Advances in the fatigue assessment of wire ropes

This paper presents the findings from an in-depth analysis of the (axial) stiffness data recorded during tension–tension fatigue tests on wire ropes, particularly in relation to how changes in stiffness during testing relate to changes in rope strength. A linear relationship between stiffness and strength is shown to exist and a methodology presented for quantifying residual strength with applied cycles. New lower bound fatigue lines for six-strand rope and spiral strand are presented which are based on a 10% loss of strength. These new lines have the advantage of having been established using a common discard criterion for wire ropes.     

Abundance of the introduced seastar, Asterias amurensis, and spatial variability in soft sediment assemblages in SE Tasmania: Clear correlations but complex interpretation

The northern Pacific seastar, Asterias amurensis, was first collected in southeast Tasmania in 1986. Mistaken for the endemic asteroid Uniophora granifera, its true identity was not realised until 1992. It is now a conspicuous predator in soft sediment habitats in this region, and is considered a major threat to native assemblages and commercial species. We examined the structure of soft sediment assemblages at different spatial scales in southeast Tasmania, and correlated spatial variation in community composition with seastar abundances. We found that the structure of soft sediment assemblages is highly variable at a range of spatial scales from metres to tens of kilometres. Clear differences in the composition of assemblages and abundances of major taxa were detected between areas with and without seastars and between areas with low and high seastar densities. However, the nature of these patterns suggests that they are more likely due to differences in sediment characteristics than due to impacts of the seastar. Thus, spatial differences in soft sediment assemblages might have been erroneously attributed to seastars without detailed information on important physical factors such as sediment characteristics. A second survey, using larger sampling units (1 m²) but across a more limited spatial extent, targeted bivalves and heart urchins that were identified as important prey of the seastar in observations of feeding and in experimental studies. Large-scale patterns of abundance and size structure were consistent with seastar effects anticipated from small-scale experimental and feeding studies for some, but not all, species. While the field survey ultimately provided evidence about the presence or absence of seastar impacts at large-scales, the identification of key ecological variables in experimental and feeding studies proved crucial to both the design and interpretation of patterns observed in the large-scale surveys. Overall, this work highlighted the necessity to consider multiple lines of evidence rather than relying on a single ‘inferential’ test, in the absence of pre-impact data.     

Ground-based FTIR Measurements with High Temporal Resolution

We outline how ground-based Fourier transform infrared (FTIR) measurements of stratospheric trace species, obtained with high temporal resolution, could be used to detect filaments of polar vortex air at mid-latitudes and therefore test high spatial resolution chemical transport models (CTMs). Vertical column abundances of HCl, ClONO2, HNO3, N2O and HF have been obtained from FTIR solar absorption measurements made throughout the day from Aberdeen, UK (57°N, 2°W) on several days during winter/spring 1993/94 and 1994/95. The short-timescale ( 2 hours) variability observed in the columns is attributed to real atmospheric variations and is often associated with the passage of high latitude air over Aberdeen. This is confirmed by 3D modelling studies which qualitatively reproduce and rationalise the observed changes in the column data on January 19 1994, January 20 1995 and February 26 1995. We describe the viewing geometry of ground-based FTIR measurements and we suggest a measurement strategy which should maximise the information retrieved on horizontal gradients in stratospheric trace species columns from FTIR measurements.     

Spatial and Temporal Variations in <Emphasis Type="Italic">Pyrodinium bahamense</Emphasis> Cyst Concentrations in the Sediments of Bioluminescent Mangrove Lagoon,St. Croix,USVI

Mangrove Lagoon, located on the island of St. Croix, US Virgin Islands (USVI), is one of few actively bioluminescent lagoons in a location experiencing significant anthropogenic impacts. The bioluminescence is due to an abundance of the dinoflagellate Pyrodinium bahamense in the water column. We recovered surface sediments and sediment cores from Mangrove Lagoon to analyze the spatial distribution and temporal variability of P. bahamense cysts in this system. Surface sediment P. bahamense cyst concentrations ranged from 0 to 466 cysts g^?1 dry sediment, with higher abundances associated with elevated surface water nutrient concentrations and a mixed terrestrial–marine organic matter source regime. In combination with available bioassay data, we hypothesize that phytoplankton utilize nutrients rapidly and subsequent decay of organic matter makes nutrients available for dinoflagellates at the sediment–water interface in the eastern and northern quadrants of the lagoon. However, the nutrients are rapidly exhausted during counterclockwise lagoon circulation resulting in the decline of primary productivity and dinoflagellate abundance in the western quadrants. Downcore profiles suggest that P. bahamense blooms have been occurring for decades, declining in recent years. No cysts were present in sediments predating dredging activities of the 1960s that created Mangrove Lagoon. Recent reductions in cyst abundance may be the result of limited primary productivity caused by restricted water exchange with Salt River Bay due to shallowing of a sill at the mouth of the lagoon. This research highlights the need for more comprehensive geochemical and fossil analyses to better understand long-term ecological variability and inform conservation efforts of these unique habitats.     

Mechanisms for the prevention of marine bioinvasions for better biosecurity

Biosecurity management allows countries to meet a number of international obligations and provides some protection from potential degradation of environmental, economic, social and cultural values. Ocean governance relies on the precepts of ecologically sustainable development to manage the multiple uses in the coastal zone. The increasing reliance on aquaculture to provide food security and economic development has led to an increase in the use of non-native target species grown as food sources. Increased economic activity has led to shifting trade patterns and increased efficiencies in vessels with the resulting increase in the number of introduced marine species via ballast water and hull fouling. Herein we review the different marine biosecurity strategies and legislation that have been implemented internationally and locally that aid in preventing and managing introduced marine species, with some attention to Australia and New Zealand as examples. Typical tools being used include quarantine, Import Health Standards, voluntary cleaning guidelines, and risk assessment, all of which aim to prevent introductions.     

Evolution of the Taupo Volcanic Center, New Zealand: petrological and thermal constraints from the Omega dacite

The 20 ka ~0.1 km³ Omega dacite, which erupted shortly after the 26.5 ka Oruanui super-eruption, compositionally stands out among Taupo Volcanic Zone (TVZ) magmas, which are overwhelmingly characterized by rhyolites (>90 % by volume). The previously reported presence of inherited zircons in this zircon-undersaturated magma has provided unequivocal evidence for the involvement of upper-crustal material in a 1–10 year timescale prior to the Omega eruption. However, whether this crustal involvement is characterized by wholesale, melting of preexisting crust or subordinate bulk assimilation into an already differentiated magma body remains unclear. To disentangle these processes, we describe the mineral chemistry of the major phases present in the Omega dacite and determine intensive parameters describing magma chamber conditions. Dominantly unimodal populations of plagioclase (An_50–60), orthopyroxene (Mg# from 58 to 68), and clinopyroxene (Mg# from 65 to 73), along with coexisting equilibrium pairs of Fe–Ti oxides, constrain pre-eruptive temperatures to 850–950 °C, a pressure between ~3 and 7 kbars, and an oxygen fugacity of ~NNO. MELTS thermodynamic modeling suggests that this phase assemblage is in equilibrium with the bulk rock and glass compositions of the Omega dacite at these estimated P–T–fO₂ pre-eruptive conditions. Combining these petrological observations with insights into conductive thermal models of magma–crust interactions, we argue that the Omega dacite more likely formed in the mid-to-lower crust via protracted processing through fractional crystallization coupled with some assimilation (AFC). Incorporation of crustal material is likely to have occurred at various stages, with the inherited zircons (and potentially parts of glomerocrysts) representing late and subordinate upper-crustal assimilants. This petrogenetic model is consistent with the presence of a differentiating crustal column, consisting of a polybaric fractional crystallization and assimilation history. On the basis of petrological, thermal, and geophysical considerations, upper-crustal reservoirs, which feed large-scale rhyolitic volcanism in the TVZ, most likely take the form of large, long-lived crystal mush zones. Following large eruptions, such as the Oruanui event, this mush is expected to crystallize significantly (up to 70–80 vol% crystals) due to syn-eruptive decompression. Hence, the Omega dacite, immediately post-dating the Oruanui event, potentially represents incoming deeper recharge of less-evolved magma that was able to penetrate the nearly solidified upper-crustal mush. Over the past 20,000 years, similar intermediate recharge magmas have incrementally reheated, reconstructed, and reactivated the upper-crustal mush zone, allowing a gradual return to rhyolitic volcanism at the Taupo Volcanic Center.     

Analytical and Numerical Modeling of Solute Intrusion,Recovery, and Rebound in Fractured Bedrock

Contaminated groundwater in fractured bedrock can expose ecosystems to undesired levels of risk for extended periods due to prolonged back-diffusion from rock matrix to permeable fractures. Therefore, it is key to characterize the diffusive mass loading (intrusion) of contaminants into the rock matrix for successful management of contaminated bedrock sites. Even the most detailed site characterization techniques often fail to delineate contamination in rock matrix. This study presents a set of analytical solutions to estimate diffusive mass intrusion into matrix blocks, it is recovered by pumping and concentration rebound when pumping ceases. The analytical models were validated by comparing the results with (1) numerical model results using the same model parameters and (2) observed chloride mass recovery, rebound concentration, and concentration in pumped groundwater at a highly fractured bedrock site in Alberta, Canada. It is also demonstrated that the analytical solutions can be used to estimate the total mass stored in the fractured bedrock prior to any remediation thereby providing insights into site contamination history. The predictive results of the analytical models clearly show that successful remediation by pumping depends largely on diffusive intrusion period. The results of initial mass from the analytical model was used to successfully calibrate a three-dimensional discrete fracture network numerical model further highlighting the utility of the simple analytical solutions in supplementing the more detailed site numerical modeling. Overall, the study shows the utility of simple analytical methods to support long-term management of a contaminated fractured bedrock site including site investigations and complex numerical modeling.     

Molecular modeling of Al and benzene interactions with Suwannee fulvic acid

The effects that Al³⁺ and benzene interactions exhibit on a model fulvic acid were investigated. Energy minimizations of the structures mimicking the interactions of Al³⁺-Suwannee fulvic acid (SFA), benzene-SFA and Al³⁺-benzene-SFA were run with a solvation sphere of 60 H₂O molecules with the semi-empirical methods PM3 and PM5. The semi-empirical method PM3 was run with Gaussian 98 and CAChe Workstation Pro 6.1.1 to compare the results of the energy minimization algorithms in the two programs. PM5 calculations were run with CAChe Workstation Pro 6.1.1. Molecular dynamics (MD) simulations were run in Cerius² (Accelrys Inc., San Diego, CA) using the Universal Force Field (UFF) 1.02 [Rappé A. K., Casewit C., Colwell K., Goddard W., and Skiff W. (1992) UFF, a full periodic-table force-field for molecular mechanics and molecular dynamics simulations. J. Am. Chem. Soc.114(25), 10024-10035] and COMPASS force field [Sun H. (1998) COMPASS: an ab initio force-field optimized for condensed-phase applications—overview with details on alkane and benzene compounds. J. Phys. Chem. B102, 7338-7364]. Single point calculations were run on the minimized structures at the B3LYP/6-31G(d) level to obtain more accurate estimates of the energy on the minimized structures derived from the PM3, PM5, and UFF methods and to normalize energies to the same reference state. This methodology was used as the standard of comparison for all the models to assess whether or not a given configuration was reasonably stable.The PM3/G03 energy minimizations predicted the lowest B3LYP/6-31G(d) potential energies of the methodologies examined in this study. Thus, this method is considered the most reliable of those tested. The PM3/G03 method predicted that there would be aromatic-aromatic interactions between benzene and SFA. The presence of Al³⁺ was predicted not to interfere with aromatic-aromatic interactions between benzene and SFA, but benzene may influence the location of metal complexation to SFA.     

Ground truth seismic events and location capability at Degelen mountain, Kazakhstan

We utilized nuclear explosions from the Degelen Mountain sub-region of the Semipalatinsk Test Site (STS), Kazakhstan, to assess seismic location capability directly. Excellent ground truth information for these events was either known or was estimated from maps of the Degelen Mountain adit complex. Origin times were refined for events for which absolute origin time information was unknown using catalog arrival times, our ground truth location estimates, and a time baseline provided by fixing known origin times during a joint hypocenter determination (JHD). Precise arrival time picks were determined using a waveform cross-correlation process applied to the available digital data. These data were used in a JHD analysis. We found that very accurate locations were possible when high precision, waveform cross-correlation arrival times were combined with JHD. Relocation with our full digital data set resulted in a mean mislocation of 2 km and a mean 95% confidence ellipse (CE) area of 6.6 km² (90% CE: 5.1 km²), however, only 5 of the 18 computed error ellipses actually covered the associated ground truth location estimate. To test a more realistic nuclear test monitoring scenario, we applied our JHD analysis to a set of seven events (one fixed) using data only from seismic stations within 40° epicentral distance. Relocation with these data resulted in a mean mislocation of 7.4 km, with four of the 95% error ellipses covering less than 570 km² (90% CE: 438 km²), and the other two covering 1730 and 8869 km² (90% CE: 1331 and 6822 km²). Location uncertainties calculated using JHD often underestimated the true error, but a circular region with a radius equal to the mislocation covered less than 1000 km² for all events having more than three observations.     

Community preparedness for lava flows from Mauna Loa and Hualālai volcanoes,Kona, Hawai‘i

Lava flows from Mauna Loa and Huallai volcanoes are a major volcanic hazard that could impact the western portion of the island of Hawaii (e.g., Kona). The most recent eruptions of these two volcanoes to affect Kona occurred in a.d. 1950 and ca. 1800, respectively. In contrast, in eastern Hawaii, eruptions of neighboring Klauea volcano have occurred frequently since 1955, and therefore have been the focus for hazard mitigation. Official preparedness and response measures are therefore modeled on typical eruptions of Klauea.The combinations of short-lived precursory activity (e.g., volcanic tremor) at Mauna Loa, the potential for fast-moving lava flows, and the proximity of Kona communities to potential vents represent significant emergency management concerns in Kona. Less is known about past eruptions of Huallai, but similar concerns exist. Future lava flows present an increased threat to personal safety because of the short times that may be available for responding.Mitigation must address not only the specific characteristics of volcanic hazards in Kona, but also the manner in which the hazards relate to the communities likely to be affected. This paper describes the first steps in developing effective mitigation plans: measuring the current state of peoples knowledge of eruption parameters and the implications for their safety. We present results of a questionnaire survey administered to 462 high school students and adults in Kona. The rationale for this study was the long lapsed time since the last Kona eruption, and the high population growth and expansion of infrastructure over this time interval. Anticipated future growth in social and economic infrastructure in this area provides additional justification for this work.The residents of Kona have received little or no specific information about how to react to future volcanic eruptions or warnings, and short-term preparedness levels are low. Respondents appear uncertain about how to respond to threatening lava flows and overestimate the minimum time available to react, suggesting that personal risk levels are unnecessarily high. A successful volcanic warning plan in Kona must be tailored to meet the unique situation there.