1,327 research outputs found
The Supernova Remnant CTB104A : Magnetic Field Structure and Interaction with the Environment
We present new, high resolution 1420 and 408 MHz continuum images and HI and
12CO (J=1-0) spectral line maps of the diffuse supernova remnant CTB104A
(G93.7-0.3). Analysis of the complex continuum emission reveals no significant
spectral index variations across the remnant. Three prominences around CTB104A
are found to be related to the SNR, while one extension to the east is
identified as an HII region associated with a background molecular shell. Small
scale polarization and rotation measure (RM) structures are turbulent in
nature, but we find a well-ordered RM gradient across the remnant, extending
from southeast to northwest. This gradient does not agree with the direction of
the global Galactic magnetic field, but does agree with a large-scale RM
anomaly inferred from rotation measure data by Cleg et al. (1992). We show that
the observed morphology of CTB104A is consistent with expansion in a uniform
magnetic field, and this is supported by the observed RM distribution. By
modeling the RM gradient with a simple compression model we have determined the
magnetic field strength within the remnant as Bo ~ 2.3 micro G. We have
identified signatures of the interaction of CTB104A with the surrounding
neutral material, and determined its distance, from the kinematics of the HI
structure encompassing the radio emission, as 1.5 kpc. We also observed clear
breaks in the HI shell that correspond well to the positions of two of the
prominences, indicating regions where hot gas is escaping from the interior of
the SNR.Comment: 7 pages, Latex with aastex and emulateapj5, 12 figures, ApJ accepte
Finite element methods for multicomponent convection-diffusion
We develop finite element methods for coupling the steady-state
Onsager--Stefan--Maxwell equations to compressible Stokes flow. These equations
describe multicomponent flow at low Reynolds number, where a mixture of
different chemical species within a common thermodynamic phase is transported
by convection and molecular diffusion. Developing a variational formulation for
discretizing these equations is challenging: the formulation must balance
physical relevance of the variables and boundary data, regularity assumptions,
tractability of the analysis, enforcement of thermodynamic constraints, ease of
discretization, and extensibility to the transient, anisothermal, and non-ideal
settings. To resolve these competing goals, we employ two augmentations: the
first enforces the mass-average constraint in the Onsager--Stefan--Maxwell
equations, while its dual modifies the Stokes momentum equation to enforce
symmetry. Remarkably, with these augmentations we achieve a Picard
linearization of symmetric saddle point type, despite the equations not
possessing a Lagrangian structure. Exploiting the structure of linear
irreversible thermodynamics, we prove the inf-sup condition for this
linearization, and identify finite element function spaces that automatically
inherit well-posedness. We verify our error estimates with a numerical example,
and illustrate the application of the method to non-ideal fluids with a
simulation of the microfluidic mixing of hydrocarbons
Utilities associated with subcutaneous injections and intravenous infusions for treatment of patients with bone metastases
Introduction: Although cost−utility models are often used to estimate the value of treatments for
metastatic cancer, limited information is available on the utility of common treatment modalities.
Bisphosphonate treatment for bone metastases is frequently administered via intravenous infusion,
while a newer treatment is administered as a subcutaneous injection. This study estimated
the impact of these treatment modalities on health state preference.
Methods: Participants from the UK general population completed time trade-off interviews
to assess the utility of health state vignettes. Respondents first rated a health state representing
cancer with bone metastases. Subsequent health states added descriptions of treatment modalities
(ie, injection or infusion) to this basic health state. The two treatment modalities were presented
with and without chemotherapy, and infusion characteristics were varied by duration (30 minutes
or 2 hours) and renal monitoring.
Results: A total of 121 participants completed the interviews (52.1% female, 76.9% white).
Cancer with bone metastases had a mean utility of 0.40 on a standard utility scale (1 = full
health; 0 = dead). The injection, 30-minute infusion, and 2-hour infusion had mean disutilities
of −0.004, −0.02, and −0.04, respectively. The mean disutility of the 30-minute infusion was
greater with renal monitoring than without. Chemotherapy was associated with substantial
disutility (−0.17). When added to health states with chemotherapy, the mean disutilities of injection,
30-minute infusion, and 2-hour infusion were −0.02, −0.03, and −0.04, respectively. The
disutility associated with injection was significantly lower than the disutility of the 30-minute
and 2-hour infusions (P , 0.05), regardless of chemotherapy status.
Conclusion: Respondents perceived an inconvenience with each type of treatment modality,
but injections were preferred over infusions. The resulting utilities may be used in cost−utility
models examining the value of treatments for the prevention of skeletal-related events in patients
with bone metastases
An Automated Method for the Detection and Extraction of HI Self-Absorption in High-Resolution 21cm Line Surveys
We describe algorithms that detect 21cm line HI self-absorption (HISA) in
large data sets and extract it for analysis. Our search method identifies HISA
as spatially and spectrally confined dark HI features that appear as negative
residuals after removing larger-scale emission components with a modified CLEAN
algorithm. Adjacent HISA volume-pixels (voxels) are grouped into features in
(l,b,v) space, and the HI brightness of voxels outside the 3-D feature
boundaries is smoothly interpolated to estimate the absorption amplitude and
the unabsorbed HI emission brightness. The reliability and completeness of our
HISA detection scheme have been tested extensively with model data. We detect
most features over a wide range of sizes, linewidths, amplitudes, and
background levels, with poor detection only where the absorption brightness
temperature amplitude is weak, the absorption scale approaches that of the
correlated noise, or the background level is too faint for HISA to be
distinguished reliably from emission gaps. False detection rates are very low
in all parts of the parameter space except at sizes and amplitudes approaching
those of noise fluctuations. Absorption measurement biases introduced by the
method are generally small and appear to arise from cases of incomplete HISA
detection. This paper is the third in a series examining HISA at high angular
resolution. A companion paper (Paper II) uses our HISA search and extraction
method to investigate the cold atomic gas distribution in the Canadian Galactic
Plane Survey.Comment: 39 pages, including 14 figure pages; to appear in June 10 ApJ, volume
626; figure quality significantly reduced for astro-ph; for full resolution,
please see http://www.ras.ucalgary.ca/~gibson/hisa/cgps1_survey
Colour break in reverse bicolour daffodils is associated with the presence of Narcissus mosaic virus
<p>Abstract</p> <p>Background</p> <p>Daffodils (<it>Narcissus pseudonarcissus</it>) are one of the world's most popular ornamentals. They also provide a scientific model for studying the carotenoid pigments responsible for their yellow and orange flower colours. In reverse bicolour daffodils, the yellow flower trumpet fades to white with age. The flowers of this type of daffodil are particularly prone to colour break whereby, upon opening, the yellow colour of the perianth is observed to be 'broken' into patches of white. This colour break symptom is characteristic of potyviral infections in other ornamentals such as tulips whose colour break is due to alterations in the presence of anthocyanins. However, reverse bicolour flowers displaying colour break show no other virus-like symptoms such as leaf mottling or plant stunting, leading some to argue that the carotenoid-based colour breaking in reverse bicolour flowers may not be caused by virus infection.</p> <p>Results</p> <p>Although potyviruses have been reported to cause colour break in other flower species, enzyme-linked-immunoassays with an antibody specific to the potyviral family showed that potyviruses were not responsible for the occurrence of colour break in reverse bicolour daffodils. Colour break in this type of daffodil was clearly associated with the presence of large quantities of rod-shaped viral particles of lengths 502-580 nm in tepals. Sap from flowers displaying colour break caused red necrotic lesions on <it>Gomphrena globosa</it>, suggesting the presence of potexvirus. Red necrotic lesions were not observed in this indicator plant when sap from reverse bicolour flowers not showing colour break was used. The reverse transcriptase polymerase reactions using degenerate primers to carla-, potex- and poty-viruses linked viral RNA with colour break and sequencing of the amplified products indicated that the potexvirus <it>Narcissisus mosaic virus </it>was the predominant virus associated with the occurrence of the colour break.</p> <p>Conclusions</p> <p>High viral counts were associated with the reverse bicolour daffodil flowers that were displaying colour break but otherwise showed no other symptoms of infection. <it>Narcissus mosaic virus </it>was the virus that was clearly linked to the carotenoid-based colour break.</p
Metabolic model integration of the bibliome, genome, metabolome and reactome of Aspergillus niger
The release of the genome sequences of two strains of Aspergillus niger has allowed systems-level investigations of this important microbial cell factory. To this end, tools for doing data integration of multi-ome data are necessary, and especially interesting in the context of metabolism. On the basis of an A. niger bibliome survey, we present the largest model reconstruction of a metabolic network reported for a fungal species. The reconstructed gapless metabolic network is based on the reportings of 371 articles and comprises 1190 biochemically unique reactions and 871 ORFs. Inclusion of isoenzymes increases the total number of reactions to 2240. A graphical map of the metabolic network is presented. All levels of the reconstruction process were based on manual curation. From the reconstructed metabolic network, a mathematical model was constructed and validated with data on yields, fluxes and transcription. The presented metabolic network and map are useful tools for examining systemwide data in a metabolic context. Results from the validated model show a great potential for expanding the use of A. niger as a high-yield production platform
Variational Problems with Fractional Derivatives: Euler-Lagrange Equations
We generalize the fractional variational problem by allowing the possibility
that the lower bound in the fractional derivative does not coincide with the
lower bound of the integral that is minimized. Also, for the standard case when
these two bounds coincide, we derive a new form of Euler-Lagrange equations. We
use approximations for fractional derivatives in the Lagrangian and obtain the
Euler-Lagrange equations which approximate the initial Euler-Lagrange equations
in a weak sense
Fractional variational calculus of variable order
We study the fundamental problem of the calculus of variations with variable
order fractional operators. Fractional integrals are considered in the sense of
Riemann-Liouville while derivatives are of Caputo type.Comment: Submitted 26-Sept-2011; accepted 18-Oct-2011; withdrawn by the
authors 21-Dec-2011; resubmitted 27-Dec-2011; revised 20-March-2012; accepted
13-April-2012; to 'Advances in Harmonic Analysis and Operator Theory', The
Stefan Samko Anniversary Volume (Eds: A. Almeida, L. Castro, F.-O. Speck),
Operator Theory: Advances and Applications, Birkh\"auser Verlag
(http://www.springer.com/series/4850
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