Metabolism of a burrowing polychaete: Precaution needed when measuring toxic effects

The technique of direct calorimetry has been used to monitor the metabolic activity of the polychaete, Neanthes virens, an organism commonly used for testing the toxic effects of chemicals in the marine environment. In these tests Neanthes showed unpredictable alternating periods of hyperactivity and rest when deprived of sediment. If used in this abnormal state for toxicity tests, the results would represent the effects of the chemicals on abnormal organisms and may not, therefore, be realistic information for judging the chemical's harmful effects on it and other species in nature. In toxicity tests with heavy metals that have been reported in the scientific literature, the shorter survival time of test organisms without sediment, as compared to those in sediment, was probably the result of the abnormally high metabolic rates of the former group.     

The relationship between reference canopy conductance and simplified hydraulic architecture

Terrestrial ecosystems are dominated by vascular plants that form a mosaic of hydraulic conduits to water movement from the soil to the atmosphere. Together with canopy leaf area, canopy stomatal conductance regulates plant water use and thereby photosynthesis and growth. Although stomatal conductance is coordinated with plant hydraulic conductance, governing relationships across species has not yet been formulated at a practical level that can be employed in large-scale models. Here, combinations of published conductance measurements obtained with several methodologies across boreal to tropical climates were used to explore relationships between canopy conductance rates and hydraulic constraints. A parsimonious hydraulic model requiring sapwood-to-leaf area ratio and canopy height generated acceptable agreement with measurements across a range of biomes (r²=0.75)$(r^2=0.75)$. The results suggest that, at long time scales, the functional convergence among ecosystems in the relationship between water-use and hydraulic architecture eclipses inter-specific variation in physiology and anatomy of the transport system. Prognostic applicability of this model requires independent knowledge of sapwood-to-leaf area. In this study, we did not find a strong relationship between sapwood-to-leaf area and physical or climatic variables that are readily determinable at coarse scales, though the results suggest that climate may have a mediating influence on the relationship between sapwood-to-leaf area and height. Within temperate forests, canopy height alone explained a large amount of the variance in reference canopy conductance (r²=0.68)$(r^2=0.68)$ and this relationship may be more immediately applicable in the terrestrial ecosystem models.     

Crustal structure and tectonic setting of the south central Andes from gravimetric analysis

Based on terrestrial gravity data, in this paper we prepared a map of Bouguer anomalies, which was filtered to separate shallow and deep gravity sources. Based on a density model and gravimetric inversion techniques, the discontinuous crust-mantle boundary and the top of crystalline basement were modeled. Subsequently, the equivalent elastic thickness (Te) was evaluated, considering information from the crust-mantle discontinuity and topographic load, finding high Te values in the eastern Andean foothills and west of the Velasco range. These results are consistent with the positive isostatic and residual Bouguer anomaly values, which suggest the presence of high-density rocks in the mid-to upper crust. In addition, petrographic and geochemical analysis conducted in surface outcrops suggest a mantle origin.     

Procedures for calibration of linear models for damage limitation in design of masonry‐infilled RC frames

Recent earthquakes have confirmed the role played by infills in the seismic response of reinforced concrete buildings. The control and limitation of damage to such nonstructural elements is a key issue in performance‐based earthquake engineering. The present work is focused on modeling and analysis of damage to infill panels, and, in particular, it is aimed towards linear analysis procedures for assessing the damage limitation limit state of infilled reinforced concrete frames. First, code provisions on infill modeling and acceptance criteria at the damage limitation limit state are reviewed. Literature contributions on damage to unreinforced masonry infill panels and corresponding displacement capacity are reported and discussed. Two procedures are then proposed aiming at a twofold goal: (i) the determination of ‘equivalent’ interstory drift ratio limits for a bare frame model and (ii) the estimation of the stiffness of equivalent struts representing infill walls in a linear model. These two quantities are determined such that a linear model ensures a reliable estimation of seismic capacity at the damage limitation limit state, providing the same intensity level as that obtained from nonlinear analyses carried out on structural models with infills. Finally, the proposed procedures are applied to four‐story and eight‐story case study‐infilled frames, designed for seismic loads according to current technical codes. The results of these application examples are presented and discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

2012 Emilia earthquake,Italy: reinforced concrete buildings response

Data of the Italian National Institute of Statistics are collected aimed at characterizing Reinforced Concrete (RC) building stock of the area struck by the 2012 Emilia earthquake (number of storeys, age of construction, structural typology). Damage observations, collected right after the event in reconnaissance reports, are shown and analyzed emphasizing typical weaknesses of RC buildings in the area. The evolution of seismic classification for Emilia region and RC buildings’ main characteristics represent the input data for the assessment of non-structural damage of infilled RC buildings, through a simplified approach (FAST method), based on EMS-98 damage scale. Peak Ground Acceleration (PGA) capacities for the first three damage states of EMS-98 are compared with registered PGA in the epicentral area. Observed damage and damage states evaluated for the PGA of the event, in the epicentral area, are finally compared. The comparison led to a fair agreement between observed and numerical data.