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1.
M. Cohen L. Porte J-P Thomas J. Tousset 《Journal of Radioanalytical and Nuclear Chemistry》1973,17(1-2):65-77
Résumé Une méthode d'étude de la composition stoéchiométrique de couches minces (10 à 500 μg/cm2) de verres chalcogénures est développée. L'étude des réactions nucléaire; induites par bombardement de protons de basse énergie
(<4 MeV) sur les éléments constitutifs Ge, As, Te et S, conduit à choisir la diffusion élastique et la détection de gammas
prompts pour le dosage simulatené. La précision et la sensibilité de la méthode sont discutées à partir des résultats obtenus.
L'utilisation de la résonance fine sur le soufre (p, p'γ) est appliquée à l'étude de l'homogénéité des cibles. 相似文献
2.
A set of amino-group possessing cyanine dyes is obtained from their N-acetyl derivatives via deprotection with boron trifluoride-methanol complex in good yields. 相似文献
3.
Vernica Herrera-Mayorga Jos Alfredo Guerrero-Snchez Domingo Mndez-lvarez Francisco A. Paredes-Snchez Luis Víctor Rodríguez-Duran Nohemí Nio-García Alma D. Paz-Gonzlez Gildardo Rivera 《Molecules (Basel, Switzerland)》2022,27(10)
Spodoptera frugiperda (S. frugiperda) remains a global primary pest of maize. Therefore, new options to combat this pest are necessary. In this study, the insecticidal activity of three crude foliar extracts (ethanol, dichloromethane, and hexane) and their main secondary metabolites (quercetin and chlorogenic acid) of the species Solidago graminifolia (S. graminifolia) by ingestion bioassays against S. frugiperda larvae was analyzed. Additionally, the extracts were phytochemically elucidated by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis. Finally, an in silico study of the potential interaction of quercetin on S. frugiperda acetylcholinesterase was performed. Organic extracts were obtained in the range from 5 to 33%. The ethanolic extract caused higher mortality (81%) with a half-maximal lethal concentration (LC50) of 0.496 mg/mL. Flavonoid secondary metabolites such as hyperoside, quercetin, isoquercetin, kaempferol, and avicularin and some phenolic acids such as chlorogenic acid, solidagoic acid, gallic acid, hexoside, and rosmarinic acid were identified. In particular, quercetin had an LC50 of 0.157 mg/mL, and chlorogenic acid did not have insecticidal activity but showed an antagonistic effect on quercetin. The molecular docking analysis of quercetin on the active site of S. frugiperda acetylcholinesterase showed a −5.4 kcal/mol binding energy value, lower than acetylcholine and chlorpyrifos (−4.45 and −4.46 kcal/mol, respectively). Additionally, the interactions profile showed that quercetin had π–π interactions with amino acids W198, Y235, and H553 on the active site. 相似文献
4.
In this work we show that the energy associated to the linear three-dimensional magneto-elastic system decays polynomially to zero as time goes to infinity, provided the initial data is smooth enough. 相似文献
5.
Liquid-crystal phase equilibria of Lennard-Jones chain fluids and the solubility of a Lennard-Jones gas in the coexisting phases are calculated from Monte Carlo simulations. Direct phase equilibria calculations are performed using an expanded formulation of the Gibbs ensemble. Monomer densities, order parameters, and equilibrium pressures are reported for the coexisting isotropic and nematic phases of: (1) linear Lennard-Jones chains, (2) a partially-flexible Lennard-Jones chain, and (3) a binary mixture of linear Lennard-Jones chains. The effect of chain length is determined by calculating the isotropic-nematic coexistence of linear Lennard-Jones chain fluids made of 8, 10, and 12 segments (8-, 10-, 12-mer). The effect of molecular flexibility on the isotropic-nematic equilibrium is studied for a Lennard-Jones 10-mer chain fluid with one freely-jointed segment at the end of the chain. An isotropic-nematic phase split and fractionation are reported for a binary mixture of linear 7-mer and 12-mer chains. Simulation results are compared with theoretical results as obtained from a recently developed analytical equation of state based on perturbation theory. Excellent agreement between theory and simulations is observed. The solubility of a monomer Lennard-Jones gas in the coexisting isotropic and nematic phases is estimated using the Widom test-particle insertion method. A linear relationship between solubility difference and density difference at isotropic-nematic coexistence is observed. It is shown that gas solubility is independent of the nematic ordering of the fluid, at constant temperature and density conditions. 相似文献
6.
H. Schmid E. Burkhardt E. Walker W. Brixel M. Clin J. -P. Rivera J. -L. Jorda M. François K. Yvon 《Zeitschrift für Physik B Condensed Matter》1988,72(3):305-322
The ferroelastic domains of the orthorhombic phase of YBa2Cu3O7- have been observed in polarized light on ceramics and single crystals. By combining polarized light microscopy with the X-ray precession technique, the correlation of the orientation of the orthorhombica- andb-axes with that of thea-b-plane bireflectance, reflection dichroism, transmission dichroism (at a thickness of about 1m), reflection tints generated with compensators and upon uncrossing of polars, as well as the orientation of etch pits has been realized on ferroelastic single domains, bi-domains and more complicated domain patterns. Four ferroelastic orthorhombic domain states have been identified, at variance with former group theoretical considerations, predicting only two states. Ensembles of lamellar domains beyond optical resolution generate strong bireflectance with principal axes rotated by 45° relative to the truea, b-directions. 相似文献
7.
Metastable 23S1 He atoms are optically oriented and their orientation is transferred to metallic ions produced by Penning collisions . If r.f. transitions are induced in the 23S1 He level, the circularly polarized light emitted by the ions in a direction perpendicular to the static magnetic field is modulated at the r.f. frequency. The variation of the modulation amplitude with frequency depends on the lifetime of the level of the excited ion.We describe an experimental apparatus with which we measure the modulation amplitude from 1 MHz to 110 MHz. In this way the lifetime of the 4f2F and 2F Mg+ levels has been determined. 相似文献
8.
Performance of laser-ultrasonic F-SAFT imaging 总被引:1,自引:0,他引:1
The resolution and signal-to-noise ratio of laser-ultrasonics to detect small and buried defects can be greatly enhanced by using the synthetic aperture focusing technique (SAFT). Originally developed in the time domain, SAFT can also be implemented in the frequency domain (F-SAFT) using the angular spectrum approach for a significant reduction in processing time. In this paper, an F-SAFT based data processing method especially adapted to laser-ultrasonic data is presented. This method allows for further significant improvements towards laser-ultrasonic imaging of small defects. It includes temporal deconvolution of the waveform data, control for an optimal aperture and frequency bandwidth as well as spatial interpolation of the subsurface images. All the above operations are well adapted to the frequency domain calculations and embedded in the F-SAFT data processing. Also, the aperture control and spatial interpolation allow a reduction of sampling requirements to further decrease both inspection and processing times. The above improvements are illustrated using laser-ultrasonic data taken from an aluminum sample with flat-bottom holes. 相似文献
9.
Humberto Bustos Rodríguez Dagoberto Oyola Lozano Yebrayl Antonio Rojas Martínez Marlene Rivera Pinilla German Antonio Pérez Alcázar 《Hyperfine Interactions》2012,206(1-3):13-18
Friedreich ataxia is a disease that is associated with defects in the gene coding for a small protein frataxin. Several different roles have been proposed for the protein, including iron chaperoning and iron storage. M?ssbauer spectroscopy was used to probe these hypotheses. Iron accumulation in mutant mitochondria unable to assemble iron sulfur clusters proved to be insensitive to overexpression of frataxin, ruling out its potential involvement as an iron storage protein similar to ferritin. Rather, it was found that frataxin negatively regulates iron sulfur cluster assembly. 相似文献
10.
We give new sufficient conditions in order that a projective tensor product of Banach spaces contains complemented copies of ?1, which provides us new examples of this situation. 相似文献