Resource utilization and trophic position of nematodes and harpacticoid copepods in and adjacent to Zostera noltii beds

This study examines the resource use and trophic position of nematodes and harpacticoid copepods at the genus/species level in an estuarine food web in Zostera noltii beds and in adjacent bare sediments using the natural abundance of stable carbon and nitrogen isotopes. Microphytobenthos and/or epiphytes are among the main resources of most taxa, but seagrass detritus and sediment particulate organic matter contribute as well to meiobenthos nutrition, which are also available in deeper sediment layers and in unvegetated patches close to seagrass beds. A predominant dependence on chemoautotrophic bacteria was demonstrated for the nematode genus Terschellingia and the copepod family Cletodidae. A predatory feeding mode is illustrated for Paracomesoma and other Comesomatidae, which were previously considered first-level consumers (deposit feeders) according to their buccal morphology. The considerable variation found in both resource use and trophic level among nematode genera from the same feeding type, and even among congeneric nematode species, shows that the interpretation of nematode feeding ecology based purely on mouth morphology should be avoided

Nematode communities from a natural oil seep off Svalbard

Cold-seep sediments, where active fluid seepage rich is observed, have been associated with the presence of endemic nematode communities. Under the scope of the AKMA project, a seep site located offshore Svalbard was sampled for the first time to investigate the Nematoda assemblages associated with methane and crude oil seepage. Replicated samples were collected by means of the blade- and push-cores, on a bacterial mat where active gas and oil seepage was observed, as well as in sediments nearby without evident seepage activity, as reference. Sediments collected were used to characterize the community structure and diversity of the meiofauna taxa, particularly the nematode assemblages, as well as key environmental parameters (i.e, sediment and pore-water geochemistry, organic content, grain size). Preliminary observations showed no major differences in total meiofauna density between microhabitats, with a predominance of nematodes (>90%), followed by harpacticoid copepods and nauplii larvae, as typically seen in other deep-sea environments. However, an in-depth investigation into the nematode assemblages, revealed a low nematode diversity in the bacterial mats sediments, by comparison, to the reference. Bacterial mat-associated assemblages were predominantly composed of Halomonhystera sp.1 (39%), followed by a single Chromadoridae species (32%). Evidence of morphological and reproductive adaptations were observed in several of the species present and could be indicative of how these organisms are able to survive the toxic environmental conditions at this seep site, namely high concentrations of hydrogen sulphide and crude oil. These observations contribute to a large gap in the understanding of how infauna thrive in extreme environments in the Arctic

Nematode communities from a natural oil seep off Svalbard.

Cold seeps are considered hotspots of energy on the seafloor, establishing unique conditions for life to thrive. In chemosynthetic-based habitats such as these, sediments from active sites are typically inhabited by endemic nematode communities which tolerate the local reduced environmental conditions, but no studies have been carried out on seep sites so far north in the Arctic. Under the scope of the AKMA project, an oil seep site located offshore Svalbard was sampled for the first time to investigate the associated meiofauna assemblages with methane and crude oil seepage. Replicated samples were collected by means of the blade and push cores handled by the ROV Ægir6000, both on bacterial mats with evident gas and oil seepage, as well as in sediments nearby without evident seepage activity, as reference. Sediments collected were used to characterize the community structure and diversity of the meiofauna taxa, particularly the nematode assemblages, as well as key environmental parameters (i.e, sediment and porewater geochemistry, organic content, grain size). Preliminary observations showed no major differences in total meiofauna density between microhabitats, with a predominance of nematodes (>90%), followed by harpacticoid copepods and nauplii larvae, typically seen in other deep-sea environments. However, an in-depth investigation into the nematode assemblages revealed that bacterial mats hosted an extremely low diversity of nematode species, by comparison, to the reference locations. Bacterial mat-associated assemblages were predominantly composed of a single species, Dichromadora sp.1, followed by Halomonhystera cf. disjuncta and Linhomoidae sp. 1. Evidence of morphological and reproductive adaptations in the species present seems to allow them to survive in this toxic environment, namely due to high concentrations of hydrogen sulfide and oil presence. The findings resulting from this study contribute to a large gap in the understanding of how infauna thrive in extreme environments with the presence of hydrocarbons in the Arcti

Occurrence of marine litter along abyssal areas of the Gloria Fracture Zone (NE Atlantic).

Marine litter pollution is a recognized form of anthropogenic disturbance that affects widely the marine environment, particularly near the continental margins, although also present at abyssal and bathyal depths. This study reports the occurrence of marine litter distribution and abundance in four abyssal basins along the Gloria fracture zone in the NE Atlantic. Litter items occurrences were analysed using TV-CTD video surveys carried out during the multidisciplinary activities of the R/V Meteor M162 cruise. The surveys reached depths between 3500-4500m and covered 16 km of seafloor, between the Terceira ridge and the Madeira-Tore Rise. Litter items were annotated and categorized by type (i.e., plastic, fishing gear, metal, glass, other unknown items). Results revealed that litter was exclusively found on soft sediment habitats across all areas, i.e. depositional areas, with the overwhelming dominance of plastics items (71%), such as plastic containers, cups and bag fragments. Although less common (6-8%), metal, glass and lost fishing gear were also observed. Litter density was on average 9 times higher in the easternmost area near the Madeira-Tore ridge, when compared to the other areas. Higher litter densities are likely explained due to the proximity to the Madeira-Tore seamount complex targeted by the fishing industry and nearimportant corridors of marine traffic between various Atlantic and Mediterranean locations

Megafauna communities from abyssal sites along the Gloria Fracture Zone (NE Atlantic)

Fracture zones are areas of poorly known abyssal landscapes and benthic faunal communities. During the R/V Meteor M162 cruise several imagery surveys were performed using a TV-CTD guided camera system along four main areas of the Gloria fault system, between the Terceira ridge and the Madeira Tore Rise. Based on these records, we were able to characterize - for the first time - the megafaunal composition, their abundance and diversity along the sub-basin of the Gloria fault at depths between 3500 and 4500m. Quantitative annotations of the observed fauna, as well as evidence of animal traces on the seafloor were explored in relation to topography, substrate type, and geochemical data acquired during surveys. Preliminary observations revealed a total of 121 morphospecies, of which Holothuroidea is the most diverse group, with 12 morphospecies. Deepest transects carried out along the main trace of Gloria Fault system showed the highest similarity among dives, predominantly characterised by soft sediment areas with Elpidiidae holothurians frequently observed. In contrast, the survey carried out at the Terceira ridge showed more diverse communities, which is likely due to a larger variability in substrate and topography. Specifically, soft-sediment sections showed a higher proportion of holothurians, ophiuroids and acorn worms, while unique Anthozoan and Porifera morphospecies were observed in areas with presence of hard substrates. The findings of this study provide unique knowledge of abyssal fauna associated with the Gloria Fault System, including areas inside of national jurisdiction and of relevance for management and conservation actions

Dba-free" Palladium Intermediates Of The Heck-matsuda Reaction."

The dba-free Heck-Matsuda reaction was investigated via direct ESI-MS(/MS) monitoring. Palladium species involved in the reduction of Pd(II) during a Wacker type reaction and several dba-free arylpalladium transient complexes were detected and characterized. Based on these findings, a more comprehensible catalytic cycle for this pivotal reaction is suggested.113277-8

DIBMA nanodiscs keep α-synuclein folded

α-Synuclein (αsyn) is a cytosolic intrinsically disordered protein (IDP) known to fold into an α-helical structure when binding to membrane lipids, decreasing protein aggregation. Model membrane enable elucidation of factors critically affecting protein folding/aggregation, mostly using either small unilamellar vesicles (SUVs) or nanodiscs surrounded by membrane scaffold proteins (MSPs). Yet SUVs are mechanically strained, while MSP nanodiscs are expensive. To test the impact of lipid particle size on α-syn structuring, while overcoming the limitations associated with the lipid particles used so far, we compared the effects of large unilamellar vesicles (LUVs) and lipid-bilayer nanodiscs encapsulated by diisobutylene/maleic acid copolymer (DIBMA) on αsyn secondary-structure formation, using human-, elephant- and whale -αsyn. Our results confirm that negatively charged lipids induce αsyn folding in h-αsyn and e-αsyn but not in w-αsyn. When a mixture of zwitterionic and negatively charged lipids was used, no increase in the secondary structure was detected at 45 °C. Further, our results show that DIBMA/lipid particles (DIBMALPs) are highly suitable nanoscale membrane mimics for studying αsyn secondary-structure formation and aggregation, as folding was essentially independent of the lipid/protein ratio, in contrast with what we observed for LUVs having the same lipid compositions. This study reveals a new and promising application of polymer-encapsulated lipid-bilayer nanodiscs, due to their excellent efficiency in structuring disordered proteins such as αsyn into nontoxic α-helical structures. This will contribute to the unravelling and modelling aspects concerning protein-lipid interactions and α-helix formation by αsyn, paramount to the proposal of new methods to avoid protein aggregation and disease.info:eu-repo/semantics/publishedVersio

Brain-inspired nanophotonic spike computing:challenges and prospects

Nanophotonic spiking neural networks (SNNs) based on neuron-like excitable subwavelength (submicrometre) devices are of key importance for realizing brain-inspired, power-efficient artificial intelligence (AI) systems with high degree of parallelism and energy efficiency. Despite significant advances in neuromorphic photonics, compact and efficient nanophotonic elements for spiking signal emission and detection, as required for spike-based computation, remain largely unexplored. In this invited perspective, we outline the main challenges, early achievements, and opportunities toward a key-enabling photonic neuro-architecture using III-V/Si integrated spiking nodes based on nanoscale resonant tunnelling diodes (nanoRTDs) with folded negative differential resistance. We utilize nanoRTDs as nonlinear artificial neurons capable of spiking at high-speeds. We discuss the prospects for monolithic integration of nanoRTDs with nanoscale light-emitting diodes and nanolaser diodes, and nanophotodetectors to realize neuron emitter and receiver spiking nodes, respectively. Such layout would have a small footprint, fast operation, and low power consumption, all key requirements for efficient nano-optoelectronic spiking operation. We discuss how silicon photonics interconnects, integrated photorefractive interconnects, and 3D waveguide polymeric interconnections can be used for interconnecting the emitter-receiver spiking photonic neural nodes. Finally, using numerical simulations of artificial neuron models, we present spike-based spatio-temporal learning methods for applications in relevant AI-based functional tasks, such as image pattern recognition, edge detection, and SNNs for inference and learning. Future developments in neuromorphic spiking photonic nanocircuits, as outlined here, will significantly boost the processing and transmission capabilities of next-generation nanophotonic spike-based neuromorphic architectures for energy-efficient AI applications. This perspective paper is a result of the European Union funded research project ChipAI in the frame of the Horizon 2020 Future and Emerging Technologies Open programme.</p

Novel precoded relay-assisted algorithm for cellular systems

Cooperative schemes are promising solutions for cellular wireless systems to improve system fairness, extend coverage and increase capacity. The use of relays is of significant interest to allow radio access in situations where a direct path is not available or has poor quality. A data precoded relay-assisted scheme is proposed for a system cooperating with 2 relays, each equipped with either a single antenna or 2-antenna array. However, because of the half-duplex constraint at the relays, relaying-assisted transmission would require the use of a higher order constellation than in the case when a continuous link is available from the BS to the UT. This would imply a penalty in the power efficiency. The simple precoding scheme proposed exploits the relation between QPSK and 16-QAM, by alternately transmitting through the 2 relays, achieving full diversity, while significantly reducing power penalty. Analysis of the pairwise error probability of the proposed algorithm with a single antenna in each relay is derived and confirmed with numerical results. We show the performance improvements of the precoded scheme, relatively to equivalent distributed SFBC scheme employing 16-QAM, for several channel quality scenarios. Copyright © 2010 Sara Teodoro, et al.European project CODIVPortuguese project CADWINPortuguese project AGILEFC