An eddy-stimulated hotspot for fixed nitrogen-loss from the Peru oxygen minimum zone

Fixed nitrogen (N) loss to biogenic N2 in intense oceanic O2 minimum zones (OMZ) accounts for a large fraction of the global N sink and is an essential control on the ocean's N budget. However, major uncertainties exist regarding microbial pathways as well as net impact on the magnitude of N-loss and the ocean's overall N budget. Here we report the discovery of a N-loss hotspot in the Peru OMZ associated with a coastally trapped mesoscale eddy that is marked by an extreme N deficit matched by biogenic N2 production, high NO2− levels, and the highest isotope enrichments observed so far in OMZ's for the residual NO3−. High sea surface chlorophyll (SSC) in seaward flowing streamers provides evidence for offshore eddy transport of highly productive, inshore water. Resulting pulses in the downward flux of particles likely stimulated heterotrophic dissimilatory NO3− reduction and subsequent production of biogenic N2. The associated temporal/spatial heterogeneity of N-loss, mediated by a local succession of microbial processes, may explain inconsistencies observed among prior studies. Similar transient enhancements of N-loss likely occur within all other major OMZ's exerting a major influence on global ocean N and N isotope budgets

Performance of Prognostic Scoring Systems in MINOCA: A Comparison among GRACE, TIMI, HEART, and ACEF Scores

Background: the prognosis of patients with myocardial infarction with non-obstructive coronary arteries (MINOCA) is not benign; thus, prompting the need to validate prognostic scoring systems for this population. Aim: to evaluate and compare the prognostic performance of GRACE, TIMI, HEART, and ACEF scores in MINOCA patients. Methods: A total of 250 MINOCA patients from January 2017 to September 2021 were included. For each patient, the four scores at admission were retrospectively calculated. The primary outcome was a composite of all-cause death and acute myocardial infarction (AMI) at 1-year follow-up. The ability to predict 1-year all-cause death was also tested. Results: Overall, the tested scores presented a sub-optimal performance in predicting the composite major adverse event in MINOCA patients, showing an AUC ranging between 0.7 and 0.8. Among them, the GRACE score appeared to be the best in predicting all-cause death, reaching high specificity with low sensitivity. The best cut-off identified for the GRACE score was 171, higher compared to the cut-off of 140 generally applied to identify high-risk patients with obstructive AMI. When the scores were tested for prediction of 1-year all-cause death, the GRACE and the ACEF score showed very good accuracy (AUC = 0.932 and 0.828, respectively). Conclusion: the prognostic scoring tools, validated in AMI cohorts, could be useful even in MINOCA patients, although their performance appeared sub-optimal, prompting the need for risk assessment tools specific to MINOCA patients

A review of nitrogen isotopic alteration in marine sediments

Key Points: Use of sedimentary nitrogen isotopes is examined; On average, sediment 15N/14N increases approx. 2 per mil during early burial; Isotopic alteration scales with water depth Abstract: Nitrogen isotopes are an important tool for evaluating past biogeochemical cycling from the paleoceanographic record. However, bulk sedimentary nitrogen isotope ratios, which can be determined routinely and at minimal cost, may be altered during burial and early sedimentary diagenesis, particularly outside of continental margin settings. The causes and detailed mechanisms of isotopic alteration are still under investigation. Case studies of the Mediterranean and South China Seas underscore the complexities of investigating isotopic alteration. In an effort to evaluate the evidence for alteration of the sedimentary N isotopic signal and try to quantify the net effect, we have compiled and compared data demonstrating alteration from the published literature. A >100 point comparison of sediment trap and surface sedimentary nitrogen isotope values demonstrates that, at sites located off of the continental margins, an increase in sediment 15N/14N occurs during early burial, likely at the seafloor. The extent of isotopic alteration appears to be a function of water depth. Depth-related differences in oxygen exposure time at the seafloor are likely the dominant control on the extent of N isotopic alteration. Moreover, the compiled data suggest that the degree of alteration is likely to be uniform through time at most sites so that bulk sedimentary isotope records likely provide a good means for evaluating relative changes in the global N cycle

The GEOTRACES Intermediate Data Product 2014

The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-? data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes

Does N2 Fixation in the Oligotrophic SE Pacific Influence N Isotopic Signals in the Peru-Chile OMZ?

residual nitrate. Through upwelling, phytoplankton assimilation, and downward particle flux, this signal is transferred to the underlying sediments and has been used to reconstruct past changes in denitrification and OMZ intensity in relation to climate change. However, there remain a number of impediments to quantitative interpretation of downcore δ15N records from OMZ’s with respect to past magnitude of N loss. One of these is knowledge of initial δ15N for nitrate prior to denitrification which cannot be assumed to be the modern oceanic average. In the case of the Peru-Chile OMZ, δ15N for nitrate in source waters from the Equatorial Undercurrent average 7‰ as compared to the oceanic average of ~5‰. This suggests processes external to the OMZ leading to isotopic enrichment such as partial phytoplankton nitrate utilization in the Subantarctic water mass formation region. In contrast, it has been surmised that initial δ15N for OMZ denitrification could be relatively low as a result of N2 fixation in geographically adjacent oligotrophic regions. High N2 fixation rates in the SE Pacifc Gyre are thought to be stimulated by low N/P waters upwelled from the Peru-Chile OMZ. As seen in the Sargasso Sea, subsurface remineralization of export production influenced by near-surface N2 fixation produces 15N-depleted nitrate in the subtropical mode water and the upper thermocline. Potentially, these SE Pacific gyre waters could mix back into the Peru-Chile OMZ at its southern boundary. We have investigated the relevance of such a phenomenon in the SE Pacific by examining samples collected during two CLIVAR repeat section (P6 and P18) which transected these highly oligotrophic water adjacent to the Peru-Chile OMZ in both the N-S and Ε-W directions. Surprisingly, nutrient data shows no positive subsurface nitrate anomaly as would be expected from significant rates of N2 fixation. Nitrate isotope data also shows no evidence of depleted values. In fact nitrate δ15N and δ18O in the upper 500 m are elevated (up to 10‰) and appear to be the result of subduction and advection of nitrate partially consumed at the surface in the vicinity of the subtropical front. At present, N2 fixation in the SE Pacific does not appear to be an important biogeochemical process and cannot be contributing a 15N-depleted signal to the Peru-Chile OM

The Fourth Conference "Computer Algebra" in Moscow

The International Conference "Computer Algebra" was held online via Zoom on June 28-29, 2021 and the conference web-site is http://www.ccas.ru/ca/conference. Co-organized by the Dorodnicyn Computing Center of Federal Research Center "Computer Science and Control" of Russian Academy of Science and the Peoples' Friendship University of Russia, the conference was devoted to inspiring discussions on computer algebra and related topics. Researchers from different countries presented talks on their latest research work. This is the fourth edition of the conference, and the previous three were in 2016, 2017 and 2019, respectively

Zenlens scleral lenses for visual rehabilitation of patients with irregular cornea: a usage experience

Scleral lenses improve visual acuity in patients with irregular corneal astigmatism, which is especially important when other methods of correction are ineffective.Purpose: to assess the efficiency of Zenlens scleral lenses in patients with irregular cornea.Material and methods. A total of 120 patients (164 eyes) were examined, including 86 males and 34 females, aged from 13 to 63 years (mean age 35 ± 12 years). The patients were divided into 4 groups. Group 1 consisted of patients with keratoconus, group 2 — postpenetrating keratoplasty, group 3 — keratoconus after cross-linking and/or corneal ring segment implantation, while group 4 consisted of patients with other diseases. The efficiency criteria included visual acuity before and after scleral lens fitting and wearing time (hours per day). To determine social significance of scleral lens wearing, we selected 30 patients (46 eyes) with average best-corrected visual acuity (BCVA) before fitting 0.21 ± 0.08 (0.1–0.3).Results. Average uncorrected visual acuity before fitting did not exceed 0.2 and average visual acuity after fitting was 0.8 ± 0.15. Average improvement in visual acuity after fitting compared to uncorrected visual acuity was at least six lines in all groups and average improvement of visual acuity was approximately three lines compared to BCVA before fitting. 74.4 % and 19.5 % of patients demonstrated long-term (> 10 hours per day) and partial (8–10 hours per day) wear, respectively. Short-term wear (< 8 hours per day) was noted in 6.1 % of patients. Visual acuity of  patients with low BCVA (mean 0.21 ± 0.08) increased by 0.57 (271.4 %).Conclusion. Scleral lenses can be successfully used for visual acuity improvement and social rehabilitation of patients with irregular cornea when other methods of correction are ineffective