A cafeína exerce efeitos positivos sobre a memória tipo episódica em ratos adultos sem influenciar a sobrevivência neural no giro dentado

The caffeine is a mild psychostimulant that has positive cognitive effects at low doses, while promotes detrimental effects on these processes at higher doses. The episodic-like memory can be evaluated in rodents through hippocampus-dependent tasks. The dentate gyrus is a hippocampal subregion in which neurogenesis occurs in adults, and it is believed that this process is related to the function of patterns separation, such as the identification of spatial and temporal patterns when discriminating events. Furthermore, neurogenesis is influenced spatial and contextual learning tasks. Our goal was to evaluate the performance of male Wistar rats in episodic-like tasks after acute or chronic caffeine treatment (15mg/kg or 30mg/kg). Moreover, we assessed the chronic effect of the caffeine treatment, as well as the influence of the hippocampus-dependent learning tasks, on the survival of new-born neurons at the beginning of treatment. For this purpose, we used BrdU to label the new cells generated in the dentate gyrus. Regarding the acute treatment, we found that the saline group presented a tendency to have better spatial and temporal discrimination than caffeine groups. The chronic caffeine group 15 mg/kg (low dose) showed the best discrimination of the temporal aspect of episodic-like memory, whereas the chronic caffeine group 30mg/kg (high dose) was able to discriminate temporal order, only in a condition of greater difficulty. Assessment of neurogenesis using immunohistochemistry for evaluating survival of new-born neurons generated in the dentate gyrus revealed no difference among groups of chronic treatment. Thus, the positive mnemonic effects of the chronic caffeine treatment were not related to neuronal survival. However, another plastic mechanism could explain the positive mnemonic effect, given that there was no improvement in the acute caffeine groups

Degradação catalítica de polietileno de alta densidade sobre a zeólita HZSM

In last years it has talked a lot about the environment and the plastic waste produced and discarded. In last decades, the increasing development of research to obtain fuel from plastic material, by catalytic degradation, it has become a very attractive looking, as these tailings are discarded to millions worldwide. These materials take a long time to degrade themselves by ways said natural and burning it has not demonstrated a viable alternative due to the toxic products produced during combustion. Such products could bring serious consequences to public health and environment. Therefore, the technique of chemical recycling is presented as a suitable alternative, especially since could be obtain fractions of liquid fuels that can be intended to the petrochemical industry. This work aims to propose alternatives to the use of plastic waste in the production of light petrochemical. Zeolites has been widely used in the study of this process due to its peculiar structural properties and its high acidity. In this work was studied the reaction of catalytic degradation of high-density polyethylene (HDPE) in the presence HZSM-12 zeolites with different acid sites concentrations by thermogravimetry and pyrolysis coupled with GC-MS. The samples of the catalysts were mixed with HDPE in the proportion of 50% in mass and submitted to thermogravimetric analyses in several heating rates. The addition of solids with different acid sites concentrations to HDPE, produced a decrease in the temperature of degradation of the polymer proportional the acidity of the catalyst. These qualitative results were complemented by the data of activation energy obtained through the non-isothermal kinetics model proposed by Vyazovkin. The values of Ea when correlated to the data of surface acidity of the catalysts indicated that there is a exponential decrease of the energy of activation in the reaction of catalytic degradation of HDPE, in function of the concentration of acid sites of the materials. These results indicate that the acidity of the catalyst added to the system is one of the most important properties in the reaction of catalytic degradation of polyethylene

Influência da densidade de carga e da massa molar da poliacrilamida na reologia de sistemas microemulsionados

The knowledge of the rheological behavior of microemulsionated systems (SME) is of fundamental importance due to the diversity of industrial applications of these systems. This dissertation presents the rheological behavior of the microemulsionated system formed by RNX 95/alcohol isopropyl/p-toulen sodium sulfonate/kerosene/distilled water with the addition of polyacrylamide polymer. It was chosen three polymers of the polyacrylamide type, which differ in molar weight and charge density. It was studied the addition of these polymers in relatively small concentration 0,1% in mass and maximum concentration of 2,0%. It was made analysis of flow to determine the appearing viscosities of the SME and rheological parameters applying Bingham, Ostwald de Waale and Herschell-Buckley models. The behavior into saline environment of this system was studied for a solution of KCl 2,0%, replacing the distilled water. It was determined the behavior of microemulsions in relation with the temperature through curves of flow in temperatures of 25 to 60ºC in variations of 5ºC. After the analysis of the results the microemulsion without the addition of polymer presented a slight increase in its viscosity, but it does not mischaracterize it as a Newtonian fluid. However the additive systems when analyzed with low concentration of polymer adjusted well to the applied models, with a very close behavior of microemulsion. The higher concentration of the polymer gave the systems a behavior of plastic fluid. The results of the temperature variation point to an increase of viscosity in the systems that can be related to structural changes in the micelles formed in the own microemulsion without the addition of polymer