Imaging sediment structure: the emerging use of Magnetic Resonance Imaging (MRI) for 3D analysis of sediment structures and internal flow processes

Magnetic Resonance Imaging (MRI) can be used for 3D analysis of small-scale porous media structure and internal flow-related processes. It offers notable advantages over traditional sediment sampling (e.g. cores or surface-based scanning) as it is capable of high spatio-temporal resolution of the full 3D volume, including the sub-surface. Similarly, compared to X-Ray tomography, the extensive catalogue of MR pulse sequences typically provides: faster capture for imaging dynamic fluid processes; greater flexibility in resolving chemical species or tracers; and a safer radiation-free methodology. To demonstrate the relevance of this technique in geomorphological research, three exemplar applications are described: porous media structure of gravel bed rivers; measurements of fluid processes within aquifer pores and fractures; and, concentration mapping of contaminants through sand/gravel frameworks. Whilst, this emerging technique offers significant potential for visualizing many other ‘black-box’ processes important to the wider discipline, attention is afforded to discussion of the present constraints of the technique in field-based analysis

Characterization of nanoparticle transport through quartz and dolomite gravels by magnetic resonance imaging

Magnetic resonance imaging (MRI) has tremendous potential for revealing transport processes in engineered and geologic systems. Here, we utilize MRI to image nanoparticle (NP) transport through a saturated coarse-grained system. Commercially available paramagnetically tagged NPs are used; the paramagnetic tag making the NP visible to MRI. NP transport was imaged as NPs migrated through packed columns of quartz and dolomite gravel. Changes in T2-weighted image intensity were calibrated to provide fully quantitative maps of NP concentration at regular time intervals (T 2 being the spin–spin relaxation time of 1H nuclei). Transport of nanoparticles was significantly retarded in dolomite compared to quartz due to electrostatic attraction between nanoparticle and dolomite surfaces. NP concentration profiles were evaluated with the CXTFIT computer package to estimate nanoparticle transport parameters at multiple points along the length of the column. This provided temporally resolved parameters that standard breakthrough curve analysis cannot provide. Particle–surface interaction energy profiles were described through Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. While dispersion coefficients and fast deposition rate constant (k fast) were found to increase with distance, deposition rate constant (k) and collision efficiency (α) were found to decrease with distance. These length-dependant variations have significant scaling-up implications for transport models used to predict NP transport in natural and engineered coarse-grained systems, such as sustainable urban drainage systems and river beds

Atherosclerotic carotid plaque composition: a 3T and 7T MRI-histology correlation study

Background and Purpose Carotid artery atherosclerotic plaque composition may influence plaque stability and risk of thromboembolic events, and non-invasive plaque imaging may therefore permit risk stratification for clinical management. Plaque composition was compared using non-invasive in-vivo (3T) and ex-vivo (7T) MRI and histopathological examination. Methods Thirty three endarterectomy cross sections, from 13 patients, were studied. The datasets consisted of in-vivo 3T MRI, ex-vivo 7T MRI and histopathology. Semi-automated segmentation methods were used to measure areas of different plaque components. Bland- Altman plots and mean difference with 95% confidence interval were carried out. Results There was general quantitative agreement between areas derived from semi-automated segmentation of MRI data and histology measurements. The mean differences and 95% confidence bounds in the relative to total plaque area between 3T versus Histology were: fibrous tissue 4.99 % (-4.56 to 14.56), lipid-rich/necrotic core (LR/NC) with haemorrhage - 1.81% (-14.11 to 10.48), LR/NC without haemorrhage -2.43% (-13.04 to 8.17), and calcification -3.18% (-11.55 to 5.18). The mean differences and 95% confidence bounds in the relative to total plaque area between 7T and histology were: fibrous tissue 3.17 % (-3.17 to 9.52), LR/NC with haemorrhage -0.55% (-9.06 to 7.95), LR/NC without haemorrhage - 12.62% (-19.8 to -5.45), and calcification -2.43% (-9.97 to 4.73). Conclusions This study provides evidence that semi-automated segmentation of 3T/7T MRI techniques can help to determine atherosclerotic plaque composition. In particular, the high resolution of ex-vivo 7T data was able to highlight greater detail in the atherosclerotic plaque composition. High field MRI may therefore have advantages for in vivo carotid plaque MR imaging

Sustaining productivity of a Vertisol at Warra, Queensland, with fertilisers, no-tillage, or legumes. 5. Wheat yields, nitrogen benefits and water-use efficiency of chickpea-wheat rotation

In this study, the benefits of chickpea–wheat rotation compared with continuous wheat cropping (wheat–wheat rotation) were evaluated for their effects on soil nitrate nitrogen, wheat grain yields and grain protein concentrations, and water-use efficiency at Warra, southern Queensland from 1988 to 1996. Benefits in terms of wheat grain yields varied, from 17% in 1993 to 61% in 1990, with a mean increase in grain yield of 40% (825 kg/ha). Wheat grain protein concentration increased from 9.4% in a wheat–wheat rotation to 10.7% in a chickpea–wheat rotation, almost a 14% increase in grain protein. There was a mean increase in soil nitrate nitrogen of 35 kg N/ha.1.2 m after 6 months of fallow following chickpea (85 kg N/ha) compared with continuous wheat cropping (50 kg N/ha). This was reflected in additional nitrogen in the wheat grain (20 kg N/ha) and above-ground plant biomass (25 kg N/ha) following chickpea. Water-use efficiency by wheat increased from a mean value of 9.2 kg grain/ha. mm in a wheat–wheat rotation to 11.7 kg grain/ha.mm in a chickpea–wheat rotation. The water-use efficiency values were closely correlated with presowing nitrate nitrogen, and showed no marked distinction between the 2 cropping sequences. Although presowing available water in soil in May was similar in both the chickpea–wheat rotation and the wheat–wheat rotation in all years except 1996, wheat in the former used about 20 mm additional water and enhanced water-use efficiency. Thus, by improving soil fertility through restorative practices such as incorporating chickpea in rotation, water-use efficiency can be enhanced and consequently water runoff losses reduced. Furthermore, beneficial effects of chickpea in rotation with cereals could be enhanced by early to mid sowing (May–mid June) of chickpea, accompanied by zero tillage practice. Wheat of ‘Prime Hard’ grade protein (≥13%) could be obtained in chickpea–wheat rotation by supplementary application of fertiliser N to wheat. In this study, incidence of crown rot of wheat caused by Fusarium graminearum was negligible, and incidence and severity of common root rot of wheat caused by Bipolaris sorokiniana were essentially similar in both cropping sequences and inversely related to the available water in soil at sowing. No other soil-borne disease was observed. Therefore, beneficial effects of chickpea on wheat yields and grain protein were primarily due to additional nitrate nitrogen following the legume crop and consequently better water-use efficiency

Acute inhibition of MEK suppresses congenital melanocytic nevus syndrome in a murine model driven by activated NRAS and Wnt signaling

Congenital melanocytic nevus (CMN) syndrome is the association of pigmented melanocytic nevi with extra-cutaneous features, classically melanotic cells within the central nervous system, most frequently caused by a mutation of NRAS codon 61. This condition is currently untreatable and carries a significant risk of melanoma within the skin, brain, or leptomeninges. We have previously proposed a key role for Wnt signaling in the formation of melanocytic nevi, suggesting that activated Wnt signaling may be synergistic with activated NRAS in the pathogenesis of CMN syndrome. Some familial pre-disposition suggests a germ-line contribution to CMN syndrome, as does variability of neurological phenotypes in individuals with similar cutaneous phenotypes. Accordingly, we performed exome sequencing of germ-line DNA from patients with CMN to reveal rare or undescribed Wnt-signaling alterations. A murine model harboring activated NRASQ61K and Wnt signaling in melanocytes exhibited striking features of CMN syndrome, in particular neurological involvement. In the first model of treatment for this condition, these congenital, and previously assumed permanent, features were profoundly suppressed by acute post-natal treatment with a MEK inhibitor. These data suggest that activated NRAS and aberrant Wnt signaling conspire to drive CMN syndrome. Post-natal MEK inhibition is a potential candidate therapy for patients with this debilitating condition

Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles

We have made the first measurements of the virtual Compton scattering (VCS) process via the H$(e,e'p)\gamma$ exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the $W$-dependence at fixed $Q^2=1$ GeV$^2$, and for the $Q^2$-dependence at fixed $W$ near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed $Q^2$-dependence is smooth. The measured ratio of H$(e,e'p)\gamma$ to H$(e,e'p)\pi^0$ cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to Real Compton Scattering (RCS) at high energy and large angles, our VCS data at the highest $W$ (1.8-1.9 GeV) show a striking $Q^2$- independence, which may suggest a transition to a perturbative scattering mechanism at the quark level.Comment: 20 pages, 8 figures. To appear in Phys.Rev.

Communication is key: a study of the development of communication key skills in China

Different countries offer alternative curricula around what might be designated language, literacy and/or communication. This paper focuses on the latter which has typically been associated with vocational education and often labelled a ‘key’ or ‘core’ skill that forms part of a wider set of life and employability skills. In recent years, as China has emerged as a global economy, education has been significant in its policy and development. This research explores staff and student responses to the introduction of a key skills communication course in three Chinese further education vocational colleges. The initiative was prompted by research in China which had suggested that communication is important not just for education (Ye and Li 2007) but also for employability, and that the ability to communicate effectively could be instrumental in individuals’ success and development (Tong and Zhong 2008). It explores what communication key skills might mean in a Chinese context and questions notions of transferability and of competence and performance in communication. It analyses how motivation could affect learner success and the relationship of pedagogy to curriculum and, finally, it considers how communication might be an element in the longer-term social and political development of critical literacies

New insights into the genetic etiology of Alzheimer's disease and related dementias.

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Operation and performance of the ATLAS semiconductor tracker

The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74±0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, δ-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations

Measurement of the correlation between flow harmonics of different order in lead-lead collisions at √sNN = 2.76 TeV with the ATLAS detector

Correlations between the elliptic or triangular flow coefficients vm (m=2 or 3) and other flow harmonics vn (n=2 to 5) are measured using √sNN=2.76 TeV Pb+Pb collision data collected in 2010 by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 7 μb−1. The vm−vn correlations are measured in midrapidity as a function of centrality, and, for events within the same centrality interval, as a function of event ellipticity or triangularity defined in a forward rapidity region. For events within the same centrality interval, v3 is found to be anticorrelated with v2 and this anticorrelation is consistent with similar anticorrelations between the corresponding eccentricities, ε2 and ε3. However, it is observed that v4 increases strongly with v2, and v5 increases strongly with both v2 and v3. The trend and strength of the vm−vn correlations for n=4 and 5 are found to disagree with εm−εn correlations predicted by initial-geometry models. Instead, these correlations are found to be consistent with the combined effects of a linear contribution to vn and a nonlinear term that is a function of v22 or of v2v3, as predicted by hydrodynamic models. A simple two-component fit is used to separate these two contributions. The extracted linear and nonlinear contributions to v4 and v5 are found to be consistent with previously measured event-plane correlations