Study of the Erosion of Copper by Hot Plasma

An exhaustive study of the erosion process of a copper cathode exposed to a hot plasma column of 2kJ of energy (T≈0.5-2.0keV) and high electron density (n≈1019-1022cm3) was made, as well as, the radiation field of charged and neutral particles. The characterization of the cumulative damage generated by the plasma/cathode interaction was made by the use of metallographic techniques, scanning electron microscopy (SEM) and by the analysis of mechanical properties. Damage accumulation produced by the impacts of deuterium plasma discharge created in the copper electrode a deep cavity similar to a crater, modifying the morphology of the surface and below it. The microhardness Vickers test was carried out making indentations from the final part of the cavity to cover 1 cm with indentations every 200 μm. Different areas of hardening were observed, the profile suggests a hardening/recovery front and simultaneous recrystallization in the sample, phenomenon associated with the heating/cooling cycles to which the copper cathode is subjected. Images were captured by SEM at different distances from the center of the surface. The region that showed involvement at the macro level corresponds to 2/3 of the radius of the sample from the center to the outside. These phenomena studied are important to understand the nature of the plasma/wall interaction in any fusion device

Lifetime of d-holes at Cu surfaces: Theory and experiment

We have investigated the hole dynamics at copper surfaces by high-resolution angle-resolved photoemission experiments and many-body quasiparticle GW calculations. Large deviations from a free-electron-like picture are observed both in the magnitude and the energy dependence of the lifetimes, with a clear indication that holes exhibit longer lifetimes than electrons with the same excitation energy. Our calculations show that the small overlap of d- and sp-states below the Fermi level is responsible for the observed enhancement. Although there is qualitative good agreement of our theoretical predictions and the measured lifetimes, there still exist some discrepancies pointing to the need of a better description of the actual band structure of the solid.Comment: 15 pages, 7 figures, 1 table, to appear in Phys. Rev.

Responsive Giant Vesicles filled with Poly(N-isopropylacrylamide) Sols or Gels

4 pagesInternational audienceWe prepared giant unilamellar vesicles (GUVs) enclosing solutions or covalent gels of Poly(Nisopropylacrylamide) (PolyNipam). Concentrated suspensions of GUVs were prepared by applying an alternative field on a lipid film hydrated by a monomer solution containing N-isopropylacrylamide, crosslinker (N,N-methylene-bis-acrylamide), initiator and sucrose. Vesicle inner medium was polymerised and crosslinked by UV irradiation of the suspension, yielding viscous vesicles enclosing a solution of linear PolyNipam chains (when no bisacrylamide was used) or elastic vesicles filled with a covalent PolyNipam gel. We show that gel-filled vesicles are responsive systems triggered by the temperature: they shrink, reducing by a factor eight their volume below the critical temperature (32 ◦C in water, lower in glucose solution) and re-swell in a reversible and reproducible way upon decreasing temperature. In both cases, we show that the vesicle lipid membrane interacts with the internal polymer, resulting in an strong resistance of the vesicles to external mechanical stresses (enhanced tension of lysis)

Toward Forecasting Volcanic Eruptions using Seismic Noise

During inter-eruption periods, magma pressurization yields subtle changes of the elastic properties of volcanic edifices. We use the reproducibility properties of the ambient seismic noise recorded on the Piton de la Fournaise volcano to measure relative seismic velocity variations of less than 0.1 % with a temporal resolution of one day. Our results show that five studied volcanic eruptions were preceded by clearly detectable seismic velocity decreases within the zone of magma injection. These precursors reflect the edifice dilatation induced by magma pressurization and can be useful indicators to improve the forecasting of volcanic eruptions.Comment: Supplementary information: http://www-lgit.obs.ujf-grenoble.fr/~fbrengui/brenguier_SI.pdf Supplementary video: http://www-lgit.obs.ujf-grenoble.fr/~fbrengui/brenguierMovieVolcano.av

Surface modification of polyethylene terephthalate (PET) by corona discharge plasma

Surface modification of polyethylene terephthalate (PET) was studied by corona discharge plasma at different exposure times using air as working gas. The modification of the surface properties are characterized, those are morphology and wettability. Corona plasma treatment was found to modify the PET surface in both morphology and wettability. The corona discharge at atmospheric pressure is a heterogeneous with multiple current pulses, which generates an asymmetric pattern of erosion on the PET surface. The corona discharge treatment erodes the surface and therefore modifies the surface morphology. The roughness of the PET surface increases in the impact point of the corona discharge on the PET surface. An increase in the wettability of PET was also observed after corona discharge treatment at atmospheric pressure

South-South Migration

The objective of this paper is to provide an overview and a preliminary discussion of policy and academic works addressing South-South Migration (SSM) in depth. In the first part, three development categorizations used by international agencies to estimate migration flows (provided by the World Bank, UN Population Division and the UNDP) are addressed, discussing differences in definitions, classification criteria and the resulting country groupings of the South and the North. In the second part, the most salient debates and their alleged relation to development are presented, in relation to the main features of South-South Migration so far identified by academic literature. Given that much of SSM research is expected to represent no more than an extension of former international migration research, and given the former neglect of the significance of South-South Migration, this study stresses the opportunity to rethink the relation between inequality and migration, as well as the need to rethink concepts which were developed under assumptions underlying the study of South-North Migration. It concludes that cross fertilization between approaches based on agency and structure can provide more complex and nuanced interpretations in the study of South-South Migration

Hole dynamics in noble metals

We present a detailed analysis of hole dynamics in noble metals (Cu and Au), by means of first-principles many-body calculations. While holes in a free-electron gas are known to live shorter than electrons with the same excitation energy, our results indicate that d-holes in noble metals exhibit longer inelastic lifetimes than excited sp-electrons, in agreement with experiment. The density of states available for d-hole decay is larger than that for the decay of excited electrons; however, the small overlap between d- and sp-states below the Fermi level increases the d-hole lifetime. The impact of d-hole dynamics on electron-hole correlation effects, which are of relevance in the analysis of time-resolved two-photon photoemission experiments, is also addressed.Comment: 4 pages, 2 figures, to appear in Phys. Rev. Let

Morphology, Crystallinity, and Molecular Weight of Poly(E-caprolactone)/Graphene Oxide Hybrids

[EN] A study was carried out to determine the effects of graphene oxide (GO) filler on the properties of poly(epsilon-caprolactone) (PCL) films. A series of nanocomposites were prepared, incorporating different graphene oxide filler contents (0.1, 0.2, and 0.5 wt%) by the solution mixing method, and an in-depth study was made of the morphological changes, crystallization, infrared absorbance, molecular weight, thermal properties, and biocompatibility as a function of GO content to determine their suitability for use in biomedical applications. The infrared absorbance showed the existence of intermolecular hydrogen bonds between the PCL's carbonyl groups and the GO's hydrogen-donating groups, which is in line with the apparent reduction in molecular weight at higher GO contents, indicated by the results of the gel permeation chromatography (GPC), and the thermal property analysis. Polarized optical microscopy (POM) showed that GO acts as a nucleating point for PCL crystals, increasing crystallinity and crystallization temperature. The biological properties of the composites studied indicate that adding only 0.1 wt% of GO can improve cellular viability and that the composite shows promise for use in biomedical applications.This work was supported by Projects GV/2016/067 of the Generalitat Valenciana and MAT2016-76039-C4-3-R of the Spanish Ministry of Economy and Competitiveness (MINECO). The authors are grateful to M. Monleon-Pradas for his helpful comments and G. Vilarino-Feltrer for his valuable advice on the cell culture experiments. A. Vidaurre would also like to express her gratitude for the support received from CIBER-BBN, an initiative funded by the VI National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. SEM, TEM and AFM were conducted by the authors at the Microscopy Service of the Universitat Politecnica de Valencia, whose advice is greatly appreciated.Castilla Cortázar, MIC.; Vidaurre, A.; Marí, B.; Campillo Fernandez, AJ. (2019). Morphology, Crystallinity, and Molecular Weight of Poly(E-caprolactone)/Graphene Oxide Hybrids. Polymers. 11(7):1-19. https://doi.org/10.3390/polym11071099S119117Hummers, W. S., & Offeman, R. E. (1958). Preparation of Graphitic Oxide. Journal of the American Chemical Society, 80(6), 1339-1339. doi:10.1021/ja01539a017Stankovich, S., Piner, R. D., Nguyen, S. T., & Ruoff, R. S. (2006). Synthesis and exfoliation of isocyanate-treated graphene oxide nanoplatelets. Carbon, 44(15), 3342-3347. doi:10.1016/j.carbon.2006.06.004Dreyer, D. R., Park, S., Bielawski, C. W., & Ruoff, R. S. (2010). The chemistry of graphene oxide. Chem. Soc. Rev., 39(1), 228-240. doi:10.1039/b917103gKonios, D., Stylianakis, M. M., Stratakis, E., & Kymakis, E. (2014). Dispersion behaviour of graphene oxide and reduced graphene oxide. Journal of Colloid and Interface Science, 430, 108-112. doi:10.1016/j.jcis.2014.05.033Kuilla, T., Bhadra, S., Yao, D., Kim, N. H., Bose, S., & Lee, J. H. (2010). Recent advances in graphene based polymer composites. Progress in Polymer Science, 35(11), 1350-1375. doi:10.1016/j.progpolymsci.2010.07.005Potts, J. R., Dreyer, D. R., Bielawski, C. W., & Ruoff, R. S. (2011). Graphene-based polymer nanocomposites. Polymer, 52(1), 5-25. doi:10.1016/j.polymer.2010.11.042Liang, J., Huang, Y., Zhang, L., Wang, Y., Ma, Y., Guo, T., & Chen, Y. (2009). Molecular-Level Dispersion of Graphene into Poly(vinyl alcohol) and Effective Reinforcement of their Nanocomposites. Advanced Functional Materials, 19(14), 2297-2302. doi:10.1002/adfm.200801776Han, D., Yan, L., Chen, W., & Li, W. (2011). Preparation of chitosan/graphene oxide composite film with enhanced mechanical strength in the wet state. Carbohydrate Polymers, 83(2), 653-658. doi:10.1016/j.carbpol.2010.08.038Luong, N. D., Hippi, U., Korhonen, J. T., Soininen, A. J., Ruokolainen, J., Johansson, L.-S., … Seppälä, J. (2011). Enhanced mechanical and electrical properties of polyimide film by graphene sheets via in situ polymerization. Polymer, 52(23), 5237-5242. doi:10.1016/j.polymer.2011.09.033Yang, X., Tu, Y., Li, L., Shang, S., & Tao, X. (2010). Well-Dispersed Chitosan/Graphene Oxide Nanocomposites. ACS Applied Materials & Interfaces, 2(6), 1707-1713. doi:10.1021/am100222mSalavagione, H. J., Gómez, M. A., & Martínez, G. (2009). Polymeric Modification of Graphene through Esterification of Graphite Oxide and Poly(vinyl alcohol). Macromolecules, 42(17), 6331-6334. doi:10.1021/ma900845wXu, Z., & Gao, C. (2010). In situ Polymerization Approach to Graphene-Reinforced Nylon-6 Composites. Macromolecules, 43(16), 6716-6723. doi:10.1021/ma1009337Kulkarni, D. D., Choi, I., Singamaneni, S. S., & Tsukruk, V. V. (2010). Graphene Oxide−Polyelectrolyte Nanomembranes. ACS Nano, 4(8), 4667-4676. doi:10.1021/nn101204dBao, C., Guo, Y., Song, L., & Hu, Y. (2011). Poly(vinyl alcohol) nanocomposites based on graphene and graphite oxide: a comparative investigation of property and mechanism. Journal of Materials Chemistry, 21(36), 13942. doi:10.1039/c1jm11662bTang, L.-C., Wan, Y.-J., Yan, D., Pei, Y.-B., Zhao, L., Li, Y.-B., … Lai, G.-Q. (2013). The effect of graphene dispersion on the mechanical properties of graphene/epoxy composites. Carbon, 60, 16-27. doi:10.1016/j.carbon.2013.03.050Song, Y. S., & Youn, J. R. (2005). Influence of dispersion states of carbon nanotubes on physical properties of epoxy nanocomposites. Carbon, 43(7), 1378-1385. doi:10.1016/j.carbon.2005.01.007Kim, H., Miura, Y., & Macosko, C. W. (2010). Graphene/Polyurethane Nanocomposites for Improved Gas Barrier and Electrical Conductivity. Chemistry of Materials, 22(11), 3441-3450. doi:10.1021/cm100477vAhmad, H., Fan, M., & Hui, D. (2018). Graphene oxide incorporated functional materials: A review. Composites Part B: Engineering, 145, 270-280. doi:10.1016/j.compositesb.2018.02.006Kai, W., Hirota, Y., Hua, L., & Inoue, Y. (2007). Thermal and mechanical properties of a poly(ε-caprolactone)/graphite oxide composite. Journal of Applied Polymer Science, 107(3), 1395-1400. doi:10.1002/app.27210Woodruff, M. A., & Hutmacher, D. W. (2010). The return of a forgotten polymer—Polycaprolactone in the 21st century. Progress in Polymer Science, 35(10), 1217-1256. doi:10.1016/j.progpolymsci.2010.04.002Wan, C., & Chen, B. (2011). Poly(ε-caprolactone)/graphene oxide biocomposites: mechanical properties and bioactivity. Biomedical Materials, 6(5), 055010. doi:10.1088/1748-6041/6/5/055010Song, J., Gao, H., Zhu, G., Cao, X., Shi, X., & Wang, Y. (2015). The preparation and characterization of polycaprolactone/graphene oxide biocomposite nanofiber scaffolds and their application for directing cell behaviors. Carbon, 95, 1039-1050. doi:10.1016/j.carbon.2015.09.011Hua, L., Kai, W. H., & Inoue, Y. (2007). Crystallization behavior of poly(ϵ-caprolactone)/graphite oxide composites. Journal of Applied Polymer Science, 106(6), 4225-4232. doi:10.1002/app.26976Sayyar, S., Murray, E., Thompson, B. C., Gambhir, S., Officer, D. L., & Wallace, G. G. (2013). Covalently linked biocompatible graphene/polycaprolactone composites for tissue engineering. Carbon, 52, 296-304. doi:10.1016/j.carbon.2012.09.031Murray, E., Sayyar, S., Thompson, B. C., Gorkin III, R., Officer, D. L., & Wallace, G. G. (2015). A bio-friendly, green route to processable, biocompatible graphene/polymer composites. RSC Advances, 5(56), 45284-45290. doi:10.1039/c5ra07210gHassanzadeh, S., Adolfsson, K. H., Wu, D., & Hakkarainen, M. (2015). Supramolecular Assembly of Biobased Graphene Oxide Quantum Dots Controls the Morphology of and Induces Mineralization on Poly(ε-caprolactone) Films. Biomacromolecules, 17(1), 256-261. doi:10.1021/acs.biomac.5b01339Kumar, S., Azam, D., Raj, S., Kolanthai, E., Vasu, K. S., Sood, A. K., & Chatterjee, K. (2015). 3D scaffold alters cellular response to graphene in a polymer composite for orthopedic applications. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 104(4), 732-749. doi:10.1002/jbm.b.33549Shin, S. R., Li, Y.-C., Jang, H. L., Khoshakhlagh, P., Akbari, M., Nasajpour, A., … Khademhosseini, A. (2016). Graphene-based materials for tissue engineering. Advanced Drug Delivery Reviews, 105, 255-274. doi:10.1016/j.addr.2016.03.007Bianco, A. (2013). Graphene: Safe or Toxic? The Two Faces of the Medal. Angewandte Chemie International Edition, 52(19), 4986-4997. doi:10.1002/anie.201209099Zhang, X., Yin, J., Peng, C., Hu, W., Zhu, Z., Li, W., … Huang, Q. (2011). Distribution and biocompatibility studies of graphene oxide in mice after intravenous administration. Carbon, 49(3), 986-995. doi:10.1016/j.carbon.2010.11.005Jasim, D. A., Murphy, S., Newman, L., Mironov, A., Prestat, E., McCaffrey, J., … Kostarelos, K. (2016). The Effects of Extensive Glomerular Filtration of Thin Graphene Oxide Sheets on Kidney Physiology. ACS Nano, 10(12), 10753-10767. doi:10.1021/acsnano.6b03358Santos, C. M., Mangadlao, J., Ahmed, F., Leon, A., Advincula, R. C., & Rodrigues, D. F. (2012). Graphene nanocomposite for biomedical applications: fabrication, antimicrobial and cytotoxic investigations. Nanotechnology, 23(39), 395101. doi:10.1088/0957-4484/23/39/395101Lim, H. N., Huang, N. M., & Loo, C. H. (2012). Facile preparation of graphene-based chitosan films: Enhanced thermal, mechanical and antibacterial properties. Journal of Non-Crystalline Solids, 358(3), 525-530. doi:10.1016/j.jnoncrysol.2011.11.007Some, S., Ho, S.-M., Dua, P., Hwang, E., Shin, Y. H., Yoo, H., … Lee, H. (2012). Dual Functions of Highly Potent Graphene Derivative–Poly-l-Lysine Composites To Inhibit Bacteria and Support Human Cells. ACS Nano, 6(8), 7151-7161. doi:10.1021/nn302215ySydlik, S. A., Jhunjhunwala, S., Webber, M. J., Anderson, D. G., & Langer, R. (2015). In Vivo Compatibility of Graphene Oxide with Differing Oxidation States. ACS Nano, 9(4), 3866-3874. doi:10.1021/acsnano.5b01290Crescenzi, V., Manzini, G., Calzolari, G., & Borri, C. (1972). Thermodynamics of fusion of poly-β-propiolactone and poly-ϵ-caprolactone. comparative analysis of the melting of aliphatic polylactone and polyester chains. European Polymer Journal, 8(3), 449-463. doi:10.1016/0014-3057(72)90109-7Luo, H., Meng, X., Cheng, C., Dong, Z., Zhang, S., & Li, B. (2010). Enzymatic Degradation of Supramolecular Materials Based on Partial Inclusion Complex Formation between α-Cyclodextrin and Poly(ε-caprolactone). The Journal of Physical Chemistry B, 114(13), 4739-4745. doi:10.1021/jp1001836Vidaurre, A., Dueñas, J. M. M., Estellés, J. M., & Cortázar, I. C. (2008). Influence of Enzymatic Degradation on Physical Properties of Poly(ε-caprolactone) Films and Sponges. Macromolecular Symposia, 269(1), 38-46. doi:10.1002/masy.200850907Honma, T., Senda, T., & Inoue, Y. (2003). Thermal properties and crystallization behaviour of blends of poly(?-caprolactone) with chitin and chitosan. Polymer International, 52(12), 1839-1846. doi:10.1002/pi.1380Ramazani, S., & Karimi, M. (2015). Aligned poly(ε-caprolactone)/graphene oxide and reduced graphene oxide nanocomposite nanofibers: Morphological, mechanical and structural properties. Materials Science and Engineering: C, 56, 325-334. doi:10.1016/j.msec.2015.06.045Coleman, M. M., & Zarian, J. (1979). Fourier-transform infrared studies of polymer blends. II. Poly(ε-caprolactone)–poly(vinyl chloride) system. Journal of Polymer Science: Polymer Physics Edition, 17(5), 837-850. doi:10.1002/pol.1979.180170509Huang, Y., Xu, Z., Huang, Y., Ma, D., Yang, J., & Mays, J. W. (2003). Characterization of Poly(ε-Caprolactone) via Size Exclusion Chromatography with Online Right-Angle Laser-Light Scattering and Viscometric Detectors. International Journal of Polymer Analysis and Characterization, 8(6), 383-394. doi:10.1080/714975019Sharaf, M. A., Kloczkowski, A., Sen, T. Z., Jacob, K. I., & Mark, J. E. (2006). Filler-induced deformations of amorphous polyethylene chains. The effects of the deformations on elastomeric properties, and some comparisons with experiments. European Polymer Journal, 42(4), 796-806. doi:10.1016/j.eurpolymj.2005.10.009Nusser, K., Neueder, S., Schneider, G. J., Meyer, M., Pyckhout-Hintzen, W., Willner, L., … Richter, D. (2010). Conformations of Silica−Poly(ethylene−propylene) Nanocomposites. Macromolecules, 43(23), 9837-9847. doi:10.1021/ma101898cVacatello, M. (2002). Chain Dimensions in Filled Polymers:  An Intriguing Problem. Macromolecules, 35(21), 8191-8193. doi:10.1021/ma020416sDuan, T., Lv, Y., Xu, H., Jin, J., & Wang, Z. (2018). Structural Effects of Residual Groups of Graphene Oxide on Poly(ε-Caprolactone)/Graphene Oxide Nanocomposite. Crystals, 8(7), 270. doi:10.3390/cryst8070270Wang, G., Wei, Z., Sang, L., Chen, G., Zhang, W., Dong, X., & Qi, M. (2013). Morphology, crystallization and mechanical properties of poly(ɛ-caprolactone)/graphene oxide nanocomposites. Chinese Journal of Polymer Science, 31(8), 1148-1160. doi:10.1007/s10118-013-1278-8Balkova, R., Hermanova, S., Voberkova, S., Damborsky, P., Richtera, L., Omelkova, J., & Jancar, J. (2013). Structure and Morphology of Microbial Degraded Poly(ε-caprolactone)/Graphite Oxide Composite. Journal of Polymers and the Environment, 22(2), 190-199. doi:10.1007/s10924-013-0630-yYıldırım, S., Demirtaş, T. T., Dinçer, C. A., Yıldız, N., & Karakeçili, A. (2018). Preparation of polycaprolactone/graphene oxide scaffolds: A green route combining supercritial CO2 technology and porogen leaching. The Journal of Supercritical Fluids, 133, 156-162. doi:10.1016/j.supflu.2017.10.009Peng, H., Han, Y., Liu, T., Tjiu, W. C., & He, C. (2010). Morphology and thermal degradation behavior of highly exfoliated CoAl-layered double hydroxide/polycaprolactone nanocomposites prepared by simple solution intercalation. Thermochimica Acta, 502(1-2), 1-7. doi:10.1016/j.tca.2010.01.009Michailidis, M., Verros, G. D., Deliyanni, E. A., Andriotis, E. G., & Achilias, D. S. (2017). An experimental and theoretical study of butyl methacrylatein situradical polymerization kinetics in the presence of graphene oxide nanoadditive. Journal of Polymer Science Part A: Polymer Chemistry, 55(8), 1433-1441. doi:10.1002/pola.28512Tsagkalias, I., Manios, T., & Achilias, D. (2017). Effect of Graphene Oxide on the Reaction Kinetics of Methyl Methacrylate In Situ Radical Polymerization via the Bulk or Solution Technique. Polymers, 9(9), 432. doi:10.3390/polym9090432Geng, L.-H., Peng, X.-F., Jing, X., Li, L.-W., Huang, A., Xu, B.-P., … Mi, H.-Y. (2016). Investigation of poly(l-lactic acid)/graphene oxide composites crystallization and nanopore foaming behaviors via supercritical carbon dioxide low temperature foaming. Journal of Materials Research, 31(3), 348-359. doi:10.1557/jmr.2016.13Song, P., Cao, Z., Cai, Y., Zhao, L., Fang, Z., & Fu, S. (2011). Fabrication of exfoliated graphene-based polypropylene nanocomposites with enhanced mechanical and thermal properties. Polymer, 52(18), 4001-4010. doi:10.1016/j.polymer.2011.06.045Bao, C., Guo, Y., Song, L., Kan, Y., Qian, X., & Hu, Y. (2011). In situ preparation of functionalized graphene oxide/epoxy nanocomposites with effective reinforcements. Journal of Materials Chemistry, 21(35), 13290. doi:10.1039/c1jm11434dSánchez-Correa, F., Vidaurre-Agut, C., Serrano-Aroca, Á., & Campillo-Fernández, A. J. (2017). Poly(2-hydroxyethyl acrylate) hydrogels reinforced with graphene oxide: Remarkable improvement of water diffusion and mechanical properties. Journal of Applied Polymer Science, 135(15), 46158. doi:10.1002/app.46158Liao, K.-H., Lin, Y.-S., Macosko, C. W., & Haynes, C. L. (2011). Cytotoxicity of Graphene Oxide and Graphene in Human Erythrocytes and Skin Fibroblasts. ACS Applied Materials & Interfaces, 3(7), 2607-2615. doi:10.1021/am200428

Anomalous Quasiparticle Lifetime in Graphite: Band Structure Effects

We report ab initio calculation of quasiparticle lifetimes in graphite, as determined from the imaginary part of the self-energy operator within the GW aproximation. The inverse lifetime in the energy range from 0.5 to 3.5 eV above the Fermi level presents significant deviations from the quadratic behavior naively expected from Fermi liquid theory. The deviations are explained in terms of the unique features of the band structure of this material. We also discuss the experimental results from different groups and make some predictions for future experiments.Comment: 4 pages, 4 figures, submitted PR

Tomography of the Alpine region from observations of seismic ambient noise

We use correlations of the ambient seismic noise to study the crust in western Europe. Cross correlation of 1 year of noise recorded at 150 three components broadband stations yields more than 3 000 Rayleigh wave group velocity measurements. These measurements are used to construct Rayleigh group velocity maps of the Alpine region and surrounding area in the 5-80 s period band. In the 5-10 s period band, the seismic noise recorded in Europe is dominated by surface waves originating from the Northern Atlantic ocean. This anisotropy of the noise and the uneven station distribution affect the azimuthal distribution of the paths where we obtain reliable group velocity measurements. As a consequence our group velocity models have better resolution in the northeast direction than in the southwest direction. Finally we invert the resulting Rayleigh wave group velocity maps to determine the Moho depth. Our results are in good agreement with the result of the numerous active experiments in the Alps and provide a continuous image of the Alpine structur