Searching for signatures of planet formation in stars with circumstellar debris discs

(Abridged) Tentative correlations between the presence of dusty debris discs and low-mass planets have been presented. In parallel, detailed chemical abundance studies have reported different trends between samples of planet and non-planet hosts. We determine in a homogeneous way the metallicity, and abundances of a sample of 251 stars including stars with known debris discs, with debris discs and planets, and only with planets. Stars with debris discs and planets have the same [Fe/H] behaviour as stars hosting planets, and they also show a similar -Tc trend. Different behaviour in the -Tc trend is found between the samples of stars without planets and the samples of planet hosts. In particular, when considering only refractory elements, negative slopes are shown in cool giant planet hosts, whilst positive ones are shown in stars hosting low-mass planets. Stars hosting exclusively close-in giant planets show higher metallicities and positive -Tc slope. A search for correlations between the -Tc slopes and the stellar properties reveals a moderate but significant correlation with the stellar radius and as well as a weak correlation with the stellar age. The fact that stars with debris discs and stars with low-mass planets do not show neither metal enhancement nor a different -Tc trend might indicate a correlation between the presence of debris discs and the presence of low-mass planets. We extend results from previous works which reported differences in the -Tc trends between planet hosts and non hosts. However, these differences tend to be present only when the star hosts a cool distant planet and not in stars hosting exclusively low-mass planets.Comment: Accepted for publication in Astronomy and Astrophysic

The bias-extension test for the analysis of in-plane shear properties of textile composite reinforcements and prepregs: a review

The bias-extension test is a rather simple experiment aiming to determine in-plane shear properties of textile composite reinforcements. However the mechanics during the test involves fibrous material at large shear strains and large rotations of the fibres. Several aspects are still being studied and are not yet modeled in a consensual manner. The standard analysis of the test is based on two assumptions: inextensibility of the fibers and rotations at the yarn crossovers without slippage. They lead to the development of zones with constant fibre orientations proper to the bias-extension test. Beyond the analysis of the test within these basic assumptions, the paper presents studies that have been carried out on the lack of verification of these hypothesis (slippage, tension in the yarns, effects of fibre bending). The effects of temperature, mesoscopic modeling and tension locking are also considered in the case of the bias-extension test

Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field

The magnetic response of irreversible type-II superconductor slabs subjected to in-plane rotating magnetic field is investigated by applying the circular, elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state models. Specifically, the models have been applied to explain experiments on a PbBi rotating disk in a fixed magnetic field ${\bm H}_a$, parallel to the flat surfaces. Here, we have exploited the equivalency of the experimental situation with that of a fixed disk under the action of a parallel magnetic field, rotating in the opposite sense. The effect of both the magnitude $H_a$ of the applied magnetic field and its angle of rotation $\alpha_s$ upon the magnetization of the superconductor sample is analyzed. When $H_a$ is smaller than the penetration field $H_P$, the magnetization components, parallel and perpendicular to ${\bm H_a}$, oscillate with increasing the rotation angle. On the other hand, if the magnitude of the applied field, $H_a$, is larger than $H_P$, both magnetization components become constant functions of $\alpha_s$ at large rotation angles. The evolution of the magnetic induction profiles inside the superconductor is also studied.Comment: 12 pages, 29 figure

Surface-induced near-field scaling in the Knudsen layer of a rarefied gas

We report on experiments performed within the Knudsen boundary layer of a low-pressure gas. The non-invasive probe we use is a suspended nano-electro-mechanical string (NEMS), which interacts with $^4$He gas at cryogenic temperatures. When the pressure $P$ is decreased, a reduction of the damping force below molecular friction $\propto P$ had been first reported in Phys. Rev. Lett. Vol 113, 136101 (2014) and never reproduced since. We demonstrate that this effect is independent of geometry, but dependent on temperature. Within the framework of kinetic theory, this reduction is interpreted as a rarefaction phenomenon, carried through the boundary layer by a deviation from the usual Maxwell-Boltzmann equilibrium distribution induced by surface scattering. Adsorbed atoms are shown to play a key role in the process, which explains why room temperature data fail to reproduce it.Comment: Article plus supplementary materia

Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. V.: A Massive Jupiter orbiting the very low metallicity giant star BD+03 2562 and a possible planet around HD~103485

We present two evolved stars from the TAPAS (Tracking Advanced PlAnetary Systems) with HARPS-N project devoted to RV precision measurements of identified candidates within the PennState - Torun Centre for Astronomy Planet Search. Evolved stars with planets are crucial to understand the dependency of the planet formation mechanism on the mass and metallicity of the parent star and to study star-planet interactions. The paper is based on precise radial velocity (RV) measurements, for HD 103485 we collected 57 epochs over 3317 days with the Hobby-Eberly Telescope and its High Resolution Spectrograph and 18 ultra-precise HARPS-N data over 919 days. For BD+03 2562 we collected 46 epochs of HET data over 3380 days and 19 epochs of HARPS-N data over 919 days. We present the analysis of the data and the search for correlations between the RV signal and stellar activity, stellar rotation and photometric variability. Based on the available data, we interpret the RV variations measured in both stars as Keplerian motion. Both stars have masses close to Solar (1.11 and 1.14), very low metallicities ([Fe/H]=-0.50 and -0.71), and, both have Jupiter planetary mass companions (m sin i=7 and 6.4 Mj), in close to terrestrial orbits (1.4 and 1.3~au), with moderate eccentricities (e=0.34 and 0.2). However, we cannot totally exclude that the signal in the case of HD~103485 is due to rotational modulation of active regions. Based on the current data, we conclude that BD+03 2562 has a bona fide planetary companion while for HD 103485 we cannot totally exclude that the best explanation for the RV signal modulations is not the existence of a planet but stellar activity. If, the interpretation remains that both stars have planetary companions they represent systems orbiting very evolved stars with very low metallicities, a challenge to the conditions required for the formation of massive giant gas planets.Comment: Acepted A&A 12 pages, 11 figure

Integrating archaeology and ancient DNA analysis to address invasive species colonization in the Gulf of Alaska

The intentional and unintentional movement of plants and animals by humans has transformed ecosystems and landscapes globally. Assessing when and how a species was introduced are central to managing these transformed landscapes, particularly in island environments. In the Gulf of Alaska, there is considerable interest in the history of mammal introductions and rehabilitating Gulf of Alaska island environments by eradicating mammals classified as invasive species. The Arctic ground squirrel (Urocitellus parryii) is of concern because it affects vegetation and seabirds on Gulf of Alaska islands. This animal is assumed to have been introduced by historic settlers; however, ground squirrel remains in the prehistoric archaeological record of Chirikof Island, Alaska, challenge this timeline and suggest they colonized the islands long ago. We used 3 lines of evidence to address this problem: direct radiocarbon dating of archaeological squirrel remains; evidence of prehistoric human use of squirrels; and ancient DNA analysis of dated squirrel remains. Chirikof squirrels dated to at least 2000 years ago, and cut marks on squirrel bones suggested prehistoric use by people. Ancient squirrels also shared a mitochondrial haplotype with modern Chirikof squirrels. These results suggest that squirrels have been on Chirikof longer than previously assumed and that the current population of squirrels is closely related to the ancient population. Thus, it appears ground squirrels are not a recent, human‐mediated introduction and may have colonized the island via a natural dispersal event or an ancient human translocation.We thank T. Rick, D. Grayson, R. Fleischer, M. Hawkins, A. West, and C. Mikeska for their contributions to this research. We also thank 3 reviewers and the editors of Conservation Biology who greatly improved this paper. This work was funded by the National Geographic Society, the University of Maine, the Smithsonian Institution, and Boston University. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service. (National Geographic Society; University of Maine; Smithsonian Institution; Boston University)Published versio

A Review On Geotrichum Lipases: Production, Purification, Immobilization And Applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Lipases are enzymes produced from innumerous microorganisms, plants and animal cells. They catalyze reactions of different lipid sources. The Geotrichum fungi are good producers of lipases with high hydrolytic activity and specificity for unsaturated fatty acids. A great number of studies have reported the importance of lipase from this genus and described important fermentation parameters for the enzyme production, such as nutrients, temperature, pH, inoculum, time of fermentation and others. Furthermore, different strategies have been used to purify and immobilize lipases from Geotrichum and innumerous applications are cited in different processes as polyunsaturated fatty acids enrichment, hydrolysis and esterification of fat and oils, synthesis of aromas, biodiesel, and many others. This review highlights fundamental aspects of the production, purification, characterization, immobilization, and the applications of lipases produced by the genus Geotrichum.304439454Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP, Brazil)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq, Brazil)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES, Brazil)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Dynamical evolution of two-planet systems and its connection with white dwarf atmospheric pollution

Asteroid material is detected in white dwarfs (WDs) as atmospheric pollution by metals, in the form of gas/dust discs, or in photometric transits. Within the current paradigm, minor bodies need to be scattered, most likely by planets, into highly eccentric orbits where the material gets disrupted by tidal forces and then accreted onto the star. This can occur through a planet-planet scattering process triggered by the stellar mass loss during the post main-sequence evolution of planetary systems. So far, studies of the $N$-body dynamics of this process have used artificial planetary system architectures built ad hoc. In this work, we attempt to go a step further and study the dynamical instability provided by more restrictive systems, that, at the same time allow us an exploration of a wider parameter space: the hundreds of multiple planetary systems found around main-sequence (MS) stars. We find that most of our simulated systems remain stable during the MS, Red and Asymptotic Giant Branch and for several Gyr into the WD phases of the host star. Overall, only $\approx$ 2.3$\%$ of the simulated systems lose a planet on the WD as a result of dynamical instability. If the instabilities take place during the WD phase most of them result in planet ejections with just 5 planetary configurations ending as a collision of a planet with the WD. Finally 3.2$\%$ of the simulated systems experience some form of orbital scattering or orbit crossing that could contribute to the pollution at a sustained rate if planetesimals are present in the same system.Comment: 18 pages, 14 figure