2,598 research outputs found
Bistable perception in normal aging: perceptual reversibility and its relation to cognition
The effects of age on the ability to resolve perceptual ambiguity are unknown, though it depends
on fronto-parietal attentional networks known to change with age. We presented the bistable
Necker cube to 24 middle-aged and older adults (OA; 56–78 years) and 20 younger adults (YA;
18–24 years) under passive-viewing and volitional control conditions: Hold one cube percept and
Switch between cube percepts. During passive viewing, OA had longer dominance durations (time
spent on each percept) than YA. In the Hold condition, OA were less able than YA to increase
dominance durations. In the Switch condition, OA and YA did not differ in performance.
Dominance durations in either condition correlated with performance on tests of executive
function mediated by the frontal lobes. Eye movements (fixation deviations) did not differ between
groups. These results suggest that OA’s reduced ability to hold a percept may arise from reduced
selective attention. The lack of correlation of performance between Hold and executive-function
measures suggests at least a partial segregation of underlying mechanisms.Published versionAccepted manuscrip
The contribution of secondary eclipses as astrophysical false positives to exoplanet transit surveys
We investigate in this paper the astrophysical false-positive configuration
in exoplanet-transit surveys that involves eclipsing binaries and giant planets
which present only a secondary eclipse, as seen from the Earth. To test how an
eclipsing binary configuration can mimic a planetary transit, we generate
synthetic light curve of three examples of secondary-only eclipsing binary
systems that we fit with a circular planetary model. Then, to evaluate its
occurrence we model a population of binaries in double and triple system based
on binary statistics and occurrence. We find that 0.061% +/- 0.017% of
main-sequence binary stars are secondary-only eclipsing binaries mimicking a
planetary transit candidate down to the size of the Earth. We then evaluate the
occurrence that an occulting-only giant planet can mimic an Earth-like planet
or even smaller planet. We find that 0.009% +/- 0.002% of stars harbor a giant
planet that present only the secondary transit. Occulting-only giant planets
mimic planets smaller than the Earth that are in the scope of space missions
like Kepler and PLATO. We estimate that up to 43.1 +/- 5.6 Kepler Objects of
Interest can be mimicked by this new configuration of false positives,
re-evaluating the global false-positive rate of the Kepler mission from 9.4%
+/- 0.9% to 11.3% +/- 1.1%. We note however that this new false-positive
scenario occurs at relatively long orbital period compared with the median
period of Kepler candidates.Comment: 9 pages, 4 figures, accepted for publication in A&
Thickness of the buccal bone wall and root angulation in the maxilla and mandible: an approach to cone beam computed tomography
Background: The objective of this paper is to anatomically describe the bone morphology in the maxillary and mandibular tooth areas, which might help in planning post-extraction implants. Methods: CBCT images (Planmeca ProMax 3D) of 403 teeth (208 upper teeth and 195 lower teeth) were obtained from 49 patients referred to the Dental School of Seville from January to December 2014. The thickness of the facial wall was measured at the crest, point A, 4mm below, point B, and at the apex, point C. The second parameter was the angle formed between the dental axis and the axis of the basal bone. Results: A total of 403 teeth were measured. In the maxilla, 89.4% of incisors, 93.94% of canines, 78% of premolars and 70.5% of molars had a buccal bone wall thickness less than the ideal 2mm. In the mandible, 73.5% of incisors, 49% of canines, 64% of premolars and 53% of molars had <1mm buccal bone thickness as measured at point B. The mean angulation in the maxilla was 11.67±6.37° for incisors, 16.88±7.93° for canines, 13.93±8.6° for premolars, and 9.89±4.8° for molars. In the mandible, the mean values were 10.63±8.76° for incisors, 10.98±7.36° for canines, 10.54±5.82° for premolars and 16.19±11.22° for molars. Conclusions: The high incidence of a buccal wall thickness of less than 2mm in over 80% of the assessed sites indicates the need for additional regeneration procedures, and several locations may also require custom abutments to solve the angulation problems for screw-retained crowns
The Herschel Comprehensive (U)LIRG Emission Survey (HERCULES): CO Ladders, Fine Structure Lines, and Neutral Gas Cooling
(Ultra) luminous infrared galaxies ((U)LIRGs) are objects characterized by their extreme infrared (8-1000 μm) luminosities (L_(LIRG) > 10^(11) L_☉ and L_(ULIRG) > 10^(12) L_☉). The Herschel Comprehensive ULIRG Emission Survey (PI: van der Werf) presents a representative flux-limited sample of 29 (U)LIRGs that spans the full luminosity range of these objects (10^(11) L_☉ ≤ L_(IR) ≤ 10^(13) L_☉). With the Herschel Space Observatory, we observe [C II] 157 μm, [O I] 63 μm, and [O I] 145 μm line emission with Photodetector Array Camera and Spectrometer, CO J = 4-3 through J = 13-12, [C I] 370 μm, and [C I] 609 μm with SPIRE, and low-J CO transitions with ground-based telescopes. The CO ladders of the sample are separated into three classes based on their excitation level. In 13 of the galaxies, the [O I] 63 μm emission line is self absorbed. Comparing the CO excitation to the InfraRed Astronomical Satellite 60/100 μm ratio and to far infrared luminosity, we find that the CO excitation is more correlated to the far infrared colors. We present cooling budgets for the galaxies and find fine-structure line flux deficits in the [C II], [Si II], [O I], and [C I] lines in the objects with the highest far IR fluxes, but do not observe this for CO 4 ≤ J_(upp) ≤ 13. In order to study the heating of the molecular gas, we present a combination of three diagnostic quantities to help determine the dominant heating source. Using the CO excitation, the CO J = 1-0 linewidth, and the active galactic nucleus (AGN) contribution, we conclude that galaxies with large CO linewidths always have high-excitation CO ladders, and often low AGN contributions, suggesting that mechanical heating is important
PASTIS: Bayesian extrasolar planet validation II. Constraining exoplanet blend scenarios using spectroscopic diagnoses
The statistical validation of transiting exoplanets proved to be an efficient
technique to secure the nature of small exoplanet signals which cannot be
established by purely spectroscopic means. However, the spectroscopic diagnoses
are providing us with useful constraints on the presence of blended stellar
contaminants. In this paper, we present how a contaminating star affects the
measurements of the various spectroscopic diagnoses as function of the
parameters of the target and contaminating stars using the model implemented
into the PASTIS planet-validation software. We find particular cases for which
a blend might produce a large radial velocity signal but no bisector variation.
It might also produce a bisector variation anti-correlated with the radial
velocity one, as in the case of stellar spots. In those cases, the full width
half maximum variation provides complementary constraints. These results can be
used to constrain blend scenarios for transiting planet candidates or radial
velocity planets. We review all the spectroscopic diagnoses reported in the
literature so far, especially the ones to monitor the line asymmetry. We
estimate their uncertainty and compare their sensitivity to blends. Based on
that, we recommend the use of BiGauss which is the most sensitive diagnosis to
monitor line-profile asymmetry. In this paper, we also investigate the
sensitivity of the radial velocities to constrain blend scenarios and develop a
formalism to estimate the level of dilution of a blended signal. Finally, we
apply our blend model to re-analyse the spectroscopic diagnoses of HD16702, an
unresolved face-on binary which exhibits bisector variations.Comment: Accepted for publication in MNRA
Laser-induced breakdown spectroscopy of trisilane using infrared C O2 laser pulses
The plasma produced in trisilane (Si3 H8) at room temperature and pressures ranging from 50 to 103 Pa by laser-induced breakdown (LIB) has been investigated. The ultraviolet-visible-near infrared emission generated by high-power IR C O2 laser pulses in Si3 H8 has been studied by means of optical emission spectroscopy. Optical breakdown threshold intensities in trisilane at 10.591 μm for laser pulse lengths of 100 ns have been measured as a function of gas pressure. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited atomic H and Si and ionic fragments Si+, Si2+, and Si3+. An excitation temperature Texc =5600±300 K was calculated by means of H atomic lines assuming local thermodynamic equilibrium. The physical processes leading to LIB of trisilane in the power density range 0.28 GW cm-2 <J<3.99 GW cm-2 have been analyzed. From our experimental observations we can propose that, although the first electrons must appear via multiphoton ionization, electron cascade is the main mechanism responsible for the breakdown in trisilane. © 2007 American Institute of Physics.This work was partially supported by the Spanish MEC Project No. CTQ2007-60177/BQU. It is a pleasure to acknowledge the excellent technical support of A. Magro. This work is dedicated in memory of Professor Antonio Pardo Martinez.Peer Reviewe
Understanding the 8 micron vs. Pa-alpha relationship on sub-arcsecond scales in Luminous Infrared Galaxies
This work explores in detail the relation between the 8 micron and the
Pa-alpha emissions for 122 HII regions identified in a sample of 10 low-z LIRGs
with nearly constant metallicity (12 + log (O/H) ~ 8.8). We use Gemini/T-ReCS
high-spatial resolution (<~ 0.4" ~ 120 pc for the average distance of 60 Mpc of
our sample) mid-infrared imaging (at 8.7 micron or 10.3 micron) together with
HST/NICMOS continuum and Pa-alpha images. The LIRG HII regions extend the
L_8micron vs. L_Pa-alpha relation found for HII knots in the high-metallicity
SINGS galaxies by about two orders of magnitude to higher luminosities. Since
the metallicity of the LIRG sample is nearly constant, we can rule out this
effect as a cause for the scatter seen in the relationship. In turn, it is
attributed to two effects: age and PAH features. The L_8micron/L_Pa-alpha
ratio, which varies by a factor of ten for the LIRG HII regions, is reproduced
by a model with instantaneous star formation and ages ranging from ~ 4 to 7.5
Myr. The remaining dispersion around the model predictions for a given age is
probably due to differential contributions of the PAH features (the 8.6 micron,
in our case) to the 8 micron emission from galaxy to galaxy.Comment: 16 pages, 9 figures, accepted for publication in ApJ; paper with
full-resolution figures can be found at:
http://damir.iem.csic.es/extragalactic
The evolutionary history of Drosophila buzzatii. XVII. Double mating and sperm predominance
Sperm predominance in males and double mating in females have been studied in 2 stocks of the cactophilic species Drosophila buzzatii. The relationship between double mating and total productivity of females was also ascertained. Our results show high values of sperm predominance and double mating. Moreover, female productivity is increased with a second mate. These results are discussed in relation to the mating strategy of this species.On a étudié la prédominance du sperme chez les mâles et le double accouplement chez les femelles dans 2 souches de l'espèce cactophile Drosophila buzzatii. La relation entre le double accouplement et la productivité totale des femelles a été aussi recherchée. Nos résultats montrent des valeurs élevées pour la prédominance du sperme et pour le double accouplement. De plus, on constate que la productivité des femelles est augmentée par un deuxième accouplement. Ces résultats sont discutés par rapport à la stratégie d'accouplement de cette espèce
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