Spherical First Passage Time: A tool to investigate area-restricted search in three-dimensional movements

A better understanding of animal movements is of crucial importance for investigating numerous ecological issues. Developments in bio-logging technologies largely contributed to the observation and recording of animal displacements. Recently, several devices were developed to track animals in a three-dimensional space. However, given the larger number of variables, these advances generated new analytical problems and currently, few methods exist to analyse 3-D movements. In this study, we present a new technique, the Spherical First Passage Time (SFPT), to determine the scale of search behaviour in a volume. Building on the development of the First Passage Time (FPT) approach, SFPT measures the time required to cross a sphere along a 3-D path. We used simulations as they provide an opportunity to better understand processes involved in a system. Moreover, they offer the advantage of considerably increasing sample size in cases where empiric data remain scarce. However, in order to be more realistic, simulations were constrained within the physiological and behavioural features inherent to a diving animal, in this case beluga whales. First, we modelled three-dimensional movements as a correlated random walk for which the vertical and horizontal dimensions were considered simultaneously. One restricted search event was included in each simulation. Spatial scales obtained with the SFPT approach were compared to those obtained from the classical FPT analysis over the corresponding horizontal path. Results indicate a significant difference between the two approaches, suggesting that, in most cases, an approach in 2-D misrepresents spatial scale of search behaviour occurring in 3-D. Although we tested the SFPT with the example of a diving marine mammal, we argue that this method is applicable for all animals moving in a three-dimensional space.     

An assessment of benthic condition in several small watersheds of the Chesapeake Bay, USA

We examined benthic condition in three small watersheds in the Chesapeake Bay. Characterization of benthic condition was based on the combined measurements of benthic fauna, sediment toxicity, and sediment contaminant loads. Significant differences between watersheds were detected for sediment contaminant concentrations and water quality. The intensity of benthic impairment was greatest in the river surrounded by the most developed watershed. Spatial patterns of benthic condition were detected within all three watersheds. In contrast to current, intense focus on nutrient pollution in the Chesapeake Bay, qualitative comparison of our findings to land-use patterns supports findings of other studies that suggest benthic condition in tributaries of the Chesapeake Bay may more closely relate to urbanization than agricultural land uses.     

Hazards from carbon dioxide capture, transport and storage

Carbon capture and storage (CCS) is a developing technology which raises a number of issues in terms of safety. CCS involves a chain of processes comprising capture of carbon dioxide, transport and injection into underground storage. In work carried out for the IEA Greenhouse Gas R&D Programme, a number of high-level hazard identification (HAZID) studies have been performed with the help of industry experts. The HAZIDs considered a carbon capture and storage chain involving capture, pipeline transport and injection. HAZID has been performed at a high-level for such a CCS chain with three types of capture technology and using pipeline transport. It is hoped that the results of the HAZID studies will be of use to those carrying out CCS projects, but should not be a substitute for them carrying out a full suite of integrated hazard management processes. A number of example hazards have been described to raise awareness of the range of hazards in a CCS process and to identify barriers which could prevent, minimise, control or mitigate CCS hazards. Bow-tie diagrams have been produced to record the information from this study and to organise it in a systematic way so that it is far less likely that contributors to and mitigators of hazards will be missed. The diagrams are available in Excel spreadsheet format so that they can be used as the starting point for development by specific CCS projects. CCS technology is still advancing and a number of knowledge gaps in terms of safety have been identified which require further development.     

Fishery Stability, Local Extinctions, and Shifts in Community Structure in Skates

Abstract: Skates are arguably the most vulnerable of exploited marine fishes. Their vulnerability is often assessed by examining fisheries catch trends, but these data are not generally recorded on a species basis except in France. Aggregated skate catch statistics tend to exhibit more stable trends than those of other elasmobranch fisheries. We tested whether such apparent stability in aggregated catch trends could mask population declines of individual species. We examined two time series of species-specific surveys of a relatively stable skate fishery in the northeast Atlantic. These surveys revealed the disappearance of two skate species, long-nose skate (   Dipturus oxyrhinchus ) and white skate (   Rostroraja alba ) and confirmed a previously documented decline of the common skate (   D. batis ). Of the remaining five skate species, the three larger ones have declined, whereas two smaller species have increased in abundance. The increase in abundance and biomass of the smaller species has resulted in the stability of the aggregated catch trends. Because there is significant dietary overlap among species, we suggest the increase in abundance of the smaller species may be due to competitive release as the larger species declined. A consequence of this kind of stability is that declining species cannot be detected without species-specific data, especially in taxa exhibiting competitive interactions. This may explain why previously documented disappearances of two species of skates went unnoticed for so long. The conservation of skates and other elasmobranchs requires species-specific monitoring and special attention to larger species.     

Cover Image

Over recent years, technical developments resulting in the feasibility of fetal cardiovascular magnetic resonance (CMR) have provided a new diagnostic tool for studying the human fetal heart and circulation. During the same period, we have witnessed the arrival of several minimally invasive fetal cardiac interventions (FCI) as a possible form of treatment in selected congenital heart diseases (CHDs). The role of fetal CMR in the planning and monitoring of FCI is not yet clear. Indeed, high-quality fetal CMR is not available or routinely offered at most centers caring for patients with prenatally detected CHD. However, in theory, fetal CMR could have much to offer in the setting of FCI by providing complementary anatomic and physiologic information relating to the specific intervention under consideration. Similarly, fetal CMR may be useful as an alternative imaging modality when ultrasound is hampered by technical limitations, for example, in the setting of oligohydramnios and in late gestation. In this review, we summarize current experience of the use of fetal CMR in the diagnosis and monitoring of fetuses with cardiopathies in the setting of a range of invasive in utero cardiac and vascular interventions and medical treatments and speculate about future directions for this versatile imaging medium.     

Development of algorithms for predicting ignition probabilities and explosion frequencies

A project was performed for the Explosion Research Cooperative to develop algorithms for predicting the frequencies of explosions based on a variety of design, operating and environmental conditions. Algorithms were developed for estimating unit-based explosion frequencies, such as those reported in API Recommended Practice 752, but in more detail and covering a much broader range of chemical process types. The project also developed methods for predicting scenario-based explosion frequencies, using frequencies of initiating events and conditional probabilities of immediate ignition and delayed ignition resulting in explosion. The algorithms were based on a combination of published data and expert opinion.     

Dissipation of sulfamethoxazole and trimethoprim antibiotics from manure-amended soils

In this study, the dissipation of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TRM), in three soils under both aerobic and anaerobic conditions are evaluated. Under aerobic conditions, SMX dissipated rapidly through biodegradation but TRM was more persistent. Within the first 20 days in biologically active soils, >50% of the SMX was lost from the clay loam and loamy sand soils, and >80% loss was noted in the loam soil. Anaerobic dissipation of both compounds was more rapid than aerobic dissipation. The addition of manure to the soil only slightly increased the initial dissipation rate of the two compounds. Little effect was found on glucose mineralisation in soil following the addition of SMX and TRM, even as mixtures at high concentrations.