Study of the presence of spherical deformations on the Al top electrode due to electroforming in rewritable organic resistive memories.

Physical deformations are observed at the top electrodes during the electroforming process in Al/PEDOT:PSS + nitrogen doped multiwalled carbon nanotube (N-MWCNTs)/Al rewritable resistive memory devices. These physical deformations arise from electrochemical reactions, i.e., a reduction reaction in the native Al oxide layer, which are similar to those reported in TiO2-based resistive memory devices. These memory devices are electroformed at the ON state using an ∼-2 V pulse or at the OFF state using an ∼3 V pulse. These processes are current-controlled; a minimum compliance current is necessary to obtain the electroforming of the device, generally between 5 to 10 mA. SEM and AFM micrographs show the presence of spherical deformations at the top electrode due to O2 gas formation generated by the reduction in the native AlOx layer during the electroformation, with a diameter of ∼7 micrometres for positive voltage or a smaller diameter of ∼3 micrometres for negative voltage. After top-electrode delamination, circular craters are found in the active layer in the vicinity of the N-MWCNTs, which only occurs when a negative voltage is used in the electroformation, indicating that film damage is induced by oxygen bubbles created at the bottom electrode/polymeric film interface.

Finite temperature orbital and spin magnetism of small Fe linear chains.

The finite temperature spin and orbital magnetism of N≤ 10 Fe(N) linear chains is theoretically studied in the framework of a spin fluctuation theory based on a realistic d-band model Hamiltonian, which includes the spin-orbit coupling interaction in a non-perturbative way. Spin and orbital magnetic moments are calculated as a function of the temperature by using an exchange Monte Carlo method that takes into account in a full way the short-range magnetic order. The finite temperature anisotropy effects on the spin and orbital cluster moment values are analysed by considering magnetization directions perpendicular to and along the chain axis. The temperature dependence of the orbital cluster moment follows a general trend similar to that of the spin one and shows clear anisotropy effects at low and intermediate temperatures, before total thermal disorder appears. Interesting anisotropy effects driven by thermal spin fluctuations are also observed for the spin results in most of the systems.

Infrared photoluminescence of composite films containing quasi-isolated multiwalled carbon nanotubes and carbon nanoshells.

Films of small irregular-shaped aggregates composed by several layers of turbostratic graphite encapsulating iron nanoparticles, like carbon nanoshells, and quasi-isolated multi-walled carbon nanotubes (MWCNTs), were synthesized by the chemical vapor deposition method on glass substrates. Quasi-isolated MWCNTs were found emerging in different directions on the agglomerates composed of carbon nanoshells. The morphological properties of the films were characterized using scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy, whereas their optical properties were investigated using optical absorption and photoluminescence (PL) spectroscopy. The studies show a high-intensity PL signal in the infrared at room temperature. This PL signal shows several peaks, which cannot be explained by a blackbody emission. However, the overall PL signal could be a combination of the black emission and electronic transitions. Furthermore, the observed infrared PL emission could be ideal for potential applications such as in gas sensors, infrared detectors and so on.

Calculation of spin and orbital magnetizations in Fe slab systems at finite temperature.

The temperature dependence of spin and orbital local magnetizations is theoretically determined for the non-bulk atomic region of (001) and (110) Fe slab systems. A d band Hamiltonian, including spin-orbit coupling terms, was used to model the slabs, which were emulated by using Fe films of sufficient thickness to reach a bulk behavior at their most inner atomic layers. The temperature effects were considered within the static approximation and a simple mean field theory was used to integrate the local magnetic moment and charge thermal fluctuations. The results reflect a clear interplay between electronic itinerancy and the local atomic environment and they can be physically interpreted from the local small charge transfers occurring in the superficial region of the slabs. For recovering the experimental behavior on the results for the (001) slab system, the geometrical relaxations at its non-bulk atomic layers and a d band filling variation are required. A study on the magnetic anisotropy aspects in the superficial region of the slabs is additionally performed by analyzing the results for the orbital local magnetization calculated along two different magnetization directions in both slab systems.

Tuning the electronic properties of armchair carbon nanoribbons by a selective boron doping.

Armchair carbon nanoribbons (ACNRs) substitutionally doped with boron atoms are investigated in the framework of first-principles density functional theory. Different boron-boron arrangements and concentrations are considered in order to simulate possible aggregation patterns, their structural stability and electronic behavior are determined as a function of ribbon size. In agreement with previous studies, our results show that the dopant atoms have in general a preference for edge sites, but specific effects appear as a function of concentration that importantly modify the properties of the ribbons compared to the pristine case. Interesting tendencies are discovered as a function of dopant concentration that significantly affect the electronic properties of the ribbons. We have found that BC(3) island formation and edge doping are the most important factors for the structural stabilization of the ribbons with high boron concentration (>7%) whereas for the cases of low boron concentrations (<5%) the structural stabilities are similar. For all the doped cases, we have found that the BC(3) island patterns give rise to highly localized B states on top of the Fermi level, resulting in semiconducting behavior. On the other hand, when the average distance between the B atoms increases beyond island stoichiometry, the localization of their states is reduced and the ribbons may become metallic due to a band crossing caused by the lowering of the Fermi level resulting from the positive charge doping. Thus, tuning the dopant interaction would be an appropriate way to tailor the electronic properties of the ribbons in a convenient manner in view of potential technological applications.

[Peliosis hepatis]. / Peliosis hepática.

A 35 years old female with peliosis hepatis is reported. She came to us complaining of muscular aches. The only positive finding at the physical examination was a normal size liver but palpable in a deep breath; it was hard, no tender, with smooth surface. The laboratory work up was negative except for a mild increase in transaminase values. The liver biopsy disclosed the characteristic lacunar spaces fulfilled with blood. This is an unusual case because it was not associated with any other former or present disease. A review of the pertinent literature was made.

[Androgenic therapy and hepatocellular carcinoma. Report of a case]. / Terapia androgénica y carcinoma hepatocelular. Informe de un caso.

A 65 years old, female patient with acquired aplastic anemia secondary to frequent exposure to hair dye. While on treatment with anabolic steroids hormone became jaundiced and developed hepatomegaly eight months later. During laparotomy the liver was enlarged, hard, with multiple whitish nodules on its surgace but was otherwise normal. Liver biopsy showed hepatocellular carcinoma, there were not cirrhosis niether hemochromatosis. A review of the related literature was done and discussed on the experimental and clinical evidences that suggested that androgens may play same role on the etiology of liver cancer.

[Adenopathies and anticonvulsants: Lymphoma or drug reaction?]. / Adenopatía y anticonvulsivantes: Linfoma o reacción medicamentosa

In this paper the authors present the clinical case of a nine years old girl with adenopathy, fever and important weight loss. 10 months after she begins with diphenidantoin the differential diagnosis was attempted between lymphoma and drug reaction. The authors reviewed the literature pointed out the development of lymphomas in patients on diphenidantoin therapy. They mention the different hipothesis to explain this drug-lymphoma interrelation concluding that there is necessary more studies and experience in future cases to clarify the certain role of the anticonvulsivants in the production of this abnormalities.