Zamora Víctor

University of Extremadura | UNEX

Graphene nanoplatelet (GNP)–reinforced TiB2 + SiC composites were fabricated by reactive spark plasma sintering (SPS) from a TiC–B4C–SiC powder mixture with equal‐volume percentages, optimizing their SPS temperature and evaluating their unlubricated sliding wear against diamond. First, it is shown that during the heating ramp of the SPS cycle, TiC...

B4C–SiC–TiB2 ceramic composites with equal volume fractions of the three phases (i.e., 1B4C–1SiC–1TiB2) were fabricated by solid-state spark-plasma sintering (SPS) from commercially available B4C, SiC, and TiB2 powders, first optimizing their densification temperature and then investigating for the first time the unlubricated sliding wear of the op...

Two fully-dense B4C–SiC composites were fabricated by spark-plasma sintering (SPS) from B4C+Si powders, one superhard (i.e., ~28.7(8) GPa) with abundant SiC by SPS of B4C+20vol.%Si at 1400°C and the other ultrahard (i.e., ~35.1(4) GPa) with little SiC by SPS of B4C+4.28vol.%Si at 1800°C, and their unlubricated sliding wear was investigated and comp...

The feasibility of fabricating novel boron carbide–silicon carbide composites by spark-plasma sintering (SPS) of B4C+Si powder mixtures at only 1400°C was investigated. First, it is shown that B4C can be fully densified at 1400°C if ~20 vol.% Si aids are used, leading to bi-particulate composites constituted by boron carbide (major phase) and SiC (...

Metformin is the first choice drug for the treatment of type 2 diabetes due to positive results in reducing hyperglycaemia and insulin resistance. However, diabetic patients have higher risk of ventricular arrhythmia and sudden cardiac death, and metformin failed to reduce ventricular arrhythmia in clinical trials. In order to explore the mechanism...

The feasibility was investigated of fabricating super wear-resistant hard B4C composites by spark plasma sintering (SPS) at ultra-low temperature (i.e., 1400 °C) using very high proportions of MoSi2 aids (i.e., 35–50 vol.%). It is shown that with 40 vol.% MoSi2 aids already sufficient Si transient liquid phase is formed in situ during SPS (by the r...

In this work, we show that valve-based bioprinting induces no measurable detrimental effects on human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The aim of the current study was three-fold: first, to assess the response of hiPSC-CMs to several hydrogel formulations by measuring electrophysiological function; second, to custom...

The sliding-wear behaviour of a newly-developed fine-grained ZrC-16.693 vol%Co cemented carbide was investigated, and critically compared under frictional contact in four media (i.e., dry wear, and wet wear in neutral water (pH∼7.1) and in highly acidic (pH∼1.1) and alkaline (pH∼13.7) aqueous solutions). It is shown that, under the testing conditio...

Seeking to fabricate B4C composites that are even more superhard (>30 GPa) at lower cost, B4C was transient liquid-phase assisted spark-plasma-sintered, somewhat counterintuitively, at lower temperature (<1750 °C) and with greater MoSi2 aid content (>15 vol.%) than ever before. It was found that just 20 vol.% MoSi2 aid enables the full densificatio...

An ultrahard ZrC-Co cemented carbide was fabricated by high-energy ball-milling (HEBM) of micrometric starting powders and spark plasma sintering (SPS), whose ultrafine-grained microstructure makes it comparatively more sliding-wear resistant. First, it is shown that prolonged HEBM activates mechanically the ZrC+Co powder mixture, enhancing markedl...

Abstract.We present a study on algebraic and geometric proofs of the Pythagorean The-orem, for Secondary Education, using free software of dynamic geometry. The categoriza-tion of the demonstrations offers the teacher a useful sample as a tool for the selection ofthe didactic resources necessary for the teaching and learning of this theorem. The se...

We live in a three-dimensional world in which all activities take place throughout our lives, so mastering this space is essential. The need to orient ourselves requires a good education in spatial orientation from the early school years, which in many cases does not occur. For this reason, we present a methodological proposal that we have develope...

With the motivation of developing B4C composites with superior wear resistance for tribological applications, an ultrafine-grained (∼200−300 nm) B4C composite was fabricated, characterized microstructurally, and tested mechanically and tribologically. First, a well-dispersed powder mixture of B4C nanopowders (∼40 nm) with coarse Ti-Al powders (∼38...

The densifiability by spark plasma sintering (SPS) and the dry sliding-wear behaviour of novel cemented carbides based on micrometre-sized ZrC with 16.7 vol.% Co binder (ZrC-Co), compositionally equivalent to the typical WC-10 wt.%Co but with ZrC in place of WC, were investigated. Firstly, detailed analysis of both the densification and the shrinka...

RESUMEN La Música es un recurso para la enseñanza y el aprendizaje de los contenidos matemáticos para la etapa de Educación Infantil (E.I.) y los primeros cursos de Educación Primaria (E.P.). En este estudio se ha realizado una exhaustiva búsqueda, selección y categorización de canciones que son una potente herramienta para facilitar el trabajo de...

Resumen: El objetivo principal de este artículo es presentar una serie de actividades que ayuden a los profesores a enseñar el Teorema de Pitágoras de una forma activa mediante la metodología de resolución de problemas. Se hace una aproximación al Teorema de Pitágoras a través de actividades en el laboratorio donde las construcciones, diseños y ref...

Since cardiotoxicity is one of the leading causes of drug failure and attrition, the design of new protocols and technologies to assess pro-arrhythmic risks on cardiac cells is in continuous development by different laboratories. Current methodologies use electrical, intracellular Ca or contractility assays to evaluate cardiotoxicity. Increasingly,...

Aims: Endurance training improves aerobic fitness and cardiac function in individuals with heart failure. However, the underlying mechanisms are not well characterized. Exercise training could therefore act as a tool to discover novel targets for heart failure treatment. We aimed to associate changes in Ca2+ handling and electrophysiology with mic...

The aim is to provide primary school teachers or future teachers with sufficient tools and materials to be able to develop the curriculum without the need to consider the textbook as the only element of teaching-learning. We apply an active method based on experience, participation through particular cases that are suggested, the corresponding gene...

A wide suite of powder mixtures of ZrB2 with five different additions of transition metal disilicides (MeSi2; 5, 17.5, or 30 vol% MoSi2; 17.5 vol% TaSi2; or 17.5 vol% ZrSi2) were prepared by high-energy ball-milling (HEBM) for different times, and their optimal densification temperatures were evaluated by dilatometric spark-plasma-sintering (SPS) t...

Este grupo de investigación, Ciberdidact, viene asistiendo a la mayoría de los congresos Ibero-Americano de Investigación Cualitativa reúne a representantes de la comunidad científica internacional, que trabajan en este área de investigación. En ellos tiene una participación muy activa pues sus miembros participan tanto en los comités científicos d...

Introduction: Voltage-sensitive optical (VSO) sensors offer a minimally invasive method to study the time course of repolarization of the cardiac action potential (AP). This Comprehensive in vitro Proarrhythmia Assay (CiPA) cross-platform study investigates protocol design and measurement variability of VSO sensors for preclinical cardiac electrop...

El presente capítulo trata de exponer las metodologías de investigación utilizadas en los trabajos de investigación del Grupo Ciberdidact, ilustrando las mismas con ejemplos de investigaciones realizadas en distintos campos (Matemáticas, Ingeniería, Educación, Sociología, etc.). Se trata de mostrar las bases teóricas que fundamentan las investigaci...

Resumen: El Teorema de Pitágoras tiene un papel fundamental en el desarrollo de las matemáticas. Dentro de sus muchas aplicaciones intentamos resaltar el interés didáctico de dicha proposición en la enseñanza y aprendizaje de las Matemáticas y en particular de la Geometría. Se aborda su estudio desde el punto de vista histórico y su demostración co...

Human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) have applications in disease modeling, cell therapy, drug screening and personalized medicine. Computational models can be used to interpret experimental findings in iPSC-CMs, provide mechanistic insights, and translate these findings to adult cardiomyocyte (CM) electrophysiology...

Introduction: Human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) are emerging as new and human-relevant source in vitro model for cardiac safety assessment that allow us to investigate a set of 20 reference drugs for predicting cardiac arrhythmogenic liability using optical action potential (oAP) assay. Methods: Here, we descr...

BACKGROUND: Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) hold promise for assessment of drug-induced arrhythmias and are being considered for use under the Comprehensive in Vitro Proarrhythmia Assay (CiPA). METHODS AND RESULTS: We studied the effects of 26 drugs and 3 drug combinations on two commercially available iPSC-CM types u...

Background: Angiotensin-(1-9) [Ang-(1-9)] is a novel peptide of the counter-regulatory axis of the renin-angiotensin-aldosterone system previously demonstrated to have therapeutic potential in hypertensive cardiomyopathy when administered via osmotic mini-pump. Here, we investigate whether gene transfer of Ang-(1-9) is cardioprotective in a murine...

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) raise many possibilities for cardiac research but they exhibit an immature phenotype, which influences experimental outcomes. The aim of our research is to investigate the effects of a topographical gradient substrate on the morphology and function of commercially available hiPSC...

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) and higher throughput platforms have emerged as potential tools to advance cardiac drug safety screening. This study evaluated the use of high bandwidth photometry applied to voltage-sensitive fluorescent dyes (VSDs) to assess drug-induced changes in action potential characterist...

Living tissues can be constructed in vitro by 3D bioprinting of cells held in hydrogel solutions which are then cross-linked to form 3D geometries analogous to in vivo tissues. Signalling from cell- To-cell and microenvironment- To-cell interaction both effect cell behaviour and life cycle. Artificial cell containing constructs must mimic a suffici...

Background: Drug-induced arrhythmias have been a leading reason for withdrawing drugs from the market and abandoning the development of new drugs. For the past decade FDA has required new drugs to be tested for block of the hERG potassium channel and QT interval prolongation. While these requirements have prevented arrhythmia-related drug recalls,...

The effect of a 2 wt% addition of particulate graphite on the spark-plasma sintering (SPS) kinetics of both ZrB2 and ZrB2+30 vol% SiC was investigated using to that end two broad sets of powder mixtures prepared by high-energy co-ball-milling. It was observed that the particulate graphite addition enhances the SPS kinetics of both systems, and it w...

The spark-plasma sintering (SPS) kinetics of ZrB2–SiC powder mixtures was investigated as a function of the degree of high-energy co-ball-milling and of the SiC content (5, 17.5, or 30 vol%). As in ZrB2 without SiC, it was found that the crystal size refinement induced by the continued milling progressively enhances the SPS kinetics of ZrB2–SiC, ag...

We have explored the feasibility of reducing the spark-plasma-sintering (SPS) temperature of additive-free ZrB2 ultra-high-temperature ceramics (UHTCs) via crystal size refinement of the starting powder down to the low nanoscale. We found that under otherwise the same SPS conditions (75 MPa pressure, and 100 °C/min heating ramp) nanoscale ZrB2 can...

Oxide impurities in ZrB2 powders promote coarsening, resulting in lower sinterability. Given its importance for sintering, we studied the oxidation of ZrB2 powders during high-energy ball-milling (the form of milling able to refine ZrB2 powders to the nanoscale) with the aid of various characterization techniques, namely fusion in inert gas, X-ray...

The in situ formation is reported of a fine-grained ZrB2 ultra-high-temperature ceramic (UHTC) containing evenly distributed ZrO2 of uniform size located at triple joints and grain boundaries of the ZrB2 grains, discovered during the spark-plasma sintering of ZrB2 powders subjected to high-energy ball-milling in air. It is found that this type of m...

The crystal-size dependence of the spark-plasma-sintering (SPS) kinetics of ZrB2 ultra-high-temperature ceramics (UHTCs) was investigated. It was found that refining the starting powder enhances the SPS kinetics, reducing the onset temperatures of sintering and of the intermediate and final sintering regimes, as well as promoting a greater maximum...

The effect of SiC addition (5, 17.5, and 30vol.%) on the high-energy ball-milling (HEBM) behaviour of ZrB2 is investigated. It was found that the presence of SiC during HEBM did not alter ZrB2 refinement mechanism of repeated brittle fracture followed by cold-welding, thereby leading to the formation of agglomerates consisting of primary nano-parti...

The contact mechanical properties of the ZrB2–30% SiC ultra-high-temperature ceramic (UHTC) were studied from room temperature up to 800°C in air, by combining Hertzian indentation tests with finite element modeling. It was found that the elastic modulus and yield stress decrease with increasing temperature, especially above 600°C. It was also foun...