Distinct spatiotemporal atrophy patterns in corticobasal syndrome are associated with different underlying pathologies.

Objective: To identify imaging subtypes of the cortico-basal syndrome (CBS) based solely on a data-driven assessment of MRI atrophy patterns, and investigate whether these subtypes provide information on the underlying pathology. Methods: We applied Subtype and Stage Inference (SuStaIn), a machine learning algorithm that identifies groups of individuals with distinct biomarker progression patterns, to a large cohort of 135 CBS cases (52 had a pathological or biomarker defined diagnosis) and 252 controls. The model was fit using volumetric features extracted from baseline T1-weighted MRI scans and validated using follow-up MRI. We compared the clinical phenotypes of each subtype and investigated whether there were differences in associated pathology between the subtypes. Results: SuStaIn identified two subtypes with distinct sequences of atrophy progression; four-repeat-tauopathy confirmed cases were most commonly assigned to the Subcortical subtype (83% of CBS-PSP and 75% of CBS-CBD), while CBS-AD was most commonly assigned to the Fronto-parieto-occipital subtype (81% of CBS-AD). Subtype assignment was stable at follow-up (98% of cases), and individuals consistently progressed to higher stages (100% stayed at the same stage or progressed), supporting the model's ability to stage progression. Interpretation: By jointly modelling disease stage and subtype, we provide data-driven evidence for at least two distinct and longitudinally stable spatiotemporal subtypes of atrophy in CBS that are associated with different underlying pathologies. In the absence of sensitive and specific biomarkers, accurately subtyping and staging individuals with CBS at baseline has important implications for screening on entry into clinical trials, as well as for tracking disease progression.

Towards Neutron Capture on Exotic Nuclei: Demonstrating (d,pγ) as a Surrogate Reaction for (n,γ).

The neutron-capture reaction plays a critical role in the synthesis of the elements in stars and is important for societal applications including nuclear power generation and stockpile-stewardship science. However, it is difficult-if not impossible-to directly measure neutron capture cross sections for the exotic, short-lived nuclei that participate in these processes. In this Letter we demonstrate a new technique which can be used to indirectly determine neutron-capture cross sections for exotic systems. This technique makes use of the (d,p) transfer reaction, which has long been used as a tool to study the structure of nuclei. Recent advances in reaction theory, together with data collected using this reaction, enable the determination of neutron-capture cross sections for short-lived nuclei. A benchmark study of the ^{95}Mo(d,p) reaction is presented, which illustrates the approach and provides guidance for future applications of the method with short-lived isotopes produced at rare isotope accelerators.

Role of the Δ Resonance in the Population of a Four-Nucleon State in the

The ^{54}Fe nucleus was populated from a ^{56}Fe beam impinging on a Be target with an energy of E/A=500 MeV. The internal decay via γ-ray emission of the 10^{+} metastable state was observed. As the structure of this isomeric state has to involve at least four unpaired nucleons, it cannot be populated in a simple two-neutron removal reaction from the ^{56}Fe ground state. The isomeric state was produced in the low-momentum (-energy) tail of the parallel momentum (energy) distribution of ^{54}Fe, suggesting that it was populated via the decay of the Δ^{0} resonance into a proton. This process allows the population of four-nucleon states, such as the observed isomer. Therefore, it is concluded that the observation of this 10^{+} metastable state in ^{54}Fe is a consequence of the quark structure of the nucleons.

Downward migration of radiocaesium in organic soils across a transect in Scotland.

Following the accident at the Chernobyl nuclear power plant in 1986, radioactive materials including (137)Cs were distributed over large parts of the former Soviet Union and Europe. Due to the relatively long physical half-life of (137)Cs (30.1 y) measurable activity concentrations can still be observed in the natural environment. We have determined the depth distribution of (137)Cs from the testing of nuclear weapons in the atmosphere and Chernobyl, in eight highly-organic soils along an approximately east to west transect across the Central Highlands of Scotland. The (137)Cs activity concentrations in the soil profiles, corrected for radioactive decay to May 1986, were between 2.8 and 14.4 kBq m(-2). There were differences in the pattern of distribution of (137)Cs in the soil profiles. The mean migration depth of (137)Cs in the soil profiles was 12.2 cm with a range between 8.2 and 17.4 cm. Quantitative mineralogical analysis of the ash obtained after heating the soil to 400 °C indicated that clay minerals alone did not have a prime role in controlling the migration of (137)Cs down the profile.

Effect of clay content and wetting-and-drying on radiocaesium behaviour in a peat and a peaty podzol.

The interaction of radiocaesium with peat under two moisture regimes was studied in laboratory experiments and by growing ryegrass in pot experiments to simulate changing field moisture conditions. A peat untreated and treated with 5% by weight of clay containing 46% illitic minerals, and a peaty podzol naturally containing 4.5% mineral matter on a dry weight basis were contaminated with (134)Cs and incubated. The soils were exposed to 8 wetting-and-drying cycles or kept constantly wet during 40 days. Extraction of the peat with 1 M CH(3)COONH(4) (pH 7) repeated after each wetting-and-drying cycle indicated increasing (134)Cs fixation with time of incubation. The peat treated with clay showed a much higher (134)Cs fixation than that without clay. The pot experiment with the incubated soils showed a (134)Cs transfer to ryegrass of the same order for the peaty podzol as for the peat treated with clay. For the peat untreated with clay the (134)Cs transfer to ryegrass was much greater. Wetting-and-drying the peat, with or without clay, increased the overall yield of grass and the concentration and uptake of (134)Cs over 5 consecutive harvests. K-fertilisation increased the yield of plant material (except for the peat with added clay), decreased the concentration of (134)Cs, but had no significant effect (p=0.05) on the resultant uptake of (134)Cs. Mixing clay with the surface layer of organic soils appears to be an effective means of decreasing radiocaesium transfer to field crops in fallout situations.

Soil- and plant-based countermeasures to reduce 137Cs and 90Sr uptake by grasses in natural meadows: the REDUP project.

The effectiveness of a set of soil- and plant-based countermeasures to reduce 137Cs and 90Sr transfer to plants was tested in natural meadows in the area affected by Chernobyl fallout. Countermeasures comprised the use of agricultural practices (disking + ploughing, liming and NPK fertilisation), addition of soil amendments and reseeding with a selection of grass species. Disking + ploughing was the most effective treatment, whereas the K fertiliser doses applied were insufficient to produce a significant increase in K concentration in soil solution. The application of some agricultural practices was economically justifiable for scenarios with a high initial transfer, such as 137Cs-contaminated organic soils. The use of soil amendments did not lead to a further decrease in transfer. Laboratory experiments demonstrated that this was because of their low radionuclide sorption properties. Finally, experiments examining the effect of plant species on radionuclide transfer showed that both transfer and biomass can depend on the plant species, indicating that those with high radionuclide root uptake should be avoided when reseeding after ploughing.

Determination of total and EDTA extractable metal distributions in the colloidal fraction of contaminated soils using SdFFF-ICP-HRMS.

Newly developed methods involving an on-line combination of sedimentation field-flow fractionation-inductively coupled plasma-high resolution mass spectrometry (SdFFF-ICP-HRMS) have been used to study the distributions of extractable heavy metals in a soil which had been treated with sewage sludge contaminated with Cu or Pb. The relationship of these metals with other elements in the colloidal fraction was also investigated. The colloidal fraction from the soil was obtained by repeated gravitational sedimentation and extracted with 0.11 M acetic acid, 0.1 M hydroxylamine hydrochloride, 0.05 M ethylenediaminetetraacetic acid disodium salt (EDTA) or aqua regia to assess the potential availability of the metals Cu and Pb. Large proportions of the Cu and Pb were extracted by EDTA, approaching that removed by aqua regia, whereas < 10% of the aqua regia extractable metals were removed by acetic acid and hydroxylamine chloride. The distributions of the heavy metals, the major mineral forming element (Al) and the elements forming sesquioxides (Fe and Mn) within different size classes (0.05-1 microm) of the colloidal fraction were measured using SdFFF-ICP-HRMS before and after extraction with EDTA. This information provides an insight into the composition of the colloids and the distributions of metal contaminants. In the contaminated soil colloids, the concentration of Fe, Mn and Pb is greatest in the smaller particles (<0.2 microm). In contrast, the Cu concentration is constant over the size range studied. Iron oxide surface coatings probably play a significant role in Pb adsorption on soil particles, but may be less important for Cu. The combination of selective chemical extraction, SdFFF and ICP-HRMS provides a means of determining the distribution of potentially available heavy metals within the colloidal fraction of contaminated soils.

Stable isotope dilution-mass spectrometry for determining total selenium levels in plants, soils and sewage sludges.

Quantitation of selenium in plants, soils and sludges was achieved by isotope dilution-mass spectrometry using a benchtop instrument. Samples for analysis were spiked with (76)Se isotope solution. Plant material was digested on a heating block at 150 degrees C using a mixture of nitric acid and hydrogen peroxide. Selenium in soils and sludges was released by treatment with nitric acid followed by digestion with nitric and hydrofluoric acids. Selenium in the digests was reduced to Se(IV) with hydrochloric acid and derivatised with nitro-1, 2-phenylenediamine to 5'-nitropiazselenol. Analysis by gas chromatography-mass spectrometry using selected ion monitoring was validated using certified reference materials (CRMs) and gave results within the certified range with a low standard deviation. The CRMs plant (Chinese cabbage leaves) and soil (Chinese soil) were found to contain (+/-95% confidence limits) 0.091(+/-0.007) mug g(-1) and 1.67(+/- 0.04) mug g(-1)Se respectively. The certified values were 0.083(+/-0.008) mug g(-1) and 1.56(+/-0.12) mug g(-1) respectively. The selenium content of four different freely drained acid Scottish soils under grasslands was in the range 0.5-0.8 mug g(-1) air-dried soil. Sewage sludges were found to contain measurably more selenium than the soils, and samples of three sludges taken from sites in the UK contained between 1.1 and 3.5 mug g(-1) dry matter.

Extraction of ergosterol from peaty soils and determination by high performance liquid chromatography.

The ergosterol content of soil can be used as an indicator of fungal activity. A method has been developed for the extraction and determination of ergosterol in organic soils, as part of a study to assess the correlation between fungal activity and the sequestration of metal pollutants. The moisture content of the soil affected the extraction process. Four consecutive extractions with methanol removed >95% of the ergosterol that can be obtained from the fresh sample (63% moisture) by exhaustive extraction. By freeze drying the soils prior to extraction (a) up to 35% more ergosterol was extracted after a single extraction, (b) >90% of the recoverable ergosterol was collected in two extractions and (c) the repeatability of the extraction was improved. Storage of soil extracts in the absence of light prevents degradation of ergosterol. A previously reported method for determination of ergosterol by HPLC has been improved by modification of the eluant composition. With 46% methanol/46% acetonitrile/8% dichloromethane, ergosterol was eluted with good resolution approximately 8 min after injection of 20 mul of the extract. The detection limit of the HPLC method was 0.5 mug/ml ergosterol, equivalent to 0.06 mug/g in 25 g fresh soil. Changes in ergosterol contents of peaty soil treated with fungicide, and in samples of the peaty podzol and a humus iron podzol in the vicinity of fungal fruiting bodies, have been determined.

Determination of dissolved organic phosphorus in soil solutions by an improved automated photo-oxidation procedure.

An improved automated photo-oxidation procedure to determine dissolved organic phosphorus in soil solutions is described. Organically combined phosphorus is converted quantitatively to orthophosphate under UV radiation and an excess of dissolved oxygen. The orthophosphate is determined spectrophotometrically using the Murphy and Riley procedure, modified by increasing the concentration of ascorbic acid. Fluoride was added to the system to overcome potential interference when working with soil solution. The limit of detection was 0.64 mug/l. PO(4)(-3) -P and calibration was linear over the range studied (5-1000 mug/l. PO(4)(-3) -P).

Acquisition and analysis of GFAAS data.

Since its inception as an analytical technique some 30 years ago atomic absorption spectrometry has become a firmly established method for the analysis of trace metals. Graphite furnace atomic absorption spectrometry provides the analyst with the capability of analysis of solutions containing mug l(-1) levels of the analyte, but, because of the transient nature of the signals, a sophisticated approach to the data aquisition and handling of data is required. Most modern commercial graphite furnace atomic absorption spectrometers have built in microprocessors for this purpose but they often have limited capability for extensible user programs and limited data storage facilities. In this communication we describe the use of an Apple IIe microcomputer for the acquisition of data from a Pye Unicam SP9 graphite furnace atomic absorption spectrometer. Details of the interface which utilizes an in-house designed AD converter, and an overview of the Pascal and assembler programs employed are given. The system allows the user to record, store and dump the graphical display of the furnace signalsfor all analyses performed. Files containing details of peak height, and area are formatted on an eight-column spreadsheet. Details of sample type, concentrations of standards, dilutions and replication are entered from the keyboard. The calibration graph is constructed using a moving quadratic fit routine and the concentrations of the analyte in unknown solutions calculated. In addition to this, greater processing power and integration of the data into other analytical schemes can be achieved by exporting the data to other software packages and computers. Details of data transfer between the Apple IIe and an Amstrad PC 1512 are given. Some examples of the use of the system in the development of an analytical methodfor silver in plant material are given.