536 research outputs found
Human oesophageal adenocarcinoma cell lines JROECL 47 and JROECL 50 are admixtures of the human colon carcinoma cell line HCT 116
In two recently described human oesophageal adenocarcinoma cell lines JROECL 47 and JROECL 50, derived from one tumour, we detected identical E-cadherin and β-catenin gene mutations as in colon carcinoma cell line HCT 116. We demonstrate by HLA-typing, mutation analysis and microsatellite analysis that cell lines JROECL 47 and JROECL 50 are admixtures of the human colon adenocarcinoma cell line HCT 116. © 2000 Cancer Research Campaig
A New Probe of the Molecular Gas in Galaxies: Application to M101
Recent studies of nearby spiral galaxies suggest that photodissociation
regions (PDRs) are capable of producing much of the observed HI in galaxy
disks. In that case, measurements of the HI column density and the
far-ultraviolet (FUV) photon flux provide a new probe of the volume density of
the local underlying H_2. We develop the method and apply it to the giant Scd
spiral M101 (NGC 5457). We find that, after correction for the best-estimate
gradient of metallicity in the ISM of M101 and for the extinction of the
ultraviolet emission, molecular gas with a narrow range of density from 30-1000
cm^-3 is found near star- forming regions at all radii in the disk of M101 out
to a distance of 12' (approximately 26 kpc), close to the photometric limit of
R_25 = 13.5'.
In this picture, the ISM is virtually all molecular in the inner parts of
M101. The strong decrease of the HI column density in the inner disk of the
galaxy at R_G < 10 kpc is a consequence of a strong increase in the dust-to-gas
ratio there, resulting in an increase of the H_2 formation rate on grains and a
corresponding disappearance of hydrogen in its atomic form.Comment: accepted for publication in The Astrophysical Journal (1 August
2000); 29 pages including 20 figures (7 gif); AAS LaTex; contact authors for
full resolution versions of gif figure
Spectral evidence for a powerful compact jet from XTE J1118+480
We present observations of the X-ray transient XTE J1118+480 during its
Low/Hard X-ray state outburst in 2000, at radio and sub-millimetre wavelengths
with the VLA, Ryle Telescope, MERLIN and JCMT. The high-resolution MERLIN
observations reveal all the radio emission (at 5 GHz) to come from a compact
core with physical dimensions smaller than 65*d(kpc) AU. The combined radio
data reveal a persistent and inverted radio spectrum, with spectral index
\~+0.5. The source is also detected at 350 GHz, on an extrapolation of the
radio spectrum. Flat or inverted radio spectra are now known to be typical of
the Low/Hard X-ray state, and are believed to arise in synchrotron emission
from a partially self-absorbed jet. Comparison of the radio and sub-millimetre
data with reported near-infrared observations suggest that the synchrotron
emission from the jet extends to the near-infrared, or possibly even optical
regimes. In this case the ratio of jet power to total X-ray luminosity is
likely to be P_J/L_X >> 0.01, depending on the radiative efficiency and
relativistic Doppler factor of the jet. Based on these arguments we conclude
that during the period of our observations XTE J1118+480 was producing a
powerful outflow which extracted a large fraction of the total accretion power.Comment: Accepted for publication as a Letter in MNRA
Dust in 3C324
The results of a deep submillimetre observation using SCUBA of the powerful
radio galaxy 3C324, at redshift z=1.206, are presented. At 850 microns,
emission from the location of the host radio galaxy is marginally detected at
the 4.2 sigma level, 3.01 +/- 0.72 mJy, but there is no detection of emission
at 450 microns to a 3 sigma limit of 21 mJy. A new 32 GHz radio observation
using the Effelsberg 100m telescope confirms that the sub-millimetre signal is
not associated with synchrotron emission. These observations indicate that both
the mass of warm dust within 3C324, and the star formation rate, lie up to an
order of magnitude below the values recently determined for radio galaxies at z
= 3 to 4. The results are compared with dust masses and star formation rates
derived in other ways for 3C324.Comment: 5 pages LaTeX, including 1 figure. Accepted for publication in MNRA
The Eastern Arm of M83 Revisited: High-Resolution Mapping of 12CO 1-0 Emission
We have used the Owens Valley Millimeter Array to map 12CO (J=1-0) along a
3.5 kpc segment of M83's eastern spiral arm at resolutions of 6.5"x3.5", 10",
and 16". The CO emission in most of this segment lies along the sharp dust lane
demarking the inner edge of the spiral arm, but beyond a certain point along
the arm the emission shifts downstream from the dust lane to become better
aligned with the young stars seen in blue and H-beta images. This morphology
resembles that of the western arm of M100. Three possibilities, none of which
is wholly satisfactory, are considered to explain the deviation of the CO arm
from the dust lane: heating of the CO by UV radiation from young stars, heating
by low-energy cosmic rays, and a molecular medium consisting of two (diffuse
and dense) components which react differently to the density wave. Regardless,
the question of what CO emission traces along this spiral arm is a complicated
one. Strong tangential streaming is observed where the arm crosses the
kinematic major axis of the galaxy, implying that the shear becomes locally
prograde in the arms. Inferred from the streaming is a very high gas surface
density of about 230 solar masses/pc**2 and an arm-interarm contrast greater
than 2.3 in the part of the arm near the major axis. Using two different
criteria, we find that the gas at this location is well above the threshold for
gravitational instability -- much more clearly so than in either M51 or M100.Comment: Accepted for publication in ApJ. 25 pages, 5 figures. Manuscript in
LaTeX, figures in pdf. Fig 3 in colo
CO(1-0), CO(2-1) and Neutral Gas in NGC 6946: Molecular Gas in a Late-Type, Gas Rich, Spiral Galaxy
We present "On The Fly" maps of the CO(1-0) and CO(2-1) emission covering a
10' X 10' region of the NGC 6946. Using our CO maps and archival VLA HI
observations we create a total gas surface density map, Sigma_gas, for NGC
6946. The predominantly molecular inner gas disk transitions smoothly into an
atomic outer gas disk, with equivalent atomic and molecular gas surface
densities at R = 3.5' (6 kpc). We estimate that the total H2 mass is 3 X 10^9
Mo, roughly 1/3 of the interstellar hydrogen gas mass, and about 2% of the
dynamical mass of the galaxy at our assumed distance of 6 Mpc. The value of the
CO(2-1)/CO(1-0) line ratio ranges from 0.35 to 2; 50% of the map is covered by
very high ratio, >1, gas. The very high ratios are predominantly from interarm
regions and appear to indicate the presence of wide-spread optically thin gas.
Star formation tracers are better correlated with the total neutral gas disk
than with the molecular gas by itself implying SFR is proportional to
Sigma_gas. Using the 100 FIR and 21 cm continuum from NGC 6946 as star
formation tracers, we arrive at a gas consumption timescale of 2.8 Gyr, which
is relatively uniform across the disk. The high star formation rate at the
nucleus appears to be due to a large accumulation of molecular gas rather than
a large increase in the star formation efficiency. The mid-plane gas pressure
in the outer (R > 10 kpc) HI arms of NGC 6946 is close to the value at the
radial limit (10 kpc) of our observed CO disk. If the mid-plane gas pressure is
a factor for the formation of molecular clouds, these outer HI gas arms should
contain molecular gas which we do not see because they are beyond our detection
limit
Star Formation Thresholds in Galactic Disks
We report the first results of a detailed study of the star formation law in
a sample of 32 nearby spiral galaxies with well-measured rotation curves, HI
and H (as traced by CO) surface density profiles, and new \Ha CCD
photometry. Our results strongly support the view that the formation of
gravitationally bound interstellar clouds regulates the onset of widespread
star formation -- at least in the outer regions of galactic disks.Comment: Will appear in July 1 ApJ. Abbreviated abstract. Postscript version
available at http://www.astro.caltech.edu/~clm
Star Formation in M51 Triggered by Galaxy Interaction
We have mapped the inner 360'' regions of M51 in the 158micron [CII] line at
55'' spatial resolution using the Far-infrared Imaging Fabry-Perot
Interferometer (FIFI) on the Kuiper Airborne Observatory (KAO). The emission is
peaked at the nucleus, but is detectable over the entire region mapped, which
covers much of the optical disk of the galaxy. There are also two strong
secondary peaks at ~43% to 70% of the nuclear value located roughly 120'' to
the north-east, and south-west of the nucleus. These secondary peaks are at the
same distance from the nucleus as the corotation radius of the density wave
pattern. The density wave also terminates at this location, and the outlying
spiral structure is attributed to material clumping due to the interaction
between M51 and NGC5195. This orbit crowding results in cloud-cloud collisions,
stimulating star formation, that we see as enhanced [CII] line emission. The
[CII] emission at the peaks originates mainly from photodissociation regions
(PDRs) formed on the surfaces of molecular clouds that are exposed to OB
starlight, so that these [CII] peaks trace star formation peaks in M51. The
total mass of [CII] emitting photodissociated gas is ~2.6x10^{8} M_{sun}, or
about 2% of the molecular gas as estimated from its CO(1-0) line emission. At
the peak [CII] positions, the PDR gas mass to total gas mass fraction is
somewhat higher, 3-17%, and at the secondary peaks the mass fraction of the
[CII] emitting photodissociated gas can be as high as 72% of the molecular
mass.... (continued)Comment: 14 pages, 6 figures, Accepted in ApJ (for higher resolution figures
contact the author
Ongoing massive star formation in the bulge of M51
We studied the HST-WFPC2 observations of the inner kpc of the interacting
galaxy M51 in six bands from 2550 to 8140 Angstrom. The images show an oval
shaped area ("bulge") of 11x16 arcsec or 450x650 pc around the nucleus,
dominated by a smooth population of old stars with overimposed dust lanes. We
found 30 bright point-like sources in the bulge of M51; many of these are
bright in the UV. They are located in elongated "strings" which follow the
general pattern of the dust lanes. The spectral energy distributions of the
pointsources are compared with those of clusters or single stars. We present
arguments that the pointsources are isolated massive stars or small groups of a
few massive stars. The energy distributions are best fitted with those of
single stars with 4000<Teff<50000 K, 4.2<log L/Lsun<7.2, and 12<Mstar<200 Msun.
We have derived upper limits to the total mass of low mass stars that could be
"hiding" within the point sources. For the bluest sources the upper limit is
only a few hundred Msun. We conclude that massive stars are formed outside
clusters (or in very low mass clusters) in the bulge of M51. The estimated star
formation rate in the bulge is 1 to 2x10^(-3) Msun/yr. This star formation rate
could be sustained for about 200 to 400 Myrs, suggesting that the ongoing
massive star formation in the bulge of M51 is fed/triggered by the interaction
with its companion about 400 Mrs ago. Theoretical cloud-models show that CO is
destroyed in low extinction clouds near the bright nucleus of M51, so that H_2,
[OI] and [CII] are the dominants coolants. This condition favors the formation
of massive stars, in agreement with the observations. This mode of massive-star
formation in the bulge of M51 may resemble the star formation in the early
Universe, when the CO and dust contents were low due to the low metallicity.Comment: 28 pages, 7 PostScript figures, uses aaspp4.sty and epsfig.sty.
Accepted for publication in ApJ, V566, February 20, 200
Recurrence and survival after resection of adenocarcinoma of the gastric cardia
In a retrospective study, the results after resection of carcinoma of the gastric cardia in the era without neoadjuvant therapy or extended lymph node dissection were evaluated. All 184 patients who underwent resection between January 1983 and December 1993 were included. Recurrence of disease, survival and prognostic factors were determined. The overall cumulative 5-year recurrence rate was 71% and the survival rate 23%. Multivariate analysis identified locoregional lymph node and distant metastases as the crucial prognosticators of recurrence of disease and survival. These results were similar to those from a previous study concerning our patients operated during the years 1983-88. The prognosis of a resected cardiacarcinoma has remained unchanged in our hands over the past 10 years. These results stress the importance of exploring new ways, such as the use of new diagnostic tools, to optimize preoperative patient selection and more aggressive treatment regimens to improve final outcom
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