The effect of magnetic activity saturation in chromospheric flux-flux relationships

We present a homogeneous study of chromospheric and coronal flux-flux relationships using a sample of 298 late-type dwarf active stars with spectral types F to M. The chromospheric lines were observed simultaneously in each star to avoid spread due to long term variability. Unlike other works, we subtract the basal chromospheric contribution in all the spectral lines studied. For the first time, we quantify the departure of dMe stars from the general relations. We show that dK and dKe stars also deviate from the general trend. Studying the flux-colour diagrams we demonstrate that the stars deviating from the general relations are those with saturated X-ray emission and that those stars also present saturation in the H$\alpha$ line. Using several age spectral indicators, we show that they are younger stars than those following the general relationships. The non-universality of flux-flux relationships found in this work should be taken into account when converting between fluxes in different chromospheric activity indicators.Comment: Accepted for publication in the Monthly Notices of the Royal Astronomical Societ

Genomics for transforming yam breeding

Yam (Dioscorea spp.), a multispecies, polyploidy, and vegetatively propagated crop, is an economically important staple food for more than 300 million people in West Africa, Asia, Oceania, and the Caribbean. The five major yam-producing countries in West Africa (Bénin, Côte d’Ivoire, Ghana, Nigeria, and Togo) account for 93% of worldwide production. Dioscorea rotundata and D. alata are the species most commonly cultivated in West Africa1. The genetic improvement of yam is faced with several constraints, including the long growth cycle (about 8 months or more), dioecy, plants that flower poorly or not at all, polyploidy, vegetative propagation, heterozygous genetic background, and poor knowledge about the genetics of the crop2

Yam breeding at IITA: achievements, challenges, and prospects

African food system Yam (Dioscorea spp.) is a multispecies, clonally propagated crop cultivated for its starchy tubers. About 10 species are widely cultivated around the world, but only D. rotundata, D. alata, and D. cayenensis are the most widely cultivated species in West Africa, accounting for 93% of the global yam production. Since inception, IITA R4D efforts have focused on developing new varieties of yam with desired agronomic and quality traits and to improve yam-based cropping systems

Metabolite profiling of yam (Dioscorea spp.) accessions for use in crop improvement programmes

Article purchased; Published online: 14 Oct. 2017Introduction Ninety-seven percent of yam (Dioscorea spp.) production takes place in low income food deficit countries (LIFDCs) and the crop provides 200 calories a day to approximately 300 million people. Therefore, yams are vital for food security. Yams have high-yield potential and high market value potential yet current breeding of yam is hindered by a lack of genomic information and genetic resources. New tools are needed to modernise breeding strategies and unlock the potential of yam to improve livelihood in LIFDCs. Objectives Metabolomic screening has been undertaken on a diverse panel of Dioscorea accessions to assess the utility of the approach for advancing breeding strategies in this understudied crop. Methods Polar and lipophilic extracts from tubers of accessions from the global yam breeding program have been comprehensively profiled via gas chromatography-mass spectrometry. Results A visual pathway representation of the measured yam tuber metabolome has been delivered as a resource for biochemical evaluation of yam germplasm. Over 200 compounds were routinely measured in tubers, providing a major advance for the chemo-typing of this crop. Core biochemical redundancy concealed trends that were only elucidated following detailed mining of global metabolomics data. Combined analysis on leaf and tuber material identified a subset of metabolites which allow accurate species classification and highlighted the potential of predicting tuber composition from leaf profiles. Metabolic variation was accessionspecific and often localised to compound classes, which will aid trait-targeting for metabolite markers. Conclusions Metabolomics provides a standalone platform with potential to deliver near-future crop gains for yam. The approach compliments the genetic advancements currently underway and integration with other ‘–omics’ studies will deliver a significant advancement to yam breeding strategies

Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter

Context: Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles and their perturbations alter the line centroids creating a radial velocity jitter that might contaminate" the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims: We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d < 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e, CaII H & K lines, to others that hold noteworthy advantages. Methods: We used high resolution (~50000) echelle optical spectra. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R'_HK index. Results: We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity to estimate the expected RV jitter for the active stars in the sample.Comment: Accepted for publication in Astronomy & Astrophysic

Exalted dual-scale surface roughening in laser ablated aluminum capped with a transparent thin film: Wetting and anti-icing behavior

Near infrared laser ablation of metals, specifically aluminum, has been systematically applied to generate surface roughness. Very high laser fluences may even lead to a so called “explosive” ablation regime where roughness becomes dramatically enhanced. In the present work we have developed an alternative methodology that, utilizing milder laser irradiation conditions (i.e. laser fluences from 0.37 to 0.72 J/cm²), renders aluminum surfaces with a dual-scale roughness character and Sp parameter values twice or even trice the value found in reference samples. This has been possible for aluminum substrates coated with a highly transparent aluminum oxynitride capping layer. The resulting surfaces, consisting of very rough partially oxidized aluminum with negligible amounts of nitrogen species, resulted highly hydrophobic and depicted long icing delay times as required for anti-icing applications. A correlation has been found between the wetting and anti-icing behaviors, the use of a capping layer and the laser irradiation conditions. To account for this exalted roughening phenomenon, we propose that the transparent capping layer confines the laser energy within the aluminum shallow zones, delays the formation of the plasma plume and produces an enhancement in the aluminum ablation, even at relatively low laser fluences.University of Seville through the VI PPIT-USMCIN/AEI/10.13039/50110001103

Magnetic properties of iron powder sintered by medium-frequency electrical resistance sintering

Medium-frequency electrical resistance sintering (MF-ERS) is a technique that uses the application of pressure and heat, heat coming from the Joule effect, simultaneously to metallic powders. In this study, this technique consolidates commercial iron powders, and the porosity distribution and hysteresis curves of the compacts were analysed. Compact consolidated by conventional powder metallurgy (PM) was compared with the results obtained

TYC 8380-1953-1: Discovery of an RS CVn binary through the XMM-Newton slew survey

In this paper we report the discovery of the chromospherically active (RS CVn type) binary TYC 8380-1953-1 through the XMM-Newton slew survey and present results of our optical and X-ray follow-up. With a flux limit of $6 \times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$ in the soft band ($0.2 - 2$ keV), the XMM-Newton slew has a similar sensitivity to the ROSAT All Sky Survey allowing interesting sources to be identified by their long-term variability. Two different types of stellar sources are detected in shallow X-ray surveys: young stars (both pre-main and main sequence stars) and chromospherically active binaries (BY Dra and RS CVn type systems). The discovery of stars in such surveys and the study of their nature through optical follow-ups is valuable to determine their spatial distribution and scale height in the Galaxy. Our analysis shows that TYC 8380-1953-1 is a double-lined spectroscopic binary with both components having similar spectral type (likely K0/2+K3/5) and luminosity. With a typical coronal temperature for an RS CVn system ($kT \sim 1.15$ keV) and an X-ray luminosity in the $0.3-10$ keV energy band higher than $4 \times 10^{31}$ erg\,s$^{-1}$, TYC 8380-1953-1 lies among the most X-ray luminous RS CVn binaries.Comment: Accepted for publication in the PASP. 18 pages, 10 figure

Development of genomic simple sequence repeat markers for yam

Yam ( Dioscorea spp.) is a major staple crop widely cultivated for its starchy tubers. To date, very few marker resources are publicly avail - able as tools for genetic and genomic studies of this economically important crop. In this study, 90 simple sequence repeat (SSR) markers were developed from an enriched genomic library of yellow Guinea yam ( D. cayenensis Lam.). Cross- amplification revealed that 85 (94.4%) and 51 (56.7%) of these SSRs could be successfully transferred to the two major cultivated species of D. rotundata Poir. and D. alata L., respec - tively. Polymorphisms in 30 markers selected on the basis of reliability and reproducibility of DNA bands were evaluated using a panel of 12 D. cayenensis , 48 D. rotundata , and 48 D. alata accessions. Accordingly, number of alleles per locus ranged from 2 to 8 in D. cayenensis (mean = 3.9), 3 to 30 in D. rotundata (mean = 13.9), and 2 to 22 in D. alata (mean = 12.1). The average observed and expected heterozygosi - ties were 0.156 and 0.634 ( D. cayenensis ), 0.326 and 0.853 ( D. rotundata ), and 0.247 and 0.836 ( D. alata ), respectively. Clustering based on six SSRs that were polymorphic in at least four of the five cultivated Dioscorea species studied, including D. cayenensis , D. rotundata , D. alata , D. dumetorum (Kunth) Pax., and D. bulbifera L., detected groups consistent with the phyloge - netic relationships of the species except for D. dumetorum . These new SSR markers are invalu - able resources for applications such as genetic diversity analysis and marker-assisted breedingYam ( Dioscorea spp.) is a major staple crop widely cultivated for its starchy tubers. To date, very few marker resources are publicly avail - able as tools for genetic and genomic studies of this economically important crop. In this study, 90 simple sequence repeat (SSR) markers were developed from an enriched genomic library of yellow Guinea yam ( D. cayenensis Lam.). Cross- amplification revealed that 85 (94.4%) and 51 (56.7%) of these SSRs could be successfully transferred to the two major cultivated species of D. rotundata Poir. and D. alata L., respec - tively. Polymorphisms in 30 markers selected on the basis of reliability and reproducibility of DNA bands were evaluated using a panel of 12 D. cayenensis , 48 D. rotundata , and 48 D. alata accessions. Accordingly, number of alleles per locus ranged from 2 to 8 in D. cayenensis (mean = 3.9), 3 to 30 in D. rotundata (mean = 13.9), and 2 to 22 in D. alata (mean = 12.1). The average observed and expected heterozygosi - ties were 0.156 and 0.634 ( D. cayenensis ), 0.326 and 0.853 ( D. rotundata ), and 0.247 and 0.836 ( D. alata ), respectively. Clustering based on six SSRs that were polymorphic in at least four of the five cultivated Dioscorea species studied, including D. cayenensis , D. rotundata , D. alata , D. dumetorum (Kunth) Pax., and D. bulbifera L., detected groups consistent with the phyloge - netic relationships of the species except for D. dumetorum . These new SSR markers are invalu - able resources for applications such as genetic diversity analysis and marker-assisted breedin