Search Results

You are looking at 1 - 10 of 10 items for

  • Author or Editor: A. Medeiros x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

TG and DSC data were used to determine the thermal parameters of prednisone drug and tablets. Two formulations of prednisone 20 mg were analysed in the form of tablets. The TG curves of prednisone drug and tablets A and B displayed six, eight and seven thermal decomposition processes, respectively. Analysis of the DSC data pointed to chemical interactions between prednisone drug and the excipients of tablets A and B, suggested by alterations in the melting temperature of prednisone. The analysis revealed that prednisone drug is more stable than tablets A and B.

Restricted access

Abstract  

In this work, the influence of attapulgite concentration on the nucleating efficiency of isotactic polypropylene (iPP) and on the kinetics of non-isothermal crystallization were ascertained.The study was conducted by DSC. The nucleating efficiency was determined according to the procedure described by Fillon and the kinetics of non-isothermal crystallization was determined using Ozawa's method using cooling rates of 2, 5 and 10C min−1.Our results indicate that both the relative crystallinity and the crystallization temperature increase with filler content and that a maximum occurs at 2% mass/mass filler content. Both parameters decrease with increasing cooling rates. The Ozawa's exponent tended to increase with temperature and filler content.

Restricted access
Restricted access
Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Ana Santos, I. Basílio, F. de Souza, A. Medeiros, Márcia Pinto, D. de Santana, and R. Macêdo

Abstract  

Thermal analysis is an essential analytical tool in development of new formulations as well as to study the interaction between drugs and excipients. This work aims to investigate the possible interactions between metformin and excipients as microcrystalline cellulose (Microcel MC101®), starch sodium glycolate (Explosol®), sodium croscarmellose (Explosel®), PVP K30, magnesium stearate, starch and lactose, usually employed in pharmaceutical products. TG, DSC and DTA techniques were used for the thermal characterization to track if the thermal properties of the drug substance were modified in the mixture. Disregard of the starch and lactose systems, no changes in thermal behavior of mixtures were found. Thermogravimetric studies (TG) of metformin and its binary mixtures showed different thermal behavior.

Restricted access

Abstract  

Samples of the MgO–Al2O3–SiO2 ternary system, constituted by 28.5 mol% ofMgO, 28.5 mol% of Al2O3 and 43mol%of SiO2, were activated in a roll mill and calcined at different temperatures. The influence of the grinding time, the used SiO2 precursor and activation medium, furthermore the mass ratio between the powdered sample and zirconia cylinders was investigated on the reactivity of the MgO–Al2O3–SiO2 ternary system. FTIR spectra and the X-ray powder diffraction patterns indicates the formation of Mg(OH)2 at 393 K, of forsterite (MgSi2O5) and enstatite (MgSiO3) at 1223 K and of spinel (MgAl2O4) between 1223 and 1523 K in some samples. The presence of cordierite (Mg2Al2Si5O18) was observed at 1523 K, a reaction pathway concerning its formation was proposed.

Restricted access

Background and aims

Gambling disorder (GD) may have its onset in a wide range of ages, from adolescents to old adults. In addition, individuals with GD tend to seek treatment at different moments in their lives. As a result of these characteristics (variable age at onset and variable age at treatment seeking), we find subjects with diverse duration of illness (DOI) in clinical practice. DOI is an important but relatively understudied factor in GD. Our objective was to investigate clinical and neurocognitive characteristics associated with different DOI.

Methods

This study evaluated 448 adults diagnosed with GD. All assessments were completed prior to treatments being commenced.

Results

Our main results were: (a) there is a negative correlation between DOI and lag between first gambling and onset of GD; (b) lifetime history of alcohol use disorder (AUD) is associated with a longer duration of GD; (c) the presence of a first-degree relative with history of AUD is associated with a more extended course of GD; and (d) there is a negative correlation between DOI and quality of life.

Discussion

This study suggests that some important variables are associated with different DOI. Increasing treatment-seeking behavior, providing customized psychological interventions, and effectively managing AUD may decrease the high levels of chronicity in GD. Furthermore, research on GD such as phenomenological studies and clinical trials may consider the duration of GD in their methodology. DOI might be an important variable when analyzing treatment outcome and avoiding confounders.

Open access
Community Ecology
Authors: C. Calderón del Cid, R. S. Rezende, A. R. Calor, J. S. Dahora, L. N. de Aragão, M. L. Guedes, A. N. Caiafa, and A. O. Medeiros

Abstract

Leaf litter breakdown is an important process in riparian ecosystems, regulated by the concomitant fluctuations of allochthonous organic matter input (quality and quantity), the environmental conditions, and the decomposer community. Our objective was to assess the effects of temporal variability of litter quantity and quality over the stream's decomposer community. We hypothesized that the litter effects over the decomposer community would be overruled by Cerrado's harsh environmental conditions. Precipitation fluctuations, especially during dry and rain seasons, did modify the litterfall periodicity, but not the average organic matter entering the system or the litterfall triggers. Fifteen riparian species were identified contributing with organic matter into the stream, however, Richeria grandis contributed with 48% of litter biomass, helping explain the nutritional intra-annual balance given by the litter chemistry, that would be determinant for ecosystem stability. Higher aquatic hyphomycetes sporulation rates and invertebrate density during the dry season suggest that the decomposer community required a more stable environment (consistent low current) in order to colonize and exploit leaf litter. Our results point out that physical fragmentation was the predominant driver of litter breakdown for our system, due to high decomposition rates, litter remaining mass correlated negatively with precipitation, and low decomposer abundance and activity. Invertebrate collectors' abundance was negatively correlated with litter remaining mass and showed no temporal variation, suggesting that this functional group may have benefited from the particulate organic matter produced by physical fragmentation. Therefore, annual temporal variations on Brazilian savanna stream systems may drive the functioning of the ecosystem.

Restricted access
Community Ecology
Authors: R. de S. Rezende, A. O. Medeiros, J. A. dos Santos Dahora, A. M. Tonin, J. F. Gonçalves Junior, and Y. Moretto

Abstract

The invertebrate biodiversity of subtropical streams depends on the seasonal input of organic matter, as much as the leaf decomposition process on stream system. However, one of the challenges in determining the importance of invertebrates for leaf breakdown in subtropical streams is the low taxonomic resolution applied in most studies. To overcome this limitation, here we used litter bags with senescent leaves to evaluate the impact of different taxonomic resolutions of trophic group classification to assess the seasonal importance of invertebrate community for leaf litter breakdown in a subtropical stream (Atlantic Forest in western of Paraná state, Brazil). Litterfall was quarterly measured over a year. The leaf litter accumulated in an interval of 30 days was retrieved, weighed, and used for the leaf breakdown experiments (by litter bags). We found a lower importance of invertebrate community richness and density (shredders and scrapers) in leaf breakdown process irrespective of the taxonomic resolution (family or genus level used). Hyphomycetes biomass and fungi sporulation also did not present changes among sample times, and consecutively, importance for leaf breakdown. However, the richness and density of Chironomidae taxa respond differently depending on the taxonomic resolution used. Low litter breakdown may be explained by the increase of consumption of microorganisms, due to high density of Chironomidae scrapers evaluated at the genus level. Moreover, temperature is the main factor responsible for breakdown over the year, in a positive way. Therefore, our results indicated the family level as the taxonomic resolution sufficient to assess the role of shredders and scrapers in the leaf litter breakdown process of this subtropical stream system.

Restricted access

Thermal analysis in sustainable development

Thermoanalytical study of faveleira seeds (Cnidoscolus quercifolius)

Journal of Thermal Analysis and Calorimetry
Authors: J. C. O. Santos, J. P. Dantas, C. A. Medeiros, P. F. Athaíde-Filho, Marta M. Conceiçăo, J. R. Santos Jr., and A. G. Souza
Restricted access