Paulo Noronha Lisboa | Universidade Estadual Paulista "Júlio de Mesquita Filho" (original) (raw)

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Papers by Paulo Noronha Lisboa

Química Nova, 2013

Recebido em 27/2/12; aceito em 23/10/12; publicado na web em 20/2/13 SYNTHESIS, CHARACTERIZATION ... more Recebido em 27/2/12; aceito em 23/10/12; publicado na web em 20/2/13 SYNTHESIS, CHARACTERIZATION AND STUDY OF THE PROPERTIES OF A NEW MONONUCLEAR QUERCETIN COMPLEX CONTAINING Ga(III) IONS. Flavonoids are one of the most important compound groups applied as medicine given their antioxidant properties, but several intrinsic properties can be improved through structural modifications to their molecules. Here, the synthesis and characterization of a new gallium (III) complex with quercetin is described. Electrochemical properties, as well as antioxidant and cytotoxic activities, were investigated and compared to the free flavonoid molecule. The mononuclear complex obtained, [Ga(C 15 H 9 O 7 ) 3 ].2H 2 O.2CH 3 OH.CH 3 CH 2 OH, seems more active as a DPPH radical scavenger given its lower oxidation potential compared to quercetin. The new complex cytotoxic responses have shown to be more effective than those of the free flavonoid and of lapachol used as a control.

Physical Review B, 2008

In the present paper we develop an algorithm to solve the time dependent Ginzburg-Landau (TDGL) e... more In the present paper we develop an algorithm to solve the time dependent Ginzburg-Landau (TDGL) equations, by using the link variables technique, for circular geometries. In addition, we evaluate the Helmholtz and Gibbs free energy, the magnetization, and the number of vortices. This algorithm is applied to a circular sector. We evaluate the superconduting-normal magnetic field transition, the magnetization, and the superconducting density. Furthermore, we study the nucleation of giant and multi-vortex states for that geometry.

Physical Review B, 2009

The dynamics of the annihilation of a vortex-antivortex pair is investigated. The pair is activat... more The dynamics of the annihilation of a vortex-antivortex pair is investigated. The pair is activated magnetically during the run of a simulated hysteresis loop on a square mesoscopic superconducting cylinder with an antidot inserted at its center. We study the nucleation of vortices and antivortices by first increasing the magnetic field, applied parallel to the axis of the sample, from zero until the first vortex is created. A further increase of the field pulls the vortex in, until it reaches the antidot. As the polarity of the field is reversed, an antivortex enters the scene, travels toward the center of the sample and eventually the pair is annihilated. Depending on the sample size, its temperature, and Ginzburg-Landau parameter, the vortex-antivortex encounter takes place at the antidot or at the superconducting sea around it. The position and velocity of the vortex and antivortex singularities were evaluated as a function of time. The current density, magnetization and order parameter topology were also calculated.

Brazilian Journal of Physics, 2002

Journal of Non-crystalline Solids, 2000

Systems consisting of magnetic particles embedded in a silica matrix have been used in magnetic r... more Systems consisting of magnetic particles embedded in a silica matrix have been used in magnetic recording, their study being thus an actual theme of research. In this work, we report some of the main results of a systematic study conducted to determine properties of the magnetic phases of the system Co 2 SiO 4 . The study also deals with the magnetic parameters of the composites Co 2 O 3 ±SiO 2 , in an attempt to establish relationships between structural environment and the magnetic properties. Polycrystalline sintered samples were prepared using a chemical route, structurally and magnetically measured using X-ray diraction (XRD), electron microscopy and magnetometry. For applied magnetic ®elds of the order of tens of Oersteds, the system has ferromagnetic (F) order, whereas for ®elds of a few thousands of Oersteds, a frustated antiferromagnetic (AF) response is detected. Our measurements detect the existence of ferromagnetic and antiferromagnetic interactions. Also, crystalline Co 2 SiO 4 is shown to have uniaxial anisotropy, detected by magnetization versus ®eld curves. Ó

Journal of Magnetism and Magnetic Materials, 2002

Journal of Physics and Chemistry of Solids, 2005

We report the effects of oxygen stoichiometry in the structure and magnetic response of spinel-ty... more We report the effects of oxygen stoichiometry in the structure and magnetic response of spinel-type NiMn 2 O 4Kd polycrystalline samples controlled by heat-treatments in different atmospheric conditions.

Physica B-condensed Matter, 2006

The use of AC/DC magnetic susceptibility and impedance measurements to detect oxygen depletion ef... more The use of AC/DC magnetic susceptibility and impedance measurements to detect oxygen depletion effects in La 0.7 Ca 0.3 MnO 3±δ and NiMn 2 O 4±δ spinel-type compounds is reported. For the NiMn 2 O 4 , for which no Mn 4+ was found, three superposed Debye relaxations were ...

Solid State Communications, 2004

Page 1. Extrinsic properties of colossal magnetoresistive samples ... Abstract In this work, we r... more Page 1. Extrinsic properties of colossal magnetoresistive samples ... Abstract In this work, we report a study on the extrinsic properties of La ...