146 research outputs found
Are more data always better? – Machine learning forecasting of algae based on long-term observations
No full textBloom-forming algae present a unique challenge to water managers as they can significantly impair provision of important ecosystem services and cause health risks to humans and animals. Consequently, effective short-term algae forecasts are important as they provide early warnings and enable implementation of mitigation strategies. In this context, machine learning (ML) emerges as a promising forecasting tool. However, the performance of ML models is heavily dependent on the availability of appropriate training data. Consequently, it is essential to determine the volume of data necessary to develop reliable ML forecasts. Understanding this will guide future monitoring strategies, optimize resource allocation, and set realistic expectations for management outcomes. In this study, we used 30 years of fortnightly measurements of 13 different parameters from a lake in the English Lake District (UK) to examine the impact of training data duration on the performance of ML models for forecasting chlorophyll-a two weeks in advance. Once training data availability exceeded four years, a Random Forest model was found to consistently outperform naive benchmarks (mean absolute percentage error 16.4 % lower than the best-performing benchmark). With more than 5 years of training data, model performance generally continued to improve, but with diminishing returns. Furthermore, it was found that equivalent and, in some cases, better performance could be achieved by only using a subset of the most important input features. Additionally, it was found that reducing the sampling frequency had negative impacts on performance, both due to the reduced number of training observations available, and increased forecast horizon. Our findings demonstrate that for lakes ecologically similar to the study site, a consistent and regular sampling programme focused on monitoring a limited number of key parameters can provide sufficient observations for generating short-term algae forecasts after approximately five years of data collection. Importantly, this result provides justification for the initiation of new monitoring programmes for sites where algal blooms are a concern, and suggests that there are likely many pre-existing monitoring datasets which would be suitable for training algae forecast models
The Role of Coordination and Cooperation for Bt-maize cultivation in Brandenburg, Germany
No full textSince 2006, several varieties of transgenic Bt-maize are approved for commercial cultivation in Germany. The German regulatory framework for growing these crops comprises ex-ante regulations as well as ex-post liability rules to protect conventional and organic farming from possible negative side effects of transgenic plants and to ensure co-existence. Public regulation is also suspected to impose additional costs to those farmers who intend to plant Bt-maize. We address the question how Bt-maize growing farmers perceive the additional costs of regulation and whether coordination or cooperation takes place in order to diminish these costs. In 2006, we carried out a case study in the Oderbruch region (Brandenburg, Germany) comprising eight Bt-maize growing farmers and six adjacent neighbours. The predominantly large farms chose intrafarm coordination to manage the construction of buffer zones within their own fields and to avoid the planting of Bt-maize close to their neighbours. Inter-farm coordination or cooperation with adjacent farmers was not regarded necessary to achieve co-existence.Coordination, Cooperation, Bt-maize, Crop Production/Industries,
The reorientation of t-butyl groups in butylated hydroxytoluene: A deuterium nuclear magnetic resonance spectral and relaxation time study
No full textDeuterium nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times were determined in order to study the dynamics of t-butyl groups in butylated hydroxytoluene. The results are consistent with a model first proposed by Beckmann et al. [J. Magn. Reson. 36, 199 (1979)], where there is an inequivalence between the methyl groups within each t-butyl group. While two methyl groups reorient rapidly relative to the whole t-butyl rotation, the remaining methyl group is more restricted in its motion, reorienting at a rate comparable to that of the t-butyl group itself. The spin-lattice relaxation data show two T1 minima, the high temperature minimum (40-degrees-C) corresponding to the combined t-butyl and "slow" methyl rotations, and the low temperature minimum corresponding to "fast" methyl group rotation. Using an explicitly defined T1 fitting function, the T1 data yield activation energies of 2.2 and 6.0 kcal/mol for the fast methyl and t-butyl rotations, respectively, both in agreement with Beckmann's values obtained from proton T1 experiments. It was also possible to simulate the low temperature deuterium NMR spectra from T = - 160-degrees-C to T = - 80-degrees-C using the aforementioned dynamical inequivalence between the t-butyl methyl groups. While the fast methyl group rotation was in the motional narrowing region for T > - 160-degrees-C, it was possible, from the simulations, to determine the t-butyl exchange rates to within 10%. The jump rates are remarkably close to the values predicted from the T1 results. Above - 80-degrees-C, the spectra could not be simulated, implying that a third motion must be present to further alter the high temperature line shapes. The effective axial asymmetry of the T > - 20-degrees spectra indicates that the additional motion involves a two site exchange.PT: J; CR: ABRAGAM A, 1961, PRINCIPLES NUCLEAR M, P451 ALBERT S, 1972, J CHEM PHYS, V56, P1332 ALBERT S, 1976, J CHEM PHYS, V6, P3277 ALBERT S, 1976, J CHEM PHYS, V64, P3277 ARONSON M, 1981, CHEM PHYS, V63, P349 BECKMANN P, 1978, J MAGN RESON, V32, P391 BECKMANN P, 1979, J MAGN RESON, V36, P199 BECKMANN P, 1981, CHEM PHYS, V63, P359 BECKMANN PA, 1984, J MAGN RESON, V59, P63 BEVINGTON PR, 1969, DATA REDUCTION ERROR, CH11 BLOEMBERGEN N, 1948, PHYS REV, V73, P679 BLOOM M, 1980, CAN J PHYS, V58, P1510 DAVIS JH, 1976, CHEM PHYS LETT, V42, P390 DAVIS JH, 1983, BIOCHIM BIOPHYS ACTA, V737, P117 DRUYAN ME, 1976, J AM CHEM SOC, V98, P4801 ELSAFFAR ZM, 1972, J CHEM PHYS, V56, P1477 FABER DH, 1974, ACTA CRYSTALLOGR B, V30, P449 FROST JC, 1980, PHILOS T ROY SOC B, V290, P567 FROST JC, 1982, J CHEM SOC FARAD T 2, V78, P2139 GALL CM, 1981, J AM CHEM SOC, V103, P5039 GOLDBERG I, 1975, ACTA CRYSTALLOGR B, V31, P2592 GRIFFIN RG, 1981, METHOD ENZYMOL, V72, P108 HASEBE T, 1985, J CHEM SOC FARAD T 2, V81, P735 HASEBE T, 1985, J CHEM SOC FARAD T 2, V81, P749 HURT CJ, 1975, ACTA CRYSTALLGR, V91, P273 LEADBETTER AJ, 1985, J CHEM SOC FARAD T 2, V81, P1067 MAZEBAUDET M, 1973, ACTA CRYSTALLOGR B, V29, P602 MCKENZIE TC, 1975, ACTA CRYSTALLOGR B, V31, P1778 MOOIBROEK S, 1985, CAN J CHEM, V63, P2926 MOOIBROEK S, 1988, CAN J CHEM, V66, P734 OREILLY DE, 1973, J CHEM PHYS, V59, P3576 OWEN NL, 1974, INTERNAL ROTATIONS M, P157 POWLES JG, 1953, J CHEM PHYS, V21, P1695 POWLES JG, 1953, J CHEM PHYS, V21, P1704 RIPMEESTER JA, 1985, J CHEM PHYS, V82, P1053 SPIESS HW, 1981, J MAGN RESON, V42, P381 STEJSKAL EO, 1958, J CHEM PHYS, V28, P388 STEJSKAL EO, 1959, J CHEM PHYS, V31, P55 TORCHIA DA, 1982, J MAGN RESON, V49, P107 VEGA AJ, 1987, J CHEM PHYS, V86, P1803 WITTEBORT RJ, 1987, J CHEM PHYS, V86, P5411; NR: 41; TC: 13; J9: J CHEM PHYS; PG: 8; GA: FA778Source type: Electronic(1
Carrier Wave Signals Interfering with Loran-C
No full textElectrical Engineering, Mathematics and Computer Scienc
Widespread phytoplankton monitoring in small lakes: a case study comparing satellite imagery from planet SuperDoves and ESA sentinel-2
No full textSatellite imagery has enabled widespread monitoring of algae in larger water bodies, however until recently, the spatial resolution of available sensors has not been sufficient to apply this to smaller lakes. Therefore, this study investigated a new dataset of high-resolution metre-scale imagery for monitoring phytoplankton at spatial and temporal scales previously impossible with satellite data. Specifically, the Planet SuperDoves constellation was used to monitor a small (0.069 km2), eutrophic lake from 2021 to 2024. Several chlorophyll-a (Chl-a) algorithms were tested on both SuperDoves and Sentinel-2 data against in situ measurements. Additionally, the suitability of citizen science data as a validation tool for widespread algal bloom monitoring was investigated by comparing reports of algal blooms in five small water bodies in central Scotland with corresponding SuperDoves Chl-a images. Chl-a was successfully retrieved using the Ocean Colour 3 algorithm (R2 = 0.64, root mean squared error (RMSE) = 0.93 g L−1), which outperformed the best performing Sentinel-2 Chl-a algorithm (R2 = 0.61, RMSE = 1.01 g L−1). Furthermore, both Sentinel-2 and SuperDoves data were equally effective for algal bloom detection, each having F1-scores of 0.89 at a Chl-a bloom threshold of 40 g L−1. This demonstrates that metre-scale satellite monitoring of algae is possible even in challenging and optically complex environments such as small, shallow water bodies. This leads towards a potential step-change in the number of remotely monitorable inland water bodies, which would be a significant advancement for global lake science, environmental management and public health protection efforts
Long-term wind-driven X-ray spectral variability of NGC 1365 with Swift
No full textWe present long-term (months–years) X-ray spectral variability of the Seyfert 1.8 galaxy NGC 1365 as observed by Swift, which provides well-sampled observations over a much longer time-scale (six years) and a much larger flux range than is afforded by other observatories. At very low luminosities, the spectrum is very soft, becoming rapidly harder as the luminosity increases and then, above a particular luminosity, softening again. At a given flux level, the scatter in hardness ratio is not very large, meaning that the spectral shape is largely determined by the luminosity. The spectra were therefore summed in luminosity bins and fitted with a variety of models. The best-fitting model consists of two power laws, one unabsorbed and another, more luminous, which is absorbed. In this model, we find a range of intrinsic 0.5–10.0 keV luminosities of approximately 1.1–3.5 erg s?1, and a very large range of absorbing columns, of approximately 1022–1024 cm?2. Interestingly, we find that the absorbing column decreases with increasing luminosity, but that this result is not due to changes in ionization. We suggest that these observations might be interpreted in terms of a wind model in which the launch radius varies as a function of ionizing flux and disc temperature and therefore moves out with increasing accretion rate, i.e. increasing X-ray luminosity. Thus, depending on the inclination angle of the disc relative to the observer, the absorbing column may decrease as the accretion rate goes up. The weaker, unabsorbed, component may be a scattered component from the wind
Hardware and software for functional and fine-grain parallelism
No full textThis thesis examines nonloop parallelism at both fine and coarse levels of granularity in numerical FORTRAN programs. Measurements of the extent of this functional parallelism in a number of FORTRAN codes are presented, as well as compiler and run-time algorithms designed to exploit it. Hardware and software embodiments of the dynamic scheduling algorithms are developed, along with the compiler optimizations necessary to make these practical.The impact of fine grain functional parallelism on instruction-level architecture is explored, and it is shown that dynamic instruction scheduling hardware based on the functional parallelism scheduling algorithms can yield a significant improvement over static scheduling on conventional RISC processors when the latency of memory accesses is highly variable. Measurements of the characteristics of a set of FORTRAN benchmark programs indicates that such a hardware realization is feasible in practice.Made available in DSpace on 2011-05-07T12:06:43Z (GMT). No. of bitstreams: 2
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Public transaction cost of agri-environmental schemes and its determinants - Analysing stakeholders’ involvement and perceptions
No full textDespite a total budget increase for rural development in the new programming period (2007- 2013), for most older Member States in the now expanded European Union the multi-annual spending plan for the period 2007-2013 predicts a substantial decrease of the budget for rural development and thus for agri-environmental schemes (AESs). It can be assumed that nothing or only part of this loss could be compensated by national funds in most countries. Therefore designing more efficient national governance structures for AESs, which decrease public transaction costs (TCs), would be an appropriate answer to this problem. The objective of this paper is to define the factors influencing these public TCs, because then appropriate action can be taken to reduce them. A statistical analysis with a proxy for public TCs is combined with an analysis of the perception on public TCs influencing factors of the stakeholders involved (not including farmers). The research showed that mainly scheme related factors are perceived to be important, although the governance structure, institutional environment and trust also play a role. High public TCs are however not necessarily a problem, if they would lead to a higher environmental effectiveness of the schemes. It is important to pay attention to the heterogeneity of the natural environment and on the basis of that decide for a more centralised or decentralised approach to AES design.Public transaction costs, agrienvironmental schemes, Environmental Economics and Policy,
Vitamin D status modulates innate immune responses and metabolomic profiles following acute prolonged cycling.
No full textThe influence of vitamin D status on exercise-induced immune dysfunction remains unclear. The aim of this study was to investigate the effects of vitamin D status (circulating 25(OH)D) on innate immune responses and metabolomic profiles to prolonged exercise. Twenty three healthy, recreationally active males (age 25 ± 7 years; maximal oxygen uptake [[Formula: see text]max] 56 ± 9 mL·kg ·min ), classified as being deficient (n = 7) or non-deficient n = 16) according to plasma concentrations of 25(OH)D, completed 2.5 h of cycling at 15% Δ (~ 55-60% [Formula: see text]max). Venous blood and unstimulated saliva samples were obtained before and after exercise. Participants with deficient plasma 25(OH)D on average had lower total lymphocyte count (mean difference [95% confidence interval], 0.5 cells × 10 L [0.1, 0.9]), p = 0.013) and greater neutrophil:lymphocyte ratio (1.3 cells × 10 L, [0.1, 2.5], p = 0.033). The deficient group experienced reductions from pre-exercise to 1 h post-exercise (- 43% [- 70, - 15], p = 0.003) in bacterial stimulated elastase in blood neutrophils compared to non-deficient participants (1% [- 20, 21], p = 1.000) Multivariate analyses of plasma metabolomic profiles showed a clear separation of participants according to vitamin D status. Prominent sources of variation between groups were purine/pyrimidine catabolites, inflammatory markers (linoleic acid pathway), lactate and tyrosine/adrenaline. These findings provide evidence of the influence of vitamin D status on exercise-induced changes in parameters of innate immune defence and metabolomic signatures such as markers of inflammation and metabolic stress. [Abstract copyright: © 2023. The Author(s).
Economics of spatial coexistence of genetically modified and conventional crops: Oilseed rape in Central France
No full textEurope is currently struggling to implement coherent coexistence regulations on genetically modified (GM) and non-GM crops in all EU Member States. We conduct simulations with the software ArcView® on a GIS dataset of a hypothetical case of GM herbicide tolerant oilseed rape cultivation in Central France. Our findings show that rigid coexistence rules, such as large distance requirements, may impose a severe burden on GM crop production in Europe. These rules are not proportional to the farmers’ basic incentives for coexistence and hence not consistent with the objectives of the European Commission. More alarming, we show that in densely planted areas a domino-effect may occur. This effect raises coexistence costs and even adds to the non-proportionality of rigid coexistence regulations. Instead, we show that flexible measures would be preferable since they are proportional to the incentives for coexistence and, hence, less counterproductive for European agriculture.regulation, GIS modelling, domino-effect, Crop Production/Industries,
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