281 research outputs found
Induction chemotherapy in the treatment of nasopharyngeal carcinoma: Clinical outcomes and patterns of care
The Spectral Types of White Dwarfs in Messier 4
We present the spectra of 24 white dwarfs in the direction of the globular
cluster Messier 4 obtained with the Keck/LRIS and Gemini/GMOS spectrographs.
Determining the spectral types of the stars in this sample, we find 24 type DA
and 0 type DB (i.e., atmospheres dominated by hydrogen and helium
respectively). Assuming the ratio of DA/DB observed in the field with effective
temperature between 15,000 - 25,000 K, i.e., 4.2:1, holds for the cluster
environment, the chance of finding no DBs in our sample due simply to
statistical fluctuations is only 6 X 10^(-3). The spectral types of the ~100
white dwarfs previously identified in open clusters indicate that DB formation
is strongly suppressed in that environment. Furthermore, all the ~10 white
dwarfs previously identified in other globular clusters are exclusively type
DA. In the context of these two facts, this finding suggests that DB formation
is suppressed in the cluster environment in general. Though no satisfactory
explanation for this phenomenon exists, we discuss several possibilities.Comment: Accepted for Publication in Astrophys. J. 11 pages including 4
figures and 2 tables (journal format
Delayed evaluation of combat-related penetrating neck trauma
ObjectiveThe approach to penetrating trauma of the head and neck has undergone significant evolution and offers unique challenges during wartime. Military munitions produce complex injury patterns that challenge conventional diagnosis and management. Mass casualties may not allow for routine exploration of all stable cervical blast injuries. The objective of this study was to review the delayed evaluation of combat-related penetrating neck trauma in patients after evacuation to the United States.MethodFrom February 2003 through April 2005, a series of patients with military-associated penetrating cervical trauma were evacuated to a single institution, prospectively entered into a database, and retrospectively reviewed.ResultsSuspected vascular injury from penetrating neck trauma occurred in 63 patients. Injuries were to zone II in 33%, zone III in 33%, and zone I in 11%. The remaining injuries involved multiple zones, including the lower face or posterior neck. Explosive devices wounded 50 patients (79%), 13 (21%) had high-velocity gunshot wounds, and 19 (30%) had associated intracranial or cervical spine injury. Of the 39 patients (62%) who underwent emergent neck exploration in Iraq or Afghanistan, 21 had 24 injuries requiring ligation (18), vein interposition or primary repair (4), polytetrafluoroethylene (PTFE) graft interposition (1), or patch angioplasty (1). Injuries occurred to the carotid, vertebral, or innominate arteries, or the jugular vein. After evacuation to the United States, all patients underwent radiologic evaluation of the head and neck vasculature. Computed tomography angiography was performed in 45 patients (71%), including six zone II injuries without prior exploration. Forty (63%) underwent diagnostic arteriography that detected pseudoaneurysms (5) or occlusions (8) of the carotid and vertebral arteries. No occult venous injuries were noted. Delayed evaluation resulted in the detection of 12 additional occult injuries and one graft thrombosis in 11 patients. Management included observation (5), vein or PTFE graft repair (3), coil embolization (2), or ligation (1).ConclusionsPenetrating multiple fragment injury to the head and neck is common during wartime. Computed tomography angiography is useful in the delayed evaluation of stable patients, but retained fragments produce suboptimal imaging in the zone of injury. Arteriography remains the imaging study of choice to evaluate for cervical vascular trauma, and its use should be liberalized for combat injuries. Stable injuries may not require immediate neck exploration; however, the high prevalence of occult injuries discovered in this review underscores the need for a complete re-evaluation upon return to the United States
Deep ACS Imaging in the Globular Cluster NGC6397: Dynamical Models
We present N-body models to complement deep imaging of the metal-poor
core-collapsed cluster NGC6397 obtained with the Hubble Space Telescope. All
simulations include stellar and binary evolution in-step with the stellar
dynamics and account for the tidal field of the Galaxy. We focus on the results
of a simulation that began with 100000 objects (stars and binaries), 5%
primordial binaries and Population II metallicity. After 16 Gyr of evolution
the model cluster has about 20% of the stars remaining and has reached
core-collapse. We compare the color-magnitude diagrams of the model at this age
for the central region and an outer region corresponding to the observed field
of NGC6397 (about 2-3 half-light radii from the cluster centre). This
demonstrates that the white dwarf population in the outer region has suffered
little modification from dynamical processes - contamination of the luminosity
function by binaries and white dwarfs with non-standard evolution histories is
minimal and should not significantly affect measurement of the cluster age. We
also show that the binary fraction of main-sequence stars observed in the
NGC6397 field can be taken as representative of the primordial binary fraction
of the cluster. For the mass function of the main-sequence stars we find that
although this has been altered significantly by dynamics over the cluster
lifetime, especially in the central and outer regions, that the position of the
observed field is close to optimal for recovering the initial mass function of
the cluster stars (below the current turn-off mass). More generally we look at
how the mass function changes with radius in a dynamically evolved stellar
cluster and suggest where the best radial position to observe the initial mass
function is for clusters of any age.Comment: 34 pages, 11 figures, submitted to AJ, companion paper to 0708.403
The Masses of Population II White Dwarfs
Globular star clusters are among the first stellar populations to have formed
in the Milky Way, and thus only a small sliver of their initial spectrum of
stellar types are still burning hydrogen on the main-sequence today. Almost all
of the stars born with more mass than 0.8 M_sun have evolved to form the white
dwarf cooling sequence of these systems, and the distribution and properties of
these remnants uniquely holds clues related to the nature of the now evolved
progenitor stars. With ultra-deep HST imaging observations, rich white dwarf
populations of four nearby Milky Way globular clusters have recently been
uncovered, and are found to extend an impressive 5 - 8 magnitudes in the
faint-blue region of the H-R diagram. In this paper, we characterize the
properties of these population II remnants by presenting the first direct mass
measurements of individual white dwarfs near the tip of the cooling sequence in
the nearest of the Milky Way globulars, M4. Based on Gemini/GMOS and Keck/LRIS
multiobject spectroscopic observations, our results indicate that 0.8 M_sun
population II main-sequence stars evolving today form 0.53 +/- 0.01 M_sun white
dwarfs. We discuss the implications of this result as it relates to our
understanding of stellar structure and evolution of population II stars and for
the age of the Galactic halo, as measured with white dwarf cooling theory.Comment: Accepted for Publication in Astrophys. J. on Aug. 05th, 2009. 19
pages including 9 figures and 2 tables (journal format
The incidence, risk factors, and outcomes associated with late right-sided heart failure in patients supported with an axial-flow left ventricular assist device
BACKGROUND: Early right-sided heart failure (RHF) after left ventricular assist device (LVAD) implantation is associated with increased mortality, but little is known about patients who develop late RHF (LRHF). We evaluated the incidence, risk factors, and clinical impact of LRHF in patients supported by axial-flow LVADs.
METHODS: Data were analyzed from 537 patients enrolled in the HeartMate II (HM II; Thoratec/St. Jude) destination therapy clinical trial. LRHF was defined as the development of clinical RHF accompanied by the need for inotropic support occurring more than 30 days after discharge from the index LVAD implant hospitalization. Clinical variables, quality of life, rehospitalizations, and survival were compared between patients with and without LRHF.
RESULTS: LRHF developed in 41 patients (8%), with a median time to LRHF of 480 days. A higher preoperative blood urea nitrogen and increased central venous pressure-to-pulmonary capillary wedge pressure ratio were independent predictors of LRHF. The Michigan and HMII RHF risk scores were both associated with an increased likelihood of LRHF (p < 0.05). Patients with LRHF had worse quality of life according to the Kansas City Cardiomyopathy Questionnaire (61 ± 26 vs 70 ± 21; p < 0.05), poorer functional capacity by 6-minute walk distance (275 ± 189 m vs 312 ± 216 m; p < 0.05), and more rehospitalizations (6 vs 3; p < 0.001). LRHF was associated with decreased survival (p < 0.001).
CONCLUSIONS: LRHF is an important complication in patients with LVADs and is associated with worse quality of life, reduced functional capacity, more frequent hospitalizations, and worse survival compared with those without LRHF
Publisher Correction: Deep coverage whole genome sequences and plasma lipoprotein(a) in individuals of European and African ancestries.
The original version of this article contained an error in the name of the author Ramachandran S. Vasan, which was incorrectly given as Vasan S. Ramachandran. This has now been corrected in both the PDF and HTML versions of the article
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Deep coverage whole genome sequences and plasma lipoprotein(a) in individuals of European and African ancestries.
Lipoprotein(a), Lp(a), is a modified low-density lipoprotein particle that contains apolipoprotein(a), encoded by LPA, and is a highly heritable, causal risk factor for cardiovascular diseases that varies in concentrations across ancestries. Here, we use deep-coverage whole genome sequencing in 8392 individuals of European and African ancestry to discover and interpret both single-nucleotide variants and copy number (CN) variation associated with Lp(a). We observe that genetic determinants between Europeans and Africans have several unique determinants. The common variant rs12740374 associated with Lp(a) cholesterol is an eQTL for SORT1 and independent of LDL cholesterol. Observed associations of aggregates of rare non-coding variants are largely explained by LPA structural variation, namely the LPA kringle IV 2 (KIV2)-CN. Finally, we find that LPA risk genotypes confer greater relative risk for incident atherosclerotic cardiovascular diseases compared to directly measured Lp(a), and are significantly associated with measures of subclinical atherosclerosis in African Americans
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