1,051 research outputs found
Coronary computed tomography angiography of spontaneous coronary artery dissection: A case report and review of the literature
Patient: Male, 23 Final Diagnosis: Spontaneous coronary artery dissection Symptoms: Chest discomfort âą chest pain Medication: â Clinical Procedure: Coronary computed tomography angiography Specialty: Radiology OBJECTIVE: Rare disease BACKGROUND: Multidetector computed tomography (MDCT) has gained wide acceptance in the evaluation of the cardiovascular system. Of particular clinical interest is its ability to non-invasively evaluate coronary arteries in patients presenting to the emergency room. In acute coronary syndromes, myocardial ischemia is most often caused by atherosclerosis. We present a case of a rare cause of acute coronary syndrome, spontaneous coronary artery dissection (SCAD), which was initially evaluated with MDCT and followed by intravascular ultrasound (IVUS) and invasive coronary angiography (ICA). We discuss the findings and role of each modality with particular attention to coronary computed tomographic angiography (CCTA) in the diagnosis and management of SCAD. As the use of CCTA in the emergency department continues to rise, radiologists must become familiar with CT appearance of SCAD. CASE REPORT: We report the multidetector computed tomography (MDCT), intravascular ultrasound (IVUS), and invasive coronary angiography (ICA) findings in a case of spontaneous coronary artery dissection of the left anterior descending artery in a previously healthy 23-year-old man. The role of coronary computed tomographic angiography (CCTA) in diagnosis and management of this potentially life-threatening condition is discussed. CONCLUSIONS: In the clinical setting of acute coronary syndrome, SCAD must be a consideration, particularly in young patients without clear risk factors for coronary artery disease and in women in the peripartum period. CCTA is a very helpful diagnostic tool to diagnose the condition in a non-invasive manner and to follow up after treatment
A New Einstein Cross: A Highly Magnified, Intrinsically Faint Lyman-Alpha Emitter at z=2.7
We report the discovery of a new Einstein cross at redshift z_S = 2.701 based
on Lyman-alpha emission in a cruciform configuration around an SDSS luminous
red galaxy (z_L = 0.331). The system was targeted as a possible lens based on
an anomalous emission line in the SDSS spectrum. Imaging and spectroscopy from
the W. M. Keck Observatory confirm the lensing nature of this system. This is
one of the widest-separation galaxy-scale lenses known, with an Einstein radius
of ~1.84 arcsec. We present simple gravitational lens models for the system and
compute the intrinsic properties of the lensed galaxy. The total mass of the
lensing galaxy within the 8.8 +/- 0.1 kpc enclosed by the lensed images is (5.2
+/- 0.1) x 10^11 M_sun. The lensed galaxy is a low mass galaxy (0.2 L*) with a
high equivalent-width Lyman-alpha line (EW_Lya_rest = 46 +/- 5 Angstroms).
Follow-up studies of this lens system can probe the mass structure of the
lensing galaxy, and can provide a unique view of an intrinsically faint,
high-redshift, star-forming galaxy at high signal-to-noise ratio.Comment: ApJ Letters, in pres
Direct Communication to Earth from Probes
A viewgraph presentation on outer planetary probe communications to Earth is shown. The topics include: 1) Science Rational for Atmospheric Probes to the Outer Planets; 2) Controlling the Scientific Appetite; 3) Learning more about Jupiter before we send more probes; 4) Sample Microwave Scan From Juno; 5) Jupiter s Deep Interior; 6) The Square Kilometer Array (SKA): A Breakthrough for Radio Astronomy; 7) Deep Space Array-based Network (DSAN); 8) Probe Direct-to-Earth Data Rate Calculations; 9) Summary; and 10) Enabling Ideas
The Sloan Lens ACS Survey. VI: Discovery and analysis of a double Einstein ring
We report the discovery of two concentric Einstein rings around the
gravitational lens SDSSJ0946+1006, as part of the Sloan Lens ACS Survey. The
main lens is at redshift zl=0.222, while the inner ring (1) is at zs1=0.609 and
Einstein radius . The wider image separation () of the outer ring (2) implies that it is at higher redshift. Its
detection in the F814W filter implies zs2<6.9. The configuration can be well
described by a total density profile with
and velocity dispersion \sigma_{SIE}=287\pm5\kms. [...] We consider whether
this configuration can be used to constrain cosmological parameters exploiting
angular distance ratios entering the lens equations. Constraints for
SDSSJ0946+1006, are uninteresting due to the sub-optimal lens and source
redshifts. We then consider the perturbing effect of the mass associated with
Ring 1 building a double lens plane compound lens model. This introduces minor
changes to the mass of the main lens and allows to estimate the mass of Ring 1
(\sigma_{SIE,s1}=94\pm30\kms). We examine the prospects of doing cosmography
with a sample of 50 double lenses, expected from future space based surveys
such as DUNE or JDEM. Taking full account of the model uncertainties, such a
sample could be used to measure and with 10% accuracy, for a
flat cosmology
Storms and the Depletion of Ammonia in Jupiter: I. Microphysics of âMushballsâ
Microwave observations by the Juno spacecraft have shown that, contrary to expectations, the concentration of ammonia is still variable down to pressures of tens of bars in Jupiter. We show that during strong storms able to loft water ice into a region located at pressures between 1.1 and 1.5 bar and temperatures between 173 and 188 K, ammonia vapor can dissolve into water ice to form a lowâtemperature liquid phase containing about oneâthird ammonia and twoâthird water. We estimate that, following the process creating hailstorms on Earth, this liquid phase enhances the growth of hailâlike particles that we call mushballs. We develop a simple model to estimate the growth of these mushballs, their fall into Jupiterâs deep atmosphere, and their evaporation. We show that they evaporate deeper than the expected water cloud base level, between 5 and 27 bar depending on the assumed abundance of water ice lofted by thunderstorms and on the assumed ventilation coefficient governing heat transport between the atmosphere and the mushball. Because the ammonia is located mostly in the core of the mushballs, it tends to be delivered deeper than water, increasing the efficiency of the process. Further sinking of the condensates is expected due to cold temperature and ammoniaâ and waterârich downdrafts formed by the evaporation of mushballs. This process can thus potentially account for the measurements of ammonia depletion in Jupiterâs deep atmosphere.Plain Language SummaryThe Juno mission has revealed that Jupiterâs atmosphere is much more complex and intriguing than previously anticipated. Most of Jupiterâs atmosphere was shown to be depleted in ammonia. While ammonia was expected to be well mixed, large scale variability of ammonia was detected at least 100 km below the cloud level where condensation occurs. We propose a mechanism to explain this depletion and variability. We show that in Jupiter, at very low temperatures (of order â90° C), water ice and ammonia vapor combine to form a liquid and we hypothesize that this subsequently triggers unexpected meteorology. During Jupiterâs violent storms, hailstones form from this liquid, similar to the process in terrestrial storms where hail forms in the presence of supercooled liquid water. Growth of the hailstones creates a slushâlike substance surrounded by a layer of ice, and these âmushballsâ fall, evaporate, and continue sinking further in the planetâs deep atmosphere, creating both ammonia depletion and variability, potentially explaining the Juno observations.Key PointsWe show that ammonia can melt waterâice crystals in Jupiterâs storms and lead to the formation of waterâammonia hailstones (mushballs)These mushballs and subsequent downdrafts transport ammonia to very deep levelsThis can potentially explain Juno measurements that Jupiterâs ammonia abundance is variable until at least 150 km below the visible cloudsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156131/2/jgre21375.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156131/1/jgre21375_am.pd
Sloan Digital Sky Survey Spectroscopic Lens Search. I. Discovery of Intermediate-Redshift Star-Forming Galaxies Behind Foreground Luminous Red Galaxies
We present a catalog of 49 spectroscopic strong gravitational lens candidates
selected from a Sloan Digital Sky Survey sample of 50996 luminous red galaxies.
Potentially lensed star-forming galaxies are detected through the presence of
background oxygen and hydrogen nebular emission lines in the spectra of these
massive foreground galaxies. This multiline selection eliminates the ambiguity
of single-line identification and provides a very promising sample of candidate
galaxy-galaxy lens systems at low to intermediate redshift, with foreground
redshifts ranging from 0.16 to 0.49 and background redshifts from 0.25 to 0.81.
Any lenses confirmed within our sample would be important new probes of
early-type galaxy mass distributions, providing complementary constraints to
those obtained from currently known lensed high-redshift quasars.Comment: 23 pages; to appear in The Astronomical Journal, 2004 April. Version
with full-resolution figures available at
http://web.mit.edu/bolton/www/speclens.ps.gz (PostScript) or
http://web.mit.edu/bolton/www/speclens.pdf (PDF
Comparison of the deep atmospheric dynamics of Jupiter and Saturn in light of the Juno and Cassini gravity measurements
The nature and structure of the observed east-west flows on Jupiter and Saturn have been a long-standing mystery in planetary science. This mystery has been recently unraveled by the accurate gravity measurements provided by the Juno mission to Jupiter and the Grand Finale of the Cassini mission to Saturn. These two experiments, which coincidentally happened around the same time, allowed the determination of the overall vertical and meridional profiles of the zonal flows on both planets. This paper reviews the topic of zonal jets on the gas giants in light of the new data from these two experiments. The gravity measurements not only allow the depth of the jets to be constrained, yielding the inference that the jets extend to roughly 3000 and 9000 km below the observed clouds on Jupiter and Saturn, respectively, but also provide insights into the mechanisms controlling these zonal flows. Specifically, for both planets this depth corresponds to the depth where electrical conductivity is within an order of magnitude of 1 Sâmâ»Âč, implying that the magnetic field likely plays a key role in damping the zonal flows. An intrinsic characteristic of any gravity inversion, as discussed here, is that the solutions might not be unique. We analyze the robustness of the solutions and present several independent lines of evidence supporting the results presented here
The use of an unsupervised learning approach for characterizing latent behaviors in accelerometer data
Acknowledgments This project and the tags deployed on both seabird's species were fund by NERC (grant number NE/K007440/1), Marine Scotland Science and Seabird Tracking and Research (STAR) Project led by the Royal Society for the Protection of Birds (RSPB). We would like to thank Rob Hughes, Tessa Cole and Ruth Brown for helping in the data collection, the Bird Observatory of Fair Isle for supporting the fieldwork and the Marine Collaboration Research Forum (MarCRF).Peer reviewedPublisher PD
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