F. M. Araujo-Moreira

Spin glass behavior in RuSr 2 Gd 1.5 Ce 0.5 Cu 2 O 10 − δ

The dynamics of the magnetic properties of polycrystalline RuSr 2 Gd 1 . 5 Ce 0 . 5 Cu 2 O 1 0 - δ (Ru-1222) have been studied by ac susceptibility and dc magnetization measurements, including relaxation and ageing studies. Ru-1222 is a reported magnetosuperconductor with Ru spins magnetic ordering at temperatures near 100 K and superconductivity in Cu-O 2 planes below T c ∼40 K. The exact nature of Ru spins magnetic ordering is still being debated, and no conclusion has been reached yet. In this work, a frequency-dependent cusp was observed in Χ a c vs T measurements, which is interpreted as a spin glass transition. The change in the cusp position with frequency follows the Vogel-Fulcher law, which is commonly accepted to describe a spin-glass with magnetically interacting clusters. Such an interpretation is supported by thermoremanent magnetization (TRM) measurements at T=60 K. TRM relaxations are well described by a stretched exponential relation, and present significant aging effects.

Pectin-coated chitosan-LDH bionanocomposite beads as potential systems for colon-targeted drug delivery.

This work introduces results on a new drug delivery system (DDS) based on the use of chitosan/layered double hydroxide (LDH) biohybrid beads coated with pectin for controlled release in the treatment of colon diseases. Thus, the 5-aminosalicylic acid (5ASA), the most used non-steroid-anti-inflammatory drug (NSAID) in the treatment of ulcerative colitis and Crohns disease, was chosen as model drug aiming to a controlled and selective delivery in the colon. The pure 5ASA drug and the hybrid material prepared by intercalation in a layered double hydroxide of Mg2Al using the co-precipitation method, were incorporated in a chitosan matrix in order to profit from its mucoadhesiveness. These compounds processed as beads were further treated with the polysaccharide pectin to create a protective coating that ensures the stability of both chitosan and layered double hydroxide at the acid pH of the gastric fluid. The resulting composite beads presenting the pectin coating are stable to water swelling and procure a controlled release of the drug along their passage through the simulated gastrointestinal tract in in vitro experiments, due to their resistance to pH changes. Based on these results, the pectin@chitosan/LDH-5ASA bionanocomposite beads could be proposed as promising candidates for the colon-targeted delivery of 5ASA, with the aim of acting only in the focus of the disease and minimizing side effects.

Specific heat at low temperatures and magnetic measurements inNd0.5Sr0.5MnO3andR0.5Ca0.5MnO3(R=Nd,Sm, Dy, and Ho) samples

We studied the magnetization as a function of temperature and magnetic field in the compounds

Meissner state in finite superconducting cylinders with uniform applied magnetic field

{\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3},

Granularity in superconductors: intrinsic properties and processing-dependent effects

{\mathrm{Nd}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},

Magnetic remanence of Josephson junction arrays

{\mathrm{Sm}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},

Magnetic and superconducting properties of Ru Sr 2 Gd 1.5 Ce 0.5 Cu 2 O 10 − δ samples: Dependence on the oxygen content and aging effects

{\mathrm{Dy}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},