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  • 101.
    Bhardwaj, Anshuman
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Sam, Lydia
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Granada, Spain.
    Zorzano Mier, María-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, Madrid, Spain.
    Distribution and Morphologies of Transverse Aeolian Ridges in ExoMars 2020 Rover Landing Site2019Inngår i: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 11, nr 8, artikkel-id 912Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aeolian processes are believed to play a major role in the landscape evolution of Mars. Investigations on Martian aeolian landforms such as ripples, transverse aeolian ridges (TARs), and dunes, and aeolian sediment flux measurements are important to enhance our understanding of past and present wind regimes, the ongoing dust cycle, landscape evolution, and geochemistry. These aeolian bedforms are often comprised of loose sand and sharply undulating topography and thus pose a threat to mobility and maneuvers of Mars rovers. Here we present a first-hand account of the distribution, morphologies, and morphometrics of TARs in Oxia Planum, the recently selected ExoMars 2020 Rover landing site. The gridded mapping was performed for contiguous stretches of TARs within all the landing ellipses using 57 sub-meter high resolution imaging science experiment (HiRISE) scenes. We also provide the morphological descriptions for all types of TARs present within the landing ellipses. We use HiRISE digital terrain models (DTMs) along with the images to derive morphometric information for TARs in Oxia Planum. In general, the average areal TAR coverage was found to be 5.4% (±4.9% standard deviation), increasing from west to east within the landing ellipses. We report the average TAR morphometrics in the form of crest–ridge width (131.1 ± 106.2 m), down-wind TAR length (17.6 ± 10.1 m), wavelength (37.3 ± 11.6 m), plan view aspect ratio (7.1 ± 2.3), inter-bedform spacing (2.1 ± 1.1), slope (10.6° ± 6.1°), predominant orientations (NE-SW and E-W), and height (1.2 ± 0.8 m). While simple TARs are predominant, we report other TAR morphologies such as forked TAR, wavy TAR with associated smaller secondary ripples, barchan-like TAR, networked TAR, and mini-TARs from the region. Our results can help in planning the rover traverses in terms of both safe passage and scientific returns favoring aeolian research, particularly improving our understanding of TARs.

  • 102.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Schröppel, Birgit
    Natural and Medical Sciences Institute (NMI), University of Tübingen.
    Kaech, Andres
    Center for Microscopy and Image Analysis, University of Zurich.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Forsmo, Seija P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Microstructure of Bentonite in Iron Ore Green Pellets2014Inngår i: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 20, nr 1, s. 33-41Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sodium-activated calcium bentonite is used as a binder in iron ore pellets and is known to increase strength of both wet and dry iron ore green pellets. In this article, the microstructure of bentonite in magnetite pellets is revealed for the first time using scanning electron microscopy. The microstructure of bentonite in wet and dry iron ore pellets, as well as in distilled water, was imaged by various imaging techniques (e.g., imaging at low voltage with monochromatic and decelerated beam or low loss backscattered electrons) and cryogenic methods (i.e., high pressure freezing and plunge freezing in liquid ethane). In wet iron ore green pellets, clay tactoids (stacks of parallel primary clay platelets) were very well dispersed and formed a voluminous network occupying the space available between mineral particles. When the pellet was dried, bentonite was drawn to the contact points between the particles and formed solid bridges, which impart strength to the solid compact.

  • 103.
    Bianchi, F
    et al.
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Careni, M
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Mangia, A
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Mattarozzi, M
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Musci, M
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Concina, Isabella
    INFM-CNR SENSOR Lab. and Physics and Chemistry Department.
    Gobbi, Emanuela
    CNR IDASC SENSOR Lab, University of Brescia.
    Characterisation of the volatile profile of orange juice contaminated with Alicyclobacillus acidoterrestris2010Inngår i: Food Chemistry, ISSN 0308-8146, E-ISSN 1873-7072, Vol. 123, nr 3, s. 653-658Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A rapid and reliable analytical method, based on the characterisation of the volatile profile by dynamic headspace extraction followed by gas chromatography mass-spectrometry, was developed in order to early detect Alicyclobacillus acidoterrestris spoilage in orange juice. Gas chromatographic peak areas were submitted to multivariate statistical analysis (principal component and linear discriminant analysis) in order to visualise clusters within samples and to detect the volatile compounds able to differentiate contaminated from not-contaminated samples. Significant differences in the volatile profile of the analysed samples were found, assessing the reliability of the proposed method to detect the A. acidoterrestris contamination in orange juice.Neither guaiacol nor 2,6-dibromophenol, usually regarded as A. acidoterrestris contamination markers, were detected in the analysed samples.

  • 104.
    Bianchi, F
    et al.
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Careri, M
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Mangia, A
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Mattarozzi, M
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Musci, M
    Univ Studi Parma, Dipartimento Chim Gen & Inorgan,.
    Concina, Isabella
    University of Brescia, CNR-INFM SENSOR Laboratory.
    Falasconi, Matteo
    CNR IDASC SENSOR Lab, University of Brescia.
    Gobbi, Emanuela
    Univ Udine.
    Pardo, Matteo
    CNR-IDASC SENSOR Lab and Dipartimento di Chimica e Fisica per l'Ingegneria e per i Materiali, University of Brescia.
    Sberveglieri, Giorgio
    SENSOR Lab, Department of Information Engineering, University of Brescia.
    Differentiation of the volatile profile of microbiologically contaminated canned tomatoes by dynamic headspace extraction followed by gas chromatography-mass spectrometry analysis2009Inngår i: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 77, nr 3, s. 962-970Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aromatic profile of microbiologically contaminated canned tomatoes was analyzed by the dynamic headspace extraction technique coupled with gas chromatography-mass spectrometry. Canned tomatoes contaminated with Escherichia coli, Saccharomyces cerevisiae and Aspergillus carbonarius were analyzed after 2 and 7 days. About 100 volatiles were detected, among which alcohols, aldehydes and ketones were the most abundant compounds. Gas chromatographic peak areas were used for statistical purposes. First, principal component analysis was carried out in order to visualize data trends and clusters. Then, linear discriminant analysis was performed in order to detect the set of volatile compounds ables to differentiate groups of analyzed samples. Five volatile compounds, i.e. ethanol, beta-myrcene,o-methyl styrene, 6-methyl-5-hepten-2-ol and 1-octanol, were found to be able to better discriminate between uncontaminated and contaminated samples. Prediction ability of the calculated model was estimated to be 100% by the "leave-one-out" cross-validation. An electronic nose device was then used to analyze the same contaminated and not contaminated canned tomato samples. Preliminary results were compared with those obtained by dynamic headspace gas chromatography-mass spectrometry, showing a good agreement.

  • 105.
    Bianchi, S.
    et al.
    CNR IDASC SENSOR Lab.
    Comini, E.
    CNR IDASC SENSOR Lab.
    Ferroni, M.
    CNR IDASC SENSOR Lab.
    Faglia, G.
    CNR IDASC SENSOR Lab.
    Vomiero, Alberto
    University of Brescia, CNR-INFM SENSOR Laboratory.
    Sberveglieri, G.
    CNR IDASC SENSOR Lab.
    Indium oxide quasi-monodimensional low temperature gas sensor2006Inngår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 118, nr 1-2, s. 204-207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the sensing properties of indium oxide nanostructures and tailored the deposition conditions in order to obtain nano-wires of indium oxide. We have comparatively tested the gas sensing properties of nano-wires with micrometric or even nanometric size. The micro-wires feature interesting gas sensitivity at room temperature, particularly in the case of nitrogen dioxide detection. The sensing performance is improved as the lateral dimension of the wire decreases. © 2006 Elsevier B.V. All rights reserved.

  • 106.
    Blaschke, D.
    et al.
    Gesellschaft für Schwerionenforschung mbH (GSI).
    Fredriksson, Sverker
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grigorian, H.
    Institut für Physik, Universität Rostock.
    Öztas, A.M.
    Department of Physics, Hacettepe University.
    Sandin, Fredrik
    The Phase diagram of three-flavor quark matter under compact star constraints2005Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 72, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phase diagram of three-flavor quark matter under compact star constraints is investigated within a Nambu-Jona-Lasinio model. Global color and electric charge neutrality is imposed for beta-equilibrated superconducting quark matter. The constituent quark masses and the diquark condensates are determined self-consistently in the plane of temperature and quark chemical potential. Both strong and intermediate diquark coupling strengths are considered. We show that in both cases, gapless superconducting phases do not occur at temperatures relevant for compact star evolution, i.e., below T~50 MeV. The stability and structure of isothermal quark star configurations are evaluated. For intermediate coupling, quark stars are composed of a mixed phase of normal (NQ) and two-flavor superconducting (2SC) quark matter up to a maximum mass of 1.21 M[sun]. At higher central densities, a phase transition to the three-flavor color flavor locked (CFL) phase occurs and the configurations become unstable. For the strong diquark coupling we find stable stars in the 2SC phase, with masses up to 1.33 M[sun]. A second family of more compact configurations (twins) with a CFL quark matter core and a 2SC shell is also found to be stable. The twins have masses in the range 1.30...1.33 M[sun]. We consider also hot isothermal configurations at temperature T=40 MeV. When the hot maximum mass configuration cools down, due to emission of photons and neutrinos, a mass defect of 0.1 M[sun] occurs and two final state configurations are possible

  • 107.
    Blaschke, David
    et al.
    Rostock University.
    Fredriksson, Sverker
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grigorian, H.
    Rostock University.
    Oztas, A.M.
    Hacettepe University, Ankara.
    Diquark condensation effects on hot quark star configurations2004Inngår i: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 736, nr 1-2, s. 203-219Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the formfactors of the interaction on the phase diagram of quark matter. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state under the condition of β-equilibrium and charge neutrality. We calculate the quark star configurations by solving the Tolman-Oppenheimer-Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of ΔMc2˜1053 erg. We find that this energy could not serve as an engine for explosive phenomena since the phase transition is not first order. Contrary to naive expectations the mass defect increases when for a given temperature we neglect the possibility of diquark condensation.

  • 108.
    Blaschke, David
    et al.
    Rostock University.
    Fredriksson, Sverker
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oztas, Ahmet Mecit
    Hacettepe University, Ankara.
    Diquark properties and the TOV equations2001Inngår i: Proceedings of the Conference on Compact Stars in the QCD Phase Diagram (CSQCD), Copenhagen, Denmark, August 15 - 18, 2001 / [ed] Rachid Ouyed ..., 2001, s. 167-173Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present various results from including diquark properties and the gap equations into the TOV equations for compact quark objects. One such property is the diquark form factor, which has a strong influence on various quantities. We discuss the consequences for quark stars.

  • 109.
    Blaschke, David
    et al.
    University of Wroclaw.
    Klahn, Thomas
    Argonne National Laboratory, Argonne, IL.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Equation of state at high densities and modern compact star observations2008Inngår i: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 35, nr 1, s. 014051-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, observations of compact stars have provided new data of high accuracy which put strong constraints on the high-density behaviour of the equation of state of strongly interacting matter otherwise not accessible in terrestrial laboratories. The evidence for neutron stars with high mass (M = 2.1 +/- 0.2 M-circle dot for PSR J0751 + 1807) and large radii (R > 12 km for RX J1856-3754) rules out soft equations of state and has provoked a debate whether the occurrence of quark matter in compact stars can be excluded as well. In this contribution, it is shown that modern quantum field theoretical approaches to quark matter including colour superconductivity, and a vector meanfield allow a microscopic description of hybrid stars which fulfil the new, strong constraints. The deconfinement transition in the resulting stiff hybrid equation of state is weakly first order so that its signals have to be expected due to specific changes in transport properties governing the rotational and cooling evolution caused by the colour superconductivity of quark matter. A similar conclusion holds for the investigation of quark deconfinement in future generations of nucleus-nucleus collision experiments at low temperatures and high baryon densities such as CBM @ FAIR.

  • 110.
    Blaschke, David
    et al.
    University of Wroclaw.
    Klähn, Thomas
    Argonne National Laboratory, Argonne, IL.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Color superconducting quark matter in compact stars2008Inngår i: Exotic States of Nuclear Matter: Proceedings of the International Symposium EXOCT07, Catania University, Italy, 11 - 15 June 2007 / [ed] Umberto Lombardo; Marcello Baldo; Fiorella Burgio; Hans-Josef Schulze, Hackensack, NJ: World Scientific and Engineering Academy and Society, 2008, s. 256-263Konferansepaper (Fagfellevurdert)
  • 111.
    Blaschke, David
    et al.
    Instytut Fizyki Teoretycznej, Uniwersytet Wrocławski.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Klähn, Thomas
    Argonne National Laboratory, Argonne, IL.
    Berdermann, Jens
    DESY Zeuthen, Berlin.
    Single-flavor CSL phase in compact stars2008Inngår i: Hadronic physics: Joint Meeting Heidelberg-Liège-Paris-Wroclaw, HLPW 2008, Spa, Belgium, 6 - 8 March 2008 / [ed] Joseph Cugnon; Jean-Philippe Lansberg, Melville, NY: American Institute of Physics (AIP), 2008, s. 183-192Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We suggest a scenario where the three light quark flavors are sequentially deconfined under increasing pressure in cold asymmetric nuclear matter as, e.g., in neutron stars. The basis for our analysis is a chiral quark matter model of Nambu-Jona-Lasinio (NJL) type with diquark pairing in the spin-1 single flavor (CSL), spin-0 two flavor (2SC) and three flavor (CFL) channels. We find that nucleon dissociation sets in at about the saturation density, n0, when the down-quark Fermi sea is populated (d-quark dripline) due to the flavor asymmetry induced by β-equilibrium and charge neutrality. At about 3n0 u-quarks appear and a two-flavor color superconducting (2SC) phase is formed. The s-quark Fermi sea is populated only at still higher baryon density, when the quark chemical potential is of the order of the dynamically generated strange quark mass. We construct two different hybrid equations of state (EoS) using the Dirac-Brueckner Hartree-Fock (DBHF) approach and the EoS by Shen et al. in the nuclear matter sector. The corresponding hybrid star sequences have maximum masses of, respectively, 2.1 and 2.0 M⊙. Two- and three-flavor quark-matter phases exist only in gravitationally unstable hybrid star solutions in the DBHF case, while the Shen-based EoS produce stable configurations with a 2SC phase component in the core of massive stars. Nucleon dissociation due to d-quark drip at the crust-core boundary fulfills basic criteria for a deep crustal heating process which is required to explain superbusts as well as cooling of X-ray transients.

  • 112.
    Borgani, Riccardo
    et al.
    Nanostructure Physics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Gilzad Kohan, Mojtaba
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Haviland, David B.
    Nanostructure Physics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Fast Multifrequency Measurement of Nonlinear Conductance2019Inngår i: Physical Review Applied, E-ISSN 2331-7019, Vol. 11, nr 4, artikkel-id 044062Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe a phase-coherent multifrequency lock-in measurement technique that uses the inverse Fourier transform to reconstruct the nonlinear current-voltage characteristic of a nanoscale junction. The method provides separation of the galvanic and displacement currents in the junction and easy cancellation of the parasitic displacement current from the measurement leads. These two features allow us to overcome traditional limitations imposed by the low conductance of the junction and the high capacitance of the leads, thus providing an increase in measurement speed of several orders of magnitude. We demonstrate the method in the context of conductive atomic force microscopy, acquiring current-voltage characteristics at every pixel while scanning at standard imaging speed.

  • 113.
    Bortoluzzi, Marco
    et al.
    Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia.
    Castro, Jesús
    Departamento de Química Inorgánica, Universidade de Vigo, Facultade de Química, Edificio de Ciencias Experimentais.
    Enrichi, Francesco
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Consorzio Interuniversitario Reattività Chimica e Catalisi (CIRCC) .
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Busato, Marta
    Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia.
    Huang, Weizhe
    Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia.
    Green-emitting manganese (II) complexes with phosphoramide and phenylphosphonic diamide ligands2018Inngår i: Inorganic Chemistry Communications, ISSN 1387-7003, E-ISSN 1879-0259, Vol. 92, s. 145-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tetrahedral manganese(II) complexes having formulae [MnX2{O = PR(NMe2)2}2] (X = Br, I; R = NMe2, Ph) were isolated and characterized, and in the case of [MnBr2{O = PPh(NMe2)2}2] the structure was ascertained by means of single crystal X-ray diffraction. All the complexes showed intense green emission assigned to the Mn(II) 4T1(4G) → 6A1(6S) transition upon excitation with UV light, with photoluminescence lifetimes in the range 100–1000 μs. Bromo-complexes maintain their luminescence features once dispersed in polycaprolactone matrix.

  • 114.
    Bortoluzzi, Marco
    et al.
    Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, Mestre, VE, Italy;Consorzio Interuniversitario Reattività Chimica e Catalisi (CIRCC), Bari, Italy.
    Castro, Jesús
    Departamento de Química Inorgánica, Universidade de Vigo, Facultade de Química, Edificio de Ciencias Experimentais, Galicia, Spain.
    Girotto, Matteo
    Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, Mestre, VE, Italy.
    Enrichi, Francesco
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, Mestre, VE, Italy.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, Mestre, VE, Italy.
    Luminescent copper(I) coordination polymer with 1-methyl-1H-benzotriazole, iodide and acetonitrile as ligands2019Inngår i: Inorganic Chemistry Communications, ISSN 1387-7003, E-ISSN 1879-0259, Vol. 102, s. 141-146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Cu(I) coordination polymer [Cu33-I)3(μ-btzMe)(NCCH3)]n (btzMe = 1-methyl-1H-benzotriazole) was prepared and characterized by X-Ray diffraction. The compound showed strong green emission upon excitation with wavelengths below 475 nm, with lifetime of 47 μs. The emission was attributed to 3(X,M)LCT transition on the basis of experimental data and DFT calculations.

  • 115.
    Bortoluzzi, Marco
    et al.
    Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia.
    Reolon, Andrea
    Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia.
    Scrivanti, Alberto
    Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia.
    Enrichi, Francesco
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia; Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi.
    The conjugate base of malonaldehyde as antenna-ligand towards trivalent europium and terbium ions2018Inngår i: Chemické zvesti, ISSN 0366-6352, E-ISSN 1336-9075, Vol. 72, nr 4, s. 809-819Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Coordination compounds having formulae [M(MA)3]n and M(MA)(Me2Tp)2 (M = Y, Eu, Tb; MA = conjugate base of malonaldehyde; Me2Tp = tris(3,5-dimethyl-pyrazol-1-yl)borate) were synthesized and characterized. The photoluminescence features of the europium and terbium derivatives were investigated. By comparing the herein reported photoluminescence data with those relative to analogous nitro- and bromomalonaldehyde derivatives, it appears that the conjugate base of malonaldehyde is a more efficient antenna-ligand for the sensitization of Tb(III) luminescence. The experimental data were rationalized on the basis of DFT calculations. Tb(MA)(Me2Tp)2 was used as dopant for the preparation of luminescent plastic materials based on poly(methyl methacrylate).

  • 116.
    Boscarino, Diego
    et al.
    INFN Laboratori Nazionali di Legnaro.
    Vomiero, Alberto
    INFN Laboratori Nazionali di Legnaro.
    Mattei, Giovanni
    INFM Unit̀ di Ricerca di Padova.
    Quaranta, Alberto
    INFN Laboratori Nazionali di Legnaro.
    Mazzoldi, Paolo
    INFM Unit̀ di Ricerca di Padova.
    Mea, Gianantonio Della
    INFN Laboratori Nazionali di Legnaro.
    Deposition of silica-silver nanocomposites by magnetron cosputtering2005Inngår i: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 23, nr 1, s. 11-19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin films have been grown on silicon and silica substrates by cosputtering of silica and silver in Ar, Ar+2.5% O2, and Ar+5% O2 gas mixtures. Rutherford backscattering spectrometry showed that the films have Ag atomic fractions xAg in the range of ∼1 to ∼10 at. %, and, by valence considerations, that the fraction of oxidized Ag in the films deposited in presence of oxygen is limited. Transmission electron microscopy images revealed the presence of Ag nanoclusters, with a mean size diameter not larger than 5 nm. The clusters are preferentially arranged along columns. It is suggested that the columns are regions with diameter in the nanometer range in which the density of the dielectric matrix is lower, thus favoring the formation of metal clusters. In presence of O2, the clusters were observed to have a more regular spherical shape. The optical absorption spectra of films grown in presence of O2 are distinguished from those grown in Ar by specific features, which are attributed to oxidation at the cluster surface. © 2005 American Vacuum Society.

  • 117.
    Botella, Pablo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Devaux, Xavier
    Institut Jean Lamour, UMR 7198 CNRS–Université de Lorraine.
    Dossot, Manuel
    LCPME UMR 7564 CNRS-Université de Lorraine.
    Garashchenko, Viktor
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Beltzung, Jean Charles
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Physics Harvard University, Cambridge.
    Ananev, Sergey
    Joint Institute for High Temperatures of RAS.
    Single-Walled Carbon Nanotubes Shock-Compressed to 0.5 Mbar2017Inngår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, nr 11, artikkel-id 1700315Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNTs) have been dynamically (shock) compressed to 0.5 Mbar, above the limit of their structural integrity. Two distinct types of material are identified by high-resolution transmission electron microscopy (HRTEM) and multi-wavelength Raman spectroscopy in the sample recovered after shock: multi-layer graphene (MLG) and a two-phase material composed of nano-clustered graphene and amorphous carbon whereas no diamond-like carbon or carbon nano-onions are found. Peak decomposition of the Raman spectra was used to estimate the coherent scatterers (clusters) size in MLG at 36 nm from the D- to G-band intensity ratio dependence on the photon excitation energy. Botella et al. (article no. 1700315) propose the peak fitting model for decomposition of the Raman spectra of highly disordered carbon material containing graphene nano-clusters and stress the importance of accounting for heptagonal- and pentagonal-ring defects in graphene layers for the analysis of such spectra. The cover image shows HRTEM images and the correspondent Raman spectra of the two types of material along with peak decomposition of the two-phase material with the peaks assigned to heptagons (a) and pentagons (b). Particulars of the SWCNTs transformation to other structural forms of carbon at high pressure/temperature are discussed

  • 118.
    Botella, Pablo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Devaux, Xavier
    Institut Jean Lamour, UMR 7198 CNRS–Université de Lorraine.
    Dossot, Manuel
    LCPME UMR 7564 CNRS-Université de Lorraine.
    Garashchenko, Viktor
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Beltzung, Jean Charles
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Physics Harvard University, Cambridge.
    Ananev, Sergey
    Joint Institute for High Temperatures of RAS.
    Single-Walled Carbon Nanotubes Shock-Compressed to 0.5 Mbar2017Inngår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254, nr 11, artikkel-id 1770259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNTs) have been dynamically (shock) compressed to 0.5 Mbar, above the limit of their structural integrity. Two distinct types of material are identified by high-resolution transmission electron microscopy (HRTEM) and multi-wavelength Raman spectroscopy in the sample recovered after shock: multi-layer graphene (MLG) and a two-phase material composed of nano-clustered graphene and amorphous carbon whereas no diamond-like carbon or carbon nano-onions are found. Peak decomposition of the Raman spectra was used to estimate the coherent scatterers (clusters) size in MLG at 36 nm from the D- to G-band intensity ratio dependence on the photon excitation energy. Botella et al. (article no. 1700315) propose the peak fitting model for decomposition of the Raman spectra of highly disordered carbon material containing graphene nano-clusters and stress the importance of accounting for heptagonal- and pentagonal-ring defects in graphene layers for the analysis of such spectra. The cover image shows HRTEM images and the correspondent Raman spectra of the two types of material along with peak decomposition of the two-phase material with the peaks assigned to heptagons (a) and pentagons (b). Particulars of the SWCNTs transformation to other structural forms of carbon at high pressure/temperature are discussed

  • 119.
    Botella, Pablo
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Errandonea, D.
    Universidad de Valencia, Valencia, Spain.
    Garg, A.B.
    Bhabha Atomic Research Centre, Mumbai, India. Homi Bhabha National Institute, Mumbai, India.
    Rodriguez-Hernandez, P.
    Universidad de La Laguna, La Laguna, Spain.
    Muñoz, A.
    Departamento de Física, Instituto de Materiales y Nanotecnología, MALTA Consolider Team, Universidad de La Laguna, La Laguna, Spain.
    Achary, S.N
    Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    High-pressure characterization of the optical and electronic properties of InVO4, InNbO4, and InTaO42019Inngår i: SN Applied Sciences, ISSN 2523-3963, Vol. 1, nr 5, artikkel-id 389Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied the electronic properties at ambient pressure and under high pressure of InVO4, InNbO4, and InTaO4 powders, three candidate materials for hydrogen production by means of photocatalytic water splitting using solar energy. A combination of optical absorption and resistivity measurements and band structure calculations have allowed us to determine that these materials are wide band-gap semiconductors with a band-gap energy of 3.62(5), 3.63(5), and 3.79(5) eV for InVO4, InNbO4, and InTaO4, respectively. The last two compounds are indirect band-gap materials, and InVO4 is a direct band-gap material. The pressure dependence of the band-gap energy and the electrical resistivity have been determined too. In the three compounds, the band gap opens under compression until reaching a critical pressure, where a phase transition occurs. The structural transition triggers a band-gap collapse larger than 1.2 eV in the three materials, being the abrupt decrease in the band-gap energy related to an increase in the pentavalent cation coordination number. The phase transitions also cause changes in the electrical resistivity, which can be correlated with changes induced by pressure in the band structure. An explanation to the reported results is provided based upon ab initio calculations. The conclusions attained are of significance for technological applications of the studied oxides.

  • 120.
    Braga, Antonio
    et al.
    Photovoltaic and Optoelectronic Devices Group.
    Giménez, Sixto
    Photovoltaic and Optoelectronic Devices Group.
    Concina, Isabella
    Department of Physics and Chemistry, INFM — University of Brescia.
    Vomiero, Alberto
    Department of Physics and Chemistry for Materials and Engineering and CNR-IDASC SENSOR Lab, Brescia University.
    Mora-Seró, Iván
    Photovoltaic and Optoelectronic Devices Group.
    Panchromatic sensitized solar cells based on metal sulfide quantum dots grown directly on nanostructured TiO2 electrodes2011Inngår i: Journal of Physical Chemistry Letters, Vol. 2, nr 5, s. 454-460Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of narrow band gap semiconductors such as PbS may expand the light absorption range to the near-infrared region in quantum-dot-sensitized solar cells (QDSCs), increasing the generated photocurrent. However, the application of PbS as a sensitizer in QDSCs causes some problems of stability and high recombination. Here, we show that the direct growth of a CdS coating layer on previously deposited PbS by the simple method of successive ionic layer adsorption and reaction (SILAR) minimizes these problems. A remarkable short-circuit current density for PbS/CdS QDSCs is demonstrated, ∼11 mA/cm2, compared to that of PbS QDSCs, with photocurrents lower than 4 mA/cm2, using polysulfide electrolyte in both cells. The cell efficiency reached a promising 2.21% under 1 sun of simulated irradiation (AM1.5G, 100 mW/cm2). Enhancement of the solar cell performance beyond the arithmetic addition of the efficiencies of the single constituents (PbS and CdS) is demonstrated for the nanocomposite PbS/CdS configuration. PbS dramatically increases the obtained photocurrents, and the CdS coating stabilizes the solar cell behavior. © 2011 American Chemical Society.

  • 121.
    Brindt, Lars
    et al.
    Luleå tekniska universitet.
    Hauska, Hans
    Luleå tekniska universitet.
    Direction dependent interpolation of aeromagnetic data1985Inngår i: Machine Processing of Remotely Sensed Data: with special emphasis on quantifying global process ; models, sensor systems, and analytical methods; 11th International Symposium, June 25-27, 1985 / [ed] S.K. Mengel, West Lafayette, Ind: Purdue University Press, 1985, s. 86-95Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A method for level correction and interpolation of anisotropically sampled aeromagnetic data is described. The level-correction is based on a piecewise comparison of adjacent flight-lines. The interpolation scheme is based on cubic splines and preserves thin linear structures in anisotropic potential field data. The design of such a method is seen as an important building block in the design of an image-based information system for geologic applications

  • 122.
    Brodin, Gert
    et al.
    Umeå universitet.
    Lundberg, Jonas
    Luleå tekniska universitet.
    Excitation of electromagnetic wake fields in a magnetized plasma1998Inngår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 57, nr 6, s. 7041-7047Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider propagation of short electromagnetic pulses in a magnetized plasma. A self-consistent system of equations describing wake-field generation in the weakly nonlinear limit is derived. Due to the external magnetic field, the generated wake field becomes partially electromagnetic. The equations are applicable for arbitrary directions of propagation as compared to the external magnetic field. The conservation laws for the system are discussed in detail. The energy decrease rate and the frequency decrease rate of the short pulse are determined

  • 123.
    Buser, Michael
    et al.
    University of Texas, Physics Department.
    Frommhold, Lothar
    University of Texas, Physics Department.
    Gustafsson, Magnus
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Moraldi, Massimo
    Dipartimento di Fisica, Universitá di Firenze and INFM, Unitá di Firenze.
    Champagne, Mark H.
    Department of Chemistry, Michigan State University.
    Hunt, Katherine L.C.
    Department of Chemistry, Michigan State University.
    Far-infrared absorption by collisionally interacting nitrogen and methane molecules2004Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, nr 6, s. 2616-2621Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum line shape calculations of the rototranslational enhancement spectra of nitrogen-methane gaseous mixtures are reported. The calculations are based on a recent theoretical dipole function for interactingN2 and CH4 molecules, which accounts for the long-range induction mechanisms: multipolar inductions and dispersion force-induced dipoles. Multipolar induction alone was often found to approximate the actual dipole surfaces of pairs of interacting linear molecules reasonably well. However, in the case of the N2-CH4 pair, the absorption spectra calculated with such a dipole function still show a substantial intensity defect at the high frequencies (>250 cm−1) when compared to existing measurements at temperatures from 126 to 297 K, much as was previously reported.

  • 124.
    Bäckström, Lars
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Berggård, Glenn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Gedda, Oskar
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Pedagogik språk och Ämnesdidaktik.
    Persson, Anders J
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Prellwitz, Maria
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Hälsa och rehabilitering.
    Weber, Hans
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Wikberg-Nilsson, Åsa
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Det uppkopplade samhället och högre utbildning2014Inngår i: NU 2014: Umeå 8-10 oktober : abstracts, Umeå: Umeå universitet. Pedagogiska institutionen , 2014, s. 123-Konferansepaper (Fagfellevurdert)
  • 125.
    Caciolli, A.
    et al.
    Istituto Nazionale di Fisica Nucleare (INFN).
    Mazzocchi, C.
    Università Degli Studi di Milano and INFN.
    Capogrosso, V.
    Università Degli Studi di Milano and INFN.
    Bemmerer, D.
    Helmholtz-Zentrum Dresden-Rossendorf.
    Broggini, C.
    Istituto Nazionale di Fisica Nucleare (INFN).
    Corvisiero, P.
    Università di Genova.
    Costantini, H.
    Università di Genova.
    Elekes, Z.
    Institute of Nuclear Research (ATOMKI), Debrecen.
    Formicola, A.
    INFN.
    Fülöp, Zs
    Institute of Nuclear Research (ATOMKI), Debrecen.
    Gervino, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Guglielmetti, A.
    Università Degli Studi di Milano and INFN.
    Gustavino, C.
    INFN.
    Gyürky, Gy
    Institute of Nuclear Research (ATOMKI), Debrecen.
    Imbriani, G.
    Dipartimento di Scienze Fisiche, Universitá Federico II.
    Junker, M.
    INFN.
    Lemut, A.
    Università di Genova.
    Marta, M.
    Helmholtz-Zentrum Dresden-Rossendorf.
    Menegazzo, R.
    Istituto Nazionale di Fisica Nucleare (INFN).
    Palmerini, S.
    Dipartimento di Fisica, Università di Roma “La Sapienza”, Rome.
    Prati, P.
    Università di Genova.
    Roca, V.
    Dipartimento di Scienze Fisiche, Universitá Federico II.
    Rolfs, C.
    Institut für Experimentalphysik.
    Alvarez, C. Rossi
    Istituto Nazionale di Fisica Nucleare (INFN).
    Somorjai, E.
    Institute of Nuclear Research (ATOMKI), Debrecen.
    Vomiero, Alberto
    CNR-IDASC SENSOR Lab and Dipartimento di Chimica e Fisica per l'Ingegneria e per i Materiali.
    Revision of the 15N(p, γ)16O reaction rate and oxygen abundance in H-burning zones2011Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 533, artikkel-id A66Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. The NO cycle takes place in the deepest layer of a H-burning core or shell, when the temperature exceeds T ≈ 30 × 106 K. The O depletion observed in some globular cluster giant stars, always associated with a Na enhancement, may be due to either a deep mixing during the red giant branch (RGB) phase of the star or to the pollution of the primordial gas by an early population of massive asymptotic giant branch (AGB) stars, whose chemical composition was modified by the hot bottom burning. In both cases, the NO cycle is responsible for the O depletion. Aims. The activation of this cycle depends on the rate of the 15N(p, γ)16O reaction. A precise evaluation of this reaction rate at temperatures as low as experienced in H-burning zones in stellar interiors is mandatory to understand the observed O abundances. Methods. We present a new measurement of the 15N(p, γ)16O reaction performed at LUNA covering for the first time the center of mass energy range 70-370 keV, which corresponds to stellar temperatures between 65 × 106 K and 780 × 106 K. This range includes the 15N(p, γ)16O Gamow-peak energy of explosive H-burning taking place in the external layer of a nova and the one of the hot bottom burning (HBB) nucleosynthesis occurring in massive AGB stars. Results. With the present data, we are also able to confirm the result of the previous R-matrix extrapolation. In particular, in the temperature range of astrophysical interest, the new rate is about a factor of 2 smaller than reported in the widely adopted compilation of reaction rates (NACRE or CF88) and the uncertainty is now reduced down to the 10% level. © 2011 ESO.

  • 126.
    Cailotto, Simone
    et al.
    Department of Molecular Sciences and Nanosystems, Università Ca’ Foscari Venezia, Via Torino 155, 30172 Venezia Mestre, Italy.
    Mazzaro, Raffaello
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Enrichi, Francesco
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Piazza del Viminale 1, 00184 Roma, Italy.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Selva, Maurizio
    Department of Molecular Sciences and Nanosystems, Università Ca’ Foscari Venezia, Via Torino 155, 30172 Venezia Mestre, Italy.
    Cattaruzza, Elti
    Department of Molecular Sciences and Nanosystems, Università Ca’ Foscari Venezia, Via Torino 155, 30172 Venezia Mestre, Italy.
    Cristofori, Davide
    Department of Molecular Sciences and Nanosystems, Università Ca’ Foscari Venezia, Via Torino 155, 30172 Venezia Mestre, Italy;Centro di microscopia elettronica “G. Stevanato”, Via Torino 155b, 30172 Venezia-Mestre, Italy.
    Amadio, Emanuele
    Department of Molecular Sciences and Nanosystems, Università Ca’ Foscari Venezia, Via Torino 155, 30172 Venezia Mestre, Italy.
    Perosa, Alvise
    Department of Molecular Sciences and Nanosystems, Università Ca’ Foscari Venezia, Via Torino 155, 30172 Venezia Mestre, Italy.
    Design of Carbon Dots for Metal-free Photoredox Catalysis2018Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, nr 47, s. 40560-40567Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The photoreduction potential of a set of four different carbon dots (CDs) was investigated. The CDs were synthesized by using two different preparation methods—hydrothermal and pyrolytic—and two sets of reagents—neat citric acid and citric acid doped with diethylenetriamine. The hydrothermal syntheses yielded amorphous CDs, which were either nondoped (a-CDs) or nitrogen-doped (a-N-CDs), whereas the pyrolytic treatment afforded graphitic CDs, either non-doped (g-CDs) or nitrogen-doped (g-N-CDs). The morphology, structure, and optical properties of four different types of CDs revealed significant differences depending on the synthetic pathway. The photocatalytic activities of the CDs were investigated as such, that is, in the absence of any other redox mediators, on the model photoreduction reaction of methyl viologen. The observed photocatalytic reaction rates: a-N-CDs ≥ g-CDs > a-CDs ≥ g-N-CDs were correlated with the presence/absence of fluorophores, to the graphitic core, and to quenching interactions between the two. The results indicate that nitrogen doping reverses the photoredox reactivity between amorphous and graphitic CDs and that amorphous N-doped CDs are the most photoredox active, a yet unknown fact that demonstrates the tunable potential of CDs for ad hoc applications.

  • 127. Carlsson, Ella
    Finding Mars on Svalbard: a study of Martian gullies on Earth2008Inngår i: Polarforskningssekretariatet: årsbok 2008, Stockholm: Swedish Polar Research Secretariat , 2008, s. 34-35Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 128. Carlsson, Ella
    Finns det liv på Mars?2007Inngår i: Nya Upplagan, nr 10, s. 10-Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 129.
    Carlsson, Ella
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Framåt Mars !2006Bok (Annet (populærvitenskap, debatt, mm))
  • 130.
    Carlsson, Ella
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mars: environment, surface and exploration ethics2006Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This licentiate thesis treats the solar wind interaction with the martian atmosphere and the water related features known as gullies, as well as some ethical issues related to the human exploration of Mars. The composition of the escaping plasma at Mars has been investigated in an analysis of data from the IMA sensor, which is part of the ASPERA-3 instrument suit onboard the European satellite Mars Express. The cause for the investigation is to determine if there are any large abundances of escaping ion species incorporating carbon, such as in CO_2^+. The most abundant ion species was found to be O^+ and O_2^+, followed by CO_2^+. The following ratios were identified: (CO_2^+)/(O^+)=0.2 and (O_2^+)/(O^+)=0.9. The loss of CO_2^+ was estimated to 4.0x10^(24) s^(-1) (0.29 kg/s). The escaping plasma in form of ion beam events has also been correlated to the magnetic anomalies found on the surface, where no clear association was found. This study is important in order to understand the evolution of Mars, since some evidence reveals that ancient Mars was once a wetter planet. The gully formations have been investigated with data from the MOC and MOLA instruments onboard the satellite Mars Global Surveyor. The intriguing features suggest that there has been fluvial erosion on the surface of Mars. The shallow and deep aquifer models remain the most plausible formation theories. Gully formation is another important piece to the puzzle regarding the lost water on Mars. Since Mars once harbored stable water on the surface in the past, astrobiologists believe that life could have existed on Mars. Some even argue for a slight possibility to find life thriving in the subsurface today, where the water can be found in a stable liquid form. If this would be the case we need to consider whether we should continue with our in-situ exploration of the surface, or if we should leave Mars to the Martians.

  • 131. Carlsson, Ella
    Mars Express and Venus Express multi-point observations of geoeffective solar flare events in December 20062008Inngår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 56, s. 873-880Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In December 2006, a single active region produced a series of proton solar flares, with X-ray class up to the X9.0 level, starting on 5December 2006 at 10:35 UT. A feature of this X9.0 flare is that associated MeV particles were observed at Venus and Mars by VenusExpress (VEX) and Mars Express (MEX), which were 801 and 1251 east of the flare site, respectively, in addition to the Earth, whichwas 791 west of the flare site. On December 5, 2006, the plasma instruments ASPERA-3 and ASPERA-4 on board MEX and VEXdetected a large enhancement in their respective background count levels. This is a typical signature of solar energetic particle (SEP)events, i.e., intensive MeV particle fluxes. The timings of these enhancements were consistent with the estimated field-aligned travel timeof particles associated with the X9.0 flare that followed the Parker spiral to reach Venus and Mars. Coronal mass ejection (CME)

  • 132. Carlsson, Ella
    Mars finns redan på jorden2004Inngår i: Populär astronomi, ISSN 1650-7177, Vol. 5, nr 2, s. 30-33Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 133.
    Carlsson, Ella
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mars: plasma environment and surface2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This doctoral thesis treats parts of the solar wind interaction with the Martian atmosphere and the water-related features known as gullies. The composition of the escaping plasma at Mars has been investigated in an analysis of data from the IMA sensor, which is a part of the ASPERA-3 instrument suit onboard the European satellite Mars Express. The goal of the investigation is to determine if there are any high abundances of escaping ion species incorporating carbon, such as in CO_2^+ . The most abundant ion species was found to be O^+ and O_2^+, followed by CO_2^+. The following ratios were identifed: CO_2^+/O^+ = 0:2 and O_2^+ /O^+ = 0:9. The escaping plasma, in form of ion beam events, has also been correlated to the magnetic anomalies found on the surface, where no clear association was found. Similar ion beams have also been detected on Venus, which does not have any crustal magnetic fields, and hence the fields are not required for the formation process of the beams. The ion beams' dependence of the direction of the solar wind convection electric field has also been studied, where a correlation was found, suggesting that the ion beams are accelerated by this field. The studies mentioned above are important in order to understand the evolution of Mars and its atmosphere, as well as plasma acceleration processes at non-magnetized planetary bodies. On 5 December 2006 the ASPERA instruments of both Venus Express and Mars Express detected a large enhancement in their respective background count level. These readings are associated with events of SEPs (Solar Energetic Particles), which are believed to be coupled with the CMEs (Coronal Mass Ejection) identified 43 ¡ 67 hours after the SEPs. The CMEs occurred on the far side of the sun (with respect to the locations of Venus and Mars), which indicates that these events can a®ect the space weather in areas situated 90 degrees in both azimuthal directions in the heliosphere with respect to the target. During this event the heavy ion outflow from the atmosphere of Mars increased by one order of magnitude, suggesting that EUV flux levels significantly affect the atmospheric loss from unmagnetized bodies. The gully formations have been investigated with data from the MOC, MOLA and TES instruments onboard the satellite Mars Global Surveyor. The features suggest that there has been fluvial erosion on the surface of Mars. The shallow and deep aquifer models remain the most plausible formation theories. Gully formation processes are important to understand since their eroding agent may be liquid water.

  • 134.
    Carlsson, Ella
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Martian rights?2005Inngår i: International Space Review, ISSN 1746-1588, nr 3, s. 5-6Artikkel i tidsskrift (Annet vitenskapelig)
  • 135. Carlsson, Ella
    Mot rymden för att rädda jorden!2007Inngår i: Texter om kosmos: en antologi, Lidingö: Adoxa , 2007, s. 231-245Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 136.
    Carlsson, Ella
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Cold Mars2006Konferansepaper (Annet vitenskapelig)
  • 137.
    Carlsson, Ella
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Swedish Institute of Space Physics, Kiruna, Sweden.
    Barabash, Stas
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Fedorov, A.
    Centre d’Etude Spatiale des Rayonnements, Toulouse, France.
    Budnik, E.
    Centre d’Etude Spatiale des Rayonnements, Toulouse, France.
    Grigoriev, Alexander
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Futaana, Y.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Gunell, H.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Nilsson, H.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Lundin, R.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Analysis of the mass composition of the escaping plasma at Mars2006Inngår i: 2006 European Geosciences Union General Assembly (EGU 2006), Austria Center Vienna, Vienna (Austria), 2-7 Apr 2006, European Geosciences Union (EGU), 2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Results from Mars Express, Mars Exploration Rovers and Mars Global Surveyor indicate that Mars harbored large amounts of liquid water on the surface in the past. In order for the water-associated geomorphologic features to form, the pressure in the atmosphere must have been at least a hundred times higher to produce the necessary greenhouse effect required to hold liquid water stable. The present atmospheric pressure is only 6-9 mbar and moreover, the spectral imaging of Mars suggests that the amount of carbonates stored in the surface is too low in order to explain the denser atmosphere in the past. This controversy led us to investigate the escaping plasma by analyzing the data from the IMA sensor (Ion Mass Analyzer) of the ASPERA-3 instrument suite onboard Mars Express. The IMA sensor measures the differential flow of ion components in the energy range of 0.01-30 keV/q.Since the instrument design was optimized for studies of plasma dynamics, the mass resolution is not adequate enough to directly resolve CO+2 from O+2 , which is the main molecular ion composing the Mars ionosphere according to theoretical models. Therefore, a special multi-species fitting technique, using calibration and in-flight data, was developed to resolve the CO+2 peak from the neighboring and much more intense O+2 peak. This technique was applied to the observations covering the period from April 4, 2004 to October 2, 2005. The events of heavy ion escape were identified inside the induced magnetosphere boundary and the Martian eclipse. We report the results of statistical studies of these ion-beam events which permitted to determine CO+2 / O+ and the O+2 / O+ ratio of the escaping plasma at Mars.

  • 138. Carlsson, Ella
    et al.
    Brain, D.
    Space Science Laboratory, University of California, Berkeley.
    Luhmann, J.
    Space Science Laboratory, University of California, Berkeley.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Grigoriev, Alexander
    Nilsson, H.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Lundin, R.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Influence of IMF draping direction and crustal magnetic field location on Martian ion beams2008Inngår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 56, nr 6, s. 861-867Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite onboard Mars Express and data from the Magnetometer/Electron Reflectometer (MAG/ER) on Mars Global Surveyor have been analyzed to determine whether ion beam events (IBEs) are correlated with the direction of the draped interplanetary magnetic field (IMF) or the proximity of strong crustal magnetic fields to the subsolar point. We examined 150 IBEs and found that they are organized by IMF draping direction. However, no clear dependence on the subsolar longitude of the strongest magnetic anomaly is evident, making it uncertain whether crustal magnetic fields have an effect on the formation of the beams. We also examined data from the IMA sensor of the ASPERA-4 instrument suite on Venus Express and found that IBEs are observed at Venus as well, which indicates the morphology of the Martian and Venusian magnetotails are similar.

  • 139.
    Carlsson, Ella
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Swedish Institute of Space Physics, Kiruna, Sweden.
    Euler, M. von
    Lunds universitet.
    Grigoriev, Alexander
    Swedish Institute of Space Physics, Kiruna, Sweden.
    McCann, David
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Habitat for Mars: a new conceptual design2007Inngår i: Geophysical Research Abstracts, European Geosciences Union (EGU), 2007, Vol. 9Konferansepaper (Annet vitenskapelig)
  • 140.
    Carlsson, Ella
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Fedorov, A.
    Centre d’Etude Spatiale des Rayonnements, Toulouse.
    Barabash, S.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Dierker, C.
    Technical University of Braunschweig.
    Mass composition of the escaping plasma at Mars2006Inngår i: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 182, nr 2, s. 320-328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO2+/O+ and O-2(+)/O+. The following ratios averaged over all events and energies were identified: CO2+/O+ = 0.2 and O-2(+)/O+ = 0.9. The values measured are significantly higher, by a factor of 10 for O-2(+)/O+, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O+, followed by O-2(+) and CO2+. We estimate the loss of CO2+ to be 4.0 x 10(24) s(-1) (0.29 kg s(-1)) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.

  • 141. Carlsson, Ella
    et al.
    Fedorov, A.
    Budnik, E.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Fredriksson, Sverker
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    First results from ASPERA-3 Ion Mass Analyzer (IMA) on CO2+ escape2005Konferansepaper (Annet vitenskapelig)
  • 142.
    Carturan, S.
    et al.
    University of Padova.
    Quaranta, A.
    University of Trento, Department of Materials Engineering and Industrial Technologies.
    Bonafini, M.
    Istituto Nazionale di Fisica Nucleare (INFN).
    Vomiero, Alberto
    Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro.
    Maggioni, G.
    University of Padova.
    Mattei, G.
    Fernández, C. De Julián
    Bersani, M.
    Mazzoldi, P.
    Mea, G. Della
    University of Trento, Department of Materials Engineering and Industrial Technologies.
    Formation of silver nanoclusters in transparent polyimides by Ag-K ion-exchange process2007Inngår i: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 42, nr 2, s. 243-251Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silver nanoclusters embedded in two transparent fluorinated polyimides, 4,4'-hexafluoroisopropylidene diphthalic anhydride - 2,3,5,6-tetramethyl paraphenylene diamine (6FDA-DAD) and 3,3',4,4' - biphenyltetracarboxylic acid dianhydride - 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (BPDA-3F), have been produced by surface modification with KOH aqueous solution followed by K-assisted Ag doping and thermal reduction in hydrogen atmosphere. The reaction rate of the nucleophilic hydrolysis in KOH, studied by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectrometry (RBS), depends on the polyimide chemical structure. After ion-exchange in AgNO 3 solution and subsequent annealing, the polyimide structure recovery was monitored by FT-IR whereas the characteristic surface plasmon absorption band of silver nanoparticles was evidenced by optical absorption measurements. The structure of silver nanoclusters as related to size and size distribution in the different polyimide matrices was thoroughly investigated by Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The collected data evidenced a uniform distribution of Ag clusters of nanometric size after thermal treatment at 300 °C in both polyimides. For the same ion-exchange treatment parameters and annealing temperature, XRD analyses evidenced the presence of crystallites with similar sizes. © EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007.

  • 143. Carturan, S.
    et al.
    Quaranta, A.
    Laboratori Nazionali di Legnaro.
    Vomiero, Alberto
    INFN Laboratori Nazionali di Legnaro.
    Bonafini, M.
    Laboratori Nazionali di Legnaro.
    Maggioni, G.
    Mea, G. Della
    Laboratori Nazionali di Legnaro.
    Polyimide-based scintillators studied by ion beam induced luminescence2004Inngår i: IEEE Nuclear Science Symposium Conference Record, ISSN 1095-7863, Vol. 2, s. 869-873Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    New organic scintillators for ionizing radiation sensors are synthesized by dispersing dye molecules into chemically imidized polyimide hosts in order to obtain detection systems with improved radiation resistance with respect to the traditional polyvinyltoluene based materials. Nile Red and Rhodamine B are dispersed at different concentrations in polyimides derived from the following monomers 6FDA-DAD, 6FDA-DAB and BPDA-3F. Scintillating thin films are produced by the spin coating technique. Scintillation tests are performed both on pure polyimides and on binary systems by means of Ion Beam Induced Luminescence (IBIL), in which the emission spectrum is collected during the irradiation of the films with a 4He+ beam. From the intensity and the degradation rate of the IBIL signal during irradiation, the scintillation efficiency with respect to NE102 and the radiation hardness of the produced films are calculated. © 2004 IEEE.

  • 144. Carturan, S.
    et al.
    Quaranta, A.
    Laboratori Nazionali di Legnaro.
    Vomiero, Alberto
    Department of Physics, University of Padova.
    Bonafini, M.
    Department of Engineering Materials, Department of Mechanical Engineering, Linköping University.
    Maggioni, G.
    Mea, G. Della
    Laboratori Nazionali di Legnaro.
    Polyimide-based scintillators studied by ion beam induced luminescence2005Inngår i: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 52, nr 3 II, s. 748-751Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    New organic scintillators for ionizing radiation sensors are synthesized by dispersing dye molecules into chemically imidized polyimide hosts in order to obtain detection systems with improved radiation resistance with respect to the traditional polyvinyltoluene-based materials. Nile red (NR) and rhodamine B (RB) are dispersed at different concentrations in polyimides derived from the following monomers: 6FDA-DAD, 6FDA-DAB, and BPDA-3F. Scintillating thin films are produced by the spin coating technique. Scintillation tests are performed both on pure polyimides and on binary systems by means of ion beam induced luminescence (IBIL), in which the emission spectrum is collected during the irradiation of the films with a 4He+ beam. From the intensity and the degradation rate of the IBIL signal during irradiation, the scintillation efficiency with respect to NE102 and the radiation hardness of the produced films are calculated. © 2005 IEEE.

  • 145.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Engström, Niclas
    LKAB, SE-981-86 Kiruna, Sweden.
    Grönlund, Ulrika
    Autoliv Sverige AB, Active Saftey Tech Center, Linköping, Sweden.
    Evaluation of velocity and curvature dependence for roadgrip measured by low lateral slip2017Inngår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 12, nr 1/2, s. 1-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Roadgrip is an important parameter for vehicle testing and road maintenance. Therefore, an evaluation of the velocity and curvature effects on roadgrip measurement was performed on asphalt roads and on two ice tracks using the continuous roadgrip apparatus RT3 Curve. The aim was to find suitable driving patterns for measurements on public roads and test tracks to ensure the repeatability of roadgrip measurements. During the evaluation, it was concluded that in order to achieve a reliable roadgrip value, regardless of road conditions, the radius of curvature should not be less than 20 m. The velocity dependency of the RT3 Curve is different for the two road conditions, with the measurements on ice being much more sensitive to velocity changes than the measurements on the dry asphalt.

  • 146. Cataudella, Vittorio
    et al.
    Minnhagen, Petter
    Weber, Hans
    Renormalisation equations for the two-dimensional Coulomb gas: inclusion of the single-particle charge distribution and comparison with Monte Carlo simulations1990Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 2, s. 2345-2354Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A set of self-consistent equations for the high-temperature phase of the two-dimensional Coulomb gas is solved numerically. These equations explicitly include the charge distribution of a single particle. Comparisons are made with Monte Carlo simulations as well as with the 'point-charge'-limit of the equations. The results are discussed in the context of type II superconducting films

  • 147. Chen, W.
    et al.
    Cameron, S.
    Göthelid, M.
    Hammar, M.
    Paul, Jan
    Redox properties of titanium oxides on Pt3Ti1995Inngår i: Journal of Physical Chemistry, ISSN 0022-3654, Vol. 99, nr 34, s. 12892-12895Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The morphology and electronic structure of surface-segregated titanium oxides on Pt3Ti(111) are presented. Core level photoemission spectra at grazing emission reveal two states of oxidation: a dominant and reducible four-valent oxide together with a small amount of a three-valent oxide is produced by oxidation in 0 2 at and below 400°C; an irreducible three-valent oxide by oxidation in 02 at and above 450 °C. The ratio between the active four-valent and the inactive three-valent oxides decreases with increasing oxidation temperature. The probability for reduction by CO is almost unity for the Ti 4+ oxide, and the conclusion must be that the four-valent oxide plays an active role for catalytic reactions. Scanning tunneling measurements relate these observations to changes in the dispersion and nucleation of the oxide overlayer. The four-valent oxide grows as islands with remaining areas open for CO adsorption while the three-valent oxide spreads on and blocks the crystal surface. Photoemission spectra relate these dispersion effects to an electronic interaction between the Ti 3+ oxide and adjacent Pt atoms. The above observations are in accordance with the common picture of dispersion effects in titania-supported SMSI catalysts and prove that interfacial energies play a crucial role whether the dominant phase is metallic or an oxide.

  • 148. Chen, W.
    et al.
    Chulkov, E.
    Paul, Jan
    Band structure calculations of Pt and Pt3Ti1996Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 54, nr 4, s. 392-396Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Linearized Augmented Plane Wave (LAPW) calculations of the Pt and Pt3Ti bulk electron structures are presented. We emphasis on hybridization, charge transfer effects and the impact on chemisorption properties Densities of States (DOS) and novel band-structures are also provided. The delocalized character of free electron states documents itself by sp-orbitals largely unaffected by alloy formation i.e. the Pt and Ti projected sp-densities are similar and also akin to the distribution of sp-states for pure platinum. The strong Pt-Ti interaction comes from d and f orbitals with a significantly lowered Pt d center-of-mass for the alloy and an intense Ti d structure above the Fermi level. The f-projected density of states gives two narrow peaks: a Ti peak below the Fermi level and an unoccupied Pt peak near Ef. Together the d and f interactions result in a much lowered DOS(Ef). Our results are of direct relevance for adsorption systems modelling titania supported platinum, a well known catalyst for CO hydrogenation. The ordered alloy, Pt3Ti, forms in the industrial catalyst under reducing conditions at elevated temperatures, a phenomenon related to the Strong Metal Support Interaction (SMSI) effect in catalysis, and much work has addressed special adsorption sites for enhanced methanation rates.

  • 149. Chen, W.
    et al.
    Paul, Jan
    Barbieri, A.
    Hove, M.A. van
    Cameron, S.
    Structure determination of Pt3Ti(111) by automated tensor LEED1993Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 5, s. 4585-4594Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An analysis of low-energy electron diffraction (LEED) I-V spectra from the clean Pt3Ti(111) surface was performed by comparing measured intensities with data calculated using an automated tensor LEED program, which employs a directed search optimization procedure. It was found that the topmost layer is pure Pt and that the other layers have the bulk composition. The first and second interlayer spacings are 2.23+or-0.03 AA and 2.21+or-0.03 AA respectively, corresponding to a contraction of 0.9% and 1.8% of the bulk value. The perpendicular buckling is 0.04 AA +or-0.05 AA in the top layer and 0.15 AA +or-0.04 AA in the second layer. The results are in full accordance with previous investigations of the physical and chemical properties of this surface.

  • 150. Chen, Wenhua
    et al.
    Lu, Hua
    Pradier, Claire-Marie
    Paul, Jan
    Flodström, Anders
    Reduction of NO by C4 hydrocarbons on platinum in the presence of oxygen: influence of sulfur dioxide1997Inngår i: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 172, nr 1, s. 3-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reduction of NO, in the presence of i-C4H10or i-C4H8and O2, catalyzed by a platinum foil, was studied in order to understand better the catalytic activity of platinum metal, free of any support or dispersion effects. The reaction products were analyzed by mass spectrometry, and the surface was characterized by X-ray photoelectron spectroscopy at different stages of the reaction. A correlation between the catalytic activity for NO conversion and the presence of adsorbed intermediates is demonstrated. The role of oxygen is interpreted as twofold: formation of active intermediates and deactivation of the surface. The effect of traces of sulfur dioxide in the reacting phase on the reduction of NO by isobutene was investigated. The influence of SO2is very much dependent upon its initial concentration in the gas phase. Low concentrations (<15 ppm) promote the reduction of NO, whereas higher levels poison the reaction by a surface site blocking effect.

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