Microcantilever sensors coated with doped polyaniline for the detection of water vapor.

In the present work, PANI (polyaniline) emeraldine salt (doped) and base (dedoped) were used as the sensitive layer of a silicon microcantilever, and the mechanical response (deflection) of the bimaterial (coated microcantilever) was investigated under the influence of humidity. PANI in the emeraldine base oxidation state was obtained by interfacial synthesis and was deposited on the microcantilever surface by spin-coating (dedoped). Next, the conducting polymer was doped with 1 M HCl (hydrochloric acid). A four-quadrant AFM head with an integrated laser and a position-sensitive detector (AFM Veeco Dimension V) was used to measure the optical deflection of the coated microcantilever. The deflection of the coated (doped and undoped PANI) and uncoated microcantilever was measured under different humidities (in triplicate) at room pressure and temperature in a closed chamber to evaluate the sensor's sensitivity. The relative humidity (RH) in the chamber was varied from 20% to 70% using dry nitrogen as a carrier gas, which was passed through a bubbler containing water to generate humidity. The results showed that microcantilevers coated with sensitive layers of doped and undoped PANI films were sensitive (12,717 ± 6% and 6,939 ± 8%, respectively) and provided good repeatability (98.6 ± 0.015% and 99 ± 0.01%, respectively) after several cycles of exposure to RH. The microcantilever sensor without a PANI coating (uncoated) was not sensitive to humidity. The strong effect of doping on the sensitivity of the sensor was attributed to an increased adsorption of water molecules dissociated at imine nitrogen centers, which improves the performance of the coated microcantilever sensor. Moreover, microcantilever sensors coated with a sensitive layer provided good results in several cycles of exposure to RH (%).

Doping in poly(o-ethoxyaniline) nanostructured films studied with atomic force spectroscopy (AFS).

The study of intermolecular interactions at interfaces is essential for a number of applications, in addition to the understanding of mechanisms involved in sensing and biosensing with liquid samples. There are, however, only a few methods to probe such interfacial phenomena, one of which is the atomic force spectroscopy (AFS) where the force between an atomic force microscope tip and the sample surface is measured. In this study, we used AFS to estimate adhesion forces for a nanostructured film of poly(o-ethoxyaniline) (POEA) doped with various acids, in measurements performed in air. The adhesion force was lower for POEA doped with inorganic acids, such as HCl and H(2)SO(4), than with organic acids, because the counterions were screened by the ethoxy groups. Significantly, the morphology of POEA both in the film and in solution depends on the doping acid. Using small-angle X-ray scattering (SAXS) we observed that POEA dissolved in a mixture of dimethyl acetamide exhibits a more extended coil-like conformation, with smaller radius of gyration, than for POEA in water, as in the latter POEA solubility is lower. In AFS measurements in a liquid cell, the force curves for a POEA layer displayed an attractive region for pH>or=5 due to van der Waals interactions, with no contribution from a double-layer since POEA was dedoped. In contrast, for pH

Atomic force spectroscopy on poly(o-ethoxyaniline) nanostructured films: sensing nonspecific interactions.

Atomic force spectroscopy (AFS) was used to measure interaction forces between the tip and nanostructured layers of poly(o-ethoxyaniline) (POEA) in pure water and CuSO4 solutions. When the tip approach and retraction were carried out at low speeds, POEA chains could be physisorbed onto the Si3N4 tip via nonspecific interactions. We conjecture that while detaching, POEA chains were stretched and the estimated chain lengths were consistent with the expected values from the measured POEA molecular weight. The effects from POEA doping could be investigated directly by performing AFS measurements in a liquid cell, with the POEA film exposed to liquids of distinct pH values. For pH > or = 6.0, the force curves normally displayed an attractive region for POEA, but at lower pH values-where POEA is protonated-the repulsive double-layer forces dominated. Measurements in the liquid cell could be further exploited to investigate how the film morphology and the force curve are affected when impurities are deliberately introduced in the liquid. The shape of the force curves and the film morphology depended on the concentration of heavy metal in the liquid cell. AFS may therefore be used to study the interaction between film and analyte, with important implications for the understanding of mechanisms governing the sensing ability of taste sensors.

Investigation of sisal fibers by atomic force microscopy: morphological and adhesive characteristics.

Atomic force microscopy (AFM) was used to study the nanoscale surface chemistry and morphological changes caused by chemical treatment of sisal fibers. Scanning Electron Microscopy (SEM) micrographs indicated that sisal in natura (bundle of fibers) is formed by fibers with diameters of approximately 10 microm. AFM images showed that these fibers consist of microfibrils with diameters varying from 250 to 600 nm, which are made up of nanofibrils of ca. 20 nm in diameter. The adhesion force (pull-off force) between the AFM tip and the fibers surface increased after benzylation, pointing to a decrease in the polar groups on the sisal fiber. The adhesion map measured over a scan range of 3 microm was heterogeneous in samples treated with 40% NaOH and the low adhesion sites disappeared after benzylation. Using an established mathematical model, it was possible to evaluate the increase in adhesion work and consequently in the interaction between the AFM tip and sisal fibers. These results indicated that AFM can detect heterogeneity in the wettability of sisal fibers with nanometer resolution and can be applied in the study of fiber-matrix adhesion in polymer composites.

Evaluación de arterias coronarias con tomografía multicorte / Evaluation of coronary arteries with multislice computed tomography

La resonancia magnética (RM) tiene un tremendo potencial para el estudio de la cardiopatía coronaria. Actualmente la RM en cine es considerada el estándar de referencia para la medición de varios parámetros de función ventricular global como los volúmenes ventriculares, fracción de eyección y masa ventricular. En comparación con otras técnicas, la RM presenta menor variabilidad intra e interobservador en la medición de volúmenes ventriculares. Tiene la ventaja de no utilizar radiación ionizante y es un examen independiente del operador. Con RM también es posible analizar la función miocárdica regional visualizando los distintos segmentos del ventrículo izquierdo durante el ciclo cardiaco. Por otra parte, la RM con uso de gadolinio EV es capaz de mostrar las zonas de infarto y reemplazo fibroso con gran exactitud. Cuando se asocia la detección de fibrosis miocárdica con la evaluación del movimiento segmentario de la pared, es posible predecir recuperación contráctil después de la revascularización.

The magnetic resonance (MR) is a technique in constant evolution for evaluation of coronary artery disease. Cine-MR techniques are currently the main imaging tools for measurement of several parameters of global ventricular function such as ventricular volumes, ejection fraction and the ventricular mass. MR has shown less variability inter-observer than other techniques for measurement of ventricular volumes; it does not use radiation and is operator independent. Regional contractile function is also well assessed by cine-MR with visual inspection of wall motion and thickening for the left ventricle. After gadolinium administration, MR can assess myocardial infarct and replacement fibrosis. When the detection of myocardial fibrosis is associated with segmental wall motion analysis by cine images, it can be possible to predict improvement recover of contractile function after revascularization.

Rol de la resonancia magnética en cardiopatía isquémica / Role of magnetic resonance in ischemic cardiopaty

La resonancia magnética (RM) tiene un tremendo potencial para el estudio de la cardiopatía coronaria. Actualmente la RM en cine es considerada el estándar de referencia para la medición de varios parámetros de función ventricular global como los volúmenes ventriculares, fracción de eyección y masa ventricular. En comparación con otras técnicas, la RM presenta menor variabilidad intra e interobservador en la medición de volúmenes ventriculares. Tiene la ventaja de no utilizar radiación ionizante y es un examen independiente del operador. Con RM también es posible analizar la función miocárdica regional visualizando los distintos segmentos del ventrículo izquierdo durante el ciclo cardiaco. Por otra parte, la RM con uso de gadolinio EV es capaz de mostrar las zonas de infarto y reemplazo fibroso con gran exactitud. Cuando se asocia la detección de fibrosis miocárdica con la evaluación del movimiento segmentario de la pared, es posible predecir recuperación contráctil después de la revascularización.

The magnetic resonance (MR) is a technique in constant evolution for evaluation of coronary artery disease. Cine-MR techniques are currently the main imaging tools for measurement of several parameters of global ventricular function such as ventricular volumes, ejection fraction and the ventricular mass. MR has shown less variability inter-observer than other techniques for measurement of ventricular volumes; it does not use radiation and is operator independent. Regional contractile function is also well assessed by cine-MR with visual inspection of wall motion and thickening for the left ventricle. After gadolinium administration, MR can assess myocardial infarct and replacement fibrosis. When the detection of myocardial fibrosis is associated with segmental wall motion analysis by cine images, it can be possible to predict improvement recover of contractile function after revascularization.

Identification of toxigenic Vibrio cholerae from the Argentine outbreak by PCR for ctx A1 and ctx A2-B.

A polymerase chain reaction (PCR) to detect a region of the A1 cholera toxin gene was applied to the identification of 43 Vibrio cholerae strains isolated from the recent outbreak in Argentina. A good correlation was observed between the GM1-enzyme-linked immunosorbent assay (GM1-ELISA) to detect the B subunit of the enterotoxin and PCR. However, a V. cholerae non-01 strain that was negative by the ELISA test, was positive by the PCR assay for the A1 region. A second PCR test to detect the A2-B coding region was developed to solve this case. We propose that routine detection of toxigenic V. cholerae by PCR should include analysis of A2-B coding region or the whole cholera toxin operon.

The phenomenon of stunting as the core problem in a community based, multisectoral project in northern Peru.

In a nutrition and health project in the countryside of the Highlands of Northern Peru, an anthropometric study was conducted on 306 pre-school children. The results showed a primarily stunted, but not wasted, population in which the process of stunting started after the first 6 months of life, with a modest linear progression over all age-groups. However, the rates of stunted children increased dramatically between the ages of 6 months and 2 years. Evidence with regard to the social dimension of the problem of becoming stunted was revealed by the significant differences between rates of stunted children according to the degree of community participation in their home villages.