6,368 research outputs found
Spurious Eccentricities of Distorted Binary Components
I discuss the effect of physical distortion on the velocities of close binary
components and how we may use the resulting distortion of velocity curves to
constrain some properties of binary systems, such as inclination and mass
ratio. Precise new velocities for 5 Cet convincingly detect these distortions
with their theoretically predicted phase dependence. We can even use such
distortions of velocity curves to test Lucy's theory of convective gravity
darkening. The observed distortions for TT Hya and 5 Cet require the contact
components of those systems to be gravity darkened, probably somewhat more than
predicted by Lucy's theory but clearly not as much as expected for a radiative
star. These results imply there is no credible evidence for eccentric orbits in
binaries with contact components. I also present some speculative analyses of
the observed properties of a binary encased in a non-rotating common envelope,
if such an object could actually exist, and discuss how the limb darkening of
some recently calculated model atmospheres for giant stars may bias my resuts
for velocity-curve distortions, as well as other results from a wide range of
analyses of binary stars.Comment: 14 pp, 2 tables, 12 fig; under review by Ap
The Effect of Mood-Context on Visual Recognition and Recall Memory
Although it is widely known that memory is enhanced when encoding and retrieval occur in the same state, the impact of elevated stress/arousal is less understood. This study explores mood-dependent memory's effects on visual recognition and recall of material memorized either in a neutral mood or under higher stress/arousal levels. Participants’ (N = 60) recognition and recall were assessed while they experienced either the same or a mismatched mood at retrieval. The results suggested that both visual recognition and recall memory were higher when participants experienced the same mood at encoding and retrieval compared with those who experienced a mismatch in mood context between encoding and retrieval. These findings offer support for a mood dependency effect on both the recognition and recall of visual information
A comparison of Olpidium isolates from a range of host plants using internal transcribed spacer sequence analysis and host range studies
Olpidium brassicae is a ubiquitous obligate root-infecting fungal pathogen. It is an important vector of a wide range of plant viruses. Olpidium isolates that infected brassica plants did not infect lettuce plants and vice-versa. Host range tests, PCR amplification and sequencing of the internal transcribed spacer (ITS) and 5.8S regions of 25 Olpidium isolates from brassica, carrot, cucumber and lettuce originating from four continents revealed differences between isolates. Based on their ability to infect lettuce and brassicas and the differences between their ITS1, 5.8S and ITS2 regions they could be separated into a number of distinct groups. Comparisons with other published sequences revealed two distinct genetic groups of brassica-infecting isolates, two distinct groups of lettuce-infecting isolates, one of which contained a carrot-infecting isolate and a distinct group comprising a cucumber-infecting isolate and a melon-infecting isolate. The possibility of the isolates belonging to three distinct species is discussed
Simon-Task Reveals Balanced Visuomotor Control in Experienced Video-Game Players
Both short and long-term video-game play may result in superior performance on visual and attentional tasks. To further these findings, we compared the performance of experienced male video-game players (VGPs) and non-VGPs on a Simon-task. Experienced-VGPs began playing before the age of 10, had a minimum of 8 years of experience and a minimum play time of over 20 h per week over the past 6 months. Our results reveal a significantly reduced Simon-effect in experienced-VGPs relative to non-VGPs. However, this was true only for the right-responses, which typically show a greater Simon-effect than left-responses. In addition, experienced-VGPs demonstrated significantly quicker reaction times and more balanced left-versus-right-hand performance than non-VGPs. Our results suggest that experienced-VGPs can resolve response-selection conflicts more rapidly for right-responses than non-VGPs, and this may in part be underpinned by improved bimanual motor control
Increasing phosphorus supply is not the mechanism by which arbuscular mycorrhiza increase attractiveness of bean (Vicia faba) to aphids
Peer reviewedPublisher PD
The Inner Rim of YSO Disks: Effects of dust grain evolution
Dust-grain growth and settling are the first steps towards planet formation.
An understanding of dust physics is therefore integral to a complete theory of
the planet formation process. In this paper, we explore the possibility of
using the dust evaporation front in YSO disks (`the inner rim') as a probe of
the dust physics operating in circumstellar disks. The geometry of the rim
depends sensitively on the composition and spatial distribution of dust. Using
radiative transfer and hydrostatic equilibrium calculations we demonstrate that
dust growth and settling can curve the evaporation front dramatically (from a
cylindrical radius of about 0.5 AU in the disk mid-plane to 1.2 AU in the disk
upper layers for an A0 star). We compute synthetic images and interferometric
visibilities for our representative rim models and show that the current
generation of near-IR long-baseline interferometers (VLTI, CHARA) can strongly
constrain the dust properties of circumstellar disks, shedding light on the
relatively poorly understood processes of grain growth, settling and turbulent
mixing.Comment: 26 pages, 9 figures. Accepted for publication in Ap
Westerlund 1 as a Template for Massive Star Evolution
With a dynamical mass M_dyn ~ 1.3x10e5 M_sun and a lower limit M_cl>5x10e4
M_sun from star counts, Westerlund 1 is the most massive young open cluster
known in the Galaxy and thus the perfect laboratory to study massive star
evolution. We have developed a comprehensive spectral classification scheme for
supergiants based on features in the 6000-9000A range, which allows us to
identify >30 very luminous supergiants in Westerlund 1 and ~100 other less
evolved massive stars, which join the large population of Wolf-Rayet stars
already known. Though detailed studies of these stars are still pending,
preliminary rough estimates suggest that the stars we see are evolving to the
red part of the HR diagram at approximately constant luminosity.Comment: To be published in Proceedings of IAU Symposium 250: Massive Stars as
Cosmic Engines, held in Kaua'i (Hawaii, USA), Dec 2007, edited by F.
Bresolin, P.A. Crowther & J. Puls (Cambridge University Press
Physiological and Behavioral Differences in Sensory Processing: A Comparison of Children with Autism Spectrum Disorder and Sensory Modulation Disorder
A high incidence of sensory processing difficulties exists in children with Autism Spectrum Disorder (ASD) and children with Sensory Modulation Disorder (SMD). This is the first study to directly compare and contrast these clinical disorders. Sympathetic nervous system markers of arousal and reactivity were utilized in a laboratory paradigm that administered a series of sensory challenges across five sensory domains. The Short Sensory Profile, a standardized parent-report measure, provided a measure of sensory-related behaviors. Physiological arousal and sensory reactivity were lower in children with ASD whereas reactivity after each sensory stimulus was higher in SMD, particularly to the first stimulus in each sensory domain. Both clinical groups had significantly more sensory-related behaviors than typically developing children, with contrasting profiles. The ASD group had more taste/smell sensitivity and sensory under-responsivity while the SMD group had more atypical sensory seeking behavior. This study provides preliminary evidence distinguishing sympathetic nervous system functions and sensory-related behaviors in Autism Spectrum Disorder and Sensory Modulation Disorder. Differentiating the physiology and sensory symptoms in clinical groups is essential to the provision of appropriate interventions
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