Search results for "MATTER"
showing 10 items of 16762 documents
Priming effect increases with depth in a boreal forest soil
2016
Abstract Climate warming increases labile carbon (C) inputs to soil through increased photosynthesis and C allocation belowground. This could counterintuitively lead to losses of soil C via priming effects (PE): the stimulation of soil organic matter (SOM) decomposition caused by labile C addition. Systematic quantification of PEs in different ecosystems is needed. We measured PEs of free-living soil microbes in different layers of a boreal forest soil, and found that the relative magnitude of the PE increased with soil depth. The relationship between relative PE and the added glucose amount also depended on the soil layer. Our results indicate that the decomposition of SOM in deeper soil l…
Procédé multiéchelle pour la reconstruction des courbes d'émission acoustique révélatrices des ruptures de fibres au sein d'un composite unidirection…
2006
International audience; Dans cette étude, la première partie du travail consiste en une analyse fine, par éléments finis, des mécanismes de report de charge entre lesfibres rompues et intactes d'un composite unidirectionnel. On considère différentes configurations d'endommagement du composite et deux types de comportement matriciel (élastique et viscoélastique) avec ou sans décohésion à l'interface fibre rompue/matrice. En raison de ces différents aspects, les limites habituelles des approches faites jusqu'à présent sont repoussées et notamment celles des modèles analytiques. La seconde partie du travail consiste en la mise en place d'un procédé multiéchelles qui synthétise les phénomènes m…
Productive Efficiency of Decanters with Short and Variable Dynamic Pressure Cones
2003
Abstract This paper presents the results of experimental trials carried out on third-generation, variable dynamic pressure cone decanters to assess machine performance and adjust the process parameters for optimum extraction yield. The results obtained led to the following conclusions: the regulation of the differential velocity screw/bowl allows a better performance of the decanter at low dilutions of the olive paste; it is possible to obtain high efficiency at a low dilution of the olive paste achieving a higher minor compounds content and the more advanced system of regulation leads to better results according to the variations of the ratio between liquid and solid phases, thus optimisin…
PROPAGATING INTERFACES IN A TWO-LAYER BISTABLE NEURAL NETWORK
2006
The dynamics of propagating interfaces in a bistable neural network is investigated. We consider the network composed of two coupled 1D lattices and assume that they interact in a local spatial point (pin contact). The network unit is modeled by the FitzHugh–Nagumo-like system in a bistable oscillator mode. The interfaces describe the transition of the network units from the rest (unexcited) state to the excited state where each unit exhibits periodic sequences of excitation pulses or action potentials. We show how the localized inter-layer interaction provides an "excitatory" or "inhibitory" action to the oscillatory activity. In particular, we describe the interface propagation failure a…
Pinning of a kink in a nonlinear diffusive medium with a geometrical bifurcation: Theory and experiments
2004
International audience; We study the dynamics of a kink propagating in a Nagumo chain presenting a geometrical bifurcation. In the case of weak couplings, we define analytically and numerically the coupling conditions leading to the pinning of the kink at the bifurcation site. Moreover, real experiments using a nonlinear electrical lattice confirm the theoretical and numerical predictions.
Multifacial Recognition in Binary and Ternary Cocrystals from 5-Halouracil and Aminoazine Derivatives
2018
A systematic analysis using single crystal X-ray diffraction was performed to explore the role exerted by potential intercomponent proton-transfer reactions in the supramolecular structures of A–B cocrystals formed by 5-haloderivatives of uracil (A), coupled with 2-aminoadenine simulants (aminoazines, B). Twelve new heterodimers were synthesized in different stoichiometries and cocrystallized by solvent cogrinding followed by solution crystallization. In the binary cocrystals, uracil or 1-methyluracil with halide modification at the 5 position (F, Cl, Br, I) was coupled with amino-aromatic N-heterocycles (melamine, 2,4,6-triaminopyrimidine, 2,6-diaminopyridine) as a multivalent site for pyr…
Ultrafast Interface Charge Separation in Carbon Nanodot-Nanotube Hybrids
2021
Carbon dots are an emerging family of zero-dimensional nanocarbons behaving as tunable light harvesters and photoactivated charge donors. Coupling them to carbon nanotubes, which are well-known electron acceptors with excellent charge transport capabilities, is very promising for several applications. Here, we first devised a route to achieve the stable electrostatic binding of carbon dots to multi- or single-walled carbon nanotubes, as confirmed by several experimental observations. The photoluminescence of carbon dots is strongly quenched when they contact either semiconductive or conductive nanotubes, indicating a strong electronic coupling to both. Theoretical simulations predict a favo…
Intramolecular Hydrogen Bond, Hirshfeld Analysis, AIM; DFT Studies of Pyran-2,4-dione Derivatives
2021
Intra and intermolecular interactions found in the developed crystals of the synthesized py-ron-2,4-dione derivatives play crucial rules in the molecular conformations and crystal stabili-ties, respectively. In this regard, Hirshfeld calculations were used to quantitatively analyze the different intermolecular interactions in the crystal structures of some functionalized py-ran-2,4-dione derivatives. The X-ray structure of pyran-2,4-dione derivative namely (3E,3′E)-3,3′-((ethane-1,2-diylbis(azanediyl))bis(phenylmethanylylidene))bis(6-phenyl-2H-pyran-2,4(3H)-dione) was determined. It crystallized in the monoclinic crystal system and C2/c space group with unit cell parameters: a = 14.0869(4) …
Crystal structure of the pyridine–diiodine (1/1) adduct
2015
In the title adduct, C5H5N·I2, the N—I distance [2.424 (8) Å] is remarkably shorter than the sum of the van der Waals radii. The line through the I atoms forms an angle of 78.39 (16)° with the normal to the pyridine ring.
Pyrolytic behavior of lignocellulosic-based polysaccharides
2018
The thermochemical behavior of cellulose, glucomannan, and xylan was investigated by pyrolysis–gas chromatographymass spectrometry (Py-GC/MS). In each case, major GC-amenable condensable products were classified into several compound groups, and the formation of these monomer-related fragments from the model substance samples was determined at 500, 600, and 700 C with a residence time of 5 s and 20 s. The results revealed that despite some general formation trends, no compound group was selectively formed at certain temperatures. Of the 11 product groups, the primary ones, including lactone, furan, and cyclopentenone derivatives, accounted for 72–85% (from cellulose), 86–90% (from glucomann…