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Wang, Fan, Wensheng Ge, Hao Luo, Ji-Hye Seo et Greg Michalski. « Oxygen-17 anomaly in soil nitrate : A new precipitation proxy for desert landscapes ». Earth and Planetary Science Letters 438 (mars 2016) : 103–11. http://dx.doi.org/10.1016/j.epsl.2016.01.002.
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Zhang, Wenqi, et Yanlin Zhang. « Oxygen isotope anomaly (Δ<sup>17</sup>O) in atmospheric nitrate : A review ». Chinese Science Bulletin 64, no 7 (30 janvier 2019) : 649–62. http://dx.doi.org/10.1360/n972018-01028.
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Morin, S., R. Sander et J. Savarino. « Simulation of the diurnal variations of the oxygen isotope anomaly (Δ<sup>17</sup>O) of reactive atmospheric species ». Atmospheric Chemistry and Physics Discussions 10, no 12 (14 décembre 2010) : 30405–51. http://dx.doi.org/10.5194/acpd-10-30405-2010.
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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.
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Schütte, Florian, Johannes Karstensen, Gerd Krahmann, Helena Hauss, Björn Fiedler, Peter Brandt, Martin Visbeck et Arne Körtzinger. « Characterization of “dead-zone” eddies in the eastern tropical North Atlantic ». Biogeosciences 13, no 20 (28 octobre 2016) : 5865–81. http://dx.doi.org/10.5194/bg-13-5865-2016.
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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.
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Morin, S., R. Sander et J. Savarino. « Simulation of the diurnal variations of the oxygen isotope anomaly (Δ<sup>17</sup>O) of reactive atmospheric species ». Atmospheric Chemistry and Physics 11, no 8 (19 avril 2011) : 3653–71. http://dx.doi.org/10.5194/acp-11-3653-2011.
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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.
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Digtiar, V. A., D. G. Vernihora, Yu V. Zavorotnya, A. P. Gladkiy et M. O. Kaminska. « Application of Near-infrared reflectance spectroscopy in the diagnosis of varicocele in children and adolescents ». Medicni perspektivi 29, no 1 (1 avril 2024) : 101–8. http://dx.doi.org/10.26641/2307-0404.2024.1.300597.
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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.
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Wang, Kun, Shohei Hattori, Mang Lin, Sakiko Ishino, Becky Alexander, Kazuki Kamezaki, Naohiro Yoshida et Shichang Kang. « Isotopic constraints on atmospheric sulfate formation pathways in the Mt. Everest region, southern Tibetan Plateau ». Atmospheric Chemistry and Physics 21, no 10 (1 juin 2021) : 8357–76. http://dx.doi.org/10.5194/acp-21-8357-2021.
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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.
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Maaziz, Nada, Mathilde Jaillard, Céline Garrec, Fabrice Airaud, Bernard Aral, Stephane Bezieau, Betty Gardie et Francois Girodon. « Hereditary Erythrocytosis : Results from Europe's Largest Idiopathic Erythrocytosis Database ». Blood 144, Supplement 1 (5 novembre 2024) : 3842. https://doi.org/10.1182/blood-2024-207790.
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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, >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 >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 < 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 (<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.
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Balting, Daniel F., Monica Ionita, Martin Wegmann, Gerhard Helle, Gerhard H. Schleser, Norel Rimbu, Mandy B. Freund, Ingo Heinrich, Diana Caldarescu et Gerrit Lohmann. « Large-scale climate signals of a European oxygen isotope network from tree rings ». Climate of the Past 17, no 3 (7 mai 2021) : 1005–23. http://dx.doi.org/10.5194/cp-17-1005-2021.
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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.
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Liblik, Taavi, Yijing Wu, Daidu Fan et Dinghui Shang. « Wind-driven stratification patterns and dissolved oxygen depletion off the Changjiang (Yangtze) Estuary ». Biogeosciences 17, no 10 (29 mai 2020) : 2875–95. http://dx.doi.org/10.5194/bg-17-2875-2020.
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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.
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Walters, Wendell W., Masayuki Takeuchi, Nga L. Ng et Meredith G. Hastings. « Incorporating Oxygen Isotopes of Oxidized Reactive Nitrogen in the Regional Atmospheric Chemistry Mechanism, version 2 (ICOIN-RACM2) ». Geoscientific Model Development 17, no 11 (13 juin 2024) : 4673–87. http://dx.doi.org/10.5194/gmd-17-4673-2024.
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Abstract. The oxygen isotope anomaly (Δ17O = δ17O − 0.52 × δ18O > 0) has proven to be a robust tool for probing photochemical cycling and atmospheric formation pathways of oxidized reactive nitrogen (NOy). Several studies have developed modeling techniques to implicitly model Δ17O of NOy molecules based on numerous assumptions that may not always be valid. Thus, these models may be oversimplified and limit our ability to compare model Δ17O values of NOy with observations. In this work, we introduce a novel method for explicitly tracking Δ17O transfer and propagation into NOy and odd oxygen (Ox), integrated into the Regional Atmospheric Chemistry Mechanism, version 2 (RACM2). Termed ICOIN-RACM2 (InCorporating Oxygen Isotopes of NOy in RACM2), this new model includes the addition of 55 new species and 729 replicate reactions to represent the propagation of Δ17O derived from O3 into NOy and Ox. Employing this mechanism within a box model, we simulate Δ17O for various NOy and Ox molecules for chamber experiments with varying initial nitrogen oxides (NOx = NO + NO2) and α-pinene conditions, revealing response shifts in Δ17O linked to distinct oxidant conditions. Furthermore, diel cycles are simulated under two summertime scenarios, representative of an urban and rural site, revealing pronounced Δ17O diurnal patterns for several NOy components and substantial Δ17O differences associated with pollution levels (urban vs. rural). Overall, the proposed mechanism offers the potential to assess NOy oxidation chemistry in chamber studies and air quality campaigns through Δ17O model comparisons against observations. The integration of this mechanism into a 3-D atmospheric chemistry transport model is expected to notably enhance our capacity to model and anticipate Δ17O across landscapes, consequently refining model representations of atmospheric chemistry and tropospheric oxidation capacity.
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De La Fuente, Patricia, Josep L. Pelegrí, Antonio Canepa, Marc Gasser, Francisco Domínguez et Cèlia Marrasé. « A Simple Nonlinear and End-Member-Free Approach for Obtaining Ocean Remineralization Patterns ». Journal of Atmospheric and Oceanic Technology 34, no 11 (novembre 2017) : 2443–55. http://dx.doi.org/10.1175/jtech-d-17-0090.1.
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AbstractThe variability of a biogeochemical property in the ocean is the outcome of both nonconservative (such as respiration and photosynthesis) and conservative (mixing of water masses with distinct concentrations at origin) processes. One method to separate both contributions is based on a multiple regression of the biogeochemical property in terms of temperature θ and salinity S as conservative proxies of water masses. This regression delivers the variability related to the conservative fraction and hence allows for identifying the residual as the biogeochemical anomaly. Here, the standard multiple linear regression (MLR) method, which assumes that water masses mix locally and linearly, is compared with a nonlinear polynomial regression (PR) over the entire (θ, S) space. The PR method has two important advantages over MLR: allows for simultaneous nonlinear mixing of all water masses and does not require knowing the end-member water types. Both approaches are applied to data along 7.5°N in the equatorial Atlantic Ocean, and the biogeochemical anomalies are calculated for humic-like fluorescent dissolved organic matter, apparent oxygen utilization, and nitrate—all of them related through in situ remineralization processes. The goodness of both approaches is assessed by analyzing the linear dependence and the coefficient of correlation between the anomalies. The results show that the PR method can be applied over the entire water column and yet retains the local variability associated with nonconservative processes. The potential of the PR approach is also illustrated by calculating the oxygen–nitrate stoichiometric ratio for the entire 7.5°N transatlantic section.
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Morin, S., J. Savarino, S. Bekki, S. Gong et J. W. Bottenheim. « Signature of Arctic surface ozone depletion events in the isotope anomaly (Δ<sup>17</sup>O) of atmospheric nitrate ». Atmospheric Chemistry and Physics 7, no 5 (13 mars 2007) : 1451–69. http://dx.doi.org/10.5194/acp-7-1451-2007.
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Abstract. We report the first measurements of the oxygen isotope anomaly of atmospheric inorganic nitrate from the Arctic. Nitrate samples and complementary data were collected at Alert, Nunavut, Canada (82°30 ' N, 62°19 ' W) in spring 2004. Covering the polar sunrise period, characterized by the occurrence of severe boundary layer ozone depletion events (ODEs), our data show a significant correlation between the variations of atmospheric ozone (O3) mixing ratios and Δ17O of nitrate (Δ17O(NO−3)). This relationship can be expressed as: Δ17O(NO−3)/‰, =(0.15±0.03)×O3/(nmol mol–1)+(29.7±0.7), with R2=0.70(n=12), for Δ17O(NO−3) ranging between 29 and 35 ‰. We derive mass-balance equations from chemical reactions operating in the Arctic boundary layer, that describe the evolution of Δ17O(NO−3) as a function of the concentrations of reactive species and their isotopic characteristics. Changes in the relative importance of O3, RO2 and BrO in the oxidation of NO during ODEs, and the large isotope anomalies of O3 and BrO, are the driving force for the variability in the measured Δ17O(NO−3) . BrONO2 hydrolysis is found to be a dominant source of nitrate in the Arctic boundary layer, in agreement with recent modeling studies.
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Morin, S., J. Savarino, S. Bekki, S. Gong et J. W. Bottenheim. « Pronounced signature of arctic surface ozone depletion events after polar sunrise on Δ<sup>17</sup>O in atmospheric nitrate ». Atmospheric Chemistry and Physics Discussions 6, no 4 (12 juillet 2006) : 6255–97. http://dx.doi.org/10.5194/acpd-6-6255-2006.
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Abstract. We report in this paper the first measurements of the isotopic anomaly of oxygen in Arctic atmospheric inorganic nitrate. Data and samples were collected at Alert, Nunavut, Canada (82°30' N, 62°19' W) in spring 2004. Focusing on the polar sunrise period, characterized by the occurrence of severe boundary layer ozone depletion events (ODEs), our data show a significant correlation between the evolution of atmospheric ozone (O3) mixing ratios and Δ17O in nitrate Δ17O(NO−3)). This relationship can be expressed as: Δ17O(NO−3)/‰=0.15 O3/ (nmol mol−1) + 28.6, with R2=0.70 (n=12), for Δ17O(NO−3) ranging between 29 and 34. To quantitatively interpret this relationship, we derive from mechanisms at play in the arctic boundary layer isotopic mass-balance equations, which depend on the concentrations of reactive species and their isotopic characteristics. Changes in the relative importance of O3, RO2 and BrO in the oxidation of NOx during ODEs, and the large isotopic anomalies that O3 and BrO carry, are the driving force for the high variability in the measured Δ17O(NO−3). BrONO2 hydrolysis is found to be the major source of nitrate in the arctic boundary layer, in agreement with recent modeling studies. In addition, the isotopic fingerprint of the activity of ozone in a relatively stable compound appears somewhat promising in the perspective of using the isotopic composition of nitrate embedded in polar ice-cores as a paleo-indicator of the atmospheric ozone level that may yield an indirect proxy for the oxidative power of past atmospheres.
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Bao, Huiming, Mark H. Thiemens, David B. Loope et Xun-Lai Yuan. « Sulfate oxygen-17 anomaly in an Oligocene ash bed in mid-North America : Was it the dry fogs ? » Geophysical Research Letters 30, no 16 (août 2003). http://dx.doi.org/10.1029/2003gl016869.
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Bellamoli, Francesca, Marco Vian, Mattia Di Iorio et Farid Melgani. « Domain adaptation through active learning strategies for anomaly classification in wastewater treatment plants ». Water Science & ; Technology, 27 novembre 2024. http://dx.doi.org/10.2166/wst.2024.387.
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ABSTRACT The increasing use of intermittent aeration controllers in wastewater treatment plants (WWTPs) aims to reduce aeration costs via continuous ammonia and oxygen measurements but faces challenges in detecting sensor and process anomalies. Applying machine learning to this unbalanced, multivariate, multiclass classification challenge requires much data, difficult to obtain from a new plant. This study develops a machine learning algorithm to identify anomalies in intermittent aeration WWTPs, adaptable to new plants with limited data. Utilizing active learning, the method iteratively selects samples from the target domain to fine-tune a gradient-boosting model initially trained on data from 17 plants. Three sampling strategies were tested, with low probability and high entropy sampling proving effective in early adaptation, achieving an F2-score close to the optimal with minimal sample use. The objective is to deploy these models as decision support systems for WWTP management, providing a strategy for efficient model adaptation to new plants, and optimizing labeling efforts.
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Hock, J., N. Nagdyman, C. Meierhofer, P. Ewert et A. Hager. « Are there correlations between lung volume and exercise capacity in children and adolescents with native Ebstein's anomaly ? » European Journal of Preventive Cardiology 29, Supplement_1 (1 mai 2022). http://dx.doi.org/10.1093/eurjpc/zwac056.202.
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Abstract Funding Acknowledgements Type of funding sources: None. Background Patients with Ebstein’s Anomaly (EA) represent a wide clinical range with patients needing surgery in infancy and others needing no surgery throughout life. Exercise capacity in EA is often impaired. However, lung function is rarely investigated. Purpose This study examines lung volumes in native EA and their correlation with exercise capacity. Methods This retrospective study investigated 35 children with native EA (14 ± 4 years, 17 female), who underwent a cardiopulmonary exercise test (CPET) including spirometry to examine peak oxygen uptake (peakV’O2), forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and its ratio (FEV/FVC). Percentage in peakV’O2 <80% represents a reduced exercise capacity, and values <60% are defined as impaired. Z-scores below -1.64 categorize restrictive (FVC) or obstructive (FEV1/FVC) patterns. To analyse correlations between CPET and lung volumes Spearman’s rank test was performed. Results Reduced exercise capacity was found in 17 children (47%), and further seven (20%) children showed impaired exercise capacity. Seven patients (20%) had a restrictive lung volume pattern and three patients (9%) showed obstructive patterns. One patient showed both. Eleven (92%) patients with an impaired lung function had at least a reduced exercise capacity with a median of 64 [53;73] %predicted. Lung volumes correlate significantly with %peakV’O2 (z-FVC: r=0.500, p=0.002 and z-FEV1: r=0.443, p=0.008). Conclusions Most young patients with native EA have impaired results in exercise capacity and a third has reduced lung volumes. Low lung volumes correlate with worse exercise capacity. Thus, the lung function should also be taken into consideration when looking at the performance of these and medical aftercare.
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Radke, R. M., M. Bietenbeck, C. Meier, S. Orwat, H. Baumgartner et A. Yilmaz. « P608Exercise testing and multi-parametric CMR assessment in patients with Ebstein anomaly ». European Heart Journal 40, Supplement_1 (1 octobre 2019). http://dx.doi.org/10.1093/eurheartj/ehz747.0217.
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Abstract Background Ebstein anomaly (EA) is a rare congenital heart disease characterized by an apically displaced tricuspid valve. It is associated with tricuspid valve regurgitation and right heart dilatation leading to significant morbidity. While echocardiography remains the mainstay of routine outpatient cardiac imaging, assessment of right ventricular (RV) anatomy and function is still challenging. Cardiovascular magnetic resonance imaging (CMR) has been shown to be of advantage in these patients being free from acoustic window limitations and offering superior volume quantification. In the present study, parameters obtained from cardiopulmonary exercise testing (CPET) were compared to conventional and novel CMR parameters in patients with EA. Methods In this prospective single centre study, N=17 patients with EA (mean age = 33.8±12.7yrs; N=10 females) underwent clinical assessment, CPET and multi-parametric CMR. Maximal work load (maxWL) and peak oxygen uptake (maxO2) were derived from CPET. CMR studies were performed on a 1.5-T Philips scanner and respective CMR parameters comprised a) anatomical, b) functional and c) myocardial deformation values of both ventricles. Results The majority of patients presented in NYHA class I or II (mean NYHA = 1.6±0.7) and with normal or mildly elevated NT-proBNP values (mean NT-proBNP = 189±158pg/ml). CPET-based maxWL was 147.14±55 watts and maxO2 19.32±5 ml/kg/min. CMR-based mean LVEF was 57.1±6.4% and RVEF was 46.5±11.1%, respectively. Deformation imaging revealed (amongst others) a LV global longitudinal strain (LV-gLS) of −13.7±3.0 and a RV global longitudinal strain (RV-gLS) of −14.7±5.0. Non-ischemic presence of late-gadolinium-enhancement was documented in 36% of our patients. Comprehensive correlation analysis revealed a substantial correlation a) between LV-gLS and NYHA class (r=0.64, p=0.01), but not between RV-gLS and NYHA class (r=0.19, p=0.46), b) between serum NT-proBNP levels and maxO2 (r=−0.53, p=0.03) as well as maxWL (r=−0.63, p=0.02), and c) between LV-EF and LV-gLS (r=−0.64, p=0.01). Conclusion Our preliminary data suggest that serum markers such as NT-proBNP and novel CMR parameters such as LV-gLS – but not RV-gLS - correlate with CPET-derived exercise parameters in patients with EA. The predictive value of these parameters regarding cardiac disease progression in EA has to be evaluated in future follow-up studies.
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Walters, Wendell W., Havala O. T. Pye, Heejeong Kim et Meredith G. Hastings. « Modeling the Oxygen Isotope Anomaly (Δ17O) of Reactive Nitrogen in the Community Multiscale Air Quality Model : Insights into Nitrogen Oxide Chemistry in the Northeastern United States ». ACS ES&T Air, 22 avril 2024. http://dx.doi.org/10.1021/acsestair.3c00056.
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Ostenfeld, E., F. Simard, G. Smith, S. Ghonim, R. Rydman, D. Pennell, M. A. Gatzoulis, W. Li et S. V. Babu-Narayan. « 1162 Improved exercise tolerance and cardiac index at mid-term follow up after tricuspid valve surgery of Ebsteins anomaly ». European Heart Journal - Cardiovascular Imaging 21, Supplement_1 (1 janvier 2020). http://dx.doi.org/10.1093/ehjci/jez319.666.
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Abstract Funding Acknowledgements Swedish Heart-Lung Foundation, Swedish Society of Medicine, Swedish Heart Association, Skåne University Hospital, Region Skåne, and Lund University Background Ebstein’s anomaly (EA) is due to failed delamination of the tricuspid valve (TV) causing TV regurgitation (TR) and right ventricular (RV) dilatation, reduced exercise capacity and survival. TV repair/replacement (TVR) aims to reduce morbidity and mortality by reducing regurgitation and RV dilatation. Exercise capacity measured by predicted peak oxygen uptake (VO2%) and ventilatory expiratory slope (VE/CO2) is often impaired in EA and both are markers for mortality in adult congenital heart disease. Cardiovascular magnetic resonance (CMR) derived risk factors for adverse events (MACE) in unrepaired EA include reduced biventricular ejection fraction (EF) and low cardiac index. Whether and how these markers are modulated by TVR requires study. Purpose We aimed to assess whether TVR modulates known markers of exercise intolerance and CMR risk factors for MACE in EA. Methods Thirty-six consecutive EA adult (age≥16 years) patients (age at operation 37.4 ± 15.4 years, 13/12 ASD/PFO closures, 64% women) who underwent TV repair/replacement (15/21) between 2004-2014 and had pre-TVR CMR were retrospectively included. Twenty-four had CMR (in median 1.7 years) after TVR. Thirty-four had cardiopulmonary exercise test with VO2% and VE/CO2 prior to TVR, 23 one year and 17 five years after TVR. For CMR biventricular assessment, delineations were performed in short-axis cine stacks. Cardiac index was computed from velocity encoded phase contrast images from aortic flow. All volumes were indexed to body surface area. TR was graded none to severe (0-3). Results Thirty patients were in NYHA class ≥2 pre-TVR, 10 at 1-year and 8 at 5-year post-TVR (Figure 1). Compared to pre-TVR, VO2% continued to increase 5 years post-TVR (60 ± 16% vs 72 ± 14%, p = 0.002), but was not significantly increased at 1-year post-TVR (69 ± 19%, p = 0.06). For VE/CO2, pre-TVR values (40 ± 15) were increased compared to 1-year post-TVR (33 ± 6, p = 0.02) but without further amelioration after 5 years (33 ± 6). Cardiac index increased (2.4 ± 0.7 vs 2.8 ± 0.5/min/m2, p = 0.02). However, RVEF decreased (52 ± 7 vs 46 ± 9%, p = 0.003) and LVEF remained unchanged (68 ± 8 vs 67 ± 8%, p = 0.3) after TVR. As expected, surgery reduced TR grade (median 3 vs 1.5), RVEDVi (174 ± 51 vs 109 ± 22ml/m2) and RV/LV ratio (2.9 ± 1.1 vs 1.7 ± 0.3, all p < 0.0001). Conclusions TV surgery for Ebstein’s anomaly clearly modulates known risk factors for adverse outcome and was associated with improved subjective and objective exercise tolerance early and mid-term after intervention. This may be due to the concurrent increase in cardiac index demonstrated by CMR and secondary to augmented LV end diastolic volume at a stable LVEF. These findings are suggestive of improved future freedom from MACE. But this needs testing including the degree to which the RVEF decline seen post-TVR mitigates potential benefits beyond symptoms. The improvement in VO2% continued for 5 years which indicates clinical improvement after TVR continues past the first year. Abstract 1162 Figure 1
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Kuwahara, Yuta, Yukihiro Takahashi, Yuya Komori, Naohiro Kabuto et Naoki Wada. « Neonatal intra-atrial baffle repair for isolated ventricular inversion with left isomerism : a case report ». Surgical Case Reports 6, no 1 (29 septembre 2020). http://dx.doi.org/10.1186/s40792-020-01016-3.
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Abstract Background Discordant atrioventricular connection with concordant ventriculoarterial connection, otherwise known as isolated ventricular inversion (IVI), is an extremely rare congenital cardiac malformation. Reports on the corrective surgery for this anomaly in neonates are few, and the procedure is difficult and complicated. Herein, we report our use of atrial septostomy as a palliative procedure followed by corrective surgery for the repair of neonatal IVI with situs ambiguous(inversus) morphology. Case presentation A 2-day-old girl weighing 3.5 kg was admitted to our hospital with a low oxygen saturation (SpO2) of 70% She was diagnosed with IVI [situs ambiguous(inversus), D-loop, and D-Spiral], atrial septal defect, patent ductus arteriosus (PDA), interrupted inferior vena cava with azygos continuation to the left superior vena cava (SVC), and polysplenia by transthoracic echocardiography and cardiac computed tomography. We planned to perform corrective surgery and decided to first increase interatrial mixing by performing surgical atrial septostomy and PDA ligation 7 days after birth. However, despite the surgical septostomy, pulmonary venous blood flowed toward the right ventricle via the tricuspid valve rather than toward the left-sided atrium and hypoxemia persisted. We decided to perform the intra-atrial switch procedure at the age of 17 days via a re-median sternotomy. The cardiopulmonary bypass (CPB) circuit was established with ascending aorta and venous drainage through the SVC and hepatic veins. Utilizing a left-sided atrium(l-A) approach, a bovine pericardial patch was used for the intra-atrial baffle, which was trimmed into a trouser-shaped patch. Continuous suture using the patch was lying from the front of the right-sided upper pulmonary vein and rerouted SVC, hepatic vein, and coronary sinus to the tricuspid valve. Overall, CPB weaning proceeded smoothly; however, direct current cardioversion was performed for junctional ectopic tachycardia. The postoperative course was uneventful. Her postoperative SpO2 improved (approximately 99–100%); overall, the patient showed clinical improvement. Discharge echocardiography showed normal biventricular function and an intact atrial baffle with no venoatrial or atrioventricular obstruction. Conclusion We successfully performed an intra-atrial switch procedure for isolated ventricular inversion in a neonate. Long-term follow-up will be necessary to ensure the maintenance of optimal cardiac function.
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Zhang, Zhongyi, Zhuang Jiang, Tao Zhou et Lei Geng. « Reconciling Modeled and Observed Δ17O(NO3−) in Beijing Winter Haze With Heterogeneous Chlorine Chemistry ». Journal of Geophysical Research : Atmospheres 129, no 6 (18 mars 2024). http://dx.doi.org/10.1029/2023jd039740.
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AbstractThe fine particulate matter (PM2.5) in Chinese megacities has declined significantly after the implementation of strict mitigation strategies since 2013. However, the concentration of wintertime nitrate in PM2.5 (p‐NO3‐) has only changed slightly and became the dominant inorganic component despite considerable precursor emission reductions. Discerning chemical mechanisms leading to nitrate growth during haze events is critical to implementing effective pollution mitigation policies. The oxygen isotope anomaly of nitrate (Δ17O(NO3−)) is a powerful means to distinguish nitrate formation mechanisms. Nevertheless, the observed high Δ17O(NO3−) values were significantly underestimated by chemical transport models during extreme haze events (PM2.5 > 225 μg m−3) in Beijing, indicating an incomplete understanding of nitrate chemistry. To reconcile this model‐observation discrepancy, we compiled reported Δ17O(NO3−) data in Beijing haze along with relevant observational parameters (e.g., hydroxyl (OH) reactivity, peroxyl radical concentrations), then tested assumptions on Δ17O of key precursors (e.g., OH and nitrogen dioxide (NO2)), recalculated Δ17O(NO3−) and compared them with observations. Our results indicate that considering heterogeneous dinitrogen pentoxide reactions on chlorine‐containing aerosols (N2O5 + Cl− chemistry) with a nitryl chloride (ClNO2) yield of ∼0.75 can explain the observed high Δ17O(NO3−) during extreme haze events. According to the Δ17O(NO3−) data, on average this heterogeneous N2O5 + Cl− chemistry can explain ∼60% of nighttime nitrate production and make daytime and nocturnal pathways equally important in winter Beijing haze (PM2.5 > 75 μg m−3). Our results highlight the critical role of reactive chlorine chemistry in air pollution/chemistry in inland cities.