Enhanced extra mixing in low-mass stars approaching the RGB tip and the problem of Li-rich red-clump stars

A few percent of red giants are enriched in Lithium with $A(\mathrm{Li}) > 1.5$. The evolutionary phase of the Li-rich red giants has remained uncertain because they could be placed both on the red-giant branch (RGB) near the bump luminosity and in the red clump (RC) region. However, thanks to asteroseismology, it has been found that most of them are actually RC stars. Starting at the bump luminosity, RGB progenitors of the RC stars experience extra mixing in the radiative zone separating the H-burning shell from the convective envelope followed by a series of convective He-shell flashes at the RGB tip, known as the He-core flash. Therefore, the He-core flash was proposed to cause fast extra mixing in the stars at the RGB tip that is needed for the Cameron-Fowler mechanism to produce Li. Alternatively, we propose that the RGB stars are getting enriched in Li by the same extra mixing that starts at the bump luminosity and initially leads to a decrease of the surface Li abundance but that is getting enhanced and begins to produce Li when the stars are approaching the RGB tip. We discuss five mechanisms of the RGB extra mixing, namely, the joint operation of rotation-driven meridional circulation and turbulent diffusion, the Azimuthal Magneto-Rotational Instability (AMRI), thermohaline convection, buoyancy of magnetic flux tubes, and internal gravity waves, and, based on results of (magneto-) hydrodynamics simulations, come to the conclusion that it is the mechanism of the AMRI that is most likely to support our hypothesis.Comment: 14 pages, 7 figures, submitted to MNRA

Molecular characterisation of viruses from Kiwifruit

In 2003 Apple stem grooving virus was discovered in Actinidia accessions from China, being held in quarantine in Auckland. Subsequent examination of kiwifruit germplasm from the same source has detected several additional viruses, including a ~300 nm rigid rod related to Ribgrass mosaic virus (Tobamovirus), a 700-750 nm flexuous virus related to Citrus leaf blotch virus (Flexiviridae) and a novel vitivirus. Currently these viruses have not been reported from commercial kiwifruit crops in New Zealand or elsewhere. The biological properties of the viruses from kiwifruit and their phylogenetic relationships with similar viruses from other plants will be described, and the possible implications for the international movement of Actinidia germplasm are discussed

On the Nature of Ultracool White Dwarfs: Not so Cool Afterall

A recent analysis of the 100 pc white dwarf sample in the SDSS footprint demonstrated for the first time the existence of a well defined ultracool -- or IR-faint -- white dwarf sequence in the Hertzsprung-Russell diagram. Here we take advantage of this discovery to enlarge the IR-faint white dwarf sample threefold. We expand our selection to the entire Pan-STARRS survey footprint as well as the Montreal White Dwarf Database 100 pc sample, and identify 37 candidates with strong flux deficits in the optical. We present follow-up Gemini optical spectroscopy of 30 of these systems, and confirm all of them as IR-faint white dwarfs. We identify an additional set of 33 objects as candidates based on their colors and magnitudes. We present a detailed model atmosphere analysis of all 70 newly identified IR-faint white dwarfs together with 35 previously known objects reported in the literature. We discuss the physics of model atmospheres and show that the key physical ingredient missing in our previous generation of model atmospheres was the high-density correction to the He-minus free-free absorption coefficient. With new model atmospheres calculated for the purpose of this analysis, we now obtain significantly higher effective temperatures and larger stellar masses for these IR-faint white dwarfs than the Teff and M values reported in previous analyses, thus solving a two decade old problem. In particular, we identify in our sample a group of ultramassive white dwarfs in the Debye cooling phase with stellar parameters never measured before.Comment: Accepted for publication in The Astrophysical Journal (33 pages, 21 figures

Effects of Risedronate in Runx2 Overexpressing Mice, an Animal Model for Evaluation of Treatment Effects on Bone Quality and Fractures

Young mice overexpressing Runx2 specifically in cells of the osteoblastic lineage failed to gain bone mass and exhibited a dramatic increase in bone resorption, leading to severe osteopenia and spontaneous vertebral fractures. The objective of the current study was to determine whether treatment with a bisphosphonate (risedronate, Ris), which reduces fractures in postmenopausal as well as in juvenile osteoporosis, was able to improve bone quality and reduce vertebral fractures in mice overexpressing Runx2. Four-week-old female Runx2 mice received Ris at 2 and 10 μg/kg subcutaneously twice a week for 12 weeks. Runx2 and wild-type mice received vehicle (Veh) as control. We measured the number of new fractures by X-ray and bone mineral density (BMD) by DEXA. We evaluated bone quality by histomorphometry, micro-CT, and Fourier transform infrared imaging (FTIRI). Ris at 20 μg/kg weekly significantly reduced the average number of new vertebral fractures compared to controls. This was accompanied by significantly increased BMD, increased trabecular bone volume, and reduced bone remodeling (seen in indices of bone resorption and formation) in the vertebrae and femoral metaphysis compared to Runx2 Veh. At the femur, Ris also increased cortical thickness. Changes in collagen cross-linking seen on FTIRI confirmed that Runx2 mice have accelerated bone turnover and showed that Ris affects the collagen cross-link ratio at both forming and resorbing sites. In conclusion, young mice overexpressing Runx2 have high bone turnover-induced osteopenia and spontaneous fractures. Ris at 20 μg/kg weekly induced an increase in bone mass, changes in bone microarchitecture, and decreased vertebral fractures

Bayesian parentage analysis with systematic accountability of genotyping error, missing data, and false matching

Motivation: The goal of any parentage analysis is to identify as many parent-offspring relationships as possible, while minimizing incorrect assignments. Existing methods can achieve these ends, but require additional information in the form of demographic data, thousands of markers, and/or estimates of genotyping error rates. For many non-model systems, it is simply not practical, cost-effective, or logistically feasible to obtain this information. Here, we develop a Bayesian parentage method that only requires the sampled genotypes in order to account for genotyping error, missing data, and false matches. Results: Extensive testing with microsatellite and SNP data sets reveals that our Bayesian parentage method reliably controls for the number of false assignments, irrespective of the genotyping error rate. When the number of loci is limiting, our approach maximizes the number of correct assignments by accounting for the frequencies of shared alleles. Comparisons with exclusion and likelihood-based methods on an empirical salmon data set revealed that our Bayesian method had the highest ratio of correct to incorrect assignments. Availability: Our program SOLOMON is available as an R package from the CRAN website. SOLOMON comes with a fully functional graphical user interface, requiring no user knowledge about the R programming environment. In addition to performing Bayesian parentage analysis, SOLOMON includes Mendelian exclusion and a priori power analysis modules. Further information and user support can be found at https://sites.google.com/site/parentagemethods/.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Oxford University Press and can be found at: http://bioinformatics.oxfordjournals.org/

The contribution of the pericanalicular matrix to mineral content in human osteonal bone

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.The osteocyte lacunar-canalicular network (LCN) penetrates bone and houses the osteocytes and their processes. Despite its rather low volume fraction, the LCN represents an outstanding large surface that is possibly used by the osteocytes to interact with the surrounding mineralized bone matrix thereby contributing to mineral homeostasis. The aim of this study was to quantitatively describe such contributions by spatially correlating the local density of the LCN with the mineral content at the same location in micrometer-sized volume elements in human osteons. For this purpose, 65 osteons from the femur midshaft from healthy adults (n = 4) and children (n = 2) were structurally characterized with two different techniques. The 3D structure of the LCN in the osteons was imaged with confocal laser scanning microscopy after staining the bone samples with rhodamine. Subsequent image analysis provided the canalicular length density, i.e. the total length of the canaliculi per unit volume (μm/μm3). Quantitative information on the mineral content (wt%Ca) from the identical regions was obtained using quantitative backscattered electron imaging. As the LCN-porosity lowers the mineral content, a negative correlation between Ca content and network density was expected. Calculations predict a reduction of around −0.97 fmol Ca per μm of network. However, the experiment revealed for 62 out of 65 osteons a positive correlation resulting in an average additional Ca loading of +1.15 fmol per μm of canalicular network, i.e. an accumulation of mineral has occurred at dense network regions. We hypothesize that this accumulation happens in the close vicinity of canaliculi forming mineral reservoirs that can be utilized by osteocytes. Significant differences found between individuals indicate that the extent of mineral loading of the reservoir zone reflects an important parameter for mineral homeostasis.German Federal Ministry of Education and ResearchAUVA (Research Funds of the Austrian Workers Compensation Board, Austria)WGKK (Viennese sickness insurance funds, Austria)

Development of Non-Destructive Condition Monitoring Techniques for Low-Voltage Cables

NRC publication: Ye

Evidence for cognitive vestibular integration impairment in idiopathic scoliosis patients

<p>Abstract</p> <p>Background</p> <p>Adolescent idiopathic scoliosis is characterized by a three-dimensional deviation of the vertebral column and its etiopathogenesis is unknown. Various factors cause idiopathic scoliosis, and among these a prominent role has been attributed to the vestibular system. While the deficits in sensorimotor transformations have been documented in idiopathic scoliosis patients, little attention has been devoted to their capacity to integrate vestibular information for cognitive processing for space perception. Seated idiopathic scoliosis patients and control subjects experienced rotations of different directions and amplitudes in the dark and produced saccades that would reproduce their perceived spatial characteristics of the rotations (vestibular condition). We also controlled for possible alteration of the oculomotor and vestibular systems by measuring the subject's accuracy in producing saccades towards memorized peripheral targets in absence of body rotation and the gain of their vestibulo-ocular reflex.</p> <p>Results</p> <p>Compared to healthy controls, the idiopathic scoliosis patients underestimated the amplitude of their rotations. Moreover, the results revealed that idiopathic scoliosis patients produced accurate saccades to memorized peripheral targets in absence of body rotation and that their vestibulo-ocular reflex gain did not differ from that of control participants.</p> <p>Conclusion</p> <p>Overall, results of the present study demonstrate that idiopathic scoliosis patients have an alteration in cognitive integration of vestibular signals. It is possible that severe spine deformity developed partly due to impaired vestibular information travelling from the cerebellum to the vestibular cortical network or alteration in the cortical mechanisms processing the vestibular signals.</p

A robust SNP barcode for typing Mycobacterium tuberculosis complex strains

Strain-specific genomic diversity in the Mycobacterium tuberculosis complex (MTBC) is an important factor in pathogenesis that may affect virulence, transmissibility, host response and emergence of drug resistance. Several systems have been proposed to classify MTBC strains into distinct lineages and families. Here, we investigate single-nucleotide polymorphisms (SNPs) as robust (stable) markers of genetic variation for phylogenetic analysis. We identify ~92k SNP across a global collection of 1,601 genomes. The SNP-based phylogeny is consistent with the gold-standard regions of difference (RD) classification system. Of the ~7k strain-specific SNPs identified, 62 markers are proposed to discriminate known circulating strains. This SNP-based barcode is the first to cover all main lineages, and classifies a greater number of sublineages than current alternatives. It may be used to classify clinical isolates to evaluate tools to control the disease, including therapeutics and vaccines whose effectiveness may vary by strain type