30 research outputs found
Highly Permeable Perfluorinated Sulfonic Acid Ionomers for Improved Electrochemical Devices: Insights into Structure-Property Relationships.
Rapid improvements in polymer-electrolyte fuel-cell (PEFC) performance have been driven by the development of commercially available ion-conducting polymers (ionomers) that are employed as membranes and catalyst binders in membrane-electrode assemblies. Commercially available ionomers are based on a perfluorinated chemistry comprised of a polytetrafluoroethylene (PTFE) matrix that imparts low gas permeability and high mechanical strength but introduces significant mass-transport losses in the electrodes. These transport losses currently limit PEFC performance, especially for low Pt loadings. In this study, we present a novel ionomer incorporating a glassy amorphous matrix based on a perfluoro(2-methylene-4-methyl-1,3-dioxolane) (PFMMD) backbone. The novel backbone chemistry induces structural changes in the ionomer, restricting ionomer domain swelling under hydration while disrupting matrix crystallinity. These structural changes slightly reduce proton conductivity while significantly improving gas permeability. The performance implications of this trade-off are assessed, which reveal the potential for substantial performance improvement by incorporation of highly permeable ionomers as the functional catalyst binder. These results underscore the significance of tailoring material chemistry to specific device requirements, where ionomer chemistry should be rationally designed to match the local transport requirements of the device architecture
Multi-band Optical Variability of the TeV Blazar PG 1553+113 in 2019
We report the flux and spectral variability of PG 1553+113 on intra-night
(IDV) to short-term timescales using BVRI data collected over 91 nights from 28
February to 8 November 2019 employing ten optical telescopes: three in
Bulgaria, two each in India and Serbia, and one each in Greece, Georgia, and
Latvia. We monitored the blazar quasi-simultaneously for 16 nights in the V and
R bands and 8 nights in the V, R, I bands and examined the light curves (LCs)
for intra-day flux and colour variations using two powerful tests: the
power-enhanced F-test and the nested ANOVA test. The source was found to be
significantly (> 99%) variable in 4 nights out of 27 in R-band, 1 out of 16 in
V-band, and 1 out of 6 nights in I-band. No temporal variations in the colours
were observed on IDV timescale. During the course of these observations the
total variation in R-band was 0.89 mag observed. We also investigated the
spectral energy distribution (SED) using B, V, R, and I band data. We found
optical spectral indices in the range of 0.878+-0.029 to 1.106+-0.065 by
fitting a power law to these SEDs of PG 1553+113. We found that the source
follows a bluer-when-brighter trend on IDV timescales. We discuss possible
physical causes of the observed spectral variability.Comment: 13 pages,8 figures, 7 tables, Accepted for publication in MNRA
CLASP2 is involved in the EMT and early progression after transurethral resection of the bladder tumor
The DNA Methylome of Human Peripheral Blood Mononuclear Cells
Analysis across the genome of patterns of DNA methylation reveals a rich landscape of allele-specific epigenetic modification and consequent effects on allele-specific gene expression
Geometric effects of sustainable auxetic structures integrating the particle swarm optimization and finite element method
The development of new materials based on industrial wastes has been the focus of much research for a sustainable world. The growing demand for tyres has been every year exacerbating environmental problems due to indiscriminate disposal in the nature, making a potentially harmful waste to public health. The incorporation of rubber particles from scrap tyres into polymeric composites has achieved high toughness and moderate mechanical properties. This work investigates the geometric effects (thickness, width and internal cell angle) of auxetic structures made of recycled rubber composites based on experimental and numerical data. The response surface models integrated with the swarm intelligence and finite element analysis were proposed in order to obtain a range of solutions that provides useful information to the user during the selection of geometric parameters for reentrant cells. The results revealed the cell thickness ranges from 39-40 mm and 5.98-6 mm, and the cell angle range from -0.01 to -0.06º maximize the ultimate strength. The same parameters were able to optimize the modulus of elasticity of rubber auxetic structures, excepting for the angle factor which must be set between -30º and 27.7º. The optimal Poisson's ratio was found when the cell angle ranged from -30º to -28.5º, cell width ranged from 5-5.6 mm and 2 mm in thickness
Maspin enhances cisplatin chemosensitivity in bladder cancer T24 and 5637 cells and correlates with prognosis of muscle-invasive bladder cancer patients receiving cisplatin based neoadjuvant chemotherapy
Broadband multi-wavelength properties of M87 during the 2017 Event Horizon Telescope campaign
In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the
center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations
for a weakly accreting supermassive black hole of mass ∼6.5 × 109Me. The EHTC also partnered with several
international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength
campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a
legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at
high energies, making it possible to combine core flux constraints with the more spatially precise very long
baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active
nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one
broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the
basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude
that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the
EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of
HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and
secondaries cannot yet be excluded.http://iopscience.iop.org/2041-8205am2022Physic
Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
Abstract: In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M ⊙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87’s spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded
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Highly Permeable Perfluorinated Sulfonic Acid Ionomers for Improved Electrochemical Devices: Insights into Structure-Property Relationships.
Rapid improvements in polymer-electrolyte fuel-cell (PEFC) performance have been driven by the development of commercially available ion-conducting polymers (ionomers) that are employed as membranes and catalyst binders in membrane-electrode assemblies. Commercially available ionomers are based on a perfluorinated chemistry comprised of a polytetrafluoroethylene (PTFE) matrix that imparts low gas permeability and high mechanical strength but introduces significant mass-transport losses in the electrodes. These transport losses currently limit PEFC performance, especially for low Pt loadings. In this study, we present a novel ionomer incorporating a glassy amorphous matrix based on a perfluoro(2-methylene-4-methyl-1,3-dioxolane) (PFMMD) backbone. The novel backbone chemistry induces structural changes in the ionomer, restricting ionomer domain swelling under hydration while disrupting matrix crystallinity. These structural changes slightly reduce proton conductivity while significantly improving gas permeability. The performance implications of this trade-off are assessed, which reveal the potential for substantial performance improvement by incorporation of highly permeable ionomers as the functional catalyst binder. These results underscore the significance of tailoring material chemistry to specific device requirements, where ionomer chemistry should be rationally designed to match the local transport requirements of the device architecture
Highly Permeable Perfluorinated Sulfonic Acid Ionomers for Improved Electrochemical Devices: Insights into Structure-Property Relationships
Rapid
improvements in polymer-electrolyte fuel-cell (PEFC) performance have been
driven by the development of commercially available ion-conducting polymers
(ionomers) that are employed as membranes and catalyst binders in membrane-electrode
assemblies. Commercially available ionomers are based on a perfluorinated
chemistry comprised of a polytetrafluoroethylene (PTFE) matrix that imparts low
gas permeability and high mechanical strength but introduces significant
mass-transport losses in the electrodes. These transport losses currently limit
PEFC performance, especially for low Pt loadings. In this study, we present a
novel ionomer incorporating a glassy amorphous matrix based on a
perfluoro(2-methylene-4-methyl-1,3-dioxolane) (PFMMD) backbone. The novel
backbone chemistry induces structural changes in the ionomer, restricting
ionomer domain swelling under hydration while disrupting matrix crystallinity.
These structural changes slightly reduce proton conductivity while
significantly improving gas permeability. The performance implications of this
tradeoff are assessed, which reveal the potential for substantial performance
improvement by incorporation of highly permeable ionomers as the functional catalyst
binder. These results underscore the significance of tailoring material chemistry
to specific device requirements, where ionomer chemistry should be rationally
designed to match the local transport requirements of the device architecture.</p