This work proposes thermal characterization as analytical methodology for the identification and purity assay of warifteine,
an alkaloid in Cissampelos sympodialis Eichl. Thermal and kinetic parameters were determined by means of TG and DSC photovisual studies. The TG results showed that
the decomposition of warifteine in air and nitrogen atmospheres proceeds in three and four steps, respectively. The TG data
allowed calculation of the kinetic parameters of warifteine. The activation energy values obtained by different methods displayed
a good correlation. With the DSC photovisual system applied it is possible to detect the impurity level in warifteine after
Authors:J. Gonçalves, R. Toledo Filho, and E. Fairbairn
This paper reports an experimental study on the magnesium sulphate resistance of mortar specimens incorporating 0, 10 and
20% of metakaolin (MK). The evidence of the attack was evaluated through the content of calcium hydroxide (portlandite) and
formation of magnesium hydroxide (brucite) by thermal analysis (thermogravimetric and derivative thermogravimetric analysis).
The mechanical degradation of the mortar specimens was evaluated through splitting tensile tests after 200 days of exposition
to the magnesium solution. The addition of metakaolin resulted in a reduction in the content of calcium hydroxide and in a
smaller formation of brucite in comparison with reference mixture. A tensile strength loss of about 7% was observed for the
metakaolin mortars submitted to the magnesium solution attack for 200 days.
The study of fossil materials is very important in the geological and biological researches. They can involve ancient past,
evolution or extinction of species, oil prospecting and the understanding of different areas such as: paleoclimate, paleoecology,
paleogeography, in addition of climate, environmental changes and life. Araripe Geopark is located in the south area of the
Ceará state in the Northeast of Brazil and it provides a general overview of the Earth’s History. In this study the vertebral
column extinct fish, Cladocyclus ferox and its nodule from Santana Formation, Northeast of Brazil, calcite and apatite minerals, and vertebral column of recent
fish, Opisthonema oglinum were investigated by means of thermal analysis. TG/DTG and DTA curves showed decomposition processes, suggesting water evolution,
calcium carbonate and phosphate decomposition and thermal transitions indicated that fossilization processes of fish, carbonaceous
material involved the fossil after its death and the organic substance was replaced by inorganic compounds.
Among other objectives, forest inventories are aimed to identify ecological communities and to correlate community composition with environmental variables. The identification of different communities would require several forest inventories, each covering small sampling areas with relatively homogeneous environmental conditions. The multiple plot sampling method, traditionally used in local inventories of tropical forests, cannot assure such homogeneity, since even small sampling areas would show environmental heterogeneity influencing vegetation. In this paper we assessed the consequences of this heterogeneity for sampling by quantifying the variability of species abundance ranks for species sampled with 10 or more individuals in a set of plots covering a small sampling area. The species reference abundance ranks were obtained from a sample of 100 plots of 10 m × 10 m each randomly set in a sampling area of 6.5 ha in a tropical forest fragment (Southeastern Brazil). For each species we used resamplings (30 trials) to obtain the species abundance ranks in sub-samples, considering different sampling intensities (n = 25, 50 and 75 plots), and compared these ranks with the species reference rank (n = 100 plots). Then, we compared the species ranks in sub-samples of 50 plots (10.000 trials) with the reference rank and assessed the frequency and extent of rank displacements. Species rank was highly variable across resampling trials for the sampling intensities of n = 25 and n = 50, but decreased considerable with a sampling intensity of n = 75 plots. The mean rank variability and especially the maximum displacement raised significantly from the seventh most abundant species on, and some species occupied quite discrepant abundance ranks in up to 10% of the 10.000 resampling trials. This high internal variability of forest samples may impair the search for floristic patterns as scale lessens, say, to the meso-scale (1–100 km2). We discussed some possible ways to increase internal homogeneity of tropical forest samples with the multiple plot sampling method. Among these, objective entitation, based on an ancient phytosociological procedure, is suggested as the most appropriate for use on the hilly relieves of the Atlantic forest biome.
Authors:R. Cielo Filho, F.R. Martins, and A. Gneri
The species abundance distribution of ecological communities has been represented through several mathematical models, of which the most common are: geometric series, logseries, lognormal, and a type of broken stick, this latter found only in animal communities. There is no consensus on the underlying biological processes, but initial observations on plant communities related these models to equilibrium and high richness (lognormal), stress or disturbance and low richness (logseries and geometric series). Recently the value of these relationships was challenged, and other descriptors were considered better predictors of richness, disturbance and stress. We aimed at investigating how these models and their parameters, as well as dominance and evenness are related with species richness, stress and disturbance in six tropical forest communities, SE Brazil: two well-conserved fragments, two disturbed by fire, and two swampy forests (anoxic stress). The models did not show consistent relationships with richness, disturbance or stress. The parameters and indices of diversity a (logseries) and l (lognormal) varied closely with richness, and the dominance was larger in the communities submitted to stress or disturbance. Our results indicate the need of further studies in order to validate (or refute) the use of abundance distribution models for detection of patterns related to richness, stress or disturbance in tropical arboreal communities. On the other hand, richness and dominance did respond to disturbance and stress.
Authors:R. Parise Filho, A. Araújo, M. Santos Filho, J. Matos, M. Silveira, and C. Brandt
Oxamniquine (OXA) is a schistosomicide agent that causes some adverse effects in central nervous system. Intending to improve
OXA therapeutic properties, a polymeric prodrug was designed. Currently, there is an increasing interest of thermal analytical
techniques in the pharmaceutical area, so differential thermal analysis (DTA) and thermogravimetry (TG) were carried out to
evaluate the thermal behavior of OXA, polymethacrylic acid (PMA), [poly(methacrylic-co-oxamniquine methacrylate)acid] (PMOXA)
and physical mixture (OXA+PMA). The thermoanalytical profile of the physical mixture showed characteristic events of the thermal
decomposition of OXA and PMA. Distinctly, PMOXA DTA curve did not show an endothermic peak at 148.5C indicating that the
drug was incorporated into the polymeric system. These results were corroborated by the IR spectroscopy and X-ray diffraction
Authors:R. Filho, P. Franco, E. Conceição, and M. Leles
A formulation of nifedipine tablets was prepared in the present research. The tablets were conditioned in amber-colored glass
containers and placed in a climatized room at 40°C and relative humidity of 75% for 180 days. Differential scanning calorimetry
(DSC) and thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two
well-known nifedipine degradation products. The results demonstrated that there is no evidence on the interaction between
nifedipine and excipients, or degradation products.
Authors:R. Filho, P. Franco, E. Conceição, and M. Leles
A new formulation of nifedipine tablets was prepared. The tablets were conditioned in amber-colored glass containers and placed
in a climatized room at 40 °C and relative humidity of 75% for 180 days. Differential scanning calorimetry (DSC) and Thermogravimetry
(TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two well-known nifedipine degradation
products. There is no evidence of interaction between nifedipine and excipients or degradation products. High performance
liquid chromatography (HPLC) was used in the dosage of nifedipine tablets before and after acclimatized exposure. Results
show that DSC and TG offer important data for a more detailed assessment of the stability of a pharmaceutical formulation.
Authors:R. Cunha e Silva, E. Almeida, E. Valencia, and V. Filho
Total reflection X-ray fluorescence (TXRF) was used to determine simultaneously the concentration of Cu, Fe and Zn in seven
sugar-cane spirit samples (“aguardente”), a processed alcoholic beverage made from the fermentation and distillation of sugar-cane
juice. The limits of detection ranged from 35 to 8 ng.ml-1 for V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As and Se. Excluding Fe, Cu and Zn, the concentrations were below their limits. Two samples
showed Cu concentrations higher than the value allowed by Brazilian legislation (5 µg.ml-1), and concerning Fe and Zn, no sample were above the limits permitted by WHO for drinking water (2 and 3 µg.ml-1, respectively).