Observation and Simulation of Solid Sedimentary Flux: Examples From Northwest Africa

The sedimentary archive preserved at passive margins provides important clues about the evolution of continental topography. For example, histories of African uplift, erosion, and deposition of clastic sedimentary rock provide information about mantle convection. Furthermore, relating histories of uplift and erosion from regions where sediment is generated to measurements of efflux is important for understanding basin evolution and the distribution of natural resources. We focus on constraining Mesozoic to Recent solid sedimentary flux to northwest Africa's passive margin, which today is fed by rivers draining dynamically supported topography. Histories of sedimentary flux are calculated by mapping stratigraphy using seismic reflection and well data courtesy of Tullow Oil Plc and TGS. Stratigraphic ages, conversion from two-way time to depth and compaction, are parameterized using biostratigraphic and check-shot records from exploration, International Ocean Discovery Program and Deep Sea Drilling Project wells. Results indicate that Late Cretaceous to Oligocene (∼100–23 Ma) sedimentary flux decreased gradually. A slight increase in Neogene sedimentary flux is observed, which is concomitant with a change from carbonate to clastic sedimentation. Pliocene to Recent (∼5–0 Ma) flux increased by an order of magnitude. This history of sedimentary flux and facies change is similar to histories observed at other African deltas. To constrain sources of sedimentary flux, 14,700 longitudinal river profiles were inverted to calculate a history of continental uplift. These results were used to parameterize a simple “source-to-sink” model of fluvial erosion and sedimentary efflux. Results suggest that increased clastic flux to Africa's deltas from ∼30 Ma was driven by denudation induced by dynamic support

Temporal trends of cause-specific mortality after diagnosis of atrial fibrillation.

BACKGROUND AND AIMS: Reports of outcomes after atrial fibrillation (AF) diagnosis are conflicting. The aim of this study was to investigate mortality and hospitalisation rates following AF diagnosis over time, by cause, and by patient features. METHODS: Individuals aged ≥16 years with a first diagnosis of AF were identified from the UK Clinical Practice Research Datalink-GOLD dataset from Jan 1, 2001 to Dec 31, 2017. The primary outcomes were all-cause and cause-specific mortality and hospitalisation at 1 year following diagnosis. Poisson regression was used to calculate rate ratios (RRs) for mortality and incidence rate ratios (IRRs) for hospitalisation and 95% confidence intervals (CIs) comparing 2001/02 and 2016/17, adjusted for age, sex, region, socioeconomic status and 18 major comorbidities. RESULTS: Of 72 412 participants, mean (SD) age was 75.6 (12.4) years and 44 762 (61.8%) had ≥3 comorbidities. All-cause mortality declined (RR 2016/17 vs 2001/02 0.72; 95% CI 0.65-0.80), with large declines for cardiovascular (RR 0.46; 95% CI 0.37-0.58) and cerebrovascular mortality (RR 0.41; 95% CI 0.29-0.60) but not for non-cardio/cerebrovascular causes of death (RR 0.91; 95% CI 0.80-1.04). By 2016/17 deaths from dementia (67, 8.0%), outstripped deaths from acute myocardial infarction, heart failure and acute stroke combined (56, 6.7%, p < 0.001). Overall hospitalisation rates increased (IRR 2016/17 vs 2001/02 1.17; 95% CI, 1.13-1.22), especially for non-cardio/cerebrovascular causes (IRR 1.42; 95% CI 1.39-1.45). Older, more deprived, and hospital-diagnosed AF patients experienced higher event rates. CONCLUSIONS: After AF diagnosis, cardio/cerebrovascular mortality and hospitalisation has declined, whilst hospitalisation for non-cardio/cerebrovascular disease has increased

Band structure engineering of carbon nitride hybrid photocatalysts for CO2 reduction in aqueous solutions

Through the co-polymerisation of dicyandiamide and barbituric acid precursors, a series of visible light active carbon nitride photocatalysts has been prepared and characterized, and their photocatalytic activity has been evaluated. Structural and electronic characterisation has enabled variations in observed activity towards water splitting and CO2 reduction to be understood, both in the presence and absence of the iron porphyrin co-catalyst Feiii tetra(4-carboxylphenyl)porphyrin (FeTCPP). A combination of the most active carbon nitride catalyst using 5 wt% barbituric acid and FeTCPP provides a hybrid system where the alignment of band structure with appropriate reduction potentials and enhanced carrier lifetimes is capable of CO2 reduction in an aqueous solution with >60% selectivity for CO production. This study is one of only a few that achieves selective CO2 reduction using a hybrid molecular catalyst-carbon nitride photocatalyst in aqueous solution

Photochemical CO2 reduction using structurally controlled g-C3N4

Graphitic carbon nitride (g-C3N4) synthesised from a urea precursor is an excellent CO2 reduction photocatalyst using [Co(bpy)n]2+ as a co-catalyst. A five-fold increase in activity for the highly polymerised urea derived g-C3N4 is achieved compared to alternative precursors. Transient absorption, time-resolved and steady-state emission studies indicate that the enhanced activity is related to both an increased driving force for photoelectron transfer and a greater availability of photogenerated charges

Water Oxidation with Cobalt‐Loaded Linear Conjugated Polymer Photocatalysts

We report here the first examples of linear conjugated organic polymer photocatalysts that produce oxygen from water after loading with cobalt and in the presence of an electron scavenger. The oxygen evolution rates, which are higher than for related organic materials, can be rationalized by a combination of the thermodynamic driving force for water oxidation, the light absorption of the polymer, and the aqueous dispersibility of the relatively hydrophilic polymer particles. We also used transient absorption spectroscopy to study the best performing system and we found that fast oxidative quenching of the exciton occurs (picoseconds) in the presence of an electron scavenger, minimizing recombination

Time-Resolved Spectroscopy of ZnTe Photocathodes for Solar Fuel Production

The negative conduction band potential and small bandgap of ZnTe make the material a promising photoelectrode for solar fuels production, photocatalyst, and solar cell component. However, the factors controlling the underlying efficiencies of the light-driven processes on ZnTe are not well understood. Here we report a combined spectroelectrochemical and transient absorption (TA) spectroscopic investigation of ZnTe photoelectrodes for CO2 reduction. In the visible region TA spectra are dominated by a broad positive photoinduced absorption at 540 nm following initial charge carrier relaxation (1150 nm. Shallow trapped electrons are generated and accumulate at potentials where photoelectrochemical H2 evolution and CO2 reduction occur, and we show these charges are able to undergo interfacial electron transfer to an acceptor molecule. The passivation of sites related to deep traps is proposed to be the key to optimize the photocatalytic and photoelectrochemical performance of ZnTe