95 research outputs found
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Evidence for suboxic nitrification in recent marine sediments
No full textThe classical scheme of biogeochemical zones (BGZ) is known to be an oversimplification
of the microbial processes that occur in organic-rich marine sediments. Results from a coupled
deployment of pore-water gel probes in Loch Duich, Scotland, provide direct evidence for rapid
recycling within the iron reduction (FeR) and sulphate reduction (SR) zones. High resolution porewater
profiles obtained using diffusive equilibrium in thin films (DET) gel probes found a nitrate peak
at the boundary between the FeR and SR zones. This non-steady state feature is consistent with recycling
of reduced N occurring throughout the FeR zone. Both conventional pore-water iron profiles
and results from diffusive gradient in thin films (DGT) probes indicate that iron is solubilised and precipitated
in rapid Fe/S recycling reactions throughout the SR zone. The presence of such complex
recycling reactions confirms the oversimplification of the classical BGZ scheme
2-D optical quantification of particle reworking activities in marine surface sediments
No full textParticle and solute transport by faunal activities may significantly influence rates and pathways of organic matter mineralization during early diagenesis in surface sediments. One of the most frequently utilized techniques to quantify benthic biological reworking activities involves the calculation of a biodiffusion coefficient (Db) estimated from model predictions of 1-D tracer distribution patterns. This technique is labor-intensive and time-demanding. Furthermore, it is normally used for measurements over several days and averages overall transport mechanisms from 3-D to 1-D on a cm scale. In the frame of this work, we developed a new technique based on the nondestructive screening of fluorescent particles (luminophores) using optical discrimination and CCD camera detection of fluorescence (2-D). At a site characterized by a dense population of the brittle star Amphiura filiformis and a high biodiffusion coefficient (obtained from 1-D distributions; Db=35.5±3.7 cm−2 year−1; n=3), the optical reworking coefficient (ORC), estimated from the 2-D luminophore distribution patterns, was calculated (ORC=27.4±9.1 View the MathML source cm−2 h−1; n=24). A nondestructive 2-D approach to quantify particle reworking may provide a powerful and complementary tool to further understand particle transport by the benthic fauna in surface sediments. The optical technique for 2-D detection of luminophores is relatively fast and easy to perform, with the ability to detect small scale (mm) particle movements on a time resolution of minutes or less
Sediment reworking by marine benthic species from the Gullmar Fjord (Western Sweden): Importance of faunal biovolume
No full textIn order to compare and quantify sediment reworking activities by different species/functional groups of macrofauna, a laboratory experiment was carried out with species from the Gullmarsfjord (Western Sweden). Monospecific communities of Amphiura filiformis, Echinocardium cordatum, Scalibregma inflatum and Abra nitida were introduced in experimental mesocosms, with identical densities (795 ind. m−2), for 10 days. Sediment reworking was studied by quantifying downward and upward movements of fluorescent inert tracers (luminophores). Luminophores with different colour were initially deposited both at the sediment surface and within the sediments. Population biomass and biovolume were also determined. Surface tracers reworking coefficients ranged from 0.6 to 2.2 cm2 y−1 and 0.9 to 4.1 y−1, respectively for the biodiffusive-like and non-local transports. Calculated biodiffusive-like coefficient was between 1.0 and 2.3 cm2 y−1 for the deep tracers. For both tracers, the E. cordatum population presented the highest reworking coefficients. Among the morphological and/or ethological parameters that could determine overall patterns of reworking and differences between species, results have shown a direct relationship between the apparent biodiffusive mixing and the biovolume of the individuals (Db=0.35 ⁎ Biovolume). This suggests that the biovolume of macrofauna may allow a rough estimate of the biodiffusive-like reworking intensity of particles deposited on the sediment surface
An intracellular pH gradient in the anammox bacterium Kuenenia stuttgartiensis as evaluated by (31)P NMR
No full textThe cytoplasm of anaerobic ammonium oxidizing (anammox) bacteria consists of three compartments separated by membranes. It has been suggested that a proton motive force may be generated over the membrane of the innermost compartment, the “anammoxosome”. 31P nuclear magnetic resonance (NMR) spectroscopy was employed to investigate intracellular pH differences in the anammox bacterium Kuenenia stuttgartiensis. With in vivo NMR, spectra were recorded of active, highly concentrated suspensions of K. stuttgartiensis in a wide-bore NMR tube. At different external pH values, two stable and distinct phosphate peaks were apparent in the recorded spectra. These peaks were equivalent with pH values of 7.3 and 6.3 and suggested the presence of a proton motive force over an intracytoplasmic membrane in K.stuttgartiensis. This study provides for the second time—after discovery of acidocalcisome-like compartments in Agrobacterium tumefaciens—evidence for an intracytoplasmic pH gradient in a chemotrophic prokaryotic cell.BiotechnologyApplied Science
IceCube-Gen2: A Vision for the Future of Neutrino Astronomy in Antarctica
No full text20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)The recent observation by the IceCube neutrino observatory of an astrophysical flux of neutrinos represents the "first light" in the nascent field of neutrino astronomy. The observed diffuse neutrino flux seems to suggest a much larger level of hadronic activity in the non-thermal universe than previously thought and suggests a rich discovery potential for a larger neutrino observatory. This document presents a vision for an substantial expansion of the current IceCube detector, IceCube-Gen2, including the aim of instrumenting a volume of clear glacial ice at the South Pole to deliver substantial increases in the astrophysical neutrino sample for all flavors. A detector of this size would have a rich physics program with the goal to resolve the sources of these astrophysical neutrinos, discover GZK neutrinos, and be a leading observatory in future multi-messenger astronomy programs
Burial and reactivity of sedimentary microalgal lipids in bioturbated Mediterranean coastal sediments
No full textThe fate of microalgal lipid biomarkers in marine coastal sediments when acted on by natural bioturbation processes
(Carteau Bay, Gulf of Fos, Mediterranean Sea) was studied under laboratory conditions. Both dead phytoplanktonic cells
(Nannochloropsis salina) and luminophores (inert fluorescent particulate tracers) were deposited at the surface of intact sediment cores which were then incubated for 22, 44 and 63 days. Sediment reworking and concentration profiles of specific lipid components of N. salina (n-alkenes, alkyl diols, sterols and fatty acids) were determined as a function of time and depth. The results show that, in the sediment investigated, bioturbation occurs essentially as a biodiffusive process and that it has a rapid and significant impact on the qualitative and quantitative record of sedimentary lipids. Whereas most of the biomarkers were detected in the entire reworked layer (0–6 cm) after 22 days, n-alkenes were never detected below 3 cm due to their low concentration and their high reactivity. For each individual lipid, the comparison of the amounts obtained from the inventories
of biomarkers in the reworked zone, with the amount deposited initially at the sediment surface, allowed the determination of its extent and rate of degradation. These ranged from 72% to 99% and from 0.010 to 0.047 day-1, respectively, depending on the biomarker considered, with polyunsaturated fatty acids (PUFAs) and alkenes being degraded faster than the other components. Comparison with previous work suggests that, in biologically reworked sediments, the apparent reactivity of lipids is: (i) positively correlated with the biological mixing coefficient (Db) and, (ii) generally much higher than in non-bioturbated (anoxic) sediments. Our results also support the idea that degradation of lipids in reworked sediments involves the combined effects of aerobic and anaerobic degradation processes, but that biological mixing results in diagenetic properties more characteristic of
completely oxidized conditions
European initiative on CDIO in raw material programmes
No full textOne of five Knowledge and Innovation Communities (KICs), was launched in Europe in 2014
and has its focus on exploration, extraction, mineral processing, metallurgy, recycling and
material substitution of raw materials. To reach the vision, where the European Union’s
industrial strength is based on a cost-efficient, secure, sustainable supply and use of raw
materials, a new generation of skilled people entering industry, universities and research
needs to be developed. Today’s technical MSc graduates in raw materials and especially
primary resources (i.e. exploration, extraction, mining and mineral processing and metallurgy)
best suits large companies where they often act as specialists and experts. For small to
medium enterprises as well as for our future engineers other skills than technical are
necessary. As a part of the KIC Raw Materials, the education project “The implementation of
CDIO in raw material programmes” started in 2016. The project focuses, during 2016-2017,
on (WP1) faculty- and (WP2) pilot case development. There are no academic institutes in
Europe that have yet applied CDIO for primary resource related MSc programmes. This
paper describes an education project within the KIC Raw material and presents key outputs
with implementing CDIO in mining and metallurgy related programmes
The trigger and data acquisition for the NEMO-Phase 2 tower
No full textIn the framework of the Phase 2 of the NEMO neutrino telescope project, a tower with 32 optical modules is
being operated since march 2013. A new scalable Trigger and Data Acquisition System (TriDAS) has been developed and
extensively tested with the data from this tower. Adopting the all-data-to-shore concept, the NEMO TriDAS is optimized
to deal with a continuous data-stream from off-shore to on-shore with a large bandwidth. The TriDAS consists of four
computing layers: (i) data aggregation of isochronal hits from all optical modules; (ii) data filtering by means of concurrent
trigger algorithms; (iii) composition of the filtered events into post-trigger files; (iv) persistent data storage. The TriDAS
implementation is reported together with a review of dedicated on-line monitoring tools
Underwater acoustic positioning system for the SMO and KM3NeT - Italia projects
No full textIn the underwater neutrino telescopes, the positions of the Cherenkov light sensors and their movements must be known with an accuracy of few tens of centimetres. In this work, the activities of the SMO and KM3NeT-Italia teams for the development of an acoustic positioning system for KM3NeT-Italia project are presented. The KM3NeT-Italia project foresees the construction, within two years, of 8 towers in the view of the several km3
-scale neutrino telescope KM3NeT
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