Change search
Refine search result
45678910 301 - 350 of 3670
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 301.
    Baek, Seung Ki
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kim, Beom Jun
    Dept. of Physics, Sungkyunkwan Univ., Suwon, Korea.
    Numerical Study of Game Theory2010In: New Physics, ISSN 0374-4914, Vol. 60, no 9, p. 943-951Article in journal (Other academic)
    Abstract [en]

    Game-theoretic approach has been providing a powerful tool in qualitative understanding of macroscopic social phenomena in social sciences, e.g., in economics and political science. Recently, researchers in physics, especially in statistical physics, use these game-theoretic approaches but in more quantitative way and have been producing a variety of interesting results in the new research area called ’sociophysics’ by studying human society as a complex system. This work introduces recent works that have tackled combinatorial complexities arising in game-theoretic studies with the aid of simplified assumptions and numerical computations. We first show how cooperation emerges in the prisoner’s dilemma game when each player’s memory capacity is enhanced and suggest that the intelligent tit-for-tat strategy plays a crucial role in the history of cooperation. And then it is numerically shown that there is a certain case of simultaneous coordination among many players where the system has a high risk of failure when everyone is willing to follow the coordination, which is actually higher than when some are not concerned about it. Lastly, we discuss mathematical treatment of an equilibrium solution for a reverse auction game, which is a variant of the minority game, and its computational approach.

  • 302.
    Baek, Seung Ki
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Minnhagen, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Non-Kosterlitz-Thouless transitions for the q-state clock models2010In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 82, no 3, p. 031102-Article in journal (Refereed)
    Abstract [en]

    The $q$-state clock model with the cosine potential has a single phasetransition for $q\leq4$ and two transitions for $q\geq5$. It is shown byMonteCarlo simulations that the helicity modulus for the five-state clock model($q=5$) does not vanish at the high-temperature transition. This is incontrast to the clock models with $q\geq6$ for which the helicity modulusvanishes. This means that the transition for the five-state clock modeldiffers from the Kosterlitz-Thouless (KT) transition. It is also shown thatthis change in the transition is caused by an interplay between the numberof angular directions and the interaction potential: by slightly modifyingthe interaction potential, the KT transition for $q=6$ turns into the samenon-KT transition. Likewise, the KT transition is recovered for $q=5$ whenthe Villain potential is used. Comparisons with other clock-model resultsare made and discussed.

  • 303.
    Baek, Seung Ki
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Minnhagen, Petter
    Umeå University, Faculty of Science and Technology, Physics.
    Bernhardsson, Sebastian
    Umeå University, Faculty of Science and Technology, Physics.
    Choi, Kweon
    Gyeonggi Science High School.
    Kim, Beom Jun
    Department of Energy Science and BK21 Physics Research Division, Sungkyunkwan University, Suwon 440-746, Korea.
    Flow improvement caused by agents who ignore traffic rules2009In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 80, no 1, p. 016111-Article in journal (Refereed)
    Abstract [en]

    A system of agents moving along a road in both directions is studied numerically within a cellular-automata formulation. An agent steps to the right with probability $q$ or to the left with $1-q$ when encountering other agents. Our model is restricted to two agent types, traffic-rule abiders ($q=1$) and traffic-rule ignorers ($q=1/2$). The traffic flow, resulting from the interaction between these two types of agents, is obtained as a function of density and relative fraction. The risk for jamming at a fixed density, when starting from a disordered situation, is smaller when every agent abides by a traffic rule than when all agents ignore the rule. Nevertheless, the absolute minimum occurs when a smallfraction of ignorers are present within a majority of abiders. The characteristic features for the spatial structure of the flow pattern are obtained and discussed.

  • 304.
    Baek, Seung Ki
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Minnhagen, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kim, Beom Jun
    Department of Physics, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
    The Ten Thousand Kims2011In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, p. 073036-Article in journal (Refereed)
    Abstract [en]

    In the Korean culture the family members are recorded in special familybooks. This makes it possible to follow the distribution of Korean familynames far back in history. It is here shown that these name distributionsare well described by a simple null model, the random group formation (RGF)model. This model makes it possible to predict how the name distributionschange and these predictions are shown to be borne out. In particular, theRGF model predicts that, for married women entering a collection of familybooks in a certain year, the occurrence of the most common family name``Kim'' should be directly proportional the total number of married womenwith the same proportionality constant for all the years. This prediction isalso borne out to high degree. We speculate that it reflects some inherentsocial stability in the Korean culture. In addition, we obtain an estimate ofthe total population of the Korean culture down to year 500 AD, based on theRGF model and find about ten thousand Kims.

  • 305.
    Baek, Seung Ki
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Shima, Hiroyuki
    Department of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
    Kim, Beom Jun
    BK21 Physics Research Division and Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea.
    Curvature-induced frustration in the XY model on hyperbolic surfaces2009In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 79, no 6, p. 060106(R)-Article in journal (Refereed)
    Abstract [en]

    We study low-temperature properties of the XY spin model on a negatively curved surface. Geometric curvature of the surface gives rise to frustration in local spin configuration, which results in the formation of high-energy spin clusters scattered over the system. Asymptotic behavior of the spin-glass susceptibility suggests a zero-temperature glass transition, which is attributed to multiple optimal configurations of spin clusters due to nonzero surface curvature of the system. It implies that a constant ferromagnetic spin interaction on a regular lattice can exhibit glasslike behavior without possessing any disorder if the lattice is put on top of a negatively curved space such as a hyperbolic surface.

  • 306.
    Baghban, Mohammad Amin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Impact of longitudinal fields on second harmonic generation in lithium niobate nanopillars2016In: APL Photonics, ISSN 2378-0967, Vol. 1, no 6, article id 061302Article in journal (Refereed)
    Abstract [en]

    An optimized focused ion beam process is used to fabricate micrometer-long LiNbO3 nanopillars with diameters varying between 150 and 325 nm. Polarimetric mappings of second harmonic generation from a wavelength of 850 nm demonstrate the ability to modify the polarization features of the nonlinearresponse through a fine adjustment of the pillar size. The effect is ascribed to the non-negligible contribution of the longitudinal fields associated with sub-wavelength light confinement in the LiNbO3nanopillars. The results also highlight the importance of a fine control over the nanopillar size in order to effectively engineer their nonlinear response.

  • 307.
    Baghban, Mohammad Amin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Phase-Shifted Bragg Grating Resonators in Thin-Film Lithium Niobate Waveguides2019In: 2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), 2019Conference paper (Refereed)
    Abstract [en]

    We demonstrate narrowband integrated filters with 0.23 mm-long phase-shifted Bragg gratings in corrugated single-mode thin-film LiNbO3 photonic wires, achieving quality factors of 1.24x10(4) and extinction ratios up to 24 dB at telecom wavelengths.

  • 308.
    Baghban, Mohammad Amin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Mahato, Sunil Kumar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Low-loss ridge waveguides in thin film lithium niobate-on-insulator (LNOI) fabricated by reactive ion etching2016In: Proceedings Advanced Photonics 2016, OSA Publishing , 2016Conference paper (Refereed)
    Abstract [en]

    We report on the fabrication of waveguides in 300 nm-thick Y-cut lithium niobate onsilicon through optimized reactive ion etching, yielding sidewall roughness of 22.9 nm andpropagation losses of 8.62 dB/cm at 1550 nm.

  • 309.
    Baghban, Mohammad Amin
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Schollhammer, Jean
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Errando-Herranz, Carlos
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Gylfason, Kristinn B
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Bragg gratings in thin-film LiNbO3 waveguides2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Optics Express, ISSN 1094-4087, Vol. 25, no 26, p. 32323-32332Article in journal (Refereed)
    Abstract [en]

    We design, fabricate and characterize sidewall corrugated Bragg gratings in a high confinement integrated optics lithium niobate platform, comprising submicrometric photonic wires, tapers and grating couplers to interface off-chip standard telecom optical fibers. We analyze the grating performance as band-rejection filter for TE-polarized signals in the telecom C-band, considering both rectangular and sinusoidal sidewall profiles, and demonstrate record extinction ratios as high as 27 dB and rejection bandwidths as narrow as 3 nm. The results show the potential for an efficient integration of novel photonic functionalities into low-footprint LiNbO3 nonlinear and electro-optical waveguide devices.

  • 310.
    Bagheri, Faranggis
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Mitra, Dhrubaditya
    NORDITA.
    Perlekar, Prasad
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Statistics of polymer extensions in turbulent channel flow2012In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 86, no 5, p. 056314-Article in journal (Refereed)
    Abstract [en]

    We present direct numerical simulations of turbulent channel flow with passive Lagrangian polymers. To understand the polymer behavior we investigate the behavior of infinitesimal line elements and calculate the probability distribution function (PDF) of finite-time Lyapunov exponents and from them the corresponding Cramer's function for the channel flow. We study the statistics of polymer elongation for both the Oldroyd-B model (for Weissenberg number Wi<1) and the FENE model. We use the location of the minima of the Cramer's function to define the Weissenberg number precisely such that we observe coil-stretch transition at Wi1. We find agreement with earlier analytical predictions for PDF of polymer extensions made by Balkovsky, Fouxon, and Lebedev for linear polymers (Oldroyd-B model) with Wi <1 and by Chertkov for nonlinear FENE-P model of polymers. For Wi >1 (FENE model) the polymer are significantly more stretched near the wall than at the center of the channel where the flow is closer to homogenous isotropic turbulence. Furthermore near the wall the polymers show a strong tendency to orient along the streamwise direction of the flow, but near the center line the statistics of orientation of the polymers is consistent with analogous results obtained recently in homogeneous and isotropic flows.

  • 311. Bakari, D
    et al.
    Becherini, Yvonne
    Spurio, M
    Estimate of the energy of upgoing muons with multiple coulomb scattering2001In: Cosmic Radiations: from Astronomy to Particle Physics / [ed] Giacommelli, G; Spurio, M; Derkaoui, JE, Dordrecht: Springer, 2001, Vol. 42, p. 135-140Conference paper (Other academic)
  • 312.
    Baks, Tim
    et al.
    Friesland Campina Research, The Netherlands.
    Boom, Remco
    Wageningen University & Research centre, The Netherlands.
    Devid, Edwin
    Leiden University, The Netherlands.
    Dresselhuis, Diane
    Friesland Campina Research, The Netherlands.
    Falco, Gianmaria
    University of Cologne, Germany .
    de Folter, Julius
    Utrecht University, The Netherlands.
    Leermakers, Frans
    Wageningen University & Research centre, The Netherlands.
    Li, Jianan
    VU University Amsterdam, The Netherlands.
    Muntean, Andrea
    Eindhoven University of Technology, The Netherlands.
    Poortinga, Albert
    Friesland Campina Research, The Netherlands.
    Robijn, Gerard
    Friesland Campina Research, The Netherlands.
    Stoyanov, Simeon
    Unilever R&D, The Netherlands.
    Teapal, Juliane
    Wageningen University & Research centre, The Netherlands.
    van der Voort Maarschalk, Kees
    University of Groningen, The Netherlands.
    Schrödinger's capsule: a (micro) capsulate that is open and closed, almost, at the same time2010In: Proceedings of the Physics with Industry 2010, 11-15 October 2010, Leiden, The Netherlands / [ed] Lorentz Center Leiden, Lorentz Center Leiden , 2010Conference paper (Refereed)
    Abstract [en]

    We exploit different routes for encapsulation of food additives, such as minerals or vitamins, in a polymeric capsule. The added active ingredients should remain inside the capsule for at least a year in an aqueous environment (e.g. a dairy product), since sensory properties or functionality of the ingredients may otherwise be affected. However, after intake the active compound should readily (within 1 h) be released due to the acidic environment in the stomach. First, we propose a phenomenological model in order to study how a polymeric matrix may limit the diffusion of incorporated active molecules. The relation between the release rate of the active compound and its molecular weight is elucidated. Second, the desired capsules may be obtained by specific binding between subunits within the capsule and the active ingredient. We show two examples that rely on this mechanism: amylose-lipid complexes and mixed metal hydroxides. Amylose is able to form inclusion complexes with various types of ligands, including iodine, monoglycerides, fatty acids and alcohols, where the hydrophobic parts of the ligands are entrapped in the hydrophobic helical cavity of amylose. Mixed metal hydroxides are a versatile class of inorganic solids that consist of sheets of metal cations that are octahedrally surrounded by hydroxide molecules. In between these layers anionic species compensate for charge neutrality. In this way, various metal cations (minerals) may be incorporated with a high loading, and negatively charged actives may be placed between the layers. Upon digestion the particles dissolve and the ingredients are digested. Finally, we show that nature has already developed many intriguing capsules.

  • 313. Balinsky, Michael
    et al.
    Ranjbar, Mojtaba
    Haidar, Mohammad
    Durrenfeld, Philipp
    Khartsev, Sergiy
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Slavin, Andrei
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. University of Gothenburg, Sweden.
    Dumas, Randy K.
    Spin Pumping and the Inverse Spin-Hall Effect via Magnetostatic Surface Spin-Wave Modes in Yttrium-Iron Garnet/Platinum Bilayers2015In: IEEE Magnetics Letters, ISSN 1949-307X, E-ISSN 1949-3088, Vol. 6, no 3000604Article in journal (Refereed)
    Abstract [en]

    Spin pumping at a boundary between a yttrium-iron garnet (YIG) film and a thin platinum (Pt) layer is studied under conditions in which a magnetostatic surface spin wave (MSSW, or Damon-Eshbach mode) is excited in YIG by a narrow strip-line antenna. It is shown that the voltage created by the inverse spin-Hall effect (ISHE) in Pt is strongly dependent on the wavevector of the excited MSSW. For YIG film thicknesses of 41 and 0.9 mu m, the maximum ISHE voltage corresponds to the maximum of efficiently excited MSSW wavevectors and does not coincide with the maximum of absorbed microwave power. For a thinner (0.175 mu m) YIG film, the maximum of the ISHE voltage moves closer to the ferromagnetic resonance and almost coincides with the region of the maximum microwave absorption. We show that the effect is related to the change in the thickness profile and the wavenumber spectrum of the excited MSSW taking place when the YIG film thickness is increased.

  • 314.
    Balliu, Enkeleda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Engholm, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    A compact, single-frequency, high-power, SBS-free, Yb-doped single-stage fiber amplifier2019In: Proceedings of SPIE - The International Society for Optical Engineering / [ed] W. Andrew Clarkson and Ramesh K. Shori, SPIE - International Society for Optical Engineering, 2019, Vol. 10896, p. 6pp-, article id 1089618Conference paper (Refereed)
    Abstract [en]

    Interest in compact, single-frequency fiber amplifier has increased within many scientific and industrial applications. The main challenge is the onset of nonlinear effects, which limit their power scaling. Here we demonstrate a compact, high-power, single-frequency, polarization-maintaining, continous-wave fiber amplifier using only one amplification stage. We developed the fiber amplifier using a master oscillator fiber amplifier architecture, where a low-noise, single-frequency, solid-state laser operating at 1064 nm was used as a seed source. We evaluated the amplifier's performance by using several state-of-the-art, small-core, Ytterbium (yb)-doped fibers, as well as an in-house-made, highly Yb-doped fiber. An output power of 82 W was achieved with no sign of stimulated Brillouin scattering. A good beam quality and a polarization extinction ratio (PER) of > 25 dB were achieved. The compact fiber amplifier can be a competitive alternative to multi stage designed fiber amplifiers.

  • 315.
    Balliu, Enkeleda
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thontakudi, Anjali
    Monta Vista High School, Cupertino, CA USA.
    Knall, Jenny M.
    Stanford University, Stanford, CA USA.
    Digonnet, Michel J. F.
    Stanford University, Stanford, CA USA.
    Predictive comparison of anti-Stokes fluorescence cooling in oxide and non-oxide fiber hosts doped with Er3+, Pr3+, or Yb3+2019In: Proceedings of SPIE - The International Society for Optical Engineering: Photonic Heat Engines: Science and Applications, SPIE - International Society for Optical Engineering, 2019, Vol. 10936, article id 109360JConference paper (Refereed)
    Abstract [en]

    A comprehensive study was performed to quantify anti-Stokes-fluorescence (ASF) cooling in fibers of various host compositions (telluride, fluorozirconates, fluorophosphates, phosphates, and chalcogenides) doped with Yb3+ or Er3+. Published expressions were used to calculate the maximum heat that can be extracted per unit length and time from a single-mode fiber in the limit of negligible absorptive loss, and the associated cooling efficiency. These expressions consider host- and ion-dependent parameters, namely the absorption and emission cross-section spectra, the radiative and nonradiative lifetimes, and the critical concentration for quenching. Using these expressions with published values for these parameters, the maximum extractable heat was calculated for a large-mode-area fiber (NA = 0.05) doped with either Yb3+ or Er3+ in a variety of hosts. The results show that for a given ion, the maximum heat that can be extracted depends strongly on the host due to the strong dependence of quenching on host composition. In contrast, the cooling efficiency (ratio of extracted heat to pump power absorbed) depends very weakly on the host. The cooling efficiency is also almost twice as high for Er3+ (average of 3.8%) than for Yb3+ (average of 2.2%) due to the larger gap between the pump and mean fluorescence energy in Er3+. Of the limited number of materials for which a full set of data was found in the literature, the highest extractable heat for Yb3+ is in phosphate (-51.5 mW/m), and for Er3+ is in chalcogenide (-10.3 mW/m). This work provides a simple methodology to evaluate the quantitative cooling performance of these and other rare-earth ions in any amorphous host, a procedure that should guide researchers in the selection of optimum materials for ASF cooling of fibers.

  • 316. Balobaid, Laila
    et al.
    Carville, N. Craig
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Collins, Liam
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Rodriguez, Brian J.
    Photoreduction of metal nanostructures on periodically proton exchanged MgO-doped lithium niobate crystals2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 18, p. 182904-Article in journal (Refereed)
    Abstract [en]

    Local reactivity on periodically proton exchanged lithium niobate (PPE: LN) surfaces is a promising route for the fabrication of regularly spaced nanostructures. Here, using MgO-doped PPE: LN templates, we investigate the influence of the doping on the nanostructure formation as a function of the proton exchange (PE) depth. The deposition is found to occur preferentially along the boundary between MgO-doped LN and the PE region when the PE depth is at least 1.73 mu m, however, for shallower depths, deposition occurs across the entire PE region. The results are found to be consistent with an increased photoconductivity of the MgO-doped LN.

  • 317. Banerjee, Souvik
    et al.
    Engelsöy, Julius
    Stockholm University, Faculty of Science, Department of Physics.
    Larana-Aragon, Jorge
    Stockholm University, Faculty of Science, Department of Physics.
    Sundborg, Bo
    Stockholm University, Faculty of Science, Department of Physics.
    Thorlacius, Larus
    Stockholm University, Faculty of Science, Department of Physics.
    Wintergerst, Nico
    Quenched coupling, entangled equilibria, and correlated composite operators: a tale of two O(N) modelsIn: Article in journal (Refereed)
  • 318.
    Banerjee, Souvik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics. Julius Maximilians Univ Wurzburg, Inst Theoret Phys & Astrophys, D-97074 Wurzburg, Germany..
    Erdmenger, Johanna
    Julius Maximilians Univ Wurzburg, Inst Theoret Phys & Astrophys, D-97074 Wurzburg, Germany.;Max Planck Inst Phys & Astrophys, Werner Heisenberg Inst, Fohringer Ring 6, D-80805 Munich, Germany..
    Sarkar, Debajyoti
    Max Planck Inst Phys & Astrophys, Werner Heisenberg Inst, Fohringer Ring 6, D-80805 Munich, Germany.;Ludwig Maximilians Univ Munchen, Arnold Sommerfeld Ctr, Theresienstr 37, D-80333 Munich, Germany..
    Connecting Fisher information to bulk entanglement in holography2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 8, article id 001Article in journal (Refereed)
    Abstract [en]

    In the context of relating AdS/CFT to quantum information theory, we propose a holographic dual of Fisher information metric for mixed states in the boundary field theory. This amounts to a holographic measure for the distance between two mixed quantum states. For a spherical subregion in the boundary we show that this is related to a particularly regularized volume enclosed by the Ryu-Takayanagi surface. We further argue that the quantum correction to the proposed Fisher information metric is related to the quantum correction to the boundary entanglement entropy. We discuss consequences of this connection.

  • 319. Baraldi, Alessandro
    et al.
    Vesselli, Erik
    Bianchettin, Laura
    Comelli, Giovanni
    Lizzit, Silvano
    Petaccia, Luca
    de Gironcoli, Stefano
    Locatelli, Andrea
    Mentes, T. Onur
    Aballe, Lucia
    Weissenrieder, Jonas
    Lund University.
    Andersen, Jesper N.
    The (1x1)-> hexagonal structural transition on Pt(100) studied by high-energy resolution core level photoemission2007In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 16Article in journal (Refereed)
    Abstract [en]

    The (1 x 1)-> quasihexagonal (HEX) phase transition on a clean Pt(100) surface was investigated by monitoring the time evolution of the Pt4f(7/2) core level photoemission spectra. The spectral component originating from the atoms forming the (1 x .1) metastable unreconstructed surface was found at -570 +/- 20 meV with respect to the bulk peak. Ab initio calculations based on density functional theory confirmed the experimental assignment. At temperatures above 370 K, the (1 x 1) phase irreversibly reverts to the more stable HEX phase, characterized by a surface core level shifted component at -185 +/- 40 meV. By analyzing the intensity evolution of the core level components, measured at different temperatures in the range of 393-475 K, we determined the activation energy of the phase transformation, E=0.76 +/- 0.04 eV. This value is considerably lower than the one previously determined by means of low energy electron diffraction. Possible reasons for this discrepancy are discussed.

  • 320.
    Baran, Jakub D.
    et al.
    School of Chemistry, University of Bath.
    Jarvis, Samuel P.
    School of Physics and Astronomy, University of Nottingham.
    Taylor, Simon
    School of Physics and Astronomy, University of Nottingham.
    Thompson, Damien
    Department of Physics and Energy, Materials and Surface Science Institute, University of Limerick.
    Saywell, Alex
    Fritz Haber Institute of the Max-Planck Society.
    Mangham, Berry
    School of Chemistry, the University of Nottingham.
    Champness, Neil R.
    School of Chemistry, the University of Nottingham.
    Moriarty, Philip
    School of Physics and Astronomy, University of Nottingham.
    Larsson, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    A Case of Unusually Large Density of States Changes For Physisorption - TetraPhenyl-Porphyrins on Cu(111)2015Conference paper (Other academic)
    Abstract [en]

    Conformational changes caused by surface adsorption can dramatically affect a molecule’s properties. The conformational flexibility of the porphyrin family of molecules has been exploited particularly well in a number of contexts, including prototypical molecular switches. Despite this level of study, however, the exact mechanisms underpinning conformational switching are often unclear. We show that the conformation of the tetra(4-bromophenyl) porphyrin (Br4TPP) on Cu(111) depends critically on the precise adsorption site of the molecule, and that, remarkably, large conformational changes are driven entirely by van der Waals (vdW) interactions between the molecule and the substrate surface. A combination of scanning probe microscopy, low temperature single molecule manipulation, dispersion-corrected density functional theory (DFT) and molecular dynamics (MD) simulations shows that van der Waals forces dominate the adsorption of TPP molecules, causing significant distortions of the molecular architecture so that the porphyrin can adopt one of two low energy conformations. In addition, scanning probe manipulation has been used to translate and switch the Br4TPP molecule between conformations via an intermediary, ‘hybrid’ structure. We have used the generalized gradient approximation (GGA) parameterization by Perdew—Burke—Ernzerhof (PBE), and the sparse-matter optBP86b-vdW20 (vdW-DFT) exchange and correlation functional to account for the missing dispersion forces. In order to check for the presence of chemical bonding we have analyzed the molecule-surface complexes using electron localization function (ELF) and Bader charges. We find that vdW-forces alone are capable of causing large shifts in the molecular density of states, despite the complete absence of chemical interactions.

  • 321.
    Baran, Jakub D.
    et al.
    Tyndall National Institute, University College Cork.
    Kołodziejczyk, Wojciech
    Tyndall National Institute, University College Cork.
    Larsson, Peter O.
    Division of Materials Theory, Department of Physics and Astronomy, Uppsala University.
    Ahuja, Rajeev B.
    Division of Materials Theory, Department of Physics and Astronomy, Uppsala University.
    Larsson, Andreas
    On the stability of single-walled carbon nanotubes and their binding strengths2012In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 131, no 9, p. 1-8Article in journal (Refereed)
    Abstract [en]

    We have studied the relative stability of hydrogen-terminated single-walled carbon nanotubes (SWNTs) segments, and open-ended SWNT fragments of varying diameter and chirality that are present at the interface of the catalytic metal particles during growth. We have found that hydrogen-terminated SWNTs differ by <1 eV in stability among different chiralities, which presents a challenge for selective and property-controlled growth. In addition, both zigzag and armchair tubes can be the most stable chirality of hydrogen-terminated SWNTs, which is a fundamental obstacle for property-controlled growth utilizing thermodynamic stability. In contrast, the most armchair-like open-ended SWNTs segments are always the most stable ones, followed in sequence by chiral index up to the least stable zigzag segments. We explain the ordering by triple bond stabilization of the carbon dangling bonds at the open ends, which is a fragment stabilization effect that is only manifested when all bonds between two layers are broken. We show convincingly that the bond strength difference between zigzag and armchair tubes is not present when individual bonds are broken or formed

  • 322.
    Baran, Jakub D.
    et al.
    Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Structure and energetics of shuttlecock-shaped tin-phthalocyanine on Ag(111: A density functional study employing dispersion correction2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, p. 9487-9497Article in journal (Refereed)
    Abstract [en]

    The reversible switch between two electronically and/or geometrically distinct states of a single molecule adsorbed on a well-characterized substrate is of high technological interest due to its possible use as single molecule devices and novel molecular memories. We have studied shuttlecock-shaped metal phthalocyanines, which can adsorb on surfaces in two distinct adsorption configurations, depending on if the central metal atom points toward or away from the surface, and we report on the adsorption of tin-phthalocyanine (SnPc) on an Ag(111) surface using density functional theory (DFT) including a semiempirical dispersion correction (DFT-D).We discuss the binding mechanism in detail and show that the adsorption of SnPc in these two orientations is driven by very different interactions. While "Sn-down" adsorption involves chemical bonding between Sn and the surface (chemisorption), the "Sn-up" configuration is bound only by weak van der Waals forces (physisorption). By comparing our theoretical results with a broad range of experimental data, we assess the effect of dispersion forces for the SnPc/Ag(111) system and how these impact adsorption energies, geometries, and the electronic structure. We show that an inclusion of dispersion forces improves the adsorption geometry with respect to experiment and is essential in order to capture the subtle electronic effects at molecule-metal interfaces. By analyzing the geometric and electronic structure of the adsorbed molecules we, in addition, shed light on the surprising 2-fold symmetry reduction of metal phthalocyanine molecules that has been observed upon adsorption on surfaces

  • 323.
    Baran, Jakub D.
    et al.
    Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Theoretical insights into adsorption of cobalt phthalocyanine on Ag(111): A combination of chemical and van der Waals bonding2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 45, p. 23887-23898Article in journal (Refereed)
    Abstract [en]

    In this article we study in detail the interaction of cobalt phthalocyanine (CoPc) with the Ag(111) surface by means of density functional theory calculations (DFT). We discuss the electronic and geometric differences of the adsorbed CoPc as it interacts with the different binding sites of the surface, yielding deeper insight into the adsorption mechanism of organometallic molecules with noble metal surfaces. We interpret the experimentally observed 4-fold to 2-fold symmetry reduction upon interaction of phthalocyanine molecules with metal surfaces as caused by electronic effects originating from nonsymmetric interactions between the molecule and the surface. To asses the role of dispersion forces in bonding of CoPc to the surface we employ a semiempirical dispersion correction to standard DFT and compare the obtained molecule-surface separation with experimental measurements. We show that, in the case of CoPc, the molecule bonds to the surface mostly due to covalent bonding between Co and Ag, but with a considerable contribution from van der Waals bonding between the Pc ligand and the surface. We show in this case where the molecule-surface separation is mostly governed by covalent bonding between the central metal atom and the surface atoms that standard DFT performs reasonably well, as compared to the available experimental data.

  • 324. Baranowski, M.
    et al.
    Kudrawiec, R.
    Misiewicz, J.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Nitrogen-related changes in exciton localization and dynamics in GaInNAs/GaAs quantum wells grown by metalorganic vapor phase epitaxy2015In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 118, no 2, p. 479-486Article in journal (Refereed)
    Abstract [en]

    In this work, we show the results of low-temperature photoluminescence (PL), time-resolved photoluminescence, and photoreflectance (PR) investigations, performed on a series of three Ga0.64In0.34As1-x N (x) /GaAs single quantum wells (SQW) grown by metalorganic vapor phase epitaxy with the nitrogen content of 0, 0.5, and 0.8 %. Comparing the PL and PR data, we show that at low excitation intensity and temperature, the radiative recombination occurs via localizing centers (LCs) in all samples. The excitation intensity-dependent PL measurements combined with theoretical modeling of hopping excitons in this system allow us to provide quantitative information on the disorder parameters describing population of LCs. It has been found that the average energy of LCs increases about two times and simultaneously the number of LCs increases about 10 and 20 times after the incorporation of 0.5 and 0.8 % of nitrogen, respectively. The value of average localization energy E > (0) determined for N-containing samples (similar to 6-7 meV) is in the range typical for dilute nitride QWs grown by molecular beam epitaxy (MBE). On the other hand, the "effective" concentration of LCs seems to be higher than for GaInNAs/GaAs QW grown by MBE. The dramatic increase in localizing centers also affects the PL dynamics. Observed PL decay time dispersion is much stronger in GaInNAs SQW than in nitrogen-free SQW. The change in PL dynamic is very well reproduced by model of hopping excitons.

  • 325.
    Baratto, Camilla
    et al.
    University of Brescia.
    Comini, Elisabetta
    University of Brescia.
    Faglia, Guido
    University of Brescia.
    Ferroni, Matteo
    University of Brescia.
    Ponzoni, Andrea
    University of Brescia.
    Vomiero, Alberto
    University of Brescia, CNR-INFM SENSOR Laboratory.
    Sberveglieri, Giorgio
    University of Brescia.
    Transparent Metal Oxide Semiconductors as Gas Sensors2010In: Transparent Electronics: From Synthesis to Applications, John Wiley and Sons , 2010, p. 417-442Chapter in book (Refereed)
  • 326. Barbercheck Epler, Chelsea R.
    et al.
    Bullitt, Esther
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bacterial adhesion pili2018In: Membrane protein complexes: structure and function / [ed] J. Robin Harris, Egbert Boekema, Springer Publishing Company, 2018, , p. 18p. 1-18Chapter in book (Refereed)
    Abstract [en]

    Escherichia coli bacterial cells produce multiple types of adhesion pili that mediate cell-cell and cell-host attachments. These pili (also called 'fimbriae') are large biopolymers that are comprised of subunits assembled via a sophisticated micro-machinery into helix-like structures that are anchored in the bacterial outer membrane. They are commonly essential for initiation of disease and thus provide a potential target for antibacterial prevention and treatment. To develop new therapeutics for disease prevention and treatment we need to understand the molecular mechanisms and the direct role of adhesion pili during pathogenesis. These helix-like pilus structures possess fascinating and unique biomechanical properties that have been thoroughly investigated using high-resolution imaging techniques, force spectroscopy and fluid flow chambers. In this chapter, we first discuss the structure of pili and the micro-machinery responsible for the assembly process. Thereafter, we present methods for measurement of the biomechanics of adhesion pili, including optical tweezers. Data demonstrate unique biomechanical properties of pili that allow bacteria to sustain binding during in vivo fluid shear forces. We thereafter summarize the current biomechanical findings related to adhesion pili and show that pili biomechanical properties are niche-specific. That is, the data suggest that there is an organ-specific adaptation of pili that facilitates infection of the bacteria's target tissue. Thus, pilus biophysical properties are an important part of Escherichia coli pathogenesis, allowing bacteria to overcome hydrodynamic challenges in diverse environments.

  • 327. Baricordi, S.
    et al.
    Biryukov, V. M.
    Institute for High Energy Physics.
    Carnera, A.
    Chesnokov, Yu A.
    Institute for High Energy Physics.
    Mea, G. Della
    University of Trento, Department of Materials Engineering and Industrial Technologies.
    Guidi, V.
    Ivanov, Yu M.
    Petersburg Institute for Nuclear Physics.
    Martinelli, G.
    Milan, E.
    Restello, S.
    INFN.
    Sambo, A.
    Scandale, W.
    CERN.
    Vomiero, Alberto
    Department of Physics, University of Padova.
    Low-energy-channeling surface analysis on silicon crystals designed for high-energy-channeling in accelerators2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 9, article id 94102Article in journal (Refereed)
    Abstract [en]

    Channeling of relativistic particles in bent Si crystals is a powerful technique for use with accelerators. Its efficiency can be found to be highly dependent on the state of the surface of the crystal steering the particles. We investigated the morphology and structure of the surface of the samples that have been used with high efficiency for channeling in accelerators. Low-energy channeling of 2 MeVα particles or protons was used as a probe. We found that mechanical treatment of the samples leads to a superficial damaged layer, which is correlated to efficiency limitations of the crystal in accelerators. In contrast, chemical etching, which was used to treat the surface of the most efficient crystals, leaves a surface with superior perfection. © 2005 American Institute of Physics.

  • 328.
    Basso, Simone
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Konovalenko, Alexander
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Kudinov, Pavel
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Development of scalable empirical closures for self-leveling of particulate debris bed2014In: Proceedings of ICAPP 201,  Paper 14330, American Nuclear Society, 2014, p. 14330-Conference paper (Refereed)
    Abstract [en]

    Melt fragmentation, quenching and long term coolability in a deep pool of water under reactor vessel is employed as a severe accident mitigation strategy in several designs of light water reactors. Geometrical configuration of the debris bed is one of the factors which define if the decay heat can be removed from the debris bed by natural circulation. A bed can be coolable if spread uniformly, while the same debris forming a tall mound-shape debris bed can be non-coolable. Two-phase flow inside the bed serves as a source of mechanical energy which can move debris, thus flatten and gradually reduce the height of the debris bed. There is a competition between the time scales for (i) reaching a coolable configuration of the bed by such “self-leveling” phenomenon, and (ii) onset of dryout and re-melting of the debris. In the previous work we have demonstrated that the rate of particulate debris spreading is determined by local (i) gas velocity, and (ii) slope angle of the bed. The goal of this work is to obtain a dependency of particle motion rate on local slope angle and gas velocity expressed in non-dimensional variables, universal for particles of different shapes, sizes and materials. Such scaling approach is proposed in this work and validated against experimental data.

  • 329.
    Basso, Simone
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Konovalenko, Alexander
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Kudinov, Pavel
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Sensitivity and uncertainty analysis for predication of particulate debris bed self-leveling in prototypic Severe Accident (SA) conditions2014In: Proceedings of ICAPP 2014: Proceedings of ICAPP 2014, Paper 14329, American Nuclear Society, 2014, p. 14329-Conference paper (Refereed)
    Abstract [en]

    Melt fragmentation, quenching and long term coolability in a deep pool of water under reactor vessel are employed as a severe accident mitigation strategy in several designs of light water reactors. Success of the strategy is contingent upon effectiveness of natural circulation in removing the decay heat generated by the porous debris bed. Geometrical configuration of the bed is one of the factors which affect coolability of the bed. Boiling and two-phase flow inside the bed serve as a source of mechanical energy which can change the geometry of the debris bed by so called “self-leveling” phenomenon. The goals of this work are (i) to further develop self-leveling modeling approach and validate it against data produced in a new series of PDS-C (Particulate Debris Spreading Closures) experiments, and (ii) to carry out sensitivity-uncertainty analysis for the debris bed spreading for the selected cases of prototypic severe accident conditions. The model has been extended to predict spreading in both planar and axisymmetric geometries. The performed sensitivity analysis ranks the importance of different uncertain input parameters such as accident conditions, debris bed properties, modeling parameters and closures. The knowledge about the most influential parameters is important for further improvement of the model and for efficient reduction of output uncertainties through focused, separate-effect experimental studies. Finally, we report results for particulate debris spreading in prototypic severe accident scenarios with assessment of uncertainties.

  • 330.
    Basso, Simone
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Konovalenko, Alexander
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Yakush, Sergey
    Institute for Problems in Mechanics, Russian Academy of Sciences, Ave. Vernadskogo 101 Bldg 1, Moscow, 119526, Russia.
    Kudinov, Pavel
    Validation of DECOSIM code against experiments on particle spreading by two-phase flows in water pool2016In: Proceedings of the 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety, NUTHOS-11, 2016, article id N11A0531Conference paper (Refereed)
    Abstract [en]

    Validation simulations by DECOSIM code are performed against recent PDS-P experiments on particle spreading in a planar vertical water pool with bottom air injection. The model implemented in the code considers two-fluid formulation (water, air), turbulence effects in liquid phase are taken into account by k-epsilon model with additional generation terms accounting for two-phase effects. Particles are described by Lagrangian model, with turbulent dispersion modeled by random-walk model. Simulations are performed in conditions corresponding to experimental setup, the test section was a plane rectangular tank of variable length (0.9 and 1.5 m) and pool depth (0.5, 0.7, and 0.9 m), the superficial gas injection velocity ranged between 0.12 and 0.69 m/s. Sedimentation of spherical stainless steel (1.5 and 3 mm) and glass (3 mm) particles was calculated and compared with experiments with respect to the mean spreading distance and lateral distributions of mass fraction of particles. Reasonable agreement between the results obtained and experimental measurements is achieved for all pool geometries, gas injection rates, and particle types, confirming adequacy of the modeling approach and suitability of DECOSIM code for severe accident analysis related to debris bed formation. Possible ways to further reduction of uncertainty in model validation are discussed.

  • 331.
    Basu, Kaustubh
    et al.
    Institut National de la Recherche Scientifique-Énergie, Matériaux et Télécommunications, Université du Québec, Varennes.
    Benetti, Daniele
    Institut National de la Recherche Scientifique-Énergie, Matériaux et Télécommunications, Université du Québec, Varennes.
    Zhao, Haiguang
    Institut National de la Recherche Scientifique Energie Varennes, Institut National de la Recherche Scientifique-Énergie, Matériaux et Télécommunications, Université du Québec, Varennes.
    Jin, Lei
    Institut National de la Recherche Scientifique Energie Varennes, Institut National de la Recherche Scientifique-Énergie, Matériaux et Télécommunications, Université du Québec, Varennes.
    Vetrone, Fiorenzo
    Institut National de la Recherche Scientifique-Énergie, Matériaux et Télécommunications, Université du Québec, Varennes.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rosei, Frederico
    Institut National de la Recherche Scientifique Energie Varennes, Institut National de la Recherche Scientifique-Énergie, Matériaux et Télécommunications, Université du Québec, Varennes.
    Enhanced photovoltaic properties in dye sensitized solar cells by surface treatment of SnO2 photoanodes2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 23312Article in journal (Refereed)
    Abstract [en]

    We report the fabrication and testing of dye sensitized solar cells (DSSC) based on tin oxide (SnO2) particles of average size ~20 nm. Fluorine-doped tin oxide (FTO) conducting glass substrates were treated with TiOx or TiCl4 precursor solutions to create a blocking layer before tape casting the SnO2 mesoporous anode. In addition, SnO2 photoelectrodes were treated with the same precursor solutions to deposit a TiO2 passivating layer covering the SnO2 particles. We found that the modification enhances the short circuit current, open-circuit voltage and fill factor, leading to nearly 2-fold increase in power conversion efficiency, from 1.48% without any treatment, to 2.85% achieved with TiCl4 treatment. The superior photovoltaic performance of the DSSCs assembled with modified photoanode is attributed to enhanced electron lifetime and suppression of electron recombination to the electrolyte, as confirmed by electrochemical impedance spectroscopy (EIS) carried out under dark condition. These results indicate that modification of the FTO and SnO2 anode by titania can play a major role in maximizing the photo conversion efficiency

  • 332.
    Bathen, M. E.
    et al.
    Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, Oslo, Norway.
    Coutinho, J.
    Department of Physics and I3N, University of Aveiro, Campus Santiag, Aveiro, Portugal.
    Ayedh, H. M.
    Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, Oslo, Norway.
    Hassan, J. Ul
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Farkas, I.
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Frodason, Y. K.
    Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, Oslo, Norway.
    Svensson, B. G.
    Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, Oslo, Norway.
    Vines, L.
    Department of Physics/Centre for Materials Science and Nanotechnology, University of Oslo, Oslo, Norway.
    Anisotropic and plane-selective migration of the carbon vacancy in SiC: Theory and experiment2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 1, article id 014103Article in journal (Refereed)
    Abstract [en]

    We investigate the migration mechanism of the carbon vacancy (VC) in silicon carbide (SiC) using a combination of theoretical and experimental methodologies. The VC, commonly present even in state-of-the-art epitaxial SiC material, is known to be a carrier lifetime killer and therefore strongly detrimental to device performance. The desire for VC removal has prompted extensive investigations involving its stability and reactivity. Despite suggestions from theory that VC migrates exclusively on the C sublattice via vacancy-atom exchange, experimental support for such a picture is still unavailable. Moreover, the existence of two inequivalent locations for the vacancy in 4H-SiC [hexagonal, VC(h), and pseudocubic, VC(k)] and their consequences for VC migration have not been considered so far. The first part of the paper presents a theoretical study of VC migration in 3C- and 4H-SiC. We employ a combination of nudged elastic band (NEB) and dimer methods to identify the migration mechanisms, transition state geometries, and respective energy barriers for VC migration. In 3C-SiC, VC is found to migrate with an activation energy of EA=4.0 eV. In 4H-SiC, on the other hand, we anticipate that VC migration is both anisotropic and basal-plane selective. The consequence of these effects is a slower diffusivity along the axial direction, with a predicted activation energy of EA=4.2 eV, and a striking preference for basal migration within the h plane with a barrier of EA=3.7 eV, to the detriment of the k-basal plane. Both effects are rationalized in terms of coordination and bond angle changes near the transition state. In the second part, we provide experimental data that corroborates the above theoretical picture. Anisotropic migration of VC in 4H-SiC is demonstrated by deep level transient spectroscopy (DLTS) depth profiling of the Z1/2 electron trap in annealed samples that were subject to ion implantation. Activation energies of EA=(4.4±0.3) eV and EA=(3.6±0.3) eV were found for VC migration along the c and a directions, respectively, in excellent agreement with the analogous theoretical values. The corresponding prefactors of D0=0.54cm2/s and 0.017cm2/s are in line with a simple jump process, as expected for a primary vacancy point defect.

  • 333.
    Battie, Yann
    et al.
    LCP-A2MC, Université de Lorraine.
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine, LCPME UMR 7564 CNRS-Université de Lorraine.
    Allali, Naoual
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mamane, Victor
    Laboratoire de Synthèse Organométallique et Réactivité, Université Henri Poincaré - Nancy, Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, Nancy Université, SRSMC UMR 7565 CNRS-Université de Lorraine, Faculté des Sciences et Techniques.
    Naciri, Aotmane En
    LCP-A2MC, Université de Lorraine.
    Broch, Laurent
    LCP-A2MC, Université de Lorraine.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mild covalent functionalization of single-walled carbon nanotubes highlighted by spectroscopic ellipsometry2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 96, p. 557-564Article in journal (Refereed)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNT) synthesized using the HiPco® process and purified thereafter were submitted to two covalent functionalization processes: i) a mild oxidation in a concentrated HNO3 solution using microwave irradiation and ii) a radical functionalization to graft methoxyphenyl groups. The samples were analyzed by Raman spectroscopy and spectroscopic ellipsometry in the energy window 0.07-4.96 eV. The complex dielectric function was analytically calculated in order to extract the real (εr) and imaginary (εi) parts of this function vs. the incident energy of the light. The ellipsometric data in the infrared part of the spectrum revealed that process i) mainly affected the amorphous carbon deposited on the surface of SWCNTs while process ii) strongly changed the electronic nature of the film due to a charge transfer between methoxyphenyl groups and SWCNTs. These results demonstrate the richness of information that spectroscopic ellipsometry is able to bring about on an entire carbon nanotube ensemble compared to Raman spectroscopy, while not suffering from limitation on their electronic structure and/or aggregate state/presence of surfactants.

  • 334. Battistin, C.
    et al.
    Hertz, John
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Niels Bohr Institute, Denmark .
    Tyrcha, J.
    Roudi, Yasser
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Centre for Neural Computation, Norway.
    Belief propagation and replicas for inference and learning in a kinetic Ising model with hidden spins2015In: Journal of Statistical Mechanics: Theory and Experiment, ISSN 1742-5468, E-ISSN 1742-5468, no 5, article id P05021Article in journal (Refereed)
    Abstract [en]

    We propose a new algorithm for inferring the state of hidden spins and reconstructing the connections in a synchronous kinetic Ising model, given the observed history. Focusing on the case in which the hidden spins are conditionally independent of each other given the state of observable spins, we show that calculating the likelihood of the data can be simplified by introducing a set of replicated auxiliary spins. Belief propagation (BP) and susceptibility propagation (SusP) can then be used to infer the states of hidden variables and to learn the couplings. We study the convergence and performance of this algorithm for networks with both Gaussian-distributed and binary bonds. We also study how the algorithm behaves as the fraction of hidden nodes and the amount of data are changed, showing that it outperforms the Thouless-Anderson-Palmer (TAP) equations for reconstructing the connections.

  • 335. Battiston, S.
    et al.
    Fiameni, S.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Boldrini, S.
    Famengo, A.
    Agresti, F.
    Stingaciu, M.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Fabrizio, M.
    Barison, S.
    Synthesis and Characterization of Al-Doped Mg2Si Thermoelectric Materials2013In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 42, no 7, p. 1956-1959Article in journal (Refereed)
    Abstract [en]

    Magnesium silicide (Mg2Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion for the middle to high range of temperature. These materials are very attractive for TE research because of the abundance of their constituent elements in the Earth's crust. Mg2Si could replace lead-based TE materials, due to its low cost, nontoxicity, and low density. In this work, the role of aluminum doping (Mg2Si:Al = 1:x for x = 0.005, 0.01, 0.02, and 0.04 molar ratio) in dense Mg2Si materials was investigated. The synthesis process was performed by planetary milling under inert atmosphere starting from commercial Mg2Si pieces and Al powder. After ball milling, the samples were sintered by means of spark plasma sintering to density > 95%. The morphology, composition, and crystal structure of the samples were characterized by field-emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction analyses. Moreover, Seebeck coefficient analyses, as well as electrical and thermal conductivity measurements were performed for all samples up to 600A degrees C. The resultant estimated ZT values are comparable to those reported in the literature for these materials. In particular, the maximum ZT achieved was 0.50 for the x = 0.01 Al-doped sample at 600A degrees C.

  • 336. Baykal, Abdulhadi
    et al.
    Karaoglu, Ebubekir
    Sozeri, Huseyin
    Uysal, Emre
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Synthesis and Characterization of High Catalytic Activity Magnetic Fe3O4 Supported Pd Nanocatalyst2013In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, Vol. 26, no 1, p. 165-171Article in journal (Refereed)
    Abstract [en]

    This study reports the fabrication and characterization of magnetically recyclable catalysts of Fe3O4-Pd nanocomposite as highly effective catalysts for reduction reactions in liquid phase. The characterization of Fe3O4-Pd MRCs were done by X-ray powder diffraction, A +/- nfrared spectroscopy, thermal analyzer, transmission electron spectroscopy, A +/- nductively coupled plasma, UV-Vis spectroscopy, vibrating sample magnetometer, respectively. The reduction of Pd2+ was accomplished with polyethylene glycol 400 (PEG-400) and Fe3O4 nanoparticles were prepared by co-precipitation of FeCI(3)a <...6H(2)O and FeCl(2)a <...4H(2)O. Thus formed Fe3O4-Pd MRCs showed a very high activity in reduction reactions of 4-nitro-aniline and 1,3-di-nitrobenzene in liquid phase. Magnetic character of this system allowed recovery and multiple use without significant loss of its catalytic activity.

  • 337.
    Beaulieu, Luc
    et al.
    Centre hospitalier universitaire de Québec, Canada and Université Laval, Québec, Canada .
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Carrier, Jean-François
    Centre hospitalier de l’Université de Montréal, Québec, Canada and Département de physique, Université de Montréal, Québec Canada .
    Davis, Stephen D.
    University of Wisconsin-Madison, USA and McGill University Health Centre, Montréal, Québec, Canada .
    Mourtada, Firas
    Helen F. Graham Cancer Center, Christiana Care Health System, Newark, Delaware, USA.
    Rivard, Mark J.
    Tufts University School of Medicine, Boston, Massachusetts, USA.
    Thomson, Rowan M.
    Carleton University, Ottawa, Ontario, Canada.
    Verhaegen, Frank
    Maastricht University Medical Center, the Netherlands and McGill University Health Centre, Montréal, Québec, Canada .
    Wareing, Todd A.
    Transpire Inc., Gig Harbor, Washington, USA.
    Williamson, Jeffrey F.
    Virginia Commonwealth University, Richmond, USA.
    Report of the Task Group 186 on model-based dose calculation methods in brachytherapy beyond the TG-43 formalism: Current status and recommendations for clinical implementation2012In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 39, no 10, p. 6208-6236Article in journal (Refereed)
    Abstract [en]

    The charge of Task Group 186 (TG-186) is to provide guidance for early adopters of model-based dose calculation algorithms (MBDCAs) for brachytherapy (BT) dose calculations to ensure practice uniformity. Contrary to external beam radiotherapy, heterogeneity correction algorithms have only recently been made available to the BT community. Yet, BT dose calculation accuracy is highly dependent on scatter conditions and photoelectric effect cross-sections relative to water. In specific situations, differences between the current water-based BT dose calculation formalism (TG-43) and MBDCAs can lead to differences in calculated doses exceeding a factor of 10. MBDCAs raise three major issues that are not addressed by current guidance documents: (1) MBDCA calculated doses are sensitive to the dose specification medium, resulting in energy-dependent differences between dose calculated to water in a homogeneous water geometry (TG-43), dose calculated to the local medium in the heterogeneous medium, and the intermediate scenario of dose calculated to a small volume of water in the heterogeneous medium. (2) MBDCA doses are sensitive to voxel-by-voxel interaction cross sections. Neither conventional single-energy CT nor ICRU∕ICRP tissue composition compilations provide useful guidance for the task of assigning interaction cross sections to each voxel. (3) Since each patient-source-applicator combination is unique, having reference data for each possible combination to benchmark MBDCAs is an impractical strategy. Hence, a new commissioning process is required. TG-186 addresses in detail the above issues through the literature review and provides explicit recommendations based on the current state of knowledge. TG-43-based dose prescription and dose calculation remain in effect, with MBDCA dose reporting performed in parallel when available. In using MBDCAs, it is recommended that the radiation transport should be performed in the heterogeneous medium and, at minimum, the dose to the local medium be reported along with the TG-43 calculated doses. Assignments of voxel-by-voxel cross sections represent a particular challenge. Electron density information is readily extracted from CT imaging, but cannot be used to distinguish between different materials having the same density. Therefore, a recommendation is made to use a number of standardized materials to maintain uniformity across institutions. Sensitivity analysis shows that this recommendation offers increased accuracy over TG-43. MBDCA commissioning will share commonalities with current TG-43-based systems, but in addition there will be algorithm-specific tasks. Two levels of commissioning are recommended: reproducing TG-43 dose parameters and testing the advanced capabilities of MBDCAs. For validation of heterogeneity and scatter conditions, MBDCAs should mimic the 3D dose distributions from reference virtual geometries. Potential changes in BT dose prescriptions and MBDCA limitations are discussed. When data required for full MBDCA implementation are insufficient, interim recommendations are made and potential areas of research are identified. Application of TG-186 guidance should retain practice uniformity in transitioning from the TG-43 to the MBDCA approach.

  • 338. Bech, Morten L
    et al.
    Bergstrom, Carl T
    Rosvall, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Garratt, Rodney J
    Mapping change in the overnight money market2015In: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 424, p. 44-51Article in journal (Refereed)
    Abstract [en]

    We use an information-theoretic approach to describe changes in lending relationships between financial institutions around the time of the Lehman Brothers failure. Unlike previous work that conducts maximum likelihood estimation on undirected networks our analysis distinguishes between borrowers and lenders and looks for broader lending relationships (multi-bank lending cycles) that extend beyond the immediate counter-parties. We detect significant changes in lending patterns following implementation of the Interest on Required and Excess Reserves policy by the Federal Reserve in October 2008. Analysis of micro-scale rates of change in the data suggests these changes were triggered by the collapse of Lehman Brothers a few weeks before.

  • 339.
    Becherini, Yvonne
    University of Bologna .
    MACRO results on atmospheric neutrino oscillations2003In: Neutrino Physics / [ed] Bellotti, E; Declais, Y; Strolin, P; Zanotti, L, Amsterdam: IOS Press, 2003, Vol. 152, p. 269-273Conference paper (Other academic)
  • 340. Becherini, Yvonne
    et al.
    Margiotta, A
    Sioli, M
    Spurio, M
    A parameterisation of single and multiple muons in the deep water or ice2006In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 25, no 1, p. 1-13Article in journal (Refereed)
    Abstract [en]

    Atmospheric muons play an important role in underwater/ice neutrino detectors. In this paper, a parameterisation of the flux of single and multiple muon events, their lateral distribution and of their energy spectrum is presented. The kinematics parameters were modelled starting from a full Monte Carlo simulation of the interaction of primary cosmic rays with atmospheric nuclei; secondary muons reaching the sea level were propagated in the deep water. The parametric formulas are valid for a vertical depth of 1.5-5 km.w.e. and lip to 85 degrees for the zenith angle, and can be used as input for a fast simulation of atmospheric muons in underwater/ice detectors. (c) 2005 Elsevier B.V. All rights reserved.

  • 341. Becker, Chandler A.
    et al.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Baricco, Marcello
    Chen, Qing
    Decterov, Sergei A.
    Kattner, Ursula R.
    Perepezko, John H.
    Pottlacher, Gernot R.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Thermodynamic modelling of liquids: CALPHAD approaches and contributions from statistical physics2014In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 251, no 1, p. 33-52Article in journal (Refereed)
    Abstract [en]

    We describe current approaches to thermodynamic modelling of liquids for the CALPHAD method, the use of available experimental methods and results in this type of modelling, and considerations in the use of atomic-scale simulation methods to inform a CALPHAD approach. We begin with an overview of the formalism currently used in CALPHAD to describe the temperature dependence of the liquid Gibbs free energy and outline opportunities for improvement by reviewing the current physical understanding of the liquid. Brief descriptions of experimental methods for extracting high-temperature data on liquids and the preparation of undercooled liquid samples are presented. Properties of a well-determined substance, B-2 O-3, including the glass transition, are then discussed in detail to emphasize specific modelling requirements for the liquid. We then examine the two-state model proposed for CALPHAD in detail and compare results with experiment and theory, where available. We further examine the contributions of atomic-scale methods to the understanding of liquids and their potential for supplementing available data. We discuss molecular dynamics (MD) and Monte Carlo methods that employ atomic interactions from classical interatomic potentials, as well as contributions from ab initio MD. We conclude with a summary of our findings.

  • 342.
    Beek, C. J. van der
    et al.
    Laboratoire des Solides Irradiés, CNRS-UMR 7642 & CEA/DSM/DRECAM, Ecole Polytechnique, Palaiseau cedex.
    Klein, Thierry
    Institut Néel, Grenoble.
    Brusetti, René
    Institut Néel, Grenoble.
    Marcenat, Christophe
    Commissariat à l'Energie Atomique, Grenoble.
    Wallin, Mats
    Kungliga tekniska högskolan, KTH.
    Teitel, S.
    University of Rochester.
    Weber, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thermodynamics of a heavy-ion-irradiated superconductor: the zero-field transition2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 10Article in journal (Refereed)
    Abstract [en]

    Specific heat measurements show that the introduction of amorphous columnar defects considerably affects the transition from the normal to the superconducting state in zero magnetic field. Experimental results are compared to numerical simulations of the three-dimensional XY model for both the pure system and the system containing random columnar disorder. The numerics reproduce the salient features of experiment, showing in particular that the specific heat peak changes from cusplike to smoothly rounded when columnar defects are added. By considering the specific heat critical exponent α, we argue that such behavior is consistent with recent numerical work [A. Vestergren et al., Phys. Rev. B 70, 054508 (2004)] showing that the introduction of columnar defects changes the universality class of the transition.

  • 343.
    Bejhed Stjernberg, Rebecca
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tian, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Eriksson, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Oscarsson, Sven
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, SE-10691 Stockholm, Sweden..
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Magnetophoretic Transport Line System for Rapid On-Chip Attomole Protein Detection2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 37, p. 10296-10302Article in journal (Refereed)
    Abstract [en]

    A lab-on-a-chip traveling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micrometer-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized, forming a sandwich-type assay. The MBs were transported across a detection area, and the presence of target molecules resulted in the immobilization of MBs within this area. Target quantification was accomplished by MB counting in the detection area using an optical microscope. In order to demonstrate the versatility of the microarray, biotinylated antiavidin was selected as the target protein. In this case, avidin-functionalized MBs and an avidin-functionalized detection area were used. With a total assay time of 1 to 1.5 h (depending on the labeling approach used), a limit of detection in the attomole range was achieved. Compared to on-chip surface plasmon resonance biodetection systems, our method has a larger dynamic range and is about a factor of 500 times more sensitive. Furthermore, our MB transportation system can operate in any chip-based biosensor platform, thereby significantly improving traditional biosensors.

  • 344.
    Bejmer, Klaes-Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Malm, Christian
    PWR fuel of high enrichment with erbia and enriched gadolinia2011Conference paper (Refereed)
  • 345.
    Belicev, P. P.
    et al.
    University of Belgrade, Serbia.
    Gligoric, G.
    University of Belgrade, Serbia.
    Maluckov, A.
    University of Belgrade, Serbia.
    Stepic, M.
    University of Belgrade, Serbia.
    Johansson, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Localized gap modes in nonlinear dimerized Lieb lattices2017In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 96, no 6, article id 063838Article in journal (Refereed)
    Abstract [en]

    Compact localized modes of ring type exist in many two-dimensional lattices with a flat linear band, such as the Lieb lattice. The uniform Lieb lattice is gapless, but gaps surrounding the flat band can be induced by various types of bond alternations (dimerizations) without destroying the compact linear eigenmodes. Here, we investigate the conditions under which such diffractionless modes can be formed and propagated also in the presence of a cubic on-site (Kerr) nonlinearity. For the simplest type of dimerization with a three-site unit cell, nonlinearity destroys the exact compactness, but strongly localized modes with frequencies inside the gap are still found to propagate stably for certain regimes of system parameters. By contrast, introducing a dimerization with a 12-site unit cell, compact (diffractionless) gap modes are found to exist as exact nonlinear solutions in continuation of flat band linear eigenmodes. These modes appear to be generally weakly unstable, but dynamical simulations show parameter regimes where localization would persist for propagation lengths much larger than the size of typical experimental waveguide array configurations. Our findings represent an attempt to realize conditions for full control of light propagation in photonic environments.

  • 346. Bellier, Q.
    et al.
    Bouit, P. -A
    Kamada, K.
    Feneyrou, P.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Maury, O.
    Andraud, C.
    Design of near-infrared dyes for nonlinear optics: Towards optical limiting applications at telecommunication wavelengths2009In: Optical Materials in Defence Systems Technology VI, SPIE - International Society for Optical Engineering, 2009, p. 74870G-Conference paper (Refereed)
    Abstract [en]

    The rapid development of frequency-tunable pulsed lasers up to telecommunication wavelengths (1400-1600 nm) led to the design of new materials for nonlinear absorption in this spectral range. In this context, two families of near infra-red (NIR) chromophores, namely heptamethine cyanine and aza-borondipyrromethene (aza-bodipy) dyes were studied. In both cases, they show significant two-photon absorption (TPA) cross-sections in the 1400-1600 nm spectral range and display good optical power limiting (OPL) properties. OPL curves were interpreted on the basis of TPA followed by excited state absorption (ESA) phenomena. Finally these systems have several relevant properties like nonlinear absorption properties, gram scale synthesis and high solubility. In addition, they could be functionalized on several sites which open the way to numerous practical applications in biology, solid-state optical limiting and signal processing.

  • 347.
    Belonoshko, Anatoly B.
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Rosengren, Anders
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    A possible mechanism of copper corrosion in anoxic water2012In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 92, no 36, p. 4618-4627Article in journal (Refereed)
    Abstract [en]

    Recent experiments show that solid Cu reacts with anoxic water. The reaction is observed by measuring the hydrogen release. This release is continuous and stable over a period of months. We have since theoretically found that water adsorbs dissociatively at a copper surface. But this adsorption is not enough to explain the amount of hydrogen released in the experiment. This observation calls for the explanation of the removal of the reaction product from the surface to provide a clean Cu surface where the water dissociation takes place. In this paper we investigate, by first-principles calculations, two possible mechanisms for this removal: first the possibility of Cu-O-H nanoparticulate formation, and second the diffusion of the dissociation products into Cu. We show that while the formation of nanoparticulates is energetically unfavorable, the diffusion of OH along grain boundaries can be substantial. The OH being placed in a grain boundary of the Cu sample quickly dissociates and O and H atoms diffuse independently of each other. Such a diffusion is markedly larger than the diffusion in bulk Cu. Thus, grain boundary diffusion is a viable mechanism for providing a clean Cu surface for the dissociation of water at the Cu surface. An order-of-magnitude estimate of the amount of hydrogen released in this case agrees with experiment. But this mechanism is not enough to explain the result of the experiment. We propose the formation of nanocrystals of copper oxide as a second step. A decisive experiment is proposed. 

  • 348. Belotelov, V. I.
    et al.
    Kreilkamp, L. E.
    Kalish, A. N.
    Akimov, I. A.
    Bykov, D. A.
    Kasture, S.
    Yallapragada, V. J.
    Gopal, A. V.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Khartsev, Sergiy I.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Nur-E-Alam, M.
    Vasiliev, M.
    Doskolovich, L. L.
    Yakovlev, D. R.
    Alameh, K.
    Zvezdin, A. K.
    Bayer, M.
    Magnetophotonic intensity effects in hybrid metal-dielectric structures2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 4, p. 045118-Article in journal (Refereed)
    Abstract [en]

    The magneto-optical properties of a hybrid metal-dielectric structure consisting of a one-dimensional gold grating on top of a magnetic waveguide layer are studied experimentally and theoretically. It is demonstrated that a magnetic field applied in the longitudinal configuration (in the plane of the magnetic film and perpendicular to the slits in the gold grating) to the metal-dielectric structure modifies the field distribution of the optical modes and thus changes the mode excitation conditions. In the optical far field, this manifests in the alteration of the optical transmittance or reflectance when the structure becomes magnetized. This magneto-optical effect is shown to represent a novel class of effects related to the magnetic-field-induced modification of the Bloch modes of the periodic hybrid structure. That is why we define this effect as "longitudinal magnetophotonic intensity effect" (LMPIE). The LMPIE has two contributions, odd and even in magnetization. While the even LMPIE is maximal for the light polarized perpendicular to the grating slits (TM) and minimal for the orthogonal polarization (TE), the odd LMPIE takes maximum values at some intermediate polarization and vanishes for pure TM and TE polarizations. Two principal modes of the magnetic layer - TM and TE - acquire in the longitudinal magnetic field additional field components and thus turn into quasi-TM and quasi-TE modes, respectively. The largest LMPIE is observed for excitation of the antisymmetrical quasi-TE mode by TM-polarized light. The value of the LMPIE measured for the plasmonic structure with a magnetic film of Bi2Dy1Fe4Ga1O12 composition is about 1% for the even effect and 2% for the odd one. However, the plasmonic structure with a magnetic film with a higher concentration of bismuth (Bi2.97Er0.03Fe4Al0.5Ga0.5O12) gives significantly larger LMPIE: even LMPIE reaches 24% and odd LMPIE is 9%. Enhancement of the magneto-optical figure of merit (defined as the ratio of the specific Faraday angle of a magnetic film to its absorption coefficient) of the magnetic films potentially causes the even LMPIE to exceed 100% as is predicted by calculations. Thus, the nanostructured material described here may be considered as an ultrafast magnetophotonic light valve.

  • 349.
    Bemmerer, D.
    et al.
    INFN.
    Confortola, F.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Lemut, A.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Bonetti, R.
    Istituto di Fisica Generale Applicata.
    Broggini, C.
    INFN.
    Corvisiero, P.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Costantini, H.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Cruz, J.
    Centro de Fısica Nuclear da Universidade de Lisboa.
    Formicola, A.
    Laboratori Nazionali del Gran Sasso.
    Fülöp, Zs
    Institute of Nuclear Research (ATOMKI), Debrecen.
    Gervino, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Guglielmetti, A.
    Istituto di Fisica Generale Applicata.
    Gustavino, C.
    Laboratori Nazionali del Gran Sasso.
    Gyürky, Gy
    Institute of Nuclear Research (ATOMKI), Debrecen.
    Imbriani, G.
    Dipartimento di Scienze Fisiche, Universitá Federico II.
    Jesus, A. P.
    Centro de Fısica Nuclear da Universidade de Lisboa.
    Junker, M.
    Laboratori Nazionali del Gran Sasso.
    Limata, B.
    Dipartimento di Scienze Fisiche, Universitá Federico II.
    Menegazzo, R.
    INFN.
    Prati, P.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Roca, V.
    Dipartimento di Scienze Fisiche, Universitá Federico II.
    Rogalla, D.
    Seconda Università di Napoli.
    Rolfs, C.
    Institut Für Experimentalphysik III.
    Romano, M.
    Dipartimento di Scienze Fisiche, Universitá Federico II.
    Alvarez, C. Rossi
    INFN.
    Vomiero, Alberto
    INFN Laboratori Nazionali di Legnaro.
    Feasibility of low-energy radiative-capture experiments at the LUNA underground accelerator facility2005In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 24, no 2, p. 313-319Article in journal (Refereed)
    Abstract [en]

    The LUNA (Laboratory Underground for Nuclear Astrophysics) facility has been designed to study nuclear reactions of astrophysical interest. It is located deep underground in the Gran Sasso National Laboratory, Italy. Two electrostatic accelerators, with 50 and 400 kV maximum voltage, in combination with solid and gas target setups allowed to measure the total cross-sections of the radiative-capture reactions 2H2H(p, γ) 3He3Heand 14N14N(p, γ) 15O15Owithin their relevant Gamow peaks. We report on the gamma background in the Gran Sasso laboratory measured by germanium and bismuth germanate detectors, with and without an incident proton beam. A method to localize the sources of beam-induced background using the Doppler shift of emitted gamma rays is presented. The feasibility of radiative-capture studies at energies of astrophysical interest is discussed for several experimental scenarios. © Società Italiana di Fisica/Springer-Verlag 2005.

  • 350.
    Benavides, Vicente
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Chernogorova, Olga
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow, Baikov Institute of Metallurgy and Materials Science (IMET), Russian Academy of Sciences.
    Drozdova, Ekaterina I.
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow.
    Ushakova, Iraida N.
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Raman and electron microscopy study of C60 collapse/transformation to a nanoclustered graphene-based disordered carbon phase at high pressure/temperature2015In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 252, no 11, p. 2626-2629Article in journal (Refereed)
    Abstract [en]

    Transformation of C60 polymers to a superelastic hard carbon (nanoclustered graphene phase (NGP)) occurring in metal matrix at 5 GPa in a temperature interval of 1000–1100 K was studied by optical, scanning electron microscopy (SEM), and Raman spectroscopy. Raman spectral scan across the sample surface allowed us to identify different stages of the structural transformation. The SEM and Raman spectroscopy data testify for the NGP appearance at the defects concentration sites in the parent fullerite structure. We propose that the buckyballs collapse/formation of the NGP is governed by nucleation and growth (diffusive) mechanism unlike earlier discussed in the literature possibility of the martensitic-type (displacive) character of this transformation.

45678910 301 - 350 of 3670
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf