Conductance of partially disordered graphene: crossover from temperature-dependent to field-dependent variable-range hopping.

We report an analysis of low-temperature measurements of the conductance of partially disordered reduced graphene oxide, finding that the data follow a simple crossover scenario. At room temperature, the conductance is dominated by two-dimensional (2D) electric field-assisted, thermally driven (Pollak-Riess) variable-range hopping (VRH) through highly disordered regions. However, at lower temperatures T, we find a smooth crossover to follow the exp(-E0/E)(1/3) field-driven (Shklovskii) 2D VRH conductance behaviour when the electric field E exceeds a specific crossover value EC(T)(2D) = (EaE(1/3)0 /3)(3/4) determined by the scale factors E0 and Ea for the high-field and intermediate-field regimes respectively. Our crossover scenario also accounts well for experimental data reported by other authors for three-dimensional disordered carbon networks, suggesting wide applicability.

Taquicardia de QRS ancho en mujer joven con síndrome coronario agudo secundario a disección coronaria espontánea / Wide QRS tachycardia in a young woman with acute coronary syndrome secondary to spontaneous coronary dissection

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Trombosis protésica tricúspide sometida a fibrinolisis con control ecocardiográfico seriado / Tricuspid prosthetic trombosis treated with fibronolisis with sequential echocardiographic control

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Conductance oscillations in squashed carbon nanotubes.

We report measurements on the radial electromechanical properties of single walled carbon nanotubes. By measuring the conductance of the nanotube, we show that a gap is opened while squashing the nanotubes and that during the deformation stages we observe at least two open-close cycles of the gap. We employ a novel experimental setup where an atomic force microscope tip is used both as an electrode and to induce radial deformations. In contrast with prior experiments reported, this technique allows direct probing of the local electronic structure of carbon nanotubes as they are radially deformed.

Miocardiopatía chagásica en España: un diagnóstico a tener en cuenta / Chagasic cardiomyopathy in Spain: a diagnosis to bear in mind

La enfermedad de Chagas es un importante problema de salud en Latinoamérica y una de las causas secundarias de miocardiopatía dilatada. La miocardiopatía chagásica crónica es su consecuencia más devastadora y principal causa de mortalidad. Las migraciones de poblaciones rurales hacia las ciudades y al extranjero han modificado su epidemiología clásica, haciendo posible su presencia en Estados Unidos y Europa. Presentamos el caso de un paciente que ingresó en situación de insuficiencia cardiaca congestiva y que fue diagnosticado de miocardiopatía chagásica crónica. Hasta donde conocemos, es el primer caso en la bibliografía de una miocardiopatía dilatada de etiología chagásica en España

Chagas’ disease is an important public health problem in Latin America and one of the specific causes of dilated cardiomyopathy. Chronic chagasic cardiomyopathy is the worse result of this disease and its main cause of mortality. Rural migrations from endemic to nonendemic countries make possible observing affected patients in United States and Europe. We report the case of a patient with congestive heart failure who was diagnosed with chronic chagasic cardiomyopathy. This is the first case of chagasic dilated cardiomyopathy in Spain

[Mitral prosthetic valve and presyncope]. / Prótesis mecánica mitral y cuadros presincopales.

The incidence of mitral prosthetic valve thrombosis is low and generally dependent on low levels of anticoagulation. The clinical presentation is highly variable and ranges from asymptomatic patient though to arterial embolism or hemodynamic symptoms of valve obstruction. We report a case of a patient with presyncope and prosthetic mitral valve dysfunction with intermittent flow obstruction.

Tuning the conductance of single-walled carbon nanotubes by ion irradiation in the Anderson localization regime.

Carbon nanotubes are a good realization of one-dimensional crystals where basic science and potential nanodevice applications merge. Defects are known to modify the electrical resistance of carbon nanotubes; they can be present in as-grown carbon nanotubes, but controlling their density externally opens a path towards the tuning of the electronic characteristics of the nanotube. In this work, consecutive Ar+ irradiation doses are applied to single-walled nanotubes (SWNTs) producing a uniform density of defects. After each dose, the room-temperature resistance versus SWNT length (R(L)) along the nanotube is measured. Our data show an exponential dependence of R(L) indicating that the system is within the strong Anderson localization regime. Theoretical simulations demonstrate that mainly di-vacancies contribute to the resistance increase induced by irradiation, and that just a 0.03% of di-vacancies produces an increase of three orders of magnitude in the resistance of a SWNT of 400 nm length.

Prótesis mecánica mitral y cuadros presincopales / Mitral prosthetic valve and presyncope

La trombosis protésica mitral es una entidad poco frecuente, cuya incidencia se relaciona habitualmente con niveles bajos de anticoagulación. La presentación clínica varía desde pacientes asintomáticos, embolismo arterial o compromiso hemodinámico por obstrucción. Presentamos el caso de una disfunción protésica mitral con cuadros presincopales por obstrucción intermitente al flujo

The incidence of mitral prosthetic valve thrombosis is low and generally dependent on low levels of anticoagulation. The clinical presentation is highly variable and range from asintomatic patient though to arterial embolism or hemodinamic symptoms of valve obstruction. We report a case of a patient with presyncope and prosthetic mitral valve dysfunction with intermitent flow obstruction

[Chagasic cardiomyopathy in Spain: a diagnosis to bear in mind]. / Miocardiopatía chagásica en España: un diagnóstico a tener en cuenta.

Chagas' disease is an important public health problem in Latin America and one of the specific causes of dilated cardiomyopathy. Chronic chagasic cardiomyopathy is the worse result of this disease and its main cause of mortality. Rural migrations from endemic to nonendemic countries make possible observing affected patients in United States and Europe. We report the case of a patient with congestive heart failure who was diagnosed with chronic chagasic cardiomyopathy. This is the first case of chagasic dilated cardiomyopathy in Spain.

Ordered self-assembled monolayers of Peptide nucleic acids with DNA recognition capability.

We report on the formation of ordered self-assembled monolayers (SAMs) of single-stranded peptide nucleic acids (ssPNA). In spite of their remarkable length (7 nm) thiolated PNAs assemble standing up on gold surfaces similarly to the SAMs of short alkanethiols. SAMs of ssPNA recognize complementary nucleic acids, acting as specific biosensors that discriminate even a point mutation in target ssDNA. These results are obtained by surface characterization techniques that avoid labeling of the target molecule: x-ray photoemission, x-ray absorption and atomic force microscopy.

Contactless experiments on individual DNA molecules show no evidence for molecular wire behavior.

A fundamental requirement for a molecule to be considered a molecular wire (MW) is the ability to transport electrical charge with a reasonably low resistance. We have carried out two experiments that measure first, the charge transfer from an electrode to the molecule, and second, the dielectric response of the MW. The latter experiment requires no contacts to either end of the molecule. From our experiments we conclude that adsorbed individual DNA molecules have a resistivity similar to mica, glass, and silicon oxide substrates. Therefore adsorbed DNA is not a conductor, and it should not be considered as a viable candidate for MW applications. Parallel studies on other nanowires, including single-walled carbon nanotubes, showed conductivity as expected.

Nonlinear resistance versus length in single-walled carbon nanotubes.

In this work fundamental properties of the electrical transport of single-walled carbon nanotubes as a function of their length are investigated. For this purpose, we have developed a new technique that allows us to characterize electronic transport properties of single-walled carbon nanotubes by probing them at different spots. This technique uses scanning force microscopy to make mechanical and electrical nanocontacts at any selected spot of a given image. We have applied this technique to molecules with high intrinsic resistance. The results show a nonlinear resistance vs distance behavior as the nanotube is probed along its length. This is an indication of elastic electronic transport in one-dimensional systems.