Showing papers by "Federal University of Roraima published in 2004"
TL;DR: An overview about the role of alkoxides in the most recent uses of the sol-gel process in the synthesis of new materials is presented in this paper, with special attention focused on the uses of silicon, aluminum, zirconium and titanium alkoxide.
Abstract: An overview about the role of alkoxides in the most recent uses of the sol-gel process in the synthesis of new materials is presented. Special attention is focused on the uses of silicon, aluminum, zirconium and titanium alkoxides. This review shows that the alkoxides enable the synthesis of new matrices with controlled surface area, acidity and porosity, as well as some unusual properties. The property associated with the solubility of metal alkoxides opens enormous possibilities of combining them for the synthesis films of powders with a very large range of metal compositions.
17 citations
TL;DR: In this article, the synthesis, characterization and thermal degradation study of gadolinium and lutetium methanesulfonates is reported, where the prepared salts were characterized by elemental analysis and infrared spectroscopy.
16 citations
TL;DR: In this article, an investigation about the thermal degradation of acetylsalicylic acid (ASA) is performed, and it is verified that the degradation of ASA produces not only SALICYCLIC acid (SA) and acetic acid (AA), but also an ASA polymer, which is transparent and solid.
10 citations
TL;DR: The observed adsorption affinity sequence can be explained by taking into account the velocity constant for the substitution of water molecules into the cation coordination spheres, as well as the Irving-Williams series.
8 citations
TL;DR: In this article, the coordination compounds EuCl3·1.5hmta·H2O, TmCl 3·hmTa·H 2O, Cr(CH3COO)2·2hmta, FeCl3 · hmta·3H 2 O, Co(NO3) 2·3hmta.
Abstract: The coordination compounds EuCl3·1.5hmta·H2O, TmCl3·hmta·H2O, Cr(CH3COO)2·2hmta, FeCl3· hmta·3H2O, Co(NO3)2·3hmta, CuSO4·3hmta, PbCl2·0.5hmta·5H2O, HgCl2·hmta and NiCl2·hmta·H2O (hmta = hexamethylenetetraamine) were synthesized and characterized by elemental analysis, infrared spectroscopy and thermogravimetry. The infrared data are in agreement with coordination through nitrogen. For the hydrated compounds, a first mass-loss step, associated with the release of water molecules, followed by release of an hmta molecule was observed. The anhydrous adducts exhibit a first single-mass loss associated with the release of hmta. For Cr(CH3COO)2·2hmta, the first mass-loss step is due to release of hmta, and the second is due to the acetate, consistent with the proposed structural formula.
6 citations
01 Sep 2004
TL;DR: O intervalo entre os sintomas iniciais e o diagnostico ainda continua elevado na nossa Regiao devido ao somatorio de varios fatores.
Abstract: OBJETIVOS: descrever uma serie de casos de colite ulcerativa inespecifica, com enfase nas manifestacoes iniciais, propedeutica e intervalo entre os primeiros sintomas e o diagnostico. METODOS: analise retrospectiva de casos de colite ulcerativa inespecifica, cujos sintomas iniciaram antes de 20 anos de idade. Os pacientes foram selecionados nos Servicos de Gastroenterologia Pediatrica do Hospital das Clinicas da Universidade Federal de Minas Gerais e do Instituto Materno Infantil de Pernambuco. RESULTADOS: foram encontrados 29 pacientes com diagnostico de colite ulcerativa inespecifica, sendo 15 (51,7%) pacientes do sexo masculino. A idade ao inicio dos sintomas variou entre 0,3 a 15,8 anos. Os sintomas mais frequentes ao diagnostico foram diarreia (89,7%) e dor abdominal (82,8%). A manifestacao extra-intestinal mais comum foi artralgia/artrite (41,4%). A relacao peso para a idade estava abaixo do percentil 3 em 13,8% dos pacientes. O intervalo de tempo entre o inicio dos sintomas e o diagnostico variou entre 0,1 e 10,9 anos. CONCLUSOES: o intervalo entre os sintomas iniciais e o diagnostico ainda continua elevado na nossa Regiao devido ao somatorio de varios fatores.
3 citations
TL;DR: In this article, the synthesis, characterization and thermal (TG and DSC) study of the coordination compounds Y(MS)3A(py-NO)2AH2O, Y( MS)3B(2-picNO)3, YMS3C(3B)(3-pic NO)2 and La(MS 3A(4-picNo)2)2 are reported.
Abstract: The synthesis, characterization and thermal (TG and DSC) study of the coordination compounds Y(MS)3A(py-NO)2AH2O, Y(MS)3A(2-picNO)3, Y(MS)3A(3-picNO)2 and La(MS)3A(4-picNO)2 are reported (MS = methanesulfonate, py-NO = pyridine N-oxide, and 2-picNO, 3-picNO and 4-picNO are 2-, 3- and 4-picoline N-oxides, respectively). The observed thermal stability trend is: 2-picNO ≈ 4-picNO< 3-picNO< py-NO. Release of ligand molecules (endothermic) is followed by thermal degradation of the ligands (exothermic) with an increase in the exothermic values from 2-picNO to 4-picNO.
2 citations
TL;DR: By dissolution of respective acetates and conducting polymer in dimethylformamide, homogeneous zinc acetate and cadmium acetate-polyaniline (PANI) hybrids were synthesized and characterized by infrared spectroscopy, thermogravimetry and SEM microscopy as mentioned in this paper.
2 citations
TL;DR: In this article, the authors presented four known deductions of the equation E = mc2, including the original, and compared the physical concepts and the mathematical tools in each case and verified that three deductions are accessible to the student of the secondary education.
Abstract: In this work, we present four known deductions of the equation E = mc2, including the original. We relate the physical concepts and the mathematical tools in each case and compare the deductions. After the analysis, we verify that three deductions are accessible to the student of the Secondary Education.
1 citations