Characterization of pore network structure in catalyst layers of polymer electrolyte fuel cells

We model and validate the effect of ionomer content and Pt nanoparticles on nanoporous structure of catalyst layers in polymer electrolyte fuel cells. By employing Pore network modeling technique and analytical solutions, we analyze and reproduce experimental N2-adsorption isotherms of carbon, Pt/ carbon and catalyst layers with various ionomer contents. The porous catalyst layer structures comprise of Ketjen Black carbon, Pt and Nafion ionomer. The experimental pore size distributions obtained by N2- adsorption are used as an input to generate porous media using the pore network approach. Subsequently, the simulated porous structures are used to produce simulated N2-adsorption isotherms, which are then compared to the experimentally measured isotherms. The results show a good agreement in the prediction of the effect of the ionomer content on the microstructure of catalyst layers. Moreover, the analysis of the isotherms confirms the hypothesis of ionomer distribution on the surface of agglomerates as well as the existence of different sorption regimes in primary and secondary pores of fuel cell catalyst layers

The effect of altering loading distance on skeleton start performance: Is higher pre-load velocity always beneficial?

Athletes initiating skeleton runs differ in the number of steps taken before loading the sled. We aimed to understand how experimentally modifying loading distance influenced sled velocity and overall start performance. Ten athletes (five elite, five talent; 67% of all national athletes) underwent two to four sessions, consisting of two dry-land push starts in each of three conditions (preferred, long and short loading distances). A magnet encoder on the sled wheel provided velocity profiles and the overall performance measure (sled acceleration index). Longer pre load distances (12% average increase from preferred to long distances) were related to higher pre-load velocity (r = 0.94), but lower load effectiveness (r = 0.75; average reduction 29%). Performance evaluations across conditions revealed that elite athletes’ preferred distance push starts were typically superior to the other conditions. Short loading distances were generally detrimental, whereas pushing the sled further improved some talent-squad athletes’ performance. Thus, an important trade-off between generating high pre load velocity and loading effectively was revealed, which coaches should consider when encouraging athletes to load later. This novel intervention study conducted within a real-world training setting has demonstrated the scope to enhance push-start performance by altering loading distance, particularly in developing athletes with less extensive training experience

Preparation and Characterization of Semi-fluorinated Composite PEM with Phosphotungstic Acid Immobilized on Clays Using Melt Processing Technologies

Peer reviewed: YesNRC publication: Ye

Training-related changes in force-power profiles:Implications for the skeleton start

Purpose: Athletes' force-power characteristics influence sled velocity during the skeleton start, which is a crucial determinant of performance. This study characterized force-power profile changes across an 18-month period and investigated the associations between these changes and start performance. Methods: Seven elite- and 5 talent-squad skeleton athletes' (representing 80% of registered athletes in the country) force-power profiles and dry-land push-track performances were assessed at multiple time points over two 6-month training periods and one 5-month competition season. Force-power profiles were evaluated using an incremental leg-press test (Keiser A420), and 15-m sled velocity was recorded using photocells. Results: Across the initial maximum strength development phases, increases in maximum force (Fmax) and decreases in maximum velocity (Vmax) were typically observed. These changes were greater for talent (23.6% and-12.5%, respectively) compared with elite (6.1% and-7.6%, respectively) athletes. Conversely, decreases in Fmax (elite-6.7% and talent-10.3%) and increases in Vmax (elite 8.1% and talent 7.7%) were observed across the winter period, regardless of whether athletes were competing (elite) or accumulating sliding experience (talent).When the training emphasis shifted toward higher-velocity, sprint-based exercises in the second training season, force-power profiles seemed to becomemore velocity oriented (higher Vmax andmore negative force-velocity gradient), which was associated with greater improvements in sled velocity (r = .42 and-.45, respectively). Conclusions: These unique findings demonstrate the scope to influence force-power-generating capabilities in well-trained skeleton athletes across different training phases. To enhance start performance, it seems important to place particular emphasis on increasing maximum muscle-contraction velocity.</p

The effect of altering loading distance on skeleton start performance: Is higher pre-load velocity always beneficial?

Athletes initiating skeleton runs differ in the number of steps taken before loading the sled. We aimed to understand how experimentally modifying loading distance influenced sled velocity and overall start performance. Ten athletes (five elite, five talent; 67% of all national athletes) underwent two to four sessions, consisting of two dry-land push starts in each of three conditions (preferred, long and short loading distances). A magnet encoder on the sled wheel provided velocity profiles and the overall performance measure (sled acceleration index). Longer pre load distances (12% average increase from preferred to long distances) were related to higher pre-load velocity (r = 0.94), but lower load effectiveness (r = 0.75; average reduction 29%). Performance evaluations across conditions revealed that elite athletes’ preferred distance push starts were typically superior to the other conditions. Short loading distances were generally detrimental, whereas pushing the sled further improved some talent-squad athletes’ performance. Thus, an important trade-off between generating high pre load velocity and loading effectively was revealed, which coaches should consider when encouraging athletes to load later. This novel intervention study conducted within a real-world training setting has demonstrated the scope to enhance push-start performance by altering loading distance, particularly in developing athletes with less extensive training experience

Increased capsaicin receptor TRPV1 in skin nerve fibres and related vanilloid receptors TRPV3 and TRPV4 in keratinocytes in human breast pain

BACKGROUND: Breast pain and tenderness affects 70% of women at some time. These symptoms have been attributed to stretching of the nerves with increase in breast size, but tissue mechanisms are poorly understood. METHODS: Eighteen patients (n = 12 breast reduction and n = 6 breast reconstruction) were recruited and assessed for breast pain by clinical questionnaire. Breast skin biopsies from each patient were examined using immunohistological methods with specific antibodies to the capsaicin receptor TRPV1, related vanilloid thermoreceptors TRPV3 and TRPV4, and nerve growth factor (NGF). RESULTS: TRPV1-positive intra-epidermal nerve fibres were significantly increased in patients with breast pain and tenderness (TRPV1 fibres / mm epidermis, median [range] – no pain group, n = 8, 0.69 [0–1.27]; pain group, n = 10, 2.15 [0.77–4.38]; p = 0.0009). Nerve Growth Factor, which up-regulates TRPV1 and induces nerve sprouting, was present basal keratinocytes: some breast pain specimens also showed NGF staining in supra-basal keratinocytes. TRPV4-immunoreactive fibres were present in sub-epidermis but not significantly changed in painful breast tissue. Both TRPV3 and TRPV4 were significantly increased in keratinocytes in breast pain tissues; TRPV3, median [range] – no pain group, n = 6, 0.75 [0–2]; pain group, n = 11, 2 [1-3], p = 0.008; TRPV4, median [range] – no pain group, n = 6, [0–1]; pain group, n = 11, 1 [0.5–2], p = 0.014). CONCLUSION: Increased TRPV1 intra-epidermal nerve fibres could represent collateral sprouts, or re-innervation following nerve stretch and damage by polymodal nociceptors. Selective TRPV1-blockers may provide new therapy in breast pain. The role of TRPV3 and TRPV4 changes in keratinocytes deserve further study

"Man up": Medical students’ perceptions of gender and learning in clinical practice: A qualitative study

Context Gender‐related inequality and disparity hinders efforts to develop a medical workforce that facilitates universal access to safe, just and equitable health care. Little is known about how medical students perceive the impact of their gender on their learning in clinical practice. Our aim in this study was to address this gap, establishing students’ perceptions of the impact of their gender on learning in the clinical context as part of the wider medical education community of practice. Methods We undertook a qualitative study that simultaneously gathered data through narrative individual interviews and online case reports from male and female students (n = 31) from different academic cohorts with prior experience of clinical practice in a Russell Group University medical school in the UK. Interviews were transcribed and analysed thematically alongside case report data. Results and discussion The participants revealed that there was a culture in clinical practice where their gender influenced how they were taught and supported by senior medical and surgical colleagues. Gender was also said to determine the clinical learning opportunities afforded to students, especially with regards to the care of patients of a different gender. The mentorship and support for learning provided to students in clinical practice was also said to be influenced by the medical student's gender. Conclusion Our findings suggest that students undergo a gendered clinical apprenticeship within what are in effect gendered communities of practice with some distinct features. These findings underscore the imperative for further work to establish how medical students of all genders can be supported to fulfil their potential in clinical practice

Effects of estrogens and bladder inflammation on mitogen-activated protein kinases in lumbosacral dorsal root ganglia from adult female rats

BACKGROUND: Interstitial cystitis is a chronic condition associated with bladder inflammation and, like a number of other chronic pain states, symptoms associated with interstitial cystitis are more common in females and fluctuate during the menstrual cycle. The aim of this study was to determine if estrogens could directly modulate signalling pathways within bladder sensory neurons, such as extracellular signal-related kinase (ERK) and p38 mitogen-activated protein (MAP) kinases. These signalling pathways have been implicated in neuronal plasticity underlying development of inflammatory somatic pain but have not been as extensively investigated in visceral nociceptors. We have focused on lumbosacral dorsal root ganglion (DRG) neurons projecting to pelvic viscera (L1, L2, L6, S1) of adult female Sprague-Dawley rats and performed both in vitro and in vivo manipulations to compare the effects of short- and long-term changes in estrogen levels on MAPK expression and activation. We have also investigated if prolonged estrogen deprivation influences the effects of lower urinary tract inflammation on MAPK signalling. RESULTS: In studies of isolated DRG neurons in short-term (overnight) culture, we found that estradiol and estrogen receptor (ER) agonists rapidly stimulated ER-dependent p38 phosphorylation relative to total p38. Examination of DRGs following chronic estrogen deprivation in vivo (ovariectomy) showed a parallel increase in total and phosphorylated p38 (relative to beta-tubulin). We also observed an increase in ERK1 phosphorylation (relative to total ERK1), but no change in ERK1 expression (relative to beta-tubulin). We observed no change in ERK2 expression or phosphorylation. Although ovariectomy increased the level of phosphorylated ERK1 (vs. total ERK1), cyclophosphamide-induced lower urinary tract inflammation did not cause a net increase of either ERK1 or ERK2, or their phosphorylation. Inflammation did, however, cause an increase in p38 protein levels, relative to beta-tubulin. Prior ovariectomy did not alter the response to inflammation. CONCLUSIONS: These results provide new insights into the complex effects of estrogens on bladder nociceptor signalling. The diversity of estrogen actions in these ganglia raises the possibility of developing new ways to modulate their function in pelvic hyperactivity or pain states

Combined Point-of-Care Nucleic Acid and Antibody Testing for SARS-CoV-2 following Emergence of D614G Spike Variant

Rapid COVID-19 diagnosis in the hospital is essential, although this is complicated by 30%–50% of nose/throat swabs being negative by SARS-CoV-2 nucleic acid amplification testing (NAAT). Furthermore, the D614G spike mutant dominates the pandemic and it is unclear how serological tests designed to detect anti-spike antibodies perform against this variant. We assess the diagnostic accuracy of combined rapid antibody point of care (POC) and nucleic acid assays for suspected COVID-19 disease due to either wild-type or the D614G spike mutant SARS-CoV-2. The overall detection rate for COVID-19 is 79.2% (95% CI 57.8–92.9) by rapid NAAT alone. The combined point of care antibody test and rapid NAAT is not affected by D614G and results in very high sensitivity for COVID-19 diagnosis with very high specificity