Heterogeneous electrocatalysis in porous cathodes of solid oxide fuel cells

A general physics-based model is developed for heterogeneous electrocatalysis in porous electrodes and used to predict and interpret the impedance of solid oxide fuel cells. This model describes the coupled processes of oxygen gas dissociative adsorption and surface diffusion of the oxygen intermediate to the triple phase boundary, where charge transfer occurs. The model accurately captures the Gerischer-like frequency dependence and the oxygen partial pressure dependence of the impedance of symmetric cathode cells. Digital image analysis of the microstructure of the cathode functional layer in four different cells directly confirms the predicted connection between geometrical properties and the impedance response. As in classical catalysis, the electrocatalytic activity is controlled by an effective Thiele modulus, which is the ratio of the surface diffusion length (mean distance from an adsorption site to the triple phase boundary) to the surface boundary layer length (square root of surface diffusivity divided by the adsorption rate constant). The Thiele modulus must be larger than one in order to maintain high surface coverage of reaction intermediates, but care must be taken in order to guarantee a sufficient triple phase boundary density. The model also predicts the Sabatier volcano plot with the maximum catalytic activity corresponding to the proper equilibrium surface fraction of adsorbed oxygen adatoms. These results provide basic principles and simple analytical tools to optimize porous microstructures for efficient electrocatalysis

Mycoplasma genitalium screening in a specialized French unit: A retrospective study

International audienceOBJECTIVE: Mycoplasma genitalium (MG) infection accounts for 10-35% of non-gonococcal non-chlamydial (NGNC) urethritis. However, given that most people infected with MG do not develop symptoms and that antimicrobial resistance is increasing worldwide, there is no evidence of any benefits of screening asymptomatic individuals. We conducted this study to describe MG screening practices and outcomes at a French Sexually Transmitted Infections (STI) center in which MG testing was performed selectively and multiplex assays were not carried out [i.e., simultaneous screening for Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and MG]. METHODS: A retrospective, observational, single-center study was conducted at the STI unit of Saint-Louis Hospital in Paris. The records of all patients undergoing MG testing from January 1st, 2017, to December 31st, 2018, were reviewed. The primary aim of the study was to describe and evaluate the proportion of MG-positive (MG+) patients among those tested. Secondary objectives were determination of the prevalence of MG+ status among symptomatic patients, risk factors associated with MG infection, and therapeutic modalities and efficacy. RESULTS: Two hundred and forty-nine patients underwent MG testing, 28 (11%) of whom were positive (MG+). The prevalence of MG+ status among symptomatic NGNC patients was 12%. HIV-positive (HIV+) status was significantly associated with MG+ status in univariate and multivariate analyses (Odds Ratio=7.3, 95% Confidence Interval 1.3-41.7; P=0.02). Twenty-three patients (85%) received antibiotics. Eighteen (67%) received azithromycin for 5 days, but 7 had clinical resistance. No quinolone resistance was reported. CONCLUSION: Despite unavailability of multiplex testing at our facility, which led to targeted-only screening for MG, its relatively high local prevalence is in keeping with what is generally observed at similar facilities across the world, where use of multiplex tests enables systematic screening for MG alongside NG and CT. This reinforces the current recommendations in Europe, France and the US against systematic MG testing or treatment in asymptomatic patients

Early major adverse cardiovascular events following the initiation of the anti-interleukin 12/23 antibody ustekinumab. A population-based case-time-control study

International audienceUstekinumab, a monoclonal antibody that targets interleukin (IL)-12/23, is used to treat psoriasis, psoriatic arthritis and Crohn disease. In 2011, a meta-analysis of randomized trials alerted on a potential risk of major adverse cardiovascular events (MACE) within the first months after the initiation of anti-IL-12/23 antibodies. Our objective was to assess if ustekinumab initiation may trigger MACE. Using the French National Health Insurance database, covering 66 million subjects, we included all patients exposed to ustekinumab between 2010 and 2016, classified according to their cardiovascular risk level (high vs. low risk). We conducted a case-time-control study. We defined the ‘risk’ period as the 6 months before MACE, defined as myocardial infarctions and strokes, and the ‘reference’ period as the 6 months before the risk period. The initiation of ustekinumab was screened in both periods, enabling to assess the odds-ratio (OR) between the initiation of ustekinumab and MACE. Among the 9290 patients exposed to ustekinumab, 179 displayed MACE: 65 myocardial infarctions, 68 unstable anginas and 46 strokes. Among patients at high-level cardiovascular risk, a significant association between ustekinumab initiation and MACE occurrence was identified (OR, 4.17; 95% CI, 1.19-14.59). Conversely, no association was found in patients at low-level cardiovascular risk (OR, 0.30; 95% CI, 0.03-3.13). From real-world data, we suggest that ustekinumab initiation could trigger MACE in patients at high cardiovascular risk, in line with current immunologic models of atherosclerotic disease. These results should call for caution regarding the prescription of ustekinumab in patients at high cardiovascular risk

Int J Epidemiol

BACKGROUND: Isotretinoin is the only effective treatment for severe acne. An isotretinoin-related suicide risk is still debated and under scrutiny by regulatory agencies. Our objectives were: to assess the risk of suicide attempt before, during and after isotretinoin treatment; to detect any potential triggering effect of isotretinoin initiation on suicide attempt. METHODS: We implemented a cohort and nested case-time-control study of subjects treated with oral isotretinoin (course or initiation) aged 10-50 years, using the Nationwide French Health Insurance data (2009-2016). The main outcome was hospitalized suicide attempt. Standardized incidence ratios for hospitalized suicide attempts were calculated before, during and after isotretinoin treatment. The number of isotretinoin initiations was compared in risk and control periods of 2 months using a case-time-control analysis. RESULTS: In all, 443 814 patients (median age 20.0 years; interquartile range 17.0-27.0 years) were exposed to isotretinoin, amounting to 244 154 person-years, with a marked seasonality for treatment initiation. Compared with the French general population, the occurrence of suicide attempts under isotretinoin treatment was markedly lower, with a standardized incidence ratio of 0.6 [95% confidence interval (CI) = 0.53-0.67]; the same applied, to a lesser extent, before and after isotretinoin treatment. In the case-time-control analysis, among cases of suicide attempt, 108 and 127 isotretinoin initiations were observed in the risk and control periods respectively (i.e. 0-2 months and 2-4 months before the date of suicide attempt). The comparison with the 1199 and 1253 initiations observed among matched controls in the same two periods yielded a case-time-control odds ratio of 0.89 (95% CI = 0.68-1.16). A sensitivity analysis using three-month periods and a complementary analysis adding completed suicides for case definition showed consistent results. CONCLUSION: Compared with the general population, a lower risk of suicide attempt was observed among patients exposed to isotretinoin and there was no evidence for a triggering effect of isotretinoin initiation on suicide attempt. A selection of patients at lower risk for suicidal behaviour and appropriate treatment management could explain these findings. Risk management plans should therefore be maintained

Drug survival and post-drug survival of systemic treatments in a national French cohort of children with atopic dermatitis

International audienceSystemic immunosuppressive treatments (IS) are restricted to severe atopic dermatitis (AD) in children. We described the IS use (first and second-line) for children with AD in a French retrospective national cohort, by using two survival analyses 'drug survival' (DS, defined as the duration of treatment) and 'post-drug survival' (PDS, defined as the time between the end of first-line and the beginning of second-line)

Promoting clinical research in community-based practice: Threats and opportunities

International audienceNo abstract availabl

Promouvoir la recherche clinique en dermatologie libérale : freins et opportunités

National audienc

Isotretinoin: Past, present and future. A French perspective

International audienc