on the structure, dynamics and energetics of water on mineral surfaces: MD modeling study. Geochim. Cosmochim. Acta, 70, 562-582. Wang J., Kalinichev A.G., Kirkpatrick R.J. (2009) Asymmetric hydrogen bonding and orientational ordering of water at hydrophobic and hydrophilic surfaces: A comparison of water/vapor, water/talc, and water/mica interfaces. J.Phys.Chem.C, 113, 11077-11085.

     

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    Übergeordneter Titel: NATO Advanced Research Workshop on the Physical Chemistry of Capillary and Bound/Confined Liquids ; http://hal.in2p3.fr/in2p3-00769209 ; NATO Advanced Research Workshop on the Physical Chemistry of Capillary and Bound/Confined Liquids, May 2012, Ein Bokek, Israel
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  11. Computational molecular modeling for nuclear waste management and other radiochemical applications (invited talk)
    Erschienen: 2012
    Verlag:  HAL CCSD

    Safe and sustainable management of nuclear energy poses major scientific and engineering challenges, one of which is the necessity to make the environmental impacts of the long-term nuclear waste storage as small as possible. This requires... mehr

     

    Safe and sustainable management of nuclear energy poses major scientific and engineering challenges, one of which is the necessity to make the environmental impacts of the long-term nuclear waste storage as small as possible. This requires significant improvements in our understanding of the behaviour of radionuclides and their retention mechanisms in geological formations of nuclear waste repositories over the ranges of time and distance spanning many orders of magnitude. Detailed molecular scale knowledge of the complex chemical and physical processes controlling the interaction of radionuclides with clay and cementitious materials is crucial for building better predictive models of their adsorption and mobility in natural and engineered barriers of the nuclear waste repositories. The presence of natural organic matter (NOM) in clayey formations and its complexation with metal ions in aqueous solutions has significant effect on the transport properties of the radionuclides. In this presentation, we will overview our current efforts to apply computational molecular modeling techniques to address these problems on the fundamental molecular level. We use classical molecular dynamics (MD) simulations for detailed quantitative studies of the structural, energetic and dynamic aspects of interactions between radionuclides, organic matter and clay particles. Structural and thermodynamic parameters are obtained by studying different processes such as hydration, adsorption, complexation, and intercalation. The complexation mechanisms of organic molecules with aqueous metal ions will then be presented using the free energy calculations. Metal cations can strongly associate with negatively charged functional groups of organic molecules and with negatively charged clay surfaces. This allows us to predict that cationic bridging could be the most probable mechanism responsible for the controlling effects of organics on the behaviour of radionuclides is clays and other repository materials. Our most recent results demonstrating how the nature of the adsorbed cations affects the structural and dynamic properties of the mineral-water interface and also the effect of disordered substitution in on the adsorption and swelling behaviour of clay minerals will then be discussed briefly.

     

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    Übergeordneter Titel: Journée GRIM3 2012, Groupe de Recherche Interdisciplinaire sur les Matériaux, les Molécules et la Matière ; http://hal.in2p3.fr/in2p3-00769210 ; Journée GRIM3 2012, Groupe de Recherche Interdisciplinaire sur les Matériaux, les Molécules et la Matière, Mar 2012, Nantes, France
    Schlagworte: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.MATE]Chemical Sciences/Material chemistry; [SDE.IE]Environmental Sciences/Environmental Engineering; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDU.STU.MI]Sciences of the Universe [physics]/Earth Sciences/Mineralogy
  12. Radiolytic Corrosion of Grain Boundaries onto the UO2 TRISO Particle Surface
    Erschienen: 2012
    Verlag:  HAL CCSD

    This work is dealing with the understandingof the corrosion mechanisms at solid/solutioninterface and taking into account for the4He2+ions irradiation effects on these mechanisms.These corrosion and4He2+ions radiolysis phenomena append at... mehr

     

    This work is dealing with the understandingof the corrosion mechanisms at solid/solutioninterface and taking into account for the4He2+ions irradiation effects on these mechanisms.These corrosion and4He2+ions radiolysis phenomena append at solid/solution interface andwill be studied at a μmetric scale by the Raman spectroscopy. Moreover, a4He2+ionsirradiation affects a small low volume and allowsus to control the irradiated area (solution,solid or interface). For the solid,the chemical species induced by4He2+ions radiolysis ofwater are reactive and are involved inclassical corrosion mechanisms of UO2. Moreover, wewant to study the impact of the4He2+ions radiolysis of waterlayers physisorbed into thesurface onto corrosion mechanisms. That is thereason why we want touse a local irradiation,allowed by the4He2+ions ion beam provided by theARRONAX cyclotron (E = 64.7 MeV).In this work an experimental apparatus will be performed in order to characterizesolid/solution interface at μmetric scale by Raman spectroscopy under4He2+ions irradiationprovided by the cyclotron ARRONAX facility.The leaching experiments under irradiationwill be performed for a short time in order tostudy the parameters during the fast instantrelease step. The grain boundaries effect will be studied by the comparison between oneTRISO particles set (solids with grain boundaries) and one TRISO particles set previouslywashed by one acid solution (solid without grain boundaries). The role of H2will be studiedby the comparison between experiments under Ar or Ar/H2atmosphere. The dose rate rangewill be between 0 and 100 Gy/min by using the alpha ion beam which let us control the doseset down into the sample. For all these experiments, measurements will be performed by thein situRaman spectroscopy during the irradiation in order to follow theformation/consumption of the secondary phases formed onto the solid. The SEM will beperformed in order to characterize the grain boundaries and the secondary phases formed bythe leaching/irradiation experiments.The μGC is used to measure the PH2into the irradiationcell to follow the production/consumption of this gaseous species formed by the waterradiolysis and consumedby the leaching process.

     

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    Übergeordneter Titel: 1st Annual Workshop Proceedings of the Collaborative Project “Fast / Instant Release of Safety Relevant Radionuclides from Spent Nuclear Fuel” (7th EC FP CP FIRST-Nuclides) ; http://hal.in2p3.fr/in2p3-00772168 ; 1st Annual Workshop Proceedings of the Collaborative Project “Fast / Instant Release of Safety Relevant Radionuclides from Spent Nuclear Fuel” (7th EC FP CP FIRST-Nuclides), Oct 2012, Budapest, Hungary
    Schlagworte: [CHIM.RADIO]Chemical Sciences/Radiochemistry
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  13. Generalized liquid drop model and fission, fusion, alpha and cluster radioactivity and superheavy nuclei
    Autor*in: Royer, Guy
    Erschienen: 2012
    Verlag:  HAL CCSD

    International audience ; A particular version of the liquid drop model taking into account both the mass and charge asymmetries, the proximity energy, the rotational energy, the shell and pairing energies and the temperature has been developed to... mehr

     

    International audience ; A particular version of the liquid drop model taking into account both the mass and charge asymmetries, the proximity energy, the rotational energy, the shell and pairing energies and the temperature has been developed to describe smoothly the transition between one and two-body shapes in entrance and exit channels of nuclear reactions. In the quasi-molecular shape valley where the proximity energy is optimized, the calculated l-dependent fusion and fission barriers, alpha and cluster radioactivity half-lives as well as actinide half-lives are in good agreement with the available experimental data. In this particular deformation path, double-humped potential barriers begin to appear even macroscopically for heavy nuclear systems due to the influence of the proximity forces and, consequently, quasi-molecular isomeric states can survive in the second minimum of the potential barriers in a large angular momentum range.

     

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    Übergeordneter Titel: Proceedings of the 4th International Conference : Current Problems in Nuclear Physics and Atomic Energy ; 4th International Conference : Current Problems in Nuclear Physics and Atomic Energy ; http://hal.in2p3.fr/in2p3-00836112 ; 4th International Conference : Current Problems in Nuclear Physics and Atomic Energy, Sep 2012, Kiev, Ukraine. pp.62-69
    Schlagworte: [PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th]
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  14. Spectrophotometric study of the behaviour of pertechnetate in trifluoromethanesulfonic acid: effect of alpha irradiation on the stability of Tc(VII)
    Erschienen: 2012
    Verlag:  HAL CCSD

    International audience ; This paper is devoted to the stability of pertechnetate in trifluoromethanesulfonic acid (HTFMS) in presence or absence of alpha irradiation. The irradiations were performed using alpha particles (4He2+) generated by ARRONAX... mehr

     

    International audience ; This paper is devoted to the stability of pertechnetate in trifluoromethanesulfonic acid (HTFMS) in presence or absence of alpha irradiation. The irradiations were performed using alpha particles (4He2+) generated by ARRONAX cyclotron with an external beam energy of 70 MeV. The stability has been determined by UV-Visible spectroscopy. In the absence of alpha irradiation, the results have shown that Tc(VII) is reduced in HTFMS between 4 and 11 M. UV-Visible spectroscopy measurements in 4-8 M show the presence of one phase of Tc(IV) oxopolymeric species. At 9 M HTFMS, the change of UV-Visible spectrum with respect to lower concentrations suggests the formation of a second new species of Tc(IV). At highly concentrated HTFMS (11 M), the Tc(VII) species remains stable. These findings exhibit the formation of reduced Tc species by partial thermal decomposition and hydrolysis processes due to the highly exothermic hydration reaction of triflic acid with water. Under alpha irradiation, the same reduced Tc species as those observed without external irradiation were obtained with higher reduction kinetics. The formation of oxopolymeric technetium at important radiolytic yield resulted from reducing radiolytic products of both water and acid.

     

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    Übergeordneter Titel: Journal of Radioanalytical and Nuclear Chemistry ; MARC-IX Conference ; http://hal.in2p3.fr/in2p3-00864037 ; MARC-IX Conference, Mar 2012, Kona, United States. pp.149-155, &#x27E8;10.1007/s10967-012-2098-y&#x27E9;
    Schlagworte: [CHIM.RADIO]Chemical Sciences/Radiochemistry
  15. RADIOLYTIC CORROSION OF GRAIN BOUNDARIES ONTO THE UO2 TRISO PARTICLE SURFACE
    Erschienen: 2012
    Verlag:  HAL CCSD

    International audience ; This work is dealing with the understandingof the corrosion mechanisms at solid/solutioninterface and taking into account for the4He2+ions irradiation effects on these mechanisms.These corrosion and4He2+ions radiolysis... mehr

     

    International audience ; This work is dealing with the understandingof the corrosion mechanisms at solid/solutioninterface and taking into account for the4He2+ions irradiation effects on these mechanisms.These corrosion and4He2+ions radiolysis phenomena append at solid/solution interface andwill be studied at a μmetric scale by the Raman spectroscopy. Moreover, a4He2+ionsirradiation appends onto a low volume and let usto control the irradiated area (solution, solidor interface). For the solid, the chemical species induced by4He2+ions radiolysis of water aresuch reactive and are involved in classical corrosion mechanisms of UO2. Moreover, we wantto study the impact of the4He2+ions radiolysis of water layers physisorbed into the surfaceonto corrosion mechanisms. That is the reason why we want to use a local irradiation, allowedby the4He2+ions ion beam provided by the ARRONAX cyclotron (E = 64.7 MeV). In thiswork an experimental apparatus will be performed in order to characterize solid/solutioninterface at μmetric scale by Raman spectroscopy under4He2+ions irradiation provided by thecyclotron ARRONAX facility. The leaching experiments under irradiation will be performedfor a short time in order to study the parametersduring the fast instantrelease step. The grainboundaries effect will be studied by the comparison between one TRISO particles set (solidswith grain boundaries) and oneTRISO particles set previously washed by one acid solution(solid without grain boundaries). The role of H2will be studied by the comparison betweenexperiments under Ar or Ar/H2atmosphere. The dose rate range will be between 0 and 100Gy/min by using the alpha ion beam which letus control the dose set down into the sample.For all these experiments, measurements will be performed by thein situRaman spectroscopyduring the irradiation in orderto follow the formation/consumption of the secondary phasesformed onto the solid. The SEM will be performed in order to characterize the grainboundaries and the secondary phases formed bythe leaching/irradiation experiments. TheμGC is used to measure the PH2into the irradiation cell tofollow the production/consumptionof this gaseous species formed by the water radiolysis and consumed by the leaching process.

     

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    Übergeordneter Titel: 7th EC FP CP FIRST-Nuclides 1st Annual Workshop 2012 ; http://hal.in2p3.fr/in2p3-00911332 ; 7th EC FP CP FIRST-Nuclides 1st Annual Workshop 2012, Oct 2012, Budapest, Hungary
    Schlagworte: [CHIM.RADIO]Chemical Sciences/Radiochemistry
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  16. Mittelalter im Kinder- und Jugendbuch. Akten der Tagung Bamberg 2010

    In den Beiträgen des vorliegenden Tagungsbandes sind die Ergebnisse einer Tagung zu „Mittelalter im Kinder- und Jugendbuch“ zusammengetragen. Vertreter der Fachwissenschaften, der Didaktik und der Lehrerschaft stellen Themen, Ansatzpunkte und... mehr

     

    In den Beiträgen des vorliegenden Tagungsbandes sind die Ergebnisse einer Tagung zu „Mittelalter im Kinder- und Jugendbuch“ zusammengetragen. Vertreter der Fachwissenschaften, der Didaktik und der Lehrerschaft stellen Themen, Ansatzpunkte und Methoden vor, wie das Mittelalter über die Beschäftigung mit Kinder- und Jugendliteratur im Schulunterricht verschiedener Altersstufen fruchtbar gemacht werden kann, und diskutieren den Mehrwert eines so ausgerichteten Unterrichts.

     

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    DDC Klassifikation: Literaturen germanischer Sprachen; Deutsche Literatur (830)
    Schlagworte: Deutsch; Jugendliteratur; Mittelalter; Motiv; Deutschunterricht; Kongress; Kinderliteratur
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  17. Die Gewalt der Zeichen. Terrorismus als symbolisches Phänomen ; The force of the sign. Terrorism as a symbolic phenomenon

    Seit der radikalen Änderung der weltpolitischen Lage durch das Selbstmordattentat islamistischer Terroristen auf die Supermacht U.S.A. am 11.9.01 versucht die Weltöffentlichkeit, dem Phänomen des Terrorismus durch die verschiedensten... mehr

     

    Seit der radikalen Änderung der weltpolitischen Lage durch das Selbstmordattentat islamistischer Terroristen auf die Supermacht U.S.A. am 11.9.01 versucht die Weltöffentlichkeit, dem Phänomen des Terrorismus durch die verschiedensten Erklärungsstrategien Herr zu werden. Man führt den Kampf der Kulturen oder Religionen an, verweist auf die Ausbeutung der Peripherie des kapitalistischen Weltsystems durch den Hegemon U.S.A. oder pathologisiert bzw. dämonisiert die Taten der Terroristen. Uns scheinen diese Erklärungsstrategien den Machtkonstellationen der postmodernen Gesellschaften nicht gerecht zu werden, da sie ein zentrales soziales Phänomen der vergangenen Jahrzehnte nicht beachten: das Unbehagen an der pluralistischen Gesellschaft und der konsensuell-repräsentativen Demokratie. Um dieses Unbehagen angemessen beschreiben zu können, wollen wir uns ihm aus einer zeichentheoretischen Perspektive nähern, die soziale Formationen nicht durch (kooperative) Arbeit determiniert sieht, sondern durch die Instanz des Codes. Für Jean Baudrillard ist die Wahl des Ziels der beiden Türme bedeutend, die sich wechselseitig reflektieren und das System nach allen Seiten hin abschließen. Mit ihnen wurde das neuralgische Zentrum des Systems getroffen, das sich auf einem binären Code gründet. Die Twintowers bedeuteten nicht nur das Ende jedweder originalen Referenz, sondern auch den Abschluss des Bezeichneten durch die Wiederholung des Zeichens. Der Code führt eine symbolische Verteilung der gesellschaftlichen Körper durch und zielt auf eine möglichst genaue Übereinstimmung der Gemeinschaft mit sich selbst gemäß eines arithmetischen und geometrischen Kalküls. Die integrative Kraft dieses auf dem Identitätsprinzip basierenden Systems scheint immer häufiger nicht mehr in der Lage zu sein, das negative Potential antagonistischer Strategien binden zu können, die in Form von zivilem Ungehorsam, Politik von Minoritäten oder terroristischen Akten die symbolische Ordnung der westlichen Gesellschaften unterhöhlen. In diesem Tagungsband diskutieren wir das Ausmaß der Krise der konsensuellen Demokratie und ihrer Institutionen. Die Aufsätze behandeln folgende Themen: • Die Krise der pluralistischen Gesellschaft: Wie verständlich ist das kulturelle, politische und religiöse Unbehagen am westlichen Wertekanon? • Die Funktion der Medien in der konsensuellen Demokratie; die gesellschaftliche Wirkung der medialen Reproduktion terroristischer Akte; das Bild des Terrorismus in der Populärkultur • Ästhetischer Terror: Die Vernichtung von Sinn und Bedeutung in der zeitgenössischen Kunst und Kunsttheorie • Die politische Logik des Terrorismus (Ziele, Bedingungen u. Legitimität des Terrorismus in Abgrenzung zu alternativen politischen Ausdrucksformen wie z.B. dem zivilen Ungehorsam; die Bedeutung des terroristischen Opfertodes) • Geschichte des Terrorismus (speziell der Terrorismus der RAF) • Terror als irrationale Gewalt (der ontologische Status des Terrorismus) ; Since the radical changes in international politics caused by the suicide attacks on the USA by Islamic terrorists on the 11th of September in 2001, the world public tries to grasp the phenomenon of „Terrorism“ through different explanatory strategies. These include referring to the clash of cultures and of religions, to the exploitation of the periphery by the capitalist system incarnated by the USA, or pathologizing as well as demonizing the deeds of the terrorists. All these explanatory attempts do not seem to do justice to the actual constellations of power in postmodern societies, because they do not take a widespread social phenomenon of the past decades in consideration: the discomfort with the pluralistic society and with the concurrent-representative democracy. In order to describe this discomfort adequately we would like to approach the phenomenon from a semiotic perspective which does not consider social formations as determined by cooperative work but rather by the authority of the code. For Jean Baudrillard the target was meaningful since the two towers not only reflect each other but also completely close the system. With them the neuralgic center which is based upon the binary code was severely hit. The twin towers not only meant the end of every original reference but also the completion of the signified by the reduplication of the sign. The code conducts a symbolic distribution of the social bodies and aims at an as accurate as possible identification of the community with itself corresponding to an arithmetic and geometric calculus. The system which is based upon the principle of identity does not seem to have the ability to integrate antagonist energies properly. So these antagonist powers undermine the symbolic order of western societies in terms of civil disobedience, politics of minorities or terroristic acts. In this conference transcript we discuss the degree of crisis of consensual democracy and ist institutions. The essays cover the following topics: • The crisis of the pluralistic society: How comprehensible and justified is the cultural, political, and religious discomfort with western values? • The function of mass media in democratic systems: What is the impact of the reproduction of terrorist acts on society? How does popular culture deal with terrorism? • Aesthetic terror: the destruction of sense and meaning in contemporary arts and art theory • The political logic of terrorism (aims, legitimacy of terrorism as opposed to other forms of opposition like civil disobedience; the meaning of the terrorist self-sacrifice death) • History of terrorism (e.g. The German terrorism of the RAF) • Terrorism as an irrational power (ontological status of terrorism)

     

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    DDC Klassifikation: Publizistische Medien, Journalismus, Verlagswesen (070); Sozialwissenschaften (300); Politikwissenschaft (320); Literatur und Rhetorik (800)
    Schlagworte: Terrorismus; Symbolik; Aufsatzsammlung; Online-Publikation
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  18. Postgraduate Forum 2012
  19. Postgraduate Forum 2003
  20. Tagungsbericht Postgraduate Forum 2011 (Gießen)
  21. Digital Humanities 2012 - Conference Abstracts : University of Hamburg, Germany; July 16–22, 2012

    ‘Digital Diversity: Cultures, Languages and Methods’ is the motto for this year’s Digital Humanities conference; it relates methodical and technical innovation to the traditional research agenda of the Humanities. The conference schedule includes... mehr

     

    ‘Digital Diversity: Cultures, Languages and Methods’ is the motto for this year’s Digital Humanities conference; it relates methodical and technical innovation to the traditional research agenda of the Humanities. The conference schedule includes contributions on a wide range of topics, reflecting the increasing breadth in the field on all levels. A recurring theme at Digital Humanities conferences in recent years has been the high number of submissions, and this year has continued the upward trend, with close to 400 submissions across the different categories: pre-conference workshops/tutorials, long papers, short papers, posters and multipaper sessions (including panels). This Book of Abstracts shows the diversity of this year's conference. The PDF version is freely available (open access; please download the file "HamburgUP_dh2012_B-o-A.pdf" ). An elaborated version of the Book with color photos and zoom function is available at www.dh2012.uni-hamburg.de/conference/programme/abstracts/ . ; ‘Digital Diversity: Cultures, Languages and Methods’ is the motto for this year’s Digital Humanities conference; it relates methodical and technical innovation to the traditional research agenda of the Humanities. The conference schedule includes contributions on a wide range of topics, reflecting the increasing breadth in the field on all levels. A recurring theme at Digital Humanities conferences in recent years has been the high number of submissions, and this year has continued the upward trend, with close to 400 submissions across the different categories: pre-conference workshops/tutorials, long papers, short papers, posters and multipaper sessions (including panels). This Book of Abstracts shows the diversity of this year's conference. The PDF version is freely available (open access; please download the file "HamburgUP_dh2012_B-o-A.pdf" ). An elaborated version of the Book with color photos and zoom function is available at www.dh2012.uni-hamburg.de/conference/programme/abstracts/ .

     

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    DDC Klassifikation: Literatur und Rhetorik (800)
    Schlagworte: Digital Humanities; Humanities Computing; Conference; Abstracts; Hamburg; Literature and rhetoric
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  22. Lebendiger Umgang mit den Toten – der moderne Familienroman in Europa und Übersee

    Seit den Neunzigerjahren des letzten Jahrhunderts gibt es in Deutschland wieder Familienromane. Sie sind eine neue Modellserie der ,Väterromane‘, die ihnen vorausgegangen sind. Die ,Generationenromane‘ nehmen die forschende Geste der Väterromane auf.... mehr

     

    Seit den Neunzigerjahren des letzten Jahrhunderts gibt es in Deutschland wieder Familienromane. Sie sind eine neue Modellserie der ,Väterromane‘, die ihnen vorausgegangen sind. Die ,Generationenromane‘ nehmen die forschende Geste der Väterromane auf. Die in diesem Band versammelten Beiträge nehmen sich des Themas an und widmen sich beispielhaften Romanen aus Europa und Übersee. ; Since the nineties of the last century there his an increase of family novels in Germany. Theese novels represent a new model series of so-called 'father novels' that preceded them. The new 'generational novels' take up the exploratory gesture of the father novels. The contributions collected in this volume address the topic and dedicate themselves to exemplary novels from Europe and overseas.

     

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  23. Über mediävistische Literatur- und Kulturwissenschaft
    Erschienen: 12.01.2012

    Was die altgermanistische Fachidentität wo nicht zu gefährden droht, da doch neu zu bestimmen nahe legt, das lässt sich am einfachsten unter jenem gängigen Stichwort 'Kulturwissenschaft' fassen, welches überhaupt in den Programm- und... mehr

     

    Was die altgermanistische Fachidentität wo nicht zu gefährden droht, da doch neu zu bestimmen nahe legt, das lässt sich am einfachsten unter jenem gängigen Stichwort 'Kulturwissenschaft' fassen, welches überhaupt in den Programm- und Legitimierungdebatten solcher akademischen Fächer eine zentrale Rolle spielt, die man einmal ohne weiteres die Geisteswissenschaften nannte. Dabei scheint durchaus umstritten zu sein, ob mit 'Kulturwissenschaften' ein Bruch mit den Traditionen der Deutschen Philologie angesagt ist oder im Gegenteil deren neuerliche Stabilisierung.

     

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    Sprache: Deutsch
    Medientyp: Konferenzveröffentlichung; Konferenzveröffentlichung
    Format: Online
    ISBN: 3-87192-853-4
    DDC Klassifikation: Literatur und Rhetorik (800)
    Schlagworte: Literaturwissenschaft; Kulturwisschenschaft; Hochschulpolitik; Altgermanistik
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  24. Sternenschrift : Textmodelle höfischen Erzählens
    Erschienen: 16.01.2012

    The discourses on textuality and literacy that can be observed in the Kyot-Excursus in 'Parcival' by Wolfram von Eschenbach and in the Magnetbergerzählung of the 'Reinfried von Braunschweig' will serve here as examples in an attempt to historicize... mehr

     

    The discourses on textuality and literacy that can be observed in the Kyot-Excursus in 'Parcival' by Wolfram von Eschenbach and in the Magnetbergerzählung of the 'Reinfried von Braunschweig' will serve here as examples in an attempt to historicize textual models. My essay will focus on how the limits of textuality could be defines within those 13th-century aristocratic orders of knowledge to which court literature can provide an access. What emerges within this context are concepts and ideas that lie beyond the scope of modern scholarly systems; these narratives indicate a way of dealing with textuality and literacy that, rather than referring to the textual discourse, may remain instead on the phenomenal surface of the material or (as if the textual discourse did not exist) may embody implicitly the circumstances that it signifies.

     

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    Format: Online
    ISBN: 3-503-07994-7
    DDC Klassifikation: Literaturen germanischer Sprachen; Deutsche Literatur (830)
    Schlagworte: Epik; Wolfram <von Eschenbach>; Mittelalter; Reinfried <von Braunschweig>
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  25. Schwank und Schwankzyklus, Weltordnung und Erzählordnung im "Pfaffen von Kalenberg" und "Neithart Fuchs"
    Erschienen: 16.01.2012

    Die Forschung bediente sich (…) [des Begriffes Schwankroman] im Sinnes eine Gattungsbegriffes, auch wenn sie nicht übersah, daß 'Schwankroman' bei aller Praktikabilität zugleich Ausdruck einer Verlegenheit ist, in welche ursprünglich wohl die... mehr

     

    Die Forschung bediente sich (…) [des Begriffes Schwankroman] im Sinnes eine Gattungsbegriffes, auch wenn sie nicht übersah, daß 'Schwankroman' bei aller Praktikabilität zugleich Ausdruck einer Verlegenheit ist, in welche ursprünglich wohl die ästhetische Norm von der geschlossenen Einheitlichkeit jeder Dichtung, die diesen Namen verdienen soll, geführt hat, einer Verlegenheit nämlich angesichts der offenkundig episodischen Struktur der genannten epischen Großerzählungen, die ihr Zusammengesetztsein aus kurzen, in sich weithin vollständigen Erzähleinheiten kaum je verleugnen. Dieses Dilemma schlägt sich nieder in der Binnenspannung zwischen den beiden Komponenten des Begriffs auf quantitativer, formal-struktureller und kategorialer Ebene: (…)

     

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    Format: Online
    ISBN: 3-506-78460-9
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