1,038 research outputs found

    Light and Vision in the Deep-Sea Benthos: I. Bioluminescence at 500-1000 m Depth in the Bahamian Islands

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    Bioluminescence is common and well studied in mesopelagic species. However, the extent of bioluminescence in benthic sites of similar depths is far less studied, although the relatively large eyes of benthic fish, crustaceans and cephalopods at bathyal depths suggest the presence of significant biogenic light. Using the Johnson-Sea-Link submersible, we collected numerous species of cnidarians, echinoderms, crustaceans, cephalopods and sponges, as well as one annelid from three sites in the northern Bahamas (500–1000 m depth). Using mechanical and chemical stimulation, we tested the collected species for light emission, and photographed and measured the spectra of the emitted light. In addition, in situ intensified video and still photos were taken of different benthic habitats. Surprisingly, bioluminescence in benthic animals at these sites was far less common than in mesopelagic animals from similar depths, with less than 20% of the collected species emitting light. Bioluminescent taxa comprised two species of anemone (Actinaria), a new genus and species of flabellate Parazoanthidae (formerly Gerardia sp.) (Zoanthidea), three sea pens (Pennatulacea), three bamboo corals (Alcyonacea), the chrysogorgiid coral Chrysogorgia desbonni (Alcyonacea), the caridean shrimp Parapandalus sp. and Heterocarpus ensifer (Decapoda), two holothuroids (Elasipodida and Aspidochirota) and the ophiuroid Ophiochiton ternispinus (Ophiurida). Except for the ophiuroid and the two shrimp, which emitted blue light (peak wavelengths 470 and 455 nm), all the species produced greener light than that measured in most mesopelagic taxa, with the emissions of the pennatulaceans being strongly shifted towards longer wavelengths. In situ observations suggested that bioluminescence associated with these sites was due primarily to light emitted by bioluminescent planktonic species as they struck filter feeders that extended into the water column

    A Model To Measure Supination And Pronation Of The Foot Over Different Levels Of Physiological Stress Using An In-Shoe Force Monitoring System

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    The purpose of this study was to create a diagnostic model of supination and pronation of the foot using vertical ground reaction forces. A size adjustable capacitive transducer retaining 960 individual pressure cells was used to assess orthopaedic parameters of gait cyale timing and vertical ground reaction forces. A pilot sample of five males were used for this model. The subjects were exposed to six experimental conditions. These being; a) a walk, b) jog, c) walk on treadmill, and d) three levels of perceived exertion (mild, moderate and hard running). Perceived exertion was measured with the Borg (RPE) scale. All subjects were measured in the same brand of athletic shoe to control for intershoe differences. The ptonation/supination model was determined by medial/lateral force and timing measurements of the calcaneus, forefoot prominence, arch, the first and fifth metatarsal heads and the toe off (end of gait cycle). Results indicated bi-Iateral differences in the medial and lateral force measurements of the calcaneus. Timing in this area was slightly different. Medial to lateral timing pronation was evidenced in the treadmill walking and moderate running condition. As well, the loading of the first and fifth metatarsal heads as a percentage of the gait cycle did not change over the running conditions. The preliminary results of five subjects provides for limited support of a vertical ground reaction model to assess pronation and supination. Further research with techniques such as high speed photography will allow for clarification of this model

    DYNAMIC MEASUREMENT OF FORCE WITHIN THE SHOE DURING CONDITIONS OF PERCEIVED EXERTION

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    INTRODUCTION Athletics and recreation are becoming a very large component of modem day society. Now, more than ever, more people are becoming very active and involved in recreational pursuits that include aerobics and running/jogging. The resultant increase in activity has lead to a noted increase in injuries (Nigg, 1985; Mckenzie et al., 1985). James et al (cited in Cavanagh, 1990), in a study of 180 injured runners identified three categories of running injury problem areas. These areas being: a) training errors; b)anatomic factors (biomechanics); and c) shoes and surfaces. Two thirds of these injuries were accounted for by training errors (increased mileage or increased intensity). Training errors concerning sudden increases in mileage or intensity tend to subject the body to new or greater than expected physiological stressors. Voloshin and Wosk (1981), have investigated the relationship between heel strike shock wave transmission and joint degeneration in walking subjects. Taken one step further, the implications of damage to the muscle-skeletal system by running is noted by Cavanagh (1990). This combined with the Nigg et al. (1983) data that suggests a relationship between the hardness of the athletic (running) surface and the incidence of injury has serious implications for the recreational runner/athlete. Clarke et al. (1985) have highlighted the possible injurious force involved in tibial accelerations that are the result of the runner taking longer strides. Since most people retain a constant stride frequency, as velocity increases, the athlete tends to increase their stride length. The resultant increase in stride length increases impact forces at the joint. This combined with the increase of ground reaction forces with higher running speeds (Munro et al., 1987) identifies high impact forces as a major factor to be considered when investigating the causal nature of running injuries. Research into the type of shoe and ground reaction forces has been equivocal. Nigg and Bahlsen (1988) have stated that shoes with the hardest mid soles elicit the lowest maximal vertical forces. Conversely other research has indicated that shoe hardness is related to higher (vertical) loading rates. Listed above are a number of factors involved in the prediction of running injuries. Further research is needed to discover the causative factors involved in etiology of sport medicine running injuries. An analysis of running shoes, in particular the vertical ground reaction forces, may account for dynamic patterns of gait. Running at different levels of perceived exertion may elicit clues as to the biomechanics patterns that may be injurious to runners. For example, the gait of a runner at the beginning of the run may be markedly different from the gait at the end of the run. Variables such as intensity and distance will greatly affect the athlete's form as they become more tired. Thus, the number of running injuries (2/3 of Clarke's population) as a result of improper training may be the function of bad form (gait mechanics). An analysis under different levels of exertion will identify patterns of pressure with the foot that may have implications for the construction and design of athletic footwear as well as training methods for runners. This study was an attempt to understand the dynamic of in-shoe vertical ground reaction forces within the shoe under differing levels of perceived exertion. Research in the area of running shoe forces may lead to the development of a better product that will decrease the rate and type of running injuries

    Tackling the jelly web: Trophic ecology of gelatinous zooplankton in oceanic food webs of the eastern tropical Atlantic assessed by stable isotope analysis

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    Gelatinous zooplankton can be present in high biomass and taxonomic diversity in planktonic oceanic food webs, yet the trophic structuring and importance of this “jelly web” remain incompletely understood. To address this knowledge gap, we provide a holistic trophic characterization of a jelly web in the eastern tropical Atlantic, based on ή13C and ή15N stable isotope analysis of a unique gelatinous zooplankton sample set. The jelly web covered most of the isotopic niche space of the entire planktonic oceanic food web, spanning > 3 trophic levels, ranging from herbivores (e.g., pyrosomes) to higher predators (e.g., ctenophores), highlighting the diverse functional roles and broad possible food web relevance of gelatinous zooplankton. Among gelatinous zooplankton taxa, comparisons of isotopic niches pointed to the presence of differentiation and resource partitioning, but also highlighted the potential for competition, e.g., between hydromedusae and siphonophores. Significant differences in spatial (seamount vs. open ocean) and depth‐resolved patterns (0–400 m vs. 400–1000 m) pointed to additional complexity, and raise questions about the extent of connectivity between locations and differential patterns in vertical coupling between gelatinous zooplankton groups. Added complexity also resulted from inconsistent patterns in trophic ontogenetic shifts among groups. We conclude that the broad trophic niche covered by the jelly web, patterns in niche differentiation within this web, and substantial complexity at the spatial, depth, and taxon level call for a more careful consideration of gelatinous zooplankton in oceanic food web models. In light of climate change and fishing pressure, the data presented here also provide a valuable baseline against which to measure future trophic observations of gelatinous zooplankton communities in the eastern tropical Atlantic

    British Lung Foundation/United Kingdom primary immunodeficiency network consensus statement on the definition, diagnosis, and management of granulomatous-lymphocytic interstitial lung disease in common variable immunodeficiency disorders

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    A proportion of people living with common variable immunodeficiency disorders develop granulomatous-lymphocytic interstitial lung disease (GLILD). We aimed to develop a consensus statement on the definition, diagnosis, and management of GLILD. All UK specialist centers were contacted and relevant physicians were invited to take part in a 3-round online Delphi process. Responses were graded as Strongly Agree, Tend to Agree, Neither Agree nor Disagree, Tend to Disagree, and Strongly Disagree, scored +1, +0.5, 0, −0.5, and −1, respectively. Agreement was defined as greater than or equal to 80% consensus. Scores are reported as mean ± SD. There was 100% agreement (score, 0.92 ± 0.19) for the following definition: “GLILD is a distinct clinico-radio-pathological ILD occurring in patients with [common variable immunodeficiency disorders], associated with a lymphocytic infiltrate and/or granuloma in the lung, and in whom other conditions have been considered and where possible excluded.” There was consensus that the workup of suspected GLILD requires chest computed tomography (CT) (0.98 ± 0.01), lung function tests (eg, gas transfer, 0.94 ± 0.17), bronchoscopy to exclude infection (0.63 ± 0.50), and lung biopsy (0.58 ± 0.40). There was no consensus on whether expectant management following optimization of immunoglobulin therapy was acceptable: 67% agreed, 25% disagreed, score 0.38 ± 0.59; 90% agreed that when treatment was required, first-line treatment should be with corticosteroids alone (score, 0.55 ± 0.51)

    Comments on Systematic Effects in the NIST Beam Neutron Lifetime Experiment

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    We discuss issues raised by Serebrov, et al. in a recent paper regarding systematic effects in the beam neutron lifetime experiment performed at NIST. We show that these effects were considered in the original analyses and that our corrections and systematic uncertainties were appropriate. We point out some misconceptions and erroneous assumptions in the analysis of Serebrov, et al. None of the issues raised in Serebrov, et al lead us to alter the value of the neutron lifetime reported previously.Comment: arXiv admin note: substantial text overlap with arXiv:nucl-ex/0411041, arXiv:2004.0116

    Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea

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    An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site of the ANTARES neutrino telescope near Toulon, France, thus providing a unique opportunity to compare high-resolution acoustic and optical observations between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward vertical currents of magnitudes up to 0.03 m s-1 in late winter and early spring 2006. In the same period, observations were made of enhanced levels of acoustic reflection, interpreted as suspended particles including zooplankton, by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These observations coincided with high light levels detected by the telescope, interpreted as increased bioluminescence. During winter 2006 deep dense-water formation occurred in the Ligurian subbasin, thus providing a possible explanation for these observations. However, the 10-20 days quasi-periodic episodes of high levels of acoustic reflection, light and large vertical currents continuing into the summer are not direct evidence of this process. It is hypothesized that the main process allowing for suspended material to be moved vertically later in the year is local advection, linked with topographic boundary current instabilities along the rim of the 'Northern Current'.Comment: 30 pages, 7 figure
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