41,666 research outputs found
Shipboard measurements of sediment stability using a small annular flume—Core Mini Flume (CMF)
No full textEstimates of bed stability in coastal environments are essential to physical, biological, and chemical investigations of cohesive sediments. The Core Mini Flume (CMF), a 200 mm diameter annular flume has been designed to undertake sediment stability experiments on collected intact sediment box cores. Bed properties were assessed for replicate box cores at 3 contrasting sites in UK coastal waters (Tyne [in 2011 and 2012], Plymouth and Celtic Deep), each covering a maximum area of 80 m2. No significant horizontal spatial variations were found for grain size, bulk density, porosity, or oxygen penetration at the sites. Resuspension experiments performed on replicate cores yielded highly replicable results for each site, giving average erosion thresholds of 0.33 ± 0.02 (Tyne 2011), 0.215 ± 0.03 (Tyne 2012), 0.23 ± 0.01 (Plymouth), and 0.09 ± 0.006 (Celtic Deep) Pa and erosion depths of 10.7 ± 1.7, 6.63 ± 1.10, 3.65 ± 0.95, and 4.6 ± 0.5 mm. Using an already established methodology, the CMF allowed detailed replicate experiments to be performed on-board ship rapidly after sediment collection, while minimizing the time spent at each station. The use of intact box cores minimized the disturbance to the bed often associated with recovering material to a laboratory or remoulding a bed. We have demonstrated that the convenience of laboratory-based methodologies can be combined with the benefit of prompt investigations on undisturbed beds complete with overlying in situ water to produce robust measurements of sediment stability
Simultaneous determination of in situ vertical transitions of color, pore-water metals, and visualization of infaunal activity in marine sediments
No full textThe vertical color transition from brown to gray-green in marine sediments is linked to the Fe redox boundary and is commonly used as a proxy for biogeochemical state. We combine time-lapse sediment profile imaging with diffusive gradient thin (DGT) gels to obtain simultaneous in situ measurements of sediment color profiles, pore-water Fe and Mn profiles, and qualitative estimates of faunal activity at the Oyster Ground and North Dogger (North Sea). Analysis of Fe and Mn profiles using generalized additive modeling reveals that high variability between profiles within the sites makes it difficult to determine any intersite differences in trace metal behavior. At the Oyster Ground, the depth of sediment color transition (4.78 +/- 0.76 cm) was not significantly different from the Fe redox boundary (7.67 +/- 4.04 cm). At the North Dogger, there was a significant discrepancy between the depth of the sediment color transition (2.86 +/- 0.78 cm) and the Fe redox boundary (10.17 +/- 1.04 cm), which most likely results from high sulfate reduction rates at the North Dogger, leading to complexation of reduced iron to a form not available to the DGT technique. The differences in the coupling of sediment color and the Fe redox boundary between stations is likely to be related to variations in recent infaunal bioturbation activity, rather than variations in sediment source or fundamental differences in bulk sediment chemistry. Our results highlight the importance of the infaunal community in mediating Fe and Mn cycles, which are key pathways in the degradation of organic matter, and suggest that descriptions of bulk chemistry alone may be insufficient to understand the dynamics of biogeochemical cycling
Contribuição ao estudo da técnica de escovação dentária de fones /
No full textDissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde
High-resolution metal gradients measured by in situ DGT/DET deployment in Black sea sediments using an autonomous benthic lander
No full textDET (Diffusive equilibration in thin films) and DGT (diffusive gradients in thin films) have been deployed in situ using an autonomous benthic lander to measure concentrations and induced fluxes of Fe and Mn (DET/DGT) and trace metals (DGT) in pore waters at millimeter spatial resolutions. The newly developed deployment system is described, and based on these first results, its strengths and weaknesses are discussed. Deployments were made in the Western Black Sea in shelf sediments overlain by well‐oxygenated water at a water depth of 77 m. Maxima of the redox‐sensitive metals at 4 and 8 cm deep within the sediment indicated that two zones of reduction dominated the geochemistry. Sharp, but systematic, features were superimposed on this general picture and were well replicated in the profiles of Mn, Co, and Cd, but the sharp features in the Fe profile were offset from those of the others elements by several millimeters. Detection of this functional discrimination between Fe and Mn as regulators of trace metals would not have been possible using more conventional sampling procedures
The dialogue between the author and the hero in the “Notes” of G. R. Derzhavin
No full textВ центре внимания автора статьи «Записки» Г. Р. Державина, представляющие по своей сути его автобиографию. Труд этот был создан на закате жизни, он включает все важнейшие события жизни Г. Р. Державина, поэта и государственного деятеля. Рассказ ведется от третьего лица, что придает особую атмосферу повествованию, выстраивается своеобразный диалог между автором и героем, все это и является предметом исследования автора статьи.The focus of the author of the article “Notes” G. R. Derzhavin, representing in essence his autobiography. This work was created at the end of his life; it includes all the most important events in the life of G. R. Derzhavin, poet and statesman. The story is told in a third person, which gives a special atmosphere to the story, a certain dialogue emerges between the author and the hero, all this is the subject of the author's research
Gravastars in f(R, G) gravity
No full textThis paper is focused on the study of gravitational vacuum stars or, briefly, gravastars in f(R, G) gravity, where R and G stand for the Ricci scalar and Gauss–Bonnet invariant term, respectively. Due to the involvement of highly non-linear differential equations, solutions are found by using some appropriate numerical techniques. The main structure of gravastars has been discussed according to core, shell, and exterior regions for a well-known f(R, G) gravity cosmological model. Mass–radius evolution is described graphically for the considered gravastar, and it is shown that the mass is directly proportional to the radius.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Introduction: Starring the Author
No full textLiterary celebrity is by now a familiar feat of contemporary literary culture, but it continues to raise complex questions about the history and development of fame, the interplay between the cultural marketplace and the official culture of critics and the canon, and the relation between authorial agency and public appropriation. This introduction addresses these questions by approaching literary celebrity as a merging of two discursive constructions: the celebrity-function and the author-function. By combining insights from celebrity studies, literary history and cultural memory studies, the introduction conceptualizes literary celebrity as a discursive construction with several variables, such as the author’s self-presentation, the circulation of his public identity, changing opinions on literature and writership, and the public afterlife of the author’s image
Spherically symmetric solution of f(R,G) gravity at low energy
No full textThe weak-field and slow-motion limit of f(R,G) gravity is developed up to (v/c)(4) order in a spherically symmetric background. Considering the Taylor expansion of a general function f around vanishing values of R and G, we present general vacuum solutions up to (v/c)(4) order for the gravitational field generated by a ball-like source. The spatial behaviors at (v/c)(2) order are the same for f(R,G) gravity and f(R) gravity, and their corresponding real valued static behaviors are presented and compared with the one in general relativity. The static Yukawa-like behavior is proved to be compatible with the previous result of the most general fourth-order theory. At (v/c)(4) order, the static corrections to the Yukawa-like behavior for f(R,G) gravity, f(R) gravity, and the Starobinsky gravity are presented and compared with the one in general relativity.National Natural Science Foundation of China [11120101004, 11475006]SCI(E)[email protected]; [email protected]
Real Estate Development: An overview
No full textGreen Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Urban Development Managemen
An autonomous benthic lander: preliminary observations from the UK BENBO thematic programme
No full textA new, multi-purpose autonomous benthic lander is described, and preliminary experimental data are presented relating to deployments in the Atlantic Frontier (eastern north Atlantic) during the recent UK Thematic Programme ‘BENBO’. The autonomous lander was deployed at two contrasting sites — Site A (mouth of Rockall Trough; 3570 m) and Site B (Hatton-Rockall Bank; 1100 m) — before and following the spring-time surface ocean phytoplankton bloom (May & July, 1998, respectively). Diffusive oxygen uptake and nutrient flux data were obtained using two interchangeable modules — a profiling oxygen micro-electrode unit and a benthic chamber unit. Diffusive O2 uptake across the sediment–water interface and the O2 penetration depths within the sediment were determined from the oxygen micro-profiles. The shallower site, which had previously received phyto-detrital input, had a comparatively large diffusive oxygen uptake within the sediment (1.2 mmol m?2 d?1) and a maximum penetration depth of only 21 mm. The deeper site had greater oxygen penetration depths (80 mm) but a lower diffusive oxygen uptake of 0.6 mmol m?2 d?1, indicative possibly of little or no phyto-detrital input. Visual observations of retrieved sediment cores support this conclusion, however Site A has also displays generally lower organic content and lower macrobenthic biomass which may contribute to this observation. Nutrient pore water profile data indicated fluxes of nitrate of 0.161 mmol m?2 d?1 and phosphate 0.0008 mmol m?2 d?1 into the overlying water. However, the benthic chamber studies showed virtually no change in nutrient concentrations, due probably to the relatively short deployment time used.<br/
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