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- Author or Editor: M. Souza x
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Thermal and kinetic study of statins
Simvastatin and lovastatin
Abstract
Statins are a group of lipoproteins that are used in medicine to treat the high cholesterol level. The effectiveness of statins in reducing the cholesterol level is significant and in long time scale the reduction of the cholesterol level helps to avoid the incidence of degenerative diseases. Simvastatin and lovastatin are belonging to the ‘statins’ family, one of the pharmacologic groups used in the control of dislipidemy. The objective of this work is the thermal stability and kinetic study of the active forms of simvastatin and lovastatin. Thermal data indicated that lovastatin and simvastatin are stable up to 190 and 170°C in air and up to 205 and 203°C in nitrogen, respectively. For melting temperatures DSC curves showed good correlation with the literature data. Comparing the activation energies of the statins at heating rate of 10°C min–1, lovastatin is more stable than simvastatin under the applied experimental conditions.
Abstract
A short-term greenhouse pot culture study was carried out to study the agronomy efficacy of P sources for cotton crop in a vertisol. The sources of P were single super phosphate (SSP), diammonium phosphate (DAP) and nitrophosphate tagged with 32P and applied at three rates (30, 60 and 90 kg P2O5 ha−1). The results indicated that the dry matter yield (DMY) of cotton shoot, P uptake, percent P derived from fertilizer (%Pdff) and Avalue of the soil increased significantly with increasing fertilizer rate, whereas the percent fertilizer P utilization (%FUP) was found to be higher at lower fertilizer rates. Among the fertilizer sources SSP was found to be superior in enhancing DMY of cotton, P uptake and %FUP as compared to other fertilizers. %Pdff was found to be at par in SSP and DAP treatments and was significantly higher in comparison to NP and reverse was true in case of A-value of the soil. Results on equivalent ratio showed that SSP and DAP are equally efficient, whereas, 1 kg P as SSP was equivalent to 7.47 kg P as NP. In general, efficacy of phosphatic fertilizers for cotton crop in vertisol was found to be in order of SSP>DAP>NP.
Abstract
The color efficiency of ceramic glaze blue pigments obtained by the Pechini method was presented in this work. The fired pigments and enameled samples were characterized by thermogravimetry (TG) and differential thermal analysis (DTA), XRD, UV-VIS-NIR spectroscopy and CIE-L*a*b* color-measurements. The pigments obtained by the Pechini method present a better solubility in the molten glazes than the pigments obtained by the mechanical mixture of the precursor oxides.
Abstract
The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 >Cd(S2 CNPrn 2 )2 >Cd(S2 CNBui 2 )2 >Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.
Abstract
The most feasible alternative among fuels derived from biomass seems to be the biodiesel, having the required characteristics for a total or partial substitution of diesel oil. Therefore, the aim of this work is to evaluate the thermal and rheological behavior of the blends of diesel with the methanol biodiesel obtained from soybean oil, using B5, B15 and B25 blends. All thermogravimetric curves exhibited one overlapping mass loss step in the 35–280C temperature range at air atmosphere and one step between 37–265C in nitrogen. The rheological study showed a Newtonian behavior (n=1) for all blends.
Abstract
Pt/WOx–ZrO2 bifunctional catalysts were synthesized using impregnation and polymeric precursor methods. After the synthesis process the samples were calcined at 600, 700 and 800C and characterized by X-ray diffraction, nitrogen adsorption and temperature programmed reduction study by thermogravimetry. DTG-TPR profiles showed between three and five reduction events at different temperatures attributed to platinum reduction and to different stages of tungsten species reduction. A comparative study of the synthesis method influence on the DTG-TPR curves was accomplished.
Abstract
The thermo-programmed reduction study of Pt/WOx–ZrO2 materials prepared with different tungsten loading were performed by thermogravimetry. The samples were synthesized by impregnation method and calcined at 600, 700 and 800°C. The characterizations of both un-calcined and calcined materials were carried out using different techniques: thermal analysis (TG and DTA), X-ray diffraction (XRD) and thermo-programmed reduction (TPR). TG and DTA analysis of un-calcined were used to determination of calcination temperatures of the samples. XRD diffractograms were useful to help us in the determination of phase presents. TPR profiles showed between three and four events at different temperatures attributed to platinum reduction and the different stages of tungsten specie reduction.
Abstract
The pigments used in ceramic applications are of nature predominantly inorganic and they should be thermally stable, insoluble in glazing, resistant to the chemical and physical agents' attacks. This work aimed at the synthesis by the polymeric precursor method of ZrO2-based inorganic pigments, doped with Fe, Ni, Co, Cr and Cu cations. The fired pigments were characterized by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). Among the metals used to zirconium-doping, the best result was achieved with the cations Cu, which presented the monophase pigment, even as 20 mol% of dopant. Up to the temperature of 1000C the pigments presented a good thermal stability.
Abstract
The high-density polyethylene, thermoplastic widely-used in the production of industrial domestic utilities, was collected in two situations: virgin high-density polyethylene (JV 060) and post-consumption high-density polyethylene (with features of low-density polyethylene). After collecting the samples, they were submitted to natural aging with the quantification of the incident solar radiation for 180 days. The samples were characterized by melt flow index, differential scanning calorimetry, tensile strength, rupture load, elongation at break and infrared. The results showed that after 180 days of exposure the virgin high-density polyethylene presented physical properties similar to the post-consumption polyethylene.
Abstract
The thermodynamic and kinetic parameters of the thermal decomposition of Zn(S2CNR2)2 complexes (R=CH3, C2H5 and n-C3H7) were determined with the dynamic thermogravimetric method. Superimposed TG/DTG/DSC curves show that thermal decomposition reactions for chelates with R=C2H5 and n-C3H7 occur in the liquid phase, at temperatures far away from their melting points, whereas for the complex with R=CH3 the thermal decomposition begins at a temperature closer to its melting point, suggesting a rather complex decomposition mechanism.
