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An Ice-Ocean Model Study of the Mid-2000s Regime Change in the Barents Sea
Get PDFAbstractOver the satellite record, the Barents Sea winter maximum in sea ice extent has declined and was increasingly limited to areas north of the Polar Front after 2005 by warming Atlantic Water (AW) and Barents Sea Water (BSW). Sea ice extent here continues to garner interest, not least because it is associated with extreme winter weather in Europe and Asia. Previous model studies suggest there is a possibility that natural variability will cause southward re‐expansion of the lost sea ice cover but reducing uncertainties requires a better understanding of the processes driving BSW variability. To address questions about BSW variability, we used a high‐resolution model validated with observations over 1985–2014 to calculate the watermass transport, heat, and freshwater budgets within the central Barents Sea, south of the Polar Front. The model shows BSW volume minima events in years centering at 1990 and 2004, meaning a reduction in the Barents Sea's volume reservoir (also termed “memory”) of water that is consistent with historical BSW properties. Both events were preceded by extensive winter sea ice and substantial summer net sea ice melt. The event in 2004 was more extreme and led to warming AW occupying a greater volume in the Barents Sea after 2005. The reduced “memory” of BSW volume could impede a return to the more extensive winter sea ice regime and make further reduction in winter sea ice possible
Exercise testing in the acute setting – the utility of exercise testing to predict safe discharge in acute cardiopulmonary disease including validation of the 40 steps desaturation test in the assessment of acute or suspected COVID-19
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DSP-Based Physical Layer Security for Coherent Optical Communication Systems
Get PDFA novel digital signal processing (DSP)-based scheme for physical layer security in coherent optical communication systems is proposed and numerically investigated. The optical layer signal encryption is accomplished by two dispersive elements and one phase modulator (PM) driven by a DSP-generated encryption key, whilst signal decryption uses similar components but with inverted dispersion values and security keys. A critical aspect of the DSP-based physical layer security is that the security keys, driving the PMs to hide/recover the data signals, must be highly unpredictable and noise-like, thus orthogonal frequency division multiplexing (OFDM) signals are employed as they possess these characteristics, they can also be easily generated and cover a suitably wide range of unique keys. Numerical simulations are conducted to determine optimum system parameters for achieving a high level of security, the key parameters requiring optimization are the dispersion of the dispersive elements and the bandwidth of the security keys. Using these determined optimum parameters, in-depth investigations are undertaken of encryption/decryption induced transmission performance penalties, sensitives to various parameter offsets and operation over various transmission distances. To observe any data signal dependencies, various performance metrics are investigated for different combinations of modulation formats (DQPSK and 16QAM) and baud rates (40Gbaud and 100Gbaud) for the transmitted data signals. The proposed DSP-based physical layer security scheme is shown to have the potential to achieve, in a low-cost and highly effective manner, a high level of physical layer security with acceptable performance penalties for existing coherent optical communication systems
The environmental and social impacts of modified wood production: effect of timber sourcing
Get PDFThis study assesses the environmental and social impacts of a modified softwood produced using radiata pine sourced from New Zealand or Chile. The LCA found that differing forestry and transport burdens associated with each location broadly cancelled each other out, giving overall product footprints that were very similar. Boiler gas and phenol-formaldehyde resin were the biggest emitters of GHG emissions, and normalization highlighted toxicity impacts as significant, largely due to the resin input. SLCA hotspots analyses suggest that the forestry sector in Chile has more potential social risks than the equivalent sector in New Zealand. However, each sector scored poorly in different social aspects making it difficult to recommend a sector without introducing subjective judgements. Combining LCA with SLCA is still novel, but this study found it added useful insights into a broader range of impacts associated with sustainable production, especially given the similarity of the environmental LCA results taken alone
Epigenetic divergence during early stages of speciation in an African crater lake cichlid fish
Get PDFEpigenetic variation can alter transcription and promote phenotypic divergence between populations facing different environmental challenges. Here, we assess the epigenetic basis of diversification during the early stages of speciation. Specifically, we focus on the extent and functional relevance of DNA methylome divergence in the very young radiation of Astatotilapia calliptera in crater Lake Masoko, southern Tanzania. Our study focuses on two lake ecomorphs that diverged approximately 1,000 years ago and a population in the nearby river from which they separated approximately 10,000 years ago. The two lake ecomorphs show no fixed genetic differentiation, yet are characterized by different morphologies, depth preferences and diets. We report extensive genome-wide methylome divergence between the two lake ecomorphs, and between the lake and river populations, linked to key biological processes and associated with altered transcriptional activity of ecologically relevant genes. Such genes differing between lake ecomorphs include those involved in steroid metabolism, hemoglobin composition and erythropoiesis, consistent with their divergent habitat occupancy. Using a common-garden experiment, we found that global methylation profiles are often rapidly remodeled across generations but ecomorph-specific differences can be inherited. Collectively, our study suggests an epigenetic contribution to the early stages of vertebrate speciation
The Impact of Regulatory Reforms on European Bank Behaviour: A Dynamic Structural Estimation
Get PDFThis paper develops a dynamic structural model of bank behaviour. Banks can vary their financing structure, business model and decide on rating solicitation, in the presence of costly debt, corporation tax, insolvency costs and convex adjustment costs. The model is then simulated to examine the impact of regulation on banks’ behaviour. A bail-in regime leads to reduced bank lending activity, while having little impact on bank insolvency rates. Stringent capital requirements reduce bank insolvency rates in a crisis period, while mitigating the reduction in lending activity due to an increased uptake in marginal investments. More lenient credit ratings are associated with increased bank failures. These findings offer wide-ranging implications for policy makers and the banking industry