A high resolution,multiproxy Late‐glacial record of climate change and intrasystem responses in northwest England

A lacustrine carbonate sequence from Hawes Water, Lancashire, UK, has been studied using stable isotopic, lithological, pollen and mineral magnetic analysis. The data reveal four abrupt climatic oscillations in the Late‐glacial Interstadial leading up to the onset of the Loch Lomond Stadial. The data also point to climatic warming relatively early within the stadial, ca. 12 500 GRIP yr, prior to the onset of the Holocene. The oxygen isotope record is taken as a signature of climate forcing against which the response of the lake‐system can be monitored. By adopting this approach it is revealed that the response of the biological system to the rapid climatic oscillations is non‐linear and primarily a function of the antecedent conditions. A significant end‐Devensian isotopic excursion (A) is matched by only minor changes in the cold‐adapted floras and faunas. During the warmer interstadial, the response of the biological ecosystem (events B–D) is clearly influenced by thresholds: major changes in the catchment vegetation associated with relatively minor oscillations in the isotopic signature. The stratigraphical patterns reveal significant lag effects between the onset of climate deterioration and resulting changes in vegetation. Copyright © 2002 John Wiley & Sons, Ltd.     

Pilot‐scale field validation of the long electrode electrical resistivity tomography method

A validation experiment, carried out in a scaled field setting, was attempted for the long electrode electrical resistivity tomography method in order to demonstrate the performance of the technique in imaging a simple buried target. The experiment was an approximately 1/17 scale mock‐up of a region encompassing a buried nuclear waste tank on the Hanford site. The target of focus was constructed by manually forming a simulated plume within the vadose zone using a tank waste simulant. The long electrode results were compared to results from conventional point electrodes on the surface and buried within the survey domain. Using a pole‐pole array, both point and long electrode imaging techniques identified the lateral extents of the pre‐formed plume with reasonable fidelity but the long electrode method was handicapped in reconstructing vertical boundaries. The pole‐dipole and dipole‐dipole arrays were also tested with the long electrode method and were shown to have the least favourable target properties, including the position of the reconstructed plume relative to the known plume and the intensity of false positive targets. The poor performance of the pole‐dipole and dipole‐dipole arrays was attributed to an inexhaustive and non‐optimal coverage of data at key electrodes, as well as an increased noise for electrode combinations with high geometric factors. However, when comparing the model resolution matrix among the different acquisition strategies, the pole‐dipole and dipole‐dipole arrays using long electrodes were shown to have significantly higher average and maximum values within the matrix than any pole‐pole array. The model resolution describes how well the inversion model resolves the subsurface. Given the model resolution performance of the pole‐dipole and dipole‐dipole arrays, it may be worth investing in tools to understand the optimum subset of randomly distributed electrode pairs to produce maximum performance from the inversion model.     

Shark interactions in pelagic longline fisheries

Substantial ecological, economic and social problems result from shark interactions in pelagic longline fisheries. Improved understanding of industry attitudes and practices towards shark interactions assists with managing these problems. Information on fisher knowledge and new strategies for shark avoidance may benefit sharks and fishers. A study of 12 pelagic longline fisheries from eight countries shows that incentives to avoid sharks vary along a continuum, based on whether sharks represent an economic disadvantage or advantage. Shark avoidance practices are limited, including avoiding certain areas, moving when shark interaction rates are high, using fish instead of squid for bait and deeper setting. Some conventionally employed fishing gear and methods used to target non-shark species contribute to shark avoidance. Shark repellents hold promise; more research and development is needed. Development of specifically designed equipment to discard sharks could improve shark post release survival prospects, reduce gear loss and improve crew safety. With expanding exploitation of sharks for fins and meat, improved data collection, monitoring and precautionary shark management measures are needed to ensure that shark fishing mortality levels are sustainable.     

Effectiveness of simple approaches in mitigating residual deformations in buildings

Developments in performance‐based seismic design and assessment approaches have emphasized the importance of considering residual deformations. Recent investigations have also led to a proposed direct displacement‐based design (DDBD) approach which includes an explicit consideration of the expected residual deformations as an integral part of the design process. Having estimated the expected residual deformations in a structure, engineers are faced with the problem of reducing them to meet the targeted performance levels under pre‐defined seismic hazard levels. Previous studies have identified the post‐yield stiffness as a primary factor influencing the magnitude of residual deformations in single degree of freedom and multiple degree of freedom structures. In this paper, a series of simple approaches to increase the post‐yield stiffness of traditional framed and braced systems for the purpose of reducing residual deformations are investigated. These methods do not utilize recentring post‐tensioned technology. This contribution addresses the feasibility of altering the lateral post‐yield stiffness of structural systems by: (i) using different reinforcement materials with beneficial features in their stress–strain behaviour; (ii) re‐designing the section geometry and properties of primary seismic‐resisting elements; and (iii) introducing a secondary elastic frame to act in parallel with the primary system. The efficiency of each of these techniques is investigated through monotonic and cyclic moment‐curvature and non‐linear time‐history analyses. Of these approaches the design and introduction of an elastic secondary system was found to be most effective and consistent in reducing residual deformations. A simplified design approach for achieving the desired increase of a system's post‐yield stiffness is also presented. Copyright © 2007 John Wiley & Sons, Ltd.     

Wave enhancement due to blockage in semi-submersible and TLP structures

An exact analytical method is described to solve the diffraction problem of a group of truncated vertical cylinders. In order to account for the interaction between the cylinders, Kagemoto and Yue's exact algebraic method is utilised (Kagemoto, H., Yue, D.K.P., 1986. Interactions among multiple three-dimensional bodies in water waves: an exact algebraic method. J Fluid Mech, 46, 129–139). The isolated cylinder diffraction potential is obtained using Garret's solution and evanescent mode solutions are derived in a similar manner (Garret, C.J.R., 1971. Wave forces on a circular dock. J Fluid Mech, 46, 129–139).Free surface elevations are calculated for an array of four cylinders and compared with experiments. Comparisons show good agreement.     

Sedimentology and origin of deposits from a small ice-dammed lake, Leirbreen, Norway

This paper describes recent proglacial lacustrine sediments exposed by the drainage of a small (probably never more than 0·03 km²) ice-dammed lake basin at Leirbreen, central Jotunheimen, Norway. The dominant facies include ripple-laminated, massive and horizontally-stratified sands, massive and horizontally-laminated silts, and irregularly-laminated fine sands and silts. The major control on lake circulation and the nature and distribution of these facies was an underflow driven by a subglacial meltwater stream which formed the major lake input. Although much of the sedimentary sequence indicates a pulsatory input, the proximal character of this small lake prevented the development of classic varved silts. Compressional deformation of shoreline sediments was due to winter lake ice push. Other deformational processes included the grounding of icebergs, water escape and syn-sedimentary downslope collapse. Observations from an adjacent small ice-marginal lake at Leirbreen provide support for several of the inferences drawn from the sediments of the former ice-dammed lake.     

Melt Generation and Fluid Flow in the Thermal Aureole of the Bushveld Complex

Granite sheets emplaced into the migmatite zone of the easterncontact aureole of the Bushveld Complex resulted from fluid-enhanced,incongruent biotite melting of the underlying Silverton Formationshales during prograde metamorphism. Ba concentrations are extremein both the sheets (>1000 ppm) and the hornfels (>800ppm) into which they have been emplaced. We conclude that aBa-rich, hydrothermal fluid induced melting in the aureole,and that fluid transport of Ba²⁺, and to a lesser extent, Sr²⁺and Eu²⁺, persisted in the melt zones under subsolidus conditions.Sr-isotope systematics from high-Ba localities define an errorchronof 2161 ± 106 Ma with an initial (⁸⁷Sr/⁸⁶Sr) ratio of0·705 ± 0·001. Metasedimentary rocks unaffectedby fluid infiltration were homogenized at the same time butwith an increased initial ratio, suggesting that whereas isotopehomogenization was achieved between outcrops permeated by fluids,there is no evidence of regional homogenization. Oxygen-isotopecompositions of psammitic metasediments in the aureole are uncorrelatedwith distance from the contact, suggesting the infiltratingfluid equilibrated isotopically with the metasediments. Theirelevated     

A non-main-sequence secondary in SY Cancri

Simultaneous spectroscopic and photometric observations of the Z Cam type dwarf nova SY Cancri were used to obtain absolute flux calibrations. A comparison of the photometric calibration with a wide-slit spectrophotometric calibration showed that either method is equally satisfactory. A radial velocity study of the secondary star, made using the far-red Na  i doublet, yielded a semi-amplitude of   K ₂= 127 ± 23 km s⁻¹  . Taking the published value of  86 ± 9 km s⁻¹  for K ₁ gives a mass ratio of   q = M ₂/ M ₁= 0.68 ± 0.14  ; this is very different from the value of  1.13 ± 0.35  quoted in the literature. Using the new lower mass ratio, and constraining the mass of the white dwarf to be within reasonable limits, then leads to a mass for the secondary star that is substantially less than would be expected for its orbital period if it satisfied a main-sequence mass–radius relationship. We find a spectral type of M0 that is consistent with that expected for a main-sequence star of the low mass we have found. However, in order to fill its Roche lobe, the secondary must be significantly larger than a main-sequence star of that mass and spectral type. The secondary is definitely not a normal main-sequence star.