Hydrothermal 15N15N abundances constrain the origins of mantle nitrogen.

Nitrogen is the main constituent of the Earth's atmosphere, but its provenance in the Earth's mantle remains uncertain. The relative contribution of primordial nitrogen inherited during the Earth's accretion versus that subducted from the Earth's surface is unclear1-6. Here we show that the mantle may have retained remnants of such primordial nitrogen. We use the rare 15N15N isotopologue of N2 as a new tracer of air contamination in volcanic gas effusions. By constraining air contamination in gases from Iceland, Eifel (Germany) and Yellowstone (USA), we derive estimates of mantle δ15N (the fractional difference in 15N/14N from air), N2/36Ar and N2/3He. Our results show that negative δ15N values observed in gases, previously regarded as indicating a mantle origin for nitrogen7-10, in fact represent dominantly air-derived N2 that experienced 15N/14N fractionation in hydrothermal systems. Using two-component mixing models to correct for this effect, the 15N15N data allow extrapolations that characterize mantle endmember δ15N, N2/36Ar and N2/3He values. We show that the Eifel region has slightly increased δ15N and N2/36Ar values relative to estimates for the convective mantle provided by mid-ocean-ridge basalts11, consistent with subducted nitrogen being added to the mantle source. In contrast, we find that whereas the Yellowstone plume has δ15N values substantially greater than that of the convective mantle, resembling surface components12-15, its N2/36Ar and N2/3He ratios are indistinguishable from those of the convective mantle. This observation raises the possibility that the plume hosts a primordial component. We provide a test of the subduction hypothesis with a two-box model, describing the evolution of mantle and surface nitrogen through geological time. We show that the effect of subduction on the deep nitrogen cycle may be less important than has been suggested by previous investigations. We propose instead that high mid-ocean-ridge basalt and plume δ15N values may both be dominantly primordial features.

Author Correction: Forearc carbon sink reduces long-term volatile recycling into the mantle.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Author Correction: Forearc carbon sink reduces long-term volatile recycling into the mantle.

Change history: In this Article, the original affiliation 2 was not applicable and has been removed. In addition, in the Acknowledgements there was a statement missing and an error in a name. These errors have been corrected online.

Forearc carbon sink reduces long-term volatile recycling into the mantle.

Carbon and other volatiles in the form of gases, fluids or mineral phases are transported from Earth's surface into the mantle at convergent margins, where the oceanic crust subducts beneath the continental crust. The efficiency of this transfer has profound implications for the nature and scale of geochemical heterogeneities in Earth's deep mantle and shallow crustal reservoirs, as well as Earth's oxidation state. However, the proportions of volatiles released from the forearc and backarc are not well constrained compared to fluxes from the volcanic arc front. Here we use helium and carbon isotope data from deeply sourced springs along two cross-arc transects to show that about 91 per cent of carbon released from the slab and mantle beneath the Costa Rican forearc is sequestered within the crust by calcite deposition. Around an additional three per cent is incorporated into the biomass through microbial chemolithoautotrophy, whereby microbes assimilate inorganic carbon into biomass. We estimate that between 1.2 × 108 and 1.3 × 1010 moles of carbon dioxide per year are released from the slab beneath the forearc, and thus up to about 19 per cent less carbon is being transferred into Earth's deep mantle than previously estimated.

Expanding CEP290 mutational spectrum in ciliopathies.

Ciliopathies are an expanding group of rare conditions characterized by multiorgan involvement, that are caused by mutations in genes encoding for proteins of the primary cilium or its apparatus. Among these genes, CEP290 bears an intriguing allelic spectrum, being commonly mutated in Joubert syndrome and related disorders (JSRD), Meckel syndrome (MKS), Senior-Loken syndrome and isolated Leber congenital amaurosis (LCA). Although these conditions are recessively inherited, in a subset of patients only one CEP290 mutation could be detected. To assess whether genomic rearrangements involving the CEP290 gene could represent a possible mutational mechanism in these cases, exon dosage analysis on genomic DNA was performed in two groups of CEP290 heterozygous patients, including five JSRD/MKS cases and four LCA, respectively. In one JSRD patient, we identified a large heterozygous deletion encompassing CEP290 C-terminus that resulted in marked reduction of mRNA expression. No copy number alterations were identified in the remaining probands. The present work expands the CEP290 genotypic spectrum to include multiexon deletions. Although this mechanism does not appear to be frequent, screening for genomic rearrangements should be considered in patients in whom a single CEP290 mutated allele was identified.

[Cardiovascular risk factors and the value of changes in lifestyle. Results from a study of people aged 35-65 in a small rural community in Iceland.].

OBJECT: To find the prevalence of cardiovascular risk factors in Oxarfjaretharhéraeth, a small rural community in north-eastern Iceland, and to see if these risk factors could be influenced with simple measurements and interventions in the community. MATERIAL AND METHODS: The study group included every person between the age of 35-65, living in the community. The participants were interviewed by a nurse. Cardiovascular risk factors were registered and measured. The results were discussed with each person individually and verbal and written advise given by the nurse, with emphasis on each individual's own responsibility regarding lifestyle changes. A total of 126 persons came to the initial interview, or 97%. A follow-up interview was carried out after six to seven months for those two thirds of the sample who had one or more risk factors. Sixty-eight attended, or 80%. RESULTS: Two thirds of the study population had some risk factors for cardiovascular disease, thereof 35 individuals with s-cholesterol >6.0 mmol/1. Average weight for men was 84.7 kg and women 77.1 kg. Average cholesterol was 6.0 mmol/1 for men and 5.9 for women. Four new hypertensives were found and treated. From the second interview we found that 40-46% of those who had been told that they had high s-cholesterol had increased their physical activity and reduced food fat and sugar. This same group also proved to have decreased their average weight (-1.6 kg) and s-cholesterol (-1.1 mmol/1) significantly. No significant changes were found regarding smoking or blood pressure. CONCLUSION: A short interview and simple measurements at a local health centre are effective, at least in the short term in altering life style factors such as physical activity and intake of fat and sugar in certain risk groups, thereby inducing a significant decrease in s- cholesterol and thus hopefully reduce the incidence of premature cardiovascular events. In view of the above, we encourage all health care workers to introduce these simple lifestyle changes to their clients.

[Prevalence of female urinary incontinence and the effect of simple treatment measures at a health centre.].

The purpose of this study was to find out the prevalence of female urinary incontinence outside institutions, its effects on daily life and to see if effective treatment was possible with relatively simple diagnostic and treatment measures at the local health centre. A questionnaire was sent to all women (131) over the age of 20 living in private homes in Oxarfjörethur, a small rural community in Iceland. The results showed a 56% overall prevalence of self-reported incontinence, thereof 29% with moderate or severe symptoms. About 70% of the women with incontinence had typical stress incontinence, 14% urgency incontinence and 16% mixed symptoms. There was a statistically significant relationship between incontinence and number of childbirths but not regarding age. The incontinence had some adverse effects on daily life for 39% of women with incontinence or 20% of the whole sample. Some treatment for incontinence had been given earlier to 26 women with variable results. Only four women had a registered incontinence diagnosis at the health centre. All women with incontinence were invited to participate in pelvic floor exercise groups or offered written instructions of pelvic floor exercises. Those with moderate or severe symptoms were offered a more extensive evaluation and examination at the health centre, resulting in a number of cases in other treatment like antibiotics or oestrogen's. A new questionnaire 10 months later showed that 61% of the women had improved. The improvement was statistically significant for the group with stress incontinence and for those attending the treatment groups. Pelvic floor exercises were helpful even when symptoms were severe and though they were only performed once or twice a week. We recommend an active diagnostic approach and a trial of systematic pelvic floor exercises and post- menopausal hormone treatment before resorting to surgical treatment for urinary incontinence.

Childhood blindness in Iceland. A study of legally blind and partially seeing children in Iceland 1978.

In 1978, a study was made of legally blind (corrected visual acuity 6/60 or less) and partially seeing (CVA 6/18 to 6/60) children under 15 years of age in Iceland. A total of 43 children were found, of whom 23 were legally blind and 20 partially seeing. The prevalence rates, expressed as the number per 100,000, children of similar age, 36.4 for legal blindness and 31.6 for partial sight. In all 43 children, the visual loss was attributable to heritable, congenital, or developmental defects. The most common causes of visual loss were optic nerve atrophy and cataracts. Other causes are listed and discussed. No cases of acquired visual loss were found. In addition to visual loss, other congenital birth defects were found in 24 of the children. CNS affection was found in 20 of the children, and of these, 15 were mentally retarded.