Cementos de ionómero de vidrio. A propósito del cemento Ketak-Cem (Espe)

En este artículo se describen los cementos de ionómero de vidrio, de forma muy exhaustiva. Se estudia su composición química, sus propiedades, su manejo clínico, y sus indicaciones y contraindicaciones. Finalmente también se describe uno de los cementos de ionómero de vidrio más conocidos y de uso más frecuente, el cemento Ketac Cem ®

Four lectures on secant varieties

This paper is based on the first author's lectures at the 2012 University of Regina Workshop "Connections Between Algebra and Geometry". Its aim is to provide an introduction to the theory of higher secant varieties and their applications. Several references and solved exercises are also included.Comment: Lectures notes to appear in PROMS (Springer Proceedings in Mathematics & Statistics), Springer/Birkhause

Rheo-PIV of a shear-banding wormlike micellar solution under large amplitude oscillatory shear

We explore the behavior of a wormlike micellar solution under both steady and large amplitude oscillatory shear (LAOS) in a cone–plate geometry through simultaneous bulk rheometry and localized velocimetric measurements. First, particle image velocimetry is used to show that the shear-banded profiles observed in steady shear are in qualitative agreement with previous results for flow in the cone–plate geometry. Then under LAOS, we observe the onset of shear-banded flow in the fluid as it is progressively deformed into the non-linear regime—this onset closely coincides with the appearance of higher harmonics in the periodic stress signal measured by the rheometer. These harmonics are quantified using the higher-order elastic and viscous Chebyshev coefficients e [subscript n] and v [subscript n] , which are shown to grow as the banding behavior becomes more pronounced. The high resolution of the velocimetric imaging system enables spatiotemporal variations in the structure of the banded flow to be observed in great detail. Specifically, we observe that at large strain amplitudes (γ [subscript 0] ≥ 1), the fluid exhibits a three-banded velocity profile with a high shear rate band located in-between two lower shear rate bands adjacent to each wall. This band persists over the full cycle of the oscillation, resulting in no phase lag being observed between the appearance of the band and the driving strain amplitude. In addition to the kinematic measurements of shear banding, the methods used to prevent wall slip and edge irregularities are discussed in detail, and these methods are shown to have a measurable effect on the stability boundaries of the shear-banded flow.Spain. Ministerio de Educación y Ciencia (MEC) (Project FIS2010-21924-C02-02

Is Eddington–Born–Infeld theory really free of cosmological singularities?

The Eddington-inspired-Born-Infeld (EiBI) theory has been recently resurrected. Such a theory is characterized by being equivalent to Einstein theory in vacuum but differing from it in the presence of matter. One of the virtues of the theory is to avoid the Big Bang singularity for a radiation filled universe. In this paper, we analyze singularity avoidance in this kind of model. More precisely, we analyze the behavior of a homogeneous and isotropic universe filled with phantom energy in addition to the dark and baryonic matter. Unlike the Big Bang singularity that can be avoided in this kind of model through a bounce or a loitering effect on the physical metric, we find that the Big Rip singularity is unavoidable in the EiBI phantom model even though it can be postponed towards a slightly further future cosmic time as compared with the same singularity in other models based on the standard general relativity and with the same matter content described above.Comment: 5 page

Análisis y clasificación de las urgencias hospitalarias mediante los Ambulatory Patient Groups

Objetivo: Describir la factibilidad y el resultado de la aplicación del sistema Ambulatory Patient Groups (APG) a la casuística atendida en los servicios de urgencias de seis hospitales del área de Barcelona. Métodos: Confección de un conjunto mínimo básico de datos específico para urgencias (CMBDAU). Obtención de las variables necesarias en una muestra aleatoria de visitas atendidas, a partir de los informes de asistencia correspondientes. Aplicación del sistema APG a los episodios seleccionados. Resultados: Se ha codificado y agrupado en APG un total de 11.188 visitas de urgencias. Quince diagnósticos identifican el 25% de los episodios. El 50% de los procedimientos de urgencias son exploraciones complementarias sencillas. Quince APG agrupan el 50% de la casuística atendida en urgencias. Conclusiones: El CMBDAU es válido para describir la casuística de urgencias y su agrupación en APG proporciona resultados consistentes e interpretables. La aplicación generalizada de sistemas como los APG en urgencias requiere una validación previa en nuestro entorno de los valores de peso norteamericanos. También debe valorarse la disponibilidad de recursos técnicos y humanos suficientes para garantizar la calidad y la continuidad de un registro de estas características

Análisis y clasificación de las urgencias hospitalarias mediante los Ambulatory Patient Groups Analysis and classification of hospital emergencies through Ambulatory Patient Groups

Objetivo: Describir la factibilidad y el resultado de la aplicación del sistema Ambulatory Patient Groups (APG) a la casuística atendida en los servicios de urgencias de seis hospitales del área de Barcelona. Métodos: Confección de un conjunto mínimo básico de datos específico para urgencias (CMBDAU). Obtención de las variables necesarias en una muestra aleatoria de visitas atendidas, a partir de los informes de asistencia correspondientes. Aplicación del sistema APG a los episodios seleccionados. Resultados: Se ha codificado y agrupado en APG un total de 11.188 visitas de urgencias. Quince diagnósticos identifican el 25% de los episodios. El 50% de los procedimientos de urgencias son exploraciones complementarias sencillas. Quince APG agrupan el 50% de la casuística atendida en urgencias. Conclusiones: El CMBDAU es válido para describir la casuística de urgencias y su agrupación en APG proporciona resultados consistentes e interpretables. La aplicación generalizada de sistemas como los APG en urgencias requiere una validación previa en nuestro entorno de los valores de peso norteamericanos. También debe valorarse la disponibilidad de recursos técnicos y humanos suficientes para garantizar la calidad y la continuidad de un registro de estas características.Aim: To assess the feasibility and results of application of Ambulatory Patient Groups (APG) patient's classification system to the case-mix of patients seen at the Emergency Departments (ED) of 6 Barcelona metropolitan area hospitals. Methods: Development of a minimum discharge data set specific for the Emergency Departments (CMBDAU). Gathering of relevant variables from a random sample of patients seen at the ED using the ED discharge reports. Use of the APG classification system to those episodes. Results: A total of 11.188 episodes were codified and grouped with the APG system. Fifteen diagnostics identified 25% of all episodes. Nearly 50% of all procedures performed at the ED were common and simple procedures. Fifteen APG's grouped 50% of all cases seen at the ED. Conclusions: The ED Uniform Discharge Data Set (CMBDAU) developed is a valid instrument for describing the case-mix seen at the ED, and its grouping by means of the APG system provides consistent and meaningful results. The widespread use of systems like APG in the ED requires a former validation of relative weights assigned in the US system. The availability of human and technical resources must also be assessed, in order to guarantee the quality and sustainability of such a system

Soil micro‐organisms and competitive ability of a tussock grass species in a dry ecosystem

1. Drylands are among the most threatened ecosystems in the world because of the effects of global change and because they are not particularly resilient. Regeneration after disturbance is quite slow and secondary succession can be delayed to the point of nearly stop. This is exacerbated when the community is strongly dominated by a single species able to quickly respond after disturbance. One example of such monospecific dominance is the colonization of abandoned fields in SE Spain by an early successional and native tussock grass, Lygeum spartum, that seems to halt succession. 2. Here we tested the competitive ability of Lygeum against Salsola oppositifolia, a shrub species that can be found interspersed with Lygeum in mid‐successional stages, and assessed how plant–soil interactions mediate the outcome of plant– plant competition. To do so, we sowed seeds and grew plants of Lygeum and Salsola in either intra‐ or interspecific competition under controlled conditions using sterile field soils inoculated with either live (i.e., with micro‐organisms) or sterile soil extracts from the understories of either Lygeum or Salsola. Soil nutrient content, seed germination rate, and shoot mass growth were determined after 5 months, and soil bacterial communities were characterized by sequencing. 3. Lygeum soil micro‐organisms and soil properties, such as the high content of N and organic matter, enhanced seed germination rate of Lygeum individuals. By contrast, Salsola adults outperformed Lygeum when growing in interspecific competition. 4. Synthesis. The enhanced competitive ability of Lygeum, which was mediated by soil micro‐organisms, may lead to complete dominance of Lygeum in the plant community right after abandonment of agricultural fields. However, when the plant community is already developed, Lygeum would be unable to enforce such dominance. We conclude that positive plant–soil feedbacks combined with certain plant traits such as clonal growth support the strong resilience of Lygeum and allow for its dominance in extreme habitats.AEI, Grant/Award Number: CGL2017‐84515‐R; Junta de Andalucía Regional Government, Grant/Award Number: P09‐RNM‐4821Peer reviewe