Context. The space mission Kepler provides us with long and uninterrupted photometric time series of red giants. We are now able to probe the rotational behaviour in their deep interiors using the ...observations of mixed modes. Aims. We aim to measure the rotational splittings in red giants and to derive scaling relations for rotation related to seismic and fundamental stellar parameters. Methods. We have developed a dedicated method for automated measurements of the rotational splittings in a large number of red giants. Ensemble asteroseismology, namely the examination of a large number of red giants at different stages of their evolution, allows us to derive global information on stellar evolution. Results. We have measured rotational splittings in a sample of about 300 red giants. We have also shown that these splittings are dominated by the core rotation. Under the assumption that a linear analysis can provide the rotational splitting, we observe a small increase of the core rotation of stars ascending the red giant branch. Alternatively, an important slow down is observed for red-clump stars compared to the red giant branch. We also show that, at fixed stellar radius, the specific angular momentum increases with increasing stellar mass. Conclusions. Ensemble asteroseismology indicates what has been indirectly suspected for a while: our interpretation of the observed rotational splittings leads to the conclusion that the mean core rotation significantly slows down during the red giant phase. The slow-down occurs in the last stages of the red giant branch. This spinning down explains, for instance, the long rotation periods measured in white dwarfs.
Understanding how super-massive black holes form and grow in the early Universe has become a major challenge
since it was discovered that luminous quasars existed only 700 million years after the Big ...Bang
. Simulations indicate an evolutionary sequence of dust-reddened quasars emerging from heavily dust-obscured starbursts that then transition to unobscured luminous quasars by expelling gas and dust
. Although the last phase has been identified out to a redshift of 7.6 (ref.
), a transitioning quasar has not been found at similar redshifts owing to their faintness at optical and near-infrared wavelengths. Here we report observations of an ultraviolet compact object, GNz7q, associated with a dust-enshrouded starburst at a redshift of 7.1899 ± 0.0005. The host galaxy is more luminous in dust emission than any other known object at this epoch, forming 1,600 solar masses of stars per year within a central radius of 480 parsec. A red point source in the far-ultraviolet is identified in deep, high-resolution imaging and slitless spectroscopy. GNz7q is extremely faint in X-rays, which indicates the emergence of a uniquely ultraviolet compact star-forming region or a Compton-thick super-Eddington black-hole accretion disk at the dusty starburst core. In the latter case, the observed properties are consistent with predictions from cosmological simulations
and suggest that GNz7q is an antecedent to unobscured luminous quasars at later epochs.
We use asteroseismic data obtained by the NASA Kepler mission to estimate the fundamental properties of more than 500 main-sequence and sub-giant stars. Data obtained during the first 10 months of ...Kepler science operations were used for this work, when these solar-type targets were observed for one month each in survey mode. Stellar properties have been estimated using two global asteroseismic parameters and complementary photometric and spectroscopic data. Homogeneous sets of effective temperatures, Tsubeff , were available for the entire ensemble from complementary photometry; spectroscopic estimates of Tsubeff and Fe/H were available from a homogeneous analysis of ground-based data on a subset of 87 stars. We adopt a grid-based analysis, coupling six pipeline codes to 11 stellar evolutionary grids. Future analyses using individual oscillation frequencies will offer significant improvements on up to 150 stars, in particular for estimates of the ages, where having the individual frequency data is most important.
First-principles calculations within the framework of real-space time-dependent density functional theory have been performed for the complete chlorophyll (Chl) network of the light-harvesting ...complex from green plants, LHC-II. A local-dipole analysis method developed for this work has made possible the studies of the optical response of individual Chl molecules subjected to the influence of the remainder of the chromophore network. The spectra calculated using our real-space TDDFT method agree with previous suggestions that weak interaction with the protein microenvironment should produce only minor changes in the absorption spectrum of Chl chromophores in LHC-II. In addition, relative shifting of Chl absorption energies leads the stromal and lumenal sides of LHC-II to absorb in slightly different parts of the visible spectrum providing greater coverage of the available light frequencies. The site-specific alterations in Chl excitation energies support the existence of intrinsic energy transfer pathways within the LHC-II complex.
The aim of this study was to evaluate the effect of different progesterone (P4) concentrations during the follicular growth on the intensity of estrous expression, ovarian response to the ...superovulatory treatment, and embryo production and quality in superovulated heifers. A total of 63 Holstein heifers were randomly assigned into 2 experimental groups: Low P4 (n = 31) and High P4 (n = 32). Animals received a pre-synchronization protocol followed by a protocol of superovulation that included the allocated P4 treatment. Activity was monitored continuously by an automated activity monitor, and estrus characteristics (maximum intensity and duration) were recorded. Embryo collection was performed 7 d post artificial insemination (AI). Embryos were counted and graded from good or excellent (1) to degenerated (4). The outcomes of interest were: number and diameter of follicles at the time of AI, ovulation success (confirmed 7 d post-AI), time to estrus event, maximum intensity and duration of estrus, number and quality of embryos. Data were analyzed according to the type of outcome variable using logistic, linear, or Poisson regression models. A total of 105 embryos (High P4: n = 42; Low P4: n = 63) were graded for quality. Different P4 levels did not affect the maximum intensity (High P4 = 497.8 ± 23.9%; Low P4 = 542.2 ± 23.5%) or the duration (High P4 = 13.5 ± 1.5 h; Low P4 = 14.3 ± 1.4 h) of estrus. Heifers in the High P4 treatment had greater number of follicles at time of AI (High P4 = 16.6 ± 1.6 follicles; Low P4 = 13.9 ± 1.2 follicles), but with smaller diameter (High P4 = 11.3 ± 0.1 mm; Low P4 = 12.0 ± 0.1 mm) compared with Low P4. High P4 heifers tended to have better embryo quality compared with Low P4 heifers (odds ratio = 1.98; 95% CI = 0.90-4.35). High P4 heifers had less embryos than Low P4 heifers, but this was modified by the CIDR (intravaginal implant of P4) removal to estrus interval (interval 0-21 h: mean ratio = 1.15, 95% CI = 0.42-1.87; interval 22-46 h: mean ratio = 0.58, 95% CI = 0.27-0.96). Although estrous expression was not associated with embryo quality, as the duration and the maximum intensity of estrous expression increased, the number of embryos recovered 7 d post-AI increased (duration: mean ratio = 1.04; 95% CI = 1.03-1.05; maximum intensity: mean ratio = 1.50; 95% CI = 1.42-1.58). In conclusion, P4 during the follicular growth, and intensity of estrus, are playing a role in regulating the quality and the number of embryos produced by superovulated heifers. This study was supported by contributions from Resilient Dairy Genome Project and the Natural Sciences and Engineering Research Council.
Abstract
This work reports the effect of different processing parameters on the structural and morphological characteristics of MoSe
2
layers grown by chemical vapour deposition (CVD), using MoO
3
...and Se powders as solid precursors. It shows the strong dependence of the size, shape and thickness of the MoSe
2
layers on the processing parameters. The morphology of the samples was investigated by field emission scanning electron microscopy (FESEM) and the thickness of the deposited layers was determined by atomic force microscopy (AFM). Raman and photoluminescence (PL) spectroscopies were used to confirm the high quality of the MoSe
2
layers. Surface composition was examined by photoelectron spectroscopy (XPS). Moreover, the MoSe
2
/SiO
x
/Si heterojunctions exhibit diode behaviour, with a rectification ratio of 10, measured at ±2.0 V, which is due to the p-i-n heterojunctions formed at the p-Si/SiO
x
/MoSe
2
interface. A photovoltaic effect was observed with a short circuit current density (
J
sc
), open circuit voltage (
V
OC
) and efficiency of −0.80 mA/cm
2
, 1.55 V and 0.5%, respectively. These results provide a guide for the preparation of p-i-n heterojunctions based on few-layer MoSe
2
with improved photovoltaic response.
Abstract
Habitat transitions are key potential explanations for why some lineages have diversified and others have not—from Anolis lizards to Darwin's finches. The ecological ramifications of ...marine-to-freshwater transitions for fishes suggest evolutionary contingency: some lineages maintain their ancestral niches in novel habitats (niche conservatism), whereas others alter their ecological role. However, few studies have considered phenotypic, ecological, and lineage diversification concurrently to explore this issue. Here, we investigated the macroevolutionary history of the taxonomically and ecologically diverse Neotropical freshwater river rays (subfamily Potamotrygoninae), which invaded and diversified in the Amazon and other South American rivers during the late Oligocene to early Miocene. We generated a time-calibrated, multi-gene phylogeny for Potamotrygoninae and reconstructed evolutionary patterns of diet specialization. We measured functional morphological traits relevant for feeding and used comparative phylogenetic methods to examine how feeding morphology diversified over time. Potamotrygonine trophic and phenotypic diversity are evenly partitioned (non-overlapping) among internal clades for most of their history, until 20–16 mya, when more recent diversification suggests increasing overlap among phenotypes. Specialized piscivores (Heliotrygon and Paratrygon) evolved early in the history of freshwater stingrays, while later trophic specialization (molluscivory, insectivory, and crustacivory) evolved in the genus Potamotrygon. Potamotrygonins demonstrate ecological niche lability in diets and feeding apparatus; however, diversification has mostly been a gradual process through time. We suggest that competition is unlikely to have limited the potamotrygonine invasion and diversification in South America.
We investigated experimentally and theoretically x-ray properties of Mg, Al and Si to assess for new reliable x-ray useful quantities. We measured the KL0– diagram, and KL1– and KL2– satellite lines ...in Mg, Al, and Si, ionized by photon excitation, using a high-resolution anti-parallel double-crystal x-ray spectrometer. Their energy values, full width at half maxima (FWHM), and relative intensities are obtained by the multiple fitting methods and compared with those reported by other excitation processes. It was found that the relative intensity of Mg and Si KL1 and KL2 satellite lines to the KL0 diagram lines depend on the method used to produce the K hole. The evidence of a new transition between Kα3 and Kα4 in Mg, Al, and S KL1 satellite lines is suggested. These x-ray diagram and satellite lines were investigated theoretically and we found that Mg Kα1,2 diagram lines with hidden satellites are especially in very good agreement with the corresponding experimental ones. Moreover, we also determined the mass attenuation coefficients in a wide energy range covering the K-absorption edge, including a detailed evaluation of the associated uncertainties. From the absorption spectra of Mg and Al, the cross sections of the multi-electron transition processes were estimated and match the theoretical values.
•High-resolution spectra of the Kα lines of Mg, Al and Si and their satellites.•New theoretical values for the Kα lines of Mg, Al and Si and their satellites.•Experimental mass attenuation coefficients for Mg, Al and Si on a wide energy range.•Multi-electrons transition probabilities.
Chance Marques de Sa, Joaquim P
2008, 2008-02-22
eBook
With its many easy-to-follow mathematical examples, this book takes the reader on an almost chronological trip through the fascinating and amazing laws of chance, omnipresent in the natural world and ...in our daily lives. Along the route many fascinating topics are discussed, such as: challenging probability paradoxes, 'paranormal' coincidences, game odds, causes and effects, interpretation of opinion polls, winning chances as a game proceeds, the nature of randomness, entropy and randomness, randomness in life, algorithmic complexity and the undecidability of randomness, possibilities and limitations of learning the laws of a Universe immersed in chance events. This charming book will inform and entertain the scientist and non-scientist alike.
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