• Other research productsclose
• UK Research and Innovation close

Methane (CH4) is a strong greenhouse gas known to have perturbed global climate in the past, especially when released in large quantities over short time periods from continental or marine sources. It is therefore crucial to understand and, if possible, quantify the individual and combined response of these variable methane sources to natural climate variability. However, past changes in the stability of greenhouse gas reservoirs remain uncertain and poorly constrained by geological evidence. Here, we present a record from the Congo fan of a highly specific bacteriohopanepolyol (BHP) biomarker for aerobic methane oxidation (AMO), 35-aminobacteriohopane-30,31,32,33,34-pentol (aminopentol), that identifies discrete periods of increased AMO as far back as 1.2 Ma. Fluctuations in the concentration of aminopentol, and other 35-aminoBHPs, follow a pattern that correlates with late Quaternary glacial-interglacial climate cycles, with highest concentrations during warm periods. We discuss possible sources of aminopentol, and the methane consumed by the precursor methanotrophs, within the context of the Congo River setting, including supply of methane oxidation markers from terrestrial watersheds and/or marine sources (gas hydrate and/or deep subsurface gas reservoir). Compound-specific carbon isotope values of -30 per mil to -40 per mil for BHPs in ODP 1075 and strong similarities between the BHP signature of the core and surface sediments from the Congo estuary and floodplain wetlands from the interior of the Congo River Basin, support a methanotrophic and likely terrigenous origin of the 35-aminoBHPs found in the fan sediments. This new evidence supports a causal connection between marine sediment BHP records of tropical deep sea fans and wetland settings in the feeding river catchments, and thus tropical continental hydrology. Further research is needed to better constrain the different sources and pathways of methane emission. However, this study identifies the large potential of aminoBHPs, in particular aminopentol, to trace and, once better calibrated and understood, quantify past methane sources and fluxes from terrestrial and potentially also marine sources.

This upload contains the neural networks used in the paper "Improving filling level classification with adversarial training". The networks are already pre-trained on the 3 splits (S1, S2, S3) of the C-CCM dataset, using six different training strategies. The networks are implemented in PyTorch. More information regarding the C-CCM dataset can be found here: https://corsmal.eecs.qmul.ac.uk/filling.html The CCM_Filling_Level_Pretrained_Models.zip file contains: 3 folders (S1, S2, S3) that correspond to the different dataset splits Each of S1, S2, S3 folders contains 6 subfolders (ST, AT, ST-FT, ST-AFT, AT-FT, AT-AFT) which correspond to the different training strategies used in the paper. Each of the ST, AT, ..., AT-AFT subfolders contains a PyTorch file named last.t7. This is the PyTorch ResNet-18 model that is trained on the corresponding split (S1/S2/S3) using the corresponding training strategy (ST, AT, ..., AT-AFT). A Python example script for loading the models is also provided (load_model.py).

This invited paper considers a key next step in the design of radio architectures aimed at supporting low energy consumption in 5G heterogeneous radio access networks. State-of-the-art mobile radios usually require one RF transceiver per standard, each working separately at any given time. Software defined radios, while spanning a wide range of standards and frequency bands, also work separately at any specific time. In 5G radio access networks, where continuous, multiband connectivity is envisaged, this conventional radio architecture results in high network power consumption. In this paper, we propose the novel concept of a concurrent multiband frequency-agile radio (CM-FARAD) architecture, which simultaneously supports multiple standards and frequency bands using a single, tunable transceiver. We discuss the subsystem radio design approaches for enabling the CM-FARAD architecture, including antennas, power amplifiers, low noise amplifiers and analogue to digital converters. A working prototype of a dual-band CM-FARAD test-bed is also presented together with measured salient performance characteristics.

Version 1 (still some edits to make it more user-friendly)

These datasets were used to describe the diversity, ecology and role of non-scleractinian corals on scleractinian cold-water coral carbonate mounds in the Logachev Mound Province, Rockall Bank, NE Atlantic. Cold-water coral carbonate mounds, created by framework-building scleractinian corals, are also important habitats for non-scleractinian corals, whose ecology and role are understudied in deep-sea environments. In total ten non-scleractinian species were identified, which were mapped out along eight ROV video transects. Eight species were identified as black corals (three belonging to the family Schizopathidae, one each to the Leiopathidae, Cladopathidae, and Antipathidae and two to an unknown family) and two as gorgonians (Isididae and Plexauridae). The most abundant species were Leiopathes sp. and Parantipathes sp. 2. Areas with a high diversity of non-scleractinian corals are interpreted to offer sufficient food, weak inter-species competition and the presence of heterogeneous and hard settlement substrates. A difference in the density and occurrence of small vs. large colonies of Leiopathes sp. was also observed, which is likely related to a difference in the stability of the substrate they choose for settlement. Non-scleractinian corals, especially black corals, are an important habitat for crabs, crinoids, and shrimps in the Logachev Mound Province.

Atmospheric _p_CO~2~ is a critical component of the global carbon system and is considered to be the major control of Earth's past, present and future climate. Accurate and precise reconstructions of its concentration through geological time are, therefore, crucial to our understanding of the Earth system. Ice core records document _p_CO~2~ for the past 800 kyrs, but at no point during this interval were CO~2~ levels higher than today. Interpretation of older _p_CO~2~ has been hampered by discrepancies during some time intervals between two of the main ocean-based proxy methods used to reconstruct _p_CO~2~: the carbon isotope fractionation that occurs during photosynthesis as recorded by haptophyte biomarkers (alkenones) and the boron isotope composition (δ^11^B) of foraminifer shells. Here we present alkenone and δ^11^B-based _p_CO~2~ reconstructions generated from the same samples from the Plio-Pleistocene at ODP Site 999 across a glacial-interglacial cycle. We find a muted response to _p_CO~2~ in the alkenone record compared to contemporaneous ice core and δ^11^B records, suggesting caution in the interpretation of alkenone-based records at low _p_CO~2~ levels. This is possibly caused by the physiology of CO~2~ uptake in the haptophytes. Our new understanding resolves some of the inconsistencies between the proxies and highlights that caution may be required when interpreting alkenone-based reconstructions of _p_CO~2~.

Since their first demonstration in 2002, the development of terahertz frequency quantum cascade lasers has been extremely rapid. We overview some of the advances that have taken place and which have made the terahertz quantum cascade laser such a ubiquitous source. We also consider potential future directions for terahertz quantum cascade laser technology, including its use in satellite-borne instrumentation for future Earth observation and planetary science missions.

Past millennial-scale changes in atmospheric CO2 (CO2,atm) levels have often been attributed to variations in the overturning timescale of the ocean that result in changes in the marine carbon inventory. There remains a paucity of proxy evidence that documents changes in marine carbon storage globally, and that links them to distinct abrupt climate variability in the northern hemi-sphere that involve perturbations of the Atlantic Meridional Overturning Circulation (AMOC). The last two glacial periods were suggested to differ in the extent and sensitivity of the AMOC to changes, and therefore provide an opportunity to study their role in marine carbon cycling. Here, we reconstruct variations in respired carbon storage (via oxygenation) and the AMOC 'geometry' (via carbonate ion saturation) in the deep South Atlantic during the past two glacial periods. We infer decreases in deep South Atlantic respired carbon levels at times of weakened AMOC and rising CO2,atm concentrations during both glacial periods. These findings suggest a consistent pat-tern of increased Southern Ocean convection and/or air-sea CO2 fluxes during northern-hemisphere stadials accompanying AMOC perturbations and promoting a rise in CO2,atm levels, despite potential differences in the magnitude of the forcing, the climate (and hence, AMOC) background conditions and the rate of ocean-atmospheric CO2 fluxes. We find that net ocean car-bon loss, and hence the magnitude of CO2,atm rise, during a glacial is largely determined by the stadial duration. North Atlantic climate anomalies may therefore significantly affect Southern Ocean carbon cycling through oceanic (e.g., 'ventilation' seesaw) and/or atmospheric processes (e.g., Ekman pumping).

Recent years have witnessed an ever-increasing growth for cloud computing services and applications housed by data centers. PON based optical interconnects for data center networks is a promising technology to offer high bandwidth, efficient utilization of resources, reduced latency and reduced energy consumption compared to current data center networks based on electronic switches. This paper presents our proposed scheme for data center interconnection to manage intra/inter communication traffic based on readily available low cost and power PON components. In this work, we tackle the problem of resource provisioning optimization for cloud applications in our proposed PON data centers architecture. We use Mixed Integer Linear Programming (MILP) to optimize the power consumption and delay for different cloud applications. The results show that delay can be decreased by 62% for delay-sensitive applications and power consumption can be decreased by 22% for non-delay sensitive applications.