University of Exeter

About: University of Exeter is a education organization based out in Exeter, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 15820 authors who have published 50650 publications receiving 1793046 citations. The organization is also known as: Exeter University & University of the South West of England.

Spatiotemporal patterns of terrestrial gross primary production: A review

Abstract: Great advances have been made in the last decade in quantifying and understanding the spatiotemporal patterns of terrestrial gross primary production (GPP) with ground, atmospheric, and space observations. However, although global GPP estimates exist, each data set relies upon assumptions and none of the available data are based only on measurements. Consequently, there is no consensus on the global total GPP and large uncertainties exist in its benchmarking. The objective of this review is to assess how the different available data sets predict the spatiotemporal patterns of GPP, identify the differences among data sets, and highlight the main advantages/disadvantages of each data set. We compare GPP estimates for the historical period (1990-2009) from two observation-based data sets (Model Tree Ensemble and Moderate Resolution Imaging Spectroradiometer) to coupled carbon-climate models and terrestrial carbon cycle models from the Fifth Climate Model Intercomparison Project and TRENDY projects and to a new hybrid data set (CARBONES). Results show a large range in the mean global GPP estimates. The different data sets broadly agree on GPP seasonal cycle in terms of phasing, while there is still discrepancy on the amplitude. For interannual variability (IAV) and trends, there is a clear separation between the observation-based data that show little IAV and trend, while the process-based models have large GPP variability and significant trends. These results suggest that there is an urgent need to improve observation-based data sets and develop carbon cycle modeling with processes that are currently treated either very simplistically to correctly estimate present GPP and better quantify the future uptake of carbon dioxide by the world's vegetation.

Source type ascription for fluvial suspended sediment based on a quantitative composite fingerprinting technique

Abstract: We report the successful application of a quantitative composite fingerprinting technique, incorporating both a rigorous statistical verification procedure for composite signatures and a multivariate mixing model, to evaluate sediment source type in the Dart catchment, Devon, UK and the Plynlimon experimental catchment, Powys, UK. Quantitative ascription of source types is discussed in terms of the mean contributions and potential seasonal, inter- and intea-storm variations in the relative contributions of surface erosion from a number of distinct land use categories and of channel erosion to the suspended sediment load sampled at various sites within the study areas. Surface erosion of pasture soils is generally important in both study catchments but the impacts of spring and autumn cultivation in the Dart, and of autumn and winter forestry activity at Plynlimon, are also evident. Inter-storm variations in sediment source type reflect antecedent conditions, variable contributing areas and timing of sediment sample collection, and highlight the individuality of catchment response for the sampled flood events. Intra-storm variations in source type contributions emphasize the necessity for detailed sampling programmes for suspended sediment in storm periods, when using the fingerprinting approach to investigate sediment origin.

Strong coupling between surface plasmon-polaritons and organic molecules in subwavelength hole arrays

Abstract: The interaction of a $J$-aggregate and surface plasmon polariton modes of a subwavelength hole array have been studied in detail. By measuring the effects of hole array period, angular dispersion and concentration of the $J$-aggregate on the transmission of the array, the existence of a strong coupling regime is demonstrated with a Rabi splitting of 250 meV. This large splitting is explained not only by the high oscillator strength of the dye but also by the high local field amplitudes generated by surface plasmons of the metallic structure.

Negative thermal expansion: a review

Abstract: Most materials demonstrate an expansion upon heating, however a few are known to contract, i.e. exhibit a negative coefficient of thermal expansivity (NTE). This naturally occurring phenomenon has been shown to occur in a range of solids including complex metal oxides, polymers and zeolites, and opens the door to composites with a coefficient of thermal expansion (CTE) of zero. The state of the art in NTE solids is reviewed, and understanding of the driving mechanisms of the effect is considered along with experimental and theoretical evidence. The various categories of solids with NTE are explored, and experimental methods for their experimental characterisation and applications for such solids are proposed. An abstraction for an underlying mechanism for NTE at the supramolecular level and its applicability at the molecular level is discussed.

Rebels with a Cause: Group Identification as a Response to Perceived Discrimination from the Mainstream

Abstract: Two studies involving people with body piercings tested the hypothesis that perceived discrimination increases group identification. In Study 1, group identification mediated the positive relationship between perceived discrimination and attempts to differentiate the ingroup from the mainstream. In Study 2, perceived discrimination against people with body piercings was manipulated and was found to increase group identification. Support was found for the prediction that group identification mediates the relation-ship between perceptions of discrimination and collective self-esteem. Results demonstrate the importance of group identification for both the meaning of group membership and its consequences for well-being among members of disadvantaged groups.