Добірка наукової літератури з теми "Oxygen-17 anomaly"

Abstract. The isotope anomaly (Δ17O) of secondary atmospheric species such as nitrate (NO3−) or hydrogen peroxyde (H2O2) has potential to provide useful constrains on their formation pathways. Indeed, the Δ17O of their precursors (NOx, HOx etc.) differs and depends on their interactions with ozone, which is the main source of non-zero Δ17O in the atmosphere. Interpreting variations of Δ17O in secondary species requires an in-depth understanding of the Δ17O of their precursors taking into account non-linear chemical regimes operating under various environmental settings. We present results from numerical simulations carried out using the atmospheric chemistry box model (CAABA/MECCA) to explicitly compute the diurnal variations of the isotope anomaly of short-lived species such as NOx and HOx. Δ17O was propagated from ozone to other species (NO, NO2, OH, HO2, RO2, NO3, N2O5, HONO, HNO3, HNO4, H2O2) according to the classical mass-balance equation, through the implementation of various sets of hypotheses pertaining to the transfer of Δ17O during chemical reactions. The model confirms that diurnal variations in Δ17O of NOx are well predicted by the photochemical steady-state relationship during the day, but that at night a different approach must be employed (i.e. "fossilization" of the Δ17O of NOx as soon as the photolytical lifetime of NOx drops below ca. 5 min). We quantify the diurnally-integrated isotopic signature (DIIS) of sources of atmospheric nitrate and H2O2 under the various environmental conditions analyzed, which is of particular relevance to larger-scale implementations of Δ17O where high computational costs cannot be afforded.

Abstract. Localized open-ocean low-oxygen “dead zones” in the eastern tropical North Atlantic are recently discovered ocean features that can develop in dynamically isolated water masses within cyclonic eddies (CE) and anticyclonic mode-water eddies (ACME). Analysis of a comprehensive oxygen dataset obtained from gliders, moorings, research vessels and Argo floats reveals that “dead-zone” eddies are found in surprisingly high numbers and in a large area from about 4 to 22° N, from the shelf at the eastern boundary to 38° W. In total, 173 profiles with oxygen concentrations below the minimum background concentration of 40 µmol kg−1 could be associated with 27 independent eddies (10 CEs; 17 ACMEs) over a period of 10 years. Lowest oxygen concentrations in CEs are less than 10 µmol kg−1 while in ACMEs even suboxic (< 1 µmol kg−1) levels are observed. The oxygen minimum in the eddies is located at shallow depth from 50 to 150 m with a mean depth of 80 m. Compared to the surrounding waters, the mean oxygen anomaly in the core depth range (50 and 150 m) for CEs (ACMEs) is −38 (−79) µmol kg−1. North of 12° N, the oxygen-depleted eddies carry anomalously low-salinity water of South Atlantic origin from the eastern boundary upwelling region into the open ocean. Here water mass properties and satellite eddy tracking both point to an eddy generation near the eastern boundary. In contrast, the oxygen-depleted eddies south of 12° N carry weak hydrographic anomalies in their cores and seem to be generated in the open ocean away from the boundary. In both regions a decrease in oxygen from east to west is identified supporting the en-route creation of the low-oxygen core through a combination of high productivity in the eddy surface waters and an isolation of the eddy cores with respect to lateral oxygen supply. Indeed, eddies of both types feature a cold sea surface temperature anomaly and enhanced chlorophyll concentrations in their center. The low-oxygen core depth in the eddies aligns with the depth of the shallow oxygen minimum zone of the eastern tropical North Atlantic. Averaged over the whole area an oxygen reduction of 7 µmol kg−1 in the depth range of 50 to 150 m (peak reduction is 16 µmol kg−1 at 100 m depth) can be associated with the dispersion of the eddies. Thus the locally increased oxygen consumption within the eddy cores enhances the total oxygen consumption in the open eastern tropical North Atlantic Ocean and seems to be an contributor to the formation of the shallow oxygen minimum zone.

Abstract. The isotope anomaly (Δ17O) of secondary atmospheric species such as nitrate (NO3−) or hydrogen peroxide (H2O2) has potential to provide useful constrains on their formation pathways. Indeed, the Δ17O of their precursors (NOx, HOx etc.) differs and depends on their interactions with ozone, which is the main source of non-zero Δ17O in the atmosphere. Interpreting variations of Δ17O in secondary species requires an in-depth understanding of the Δ17O of their precursors taking into account non-linear chemical regimes operating under various environmental settings. This article reviews and illustrates a series of basic concepts relevant to the propagation of the Δ17O of ozone to other reactive or secondary atmospheric species within a photochemical box model. We present results from numerical simulations carried out using the atmospheric chemistry box model CAABA/MECCA to explicitly compute the diurnal variations of the isotope anomaly of short-lived species such as NOx and HOx. Using a simplified but realistic tropospheric gas-phase chemistry mechanism, Δ17O was propagated from ozone to other species (NO, NO2, OH, HO2, RO2, NO3, N2O5, HONO, HNO3, HNO4, H2O2) according to the mass-balance equations, through the implementation of various sets of hypotheses pertaining to the transfer of Δ17O during chemical reactions. The model results confirm that diurnal variations in Δ17O of NOx predicted by the photochemical steady-state relationship during the day match those from the explicit treatment, but not at night. Indeed, the Δ17O of NOx is "frozen" at night as soon as the photolytical lifetime of NOx drops below ca. 10 min. We introduce and quantify the diurnally-integrated isotopic signature (DIIS) of sources of atmospheric nitrate and H2O2, which is of particular relevance to larger-scale simulations of Δ17O where high computational costs cannot be afforded.

Varicocele is a venous anomaly characterized by the enlargement of the plexus of veins in the testicle. In pediatric cases, indications for surgical intervention in varicocele include palpable dilatation of the enlargement of the plexus veins, intermittent pain in the ipsilateral testicle, and a 20% reduction in size of the ipsilateral testicle compared to the contralateral healthy one. The limitations of evaluating these criteria and the need to assess semen parameters prompt clinicians to explore new diagnostic methods for timely surgical interventions in adolescents. One such promising study involves Near-infrared reflectance spectroscopy (NIRS) in the Near-infrared range. The aim of the research is to evaluate the diagnostic capabilities of NIRS in children with varicocele to determine the indications for surgical intervention. The study included 65 boys aged 11 to 17 years with left-sided grade III varicocele (main group) and 29 healthy boys as a control group. Monitoring of regional oxygen saturation (rSO2) of testicular tissues was conducted using optical spectroscopy. NIRS examination of testicular tissues in both study and control groups showed statistically homogeneous data for regional oxygen saturation in the healthy (right) testicle. However, the NIRS study revealed significantly lower oxygen saturation (rSO2) in the testicular tissue of the left testicle in patients with varicocele compared to the control group. The diagnostic significance of the difference in bilateral NIRS monitoring Δ rSO2 >13% reliably characterized the presence of testicular hypotrophy by more than 20% compared to the healthy contralateral side (AUC=0.64, 95% CI (0.505-0.775), sensitivity – 79%, specificity – 50%, p=0.042). Δ rSO2 >11% values indicated disturbances in spermogram related to oxidative stress (AUC=0.702, 95% DI (0.51-0.88), sensitivity – 82%, specificity – 61%, p=0.031). Therefore, NIRS study data have potential valuable information for the diagnosis and selection of treatment for varicocele in children. The research utilizing Near-infrared Reflectance Spectroscopy revealed a significant potential of this method for diagnosing and assessing the impact of varicocele on the microcirculation of testicular tissue in children. The diagnostic significance of the difference in bilateral monitoring using this non-invasive technique in determining the state of testicles and the possibility of addressing the question of the necessity of surgical intervention is established.

Abstract. As an important atmosphere constituent, sulfate aerosols exert profound impacts on climate, the ecological environment, and human health. The Tibetan Plateau (TP), identified as the “Third Pole”, contains the largest land ice masses outside the poles and has attracted widespread attention for its environment and climatic change. However, the mechanisms of sulfate formation in this specific region still remain poorly characterized. An oxygen-17 anomaly (Δ17O) has been used as a probe to constrain the relative importance of different pathways leading to sulfate formation. Here, we report the Δ17O values in atmospheric sulfate collected at a remote site in the Mt. Everest region to decipher the possible formation mechanisms of sulfate in such a pristine environment. Throughout the sampling campaign (April–September 2018), the Δ17O in non-dust sulfate show an average of 1.7 ‰±0.5 ‰, which is higher than most existing data on modern atmospheric sulfate. The seasonality of Δ17O in non-dust sulfate exhibits high values in the pre-monsoon and low values in the monsoon, opposite to the seasonality in Δ17O for both sulfate and nitrate (i.e., minima in the warm season and maxima in the cold season) observed from diverse geographic sites. This high Δ17O in non-dust sulfate found in this region clearly indicates the important role of the S(IV)+O3 pathway in atmospheric sulfate formation promoted by conditions of high cloud water pH. Overall, our study provides an observational constraint on atmospheric acidity in altering sulfate formation pathways, particularly in dust-rich environments, and such identification of key processes provides an important basis for a better understanding of the sulfur cycle in the TP.

Introduction Increased hemoglobin (Hb) and hematocrit values are frequent reasons for out patient clinic in hematology. In the majority of cases, a simple work-up leads to the diagnosis of either Polycythaemia Vera or acquired polycythaemia secondary to chronic hypoxia, EPO secreting tumour, etc. Hereditary erythrocytosis (HE) is a group of rare diseases, most often linked to mutations in genes involved in erythropoiesis. We report here on the main causes of HE, based on Europe's largest database of idiopathic erythrocytoses. Materials and methods Between 2015 and 2024, after written informed consent, over 900 French patients with idiopathic erythrocytosis benefited from NGS using a panel of erythrocytosis-specific genes including EPAS1 (HIF2A), EGLN1 (PHD2), VHL, EPOR, JAK2, SH2B3(LNK), BPGM, PIEZO1, HBB/HBA. This genomic exploration followed a complete diagnostic workup that included screening for the JAK2V617F and exon 12 mutations, serum EPO, blood electrolytes, iron and hemolysis status, venous (to assess P50) and arterial blood gases, measurement of red cell mass using isotope or CO-rebreathing methods, abdominal ultrasound, functional respiratory tests, search for sleep apnea syndrome, bone marrow biopsy and progenitors growth cultures if necessary. Results Of the 909 patients studied, with a median age of 50 years old [1-90], 86% were men. The distribution was respectively 7%, 24%, 38% and 31% for the age groups 0-19 years, 20-39 years, 40-59 years, &gt;60 years. A pathogen or likely pathogen mutation was noted in 72 (7.9%) patients (78% male, 22% female), with the following age distribution: 11 (17%), 23 (10%), 23 (6.6%), 15 (5.3%) in 0-19, 20-39, 40-59 and &gt;60 years respectively. The gene distribution was as follows: EPAS1 n=20, EGLN1 n=13, SH2B3 n= 10, HBB/HBA n=8, JAK2 n= 7, EPOR n=5, PIEZO1 n=5, VHL n=3, BPGM n=1. The discovery of a mutation in patients led to a second screening for erythrocytosis in 30 relatives. Few thrombotic complications were noted in HE patients. Surprisingly 3 patients with an EPAS1 mutation had a very low variant allelic frequency (from 1.5 to 4%) due to mosaicism, including one case associated with paragangliomas. PIEZO1 mutations were observed in patients with mild erythrocytosis, associated with splenomegaly, biological hemolysis, iron overload, moderately lowered venous P50, and a typically shifted ektacytometry curve. Discussion We report here the sequencing results of Europe's largest database of erythrocytoses, for which a genetic cause was identified in less than 10% of patients, and reveal HE in 30 relatives, enabling diagnosis for these individuals by targeted sequencing and saving all additional diagnostic tests. While the presence of high affinity Hb is the leading cause of HE, its low proportion (11% in our cohort) can be explained by the fact that this type of anomaly was normally detected prior to NGS by performing venous blood gases to assess P50: if this was &lt; 23 mmHg, targeted Sanger sequencing of the HBB and HBA genes was then performed without recourse to NGS. The paradoxical finding of 8 patients with high affinity Hb in our series, despite the P50 filter, can be explained either by arterial rather than venous blood gases, or by the presence of air bubbles in the syringe, which falsified the result. Similarly, the surprising finding of JAK2 mutations in 7 patients in our series, which had to be negative to benefit from NGS, can be explained by the presence of 3 atypical JAK2 mutations undetected by conventional methods, and a low allelic burden (&lt;15%) of the JAK2 exon 12 mutations undetected by Sanger sequencing in 4 patients. The use of NGS makes it possible to avoid these pitfalls. Mutations in genes involved in oxygen sensing pathway (EPAS1, EGLN1 and VHL) account for 50% of HE in our cohort, mainly represented by EPAS1 mutations (n=20, nearly 30% of total HE). Consistently, the probability of finding a mutation was inversely proportional to age, ranging from 17% for patients under 20, to 5% for those over 60. Conclusion The study of idiopathic erythrocytoses using NGS analysis enables the diagnosis of HE in around 10% of patients, with mutations mostly linked to oxygen sensing pathway. There is still considerable scope for progress in the discovery of other molecular markers for HE. The recent availability of HIF2a-inhibitors holds out the prospect of better management of patients with oxygen sensing pathway genes mutations thanks to these targeted therapies.

Abstract. We investigate the climate signature of δ18O tree-ring records from sites distributed all over Europe covering the last 400 years. An empirical orthogonal function (EOF) analysis reveals two distinct modes of variability on the basis of the existing δ18O tree-ring records. The first mode is associated with anomaly patterns projecting onto the El Niño–Southern Oscillation (ENSO) and reflects a multi-seasonal climatic signal. The ENSO link is pronounced for the last 130 years, but it is found to be weak over the period from 1600 to 1850, suggesting that the relationship between ENSO and the European climate may not be stable over time. The second mode of δ18O variability, which captures a north–south dipole in the European δ18O tree-ring records, is related to a regional summer atmospheric circulation pattern, revealing a pronounced centre over the North Sea. Locally, the δ18O anomalies associated with this mode show the same (opposite) sign with temperature (precipitation). Based on the oxygen isotopic signature derived from tree rings, we argue that the prevailing large-scale atmospheric circulation patterns and the related teleconnections can be analysed beyond instrumental records.

Abstract. Multiple factors have been accused of triggering coastal hypoxia off the Changjiang Estuary, and their interactions lead to high yearly variation in hypoxia development time window and distribution extent. Two oceanographic cruises, conducted in July 2015 and August–September 2017, were complemented by river discharge, circulation simulation, remotely sensed wind, salinity and sea level anomaly data to study the dissolved oxygen (DO) depletion off the Changjiang Estuary from synoptic to interannual timescales. Intensification of the Chinese Coastal Current and Changjiang Diluted Water (CDW) spreading to the south together with coastal downwelling caused by the northerly wind was observed in the summer of 2015. This physical forcing led to a well-ventilated area in the north and a hypoxic area of 1.3×104 km2 in the south, while in 2017 the summer monsoon (southerly winds) induced offshore transport in the surface layer that caused a subsurface intrusion of Kuroshio-derived water to the shallower areas (<10 m depth) in the north and upwelling in the south. Wind-driven Ekman surface flow and reversal of the geostrophic current related to the upwelling compelled alteration of the Chinese Coastal Current. Consequently, intense hypoxia (DO down to 0.6 mg L−1) starting from 4 to 8 m depth connected to CDW and deep water intrusion in the north and coastal hypoxia linked to the upwelling in the south were observed in 2017. Distinct situations of stratification and DO distributions can be explained by wind forcing and concurrent features in surface and deep layer circulation, upwelling and downwelling events. Enhanced primary production in the upper layer of the CDW or the upwelled water determines the location and extent of DO depletion. Likewise, the pycnocline created by Kuroshio subsurface water intrusion is an essential precondition for hypoxia formation. Wind forcing largely controls the interannual change of hypoxic area location and extent. If the summer monsoon prevails, extensive hypoxia more likely occurs in the north. Hypoxia in the south occurs if the summer monsoon is considerably weaker than the long-term mean.

Les biocarbonates produits par les organismes marins tels que les foraminifères ou les coraux sont des archives importantes pour étudier les environnements et climats du passé. Depuis les travaux de H. Urey en 1947, il est établi que la composition isotopique en oxygène-18 (δ18O) des carbonates reflète à la fois la température de formation et le rapport isotopique (18O/16O) de l'eau de mer. Cette relation, supposément fondée sur l'équilibre thermodynamique entre l'eau et le carbonate, peut cependant être perturbée soit par des paramètres environnementaux, soit par des mécanismes biologiques . Chez certains organismes, comme les coraux, ces « effets vitaux » se manifestent par des déséquilibres isotopiques flagrants, qui compliquent l'interprétation d'une partie non négligeable du registre sédimentaire fossile. En réponse à ces problèmes, cette thèse adopte une approche novatrice en tirant partie de nouveaux traceurs isotopiques, les anomalies d'oxygèen-17 (Δ17O) et les « clumped isotopes » (Δ47, Δ48), en complément des mesures traditionnelles de δ13C et δ18O. En travaillant à partir d'échantillons modernes dont les conditions de croissance sont bien documentées, les contraintes supplémentaires fournies par ces traceurs permettent de mieux caractériser les facteurs qui influençent la composition isotopique des biocarbonates.Ce travail a commencé par une première étape exploratoire, visant d'une part (1) à identifier les organismes / cas d'étude à cibler en priorité, en associant des mesures isotopiques à faible résolution spatiale avec des observations in situ fournissant des informations minéralogiques, élémentaires et isotopiques à bien plus haute résolution, et d'autre part (2) à établir des protocoles expérimentaux optimisés pour les techniques instrumentales de pointe utilisées pour les mesures de Δ47/Δ48 (par spectrométrie de masse à très haute sensibilité) et de Δ17O (par VCOF-CRDS, une technologie spectroscopique innovante). Le premier volet de ce travail a donné lieu à la première l'étude publiée sur les clumped isotopes dans les squelettes de bryozoaires. Les résultats mettent en évidence une forte influence de la minéralogie sur le signal Δ47, qui semble résulter d'un simple effet thermodynamique. Par contre, il apparaît que les organismes de certains sites présentent des déséquilibres isotopiques spécifiques, potentiellement associés à la salinité locale. Ces résultats suscitent de nouvelles interrogations sur l'influence de certains paramètres environnementaux sur l'activité de certaines enzymes, en particulier l'anhydrase carbonique qui joue un rôle majeur dans le maintien de l'équilibre isotopique entre l'eau et le carbone inorganique dissous (CID). Le second volet porte sur la caractérisation, chez les coraux d'eau froide, des écarts à l'équilibre dans cinq dimensions isotopique (δ13C, δ18O, Δ17O, Δ47, Δ48), observées ici conjointement pour la première fois. Les observations sur Δ47 et Δ48 sont en accord avec une publication indépendante récente, et cohérentes avec un modèle théorique du CID, suggérant que la signature isotopique des coraux profonds est principalement contrôlée par des effets cinétiques liés à l'absorption du CO₂ métabolique. Cependant, les prédictions de ce même modèle sont en désaccord avec nos mesures de Δ17O (qui ont été depuis confirmées par des observations indépendantes), soulignant la nécessité de réviser certains paramètres du modèle. La richesse des questions nouvelles suscitées par ce travail de thèse illustre l'intérêt de combiner les observations dans un espace multi-isotopique à 5 dimensions avec des modèles théoriques quantitatifs, tout en confrontant ces modèles aux spécificités biologiques de chaque organisme marin, permettant tout à la fois de mieux comprendre les mécanismes de biominéralisation et de quantifier l'influence des effets vitaux dans les biocarbonates sur les paléo-reconstructions
Biocarbonates produced by marine organisms such as foraminifera or corals serve as important archives for studying past environments and climates. Since the work of H. Urey in 1947, it has been established that the oxygen-18 isotopic composition (δ18O) of carbonates reflects both the formation temperature and the isotopic ratio (18O/16O) of seawater. However, this relationship, supposedly based on the thermodynamic equilibrium between carbonate and water, can be disturbed by either environmental parameters or biological mechanisms. In certain organisms, such as corals, these "vital effects" manifest as significant isotopic disequilibrium, complicating the interpretation of a substantial portion of the fossil sedimentary record.In response to these challenges, this thesis adopts an innovative approach by leveraging new isotopic tracers, namely oxygen-17 anomalies (Δ17O) and "clumped isotopes" (Δ47, Δ48), in addition to traditional δ13C and δ18O measurements. By working with modern samples for which growth conditions are well documented, the additional constraints provided by these tracers allow for a better characterization of the factors influencing the isotopic composition of biocarbonates.This work began with an exploratory phase, aimed at (1) identifying the organisms/case studies by combining low spatial resolution isotopic measurements with in situ observations that provide mineralogical, elemental, and isotopic information at much higher resolution, and (2) establishing optimized experimental protocols for cutting-edge instrumental techniques used for Δ47/Δ48 measurements (via ultra-high sensitivity mass spectrometry) and Δ17O (via VCOF-CRDS, an innovative spectroscopic technology).The first part of this work resulted in the first published study on clumped isotopes in bryozoan skeletons. The results highlight a strong influence of mineralogy on the Δ47 signal, which seems to result from a simple thermodynamic effect. However, it appears that organisms from certain sites exhibit specific isotopic disequilibrium, potentially linked to local salinity. These findings raise new questions about the influence of certain environmental parameters on the activity of specific enzymes, particularly carbonic anhydrase, which plays a key role in maintaining isotopic equilibrium between water and dissolved inorganic carbon (DIC).The second part focuses on characterizing isotopic disequilibria in five isotopic dimensions (δ13C, δ18O, Δ17O, Δ47, Δ48) in cold-water corals, observed together here for the first time. The observations on Δ47 and Δ48 are consistent with a recent independent publication and align with a theoretical DIC model, suggesting that the isotopic signature of deep-sea corals is primarily controlled by kinetic effects related to the absorption of metabolic CO₂. However, the predictions of this same model are at odds with our Δ17O measurements (which have since been confirmed by independent observations), underscoring the need to revise certain model parameters.The richness of new questions raised by this thesis highlights the value of combining observations in a five-dimensional multi-isotopic space with quantitative theoretical models, while confronting these models with the biological specifics of each marine organism. This approach enables a deeper understanding of biomineralization mechanisms and allows for a more precise quantification of the influence of vital effects in biocarbonates on paleo-reconstructions