Anderson Fernandes da Silva

Thermolysis mechanism of samarium nitrate hexahydrate

Thermal decomposition of samarium nitrate hexahydrate Sm(NO3)3·6H2O has been investigated by thermogravimetry, differential scanning calorimetry, infrared spectroscopy, and X-ray diffractometry. This is a complex process that involves slow dehydration and fast concomitant internal hydrolysis. It is markedly different from the processes described for other members of the lanthanide series. At the first stage, pyrolysis is accompanied by removal of water and nitric acid to form samarium pentahydrate Sm(NO3)3·5H2O and intermediate oxonitrates containing O–Sm–OH groups. No traces of SmONO3 were detected. It is assumed that the existence of intermediate structures with six atoms of samarium best fits the experimental results. At higher temperatures, these products undergo further degradation, lose nitrogen dioxide, water, and oxygen, and finally, after having lost lattice water, are transformed into a cubic form of samarium oxide.

Thermolysis mechanism of dysprosium hexahydrate nitrate Dy(NO3)3·6H2O and modeling of intermediate decomposition products

The thermal decomposition of dysprosium nitrate is a complex process which begins with the simultaneous condensation of the initial monomer Dy(NO3)3·6H2O into a cyclic hexamer 6[Dy(NO3)3·6H2O]. This cluster gradually loses water and nitric acid, and intermediate oxynitrates Dy6O7(NO3)4·6H2O and Dy6O8(NO3)2·5H2O are formed. At higher temperatures, these products undergo further degradation, lose nitrogen dioxide, water, and oxygen, and finally, after having lost lattice water, are transformed into the cubic form of dysprosium oxide. The models of intermediate oxynitrates represent a reasonably good approximation to the real structures and a proper interpretation of experimental data. The comparison of the potential energies of consecutive oxynitrates permitted an evaluation of their stability. The mechanism was studied by thermal analysis, differential scanning calorimetry, infrared spectroscopy, and X-ray diffraction. The mass losses were related to the vibrational energy levels of the evolved gases.

In vitro and in vivo antioxidant activity of the pulp of Jatobá-do-cerrado

Oxygen metabolism in cells causes the production of free radicals, which produce damage, including changes in cell structure and function. Antioxidants are substances that, at low concentrations, slow down or prevent oxidation. Fruits and vegetables contribute to the dietary supply of these compounds. The flora of the Cerrado in Brazil has shown to have high levels of bioactive compounds. This study aimed to characterize the antioxidant activity of the pulp of jatoba-do-cerrado in vitro and in vivo.In vitro antioxidant activity of the aqueous, ethanol and aqueous acetone extracts was evaluated by the DPPH method. We determined total phenols by the Folin-Ciocalteu assay and tannins by the Folin-Denis method.In vivo antioxidant potential of the aqueous acetone extract was evaluated by the TBARS technique. The aqueous acetone extract had the highest antioxidant capacity, followed by the aqueous and ethanol extracts. The same pattern occurred in the extraction of phenols and in the extraction of tannins. In vivo administration of the aqueous acetone extract inhibited lipid peroxidation compared to the control group. The inhibition of peroxidation has increased by elevating the dosage concentration of the extracts, demonstrating a significant antioxidant potential in vivo as well as in vitro.

Investigation of Campomanesia Components: A Fruit of Brazilian Cerrado

A survey of chemical composition of the fruit of Campomanesia adamantium used by rural and urban inhabitants of the cities of the Campo Grande, Mato Grosso do Sul State, Brazil, was carried out by inductively coupled plasma-optical emission spectroscopy (ICP-OES) aiming at the detection of minerals. Fifteen minerals were detected in the peel, pulp, and seeds of plant. The concentrations of elements K, Ca, Na, and P are found to be present at the major level in peel, pulp, and seeds of fruit. The zinc concentration is very low compared to other detected elements. The levels of some chemical elements in the fruit do not exceed the limits established by international legislation. Animal studies should be performed. The knowledge of the chemical elements in plants has economic interest, and involves global health problem.

Método variacional aplicado ao estudo de um gás de átomos de Fermi em um estado superfluido aprisionados por uma rede óptica quase periódica

In this work, we consider a model derived from energy density for a Fermi gas in the Bardeen-Cooper-Schrieffer (BCS) superfluid state, trapped in a quasiperiodic one-dimensional optical lattice (OL). Reducing the equation to the 3D to 1D form, we construct families of stable 1D gap solitons (GSs) by the variational approximation (VA). In the linear limit, the VA predicts almost exact positions of narrow Bloch bands that separate the first gaps. Through the variational approximation, we show the possibility that the nonlinearity coefficient acting in a combination with the potential of the quasiperiodic one-dimensional optical lattice, allows one dimensional bright gap solitons to arise. Varying the amplitude of the optical lattice, we analyze the existence and stability of bright gap solitons using a gaussian ansatz. GSs are stable against small variations of the quasiperiodic optical lattice. This paper can be used as a learning guide in the study of cold atoms. Students are encouraged to perform variational calculations for other amplitude values of optical lattices.

First Comprehensive Study on Total Determination of Nutritional Elements in the Fruit of the Campomanesia Adamantium (Cambess.): Brazilian Cerrado Plant

Introduction: Composition of fruits and leaves of Campomanesia adamantium (Cambess.) O. Berg commonly called guavira are used in dietary or as a mode of treatment of variety of ailments in indigenous and urban populations in the city of the Campo Grande, State of Mato Grosso do Sul, Brazil. However, comprehensive studies on their mineral composition are scarce. Objective: In the present study, evaluation of mineral contents (Na, K, Ca, Mg, P, Fe, Zn, Ni, Mn, Co, Cu, Mo, Cr, Si and Al) from peel, pulp and seeds of guavira was carried out. Method: The peel, pulp and seeds of guavira were studied by ICP-OES with microwave digestion. The contents of the elements in the parts of the guavira, were compared to the Recommended Dietary Allowance (RDA), values Adequate Intake (AI) and tolerable upper intake levels (ULs). Results: The results are considered in terms of the utility of the natural herbal medicaments as rich (Cu, P, Cr and Mo) or a source of minerals indispensable for proper functioning of the human organism. The concentration of elements in seeds, pulp and peel the guavira was compared with value of UL and does not cause toxicity. The concentration of elements K, Ca, Na, P are found present at the major level in peel, pulp and seeds of fruit. The contents of Chromium (Cr) were reportedly found higher than the permissible levels as recommended by the WHO. Conclusion: The lack of knowledge of the elemental constituents of several species of medicinal plants often poses human lives at risk, these elements can also be dangerous and toxic, and involves global health problem. The gaps in knowledge about the level of contents in the Campomanesia adamantium (Cambess.) O. Berg was completed in this work. The data obtained would serve as a tool for deciding the dosage of prepared from this plant with medicinal and nutritional purposes. Keywords: Medicinal plants; Guavira; Inductively coupled plasma mass spectrometry.

Structural Modeling of Djenkolic Acid with Sulfur Replaced by Selenium and Tellurium

The comparative structural modeling of djenkolic acid and its derivatives containing selenium and tellurium in chalcogen sites (Ch = Se, Te) has provided detailed information about the bond lengths and bond angles, filling the gap in what we know about the structural characteristics of these aminoacids. The investigation using the molecular mechanics technique with good approximation confirmed the available information on X-ray refinements for the related compounds methionine and selenomethionine, as well as for an estimate made earlier for telluromethionine. It was shown that the Ch-C(3) and Ch-C(4) bond lengths grow in parallel with the increasing anionic radii. Although the distances C-C, C-O, and C-N are very similar, the geometry of conformers is quite different owing to the possibility of rotation about four carbon atoms, hence the remarkable variability observed in dihedral angles. It was shown that the compounds contain a rigid block with two Ch atoms connected through a methylene group. The standard program Gaussian 03 with graphical interface Gaussview 4.1.2 has proved to be satisfactory tool for the structural description of less-common bioactive compositions when direct X-ray results are absent.