767 research outputs found
âCort short on a mountaintopâ â Eight new species of sequestrate Cortinarius from sub-alpine Australia and affinities to sections within the genus
During the course of research on mammal mycophagy and movement in the Northern Tablelands of New South Wales, Australia, extensive collections of sequestrate fungi were made, including numerous cortinarioid taxa. Historically any novel taxa would have been described in the cortinarioid sequestrate genera Descomyces, Hymenogaster, Protoglossum, Quadrispora, Thaxterogaster or Timgrovea based on broad morphological similarities of the sporocarps and spore ornamentation. However, consistent with other recent analyses of nuclear DNA regions, taxa from sequestrate genera were found to have affinities with Cortinarius and Descolea or Hebeloma, and to be scattered across many sections within Cortinarius. None of the historical sequestrate cortinarioid genera are monophyletic in our analyses. In particular, the gastroid genus Hymenogaster is paraphyletic, with one clade including two species of Protoglossum in Cortinarius, and a second clade sister to Hebeloma. Eight new species of sequestrate Cortinarius are described and illustrated, and discussion of their affinities with various sections provided: C. argyronius, C. caesibulga and C. cinereoroseolus in section Purpurascentes, C. maculobulga in section Rozites, C. sinapivelus in section Splendidi, C. kaputarensis in a mixed section Phlegmacium/Myxacium within a broader section Dermocybe, C. basorapulus in section Percomes and C. nebulobrunneus in section Pseudotriumphantes. Keys to genera of the Bolbitiaceae and Cortinariaceae containing sequestrate taxa and to currently known Australian species of sequestrate Cortinarius and Protoglossum are provided. As with the related agaricoid taxa, macroscopic characters such as colour and texture of basidioma, degree of loculisation of the hymenophore, and stipe-columella development and form remain useful for distinguishing species, but are generally not so useful at the sectional level within Cortinarius. Microscopic characters such as spore shape, size, and ornamentation, and pileipellis structure (simplex vs duplex and size of hyphal elements) are essential for determining species, and also appear to follow sectional boundaries
The Distance to the Vela Supernova Remnant
We have obtained high resolution Ca II and Na I absorption line spectra
toward 68 OB stars in the direction of the Vela Supernova Remnant. The stars
lie at distances of 190 -- 2800 pc as determined by Hipparcos and spectroscopic
parallax estimations. The presence of high velocity absorption attributable to
the remnant along some of the sight lines constrains the remnant distance to
250+/-30 pc. This distance is consistent with several recent investigations
that suggest that the canonical remnant distance of 500 pc is too large.Comment: To be published in The Astrophysical Journal Letters Figure 1 y-axis
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Cloud Structure and Physical Conditions in Star-forming Regions from Optical Observations. I. Data and Component Structure
We present high-resolution optical spectra (at ~0.6--1.8 km s-1) of
interstellar CN, CH, CH^+, \ion{Ca}{1}, \ion{K}{1}, and \ion{Ca}{2} absorption
toward 29 lines of sight in three star-forming regions, \rho Oph, Cep OB2, and
Cep OB3. The observations and data reduction are described. The agreement
between earlier measurements of the total equivalent widths and our results is
quite good. However, our higher resolution spectra reveal complex structure and
closely blended components in most lines of sight. The velocity component
structure of each species is obtained by analyzing the spectra of the six
species for a given sight line together. The tabulated column densities and
Doppler parameters of individual components are determined by using the method
of profile fitting. Total column densities along lines of sight are computed by
summing results from profile fitting for individual components and are compared
with column densities from the apparent optical depth method. A more detailed
analysis of these data and their implications will be presented in a companion
paper.Comment: 66 pages, 15 figures, accepted to ApJ
Photospheric and chromospheric activity in four young solar-type stars
We present a photometric and spectroscopic study of four G-K dwarfs, namely
HD 166, epsilon Eri, chi1 Ori and kappa1 Cet. In three cases, we find a clear
spatial association between photospheric and chromospheric active regions. For
chi1 Ori we do not find appreciable variations of photospheric temperature, and
chromospheric Halpha emission. We applied a spot/plage model to the observed
rotational modulation of temperature and flux to derive spot/plage parameters
and to reconstruct a rough three-dimensional map of the outer atmosphere of
kappa1 Cet, HD 166 and epsilon Eri.Comment: 12 pages, 3 tables, 9 figures. Submitted to Ap
Embedded researchers as part of a whole systems approach to physical activity: Reflections and recommendations
Whole systems approaches are increasingly being advocated as a way of responding to complex public health priorities such as obesity and physical inactivity. Due to the complex and adaptive nature of such systems, researchers are increasingly being embedded within host organisations (i.e., those which facilitate the whole systems approach) to work with key stakeholders to illuminate and understand mechanisms of change and develop a culture of continuous improvement. While previous literature has reported on the benefits and challenges of embedded researchers in health care, little is known about the experiences and learnings of those situated within these complex whole systems approaches. In this paper, we present our reflections of being embedded researchers within four distinct whole systems approaches and outline recommendations and considerations for commissioners working with or seeking support from an embedded researcher
CH 3 GHz Observations of Molecular Clouds Along the Galactic Plane
Spectra in the CH , J=1/2, F=1-1 transition at 3335 MHz were
obtained in three 5-point crosses centered on the Galactic plane at
50\arcdeg, 100\arcdeg, and 110\arcdeg. The lines of sight traverse both
Giant Molecular Clouds (GMCs) and local, smaller entities. This transition is a
good tracer of low-density molecular gas and the line profiles are very similar
to CO(1-0) data at nearly the same resolution. In addition, the CH 3335 MHz
line can be used to calibrate the CO-H conversion factor (X) in
low-density molecular gas. Although this technique underestimates X
in GMCs, our results are within a factor of two of X values
calibrated for GMCs by other techniques. The similarity of CH and CO line
profiles, and that of X values derived from CH and more traditional
techniques, implies that most of the molecular gas along the observed lines of
sight is at relatively low densities ( 10 cm).Comment: 26 pages, 12 figures, submitted to the AJ, revised after referee
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Evidence of a Supermassive Black Hole in the Galaxy NGC 1023 from the Nuclear Stellar Dynamics
We analyze the nuclear stellar dynamics of the SB0 galaxy NGC 1023, utilizing
observational data both from the Space Telescope Imaging Spectrograph aboard
the Hubble Space Telescope and from the ground. The stellar kinematics measured
from these long-slit spectra show rapid rotation (V = 70 km/s at a distance of
0.1 arcsec = 4.9 pc from the nucleus) and increasing velocity dispersion toward
the nucleus (where sigma = 295 +/- 30 km/s). We model the observed stellar
kinematics assuming an axisymmetric mass distribution with both two and three
integrals of motion. Both modeling techniques point to the presence of a
central dark compact mass (which presumably is a supermassive black hole) with
confidence > 99%. The isotropic two-integral models yield a best-fitting black
hole mass of (6.0 +/- 1.4) x 10^7 M_sun and mass-to-light ratio (M/L_V) of 5.38
+/- 0.08, and the goodness-of-fit (chi^2) is insensitive to reasonable values
for the galaxy's inclination. The three-integral models, which
non-parametrically fit the observed line-of-sight velocity distribution as a
function of position in the galaxy, suggest a black hole mass of (3.9 +/- 0.4)
x 10^7 M_sun and M/L_V of 5.56 +/- 0.02 (internal errors), and the edge-on
models are vastly superior fits over models at other inclinations. The internal
dynamics in NGC 1023 as suggested by our best-fit three-integral model shows
that the velocity distribution function at the nucleus is tangentially
anisotropic, suggesting the presence of a nuclear stellar disk. The nuclear
line of sight velocity distribution has enhanced wings at velocities >= 600
km/s from systemic, suggesting that perhaps we have detected a group of stars
very close to the central dark mass.Comment: 21 pages, 12 figures, accepted in the Astrophysical Journa
Menkes kinky hair disease: A case report
An eight month old male infant with protein energy malnutrition was admitted in the hospital with the history of repeated attacks of convulsion since four months of age. He was also suffering from frequent attacks of cough and cold since 6 months of age which was marked prior to admission. The infant had fair complexion, sparse fuzzy wooly hair with marked trunkal hypotonia. He had also mental retardation. Serum copper and ceruloplasmin levels were low, MRI showed prominent extraaxial spaces with gliosis, MR angiography revealed tortuosity of cerebral vessels. Microscopic examination of hair revealed pili torti. The patient was diagnosed as Menkes disease and treated symptomatically. For lack of facilities we were not able to do genetic study
Observations of H3+ in the Diffuse Interstellar Medium
Surprisingly large column densities of H3+ have been detected using infrared
absorption spectroscopy in seven diffuse cloud sightlines (Cygnus OB2 12,
Cygnus OB2 5, HD 183143, HD 20041, WR 104, WR 118, and WR 121), demonstrating
that H3+ is ubiquitous in the diffuse interstellar medium. Using the standard
model of diffuse cloud chemistry, our H3+ column densities imply unreasonably
long path lengths (~1 kpc) and low densities (~3 cm^-3). Complimentary
millimeter-wave, infrared, and visible observations of related species suggest
that the chemical model is incorrect and that the number density of H3+ must be
increased by one to two orders of magnitude. Possible solutions include a
reduced electron fraction, an enhanced rate of H2 ionization, and/or a smaller
value of the H3+ dissociative recombination rate constant than implied by
laboratory experiments.Comment: To be published in Astrophysical Journal, March 200
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