Differential electrochemical mass spectrometry (DEMS) analysis of the oxygen isotopologues produced by (18)O-labeled Co-OEC in H2(16)O reveals that water splitting catalysis proceeds by a mechanism that involves direct coupling between oxygens bound to dicobalt edge sites of Co-OEC. The edge site chemistry of Co-OEC has been probed by using a dinuclear cobalt complex. (17)O NMR spectroscopy shows that ligand exchange of OH/OH2 at Co(III) edge sites is slow, which is also confirmed by DEMS experiments of Co-OEC. In borate (Bi) and phosphate (Pi) buffers, anions must be displaced to allow water to access the edge sites for an O-O bond coupling to occur. Anion exchange in Pi is slow, taking days to equilibrate at room temperature. Conversely, anion exchange in Bi is rapid (kassoc = 13.1 ± 0.4 M(-1) s(-1) at 25 °C), enabled by facile changes in boron coordination. These results are consistent with the OER activity of Co-OEC in Bi and Pi. The Pi binding kinetics are too slow to establish a pre-equilibrium sufficiently fast to influence the oxygen evolution reaction (OER), consistent with the zero-order dependence of Pi on the OER current density; in contrast, Bi exchange is sufficiently facile such that Bi has an inhibitory effect on OER. These complementary studies on Co-OEC and the dicobalt edge site mimic allow for a direct connection, at a molecular level, to be made between the mechanisms of heterogeneous and homogeneous OER.
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http://dx.doi.org/10.1021/jacs.6b00762 | DOI Listing |
Urol Oncol
December 2024
Department of Urology, University of Texas Southwestern Medical Center, Dallas, TX.
Introduction: Utilization of neoadjuvant systemic therapy (NAT) prior to radical nephroureterectomy (RNU) for upper tract urothelial carcinoma (UTUC) is inconsistent, and optimal patient selection for NAT is unclear. The purpose of this study was to evaluate the clinical benefit of NAT in high grade UTUC undergoing RNU.
Materials And Methods: The UTUC Collaborative Network (UCAN) identified patients who underwent RNU for high grade UTUC between 2000 and 2022.
Plant Biol (Stuttg)
December 2024
Echigo-Matsunoyama Museum of Natural Science 'Kyororo', Tokamachi, Niigata, Japan.
Autumn leaf colour brightness is an important cultural ecosystem service. As its spatial patterns and ecophysiological mechanisms remain unclear, we analysed relationships among autumn leaf colour brightness, late summer chlorophyll content, and topographic position in both canopy-based micro-scale analysis and site-based macro-scale analysis. Multispectral drone observations were made in three Fagus crenata forests at elevations of 300, 600, and 900 m in Niigata Prefecture, Japan.
View Article and Find Full Text PDFSmall
December 2024
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
A mixed-ligand-based thermo-chemically robust and undulated metal-organic framework (MOF) is developed that embraces carboxamide moiety-grafted porous channels and activation-induced generation of open-metal site (OMS). The guest-free MOF acts as an outstanding heterogeneous catalyst in Hantzsch condensation for electronically assorted substrates with low catalyst loading and short duration under greener conditions than the reported materials. Besides Lewis acidic OMS, the carboxamide group activates the substrate via two-point hydrogen bonding, highlighting the effectiveness of custom-made functionalities in this multi-component reaction.
View Article and Find Full Text PDFInt J Prison Health (2024)
December 2024
UK Health Security Agency, London, UK.
Purpose: People in prison face a disproportionate risk of sexually transmitted infections (STIs), but there is a paucity of evidence on trends in STIs in prisons in England. This study aims to describe trends in chlamydia test-positivity and syphilis prevalence by using two different methodologies in prison settings.
Design/methodology/approach: This study used routinely collected chlamydia surveillance data reported by all primary diagnostic laboratories in England from 2018 to 2022 to identify tests undertaken in prisons.
J Am Chem Soc
December 2024
Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, United States.
The catalytic behavior of a material is influenced by ensembles─the geometric configuration of atoms on the surface. In conventional material systems, ensemble effects and the electronic structure are coupled because these strategies focus on varying the material composition, making it difficult to understand the role of ensembles in isolation. This study introduces a methodology that separates geometric effects from the electronic structure.
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