432 research outputs found
Dust rings and filaments around the isolated young star V1331 Cygni
We characterize the small and large scale environment of the young star V1331
Cygni with high resolution HST/WFPC2 and Digitized Sky Survey images. In
addition to a previously known outer dust ring (~30'' in diameter), the
HST/WFPC2 scattered light image reveals an inner dust ring for the first time.
This ring has a maximum radius of 6.5'' and is possibly related to a molecular
envelope. Large-scale optical images show that V1331 Cyg is located at the tip
of a long dust filament linking it to the dark cloud LDN 981. We discuss the
origin of the observed dust morphology and analyze the object's relation to its
parent dark cloud LDN 981. Finally, based on recent results from the
literature, we investigate the properties of V1331 Cyg and conclude that in its
current state the object does not show suffcient evidence to be characterized
as an FU Ori object.Comment: 15 pages ApJ preprint style including 3 figures, accepted for
publication in ApJ (Feb. 2007
FU Orionis - The MIDI/VLTI Perspective
We present the first mid-infrared interferometric measurements of FU Orionis.
We clearly resolve structures that are best explained with an optically thick
accretion disk. A simple accretion disk model fits the observed SED and
visibilities reasonably well and does not require the presence of any
additional structure such as a dusty envelope. The inclination and also the
position angle of the disk can be constrained from the multibaseline
interferometric observations. Our disk model is in general agreement with most
published near-infrared interferometric measurements. From the shape and
strength of the 8-13 micrometer spectrum the dust composition of the accretion
disk is derived for the first time. We conclude that most dust particles are
amorphous and already much larger than those typically observed in the ISM.
Although the high accretion rate of the system provides both, high temperatures
out to large radii and an effective transport mechanism to distribute
crystalline grains, we do not see any evidence for crystalline silicates
neither in the total spectrum nor in the correlated flux spectra from the inner
disk regions. Possible reasons for this non-detection are mentioned. All
results are discussed in context with other high-spatial resolution
observations of FU Ori and other FU Ori objects. We also address the question
whether FU Ori is in a younger evolutionary stage than a classical TTauri star.Comment: 41 pages (aastex style), 11 figures, 8 tables, accepted by Ap
Star Formation in the Gulf of Mexico
We present an optical/infrared study of the dense molecular cloud, L935,
dubbed "The Gulf of Mexico", which separates the North America and the Pelican
nebulae, and we demonstrate that this area is a very active star forming
region. A wide-field imaging study with interference filters has revealed 35
new Herbig-Haro objects in the Gulf of Mexico. A grism survey has identified 41
Halpha emission-line stars, 30 of them new. A small cluster of partly embedded
pre-main sequence stars is located around the known LkHalpha 185-189 group of
stars, which includes the recently erupting FUor HBC 722.Comment: Submitted to A&A, 14 pages, 18 figure
Epithelial-mesenchymal transition in cancer metastasis through the lymphatic syste
It was already in the 18th century when the French surgeon LeDran first noted that breast cancer patients with spread of tumor cells to their axillary lymph nodes had a drastically worse prognosis than patients without spread (LeDran et al., ). Since then, metastatic spread of cancer cells to regional lymph nodes has been established as the most important prognostic factor in many types of cancer (Carter et al., ; Elston and Ellis, ). However, despite its clinical importance, lymph metastasis remains an underexplored area of tumor biology. Fundamental questions, such as when, how, and perhaps most importantly, why tumor cells disseminate through the lymphatic system, remain largely unanswered. Accordingly, no treatment strategies exist that specifically target lymph metastasis. The identification of epithelial-mesenchymal transition (EMT) as a mechanism, which allows cancer cells to dedifferentiate and acquire enhanced migratory and invasive properties, has been a game changer in cancer research. Conceptually, EMT provides an explanation for why epithelial cancers with poor differentiation status are generally more aggressive and prone to metastasize than more differentiated cancers. Inflammatory cytokines, such as TGF-ÎČ, which are produced and secreted by tumor-infiltrating immune cells, are potent inducers of EMT. Thus, reactivation of EMT also links cancer-related inflammation to invasive and metastatic disease. Recently, we found that breast cancer cells undergoing TGF-ÎČ- induced EMT acquire properties of immune cells allowing them to disseminate in a targeted fashion through the lymphatic system similar to activated dendritic cells during inflammation. Here, we review our current understanding of the mechanisms by which cancer cells spread through the lymphatic system and the links to inflammation and the immune system. We also emphasize how imaging techniques have the potential to further expand our knowledge of the mechanisms of lymph metastasis, and how lymph nodes serve as an interface between cancer and the immune system
First Lidar Observations of Middle Atmosphere Temperatures, Fe Densities, and Polar Mesospheric Clouds Over the North and South Poles
An Fe Boltzmann temperature lidar was used to
obtain the first measurements of middle atmosphere temperatures,
Fe densities, and polar mesosphericlouds (PMCs)
over the North and South Poles during the 1999-2000 summer
seasons. The measured temperature structure of the
mesopause and lower thermosphere regions in mid-summer
at both Poles is consistent with the MSIS90 model. The
density profiles of the normal Fe layer between 80-100 km
at summer solstice are similar at both the North and South
Poles with maximum densities of about 2000 cm -a. Sporadic
Fe (Fes) layers were observed at both Poles with peak
densities at 106 km altitude. The maximum densities of the
Fes layers were 232x10 a cm -a at North Pole and 6.52x10 a
cm -a at South Pole. PMCs were detected above both Poles.
The altitudes of PMCs over the South Pole were consistently
2-3 km higher than those observed over the North Pole.Ope
High-Resolution Spectroscopy of FUors
High-resolution spectroscopy was obtained of the FUors FU Ori and V1057 Cyg
between 1995 and 2002 with SOFIN at NOT and with HIRES at Keck I. During those
years FU Ori remained about 1 mag. (in B) below its 1938-39 maximum brightness,
but V1057 Cyg (B ~ 10.5 at peak in 1970-71) faded from about 13.5 to 14.9 and
then recovered slightly. Their photospheric spectra resemble a rotating G0 Ib
supergiant, with v_eq sin i = 70 km/s for FU Ori and 55 km/s for V1057 Cyg. As
V1057 Cyg faded, P Cyg structure in Halpha and the IR CaII lines strengthened
and a complex shortward-displaced shell spectrum increased in strength,
disappeared in 1999, and reappeared in 2001. Night-to-night changes in the wind
structure of FU Ori show evidence of sporadic infall. The strength of P Cyg
absorption varied cyclically with a period of 14.8 days, with phase stability
maintained over 3 seasons, and is believed to be the rotation period. The
structure of the photospheric lines also varies cyclically, but with a period
of 3.54 days. A similar variation may be present in V1057 Cyg. As V1057 Cyg has
faded, the emission lines of a pre-existing low-excitation chromosphere have
emerged, so we believe the `line doubling' in V1057 Cyg is produced by these
central emission cores in the absorption lines, not by orbital motion in an
inclined Keplerian disk. No dependence of v_eq sin i on wavelength or
excitation potential was detected in either star, again contrary to expectation
for a self-luminous accretion disk. Nor are critical lines in the near infrared
accounted for by synthetic disk spectra. A rapidly rotating star near the edge
of stability (Larson 1980), can better explain these observations. FUor
eruptions may not be a property of ordinary TTS, but may be confined to a
special subspecies of rapid rotators having powerful quasi-permanent winds.Comment: 41 pages (including 32 figures and 9 tables); ApJ, in press; author
affiliation, figs. 3 and 9 correcte
Mc Neil's Nebula in Orion: The Outburst History
We present a sequence of I-band images obtained at the Venezuela 1m Schmidt
telescope during the outburst of the nebula recently discovered by J.W. McNeil
in the Orion L1630 molecular cloud. We derive photometry spanning the
pre-outburst state and the brightening itself, a unique record including 14
epochs and spanning a time scale of ~5 years. We constrain the beginning of the
outburst at some time between Oct. 28 and Nov. 15, 2003. The light curve of the
object at the vertex of the nebula, the likely exciting source of the outburst,
reveals that it has brightened ~5 magnitudes in about 4 months. The time scale
for the nebula to develop is consistent with the light travel time, indicating
that we are observing light from the central source scattered by the ambient
cloud into the line of sight. We also show recent FLWO optical spectroscopy of
the exciting source and of the nearby HH 22. The spectrum of the source is
highly reddened; in contrast, the spectrum of HH 22 shows a shock spectrum
superimposed on a continuum, most likely due to reflected light from the
exciting source reaching the HH object through a much less reddened path. The
blue portion of this spectrum is consistent with an early B spectral type,
similar to the early outburst spectrum of the FU Ori variable V1057 Cyg; we
estimate a luminosity of L ~219 Lsun. The eruptive behavior of the McNeil
nebula source, its spectroscopic characteristics and luminosity, suggest we may
be witnessing an FU Ori event on its way to maximum. Further monitoring of this
object will decide whether it qualifies as a member of this rare class of
objects.Comment: 13 pages, 4 figures, accepted to ApJ Letter
Coping strategies, stress, physical activity and sleep in patients with unexplained chest pain
BACKGROUND: The number of patients suffering from unexplained chest pain (UCP) is increasing. Intervention programmes are needed to reduce the chest pain and suffering experienced by these patients and effective preventive strategies are also required to reduce the incidence of these symptoms. The aim of this study was to describe general coping strategies in patients with UCP and examine the relationships between coping strategies, negative life events, sleep problems, physical activity, stress and chest pain intensity. METHOD: The sample consisted of 179 patients younger than 70 years of age, who were evaluated for chest pain at the emergency department daytime Monday through Friday and judged by a physician to have no organic cause for their chest pain. The study had a cross-sectional design. RESULTS: Emotive coping was related to chest pain intensity (r = 0.17, p = 0.02). Women used emotive coping to a greater extent than did men (p = 0.05). In the multivariate analysis was shown that physical activity decreased emotive coping (OR 0.13, p < 0.0001) while sex, age, sleep, mental strain at work and negative life events increased emotive coping. Twenty-seven percent of the patients had sleep problems 8 to14 nights per month or more. Permanent stress at work during the last year was reported by 18% of the patients and stress at home by 7%. Thirty-five percent of the patients were worried often or almost all the time about being rushed at work and 23% were worried about being unable to keep up with their workload. Concerning total life events, 20% reported that a close relative had had a serious illness and 27% had reasons to be worried about a close relative. CONCLUSION: Our results indicated that patients with more intense UCP more often apply emotive coping in dealing with their pain. Given that emotive coping was also found to be related to disturbed sleep, negative life events, mental strain at work and physical activity, it may be of value to help these patients to both verbalise their emotions and to become cognizant of the influence of such factors on their pain experience
The photometric evolution of FU Orionis objects: disc instability and wind-envelope interaction
We present the results of a photometric monitoring campaign of three well
studied FU Orionis systems (FU Orionis, V1057 Cygni and V1515 Cygni) undertaken
at Maidanak Observatory between 1981 and 2003. When combined with photometric
data in the literature, this database provides a valuable resource for
searching for short timescale variability - both periodic and aperiodic - as
well as for studying the secular evolution of these systems. In the case of
V1057 Cyg (which is the system exhibiting the largest changes in brightness
since it went into outburst) we compare the photometric data with time
dependent models. We show that prior to the end of the `plateau' stage in 1996,
the evolution of V1057 Cyg in the colour-magnitude diagram is well
represented by disc instability models in which the outburst is triggered by
some agent - such as an orbiting planet - in the inner disc. Following the end
of the plateau phase in 1996, the dimming and irregular variations are
consistent with occultation of the source by a variable dust screen, which has
previously been interpreted in terms of dust condensation events in the
observed disc wind. Here we instead suggest that this effect results from the
interaction between the wind and an infalling dusty envelope, the existence of
this envelope having been previously invoked in order to explain the mid
infrared emissio of FU Orionis systems. We discuss how this model may explain
some of the photometric and spectroscopic characteristics of FU Orionis systems
in general.Comment: 14 pages, 12 figures, MNRAS, accepted. Data files with detailed
photometry can be found at http://www.ast.cam.ac.uk/~giuseppe/Publications
Extinction with 2MASS: star counts and reddening toward the North America and the Pelican Nebulae
We propose a general method for mapping the extinction in dense molecular
clouds using 2MASS near-infrared data. The technique is based on the
simultaneous utilization of star counts and colors. These two techniques
provide independent estimations of the extinction and each method reacts
differently to foreground star contamination and to star clustering. We take
advantage of both methods to build a large scale extinction map (2.5 x 2.5
degrees) of the North America-Pelican nebulae complex. With Ks star counts and
H-Ks color analysis the visual extinction is mapped up to 35 mag. Regions with
visual extinction greater than 20 mag account for less than 3% of the total
mass of the cloud. Color is generally a better estimator for the extinction
than star counts. Nine star clusters are identified in the area, seven of which
were previously unknown.Comment: 33 pages, 14 figures, accepted in A
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