Macrofaunal response to artificial enrichments and depressions in a deep-sea habitat

To test whether colonizing macrofauna specialize on different types of small-scale patches of food and disturbance in the deep sea, sediment tray and artificial depression colonization experiments were conducted on the deep-sea floor at 900-m depth, south of St. Croix, U.S. Virgin Islands. Trays and depressions were unenriched (Unenriched Controls) or enriched with either Thalassiosira sp. or Sargassum sp. Concurrent deployment of different types of enrichment and disturbance made it possible to evaluate whether macrofauna specialize on different patches, and thus avoid species interactions that might lead to competitive exclusion. Depressions create a hydrodynamic regime that traps passive particles, allowing tests of the relative importance of active selection of different patch types versus passive deposition for abundant colonizers. After 23 d, total densities and densities of the four abundant colonizers (Capitella spp., Nereimyra punctata, Cumella sp. and Nebalia sp.) were extremely high in enriched trays, despite relatively low ambient densities. Densities in Unenriched Control Trays were very low, and did not attain ambient densities. After 24 d, total densities in all depression treatments were considerably lower than in enriched tray treatments, and only Sargassum Depression densities exceeded those in the ambient environment. Lower densities of organisms in depression treatments compared with trays and differences in densities among depression treatments suggest that the dominant colonizers were highly active and selective, and were not passively entrained in depressions. Faunal analysis indicated that trays and depressions were very different, and Sargassum Depression fauna was very different from other depression types. A strong difference was not observed between fauna in ambient sediments and Thalassiosira sp. or Unenriched Control Depressions, perhaps because Thalassiosira sp. was dropped in depressions on the sediment surface and may have been more readily available to consumers and more rapidly consumed than in trays. Thalassiosira Trays were colonized by a lower diversity fauna than Sargassum Trays, and Unenriched Control Trays were colonized by very low densities of a fauna that was comparable in diversity to the ambient community. Diversity in Sargassum Depressions was higher than in enriched trays but lower than in other artificial depressions and the ambient fauna. Thalassiosira Depressions and Unenriched Control Depressions were comparable in diversity to ambient fauna and natural depressions, which were highly diverse. These experiments suggest that fauna may respond quickly and selectively to artificial food patches and disturbance, and this fauna is different from that observed in the ambient sediment. Thus, a patch mosaic may be part of the reason for the high species diversity that is observed in deep-sea ecosystems. The different, highly diverse, fauna observed in natural depressions compared with flat ambient sediment suggests that natural analogs of these experiments have unique faunas that may contribute to the species richness of deep-sea habitats

Potential flow artifacts associated with benthic experimental gear: Deep-sea mudbox examples

In response to the growing recognition of the potential effects of near-bed hydrodynamics on various benthic processes, flume studies were conducted to document fine-scale flow patterns over several types of mudboxes that have been used to study colonization by deep-sea organisms. Mudboxes are typically filled with natural sediments or sediment treatments and placed in the field to observe how timing, larval supply and sediment composition may affect larval settlement. This study addresses potential hydrodynamic biases of mudbox structures as obstructions to the near-bed flow. Detailed velocity profiles were made over two types of “free vehicle” mudboxes that could be deployed and recovered from a surface vessel. One of these (“Old Free Vehicle”) was not designed with regard for potential hydrodynamic biases whereas the other (“New Free Vehicle”) was designed specifically to minimize flow disturbances and maintain a realistic boundary-layer flow over the mudbox sediments. Flume velocity profiles also were made over two smaller mudboxes designed to be deployed by a submersible, one (“Flush Sediment Tray”) which was designed to be placed flush with the ocean bottom, thus minimizing flow disturbance, and another (“Raised Mudbox”) which was not. Flume simulations indicated that the Old Free Vehicle and the Raised Mudbox cause considerable disturbance to the near-bed flow regime; flows over the mudbox sediment surface differed markedly from those predicted for the natural seabed and those observed over the flume bed in the absence of the mudboxes. Flow accelerations, growing secondary boundary layers and eddy formation were observed over these mudbox sediments, and vertical velocity profiles varied considerably in the along-channel direction. The alternative mudbox designs (New Free Vehicle and Flush Sediment Tray) were largely successful in reducing or eliminating these flow artifacts. Boundary-layer flows over both the New Free Vehicle and the Flush Sediment Tray were much more uniform, and velocity profiles over the sediment surfaces were very similar to those in the empty flume channel and those predicted for a natural deep-sea habitat. In addition, there was no evidence of eddy formation and other major flow disturbances. These flume studies underscore the benefit of considering potential hydrodynamic effects in designing benthic experimental sampling gear to reduce potential flow disturbances that may bias data collections and confound data interpretation

Performing under pressure: Quiet eye training improves surgical knot-tying performance

Background: We examined the effectiveness of traditional technical training (TT) and quiet eye training (QET) on the performance of one-handed square knot tying in first-year surgery residents under normal and high anxiety conditions. Methods: Twenty surgery residents were assigned randomly to the two groups and completed pretest, training, and simple and complex retention tests under conditions of high and low anxiety. The TT group received traditional instruction on improving hand movements; the QET group received feedback on their gaze behaviors. Participants wore an eye tracker that recorded simultaneously their gaze and hand movements. Dependent variables were: knot tying performance (%), quiet eye duration (%), number of fixations, and total movement time (s). Results: Both groups improved their knot tying performance (p 0.05). The QET group also demonstrated more efficient gaze and hand movements post training. Conclusions: These data demonstrate the effectiveness of training gaze behaviors, not only to improve the effectiveness and efficiency of performance, but also to mediate any negative effects of anxiety on performance. These findings may have important implications for medical educators and practitioners, as well as surgeons who may be (re)training or learning new procedures

Quiet eye training improves surgical knot tying more than traditional technical training: A randomized controlled study

Background We examined the effectiveness of technical training (TT) and quiet eye training (QE) on the performance of one-handed square knot tying in surgical residents. Methods Twenty surgical residents were randomly assigned to the 2 groups and completed pretest, training, retention, and transfer tests. Participants wore a mobile eye tracker that simultaneously recorded their gaze and hand movements. Dependent variables were knot tying performance (%), QE duration (%), number of fixations, total movement time (s), and hand movement phase time (s). Results The QE training group had significantly higher performance scores, a longer QE duration, fewer fixations, faster total knot tying times, and faster movement phase times compared with the TT group. The QE group maintained performance in the transfer test, whereas the TT group significantly decreased performance from retention to transfer. Conclusions QE training significantly improved learning, retention, and transfer of surgical knot tying compared with a traditional technical approach. Both performance effectiveness (performance outcome) and movement efficiency (hand movement times) were improved using QE modeling, instruction, and feedback. © 2014 Elsevier Inc. All rights reserved

Greek research reactor performance characteristics after addition of beryllium reflector and LEU fuel

The GRR-1 is a 5-MW pool-type, light-water-moderated and-cooled reactor fueled with MTR-type fuel elements. Recently received Be reflector blocks will soon be added to the core to add additional reactivity until fresh LEU fuel arrives. REBUS-3 xy fuel cycle analyses, using burnup dependent cross sections, were performed to assist in fuel management decisions for the water- and Be-reflected HEU nonequilibrium cores. Cross sections generated by EPRI-CELL have been benchmarked to identical VIM Monte Carlo models. The size of the Be-reflected LEU core has been reduced to 30 elements compared to 35 for the HEU water-reflected core, and an equilibrium cycle calculation has been performed

The role of colonization in establishing patterns of community composition and diversity in shallow-water sedimentary communities

To determine whether pattern and diversity in benthic sedimentary communities are set primarily at colonization or by post-settlement biological interactions, we collected faunal cores and conducted reciprocal sediment transplant experiments at a sandy and a muddy site at 12 m depth, ~3 km apart off New Jersey. Multivariate analyses of cores collected at these sites in September 1994 indicated differences in the taxa determining local pattern, with the bivalve Spisula solidissima and the polychaete Polygordius sp. being dominant at the sandy site, and oligochaetes, several polychaete species and the bivalve Nucula annulata dominant at the muddy site. Individual cores from the sandy site were significantly less diverse than those at the muddy site. Short-term experiments (3-5 d) were deployed by divers at three different times (August-September, 1994). Replicate trays (100 cm2) filled with azoic sand or mud were placed flush with the ambient seafloor at both sites. Multivariate comparisons indicated that sediment treatment in trays played a greater role in determining colonization patterns in the first experiment, site played a greater role in the second, and both variables contributed in the third. This pattern suggests that larval settlement and habitat choice played an important role in the first and third experiments, and that local transport of recently settled juveniles from the surrounding sediments was important in the second and third experiments. Sandy-site trays had significantly lower diversity than muddy-site trays, but there was no effect of sediment type in trays on diversity of colonizers. These experiments focused on small spatial scales and three short time periods, but they demonstrate that species patterns in some environments may be set by habitat selection by larvae and by juvenile colonization from the surrounding community. Post-colonization processes such as predation and competition likely play a major role for some species, but patterns of initial colonization corresponded well with those in the local community

Use of silicide fuel in the Ford Nuclear Reactor - to lengthen fuel element lifetimes

Based on economic considerations, it has been proposed to increase the lifetime of LEU fuel elements in the Ford Nuclear Reactor by raising the {sup 235}U plate loading from 9.3 grams in aluminide (UAl{sub x}) fuel to 12.5 grams in silicide (U{sub 3}Si{sub 2}) fuel. For a representative core configuration, preliminary neutronic depletion and steady state thermal hydraulic calculations have been performed to investigate core characteristics during the transition from an all-aluminide to an all-silicide core. This paper discusses motivations for this fuel element upgrade, results from the calculations, and conclusions

Development and transfer of fuel fabrication and utilization technology for research reactors

Approximately 300 research reactors supplied with US-enriched uranium are currently in operation in about 40 countries, with a variety of types, sizes, experiment capabilities and applications. Despite the usefulness and popularity of research reactors, relatively few innovations in their core design have been made in the last fifteen years. The main reason can be better understood by reviewing briefly the history of research reactor fuel technology and enrichment levels. Stringent requirements on the enrichment of the uranium to be used in research reactors were considered and a program was launched to assist research reactors in continuing their operation with the new requirements and with minimum penalties. The goal of the new program, the Reduced Enrichment Research and Test Reactor (RERTR) Program, is to develop the technical means to utilize LEU instead of HEU in research reactors without significant penalties in experiment performance, operating costs, reactor modifications, and safety characteristics. This paper reviews briefly the RERTR Program activities with special emphasis on the technology transfer aspects of interest to this conference

Pediatric severe asthma with fungal sensitization is mediated by steroid-resistant IL-33

Background: The mechanism underlying severe asthma with fungal sensitization (SAFS) is unknown. IL-33 is important in fungus-induced asthma exacerbations, but its role in fungal sensitization is unexplored. Objective: We sought to determine whether fungal sensitization in children with severe therapy-resistant asthma is mediated by IL-33. Methods: Eighty-two children (median age, 11.7 years; 63% male) with severe therapy-resistant asthma were included. SAFS (n= 38) was defined as specific IgE or skin prick test response positivity to Aspergillus fumigatus, Alternaria alternata, or Cladosporium herbarum. Clinical features and airway immunopathology were assessed. Chronic exposure to house dust mite and A alternata were compared in a neonatal mouse model. Results: Children with SAFS had earlier symptom onset (0.5 vs 1.5 years, P= .006), higher total IgE levels (637 vs 177 IU/mL, P= .002), and nonfungal inhalant allergen-specific IgE. Significantly more children with SAFS were prescribed maintenance oral steroids (42% vs 14%, P= .02). SAFS was associated with higher airway IL-33 levels. In neonatal mice A alternata exposure induced higher serum IgE levels, pulmonary IL-33 levels, and IL-13+ innate lymphoid cell (ILC) and TH2 cell numbers but similar airway hyperresponsiveness (AHR) compared with those after house dust mite exposure. Lung IL-33 levels, IL-13+ ILC numbers, TH2 cell numbers, IL-13 levels, and AHR remained increased with inhaled budesonide during A alternata exposure, but all features were significantly reduced in ST2-/- mice lacking a functional receptor for IL-33. Conclusion: Pediatric SAFS was associated with more oral steroid therapy and higher IL-33 levels. A alternata exposure resulted in increased IL-33-mediated ILC2 numbers, TH2 cell numbers, and steroid-resistant AHR. IL-33 might be a novel therapeutic target for SAFS

Artificial reefs: from ecological processes to fishing enhancement tools

info:eu-repo/semantics/publishedVersio