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  • 1
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    Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter (2020)
    Details
    Publication Date: 2020-03-19
    Description: Global dust storms on Mars are rare1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere3, primarily owing to solar heating of the dust3. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars4. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes5,6, as well as a decrease in the water column at low latitudes7,8. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H2O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals3. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere.
    Description: Published
    Description: 521–525
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Electronic Resource
    Electronic Resource
    In situ probing at the growth temperature of the surface composition of (InGa)As and (InAl)As (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2096-2098 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A sudden shift from a bidimensional to a three-dimensional growth mode is observed when InAs is deposited by molecular-beam epitaxy on a pseudomorphic buffer layer grown on GaAs. The critical thickness for this shift is merely sensitive to the indium composition of the surface monolayer prior to growth. This property allows a direct in situ probing of the surface composition at the temperature of the growth. A detailed quantitative study of the surface segregation of indium atoms is performed for (InGa)As and (InAl)As alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108318
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  • 3
    Electronic Resource
    Electronic Resource
    Growth of InGaAs/GaAs quantum wells with perfectly abrupt interfaces by molecular beam epitaxy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3452-3454 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The abruptness of InxGa1−xAs-on-GaAs as well as GaAs-on-InxGa1−xAs interfaces grown by molecular beam epitaxy is usually intrinsically limited by the surface segregation of indium atoms. The deposition of a one-monolayer-thick indium-rich prelayer of InGaAs (or of a submonolayer amount of InAs) prior to growth of InxGa1−xAs allows, however, the formation of a perfectly abrupt InxGa1−xAs-on-GaAs interface, as shown (for x=0.06 and x=0.11) by a detailed study of the surface composition at various stages of the growth of this heterostructure. A thermal annealing can also be performed at the GaAs-on-InGaAs interface so as to desorb surface indium atoms and suppress In incorporation in the GaAs overlayer. Both techniques preserve the optical quality of InxGa1−xAs/GaAs quantum wells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109046
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  • 4
    Electronic Resource
    Electronic Resource
    Organization and functional analysis of three T-DNAs from the vitopine Ti plasmid pTiS4 (1992)
    Springer
    Molecular genetics and genomics 235 (1992), S. 292-303 
    Details
    ISSN: 1617-4623
    Keywords: Agrobacterium ; Ti plasmid ; T-DNA ; Vitopine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The vitopine Ti plasmid pTiS4 of Agrobacterium vitis has an unusual T-DNA organization. The pTiS4 oncogenes, localized by screening selected pTiS4 clones for growth-inducing activity, are localized on three T-DNAs, whereas in all other characterized Ti plasmids one or two T-DNAs are found. The nucleotide sequences and predicted amino acid sequences of the pTiS4 oncogenes set them apart from the corresponding genes from other Ti or Ri plasmids. The oncogenes induce the same type of reaction on various test plants as the well-known pTiAch5 oncogenes but the pTiS4 ipt gene induces considerably more shoots than its Ach5 homologue. We have also identified the gene coding for vitopine synthase as well as a vitopine synthase pseudogene. Both sequences show homology to the octopine synthase gene. In terms of both nucleotide sequence and overall organization, the pTiS4 T-DNAs appear to be only distantly related to previously characterized T-DNAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00279373
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization and role of an elastomeric interphase on carbon fibers reinforcing an epoxy matrix (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 568-577 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Oxidized carbon fibers were coated using an on-line filament winding process with an elastomeric adduct crosslinkable and compatible with an epoxy matrix. The coating and modifications of the epoxy network were studied by dynamic mechanical measurements. Assuming that apparent activation energies of the secondary relaxation βe of the epoxy network and main relaxation αa of adduct are very different, it is possible at low frequencies to separate the two peaks. The composite material can be described as a three phase system: an epoxy network as matrix, carbon fibers, and a soft interlayer. The mechanical behavior of unidirectional composite materials studied by impact and bending tests is strongly dependent on the presence and the thickness of the coating at the carbon fiber surface.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760280905
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  • 6
    Electronic Resource
    Electronic Resource
    Polyuréthannes à propriétés émulsifiantes et électrolytiques, 1. Cinétique de condensation des alkylimino-2,2′ diéthanols et de leurs dérivés sulfobétaïniques avec divers monoisocyanatesA la demande de l'auteur, la publication a été retenue. (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 1693-1717 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work deals with model reactions allowing the synthesis of low-molecular-weight polyurethanes with electrolytic and emulsifier properties. The kinetics of addition reactions of 2,2′-alkyliminodiethanols (3a - c) and their ammonium sulfonate derivatives 5 and 6 with propyl (8a) and cyclohexyl isocyanate (8b) were studied in DMSO and in the bulk. The tertiary amino groups of 3 exhibit catalytic effects, whereas the ammonium sulfonate internal salts inhibit the reaction. 8a is 2 - 3 times more reactive than 8b and the addition rates decrease with increasing R. Autoassociations (OH ··· OH) should mainly be intramolecular because of the proximity of the alcohol groups. In bulk the 8a + 3 additions apparently follow second order kinetics. On the other hand, the third order law must be taken into account with 8b. In contrast, in DMSO, due to the strong (solvent, —OH and/or —NCO) complexations, the kinetics do neither follow the simple second order, nor the third order law. By the use of two successive second order kinetics, diols were found more reactive than their monoalcohol-monocarbamate derivatives. However, the difference in reactivity decreases with increasing reaction temperatures. Sulfobetaine units may be inserted into the polyurethane chains if diols with ammonium sulfonate groups are used as comonomer, but their weak reactivity must be taken into account.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890724
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  • 7
    Electronic Resource
    Electronic Resource
    Polyuréthannes à propriétés emulsifiantes et électrolytiques, 2Partie 1: cf.1. Cinétique de polycondensation en solution des alkylimino-2,2′ diéthanols avec le diisocyanate d'isophorone. Etude par 1H et 13C NMR (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 1719-1737 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 13C NMR analysis of carbamates and substituted ureas as model compounds, derived from 5-isocyanato-1,3,3-trimethylcyclohexylmethyl isocyanate (isophorone diisocyanate) (3), allowed the quantitative determination of global conversions of hydroxyl and NCO groups. The individual conversions of the two NCO groups, as observed in the polycondensations of 2,2′-methylimino- and 2,2′-dodecyliminodiethanol (1a and 1b) with 3 in toluene, were examined. The primary NCO group of 3 was found to be two times more reactive than the secondary one. The global kinetics of the polycondensations followed the 2nd and 3rd order for conversions lower than 50%. Beyond 50% of conversion, zero order kinetics were observed because of the decrease of the rate due to the steric hindrance of both cyclohexyl and alkyl residues. Alkyl radical length in 1 and hydroxyl auto-association equilibria were found to have the same effect on polycondensation as on condensation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890725
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  • 8
    Electronic Resource
    Electronic Resource
    Simultaneous kinetic and microdielectric studies of some epoxy-amine systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2911-2921 
    Details
    ISSN: 0887-6266
    Keywords: epoxy ; amine ; microdielectrometry ; conductivity ; conversion ; glass transition temperature ; curing ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three reactive epoxy-amine systems based on diglycidyl ether of bisphenol A (DGEBA) with 4,4′-diaminodiphenylsulfone (DDS), 4,4′-methylenebis [3-chloro 2,6-diethylaniline] (MCDEA), and 4,4′-methylenebis [2,6-diethylaniline] (MDEA), were studied during isothermal curings at 140 and 160°C. The simultaneous kinetic and dielectric studies allow to express conductivity, σ, in terms of conversion, x, and of glass transition temperature, Tg. The conductivity, σ0, of the initial monomer mixture and, σ∞ of the fully cured network are measured. It is found that: The glass transition temperature, Tg, versus conversion, x, curves follows the equation of Di Benedetto modified by Pascault and WilliamsThere exists a linear relation between log σ/log σ0 and Tg.So, it is possible to predict both kinetic and dielectric behaviors of these epoxy-amine systems by the knowledge of Tg0, ΔCp0, and σ0, respectively, glass transition temperature, heat capacity, and conductivity of initial monomer mixture, Tg∞ and ΔCp∞, and σ∞, respectively, glass transition temperature and heat capacity and conductivity of fully cured network. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2911-2921, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Morphology of unsaturated polyester resin-additive blends (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 1585-1590 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The morphologies and impact behavior of blends based on an unsaturated polyester matrix and different added rubbers were studied by scanning electron microscopy (SEM). These rubbers were prepared from a carboxy-terminated acrylonitrile-butadiene copolymer (CTBN). The introduction of an epoxy-terminated triblock copolymer (ETON) by exchanging 10% by weight of the CTBN rubber compatibilizes the initial blend by reducing the interfacial tension between the components. Consequently, the morphology of dispersed phase was modified: decreasing of the particle size and reducing the number of large particles. For a blend with 5 phr of rubber, Charpy impact behavior was enhanced and the number of catastrophic failures was reduced. This study displays the existence of relationships between the interfacial tension between components and the morphology of the resulting materials.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760302405
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of chain flexibility and crosslink density on mechanical properties of epoxy/amine networks (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1572-1580 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of a bisphenol A diglycidyl ether prepolymer and an aliphatic diepoxy diluent crosslinked with a cycloaliphatic diamine were studied. These model networks have the characteristic that the crosslink density and the chain flexibility increase with the amount of diluent. These combined effects were studied by observing their mechanical properties. The decreases in the Young's modulus and the ultrasonic modulus were associated with the secondary thermomechanical relaxations that have been recorded and identified. Pre-plastic and plastic behaviors were discussed in terms of flexibility and crosslink density. A linear relationship was established between pre-plastic activation volume and crosslink density at temperatures lower than the activation of molecular chain motions responsible for the sub-Tg relaxations. At 0°C, a temperature above these secondary transitions, the higher the flexibility, the more defect nucleation and propagation increased. The work hardening rate and the upper yield stress decreased as the amount of diluent was increased. Fracture toughness was improved as the amount of diluent was increased. Crack propagation was related to the ability of the networks to deform plastically.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760312204
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