Identification of fossilized eggshells from the Taung hominin locality, Taung, Northwest Province, South Africa

While an avian component within faunal remains from the Dart Deposits, Taung, South Africa, has been discussed for nearly a century, the taxa present have not been identified to species. Here we conduct a systematic analysis of fossilized eggshell fragments in order to document the presence of specific avian taxa at Taung during the Plio-Pleistocene. A comparative analysis of surface morphology and surface curvatures of fragmentary eggshells eliminated all but three extant avian taxa as potential sources for the fossilized fragments: a large eagle, an eagle owl (Bubo sp.) or a guinea fowl (subfamily Numidinae). The likelihood for each of these three taxa as a source is discussed by evaluating surface curvature matches between the fossilized fragments and extant eggshells. The two most complete fossil eggshells recovered from Taung have distinct carbon isotope signatures indicating that they belong to two different, granivorous and carnivorous, guilds. While these identifications contribute to the debate over whether or not there was an avian agent of collection for the Taung fossils, including perhaps the Taung Child, by establishing direct evidence for a raptor component in the Taung faunal assemblage, they cannot address specific predator-prey behaviour

MADIBA: A web server toolkit for biological interpretation of Plasmodium and plant gene clusters

<p>Abstract</p> <p>Background</p> <p>Microarray technology makes it possible to identify changes in gene expression of an organism, under various conditions. Data mining is thus essential for deducing significant biological information such as the identification of new biological mechanisms or putative drug targets. While many algorithms and software have been developed for analysing gene expression, the extraction of relevant information from experimental data is still a substantial challenge, requiring significant time and skill.</p> <p>Description</p> <p>MADIBA (MicroArray Data Interface for Biological Annotation) facilitates the assignment of biological meaning to gene expression clusters by automating the post-processing stage. A relational database has been designed to store the data from gene to pathway for <it>Plasmodium</it>, rice and <it>Arabidopsis</it>. Tools within the web interface allow rapid analyses for the identification of the Gene Ontology terms relevant to each cluster; visualising the metabolic pathways where the genes are implicated, their genomic localisations, putative common transcriptional regulatory elements in the upstream sequences, and an analysis specific to the organism being studied.</p> <p>Conclusion</p> <p>MADIBA is an integrated, online tool that will assist researchers in interpreting their results and understand the meaning of the co-expression of a cluster of genes. Functionality of MADIBA was validated by analysing a number of gene clusters from several published experiments – expression profiling of the <it>Plasmodium </it>life cycle, and salt stress treatments of <it>Arabidopsis </it>and rice. In most of the cases, the same conclusions found by the authors were quickly and easily obtained after analysing the gene clusters with MADIBA. </p

Ariel - Volume 4 Number 6

Editors David A. Jacoby Eugenia Miller Tom Williams Associate Editors Paul Bialas Terry Burt Michael Leo Gail Tenikat Editor Emeritus and Business Manager Richard J. Bonnano Movie Editor Robert Breckenridge Staff Richard Blutstein Mary F. Buechler J.D. Kanofsky Rocket Weber David Maye

Coherent Control of Ballistic Photocurrents in Multilayer Epitaxial Graphene Using Quantum Interference

International audienceWe report generation of ballistic electric currents in unbiased epitaxial graphene at 300 K via quantum interference between phase-controlled cross-polarized fundamental and second harmonic 220 fs pulses. The transient currents are detected via the emitted terahertz radiation. Because of graphene's special structure symmetry, the injected current direction can be well controlled by the polarization of the pump beam in epitaxial graphene. This all optical injection of current provides not only a noncontact way of injecting directional current in graphene but also new insight into optical and transport process in epitaxial graphene

The homotopy theory of simplicial props

The category of (colored) props is an enhancement of the category of colored operads, and thus of the category of small categories. In this paper, the second in a series on "higher props," we show that the category of all small colored simplicial props admits a cofibrantly generated model category structure. With this model structure, the forgetful functor from props to operads is a right Quillen functor.Comment: Final version, to appear in Israel J. Mat

Group actions on Segal operads

We give a Quillen equivalence between model structures for simplicial operads, described via the theory of operads, and Segal operads, thought of as certain reduced dendroidal spaces. We then extend this result to give an Quillen equivalence between the model structures for simplicial operads equipped with a group action and the corresponding Segal operads.Comment: Revised version. Accepted to Isr J Mat

A Chandra Observation of the TW Hydrae Association Brown Dwarf 2MASSW J1139511-315921

We report on a sequence of Chandra X-ray Observatory observations of the TW Hydrae brown dwarf (BD) 2MASSW J1139511-315921 (2M1139). In the combined 31 ks ACIS-S exposure, 2M1139 is detected at the 3-sigma confidence level. We find an X-ray luminosity of L_X = 1.4^(+2.7)_(-1.0) x 10^26 ergs s^-1 or log(L_X/L_bol) = -4.8 +/- 0.3. This object is similar to another TW Hydrae BD member, CD-33 7795B (TWA 5B): both have H-alpha emission, both show no signatures of accretion, and both have comparable ages and spectral types. TWA 5B was previously detected in X-rays with a luminosity of L_X = 4 x 10^27 ergs s^-1 or log(L_X/L_bol) = -3.4, an order of magnitude more luminous in X-rays than 2M1139. We find that the discrepancy between the X-ray luminosity of 2M1139 and TWA 5B is consistent with the spread in X-ray luminosity in the Orion Nebula Cluster (ONC) for BDs of similar spectral types. Though rotation may play a role in the X-ray activity of ultracool dwarfs like 2M1139 and TWA 5B, the discrepancy cannot be explained by rotation alone. We also examine two X-ray bright objects in the FOV of our Chandra observations and find one to be of spectral type K0IV and identify it as a possible RS Canum Venaticorum (RS CVn), and another X-ray bright object whose light-curve clearly shows the decay phase of an X-ray flare.Comment: 26 pages, 6 figures, accepted in Ap

The Tidal Disruption Event AT 2018hyz II: Light Curve Modeling of a Partially Disrupted Star

AT 2018hyz (=ASASSN-18zj) is a tidal disruption event (TDE) located in the nucleus of a quiescent E+A galaxy at a redshift of $z = 0.04573$, first detected by the All-Sky Automated Survey for Supernovae (ASAS-SN). We present optical+UV photometry of the transient, as well as an X-ray spectrum and radio upper limits. The bolometric light curve of AT 2018hyz is comparable to other known TDEs and declines at a rate consistent with a $t^{-5/3}$ at early times, emitting a total radiated energy of $E = 9\times10^{50}$ erg. An excess bump appears in the UV light curve about 50 days after bolometric peak, followed by a flattening beyond 250 days. The light curve shows an excess bump in the UV about 50 days after bolometric peak lasting for at least 100 days, which may be related to an outflow. We detect a constant X-ray source present for at least 86 days. The X-ray spectrum shows a total unabsorbed flux of $\sim 4\times10^{-14}$ erg cm$^{-2}$ s$^{-1}$ and is best fit by a blackbody plus power-law model with a photon index of $\Gamma = 0.8$. A thermal X-ray model is unable to account for photons $> 1$ keV, while the radio non-detection favors inverse-Compton scattering rather than a jet for the non-thermal component. We model the optical and UV light curves using the Modular Open-Source Fitter for Transients (MOSFiT) and find a best fit for a black hole of $5.2\times10^6$ M$_\odot$ partially disrupting a $0.1$ M$_\odot$ star (stripping a mass of $\sim 0.01$ M$_\odot$ for the inferred impact parameter, $\beta=0.6$). The low optical depth implied by the small debris mass may explain how we are able to see hydrogen emission with disk-like line profiles in the spectra of AT 2018hyz (see our companion paper, Short et al.~2020).Comment: 10 pages, 10 figures, published in MNRA

Stellar Diameters and Temperatures II. Main Sequence K & M Stars

We present interferometric diameter measurements of 21 K- and M- dwarfs made with the CHARA Array. This sample is enhanced by literature radii measurements to form a data set of 33 K-M dwarfs with diameters measured to better than 5%. For all 33 stars, we compute absolute luminosities, linear radii, and effective temperatures (Teff). We develop empirical relations for \simK0 to M4 main- sequence stars between the stellar Teff, radius, and luminosity to broad-band color indices and metallicity. These relations are valid for metallicities between [Fe/H] = -0.5 and +0.1 dex, and are accurate to ~2%, ~5%, and ~4% for Teff, radius, and luminosity, respectively. Our results show that it is necessary to use metallicity dependent transformations to convert colors into stellar Teffs, radii, and luminosities. We find no sensitivity to metallicity on relations between global stellar properties, e.g., Teff-radius and Teff-luminosity. Robust examinations of single star Teffs and radii compared to evolutionary model predictions on the luminosity-Teff and luminosity-radius planes reveals that models overestimate the Teffs of stars with Teff < 5000 K by ~3%, and underestimate the radii of stars with radii < 0.7 R\odot by ~5%. These conclusions additionally suggest that the models overestimate the effects that the stellar metallicity may have on the astrophysical properties of an object. By comparing the interferometrically measured radii for single stars to those of eclipsing binaries, we find that single and binary star radii are consistent. However, the literature Teffs for binary stars are systematically lower compared to Teffs of single stars by ~ 200 to 300 K. Lastly, we present a empirically determined HR diagram for a total of 74 nearby, main-sequence, A- to M-type stars, and define regions of habitability for the potential existence of sub-stellar mass companions in each system. [abridged]Comment: 73 pages, 12 Tables, 18 Figures. Accepted for publication in The Astrophysical Journa

SPECULOOS exoplanet search and its prototype on TRAPPIST

One of the most significant goals of modern science is establishing whether life exists around other suns. The most direct path towards its achievement is the detection and atmospheric characterization of terrestrial exoplanets with potentially habitable surface conditions. The nearest ultracool dwarfs (UCDs), i.e. very-low-mass stars and brown dwarfs with effective temperatures lower than 2700 K, represent a unique opportunity to reach this goal within the next decade. The potential of the transit method for detecting potentially habitable Earth-sized planets around these objects is drastically increased compared to Earth-Sun analogs. Furthermore, only a terrestrial planet transiting a nearby UCD would be amenable for a thorough atmospheric characterization, including the search for possible biosignatures, with near-future facilities such as the James Webb Space Telescope. In this chapter, we first describe the physical properties of UCDs as well as the unique potential they offer for the detection of potentially habitable Earth-sized planets suitable for atmospheric characterization. Then, we present the SPECULOOS ground-based transit survey, that will search for Earth-sized planets transiting the nearest UCDs, as well as its prototype survey on the TRAPPIST telescopes. We conclude by discussing the prospects offered by the recent detection by this prototype survey of a system of seven temperate Earth-sized planets transiting a nearby UCD, TRAPPIST-1.Comment: Submitted as a chapter in the "Handbook of Exoplanets" (editors: H. Deeg & J.A. Belmonte; Section Editor: N. Narita). 16 pages, 4 figure