ABSTRACT
Small low-mass stars are favourable targets for the detection of rocky habitable planets. In particular, planetary systems in the solar neighbourhood are interesting and suitable for precise ...characterization. The RedDots campaigns seek to discover rocky planets orbiting nearby low-mass stars. The 2018 campaign targeted GJ 1061, which is the 20th nearest star to the Sun. For three consecutive months we obtained nightly, high-precision radial velocity measurements with the HARPS spectrograph. We analysed these data together with archival HARPS data. We report the detection of three planet candidates with periods of 3.204 ± 0.001, 6.689 ± 0.005, and 13.03 ± 0.03 d, which are close to 1:2:4 period commensurability. After several considerations related to the properties of the noise and sampling, we conclude that a fourth signal is most likely explained by stellar rotation, although it may be due to a planet. The proposed three-planet system (and the potential four-planet solution) is long-term dynamically stable. Planet–planet gravitational interactions are below our current detection threshold. The minimum masses of the three planets range from 1.4 ± 0.2 to 1.8 ± 0.3 M⊕. Planet d, with msin i = 1.64 ± 0.24 M⊕, receives a similar amount of energy as Earth receives from the Sun. Consequently it lies within the liquid-water habitable zone of the star and has a similar equilibrium temperature to Earth. GJ 1061 has very similar properties to Proxima Centauri but activity indices point to lower levels of stellar activity.
Abstract
The search for Earth-like planets around late-type stars using ultrastable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, ...since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard’s Star (Gl 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5 yr and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1 yr and comes from four different photometric sources: ASAS, FCAPT–RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (H α, Ca ii HK, and Na i D), as well as the full width at half-maximum (FWHM), of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of generalized Lomb–Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 ± 15 d, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1 m s−1. We also find evidence of a long-term cycle of 10 ± 2 yr that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals.
Increased blood lipid levels are heritable risk factors of cardiovascular disease with varied prevalence worldwide owing to different dietary patterns and medication use
. Despite advances in ...prevention and treatment, in particular through reducing low-density lipoprotein cholesterol levels
, heart disease remains the leading cause of death worldwide
. Genome-wideassociation studies (GWAS) of blood lipid levels have led to important biological and clinical insights, as well as new drug targets, for cardiovascular disease. However, most previous GWAS
have been conducted in European ancestry populations and may have missed genetic variants that contribute to lipid-level variation in other ancestry groups. These include differences in allele frequencies, effect sizes and linkage-disequilibrium patterns
. Here we conduct a multi-ancestry, genome-wide genetic discovery meta-analysis of lipid levels in approximately 1.65 million individuals, including 350,000 of non-European ancestries. We quantify the gain in studying non-European ancestries and provide evidence to support the expansion of recruitment of additional ancestries, even with relatively small sample sizes. We find that increasing diversity rather than studying additional individuals of European ancestry results in substantial improvements in fine-mapping functional variants and portability of polygenic prediction (evaluated in approximately 295,000 individuals from 7 ancestry groupings). Modest gains in the number of discovered loci and ancestry-specific variants were also achieved. As GWAS expand emphasis beyond the identification of genes and fundamental biology towards the use of genetic variants for preventive and precision medicine
, we anticipate that increased diversity of participants will lead to more accurate and equitable
application of polygenic scores in clinical practice.
Common single-nucleotide polymorphisms (SNPs) are predicted to collectively explain 40-50% of phenotypic variation in human height, but identifying the specific variants and associated regions ...requires huge sample sizes
. Here, using data from a genome-wide association study of 5.4 million individuals of diverse ancestries, we show that 12,111 independent SNPs that are significantly associated with height account for nearly all of the common SNP-based heritability. These SNPs are clustered within 7,209 non-overlapping genomic segments with a mean size of around 90 kb, covering about 21% of the genome. The density of independent associations varies across the genome and the regions of increased density are enriched for biologically relevant genes. In out-of-sample estimation and prediction, the 12,111 SNPs (or all SNPs in the HapMap 3 panel
) account for 40% (45%) of phenotypic variance in populations of European ancestry but only around 10-20% (14-24%) in populations of other ancestries. Effect sizes, associated regions and gene prioritization are similar across ancestries, indicating that reduced prediction accuracy is likely to be explained by linkage disequilibrium and differences in allele frequency within associated regions. Finally, we show that the relevant biological pathways are detectable with smaller sample sizes than are needed to implicate causal genes and variants. Overall, this study provides a comprehensive map of specific genomic regions that contain the vast majority of common height-associated variants. Although this map is saturated for populations of European ancestry, further research is needed to achieve equivalent saturation in other ancestries.
Blood pressure is a heritable trait influenced by several biological pathways and responsive to environmental stimuli. Over one billion people worldwide have hypertension (≥140 mm Hg systolic blood ...pressure or ≥90 mm Hg diastolic blood pressure). Even small increments in blood pressure are associated with an increased risk of cardiovascular events. This genome-wide association study of systolic and diastolic blood pressure, which used a multi-stage design in 200,000 individuals of European descent, identified sixteen novel loci: six of these loci contain genes previously known or suspected to regulate blood pressure (GUCY1A3-GUCY1B3, NPR3-C5orf23, ADM, FURIN-FES, GOSR2, GNAS-EDN3); the other ten provide new clues to blood pressure physiology. A genetic risk score based on 29 genome-wide significant variants was associated with hypertension, left ventricular wall thickness, stroke and coronary artery disease, but not kidney disease or kidney function. We also observed associations with blood pressure in East Asian, South Asian and African ancestry individuals. Our findings provide new insights into the genetics and biology of blood pressure, and suggest potential novel therapeutic pathways for cardiovascular disease prevention.
Using genome-wide data from 253,288 individuals, we identified 697 variants at genome-wide significance that together explained one-fifth of the heritability for adult height. By testing different ...numbers of variants in independent studies, we show that the most strongly associated ∼2,000, ∼3,700 and ∼9,500 SNPs explained ∼21%, ∼24% and ∼29% of phenotypic variance. Furthermore, all common variants together captured 60% of heritability. The 697 variants clustered in 423 loci were enriched for genes, pathways and tissue types known to be involved in growth and together implicated genes and pathways not highlighted in earlier efforts, such as signaling by fibroblast growth factors, WNT/β-catenin and chondroitin sulfate-related genes. We identified several genes and pathways not previously connected with human skeletal growth, including mTOR, osteoglycin and binding of hyaluronic acid. Our results indicate a genetic architecture for human height that is characterized by a very large but finite number (thousands) of causal variants.
The Wellcome Trust Case Control Consortium (WTCCC) identified nine single SNPs putatively associated with rheumatoid arthritis at P = 1 × 10−5 − 5 × 10−7 in a genome-wide association screen. One, ...rs6920220, was unequivocally replicated (trend P = 1.1 × 10−8) in a validation study, as described here. This SNP maps to 6q23, between the genes oligodendrocyte lineage transcription factor 3 (OLIG3) and tumor necrosis factor-α-induced protein 3 (TNFAIP3).
Herein, we demonstrate a method for the functionalization of cubic phase lipid nanoparticles (cubosomes) with a series of magnetite (Fe3O4), copper oxide (Cu2O), and silver (Ag) nanocrystals, with ...prospective applications across a wide range of fields, including antimicrobial treatments. The resulting cubosomes are characterized using small-angle X-ray scattering and dynamic light scattering, demonstrating the retention of a typical cubic phase structure and particle size following nanocrystal encapsulation at concentrations up to 20% w/w. Cryogenic transmission electron microscopy reveals significant loading and association of each nanocrystal type with both monoolein- and phytantriol-based cubosomes. The antibiotic potential of these hybrid nanoparticles is demonstrated for the first time; cubosomes with embedded silver nanocrystals display a high level of antimicrobial activity against both Gram-positive and Gram-negative bacteria, with observed minimum inhibitory concentration values ranging from 15.6–250 μg/mL. Lastly, total internal reflection fluorescence microscopy is used to visualize cubosome–bacteria interactions, suggesting the involvement of particle interactions as a delivery mechanism.
AU Mic b is a Neptune-sized planet on an 8.47-day orbit around the nearest pre-main sequence (~20 Myr) star to the Sun, the bright (
V
= 8.81) M dwarf AU Mic. The planet was preliminary detected in ...Doppler radial velocity time series and recently confirmed to be transiting with data from the TESS mission. AU Mic b is likely to be cooling and contracting and might be accompanied by a second, more massive planet, in an outer orbit. Here, we present the observations of the transit of AU Mic b using ESPRESSO on the Very Large Telescope. We obtained a high-resolution time series of spectra to measure the Rossiter-McLaughlin effect, to constrain the spin-orbit alignment of the star and planet, and to simultaneously attempt to retrieve the planet’s atmospheric transmission spectrum. These observations allowed us to study, for the first time, the early phases of the dynamical evolution of young systems. We applied different methodologies to derive the spin-orbit angle of AU Mic b, and all of them retrieve values consistent with the planet being aligned with the rotation plane of the star. We determined a conservative spin-orbit angle
λ
value of −2.96
−10.30
+10.44
degrees, indicative that the formation and migration of the planets of the AU Mic system occurred within the disc. Unfortunately, and despite the large signal-to-noise ratio of our measurements, the degree of stellar activity prevented us from detecting any features from the planetary atmosphere. In fact, our results suggest that transmission spectroscopy for recently formed planets around active young stars is going to remain very challenging, if at all possible, for the near future.
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