Uranium in thorium matrixes or in minerals and ores containing thorium is determined by epithermal neutron activation analysis
(ENAA). In some minerals and ores, such as monazite sands, the analysis can be carried out by purely instrumental means with
no chemical separation of uranium or thorium from the irradiated matrix. For thorium compound matrixes with very low uranium
contents, a rapid radiochemical separation method, based on the retention of uranyl ion on anion-exchange resins, is first
carried out, before counting the gamma-ray peaks for239U in multichannel analysers coupled to NaI(Tl) scintillators or to Ge(Li) detectors.
A program in “INSTRUMENT BASIC” language is proposed for analysis of gamma-ray spectra obtained with Ge(Li) detectors and
accumulated in multichannel analysers on-line with minicomputers. The program locates the peaks, evaluates the corresponding
energy values, the net peak areas and the standard deviations on the areas.
Authors:Araceli Lima, T. Fehervari, L. H. Paasch, and Norma L. Calderón
In the present study, specific-pathogen-free, 2-week-old Leghorn chickens were experimentally infected with strain 73688 of infectious bursal disease virus (IBDV) in order to evaluate haematological and histological changes that might suggest a pathomechanism for haemorrhages in this disease. At 96 hours post infection (hpi) a significant increase in prothrombin time was detected in the absence of visible lesions in myeloid bone marrow tissue and of significant thrombocytopenia. The aforementioned findings suggest alteration of the secondary coagulation mechanisms and not a direct effect of virus on thrombocytes or its precursors.
Authors:J. Santana, L. Lima, J. Torres, F. Martínez, and S. Olivares
Vegetable tannin sorbent is evaluated as ion exchange resin using a multitracer study on the adsorption behavior of various elements. Lisiloma latisiliqua L. tannins, polycondensated into spherical pellets were chosen as sorbent resin material. Sorption evaluation of Ce, Cu(II), U(VI), Eu, Fe(III), Th, Nd as representatives of different classes of metal ions were done at different pH values. The distribution ratio of the studied elements was calculated from laboratory experiments. Tannic ion exchange material shows excellent ability for actinides and rare earth elements adsorption from waters. Using radiotracers, the number of catechins subunits involve in each tannin-metal complex was determined.
Authors:J. Santos, L. Lima, Iêda Santos, and A. Souza
The thermal degradation process of mineral base lubricating oils was
studied in this work by means of thermal, spectroscopic and rheologic analysis.
The lubricating oils were degraded at temperatures varying from 150 to 210C,
and for degradation times from 1 to 48 h. After the degradation, the lubricating
oils were characterized by X-ray fluorescence, IR and NMR spectroscopies,
rheological properties and thermal analyses (TG/DSC). The spectroscopic analyses
determined the oxidation reaction products. TG curves indicate that the thermal
stability of lubricating oils is below 161C. TG curves in air present
three mass loss stages, whereas in nitrogen there are only two mass loss steps.
DSC analyses in air indicate two highly exothermic peaks related to hydrocarbon
oxidation and combustion processes, while in nitrogen only two endothermic
peaks were observed. The decrease in the degradation temperature led to a
decrease of the lubricant viscosity.
Authors:I. C. B. Lima, L. F. Oliveira, and R. T. Lopes
One of the great 3D micro tomography (3D-mCT) applications in the medical area is the characterization of bone architecture,
especially when it is spoken in osteoporosis because, among other factors, is characterized by the deterioration of the architecture.
This work shows the 3D quantification, based on stereological concepts, of the bone tissue through 3D-mCT in real time. The
analyses were carried out in femur rat and the 3D visualizations helped to understand bones morphology. The results showed
the potential of this computational technique to verify the capability of characterization of the internal bone structures
and the importance of the threshold level in the binarization process.
Authors:J. Torres, S. Olivares, D. De La Rosa, L. Lima, F. Martínez, C. Munita, and D. Favaro
Adsorption of mercury(II) and methylmercury by two tannin sorbents was investigated using radiotracers. High sorption capacities
for mercury are registered for both sorbents at pH 7. ForEucaliptus Saligna Sm sorbent (ETS) the maximum sorption capacity was 1.2±0.2 mmol/g and forLysiloma latisiliqua sorbent (LTS) was 8.5±0.2 mmol/g. Methylmercury adsorption maximum was recorded at pH 4 and in buffered solutions at pH2.
This species can be recovered in the presence of mercury(II). Influence of different ions present in water was examined. High
recoveries were reported for ETS in tap water samples but a decrease of uptake is observed for seawater.
Authors:L. Lima, S. Olivares, F. Martínez, J. Torres, D. de la Rosa, and C. Sepúlveda
Adsorption of Cr(VI) by two tannin sorbents is evaluated using radiotracers. Evaluation of the sorption process shows that
the Cr(VI)-tannin molecule binding is the principal responsible for chromium adsorption. High sorption capacities were registered
for both sorbents at pH 2. ForEucaliptus Saligna Sm sorbent (ETS) sorption capacity is 0.92±0.03 mmol/g and forLysiloma latisiliqua sorbent (LTS) is 3.8±0.3 mmol/g. Influence of different ions present in water is examined. High sorption capacity is reported
for LTS in sea and tap water samples. It represents 90–94% of adsorption in distillated water.
Authors:C. T. Carvalho, F. J. Caires, L. S. Lima, and M. Ionashiro
Solid-state M-2-MeO-CP compounds, where M represents bivalent Mn, Fe, Co, Ni, Cu, Zn and 2-MeO-CP is 2-methoxycinnamylidenepyruvate, were synthesized for the first time. Simultaneous thermogravimetry and differential thermal analysis, differential scanning calorimetry, X-ray powder diffractometry, infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry have been used to characterize and to study the thermal behaviour of the compounds. The dehydration in all the compounds, except for iron occurs in a single step. The thermal decomposition of the anhydrous compounds occurs in two or three steps with the formation of the respective oxides, Mn3O4, Fe2O3, Co3O4, NiO, CuO and ZnO, as final residue. The results also provided information concerning the thermal behaviour and identification of the gaseous products evolved during the heating of these compounds.
Authors:D. Melo, F. Borges, F. Lima, H. Scatena, L. Zinner, V. Fernandes, W. Souza, and Z. Silva
In this work, a cobalt complex with dmit (1,3-dithiol-2-thione-4,5-dithiolate) as ligand was prepared and its thermal stability
was studied by thermogravimetric analysis and kinetics by means of the Zsak method and a non-linear method. For both methods,
numerical binomial and polynomial filters were used, where points in the central interval were utilized.