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Nat Commun ; 11(1): 33, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31911585


Electrochemical CO[Formula: see text] reduction is a potential route to the sustainable production of valuable fuels and chemicals. Here, we perform CO[Formula: see text] reduction experiments on Gold at neutral to acidic pH values to elucidate the long-standing controversy surrounding the rate-limiting step. We find the CO production rate to be invariant with pH on a Standard Hydrogen Electrode scale and conclude that it is limited by the CO[Formula: see text] adsorption step. We present a new multi-scale modeling scheme that integrates ab initio reaction kinetics with mass transport simulations, explicitly considering the charged electric double layer. The model reproduces the experimental CO polarization curve and reveals the rate-limiting step to be *COOH to *CO at low overpotentials, CO[Formula: see text] adsorption at intermediate ones, and CO[Formula: see text] mass transport at high overpotentials. Finally, we show the Tafel slope to arise from the electrostatic interaction between the dipole of *CO[Formula: see text] and the interfacial field. This work highlights the importance of surface charging for electrochemical kinetics and mass transport.

J Matern Fetal Neonatal Med ; 28(2): 146-8, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24735485


OBJECTIVE: To determine whether meconium-contaminated amniotic fluid falsely elevates the lamellar body count in fetal lung maturity testing. METHODS: Thirty mothers undergoing amniocentesis for fetal lung maturity testing were prospectively consented. A 2 mL portion of the patient's sample was mixed with a 10% meconium solution and the meconium-stained sample was then run in tandem with the patient's sample used in clinical management. Pure meconium samples without amniotic fluid were also run through the cell counter for analysis. RESULTS: Following meconium contamination, the lamellar body count value increased in 67% of the cases, decreased in 23% and remained the same in 10%. There were 13 test results that had "immature" values in the uncontaminated patient management sample group and nine of these (69%) became elevated to a "mature" level (a false elevation) following the addition of meconium. All of the 10 pure liquid meconium samples devoid of amniotic fluid processed by the cell counter identified and quantified some particle the size of platelets. CONCLUSIONS: The lamellar body count test result is not reliable in meconium-stained amniotic fluid specimens. There is some unknown particle found in meconium that is the size of platelets/lamellar bodies that can falsely elevate the test result. Currently, the only reliable fetal lung maturity test in meconium-stained amniotic fluid is the presence of phosphatidylglycerol.

Líquido Amniótico/citologia , Maturidade dos Órgãos Fetais , Pulmão/citologia , Mecônio/fisiologia , Diagnóstico Pré-Natal/métodos , Amniocentese , Contagem de Células , Micropartículas Derivadas de Células/patologia , Micropartículas Derivadas de Células/fisiologia , Feminino , Humanos , Recém-Nascido , Pulmão/embriologia , Gravidez , Diagnóstico Pré-Natal/normas , Reprodutibilidade dos Testes , Manejo de Espécimes
ACS Appl Mater Interfaces ; 6(18): 15860-7, 2014 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-25158125


The sodium electrochemistry of evaporatively deposited tin, germanium, and alloys of the two elements is reported. Limiting the sodium stripping voltage window to 0.75 V versus Na/Na+ improves the stability of the tin and tin-rich compositions on repeated sodiation/desodiation cycles, whereas the germanium and germanium-rich alloys were stable up to 1.5 V. The stability of the electrodes could be correlated to the surface mobility of the alloy species during deposition suggesting that tin must be effectively immobilized in order to be successfully utilized as a stable electrode. While the stability of the alloys is greatly increased by the presence of germanium, the specific Coulombic capacity of the alloy decreases with increasing germanium content due to the lower Coulombic capacity of germanium. Additionally, the presence of germanium in the alloy suppresses the formation of intermediate phases present in the electrochemical sodiation of tin. Four-point probe resistivity measurements of the different compositions show that electrical resistivity increases with germanium content. Pure germanium is the most resistive yet exhibited the best electrochemical performance at high current densities which indicates that electrical resistivity is not rate limiting for any of the tested compositions.