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  • Author or Editor: P. A. Oliveira x
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Summary This paper studies annihilating properties of operators generated by spherical convolution over the unit sphere O2q of C q . Its specific aim is to answer the following question: given a complex number ?, |?|=1, to determine what functions of L 2(O2q ) have zero average over every section  O w ?,q  :={ z ?O2q : <z,w> = ?} of O2q . Here, <.,.>stands for the usual inner product of C q .

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Abstract  

In this work 80 ceramic fragments from six archaeological sites were studied by considering two main aspects: (1) mineralogical/petrographic examination to identify the compounds and minerals present, and (2) elemental analysis via INAA to determine the concentration of As, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn. Petrographic analysis showed that the samples from all sites are quite similar in general paste characteristics. The paste is rich in sand, mica and opaque minerals, especially iron and titanium oxides. Principal component analysis was carried out using the log transformed concentrations of determined elemental concentrations. Three components with eigenvalues greater than 1 had been extracted from the variance-covariance matrix that explained 74% of the total variation. Bivariate plot of the first two principal components showed a high degree chemically homogeneous group, providing a high degree of chemical similarity between the samples.

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The effect of light on the stability and stabilization of the anthocyanins isolated from freeze-dried aqueous extracts of fruits of Euterpe oleracea were studied, using crude and purified extracts at pH 2.2 and 3.0. Crude extract was 80.0 times more stable than the purified one at pH 2.2 and 24.3 at pH 3.0. Stabilization with tannic acid was attempted and resulted in 65% half-life increase of the anthocyanins of the crude and a considerable half-life increase (610%) of the purified one.

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Abstract  

Membranes of latex extracted of the seringueira tree (Hevea brasiliensis), genetically improved by selection and statistics methods, were prepared by air drying a 10 mL suspension of the ammonia in latex 10% (v/v). TG-DTG and DSC curves were used to characterize the membranes. Thermal stability and thermal decomposition of these compounds were analyzed. The results obtained show no differences among latex from different clones.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
L. Pirani
,
L. De Oliveira
,
P. Petchevist
,
M. Moreira
,
D. Ila
, and
A. De Almeida

Abstract  

Dosimetric gel is used in several measurements due to its linearity, low cost, and possibility for 3D measurements. This work brings a new possibility to apply the Fricke Xylenol Gel recipe in the diagnostic measurements region. The Fricke Xilenol Gel (FXG) dosimeter is associated with the Fe(II) to Fe(III) oxidation, when irradiated, being the final ion concentration proportional to the absorbed dose. To achieve the scope, the former dosimeter was modified through the benzoic acid addition in the original recipe forming a new dosimeter, the Benzoic Xylenol Gel (BFXG). The results obtained with this new dosimeter demonstrated a higher sensibility for low absorbed dose values, bringing down the absorbed dose inferior limit from 0.1 to 0.006 Gy, that is more adequate for radiodiagnostic absorbed dose measurements. This result shows the possibly of BFXG dosimeter to be used for measurements in the radiodiagnostic region, as for tomography and mammography techniques.

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Summary  

In the present work, we investigated the immunological behavior of bothropstoxin-1, a K49 phospholipase from Bothrops jararacussu, and of ovalbumin before and after irradiation with 60Co g-rays. Isogenic mice were immunized with either native or irradiated proteins. The circulating antibodies were isotyped and titrated by ELISA. Results indicate that irradiated proteins were immunogenic and the antibodies elicited by them were able to recognize the native proteins in ELISA. Data also indicate that the irradiated protein induced higher titers of IgG2a and IgG2b, suggesting that Th1 cells were predominantly involved in the immune response. Structural modifications of the proteins were investigated by SDS-PAGE, mass spectrometry and size exclusion chromatography. According to our data, irradiation promoted structural modifications on both proteins, characterized by higher molecular weight forms (aggregates and oligomers). When analyzed by mass spectrometry, the irradiated bothropstoxin appeared in several oxidized forms. These results indicate that irradiation of toxic proteins can promote significant modifications in their structures, but still retain many of the original antigenic and immunological properties of native form.

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Hydrolytic parameters were tested to prepare casein hydrolysates with high oligopeptide content for dietetic purpose, using papain. Employing a temperature of 37 °C and an E:S ratio of 2% was the most economical condition for large-scale manufacture. The encapsulation in liposomes was used for masking the bitterness, and was also able to reduce the hydrophobicity as well as to keep the chemical stability during 60 days of storage. The UV spectrometry with second derivative transformation was used to measure the encapsulation rate, which changed from 56% to 62%. The size distribution of vesicles was in the range of 500 to 1000 nm.

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Abstract  

Sediments from the Admiralty Bay, King George Island, Antarctica, were investigated by 57Fe Mössbauer spectroscopy, X-ray diffractometry, and radiometry. Quartz, feldspar, chlorite, calcite, dolomite, mica, kaolinite, hematite and magnetite were identified as constituent minerals in the sediment samples. The phase composition and the iron distribution among the crystallographic sites of iron-bearing minerals (silicates, magnetite and hematite) of samples from different location have been derived from the complex Mössbauer spectra. At different locations sediments had significant characteristic differences in the mineral composition, in the iron distribution among the crystallographic site of silicates, and in the specific radioactivity of Cs radionuclides. These results indicate differences in the rock formation and alteration by the sediments in this maritime part of Antarctica. There is a much higher amount of iron oxides in the sediments from south part of the geological fault across the Admiralty Bay than in the north part. This can be associated with much more alteration in the rocks in the south part compared to the northern one. This finding can contribute to the question of the history of the formation and alteration of volcanic rocks in the border of Antarctica.

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