1,971 research outputs found
The âmaternal effectâ on epilepsy risk: Analysis of familial epilepsies and reassessment of prior evidence
Objective: Previous studies have observed that epilepsy risk is higher among offspring of affected women thanoffspring of affected men. We tested whether this âmaternal effectâ was present in familial epilepsies, which areenriched for genetic factors that contribute to epilepsy risk.Methods: We assessed evidence of a maternal effect in a cohort of families containing â„3 persons with epilepsyusing three methods: (1) âdownward-lookingâ analysis, comparing the rate of epilepsy in offspring of affectedwomen versus men; (2) âupward-lookingâ analysis, comparing the rate of the epilepsy among mothers versusfathers of affected individuals; (3) lineage analysis, comparing the the proportion of affected individuals withfamily history of epilepsy on the maternal versus paternal side.Results: Downward-looking analysis revealed no difference in epilepsy rates among offspring of affectedmothers versus fathers (prevalence ratio 1.0, 95% CI 0.8, 1.2). Upward-looking analysis revealed more affectedmothers than affected fathers; this effect was similar for affected and unaffected sibships (odds ratio 0.8, 95%CI 0.5, 1.2) and was explained by a combination of differential fertility and participation rates. Lineage analysisrevealed no significant difference in the likelihood of maternal versus paternal family history of epilepsy.Interpretation: We found no evidence of a maternal effect on epilepsy risk in this familial epilepsy cohort.Confounding sex imbalances can create the appearance of a maternal effect in upward-looking analyses andmay have impacted prior studies. We discuss possible explanations for the lack of evidence, in familialepilepsies, of the maternal effect observed in population-based studie
Locally continuously perfect groups of homeomorphisms
The notion of a locally continuously perfect group is introduced and studied.
This notion generalizes locally smoothly perfect groups introduced by Haller
and Teichmann. Next, we prove that the path connected identity component of the
group of all homeomorphisms of a manifold is locally continuously perfect. The
case of equivariant homeomorphism group and other examples are also considered.Comment: 14 page
X-ray Line Emission from the Hot Stellar Wind of theta 1 Ori C
We present a first emission line analysis of a high resolution X-ray spectrum
of the stellar wind of theta 1 Ori C obtained with the High Energy Transmission
grating Spectrometer onboard the Chandra X-ray Observatory. The spectra are
resolved into a large number of emission lines from H- and He-like O, Ne, Mg,
Si, S, Ar and Fe ions. The He-like Fe XXV and Li-like Fe XXIV appear quite
strong indicating very hot emitting regions. From H/He flux ratios, as well as
from Fe He/Li emission measure ratios we deduce temperatures ranging from 0.5
to 6.1 x 10^7 K. The He-triplets are very sensitive to density as well. At
these temperatures the relative strengths of the intercombination and forbidden
lines indicate electron densities well above 10^12 cm^-3. The lines appear
significantly broadened from which we deduce a mean velocity of 770 km/s with a
spread between 400 and 2000 km/s. Along with results of the deduced emission
measure we conclude that the X-ray emission could originate in dense and hot
regions with a characteristic size of less then 4 x 10^10 cm.Comment: 4 pages, 3 figure
Coronal X-ray emission from an intermediate-age brown dwarf
We report the X-ray detection of the brown dwarf (BD) companion TWA 5B in a
Myr old pre-main sequence binary system. We clearly resolve the
faint companion (35 photons) separated from the X-ray luminous primary by 2
arcsec in a {\it Chandra} ACIS image. TWA 5B shows a soft X-ray spectrum with a
low plasma temperature of only 0.3 keV and a constant flux during the 3 hour
observation, of which the characteristics are commonly seen in the solar
corona. The X-ray luminosity is 4 erg s (0.1--10 keV
band) or .
Comparing these properties to both younger and older BDs, we discuss the
evolution of the X-ray emission in BDs. During their first few Myr, they
exhibit high levels of X-ray activity as seen in higher mass pre-main sequence
stars. The level in TWA 5B is still high at Myr in while has already substantially cooled
Indirect search for Dark Matter with H.E.S.S
Observations of the Galactic center region with the H.E.S.S. telescopes have
established the existence of a steady, extended source of gamma-ray emission
coinciding with the position of the super massive black hole Sgr A*. This is a
remarkable finding given the expected presence of dense self-annihilating Dark
Matter in the Galactic center region. The self-annihilation process is giving
rise to gamma-ray production through hadronization including the production of
neutral pions which decay into gamma-rays but also through (loop-suppressed)
annihilation into final states of almost mono-energetic photons. We study the
observed gamma-ray signal (spectrum and shape) from the Galactic center in the
context of Dark Matter annihilation and indicate the prospects for further
indirect Dark matter searches with H.E.S.S.Comment: 9 pages, 3 figures. Accepted for Publication in Advances is Space
Research, COSPAR meeting Beijing (2006
First Detection of HCO+ Emission at High Redshift
We report the detection of HCO+(1-0) emission towards the Cloverleaf quasar
(z=2.56) through observations with the Very Large Array. This is the first
detection of ionized molecular gas emission at high redshift (z>2). HCO+
emission is a star formation indicator similar to HCN, tracing dense molecular
hydrogen gas (n(H_2) ~= 10^5 cm^{-3}) within star-forming molecular clouds. We
derive a lensing-corrected HCO+ line luminosity of L'(HCO+) = 3.5 x 10^9 K km/s
pc^2. Combining our new results with CO and HCN measurements from the
literature, we find a HCO+/CO luminosity ratio of 0.08 and a HCO+/HCN
luminosity ratio of 0.8. These ratios fall within the scatter of the same
relationships found for low-z star-forming galaxies. However, a HCO+/HCN
luminosity ratio close to unity would not be expected for the Cloverleaf if the
recently suggested relation between this ratio and the far-infrared luminosity
were to hold. We conclude that a ratio between HCO+ and HCN luminosity close to
1 is likely due to the fact that the emission from both lines is optically
thick and thermalized and emerges from dense regions of similar volumes. The
CO, HCN and HCO+ luminosities suggest that the Cloverleaf is a composite
AGN--starburst system, in agreement with the previous finding that about 20% of
the total infrared luminosity in this system results from dust heated by star
formation rather than heating by the AGN. We conclude that HCO+ is potentially
a good tracer for dense molecular gas at high redshift.Comment: 5 pages, 3 figures, ApJL, in press (accepted May 17, 2006
Australia Telescope Compact Array Radio Continuum 1384 and 2368 Mhz Observations of Sagittarius B
We present images of the Sagittarius (Sgr) B giant molecular cloud at 2368
and 1384 MHz obtained using new, multi-configuration Australia Telescope
Compact Array (ATCA) observations. We have combined these observations with
archival single-dish observations yielding images at resolutions of 47" by 14"
and 27" by 8" at 1384 and 2368 MHz respectively. These observations were
motivated by our theoretical work (Protheroe et al. 2008) indicating the
possibility that synchrotron emission from secondary electrons and positrons
created in hadronic cosmic ray (CR) collisions with the ambient matter of the
Sgr B2 cloud could provide a detectable (and possibly linearly polarized)
non-thermal radio signal. We find that the only detectable non-thermal emission
from the Sgr B region is from a strong source to the south of Sgr B2, which we
label Sgr B2 Southern Complex (SC). We find Sgr B2(SC) integrated flux
densities of 1.2+/-0.2 Jy at 1384 MHz and 0.7+/-0.1 Jy at 2368 MHz for a source
of FWHM size at 1384 MHz of ~54". Despite its non-thermal nature, the
synchrotron emission from this source is unlikely to be dominantly due to
secondary electrons and positrons. We use polarization data to place 5-sigma
upper limits on the level of polarized intensity from the Sgr B2 cloud of 3.5
and 3 mJy/beam at 1384 and 2368 MHz respectively. We also use the angular
distribution of the total intensity of archival 330 MHz VLA and the total
intensity and polarized emission of our new 1384 MHz and 2368 MHz data to
constrain the diffusion coefficient for transport of the parent hadronic CRs
into the dense core of Sgr B2 to be no larger than about 1% of that in the
Galactic disk. Finally, we have also used the data to perform a spectral and
morphological study of the features of the Sgr B cloud and compare and contrast
these to previous studies.Comment: 7 pages, 4 figures, matches version published in the Astronomical
Journa
Intensity of singular stress fields of an embedded fibre under pull-out force
Previous experimental studies of fibre pull-out test show two dangerous points on the interface. Failure usually occurs at the bonded end of the fibre (Point A) or at the entry point on the surface of the matrix (Point E). Both points have different singular stress fields which causes crack initiation, crack propagation, and final failure. In this paper, intensity of singular stress fields (ISSF) at the fibre bonded end A and ISSF at the intersection point E of the fibre and the surface are discussed. The analysis method focuses on calculating the finite element method (FEM) stress radio by using a reference model and an unknown model. In the unknown model and the reference model, same FEM mesh pattern is applied. To analyse the ISSF at A, the body force method solution is used as the reference model. To analyse the ISSF at E, the reciprocal work contour integral method (RWCIM) solution is used as the reference model. Then, the two ISSFs are compared and discussed by varying the fibre embedded length l in. When l in is shorter, the singular stress at A is larger than the singular stress at E. When l in is longer, the singular stress at E is larger than the ISSF at A.2018 5th Global Conference on Polymer and Composite Materials (PCM 2018), April 10th - 13th, 2018, Kitakyushu, Japa
The X-ray lightcurve of Sgr A* over the past 150 years inferred from Fe-Ka line reverberation in Galactic Centre molecular clouds
We examine the temporal and spectral properties of nine Fe-Ka bright
molecular clouds within about 30 pc of Sgr A*, in order to understand and
constrain the primary energising source of the Fe fluorescence. Significant
Fe-Ka variability was detected, with a spatial and temporal pattern consistent
with that reported in previous studies. The main breakthrough that sets our
paper apart from earlier contributions on this topic is the direct measurement
of the column density and the Fe abundance of the MCs in our sample. We used
the EW measurements to infer the average Fe abundance within the clouds to be
1.60.1 times solar. The cloud column densities derived from the spectral
analysis were typically of the order of 10 cm, which is
significantly higher than previous estimates. This in turn has a significant
impact on the inferred geometry and time delays within the cloud system. Past
X-ray activity of Sgr A* is the most likely source of ionisation within the
molecular clouds in the innermost 30 pc of the Galaxy. In this scenario, the
X-ray luminosity required to excite these reflection nebulae is of the order of
10 erg s, significantly lower than that estimated for the
Sgr B2 molecular cloud. Moreover, the inferred Sgr A* lightcurve over the past
150 years shows a long-term downwards trend punctuated by occasional
counter-trend brightening episodes of at least 5 years duration. Finally, we
found that contributions to the Fe fluorescence by X-ray transient binaries and
cosmic-ray bombardment are very likely, and suggest possible ways to study this
latter phenomenon in the near future.Comment: 23 pages, 14 figures, accepted for publication in Astronomy &
Astrophysic
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