Using hysteresis analysis of high-resolution water quality monitoring data, including uncertainty, to infer controls on nutrient and sediment transfer in catchments

A large proportion of nutrients and sediment is mobilised in catchments during storm events. Therefore understanding a catchment's hydrological behaviour during storms and how this acts to mobilise and transport nutrients and sediment to nearby watercourses is extremely important for effective catchment management. The expansion of available in-situ sensors is allowing a wider range of water quality parameters to be monitored and at higher temporal resolution, meaning that the investigation of hydrochemical behaviours during storms is increasingly feasible. Studying the relationship between discharge and water quality parameters in storm events can provide a valuable research tool to infer the likely source areas and flow pathways contributing to nutrient and sediment transport. Therefore, this paper uses 2years of high temporal resolution (15/30min) discharge and water quality (nitrate-N, total phosphorus (TP) and turbidity) data to examine hysteretic behaviour during storm events in two contrasting catchments, in the Hampshire Avon catchment, UK. This paper provides one of the first examples of a study which comprehensively examines storm behaviours for up to 76 storm events and three water quality parameters. It also examines the observational uncertainties using a non-parametric approach. A range of metrics was used, such as loop direction, loop area and a hysteresis index (HI) to characterise and quantify the storm behaviour. With two years of high resolution information it was possible to see how transport mechanisms varied between parameters and through time. This study has also clearly shown the different transport regimes operating between a groundwater dominated chalk catchment versus a surface-water dominated clay catchment. This information, set within an uncertainty framework, means that confidence can be derived that the patterns and relationships thus identified are statistically robust. These insights can thus be used to provide information regarding transport processes and biogeochemical processing within river catchments

Cardiac 123I-MIBG planar heart to mediastinum ratios depend on patient size; phantom studies suggest SPECT-CT could improve quantification.

INTRODUCTION: Planar 123I-MIBG (meta-iodobenzylguanidine) cardiac imaging is listed as an indicative biomarker in the 2017 international consensus criteria for the diagnosis of dementia with Lewy bodies. There has been very little research into the relationship between apparent cardiac uptake and patient size, or in the possible advantage of attenuation and scatter corrected SPECT-CT compared to planar imaging. We aimed to evaluate this in both a chest phantom and in older adults with normal cognition. MATERIALS AND METHODS: An anthropomorphic chest phantom was filled with 123I solution using activities typical of healthy subjects. The phantom was scanned on a Siemens Intevo gamma camera with MELP collimators using both planar and SPECT-CT techniques. Further scans were acquired with a PMMA chest plate added, then water filled plastic breasts. The SPECT-CT images were reconstructed using a resolution recovery OSEM method with and without attenuation and scatter correction (ACSC) applied. Twenty-nine adults over 60 years of age (mean 75.2 ± 8.3 years) underwent planar cardiac MIBG imaging, followed by SPECT-CT. SPECT images were reconstructed as above. Heart-to-mediastinum ratios (HMRs) were calculated for planar and SPECT images. RESULTS: Phantom planar HMR decreased by 20% with the PMMA chest plate added; 39% with plate and breasts. ACSC SPECT cardiac counts showed less dependence on phantom size than SPECT without ACSC (3% versus 37%). The body mass indices (BMI) of the older adults ranged from 22 to 38. There was a significant linear relationship between planar HMR and BMI (R2 = 0.44, p<0.01), but not for ACSC SPECT. However, there was no significant difference between the slopes for planar and ACSC SPECT (p = 0.11). CONCLUSION: Planar cardiac 123I-MIBG HMR results are correlated with BMI. Phantom results suggest that ACSC SPECT can correct for patient size. A large patient population or clinical database would be required to demonstrate a clinical effect

A comparison of visual and semiquantitative analysis methods for planar cardiac 123I-MIBG scintigraphy in dementia with Lewy bodies.

OBJECTIVES: Cardiac I-MIBG imaging is an established technique for the diagnosis of dementia with Lewy bodies but various analysis methods are reported in the literature. We assessed different methods in the same cohort of patients to inform best practice. PATIENTS AND METHODS: Seventeen patients with dementia with Lewy bodies, 15 with Alzheimer's disease and 16 controls were included. Planar images were acquired 20 min and 4 h after injection. Nine operators produced heart-to-mediastinum ratios (HMRs) using freehand and 6, 7 and 8 cm diameter circular cardiac regions. Interoperator variation was measured using the coefficient of variation. HMR differences between methods were assessed using analysis of variance. Seven raters assessed the images visually. Accuracy was compared using receiver operating characteristic analysis. RESULTS: There were significant differences in HMR between region methods (P=0.006). However, with optimised cut-offs there was no significant difference in accuracy (P=0.2-1.0). The sensitivity was 65-71% and specificity 100% for all HMR methods. Variation was lower with fixed regions than freehand (P<0.001). Visual rating sensitivity and specificity were 65 and 77% on early images and 76 and 71% on delayed images. There was no significant difference in HMR between early and delayed images (P=0.4-0.7) although a greater separation between means was seen on delayed images (0.73 vs. 0.95). CONCLUSION: HMR analysis using a suitable cut-off is more accurate than visual rating. Accuracy is similar for all methods, but freehand regions are more variable and 6 cm circles easiest to place. We recommend calculating HMR using a 6 cm circular cardiac region of interest on delayed images

18F-FDG PET and perfusion SPECT in the diagnosis of Alzheimer and Lewy body dementias.

UNLABELLED: Brain imaging with glucose ((18)F-FDG) PET or blood flow (hexamethylpropyleneamine oxime) SPECT is widely used for the differential diagnosis of dementia, though direct comparisons to clearly establish superiority of one method have not been undertaken. METHODS: Subjects with Alzheimer disease (AD; n = 38) and dementia with Lewy bodies (DLB; n = 30) and controls (n = 30) underwent (18)F-FDG PET and SPECT in balanced order. The main outcome measure was area under the curve (AUC) of receiver-operating-characteristic analysis of visual scan rating. RESULTS: Consensus diagnosis with (18)F-FDG PET was superior to SPECT for both dementia vs. no-dementia (AUC = 0.93 vs. 0.72, P = 0.001) and AD vs. DLB (AUC = 0.80 vs. 0.58, P = 0.005) comparisons. The sensitivity and specificity for dementia/no-dementia was 85% and 90%, respectively, for (18)F-FDG PET and 71% and 70%, respectively, for SPECT. CONCLUSION: (18)F-FDG PET was significantly superior to blood flow SPECT. We recommend (18)F-FDG PET be performed instead of perfusion SPECT for the differential diagnosis of degenerative dementia if functional imaging is indicated.We thank the Dementia and Neurodegenerative Diseases Research Network (DeNDRoN) for valuable support with clinical recruitment. We also thank the National Institute for Health Research.This research was originally published in JNM. O’Brien JT, Firbank MJ, Davison C, Barnett N, Bamford C, Donaldson C, Olsen K, Herholz K, Williams D, Lloyd J. 18F-FDG PET and Perfusion SPECT in the Diagnosis of Alzheimer and Lewy Body Dementias. JNM. 2014;55:1959–1965. © by the Society of Nuclear Medicine and Molecular Imaging, Inc

High-resolution monitoring of catchment nutrient response to the end of the 2011-2012 drought in England, captured by the demonstration test catchments.

The Demonstration Test Catchments (DTC) project is a UK Government funded initiative to test the effectiveness of on-farm mitigation measures designed to reduce agricultural pollution without compromising farm productivity. Three distinct catchments in England have been chosen to test the efficacy of mitigation measures on working farms in small tributary sub-catchments equipped with continuous water quality monitoring stations. The Hampshire Avon in the south is a mixed livestock and arable farming catchment, the River Wensum in the east is a lowland catchment with predominantly arable farming and land use in the River Eden catchment in the north-west is predominantly livestock farming. One of the many strengths of the DTC as a national research platform is that it provides the ability to investigate catchment hydrology and biogeochemical response across different landscapes and geoclimatic characteristics, with a range of differing flow behaviours, geochemistries and nutrient chemistries. Although numerous authors present studies of individual catchment responses to storms, no studies exist of multiple catchment responses to the same rainfall event captured with in situ high-resolution nutrient monitoring at a national scale. This paper brings together findings from all three DTC research groups to compare the response of the catchments to a major storm event in April 2012. This was one of the first weather fronts to track across the country following a prolonged drought period affecting much of the UK through 2011–2012, marking an unusual meteorological transition when a rapid shift from drought to flood risk occurred. The effects of the weather front on discharge and water chemistry parameters, including nitrogen species (NO3-N and NH4-N) and phosphorus fractions (total P (TP) and total reactive P (TRP)), measured at a half-hourly time step are examined. When considered in the context of one hydrological year, flow and concentration duration curves reveal that the weather fronts resulted in extreme flow, nitrate and TP concentrations in all three catchments but with distinct differences in both hydrographs and chemographs. Hysteresis loops constructed from high resolution data are used to highlight an array of potential pollutant sources and delivery pathways. In the Hampshire Avon DTC, transport was dominated by sub-surface processes, where phosphorus, largely in the soluble form, was found to be transport-limited. In the Wensum DTC, transport was largely dominated by rapid sub-surface movement due to the presence of under-drainage, which mobilised large quantities of nitrate during the storm. In the Eden DTC, transport was found to be initially dominated by surface runoff, which switched to subsurface delivery on the falling limb of the hydrograph, with the surface delivery transporting large amounts of particulate phosphorus to the river, with a transport-limited response. The lack of exhaustion of nutrient delivery in response to such extreme flow generation indicates the size of the nutrient pools stored in these catchments, and highlights the scale of the challenges faced by environmental managers when designing mitigation measures to reduce the flux of nutrients to UK river systems from diffuse agricultural sources

Microstructural evolution and transmutation in tungsten under ion and neutron irradiation

This study aims to compare the effects of neutron and self-ion irradiation on the mechanical properties and microstructural evolution in W. Neutron irradiation at the HFR reactor to 1.67 dpa at 800 °C resulted in the formation of large Re and Os rich clusters and voids. The post-irradiation composition was measured using APT and verfified against FISPACT modelling. The measured Re and Os concentration was used to create alloys with equivalent concentrations of Re and Os. These alloys were exposed to self-ion irradiation to a peak dose of 1.7 dpa at 800 °C. APT showed that self-ion irradiation leads to the formation of small Os clusters, wheras under neutron irradiation large Re/Os clusters form. Voids are formed by both ion and neutron irradiation, but the voids formed by neutron irradiation are larger. By comparing the behaviour of W-1.4Re and W-1.4Re-0.1Os, suppression of Re cluster formation was observed. Irradiation hardening was measured using nanoindentation and was found to be 2.7 GPa, after neutron irradiation and 1.6 GPa and 0.6 GPa for the self-ion irradiated W-1.4Re and W-1.4Re-0.1Os. The higher hardening is attributed to the barrier strength of large voids and Re/Os clusters that are observed after neutron irradiation

In vivo nucleus basalis of Meynert degeneration in mild cognitive impairment with Lewy bodies.

OBJECTIVES: To investigate in vivo degeneration of the cholinergic system in mild cognitive impairment with Lewy bodies (MCI-LB), we studied nucleus basalis of Meynert (NBM) volumes from structural MR images and its relation to EEG slowing and cognitive impairment. METHODS: We studied the NBM using structural MR images in 37 patients with MCI-LB, 34 patients with MCI with Alzheimer's disease (MCI-AD), and 31 healthy control participants. We also tested correlations between NBM volumes and measures of overall cognition and measures of EEG slowing in the MCI groups. RESULTS: Overall NBM volume was reduced in MCI-LB compared to controls with no significant difference between MCI-AD and controls or between the two MCI groups. The voxel-wise analysis revealed bilateral clusters of reduced NBM volume in MCI-LB compared to controls and smaller clusters in MCI-AD compared to controls. There was a significant association between overall NBM volume and measures of overall cognition in MCI-LB, but not in MCI-AD. In both MCI groups, reduced NBM volume was correlated with more severe EEG slowing. CONCLUSIONS: This study provides in vivo evidence that early cholinergic degeneration in DLB occurs at the MCI stage and is related to the severity of cognitive impairment. Furthermore, the results suggest that early EEG slowing in MCI-LB might be in part cholinergically driven. Importantly, these findings suggest an early cholinergic deficit in MCI-LB that may motivate further testing of the effectiveness of cholinesterase inhibitors in this group

Accuracy of dopaminergic imaging as a biomarker for mild cognitive impairment with Lewy bodies.

BACKGROUND: Dopaminergic imaging is an established biomarker for dementia with Lewy bodies, but its diagnostic accuracy at the mild cognitive impairment (MCI) stage remains uncertain. AIMS: To provide robust prospective evidence of the diagnostic accuracy of dopaminergic imaging at the MCI stage to either support or refute its inclusion as a biomarker for the diagnosis of MCI with Lewy bodies. METHOD: We conducted a prospective diagnostic accuracy study of baseline dopaminergic imaging with [123I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane single-photon emission computerised tomography (123I-FP-CIT SPECT) in 144 patients with MCI. Images were rated as normal or abnormal by a panel of experts with access to striatal binding ratio results. Follow-up consensus diagnosis based on the presence of core features of Lewy body disease was used as the reference standard. RESULTS: At latest assessment (mean 2 years) 61 patients had probable MCI with Lewy bodies, 26 possible MCI with Lewy bodies and 57 MCI due to Alzheimer's disease. The sensitivity of baseline FP-CIT visual rating for probable MCI with Lewy bodies was 66% (95% CI 52-77%), specificity 88% (76-95%) and accuracy 76% (68-84%), with positive likelihood ratio 5.3. CONCLUSIONS: It is over five times as likely for an abnormal scan to be found in probable MCI with Lewy bodies than MCI due to Alzheimer's disease. Dopaminergic imaging appears to be useful at the MCI stage in cases where Lewy body disease is suspected clinically