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121.
Sébastien Fumeron Bertrand Berche Fernando Moraes Fernando A. N. Santos Erms Pereira 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(5):95
The presence of topological defects in a material can modify its electrical, acoustic or thermal properties. However, when a group of defects is present, the calculations can become quite cumbersome due to the differential equations that can emerge from the modeling. In this work, we express phonons as geodesics of a 2 + 1 spacetime in the presence of a channel of dislocation dipoles in a crystalline environment described analytically in the continuum limit with differential geometry methods. We show that such a simple model of 1D array of topological defects is able to guide phonon waves. The presence of defects indeed distorts the effective metric of the material, leading to an anisotropic landscape of refraction index which curves the path followed by phonons, with focusing/defocusing properties depending on the angle of the incident wave. As a consequence, using Boltzmann transfer equation, we show that the defects may induce an enhancement or a depletion of the elastic energy transport. We comment on the possibility of designing artificial materials through the presence of topological defects. 相似文献
122.
123.
Alex Neves Junior Romildo Dias Toledo Filho Eduardo de Moraes Rego Fairbairn Jo Dweck 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1577-1584
During the formation of pastes, mortar and concretes have been used to capture CO2. This work presents a methodology to estimate the carbon dioxide (CO2) sequestered by high strength and sulfate-resistant Portland cement pastes during their early stages of hydration, by Thermogravimetry and Derivative Thermogravimetry. Water to cement ratio equal to 0.50 and 0.70 were evaluated and the captured CO2 amount was determined through TG/DTG curve data on initial cement mass basis, obtained during accelerated carbonation from the fluid state and accelerated carbonation after a first hydration process. The experiments were performed in a controlled chamber, maintaining the CO2 content at 20 vol % and the temperature at 25 °C, at different relative humidity (RH) (60 and 80 %) ambient. The procedure allows one to estimate the amount of CO2 sequestered by the initial cement mass of a given volume of paste, as well as to evaluate the RH and W/C ratio influence on the amount of hydrated formed products, mainly on the Ca(OH)2, important for CO2 fixation. 相似文献
124.
Fernando C. Moraes Tiago A. Silva Ivana Cesarino Marcos R. V. Lanza Sergio A. S. Machado 《Electroanalysis》2013,25(9):2092-2099
A sensitive way to determine levofloxacin using a sensor based on vertical aligned carbon nanotubes is described. The morphology and the electrochemical performance of the electrodes were characterised by atomic force microscopy, cyclic voltammetry and square wave voltammetry. A scan‐rate study and electrochemical impedance spectroscopy showed that the levofloxacin oxidation product is adsorbed on the electrode surface. Differential pulse voltammetry in phosphate‐buffer solution allowed the development of a method to determine levofloxacin levels in the range of 1.0–10.0 µmol L?1, with a detection limit of 75.2 nmol L?1. The proposed sensor was successfully applied in the determination of levofloxacin in urine, and the obtained results were in full agreement with those from the HPLC procedure. 相似文献
125.
Analysis of ibuprofen enantiomers in rat plasma by liquid chromatography with tandem mass spectrometry 下载免费PDF全文
Juciane Lauren Cavalcanti Cardoso Vera Lucia Lanchote Maria Paula Marques Pereira Natália Valadares de Moraes José Salvador Lepera 《Journal of separation science》2014,37(8):944-949
A sensitive and selective method for the analysis of ibuprofen enantiomers by LC–MS/MS was developed and validated for the purpose of application in pharmacokinetic studies in small experimental animals. Aliquots of 200 μL plasma were submitted to liquid–liquid extraction with hexane/diisopropylether (50:50 v/v) in acid pH. Separation was accomplished in a Chirex® 3005 (250 × 4.6 mm, 5 μm) column at 25°C with a mobile phase that consisted of 0.01 M ammonium acetate in methanol at a flow rate of 1.1 mL/min. The mass spectrometer consisted of an ESI interface operating at negative ionization mode and multiple reaction monitoring. The transitions 205 > 161 and 240 > 197 were monitored for ibuprofen enantiomers and fenoprofen (internal standard), respectively. Method validation included the evaluation of the matrix effect, stability, linearity, lower LOQ, within‐run and between‐run precision, and accuracy. The lower LOQ was 25 ng/mL for each ibuprofen enantiomer, and the calibration curves showed good linearity in the range 0.025–50 μg/mL. The method was successfully applied in the investigation of pharmacokinetic disposition of ibuprofen enantiomers in rats treated orally with 25 mg/kg of the racemate. Enantioselective kinetic disposition was observed with accumulation of (+)‐(S)‐ibuprofen in rats following single oral administration. 相似文献
126.
Carlos Eduardo Barão Fátima Paiva-Martins Gisella Maria Zanin Flavio Faria De Moraes 《Journal of inclusion phenomena and macrocyclic chemistry》2014,78(1-4):465-470
Oleuropein (OLE) is a major phenolic compound of olive leaf (Olea europaea) and has many therapeutic properties associated with olive leaf extracts. This work concerns the determination of the inclusion complex constant between OLE and cyclodextrins (CDs), based on the competition of two guests for the CD cavity, one being a dye and the other OLE. The dye used was methylorange (MO) and pH 3 was selected, since MO molar absorptivity at 500 nm is at maximum in this condition. A solution of MO, OLE, and α-CD or β-CD, with citrate buffer was used for determining the absorbance values. From these data and by appropriate mathematical modeling, the equilibrium constant for the formation of OLE:CD complexes were obtained: for OLE:α-CD K = 1,352.4 L mol?1 (R 2 = 0.9975) and for OLE:β-CD K = 1,827.9 L mol?1 (R 2 = 0.9991). The results show that OLE has a greater affinity for β-CD than for α-CD and given the relatively high constants, OLE:CD complexes have potential for giving longer shelf lives for OLE medicinal and food additive preparations. 相似文献
127.
Zanin Gisella M. Kambara Lauro M. Calsavara Luiza P. V. De Moraes Flavio F. 《Applied biochemistry and biotechnology》1994,45(1):627-640
Applied Biochemistry and Biotechnology - Saccharification of α-amylase liquefied cassava starch was carried out at pH 4.5 and 45?C, in both fixed and fluidized bed reactors, using... 相似文献
128.
G. Carelli N. Ioli J. C. S. Moraes A. Moretti F. Strumia G. E. Annino A. Bertolini 《International Journal of Infrared and Millimeter Waves》1996,17(6):1023-1030
The results described in this work are part of a systematic search for long wavelength laser lines to be used in high magnetic field EPR applications and in plasma diagnostic. Four new far-infrared laser lines of CH2 = CF2 (1,1 difluoroethylene), optically pumped by a waveguide CO2 laser, have been discovered and characterized in wavelength, polarization relative to the pumping radiation and offset relative to the CO2 center frequency. New measurements of polarization and offset of 5 already known laser lines are also reported. A table of all of the known CO2 pumped FIR laser lines from this molecule is given. 相似文献
129.
Sandra R Moraes 《European Polymer Journal》2004,40(9):2033-2041
Polyaniline (PAni) was synthesized from aqueous phosphate buffer solution (1.7 ? pH ? 2.2) containing 0.1 mol l−1 aniline, electrochemically on a platinum electrode and chemically using ammonium persulfate as oxidant agent. The polymers obtained were characterized by electrochemical response, UV-vis and IR spectrocopies, conductivity measurements and morphological analysis. In general, the polymer growth rate and the characteristics of the polymeric materials are similar to those prepared in sulfuric acid medium. However, phosphate medium presents as advantage the formation of phosphate layers interpenetrated with PAni on active metallic surfaces like steels, aluminum and aluminum alloys, with a wide range of application in corrosion protection. 相似文献
130.
D. Pereira J. C. S. Moraes E. M. Telles A. Scalabrin F. Strumia A. Moretti G. Carelli C. A. Massa 《International Journal of Infrared and Millimeter Waves》1994,15(1):1-44
The technique of optical pumping in polar molecules is the most efficient for Far-Infrared (FIR) laser generation, providing also a versatile and powerful tool for molecular spectroscopy in this spectral region. Methanol (CH3OH) and its isotopic varieties are the best media for optically pumped FIR laser, with over thousand lines observed, and the most widely used for investigations and applications. In this sense, it is important organize and make available catalogues of FIR laser lines as complete as possible. Since the last critical reviews of 1984 [1] on methanol and its isotopic varieties [2,3,4], over hundred papers have been published dealing with hundreds of new FIR laser lines. In 1992 a review of FIR laser lines from CH3OH was presented [5]. In this communication we extend this work to the other methanol isotopes, namely CH3OD, CD3OH, CD3OD,13CH3OH,13CD3OH,13CD3OD, CH3
18OH, CH2DOH, CHD2OH and CH2DOD.Work supported by FAPESP, CNPq, FAEP-Brasil, and CNR-Italia 相似文献