25,618 research outputs found
The Actions and Feelings Questionnaire in Autism and Typically Developed Adults
Open access via Springer Compact Agreement We are grateful to Simon Baron-Cohen and Paula Smith of the Cambridge Autism Centre for the use of the ARC database in distributing the questionnaire, to all participants for completing it, to Eilidh Farquar for special efforts in distributing the link and to Gemma Matthews for advice on using AMOS 23. JHGW is supported by the Northwood Trust.Peer reviewedPublisher PD
The instability of stellar structures intermediate between white dwarfs and neutron stars
Instability of stellar structures intermediate between dwarfs and neutron star
Effect of delayed acquisition times on Gadolinium-enhanced MRI of the presumably normal canine brain
A delay in imaging following intravenous contrast medium administration has been recommended to reduce misdiagnoses. However, the normal variation of contrast enhancement in dogs following a delay has not been characterized. Contrast enhanced MR imaging of 22 dogs was assessed, in terms of identification of normal anatomic structures, to investigate the variation associated with 10 minute delay between contrast medium administration and imaging. All dogs had a normal brain MR imaging study and unremarkable CSF. Specific ROIs were assessed both objectively, using computer software, and subjectively using three observers. Mean contrast enhancement greater than 10% was seen in the pituitary gland, choroid plexus, meninges, temporal muscle, trigeminal nerve and the trigeminal nerve root. Structures with an active blood-brain-barrier had minimal contrast enhancement (<6%). Enhancing structures had significantly more contrast enhancement at t=1min versus t=10min, except in temporal muscle, the trigeminal nerve and the trigeminal nerve root. Inter-observer agreement was moderate to good in favor of the initial post contrast T1w sequence. The observers found either no difference or poor agreement in identification of the non-vascular structures. Intra-observer agreement was very good with all vascular structures and most non-vascular structures. A degree of meningeal enhancement was a consistent finding. The initial acquisition had higher enhancement characteristics and observer agreement for some structures; however, contrast-to-noise was comparable in the delayed phase or not significantly different. We provide baseline references and suggest that the initial T1w post contrast sequence is preferable but not essential should a delayed post contrast T1w sequence be performed
Rotationally Modulated X-ray Emission from T Tauri Stars
We have modelled the rotational modulation of X-ray emission from T Tauri
stars assuming that they have isothermal, magnetically confined coronae. By
extrapolating surface magnetograms we find that T Tauri coronae are compact and
clumpy, such that rotational modulation arises from X-ray emitting regions
being eclipsed as the star rotates. Emitting regions are close to the stellar
surface and inhomogeneously distributed about the star. However some regions of
the stellar surface, which contain wind bearing open field lines, are dark in
X-rays. From simulated X-ray light curves, obtained using stellar parameters
from the Chandra Orion Ultradeep Project, we calculate X-ray periods and make
comparisons with optically determined rotation periods. We find that X-ray
periods are typically equal to, or are half of, the optical periods. Further,
we find that X-ray periods are dependent upon the stellar inclination, but that
the ratio of X-ray to optical period is independent of stellar mass and radius.Comment: 10 pages, 8 figures, accepted for publication in MNRA
Fully anharmonic infrared cascade spectra of polycyclic aromatic hydrocarbons
The infrared (IR) emission of polycyclic aromatic hydrocarbons (PAHs)
permeates our universe; astronomers have detected the IR signatures of PAHs
around many interstellar objects. The IR emission of interstellar PAHs differs
from their emission as seen under conditions on Earth, as they emit through a
collisionless cascade down through their excited vibrational states from high
internal energies. The difficulty in reproducing interstellar conditions in the
laboratory results in a reliance on theoretical techniques. However, the size
and complexity of PAHs requires careful consideration when producing the
theoretical spectra. In this work we outline the theoretical methods necessary
to lead to a fully theoretical IR cascade spectra of PAHs including: an
anharmonic second order vibrational perturbation theory (VPT2) treatment; the
inclusion of Fermi resonances through polyads; and the calculation of
anharmonic temperature band shifts and broadenings (including resonances)
through a Wang--Landau approach. We also suggest a simplified scheme to
calculate vibrational emission spectra that retains the essential
characteristics of the full IR cascade treatment and can directly transform low
temperature absorption spectra in IR cascade spectra. Additionally we show that
past astronomical models were in error in assuming a 15 cm correction
was needed to account for anharmonic emission effects
Are there spurious temperature trends in the United States Climate Division database
The United States (U.S.) Climate Division data set is commonly used in applied climatic studies in the United States. The divisional averages are calculated by including all available stations within a division at any given time. The averages are therefore vulnerable to shifts in average station location or elevation over time, which may introduce spurious trends within these data. This paper examines temperature trends within the 15 climate divisions of New England, comparing the NCDC\u27s U.S. Divisional Data to the U.S. Historical Climate Network (USHCN) data. Correlation and multiple regression revealed that shifts in latitude, longitude, and elevation have affected the quality of the NCDC divisional data with respect to the USHCN. As a result, there may be issues with regard to their use in decadal- to century-scale climate change studies
Formation of Kuiper Belt Binaries
The discovery that a substantial fraction of Kuiper Belt objects (KBOs)
exists in binaries with wide separations and roughly equal masses, has
motivated a variety of new theories explaining their formation. Goldreich et
al. (2002) proposed two formation scenarios: In the first, a transient binary
is formed, which becomes bound with the aid of dynamical friction from the sea
of small bodies (L^2s mechanism); in the second, a binary is formed by three
body gravitational deflection (L^3 mechanism). Here, we accurately calculate
the L^2s and L^3 formation rates for sub-Hill velocities. While the L^2s
formation rate is close to previous order of magnitude estimates, the L^3
formation rate is about a factor of 4 smaller. For sub-Hill KBO velocities (v
<< v_H) the ratio of the L^3 to the L^2s formation rate is 0.05 (v/v_H)
independent of the small bodies' velocity dispersion, their surface density or
their mutual collisions. For Super-Hill velocities (v >> v_H) the L^3 mechanism
dominates over the L^2s mechanism. Binary formation via the L^3 mechanism
competes with binary destruction by passing bodies. Given sufficient time, a
statistical equilibrium abundance of binaries forms. We show that the frequency
of long-lived transient binaries drops exponentially with the system's lifetime
and that such transient binaries are not important for binary formation via the
L^3 mechanism, contrary to Lee et al. (2007). For the L^2s mechanism we find
that the typical time, transient binaries must last, to form Kuiper Belt
binaries (KBBs) for a given strength of dynamical friction, D, increases only
logarithmically with D. Longevity of transient binaries only becomes important
for very weak dynamical friction (i.e. D \lesssim 0.002) and is most likely not
crucial for KBB formation.Comment: 20 pages, 3 figures, Accepted for publication in ApJ, correction of
minor typo
On the Snow Line in Dusty Protoplanetary Disks
The snow line, in Hayashi's (1981) model, is where the temperature of a black
body that absorbed direct sunlight and re-radiated as much as it absorbed,
would be 170~K. It is usually assumed that the cores of the giant planets,
e.g., Jupiter, form beyond the snow line. Since Hayashi, there have been a
series of more detailed models of the absorption by dust of the stellar
radiation, and of accretional heating, which alter the location of the snow
line. We have attempted a "self-consistent" model of a T Tauri disk in the
sense that we used dust properties and calculated surface temperatures that
matched observed disks. We then calculated the midplane temperature for those
disks, with no accretional heating or with small (<10^-8) accretion rates. Our
models bring the snow line in to the neighbourhood of 1 AU; not far enough to
explain the close planetary companions to other stars, but much closer than in
recent starting lines for orbit migration scenarios.Comment: 9 pages, 1 figure, to appear in ApJ,528,200
Perceiving and expressing feelings through actions in relation to individual differences in empathic traits : the Action and Feelings Questionnaire (AFQ)
Peer reviewedPublisher PD
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