836 research outputs found
K 3-22: a D-type symbiotic star
A goal of the IPHAS survey is to determine the frequency and nature of
emission-line sources in the Galactic plane. According to our selection
criteria, K 3-22 is a candidate symbiotic star, but it was previously
classified as a planetary nebula. To determine its nature, we acquired a
low-resolution optical spectrum of K 3-22. Our analysis of our spectroscopy
demonstrates that K 3-22 is indeed a D-type symbiotic star, because of its high
excitation nebular spectrum and the simultaneous presence of Raman-scattered O
VI emission at 6825 and 7082 angstrom, which is detected primarily in symbiotic
stars.Comment: 3 pages, 1 figure. Accepted for publication on Astronomy and
Astrophysic
Late Gothic altarpieces as sources of information on medieval wood use: A dendrochronological and art historical survey
A
Trigonometric Parallaxes of Central Stars of Planetary Nebulae
Trigonometric parallaxes of 16 nearby planetary nebulae are presented,
including reduced errors for seven objects with previous initial results and
results for six new objects. The median error in the parallax is 0.42 mas, and
twelve nebulae have parallax errors less than 20 percent. The parallax for
PHL932 is found here to be smaller than was measured by Hipparcos, and this
peculiar object is discussed. Comparisons are made with other distance
estimates. The distances determined from these parallaxes tend to be
intermediate between some short distance estimates and other long estimates;
they are somewhat smaller than estimated from spectra of the central stars.
Proper motions and tangential velocities are presented. No astrometric
perturbations from unresolved close companions are detected.Comment: 24 pages, includes 4 figures. Accepted for A
The 600 yr eruptive history of Villarrica Volcano (Chile) revealed by annually laminated lake sediments
Lake sediments contain valuable information about past volcanic and seismic events that have affected the lake catchment, and they provide unique records of the recurrence interval and magnitude of such events. This study uses a multilake and multiproxy analytical approach to obtain reliable and high-resolution records of past natural catastrophes from similar to 600-yr-old annually laminated (varved) lake sediment sequences extracted from two lakes, Villarrica and Calafquen, in the volcanically and seismically active Chilean Lake District. Using a combination of micro-X-ray fluorescence (mu XRF) scanning, microfacies analysis, grain-size analysis, color analysis, and magnetic-susceptibility measurements, we detect and characterize four different types of event deposits (lacustrine turbidites, tephra-fall layers, runoff cryptotephras, and lahar deposits) and produce a revised eruption record for Villarrica Volcano, which is unprecedented in its continuity and temporal resolution. Glass geochemistry and mineralogy also reveal deposits of eruptions from the more remote Carran-Los Venados volcanic complex, Quetrupillan Volcano, and the Huanquihue Group in the studied lake sediments. Time-series analysis shows 112 eruptions with a volcanic explosivity index (VEI) >= 2 from Villarrica Volcano in the last similar to 600 yr, of which at least 22 also produced lahars. This significantly expands our knowledge of the eruptive frequency of the volcano in this time window, compared to the previously known eruptive history from historical records. The last VEI >= 2 eruption of Villarrica Volcano occurred in 1991. Based on the last similar to 500 yr, for which we have a complete record from both lakes, we estimate the probability of the occurrence of future eruptions from Villarrica Volcano and statistically demonstrate that the probability of a 22 yr repose period (anno 2013) without VEI >= 2 eruptions is <= 1.7%. This new perspective on the recurrence interval of eruptions and historical lahar activity will help improve volcanic hazard assessments for this rapidly expanding tourist region, and it highlights how lake records can be used to significantly improve historical eruption records in areas that were previously uninhabited
SPITZER SAGE Observations of Large Magellanic Cloud Planetary Nebulae
We present IRAC and MIPS images and photometry of a sample of previously
known planetary nebulae (PNe) from the SAGE survey of the Large Magellanic
Cloud (LMC) performed with the Spitzer Space Telescope. Of the 233 known PNe in
the survey field, 185 objects were detected in at least two of the IRAC bands,
and 161 detected in the MIPS 24 micron images. Color-color and color-magnitude
diagrams are presented using several combinations of IRAC, MIPS, and 2MASS
magnitudes. The location of an individual PN in the color-color diagrams is
seen to depend on the relative contributions of the spectral components which
include molecular hydrogen, polycyclic aromatic hydrocarbons (PAHs), infrared
forbidden line emission from the ionized gas, warm dust continuum, and emission
directly from the central star. The sample of LMC PNe is compared to a number
of Galactic PNe and found to not significantly differ in their position in
color-color space. We also explore the potential value of IR PNe luminosity
functions (LFs) in the LMC. IRAC LFs appear to follow the same functional form
as the well-established [O III] LFs although there are several PNe with
observed IR magnitudes brighter than the cut-offs in these LFs.Comment: 18 pages, 10 figures, 3 tables, to be published in the Astronomical
Journal. Additional online data available at
http://www.cfa.harvard.edu/irac/publications
Hubble Space Telescope Expansion Parallaxes of the Planetary Nebulae NGC 6578, NGC 6884, NGC 6891, and IC 2448
We have combined two epochs of Hubble Space Telescope WFPC2 imaging data with
ground-based expansion velocities to determine distances to three planetary
nebulae (NGC 6578, NGC 6884, and IC 2448). We used two variants of the
expansion parallax technique--a gradient method and a magnification method--to
determine the distances. The results from the two methods agree to within the
errors. A fourth nebula was included in the study (NGC 6891), but the expansion
was too small to determine the distance, and only a lower limit was obtained.
This is the first paper in a series which will examine at least 24 nebulae in
total.Comment: 26 pages, 6 figures, figure 2 is color. accepted AJ, March 200
Pathophysiology of acute experimental pancreatitis: Lessons from genetically engineered animal models and new molecular approaches
The incidence of acute pancreatitis is growing and worldwide population-based studies report a doubling or tripling since the 1970s. 25% of acute pancreatitis are severe and associated with histological changes of necrotizing pancreatitis. There is still no specific medical treatment for acute pancreatitis. The average mortality resides around 10%. In order to develop new specific medical treatment strategies for acute pancreatitis, a better understanding of the pathophysiology during the onset of acute pancreatitis is necessary. Since it is difficult to study the early acinar events in human pancreatitis, several animal models of acute pancreatitis have been developed. By this, it is hoped that clues into human pathophysiology become possible. In the last decade, while employing molecular biology techniques, a major progress has been made. The genome of the mouse was recently sequenced. Various strategies are possible to prove a causal effect of a single gene or protein, using either gain-of-function (i.e., overexpression of the protein of interest) or loss-of-function studies (i.e., genetic deletion of the gene of interest). The availability of transgenic mouse models and gene deletion studies has clearly increased our knowledge about the pathophysiology of acute pancreatitis and enables us to study and confirm in vitro findings in animal models. In addition, transgenic models with specific genetic deletion or overexpression of genes help in understanding the role of one specific protein in a cascade of inflammatory processes such as pancreatitis where different proteins interact and co-react. This review summarizes the recent progress in this field. Copyright (c) 2005 S. Karger AG, Basel
A comparative study between catalase gene therapy and the cardioprotector monohydroxyethylrutoside (MonoHER) in protecting against doxorubicin-induced cardiotoxicity in vitro
50) limited the possibility to increase catalase activity more than 3.5-fold, which was not enough to protect infected NeRCaMs against doxorubicin-induced cardiotoxicity and (2) confirms the efficacy of monoHER as a cardioprotector. Thus, the use of monoHER proves more suitable for the prevention of doxorubicin-induced cardiotoxicity than catalase gene transfer employing adenovirus vectors
Improving total saccharification yield of Arabidopsis plants by vessel-specific complementation of caffeoyl shikimate esterase (cse) mutants
Chemical Abundances and Dust in Planetary Nebulae in the Galactic Bulge
We present mid-infrared Spitzer spectra of eleven planetary nebulae in the
Galactic Bulge. We derive argon, neon, sulfur, and oxygen abundances for them
using mainly infrared line fluxes combined with some optical line fluxes from
the literature. Due to the high extinction toward the Bulge, the infrared
spectra allow us to determine abundances for certain elements more accurately
that previously possible with optical data alone. Abundances of argon and
sulfur (and in most cases neon and oxygen) in planetary nebulae in the Bulge
give the abundances of the interstellar medium at the time their progenitor
stars formed; thus these abundances give information about the formation and
evolution of the Bulge. The abundances of Bulge planetary nebulae tend to be
slightly higher than those in the Disk on average, but they do not follow the
trend of the Disk planetary nebulae, thus confirming the difference between
Bulge and Disk evolution. Additionally, the Bulge planetary nebulae show
peculiar dust properties compared to the Disk nebulae. Oxygen-rich dust feature
(crystalline silicates) dominate the spectra of all of the Bulge planetary
nebulae; such features are more scarce in Disk nebulae. Additionally,
carbon-rich dust features (polycyclic aromatic hydrocarbons) appear in roughly
half of the Bulge planetary nebulae in our sample, which is interesting in
light of the fact that this dual chemistry is comparatively rare in the Milky
Way as a whole.Comment: 16 pages, 5 figures, accepted to Ap
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