The effect of cluster reconfiguration and non-stoichiometry on uranium vacancy migration in UO2

During reactor operation the release of fission gases from the fuel pellet is an important safety issue as it can lead to over-pressurization and failure of the fuel cladding. Uranium vacancy migration has been identified as the limiting step in the diffusion of fission gases through bulk UO2. The uranium vacancy migration energy is, therefore, an important parameter in this phenomenon, as well as other atomic scale processes, such as recovery from radiation damage. Chemical changes under taken by the fuel during irradiation lead to deviations from stoichiometric UO2 and the charge compensating defects that bind to the uranium vacancy also change. Therefore, we have examined the change in the migration energy for a uranium vacancy when bound to either two oxygen vacancies (Schottky defect) or to four U5+ cations (hole defects) representing UO2 and UO2+x respectively. By using empirical potentials within statics we were able to sample a large array of metastable cluster configurations to identify lower energy migration pathways that involve the reconfiguration of the cluster from the ground state configuration to metastable configurations (see UO2+x results in Figure 1). The work is published in ref [1]. Please click Additional Files below to see the full abstract

Neonatal local noxious insult affects gene expression in the spinal dorsal horn of adult rats

Neonatal noxious insult produces a long-term effect on pain processing in adults. Rats subjected to carrageenan (CAR) injection in one hindpaw within the sensitive period develop bilateral hypoalgesia as adults. In the same rats, inflammation of the hindpaw, which was the site of the neonatal injury, induces a localized enhanced hyperalgesia limited to this paw. To gain an insight into the long-term molecular changes involved in the above-described long-term nociceptive effects of neonatal noxious insult at the spinal level, we performed DNA microarray analysis (using microarrays containing oligo-probes for 205 genes encoding receptors and transporters for glutamate, GABA, and amine neurotransmitters, precursors and receptors for neuropeptides, and neurotrophins, cytokines and their receptors) to compare gene expression profiles in the lumbar spinal dorsal horn (LDH) of adult (P60) male rats that received neonatal CAR treatment within (at postnatal day 3; P3) and outside (at postnatal 12; P12) of the sensitive period. The data were obtained both without inflammation (at baseline) and during complete Freund's adjuvant induced inflammation of the neonatally injured paw. The observed changes were verified by real-time RT-PCR. This study revealed significant basal and inflammation-associated aberrations in the expression of multiple genes in the LDH of adult animals receiving CAR injection at P3 as compared to their expression levels in the LDH of animals receiving either no injections or CAR injection at P12. In particular, at baseline, twelve genes (representing GABA, serotonin, adenosine, neuropeptide Y, cholecystokinin, opioid, tachykinin and interleukin systems) were up-regulated in the bilateral LDH of the former animals. The baseline condition in these animals was also characterized by up-regulation of seven genes (encoding members of GABA, cholecystokinin, histamine, serotonin, and neurotensin systems) in the LDH ipsilateral to the neonatally-injured paw. The largest aberration in gene expression, however, was observed during inflammation of the neonatally injured hindpaws in the ipsilateral LDH, which included thirty-six genes (encoding numerous members of glutamate, serotonin, GABA, calcitonin gene-related peptide, neurotrophin, and interleukin systems). These findings suggest that changes in gene expression may be involved in the long-term nociceptive effects of neonatal noxious insult at the spinal level

Neutrino Mass and μ→e+γ\mu \rightarrow e + \gamma from a Mini-Seesaw

The recently proposed "mini-seesaw mechanism" combines naturally suppressed Dirac and Majorana masses to achieve light Standard Model neutrinos via a low-scale seesaw. A key feature of this approach is the presence of multiple light (order GeV) sterile-neutrinos that mix with the Standard Model. In this work we study the bounds on these light sterile-neutrinos from processes like \mu ---> e + \gamma, invisible Z-decays, and neutrinoless double beta-decay. We show that viable parameter space exists and that, interestingly, key observables can lie just below current experimental sensitivities. In particular, a motivated region of parameter space predicts a value of BR(\mu ---> e + \gamma) within the range to be probed by MEG.Comment: 1+26 pages, 7 figures. v2 JHEP version (typo's fixed, minor change to presentation, results unchanged

SCF Ensures Meiotic Chromosome Segregation Through a Resolution of Meiotic Recombination Intermediates

The SCF (Skp1-Cul1-F-box) complex contributes to a variety of cellular events including meiotic cell cycle control, but its function during meiosis is not understood well. Here we describe a novel function of SCF/Skp1 in meiotic recombination and subsequent chromosome segregation. The skp1 temperature-sensitive mutant exhibited abnormal distribution of spindle microtubules in meiosis II, which turned out to originate from abnormal bending of the spindle in meiosis I. Bent spindles were reported in mitosis of this mutant, but it remained unknown how SCF could affect spindle morphology. We found that the meiotic bent spindle in skp1 cells was due to a hypertension generated by chromosome entanglement. The spindle bending was suppressed by inhibiting double strand break (DSB) formation, indicating that the entanglement was generated by the meiotic recombination machinery. Consistently, Rhp51/Rad51-Rad22/Rad52 foci persisted until meiosis I in skp1 cells, proving accumulation of recombination intermediates. Intriguingly bent spindles were also observed in the mutant of Fbh1, an F-box protein containing the DNA helicase domain, which is involved in meiotic recombination. Genetic evidence suggested its cooperation with SCF/Skp1. Thus, SCF/Skp1 together with Fbh1 is likely to function in the resolution of meiotic recombination intermediates, thereby ensuring proper chromosome segregation

Individual Facial Coloration in Male Eulemur fulvus rufus: A Condition-dependent Ornament?

Researchers studying individual variation in conspicuous skin coloration in primates have suggested that color indicates male quality. Although primate fur color can also be flamboyant, the potential condition dependence and thus signaling function of fur remains poorly studied. We studied sources of variation in sexually dichromatic facial hair coloration in red-fronted lemurs (Eulemur fulvus rufus). We collected data on 13 adult males in Kirindy Forest, Madagascar, during two study periods in 2006 and 2007, to determine whether variation in facial hair coloration correlates with male age, rank, androgen status, and reproductive success. We quantified facial hair coloration via standardized digital photographs of each male, assessed androgen status using fecal hormone measurements, and obtained data on reproductive success through genetic paternity analyses. Male facial hair coloration showed high individual variation, and baseline coloration was related to individual androgen status but not to any other parameter tested. Color did not reflect rapid androgen changes during the mating season. However, pronounced long-term changes in androgen levels between years were accompanied by changes in facial hair coloration. Our data suggest that facial hair coloration in red-fronted lemur males is under proximate control of androgens and may provide some information about male quality, but it does not correlate with dominance rank or male reproductive success

Widespread Contribution of Gdf7 Lineage to Cerebellar Cell Types and Implications for Hedgehog-Driven Medulloblastoma Formation

The roof plate is a specialized embryonic midline tissue of the central nervous system that functions as a signaling center regulating dorsal neural patterning. In the developing hindbrain, roof plate cells express Gdf7 and previous genetic fate mapping studies showed that these cells contribute mostly to non-neural choroid plexus epithelium. We demonstrate here that constitutive activation of the Sonic hedgehog signaling pathway in the Gdf7 lineage invariably leads to medulloblastoma. Lineage tracing analysis reveals that Gdf7-lineage cells not only are a source of choroid plexus epithelial cells, but are also present in the cerebellar rhombic lip and contribute to a subset of cerebellar granule neuron precursors, the presumed cell-of-origin for Sonic hedgehog-driven medulloblastoma. We further show that Gdf7-lineage cells also contribute to multiple neuronal and glial cell types in the cerebellum, including glutamatergic granule neurons, unipolar brush cells, Purkinje neurons, GABAergic interneurons, Bergmann glial cells, and white matter astrocytes. These findings establish hindbrain roof plate as a novel source of diverse neural cell types in the cerebellum that is also susceptible to oncogenic transformation by deregulated Sonic hedgehog signaling

Assessing the Value of Recreational Divers for Censusing Elasmobranchs

BACKGROUND: Around the world, researchers are using the observations and experiences of citizens to describe patterns in animal populations. This data is often collected via ongoing sampling or by synthesizing past experiences. Since elasmobranchs are relatively rare, obtaining data for broad-scale trend analysis requires high sampling effort. Elasmobranchs are also relatively large and conspicuous and therefore it may be possible to enlist recreational divers to collect data on their occurrence and relative abundance from daily dive activities. For this, however, a good understanding of the value of data collected by recreational divers is essential. METHODOLOGY/PRINCIPAL FINDINGS: Here, we explore the value of recreational divers for censusing elasmobranchs using a diverse set of data sources. First, we use a simulation experiment to explore detection rates of the roving diver technique, used by recreational divers, across a range of fish densities and speeds. Next, using a field survey, we show that inexperienced recreational divers detect and count elasmobranchs as well as experienced recreational divers. Finally, we use semi-structured interviews of recreational dive instructors to demonstrate the value of their recollections in terms of effort and their descriptions of spatial and temporal distributions of sharks in Thailand. CONCLUSIONS/SIGNIFICANCE: Overall, this study provides initial ground-work for using recreational divers for monitoring elasmobranch populations. If used appropriately, citizen-collected data may provide additional information that can be used to complement more standardized surveys and to describe population trends across a range of spatial and temporal scales. Due to the non-extractive nature of this data, recreational divers may also provide important insight into the success of conservation initiatives, such as shark sanctuaries and no-take zones

Ecological Niche Modelling and nDNA Sequencing Support a New, Morphologically Cryptic Beetle Species Unveiled by DNA Barcoding

DNA sequencing techniques used to estimate biodiversity, such as DNA barcoding, may reveal cryptic species. However, disagreements between barcoding and morphological data have already led to controversy. Species delimitation should therefore not be based on mtDNA alone. Here, we explore the use of nDNA and bioclimatic modelling in a new species of aquatic beetle revealed by mtDNA sequence data. The aquatic beetle fauna of Australia is characterised by high degrees of endemism, including local radiations such as the genus Antiporus. Antiporus femoralis was previously considered to exist in two disjunct, but morphologically indistinguishable populations in south-western and south-eastern Australia. We constructed a phylogeny of Antiporus and detected a deep split between these populations. Diagnostic characters from the highly variable nuclear protein encoding arginine kinase gene confirmed the presence of two isolated populations. We then used ecological niche modelling to examine the climatic niche characteristics of the two populations. All results support the status of the two populations as distinct species. We describe the south-western species as Antiporus occidentalis sp.n. In addition to nDNA sequence data and extended use of mitochondrial sequences, ecological niche modelling has great potential for delineating morphologically cryptic species

Finding Diagnostically Useful Patterns in Quantitative Phenotypic Data.

Trio-based whole-exome sequence (WES) data have established confident genetic diagnoses in ∼40% of previously undiagnosed individuals recruited to the Deciphering Developmental Disorders (DDD) study. Here we aim to use the breadth of phenotypic information recorded in DDD to augment diagnosis and disease variant discovery in probands. Median Euclidean distances (mEuD) were employed as a simple measure of similarity of quantitative phenotypic data within sets of ≥10 individuals with plausibly causative de novo mutations (DNM) in 28 different developmental disorder genes. 13/28 (46.4%) showed significant similarity for growth or developmental milestone metrics, 10/28 (35.7%) showed similarity in HPO term usage, and 12/28 (43%) showed no phenotypic similarity. Pairwise comparisons of individuals with high-impact inherited variants to the 32 individuals with causative DNM in ANKRD11 using only growth z-scores highlighted 5 likely causative inherited variants and two unrecognized DNM resulting in an 18% diagnostic uplift for this gene. Using an independent approach, naive Bayes classification of growth and developmental data produced reasonably discriminative models for the 24 DNM genes with sufficiently complete data. An unsupervised naive Bayes classification of 6,993 probands with WES data and sufficient phenotypic information defined 23 in silico syndromes (ISSs) and was used to test a "phenotype first" approach to the discovery of causative genotypes using WES variants strictly filtered on allele frequency, mutation consequence, and evidence of constraint in humans. This highlighted heterozygous de novo nonsynonymous variants in SPTBN2 as causative in three DDD probands