Nonlinear dynamical model for the assessment of the seismic behaviour of ferrocement houses

En este trabajo se evalúa el comportamiento cíclico de un prototipo de vivienda de ferrocemento, ensamblado mediante muros prefabricados de pared delgada, con la finalidad de identificar sus parámetros estructurales y proponer un modelo dinámico no lineal para simular el comportamiento de viviendas bajo movimientos sísmicos. Para ello se construyó un prototipo a escala real 1:1 y se probó bajo carga cíclica. De los resultados experimentales se obtuvieron: el comportamiento histerético, la rigidez elástica, la resistencia a cortante, la resistencia máxima, la ductilidad, la capacidad de disipación de energía, el amortiguamiento y el coeficiente de capacidad de disipación de energía; todos ellos, parámetros necesarios para la evaluación dinámica de la vivienda de ferrocemento bajo movimientos sísmicos. Al final se implementó el modelo dinámico no lineal de Bouc-Wen-Baber-Noori (BWBN). Este modelo permitió realizar la evaluación sísmica de la vivienda prefabricada de ferrocemento bajo sismos ocurridos.This article evaluates the cyclic behaviour of a prototype of a precast ferrocement house, which is assembled using precast thin walls, in order to identify its structural parameters and propose a nonlinear dynamical model which is able to simulate the behaviour of those houses when subjected to seismic loading. For this purpose, a full-scale precast ferrocement house was tested under cyclic loading conditions. From the experimental results, the hysteretic behaviour, the elastic stiffness, the shear resistance, the maximum strength, the ductility, the energy dissipation, the equivalent damping and its coefficient of energy dissipation were assessed; those parameters are needed in order to evaluate the dynamic behaviour of ferrocement dwellings when subjected to earthquakes. At the end, the Bouc-Wen-Baber-Noori (BWBN) model of hysteresis was implemented. The model allowed performing the seismic evaluation of the precast ferrocement house under seismic activity.Peer Reviewe

Be outraged: there are alternatives

Pushed to extremes, austerity is bad economics, bad arithmetic, and ignores the lessons of history. We, an international group of economists and social scientists, are outraged at the narrow range of austerity policies which are bringing so many people around the world to their knees, especially in Europe. Austerity and cutbacks are reducing growth and worsening poverty. In our professional opinions, there are alternatives – for Britain, Europe and all countries that currently imagine that government cutbacks are the only way out of debt. The low-growth, no-growth trap means that the share of debt in GNP falls ever more slowly, if at all. It may even rise – as it has in some countries

Probing Ion-Ion and Electron-Ion Correlations in Liquid Metals within the Quantum Hypernetted Chain Approximation

We use the Quantum Hypernetted Chain Approximation (QHNC) to calculate the ion-ion and electron-ion correlations for liquid metallic Li, Be, Na, Mg, Al, K, Ca, and Ga. We discuss trends in electron-ion structure factors and radial distribution functions, and also calculate the free-atom and metallic-atom form-factors, focusing on how bonding effects affect the interpretation of X-ray scattering experiments, especially experimental measurements of the ion-ion structure factor in the liquid metallic phase.Comment: RevTeX, 19 pages, 7 figure

Diastolic shock index and clinical outcomes in patients with septic shock

Background: Loss of vascular tone is a key pathophysiological feature of septic shock. Combination of gradual diastolic hypotension and tachycardia could reflect more serious vasodilatory conditions. We sought to evaluate the relationships between heart rate (HR) to diastolic arterial pressure (DAP) ratios and clinical outcomes during early phases of septic shock. Methods: Diastolic shock index (DSI) was defined as the ratio between HR and DAP. DSI calculated just before starting vasopressors (Pre-VPs/DSI) in a preliminary cohort of 337 patients with septic shock (January 2015 to February 2017) and at vasopressor start (VPs/DSI) in 424 patients with septic shock included in a recent randomized controlled trial (ANDROMEDA-SHOCK; March 2017 to April 2018) was partitioned into five quantiles to estimate the relative risks (RR) of death with respect to the mean risk of each population (assumed to be 1). Matched HR and DAP subsamples were created to evaluate the effect of the individual components of the DSI on RRs. In addition, time-course of DSI and interaction between DSI and vasopressor dose (DSI*NE.dose) were compared between survivors and non-survivors from both populations, while ROC curves were used to identify variables predicting mortality. Finally, as exploratory observation, effect of early start of vasopressors was evaluated at each Pre-VPs/DSI quintile from the preliminary cohort. Results: Risk of death progressively increased at gradual increments of Pre-VPs/DSI or VPs/DSI (One-way ANOVA, p < 0.001). Progressive DAP decrease or HR increase was associated with higher mortality risks only when DSI concomitantly increased. Areas under the ROC curve for Pre-VPs/DSI, SOFA and initial lactate were similar, while mean arterial pressure and systolic shock index showed poor performances to predict mortality. Time-course of DSI and DSI*NE.dose was significantly higher in non-survivors from both populations (repeated-measures ANOVA, p < 0.001). Very early start of vasopressors exhibited an apparent benefit at higher Pre-VPs/DSI quintile. Conclusions: DSI at pre-vasopressor and vasopressor start points might represent a very early identifier of patients at high risk of death. Isolated DAP or HR values do not clearly identify such risk. Usefulness of DSI to trigger or to direct therapeutic interventions in early resuscitation of septic shock need to be addressed in future studies

Effects of very early start of norepinephrine in patients with septic shock: a propensity score-based analysis

BACKGROUND: Optimal timing for the start of vasopressors (VP) in septic shock has not been widely studied since it is assumed that fluids must be administered in advance. We sought to evaluate whether a very early start of VP, even without completing the initial fluid loading, might impact clinical outcomes in septic shock. METHODS: A total of 337 patients with sepsis requiring VP support for at least 6 h were initially selected from a prospectively collected database in a 90-bed mixed-ICU during a 24-month period. They were classified into very-early (VE-VPs) or delayed vasopressor start (D-VPs) categories according to whether norepinephrine was initiated or not within/before the next hour of the first resuscitative fluid load. Then, VE-VPs (n = 93) patients were 1:1 propensity matched to D-VPs (n = 93) based on age; source of admission (emergency room, general wards, intensive care unit); chronic and acute comorbidities; and lactate, heart rate, systolic, and diastolic pressure at vasopressor start. A risk-adjusted Cox proportional hazard model was fitted to assess the association between VE-VPs and day 28 mortality. Finally, a sensitivity analysis was performed also including those patients requiring VP support for less than 6 h. RESULTS: Patients subjected to VE-VPs received significantly less resuscitation fluids at vasopressor starting (0[0-510] vs. 1500[650-2300] mL, p < 0.001) and during the first 8 h of resuscitation (1100[500-1900] vs. 2600[1600-3800] mL, p < 0.001), with no significant increase in acute renal failure and/or renal replacement therapy requirements. VE-VPs was related with significant lower net fluid balances 8 and 24 h after VPs. VE-VPs was also associated with a significant reduction in the risk of death compared to D-VPs (HR 0.31, CI95% 0.17-0.57, p < 0.001) at day 28. Such association was maintained after including patients receiving vasopressors for < 6 h. CONCLUSION: A very early start of vasopressor support seems to be safe, might limit the amount of fluids to resuscitate septic shock, and could lead to better clinical outcomes

Measurement of the top pair production cross section in 8 TeV proton-proton collisions using kinematic information in the lepton plus jets final state with ATLAS

A measurement is presented of the $t\bar{t}$ inclusive production cross-section in $pp$ collisions at a center-of-mass energy of $\sqrt{s}=8$ TeV using data collected by the ATLAS detector at the CERN Large Hadron Collider. The measurement was performed in the lepton+jets final state using a data set corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The cross-section was obtained using a likelihood discriminant fit and $b$-jet identification was used to improve the signal-to-background ratio. The inclusive $t\bar{t}$ production cross-section was measured to be $260\pm 1{\textrm{(stat.)}} ^{+22}_{-23} {\textrm{(syst.)}}\pm 8{\textrm{(lumi.)}}\pm 4{\mathrm{(beam)}}$ pb assuming a top-quark mass of 172.5 GeV, in good agreement with the theoretical prediction of $253^{+13}_{-15}$ pb. The $t\bar{t}\to (e,\mu)+{\mathrm{jets}}$ production cross-section in the fiducial region determined by the detector acceptance is also reported.Comment: Published version, 19 pages plus author list (35 pages total), 3 figures, 2 tables, all figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2013-06