At least one in a dozen stars shows evidence of planetary ingestion.

Stellar chemical compositions can be altered by ingestion of planetary material1,2 and/or planet formation, which removes refractory material from the protostellar disk3,4. These 'planet signatures' appear as correlations between elemental abundance differences and the dust condensation temperature3,5,6. Detecting these planet signatures, however, is challenging owing to unknown occurrence rates, small amplitudes and heterogeneous star samples with large differences in stellar ages7,8. Therefore, stars born together (that is, co-natal) with identical compositions can facilitate the detection of planet signatures. Although previous spectroscopic studies have been limited to a small number of binary stars9-13, the Gaia satellite14 provides opportunities for detecting stellar chemical signatures of planets among co-moving pairs of stars confirmed to be co-natal15,16. Here we report high-precision chemical abundances for a homogeneous sample of ninety-one co-natal pairs of stars with a well defined selection function and identify at least seven instances of planetary ingestion, corresponding to an occurrence rate of eight per cent. An independent Bayesian indicator is deployed, which can effectively disentangle the planet signatures from other factors, such as random abundance variation and atomic diffusion17. Our study provides evidence of planet signatures and facilitates a deeper understanding of the star-planet-chemistry connection by providing observational constraints on the mechanisms of planet engulfment, formation and evolution.

Testosterone secretion in a socially monogamous but sexually promiscuous migratory passerine.

The steroid hormone testosterone (T) influences a multitude of traits critical to reproduction in vertebrates. In birds, high male T supports territory establishment and mate attraction, but is thought to interfere with parental care. Interspecific comparisons indicate that migratory species with short, synchronous breeding seasons have the highest peak T, and that the seasonal profile of T exhibits a rapid decline with the onset of incubation by females. We describe the T profile of the migratory, socially monogamous, and biparental Eastern Kingbird (Tyrannus tyrannus) from the high desert of eastern Oregon, USA, where breeding occurs within a short 2-3 month period. Eastern Kingbirds are socially monogamous but exhibit high rates of extra-pair paternity as ∼60% of broods contain extra-pair young. We therefore evaluate whether Eastern Kingbirds exhibit the "typical" T profile expected for a synchronously breeding migratory species, or whether T is maintained at a more constant level as would be predicted for a species with opportunities for mating that extend over a majority of the breeding season. Our samples were divided into six periods of the reproductive cycle from territory establishment to the feeding of fledglings. T did not change across stages of the nest cycle. Instead, T declined with sampling date and nest density, and increased with the number of fertile females in the population. Male kingbirds advertise their presence through song for most of the breeding season, and we suggest that T is maintained throughout most of the breeding season because male fitness is equally dependent on within- and extra-pair reproductive success.

The effect of knee flexion contracture following total knee arthroplasty on the energy cost of walking.

This study evaluated the energy cost of walking (Cw) with knee flexion contractures (FC) simulated with a knee brace, in total knee arthroplasty (TKA) recipients (n=16) and normal controls (n=15), and compared it to baseline (no brace). There was no significant difference in Cw between the groups at baseline but TKA recipients walked slower (P=0.048) and with greater knee flexion in this condition (P=0.003). Simulated FC significantly increased Cw in both groups (TKA P=0.020, control P=0.002) and this occurred when FC exceeded 20° in the TKA group and 15° in the controls. Reported perceived exertion was only significantly increased by FC in the control group (control P<0.001, TKA P=0.058). Simulated knee FCs less than 20° do not increase Cw or perceived exertion in TKA recipients.

Birmingham Mid-Head Resection hip arthroplasty in a young man with gigantism.

The Birmingham Mid-Head Resection (Smith & Nephew Ltd, Warwick, United Kingdom) arthroplasty is a new bone-conserving procedure that, like hip resurfacing, is used in younger, active patients. We present the case of a young man with Sotos syndrome (cerebral gigantism) with associated extraordinary stature (height, 2.16 m; weight, 157 kg) who underwent Birmingham Mid-Head Resection arthroplasty. The large stature of this patient required a custom manufactured prosthesis (a femoral head 68 mm in diameter with an acetabular cup 76 mm in diameter). We believe this to be the largest metal-on-metal resurfacing articulation and hip arthroplasty reported to date.

A limit on variations in the fine-structure constant from spectra of nearby Sun-like stars.

The fine structure constant α sets the strength of the electromagnetic force. The Standard Model of particle physics provides no explanation for its value, which could potentially vary. The wavelengths of stellar absorption lines depend on α but are subject to systematic effects owing to astrophysical processes in stellar atmospheres. We measured precise line wavelengths from observations of 17 stars, selected to have almost identical atmospheric properties to those of the Sun (solar twins), which reduces those systematic effects. We found that α varies by [Formula: see text] parts per billion within 50 parsecs from Earth. Combining the results from all 17 stars provides an empirical local reference for stellar measurements of α, with an ensemble precision of 12 parts per billion.

Selection ratios on community aggregated traits estimate ecological filters imposed on species by sites.

Variation in community structure is mediated by interactions between species traits and a site's environmental characteristics. Previously, data on community composition at sites has been employed to correlate trait and environmental variables (e.g., RLQ analysis) and to predict community-level expression of quantitative traits (i.e., community aggregated traits). Here, we demonstrate that the selection ratio, a method originating in animal resource selection studies, can estimate the ecological filters that site conditions impose on species traits by combining observed community aggregated traits with null models of species availability. This flexible, nonparametric approach expresses the filter at each site as a probability density function for the selection of individuals possessing a given trait value. By doing so, it generalizes the community aggregated trait concept to include categorical as well as continuous traits and allows for both intraspecific variation in trait expression and differences in species availability among sites. The resulting site-level filter functions can be related to environmental covariates by standard statistical approaches (e.g., regression). The method complements existing techniques for analyzing trait-environment interactions in community ecology.

Extraordinary photoresponse in two-dimensional In(2)Se(3) nanosheets.

We demonstrate extraordinary photoconductive behavior in two-dimensional (2D) crystalline indium selenide (In2Se3) nanosheets. Photocurrent measurements reveal that semiconducting In2Se3 nanosheets have an extremely high response to visible light, exhibiting a photoresponsivity of 3.95 × 10(2) A·W(-1) at 300 nm with an external quantum efficiency greater than 1.63 × 10(5) % at 5 V bias. The key figures-of-merit exceed that of graphene and other 2D material-based photodetectors reported to date. In addition, the photodetector has a fast response time of 1.8 × 10(-2) s and a specific detectivity of 2.26 × 10(12) Jones. The photoconductive response of α-In2Se3 nanosheets extends into ultraviolet, visible, and near-infrared spectral regions. The high photocurrent response is attributed to the direct band gap (EG = 1.3 eV) of In2Se3 combined with a large surface-area-to-volume ratio and a self-terminated/native-oxide-free surface, which help to reduce carrier recombination while keeping fast response, allowing for real-time detection under very low-light conditions.

Strong limit on a variable proton-to-electron mass ratio from molecules in the distant universe.

The Standard Model of particle physics assumes that the so-called fundamental constants are universal and unchanging. Absorption lines arising in molecular clouds along quasar sightlines offer a precise test for variations in the proton-to-electron mass ratio, mu, over cosmological time and distance scales. The inversion transitions of ammonia are particularly sensitive to mu as compared to molecular rotational transitions. Comparing the available ammonia spectra observed toward the quasar B0218+357 with new, high-quality rotational spectra, we present the first detailed measurement of mu with this technique, limiting relative deviations from the laboratory value to |Deltamu/mu| < 1.8 x 10(-6) (95% confidence level) at approximately half the universe's current age-the strongest astrophysical constraint to date. Higher-quality ammonia observations will reduce both the statistical and systematic uncertainties in these observations.

Stringent null constraint on cosmological evolution of the proton-to-electron mass ratio.

We present a strong constraint on variation of the proton-to-electron mass ratio mu over cosmological time scales using molecular hydrogen transitions in optical quasar spectra. Using high quality spectra of quasars Q0405-443, Q0347-383, and Q0528-250, variation in micro relative to the present day value is limited to Deltamicro/micro=(2.6+/-3.0)x10;{-6}. We reduce systematic errors compared to previous works by substantially improving the spectral wavelength calibration method and by fitting absorption profiles to the forest of hydrogen Lyman alpha transitions surrounding each H2 transition. Our results are consistent with no variation, and inconsistent with a previous approximately 4sigma detection of mu variation involving Q0405-443 and Q0347-383. If the results of this work and those suggesting that alpha may be varying are both correct, then this would tend to disfavor certain grand unification models.

Laser frequency combs for astronomical observations.

A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of approximately 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrated the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of approximately 9 meters per second at approximately 1.5 micrometers-beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceleration.