The approach to vortex reconnection

We present numerical solutions of the Gross--Pitaevskii equation corresponding to reconnecting vortex lines. We determine the separation of vortices as a function of time during the approach to reconnection, and study the formation of pyramidal vortex structures. Results are compared with analytical work and numerical studies based on the vortex filament method.Comment: 11 pages, 9 figure

Regional-scale high spatial resolution mapping of aboveground net primary productivity (ANPP) from field survey and Landsat data: a case study for the country of Wales

This paper presents an alternative approach for high spatial resolution vegetation productivity mapping at a regional scale, using a combination of Normalised Difference Vegetation Index (NDVI) imagery and widely distributed ground-based Above-ground Net Primary Production (ANPP) estimates. Our method searches through all available single-date NDVI imagery to identify the images which give the best NDVI–ANPP relationship. The derived relationships are then used to predict ANPP values outside of field survey plots. This approach enables the use of the high spatial resolution (30 m) Landsat 8 sensor, despite its low revisit frequency that is further reduced by cloud cover. This is one of few studies to investigate the NDVI–ANPP relationship across a wide range of temperate habitats and strong relationships were observed (R2 = 0.706), which increased when only grasslands were considered (R2 = 0.833). The strongest NDVI–ANPP relationships occurred during the spring “green-up” period. A reserved subset of 20% of ground-based ANPP estimates was used for validation and results showed that our method was able to estimate ANPP with a RMSE of 15–21%. This work is important because we demonstrate a general methodological framework for mapping of ANPP from local to regional scales, with the potential to be applied to any temperate ecosystems with a pronounced green up period. Our approach allows spatial extrapolation outside of field survey plots to produce a continuous surface product, useful for capturing spatial patterns and representing small-scale heterogeneity, and well-suited for modelling applications. The data requirements for implementing this approach are also discussed

XRCC1 haploinsufficiency in mice has little effect on aging, but adversely modifies exposure-dependent susceptibility

Oxidative DNA damage plays a role in disease development and the aging process. A prominent participant in orchestrating the repair of oxidative DNA damage, particularly single-strand breaks, is the scaffold protein XRCC1. A series of chronological and biological aging parameters in XRCC1 heterozygous (HZ) mice were examined. HZ and wild-type (WT) C57BL/6 mice exhibit a similar median lifespan of ~26 months and a nearly identical maximal life expectancy of ~37 months. However, a number of HZ animals (7 of 92) showed a propensity for abdominal organ rupture, which may stem from developmental abnormalities given the prominent role of XRCC1 in endoderm and mesoderm formation. For other end-points evaluated—weight, fat composition, blood chemistries, condition of major organs, tissues and relevant cell types, behavior, brain volume and function, and chromosome and telomere integrity—HZ mice exhibited by-and-large a normal phenotype. Treatment of animals with the alkylating agent azoxymethane resulted in both liver toxicity and an increased incidence of precancerous lesions in the colon of HZ mice. Our study indicates that XRCC1 haploinsufficiency in mammals has little effect on chronological longevity and many key biological markers of aging in the absence of environmental challenges, but may adversely affect normal animal development or increase disease susceptibility to a relevant genotoxic exposure

XRCC1 haploinsufficiency in mice has little effect on aging, but adversely modifies exposure-dependent susceptibility

Oxidative DNA damage plays a role in disease development and the aging process. A prominent participant in orchestrating the repair of oxidative DNA damage, particularly single-strand breaks, is the scaffold protein XRCC1. A series of chronological and biological aging parameters in XRCC1 heterozygous (HZ) mice were examined. HZ and wild-type (WT) C57BL/6 mice exhibit a similar median lifespan of ~26 months and a nearly identical maximal life expectancy of ~37 months. However, a number of HZ animals (7 of 92) showed a propensity for abdominal organ rupture, which may stem from developmental abnormalities given the prominent role of XRCC1 in endoderm and mesoderm formation. For other end-points evaluated—weight, fat composition, blood chemistries, condition of major organs, tissues and relevant cell types, behavior, brain volume and function, and chromosome and telomere integrity—HZ mice exhibited by-and-large a normal phenotype. Treatment of animals with the alkylating agent azoxymethane resulted in both liver toxicity and an increased incidence of precancerous lesions in the colon of HZ mice. Our study indicates that XRCC1 haploinsufficiency in mammals has little effect on chronological longevity and many key biological markers of aging in the absence of environmental challenges, but may adversely affect normal animal development or increase disease susceptibility to a relevant genotoxic exposure

Optical types of inland and coastal waters

Inland and coastal waterbodies are critical components of the global biosphere. Timely monitoring is necessary to enhance our understanding of their functions, the drivers impacting on these functions and to deliver more effective management. The ability to observe waterbodies from space has led to Earth observation (EO) becoming established as an important source of information on water quality and ecosystem condition. However, progress toward a globally valid EO approach is still largely hampered by inconsistences over temporally and spatially variable in-water optical conditions. In this study, a comprehensive dataset from more than 250 aquatic systems, representing a wide range of conditions, was analyzed in order to develop a typology of optical water types (OWTs) for inland and coastal waters. We introduce a novel approach for clustering in situ hyperspectral water reflectance measurements (n = 4045) from multiple sources based on a functional data analysis. The resulting classification algorithm identified 13 spectrally distinct clusters of measurements in inland waters, and a further nine clusters from the marine environment. The distinction and characterization of OWTs was supported by the availability of a wide range of coincident data on biogeochemical and inherent optical properties from inland waters. Phylogenetic trees based on the shapes of cluster means were constructed to identify similarities among the derived clusters with respect to spectral diversity. This typification provides a valuable framework for a globally applicable EO scheme and the design of future EO missions

XRCC1 mutation is associated with PARP1 hyperactivation and cerebellar ataxia

XRCC1 is a molecular scaffold protein that assembles multi-protein complexes involved in DNA single-strand break repair1,2. Here we show that biallelic mutations in the human XRCC1 gene are associated with ocular motor apraxia, axonal neuropathy, and progressive cerebellar ataxia. Cells from a patient with mutations in XRCC1 exhibited not only reduced rates of single-strand break repair but also elevated levels of protein ADP-ribosylation. This latter phenotype is recapitulated in a related syndrome caused by mutations in the XRCC1 partner protein PNKP3,4,5 and implicates hyperactivation of poly(ADP-ribose) polymerase/s as a cause of cerebellar ataxia. Indeed, remarkably, genetic deletion of Parp1 rescued normal cerebellar ADP-ribose levels and reduced the loss of cerebellar neurons and ataxia in Xrcc1-defective mice, identifying a molecular mechanism by which endogenous single-strand breaks trigger neuropathology. Collectively, these data establish the importance of XRCC1 protein complexes for normal neurological function and identify PARP1 as a therapeutic target in DNA strand break repair-defective disease

Tree method for quantum vortex dynamics

We present a numerical method to compute the evolution of vortex filaments in superfluid helium. The method is based on a tree algorithm which considerably speeds up the calculation of Biot-Savart integrals. We show that the computational cost scales as Nlog{(N) rather than N squared, where $N$ is the number of discretization points. We test the method and its properties for a variety of vortex configurations, ranging from simple vortex rings to a counterflow vortex tangle, and compare results against the Local Induction Approximation and the exact Biot-Savart law.Comment: 12 pages, 10 figure

Disparate requirements for the Walker A and B ATPase motifs of human RAD51D in homologous recombination

In vertebrates, homologous recombinational repair (HRR) requires RAD51 and five RAD51 paralogs (XRCC2, XRCC3, RAD51B, RAD51C and RAD51D) that all contain conserved Walker A and B ATPase motifs. In human RAD51D we examined the requirement for these motifs in interactions with XRCC2 and RAD51C, and for survival of cells in response to DNA interstrand crosslinks (ICLs). Ectopic expression of wild-type human RAD51D or mutants having a non-functional A or B motif was used to test for complementation of a rad51d knockout hamster CHO cell line. Although A-motif mutants complement very efficiently, B-motif mutants do not. Consistent with these results, experiments using the yeast two- and three-hybrid systems show that the interactions between RAD51D and its XRCC2 and RAD51C partners also require a functional RAD51D B motif, but not motif A. Similarly, hamster Xrcc2 is unable to bind to the non-complementing human RAD51D B-motif mutants in co-immunoprecipitation assays. We conclude that a functional Walker B motif, but not A motif, is necessary for RAD51D's interactions with other paralogs and for efficient HRR. We present a model in which ATPase sites are formed in a bipartite manner between RAD51D and other RAD51 paralogs

The DESiGN trial (DEtection of Small for Gestational age Neonate), evaluating the effect of the Growth Assessment Protocol (GAP): study protocol for a randomised controlled trial.

BACKGROUND: Stillbirth rates in the United Kingdom (UK) are amongst the highest of all developed nations. The association between small-for-gestational-age (SGA) foetuses and stillbirth is well established, and observational studies suggest that improved antenatal detection of SGA babies may halve the stillbirth rate. The Growth Assessment Protocol (GAP) describes a complex intervention that includes risk assessment for SGA and screening using customised fundal-height growth charts. Increased detection of SGA from the use of GAP has been implicated in the reduction of stillbirth rates by 22%, in observational studies of UK regions where GAP uptake was high. This study will be the first randomised controlled trial examining the clinical efficacy, health economics and implementation of the GAP programme in the antenatal detection of SGA. METHODS/DESIGN: In this randomised controlled trial, clusters comprising a maternity unit (or National Health Service Trust) were randomised to either implementation of the GAP programme, or standard care. The primary outcome is the rate of antenatal ultrasound detection of SGA in infants found to be SGA at birth by both population and customised standards, as this is recognised as being the group with highest risk for perinatal morbidity and mortality. Secondary outcomes include antenatal detection of SGA by population centiles, antenatal detection of SGA by customised centiles, short-term maternal and neonatal outcomes, resource use and economic consequences, and a process evaluation of GAP implementation. Qualitative interviews will be performed to assess facilitators and barriers to implementation of GAP. DISCUSSION: This study will be the first to provide data and outcomes from a randomised controlled trial investigating the potential difference between the GAP programme compared to standard care for antenatal ultrasound detection of SGA infants. Accurate information on the performance and service provision requirements of the GAP protocol has the potential to inform national policy decisions on methods to reduce the rate of stillbirth. TRIAL REGISTRATION: Primary registry and trial identifying number: ISRCTN 67698474 . Registered on 2 November 2016