Fuel cell electrode degradation followed by identical location transmission electron microscopy

Identical location transmission electron microscopy (IL-TEM) is a powerful technique that has previously been used to study degradation of catalyst materials for proton exchange membrane fuel cells (PEMFCs) in half-cell environments. Here, we demonstrate that IL-TEM can be used to follow degradation at the top of the catalytic Pt/C layer in a real PEMFC on the atomic scale under operation. We find that during an accelerated stress test (AST), mimicking normal operation, Pt nanoparticles grow mainly by Ostwald ripening, while the carbon support is stable. Under AST mimicking start-up/shutdown conditions, the carbon support degrades mainly by loss of volume and collapse, which forces the Pt nanoparticles closer, promoting additional particle growth. The observed degradation correlates with the measured decrease in electrochemical performance for the respective AST. The results show the feasibility of performing IL-TEM imaging in PEMFCs under real-operating conditions, opening up the possibility for similar studies in other fully operational systems

Impact of Accelerated Stress Tests on the Cathodic Catalytic Layer in a Proton Exchange Membrane (PEM) Fuel Cell Studied by Identical Location Scanning Electron Microscopy

Platinum is the most used electrocatalyst in proton exchange membrane fuel cells (PEMFCs). Nonetheless, it suffers from various types of degradation. Identical location electron microscopy has previously been used to observe local catalyst changes under accelerated stress tests (ASTs), giving insight into how individual catalyst particles degrade. However, it is important that such studies are carried out under relevant reaction conditions, as these can differ substantially between liquid half-cells and real PEMFC conditions. In this work, a single cell PEMFC was used to study the degradation of a commercial Pt-catalyzed membrane electrode assembly by performing square wave voltage ASTs in a potential range of 0.6 to 1.0 V. Identical location scanning electron microscopy (IL-SEM) was used to follow the degradation of the cathodic catalytic layer (CL) throughout 14,000 AST cycles. From the IL-SEM, we can conclude that the Pt nanoparticles degrade via Ostwald ripening, crystal migration, and coalescence. Small Pt nanoparticles agglomerate to larger particles or dissolve and redeposit to more stable particles, increasing the average particle size during the ASTs. In addition, cross-sectional TEM images show thinning of the ionomer layer during the AST procedure. The IL-SEM technique facilitates observation of local degradation of the CL in real PEMFCs, which will help to understand different degradation mechanisms, allowing for better solutions to be designed

Comparison of Oxygen Adsorption and Platinum Dissolution in Acid and Alkaline Solutions Using Electrochemical Quartz Crystal Microbalance

Platinum (Pt) is a widely used electrocatalyst material in fuel cells and electrolysers. Proton exchange membrane (PEM) fuel cells and electrolysis operate under highly acidic conditions whereas the more recently developed anion exchange membrane (AEM) processes take place under alkaline conditions. Pt dissolution and Pt oxidation during operation and varying potentials has been studied mainly for the acidic PEM and less for the alkaline AEM. This study presents a comparison of Pt dissolution and Pt oxidation in 0.5 M H2SO4 and 1 M KOH using electrochemical quartz crystal microbalance (EQCM) on Pt thin films. Physical characterisation using electron microscopy and atomic force microscopy (AFM) revealed small, yet significant differences in the Pt film surface structure, which is related to differences in measured electrochemical surface area (ECSA). The mass increase from adsorption of oxygenated species and Pt oxidation is higher in alkaline conditions compared to in acid while dissolution of Pt is similar

Chemotherapy with or without avelumab followed by avelumab maintenance versus chemotherapy alone in patients with previously untreated epithelial ovarian cancer (JAVELIN Ovarian 100): an open-label, randomised, phase 3 trial

BACKGROUND: Although most patients with epithelial ovarian cancer respond to frontline platinum-based chemotherapy, around 70% will relapse within 3 years. The phase 3 JAVELIN Ovarian 100 trial compared avelumab (anti-PD-L1 monoclonal antibody) in combination with chemotherapy followed by avelumab maintenance, or chemotherapy followed by avelumab maintenance, versus chemotherapy alone in patients with treatment-naive epithelial ovarian cancer. METHODS: JAVELIN Ovarian 100 was a global, open-label, three-arm, parallel, randomised, phase 3 trial run at 159 hospitals and cancer treatment centres in 25 countries. Eligible women were aged 18 years and older with stage III-IV epithelial ovarian, fallopian tube, or peritoneal cancer (following debulking surgery, or candidates for neoadjuvant chemotherapy), and had an Eastern Cooperative Oncology Group performance status of 0 or 1. Patients were randomly assigned (1:1:1) via interactive response technology to receive chemotherapy (six cycles; carboplatin dosed at an area under the serum-concentration-time curve of 5 or 6 intravenously every 3 weeks plus paclitaxel 175 mg/m2 every 3 weeks or 80 mg/m2 once a week [investigators' choice]) followed by avelumab maintenance (10 mg/kg intravenously every 2 weeks; avelumab maintenance group); chemotherapy plus avelumab (10 mg/kg intravenously every 3 weeks) followed by avelumab maintenance (avelumab combination group); or chemotherapy followed by observation (control group). Randomisation was in permuted blocks of size six and stratified by paclitaxel regimen and resection status. Patients and investigators were masked to assignment to the two chemotherapy groups without avelumab at the time of randomisation until completion of the chemotherapy phase. The primary endpoint was progression-free survival assessed by blinded independent central review in all randomly assigned patients (analysed by intention to treat). Safety was analysed in all patients who received at least one dose of study treatment. This trial is registered with ClinicalTrials.gov, NCT02718417. The trial was fully enrolled and terminated at interim analysis due to futility, and efficacy is no longer being assessed. FINDINGS: Between May 19, 2016 and Jan 23, 2018, 998 patients were randomly assigned (avelumab maintenance n=332, avelumab combination n=331, and control n=335). At the planned interim analysis (data cutoff Sept 7, 2018), prespecified futility boundaries were crossed for the progression-free survival analysis, and the trial was stopped as recommended by the independent data monitoring committee and endorsed by the protocol steering committee. Median follow-up for progression-free survival for all patients was 10·8 months (IQR 7·1-14·9); 11·1 months (7·0-15·3) for the avelumab maintenance group, 11·0 months (7·4-14·5) for the avelumab combination group, and 10·2 months (6·7-14·0) for the control group. Median progression-free survival was 16·8 months (95% CI 13·5-not estimable [NE]) with avelumab maintenance, 18·1 months (14·8-NE) with avelumab combination treatment, and NE (18·2 months-NE) with control treatment. The stratified hazard ratio for progression-free survival was 1·43 (95% CI 1·05-1·95; one-sided p=0·99) with the avelumab maintenance regimen and 1·14 (0·83-1·56; one-sided p=0·79) with the avelumab combination regimen, versus control treatment. The most common grade 3-4 adverse events were anaemia (69 [21%] patients in the avelumab maintenance group, 63 [19%] in the avelumab combination group, and 53 [16%] in the control group), neutropenia (91 [28%], 99 [30%], and 88 [26%]), and neutrophil count decrease (49 [15%], 45 [14%], and 59 [18%]). Serious adverse events of any grade occurred in 92 (28%) patients in the avelumab maintenance group, 118 (36%) in the avelumab combination group, and 64 (19%) in the control group. Treatment-related deaths occurred in one (<1%) patient in the avelumab maintenance group (due to atrial fibrillation) and one (<1%) patient in the avelumab combination group (due to disease progression). INTERPRETATION: Although no new safety signals were observed, results do not support the use of avelumab in the frontline treatment setting. Alternative treatment regimens are needed to improve outcomes in patients with advanced epithelial ovarian cancer. FUNDING: Pfizer and Merck KGaA, Darmstadt, Germany

Peripheral electrical stimulation in Alzheimer's Disease: A randomized controlled trial on cognition and behavior

In a number of studies, peripheral electrical nerve stimulation has been applied to Alzheimer's disease (AD) patients who lived in a nursing home. Improvements were observed in memory, verbal fluency, affective behavior, activities of daily living and on the rest-activity rhythm and pupillary light reflex. The aim of the present, randomized, placebo-controlled, parallel-group clinical trial was to examine the effects of electrical stimulation on cognition and behavior in AD patients who still live at home. Repeated measures analyses of variance revealed no effects of the intervention in the verum group (n = 32) compared with the placebo group (n = 30) on any of the cognitive and behavioral outcome measures. However, the majority of the patients and the caregivers evaluated the treatment procedure positively, and applying the daily treatment at home caused minimal burden. The lack of treatment effects calls for reconsideration of electrical stimulation as a symptomatic treatment in A

Health and working conditions of pregnant women working inside and outside the home in Mexico City

BACKGROUND: To explore differences related to health and working conditions by comparing socio-demographic parameters, reproductive and prenatal care characteristics and working conditions among pregnant women who are employed outside the home (extra-domestic) while still performing a domestic workload versus those who perform exclusively domestic work in the home (intra-domestic). METHODS: A cross-sectional study was carried out at Family Medicine Unit N 31 of the Mexican Institute of Social Security (IMSS) in Mexico City between April and July 2003. Interviews were conducted with 537 pregnant women engaged in either extra-domestic work plus intra-domestic tasks, or those performing strictly intra-domestic work. Information was obtained regarding their demographic status, prenatal care, reproductive, work characteristics, and health during pregnancy. RESULTS: One hundred ninety-six (36.5%) of the interviewed women had paid jobs outside the home in addition to domestic tasks, while three hundred forty-one (63.5 %) engaged in exclusively intra-domestic occupations. Of the women with paid jobs, 78.6% worked as clerks. Among domestic tasks, we found that the greatest workload was associated with washing of clothes, and our micro-ergonomic analysis revealed that women who worked strictly inside the home had a higher domestic workload versus employed women (69.2 vs. 44.9%). When we analyzed the effect of work on health during pregnancy, we observed that women who worked strictly inside the home were at a higher risk for musculoskeletal and genitourinary symptoms than those employed outside the home. CONCLUSION: These findings suggest that the effect of intra-domestic work should not be ignored when considering women's health during pregnancy, and that greater attention should be paid to women's working conditions during intra and extra-domestic work

Ticks Associated with Macquarie Island Penguins Carry Arboviruses from Four Genera

Macquarie Island, a small subantarctic island, is home to rockhopper, royal and king penguins, which are often infested with the globally distributed seabird tick, Ixodes uriae. A flavivirus, an orbivirus, a phlebovirus, and a nairovirus were isolated from these ticks and partial sequences obtained. The flavivirus was nearly identical to Gadgets Gully virus, isolated some 30 year previously, illustrating the remarkable genetic stability of this virus. The nearest relative to the orbivirus (for which we propose the name Sandy Bay virus) was the Scottish Broadhaven virus, and provided only the second available sequences from the Great Island orbivirus serogroup. The phlebovirus (for which we propose the name Catch-me-cave virus) and the previously isolated Precarious Point virus were distinct but related, with both showing homology with the Finnish Uukuniemi virus. These penguin viruses provided the second and third available sequences for the Uukuniemi group of phleboviruses. The nairovirus (for which we propose the name Finch Creek virus) was shown to be related to the North American Tillamook virus, the Asian Hazara virus and Nairobi sheep disease virus. Macquarie Island penguins thus harbour arboviruses from at least four of the seven arbovirus-containing genera, with related viruses often found in the northern hemisphere

Work satisfaction of professional nurses in South Africa: a comparative analysis of the public and private sectors

<p>Abstract</p> <p>Background</p> <p>Work satisfaction of nurses is important, as there is sufficient empirical evidence to show that it tends to affect individual, organizational and greater health and social outcomes. Although there have been several studies of job satisfaction among nurses in South Africa, these are limited because they relate to studies of individual organizations or regions, use small samples or are dated. This paper presents a national study that compares and contrasts satisfaction levels of nurses in both public and private sectors.</p> <p>Methods</p> <p>This was a cross-sectional survey of professional nurses conducted throughout South Africa using a pretested and self-administered questionnaire. Univariate and bivariate statistical models were used to evaluate levels of satisfaction with various facets of work and to elicit the differences in satisfaction levels between different groups of nurses. A total of 569 professional nurses participated in the study.</p> <p>Results</p> <p>Private-sector nurses were generally satisfied, while public-sector nurses were generally dissatisfied. Public-sector nurses were most dissatisfied with their pay, the workload and the resources available to them. They were satisfied only with the social context of the work. Private-sector nurses were dissatisfied only with their pay and career development opportunities. Professional nurses in the more rural provinces, those intending to change sectors and those more likely not to be in their current positions within the next five years were also more likely to be dissatisfied with all facets of their work.</p> <p>Conclusion</p> <p>This study highlighted the overall dissatisfaction among South African nurses and confirmed the disparity between the levels of job satisfaction between the public and private sectors. Health managers should address those factors that affect job satisfaction, and therefore retention, of nurses in South Africa. Improving the work environment so that it provides a context congruent with the aspirations and values systems of nurses is more likely to increase the satisfaction of nurses and consequently have a positive effect on individual, organizational and health outcomes.</p

Search for Kaluza-Klein Graviton Emission in ppˉp\bar{p} Collisions at s=1.8\sqrt{s}=1.8 TeV using the Missing Energy Signature

We report on a search for direct Kaluza-Klein graviton production in a data sample of 84 ${pb}^{-1}$ of \ppb collisions at $\sqrt{s}$ = 1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and one or two high energy jets. We compare the data with the predictions from a $3+1+n$-dimensional Kaluza-Klein scenario in which gravity becomes strong at the TeV scale. At 95% confidence level (C.L.) for $n$=2, 4, and 6 we exclude an effective Planck scale below 1.0, 0.77, and 0.71 TeV, respectively.Comment: Submitted to PRL, 7 pages 4 figures/Revision includes 5 figure

Measurement of the average time-integrated mixing probability of b-flavored hadrons produced at the Tevatron

We have measured the number of like-sign (LS) and opposite-sign (OS) lepton pairs arising from double semileptonic decays of $b$ and $\bar{b}$-hadrons, pair-produced at the Fermilab Tevatron collider. The data samples were collected with the Collider Detector at Fermilab (CDF) during the 1992-1995 collider run by triggering on the existence of $\mu \mu$ and $e \mu$ candidates in an event. The observed ratio of LS to OS dileptons leads to a measurement of the average time-integrated mixing probability of all produced $b$-flavored hadrons which decay weakly, $\bar{\chi} = 0.152 \pm 0.007$ (stat.) $\pm 0.011$ (syst.), that is significantly larger than the world average $\bar{\chi} = 0.118 \pm 0.005$.Comment: 47 pages, 10 figures, 15 tables Submitted to Phys. Rev.