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41.
42.
A. F.R. Rodriguez J. G. Santos L. B. Silveira A. C. Oliveira P. C. Morais O. A.C. Nunes 《The European physical journal. Special topics》2008,153(1):543-546
Photoacoustic spectroscopy (PAS) was used to investigate
samples produced from Baru (Dipteryx alata Vog.), a typical fruit from the Brazilian
Cerrado, which is considered as a good source of nutrients. The
photoacoustic (PA) spectra of samples prepared from Baru seeds present three
different absorption bands in the wavelength range 0.3–1.0 μm, named
Band-C, Band-S, and Band-L. We found that PAS can be useful for monitoring
the strong absorption of visible light by Baru's seeds constituents mainly
in the shorter wavelength measured range. This study is important from both
agricultural and commercial point of view once it introduces PAS as a
potential characterization technique allowing better control of fruit and
seed selection, storage and transportation. 相似文献
43.
Carlos A. FlorentinoJosé M. Mourão João P. Nunes 《Journal of Functional Analysis》2002,192(2):410-424
We extend the coherent state transform (CST) of Hall to the context of abelian varieties by considering them as quotients of the complexification of the abelian group K=U(1)g. We show that this transform, applied to appropriate distributions on K, gives all classical theta functions, and that, by defining on this space of theta functions an inner product related to the K-averaged heat kernel, the unitarity of the CST transform is still preserved. 相似文献
44.
O.A.C. Nunes 《Solid State Communications》1983,45(6):521-525
The free-carrier multiphoton absorption of laser radiation in magnetic semiconductors in the presence of quantizing magnetic fields is discussed. It is found that for the laser frequency near the cyclotron frequency of the free carrier the magnon population may become unstable. 相似文献
45.
Uranium analysis in fish, echinoderms and shellfish samples collected in the north part of the Adriatic Sea is presented. The aim of the work was to evaluate uranium concentrations in samples of this kind, and also to investigate possible contamination from depleted uranium (DU) in consequence of the war operations previously conducted in that area. DU contamination was checked by measuring the (235)U/(238)U isotope ratio. The samples were dissolved according to the EPA 3052 procedure, and the determinations were performed by inductively coupled plasma mass spectrometry (ICP-MS), optimized in order to perform isotope ratio measurements with good precision. The method was validated by evaluating the recovery from spiked samples; results in the range 93-107% were obtained. The isotope ratio measurement was evaluated in terms of accuracy and precision by analyzing the certified reference materials IAEA 326 and GBW 07305, and good agreement with the certified values was obtained here also. The concentration of uranium was higher in invertebrate samples than in fish (0.3-2 microg/g of U vs. 0.05-0.1 microg/g, respectively). The isotope ratio measurements for all the samples gave values very similar to the natural ratio, permitting exclusion of the presence of DU. 相似文献
46.
We present an investigation of the excited-state absorption and laser emission of a 1.0-at. %-Nd3+-doped YVO4 single-crystal fiber grown by the low-cost and versatile laser-heated pedestal growth technique. Efficient laser emission at 1064 nm was achieved when the fiber was pumped, in an end-pump cavity, by a Ti:sapphire laser at 808 nm. A continuous-wave threshold of 10 mW was observed with an efficiency of 42% with respect to the absorbed pump power and the maximum output power of 200 mW. These results are excellent when compared with those of a commercial bulk crystal adapted to the same cavity (48% efficiency, 250-mW maximum output power). Thus the fibers are characterized as strong candidates for the construction of compact lasers that can also be pumped by low-cost diode lasers. 相似文献
47.
Ivanov PC Nunes Amaral LA Goldberger AL Havlin S Rosenblum MG Stanley HE Struzik ZR 《Chaos (Woodbury, N.Y.)》2001,11(3):641-652
We explore the degree to which concepts developed in statistical physics can be usefully applied to physiological signals. We illustrate the problems related to physiologic signal analysis with representative examples of human heartbeat dynamics under healthy and pathologic conditions. We first review recent progress based on two analysis methods, power spectrum and detrended fluctuation analysis, used to quantify long-range power-law correlations in noisy heartbeat fluctuations. The finding of power-law correlations indicates presence of scale-invariant, fractal structures in the human heartbeat. These fractal structures are represented by self-affine cascades of beat-to-beat fluctuations revealed by wavelet decomposition at different time scales. We then describe very recent work that quantifies multifractal features in these cascades, and the discovery that the multifractal structure of healthy dynamics is lost with congestive heart failure. The analytic tools we discuss may be used on a wide range of physiologic signals. (c) 2001 American Institute of Physics. 相似文献
48.
Mariele M. Pedroso Ailton M. Watanabe Maria Cristina Roque-Barreira Paulo R. Bueno Ronaldo C. Faria 《Microchemical Journal》2008,89(2):153-158
A Quartz Crystal Microbalance (QCM) was used to monitor the mass changes on a quartz crystal surface containing immobilized lectins that interacted with carbohydrates. The strategy for lectin immobilization was developed on the basis of a multilayer system composed of Au–cystamine–glutaraldehyde–lectin. Each step of the immobilization procedure was confirmed by FTIR analysis. The system was used to study the interactions of Concanavalin A (ConA) with maltose and Jacalin with Fetuin. The real-time binding of different concentrations of carbohydrate to the immobilized lectin was monitored by means of QCM measurements and the data obtained allowed for the construction of Langmuir isotherm curves. The association constants determined for the specific interactions analyzed here were (6.4 ± 0.2) × 104 M− 1 for Jacalin–Fetuin and (4.5 ± 0.1) × 102 M− 1 for ConA–maltose. These results indicate that the QCM constitutes a suitable method for the analysis of lectin–carbohydrate interactions, even when assaying low molecular mass ligands such as disaccharides. 相似文献
49.
Ronaldo S. Nunes Felipe S. Semaan Alan T. Riga Éder T. G. Cavalheiro 《Journal of Thermal Analysis and Calorimetry》2009,97(1):349-353
The thermal properties of verapamil hydrochloride (VRP) and its physical association as binary mixtures with some common excipients
were evaluated. Thermogravimetry (TG) was used to determine the thermal mass loss, as well as to study the kinetics of VRP
thermal decomposition, using the Flynn-Wall-Ozawa model. Based on their frequent use in pharmacy, five different excipients
(microcrystalline cellulose, magnesium stearate, hydroxypropyl methylcellulose, polyvinylpyrrolidone and talc) were blended
with VRP. Samples were prepared by mixing the analyte and excipients in a proportion of 1:1 (m/m). DSC curves for pure VRP
presented an endothermic event at 143 ± 2 °C (ΔHmelt = 132 ± 4 J g−1), which corresponds to the melting (literature Tm = 143.7 °C, ΔHmelt = 130.6 J g−1). Comparisons among the observed results for each compound and their binary physical mixtures presented no relevant changes.
This suggests no interaction between the drug and excipient. 相似文献
50.
P. M. Carreira D. Nunes P. Valério M. F. Araújo 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(1):153-156
The Nuclear and Technological Institute (Instituto Tecnológico e Nuclear—ITN) in cooperation with the International Atomic
Energy Agency (IAEA) has been conducting a nationwide survey of hydrogen (2H/1H) and oxygen (18O/16O) isotopic composition of monthly precipitation since 1988. This paper focuses on basic features of spatial and temporal
distribution of δ18O and δ2H in the precipitation over Continental Portugal derived from ITN database. Phenomenological relationships between stable
isotopes composition of precipitation and various climate-related parameters (local air temperature, distance to the Atlantic
coast, altitude, amount of precipitation) are established and discussed. 相似文献