Variability and trends in stratospheric NO2 in Antarctic summer, and implications for stratospheric NOy

NO2 measurements during 1990-2007, obtained from a zenith-sky spectrometer in the Antarctic, are analysed to determine the long-term changes in NO2. An atmospheric photochemical box model and a radiative transfer model are used to improve the accuracy of determination of the vertical columns from the slant column measurements, and to deduce the amount of NOy from NO2. We find that the NO2 and NOy columns in midsummer have large inter-annual variability superimposed on a broad maximum in 2000, with little or no overall trend over the full time period. These changes are robust to a variety of alternative settings when determining vertical columns from slant columns or determining NOy from NO2. They may signify similar changes in speed of the Brewer-Dobson circulation but with opposite sign, i.e. a broad minimum around 2000. Multiple regressions show significant correlation with solar and quasi-biennial-oscillation indices, and weak correlation with El Nino, but no significant overall trend, corresponding to an increase in Brewer-Dobson circulation of 1.4+/-3.5%/decade. There remains an unexplained cycle of amplitude and period at least 15% and 17 years, with minimum speed in about 2000

Modelling uncertainty in brain fibre orientation from diffusion-weighted magnetic resonance imaging.

Diffusion-weighted magnetic resonance imaging (DW-MRI) permits in-vivo measurements of water diffusion, from which we can infer the orientation of white matter fibres in the brain. We show that by ordering the measurements, we can improve the reproducibility of the fibre-orientation estimate from partially-completed DW-MRI scans, without altering the complete data set. Tractography methods reconstruct entire fibre pathways from the local fibre-orientation estimates. Because the local fibre-orientation measurements are subject to uncertainty, the reconstructed fibre pathways are best described with a probabilistic algorithm. One way to estimate the connection probabilities is by defining a probability density function (PDF) in each voxel, and sampling from the PDF in a Monte-Carlo fashion. We propose new models of the PDF based on standard spherical statistical methods. The models improve previous work by closely modelling the dispersion of repeated noisy estimates of the fibre orientation. We compare a simple PDF (the Watson PDF) that models circular cluster of axes to a more general PDF (the Bingham PDF) that models circular or elliptical clusters of axes. We also propose models of the PDF in regions of crossing fibres, where there are two distinct fibre populations in the voxel. We validate the PDFs by comparing them to the uncertainty in fibre orientation calculated from bootstrap resampling of a repeated brain MR acquisition. We find mat the Bingham PDF produces connection probabilities that are closer to the bootstrap results man the Watson PDF. We use the new PDF models to perform a connectivity-based segmentation of the corpus callosum in eight different subjects. The results are similar to those of previous studies on corpus callosum connectivity, despite the use of finer cortical labelling, suggesting that the dominant connections from the corpus callosum project to the superior frontal gyrus, the superior parietal gyrus and the occipital gyrus

Historical abundance and distribution of the native flat oyster (Ostrea angasi) in estuaries of the Great Southern region of Western Australia help to prioritise potential sites for contemporary oyster reef restoration

Reefs of the flat oyster (Ostrea angasi) were once common along the southern coasts of Australia. Historical and current literature relating to O. angasi was used to identify bays and estuaries where this species once existed. In many estuaries of Western Australia, current populations are significantly lower than historical levels, including in Princess Royal Harbour and Oyster Harbour, near Albany. The main causes of the declines included overfishing, combined with the use of destructive fishing methods, such as dredging. Other factors, such as sedimentation, increased nutrient input and loss of seagrass, may have contributed to the loss of oyster reefs, and may have inhibited effective recovery. The possible impact of the protozoan pathogen Bonamia exitiosa is uncertain, although it is known to have severely affected flat oyster populations in other parts of the world. The fact that O. angasi reefs in Oyster Harbour did not recover after the fishery ceased suggests that restoration activities, aimed at restarting the ecosystem services that the oyster reefs once provided, should be undertaken. This paper suggests that the historical presence of O. angasi could be an effective starting point for prioritising potential restoration sites and details the prioritisation protocol that was used in recent restoration activities

Diamond like carbon coatings for potential application in biological implants – a review

Production of wear debris has been linked to the failure of numerous hip implants. With the current focus on increasing the implant longevity, thus wear and corrosion resistance is important. Hard coatings have the potential to reduce the wear and corrosion. Diamond like Carbon (DLC) coatings exhibit properties that could make them viable for implants. This paper critically reviews previously published research into usage of DLC coatings for implants. Overall DLCs seem to be an effective coating for implants but with the variance in results, further testing is required for clarification of us

MECHANICAL AND THERMAL DESIGN CONSIDERATIONS FOR RADIOACTIVE WASTEREPOSITORIES IN HARD ROCK

This report is one of a series documenting the results of the Swedish-American cooperative research program in which the cooperating scientists explore the geological, geophysical, hydrological, geochemical, and structural effects anticipated from the use of a large crystalline rock mass as a geologic repository for nuclear waste. This paper is broken down into the following 2 parts: (1) An appraisal of hard rock for potential underground repositories of radioactive waste; and (2) In situ heating experiments in hard rock--Their objectives and design

Critical Behavior of a Three-State Potts Model on a Voronoi Lattice

We use the single-histogram technique to study the critical behavior of the three-state Potts model on a (random) Voronoi-Delaunay lattice with size ranging from 250 to 8000 sites. We consider the effect of an exponential decay of the interactions with the distance,$J(r)=J_0\exp(-ar)$, with $a>0$, and observe that this system seems to have critical exponents $\gamma$ and $\nu$ which are different from the respective exponents of the three-state Potts model on a regular square lattice. However, the ratio $\gamma/\nu$ remains essentially the same. We find numerical evidences (although not conclusive, due to the small range of system size) that the specific heat on this random system behaves as a power-law for $a=0$ and as a logarithmic divergence for $a=0.5$ and $a=1.0$Comment: 3 pages, 5 figure

Quantifying MCPA load pathways at catchment scale using high temporal resolution data

Publication history: Accepted - 21 May 2022; Published online - 24 May 2022.Detection of the agricultural acid herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid) in drinking water source catchments is of growing concern, with economic and environmental implications for water utilities and wider ecosystem services. MCPA is poorly adsorbed to soil and highly mobile in water, but hydrological pathway processes are relatively unknown at the catchment scale and limited by coarse resolution data. This understanding is required to target mitigation measures and to provide a framework to monitor their effectiveness. To address this knowledge gap, this study reports findings from river discharge and synchronous MCPA concentration datasets (continuous 7 hour and with additional hourly sampling during storm events) collected over a 7 month herbicide spraying season. The study was undertaken in a surface (source) water catchment (384 km2—of which 154 km2 is agricultural land use) in the cross-border area of Ireland. Combined into loads, and using two pathway separation techniques, the MCPA data were apportioned into event and baseload components and the former was further separated to quantify a quickflow (QF) and other event pathways. Based on the 7 hourly dataset, 85.2 kg (0.22 kg km 2 by catchment area, or 0.55 kg km 2 by agricultural area) of MCPA was exported from the catchment in 7 months. Of this load, 87.7 % was transported via event flow pathways with 72.0 % transported via surface dominated (QF) pathways. Approximately 12 % of the MCPA load was transported via deep baseflows, indicating a persistence in this delayed pathway, and this was the primary pathway condition monitored in a weekly regulatory sampling programme. However, overall, the data indicated a dominant acute, storm dependent process of incidental MCPA loss during the spraying season. Reducing use and/or implementing extensive surface pathway disconnection measures are the mitigation options with greatest potential, the success of which can only be assessed using high temporal resolution monitoring techniques.This work was carried out as part of Source to Tap (IVA5018), a project supported by the European Union’s INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB)

Projected increases in potential groundwater recharge and reduced evapotranspiration under future climate conditions in West Africa

Study region West Africa, with a focus between 5°W and 5°E. Study focus The effects of changing climate and CO2 concentration (RCP8.5 between 2000 and 2100) on the West African monsoon are examined using the UPSCALE high-resolution (25 km) global climate model ensembles for present and future climate, combined with the JULES land-surface model. New hydrological insights Future climate is predicted to have an enhanced summertime Saharan heat low, changing large-scale circulation, causing monsoon rainfall generally to increase. The monsoon progresses further inland and occurs later in the year. UPSCALE rainfall projections indicate that the eastern Sahel becomes wetter (+ 12.2%) but the western Sahel drier (− 13.5%). Future evapotranspiration is reduced across most of West Africa due to the CO2 fertilisation effect causing lower transpiration. Potential groundwater recharge (soil drainage at the bottom of a 3 m deep soil column), is predicted to increase from 0% to 16% of rainfall under present climate, to 1–20% in the future, doubling from ~ 5% to ~ 10% in northern Ghana and the eastern Sahel. Potential recharge increases largely due to increased soil hydraulic conductivity, caused by higher soil moisture resulting from increased rainfall and reduced transpiration. Other factors have only a minor influence on the water balance and potential recharge, including rainfall intensity and land use type. A predicted increase in future potential groundwater recharge is significant as development of groundwater resources is seen as a key means to meet growing water demand in West Africa

The role of alkalinity generation in controlling the fluxes of CO₂ during exposure and inundation on tidal flats

Dissolved inorganic carbon (DIC), gaseous CO2 and alkalinity fluxes from intertidal sediments were investigated during periods of exposure and inundation, using laboratory core incubations, previously published field data and reactive transport model simulations. In the incubations and previous field data, it was found that during periods of alkalinity production (attributed to the accumulation of reduced sulfur species within the sediment), the flux of DIC out of the sediment was greater during inundation than the gaseous CO2 flux during exposure by a factor of up to 1.8. This finding was supported by computational simulations which indicated that large amounts of sulfate reduction and reduced sulfur burial (FeS) induce an alkalinity flux from the sediment during high tide conditions. Model simulations also found that the amount of reactive Fe in the sediment was a major driver of net alkalinity production. Our finding that CO2 fluxes can be significantly lower than total metabolism during exposure has implications for how total metabolism is quantified on tidal flats

Disease-specific, neurosphere-derived cells as models for brain disorders

There is a pressing need for patient-derived cell models of brain diseases that are relevant and robust enough to produce the large quantities of cells required for molecular and functional analyses. We describe here a new cell model based on patient-derived cells from the human olfactory mucosa, the organ of smell, which regenerates throughout life from neural stem cells. Olfactory mucosa biopsies were obtained from healthy controls and patients with either schizophrenia, a neurodevelopmental psychiatric disorder, or Parkinson's disease, a neurodegenerative disease. Biopsies were dissociated and grown as neurospheres in defined medium. Neurosphere-derived cell lines were grown in serum-containing medium as adherent monolayers and stored frozen. By comparing 42 patient and control cell lines we demonstrated significant disease-specific alterations in gene expression, protein expression and cell function, including dysregulated neurodevelopmental pathways in schizophrenia and dysregulated mitochondrial function, oxidative stress and xenobiotic metabolism in Parkinson's disease. The study has identified new candidate genes and cell pathways for future investigation. Fibroblasts from schizophrenia patients did not show these differences. Olfactory neurosphere-derived cells have many advantages over embryonic stem cells and induced pluripotent stem cells as models for brain diseases. They do not require genetic reprogramming and they can be obtained from adults with complex genetic diseases. They will be useful for understanding disease aetiology, for diagnostics and for drug discovery