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991.
Nicole Turbé 《Comptes Rendus Mecanique》2002,330(6):391-396
We study the propagation of electromagnetic waves in a guide the section of which is a thin annulus. Owing to the presence of a small parameter, explicite approximations of the eigenmodes can be computed. To cite this article: N. Turbé, C. R. Mecanique 330 (2002) 391–396. 相似文献
992.
Wesley R. Mariott Nicole C. Escudé Eugene Y.‐X. Chen 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2581-2592
This contribution reports the synthesis and characterization of stereochemically controlled, as well as crystalline stereocomplex, P(MMA)‐clay nanocomposites using metallocene complexes and alane‐intercalated clay activators. The ligand elimination and exchange reactions involving Lewis acids E(C6F5)3 (E = Al, B) and an organically modified montmorillonite clay were employed to synthesize the alane‐intercalated clay activators. When combined with dimethyl metallocenes of various symmetries, these clay activators brought about efficient MMA polymerizations leading to in situ polymerized, stereochemically controlled P(MMA)‐intercalated clay nanocomposites. The most noticeable thermal property enhancement observed for the clay nanocomposite P(MMA), when compared with the pristine P(MMA) having similar molecular weight and stereomicrostructure, has a considerable increase in Tg (≥10 °C). Mixing of dilute THF solutions of two diastereomeric nanocomposites in a 1:2 isotactic to syndiotactic ratio, followed by reprecipitation or crystallization procedures, yielded unique double‐stranded helical stereocomplex P(MMA)‐clay nanocomposites with a predominantly exfoliated clay morphology. Remarkably, the resulting crystalline stereocomplex P(MMA) matrix is resistant to the boiling‐THF extraction and its clay nanocomposites exhibit high Tm of 201 to 210 °C. Furthermore, the stereocomplex P(MMA)‐clay nanocomposite shows a one‐step, narrow decomposition temperature window and a single, high maximum rate decomposition temperature of 377 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2581–2592, 2007 相似文献
993.
We consider the scheduling problem of minimizing the average-weighted completion time on identical parallel machines when jobs are arriving over time. For both the preemptive and the nonpreemptive setting, we show that straightforward extensions of Smith's ratio rule yield smaller competitive ratios than the previously best-known deterministic on-line algorithms. 相似文献
994.
Nicole M. Trease Krishna K. Dey Philip J. Grandinetti 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(2):334-339
Central transition (CT) sensitivity enhancement schemes that transfer polarization from satellites to the CT through selective saturation or inversion of neighboring satellite transitions have provided a welcome improvement for magic-angle spinning spectra of half-integer quadrupole nuclei. While many researchers have investigated and developed different methods of creating enhanced CT populations, here we investigate the conversion of these enhanced CT populations into observable CT coherence. We show a somewhat unexpected result that a conversion pulse length optimized for maximum sensitivity on equilibrium populations may not be optimum for an enhanced (non-equilibrium) polarization. Furthermore, CT enhancements can be lost if excessive rf field strength is used to convert this enhanced polarization into CT coherence. While a maximally enhanced CT signal is expected when using a perfectly selective CT conversion pulse, we have found that significant sensitivity loss can occur when using surprisingly low rf field strengths, even for sites with relatively large quadrupole coupling constants. We have systematically investigated these issues, and present some general guidelines and expectations when optimizing the conversion of enhanced (non-equilibrium) CT populations into observable CT coherence. 相似文献
995.
Kenneth H Huang Marie-Pierre Boisvert Famane Chung Maude Loignon Don Zarowny Lise Cyr Emil Toma Nicole F Bernard 《Journal of immune based therapies and vaccines》2006,4(1):7-12
Background
Despite the benefits of highly active antitretroviral therapy (HAART) for suppressing viral replication in HIV infection, virus persists and rebounds during treatment interruption (TI). This study explored whether HAART intensification with Remune™ vaccination before TI can boost HIV-1-specific immunity, leading to improved control of viremia off HAART. 相似文献996.
Nicole D. Cook William S. Walker Gabriela C. Weaver Brandon H. Sorge 《School science and mathematics》2015,115(7):318-329
The Indiana Science Initiative (ISI) is a systemic effort to reform K–8 science education. The program provides teachers with professional development, reform‐oriented science modules, and materials support. To examine the impact of the initiative's professional development, a participant observation study was conducted in the program's pilot year. Five teachers in grades 3–6 were observed and interviewed as they implemented the ISI‐provided modules. Analysis of the observation data revealed that the teachers incorporated each of the features of inquiry science instruction. However, they did not consistently teach in a way that was aligned with the intent of the ISI. Examination of interview data provided insight into influences on teachers' use of inquiry with the ISI‐provided modules. These data revealed that teachers were aware of the intent of the ISI and attempted to align their instruction. However, teachers were influenced by their perceptions of students' behavior and abilities as well as timing and the appropriate level of teacher control needed to facilitate science instruction. The research suggests that professional development activities should prepare teachers to help learners evaluate explanations against alternatives, connect explanations to scientific knowledge, and provide strategies to address teachers' perceptions of students, timing, and teacher control. 相似文献
997.
Daniel R. Fröhlich Andrej Skerencak‐Frech Nicole Bauer André Rossberg Petra J. Panak 《Journal of synchrotron radiation》2015,22(1):99-104
The complexation of acetate with Am(III) is studied as a function of the pH (1–6) by extended X‐ray absorption fine‐structure (EXAFS) spectroscopy. The molecular structure of the Am(III)–acetate complexes (coordination numbers, oxygen and carbon distances) is determined from the raw k3‐weighted Am LIII‐edge EXAFS spectra. The results show a continuous shift of Am(III) speciation with increasing pH value towards the complexed species. Furthermore, it is verified that acetate coordinates in a bidentate coordination mode to Am(III) (Am—C distance: 2.82 ± 0.03 Å). The EXAFS data are analyzed by iterative transformation factor analysis to further verify the chemical speciation, which is calculated on the basis of thermodynamic constants, and the used structural model. The experimental results are in very good agreement with the thermodynamic modelling. 相似文献
998.
This paper investigates the uncertainty of a hyper-elastic model by random material parameters as stochastic variables. For its stochastic discretization a polynomial chaos (PC) is used to expand the coefficients into deterministic and stochastic parts. Then, from experimental data in combination with artificial data for elastomers the distribution of the force-displacement curves are known. In the numerical example the PC-based stochastic and the deterministic parameter identification are used for generation of the distribution of Ogden's material parameters. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
999.
Laure Pasquini Jean-François Munoz Nicole Rimlinger Xavier Dauchy Xavier France Marie-Noëlle Pons Tatiana Görner 《Chemical Papers》2013,67(6):601-612
Everyday domestic activity is a significant source of water pollution. The presence of six household micropollutants in an urban wastewater treatment plant (WWTP) was assessed in wastewater and sludge. A multi-target analytical method was developed for the quantification of ibuprofen, erythromycin, ofloxacin, 4-nonylphenol, 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan), and sucralose. The micropollutants were extracted from the liquid and solid phases and their concentrations were determined by LC-MS/MS. The efficiency of micropollutants’ removal within a conventional activated sludge process was assessed. From 50 % to 90 % of ibuprofen and erythromycin was removed from the wastewater liquid phase. Their removal can be attributed to biological degradation as they were not found adsorbed on the outlet sludge. Ofloxacin and triclosan were removed from the liquid phase with similar efficiencies; however, they were adsorbed on the sludge, so it was not possible to determine their removal mechanism (whether biodegradation or displacement to solid phase/sequestration). Sucralose was not removed from wastewater (3 μg L?1 in inlet and outlet liquid phase) and not adsorbed on the sludge. 4-Nonylphenol concentrations were sometimes higher in the WWTP outlet water; this may relate to the degradation of alkylphenol ethoxylates in the wastewater treatment process. 4-Nonylphenol was always present in the outlet sludge. 相似文献
1000.
Yosra Sahraoui Sana Chaliaa Abderrazak Maaref Amor Haddad Francois Bessueille Nicole Jaffrezic‐Renault 《Electroanalysis》2020,32(4):683-689
A novel Keggin‐type metatungstate hybrid POMs ((APy)6[H2W12O40])/carboxylic acid functionalized single‐walled carbon nanotube based amperometric sensing platform was successfully constructed for the sensitive detection of hydrogen peroxide. A simple and reliable procedure was implemented for the synthesis of new composite materials obtained by the covalent grafting of (APy)6[H2W12O40] onto the surface of (SWCNT‐COOH). The synergistic effect of single walled carbon nanotubes on the electrochemical behavior of (APy)6[H2W12O40] was evidenced through the increase of the oxidation and reduction peaks of the polyoxometalate. The sensitivity of hydrogen peroxide detection was increased by a factor of 38.5 in presence of SWCNTs, showing their high influence on peroxidase‐like mimics of (APy)6[H2W12O40]. The detection limit, the response time, the repeatability and the shelf lifetime were respectively 0.4 μM, 10 s, <4%, 60 days. 相似文献