A. G. Leyva

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We investigate the electric-pulse-induced resistance switching in manganite systems. We find a "complementarity" effect where the contact resistance of electrodes at opposite ends show variations of opposite sign and is reversible. The temperature dependence of the magnitude of the effect reveals a dramatic enhancement at a temperature T*, below the(More)
Polarizing microscopy (PM), scanning electron microscopy (SEM), x-ray dispersive analysis (EDAX), x-ray diffraction (XRD), and infrared spectrometry (IR) were used to study the following pathological mineralizations: calcifications and silicon(Si)-bearing mineralizations in cerebral tissue from an epileptic child; traces of Si-bearing particles in(More)
We study the resistive switching (RS) mechanism as a way to obtain multilevel cell (MLC) memory devices. In an MLC, more than 1 b of information can be stored in each cell. Here, we identify one of the main conceptual difficulties that prevented the implementation of RS-based MLCs. We present a method to overcome these difficulties and to implement a 6-b(More)
A 48-year-old Caucasian woman presented a tender effusion of small volume, with a mild increase in skin temperature in her right knee and wide spread chondrocalcinosis found radiologically. She had normal renal function, had undergone a gastrectomy, and was receiving therapeutic doses of aluminum hydroxide antacids. Synovial fluid analysis showed small,(More)
In this work, nanostructured LnxCe(1-x)O2-δ (Ln: Gd and Pr; x = 0.1 and 0.2) spheres were synthesized by microwave assisted hydrothermal homogeneous co-precipitation and their properties were characterized by synchrotron radiation XRD, X-ray absorption near-edge spectroscopy (XANES) and scanning and high-resolution electron microscopy (SEM and HRTEM). In(More)
UV/TiO(2) photocatalysis of phenylmercury salts in aqueous solutions has been performed starting from both acetate (C(6)H(5)HgCH(3)CO(2), PMA) and chloride (C(6)H(5)HgCl, PMC) salts, in the presence or the absence of oxygen at acidic pH. Removal of Hg(II) in solution took place with the simultaneous deposit of dark or pale gray solids on the photocatalyst,(More)
Resistive switching effects were studied on manganite based devices at room temperature. Thin films of La0.66Ca0.33MnO3 were grown using the pulsed laser deposition technique on top of conductive silicon substrates. Top contacts were deposited either by hand (Ag paint) or by sputtering (Cu). The Mn valence (which is correlated with the oxygen content) was(More)
We report a detailed study of the electric transport and magnetic properties of the La(5/8-y)Nd(y)Ca(3/8)MnO(3) manganite system. Substitution of La(3+) by smaller Nd(3+) ions reduces the mean ionic radius of the A-site ion. We have studied samples in the entire range between La-rich and Nd-rich compounds (0.1<y<0.625). Results of dc magnetization and(More)