364 research outputs found
Aperture Increase Options for the Dutch Open Telescope
This paper is an invitation to the international community to participate in
the usage and a substantial upgrade of the Dutch Open Telescope on La Palma
(DOT, \url{http://dot.astro.uu.nl}).
We first give a brief overview of the approach, design, and current science
capabilities of the DOT.
The DOT database (\url{http://dotdb.phys.uu.nl/DOT}) now contains many
tomographic image sequences with 0.2-0.3 arcsec resolution and up to multi-hour
duration. You are welcome to pull them over for analysis.
The main part of this contribution outlines DOT upgrade designs implementing
larger aperture. The motivation for aperture increase is the recognition that
optical solar physics needs the substantially larger telescope apertures that
became useful with the advent of adaptive optics and viable through the DOT's
open principle, both for photospheric polarimetry at high resolution and high
sensitivity and for chromospheric fine-structure diagnosis at high cadence and
full spectral sampling.
Realization of an upgrade requires external partnership(s). This report about
DOT upgrade options therefore serves also as initial documentation for
potential partners.Comment: in press,"Physics of Chromospheric Plasmas" (Coimbra), ASP 368, 573
(2007
The mass of the neutron star in SMC X-1
We present new optical spectroscopy of the eclipsing binary pulsar Sk 160/SMC
X-1. From the He I absorption lines, taking heating corrections into account,
we determine the radial velocity semi-amplitude of Sk 160 to be 21.8 +/- 1.8
km/s. Assuming Sk 160 fills its Roche-lobe, the inclination angle of the system
is i=65.3 deg +/- 1.3 deg and in this case we obtain upper limits for the mass
of the neutron star as Mx = 1.21 +/- 0.10 Msolar and for Sk 160 as Mo= 16.6 +/-
0.4 Msolar. However if we assume that the inclination angle is i=90 deg, then
the ratio of the radius of Sk 160 to the radius of its Roche-lobe is beta =
0.79 +/- 0.02, and the lower limits for the masses of the two stars are Mx =
0.91 +/- 0.08 Msolar and Mo = 12.5 +/- 0.1 Msolar. We also show that the HeII
4686A emission line tracks the motion of the neutron star, but with a radial
velocity amplitude somewhat less than that of the neutron star itself. We
suggest that this emission may arise from a hotspot where material accreting
via Roche lobe overflow impacts the outer edge of an accretion disc.Comment: Accepted for publication by A&A. 4 Figures & Table 2 will only appear
in the on-line versio
3D visualization processes for recreating and studying organismal form
The study of biological form is a vital goal of evolutionary biology and functional morphology. We review an emerging set of methods that allow scientists to create and study accurate 3D models of living organisms and animate those models for biomechanical and fluid dynamic analyses. The methods for creating such models include 3D photogrammetry, laser and CT-scanning, and 3D software. New multi-camera devices can be used to create accurate 3D models of living animals in the wild and captivity. New websites and virtual reality/augmented reality devices now enable the visualization and sharing of these data. We provide examples of these approaches for animals ranging from large whales to lizards and show applications for several areas: Natural history collections; body condition/scaling, bioinspired robotics, computational fluids dynamics (CFD), machine learning, and education. We provide two data sets to demonstrate the efficacy of CFD and machine learning approaches and conclude with a prospectus
Imaging-guided chest biopsies: techniques and clinical results
Background
This article aims to comprehensively describe indications, contraindications, technical aspects, diagnostic accuracy and complications of percutaneous lung biopsy.
Methods
Imaging-guided biopsy currently represents one of the predominant methods for obtaining tissue specimens in patients with lung nodules; in many cases treatment protocols are based on histological information; thus, biopsy is frequently performed, when technically feasible, or in case other techniques (such as bronchoscopy with lavage) are inconclusive.
Results
Although a coaxial system is suitable in any case, two categories of needles can be used: fine-needle aspiration biopsy (FNAB) and core-needle biopsy (CNB), with the latter demonstrated to have a slightly higher overall sensitivity, specificity and accuracy.
Conclusion
Percutaneous lung biopsy is a safe procedure even though a few complications are possible: pneumothorax, pulmonary haemorrhage and haemoptysis are common complications, while air embolism and seeding are rare, but potentially fatal complications
Population Connectivity of Pelagic Megafauna in the Cuba-Mexico-United States Triangle
The timing and extent of international crossings by billfishes, tunas, and sharks in the Cuba-Mexico-United States (U.S.) triangle was investigated using electronic tagging data from eight species that resulted in \u3e22,000 tracking days. Transnational movements of these highly mobile marine predators were pronounced with varying levels of bi- or tri-national population connectivity displayed by each species. Billfishes and tunas moved throughout the Gulf of Mexico and all species investigated (blue marlin, white marlin, Atlantic bluefin tuna, yellowfin tuna) frequently crossed international boundaries and entered the territorial waters of Cuba and/or Mexico. Certain sharks (tiger shark, scalloped hammerhead) displayed prolonged periods of residency in U.S. waters with more limited displacements, while whale sharks and to a lesser degree shortfin mako moved through multiple jurisdictions. The spatial extent of associated movements was generally associated with their differential use of coastal and open ocean pelagic ecosystems. Species with the majority of daily positions in oceanic waters off the continental shelf showed the greatest tendency for transnational movements and typically traveled farther from initial tagging locations. Several species converged on a common seasonal movement pattern between territorial waters of the U.S. (summer) and Mexico (winter)
Radio Astronomy
Contains reports on five research projects.National Science Foundation (Grant AST82-14296)National Aeronautics and Space Administration (Grant NAG W-373)National Aeronautics and Space Administration (Grant NAG5-537)U.S. Navy - Office of Naval Research (Contract N00014-84-C-2082)SM Systems and Research, Inc.Defense Advanced Research Project Agency (Contract MDA903-82-K-0521
Chlamydophila pneumoniae induces a sustained airway hyperresponsiveness and inflammation in mice
Background: It has been reported that Chlamydophila (C.) pneumoniae is involved in the initiation and promotion of asthma and chronic obstructive pulmonary diseases (COPD). Surprisingly, the effect of C. pneumoniae on airway function has never been investigated.Methods: In this study, mice were inoculated intranasally with C. pneumoniae (strain AR39) on day 0 and experiments were performed on day 2, 7, 14 and 21.Results: We found that from day 7, C. pneumoniae infection causes both a sustained airway hyperresponsiveness and an inflammation. Interferon-γ (IFN-γ) and macrophage inflammatory chemokine-2 (MIP-2) levels in bronchoalveolar lavage (BAL)-fluid were increased on all experimental days with exception of day 7 where MIP-2 concentrations dropped to control levels. In contrast, tumor necrosis factor-α (TNF-α) levels were only increased on day 7. From day 7 to 21 epithelial damage and secretory cell hypertrophy was observed. It is suggested that, the inflammatory cells/mediators, the epithelial damage and secretory cell hypertrophy contribute to initiation of airway hyperresponsiveness.Conclusion: Our study demonstrates for the first time that C. pneumoniae infection can modify bronchial responsiveness. This has clinical implications, since additional changes in airway responsiveness and inflammation-status induced by this bacterium may worsen and/or provoke breathlessness in asthma and COPD
On the nature of the galactic early-B hypergiants
Despite their importance to a number of astrophysical fields, the lifecycles
of very massive stars are still poorly defined. In order to address this
shortcoming, we present a detailed quantitative study of the physical
properties of four early-B hypergiants (BHGs); Cyg OB2 #12, zeta Sco, HD190603
and BP Cru. These are combined with an analysis of their long-term
spectroscopic and photometric behaviour in order to determine their
evolutionary status. The long-term datasets revealed that they are remarkably
stable over long periods (>40yr), with the possible exception of zeta Sco prior
to the 20th century, in contrast to the typical excursions that characterise
luminous blue variables (LBVs). Zeta Sco, HD190603 and BP Cru possess physical
properties intermediate between B supergiants and LBVs; we therefore suggest
that BHGs are the immediate descendants and progenitors (respectively) of such
stars (for initial masses in the range ~30-60Msun). In contrast, while the wind
properties of Cyg OB2 #12 are consistent with this hypothesis, the combination
of extreme luminosity and spectroscopic mass (~110Msun) and comparatively low
temperature means it cannot be accommodated in such a scheme. Likewise, despite
its co-location with several LBVs above the Humphreys-Davidson (HD) limit, the
lack of long term variability and its unevolved chemistry apparently excludes
such an identification. Since such massive stars are not expected to evolve to
such cool temperatures, the properties of Cyg OB2 #12 are difficult to
understand under current evolutionary paradigms. [ABRIDGED]Comment: 36 pages, 19 figures (of which 17 pages are online supplemental
material). Accepted for publication in Astronomy and Astrophysic
Observations of Accreting Pulsars
We summarize five years of continuous monitoring of accretion-powered pulsars
with the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray
Observatory. Our 20-70 keV observations have determined or refined the orbital
parameters of 13 binaries, discovered 5 new transient accreting pulsars,
measured the pulsed flux history during outbursts of 12 transients (GRO
J1744-28, 4U 0115+634, GRO J1750-27, GS 0834-430, 2S 1417-624, GRO J1948+32,
EXO 2030+375, GRO J1008-57, A 0535+26, GRO J2058+42, 4U 1145-619 and A
1118-616), and also measured the accretion torque history of during outbursts
of 6 of those transients whose orbital parameters were also known. We have also
continuously measured the pulsed flux and spin frequency for eight persistently
accreting pulsars (Her X-1, Cen X-3, Vela X-1, OAO 1657-415, GX 301-2, 4U
1626-67, 4U 1538-52, and GX 1+4). Because of their continuity and uniformity
over a long baseline, BATSE observations have provided new insights into the
long-term behavior of accreting magnetic stars. We have found that all
accreting pulsars show stochastic variations in their spin frequencies and
luminosities, including those displaying secular spin-up or spin-down on long
time scales, blurring the conventional distinction between disk-fed and
wind-fed binaries. Pulsed flux and accretion torque are strongly correlated in
outbursts of transient accreting pulsars, but uncorrelated, or even
anticorrelated, in persistent sources.Comment: LaTeX, psfig, 90 pages, 42 figures. To appear in Dec. 1997 ApJS, Vol
113, #
Low Prevalence of Chlamydia trachomatis Infection in Non-Urban Pregnant Women in Vellore, S. India
Objective: To determine the prevalence and risk factors for Chlamydia trachomatis (CT) infection in pregnant women and the rate of transmission of CT to infants. Methods: Pregnant women ($28 weeks gestation) in Vellore, South India were approached for enrollment from April 2009 to January 2010. After informed consent was obtained, women completed a socio-demographic, prenatal, and sexual history questionnaire. Endocervical samples collected at delivery were examined for CT by a rapid enzyme test and nucleic acid amplification test (NAAT). Neonatal nasopharyngeal and conjunctival swabs were collected for NAAT testing. Results: Overall, 1198 women were enrolled and 799 (67%) endocervical samples were collected at birth. Analyses were completed on 784 participants with available rapid and NAAT results. The mean age of women was 25.8 years (range 18– 39 yrs) and 22 % (95 % CI: 19.7–24.4%) were primigravida. All women enrolled were married; one reported.one sexual partner; and six reported prior STI. We found 71 positive rapid CT tests and 1/784 (0.1%; 95 % CI: 0–0.38%) true positive CT infection using NAAT. Conclusions: To our knowledge, this is the largest study on CT prevalence amongst healthy pregnant mothers in southern India, and it documents a very low prevalence with NAAT. Many false positive results were noted using the rapid test. Thes
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