Structural network efficiency is associated with cognitive impairment in small-vessel disease.

To characterize brain network connectivity impairment in cerebral small-vessel disease (SVD) and its relationship with MRI disease markers and cognitive impairment.METHODS: A cross-sectional design applied graph-based efficiency analysis to deterministic diffusion tensor tractography data from 115 patients with lacunar infarction and leukoaraiosis and 50 healthy individuals. Structural connectivity was estimated between 90 cortical and subcortical brain regions and efficiency measures of resulting graphs were analyzed. Networks were compared between SVD and control groups, and associations between efficiency measures, conventional MRI disease markers, and cognitive function were tested.RESULTS: Brain diffusion tensor tractography network connectivity was significantly reduced in SVD: networks were less dense, connection weights were lower, and measures of network efficiency were significantly disrupted. The degree of brain network disruption was associated with MRI measures of disease severity and cognitive function. In multiple regression models controlling for confounding variables, associations with cognition were stronger for network measures than other MRI measures including conventional diffusion tensor imaging measures. A total mediation effect was observed for the association between fractional anisotropy and mean diffusivity measures and executive function and processing speed.CONCLUSIONS: Brain network connectivity in SVD is disturbed, this disturbance is related to disease severity, and within a mediation framework fully or partly explains previously observed associations between MRI measures and SVD-related cognitive dysfunction. These cross-sectional results highlight the importance of network disruption in SVD and provide support for network measures as a disease marker in treatment studies

Depression in small-vessel disease relates to white matter ultrastructural damage, not disability.

OBJECTIVE: To determine whether cerebral small-vessel disease (SVD) is a specific risk factor for depression, whether any association is mediated via white matter damage, and to study the role of depressive symptoms and disability on quality of life (QoL) in this patient group. METHODS: Using path analyses in cross-sectional data, we modeled the relationships among depression, disability, and QoL in patients with SVD presenting with radiologically confirmed lacunar stroke (n = 100), and replicated results in a second SVD cohort (n = 100). We then compared the same model in a non-SVD stroke cohort (n = 50) and healthy older adults (n = 203). In a further study, to determine the role of white matter damage in mediating the association with depression, a subgroup of patients with SVD (n = 101) underwent diffusion tensor imaging (DTI). RESULTS: Reduced QoL was associated with depression in patients with SVD, but this association was not mediated by disability or cognition; very similar results were found in the replication SVD cohort. In contrast, the non-SVD stroke group and the healthy older adult group showed a direct relationship between disability and depression. The DTI study showed that fractional anisotropy, a marker of white matter damage, was related to depressive symptoms in patients with SVD. CONCLUSION: These results suggest that in stroke patients without SVD, disability is an important causal factor for depression, whereas in SVD stroke, other factors specific to this stroke subtype have a causal role. White matter damage detected on DTI is one factor that mediates the association between SVD and depression

Optical absorption driven by dynamical symmetry breaking in indium oxide

Input files for the density functional theory calculations reported in the associated publication

The Kato square root problem on vector bundles with generalised bounded geometry

We consider smooth, complete Riemannian manifolds which are exponentially locally doubling. Under a uniform Ricci curvature bound and a uniform lower bound on injectivity radius, we prove a Kato square root estimate for certain coercive operators over the bundle of finite rank tensors. These results are obtained as a special case of similar estimates on smooth vector bundles satisfying a criterion which we call generalised bounded geometry. We prove this by establishing quadratic estimates for perturbations of Dirac type operators on such bundles under an appropriate set of assumptions.Comment: Slight technical modification of the notion of "GBG constant section" on page 7, and a few technical modifications to Proposition 8.4, 8.6, 8.

Structural Evolution of Electrochemically Lithiated MoS2_{2} Nanosheets and the Role of Carbon Additive in Li-Ion Batteries

Understanding the structure and phase changes associated with conversion-type materials is key to optimizing their electrochemical performance in Li-ion batteries. For example, molybdenum disulfide (MoS$_{2}$) offers a capacity up to 3-fold higher (∼1 Ah/g) than the currently used graphite anodes, but they suffer from limited Coulombic efficiency and capacity fading. The lack of insights into the structural dynamics induced by electrochemical conversion of MoS$_{2}$ still hampers its implementation in high energy-density batteries. Here, by combining $\textit{ab initio}$ density-functional theory (DFT) simulation with electrochemical analysis, we found new sulfur-enriched intermediates that progressively insulate MoS$_{2}$ electrodes and cause instability from the first discharge cycle. Because of this, the choice of conductive additives is critical for the battery performance. We investigate the mechanistic role of carbon additive by comparing equal loading of standard Super P carbon powder and carbon nanotubes (CNTs). The latter offer a nearly 2-fold increase in capacity and a 45% reduction in resistance along with Coulombic efficiency of over 90%. These insights into the phase changes during MoS$_{2}$ conversion reactions and stabilization methods provide new solutions for implementing cost-effective metal sulfide electrodes, including Li-S systems in high energy-density batteries.C.G and M.D.V acknowledge the support from ERC starting grant 337739-HIENA. A.J.M. acknowledges the support from the Winton Programme for the Physics of Sustainability. Computational resources were provided by the Cambridge High Performance Computing service. M.H.M acknowledges the support from EPSRC Cambridge NanoDTC, EP/G037221/1

Microform-scale variations in peatland permeability and their ecohydrological implications

1. The acrotelm-catotelm model of peatland hydrological and biogeochemical processes posits that the permeability of raised bogs is largely homogenous laterally but varies strongly with depth through the soil profile; uppermost peat layers are highly permeable while deeper layers are, effectively, impermeable. 2. We measured down-core changes in peat permeability, plant macrofossil assemblages, dry bulk density and degree of humification beneath two types of characteristic peatland microform – ridges and hollows – at a raised bog in Wales. Six 1424 C dates were also collected for one hollow and an adjacent ridge. 3. Contrary to the acrotelm-catotelm model, we found that deeper peat can be as highly permeable as near-surface peat and that its permeability can vary by more than an order of magnitude between microforms over horizontal distances of 1-5 metres. 4. Our palaeo-ecological data paint a complicated picture of microform persistence. Some microforms can remain in the same position on a bog for millennia, growing vertically upwards as the bog grows. However, adjacent areas on the bog (< 10 m distant) show switches between microform type over time, indicating a lack of persistence. 5. Synthesis. We suggest that the acrotelm-catotelm model should be used cautiously; spatial variations in peatland permeability do not fit the simple patterns suggested by the model. To understand how peatlands as a whole function both hydrologically and ecologically it is necessary to understand how patterns of peat physical properties and peatland vegetation develop and persist

EnRoot: a narrow, inexpensive and partially 3D-printable minirhizotron for imaging fine root production

Background Fine root production is one of the least well understood components of the carbon cycle in terrestrial ecosystems. Minirhizotrons allow accurate and non-destructive sampling of fine root production. Small and large scale studies across a range of ecosystems are needed to have baseline data on fine root production and further assess the impact of global change upon it; however, the expense and the low adaptability of minirhizotrons prevent such data collection, in worldwide distributed sampling schemes, in low-income countries and in some ecosystems (e.g. tropical forested wetlands). Results We present EnRoot, a narrow minirhizotron of 25 mm diameter, that is partially 3D printable. EnRoot is inexpensive (€150), easy to construct (no prior knowledge required) and adapted to a range of ecosystems including tropical forested wetlands (e.g. mangroves, peatlands). We tested EnRoot’s accuracy and precision for measuring fine root length and diameter, and it yielded Lin’s concordance correlation coefficient values of 0.95 for root diameter and 0.92 for length. As a proof of concept, we tested EnRoot in a mesocosm study, and in the field in a tropical mangrove. EnRoot proved its capacity to capture the development of roots of a legume (Medicago sativa) and a mangrove species (seedlings of Rhizophora mangle) in laboratory mesocosms. EnRoot’s field installation was possible in the root-dense tropical mangrove because its narrow diameter allowed it to be installed between larger roots and because it is fully waterproof. EnRoot compares favourably with commercial minirhizotrons, and can image roots as small as 56 µm. Conclusion EnRoot removes barriers to the extensive use of minirhizotrons by being low-cost, easy to construct and adapted to a wide range of ecosystem. It opens the doors to worldwide distributed minirhizotron studies across an extended range of ecosystems with the potential to fill knowledge gaps surrounding fine root production

Visual dysfunction in Parkinson's disease

Patients with Parkinson's disease have a number of specific visual disturbances. These include changes in colour vision and contrast sensitivity and difficulties with complex visual tasks such as mental rotation and emotion recognition. We review changes in visual function at each stage of visual processing from retinal deficits, including contrast sensitivity and colour vision deficits to higher cortical processing impairments such as object and motion processing and neglect. We consider changes in visual function in patients with common Parkinson's disease-associated genetic mutations including GBA and LRRK2 We discuss the association between visual deficits and clinical features of Parkinson's disease such as rapid eye movement sleep behavioural disorder and the postural instability and gait disorder phenotype. We review the link between abnormal visual function and visual hallucinations, considering current models for mechanisms of visual hallucinations. Finally, we discuss the role of visuo-perceptual testing as a biomarker of disease and predictor of dementia in Parkinson's disease

Structure Prediction of Li--Sn and Li--Sb Intermetallics for Lithium-ion Batteries Anodes.

A variety of new stable and metastable Li–Sn and Li–Sb intermetallics are presented using the ab initio random structure searching (AIRSS) and species swapping methods. There include LiSn2–P4/mmm, Li2Sn3–P-1, Li7Sn9–P42/n, Li3Sn2–P21/m, Li5Sn3–Im-3m, Li2Sn– Cmcm, Li8Sn3–R-3m, Li3Sn–P32, Li7Sn2–P-1, Li4Sn–P21, Li5Sn–P6/mmm, Li7Sn–Fmmm, LiSb–P4/mmm, Li8Sb5–Fd-3m, Li8Sb3–P2/c, Li4Sb–C2/m, Li9Sb2–P-3m1, Li5Sb–P6/mmm, Li6Sb–R-3m, Li8Sb–Pc and Li9Sb–Cmcm. The Li–Sn theoretical voltage curve was calculated to high–accuracy mainly from experimentally known structures and shows excellent agreement with experimental electrochemical cycling measurements previously reported. Li2Sn was found on the convex hull to within density–functional theory accuracy and its mechanical stability was investigated by calculating the density of states of the phonon spectrum. The new structures obtained by AIRSS show a consistent structural evolution of Li–Sn phases as Li concentration is increased. First principles NMR calculations on the hexagonal– and cubic–Li3Sb phases are performed. Our NMR results are compared to findings of Johnston et al., Chemistry of Materials (2016) 28, 4032 and proposed as a diagnostic tool to interpret experimental data

Comparison of growth patterns in healthy dogs and dogs in abnormal body condition using growth standards

In dogs, optimal growth is critical for future health and wellbeing. Recently, a series of evidence-based growth standards, based on bodyweight, were developed for male and female dogs across 5 different size categories. The aim of the current study was to compare growth curves depicted by the standards with patterns of growth in dogs that were either healthy, had abnormal body condition, or had various diseases with the potential to affect growth. The data came from 2 research colonies in Europe (France and UK), and a large corporate network of primary care veterinary hospitals across the USA. Age and bodyweight data were used to model growth in healthy dogs, in dogs that became overweight or underweight by 3 years of age, and in dogs with diseases associated with altered growth. Centile line crossing during the growth phase was uncommon in healthy dogs, with 2 centile lines. In contrast, centile line crossing was more frequent in dogs with abnormal growth patterns or abnormal body condition. Dogs that developed obesity by 3 years grew faster than the growth standards predicted, and 68% crossed ≥2 centile lines in an upwards direction. Dogs with conditions associated with accelerated growth also grew faster than expected, and 54% crossed ≥2 centile lines. In contrast dogs that became underweight by 3 years gained weight slower than expected, and 49% crossed ≥2 centile lines in a downwards direction. These results suggest that the growth standards are useful for monitoring healthy growth in dogs. Prospective studies are now required to confirm these findings and to determine whether early intervention can prevent the development of diseases