Partículas inteligentes de poli (nisopropilacrilamida), quitosana e poli (ácido acrílico): efeito da temperatura e do pH sobre suas propriedades em suspensões aquosas

The present study describes the stability and rheological behavior of suspensions of poly (N-isopropylacrylamide) (PNIPAM), poly (N-isopropylacrylamide)-chitosan (PNIPAMCS), and poly (N-isopropylacrylamide)-chitosan-poly (acrylic acid) (PNIPAM-CS-PAA) crosslinked particles sensitive to pH and temperature. These dual-sensitive materials were simply obtained by one-pot method, via free-radical precipitation copolymerization with potassium persulfate, using N,N -methylenebisacrylamide (MBA) as a crosslinking agent. Incorporation of the precursor materials into the chemical networks was confirmed by elementary analysis and infrared spectroscopy. The influence of external stimuli such as pH and temperature, or both, on particle behavior was investigated through rheological measurements, visual stability tests and analytical centrifugation. The PNIPAM-CS particles showed higher stability in acid and neutral media, whereas PNIPAM-CS-PAA particles were more stable in neutral and alkaline media, both below and above the LCST of poly (Nisopropylacrylamide) (stability data). This is due to different interparticle interactions, as well as those between the particles and the medium (also evidenced by rheological data), which were also influenced by the pH and temperature of the medium. Based on the results obtained, we found that the introduction of pH-sensitive polymers to crosslinked poly (Nisopropylacrylamide) particles not only produced dual-sensitive materials, but allowed particle stability to be adjusted, making phase separation faster or slower, depending on the desired application. Thus, it is possible to adapt the material to different media

As razões da esquerda radical PCB, PSTU e PSOL: estrutura organizativa e objetivos políticos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Imaginário radical e educação física: trajetória esportiva de corredores de longa distância

Cette étude propose une lecture du sport d endurance, prenant comme perspective théorique l imaginaire radical et considérant les dimensions socio-historiques e subjectives de la pratique de courses de longue distance. D abord, l échantillon la recherche a été composé de huit sujets-atlètes du groupe de courreurs de rue Sport Vida. Ainsi, em même temps que nous faisons une analyse socio-historique de cette pratique sportive, nous considérons l ensemble des aspects sócio-culturels et poursuivons la recherche avec comme objectif de comprendre les sens qui lui sont attribués par les sjuets-atlètes, au-delá de l aspect économique et de la consommation. Nous observons que, même si l altétismo qui est pratiqué a des aspects competitifs (economiques), les atlètes créent d autres sens pour continuer a pratiquer ce sport, comme les amitiés, être ensemble avec les amis. Ils rompent avec la logique déterministe du sport dépasser la limite du corps, vaincre à n importe quel prix, dépasser les collègues -, en cherchant des moments de solidarité, un sport sans violence et affectif. Nous percevons néanmoins des contradictions dans le discours de quelques atlètes quand confessent que le plus important est l amour du sport, les amitiés, mais réclament du manque de sponsorts et d appui pour pouvoir s entrainer tranquillement. Cette recherche a aussi montré que dans la pratique de ce sport, les atlètes construisent une obstination, sachant le sacrifice qu il impose au corps, mais cela se transforme en plaisir, excitation et recherche d émotions fortes. Valeurs éthiques sont aussi construites et valorisées dans l atlétisme, ce qui est observé lorsque que les sujets-atlètes critiquent avec véemence a propos de l usage de substances chimiques par les sportifs. En choisissant l imaginaire radical comme principale inspiration théorique pour cette recherche, il devient évident que le sport peut être ressignifié, à partir du moment que cet imaginaire est potencialisé dans l enseignement de l éducation physique, porvocant chez les élèves une réflexion critique sur la société et sur le sport, qui passe à être redimensionné vers la solidarité, avec démocratie et autonomie. Enfin, l étude a révélé que le sport d endurance est capable de créer des liens sociaux et structurer des relations à partir de cette pratique

Avaliação da remoção de hidrocarbonetos aromáticos (BTEX) em águas utilizando materiais nanoestruturados do tipo Ti-MCM-41

Volatile Organic Compounds are pollutants coming mainly from activities that use fossil fuels. Within this class are the BTEX (benzene, toluene, ethylbenzene and xylenes) compounds that are considered hazardous. Among the various existing techniques for degradation of pollutants, there is advanced oxidation using H2O2 generating hidoxil radical ( OH). In this work, the mesoporous material of MCM-41 was synthesized by hydrothermal method and then was used as support, the impregnation of titanium by the method of synthesis with excess solvent to obtain the catalyst Ti-MCM-41. The catalyst was used in the reaction catalyzed removal of BTEX in water using H2O2 as oxidant. The materials were characterized by: XRD, TG/DTG, FTIR, nitrogen adsorption-desorption and FRX-EDX, in order to verify the method of impregnation of the mesoporous titanium support was effective. Catalytic tests were carried out in reactors of 20 mL containing BTEX (100.0 μg/L), H2O2 (2.0 M) and Ti-MCM-41 (2.0 g/L) in acid medium. The reaction occurred for 5 h at 60 °C and analysis were performed by gas chromatography with photoionization detector and static headspace sampler. The characterizations have proven the effectiveness of the synthesis method used and the incorporation of titanium lt in the support. The catalytic tests showed satisfactory results with conversion of more than 95 % for the studied compounds, where the catalyst 48% Ti-MCM-41 showed a higher removal efficiency of the compounds under study