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 & Climate change. 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.

Linking land use, erosion and sediment yields in river basins

Abstract: Results obtained from erosion plots and catchment experiments provide clear evidence of the sensitivity of erosion rates to land use change and related human activity. Evidence for the impact of land use on the sediment yields of world rivers is less clear, although examples of rivers where sediment yields have both increased and decreased in recent decades can be identified. The apparent lack of sensitivity of river sediment loads to land use change reflects, at least in part, the buffering capacity associated with many river basins. This buffering capacity is closely related to the sediment delivery ratio of a river basin, in that basins with high sediment delivery ratios are likely to exhibit a reduced buffering capacity. Investigations of the impact of land use and related human activity on sediment yields should consider the overall sediment budget of a catchment rather than simply the sediment output. Information on the sediment budget of a drainage basin is difficult to assemble using traditional techniques, but recent developments in the application of fingerprinting techniques to establish sediment sources and in the use of environmental radionuclides, such as caesium-137 and lead-210, to document sediment storage offer considerable potential for providing such information. Sediment storage within a river basin can give rise to environmental problems where sediment-associated pollutants accumulate in sediment sinks. The accumulation of phosphorus on river floodplains as a result of overbank sedimentation can, for example, represent an important phosphorus sink.

Effect of macroalgal competition on growth and survival of juvenile Caribbean corals

Abstract: Lobophora variegata and Dictyota pulchella are dominant algal components on coral reefs across the Caribbean, but the mechanisms and outcomes of spatial competition between these algae and scleractinian corals are poorly understood. In this study the effects on growth and mortal- ity of juvenile corals by 2 forms of algal competition, shading and abrasion, were investigated. The growth of small Agaricia spp. (<20 mm diameter) was monitored over a 14 mo period on shallow forereefs in Roatan, Honduras. Experimental manipulations of algal shading and algal contact with the periphery of colonies were conducted in isolation from the effects of grazing through the use of exclusion cages. Shading by L. variegata caused an overall loss of coral tissue and significantly increased colony mortality rates from 0 to 50% in 6 mo. The presence of L. variegata around the periphery of a coral colony significantly reduced the overall growth of juvenile corals, decreasing the growth rate to 60% of that of control corals, but had no detectable effect on mortality. Shading by D. pulchella resulted in 99% growth inhibition (i.e. to just 1% of the growth rate of control corals). Peripheral contact with D. pulchella (without shading) also retarded coral growth rates but to a lesser extent: to 31% of that of controls. A synthetic alga made to mimic the action of D. pulchella abrasion caused a similar reduction in growth rate to actual D. pulchella, suggesting that the reduction in coral growth occurred because of physical mechanisms rather than allelochemical inhibition. The severe inhibition of colony growth caused by the proximity of D. pulchella or L. variegata may extend a coral's period of vulnerability to whole colony mortality. Based on the monthly mortality rate observed in uncaged control corals of 0.035 ± 0.135 (SE), peripheral contact with D. pulchella could decrease the survivorship of corals reaching a 3 cm diameter from 29 to <2%. Peripheral contact with L. variegata could likewise decrease cohort survival to 11%. The ability of these common macroalgae to reduce the survivorship of juvenile corals through interference competition could contribute to the perpetuating dominance of macroalgae on many Caribbean reefs.

Rumination-focused cognitive-behavioural therapy for residual depression: phase II randomised controlled trial

Abstract: Background About 20% of major depressive episodes become chronic and medication-refractory and also appear to be less responsive to standard cognitive-behavioural therapy (CBT). Aims To test whether CBT developed from behavioural activation principles that explicitly and exclusively targets depressive rumination enhances treatment as usual (TAU) in reducing residual depression. Method Forty-two consecutively recruited participants meeting criteria for medication-refractory residual depression were randomly allocated to TAU v. TAU plus up to 12 sessions of individual rumination-focused CBT. The trial has been registered ([ISRCTN22782150][1]). Results Adding rumination-focused CBT to TAU significantly improved residual symptoms and remission rates. Treatment effects were mediated by change in rumination. Conclusions This is the first randomised controlled trial providing evidence of benefits of rumination-focused CBT in persistent depression. Although suggesting the internal validity of rumination-focused CBT for residual depression, the trial lacked an attentional control group so cannot test whether the effects were as a result of the specific content of rumination-focused CBT v . non-specific therapy effects. [1]: /external-ref?link_type=ISRCTN&access_num=ISRCTN22782150

Mutations in ATP-Sensitive K+ Channel Genes Cause Transient Neonatal Diabetes and Permanent Diabetes in Childhood or Adulthood

Abstract: Transient neonatal diabetes mellitus (TNDM) is diagnosed in the first 6 months of life, with remission in infancy or early childhood. For approximately 50% of patients, their diabetes will relapse in later life. The majority of cases result from anomalies of the imprinted region on chromosome 6q24, and 14 patients with ATP-sensitive K+ channel (K(ATP) channel) gene mutations have been reported. We determined the 6q24 status in 97 patients with TNDM. In patients in whom no abnormality was identified, the KCNJ11 gene and/or ABCC8 gene, which encode the Kir6.2 and SUR1 subunits of the pancreatic beta-cell K(ATP) channel, were sequenced. K(ATP) channel mutations were found in 25 of 97 (26%) TNDM probands (12 KCNJ11 and 13 ABCC8), while 69 of 97 (71%) had chromosome 6q24 abnormalities. The phenotype associated with KCNJ11 and ABCC8 mutations was similar but markedly different from 6q24 patients who had a lower birth weight and who were diagnosed and remitted earlier (all P < 0.001). K(ATP) channel mutations were identified in 26 additional family members, 17 of whom had diabetes. Of 42 diabetic patients, 91% diagnosed before 6 months remitted, but those diagnosed after 6 months had permanent diabetes (P < 0.0001). K(ATP) channel mutations account for 89% of patients with non-6q24 TNDM and result in a discrete clinical subtype that includes biphasic diabetes that can be treated with sulfonylureas. Remitting neonatal diabetes was observed in two of three mutation carriers, and permanent diabetes occurred after 6 months of age in subjects without an initial diagnosis of neonatal diabetes.

Improved community detection in weighted bipartite networks

Abstract: Real-world complex networks are composed of non-random quantitative interactions. Identifying communities of nodes that tend to interact more with each other than the network as a whole is a key research focus across multiple disciplines, yet many community detection algorithms only use information about the presence or absence of interactions between nodes. Weighted modularity is a potential method for evaluating the quality of community partitions in quantitative networks. In this framework, the optimal community partition of a network can be found by searching for the partition that maximizes modularity. Attempting to find the partition that maximizes modularity is a computationally hard problem requiring the use of algorithms. QuanBiMo is an algorithm that has been proposed to maximize weighted modularity in bipartite networks. This paper introduces two new algorithms, LPAwb+ and DIRTLPAwb+, for maximizing weighted modularity in bipartite networks. LPAwb+ and DIRTLPAwb+ robustly identify partitions with high modularity scores. DIRTLPAwb+ consistently matched or outperformed QuanBiMo, while the speed of LPAwb+ makes it an attractive choice for detecting the modularity of larger networks. Searching for modules using weighted data (rather than binary data) provides a different and potentially insightful method for evaluating network partitions.