199 research outputs found
A binary merger origin for inflated hot Jupiter planets
We hypothesize that hot Jupiters with inflated sizes represent a separate
planet formation channel,the merging of two low-mass stars. We show that the
abundance and properties of W UMa stars and low mass detached binaries are
consistent with their being possible progenitors. The degree of inflation of
the transiting hot Jupiters correlates with their expected spiral-in life time
by tidal dissipation, and this could indicate youth if the stellar dissipation
parameter Q'* is sufficiently low. Several Jupiter-mass planets can form in the
massive compact disk formed in a merger event. Gravitational scattering between
them can explain the high incidence of excentric, inclined, and retrograde
orbits. If the population of inflated planets is indeed formed by a merger
process, their frequency should be much higher around blue stragglers than
around T Tauri stars.Comment: Accepted for publication in A&
RR-Lyrae-type pulsations from a 0.26-solar-mass star in a binary system
RR Lyrae pulsating stars have been extensively used as tracers of old stellar
populations for the purpose of determining the ages of galaxies, and as tools
to measure distances to nearby galaxies. There was accordingly considerable
interest when the RR Lyr star OGLE-BLG-RRLYR-02792 was found to be a member in
an eclipsing binary system4, as the mass of the pulsator (hitherto constrained
only by models) could be unambiguously determined. Here we report that
RRLYR-02792 has a mass of 0.26 M_sun and therefore cannot be a classical RR
Lyrae star. Through models we find that its properties are best explained by
the evolution of a close binary system that started with 1.4 M_sun and 0.8
M_sun stars orbiting each other with an initial period of 2.9 days. Mass
exchange over 5.4 Gyr produced the observed system, which is now in a very
short-lived phase where the physical properties of the pulsator happen to place
it in the same instability strip of the H-R diagram occupied by RR Lyrae stars.
We estimate that samples of RR Lyr stars may contain a 0.2 percent
contamination with systems similar to this one, implying that distances
measured with RR Lyrae stars should not be significantly affected by these
binary interlopers
Microparticle-mediated transfer of the viral receptors CAR and CD46, and the CFTR channel in a CHO cell model confers new functions to target cells
Cell microparticles (MPs) released in the extracellular milieu can embark plasma membrane and intracellular components which are specific of their cellular origin, and transfer them to target cells. The MP-mediated, cell-to-cell transfer of three human membrane glycoproteins of different degrees of complexity was investigated in the present study, using a CHO cell model system. We first tested the delivery of CAR and CD46, two monospanins which act as adenovirus receptors, to target CHO cells. CHO cells lack CAR and CD46, high affinity receptors for human adenovirus serotype 5 (HAdV5), and serotype 35 (HAdV35), respectively. We found that MPs derived from CHO cells (MP-donor cells) constitutively expressing CAR (MP-CAR) or CD46 (MP-CD46) were able to transfer CAR and CD46 to target CHO cells, and conferred selective permissiveness to HAdV5 and HAdV35. In addition, target CHO cells incubated with MP-CD46 acquired the CD46-associated function in complement regulation. We also explored the MP-mediated delivery of a dodecaspanin membrane glycoprotein, the CFTR to target CHO cells. CFTR functions as a chloride channel in human cells and is implicated in the genetic disease cystic fibrosis. Target CHO cells incubated with MPs produced by CHO cells constitutively expressing GFP-tagged CFTR (MP-GFP-CFTR) were found to gain a new cellular function, the chloride channel activity associated to CFTR. Time-course analysis of the appearance of GFP-CFTR in target cells suggested that MPs could achieve the delivery of CFTR to target cells via two mechanisms: the transfer of mature, membrane-inserted CFTR glycoprotein, and the transfer of CFTR-encoding mRNA. These results confirmed that cell-derived MPs represent a new class of promising therapeutic vehicles for the delivery of bioactive macromolecules, proteins or mRNAs, the latter exerting the desired therapeutic effect in target cells via de novo synthesis of their encoded proteins
Simulations of magneto-acoustic pulsations in atmospheres of rapidly oscillating Ap stars
Rapidly oscillating Ap stars exhibit an astrophysically interesting
combination of strong, dipolar-like magnetic fields and high-overtone p-mode
pulsations similar to the Sun. Recent time-resolved spectroscopy of these stars
unravelled a complex picture of propagating magneto-acoustic pulsation waves,
with amplitude and phase strongly changing as a function of atmospheric height.
To interpret these observations and gain a new insight into the atmospheric
dynamics of roAp stars we have carried out 2-D time-dependent, non-linear
magneto-hydrodynamical simulations of waves for a realistic atmospheric
stratification of a cool Ap star. We explore a grid of simulations in a wide
parameter space, treating oscillations of the velocity, magnetic field and
thermodynamic quantities in a self-consistent manner. Our simulations foster a
new understanding of the influence of the atmosphere and the magnetic field on
the propagation and reflection properties of magneto-acoustic waves, formation
of node surfaces, and relative variation of different quantities. Our
simulations reproduce all main features of the observed pulsational behavior of
roAp stars. We show, for the first time, that the overall depth dependence of
the pulsations in roAp atmospheres is strongly influenced by the density
inversion at the photospheric base.Comment: accepted by The Astrophysical Journa
Magnetism in Herbig Ae/Be stars and the link to the Ap/Bp stars
Among the A/B stars, about 5% host large-scale organised magnetic fields.
These magnetic stars show also abundance anomalies in their spectra, and are
therefore called the magnetic Ap/Bp stars. Most of these stars are also slow
rotators compared to the normal A and B stars. Today, one of the greatest
challenges concerning the Ap/Bp stars is to understand the origin of their slow
rotation and their magnetic fields. The favoured hypothesis for the latter is
that the fields are fosils, which implies that the magnetic fields subsist
throughout the different evolutionary phases, and in particular during the
pre-main sequence phase. The existence of magnetic fields at the pre-main
sequence phase is also required to explain the slow rotation of Ap/Bp stars.
During the last 3 years we performed a spectropolarimetric survey of the Herbig
Ae/Be stars in the field and in young clusters, in order to investigate their
magnetism and rotation. These investigations have resulted in the detection
and/or confirmation of magnetic fields in 8 Herbig Ae/Be stars, ranging in mass
from 2 to nearly 15 solar masses. In this paper I will present the results of
our survey, as well as their implications for the origin and evolution of the
magnetic fields and rotation of the A and B stars.Comment: To appear in the proceedings of "Ecole d'astronomie du CNRS et du
PNPS : Les champs magnetiques stellaires", editors: C. Neiner and J.-P. Zahn,
EAS Publications Serie
Ratunku! or just tunku! : evidence for the reliability and concurrent validity of the Language Use Inventory : LUI-Polish
Purpose: To date, there is no tool for assessing early pragmatic development of Polish-speaking children. This study aimed to adapt to Polish a standardized parent report measure, the Language Use Inventory (LUI; O’Neill, 2009, in order to enable cross-cultural comparisons and to
use the LUI-Polish to screen for pragmatic development in children 18-47 months of age. We concentrated on the sociocultural and functional adaptation of LUI and aimed to demonstrate its reliability, developmental sensitivity, and concurrent validity. Method: Parents completed an online version of LUIPolish, longitudinally at 3 time points (when the child was 20, 32, and 44 months old). In addition, parents completed the Polish adaptations of the Questionnaire for Communication and Early Language at 22 months and the Language Development Survey at 24 months. Children’s spontaneous speech was assessed at 24 months, and their expressive and receptive vocabulary was assessed at 36 months.
Results: All 3 parts of the LUI-Polish (Gestures, Words, and Sentences) showed very good levels of internal consistency at each time point. Significant correlations were observed between all parts of the LUI-Polish at all 3 measurement time points. The expected developmental trajectory was observed for boys and girls providing evidence of its developmental sensitivity for children between the ages of 2 and 4 years: an increase with age in the total score (due to an increase in Words and Sentences) and a decrease in Gestures. Supporting concurrent validity, significant correlations were found between children’s performance on (a) the LUI-Polish at 20 months and the Questionnaire for Communication and Early Language at 22 months as well as the Language Development Survey and spontaneous speech measures at 24 months and (b) the LUI-Polish at 32 months and the 2 measures of vocabulary comprehension and production at 36 months. Conclusion: The Polish adaptation of the LUI demonstrated good psychometric properties that provide a sound basis for cross-cultural comparisons and further research toward norming of the LUI-Polish. Moreover, the expected developmental trajectory in the pragmatic development of Polish children was observed
Simultaneous determination of Deoxynivalenol, Deoxynivalenol-3-Glucoside and Nivalenol in wheat grains by HPLC-PDA with immunoaffinity column cleanup
Deoxynivalenol-3-glucoside (D3G) is a modified mycotoxin formed by the metabolism of plants through the conjugation of deoxynivalenol (DON) with glucose. Toxicology studies of D3G for human and animal health are still under investigation, and the development of practical and reliable methods for its direct determination, especially in cereal matrices, is of great importance. In the present study, a methodology for simultaneous determination of D3G, DON, and nivalenol (NIV) in wheat grains, using immunoaffinity column (IAC) cleanup, separation by C18 column and detection by ultraviolet (UV) absorption, was optimized and in-house validated. The results demonstrated adequate values of D3G recovery from IAC and spiked samples. Intraday precision, linearity, limit of detection and limit of quantification (LOQ) were also adequate for the determination of these mycotoxins. Range of applicability varied from 47.1 to 1000 g/kg for D3G and from 31.3 to 1000 g/kg for DON and NIV, with recovery ranging from 84.7±7.2 % to 112.3±8.1Felipe Trombete is grateful for a doctoral fellowship provided by the Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES)
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