Search Results

You are looking at 1 - 10 of 44 items for

  • Author or Editor: L. S. Santos x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The development of an automated water target for the production of18F is described. The system was fully fested and shown to be reliable and secure. The chemical separation of18F was carried out using an anionexchange resin and K2CO3 as eluent. The18F production yields were, on average, (4.81±0.42) MBq/Ah and the specific activity was higher than 6.623×105 MBq/mmol. Heat transfer measurements and calculations were made.

Restricted access

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.

Restricted access

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.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors:
C. Santos
,
B. Capistrano
,
F. Vieira
,
M. Santos
,
S. Lima
,
E. Longo
,
C. Paskocimas
,
A. Souza
,
L. Soledade
, and
I. Santos

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.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
C. M. Silva
,
R. S. Amaral
,
A. Amaral
,
J. A. Santos Júnior
,
D. C. Santos
,
L. E. Lima
, and
S. V. Silveira

Summary  

Studies performed by the Brazilian Nuclear Corporation (NUCLEBRAS), in collaboration with the Geological Survey Company of Brazil (CPRM), identified high levels of natural uranium in the districts of Pedra and Venturosa, in the rural region of the state of Pernambuco (PE) - Brazil, where the maximum value found in rocks was 22,000 mg.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors:
Márcia Silva
,
Mary Alves
,
S. Lima
,
L. Soledade
,
Elaine Paris
,
E. Longo
,
A. Souza
, and
Iêda Santos

Abstract  

Sr(Ti,Nd)O3 was synthesized in order to evaluate the influence of the amount of neodymium on the thermal and structural properties of SrTiO3. The synthesis was carried out using the polymeric precursor method. A small mass gain was observed for the SrTiO3 and SrTi0.98Nd0.02O3 samples accompanied by an exothermic peak in the DTA curves. Other steps at higher temperatures are assigned to the combustion of the organic material and carbonate. Elimination of defects by previous calcination of the precursors is responsible by the short and long range ordering of the perovskite. Cubic phase was obtained for undoped and doped SrTiO3.

Restricted access

Abstract  

The present work investigates the influence of milling and calcination atmosphere on the thermal decomposition of SrTiO3 powder precursors. Both pure and neodymium-modified SrTiO3 samples were studied. Milling did not significantly influence numerical mass loss value, but reduced the number of decomposition steps, modifying the profiles of the TG and DTA curves. On the other hand, milling increases the amount of energy liberated by the system upon combustion of organic matter. It was also observed that the milling process, associated to the calcination in an oxygen atmosphere, considerably decreases the amount of organic matter and increases the final mass loss temperature.

Restricted access

Abstract

Poly(3-hydroxybutyrate), PHB, has been structurally modified with maleic anhydride, MA, in the presence of triethylamine, TEA. Glass transition, melting, and crystallization temperature, obtained from DSC curves, and thermal degradation temperatures obtained from TG ones, were employed to evaluate the influence of the MA proportion on the modification in the PHB chain. According to the results, most of chain modification reactions are the 80/20 and 90/10 proportions. Observations suggest that most chain modification reactions occur when the ratio of PHB/MA is 80/20 or 90/10. This suggests that modifications of PHB in the presence of MA involve main chain scission.

Restricted access

Abstract  

Neutron activation analysis has been used to determine Br, Ca, Cl, K, Mg and Na concentrations in whole blood of patients with chronic kidney disease (CKD) as well as in whole blood of normal individuals (control group). The dependence of the elements concentration in function of sex, age, time and type of treatment were investigated. The similarities and differences between healthy individuals and CKD are discussed.

Restricted access

Background and aims

Ayahuasca is a dimethyltryptamine- and β-carboline-rich hallucinogenic beverage traditionally used by indigenous groups of Northwest Amazonian for ritual and therapeutic purposes. Animal and human studies suggest that ayahuasca has antidepressant and anxiolytic potentials and has a good safety profile. However, anxiety-like reactions may also occur after ayahuasca intake, although they are rare.

Methods

Case report.

Results

Here, we describe a case of a non-medicated, symptom-free young female with generalized anxiety disorder, who experienced intense anxiety, panic, and hopelessness during and for 3 days after participating in an ayahuasca ritual. The symptoms appeared in the first hours after ayahuasca intake and were gradually reducing in the following hours/days, but were intense enough to cause significant suffering to her, who needed to seek psychiatric help and restarted pharmacological treatment.

Conclusions

Although “bad/horror trips” with anxiety features may occur during the acute effects of ayahuasca and other hallucinogens, to the best of our knowledge, this is the first report of a subacute/prolonged anxiety-like reaction to this substance. Ayahuasca should be used with caution in people with a history of anxiety disorders.

Open access