The crosslinking of epoxidized natural rubber (ENR) with dodecanedioic acid was tremendously accelerated in presence of 1,2-dimethylimidazole (DMI). The curing reaction of ENR containing 10 or 25 mol ...% epoxide groups was followed by rheology at 180 °C or 160 °C and the mechanical properties of the cured materials were examined by stress–strain experiments. An equimolar amount of accelerator and carboxylic functions was required to reach optimum tensile properties. Among a variety of usual accelerators, DMI was found the only one efficient, which was associated to the formation of reactive imidazolium carboxylates. The presence of these intermediates was supported by DSC experiments. Instead of a catalytic mechanism, the activation of the crosslinking agent is enabled by the synergetic association of DMI and diacid forming a soluble species in the rubber matrix. This simple system thus enables the efficient crosslinking of functionalized natural rubber without the use of sulphur or peroxides.
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Curing behaviour as well as mechanical properties of binary blends of epoxidized natural rubber (ENR) and dodecanedioic acid (DA) were investigated for development of self-vulcanizable elastomer ...blends. Cross-linking reaction at 180
°C of reactive functional rubber containing 25 and 10
mol% epoxide groups was followed by rheology. The properties of the cured materials were studied by dynamic mechanical analysis, stress–strain experiments, and DSC measurements. It was shown that a specific ratio ENR/DA gave rise to optimum mechanical properties. This ratio decreases together with the epoxidation level of the rubber. DSC measurements revealed that the glass transition temperature of the cured material increases nonlinearly at high concentrations of cross-linking agent. By comparing cross-linking with DA and reaction with monofunctional lauric acid, this behaviour was attributed to polar interactions due to free carboxylic groups of pending diacid grafts.
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The self-consistent quantum-electrostatic (also known as
Poisson-Schrödinger) problem is notoriously difficult in situations
where the density of states varies rapidly with energy. At low
...temperatures, these fluctuations make the problem highly non-linear
which renders iterative schemes deeply unstable. We present a stable
algorithm that provides a solution to this problem with controlled
accuracy. The technique is intrinsically convergent even in highly
non-linear regimes. We illustrate our approach with both a calculation
of the compressible and incompressible stripes in the integer quantum
Hall regime as well as a calculation of the differential conductance of
a quantum point contact geometry. Our technique provides a viable route
for the predictive modeling of the transport properties of quantum
nanoelectronics devices.
Although Josephson junctions can be viewed as highly nonlinear impedances for superconducting quantum technologies, they also possess internal dynamics that may strongly affect their behavior. Here, ...we construct a computational framework that includes a microscopic description of the junction (full fledged treatment of both the superconducting condensate and the quasiparticles) in the presence of a surrounding electrical circuit. Our approach generalizes the standard resistor capacitor Josephson model to arbitrary junctions (including, e.g., multiterminal geometries and/or junctions that embed topological or magnetic elements) and arbitrary electric circuits treated at the classical level. By treating the superconducting condensate and quasiparticles on equal footings, we capture nonequilibrium phenomena such as multiple Andreev reflection. We show that the interplay between the quasiparticle dynamics and the electrical environment leads to the emergence of new phenomena. In a RC circuit connected to single channel Josephson junction, we find out-of-equilibrium current-phase relations that are strongly distorted with respect to the (almost sinusoidal) equilibrium one, revealing the presence of the high harmonic ac Josephson effect. In an RLC circuit connected to a junction, we find that the shape of the resonance is strongly modified by the quasiparticle dynamics: close to resonance, the current can be smaller than without the resonator. Our approach provides a route for the quantitative modeling of superconducting-based circuits.
The origin of the three great epidemics of the Roman period has often been sought in Asia. We propose a review of our knowledge, taking into account the new information provided by archaeology. The ...commercial circulation between Rome and Asia is better known, in particular for the Indian Ocean. The phylogenetic analysis of microbes made possible by ancient DNA is also beginning to change our knowledge. However, it remains difficult to link the Antonine and Cyprian epidemics with Asia. Justinian's plague, on the other hand, did originate in Central Asia, and then probably took the Indian Ocean trade route.
The work focuses on crosslinking epoxidised natural rubber by dicarboxylic acids which react with the epoxy sites along the chain. The crosslinking reaction at 180 °C is followed in a rheometer, and ...the cured materials are characterised by stress-strain experiments. The cure process is tremendously accelerated (from 3 h to 20 min) in the presence of an equimolar amount of 1,2-dimethylimidazole. Thermal stability and fatigue life experiments were carried out on samples charged with carbon black and antioxidants. The results are found in between the ones obtained with standard sulphur or peroxide crosslinked samples.
While the coherent control of two-level quantum systems, qubits, is now standard, their continuum electronic equivalents, flying qubits, are much less developed. The first step in this direction has ...been achieved in dc interferometry experiments. Here, we propose a simple setup to perform the second step, the spectroscopy of these flying qubits, by measuring the dc response to a high-frequency ac voltage drive. Using two different concurring approaches (Floquet theory and time-dependent simulations) and three different models (an analytical model, a simple microscopic model, and a realistic microscopic model), we predict the power-frequency map of the multiterminal device. We argue that this spectroscopy provides a direct measurement of the flying qubit characteristic frequencies and a key validation for more advanced quantum manipulations.
Introduction au dossier Rossignol, Benoît; Dana, Dan
Antiquités africaines,
12/2020, Letnik:
56
Journal Article
Recenzirano
Odprti dostop
Les articles de notre dossier sont issus d’une rencontre organisée par le Centre ANHIMA (UMR 8210) le 18 novembre 2017, à l’INHA (Paris), elle-même issue des considérations postérieures à deux ...journées d’études organisées au même endroit les 4 et 5 décembres 2014, consacrées aux bassins de recrutement des auxiliaires aux deux premiers siècles de notre ère. Cette réflexion s’inscrit aussi plus largement dans le renouveau d’intérêt pour les auxiliaires constatable dans l’historiographie depuis ...
L’origine des trois grandes épidémies de l’époque romaine a souvent été cherchée en Asie. Nous proposons un bilan de nos connaissances tenant compte des renouvellements apportés par l’archéologie. ...Les circulations commerciales entre Rome et l’Asie sont mieux connues, en particulier pour l’océan Indien. L’analyse phylogénique des microbes permise par l’ADN ancien commence aussi à changer nos connaissances. Il reste cependant difficile de mettre en rapport l’épidémie antonine et l’épidémie dite de Cyprien avec l’Asie. En revanche, la peste de Justinien trouve bien son origine en Asie centrale, empruntant ensuite sans doute la voie commerciale de l’océan Indien.
Reddé (M.), Aux marges de la Gaule. Conquête militaire et développement économique de l'Occident romain. - Longues-sur-Mer : PHAZE, 2023. -206 p. -ISBN : 9782957224111 Crédit image. Première de ...couverture - PHAE Au début du IIIe siècle, Cassius Dion, dans son histoire romaine, place dans la bouche d'Antoine, aux funérailles de César, une description de la Gaule transformée par la conquête de César. Cultivée à l'image de l'Italie, elle est le seuil de la Bretagne (notre Grande-Bretagne), tand...
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