2024 - COSTA, FERNANDA A.T. da; CARDOSO, ELIZABETH C.L.; DUFRESNE, ALAIN; PARRA, DUCLERC F.

Polylactic acid (PLA) is a widely used biopolymer and is currently produced on a global scale. However, PLA has low melt strength, which limits its application. Poly(butylene adipate-co-terephthalate) (PBAT) is a fully biodegradable polymer and one of the most attractive polymers for hardening PLA. As PLA and PBAT are immiscible, they need to be compatibilized to improve the properties of the blend. In this context, the compatibilization of PLA/PBAT blends was investigated through an irradiation process. PLA was previously irradiated, at different absorbed doses, in a cobalt-60 source to assess the compatibility of its blends with PBAT. Differential scanning calorimetry showed a reduction in the glass transition, cold crystallization and melting temperatures, and a second melting peak was observed after polymer irradiation. Also, X-ray diffraction analyses revealed a slight increase in the crystalline fraction. Thermogravimetric analysis showed that as the absorbed dose increased, the thermal stability of PLA decreased. Fourier-transform infrared spectroscopy shows bands attributed to oxidized terminations of polymer chains with carbonyls attributed to the effect of irradiation exposure. For samples irradiated above 100 kGy, an increase in tensile strength and tensile modulus can be observed as the dose increases. Rheological measurements showed a decrease in the complex viscosity of irradiated PLA with increasing absorbed dose. The surface of the polymer blend with PLA irradiated with gamma rays at 150 kGy appears to be more homogeneous according to scanning electron analysis. The polymer blend with 150 kGy irradiated PLA showed improved interaction between the components.

2010 - CAMARGO JUNIOR, ALCEU S.; YU, ABRAHAM S.O.; NASCIMENTO, PAULO T. de S.; BELINETTI, JOSE V.; MARQUES, JOSE J.; MORILHAS, LEANDRO J.

Brazilian auto industry has changed significantly since 2003 by the introduction of the flexible fuel vehicles that can run with any mix of gasoline or sugarcane ethanol. Sugarcane ethanol is a well known renewable fuel and an efficient alternative to fossil fuel due to its high energy yield and also to its great potential for fixing carbon dioxide. Consumers see great opportunity in acquiring a flex fuel vehicle because the car owners have the option of selecting the fuel regarding primarily their relative prices. What are the benefits for Brazilian consumers of owning a flex fuel vehicle in comparison with gasoline engine cars? This study applies the real options methodology to capture the worth of owning and operating a Brazilian flex fuel vehicle as regards the relative prices of the two fuels. The more uncertain the relative prices of fuels the more valuable will be the option value embedded in Brazilian flex fuel vehicles. Sensitivity analyses regarding different scenarios on Brazilian fuel markets are developed and their impacts are discussed.

2006 - AROEIRA, LUIZ S.

Experimental Allergic Encephalomyelitis (EAE) is a neuroinflammatory, autoimmune disorder in which myelin-reactive Th1 T cells with a restricted TCRVβ repertoire play a pathogenic role. Here, I show that an engineered single-chain TCR containing dominant TCRVα/Vβ encephalitogenic elements, when administered in aluminum adjuvant, generates a marked anti-TCR humoral response that correlated with protection against the development of EAE in Vβ8-expressing B10.PL but not in Vβ8-deficient SJL mice. sc-TCR/Al vaccination was highly efficient in preventing murine EAE in a TCR-specific manner through a mechanism involving anti-TCR B cells and/or antibodies. Collectively, these data have important implications for designing preventive or therapeutic strategies combining TCR vaccination with the use of aluminum adjuvant in the treatment of multiple sclerosis and other human autoimmune inflammatory diseases.

1999 - AROEIRA, LUIZ S.; MOUTON, CONCEPCION G.; TORAN, JOSE L.; WARD. ELIZABETH S.; MARTINEZ-A, CARLOS

The mechanism involved in the maintenance of staphylococcal enterotoxin B (SEB)-induced T cell anergy is poorly understood. We demonstrated earlier that B cells play an important role in the maintenance of SEB-induced T cell anergy in vivo and in vitro. Here, we demonstrate that B cells are not essential in SEB-induced T cell activation, but are important for the maintenance of T cell memory phenotype and anergy in vivo. Studying the activated B cell repertoire, we observe that SEB treatment increases serum anti-Vβ8 antibody titer as detected by enzyme-linked immunosorbent assay using soluble Vβ8 chains as antigens, and by staining of a Vβ8-expressing thymoma. These antibodies disappear gradually after immunization with SEB, whereas the capacity of the T cells to respond to SEB in vitro is restored. Anti-Vβ8 monoclonal antibody treatment causes Vβ8+ T cell unresponsiveness to SEB in vitro (anergy), without affecting CD4Vβ8+ T cell frequency. Together, these results suggest a new mechanism to explain the maintenance of SEB-induced T cell anergy, which is depen dent on B cells and on anti-Vβ8 antibody that specifically interacts with Vβ8+ T cells.