Impaired exercise ventilatory efficiency (high ventilatory requirements for CO
Formula: see texte/Formula: see textco
) provides an indication of pulmonary gas exchange abnormalities in chronic ...obstructive pulmonary disease (COPD).
To determine
) the association between high Formula: see texte/Formula: see textco
and clinical outcomes (dyspnea and exercise capacity) and its relationship to lung function and structural radiographic abnormalities; and
) its prevalence in a large population-based cohort.
Participants were recruited randomly from the population and underwent clinical evaluation, pulmonary function, cardiopulmonary exercise testing, and chest computed tomography. Impaired exercise ventilatory efficiency was defined by a nadir Formula: see texte/Formula: see textco
above the upper limit of normal (ULN), using population-based normative values.
Participants included 445 never-smokers, 381 ever-smokers without airflow obstruction, 224 with Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 COPD, and 200 with GOLD 2-4 COPD. Participants with Formula: see texte/Formula: see textco
above the ULN were more likely to have activity-related dyspnea (Medical Research Council dyspnea scale ⩾ 2; odds ratio 5-95% confidence intervals, 1.77 1.31 to 2.39) and abnormally low peak Formula: see texto
(Formula: see texto
below the lower limit of normal; odds ratio, 4.58 3.06 to 6.86). The Kco had a stronger correlation with nadir Formula: see texte/Formula: see textco
(
= -0.38;
< 0.001) than other relevant lung function and computed tomography metrics. The prevalence of Formula: see texte/Formula: see textco
above the ULN was 24% in COPD (similar in GOLD 1 and 2 through 4), which was greater than in never-smokers (13%) and ever-smokers (12%).
Formula: see texte/Formula: see textco
above the ULN was associated with greater dyspnea and low Formula: see texto
and was present in 24% of all participants with COPD, regardless of GOLD stage. The results show the importance of recognizing impaired exercise ventilatory efficiency as a potential contributor to dyspnea and exercise limitation, even in mild COPD.
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High efficiencies, wide operation range and rapid response time have motivated the recent interest in proton exchange membrane (PEM) electrolysis for hydrogen generation with surplus ...electricity. However, degradation at high current densities and the associated mechanism has not been thoroughly explored so far. In this work, membrane electrode assemblies (MEA) from different suppliers are aged in a commercial PEM electrolyzer (2.5Nm3H2h−1), operating up to 4Acm−2 for more than 750h. In all cases, the cell voltage (Ecell) decreases during the testing period. Interestingly, the cells with Ir-black anodes exhibit the highest performance with the lowest precious metal loading (1mgcm−2). Electrochemical impedance spectroscopy (EIS) shows a progressive decrease in the specific exchange current, while the ohmic resistance decreases when doubling the nominal current density. This effect translates into an enhancement of cell efficiency at high current densities. However, Ir concurrently leaches out and diffuses into the membrane. No decrease in membrane thickness is observed at the end of the tests. High current densities do not lead to lowering the performance of the PEM electrolyzer over time, although MEA components degrade, in particular the anode.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
An exercise challenge to test for exercise-induced bronchoconstriction (EIB) is a specialized exercise stress test that can detect changes in lung function with vigorous exercise. The lung function ...is measured (with a test called spirometry) before and after exercise to look for changes that are seen with EIB. It can also be used for people who have known asthma to look for exercise-induced asthma problems (EIA). This fact sheet describes the EIB exercise challenge.
Recent work has begun to relate individual differences in brain functional organization to human behaviors and cognition, but the best brain state to reveal such relationships remains an open ...question. In two large, independent data sets, we here show that cognitive tasks amplify trait-relevant individual differences in patterns of functional connectivity, such that predictive models built from task fMRI data outperform models built from resting-state fMRI data. Further, certain tasks consistently yield better predictions of fluid intelligence than others, and the task that generates the best-performing models varies by sex. By considering task-induced brain state and sex, the best-performing model explains over 20% of the variance in fluid intelligence scores, as compared to <6% of variance explained by rest-based models. This suggests that identifying and inducing the right brain state in a given group can better reveal brain-behavior relationships, motivating a paradigm shift from rest- to task-based functional connectivity analyses.
This study reveals the source of discrepancy between the lifetime of oxygen evolution reaction (OER) catalysts determined by rotating disk electrode (RDE) measurements vs that obtained in a membrane ...electrode assembly (MEA) in an electrolyzer. We show that the accumulation of microscopic oxygen bubbles in the pores of the electro-catalyst layer during the OER takes place in both RDE and MEA measurements. However, this accumulation was found to be much more significant in RDE measurements, where the shielding of almost all of the catalyst active sites by gas bubbles leads to rapid performance deterioration. This decrease in performance, albeit largely reversible, was found to also induce irreversible catalyst degradation, which could be avoided if the accumulation of microscopic bubbles is prevented. This type of artefact results in vastly under-estimated catalyst lifetimes obtained by RDE experiments, resulting in values that are orders of magnitude shorter than those obtained using MEA measurements, and a hypothesis for this discrepancy will be proposed. Therefore, electrochemical cells with liquid electrolytes are not reliable for OER catalyst lifetime determination.
This was paper 236 presented at the Atlanta, Georgia, Meeting of the Society, October 13–17, 2019.
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