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591.
592.
Changing seasonality in Europe’s air temperature 总被引:1,自引:0,他引:1
S. M. Barbosa 《The European physical journal. Special topics》2009,174(1):81-89
593.
M.G.S. Cavalcanti H.R.C. Araújo M.H.S. Paiva G.M. Silva C.C.G.S. Barbosa L.F. Silva F.A. Brayner L.C. Alves 《Micron (Oxford, England : 1993)》2009,40(3):394-400
An alternative to identify the critical processes necessary to the parasite establishment of the host is to focus on the evolutionary stage responsible for the primary invasion, i.e. the infection structure. The objective of this study was to ultrastructurally characterize Schistosoma mansoni cercariae, using cytochemical techniques. In order to identify basic proteins, techniques such as ethanolic phosphotungstic acid (EPTA) and ammoniacal silver staining were used. Calcium sites location was achieved using the Hepler technique and to evidence anionic groups, we used cationic ferritin particles and enzyme treatment with trypsin Vibrio cholerae, chondroitinase and neuraminidase. The EPTA technique highlighted the presence of basic tegument proteins, nucleus and nucleolus from subtegumental cells, inclusion bodies and preacetabular glands. After using ammoniacal silver, we observed a strong staining in all infective larvae, particularly in the nuclei of muscle cells, circular muscle tissue and preacetabular glands. Calcium site locations were shown to be uniform, thereby limiting the inner spaces of the larvae, especially muscle cells. Samples treated with cationized ferritin particles presented strong staining at the cuticular level. Neuraminidase treatment did not alter the stained shape of such particles on the trematode surface. However, trypsin or chondroitinase treatment resulted in absence of staining on the larval surface. This information on the biochemical composition of the infecting S. mansoni larvae provides data for a better understanding of the biology of this parasite and background on the intriguing parasite–host relationship. 相似文献
594.
É. C. Lima Fernando Barbosa Jr. Francisco J. Krug 《Analytical and bioanalytical chemistry》2001,369(6):496-501
A tungsten-rhodium coating on the integrated platform of a transversely heated graphite atomiser (THGA) was used as a permanent
chemical modifier for the determination of lead in biological materials by slurry sampling in electrothermal atomic absorption
spectrometry (ETAAS). Slurries were sonicated during 20 s before being delivered to the previously W-Rh treated platform.
The number of particles of biological materials introduced into the atomiser for delivering 20 μL slurry aliquot ranged from
5,100 to 39,000. The permanent W-Rh modifier remained stable during approximately 300 analytical measurements when 20 μL of
slurries containing up to 1.5% m/v were delivered into the atomiser. In addition, the permanent modifier increases the tube
lifetime by approximately 100% when compared to untreated integrated platforms. Also, there is less decrease of sensitivity
during the atomiser lifetime when compared with the conventional modifiers, resulting in a decreased need of re-calibration
during routine analysis and consequently increasing the sample throughput. The atomiser lifetime was limited to the THGA wall
durability, because the W-Rh treated platform was intact after more than 650 analytical firings in a medium containing up
to 1.5% m/v slurry of biological material. The detection limit based on integrated absorbance was 20 ng g–1 Pb for 1.50% m/v slurries. Results from the determination of lead in slurries of biological materials using the W-Rh permanent
modifier were in agreement with those obtained with digested solutions using Pd + Mg(NO3)2.
Received: 11 August 2000 / Revised: 13 November 2000 / Accepted: 16 November 2000 相似文献
595.
Nathlia V. Barbosa Estela P. Troiani Qusia G. Silva Andr S. Afonso Ronaldo C. Faria 《Electroanalysis》2019,31(4):766-770
Herein, we reported the detection of dopamine (DA) based on use of a cathodically pretreated polyaniline (PANI) modified electrode. The PANI electrode presents a remarkable change in their electrocatalytic properties after a simple cathodic pretreatment, which consisted in applying a potential of ?0.7 V for 3 s. While the as‐prepared PANI shows no electrochemical response for DA, the cathodically pretreated PANI presented reversible electrochemical responses with well‐defined anodic and cathodic peaks. The electrochemical behavior of DA at the PANI electrode was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimized experimental conditions, the anodic peak currents increased proportionally to the DA concentration, displaying a linear relationship in the concentration range of 0.11 to 1.75×10?4 M with a detection limit of 13.7 μM (3 σ/slope). Recovery studies in pharmaceutical formulations presented values between 98 % and 104 %. The cathodically pretreated PANI electrode was successfully applied for DA detection in real samples of pharmaceutical formulation showing good agreement with spectrometric comparative method. The unexpected easily capability of modulate the electrocatalytic properties of the electropolymerized PANI film using a simple pretreatement was successfully demonstrated. The cathodically pretreatment PANI electrode showed electrochemical responses for DA with excellent selectivity, sensitivity, and high stability. 相似文献
596.
Wilton?Pereira?da?SilvaEmail author Vera?Solange?de?Oliveira Farias Gelmires?de?Araújo Neves Antonio?Gilson?Barbosa?de?Lima 《Heat and Mass Transfer》2012,48(5):809-821
The main objective of this article is to describe the drying process of ceramic roof tiles, shaped from red clay, using diffusion
models. Samples of the product with initial moisture content of 0.24 (db) were placed inside an oven in the temperatures of
55.6, 69.7, 82.7 and 98.6°C; and the data of the drying kinetics were obtained. The analytical solutions of the diffusion
equation for the parallelepiped with boundary conditions of the first and third kinds were used to describe the drying processes.
The process parameters were determined using an optimization algorithm based on inverse method coupled to the analytical solutions.
The analysis of the results makes it possible to affirm that the boundary condition of the third kind satisfactorily describes
the drying processes. The values obtained for the convective mass transfer coefficient were between 8.25 × 10−7 and 1.64 × 10−6 m s−1, and for the effective water diffusivity were between 9.21 × 10−9 and 1.80 × 10−8 m2 s−1. 相似文献
597.
Summary The proportion of organic modifier and the pH of the acetonitrile-water mixtures used as mobile phases were optimized in order
to separate a group of diuretic compounds covering a wide range of physyco-chemical properties. The Linear Solvation Energy
Relationship (LSER) formalism based either on the multiparameter π*, β and α scales or the single solvent polarity parameterE
T
N
, have been used to predict their chromatographic behaviour as a function of the percentage of acetonitrile in the eluent.
Moreover, correlation established between retention and pH of the aqueous-organic mobile phases have been used to predict
the chromatographic behaviour of the diuretic compounds studied as a function of the eluent pH. Linear correlation between
a function of the eluent pH. Linear correlation between the chromatographic retention and theE
T
N
polarity parameter of mobile phases containing different percentages of organic modifier has been obtained Based on the knowledge
of the acid-base dissociation constant the relation between retention and mobile phase pH has also been linearized. These
relationship allowed an important reduction of the experimental retention data needed for developing a given separation and
a great improvement in chromatographic optimization schemes. 相似文献
598.
Silvana Guilardi Ruggiero Maria Teresa do Prado Gambardella Marcelo Cardoso Branco Antonio Jacinto Demuner Luis Claudio A. Barbosa Dorila Pil‐Veloso 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):868-869
The crystal structure of 21α‐fluoro‐7‐norvouacapane‐17β,21α‐lactone, C20H25FO3, a new synthetic derivative of the diterpenoid 6α,7β‐dihydroxyvouacapan‐17β‐oic acid isolated from Pterodon polygalaeflorus Benth fruits, is described. 相似文献
599.
Haroldo T. Hattori Vitor M. Schneider Carmem L. Barbosa Osni Lisba 《Optics & Laser Technology》2000,32(1):59
Several gradient-index (GRIN) tapers have been analyzed in the literature, whether with a transverse parabolic index distribution or with a hyperbolic secant index profile. In this work, a new class of GRIN tapers, formed by grouping together several sections of transverse parabolic index devices is analyzed, focusing the attention on some of its limitations and advantages over ordinary tapers. Numerical simulations based upon geometric optics are conducted to analyze the behavior of these tapers. 相似文献
600.
J. G. G. S. Ramos A. F. Macedo-Junior A. L. R. Barbosa 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(11):232
We investigate statistical aspects of the entanglement production for open chaotic mesoscopic billiards in contact with superconducting parts, known as Andreev billiards. The complete distributions of concurrence and entanglement of formation are obtained by using the Altland–Zirnbauer symmetry classes of circular ensembles of scattering matrices, which complements previous studies in chaotic universal billiards belonging to other classes of random matrix theory. Our results show a unique and very peculiar behavior: the realization of entanglement in a Andreev billiard always results in non-separable state, regardless of the time reversal symmetry. The analytical calculations are supported by a numerical Monte Carlo simulation. 相似文献