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691.
Augusto Visintin 《Annali di Matematica Pura ed Applicata》2006,185(4):487-519
This work deals with an initial- and boundary-value problem for a quasilinear parabolic equation that includes a possibly
discontinuous hysteresis operator,
:
In particular the case of
equal to a so-called relay operator is studied. Well-posedness is proved, as well as regularity of the solution and its robustness w.r.t. perturbations of
. The large-time behaviour is studied; asymptotic stability and compactness are shown. For a time-periodic f, existence of a periodic solution is also established.
Mathematics Subject Classification (2000) 35K60, 35R35, 47J40 相似文献
692.
José Alberto Fracassi da Silva Nathan Vitorazzi de Castro Dosil Pereira de Jesus Adriana F. Faria Marcus V. N. De Souza Marcone Augusto Leal de Oliveira 《Electrophoresis》2010,31(3):570-574
A method for the determination of ethambutol (EMB), a first‐line drug against tuberculosis, based on CE with capacitively coupled contactless conductivity detection is proposed. The separation of EMB and its main product of degradation were achieved in less than 3 min with a resolution of 2.0 using a BGE composed of 50 mmol/L histidine and 30 mmol/L MES, pH 6.30. By raising the pH to 8.03, the analysis time was reduced to 1.0 min, but with a significant loss of resolution (0.7). Using the best separation conditions, linearity of 0.9976 (R2, five data points), sensitivity of 1.26×10?4 V min μmol?1 L, and LOD and quantification of 23.5 and 78.3 μmol/L, respectively, were obtained. Recoveries at four levels of concentration ranged from 95 to 102% and the concentration range studied ranged from 100 to 500 μmol/L. The results obtained for the determination of EMB in pharmaceutical formulations were compared with those obtained by using CE with photometric detection. 相似文献
693.
Carina de Souza Gondim Otávio Augusto Mazzoni CoelhoRonália Leite Alvarenga Roberto Gonçalves JunqueiraScheilla Vitorino Carvalho de Souza 《Analytica chimica acta》2014
The lack of well-established references for the validation of qualitative analyses and the increasing demand for reliable binary responses were the main motivating factors for this study. A detailed procedure for single-laboratory validation of qualitative methods is proposed. The experimental design and the tools for data analysis were based on the theoretical background, as well as the aspects of efficiency, convenience and simplicity. Four experimental steps were defined, as follows: (i) preliminary tests for the determination of the concentration range, (ii) a study of the rates, unreliability region, detection limit, and the accordance and concordance values, (iii) a study of the selectivity in the presence of known interferences, and (iv) a study of robustness. The applicability of the procedure was demonstrated by the validation of a qualitative commercial kit for detecting sulfonamide residues in raw milk using both the visual and instrumental reading techniques. Reliability rates of 100% were obtained for the blank samples. For the samples spiked with sulfamethazine at 10.8 and 108 μg L−1 and with sulfadimethoxine or sulfathiazole at 10 and 100 μg L−1, the reliability rates ranged from 93.3 to 100%. Selectivity was demonstrated using trimethoprim as a potential interferent. The method was considered robust for the factors of the temperature (54 and 58 °C) and time (6 and 10 min) for incubating the test strips. The estimated detection limits and unreliability regions confirmed the suitability of the kit for this purpose, based on the legislated residue limits. 相似文献
694.
Eduardo Piza Pellizzer Joel Ferreira Santiago Junior Luiz Marcelo Ribeiro Villa Victor Eduardo de Souza Batista Caroline Cantieri de Mello Daniel Augusto de Faria Almeida Heitor Marques Honório 《Applied physics. B, Lasers and optics》2014,117(1):235-244
The aim of this study was to evaluate the effects that splinting and different lengths of implants have on the stress distribution in implant-supported prostheses by photoelastic analysis. A total of five photoelastic resin models were made with different proposed situations, and 400 load applications were performed for the analysis. Compared with the unitary prosthesis, the splinted implant-supported prosthesis acted favorably in the distribution of stresses and strains to the implant (p < 0.001). The increase in length was a significant factor in the stress distribution (p < 0.05) and, ultimately, the overall reduction in stress. It was concluded that the splinted implant-supported prosthesis behaved better biomechanically compared with the unitary prosthesis. 相似文献
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699.
Silvia Capuani Marco Palombo Andrea Gabrielli Augusto Orlandi Bruno Maraviglia Francesco S. Pastore 《Magnetic resonance imaging》2013
Recently, we measured two anomalous diffusion (AD) parameters: the spatial and the temporal AD indices, called γ and α, respectively, by using spectroscopic pulse gradient field methods. We showed that γ quantifies pseudo-superdiffusion processes, while α quantifies subdiffusion processes. Here, we propose γ and α maps obtained in a controlled heterogeneous phantom, comprised of packed micro-beads in water and in excised human meningiomas. In few words, α maps represent the multi-scale spatial distribution of the disorder degree in the system, while γ maps are influenced by local internal gradients, thus highlighting the interface between compartments characterized by different magnetic susceptibility. γ maps were already obtained by means of AD stretched exponential imaging and α-type maps have been recently achieved for fixed rat brain with the aim of highlighting the fractal dimension of specific brain regions. However, to our knowledge, the maps representative of the spatial distribution of α and γ obtained on the same controlled sample and in the same excised tissue have never been compared. Moreover, we show here, for the first time, that α maps are representative of the spatial distribution of the disorder degree of the system. 相似文献
700.
Fabiana Inoue Rmulo Augusto Ando Paola Corio 《Journal of Raman spectroscopy : JRS》2011,42(6):1379-1383
Nanocomposites of carbon nanotubes and titanium dioxide (TiO2) have attracted much attention due to their photocatalytic properties. Although many examples in the literature have visualized these nanocomposites by electron microscopic images, spectroscopic characterization is still lacking with regard to the interaction between the carbon nanotube and TiO2. In this work, we show evidence of the attachment of nanostructured TiO2 to multiwalled carbon nanotubes (MWNTs) by Raman spectroscopy. The nanostructured TiO2 was characterized by both full‐width at half‐maximum (FWHM) and the Raman shift of the TiO2 band at ca 144 cm−1, whereas the average diameter of the crystallite was estimated as approximately 7 nm. Comparison of the Raman spectra of the MWNTs and MWNTs/TiO2 shows a clear inversion of the relative intensities of the G and D bands, suggesting a substantial chemical modification of the outermost tubes due to the attachment of nanostructured TiO2. To complement the nanocomposite characterization, scanning electronic microscopy and X‐ray diffraction were performed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献