Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: F. Bernardi x
Clear All Modify Search

Abstract  

Norfloxacin (NFX) is a synthetic antibacterial drug. The development of extended release tablets improves the patients’ comfort and compliance, resulting in lower discontinuation of the therapy; with consequently decrease in bacterial resistance. In the present work, the thermal behavior of NFX was investigated using TG and DSC techniques. Isothermal and non-isothermal methods were employed to determine kinetic data of decomposition process. Compatibility studies between NFX and pharmaceutical excipients, including three hydrophilic polymers were carried out in order to develop a new formulation of NFX to obtain extended release tablets with an approved quality.

Restricted access

Abstract  

The thermal analytical study of venlafaxine hydrochloride, a third generation antidepressant, was investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC). The DSC curves have shown a sharp endothermic event at 211 °C and TG demonstrated a single stage of mass loss between 254 and 283 °C. Solid-state characterization was carried out by DRIFT, SEM, and XRPD demonstrating the drug physicochemical properties including crystallinity. Drug-excipient compatibility studies investigated by DSC have shown a possible physical interaction of the drug with magnesium stearate, microcrystalline cellulose and starch. Nevertheless, these results where not confirmed by DRIFT and SEM analyses.

Restricted access

Abstract

Zinc oxide is a widely used white inorganic pigment. Transition metal ions are used as chromophores and originate the ceramic pigments group. In this context, ZnO particles doped with Co, Fe, and V were synthesized by the polymeric precursors method, Pechini method. Differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis. The TG and DSC results revealed a series of decomposition temperatures due to different exothermal events, which were identified as H2O elimination, organic compounds degradation and phase formation. The samples were structurally characterized by X-Ray diffractometry revealing the formation of single phase, corresponding to the crystalline matrix of ZnO. The samples were optically characterized by diffuse reflectance measurements and colorimetric coordinates L*, a*, b* were calculated for the pigment powders. The pigment powders presented a variety of colors ranging from white (ZnO), green (Zn0.97Co0.03O), yellow (Zn0.97Fe0.03O), and beige (Zn0.97V0.03O).

Restricted access

Little is known of how changes in plant function may influence adaptive traits amongst animals further up the food chain. We addressed the hypothesis that shifts in plant functional traits are associated with the adaptive function of animal species which have an indirect trophic link. We compared community characteristics and functional traits of two trophically detached biotic groups (vascular plants and carabid beetles) along a primary succession on terrain at the Cedec glacier in the Alps, where deglaciation events following post-Little Ice Age climate warmings are marked by moraine ridges. Morphofunctional traits were recorded: canopy height (CH), leaf dry matter content (LDMC), leaf dry weight (LDW) and specific leaf area (SLA) (for plants) and the number of brachypterous, autumn-breeding and predator species, and average body length (for carabid beetles). We found that vegetation cover and plant species richness gradually increased throughout early succession, with an abrupt increase between 40 and 150 years after deglaciation. At the early stages of the succession plant traits were typical of ruderal species (high SLA, low CH, LDW) whilst a shift in traits towards stress-tolerance (low SLA) occurred >150 years. Carabid communities and traits changed alongside changes in plant species richness and cover, with late successional vegetation hosting larger, more diverse, less mobile carabid species with longer larval development. Thus, ruderal plant strategies are the main contributors during vegetation development, determining vegetation quantity, and probably have the greatest impact on changes in carabid assemblages by regulating resource availability. Plants then require greater stress-tolerance to survive in stable vegetation, which supports high carabid diversity. This suggests that different plant strategies may affect ground beetle communities via contrasting mechanisms: both quantities (biomass, species richness) and qualities (functional traits, adaptive strategies) should be taken into account during studies of plant-animal interactions within ecosystems.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: S. X. S. Costa, M. R. Galvão, D. P. Jacomassi, M. I. B. Bernardi, A. C. Hernandes, A. N. de Souza Rastelli and M. F. Andrade

Abstract

Thermal properties and degree of conversion (DC%) of two composite resins (microhybrid and nanocomposite) and two photo-activation methods (continuous and gradual) displayed by the light-emitting diode (LED) light-curing units (LCUs) were investigated in this study. Differential scanning calorimetry (DSC) thermal analysis technique was used to investigate the glass transition temperature (T g) and degradation temperature. The DC% was determined by Fourier transform infrared spectroscopy (FT-IR). The results showed that the microhybrid composite resin presented the highest T g and degradation temperature values, i.e., the best thermal stability. Gradual photo-activation methods showed higher or similar T g and degradation temperature values when compared to continuous method. The Elipar Freelight 2TM LCU showed the lowest T g values. With respect to the DC%, the photo-activation method did not influence the final conversion of composite resins. However, Elipar Freelight 2TM LCU and microhybrid resin showed the lowest DC% values. Thus, the presented results suggest that gradual method photo-activation with LED LCUs provides adequate degree of conversion without promoting changes in the polymer chain of composite resins. However, the thermal properties and final conversion of composite resins can be influenced by the kind of composite resin and LCU.

Restricted access