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Characterisation of riverine dissolved organic matter using a complementary suite of chromatographic and mass spectrometric methods
Get PDFDissolved organic matter (DOM) plays a fundamental role in nutrient cycling dynamics in riverine systems. Recent research has confirmed that the concentration of riverine DOM is not the only factor regulating its functional significance; the need to define the chemical composition of DOM is a priority. Past studies of riverine DOM rested on bulk quantification, however technological advancements have meant there has been a shift towards analytical methods which allow the characterisation of DOM either at compound class or more recently molecular level. However, it is important to consider that all analytical methods only consider a defined analytical window. Thus, herein, we explore the use of a hierarchy of methods which can be used in combination for the investigation of a wide range of DOM chemistries. By using these methods to investigate the DOM composition of a range of streams draining catchments of contrasting environmental character, a wide range of compounds were identified across a range of polarities and molecular weight, thereby extending the analytical window. Through the elucidation of the DOM character in stream samples, information can be collected about likely the sources of DOM. The identification of individual key compounds within the DOM pool is a key step in the design of robust and informative bioassay experiments, used to understand in-stream ecosystem responses. This is critical if we are to assess the role of DOM as a bioavailable nutrient resource and/or ecotoxicological factor in freshwater
The use of GRADE-CERQual in qualitative evidence synthesis: an evaluation of fidelity and reporting
Get PDFBACKGROUND: GRADE-CERQual (Confidence in the Evidence from Reviews of Qualitative Research) is a methodological approach to systematically and transparently assess how much confidence decision makers can place in individual review findings from qualitative evidence syntheses. The number of reviews applying GRADE-CERQual is rapidly expanding in guideline and other decision-making contexts. The objectives of this evaluation were, firstly, to describe the uptake of GRADE-CERQual in qualitative evidence synthesis by review authors and, secondly, to assess both reporting of and fidelity to the approach.METHODS: The evaluation had two parts. Part 1 was a citation analysis and descriptive overview of the literature citing GRADE-CERQual. Authors worked together to code and chart the citations, first by title and abstract and second by full text. Part 2 was an assessment and analysis of fidelity to, and reporting of, the GRADE-CERQual approach in included reviews. We developed fidelity and reporting questions and answers based on the most recent guidance for GRADE-CERQual and then used NVivo12 to document assessments in a spreadsheet and code full-text PDF articles for any concerns that had been identified. Our assessments were exported to Excel and we applied count formulae to explore patterns in the data. We employed a qualitative content analysis approach in NVivo12 to sub-coding all the data illustrating concerns for each reporting and fidelity criteria.RESULTS: 233 studies have applied the GRADE-CERQual approach, with most (n = 225, 96.5%) in the field of health research. Many studies (n = 97/233, 41.6%) were excluded from full fidelity and reporting assessment because they demonstrated a serious misapplication of GRADE-CERQual, for example interpreting it as a quality appraisal tool for primary studies or reviews. For the remaining studies that applied GRADE-CERQual to assess confidence in review findings, the main areas of reporting concern involved terminology, labelling and completeness. Fidelity concerns were identified in more than half of all studies assessed.CONCLUSIONS: GRADE-CERQual is being used widely within qualitative evidence syntheses and there are common reporting and fidelity issues. Most of these are avoidable and we highlight these as gaps in knowledge and guidance for applying the GRADE-CERQual approach.</p
Arthropod herbivory and fungal pathogen damage as determinants of distribution of tropical tree species Lacistema aggregatum across a Panamanian rainfall gradient
Get PDFAddressing high processing temperatures in reactive melt infiltration for multiphase ceramic composites
Get PDFApproaches for addressing the high processing temperatures required in reactive melt infiltration (RMI) processing of state-of-the-art multiphase ceramic matrix composites (CMCs) are reviewed. Ultra-high temperature ceramic composites can be realised by reactive melt infiltration of silicon, transition metals and/or alloys designed as immiscible phases, miscible phases, silicide phases and/or silicide eutectics to lower the temperature required for RMI. Whether carbides, borides or nitrides are envisaged in the resultant ceramic matrix composite, RMI presents an optimization challenge of balancing the composition of the phases incorporated and the processing temperature to be used. Current efforts aim at preparing complex and homogeneous microstructure preforms prior to RMI, minimising damage to reinforcing phases, applying rapid heating techniques, and developing in situ real-time monitoring systems during RMI. Future opportunities include integration of additive manufacturing and RMI, the increased use of process modelling and the application of in situ alongside in operando characterization techniques
Disclosure of forward-looking information: does overlapping audit committee membership matter?
Get PDFWe examine whether overlapping audit committee (AC) membership affects the forward-looking content of the chairman reports. We use content analysis to measure levels of forward-looking disclosure (FLD) for forty-eight bank-year observations from eight banks listed on Muscat Securities Market in Oman for the period 2014-2019. Our regression analysis shows that overlapping AC membership positively affects FLD. The evidence from this study suggests that a consideration of AC directors' attributes (e.g., overcommitted AC members) is needed to understand their role in the boardroom or in the subcommittees. An implication of the result is that the Omani corporate governance code should provide guidelines on the type and proportion of the overlapping AC membership. Furthermore, the code could encourage AC members to be overlapped across different committees as this could have a positive impact on corporate disclosure practice. Our study has demonstrated, for the first time, that overlapped AC members enhance the forward-looking content of chairman reports
A horizon scan of issues affecting UK forest management within 50 years
Get PDFForests are in the spotlight: they are expected to play a pivotal role in our response to society’s greatest challenges, such as the climate and biodiversity crises. Yet, the forests themselves, and the sector that manages them, face a range of interrelated threats and opportunities. Many of these are well understood, even if the solutions remain elusive. However, there are also emerging trends that are currently less widely appreciated. We report here the results of a horizon scan to identify developing issues likely to affect UK forest management within the next 50 years. These are issues that are presently under-recognized but have potential for significant impact across the sector and beyond. As the forest management sector naturally operates over long timescales, the importance of using good foresight is self-evident. We followed a tried-and-tested horizon scanning methodology involving a diverse Expert Panel to collate and prioritize a longlist of 180 issues. The top 15 issues identified are presented in the Graphical Abstract. The issues represent a diverse range of themes, within a spectrum of influences from environmental shocks and perturbations to changing political and socio-economic drivers, with complex emerging interactions between them. The most highly ranked issue was ‘Catastrophic forest ecosystem collapse’, reflecting agreement that not only is such collapse a likely prospect but it would also have huge implications across the sector and wider society. These and many of the other issues are large scale, with far-reaching implications. We must be careful to avoid inaction through being overwhelmed, or indeed to merely focus on ‘easy wins’ without considering broader ramifications. Our responses to each of the challenges and opportunities highlighted must be synergistic and coherent, involving landscape-scale planning. A more adaptive approach to forest management will be essential, encouraging continual innovation and learning. The 15 horizon scan issues presented here are a starting point on which to build further research, prompt debate and action, and develop evidence-based policy and practice. We hope that this stimulates greater recognition of how our forests and sector may need to change to be fit for the future. In some cases, these changes will need to be fundamental and momentous
A Point-to-multipoint Flexible Transceiver for Inherently Hub-and-Spoke IMDD Optical Access Networks
Get PDFPoint-to-multipoint (P2MP) transceivers offer apromisingsolution to transform present point-to-point optical access networks into scalable and flexible P2MP networks capable ofdynamically meeting, in a cost-effective and high energy consumption efficiency manner,the requirements associated with 5G-Advance and beyond networks, including largesignal transmission capacity, fast and dense connection, high network flexibility/adaptabilityand low latency. However, the previously reported P2MP optical transceivers based on either coherent XR optics orIMDD digital filter multiplexing (DFM) techniques are not suitable for implementing in low-latency and highly cost-sensitive IMDD-dominated optical access networks.This paper proposes, experimentally demonstrates and optimisesa novel P2MP flexible transceiver incorporating a new cascaded IFFT/FFT-based multi-channel aggregation/de-aggregation technique and an orthogonal digital filtering technique. The performancesof the proposed techniqueare extensively evaluated experimentally in an upstream 55.3Gb/s@25km IMDD PON.Itis shown that in comparison with the conventional DFM transceivers, the proposed transceivers can reduce the transmitter DSP complexity by a factor that approximatesto aggregated channel count,and simultaneouslyoffer additional physical layernetworksecurity,without requiring longdigital filter lengthsand greatly compromising upstream transmission performances/spectral efficienciesas well as differentialONU launch power dynamic range
Determining patterns in the composition of dissolved organic matter in fresh waters according to land use and management
Get PDFIn fresh waters, the origins of dissolved organic matter (DOM) have been found to exert a fundamental control on its reactivity, and ultimately, its ecosystem functional role. A detailed understanding of landscape scale factors that control the export of DOM to aquatic ecosystems is, therefore, pivotal if the effects of DOM flux to fresh waters are to be fully understood. In this study we present data from a national sampling campaign across the United Kingdom in which we explore the variability in DOM composition in three broad landscape types defined by similar precipitation, geology, land use and management, hydrology, and nutrient enrichment status. We characterised samples from fifty-one sites, grouping them into one of three major underlying classifications: circumneutral streams underlain by clay and mudstone (referred to as ‘clay’), alkaline streams underlain by Cretaceous Chalk or by Carboniferous or Jurassic Limestone (‘limestone’), and acidic streams in peatland catchments underlain by a range of low permeability lithologies (‘peat’). DOM composition was assessed through organic matter stoichiometry (organic carbon: organic nitrogen; organic carbon: organic phosphorus; C/N(P)DOM) and metrics derived from ultra-violet (UV)/visible spectroscopic analysis of DOM such as specific UV absorption (a254 nm; SUVA254). We found similar SUVA254, C/NDOM and DOM/a254 relationships within classifications, demonstrating that despite a large degree of heterogeneity within environments, catchments with shared environmental character and anthropogenic disturbance export DOM with a similar composition and character. Improving our understanding of DOM characterisation is important to help predict shifts in stream ecosystem function, and ecological responses to enrichment or mitigation efforts and how these may result in species composition shifts and biodiversity loss in freshwater ecosystems
Selective foraging behavior of seabirds in small-scale slicks
Get PDFMarine predator foraging opportunities are often driven by dynamic physical processes enhancing prey accessibility. Surface slicks are ubiquitous yet ephemeral ocean features where convergent flows accumulate flotsam, concentrating marine organisms and pollutants. Slicks can manifest on the sea surface as meandering lines and seabirds often associate with slicks. Yet, how slicks may influence the fine-scale foraging behavior of seabirds is only coarsely resolved. Here we show that seabirds selectively forage in small-scale slicks. We used aerial drone technology to track surface-foraging terns (Sternidae, 107 tracks) over evolving slicks advected by the mean flow and reshaped by localized turbulence at scales of meters and seconds. Terns were more likely to switch into high-tortuosity foraging behavior when over slicks, with plunge-dive events occurring significantly more often within slicks. As we demonstrate that terns select dynamic slicks for foraging, our approach will also lend itself to interaction studies with pollutants, plumes, and fronts