Simposio RILEM sobre prácticas corrientes de control de calidad del hormigón en los países de Latinoamérica

Se analizan los métodos empleados para controlar la calidad del agua, cemento, aditivos y áridos, para realizr la toma de muestras del hormigón fresco y los métodos de ensayo usados para determinar su consistencia, trabajabilidad, % de aire, exudación y peso de la unidad de volumen, y de los procedimientos de moldeo de probetas. Se hace referencia al contenido de álcalis de los cementos y a los áridos reactivos, durabilidad del hormigón, extracción de testigos de estructuras y determinación aproximada de los contenidos de agua, aire y cemento, a partir de una muestra de hormigón endurecido. Se destaca que en las obras públicas se realiza el control de calidad del hormigón de obra, cosa que, en general no ocurre en las obras de carácter privado.Methods used in Argentina in order to control water, cement, admixtures and aggregates quality are described, as well as methods used for sampling fresh concrete, and for determining slump, workability, air content, bleeding and unit weight. Procedures for molding of specimens used to determine strength* modulus of elasticity, volume changes, etc. are explained. Reference is made to alkalies content of cements, reactive aggregates, concrete durability, sampling of hardened concrete and methods of test used to determine approximate unit water and cement contents, as well as air content, from samples of hardened concrete. Quality control of concrete is performed in public works, but this is not the case in nearly all private building structures

Las condiciones de elaboración y el control de calidad del hormigón de obra

Se analizan algunas de las causas principales a las que pueden atribuirse los recientes colapsos de estructuras, destacándose que por inteligente que sea un proyecto y por elaborados y cuidadosos que sean los cálculos, si el hormigón de obra no reúne las características ni la calidad previstas por el proyectista, todos los refinamientos de cálculo carecerán totalmente de sentido y de interés práctico. Como en nuestro medio y en el ámbito de las obras de carácter privado, prácticamente no se realizan ensayos para controlar la calidad del hormigón durante el periodo de construcción de las estructuras, se hace notar la importancia de dichos ensayos como único medio para conocer y prever la calidad de aquél con tiempo suficiente como para adoptar las medidas necesarias que aseguren la calidad deseada y con ello la estabilidad, durabilidad y seguridad de dichas estructuras. Se resumen las recomendaciones tendientes a evitar la repetición de los hechos producidas.Some of the main probable causes of recent collapses of reinforced concrete building structures are analized. Inferior concrete quality being one of them. It is pointed out that no matter how perfect the structure design is and how careful and refined the calculations are, if concrete has not the quality and strength assumed by the designer, all the refinements will be useless and lacking of practical sense and interest. As in this country, generally, and specially in the field of private concrete structures, concrete is not subject to quality control during the construction period, the importance of making tests is emphasized as the only possible mean to know and forsee concrete quality with time enough to adopt measures that will allow to obtain the assumed quality and with it the stability and structural safety. Recommended practices to be adopted in order to avoid the repetition of concrete structure failures are described

Social contact structures and time use patterns in the Manicaland Province of Zimbabwe.

BACKGROUND: Patterns of person-to-person contacts relevant for infectious diseases transmission are still poorly quantified in Sub-Saharan Africa (SSA), where socio-demographic structures and behavioral attitudes are expected to be different from those of more developed countries. METHODS AND FINDINGS: We conducted a diary-based survey on daily contacts and time-use of individuals of different ages in one rural and one peri-urban site of Manicaland, Zimbabwe. A total of 2,490 diaries were collected and used to derive age-structured contact matrices, to analyze time spent by individuals in different settings, and to identify the key determinants of individuals' mixing patterns. Overall 10.8 contacts per person/day were reported, with a significant difference between the peri-urban and the rural site (11.6 versus 10.2). A strong age-assortativeness characterized contacts of school-aged children, whereas the high proportion of extended families and the young population age-structure led to a significant intergenerational mixing at older ages. Individuals spent on average 67% of daytime at home, 2% at work, and 9% at school. Active participation in school and work resulted the key drivers of the number of contacts and, similarly, household size, class size, and time spent at work influenced the number of home, school, and work contacts, respectively. We found that the heterogeneous nature of home contacts is critical for an epidemic transmission chain. In particular, our results suggest that, during the initial phase of an epidemic, about 50% of infections are expected to occur among individuals younger than 12 years and less than 20% among individuals older than 35 years. CONCLUSIONS: With the current work, we have gathered data and information on the ways through which individuals in SSA interact, and on the factors that mostly facilitate this interaction. Monitoring these processes is critical to realistically predict the effects of interventions on infectious diseases dynamics

Operation of a LAr-TPC equipped with a multilayer LEM charge readout

A novel detector for the ionization signal in a single phase LAr-TPC, based on the adoption of a multilayer Large Electron Multiplier (LEM) replacing the traditional anodic wire arrays, has been experimented in the ICARINO test facility at the INFN Laboratories in Legnaro. Cosmic muon tracks were detected allowing the measurement of energy deposition and a first determination of the signal to noise ratio. The analysis of the recorded events demonstrated the 3D reconstruction capability of ionizing events in this device in liquid Argon, collecting a fraction of about 90% of the ionization signal with signal to noise ratio similar to that measured with more traditional wire chambersComment: 9 pages, 7 Figure

Multiversality and Unnecessary Criticality in One Dimension

We present microscopic models of spin ladders which exhibit continuous critical surfaces whose properties and existence, unusually, cannot be inferred from those of the flanking phases. These models exhibit either `multiversality' -- the presence of different universality classes over finite regions of a critical surface separating two distinct phases -- or its close cousin, `unnecessary criticality'-- the presence of a stable critical surface within a single, possibly trivial, phase. We elucidate these properties using Abelian bosonization and density-matrix renormalization-group simulations, and attempt to distill the key ingredients required to generalize these considerations.Comment: 6+23 pages, 4+17 figures (main + supplementary material). v2: minor changes to main text, expanded supplementary materials, close to published versio

Nasopharyngeal angiofibroma: review of literature

Angiofibroma of nasopharynx is a highly vascular, rare and benign tumor, with a high a incidence of recurrence and local invasity which nature always defied the researchers on the subject. The controversies start on its site of origin, till therapeutical modalities, passing by clinical and diagnostic aspects. The most serious and baffling feature, however, is the occurrence of hemorrhagic outbreaks, sometimes very intense, which may lead the patient to death. In view of this, the efforts developed towards of minimizing this problematic fact have been many, aiming adequate control of the illness. The present article presents a global review on this subject and intends to discuss the main aspects related to angiofibroma of nasopharynx in a simple and didatic form.O angiofibroma de nasofaringe é um tumor benigno, raro, altamente vascularizado, com elevado índice de recorrência e invasividade local, cuja natureza sempre desafiou os estudiosos do assunto. As controvérsias vão desde o seu local de origem, até modalidades terapêuticas, passando por aspectos clínicos e diagnósticos. A característica mais grave e desconcertante, no entanto, é a ocorrência de surtos hemorrágicos, por vezes muito intensos, podendo levar o paciente à morte. Frente a esse fato, muitos foram os esforços desenvolvidos no sentido de minimizar esse problema, visando o controle adequado da doença. Esse estudo apresenta uma revisão global sobre o tema e se propõe a expor de forma simples e didática os principais aspectos relacionados ao angiofibroma nasofaríngeo.Instituto de Assistência Médica ao Servidor Público Estadual de São PauloUNIFESP-EPMHSPE FMO Departamento de OtorrinolaringologiaHospital do Servidor Público Municipal Serviço de OtorrinolaringologiaUniversidade de São Paulo Faculdade de MedicinaHospital do Servidor Público Estadual FMO Departamento de OtorrinolaringologiaUNIFESP, EPMSciEL

A Mechanistic Approach to Cross-Domain Perceptual Narrowing in the First Year of Life

Language and face processing develop in similar ways during the first year of life. Early in the first year of life, infants demonstrate broad abilities for discriminating among faces and speech. These discrimination abilities then become tuned to frequently experienced groups of people or languages. This process of perceptual development occurs between approximately 6 and 12 months of age and is largely shaped by experience. However, the mechanisms underlying perceptual development during this time, and whether they are shared across domains, remain largely unknown. Here, we highlight research findings across domains and propose a top-down/bottom-up processing approach as a guide for future research. It is hypothesized that perceptual narrowing and tuning in development is the result of a shift from primarily bottom-up processing to a combination of bottom-up and top-down influences. In addition, we propose word learning as an important top-down factor that shapes tuning in both the speech and face domains, leading to similar observed developmental trajectories across modalities. Importantly, we suggest that perceptual narrowing/tuning is the result of multiple interacting factors and not explained by the development of a single mechanism

Free electron lifetime achievements in Liquid Argon Imaging TPC

A key feature for the success of the liquid Argon imaging TPC (LAr-TPC) technology is the industrial purification against electro-negative impurities, especially Oxygen and Nitrogen remnants, which have to be continuously kept at an exceptionally low level by filtering and recirculating liquid Argon. Improved purification techniques have been applied to a 120 liters LAr-TPC test facility in the INFN-LNL laboratory. Through-going muon tracks have been used to determine the free electron lifetime in liquid Argon against electro-negative impurities. The short path length here observed (30 cm) is compensated by the high accuracy in the observation of the specific ionization of cosmic ray muons at sea level as a function of the drift distance. A free electron lifetime of (21.4+7.3-4.3) ms, namely > 15.8 ms at 90 % C.L. has been observed over several weeks under stable conditions, corresponding to a residual Oxygen equivalent of about 15 ppt (part per trillion). At 500 V/cm, the free electron speed is 1.5 m/ms. In a LAr-TPC a free electron lifetime in excess of 15 ms corresponds for instance to an attenuation of less than 15 % after a drift path of 5 m, opening the way to the operation of the LAr-TPC with exceptionally long drift distances.Comment: 15 pages, 10 figures; Accepted for publication in JINS