Search results for "structural"
showing 10 items of 5047 documents
Induction of tcI 7 , a gene encoding a β-subunit of proteasome, in tobacco plants treated with elicitins, salicylic acid or hydrogen peroxide 1
2000
We previously isolated, by differential display and 5′ RACE (rapid amplification of cDNA ends), cDNAs corresponding to genes activated following cryptogein treatment of tobacco cell suspensions, among them tcI 7 (tcI for obacco ryptogein nduced), a gene encoding a β-subunit of proteasome. Here, we report that tcI 7 was up-regulated in tobacco plants treated with elicitins (cryptogein and parasiticein) that have been shown to induce a systemic acquired resistance (SAR). Moreover, subsequent inoculation of tobacco with the pathogen Phytophthora parasitica var. nicotianae (Ppn) was shown to induce an additional activation of tcI 7 in tobacco plants pretreated with cryptogein. We also showed an…
Stochastic dynamics of nonlinear systems with a fractional power-law nonlinear term: The fractional calculus approach
2011
Fractional power-law nonlinear drift arises in many applications of engineering interest, as in structures with nonlinear fluid viscous–elastic dampers. The probabilistic characterization of such structures under external Gaussian white noise excitation is still an open problem. This paper addresses the solution of such a nonlinear system providing the equation governing the evolution of the characteristic function, which involves the Riesz fractional operator. An efficient numerical procedure to handle the problem is also proposed.
Gaussian and non-Gaussian stochastic sensitivity analysis of discrete structural systems
2000
Abstract The derivatives of the response of a structural system with respect to the system parameters are termed sensitivities. They play an important role in assessing the effect of uncertainties in the mathematical model of the system and in predicting changes of the response due to changes of the design parameters. In this paper, a time domain approach for evaluating the sensitivity of discrete structural systems to deterministic, as well as to Gaussian or non-Gaussian stochastic input is presented. In particular, in the latter case, the stochastic input has been assumed to be a delta-correlated process and, by using Kronecker algebra extensively, cumulant sensitivities of order higher t…
Pseudo-force method for a stochastic analysis of nonlinear systems
1996
Nonlinear systems, driven by external white noise input processes and handled by means of pseudo-force theory, are transformed through simple coordinate transformation to quasi-linear systems. By means of Itô stochastic differential calculus for parametric processes, a finite hierarchy for the moment equations of these systems can be exactly obtained. Applications of this procedure to the first-order differential equation with cubic nonlinearity and to the Duffing oscillator show the versatility of the proposed method. The accuracy of the proposed procedure improves by making use of the classical equivalent linearization technique.
Anisotropic lattice distortions in biogenic calcite induced by intra-crystalline organic molecules.
2006
9 pages; International audience; We have performed precise structural measurements on five different calcitic seashells by high-resolution X-ray powder diffraction on a synchrotron beam line and by laboratory single crystal X-ray diffraction. The unit cell parameters a and c of biogenic calcite were found to be systematically larger than those measured in the non-biogenic calcite. The maximum lattice distortion (about 2.10(-3)) was detected along the c-axis. Under heat treatment above 200 degrees C, a pronounced lattice relaxation was observed, which allowed us to conclude that anisotropic lattice swelling in biogenic calcite is induced by organic macromolecules incorporated within the sing…
In situ high-pressure synchrotron X-ray diffraction study of the structural stability in NdVO4 and LaVO4
2014
Abstract Room-temperature angle-dispersive X-ray diffraction measurements on zircon-type NdVO 4 and monazite-type LaVO 4 were performed in a diamond-anvil cell up to 12 GPa. In NdVO 4 , we found evidence for a non-reversible pressure-induced structural phase transition from zircon to a monazite-type structure at 6.5 GPa. Monazite-type LaVO 4 also exhibits a phase transition but at 8.6 GPa. In this case the transition is reversible and isomorphic. In both compounds the pressure induced transitions involve a large volume collapse. Finally, the equations of state and axial compressibilities for the low-pressure phases are also determined.
An Ultrahigh CO2-Loaded Silicalite-1 Zeolite: Structural Stability and Physical Properties at High Pressures and Temperatures
2018
[EN] We report the formation of an ultrahigh CO2-loaded pure-SiO2, silicalite-1 structure at high pressure (0.7 GPa) from the interaction of empty zeolite and fluid CO, medium. The CO2-filled structure was characterized in situ by means of synchrotron powder X-ray diffraction. Rietveld refinements and Fourier recycling allowed the location of 16 guest carbon dioxide molecules per unit cell within the straight and sinusoidal channels of the porous framework to be analyzed. The complete filling of pores by CO, molecules favors structural stability under compression, avoiding pressure-induced amorphization below 20 GPa, and significantly reduces the compressibility of the system compared to th…
Structural characterization of Nigerian coals by X-ray diffraction, Raman and FTIR spectroscopy
2010
Abstract The structural parameters of six Nigerian coals were determined by X-ray diffraction, Raman and FTIR spectroscopy. This study reveals that the coals contain crystalline carbon of turbostratic structure with some amount of highly disordered amorphous carbon. The average lateral sizes ( L a ), stacking heights ( L c ) and interlayer spacing ( d 002 ) of the crystallite structures calculated from the X-ray intensities range from 16.47 to 25.70, 8.12 to 13.25 and 3.48 to 3.58 A, respectively. The L a values derived from the Raman spectra analyses using the classical linear relationship between 1/ L a and the D/G band ratio are higher (27.53–34.67 A) than values obtained from X-ray diff…
Landau theory applied to phase transitions in calcium orthotungstate and isostructural compounds
2007
The pressure-driven tetragonal-to-monoclinic phase transition in CaWO4 and related scheelite-structured orthotungstates is analysed in terms of spontaneous strains. Based upon our previous high-pressure x-ray diffraction results and the Landau theory, it is suggested that the scheelite-to-fergusonite transition is of second order in nature.
Application of clustering techniques to electron-diffraction data: determination of unit-cell parameters.
2012
A new approach to determining the unit-cell vectors from single-crystal diffraction data based on clustering analysis is proposed. The method uses the density-based clustering algorithm DBSCAN. Unit-cell determination through the clustering procedure is particularly useful for limited tilt sequences and noisy data, and therefore is optimal for single-crystal electron-diffraction automated diffraction tomography (ADT) data. The unit-cell determination of various materials from ADT data as well as single-crystal X-ray data is demonstrated.