Net and Acoustic Examination of Bathypelagic Nekton on the Mid-Atlantic Ridge

Spatial distributions of organisms play a key role in facilitating trophic interactions, which influence pelagic ecosystem structure and function. This study combines discrete net trawl sampling with continuous acoustic measurements to investigate the distribution of bathypelagic (1000- 3000 m depth) nekton biomass along the Mid-Atlantic Ridge from Iceland to the Azores. Two, previously unknown, acoustic scattering layers (ASLs) were observed using 18 kHz echosounder data. The first extended approximately 200 m from 2000 m depth and was ubiquitous wherever bottom depth allowed. The second, found within the 1500-2000 m depth stratum, only occurred south of the Sub-Polar Front. Backscatter from the 2000 m ASL was attributed to fish from a suite of bathypelagic species observed throughout the study area, rather than any specific group. No general increase in backscatter, as a proxy for pelagic nekton biomass, was observed in close proximity to the bottom (≤ 200 m), but previously unreported localized concentrations of backscatter were observed when bottom topography was steep. Together these observations demonstrate higher complexity in the spatial structuring of bathypelagic ecosystems than has been previously reported and is likely to affect local ecosystem function

Interpreting the Spatial Distribution of Bathypelagic Nekton Along the Mid-Atlantic Ridge

The spatial distribution of organisms plays a key role in facilitating biological processes, such as trophic interactions, which govern ecosystem structure and function. Attempts to understand bathypelagic (1000-4000 m depth) ecosystem dynamics have been hampered by the coarse temporal-spatial resolution and static nature of most sampling strategies. This study combines a traditional approach, based on discrete net trawls sampling small volumes, with the continuous full water column coverage provided by fisheries acoustics to investigate the distribution of biomass along the Mid-Atlantic Ridge (MAR). The limited trawl samples have been interpreted as showing a positive relationship between the presence of the MAR in the bathypelagic depth zone and biomass of bathypelagic fish species. Using 18 kHz echosounder data we explored this apparent association, and used comparisons of trawl data with the acoustic backscatter distribution to provide insights into how the distribution of biomass may influence trophic interactions in the bathypelagos. As such, this research provides a valuable case study of the potential contribution of acoustics to ecosystem studies, both within fisheries management and in a wider biological context

A Prototype for the PASS Permanent All Sky Survey

A prototype system for the Permanent All Sky Survey (PASS) project is presented. PASS is a continuous photometric survey of the entire celestial sphere with a high temporal resolution. Its major objectives are the detection of all giant-planet transits (with periods up to some weeks) across stars up to mag 10.5, and to deliver continuously photometry that is useful for the study of any variable stars. The prototype is based on CCD cameras with short focal length optics on a fixed mount. A small dome to house it at Teide Observatory, Tenerife, is currently being constructed. A placement at the antarctic Dome C is also being considered. The prototype will be used for a feasibility study of PASS, to define the best observing strategies, and to perform a detailed characterization of the capabilities and scope of the survey. Afterwards, a first partial sky surveying will be started with it. That first survey may be able to detect transiting planets during its first few hundred hours of operation. It will also deliver a data set around which software modules dealing with the various scientific objectives of PASS will be developed. The PASS project is still in its early phase and teams interested in specific scientific objectives, in providing technical expertise, or in participating with own observations are invited to collaborate.Comment: Accepted for Astronomische Nachrichten (special issue for 3rd Potsdam Thinkshop 'Robotic Astronomy' in July 2004). 4 pages, 4 fig

Older Adults’ Uptake and Adherence to Exercise Classes: Instructors’ Perspectives.

yesExercise classes provide a range of benefits for older adults, but adherence levels are poor. We know little of instructors’ experiences of delivering exercise classes to older adults. Semi-structured interviews, informed by the Theory of Planned Behaviour (TPB), were conducted with instructors (n=19) delivering multi-component exercise classes to establish their perspectives on older adults’ uptake and adherence to exercise classes. Analysis revealed ‘barriers’ related to identity, choice/control, cost, venue and ‘solutions’ including providing choice, relating exercise to identity, a personal touch and social support. ‘Barriers’ to adherence included unrealistic expectations and social influences and ‘solutions’ identified were encouraging commitment, creating social cohesion and an emphasis on achieving outcomes. Older adults’ attitudes were an underlying theme, which related to all barriers and solutions. The instructor plays an important, but not isolated, role in older adults’ uptake and adherence to classes. Instructors’ perspectives help us to further understand how we can design successful exercise classes

Radiation and shielding study for the International Ultraviolet Explorer

Technical advisory services to ensure integrity of parts and material exposed to energetic particle radiation for the IUE scientific instruments, spacecraft, and subsystems are provided. A significant potential for interference, degradation, or failure for unprotected or sensitive items was found. Vulnerable items were identified, and appropriate tests, changes, and shields were defined

Demonstration of the Complementarity of One- and Two-Photon Interference

The visibilities of second-order (single-photon) and fourth-order (two-photon) interference have been observed in a Young's double-slit experiment using light generated by spontaneous parametric down-conversion and a photon-counting intensified CCD camera. Coherence and entanglement underlie one-and two-photon interference, respectively. As the effective source size is increased, coherence is diminished while entanglement is enhanced, so that the visibility of single-photon interference decreases while that of two-photon interference increases. This is the first experimental demonstration of the complementarity between single- and two-photon interference (coherence and entanglement) in the spatial domain.Comment: 21 pages, 7 figure

Experimental Validation of Cognitive Radar Anticipation using Stochastic Control

Cognition applied to radar systems is a growing area of research. The majority of cognitive radar research is focused on theory and simulation with little experimental validation. Prior research proposed the application of anticipation within a cognitive radar, demonstrating by simulation that this can provide significant improvements in tracking performance, when compared to non-cognitive radar tracking methods. The approach applied a POMDP algorithm to control the timing of track updates for a target while anticipating the loss of measurements within a known time period/region. This work aims to expand on this concept by using data from a real radar, NetRAD, in order to validate the application of anticipation when tracking a human target

Meso- and Bathypelagic Fish Interactions with Seamounts and Mid-Ocean Ridges

The World Ocean\u27s midwaters contain the vast majority of Earth\u27s vertebrates in the form of mesoand bathypelagic (\u27deep-pelagic,\u27 in the combined sense) fishes. Understanding the ecology and variability of deep-pelagic ecosystems has increased substantially in the past few decades due to advances in sampling/observation technology. Researchers have discovered that the deep sea hosts a complex assemblage of organisms adapted to a “harsh” environment by terrestrial standards (i.e., dark, cold, high pressure). We have learned that despite the lack of physical barriers, the deep-sea realm is not a homogeneous ecosystem, but is spatially and temporally variable on multiple scales. While there is a well-documented reduction of biomass as a function of depth (and thus distance from the sun, ergo primary production) in the open ocean, recent surveys have shown that pelagic fish abundance and biomass can \u27peak\u27 deep in the water column in association with abrupt topographic features such as seamounts and mid-ocean ridges. We review the current knowledge on deep-pelagic fish interactions with these features, as well as effects of these interactions on ecosystem functioning. We highlight the recent discoveries from the Mid-Atlantic Ridge (via the Census of Marine Life field project MAR-ECO) that were presented at the international symposium “Into the Unknown, Researching Mysterious Deep-Sea Animals,” hosted by the Okinawa Churaumi Aquarium, Okinawa, Japan, Feb 2007

Deep-Pelagic Fishes and the Mid-Atlantic Ridge: Interactions and Vectoring of Gelatinous Carbon to Higher Trophic Levels?

The assemblage structure and vertical distribution of deep-pelagic fishes relative to a mid-ocean ridge system is described from an acoustic and discrete-depth trawling survey conducted as part of the international Census of Marine Life field project MAR-ECO. A survey along the Mid-Atlantic Ridge (MAR), covering the full depth range (0 to \u3e3000 m) with a combination of gear types, was conducted to understand the role of the pelagic fauna in ecosystem dynamics. A total of 205 fish species were collected by midwater sampling. Depth was by far the primary assemblage composition determinant, with ridge section secondary. The dominant ichthyofaunal component was a widespread assemblage of fishes between 750-3000 m, from Iceland to the Azores. Some zonation was apparent in the northern and southern ends of this large depth stratum, with six smaller assemblages of fishes exhibiting limited distributions. Biomass per volume reached a water column maximum in the bathypelagic zone between 1500-2300 m. This stands in stark contrast to the general “open ocean” paradigm that biomass decreases exponentially from the surface downwards. As much of the summit of the MAR extends into this depth layer, a likely explanation for this midwater maximum is ridge association. Fish density within the benthic boundary layer (within 200 m of the ridge) was nearly double that of the water column and biomass was approximately 50% higher. Of the ‘ridge-associating’ species, two species known to consume gelata, Bathylagus euryops and Scopelogadus beanii, contributed over half of the fish biomass of this layer. These data suggest that a pelagic fish-gelata trophic linkage may be a key element of benthic-pelagic coupling over mid-ocean ridges, thus supporting enhanced nekton biomass over ridges in the absence of terrigenous nutrient input. Ongoing research to better understand this trophic linkage will be presented

Non-Singular Charged Black Hole Solution for Non-Linear Source

A non-singular exact black hole solution in General Relativity is presented. The source is a non-linear electromagnetic field, which reduces to the Maxwell theory for weak field. The solution corresponds to a charged black hole with |q| \leq 2s_c m \approx 0.6 m, having metric, curvature invariants, and electric field bounded everywhere.Comment: 3 pages, RevTe