99 research outputs found
Area limit laws for symmetry classes of staircase polygons
We derive area limit laws for the various symmetry classes of staircase
polygons on the square lattice, in a uniform ensemble where, for fixed
perimeter, each polygon occurs with the same probability. This complements a
previous study by Leroux and Rassart, where explicit expressions for the area
and perimeter generating functions of these classes have been derived.Comment: 18 pages, 3 figure
Stellar Dynamics and the implications on the merger evolution in NGC6240
We report near-infrared integral field spectroscopy of the luminous merging
galaxy NGC 6240. Stellar velocities show that the two K-band peaks separated by
1.6arcsec are the central parts of inclined, rotating disk galaxies with equal
mass bulges. The dynamical masses of the nuclei are much larger than the
stellar mass derived from the K-band light, implying that the progenitor
galaxies were galaxies with massive bulges. The K-band light is dominated by
red supergiants formed in the two nuclei in starbursts, triggered ~2x10^7 years
ago, possibly by the most recent perigalactic approach. Strong feedback effects
of a superwind and supernovae are responsible for a short duration burst
(~5x10^6 years) which is already decaying. The two galaxies form a
prograde-retrograde rotating system and from the stellar velocity field it
seems that one of the two interacting galaxies is subject to a prograde
encounter. Between the stellar nuclei is a prominent peak of molecular gas
(H_2, CO). The stellar velocity dispersion peaks there indicating that the gas
has formed a local, self-gravitating concentration decoupled from the stellar
gravitational potential. NGC 6240 has previously been reported to fit the
paradigm of an elliptical galaxy formed through the merger of two galaxies.
This was based on the near-infrared light distribution which follows a
r^1/4-law. Our data cast strong doubt on this conclusion: the system is by far
not relaxed, rotation plays an important role, as does self-gravitating gas,
and the near-infrared light is dominated by young stars.Comment: 34 pages, 11 figures, using AASTEX 5.0rc3.1, paper submitted to the
Astrophysical Journal, revised versio
Unveiling the central parsec region of an AGN: the Circinus nucleus in the near infrared with the VLT
VLT J- to M\p-band adaptive optics observations of the Circinus Galaxy on
parsec scales resolve a central bright Ks-band source with a FWHM size of 1.9
0.6 pc. This source is only visible at wavelengths longward of 1.6 m
and coincides in position with the peak of the [Si VII]~2.48 m coronal
line emission. With respect to the peak of the central optical emission, the
source is shifted by 0.15\arcsec (2.8 pc) to the south-east. Indeed, it
defines the vertex of a fairly collimated beam which extends for 10 pc,
and which is seen in both continuum light shortward of 1.6 m and in
H line emission. The source also lies at the center of a 19 pc
size [Si VII] ionization {\it bicone}.
Identifying this source as the nucleus of Circinus, its size is compatible
with a putative parsec-scale torus. Its spectral energy distribution,
characterized by a prominent narrow peak, is compatible with a dust temperature
of 300 K. Hotter dust within a 1 pc radius of the center is not detected. The
AGN luminosity required to heat this dust is in the range of X-ray luminosities
that have been measured toward the central source. This in turn supports the
existence of highly obscuring material, with column densities of
cm, that must be located within 1 pc of the core.Comment: 15 pages, 4 figures; To appear in The Astrophysical Journa
Emblica Officinalis: A Novel Therapy for Acute Pancreatitis â An Experimental Study
Acute necrotising pancreatitis is associated with an unacceptably high mortality for which no
satisfactory remedy exists. Emblica officinalis (E.o.) is a plant prescribed in Ayurveda, the
Indian traditional system of medicine, for pancreas-related disorders. This study was carried
out to evaluate the protective effect of E.o. against acute necrotising pancreatitis in dogs.
Pancreatitis was induced by injecting a mixture of trypsin, bile and blood into the duodenal
opening of the pancreatic duct. Twenty eight dogs were divided into 4 groups (n = 6-8 each):
GpIâcontrol, GpIIâacute pancreatitis, GpIIIâsham-operated, GpIVâpretreatment with
28 mg E.o./kg/day for 15 days before inducing pancreatitis. Serum amylase increased from
541.99 ± 129.13 IU/ml to 1592.63 ± 327.83 IU (p<0.02) 2 hrs after the induction of pancreatitis
in GpII. The rise in serum amylase in both GpIII and GpIV was not significant. On
light microscopic examination, acinar cell damage was less and the total inflammatory score
was significantly lower in the E.o. treated group as compared to GpII. Electron microscopy
confirmed this and showed an increased amount of smooth, endoplasmic reticulum and small,
condensed granules embedded in a vacuole. More studies are needed to explore the clinical
potential of E.o. and its mechanism of action
Case studies of innovative medical device companies from India: barriers and enablers to development
A Fabry-Perot Imaging Search for Lyman-alpha Emission in Quasar Absorbers at z ~ 2.4
We have carried out a deep narrow-band imaging survey of six fields with
heavy-element quasar absorption lines, using the Goddard Fabry-Perot (FP)
system at the Apache Point Observatory (APO) 3.5-meter telescope. The aim of
these observations was to search for redshifted Ly- emission from the
galaxies underlying the absorbers at and their companion
galaxies. The 3 sensitivity levels ranged between
and erg s cm in
observed-frame Ly- flux. No significant Ly- emitters were
detected at level. The absence of significant Ly- emission
implies limits on the star formation rate (SFR) of 0.9-2.7
yr per 2-pixel x 2-pixel region, if no dust attenuation is assumed. We
compare our results with those from other emission-line studies of absorber
fields and with predictions for global average SFR based on the models of
cosmic chemical evolution. Our limits are among the tightest existing
constraints on Ly- emission from galaxies in absorber fields, but are
consistent with many other studies. In the absence of dust attenuation, these
studies suggest that SFRs in a large fraction of objects in the absorber fields
may lie below the global mean SFR. However, it is possible that dust
attenuation is responsible for the low emission line fluxes in some objects. It
is also possible that the star-forming regions are compact and at smaller
angular separations from the quasar than the width of our point spread function
and, get lost in the quasar emission. We outline future observations that could
help to distinguish between the various possibilities.Comment: Accepted for Publication in the Astrophysical Journal, 32 pages, 8
figures. NOTE: 25 of the 29 subpanels in the figures are included here at
lower resolution to keep the astroph submission size within allowed limits.
Please see http://boson.physics.sc.edu/~kulkarni/fpimaging.html for a pdf
file of the complete paper including all subpanels of all figures in the
original higher resolutio
Ultrasound imaging of apoptosis: high-resolution non-invasive monitoring of programmed cell death in vitro, in situ and in vivo
A new non-invasive method for monitoring apoptosis has been developed using high frequency (40 MHz) ultrasound imaging. Conventional ultrasound backscatter imaging techniques were used to observe apoptosis occurring in response to anticancer agents in cells in vitro, in tissues ex vivo and in live animals. The mechanism behind this ultrasonic detection was identified experimentally to be the subcellular nuclear changes, condensation followed by fragmentation, that cells undergo during apoptosis. These changes dramatically increase the high frequency ultrasound scattering efficiency of apoptotic cells over normal cells (25- to 50-fold change in intensity). The result is that areas of tissue undergoing apoptosis become much brighter in comparison to surrounding viable tissues. The results provide a framework for the possibility of using high frequency ultrasound imaging in the future to non-invasively monitor the effects of chemotherapeutic agents and other anticancer treatments in experimental animal systems and in patients. © 1999 Cancer Research Campaig
Circumstellar disks and planets. Science cases for next-generation optical/infrared long-baseline interferometers
We present a review of the interplay between the evolution of circumstellar
disks and the formation of planets, both from the perspective of theoretical
models and dedicated observations. Based on this, we identify and discuss
fundamental questions concerning the formation and evolution of circumstellar
disks and planets which can be addressed in the near future with optical and
infrared long-baseline interferometers. Furthermore, the importance of
complementary observations with long-baseline (sub)millimeter interferometers
and high-sensitivity infrared observatories is outlined.Comment: 83 pages; Accepted for publication in "Astronomy and Astrophysics
Review"; The final publication is available at http://www.springerlink.co
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