Edinburgh Napier University

About: Edinburgh Napier University is a education organization based out in Edinburgh, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 2665 authors who have published 6859 publications receiving 175272 citations.

The influence of the balance of inorganic and organic nitrogen on the trophic dynamics of microbial food webs

Abstract: A nutrient-manipulation mesocosm study was conducted in Norwegian coastal waters to determine the effect on a nitrogen-limited microbial food web of changes in the relative concentrations of dissolved organic and inorganic nitrogen (N). Four replicated treatments were studied: no N addition, inorganic N, organic N, or a 50 : 50 mix of inorganic and organic N. Comprehensive abundance, biomass, and rate measurements were made over the 20-d experiment. The form of N available influenced species composition, succession, and the efficiency of carbon (C) incorporation. Inorganic N generated a bloom of the diatom Leptocylindrus danicus, even though silicon concentrations were below 1 mmol L 21 . The c-proteobacteria initially competed effectively with diatoms for inorganic N, exhibiting high productivity and escaping grazing control. Organic N, when available alone, was utilized more slowly by the microbial community, with diatom growth, fueled by regenerated N, achieving a lower peak abundance. A more diverse diatom species assemblage was also evident. The c-proteobacteria were less prevalent and net bacterial productivity was initially lower when the N source was organic and, in contrast to the response following inorganic N addition, the bacterial community was initially grazer controlled. A rapid succession of heterotrophic grazers occurred but with differences in species and their contribution to biomass between treatments. The efficiency of C-biomass production was lower when the N source was purely organic. However, when both inorganic and organic N were available, biomass yield was greater than the mean of the two single N source treatments.

Application of Mixed Effects Limits of Agreement in the Presence of Multiple Sources of Variability: Exemplar from the Comparison of Several Devices to Measure Respiratory Rate in COPD Patients.

Abstract: Introduction The Bland-Altman limits of agreement method is widely used to assess how well the measurements produced by two raters, devices or systems agree with each other. However, mixed effects versions of the method which take into account multiple sources of variability are less well described in the literature. We address the practical challenges of applying mixed effects limits of agreement to the comparison of several devices to measure respiratory rate in patients with chronic obstructive pulmonary disease (COPD). Methods Respiratory rate was measured in 21 people with a range of severity of COPD. Participants were asked to perform eleven different activities representative of daily life during a laboratory-based standardised protocol of 57 minutes. A mixed effects limits of agreement method was used to assess the agreement of five commercially available monitors (Camera, Photoplethysmography (PPG), Impedance, Accelerometer, and Chest-band) with the current gold standard device for measuring respiratory rate. Results Results produced using mixed effects limits of agreement were compared to results from a fixed effects method based on analysis of variance (ANOVA) and were found to be similar. The Accelerometer and Chest-band devices produced the narrowest limits of agreement (-8.63 to 4.27 and -9.99 to 6.80 respectively) with mean bias -2.18 and -1.60 breaths per minute. These devices also had the lowest within-participant and overall standard deviations (3.23 and 3.29 for Accelerometer and 4.17 and 4.28 for Chest-band respectively). Conclusions The mixed effects limits of agreement analysis enabled us to answer the question of which devices showed the strongest agreement with the gold standard device with respect to measuring respiratory rates. In particular, the estimated within-participant and overall standard deviations of the differences, which are easily obtainable from the mixed effects model results, gave a clear indication that the Accelerometer and Chest-band devices performed best.

Strength grading of sawn timber in Europe: an explanation for engineers and researchers

Abstract: This paper is a concise explanation of the normative background to strength grading in Europe, addressing important aspects that are commonly misunderstood by structural engineers and timber researchers. It also highlights changes that are being made to the standards to: incorporate requirements of the construction products regulations; add improvements to the system to accommodate the latest knowledge and technology; and widen the application of the standards. Where designs need to be optimised, there is an opportunity to use the system more intelligently, in combination with the latest technology, to better fit design values to the true properties of the timber resource. This can bring a design enhancement equivalent to effort improving other aspects of the structure, such as connectors and reinforcement. Parallel to this, researchers working on other aspects of structural improvement need to understand what grades really mean in respect of the properties of the timber, in order to correctly analyse the results of testing. It is also useful to know how techniques used in grading can assist with material properties characterisation for research. The amount of destructive testing involved in establishing machine grading settings and visual grading assignments presents a barrier to greater use of local timber, and diversification of commercial species, so it is important that any researcher assessing the properties of such species should consider, from the outset, doing the research in a way that can contribute to a grading dataset at a later date. This paper provides an overview of what is required for this.

Dissolved Oxygen and Nitrification in the Upper Forth Estuary During Summer (1982–92): Patterns and Trends

Abstract: River discharge, wastewater inputs and water quality data from summer surveys in the upper Forth estuary have been reviewed for the period 1982–92. Particular attention has been given to dissolved oxygen and its possible links to the processes involved in the cycling of dissolved inorganic nitrogen species. Average dissolved oxygen (DO) concentrations for a particular year are linked with river flow; DO concentrations were lowest in years when river flow was low. Average DO concentrations in the upper Forth estuary have increased since 1959 when records began; however, the inter-annual variability in river flowprecludes the detection of any significant trend over the present study period. An important process contributing to the development of the oxygen minimum in the upper estuary is nitrification. A comparison has been made between total oxidized nitrogen (TON) concentrations (i.e. nitrate+nitrite) observed in river water, and those predicted by extrapolating down estuary TON/salinity relationships to zero. The latter are always larger than the former with the greatest discrepancies observed under low river flows. It is suggested that under low flow conditions, the longer water residence times in the upper estuary enable nitrification to proceed to a greater extent. Ample particulate organic nitrogen (PON) required for nitrification is demonstrated to exist in the turbidity maximum. This can originate from the river and/or the estuary and may be of natural or anthropogenic origin. Evidence is presented to show that the magnitude of the internally generated TON source has increased over the period under study. Maximum ammonia and nitrite concentrations in the estuary tend to be associated with years in which river flow is low. The mid-estuarine concentration maxima for nitrite are indicative of a benthic source, their locations are downstream of the nitrification-produced nitrate maximum. Their distributions are consistent with processes breaking down PON in reducing sediments (e.g. denitrification). Therefore, lower DO concentrations in the water column may be taken as indicative of more reducing conditions close to the surface sediments. An oxygen budget is constructed for the upper estuary. While gas exchange is identified as the major source of oxygen overall, DO from river water is likely to dominate at low salinity. The main sinks for oxygen in the estuary are nitrification, inputs of BOD and sediment oxygen demand. The link between high river flows and improved water quality is attributed not only to the oxygen contained in river water, but also to the associated shift of the turbidity maximum further downstream where the volume of the estuary is greater. A complex picture emerges of chemical and physical processes tending to act in concert towards low DO concentrations under low river flow conditions.