Diffusion-driven superplasticity in ceramics: Modeling and comparison with available data

The discovery of superplasticity in ceramics polycrystals led to debates about whether or not earlier models developed for metallic polycrystals can apply to these systems. In particular, all existing models require some mobility of lattice or grain-boundary dislocations whereas such activity is not observed in most ceramic systems. A model is presented that accounts for the occurrence of superplasticity in the absence of dislocation motion. It is based on a mechanism of grain-boundary sliding by pure-shear motion under stationary conditions, which is accommodated by lattice or grain-boundary diffusion. The prediction of this model regarding the temperature dependences of the stress exponent and of the effective activation energy are found in agreement with experimental results and literature data on five ceramic systems where dislocation activity could not be recorded: -SiAlON polycrystals, Al-doped SiC polycrystals, nanocrystalline MgO, yttria-tetragonal zirconia polycrystals, and alumina ceramics polycrystal

El impacto de la educación temprana en el mediano plazo

To the best of our knowledge this is the first study to evaluate the medium term impact of early childcare (0-2 years old child). This is carried out by the estimation of efective (actual) marginal returns of early childcare in a non observable heterogeneity context. We estimate the impact on cognitive tests (SIMCE) (Math and Lenguage) taken in the 4th grade of elementary school. Results suggest that early childcare attendance has a nearly zero effect on average population but a negative e¤ect on those who were treated (those who attended all levels of childcare (early, midium, Pre Kinder and Kinder) relative to those non treated (those who attended the latter three levels but not the former). The distribution of the Marginal Treatmente Effect and the estimated parameters of interest suggest that the zero-negative effect would be related to the quality of early childcare

El impacto de la educación temprana en el mediano plazo

To the best of our knowledge this is the first study to evaluate the medium term impact of early childcare (0-2 years old child). This is carried out by the estimation of efective (actual) marginal returns of early childcare in a non observable heterogeneity context. We estimate the impact on cognitive tests (SIMCE) (Math and Lenguage) taken in the 4th grade of elementary school. Results suggest that early childcare attendance has a nearly zero effect on average population but a negative e¤ect on those who were treated (those who attended all levels of childcare (early, midium, Pre Kinder and Kinder) relative to those non treated (those who attended the latter three levels but not the former). The distribution of the Marginal Treatmente Effect and the estimated parameters of interest suggest that the zero-negative effect would be related to the quality of early childcare

Genetic Testing in Children with Epilepsy: Report of a Single-Center Experience

Background: Retrospective observational study to determine diagnostic yield and utility of genetic testing in children with epilepsy attending the Epilepsy Clinic at Children\u27s Hospital, London, Ontario, Canada. Methods: Children (birth-18 years) with epilepsy, who were seen in a 10-year period (January 1, 2008-March 31, 2018), were selected using defined inclusion criteria and by combining clinic datasets and laboratory records. Results: In total, 105 children (52.38% male and 47.61% female) with a variety of seizures were included in the analysis. Developmental delay was documented in the majority (83; 79.04%). Overall, a genetic diagnosis was established in 24 (22.85%) children. The diagnostic yield was highest for whole-exome sequencing (WES), at 35.71%. The yield from microarray was 8.33%. Yields of single-gene testing (18.60%) and targeted multigene panel testing (19.23%) were very similar. Several likely pathogenic and pathogenic variants not previously reported were identified and categorized using ACMG criteria. All diagnosed patients underwent a review of anti-seizure medication management and received counseling on natural history of their disease, possible complications, recurrence risks, and possibilities of preimplantation or prenatal genetic diagnosis. Conclusions: Our study confirms the multiple benefits of detecting a genetic etiology in children with epilepsy. Similar yields in single versus multigene testing underscore the importance of accurate clinical phenotyping. Patients with epilepsy and their caregivers in Ontario would undoubtedly benefit from repatriation of multigene panels and WES to the province

Impact of microwave processing on porcelain microstructure

[EN] Microstructural evolution on sintering of porcelain powder compacts using microwave radiation was compared with that in conventionally sintered samples. Using microwaves sintering temperature was reduced by similar to 75 degrees C and dwell time from 15 min to 5 min while retaining comparable physical properties i.e. apparent bulk density, water absorption to conventionally sintered porcelain. Porcelain powder absorbed microwave energy above 600 degrees C due to a rapid increase in its loss tangent. Mullite and glass were used as indicators of the microwave effect: mullite produced using microwaves had a nanofibre morphology with high aspect ratio (similar to 32 +/- 3:1) believed associated with a vapour-liquid-solid (VLS) formation mechanism not previously reported. Microwaves also produced mullite with different chemistry having similar to 63 mol% alumina content compared to similar to 60 mol% alumina in conventional sintered porcelain. This was likely due to accelerated Al+3 diffusion in mullite under microwave radiation. Liquid glass was observed to form at relatively low temperature (similar to 900-1000 degrees C) using microwaves when compared to conventional sintering which promoted the porcelains ability to absorb them.W. Lerdprom acknowledges Imperial College London funding no. MMRE_PG54200. A. Borrell acknowledges the Spanish Ministry of Economy and Competitiveness for her Juan de la Cierva-Incorporacion contract (IJCI-2014-49839).Lerdprom, W.; Zapata-Solvas, E.; Jayaseelan, DD.; Borrell Tomás, MA.; Salvador Moya, MD.; Lee, WE. (2017). Impact of microwave processing on porcelain microstructure. Ceramics International. 43(16):13765-13771. https://doi.org/10.1016/j.ceramint.2017.07.090S1376513771431

Synthesis and sintering of ZrC1-x powders with variable stoichiometry (0

ZrC is a potential candidate for high temperature nuclear applications, such as nuclear fuel cladding on TRISO fuels and as a coating on conventional clad in the third and fourth generation of fission nuclear power plants due to its refractoriness, chemical stability, high thermal conductivity, irradiation tolerance as well as low activation under neutron irradiation [1]. The variation in C content in ZrC1-x is known to produce a significant variation in physical properties, such as thermal and electrical conductivity over the range x=0.0-0.2, and a non-monotonic change in lattice parameter that peaks in the same range of stoichiometry (figure 1.) We have investigated the evolution of the distribution of C vacancies with the C content. Usually, ZrC is prepared from ZrO2 followed by a carbothermal reduction process at high temperatures under an inert atmosphere. Recently, a work in our group showed that ZrC1-x for stoichiometry x\u3c0.2 have a non-negligible amount of O, and could be therefore considered oxy-carbides rather than carbides [2]. This may indicate that the previously reported ZrC could also contain O, since that earlier work dates back to the 1970s. Please click Additional Files below to see the full abstract

Un escenario para el aprendizaje a través de proyectos de diseño en contextos sociales: Laboratorio Estratégico de Diseño Integral (LEDI)

En este artículo se documentan algunas acciones inherentes a la enseñanza del diseño en el marco de una experiencia educativa, analizada desde la práctica proyectual en asignaturas del pregrado de Diseño Visual de la Universidad de Caldas. Se expone la experiencia docente resultante de implementar proyectos de aula, que durante 10 años (2008-2018) de trabajo ha vinculado comunidades y proyectos de ciudad con el pregrado. Se destaca el valor que cobra el contacto con problemas reales en la formación integral de los diseñadores, dando la posibilidad en algunas asignaturas de proponer y planificar acciones didácticas que conduzcan a la mejora de la experiencia de la práctica proyectual. Surge aquí la necesidad de profundizar en la planeación pedagógica, para detectar las características que las acciones didácticas deben presentar y así entender cómo abordarlas desde el diseño, mediante una observación mediada por acercamientos metodológicos cualitativos. El artículo reporta cómo algunos docentes de este pregrado han diseñado contenidos de asignaturas y propuesto escenarios idóneos para la experimentación, dándole espacio al desarrollo de iniciativas como el LEDI (Laboratorio Estratégico de Diseño Integral), que complementa el escenario académico y enfatiza en una visión integral del diseño. En esta reflexión sobre la práctica docente se plantea una documentación de algunos procesos y proyectos, de los cuales surge el interés de proponer la construcción consciente y contextualizada de los cursos bajo la mirada disciplinar de la educación debido a la necesidad de identificar cómo se orientan los contenidos, tanto teóricos como prácticos de algunas asignaturas de los programas de diseño y sumar a la estrategia educativa la posibilidad de acceder a los espacios profesionales que pueden gestionar los profesores a los cuales pueden acceder los estudiantes desde la universidad y sacar el mejor provecho de la experiencia; así mismo, reflejar la sintonía de las soluciones plantadas desde la academia con las necesidades detectadas del contexto donde influye el proceso de educación, en nuestro caso el pregrado de Diseño Visual, y poner en evidencia la importancia de comprender los espacios sociales donde actúan los diseñadores en formación y acercarlos a estos

Creep-resistant composites of alumina and single-wall carbon nanotubes

Composites of alumina Al2O3 ceramic and single-wall carbon nanotubes (SWNTs) have been tested in uniaxial compression at 1300 and 1350 °C (Ar atmosphere), and they have been found to be about two orders of magnitude more creep-resistant compared to a pure alumina of about the same grain size (0.5 micras). This is attributed to partial blocking of grain-boundary sliding by SWNTs in the composites. Since the grain boundaries in the ceramic/SWNTs composites are amenable to being engineered, this constitutes an attractive approach to the design of creep-resistant ceramic composites

Consensus-based care recommendations for congenital and childhood-onset myotonic dystrophy type 1

Purpose of reviewMyotonic dystrophy type 1 is a multisystemic disorder caused by a noncoding triplet repeat. The age of onset is variable across the lifespan, but in its most severe form, the symptoms appear at birth (congenital myotonic dystrophy) or in the pediatric age range (childhood-onset myotonic dystrophy). These children have a range of disabilities that reduce the lifespan and cause significant morbidity. Currently, there are no agreed upon recommendations for caring for these children.Recent findingsThe Myotonic Dystrophy Foundation recruited 11 international clinicians who are experienced with congenital and childhood-onset myotonic dystrophy to create consensus-based care recommendations. The experts used a 2-step methodology using elements of the single text procedure and nominal group technique. Completion of this process has led to the development of clinical care recommendations for this population.SummaryChildren with myotonic dystrophy often require monitoring and interventions to improve the lifespan and quality of life. The resulting recommendations are intended to standardize and improve the care of children with myotonic dystrophy

Creep of HfB2-based UHTCs up to 2000oC

Ultra-high temperature ceramics (UHTCs) are promising candidates for hypersonic applications as a consequence of their high melting points, in excess of 3000 ºC for ZrB2 and HfB2 UHTCs. The UHTCs community has traditionally focused on development of more oxidation-resistant UHTC composites as a consequence of poor oxidation resistance of monolithic UHTCs, which has led to the choice of SiC-reinforced MeB2 (where Me is Zr or Hf) as the baseline material for extreme environments. An overview of current understanding of high temperature creep of MeB2–based UHTCs will be described, discussing the following points: • Poor creep resistance of SiC-reinforced HfB2 and their structural instabilities. • Plastic behavior of HfB2 which deforms like an hcp-metal. • Plastic behavior of HfB2/2 wt.% La2O3 or how to maintain the creep resistance while improving the oxidation resistance. • New approaches to increase the creep resistance of HfB