Nonstoichiometric CeO2 and Ce0.25Zr0.75O2 nanoparticles with varying surface concentrations of Ce3+ were synthesized. Their surface Ce3+ concentration was measured by XPS, and their surface oxygen ...vacancy concentrations and grain size were estimated using Raman spectroscopy. The surface oxygen vacancy concentration was found to correlate well with grain size and surface Ce3+ concentration. When incorporated into a Nafion polymer electrolyte membrane (PEM), the added nonstoichiometric ceria nanoparticles effectively scavenged PEM-degradation-inducing free radical reactive oxygen species (ROS) formed during fuel cell operation. A 3-fold increase in the surface oxygen vacancy concentration resulted in an order of magnitude enhancement in the efficacy of free radical ROS scavenging by the nanoparticles. Overall, the macroscopic PEM degradation mitigation rate was lowered by up to 2 orders of magnitude using nonstoichiometric ceria nanoparticles with high surface oxygen vacancy concentrations
Functionalized organic/inorganic composite anion exchange membranes (AEMs) were prepared with quaternized cardo-poly(etherketone) (QPEK-C) and N-(trimethoxysilylpropyl)-N,N,N-trimethylammonium ...chloride (TMSP-TMA+Cl−). With an optimized loading of 20wt% of TMSP-TMA+, the sulfate ion conductivity and VO2+ permeability of the composite membrane were 8.4 ± 0.2 mScm−1 and 0.53 × 10−9cm2s−1, respectively; pristine QPEK-C AEMs had a sulfate ion conductivity of 4.5 ± 0.5 mS cm−1 and a VO2+ permeability of 1.1 × 10−9cm2s−1. Membranes with 10–20%wt% of TMSP-TMA+ exhibited better mechanical properties, with an ultimate tensile strength of 26 ± 2 MPa and an elongation at break of 32 ± 3%. The chemical and mechanical stabilities of QPEK-C/TMSP-TMA+ composite AEMs were investigated by immersing the membranes in a VO2+ solution at 30 °C and monitoring the sulfate ion conductivity and any changes in chemical structure using 1D and 2D-NMR spectroscopy. Nafion® 212, pristine QPEK-C AEM, and QPEK-C/20wt%TMSP-TMA+ composite AEMs were used as separators in an all-vanadium redox flow battery (VRFB). The coulombic efficiencies (CE) (at 100 mAcm−2) were 99% for QPEK-C and QPEK-C/20wt%TMSP-TMA+ and 95% for Nafion® 212. The battery capacity was lowered by 10% over 30 charge–discharge cycles (∼60 h) for QPEK-C and QPEK-C/20wt%TMSP-TMA+AEMs. Under similar conditions a loss of 30% of the capacity was observed for the Nafion® 212 separator.
•Quaternized cardo-poly(etherketone) AEMs were evaluated as separators for VRFB.•The composite AEMs remained mechanically stable in VO2+ solution for 2 weeks.•NMR spectroscopy confirmed the degradation of TMSP-TMA+ filler in VO2+ solution.•Composite AEMs reduce vanadium species cross-mixing.
We report a unique and highly stable electrocatalyst—platinum (Pt) supported on titanium–ruthenium oxide (TRO)—for hydrogen fuel cell vehicles. The Pt/TRO electrocatalyst was exposed to stringent ...accelerated test protocols designed to induce degradation and failure mechanisms identical to those seen during extended normal operation of a fuel cell automobile—namely, support corrosion during vehicle startup and shutdown, and platinum dissolution during vehicle acceleration and deceleration. These experiments were performed both ex situ (on supports and catalysts deposited onto a glassy carbon rotating disk electrode) and in situ (in a membrane electrode assembly). The Pt/TRO was compared against a state-of-the-art benchmark catalyst—Pt supported on high surface-area carbon (Pt/HSAC). In ex situ tests, Pt/TRO lost only 18% of its initial oxygen reduction reaction mass activity and 3% of its oxygen reduction reaction-specific activity, whereas the corresponding losses for Pt/HSAC were 52% and 22%. In in situ-accelerated degradation tests performed on membrane electrode assemblies, the loss in cell voltage at 1 A · cm ⁻² at 100% RH was a negligible 15 mV for Pt/TRO, whereas the loss was too high to permit operation at 1 A · cm ⁻² for Pt/HSAC. We clearly show that electrocatalyst support corrosion induced during fuel cell startup and shutdown is a far more potent failure mode than platinum dissolution during fuel cell operation. Hence, we posit that the need for a highly stable support (such as TRO) is paramount. Finally, we demonstrate that the corrosion of carbon present in the gas diffusion layer of the fuel cell is only of minor concern.
We analyzed the effect of time to initiation of antiretroviral therapy (ART) after diagnosis on the probability of HIV-1 transmission events (HIV-TE) in naïve HIV-1-infected men having sex with men ...(MSM).
Mathematical model.
We used discrete event simulation modeling to estimate the probability of HIV-TE in the first 8 weeks after ART initiation; we varied ART initiation from D0 to D28 after simulated "diagnosis". The model inputs used sexual behavior parameters from the MSM population of the START trial, and transmission rates per-sex act and HIV-1 RNA from recent meta-analyses. HIV-1 RNA decay curves were modeled from the databases of Single (efavirenz EFV v dolutegravir DTG), Spring-2 (raltegravir RAL v DTG), and Flamingo (darunavir/ritonavir DRVr v DTG) trials.
We found that the number of HIV-TE per index patient in the first 8 weeks after ART initiation increased linearly for same-day ART to initiation on day 28. Small but statistically significant advantages of integrase strand transfer inhibitors (INSTI) over EFV and DRVr were found.
Rapid, if not same-day initiation of INSTI-based ART to newly diagnosed HIV-infected MSM has the potential for substantial public health benefits related to decreases in HIV-TE.
Initiation of antiretroviral therapy (ART) for HIV infection using regimens that include integrase strand transfer inhibitors (INSTIs) is associated with a faster decline in HIV-1 RNA than what is ...observed with regimens that are anchored by other ART drug classes. We compared the impact of ART regimens that include dolutegravir (DTG), raltegravir (RAL), efavirenz (EFV), or darunavir/ritonavir (DRV/r), in treatment naïve men who have sex with men (MSM) on the probability of HIV-1 sexual transmission events (HIV-TE).
Mathematical model.
We used discrete event simulation modeling to estimate HIV-TE during the first 8 weeks after initiation of ART. HIV-1 RNA decay in men was modeled from the databases of three clinical trials: Single (DTG vs. EFV), Spring-2 (DTG vs. RAL) and Flamingo (DTG vs. DRV/r).
All regimens substantially reduced the number of HIV-TE compared to no treatment. DTG led to fewer HIV-TE than its comparator in each of the three trials: 22.72% fewer transmissions than EFV; 0.52% fewer transmissions than RAL; and 38.67% fewer transmissions than DRV/r. The number of patients needed to treat with DTG to prevent one transmission event instead of comparator was 48 vs EFV, 2,194 vs RAL, and 31 vs DRV/r.
Unsurprisingly, this mathematical model showed that all regimens reduced HIV-TE compared to no treatment. The results also suggest that that initial use of INSTIs, by virtue of their superior viral decay kinetics, have the potential to reduce HIV-1 horizontal transmission following initiation of ART in naïve MSM.
ClinicalTrials.gov NCT03183154.
We investigate the performance and stability of a platinum (Pt) supported on indium tin oxide (ITO) electrocatalyst. ITO was synthesized using the co-precipitation method and uniform particles with a ...B.E.T. surface area larger than 40m2/g were obtained. Pt was dispersed onto the ITO by colloidal deposition followed by reduction with formaldehyde. Previous rotating disk electrode (RDE) work has shown that Pt/ITO possesses high activity and stability for the oxygen reduction reaction (ORR). However, this catalyst exhibited very poor performance and stability in an operating polymer electrolyte fuel cell (PEFC) membrane electrode assembly (MEA). For H2/O2 PEFC operation at 80°C and 75% relative humidity (RH), the current density obtained at 0.55V was only 90mA/cm2, and the maximum current density was only 150–160mA/cm2, when Pt/ITO was used at the cathode, whereas a limiting current density of 3900mA/cm2 was readily obtained using a benchmark Pt/C catalyst under identical conditions. The low performance with Pt/ITO was primarily due to the high overall cell resistance of the MEA (>400mOhmcm2). X-ray photoelectron spectroscopy (XPS) was employed to investigate the degradation of the Pt/ITO catalyst in the PEFC electrode during operation. The deconvolution of the indium 3d XPS peak revealed the presence of two peaks: the first was assigned to indium oxide in ITO (at 445.6eV), while the second was assigned to indium hydroxide (at 446.6eV). We observed an increase in surface hydroxide concentration (compared to pristine Pt/ITO) after the Pt/ITO catalyst was used either at the cathode or anode of an operating PEFC. We postulate that the surface hydroxides form a passivating layer that increases the electrode resistance and undermines PEFC performance.
•Contrary to RDE results, low performance was observed with a Pt/ITO electrocatalyst in an operating PEFC.•X-ray photoelectron spectroscopy (XPS) revealed Pt/ITO catalyst degradation during PEFC operation.•Indium 3d XPS peak deconvolution revealed the degradation mechanism, namely the formation of surface indium hydroxides.•We postulate that the surface hydroxides form a passivating layer that increases the electrode resistance and undermines PEFC performance.
The performance of high temperature polymer electrolyte fuel cell (HT-PEMFC) using platinum supported over tin oxide and Vulcan carbon (Pt/SnOx/C) as cathode catalyst was evaluated at 160–200
°C and ...compared with Pt/C. This paper reports first time the Pt/SnOx/C preparation, fuel cell performance, and durability test up to 200
h. Pt/SnOx/C of varying SnO compositions were characterized using XRD, SEM, TEM, EDX and EIS. The face-centered cubic structure of nanosized Pt becomes evident from XRD data. TEM and EDX measurements established that the average size of the Pt nanoparticles were ∼6
nm. Low ionic resistances were derived from EIS, which ranged from 0.5 to 5
Ω-cm
2 for cathode and 0.05 to 0.1
Ω-cm
2 for phosphoric acid, doped PBI membrane. The addition of the SnOx to Pt/C significantly promoted the catalytic activity for the oxygen reduction reaction (ORR). The 7
wt.% SnO in Pt/SnO
2/C catalyst showed the highest electro-oxidation activity for ORR. High temperature PEMFC measurements performed at 180
°C under dry gases (H
2 and O
2) showed 0.58
V at a current density of 200
mA
cm
−2, while only 0.40
V was obtained in the case of Pt/C catalyst. When the catalyst contained higher concentrations of tin oxide, the performance decreased as a result of mass transport limitations within the electrode. Durability tests showed that Pt/SnOx/C catalysts prepared in this work were stable under fuel cell working conditions, during 200
h at 180
°C demonstrate as potential cathode catalyst for HT-PEMFCs.
Atherosclerotic cardiovascular disease (ASCVD) is one of the main causes of morbidity and mortality in developed countries and entails high resources use and costs for health systems. The risk of ...suffering future cardiovascular (CV) events and the consequent resources use is higher in those patients who have already had a previous cardiovascular event. The objective of the study was to determine the average annual cost of patients with a new or recurrent atherosclerotic CV event during the 2 years after the event.
Retrospective observational study of electronic medical records of patients from the BIG-PAC® database (7 integrated health areas of 7 Autonomous Communities;
= 1.8 million). Patients with a new or recurrent episode of ASCVD (angina, acute myocardial infarction, transient ischemic attack, stroke, or peripheral arterial disease) between 1-Jan-2017 and 31-Dec-2018 were included. The resources use within two years of the diagnosis was estimated in order to estimate the average cost of patient follow-up.
A total of 26,976 patients with an ASCVD episode were identified during the recruitment period; Out of them, 6,798 had a recurrent event during the follow-up period and 2,414 died. The average costs per patient were €11,171 during the first year and €9,944 during the second year.
Patients with ASCVD represent a significant economic burden for the health system and for society. Despite the perception that drug costs in the follow-up of chronic patients imply a high percentage of the costs, these accounted for only one tenth of the total amount. Implementing preventive programs and increasing the control of cardiovascular risk factors may have a significant social and health impact by helping to reduce mortality and costs for the Spanish National Health System. The costs derived from pharmacological treatments were obtained from the NHS pricing nomenclator database (https://www.sanidad.gob.es/profesionales/nomenclator.do).
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