Low-ionization galaxies and evolution in a pilot survey up to z=1

We present galactic spectroscopic data from a pencil beam of 10.75×7.5 centered on the X-ray cluster RXJ0054.0-2823 at z=0.29.We study the spectral evolution of galaxies from z=1 down to the cluster redshift in a magnitude-limited sample at R≤23,for which the statistical properties of the sample are well understood.We divide emission-line galaxies into star-forming galaxies,Low Ionization Nuclear Emission line Regions(LINERs) ,and Seyferts by using emission-line ratios of[OII],Hβ,and[OIII],and derive stella...     

Decadal-scale changes in suspended wood after riparian recruitment in managed stands in headwater streams of coastal British Columbia,Canada

Large wood (LW) affects several ecological and hydrogeomorphic processes in streams. The main source of LW is riparian trees falling inside channels. However, in confined valley floors, falling trees are more likely to be suspended above the channel. Eventually, these suspended trees will decompose and break to finally fall into the channel to better provide functions for streams. We evaluated changes in wood decay, length, diameter, and suspended status (suspended or non-suspended) 17 years post-harvest and nine years after the first sampling occurred in 2006 in 12 headwater streams of coastal British Columbia, Canada. We also evaluated whether changes differed among riparian management treatments (no-harvest buffers of 10 and 30 m in width, thinning, and unharvested reference sites), and identified the factors affecting wood changes and suspended status. Wood pieces advanced in decay, became shorter, and 34% of them (n = 108) changed status from suspended to non-suspended. Non-suspended wood pieces were more decayed and shorter than suspended wood. Suspended wood was longer, thicker, less decayed, and represented 46.5% (n = 147) of the wood sampled in 2006. Our findings revealed limited influences of riparian management on many aspects of wood changes considered in this study. Changes in wood characteristics were more likely for pieces that were smaller in diameter, longer, and suspended closer to the water. The transition from suspended to non-suspended LW can be a long-term process that can increase wood residence time and reduce LW in-stream functions particularly in confined stream valleys. The suspended stage is also an important mechanism underlying time lags in stream ecosystem responses to riparian tree fall. © 2020 John Wiley & Sons, Ltd.     

Estuarine macrofauna responses to continuous in situ nutrient addition on a tropical mudflat

A field experiment to assess the effects of continuous nutrient addition on the macrobenthic community was carried out on an estuarine mudflat on the northeast coast of Brazil. The experiment began on 5 October 2005 and ended on 8 February 2006. Macrofauna was compared at approximately four-week intervals in triplicate plots with three levels (Control – C, Low Dose – LD and High Dose – HD) of weekly fertilizer additions for 17 weeks. Inorganic fertilizer (N–P–K) was applied on nine randomly defined quadrangular plots (4 m² each). All measurements were calculated from species abundances. Multivariate analyses as well as the univariate indices (richness, abundance and Shannon–Wiener index) showed statistically significant differences between the enriched and control areas during the period of the experiment. The expected gradual response based on the succession model of Pearson and Rosenberg was not observed. The nutrient doses used were high enough to cause severe decreases in abundance, richness and evenness, and an increase in dominance.     

Analysis of clustering and selection algorithms for the study of multivariate wave climate

Recent wave reanalysis databases require the application of techniques capable of managing huge amounts of information. In this paper, several clustering and selection algorithms: K-Means (KMA), self-organizing maps (SOM) and Maximum Dissimilarity (MDA) have been applied to analyze trivariate hourly time series of met-ocean parameters (significant wave height, mean period, and mean wave direction). A methodology has been developed to apply the aforementioned techniques to wave climate analysis, which implies data pre-processing and slight modifications in the algorithms. Results show that: a) the SOM classifies the wave climate in the relevant “wave types” projected in a bidimensional lattice, providing an easy visualization and probabilistic multidimensional analysis; b) the KMA technique correctly represents the average wave climate and can be used in several coastal applications such as longshore drift or harbor agitation; c) the MDA algorithm allows selecting a representative subset of the wave climate diversity quite suitable to be implemented in a nearshore propagation methodology.     

Earthquake damage assessment for deterministic scenarios in Iquique,Chile

Risk evaluation and loss analysis is key in foreseeing the impact of disasters caused by natural hazards and may contribute effectively in improving resilience in a community through the pre-evaluation of preparedness and mitigation actions. The pilot study presented herein is for the Chilean city of Iquique, which is located at the core of a seismic gap that extends from south Perú to north Chile, and has strategic geopolitical and economic importance for the country. The region was hit April 1, 2014, by an \(M_\mathrm{w}\) 8.2 earthquake that caused only moderate damage, but seismological evidence suggests that there is still a potential for a much larger event in the region. Therefore, a careful damage assessment study is fundamental to anticipate the possible physical, social, and economic consequences that Iquique may face in the future. In this work, the HAZUS-MH platform was adapted and used to simulate a set of ten plausible physics-based future seismic scenarios with magnitudes ranging from \(M_\mathrm{w}\) 8.40 to \(M_\mathrm{w}\) 8.98, which were proposed based on an analysis of interplate locking and the residual slip potential remaining after the April 1, 2014, earthquake. Successful application of this damage assessment methodology relies on the construction of a comprehensive exposure model that takes into account regional features and a good characterization of the physical vulnerabilities. For Iquique, a large body of public and local data was used to develop a detailed inventory of physical and social assets including an aggregated building count, demographics, and essential facilities. To characterize the response of the built environment to seismic demand, appropriate HAZUS fragility curves were applied, and outcomes were validated against the damage observed in the 2014 earthquake. After satisfactory testing, a deterministic earthquake damage assessment study was carried out for the collection of predictive scenarios aimed to estimate their expected impacts. This analysis provides data for future evaluations of different physical and social mitigation measures for the city.     

Development of an innovative seismic strengthening technique for traditional load-bearing masonry walls

Traditional non-reinforced masonry walls are particularly prone to failure when subjected to out-of-plane loads and displacements caused by earthquakes. Moreover, singularities such as openings in fa?ades may trigger local collapse, for either in-plane or out-of plane motion. Bearing in mind all the former limitations, STAP, with the scientific support of ICIST and LNEC, has been developing a reduced intrusiveness seismic strengthening methodology for traditional masonry structures. The technique consists in externally applying Glass Fibre Reinforced Polymer (GFRP) composite strips to one or both faces of walls. Connection between GFRP composite strips and masonry substrate is enhanced through specifically detailed anchorages or confinement connectors. This technique has been developed and studied through an extensive series of experimental tests, which are briefly reviewed. This paper focuses more deeply on the latest experimental program, aimed at the characterization of the masonry-GFRP composite interface behaviour. This testing program comprised 29 masonry specimens, strengthened with externally bonded GFRP composite strips with anchorages. The testing variables were the number and spacing of anchorages as well as the loading history type: monotonic or repeated. Results clearly show that the use of anchorages dramatically enhances bond behaviour and that its number and spacing have a significant effect on deformation capacity and a less pronounced effect on strength. Based on experimental evidence, this paper also provides a calculation model and ULS safety assessment procedure for out-of-plane strength of reinforced masonry walls. This calculation model leads to interaction curves on strengthened masonry walls subjected to compression and out-of-plane flexure.     

Anthropogenic and climatic influences on the diatom flora within the Fallen Leaf Lake watershed,Lake Tahoe Basin,California over the last millennium

This study addresses the effects of climate, land-use, and atmospheric nitrogen (N) deposition on the Fallen Leaf Lake watershed, Lake Tahoe Basin, through diatom and geochemical analyses of sediment cores. Four diatom zones are recognized from a core taken at Fallen Leaf Lake (FLL), a site moderately impacted by human activities: (1) Pre-Little Ice Age Zone (840–1385), (2) Little Ice Age Zone (1385–1810) characterized by Stephanodiscus alpinus and Aulacoseira subarctica, (3) Transitional Zone (1810–1950) of warming and anthropogenic influence with increased Lindavia rossii-ocellata group and Discostella stelligera and decreased Pseudostaurosira brevistriata, and (4) Anthropogenic Zone (1950–2010) characterized by a rapid increase of mesotrophic diatoms of the Fragilaria tenera-nanana group, Tabellaria flocculosa strain IIIP, and Nitzschia gracilis. The Transitional Zone increases in elemental Co, Zn, and Sn that may be attributed to an increase in coal burning and smelting activities in California and Nevada. Beginning around 1910 and accelerating in the 1940s, increased building, land-use, and recreation around FLL caused an increase in terrestrial sedimentary input. Down core proxies for atmospheric N deposition in the FLL watershed are, at best, weakly expressed and appear to be overshadowed by stronger signals. Lack of support for N deposition includes the asynchrony in the appearance of the N-sensitive diatom Asterionella formosa in FLL and a lower impact site at Gilmore Lake, and an uninformative δ¹⁵N record. Asterionella formosa is a dominant component in the FLL water column today, but has been present in similar abundances for at least the last 1200 years. Asterionella formosa is present in the water column at Gilmore Lake and absent from the sediment, indicating a very recent appearance. The data collected show that the FLL record is sensitive to climatic cooling during the Little Ice Age and to anthropogenic activities commencing in the 1800s that increased throughout the latter half of the twentieth century; however the effects of anthropogenic N deposition in these lakes could not be substantiated.     

A 1500-year record of temperature and glacial response inferred from varved Iceberg Lake, southcentral Alaska

We present a varve thickness chronology from glacier-dammed Iceberg Lake in the southern Alaska icefields. Radiogenic evidence confirms that laminations are annual and record continuous sediment deposition from A.D. 442 to A.D. 1998. Varve thickness is positively correlated with Northern Hemisphere temperature trends, and more strongly with a local, ∼600 yr long tree ring width chronology. Varve thickness increases in warm summers because of higher melt, runoff, and sediment transport (as expected), but also because shrinkage of the glacier dam allows shoreline regression that concentrates sediment in the smaller lake. Varve thickness provides a sensitive record of relative changes in warm season temperatures. Relative to the entire record, temperatures implied by this chronology were lowest around A.D. 600, warm between A.D. 1000 and A.D. 1300, cooler between A.D. 1500 and A.D. 1850, and have increased dramatically since then. Combined with stratigraphic evidence that contemporary jökulhlaups (which began in 1999) are unprecedented since at least A.D. 442, this record suggests that 20th century warming is more intense, and accompanied by more extensive glacier retreat, than the Medieval Warm Period or any other time in the last 1500 yr.     

The molar volume of FeO–MgO–Fe2O3–Cr2O3–Al2O3–TiO2 spinels

We define and calibrate a new model of molar volume as a function of pressure, temperature, ordering state, and composition for spinels in the supersystem (Mg, Fe²⁺)(Al, Cr, Fe³⁺)₂O₄ ? (Mg, Fe²⁺)₂TiO₄. We use 832 X-ray and neutron diffraction measurements performed on spinels at ambient and in situ high-P, T conditions to calibrate end-member equations of state and an excess volume model for this system. The effect on molar volume of cation ordering over the octahedral and tetrahedral sites is captured with linear dependence on Mg²⁺, Al³⁺, and Fe³⁺ site occupancy terms. We allow standard-state volumes and coefficients of thermal expansion of the end members to vary within their uncertainties during extraction of the mixing properties, in order to achieve the best fit. Published equations of state of the various spinel end members are analyzed to obtain optimal values of the bulk modulus and its pressure derivative, for each explicit end member. For any spinel composition in the supersystem, the model molar volume is obtained by adding excess volume and cation order-dependent terms to a linear combination of the five end-member volumes, estimated at pressure and temperature using the high-T Vinet equation of state. The preferred model has a total of 9 excess volume and order-dependent parameters and fits nearly all experiments to within 0.02 J/bar/mol, or better than 0.5 % in volume. The model is compared to the current MELTS spinel model with a demonstration of the impact of the model difference on the estimated spinel-garnet lherzolite transition pressure.