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Rapid Increase in Soil Respiration and Reduction in Soil Nitrate Availability Following CO<sub>2</sub> Enrichment in a Mature Oak Forest
No full textIn the future, with elevated atmospheric CO2 (eCO2), forests are expected to increase woody biomass to capture more carbon (C), though this is dependent on soil nutrient availability. While young forests may access unused nutrients by growing into an unexplored soil environment, it is unclear how or if mature forests can adapt belowground under eCO2. Soil respiration (Rs) and nutrient bioavailability are integrative ecosystem measures of below-ground dynamics. At Birmingham’s Institute of Forest Research Free Air CO2 Enrichment (BIFoR FACE) facility, we investigated the effects of eCO2 (+150 ppm above ambient) on a mature oak forest during the first year of exposure. We observed an annual Rs increase of ∼21.5%; 996 ± 398 g C m–2 year–1 (ambient) to 1210 ± 483 g C m–2 year–1 (eCO2). The eCO2 impact was greater on belowground nutrient cycling, with monthly nitrate availability decreasing by up to 36%. These results show that high C uptake resulted in higher soil respiration with a concomitant decrease in the level of soil nitrate during the first year. These belowground responses and their long-term dynamics will have implications for the carbon budget of mature forest ecosystems in changing climate
The Benefits of Coarse Preferences
Get PDFWe study the strategic benefits of coarsening one’s utility by clustering payoffs together. Our solution concept, coarse-utility equilibrium (CUE) requires that (1) each player maximizes her coarse utility, given the opponent’s strategy, and (2) the classifications form best replies to one another. We characterize CUEs in various games. In particular, we show that there is a qualitative difference between CUEs in which only one of the players clusters payoffs and those in which all players cluster their payoffs, and that, in the latter type of CUE, players treat other players better than they do in Nash equilibria in games with monotone externalities
The use of multiple systems estimation to estimate the number of unattributed paintings by Modigliani
Get PDFThe number of unattributed paintings by Amedeo Modigliani is estimated, using the method of multiple systems estimation (MSE). Most major artists’ works are listed in one catalogue raisonné, but there are five catalogues purporting to list Modigliani paintings. These can be treated as list sources from which MSE can be applied. We obtain estimates by following the classical MSE approach using log-linear models, and compare these with estimates obtained via a Bayesian non-parametric latent class approach. We also consider the impact of fake paintings through sensitivity analyses. Our estimates point to there being around 20–120 unattributed Modigliani paintings
Search for diphoton resonances in the 66 to 110 GeV mass range using pp collisions at s = 13 TeV with the ATLAS detector
No full textA search is performed for light, spin-0 bosons decaying into two photons in the 66 to 110 GeV mass range, using 140 fb−1 of proton-proton collisions at s = 13 TeV produced by the Large Hadron Collider and collected by the ATLAS detector. Multivariate analysis techniques are used to define event categories that improve the sensitivity to new resonances beyond the Standard Model. A model-independent search for a generic spin-0 particle and a model-dependent search for an additional low-mass Higgs boson are performed in the diphoton invariant mass spectrum. No significant excess is observed in either search. Mass-dependent upper limits at the 95% confidence level are set in the model-independent scenario on the fiducial cross-section times branching ratio into two photons in the range of 8 fb to 53 fb. Similarly, in the model-dependent scenario upper limits are set on the total cross-section times branching ratio into two photons as a function of the Higgs boson mass in the range of 19 fb to 102 fb
Demonstration of active neutron interrogation of special nuclear materials using a high-intensity short-pulse-laser-driven neutron source
No full textDetecting shielded special nuclear material, such as nuclear explosives, is a difficult challenge pursued by non-proliferation, anti-terrorism, and nuclear security programs worldwide. Interrogation with intense fast-neutron pulses is a promising method to characterize concealed nuclear material rapidly but is limited by suitable source availability and proven instrumentation. In this study we have pioneered a demonstration of such an interrogation method using a high-intensity, short-pulse, laser-driven neutron source that offers potential benefits compared to conventional neutron sources. The measurement results reported here represent the first experimental demonstration of this interrogation approach on enriched uranium items and demonstrate the feasibility of a precise measurement using realistic nuclear materials, representative of field scenarios, even with just a single laser-driven neutron pulse. Bright pulsed sources can overcome the nuisance background of items with strong internal neutron sources, improving analytical power, while single-shot assay is attractive in high-throughput situations where time is at a premium. The science and technology of this type of neutron production is developing rapidly, and we anticipate that practical mobile interrogation systems will become available based on the detection concepts demonstrated here to meet the growing measurement needs
Nutrient availability explains distinct soil fungal colonization of angiosperm versus gymnosperm wood
Get PDFSoil fungi play an essential role in the fungal colonization of deadwood, with consequences for multiple ecosystem functions such as wood decomposition. Nutrient deposition can substantially affect fungal activity, but it is unclear how external nutrient inputs and host plant nutrient content interact to influence soil fungal colonization of deadwood. To advance understanding of fungal dynamics during deadwood decomposition, we conducted a field experiment with eight tree species (four angiosperms and four gymnosperms) under four nutrient additions (no nutrient addition, nitrogen (N)‐addition, phosphorus (P)‐addition and combined N‐ and P‐addition), to investigate fungal colonization and communities in different host plant clades (angiosperms and gymnosperms) over 3 years. The study revealed that host plant clade and nutrient availability interact significantly, which strongly influenced soil fungal colonization of deadwood. The percentage of shared fungi (present in both soil and deadwood) was higher in angiosperms (38.1%–47.3%) than in gymnosperms (26.5%–36.5%). Saprotrophs were the dominant functional group in the shared fungal community, with symbiotrophs as the next most abundant group, and the dominant fungal taxa were mainly K‐strategists, which were more abundant in gymnosperms than in angiosperms. Notably, there was a stronger connection between soil fungi and deadwood fungi in gymnosperms compared to angiosperms, which was likely related to the importance of K‐strategist fungi for decomposing wood with low nutrient content. Overall, the shared fungal community in angiosperms was more sensitive to nutrient addition than in gymnosperms, resulting in greater changes to fungal taxa and functional groups. In angiosperm wood, N‐addition significantly increased α‐diversity but decreased β‐diversity of the shared fungal community, indicating N‐limitation. In gymnosperm wood, P‐addition significantly reduced both α‐diversity and β‐diversity of the shared fungal community, indicating P‐limitation. Synthesis. Our study demonstrates the divergent effect of nutrient addition on fungal colonization in angiosperms versus gymnosperms. Considering interactions between inherent plant traits and exogenous nutrient availabilities thus provides a more comprehensive understanding of the association between soil fungi and deadwood fungi during wood decomposition
Beyond GMV : the relevance of covariance matrix estimation for risk-based portfolio construction
Get PDFWe empirically analyze the relevance of variance-covariance (VCV) estimators in equity portfolio construction. While traditional analyses of unconstrained global minimum-variance (GMV) portfolios support using shrinkage and modeling covariance dynamics, the resulting portfolios are often impractical due to high leverage, concentration, and costs. By examining constrained GMV and risk parity portfolios, we find a significantly reduced opportunity for alternative VCV estimators to outperform the sample estimator. Specifically, we show that a long-only portfolio with asset-level constraints and a transaction cost penalty produces similar results to shrinkage-based methods, even when using the sample VCV estimator. However, accounting for time-series dynamics in asset returns remains statistically relevant for volatility reduction. Our findings emphasize how the interaction between VCV estimators and portfolio construction choices shapes both the statistical and practical outcomes in portfolio management
Navigating digital skills contradictions with boys’ secondary school students : The teachers’ perspective
No full textStudents’ digital skills development seems to be a pertinent issue as we progress into the fourth industrial revolution (4IR) and involves student readiness for Education 4.0. However, literature pertaining to digital skills development is often positioned in Higher Education (HE) and often reports on the lack of students' digital skills. Factors such as poor infrastructure and insufficient teachers’ continuous professional development (CPD) have been reported as reasons for this underdevelopment. However, in the United Arab Emirates (UAE), government schools are well-resourced and serviced by digitally skilled practitioners who are regularly offered CPD, yet students’ digital skills still seem underdeveloped. As such, this paper aims to add to the discussion in the literature by focusing on secondary school teachers’ perspectives on the challenges they face when developing students’ digital skills. Underpinned by Cultural Historical Activity Theory (CHAT), the study employed a case study methodology using semi-structured group interviews with four teachers from Creative Computer Design and Innovation (CCDI), English, Math and Science. Themes relating to the lack of students’ digital and basic literacy skills, students’ attitudes and behaviours, and organisational policy emerged as challenges teachers experience whilst trying to develop students' digital skills. Consequently, the paper recommends addressing these challenges through policies that work in tandem with each other to improve digital skills within this and wider contexts
AI and Serious Online Crime
No full textAI proliferation is reshaping serious online criminality. While the use of AI by criminals remains at an early stage, there is widespread evidence emerging of a substantial acceleration in AI-enabled crime, particularly evident in areas such as financial crime, child sexual abuse material, phishing and romance scams. Criminal groups benefit from AI’s ability to automate and rapidly scale the volume of their activities, augment existing online crime types and exploit people’s psychological vulnerabilities. This report aims to equip the UK national security and law enforcement communities with the tools to plan and better position themselves to respond to novel threats over the next five years. That process will require more effective coordination and targeting of resources, and more rapid adoption of AI itself. It should start with the creation of a new AI Crime Taskforce within the National Crime Agency – which would collate data across UK law enforcement to monitor and log criminal groups’ use of AI, working with national security and industry partners on strategies to raise barriers to criminal adoption