Corrosive environment in the annulus of flexible pipes: pH measurements in confined conditions and under high pressure

International audienceAnnulus of flexible pipelines represents a specific corrosive environment for the high strength carbon steel wires, mainly due to the low V/S ratio between the volume of electrolyte and the exposed steel surface. Corrosion experiments with continuous in situ pH measurements were performed under CO 2 partial pressure from 0.01 bar and up to 10 bar, and with a V/S ratio of 0.3 mL/cm². After only a few days immersion, supersaturated pH was measured at levels close to +1 pH unit above the saturated pH calculated corresponding to iron carbonate solubility. Good correlation was found between experiments and a pH and corrosion model specially developed for confined environment. This model predicts that the corrosion rate in super-saturated conditions is considerably reduced in comparison with bulk situation. Long term behavior was also examined. It appears that the evolution of super-saturated pH with time passes by a maximum value, then decreases slowly to a new equilibrium. It was postulated that the maximum corresponds to a fully active surface. Then, as precipitation occurs, corrosion rate is decreased by corrosion scale. The decrease of corrosion rate could be quantified from the final pH value: value as low as a few µm/year was found. Even with such low corrosion rates, high confinement still induced super-saturation effect, with final pH values at +0.5 pH units above saturated pH

Prediction of the flexible pipe annulus pH at high CO2 content and high temperature

International audiencePrevious works have shown that the typical ratio between the volume of electrolyte and the exposed steel surface observed in the annulus of flexible pipelines leads to a specific corrosive environment whose pH deviate from the classical thermodynamic models. In this case, due to the supersaturation in iron ions in the annulus, the commercial models even with their most recent updates cannot precisely predict the measured pH. Due to these specificities, tests are necessary to overcome these limitations and to improve with a better accuracy the pH considered in the design of the flexible pipes. Nowadays, with the development of the Brazilian oil and gas pre-salt basins, a high CO2 partial pressure associated with high temperature are observed in the flexible pipe annulus. Due to the lack of experimental data concerning the pH evolution under these conditions, tests were carried out with a continuous pH monitoring at CO2 partial pressure and temperature up to, respectively, 70 bara and 84 °C. The test results presented in this article show an amplitude between the experimental data and the predicted pH values of at least +0.4 pH units which confirms the conservatism of the thermodynamic models at saturation. In all the tests, the pH reached a maximum value after the first days of immersion followed by a decrease and fast stabilization after this event. An impact of the temperature was verified on the pH behavior in these tests. Keywords Flexible pipes; annulus pH; high pressure; high temperature

A study by in situ Raman spectroscopy of carbon steel corrosion in CO2 and H2S environment

International audienc

Predictors of Citations in Neurosurgical Research: A 5-year Follow-Up

Introduction Citation rates are an important measure for the impact of publications. This study is the most comprehensive analysis of predictors for scientific neurosurgical research articles. Methods Scientific articles published in 13 neurosurgical journals in 2015 were selected. Data collected included: article subject, level of evidence (LOE), journal impact factor (IF), authorship, contributing centers, and study design. Citation counts were collected for each article in the Web of Science (WoS), Google Scholar (GS), and Scopus 2.5 and 5 years after publication. A generalized linear mixed effects model using the predictors of search engine, LOE, number of centers, number of authors, and IF was constructed to predict total citation count at 5 years. Results 2867 articles generated 39190 citations in WoS, 61682 in GS, and 43481 in Scopus. The median [interquartile range] number of citations per article was 10 [14] in WoS, 15 [20] in GS, and 11 [15] in Scopus. On average, for every 1 citation in WoS, Scopus and GS identified 1.11 and 1.58 citations, respectively. Significant predictors of citation count in all databases 5 years after publication included search engine, LOE, number of centers, number of authors, number of countries, journal IF, and the month of publication (p<0.05). The article subject (tumor, spine, etc.) did not significantly predict citation counts. Conclusions In the most thorough analysis of citation predictors in the neurosurgical literature, search engine, LOE, number of centers, number of authors, number of countries, journal impact factor, and month of publication influenced citations 5 years after publication

Genomic Relationships, Novel Loci, and Pleiotropic Mechanisms across Eight Psychiatric Disorders

Genetic influences on psychiatric disorders transcend diagnostic boundaries, suggesting substantial pleiotropy of contributing loci. However, the nature and mechanisms of these pleiotropic effects remain unclear. We performed analyses of 232,964 cases and 494,162 controls from genome-wide studies of anorexia nervosa, attention-deficit/hyper-activity disorder, autism spectrum disorder, bipolar disorder, major depression, obsessive-compulsive disorder, schizophrenia, and Tourette syndrome. Genetic correlation analyses revealed a meaningful structure within the eight disorders, identifying three groups of inter-related disorders. Meta-analysis across these eight disorders detected 109 loci associated with at least two psychiatric disorders, including 23 loci with pleiotropic effects on four or more disorders and 11 loci with antagonistic effects on multiple disorders. The pleiotropic loci are located within genes that show heightened expression in the brain throughout the lifespan, beginning prenatally in the second trimester, and play prominent roles in neurodevelopmental processes. These findings have important implications for psychiatric nosology, drug development, and risk prediction.Peer reviewe

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe

Corrosion and pH prediction in the annulus of flexible pipes under high pressure of CO2

International audienceAnnulus of flexible pipelines represents a specific corrosive environment for the high strength carbon steel wires, mainly due to the low V/S ratio between the volume of electrolyte and the exposed steel surface. This environment induces high super-saturation levels of dissolved iron, together with the establishment of pH values far above thermodynamic equilibrium. Nevertheless, it also induces difficulties to predict actual levels of pH in the annulus, since thermodynamic models do not apply. In order to overcome these difficulties, and to obtain trustful pH values for the design of flexible pipelines, lots of efforts were put both in the experimental and modelling directions. A kinetic model was thus developed a few years ago, taking into account electrochemical and chemical reaction rates which allowed to explain super-saturated pH levels. Specific experiments consisting of continuous in situ pH measurements in confined corrosion cells confirmed the validity of the model in a pressure range 1-10 bar and for short term exposures. In the present paper, the extension of experimental conditions to higher pressures of CO 2 is presented. A good agreement with the model prediction and the short term stabilization of in situ pH was still obtained. Furthermore, longer exposure tests were also performed. It appeared that the evolution of super-saturated pH with time went through a maximum value after a few days, but then decreased slowly to a new equilibrium. This trend was attributed to the slow build-up of an iron carbonate layer, and subsequent decrease of the corrosion rate of the metal. The first version of the kinetic model was well suited to predict the maximum pH reached after a few days, but it did not capture the slow decrease. The model was then modified, in order to take into account the impact of corrosion products precipitation on surface reactions. The new version of the model is now capable to simulate with a good accuracy the complete in-situ pH transient for durations of several weeks until stationary state is reached. It allows not only to predict stabilized super-saturated pH values, but also to quantify the steady-state corrosion rate, which usually stands below a few µm/year. Even with such low corrosion rates, high confinement still induced super-saturation effect, with final pH values at +0.5 pH units above saturated pH

Impact of off-hour endovascular therapy on outcomes for acute ischemic stroke: insights from STAR

BackgroundThe off-hour effect has been observed in the medical care of acute ischemic stroke. However, it remains unclear if time of arrival affects revascularization rates and outcomes after endovascular therapy (EVT) for emergent large vessel occlusion (ELVO). We aimed to investigate the clinical outcomes of EVT between on-hour and off-hour admissions.MethodsPatients who underwent EVT for ELVO from January 2013 to June 2019 from the STAR Registry were included. Patients were grouped based on time of groin puncture: on-hour period (Monday through Friday, 7:00 am–4:59 pm) and off-hour period (overnight 5:00pm–6:59am and the weekends). Primary outcome was final modified Rankin Scale (mRS) at 90 days on mRS-shift analysis.ResultsA total of 1919 patients were included in the study from six centers. The majority of patients (1169, 60.9%) of patients presented during the off-hour period. The mean age was 68.1 years and 50.5% were women. Successful reperfusion, as defined by a Thrombolysis In Cerebral Infarction (TICI) score of ≥2B, was achieved in 88.8% in the on-hour group and 88.0% in the off-hour group. Good clinical outcome (mRS 0–2) was obtained in 34.4% of off-hour patients and 37.7% of on-hour patients. On multivariable ordinal logistic regression analysis, time of presentation was not associated with worsened outcome (OR 1.150; 95% CI 0.96 to 1.37; P=0.122). Age, admission National Institutes of Health Stroke Scale (NIHSS), baseline mRS, and final TICI score were significantly associated with worse outcomes.ConclusionThere is no statistical difference in functional outcome in acute ischemic stroke patients who underwent EVT during on-hours versus off-hours

Real-world effects of late window neurothrombectomy: procedure rates increase without night-time bias.

INTRODUCTION: With the expansion of the interventional time window for stroke from emergent large vessel occlusion (ELVO), the rate of mechanical thrombectomy (MT) is expected to rise, potentially causing higher burnout rates and requiring hospitals to develop strategies for adequate coverage of these procedures. METHODS: Neurointerventional physicians at 10 participating stroke centers prospectively recorded time requirements for all MT consultations over 30 consecutive 24-hour call periods, including both false positive consultations and MT procedures, during mid to late 2018. Consult start time, procedure start and end time, and data regarding commute to the hospital and delay in scheduled procedures were collected and compared with those from an identical prospective study performed in 2017. RESULTS: Data were collected from a total of 300 days of call. A total of 166 procedures were performed (mean 0.55 per day), an increase from 0.32 per day in 2017. Overall mean MT direct time burden during each 24-hour call was 124 min (compared with 85 min in 2017). The percentage of consultations for thrombectomy varied based on time of day, with 87% of consults between the hours of midnight and 04:00 proceeding to thrombectomy compared with 37% between the hours of 16:00 and 20:00. CONCLUSIONS: MT procedural volumes have increased from one every 5 days in 2016 to one every 2 days in 2018. The highest percentage of consults leading to thrombectomy occur in the early morning hours after midnight. Compared with similar data from 2016 and 2017, call demands continue to escalate, representing a significant demand on neurointerventional teams

Mechanical thrombectomy decision making and prognostication: Stroke treatment Assessments prior to Thrombectomy In Neurointervention (SATIN) study

Background Mechanical thrombectomy (MT) is the standard-of-care treatment for stroke patients with emergent large vessel occlusions. Despite this, little is known about physician decision making regarding MT and prognostic accuracy. Methods A prospective multicenter cohort study of patients undergoing MT was performed at 11 comprehensive stroke centers. The attending neurointerventionalist completed a preprocedure survey prior to arterial access and identified key decision factors and the most likely radiographic and clinical outcome at 90 days. Post hoc review was subsequently performed to document hospital course and outcome. Results 299 patients were enrolled. Good clinical outcome (modified Rankin Scale (mRS) score of 0–2) was obtained in 38% of patients. The most frequently identified factors influencing the decision to proceed with thrombectomy were site of occlusion (81%), National Institutes of Health Stroke Scale score (74%), and perfusion imaging mismatch (43%). Premorbid mRS score determination in the hyperacute setting accurately matched retrospectively collected data from the hospital admission in only 140 patients (46.8%). Physicians correctly predicted the patient’s 90 day mRS tertile (0–2, 3–4, or 5–6) and final modified Thrombolysis in Ischemic Cerebral Infarction score preprocedure in only 44.2% and 44.3% of patients, respectively. Clinicians tended to overestimate the influence of occlusion site and perfusion imaging on outcomes, while underestimating the importance of pre-morbid mRS. Conclusions This is the first prospective study to evaluate neurointerventionalists’ ability to accurately predict clinical outcome after MT. Overall, neurointerventionalists performed poorly in prognosticating patient 90 day outcomes, raising ethical questions regarding whether MT should be withheld in patients with emergent large vessel occlusions thought to have a poor prognosis