Spatial variations in snowpack chemistry, isotopic composition of NO3− and nitrogen deposition from the ice sheet margin to the coast of western Greenland

The relative roles of anthropogenic nitrogen (N) deposition and climate change in causing ecological change in remote Arctic ecosystems, especially lakes, have been the subject of debate over the last decade. Some palaeoecological studies have cited isotopic signals (δ(15N)) preserved in lake sediments as evidence linking N deposition with ecological change, but a key limitation has been the lack of co-located data on both deposition input fluxes and isotopic composition of deposited nitrate (NO3−). In Arctic lakes, including those in western Greenland, previous palaeolimnological studies have indicated a spatial variation in δ(15N) trends in lake sediments but data are lacking for deposition chemistry, input fluxes and stable isotope composition of NO3−. In the present study, snowpack chemistry, NO3− stable isotopes and net deposition fluxes for the largest ice-free region in Greenland were investigated to determine whether there are spatial gradients from the ice sheet margin to the coast linked to a gradient in precipitation. Late-season snowpack was sampled in March 2011 at eight locations within three lake catchments in each of three regions (ice sheet margin in the east, the central area near Kelly Ville and the coastal zone to the west). At the coast, snowpack accumulation averaged 181 mm snow water equivalent (SWE) compared with 36 mm SWE by the ice sheet. Coastal snowpack showed significantly greater concentrations of marine salts (Na+, Cl−, other major cations), ammonium (NH4+; regional means 1.4–2.7 µmol L−1), total and non-sea-salt sulfate (SO42−; total 1.8–7.7, non-sea-salt 1.0–1.8 µmol L−1) than the two inland regions. Nitrate (1.5–2.4 µmol L−1) showed significantly lower concentrations at the coast. Despite lower concentrations, higher precipitation at the coast results in greater net deposition for NO3− as well as NH4+ and non-sea-salt sulfate (nss-SO42−) relative to the inland regions (lowest at Kelly Ville 6, 4 and 3; highest at coast 9, 17 and 11 mol ha−1 a−1 of NO3−, NH4+ and nss-SO42− respectively). The δ(15N) of snowpack NO3− shows a significant decrease from inland regions (−5.7 ‰ at Kelly Ville) to the coast (−11.3 ‰). We attribute the spatial patterns of δ(15N) in western Greenland to post-depositional processing rather than differing sources because of (1) spatial relationships with precipitation and sublimation, (2) within-catchment isotopic differences between terrestrial snowpack and lake ice snowpack, and (3) similarities between fresh snow (rather than accumulated snowpack) at Kelly Ville and the coast. Hence the δ(15N) of coastal snowpack is most representative of snowfall in western Greenland, but after deposition the effects of photolysis, volatilization and sublimation lead to enrichment of the remaining snowpack with the greatest effect in inland areas of low precipitation and high sublimation losses

Impact of anaemia at discharge following colorectal cancer surgery

Objectives: Preoperative anaemia is common in patients with colorectal cancer and increasingly optimised prior to surgery. Comparably little attention is given to the prevalence and consequences of postoperative anaemia. We aimed to investigate the frequency and short- or long-term impact of anaemia at discharge following colorectal cancer resection. Methods: A dedicated, prospectively populated database of elective laparoscopic colorectal cancer procedures undertaken with curative intent within a fully implemented ERAS protocol was utilised. The primary endpoint was anaemia at time of discharge (haemoglobin (Hb) < 120 g/L for women and < 135 g/L for men). Patient demographics, tumour characteristics, operative details and postoperative outcomes were captured. Median follow-up was 61 months with overall survival calculated with the Kaplan-Meier log rank method and Cox proportional hazard regression based on anaemia at time of hospital discharge. Results: A total of 532 patients with median 61-month follow-up were included. 46.4% were anaemic preoperatively (cohort mean Hb 129.4 g/L ± 18.7). Median surgical blood loss was 100 mL (IQR 0–200 mL). Upon discharge, most patients were anaemic (76.6%, Hb 116.3 g/L ± 14, mean 19 g/L ± 11 below lower limit of normal, p < 0.001). 16.7% experienced postoperative complications which were associated with lower discharge Hb (112 g/L ± 12 vs. 117 g/L ± 14, p = 0.001). Patients discharged anaemic had longer hospital stays (7 [5–11] vs. 6 [5–8], p = 0.037). Anaemia at discharge was independently associated with reduced overall survival (82% vs. 70%, p = 0.018; HR 1.6 (95% CI 1.04–2.5), p = 0.034). Conclusion: Anaemia at time of discharge following elective laparoscopic colorectal cancer surgery and ERAS care is common with associated negative impacts upon short-term clinical outcomes and long-term overall survival

Edible crabs “Go West”: migrations and incubation cycle of Cancer pagurus revealed by electronic tags

Crustaceans are key components of marine ecosystems which, like other exploited marine taxa, show seasonable patterns of distribution and activity, with consequences for their availability to capture by targeted fisheries. Despite concerns over the sustainability of crab fisheries worldwide, difficulties in observing crabs’ behaviour over their annual cycles, and the timings and durations of reproduction, remain poorly understood. From the release of 128 mature female edible crabs tagged with electronic data storage tags (DSTs), we demonstrate predominantly westward migration in the English Channel. Eastern Channel crabs migrated further than western Channel crabs, while crabs released outside the Channel showed little or no migration. Individual migrations were punctuated by a 7-month hiatus, when crabs remained stationary, coincident with the main period of crab spawning and egg incubation. Incubation commenced earlier in the west, from late October onwards, and brooding locations, determined using tidal geolocation, occurred throughout the species range. With an overall return rate of 34%, our results demonstrate that previous reluctance to tag crabs with relatively high-cost DSTs for fear of loss following moulting is unfounded, and that DSTs can generate precise information with regards life-history metrics that would be unachievable using other conventional means

Regional variability in the atmospheric nitrogen deposition signal and its transfer to the sediment record in Greenland lakes

Disruption of the nitrogen cycle is a major component of global environmental change. δ15N in lake sediments is increasingly used as a measure of reactive nitrogen input but problematically, the characteristic depleted δ15N signal is not recorded at all sites. We used a regionally replicated sampling strategy along a precipitation and N-deposition gradient in SW Greenland to assess the factors determining the strength of δ15N signal in lake sediment cores. Analyses of snowpack N and δ15N-NO3 and water chemistry were coupled with bulk sediment δ15N. Study sites cover a gradient of snowpack δ15N (ice sheet: −6‰; coast −10‰), atmospheric N deposition (ice sheet margin: ∼ 0.2 kg ha−1 yr−1; coast: 0.4 kg ha−1 yr−1) and limnology. Three 210Pb-dated sediment cores from coastal lakes showed a decline in δ15N of ca.−1‰ from ∼ 1860, reflecting the strongly depleted δ15N of snowpack N, lower in-lake total N (TN) concentration (∼ 300 μg N L−1) and a higher TN-load. Coastal lakes have 3.7–7.1× more snowpack input of nitrate than inland sites, while for total deposition the values are 1.7–3.6× greater for lake and whole catchment deposition. At inland sites and lakes close to the ice-sheet margin, a lower atmospheric N deposition rate and larger in-lake TN pool resulted in greater reliance on N-fixation and recycling (mean sediment δ15N is 0.5–2.5‰ in most inland lakes; n = 6). The primary control of the transfer of the atmospheric δ15N deposition signal to lake sediments is the magnitude of external N inputs relative to the in-lake N-pool

Incidence of WHO stage 3 and 4 conditions following initiation of Anti-Retroviral Therapy in resource limited settings

To determine the incidence of WHO clinical stage 3 and 4 conditions during early anti-retroviral therapy (ART) in resource limited settings (RLS)

Robust estimation of microbial diversity in theory and in practice

Quantifying diversity is of central importance for the study of structure, function and evolution of microbial communities. The estimation of microbial diversity has received renewed attention with the advent of large-scale metagenomic studies. Here, we consider what the diversity observed in a sample tells us about the diversity of the community being sampled. First, we argue that one cannot reliably estimate the absolute and relative number of microbial species present in a community without making unsupported assumptions about species abundance distributions. The reason for this is that sample data do not contain information about the number of rare species in the tail of species abundance distributions. We illustrate the difficulty in comparing species richness estimates by applying Chao's estimator of species richness to a set of in silico communities: they are ranked incorrectly in the presence of large numbers of rare species. Next, we extend our analysis to a general family of diversity metrics ("Hill diversities"), and construct lower and upper estimates of diversity values consistent with the sample data. The theory generalizes Chao's estimator, which we retrieve as the lower estimate of species richness. We show that Shannon and Simpson diversity can be robustly estimated for the in silico communities. We analyze nine metagenomic data sets from a wide range of environments, and show that our findings are relevant for empirically-sampled communities. Hence, we recommend the use of Shannon and Simpson diversity rather than species richness in efforts to quantify and compare microbial diversity.Comment: To be published in The ISME Journal. Main text: 16 pages, 5 figures. Supplement: 16 pages, 4 figure

Representations of twisted Yangians of types B, C, D: I

We initiate a theory of highest weight representations for twisted Yangians of types B, C, D and we classify the finite-dimensional irreducible representations of twisted Yangians associated to symmetric pairs of types CI, DIII and BCD0

Entomological Surveillance of Behavioural Resilience and Resistance in Residual Malaria Vector Populations.

The most potent malaria vectors rely heavily upon human blood so they are vulnerable to attack with insecticide-treated nets (ITNs) and indoor residual spraying (IRS) within houses. Mosquito taxa that can avoid feeding or resting indoors, or by obtaining blood from animals, mediate a growing proportion of the dwindling transmission that persists as ITNs and IRS are scaled up. Increasing frequency of behavioural evasion traits within persisting residual vector systems usually reflect the successful suppression of the most potent and vulnerable vector taxa by IRS or ITNs, rather than their failure. Many of the commonly observed changes in mosquito behavioural patterns following intervention scale-up may well be explained by modified taxonomic composition and expression of phenotypically plastic behavioural preferences, rather than altered innate preferences of individuals or populations. Detailed review of the contemporary evidence base does not yet provide any clear-cut example of true behavioural resistance and is, therefore, consistent with the hypothesis presented. Caution should be exercised before over-interpreting most existing reports of increased frequency of behavioural traits which enable mosquitoes to evade fatal contact with insecticides: this may simply be the result of suppressing the most behaviourally vulnerable of the vector taxa that constituted the original transmission system. Mosquito taxa which have always exhibited such evasive traits may be more accurately described as behaviourally resilient, rather than resistant. Ongoing national or regional entomological monitoring surveys of physiological susceptibility to insecticides should be supplemented with biologically and epidemiologically meaningfully estimates of malaria vector population dynamics and the behavioural phenotypes that determine intervention impact, in order to design, select, evaluate and optimize the implementation of vector control measures

Painful rib hump: a new clinical sign for detecting intraspinal rib displacement in scoliosis due to neurofibromatosis

BACKGROUND: Spinal cord compression and associate neurological impairment is rare in patients with scoliosis and neurofibromatosis. Common reasons are vertebral subluxation, dislocation, angulation and tumorous lesions around the spinal canal. Only twelve cases of intraspinal rib dislocation have been reported in the literature. The aim of this report is to present a case of rib penetration through neural foramen at the apex of a scoliotic curve in neurofibromatosis and to introduce a new clinical sign for its detection. METHODS: A 13-year-old girl was evaluated for progressive left thoracic kyphoscoliotic curve due to a type I neurofibromatosis. Clinical examination revealed multiple large thoracic and abdominal "cafe-au-lait" spots, neurological impairment of the lower limbs and the presence of a thoracic gibbous that was painful to pressure at the level of the left eighth rib (Painful Rib Hump). CT-scan showed detachment and translocation of the cephalic end of the left eighth rib into the adjacent enlarged neural foramen. The M.R.I. examination of the spine showed neither cord abnormality nor neurogenic tumor. RESULTS: The patient underwent resection of the intraspinal mobile eighth rib head and posterior spinal instrumentation and was neurologically fully recovered six months postoperatively. CONCLUSION: Spine surgeons should be aware of intraspinal rib displacement in scoliotic curves in neurofibromatosis. Painful rib hump is a valuable diagnostic tool for this rare clinical entity

Using a New Odour-Baited Device to Explore Options for Luring and Killing Outdoor-Biting Malaria Vectors: A Report on Design and Field Evaluation of the Mosquito Landing Box.

Mosquitoes that bite people outdoors can sustain malaria transmission even where effective indoor interventions such as bednets or indoor residual spraying are already widely used. Outdoor tools may therefore complement current indoor measures and improve control. We developed and evaluated a prototype mosquito control device, the 'Mosquito Landing Box' (MLB), which is baited with human odours and treated with mosquitocidal agents. The findings are used to explore technical options and challenges relevant to luring and killing outdoor-biting malaria vectors in endemic settings. Field experiments were conducted in Tanzania to assess if wild host-seeking mosquitoes 1) visited the MLBs, 2) stayed long or left shortly after arrival at the device, 3) visited the devices at times when humans were also outdoors, and 4) could be killed by contaminants applied on the devices. Odours suctioned from volunteer-occupied tents were also evaluated as a potential low-cost bait, by comparing baited and unbaited MLBs. There were significantly more Anopheles arabiensis, An. funestus, Culex and Mansonia mosquitoes visiting baited MLB than unbaited controls (P<=0.028). Increasing sampling frequency from every 120 min to 60 and 30 min led to an increase in vector catches of up to 3.6 fold (P<=0.002), indicating that many mosquitoes visited the device but left shortly afterwards. Outdoor host-seeking activity of malaria vectors peaked between 7:30 and 10:30pm, and between 4:30 and 6:00am, matching durations when locals were also outdoors. Maximum mortality of mosquitoes visiting MLBs sprayed or painted with formulations of candidate mosquitocidal agent (pirimiphos-methyl) was 51%. Odours from volunteer occupied tents attracted significantly more mosquitoes to MLBs than controls (P<0.001). While odour-baited devices such as the MLBs clearly have potential against outdoor-biting mosquitoes in communities where LLINs are used, candidate contaminants must be those that are effective at ultra-low doses even after short contact periods, since important vector species such as An. arabiensis make only brief visits to such devices. Natural human odours suctioned from occupied dwellings could constitute affordable sources of attractants to supplement odour baits for the devices. The killing agents used should be environmentally safe, long lasting, and have different modes of action (other than pyrethroids as used on LLINs), to curb the risk of physiological insecticide resistance