Holocene and Pleistocene pluvial periods in Yemen,southern Arabia

Arabia is an important potential pathway for the dispersal of Homo sapiens (“out of Africa”). Yet, because of its arid to hyper-arid climate humans could only migrate across southern Arabia during pluvial periods when environmental conditions were favorable. However, knowledge on the timing of Arabian pluvial periods prior to the Holocene is mainly based on a single and possibly incomplete speleothem record from Hoti Cave in Northern Oman. Additional terrestrial records from the Arabian Peninsula are needed to confirm the Hoti Cave record. Here we present a new speleothem record from Mukalla Cave in southern Yemen. The Mukalla Cave and Hoti Cave records clearly reveal that speleothems growth occurred solely during peak interglacial periods, corresponding to Marine Isotope Stages (MIS) 1 (early to mid-Holocene), 5.1, 5.3, 5.5 (Eemian), 7.1, 7.5 and 9. Of these humid periods, highest precipitation occurred during MIS 5.5 and lowest during early to middle Holocene.     

Effect of Pumice and Sand on the Sustainability of Granular Iron Beds for the Aqueous Removal of CuII,NiII, and ZnII

Current knowledge of the basic principles underlying the design of Fe⁰ beds is weak. The volumetric expansive nature of iron corrosion was identified as the major factor determining the sustainability of Fe⁰ beds. This work attempts to systematically verify developed concepts. Pumice and sand were admixed to 200 g of Fe⁰ in column studies (50:50 volumetric proportion). Reference systems containing 100% of each material have been also investigated. The mean grain size of the used materials (in mm) were 0.28 (sand), 0.30 (pumice), and 0.50 (Fe⁰). The five studied systems were characterized (i) by the time dependent evolution of their hydraulic conductivity (permeability) and (ii) for their efficiency for aqueous removal of Cu^II, Ni^II, and Zn^II (about 0.3 mM of each). Results showed unequivocally that (i) quantitative contaminant removal was coupled to the presence of Fe⁰, (ii) additive admixture lengthened the service life of Fe⁰ beds, and (iii) pumice was the best admixing agent for sustaining permeability while the Fe⁰/sand column was the most efficient for contaminant removal. The evolution of the permeability was well‐fitted by the approach that the inflowing solution contained dissolved O₂. The achieved results are regarded as starting point for a systematic research to optimize/support Fe⁰ filter design.     

Tests and model calibration of high‐strength steel tubular beam‐to‐column and column‐base composite joints for moment‐resisting structures

Performance‐based engineering (PBE) methodologies allow for the design of more reliable earthquake‐resistant structures. Nonetheless, to implement PBE techniques, accurate finite element models of critical components are needed. With these objectives in mind, initially, we describe an experimental study on the seismic behaviour of both beam‐to‐column (BTC) and column‐base (CB) joints made of high‐strength steel S590 circular columns filled with concrete. These joints belonged to moment‐resisting frames (MRFs) that constituted the lateral‐force‐resisting system of an office building. BTC joints were conceived as rigid and of partial strength, whereas CB joints were designed as rigid and of full strength. Tests on a BTC joint composed of an S275 steel composite beam and high‐strength steel concrete‐filled tubes were carried out. Moreover, two seismic CB joints were tested with stiffeners welded to the base plate and anchor bolts embedded in the concrete foundation as well as where part of a column was embedded in the foundation with no stiffeners. A test programme was carried out with the aim of characterising these joints under monotonic, cyclic and random loads. Experimental results are presented by means of both force–interstory drift ratio and moment–rotation relationships. The outcomes demonstrated the adequacy of these joints to be used for MRFs of medium ductility class located in zones of moderate seismic hazard. Then, a numerical calibration of the whole joint subassemblies was successfully accomplished. Finally, non‐linear time‐history analyses performed on 2D MRFs provided useful information on the seismic behaviour of relevant MRFs. Copyright © 2015 John Wiley & Sons, Ltd.