1,393 research outputs found
Medical Image Retrieval: Past and Present
With the widespread dissemination of picture archiving and communication systems (PACSs) in hospitals, the amount of imaging data is rapidly increasing. Effective image retrieval systems are required to manage these complex and large image databases. The authors reviewed the past development and the present state of medical image retrieval systems including text-based and content-based systems. In order to provide a more effective image retrieval service, the intelligent content-based retrieval systems combined with semantic systems are required
Heavy elements in Galactic and Magellanic Cloud HII regions: recombination-line versus forbidden-line abundances
We have obtained deep optical, long-slit spectrophotometry of the Galactic
HII regions M 17, NGC 3576 and of the Magellanic Cloud HII regions 30 Doradus,
LMC N11B and SMC N66, recording the optical recombination lines (ORLs) of CII,
NII and OII. Temperature-insensitive ORL C2+/O2+ and N2+/O2 ratios are obtained
for all nebulae except SMC N66. The ORL C2+/O2+ ratios show remarkable
agreement within each galactic system, while also being in agreement with the
corresponding CEL ratios. For all five nebulae, the O2+/H+ abundance derived
from multiple OII ORLs is found to be higher than the corresponding value
derived from the strong [OIII] 4959, 5007A CELs, by factors of 1.8--2.7 for
four of the nebulae. The LMC N11B nebula exhibits a more extreme discrepancy
factor for the O2+ ion, ~5. Thus these HII regions exhibit ORL/CEL abundance
discrepancy factors that are similar to those previously encountered amongst
planetary nebulae.
Our optical CEL O2+/H+ abundances agree to within 20-30 per cent with
published O2+/H+ abundances that were obtained from observations of infrared
fine-structure lines. Since the low excitation energies of the latter make them
insensitive to variations about typical nebular temperatures, fluctuations in
temperature are ruled out as the cause of the observed ORL/CEL O2+ abundance
discrepancies. We present evidence that the observed OII ORLs from these HII
regions originate from gas of very similar density (<3500 cm-3) to that
emitting the observed heavy-element optical and infrared CELs, ruling out
models that employ high-density ionized inclusions in order to explain the
abundance discrepancy. We consider a scenario whereby much of the heavy-element
ORL emission originates from cold (<=500 K) metal-rich ionized regions.Comment: 24 pages; 9 figures; accepted by Monthly Notices of the Royal
Astronomical Societ
De novo serine biosynthesis from glucose predicts sex-specific response to antifolates in non-small cell lung cancer cell lines
Lung cancer is the leading cause of cancer-related death. Intriguingly, males with non-small cell lung cancer (NSCLC) have a higher mortality rate than females. Here, we investigated the role of serine metabolism as a predictive marker for sensitivity to the antifolate pemetrexed in male and female NSCLC cell lines. Using
Heavily Obscured AGN in High Redshift Luminous Infrared Galaxies
We take advantage of the rich multi-wavelength data available in the Chandra
Deep Field South (CDF-S), including the 4 Msec Chandra observations (the
deepest X-ray data to date), in order to search for heavily-obscured
low-luminosity AGN among infrared-luminous galaxies. In particular, we obtained
a stacked rest-frame X-ray spectrum for samples of galaxies binned in terms of
their IR luminosity or stellar mass. We detect a significant signal at E~1 to 8
keV, which we interpret as originating from a combination of emission
associated with star-formation processes at low energies combined with a
heavily-obscured AGN at E>5 keV. We further find that the relative strength of
this AGN signal decays with decreasing IR luminosity, indicating a higher AGN
fraction for more luminous IR sources. Together, these results strongly suggest
the presence of a large number of obscured AGN in IR-luminous galaxies. Using
samples binned in terms of stellar mass in the host galaxy, we find a
significant excess at E=6-7 keV for sources with M>10^{11} Msun, consistent
with a large obscured AGN population in high mass galaxies. In contrast, no
strong evidence of AGN activity was found for less-massive galaxies. The
integrated intensity at high energies indicates that a significant fraction of
the total black hole growth, ~22%, occurs in heavily-obscured systems that are
not individually detected in even the deepest X-ray observations. There are
also indications that the number of low-luminosity, heavily-obscured AGN does
not evolve significantly with redshift, in contrast to the strong evolution
seen in higher luminosity sources.Comment: 5 pages, 3 figures in emulateapj format. Accepted by Astrophysical
Journal Letter
Temperature Variations from HST Spectroscopy of the Orion Nebula
We present HST/STIS long-slit spectroscopy of NGC 1976. Our goal is to
measure the intrinsic line ratio [O III] 4364/5008 and thereby evaluate the
electron temperature (T_e) and the fractional mean-square T_e variation (t_A^2)
across the nebula. We also measure the intrinsic line ratio [N II] 5756/6585 in
order to estimate T_e and t_A^2 in the N^+ region. The interpretation of the [N
II] data is not as clear cut as the [O III] data because of a higher
sensitivity to knowledge of the electron density as well as a possible
contribution to the [N II] 5756 emission by recombination (and cascading). We
present results from binning the data along the various slits into tiles that
are 0.5" square (matching the slit width). The average [O III] temperature for
our four HST/STIS slits varies from 7678 K to 8358 K; t_A^2 varies from 0.00682
to at most 0.0176. For our preferred solution, the average [N II] temperature
for each of the four slits varies from 9133 K to 10232 K; t_A^2 varies from
0.00584 to 0.0175. The measurements of T_e reported here are an average along
each line of sight. Therefore, despite finding remarkably low t_A^2, we cannot
rule out significantly larger temperature fluctuations along the line of sight.
The result that the average [N II] T_e exceeds the average [O III] T_e confirms
what has been previously found for Orion and what is expected on theoretical
grounds. Observations of the proplyd P159-350 indicate: large local extinction
associated; ionization stratification consistent with external ionization by
theta^1 Ori C; and indirectly, evidence of high electron density.Comment: MNRAS accepted: 30 pages, 3 Figures, 2 Table
Quantum Instantons and Quantum Chaos
Based on a closed form expression for the path integral of quantum transition
amplitudes, we suggest rigorous definitions of both, quantum instantons and
quantum chaos. As an example we compute the quantum instanton of the double
well potential.Comment: Extended version with new figures. Text (LaTeX), 5 Figures (epsi
files
Zero and Finite Temperature Quantum Simulations Powered by Quantum Magic
We present a comprehensive approach to quantum simulations at both zero and
finite temperatures, employing a quantum information theoretic perspective and
utilizing the Clifford + Rz transformations. We introduce the "quantum magic
ladder", a natural hierarchy formed by systematically augmenting Clifford
transformations with the addition of Rz gates. These classically simulable
similarity transformations allow us to reduce the quantumness of our system,
conserving vital quantum resources. This reduction in quantumness is essential,
as it simplifies the Hamiltonian and shortens physical circuit-depth,
overcoming constraints imposed by limited error correction. We improve the
performance of both digital and analog quantum computers on ground state and
finite temperature molecular simulations, not only outperforming the
Hartree-Fock solution, but also achieving consistent improvements as we ascend
the quantum magic ladder. By facilitating more efficient quantum simulations,
our approach enables near-term and early fault-tolerant quantum computers to
address novel challenges in quantum chemistry.Comment: 12 pages, 9 figure
Hubble Space Telescope WFC3 Grism Spectroscopy and Imaging of a Growing Compact Galaxy at z=1.9
We present HST/WFC3 grism spectroscopy of the brightest galaxy at z>1.5 in
the GOODS-South WFC3 Early Release Science grism pointing, covering the
wavelength range 0.9-1.7 micron. The spectrum is of remarkable quality and
shows the redshifted Balmer lines Hbeta, Hgamma, and Hdelta in absorption at
z=1.902, correcting previous erroneous redshift measurements from the
rest-frame UV. The average rest-frame equivalent width of the Balmer lines is
8+-1 Angstrom, which can be produced by a post-starburst stellar population
with a luminosity-weighted age of ~0.5 Gyr. The M/L ratio inferred from the
spectrum implies a stellar mass of ~4x10^11 Msun. We determine the morphology
of the galaxy from a deep WFC3 F160W image. Similar to other massive galaxies
at z~2 the galaxy is compact, with an effective radius of 2.1+-0.3 kpc.
Although most of the light is in a compact core, the galaxy has two red, smooth
spiral arms that appear to be tidally-induced. The spatially-resolved
spectroscopy demonstrates that the center of the galaxy is quiescent and the
surrounding disk is forming stars, as it shows Hbeta in emission. The galaxy is
interacting with a companion at a projected distance of 18 kpc, which also
shows prominent tidal features. The companion has a slightly redder spectrum
than the primary galaxy but is a factor of ~10 fainter and may have a lower
metallicity. It is tempting to interpret these observations as "smoking gun"
evidence for the growth of compact, quiescent high redshift galaxies through
minor mergers, which has been proposed by several recent observational and
theoretical studies. Interestingly both objects host luminous AGNs, as
indicated by their X-ray luminosities, which implies that these mergers can be
accompanied by significant black hole growth. This study illustrates the power
of moderate dispersion, low background near-IR spectroscopy at HST resolution,
which is now available with the WFC3 grism.Comment: 5 pages, 5 figures. Submitted to ApJ Letters
On the local concentration probability density function of solutes reacting upon mixing
Ruptured abdominal aortic aneurysm, a “two-hit” ischemia/reperfusion injury: Evidence from an analysis of oxidative products
AbstractPurpose: Ruptured abdominal aortic aneurysm (RAAA) remains a lethal condition despite improvements in perioperative care. The consequences of RAAA are hypothesized to result from a combination of two ischemia/reperfusion events: hemorrhagic shock and lower torso ischemia. Ischemia/reperfusion results in tissue injury by diverse mechanisms, which include oxygen free radical–mediated injury produced from activated neutrophils, xanthine oxidase, and mitochondria. Oxygen-free radicals attack membrane lipids, resulting in membrane and subsequently cellular dysfunction that contributes to postoperative organ injury/failure. The purpose of this investigation was to quantify the oxidative injury that occurs as a result of the ischemia/reperfusion events in RAAAs and elective AAAs. Methods: Blood samples were taken from 22 patients for elective AAA repair and from 14 patients for RAAA repair during the perioperative period. Plasma F2 -isoprostanes were extracted, purified, and measured with an enzyme immunoassay. Aldehydes and acyloins were purified and quantified. Neutrophil oxidative burst was measured in response to a receptor independent stimulus (phorbol 12-myristate 13-acetate) with luminol-based chemiluminescence. Results: Plasma from patients with RAAAs showed significantly elevated F2 -isoprostane levels on arrival at hospital and were significantly elevated as compared with the levels of patients for elective repair throughout the perioperative period (two-way analysis of variance, P < .0001). Multiple regression showed a significant relationship between the phagocyte oxidative activity and F2 -isoprostane levels (P < .013). Total acyloin levels were significantly higher in patients with RAAAs as compared with the levels in elective cases. Conclusion: The F2 -isoprostane levels, specific markers of lipid peroxidation, showed that patients with RAAAs had two phases of oxidative injury: before arrival at hospital and after surgery. The significant relationship between the postoperative increases in F2 -isoprostane levels and the neutrophil oxidant production implicates neutrophils in the oxidative injury that occurs after RAAA. New therapeutic interventions that attenuate neutrophil-mediated oxidant injury during reperfusion may decrease organ failure and ultimately mortality in patients with RAAAs. (J Vasc Surg 1999;30:219-28.
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