A novel electrochemical flow-cell for operando XAS investigations in X-ray opaque supports.

Improvement of electrochemical technologies is one of the most popular topics in the field of renewable energy. However, this process requires a deep understanding of the electrode-electrolyte interface behavior under operando conditions. X-ray absorption spectroscopy (XAS) is widely employed to characterize electrode materials, providing element-selective oxidation state and local structure. Several existing cells allow studies as close as possible to realistic operating conditions, but most of them rely on the deposition of the electrodes on conductive and X-ray transparent materials, from where the radiation impinges the sample. In this work, we present a new electrochemical flow-cell for operando XAS that can be used with X-ray opaque substrates, since the signal is effectively detected from the electrode surface, as the radiation passes through a thin layer of electrolyte (∼17 µm). The electrolyte can flow over the electrode, reducing bubble formation and avoiding strong reactant concentration gradients. We show that high-quality data can be obtained under operando conditions, thanks to the high efficiency of the cell from the hard X-ray regime down to ∼4 keV. We report as a case study the operando XAS investigation at the Fe and Ni K-edges on Ni-doped γ-Fe2O3 films, epitaxially grown on Pt substrates. The effect of the Ni content on the catalytic performances for the oxygen evolution reaction is discussed.

Oxide Coating Role on the Bulk Structural Stability of Active LiMn2O4 Cathodes.

The protective coating of the electrode materials is a known source of improvement of the cycling performances in battery devices. In the case of the LiMn2O4 cathodes, the coating with a thin alumina layer has been proven to show performance efficiency. However, the precise mechanism of its effect on the performance improvement of the electrodes is still not clear. In this work we investigate alumina-coating-induced effects on the structural dynamics of the active materials in correlation to the modified solid electrolyte interface dynamics. The local structures of coated and uncoated samples at different galvanostatic points are studied by both soft X-ray absorption measurements at the Mn L-edges and O K-edge (in total electron yield mode) and hard X-ray absorption at the Mn K-edge (in transmission mode). The different probing depths of the employed techniques allowed us to study the structural dynamics both at the surface and within the bulk of the active material. We demonstrate that the coating successfully hinders the Mn3+ disproportionation and, hence, the degradation of the active material. Side products (layered Li2MnO3 and MnO) and changes in the local crystal symmetry with formation of Li2Mn2O4 are observed in uncoated electrodes. The role of alumina coating on the stability of the passivation layer and its consequent effect on the structural stability of the bulk active materials is discussed.

EXAFS investigations on the pressure induced local structural changes of GeSe2glass under different hydrostatic conditions.

Pressure-induced transformations in glassy GeSe2have been studied using the x-ray absorption spectroscopy. Experiments have been carried out at the scanning-energy beamline BM23 (European Synchrotron Radiation Facility) providing a micrometric x-ray focal spot up to pressures of about 45 GPa in a diamond anvil cell. Both Se and Ge K-edge experiments were performed under different hydrostatic conditions identifying the metallization onsets by accurate determinations of the edge shifts. The semiconductor-metal transition was observed to be completed around 20 GPa when neon was used as a pressure transmitting medium (PTM), while this transition was slightly shifted to lower pressures when no PTM was used. Accurate double-edge extended x-ray absorption fine structure (EXAFS) refinements were carried out using advanced data-analysis methods. EXAFS data-analysis confirmed the trend shown by the edge shifts for this disordered material, showing that the transition from tetrahedral to octahedral coordination for Ge sites is not fully achieved at 45 GPa. Results of present high pressure EXAFS experiments have shown the absence of significant neon incorporation into the glass within the pressure range up to 45 GPa.

Efficacy and safety of intracoronary epinephrine versus conventional treatments alone in STEMI patients with refractory coronary no-reflow during primary PCI: The RESTORE observational study.

OBJECTIVES: We aimed to compare intracoronary (IC) epinephrine versus conventional treatments alone in patients with ST-elevation myocardial infarction and refractory coronary no-reflow during primary percutaneous coronary intervention (PPCI). METHODS: Thirty consecutive patients with severe refractory coronary no-reflow (TIMI 0-1, MBG 0-1) during PPCI were prospectively included after initial failure of conventional treatments. Conventional treatments used in both groups included IC nitrates, thrombectomy. Glycoprotein IIb/IIIa inhibitors and adenosine. Patients received IC epinephrine or no epinephrine. RESULTS: Intracoronary administration of epinephrine yielded significantly better coronary flow patterns (28.6% TIMI 3, 64.3% TIMI 2, 7.1% TIMI 1, and 0% TIMI 0), compared to those after treatment with conventional agents alone (18.8% TIMI 3, 12.5% TIMI 2, 37.5% TIMI 1, and 31.3% TIMI 0) (p value between groups = .004). In the IC epinephrine vs. no epinephrine group there was a significant reduction of 30-day composite of death or heart failure (35.7% vs. 81.25%), improvement of ejection fraction (p = .01) and ST-segment resolution (p = .01). CONCLUSIONS: The findings of this proof-of-concept study suggest that as compared to use of conventional agents alone, IC epinephrine provides substantial improvement of coronary flow in STEMI patients with refractory no-reflow during PPCI that may result into improved prognosis.

A giant right coronary artery related to a small fistula to the coronary sinus.

Coronary artery fistulas to the coronary sinus are very rare coronary anomalies most often resulting in extreme dilatation of the donor coronary artery and the receiving vessel. However, despite common impressive appearance, their clinical and functional impact may be extremely various from asymptomatic and benign cases to disabling and life threatening situations. To adequately stratify the inherent risks and to plan the most appropriate therapeutic strategy, an overall investigation is necessary. We herein report the case of a 56year-old woman with a giant right coronary artery related to a small and restrictive fistula to the coronary sinus that was extensively investigated by multi-imaging strategy before decision of a therapeutic abstention and long-term follow-up.

Duration of dual antiplatelet therapy after percutaneous coronary intervention with drug-eluting stent implantation: a review of the current guidelines and literature.

Dual antiplatelet therapy is the mainstay of medical treatment after percutaneous coronary intervention regarding the risk of stent thrombosis occurrence. Since the beginning of the stenting era, antiplatelet regimens have evolved according to the emerging and widespread diffusion of new devices and more challenging indications for their use. In the past years, concerns have been raised about the safety of drug-eluting stent implantation with regard to late and very late stent thrombosis. Thus, the length of dual antiplatelet therapy has been progressively increased with marked individual and local differences. However, prolonged antiplatelet therapy leads to increased risk of bleeding, especially in the setting of surgical procedures, traumas, and/or other diseases. To date, the exact duration of dual antiplatelet therapy after drug-eluting stent implantation is still debated in the literature. The aim of this article is to review the literature and the current guidelines on the risks and benefits of pursuing dual antiplatelet therapy after percutaneous coronary intervention with drug-eluting stent implantation.