Criterios de intervención y recomendaciones de diseño a sismo en las estructuras de patrimonio histórico

This paper describes the peculiar conditions of historic masonry structures subjected to seismic actions. The present seismic standards govern modern constructures with columns and beams; but masonry buildings are built upon a base of gravity systems, which work on compression, as stone materials with no tractions. In another hand, the appearance of cracks, until now, was the reason for a diagnosis of decay. Our present knowledge about classic building materials, techniques and construction stages indicates that old buildings must be considered and analyzed from a particular viewpoint. Finally, some recommendations of seismic designs for masonry structures are included.En este artículo se describen las condiciones particulares de las estructuras históricas sujetas a acciones sísmicas. Las actuales normas sísmicas están hechas desde el edificio moderno de vigas y pilares, siendo los edificios de fábrica sistemas de gravedad que trabajan a compresión, como materiales pétreos sin tracciones. Por otra parte, la aparición de grietas, hasta hoy, era motivo de diagnóstico por ruina. Nuestro actual conocimiento de los materiales clásicos, sus técnicas y fases de construcción, nos muestran que los edificios antiguos deben ser vistos y analizados desde un punto de vista particular. Finalmente, se incluyen algunas recomendaciones de diseño sísmico para estructuras de fábrica

Effect of Systemic Hypertension With Versus Without Left Ventricular Hypertrophy on the Progression of Atrial Fibrillation (from the Euro Heart Survey).

Hypertension is a risk factor for both progression of atrial fibrillation (AF) and development of AF-related complications, that is major adverse cardiac and cerebrovascular events (MACCE). It is unknown whether left ventricular hypertrophy (LVH) as a consequence of hypertension is also a risk factor for both these end points. We aimed to assess this in low-risk AF patients, also assessing gender-related differences. We included 799 patients from the Euro Heart Survey with nonvalvular AF and a baseline echocardiogram. Patients with and without hypertension were included. End points after 1 year were occurrence of AF progression, that is paroxysmal AF becoming persistent and/or permanent AF, and MACCE. Echocardiographic LVH was present in 33% of 379 hypertensive patients. AF progression after 1 year occurred in 10.2% of 373 patients with rhythm follow-up. In hypertensive patients with LVH, AF progression occurred more frequently as compared with hypertensive patients without LVH (23.3% vs 8.8%, p = 0.011). In hypertensive AF patients, LVH was the most important multivariably adjusted determinant of AF progression on multivariable logistic regression (odds ratio 4.84, 95% confidence interval 1.70 to 13.78, p = 0.003). This effect was only seen in male patients (27.5% vs 5.8%, p = 0.002), while in female hypertensive patients, no differences were found in AF progression rates regarding the presence or absence of LVH (15.2% vs 15.0%, p = 0.999). No differences were seen in MACCE for hypertensive patients with and without LVH. In conclusion, in men with hypertension, LVH is associated with AF progression. This association seems to be absent in hypertensive women

Progression From Paroxysmal to Persistent Atrial Fibrillation. Clinical Correlates and Prognosis

Objectives: We investigated clinical correlates of atrial fibrillation (AF) progression and evaluated the prognosis of patients demonstrating AF progression in a large population. Background: Progression of paroxysmal AF to more sustained forms is frequently seen. However, not all patients will progress to persistent AF. Methods: We included 1,219 patients with paroxysmal AF who participated in the Euro Heart Survey on AF and had a known rhythm status at follow-up. Patients who experienced AF progression after 1 year of follow-up were identified. Results: Progression of AF occurred in 178 (15%) patients. Multivariate analysis showed that heart failure, age, previous transient ischemic attack or stroke, chronic obstructive pulmonary disease, and hypertension were the only independent predictors of AF progression. Using the regression coefficient as a benchmark, we calculated the HATCH score. Nearly 50% of the patients with a HATCH score >5 progressed to persistent AF compared with only 6% of the patients with a HATCH score of 0. During follow-up, patients with AF progression were more often admitted to the hospital and had more major adverse cardiovascular events. Conclusions: A substantial number of patients progress to sustained AF within 1 year. The clinical outcome of these patients regarding hospital admissions and major adverse cardiovascular events was worse compared with patients demonstrating no AF progression. Factors known to cause atrial structural remodeling (age and underlying heart disease) were independent predictors of AF progression. The HATCH score may help to identify patients who are likely to progress to sustained forms of AF in the near future. \ua9 2010 American College of Cardiology Foundation

La concepción estructural de la fábrica en la arquitectura

The present article establishes the vantage required, in the author’s view, to analyze masonry structure performance. Until the nineteenth century, the entire history of architecture revolved around the various styles of such structures. The introduction of high toughness materials (cast iron and steel) with the industrial revolution and the adoption of rigidity as a parameter for compatible analysis laid the grounds, both in engineering training and professional practice, for analytical methods based on elastic rigidity (stress-strain curve). Masonry structures cannot be analyzed on such a basis: stone or brick elasticity is not readily measured. As a result, they are viewed as mere aggregates of solids working under compression only, pursuant to a statically indeterminate model of infinite order as a result of their likewise infinite number of articulated bonds. Moreover, like all structures they change with time, rendering any analytical model trivial unless account is taken of the actual conditions (fissures or cracking) prevailing in the structure at any given time of its service life.<br>This paper modestly attempts to clarify the assumptions on which analysis is built, evaluating the basic principles of equilibrium, the only valid grounds for such analysis, and the conditions in which such equilibrium can be reached. Yesterday’s builders drew exclusively from experience to ensure equilibrium: for them structural safety meant the absence of collapse. Today vector algebra, observation with high precision instruments and a priori determination of the conditions that may lead to collapse underlie accurate and reliable conjecture about the performance of masonry structures that tangibly establishes safety levels at least as precisely as sophisticated methods of analysis.<br><br>El presente artículo establece el punto de vista necesario, a juicio del autor, para analizar una estructura de fábrica desde su funcionamiento. Toda la historia de la arquitectura hasta el siglo XIX ha girado en torno a las estructuras de fábrica en todos sus estilos. La introducción de los materiales tenaces (hierro, fundición y acero) con la revolución industrial y el concepto de rigidez como método de análisis compatible, han introducido, tanto en la formación como en la práctica profesional, métodos de análisis basados en la rigidez elástica (relación tensión/ deformación). Las fábricas no pueden ser analizadas desde estos supuestos, una piedra o un ladrillo no tiene una elasticidad fácilmente mensurable, y las fábricas se tornan así como meros agregados de sólidos de trabajo a monotensión (compresión) con enlaces de infinitas articulaciones que les hacen obedecer al modelo de estructuras hiperestáticas de orden infinito, y que además, como todas las demás estructuras, mutan en el tiempo, donde cualquier modelo de análisis puede resultar baladí sino se tienen en cuenta los estados reales (fisurados o agrietados) de la estructura en cada momento de su vida útil.<br>Este escrito intenta modestamente clarificar los supuestos del análisis, valorando los principios básicos de equilibrio, únicos válidos en el análisis y las condiciones en las que este equilibrio puede realizarse. Los antiguos constructores se valieron de la experiencia como único justificante del equilibrio, para ellos, la única seguridad consistía en que la estructura no colapsaba. Hoy el álgebra vectorial, la observación afinada por instrumentación de precisión, y la determinación a priori de las situaciones de rotura (colapso), permiten realizar conjeturas más aproximadas, pero ciertas, sobre el funcionamiento de las estructuras de fábrica con un nivel de precisión no inferior a sofisticados métodos de análisis, estableciendo de forma tangible niveles de seguridad

Re-programación vertical de usos, torre en Río de Janeiro [Hojas Resumen]

Re-programación vertical de usos, torre en Río de Janeir

Re-programación vertical de usos, torre en Río de Janeiro [Hojas Resumen]

Re-programación vertical de usos, torre en Río de Janeir

Time-resolved neutron diffraction study of Ti–TiC–Al2O3 composites obtained by SHS

Cermets of the titanium matrix family have potential applications in the aeronautical and automotive fields. Self-propagating high-temperature synthesis (SHS) constitutes a good method to produce them, as it implies low processing costs and energy and time efficiency. An interesting feature of this process is to determine the mechanism of reaction. A good method to do it is the use of in situ real-time diffraction techniques. The objective of this paper is to show how the use of time-resolved neutron diffraction (TRND) providing a deeper insight into the mechanism of a typical SHS reaction by monitoring the formation of a cermet of the system Ti–TiC–Al2O3. Neutron diffraction experiments have been conducted on Instrument D20 at the Institute Max von Laue-Paul Langevin (Grenoble, France) with a high-flux medium-resolution powder diffractometer. Results show that reaction is initiated with the melting and diffusion of aluminium through the sample, and shortly after product phases are formed. The final product shows a general structure composed of a titanium matrix with the rest of the phases located in reaction domains.Authors wish to thank ILL, for beamtime granted through experiments 5-25-133 and 5-25-134. This work has been supported by the European Project NAMAMET (STREP NMP3-CT-2004-0014TO) and co-financed by the Spanish Science and Technology Agency (CICYT) under Project No. MAT2004-04923-C02-01.Peer reviewe

Self-propagating high-temperature synthesis of TiC-WC composite materials

Abstract TiC-WC composites have been obtained in situ by self-propagating high-temperature synthesis (SHS) from a mixture of compacted powders of elemental titanium, tungsten and graphite. The Rietveld method has proved to be a useful tool to quantify the different phases in the reaction and calculate the cell parameters of the solid solution found in the products. The reaction has also been followed in real time by X-ray diffraction at the European Synchrotron Radiation Facility (ESRF ID-11 Materials Science Beamline). The mechanism of the reaction is discussed in terms of the diffusion of liquid titanium to yield titanium carbide with a solid solution of tungsten. The microstructures of the materials obtained by this method are presented

Directed evolution of Saccharomyces cerevisiae to reduce acetic acid production during aerobic fermentation of grape must

Trabajo presentado en la 7th Conference on Physiology of Yeast and Filamentous, celebrado en Milán (Italia), del 24 al 27 de junio de 2019Aerobic fermentation of grape must, leading to respiro-fermentative metabolism of sugars, has been proposed as way of reducing alcohol content in wines. Despite the Crabtree effect, Saccharomyces strains can reduce significantly the ethanol content under aerobic conditions, but an excess of acetic acid under these conditions limits its usefulness for the process. Deletion of REG1, a gene involved in carbon catabolite repression, was shown useful for aerobic fermentation, due to reduced acetate yield. Interestingly, this mutant, as other carbon catabolite alleviated mutants, is able to use alternative carbon sources, in the presence of 2-deoxyglucose. In this work, four S. cerevisiae wine strains were subjected to directed evolution on glycerol/2-deoxyglucose. Evolved cultures (23 subcultures, ~ 150 generations) maintained the ability to grow on selective medium, after subculturing in permissive medium (YPD). As a trend, sugar consumption was slower in the evolved populations than in their parental strains. In addition, three of four evolved populations produced more acetic acid than their parental strains during the aerobic fermentation of natural grape must. In contrast, analysis of single isolates revealed several strains showing both higher and lower acetate production than the cognate parental strain. Some of them show potential to improved fermentation processes for lowering alcohol content of wine.We acknowledge funding by MINECO (AGL2015-63629-R) and La Rioja Government for PhD training contract for AMG. Financial support by Fundación General CSIC (Programa ComFuturo) for JT is acknowledged