Apsidal motion in the massive binary HD 152248 -- Constraining the internal structure of the stars

Apsidal motion in massive eccentric binaries offers precious information about the internal structure of the stars. This is especially true for twin binaries consisting of two nearly identical stars. We make use of the tidally induced apsidal motion in the twin binary HD152248 to infer constraints on the internal structure of the O7.5 III-II stars composing this system. We build stellar evolution models with the code Cl\'es assuming different prescriptions for the internal mixing occurring inside the stars. We identify the models that best reproduce the observationally determined present-day properties of the components of HD152248, as well as their $k_2$, and the apsidal motion rate of the system. We analyse the impact of some poorly constrained input parameters, including overshooting, turbulent diffusion, and metallicity. We further build 'single' and 'binary' GENEC models that account for stellar rotation to investigate the impacts of binarity and rotation. We discuss some effects that could bias our interpretation of the apsidal motion in terms of the internal structure constant. Reproducing the observed $k_2$ value and rate of apsidal motion simultaneously with the other stellar parameters requires a significant amount of internal mixing or enhanced mass-loss. The results suggest that a single-star evolution model is sufficient to describe the physics inside this binary system. Qualitatively, the high turbulent diffusion required to reproduce the observations could be partly attributed to stellar rotation. Higher-order terms in the apsidal motion are negligible. Only a very severe misalignment of the rotation axes could significantly impact the rate of apsidal motion, but such a high misalignment is highly unlikely in such a binary system. We infer an age estimate of $5.15\pm0.13$ Myr for the binary and initial masses of $32.8\pm0.6$ M$_\odot$ for both stars.Comment: 16 pages, A&A accepte

Comprehensive stellar seismic analysis: A preliminary application of Whosglad to 16 Cygni system

We present a first application of Whosglad method to the components A and B of the 16 Cygni system. The method was developed to provide a comprehensive analysis of stellar oscillation spectra. It defines new seismic indicators which are as uncorrelated and precise as possible and hold detailed information about stellar interiors. Such indicators, as illustrated in the present paper, may be used to generate stellar models via forward seismic modeling. Finally, seismic constraints retrieved by the method provide realistic stellar parameters.Comment: 4 pages, 3 figures. Proceedings of the meeting Physics of Oscillating Stars (PHOST), Banyuls-sur-mer, France, 2-7 September 2018 (Session First Posters Session), published on December 1st 201

A Rank-Based Nonparametric Method for Mapping Quantitative Trait Loci in Outbred Half-Sib Pedigrees: Application to Milk Production in a Granddaughter Design

We describe the development of a multipoint nonparametric quantitative trait loci mapping method based on the Wilcoxon rank-sum test applicable to outbred half-sib pedigrees. The method has been evaluated on a simulated dataset and its efficiency compared with interval mapping by using regression. It was shown that the rank-based approach is slightly inferior to regression when the residual variance is homoscedastic normal; however, in three out of four other scenarios envisaged, i.e., residual variance heteroscedastic normal, homoscedastic skewed, and homoscedastic positively kurtosed, the latter outperforms the former one. Both methods were applied to a real data set analyzing the effect of bovine chromosome 6 on milk yield and composition by using a 125-cM map comprising 15 microsatellites and a granddaughter design counting 1158 Holstein-Friesian sires

Apsidal motion in massive eccentric binaries in NGC 6231

Context. The measurement of the apsidal motion in close eccentric massive binary systems provides essential information to probe the internal structure of the stars that compose the system. Aims. Following the determination of the fundamental stellar and binary parameters, we make use of the tidally induced apsidal motion to infer constraints on the internal structure of the stars composing the binary system HD 152219. Methods. The extensive set of spectroscopic, photometric, and radial velocity observations allowed us to constrain the fundamental parameters of the stars together with the rate of apsidal motion of the system. Stellar structure and evolution models were further built with the Clés code testing different prescriptions for the internal mixing occurring inside the stars. The effect of stellar rotation axis misalignment with respect to the normal to the orbital plane on our interpretation of the apsidal motion in terms of internal structure constants is investigated. Results. Made of an O9.5 III primary star (M1 = 18.64 ± 0.47 M⊙, R1 = 9.40−0.15+0.14 R⊙, Teff,1 = 30 900 ± 1000 K, Lbol,1 = (7.26 ± 0.97)×104 L⊙) and a B1-2 V-III secondary star (M2 = 7.70 ± 0.12 M⊙, R2 = 3.69 ± 0.06 R⊙, Teff,2 = 21 697 ± 1000 K, Lbol,2 = (2.73 ± 0.51)×103 L⊙), the binary system HD 152219 displays apsidal motion at a rate of (1.198 ± 0.300)° yr−1. The weighted-average mean of the internal structure constant of the binary system is inferred: k̄2 = 0.00173 ± 0.00052. For the Clés models to reproduce the k2-value of the primary star, a significantly enhanced mixing is required, notably through the turbulent mixing, but at the cost that other stellar parameters cannot be reproduced simultaneously. Conclusions. The difficulty to reproduce the k2-value simultaneously with the stellar parameters as well as the incompatibility between the age estimates of the primary and secondary stars are indications that some physics of the stellar interior are still not completely understood

The complete linkage disequilibrium test: a test that points to causative mutations underlying quantitative traits

<p>Abstract</p> <p>Background</p> <p>Genetically, SNP that are in complete linkage disequilibrium with the causative SNP cannot be distinguished from the causative SNP. The Complete Linkage Disequilibrium (CLD) test presented here tests whether a SNP is in complete LD with the causative mutation or not. The performance of the CLD test is evaluated in 1000 simulated datasets.</p> <p>Methods</p> <p>The CLD test consists of two steps i.e. analysis I and analysis II. Analysis I consists of an association analysis of the investigated region. The log-likelihood values from analysis I are next ranked in descending order and in analysis II the CLD test evaluates differences in log-likelihood ratios between the best and second best markers. Under the null-hypothesis distribution, the best SNP is in greater LD with the QTL than the second best, while under the alternative-CLD-hypothesis, the best SNP is alike-in-state with the QTL. To find a significance threshold, the test was also performed on data excluding the causative SNP. The 5^th, 10^thand 50^thhighest T_CLDvalue from 1000 replicated analyses were used to control the type-I-error rate of the test at p = 0.005, p = 0.01 and p = 0.05, respectively.</p> <p>Results</p> <p>In a situation where the QTL explained 48% of the phenotypic variance analysis I detected a QTL in 994 replicates (p = 0.001), where 972 were positioned in the correct QTL position. When the causative SNP was excluded from the analysis, 714 replicates detected evidence of a QTL (p = 0.001). In analysis II, the CLD test confirmed 280 causative SNP from 1000 simulations (p = 0.05), i.e. power was 28%. When the effect of the QTL was reduced by doubling the error variance, the power of the test reduced relatively little to 23%. When sequence data were used, the power of the test reduced to 16%. All SNP that were confirmed by the CLD test were positioned in the correct QTL position.</p> <p>Conclusions</p> <p>The CLD test can provide evidence for a causative SNP, but its power may be low in situations with closely linked markers. In such situations, also functional evidence will be needed to definitely conclude whether the SNP is causative or not.</p

Thorough characterisation of the 16 Cygni system

Context. The advent of space-based photometry observations provided high-quality asteroseismic data for a large number of stars. These observations enabled the adaptation of advanced analyses techniques, until then restricted to the field of helioseismology, to study the best asteroseismic targets. Amongst these, the 16Cyg binary system holds a special place, as they are the brightest solar twins observed by the Kepler mission. For this specific system, modellers have access to high-quality asteroseismic, spectroscopic and interferometric data, making it the perfect testbed for the limitations of stellar models. Aims. We aim to further constrain the internal structure and fundamental parameters of 16CygA&B using linear seismic inversion techniques of both global indicators and localised corrections of the hydrostatic structure. Methods. We start from the models defined by detailed asteroseismic modelling in our previous paper and extend our analysis by applying variational inversions to our evolutionary models. We carried out inversions of so-called seismic indicators and attempted to provide local corrections of the internal structure of the two stars. Results. Our results indicate that linear seismic inversions alone are not able to discriminate between standard and non-standard models for 16CygA&B. We confirm the results of our previous studies that used linear inversion techniques, but consider that the observed differences could be linked to small fundamental parameters variations rather than to a missing process in the models. Conclusions. We confirm the robustness and reliability of the results of the modelling we performed in our previous paper. We conclude that non-linear inversions are likely required to further investigate the properties of 16CygA&B from a seismic point of view, but that these inversions have to be coupled to analyses of the depletion of light elements such as lithium and beryllium to constrain the macroscopic transport of chemicals in these stars and also to constrain potential non-standard evolutionary paths

Genetic support for a quantitative trait nucleotide in the ABCG2 gene affecting milk composition of dairy cattle

<p>Abstract</p> <p>Background</p> <p>Our group has previously identified a quantitative trait locus (QTL) affecting fat and protein percentages on bovine chromosome 6, and refined the QTL position to a 420-kb interval containing six genes. Studies performed in other cattle populations have proposed polymorphisms in two different genes (<it>ABCG2 </it>and <it>OPN</it>) as the underlying functional QTL nucleotide. Due to these conflicting results, we have included these QTNs, together with a large collection of new SNPs produced from PCR sequencing, in a dense marker map spanning the QTL region, and reanalyzed the data using a combined linkage and linkage disequilibrium approach.</p> <p>Results</p> <p>Our results clearly exclude the <it>OPN </it>SNP (<it>OPN_3907</it>) as causal site for the QTL. Among 91 SNPs included in the study, the <it>ABCG2 </it>SNP (<it>ABCG2_49</it>) is clearly the best QTN candidate. The analyses revealed the presence of only one QTL for the percentage traits in the tested region. This QTL was completely removed by correcting the analysis for <it>ABCG2_49</it>. Concordance between the sires' marker genotypes and segregation status for the QTL was found for <it>ABCG2_49 </it>only. The C allele of <it>ABCG2_49 </it>is found in a marker haplotype that has an extremely negative effect on fat and protein percentages and positive effect on milk yield. Of the 91 SNPs, <it>ABCG2_49 </it>was the only marker in perfect linkage disequilibrium with the QTL.</p> <p>Conclusion</p> <p>Based on our results, OPN_3907 can be excluded as the polymorphism underlying the QTL. The results of this and other papers strongly suggest the [A/C] mutation in <it>ABCG2_49 </it>as the causal mutation, although the possibility that <it>ABCG2_49 </it>is only a marker in perfect LD with the true mutation can not be completely ruled out.</p

CSF omeprazole concentration and albumin quotient following high dose intravenous omeprazole in dogs.

peer reviewedClinical signs of syringomyelia and hydrocephalus occur secondary to cerebrospinal fluid (CSF) accumulation within the central nervous system. Omeprazole is recommended to treat these conditions despite little evidence of its capacity to decrease CSF production in the dog. Studies into new treatments are hampered by difficulties in measuring CSF production. The albumin quotient (QAlb), the ratio between CSF and serum albumin concentrations, may reflect CSF production and any decrease in CSF production should be associated with an increase in QAlb. The primary objective of this study was to determine CSF omeprazole concentration after administration of a high intravenous dose of omeprazole and to evaluate its impact on QAlb in the dog. The second aim was to validate QAlb as a surrogate marker of CSF production. Eighteen dogs were included in this prospective crossover placebo-controlled study. Each dog received omeprazole (10 mg/kg), acetazolamide (50 mg/kg) combined with furosemide (1 mg/kg) and saline. Blood and CSF samples were obtained on day 0 and then every 7 days, one hour after drug administration. Omeprazole concentrations (2.0 ± 0.4 μmol/L) reached in CSF after high dose omeprazole were lower than the concentrations previously described as decreasing CSF production in dogs. There was no significant increase in QAlb following administration of acetazolamide/furosemide, prohibiting validation of QAlb as a surrogate marker for CSF production. Several dogs presented transient mild side effects after injection of acetazolamide/furosemide. High dose omeprazole was well tolerated in all dogs

Recent and historical recombination in the admixed Norwegian Red cattle breed

<p>Abstract</p> <p>Background</p> <p>Comparison of recent patterns of recombination derived from linkage maps to historical patterns of recombination from linkage disequilibrium (LD) could help identify genomic regions affected by strong artificial selection, appearing as reduced recent recombination. Norwegian Red cattle (NRF) make an interesting case study for investigating these patterns as it is an admixed breed with an extensively recorded pedigree. NRF have been under strong artificial selection for traits such as milk and meat production, fertility and health.</p> <p>While measures of LD is also crucial for determining the number of markers required for association mapping studies, estimates of recombination rate can be used to assess quality of genomic assemblies.</p> <p>Results</p> <p>A dataset containing more than 17,000 genome-wide distributed SNPs and 2600 animals was used to assess recombination rates and LD in NRF. Although low LD measured by r²was observed in NRF relative to some of the breeds from which this breed originates, reports from breeds other than those assessed in this study have described more rapid decline in r²at short distances than what was found in NRF. Rate of decline in r²for NRF suggested that to obtain an expected r²between markers and a causal polymorphism of at least 0.5 for genome-wide association studies, approximately one SNP every 15 kb or a total of 200,000 SNPs would be required. For well known quantitative trait loci (QTLs) for milk production traits on <it>Bos Taurus </it>chromosomes 1, 6 and 20, map length based on historic recombination was greater than map length based on recent recombination in NRF.</p> <p>Further, positions for 130 previously unpositioned contigs from assembly of the bovine genome sequence (Btau_4.0) found using comparative sequence analysis were validated by linkage analysis, and 28% of these positions corresponded to extreme values of population recombination rate.</p> <p>Conclusion</p> <p>While LD is reduced in NRF compared to some of the breeds from which this admixed breed originated, it is elevated over short distances compared to some other cattle breeds. Genomic regions in NRF where map length based on historic recombination was greater than map length based on recent recombination coincided with some well known QTL regions for milk production traits.</p> <p>Linkage analysis in combination with comparative sequence analysis and detection of regions with extreme values of population recombination rate proved to be valuable for detecting problematic regions in the Btau_4.0 genome assembly.</p