Enhancement of the CO2 Sensing/Capture through High Cationic Charge in M-ZrO2 (Li+, Mg2+, or Co3+): Experimental and Theoretical Studies.

The capture and storage of CO2 are of growing interest in atmospheric science since greenhouse gas emission has to be reduced considerably in the near future. The present paper deals with the doping of cations on ZrO2, i.e., M-ZrO2 (M = Li+, Mg2+, or Co3+), defecting the crystalline planes for the adsorption of carbon dioxide. The samples were prepared by the sol-gel method and characterized completely by different analytical methods. The deposition of metal ions on ZrO2 (whose crystalline phases: monoclinic and tetragonal are transformed into a single-phase such as tetragonal for LiZrO2 and cubic for MgZrO2 or CoZrO2) shows a complete disappearance of the XRD monoclinic signal, and it is consistent with HRTEM lattice fringes: 2.957 nm for ZrO2 (101, tetragonal/monoclinic), 3.018 nm for tetragonal LiZrO2, 2.940 nm for cubic MgZrO2, and 1.526 nm for cubic CoZrO2. The samples are thermally stable, resulting an average size of ∼5.0-15 nm. The surface of LiZrO2 creates the oxygen deficiency, while for Mg2+ (0.089 nm), since the size of the atom is relatively greater than that of Zr4+ (0.084 nm), the replacement of Zr4+ by Mg2+ in sublattice is difficult; thus, a decrease of the lattice constant was noticed. Since the high band gap energy (ΔE > 5.0 eV) is suitable for CO2 adsorption, the samples were employed for the selective detection/capture of CO2 by using electrochemical impedance spectroscopy (EIS) and direct current resistance (DCR), showing that CoZrO2 is capable of CO2 capture about 75%. If M+ ions are deposited within the ZrO2 matrix, then the charge imbalance allows CO2 to interact with the oxygen species to form CO32- which produces a high resistance (21.04 × 106 (Ω, Ohm)). The adsorption of CO2 with the samples was also theoretically studied showing that the interaction of CO2 with MgZrO2 and CoZrO2 is more feasible than with LiZrO2, subscribing to the experimental data. The temperature effect (273 to 573 K) for the interaction of CO2 with CoZrO2 was also studied by the docking method and observed the cubic structure is more stable at high temperatures as compared to the monoclinic geometry. Thus, CO2 would preferably interact with ZrO2c (ERS = -19.29 kJ/mol) than for ZrO2m (22.4 J/mmol (ZrO2c = cubic; ZrO2m = monoclinic).

Gerbode defect or left ventricular to right atrial shunt. Case report and literature review / Defecto tipo Gerbode o comunicación entre el ventrículo izquierdo y la aurícula derecha. Reporte de un caso y revisión de la literatura

Gerbode defect is a communication from the left ventricle to right atrium and it could be categorized in congenital or acquired. It is a rare condition that can represent as much as 0.08% of all septal defects. Those acquired defects can be associated to endocarditis and after valvular surgery. The objective is to report a case of Gerbode atria-ventricular septal defect in Instituto Nacional de Cardiología Ignacio Chavez. The present case is about a 36 years old male patient with a typical presentation of mitral regurgitation, the echocardiogram reports a perforation in the anterior mitral leaflet and a Gerbode ventricular septal defect, that represents the heterogeneity of the clinical presentation of this pathology, also we show the findings in imaging studies that contributed to diagnosis and its surgical resolution. Gerbode defect is an uncommon pathology, many times associated to other cardiovascular entity, difficulting diagnose. It requires image studies and a complete presurgical evaluation in order to achieve opportune diagnosis.

El defecto tipo Gerbode es una comunicación del ventrículo izquierdo a la aurícula derecha, que puede clasificarse como congénita o adquirida. Es una condición rara que puede representar hasta el 0.08% de los defectos septales congénitos. Los defectos adquiridos pueden asociarse a endocarditis y presentarse también posterior a cambios valvulares. El objetivo es reportar un caso de comunicación interventricular de Gerbode en el Instituto Nacional de Cardiología. Paciente varón, de 36 años, con presentación clínica típica de insuficiencia mitral, ecocardiografía con hallazgo de rotura de la valva anterior de la válvula mitral y comunicación interventricular tipo Gerbode. Se ponen de manifiesto la heterogeneidad clínica con la que se presenta esta patología y los hallazgos de imagen que contribuyen al diagnóstico y su resolución quirúrgica. La comunicación interventricular tipo Gerbode es una patología infrecuente, muchas veces asociada a otra afección cardiovascular, lo que la hace de difícil diagnóstico. Se requieren estudios de imagen y una evaluación preoperatoria completa para su detección oportuna.

Synthesis of p-n Heterojunctions via Aerosol Assisted Chemical Vapor Deposition to Enhance the Gas Sensing Properties of Tungsten Trioxide Nanowires: A Mini-Review.

Here we discuss the aerosol-assisted synthesis of p-n heterojunction metal oxides and we report their gas sensing properties via a short review of the latest results achieved. In particular, we show that the decoration of one-dimensional tungsten oxide (n-type) with nanoparticles of different p-type oxides from transition metals such as Ni, Co or Ir enables achieving a chemical and electronic sensitization of the resulting hybrid metal oxide materials. This leads to remarkable differences in responsiveness to gases, showing that, to some extent, a selective detection of some major pollutant gases (NO2, H2S or NH3) would be possible. Results are critically reviewed, shortcomings are identified and future research directions are given.

Severe mitral valve regurgitation secondary to Libman-Sacks endocarditis.

Although uncommon, Libman-Sack endocarditis is the most characteristic cardiac manifestation of Systemic Lupus Erythematosus (SLE). It forms vegetations made of inflammatory tissue on the cardiac valves, leading them to malfunction. Here we present a case of a young woman who presented with severe mitral valve regurgitation in need for a valve replacement. Integral evaluation of the patient revealed the diagnosis of SLE, which was aggressively treated in an outpatient setting with immunosuppressive therapy. Only after achieving medical stabilization of the underlying disease, she was able to undergo surgical mitral valve replacement. After the surgery, the patient no longer suffered from mitral regurgitation, and with a mechanical prosthesis in place, the risk of Libman-Sacks endocarditis recurrence is thought to be minimal.

Flexible Gas Sensors Employing Octahedral Indium Oxide Films.

Indium oxide octahedral nanopowders were obtained from an ionic precursor compound after an oxidation process conducted under a low-oxygen atmosphere. This method was found to produce contamination-free indium oxide nanomaterial with very similar morphological and crystalline properties to the one produced by vapor-phase transport, but at significantly lower temperatures and higher yield. The as-synthesized indium oxide was mixed to an organic vehicle and microdrop deposited to form a film bridging the interdigitated silver electrodes patterned on top of a flexible, polyimide (Kapton®), substrate. The gas sensing properties of the flexible chemoresistors towards ammonia vapors, hydrogen, and nitrogen dioxide were investigated. It was found that these sensors were remarkably sensitive to nitrogen dioxide at a low operating temperature of 150 °C. These results are consistent with the performance of vapor-phase transport synthesized indium oxide octahedra sensors on rigid, ceramic substrates. Therefore, the results presented here pave the way for the mass production of inexpensive gas sensors onto flexible substrates via additive manufacturing.

Using a Second Order Sigma-Delta Control to Improve the Performance of Metal-Oxide Gas Sensors.

Controls of surface potential have been proposed to accelerate the time response of MOX gas sensors. These controls use temperature modulations and a feedback loop based on first-order sigma-delta modulators to keep constant the surface potential. Changes in the surrounding gases, therefore, must be compensated by average temperature produced by the control loop, which is the new output signal. The purpose of this paper is to present a second order sigma-delta control of the surface potential for gas sensors. With this new control strategy, it is possible to obtain a second order zero of the quantization noise in the output signal. This provides a less noisy control of the surface potential, while at the same time some undesired effects of first order modulators, such as the presence of plateaus, are avoided. Experiments proving these performance improvements are presented using a gas sensor made of tungsten oxide nanowires. Plateau avoidance and second order noise shaping is shown with ethanol measurements.

Gas Sensing with Iridium Oxide Nanoparticle Decorated Carbon Nanotubes.

The properties of multi-wall carbon nanotubes decorated with iridium oxide nanoparticles (IrOx-MWCNTs) are studied to detect harmful gases such as nitrogen dioxide and ammonia. IrOx nanoparticles were synthetized using a two-step method, based on a hydrolysis and acid condensation growth mechanism. The metal oxide nanoparticles obtained were employed for decorating the sidewalls of carbon nanotubes. Iridium-oxide nanoparticle decorated carbon nanotube material showed higher and more stable responses towards NH3 and NO2 than bare carbon nanotubes under different experimental conditions, establishing the optimal operating temperatures and estimating the limits of detection and quantification. Furthermore, the nanomaterials employed were studied using different morphological and compositional characterization techniques and a gas sensing mechanism is proposed.