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- Author or Editor: L. Santos x
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Abstract
Internal contamination with radioactive materials of mining workers is a common problem in Brazil. This is caused by the presence of uranium, thorium, and their natural decay series associated with the mined ore. The clear examples are the workers at the niobium mine located in the state of Goiás. The niobium is associated with considerable quantities of uranium and thorium, but the mine is not legally subject to radiation protection requirements.Twenty mine workers were evaluated using 
in vitro
bioassay techniques (urine and feces). The fecal samples were analyzed by alpha spectrometry using the method developed in the Bioassay Laboratory of the Instituto de Radioproteção e Dosimetria/CNEN which evaluates thorium and uranium isotopes simultaneously. Minor modifications were introduced to measure a higher level of activity, around 1 Bq of uranium per sample. The urine samples were analyzed by alpha spectrometry for thorium and by fluorimetry for uranium. The results obtained show that a control of the occupationally-exposed workers is necessary.
Abstract
The elemental composition of potato tubers from four varieties growing in an experimental field under conventional and organic conditions was investigated. Br, Co, K, Na, Rb and Zn, determined by k 0-instrumental neutron activation analysis, were used to distinguish the tubers according to the cultivation system. The difference between organic and conventional potatoes was evidenced by cluster analysis, specially using Br, Co, K and Rb.
Abstract
In the present work, the thermal decomposition of glimepiride (sulfonylurea hypoglycemic agent) was studied using differential scanning calorimetry (DSC) and thermogravimetry/derivative thermogravimetry (TG/DTG). Isothermal and non-isothermal methods were employed to determine kinetic data of decomposition process. The physical chemical properties and compatibilities of several commonly used pharmaceutical excipients (glycolate starch, microcrystalline cellulose, stearate, lactose and Plasdone) with glimepiride were evaluated using thermoanalytical methods. The 1:1 physical mixtures of these excipients with glimepiride showed physical interaction of the drug with Mg stearate, lactose and Plasdone. On the other hand, IR results did not evidence any chemical modifications. From isothermal experiments, activation energy (E a) can be obtained from slope of lnt vs. 1/T at a constant conversion level. The average value of this energy was 123 kJ mol–1. For non-isothermal method E a can be obtained from plot of logarithms of heating rates, as a function of inverse of temperature, resulting a value of 157 and 150 kJ mol–1, respectively, in air and N2 atmosphere, from the first stage of thermal decomposition.
Abstract
Aiming at the determination of toxic and essential elements in Brazilian commercial bovine milk, 25 ultra high temperature (UHT) milk samples were acquired in the local market of Piracicaba, SP. The samples were freeze-dried and analyzed by instrumental neutron activation analysis (INAA) allowing the determination of Br, Ca, Co, Cs, Fe, K, Na, Rb and Zn. When the results were expressed as concentration (mg·l−1) no significant differences were found. However, considering the dry matter, results showed a clear difference between the mass fractions (mg·kg−1 d.w.) of skim milk and whole milk for the elements Br, Ca, K, Na, Rb and Zn, indicating that the removal of fat caused a concentration effect in the dry matter of skim milks. Discrepancies were found between the concentrations of Ca and Na measured by INAA and the values informed in the labels. Ca showed variations within 30% for most samples, while concentrations of Na were up to 190% higher than informed values. The sample preparation and the INAA procedure were appropriate for the determination of Br, Ca, Co, Cs, Fe, K, Na, Rb and Zn in milk samples.
Abstract
This study investigated the representativeness of samples for assessing chemical elements in milk bulk tanks. Milk samples were collected from a closed tank in a dairy plant and from an open top tank in a dairy farm. Samples were analyzed for chemical elements by instrumental neutron activation analysis (INAA). For both experiments, Br, Ca, Cs, K, Na, Rb and Zn did not present significant differences between samples thereby indicating the appropriateness of the sampling procedure adopted to evaluate the analytes of interest.
Abstract
In this work, spinels with the general formula Zn2−xCoxTiO4 were synthesized by the polymeric precursor method and thermally treated at 1,000 °C. The powder precursors were characterized by TG/DTA. A decrease in the DTA peak temperature with the amount of zinc was observed. After the thermal treatment, the characterizations were performed by XRD, IR, colorimetry and UV/VIS spectroscopy. The XRD patterns of all the samples showed the presence of the spinel phase. Infrared spectroscopy showed the presence of ester complexes for Zn2TiO4 after thermal treatment at 500 °C, which disappeared after cobalt addition, indicating that organic material elimination was favored.
Summary
The crude methanolic extracts of a single bean from samples of organic, natural or genetically modified (GM) soybeans [Glycine max. (Merrill) L.] were analyzed by direct infusion electrospray ionization mass spectrometry (ESI-MS). These extracts, containing the most polar natural products of soybeans (free aglycones, monoglucosides, diglucosides and esters including isoflavones and flavones) provide characteristic fingerprinting mass spectra owing to different proportions or sets of components. Spectra distinctiveness is confirmed by chemometric multivariate analysis of the ESI-MS data, which place the three-types of beans into well-defined groups. When ESI-MS is applied, these polar components constitute therefore unique chemotaxonomic markers able to provide fast soybean typification.
Abstract
The role of CD25+ regulatory T cells during the course of Trypanosoma cruzi infection has been previously analyzed, and the bulk of results have shown a limited role for this T cell subpopulation. In this study, we have used an IgM, nondepleting monoclonal antibody (mAb) aiming at blocking interleukin (IL)-2 activity on CD25+ T cells. The administration of this antibody 10 days before infection increased the resistance of outbred Swiss mice to the Colombian strain of T. cruzi. Anti-CD25-treated mice had lower parasitemia and augmented numbers of effector memory T cells. In addition, these animals showed higher numbers of splenic T cells secreting IFN-γ and TNF-α, both cytokines described to be involved in the resistance to T. cruzi infection. The same treatment also increased the numbers of splenic T cells that produced homeostatic and regulatory cytokines, such as IL-2 and IL-10, and CD4+CD25+ T cells. The administration of nondepleting anti-CD25 mAb at the beginning of the chronic phase, when parasites were cleared from the blood, halted the inflammatory process in the heart, without any signs of infection reactivation. These results indicate that nondepleting anti-CD25 monoclonal antibodies may be useful to treat chronic Chagas’ disease.
Abstract
Undoped and/or doped with 1 mol% of Co2+ Mg2TiO4 andMg2SnO4 powders were synthesized by the polymeric precursor method. The influence of the network former (Sn4+ or Ti4+) on the thermal, structural and optical properties was investigated. The recorded mass losses are due to the escape of water and adsorbed gases and to the elimination of the organic matter. Mg2TiO4 crystallizes at lower temperatures and also presents more ordered structure with a smaller unit call and having more intense green color than Mg2SnO4 has.
