15 research outputs found
Kinetic Relevance of Surface Reactions and Lattice Diffusion in the Dynamics of CeāZr Oxides ReductionāOxidation Cycles
Reductionāoxidation cycles in oxides are ubiquitous
in oxygen
storage and transport, chemical looping processes, and fuel cells.
O-atom addition and removal are mediated by coupling reactions of
oxidants and reductants at surfaces with diffusion of O-atoms within
oxide crystals, with either or both processes as limiting steps. CeO2āZrO2 solid solutions (CZO) are ubiquitous
in practice. They are used here to illustrate general experimental
strategies and reactionādiffusion formalisms for nonideal systems
that enable assessments of the kinetic relevance of the steps that
mediate O-atom addition and removal in these materials; these experiments
are described within the context of models that describe the driving
forces for reaction and diffusion rigorously in terms of oxygen chemical
potentials (Ī¼O). These strategies assess the rate
consequences of varying the fluid phase redox potential, through changes
in the identity and pressures of the reactants and products used in
redox cycles (O2; CO/CO2; H2/H2O; N2O/N2), of introducing dispersed
metal nanoparticles that capture and react lattice O-atoms in CZO
using CO or H2, and of imposing intervening dwells without
reaction within redox cycles. O-removal rates depend on reductant
pressures, even when CO/CO2 and H2/H2O ratios are chosen to maintain the same surface Ī¼O if surface reactions were quasi-equilibrated. These data, taken
together with significant rate enhancements in O-removal when Pt nanoparticles
are present at CZO crystal surfaces and with similar rates before
and after inert dwells, demonstrate that reduction rates by both CO
and H2 are limited by surface reactions without the presence
of consequential spatial gradients in Ī¼O within CZO
crystals. In contrast, O-addition rates to partially reduced CZO crystals
are similar for N2O and O2 reactants and are
not affected by the presence of Pt nanoparticles; O-addition rates
are significantly higher after intervening inert dwells during CZO
oxidation, indicative of spatial gradients in Ī¼O,
which relax during nonreactive periods. These methods and models,
illustrated here for CZO redox cycles at conditions relevant to oxygen
storage practice, allow systematic assessments of the kinetic relevance
of lattice diffusion and surface reactions for systems that use solids
for the reversible storage and release of atoms, irrespective of the
identity of the solids or the atoms (e.g., O, H, N, and S)
Additional file 1: of Ć¢ĀĀThe university should promote health, but not enforce itĆ¢ĀĀ: opinions and attitudes about the regulation of sugar-sweetened beverages in a university setting
Copy of study survey. (PDF 351 kb
Facile Synthesis and Evaluation of Nanofibrous IronāCarbon Based Non-Precious Oxygen Reduction Reaction Catalysts for LiāO<sub>2</sub> Battery Applications
Development of low cost active catalysts toward oxygen
reduction
reaction (ORR) is critical for the effective operation of LiāO<sub>2</sub> battery. Porous nonprecious ironācarbon based nanofiber
catalysts have been developed by electrospinning method. The catalysts
demonstrated similar ORR catalytic activity for ORR as the commercial
Pt-based catalysts in the aqueous half-cell voltammetry sweeps. In
the LiāO<sub>2</sub> aprotic environment, the catalyst exhibited
higher on-set potentials when compared to glassy carbon and Pt disk
electrodes. The results show that the nonprecious electrospun nanofiber
could be an effective low cost ORR catalyst at the cathode for LiāO<sub>2</sub> battery
Additional files 2: of Protocol for a cluster-randomised trial to determine the effects of advocacy actions on the salt content of processed foods
Interim outcomes: examples of the types and sources of data, and measures. Description of data: description of the interim measures, examples of the types of data to be collected, the data sources, and the measure. (PDF 175ĆĀ kb
Determination of Iron Active Sites in Pyrolyzed Iron-Based Catalysts for the Oxygen Reduction Reaction
Fe-based oxygen reduction reaction (ORR) catalyst materials
are
considered promising nonprecious alternatives to traditional platinum-based
catalysts. These catalyst materials are generally produced by high-temperature
pyrolysis treatments of readily available carbon, nitrogen, and iron
sources. Adequate control of the structure and active site formation
during pyrolysis methods is nearly impossible. Thus, the chemical
nature, structure, and ORR mechanism of catalytically active sites
in these materials is a subject of significant debate. We have proposed
a method, utilizing CN<sup>ā</sup> ions as ORR inhibitors on
Fe-based catalysts, to provide insight into the exact nature and chemistry
of the catalytically active sites. Moreover, we propose two possible
catalytically active site formation mechanisms occurring during high-temperature
pyrolysis treatments, dependent on the specific type of precursor
and synthesis methods utilized. We have further provided direct evidence
of our proposed active site formations using ToF-SIMS negative and
positive ion imaging. This knowledge will be beneficial to future
work directed at the development of Fe-based catalysts with improved
ORR activity and operational stabilities for fuel cell and battery
applications
DBP-maf inhibits tumor cell migration.
<p>LNCaP (<b>A</b>), LNCaPLN3 (<b>B</b>), PC3M (<b>C</b>) or PC3MLN4 (<b>D</b>) cells were added (150,000/well) to the top chamber of a modified Boyden chamber (+/ā DBP-maf) with 10% FBS in the bottom chamber. After 6 hours cells were removed that had not migrated and remaining cells were quantitated using an acid phosphatase assay. Results were normalized to control. Experiments were performed a minimum of three times and error is shown as +/ā SD. Compared to cell growth without DBP-maf, adding DBP-maf had a statistically significant overall reduction of cell migration at 30% (Pā=ā0.0003) for the combined four tumor cell types. Individual significant reduction rates were found with each of these tumor cell types. Compared to control, significant reduction was seen with DBP-maf at (<b>A</b>) 20% Pā=ā0.0022 (<b>B</b>) 20% Pā=ā0.0029 (<b>C</b>) 10% Pā=ā.0045 (<b>D</b>) 30% Pā=ā.0094. nā=ā3.</p
DBP-maf peptide does not inhibit expression of uPAR in PC3M or LNCaPLN3 cells.
<p>LNCaPLN3 (<b>A</b>) and PC3M cells (<b>B</b>) were treated with DBP or DBP-maf (0.001 and 1 Āµg/mL) and incubated for 24 hours then harvested. RT products (cDNA), identified as uPAR1, 2, and 3, were amplified by real-time quantitative PCR. p<0.05.</p
FACS analysis of apoptosis or necrosis.
<p>Cells were treated with or without 1 Āµg/mL DBP-maf for 48 hours, propidium iodide and annexin V were added and cells were analyzed using flow cytometry. Results are representative of three experiments.</p
DBP-maf inhibits tumor cell proliferation.
<p>LNCaP (<b>A</b>), LNCaPLN3 (<b>B</b>), PC3M (<b>C</b>) or PC3MLN4 (<b>D</b>) cells were seeded in 24 well dishes overnight, then medium +/ā DBP-maf was added with 1% FBS. After 72 hours cells were quantitated using an acid phosphatase assay. Results were normalized to control. Experiments were performed a minimum of three times and error is shown as +/ā SD. Compared to control, significant reduction was seen with DBP-maf at (<b>A</b>) 50% Pā=ā0.0001 (<b>B</b>) 50% Pā=ā0.0001 (<b>C</b>) no significant reduction (<b>D</b>) 40% Pā=ā.0073. nā=ā3.</p
DBP-maf inhibits expression of uPAR in PC3M cells.
<p>PC3M, and PC3MLN4 cells were treated with DBP or DBP-maf (0.001 and 1 Āµg/mL) and incubated for 24 hours then harvested. RT products (cDNA), identified as uPAR1, 2, and 3, were amplified by real-time quantitative PCR. p<0.05.</p