Water temperature dynamics in High Arctic river basins

Despite the high sensitivity of polar regions to climate change and the strong influence of temperature upon ecosystem processes, contemporary understanding of water temperature dynamics in Arctic river systems is limited. This research gap was addressed by exploring high-resolution water column thermal regimes for glacier-fed and non-glacial rivers at eight sites across Svalbard during the 2010 melt season. Mean water column temperatures in glacier-fed rivers (0.3-3.2 °C) were lowest and least variable near the glacier terminus but increased downstream (0.7-2.3 °C km ). Non-glacial rivers, where discharge was sourced primarily from snowmelt runoff, were warmer (mean: 2.9-5.7 °C) and more variable, indicating increased water residence times in shallow alluvial zones and increased potential for atmospheric influence. Mean summer water temperature and the magnitude of daily thermal variation were similar to those of some Alaskan Arctic rivers but low at all sites when compared with alpine glacierized environments at lower latitudes. Thermal regimes were correlated strongly (p<0.01) with incoming short-wave radiation, air temperature, and river discharge. Principal drivers of thermal variability were inferred to be (i) water source (i.e. glacier melt, snowmelt, groundwater); (ii) exposure time to the atmosphere; (iii) prevailing meteorological conditions; (iv) river discharge; (v) runoff interaction with permafrost and buried ice; and (vi) basin-specific geomorphological features (e.g. channel morphology). These results provide insight into the potential changes in high-latitude river systems in the context of projected warming in polar regions. We hypothesize that warmer and more variable temperature regimes may prevail in the future as the proportion of bulk discharge sourced from glacial meltwater declines and rivers undergo a progressive shift towards snow water and groundwater sources. Importantly, such changes could have implications for aquatic species diversity and abundance and influence rates of ecosystem functioning in high-latitude river systems

A Fast Algorithm for Robust Regression with Penalised Trimmed Squares

The presence of groups containing high leverage outliers makes linear regression a difficult problem due to the masking effect. The available high breakdown estimators based on Least Trimmed Squares often do not succeed in detecting masked high leverage outliers in finite samples. An alternative to the LTS estimator, called Penalised Trimmed Squares (PTS) estimator, was introduced by the authors in \cite{ZiouAv:05,ZiAvPi:07} and it appears to be less sensitive to the masking problem. This estimator is defined by a Quadratic Mixed Integer Programming (QMIP) problem, where in the objective function a penalty cost for each observation is included which serves as an upper bound on the residual error for any feasible regression line. Since the PTS does not require presetting the number of outliers to delete from the data set, it has better efficiency with respect to other estimators. However, due to the high computational complexity of the resulting QMIP problem, exact solutions for moderately large regression problems is infeasible. In this paper we further establish the theoretical properties of the PTS estimator, such as high breakdown and efficiency, and propose an approximate algorithm called Fast-PTS to compute the PTS estimator for large data sets efficiently. Extensive computational experiments on sets of benchmark instances with varying degrees of outlier contamination, indicate that the proposed algorithm performs well in identifying groups of high leverage outliers in reasonable computational time.Comment: 27 page

Sedimentary controls on modern sand grain coat formation

Clay coated quartz grains can influence reservoir quality evolution during sandstone diagenesis. Porosity can be reduced and fluid flow restricted where grain coats encroach into pore space. Conversely pore-lining grain coats can restrict the growth of pore-filling quartz cement in deeply buried sandstones, and thus can result in unusually high porosity in deeply buried sandstones. Being able to predict the distribution of clay coated sand grains within petroleum reservoirs is thus important to help find good reservoir quality. Here we report a modern analogue study of 12 sediment cores from the Anllóns Estuary, Galicia, NW Spain, collected from a range of sub-environments, to help develop an understanding of the occurrence and distribution of clay coated grains. The cores were described for grain size, bioturbation and sedimentary structures, and then sub-sampled for electron and light microscopy, laser granulometry, and X-ray diffraction analysis. The Anllóns Estuary is sand-dominated with intertidal sand flats and saltmarsh environments at the margins; there is a shallowing/fining-upwards trend in the estuary-fill succession. Grain coats are present in nearly every sample analysed; they are between 1 μm and 100 μm thick and typically lack internal organisation. The extent of grain coat coverage can exceed 25% in some samples with coverage highest in the top 20 cm of cores. Samples from muddy intertidal flat and the muddy saltmarsh environments, close to the margins of the estuary, have the highest coat coverage (mean coat coverage of 20.2% and 21.3%, respectively). The lowest mean coat coverage occurs in the sandy saltmarsh (10.4%), beyond the upper tidal limit and sandy intertidal flat environments (8.4%), close to the main estuary channel. Mean coat coverage correlates with the concentration of clay fraction. The primary controls on the distribution of fine-grained sediment, and therefore grain coat distribution, are primary sediment transport and deposition processes that concentrate the clay fraction in the sediment towards the margins of the estuary. Bioturbation and clay illuviation/mechanical infiltration are secondary processes that may redistribute fine-grained sediment and produce grain coats. Here we have shown that detrital grain coats are more likely in marginal environments of ancient estuary-fills, which are typically found in the fining-upward part of progradational successions

Damage in Polymer Bonded Energetic Composites: Effect of Loading Rate

Particulate composites are widely used in the materials world. An understanding of their damage behaviour under a variety of loading conditions is necessary to inform models of their response to external stimuli. In the present experimental study, fine and coarse grained RDX-HTPB composites have been used to investigate the effect of loading rate on the degree of damage produced in polymer bonded explosives subjected to varying degrees of uniaxial compression. High strain rate loading (4×10⁺³ s⁻¹) was achieved using a direct impact Hopkinson pressure bar and low strain rate loading (1×10⁻² s⁻¹) using an Instron mechanical testing machine. The causal metrics are the degree to which the samples were strained and the mechanical energy expended in straining them. The damage metric is the residual low rate compressive modulus of the samples. The quantitative, physically based, results discussed in terms of the Porter-Gould activated debonding damage model clearly demonstrate that for both fine and coarse fills there is a marked reduction in residual moduli as a function of imposed strain, and substantially less specific energy is required to cause the same level of damage at the lower strain-rate. In the case of the coarse grained composite there is some evidence for a change in damage mechanism at the higher strain-rate. We obtain a value for the measured work of adhesion and a measure of the effective modulus local to the damage site, as damage is actually occurring. The observed underlying behaviour should be broadly applicable to particulate composites, whenever stiff filler particles are held in a viscoelastic matrix.The authors wish to acknowledge financial support in the form of an Industrial CASE PhD Studentship for RLB funded by the UK Engineering and Physical Sciences Research Council (EPSRC) and by QinetiQ [EP/I501290/1]; UK MOD via a WSTC contract; DMW and APJ acknowledge the financial support of AWE.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s40870-016-0050-x The data underlying this article can be found at the following persistent URL: https://www.repository.cam.ac.uk/handle/1810/25319

Personality predicts musical sophistication

There is little research on the role of personality in musical expertise. We address this gap in the literature by using data from a large national study (N = 7,870) to examine how scores on 10 facets of the Big Five dimensions of personality predicted self-reported musical sophistication and performance on two behavioral tests (melodic memory and rhythm perception). Personality predicted musical sophistication even after controlling for demographic variables and musicianship, with Openness to Aesthetics the best trait predictor. Substance use also predicted musical sophistication for various subscales and the behavioral tests. These findings replicated in both musician and non-musician subgroups.The authors thank Robert R. McCrae for his helpful comments on an earlier draft. Data collection was made possible by the LabUK research unit of the British Broadcasting Corporation.This is the accepted manuscript of a paper published in the Journal of Research in Personality (Greenberg DM, Müllensiefen D, Lamb ME, Rentfrow PJ, Journal of Research in Personality, 2015, doi:10.1016/j.jrp.2015.06.002). The final version is available at http://dx.doi.org/10.1016/j.jrp.2015.06.00

The site of regulation of light capture in Symbiodinium: Does the peridinin-chlorophyll a-protein detach to regulate light capture?

Dinoflagellates from the genus Symbiodinium form symbiotic associations with cnidarians including corals and anemones. The photosynthetic apparatuses of these dinoflagellates possess a unique photosynthetic antenna system incorporating the peridinin-chlorophyll a-protein (PCP). It has been proposed that the appearance of a PCP-specific 77 K fluorescence emission band around 672-675 nm indicates that high light treatment results in PCP dissociation from intrinsic membrane antenna complexes, blocking excitation transfer to the intrinsic membrane-bound antenna complexes, chlorophyll a-chlorophyll c 2-peridinin-protein-complex (acpPC) and associated photosystems (Reynolds et al., 2008 Proc Natl Acad Sci USA 105:13674-13678).We have tested this model using time-resolved fluorescence decay kinetics in conjunction with global fitting to compare the time-evolution of the PCP spectral bands before and after high light exposure. Our results show that no long-lived PCP fluorescence emission components appear either before or after high light treatment, indicating that the efficiency of excitation transfer from PCP to membrane antenna systems remains efficient and rapid even after exposure to high light. The apparent increased relative emission at around 675 nm was, instead, caused by strong preferential exciton quenching of the membrane antenna complexes associated with acpPC and reaction centers. This strong non-photochemical quenching (NPQ) is consistent with the activation of xanthophyll-Associated quenching mechanisms and the generally-observed avoidance in nature of long-lived photoexcited states that can lead to oxidative damage. The acpPC component appears to be the most strongly quenched under high light exposure suggesting that it houses the photoprotective exciton quencher. © 2014 Elsevier B.V

The Relationship Between Mucosal Microbiota, Colitis, and Systemic Inflammation in Chronic Granulomatous Disorder

PURPOSE: Chronic granulomatous disorder (CGD) is a primary immunodeficiency which is frequently complicated by inflammatory colitis and is associated with systemic inflammation. Herein, we aimed to investigate the role of the microbiome in the pathogenesis of colitis and systemic inflammation. METHODS: We performed 16S rDNA sequencing on mucosal biopsy samples from each segment of 10 CGD patients’ colons and conducted compositional and functional pathway prediction analyses. RESULTS: The microbiota in samples from colitis patients demonstrated reduced taxonomic alpha-diversity compared to unaffected patients, even in apparently normal bowel segments. Functional pathway richness was similar between the colitic and non-colitic mucosa, although metabolic pathways involved in butyrate biosynthesis or utilization were enriched in patients with colitis and correlated positively with fecal calprotectin levels. One patient with very severe colitis was dominated by Enterococcus spp., while among other patients Bacteroides spp. abundance correlated with colitis severity measured by fecal calprotectin and an endoscopic severity score. In contrast, Blautia abundance is associated with low severity scores and mucosal health. Several taxa and functional pathways correlated with concentrations of inflammatory cytokines in blood but not with colitis severity. Notably, dividing patients into “high” and “low” systemic inflammation groups demonstrated clearer separation than on the basis of colitis status in beta-diversity analyses. CONCLUSION: The microbiome is abnormal in CGD-associated colitis and altered functional characteristics probably contribute to pathogenesis. Furthermore, the relationship between the mucosal microbiome and systemic inflammation, independent of colitis status, implies that the microbiome in CGD can influence the inflammatory phenotype of the condition