269 research outputs found
Description and evaluation of a ventriculo-coronary artery bypass device that provides bi-directional coronary flow
Objective: The objective of this study was to assess acute patency of a new myocardial revascularization device that connects the left ventricular cavity to a coronary artery (termed ventriculo-coronary artery bypass, VCAB) thereby providing proximal and distal blood flow from the site of the anastomosis. Methods: A device made of expanded polytetrafluoroethylene and low density polyethylene was implanted from the base of the left ventricle to the mid left anterior descending coronary artery (LAD) in 11 juvenile domestic pigs using a beating heart approach. Flow rates were measured in the distal LAD before and after implant using ultrasonic flow techniques, and patency was assessed at explant at either 2 or 4 weeks post-implantation. Myocardial perfusion using positron emission tomography (PET) was assessed in a separate set of pigs (n=2) revascularized by VCAB 2 weeks post-implant. Results: Net forward flow distal to the implanted device was 73±15% of native LAD flow. PET demonstrated that the target myocardium was perfused at 85% of that seen in the remote, control myocardium. Device patency rate was 80% (4/5) at 2 weeks in one set of pigs and 83% (5/6) at 4 weeks in a second set of pigs. Histologic analysis showed formation of neointima along the extraventricular segment of the device. Conclusions: This study demonstrates the promise of perfusing ischemic myocardium using a VCAB approach with a device that provides blood flow both proximal and distal to the anastomosis. Patency of the transmyocardial device was encouraging at 2 and 4 weeks and warrants further investigatio
Anticoagulation in Atrial Fibrillation Patients
Atrial fibrillation (AF) is the most common arrhythmia and may cause thromboembolic events, typically stroke. Advances in pharmacological approaches to anticoagulation and groundbreaking large randomized controlled trials of non-vitamin K antagonist oral anticoagulants (NOACs) have changed the paradigm of anticoagulation therapy. Furthermore, observational studies support the efficacy and safety of NOAC. Few studies address the differences among NOACs, but prescriptions should be based on a thorough understanding of their pharmacological differences, including interactions, side effects, reversibility, and practical approach. In a subset of patients with AF, warfarin may still be the preferable option. Consequently, an individualized approach to oral anticoagulation is crucial
The star catalogues of Ptolemaios and Ulugh Beg: Machine-readable versions and comparison with the modern Hipparcos Catalogue
In late antiquity and throughout the middle ages, the positions of stars on
the celestial sphere were obtained from the star catalogue of Ptolemaios. A
catalogue based on new measurements appeared in 1437, with positions by Ulugh
Beg, and magnitudes from the 10th-century astronomer al-Sufi. We provide
machine-readable versions of these two star catalogues, based on the editions
by Toomer (1998) and Knobel (1917), and determine their accuracies by
comparison with the modern Hipparcos Catalogue. The magnitudes in the
catalogues correlate well with modern visual magnitudes; the indication `faint'
by Ptolemaios is found to correspond to his magnitudes 5 and 6. Gaussian fits
to the error distributions in longitude / latitude give widths sigma ~ 27
arcmin / 23 arcmin in the range |Delta lambda, Delta beta|<50 arcmin for
Ptolemaios and sigma ~ 22 arcmin /18 arcmin in Ulugh Beg. Fits to the range
|Delta lambda, Delta beta|<100 arcmin gives 10-15 per cent larger widths,
showing that the error distributions are broader than gaussians. The fraction
of stars with positions wrong by more than 150 arcmin is about 2 per cent for
Ptolemaios and 0.1 per cent in Ulugh Beg; the numbers of unidentified stars are
1 in Ptolemaios and 3 in Ulugh Beg. These numbers testify to the excellent
quality of both star catalogues (as edited by Toomer and Knobel).Comment: to be published in Astronomy and Astrophysics; 34 pages with 57
Figures. Note changed address and email address of first autho
The ATLAS 5.5 GHz survey of the Extended Chandra Deep Field South: Catalogue, Source Counts and Spectral Indices
Star forming galaxies are thought to dominate the sub-mJy radio population,
but recent work has shown that low luminosity AGN can still make a significant
contribution to the faint radio source population. Spectral indices are an
important tool for understanding the emission mechanism of the faint radio
sources. We have observed the extended Chandra Deep Field South at 5.5 GHz
using a mosaic of 42 pointings with the Australia Telescope Compact Array
(ATCA). Our image reaches an almost uniform sensitivity of ~12 microJy rms over
0.25 deg^2 with a restoring beam of 4.9 x 2.0 arcsec, making it one of the
deepest 6cm surveys to date. We present the 5.5 GHz catalogue and source counts
from this field. We take advantage of the large amounts of ancillary data in
this field to study the 1.4 to 5.5 GHz spectral indices of the sub-mJy
population. For the full 5.5 GHz selected sample we find a flat median spectral
index, alpha_med = -0.40, which is consistent with previous results. However,
the spectral index appears to steepen at the faintest flux density levels
(S_{5.5 GHz} < 0.1 mJy), where alpha_med = -0.68. We performed stacking
analysis of the faint 1.4 GHz selected sample (40 < S_{1.4 GHz} < 200 microJy)
and also find a steep average spectral index, alpha = -0.8, consistent with
synchrotron emission. We find a weak trend of steepening spectral index with
redshift. Several young AGN candidates are identified using spectral indices,
suggesting Gigahertz Peaked Spectrum (GPS) sources are as common in the mJy
population as they are at Jy levels.Comment: 18 pages, 16 figures, accepted for publication in MNRA
Knowledge and perception about stroke among an Australian urban population
BACKGROUND: The aim of the study was to measure knowledge about the symptoms, prevalence and natural history of stroke; the level of concern about having a stroke; understanding of the possibilities for preventing stroke, and the relationship between age, sex, country of origin, educational level, income, self-reported risk factors, and the above factors. METHODS: A random sample of households was selected from an electronic telephone directory in Newcastle and Lake Macquarie area of New South Wales, Australia, between 10 September and 13 October 1999. Within each household the person who was between 18 and 80 years of age and who had the next birthday was eligible to participate in the study (1325 households were eligible). The response rate was 62%. RESULTS: The most common symptoms of stroke listed by respondents were "Sudden difficulty of speaking, understanding or reading" identified by 60.1% of the respondents, and "paralysis on one side of body" identified by 42.0% of the respondents. The level of knowledge of the prevalence of a stroke, full recovery after the stroke, and death from stroke was low and generally overestimated. 69.9% of the respondents considered strokes as being either moderately or totally preventable. There were few predictors of knowledge. CONCLUSION: The study suggests that educational strategies may be required to improve knowledge about a wide range of issues concerning stroke in the community, as a prelude to developing preventive programmes
Search for anomalous t t-bar production in the highly-boosted all-hadronic final state
A search is presented for a massive particle, generically referred to as a
Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are
sufficiently massive to produce highly Lorentz-boosted top quarks, which yield
collimated decay products that are partially or fully merged into single jets.
The analysis uses new methods to analyze jet substructure, providing
suppression of the non-top multijet backgrounds. The analysis is based on a
data sample of proton-proton collisions at a center-of-mass energy of 7 TeV,
corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits
in the range of 1 pb are set on the product of the production cross section and
branching fraction for a topcolor Z' modeled for several widths, as well as for
a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any
enhancement in t t-bar production beyond expectations of the standard model for
t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version
includes a minor typo correction that will be submitted as an erratu
Salivary Gland Sparing and Improved Target Irradiation by Conformal and Intensity Modulated Irradiation of Head and Neck Cancer
The goals of this study were to facilitate sparing of the major salivary glands while adequately treating tumor targets in patients requiring comprehensive bilateral neck irradiation (RT), and to assess the potential for improved xerostomia. Since 1994 techniques of target irradiation and locoregional tumor control with conformal and intensity modulated radiation therapy (IMRT) have been developed. In patients treated with these modalities, the salivary flow rates before and periodically after RT have been measured selectively from each major salivary gland and the residual flows correlated with glandsâ dose volume histograms (DVHs). In addition, subjective xerostomia questionnaires have been developed and validated. The pattern of locoregional recurrence has been examined from computed tomography (CT) scans at the time of recurrence, transferring the recurrence volumes to the planning CT scans, and regenerating the dose distributions at the recurrence sites. Treatment plans for target coverage and dose homogeneity using static, multisegmental IMRT were found to be significantly better than standard RT plans. In addition, significant parotid gland sparing was achieved in the conformal plans. The relationships among dose, irradiated volume, and the residual saliva flow rates from the parotid glands were characterized by dose and volume thresholds. A mean radiation dose of 26 Gy was found to be the threshold for preserved stimulated saliva flow. Xerostomia questionnaire scores suggested that xerostomia was significantly reduced in patients irradiated with bilateral neck, parotid-sparing RT, compared to patients with similar tumors treated with standard RT. Examination of locoregional tumor recurrence patterns revealed that the large majority of recurrences occurred inside targets, in areas that had been judged to be at high risk and that had received RT doses according to the perceived risk. Tangible gains in salivary gland sparing and target coverage are being achieved, and an improvement in some measures of quality of life is suggested by our findings. Additional reduction of xerostomia may be achieved by further sparing of the salivary glands and the non-involved oral cavity. A mean parotid gland dose of †26 Gy should be a planning objective if significant parotid function preservation is desired. The pattern of recurrence suggests that careful escalation of the dose to areas judged to be at highest risk may improve tumor control.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41298/1/268_2003_Article_7105.pd
The Pioneer Anomaly
Radio-metric Doppler tracking data received from the Pioneer 10 and 11
spacecraft from heliocentric distances of 20-70 AU has consistently indicated
the presence of a small, anomalous, blue-shifted frequency drift uniformly
changing with a rate of ~6 x 10^{-9} Hz/s. Ultimately, the drift was
interpreted as a constant sunward deceleration of each particular spacecraft at
the level of a_P = (8.74 +/- 1.33) x 10^{-10} m/s^2. This apparent violation of
the Newton's gravitational inverse-square law has become known as the Pioneer
anomaly; the nature of this anomaly remains unexplained. In this review, we
summarize the current knowledge of the physical properties of the anomaly and
the conditions that led to its detection and characterization. We review
various mechanisms proposed to explain the anomaly and discuss the current
state of efforts to determine its nature. A comprehensive new investigation of
the anomalous behavior of the two Pioneers has begun recently. The new efforts
rely on the much-extended set of radio-metric Doppler data for both spacecraft
in conjunction with the newly available complete record of their telemetry
files and a large archive of original project documentation. As the new study
is yet to report its findings, this review provides the necessary background
for the new results to appear in the near future. In particular, we provide a
significant amount of information on the design, operations and behavior of the
two Pioneers during their entire missions, including descriptions of various
data formats and techniques used for their navigation and radio-science data
analysis. As most of this information was recovered relatively recently, it was
not used in the previous studies of the Pioneer anomaly, but it is critical for
the new investigation.Comment: 165 pages, 40 figures, 16 tables; accepted for publication in Living
Reviews in Relativit
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