The Monitor project: rotation of low-mass stars in the open cluster NGC 2547

We report on the results of an I -band time-series photometric survey of NGC 2547 using the MPG/ESO 2.2-m telescope with Wide Field Imager, achieving better than 1 per cent photometric precision per data point over  14 ≲ I ≲ 18  . Candidate cluster members were selected from a V versus V − I colour–magnitude diagram over  12.5 < V < 24  (covering masses from  0.9 M_⊙  down to below the brown dwarf limit), finding 800 candidates, of which we expect ∼330 to be real cluster members, taking into account contamination from the field (which is most severe at the extremes of our mass range). Searching for periodic variations in these gave 176 detections over the mass range  0.1 ≲ M /M_⊙≲ 0.9  . The rotation period distributions were found to show a clear mass-dependent morphology, qualitatively intermediate between the distributions obtained from similar surveys in NGC 2362 and 2516, as would be expected from the age of this cluster. Models of the rotational evolution were investigated, finding that the evolution from NGC 2362 to 2547 was qualitatively reproduced (given the uncertainty in the age of NGC 2547) by solid body and core-envelope decoupled models from our earlier NGC 2516 study without need for significant modification.     

High‐resolution quantification of earthworm calcite granules from western European loess sequences reveals stadial–interstadial climatic variability during the Last Glacial

High concentrations of calcite fossil granules produced by earthworms (ECG) have been identified in most of the stratigraphical units along the loess‐palaeosol reference sequence of Nussloch (Germany). They are particularly abundant in interstadial brown soils and in tundra gley horizons, the latter reflecting short‐term phases of aggradation then degradation of permafrost. These granules are characterized by a radial crystalline structure produced in the earthworms by specific bio‐mineralization processes. In our study, we used this biological indicator combined with ¹⁴C and OSL dating, and sedimentological parameters to characterize millennial‐time scale climatic variations recorded in loess sequences. The approach is based on high‐resolution counts of ECG throughout a 17‐m‐thick loess sequence (332 samples). Strong increases in granule and mollusc concentrations suggest warmer climate conditions during palaeosol formation phases, associated with increasing biodiversity, biological activity and vegetation cover. Decreased granule concentrations occur within primary loess deposits, indicating a strong correlation with palaeoenvironmental conditions and demonstrating the reliability of ECG concentration variations as a new palaeoenvironmental proxy. Finally, this pattern is also recorded in loess sequences located about 600 km westward in northern France demonstrating the large‐scale validity of this new palaeoclimatic proxy.     

Lead orthophosphates—IV Formation and stability in the environment

Experimental and predicted thermochemical constants are used to assess the formation and stability of lead phosphates in soil and sedimentary environments. For the chemical conditions likely to be encountered in oxidizing environments, the stability fields of pyromorphites [Pb₅(PO₄)₃X, X = OH^?, Cl^?, Br^? and F^?] and plumbogummite [PbAl₃(PO₄)₂(OH)₅-H₂O] predominate strongly over those of the other secondary lead minerals. The theoretical phase relationships together with several field observations are used as the basis for suggesting that the interaction of lead and phosphorus (to form pyromorphites and plumbogummite in particular) is an important buffer mechanism controlling the migration and fixation of lead in the environment. Calculations using the concentrations of lead and phosphate ions in serum indicate that the solubility of lead phosphates may be the limiting factor with regard to lead ion concentration in human body. The removal of lead from wastewater by precipitation as lead chloropyromorphite is considered a spin-off of possible industrial interest.     

Development and Re‐Evaluation of Tourmaline Reference Materials for In Situ Measurement of Boron δ Values by Secondary Ion Mass Spectrometry

Six tourmaline samples were investigated as potential reference materials (RMs) for boron isotope measurement by secondary ion mass spectrometry (SIMS). The tourmaline samples are chemically homogeneous and cover a compositional range of tourmaline supergroup minerals (primarily Fe, Mg and Li end‐members). Additionally, they have homogeneous boron delta values with intermediate precision values during SIMS analyses of less than 0.6‰ (2s). These samples were compared with four established tourmaline RMs, that is, schorl IAEA‐B‐4 and three Harvard tourmalines (schorl HS#112566, dravite HS#108796 and elbaite HS#98144). They were re‐evaluated for their major element and boron delta values using the same measurement procedure as the new tourmaline samples investigated. A discrepancy of about 1.5‰ in δ¹¹B was found between the previously published reference values for established RMs and the values determined in this study. Significant instrumental mass fractionation (IMF) of up to 8‰ in δ¹¹B was observed for schorl–dravite–elbaite solid solutions during SIMS analysis. Using the new reference values determined in this study, the IMF of the ten tourmaline samples can be modelled by a linear combination of the chemical parameters FeO + MnO, SiO₂ and F. The new tourmaline RMs, together with the four established RMs, extend the boron isotope analysis of tourmaline towards the Mg‐ and Al‐rich compositional range. Consequently, the in situ boron isotope ratio of many natural tourmalines can now be determined with an uncertainty of less than 0.8‰ (2s).     

Biotite Reference Materials for Secondary Ion Mass Spectrometry 18O/16O Measurements

Five new biotite reference materials were calibrated at the SwissSIMS laboratory (University of Lausanne) for oxygen isotope determination by secondary ion mass spectrometry (SIMS) and are available to the scientific community. The oxygen isotope composition of the biotites, UNIL_B1 to B5, was determined by laser‐heating fluorination to be 11.4 ± 0.11‰, 8.6 ± 0.15‰, 6.1 ± 0.04‰, 7.1 ± 0.05‰ and 7.6 ± 0.04‰, respectively. SIMS analyses on spots smaller than 20 μm gave a measurement repeatability of 0.3‰ (2 standard deviation, 2s). The matrix effect due to solid solution in natural biotite could be expressed as a linear function of X_Mg and X_F for biotite. No effect was found for different crystallographic orientations. SIMS analysis allows the oxygen isotope composition of biotite to be measured with a measurement uncertainty of 0.3–0.4‰ (2s) for biotites with similar major element compositions. A measurement uncertainty of 0.5‰ (2s) is realistic when F poor biotites (lower than 0.2% m/m oxides) within the compositional range of X_Mg of 0.3–0.9 were compared from different sessions. The linear correlation with F content offers a reasonable working curve for F‐rich biotites, but additional reference materials are needed to confirm the model.     

Hybrid simulation testing of a self‐centering rocking steel braced frame system

The self‐centering rocking steel frame is a seismic force resisting system in which a gap is allowed to form between a concentrically braced steel frame and the foundation. Downward vertical force applied to the rocking frame by post‐tensioning acts to close the uplifting gap and thus produces a restoring force. A key feature of the system is replaceable energy‐dissipating devices that act as structural fuses by producing high initial system stiffness and then yielding to dissipate energy from the input loading and protect the remaining portions of the structure from damage. In this research, a series of large‐scale hybrid simulation tests were performed to investigate the seismic performance of the self‐centering rocking steel frame and in particular, the ability of the controlled rocking system to self‐center the entire building. The hybrid simulation experiments were conducted in conjunction with computational modules, one that simulated the destabilizing P‐Δ effect and another module that simulated the hysteretic behavior of the rest of the building including simple composite steel/concrete shear beam‐to‐column connections and partition walls. These tests complement a series of quasi‐static cyclic and dynamic shake table tests that have been conducted on this system in prior work. The hybrid simulation tests validated the expected seismic performance as the system was subjected to ground motions in excess of the maximum considered earthquake, produced virtually no residual drift after every ground motion, did not produce inelasticity in the steel frame or post‐tensioning, and concentrated the inelasticity in fuse elements that were easily replaced. Copyright © 2014 John Wiley & Sons, Ltd.     

Exploring the influence of biofilm on short‐term expansion and contraction of supratidal rock: an example from the Mediterranean

Previous geomorphological investigations using the traversing micro‐erosion meter (TMEM) have identified daily and hourly contractions and expansions of littoral rock on a range of lithologies. While organic influences on these patterns have been inferred, this has rarely been tested in a controlled way. Here, a TMEM was used to measure micro‐scale (<mm) topographic changes on supratidal limestone of the Massif des Calanques, southern France. Four TMEM monitoring sites (each 64 cm²) were set up in total, two in the Calanque de Morgiou and two in the Presqu'ile de Cassis. On both shores one TMEM bolt site was positioned on bare rock and the other on colonized rock. TMEM data were collected and the surface micro‐topography mapped for each site at two‐hourly intervals from early morning to late evening across one day in mid‐summer. Significant relative expansion and contraction was observed between measurement periods at all four sites, regardless of biofilm colonization (P < 0.001 in all instances), and sometimes between adjacent zones on the rock surface (at a scale of centimetres). Rock with and without biofilm behaved broadly similarly, but the magnitude of topographic change varied: average movement from one interval to the next was 0.03 mm on bare sites and 0.06 mm on biofilm‐colonized sites. As expected, patterns of surface change related largely to insolation, with greatest movement occurring in the morning and evening when thermal gradients were steepest. Interestingly, the presence of a biofilm intensified rock expansion, but delayed surface response to microclimatic variability. We largely attribute this effect to biofilm influences on surface albedo, and hypothesize that episodes of contraction and expansion are superimposed onto longer (annual to decadal) episodes of surface movement and downwearing. Short‐term TMEM studies therefore need to be coupled with longer‐term seasonal and annual measurements to improve understanding of rock surface dynamics. Copyright © 2014 John Wiley & Sons, Ltd.     

Mechanical and low-cycle fatigue behavior of stainless reinforcing steel for earthquake engineering applications

Use of stainless reinforcing steel (SRS) in reinforced concrete (RC) structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue behavior. Three types of SRSs (Talley S24100, Talley 316LN and Talley 2205) were tested and the results are reported in this paper. They were compared with the properties of A706 carbon reinforcing steel (RS), which is typical for seismic applications, and MMFX II, which is a high strength, corrosion resistant RS. Low-cycle fatigue tests of the RS coupons were conducted under strain control with constant amplitude to obtain strain life models of the steels. Test results show that the SRSs have slightly lower moduli of elasticity, higher uniform elongations before necking, and better low-cycle fatigue performance than A706 and MMFX II. All five types of RSs tested satisfy the requirements of the ACI 318 code on the lower limit of the tensile to yield strength ratio. Except Talley 2205, the other four types of RSs investigated meet the ACI 318 requirement that the actual yield strength does not exceed the specified yield strength by more than 18 ksi (124 MPa). Among the three types of SRSs tested, Talley S24100 possesses the highest uniform elongation before necking, and the best low-cycle fatigue performance.