Spalling uniaxial strength of Al2O3 at high strain rates

In this article research into the uniaxial tensile strength of Al2O3 monolithic ceramic is presented. The experimental procedure of the spalling of long bars is investigated from different approaches. This method is used to obtain the tensile strength at high strain rates under uniaxial conditions. Different methodologies proposed by several authors are used to obtain the tensile strength. The hypotheses needed for the experimental set-up are also checked, and the requirements of the set-up and the variables are also studied by means of numerical simulations. The research shows that the shape of the projectile is crucial to achieve successfully tests results. An experimental campaign has been carried out including high speed video and a digital image correlation system to obtain the tensile strength of alumina. Finally, a comparison of the test results provided by three different methods proposed by different authors is presented. The tensile strength obtained from the three such methods on the same specimens provides contrasting results. Mean values vary from one method to another but the trends are similar for two of the methods. The third method gives less scatter, though the mean values obtained are lower and do not follow the same trend as the other methods for the different specimens

Variability of cell wall polysaccharides composition and hemicellulose enzymatic profile in an apple progeny

The genetic variability of apple cell walls polysaccharides chemical composition and structure was assessed in a progeny of 141 individuals harvested over 2 years. The variability of the hemicelluloses oligosaccharides released by glucanase was analyzed by MALDI-TOF MS. The genetic contribution was distinguished from harvest year as well as from parental crossing patterns and scab resistance selection. Results showed that harvest year had a major impact on cell wall polysaccharide composition and structure. Within each harvest, genetic effect impact more significantly cell wall polysaccharide chemistry than does reciprocal crossing or early scab selection. Uronic acids, glucose, galactose and xylose contents as well as some glucomannan and xyloglucan structures have a high heritability. This first cell wall chemotyping of an apple progeny opens the way for future searches of genetic markers for the chemical variability of cell wall polysaccharides

Creep and shrinkage of self compacting concrete of medium-strenght

Self-compacting concrete (SCC) is an innovative concrete that does not require vibration for placing and compacting. SCC, developed in Japan in the 1980s, provides a present-day and attractive challenge for many researchers, as the long list of papers on the topic corroborates. Nevertheless, the durability of SCC, especially medium-low strength SCC, provides the researcher with opportunities for study in depth. This paper deals with the shrinkage and creep of SCC: three SCC mixtures, with 30 MPa compressive strength, are studied. The main differences among the SCCs involve the type of the cement: one SCC with type I cement and two SCCs with blended cements. The shrinkage and creep of the three SCCs are studied and compared. Fresh properties and mechanical properties are also evaluated. The shrinkage strains and creep are calculated by means of ACI 209 and Eurocode 2 models. These models overestimate the shrinkage strains and undervalue the creep for the studied concretes

Web blight

Web blight, caused by the fungus Thanatephorus cucumeris, is prevalent in tropical regions with high to moderate temp. and RH; more than 200 plant species serve as hosts to this pathogen. Hyphae can grow rapidly over healthy tissue of leaves, flowers, petioles, and pods. For efficient control, the use of disease-free seeds, elimination of harvest debris, crop rotation, mulching, using spaced furrows and intercropping; the use of adequate chemical products, the use of resistant var., and integrated control are also recommended. The symptoms and damage caused by the disease are illustrated in color. (CIAT)La mustia hilachosa, causada por el hongo Thanatephorus cucumeris, prevalece en las regiones tropicales con una temp. y HR entre moderada y alta; mas de 200 especies vegetales le sirven de hospedante al patogeno. Las hifas del hongo pueden crecer rapidamente en el tejido sano de las hojas, flores, peciolos y vainas. Para un buen control se recomienda el uso de semilla libre de patogenos, la eliminacion de residuos de cosecha, rotacion de cultivos, la utilizacion de cobertura vegetal, espaciamiento entre surcos y asociaciones; tambien se recomienda el control quimico, el uso de var. resistentes y el control integrado. Se ilustran a color los sintomas y danos causados por la enfermedad. (CIAT

Retracción y fluencia de hormigón autocompactante de resistencia moderada

Los estudios sobre el hormigón autocompactante se han centrado en obtener las dosificaciones óptimas, pero hay desconocimiento acerca de su comportamiento a largo plazo, en especial en hormigones de resistencia moderada. Este trabajo estudia la fluencia y retracción de tres hormigones autocompactantes de resistencia moderada (resistencia característica aproximada de 25 MPa), cuya dosificación y propiedades mecánicas son casi iguales, pero que emplean cementos con distintos tipos de adición. En los tres casos se emplea filler calizo. El trabajo presenta los resultados de los ensayos de retracción y fluencia, que son comparados con las predicciones del Código Modelo CEB-FIP, del ACI Concrete Practice Manual y del Euro Code 2. Además también se ha obtenido el volumen total de poros y su distribución por tamaños mediante el ensayo de porosimetría por intrusión de mercurio

Benchmark low-mass objects in Moving Groups

This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.In order to compile a sample of ultracool dwarfs that will serve as benchmarks for testing theoretical formation and evolutionary models, we selected low-mass cool (>M7) objects that are potentially members of five known young Moving Groups in the solar neighbourhood. We have studied the kinematics of the sample, finding that 49 targets belong to the young disk area, from which 36 are kinematic member of one of the five moving groups under study. Some of the identified low-mass members have been spectroscopically characterised (T-eff, log g) and confirmed as young members through a detailed study of age indicators

Therapeutic applications of probiotics

En los últimos años han comenzado a desarrollarse nuevos conceptos en nutrición como fruto de la preocupación por una elevada calidad de vida de la sociedad desarrollada. Esto ha promovido la aparición del término “alimento funcional”, que se puede defi nir como aquel producto, alimento modifi cado o ingrediente alimentario, que puede proveer benefi cios a la salud superiores a los ofrecidos por los alimentos tradicionales. Las bacterias probióticas quedan incluidas dentro del campo de los alimentos funcionales, existiendo evidencias de su efi cacia en ciertas patologías, y sufi cientes estudios experimentales en otras para justifi car posibles mecanismos de acción que faciliten el desarrollo de microorganismos más efectivos, así como para defi nir los límites de su efectividad.Over recent years new concepts in nutrition have been arising in consequence of some of the negative aspects of modern lifestyles in today’s highly developed societies. This has brought about the appearance of the term “functional foods”, which can be defi ned as a modifi ed foodstuff or ingredient that can promote better health benefi ts than those offered by traditional foods. Probiotic bacteria have been included within the concept of functional foods, given that there is suffi cient evidence to suggest their effectiveness in combating certain pathologies. Furthermore, numerous experimental studies have identifi ed the action mechanisms that facilitate the development of the most effective microorganisms, while at the same time establishing the limits of their effectiveness

Parameterized optimized effective potential for atoms

The optimized effective potential equations for atoms have been solved by parameterizing the potential. The expansion is tailored to fulfill the known asymptotic behavior of the effective potential at both short and long distances. Both single configuration and multi configuration trial wave functions are implemented. Applications to several atomic systems are presented improving previous works. The results here obtained are very close to those calculated in either the Hartree-Fock and the multi configurational Hartree-Fock framework.Comment: 8 pages, 3 figure