4,113 research outputs found
Effect of Contrast-Enhanced Echocardiograms on the Prognosis of Infective Endocarditis
Objective - Infective endocarditis (IE) is an infectious disease of the cardiac valves where bacteria colonize the valves; typically, via the formation of vegetations. Recent research has shown that the microbubbles in a contrast-enhanced ultrasound (CEUS) examination can move and dislodge bacterial vegetations in vitro. This study investigated whether CEUS resulted in faster resolution of IE in vivo by dislodging the vegetations.
Methods - This IRB approved retrospective study reviewed 36 patients who were diagnosed with IE via echocardiography. Data was sourced from patients within the Jefferson University Hospital’s Cardiology EMR system by searching for contrast and vegetation from January 1st, 2013 – January 1st, 2018. Fifteen patients were not given contrast, whereas 21 patients were given contrast via agitated saline (n=16) or an ultrasound contrast agent (n=5). All patients received an echocardiogram after blood cultures confirmed an infection, but before resolution of infection (defined by negative blood cultures). A student’s t-test was used for analyses.
Results - The study population was heterogeneous in terms of sex (67.5% male) and race (70% Caucasian, 25% African American, and 5% Asian), with an average age of 51±20 years, and an average BMI of 29.65±7.43 in the contrast group and 27.67±3.16 in the non-contrast group (p=0.37). Following ultrasound, no patients had documented stroke, pulmonary embolism, or systemic blood clot, which physicians could have attributed to a thrombus resulting from dislodging of bacterial vegetation. Overall, blood cultures did not clear faster in patients receiving CEUS compared to those undergoing standard echocardiography, (2.63±2.69 days vs. 1.34 ±1.11 days, p=0.09). CEUS also did not shorten the admission length in patients with IE, (16.9±7.7 days vs. 19.9±12.1 days; p=0.36).
Conclusion - Based on this limited sample size, patients who underwent CEUS did not have a different prognosis when compared to patients who received a non-contrast echocardiogram
X-ray Timing of PSR J1852+0040 in Kesteven 79: Evidence of Neutron Stars Weakly Magnetized at Birth
The 105-ms X-ray pulsar J1852+0040 is the central compact object (CCO) in SNR
Kes 79. We report a sensitive upper limit on its radio flux density of 12 uJy
at 2 GHz using the NRAO GBT. Timing using XMM and Chandra over a 2.4 yr span
reveals no significant change in its spin period. The 2 sigma upper limit on
the period derivative leads, in the dipole spin-down formalism, to an energy
loss rate E-dot < 7e33 ergs/s, surface magnetic field strength B_p < 1.5e11 G,
and characteristic age tau_c = P/2P-dot > 8 Myr. This tau_c exceeds the age of
the SNR by 3 orders of magnitude, implying that the pulsar was born spinning at
its current period. However, the X-ray luminosity of PSR J1852+0040, L(bol) ~
3e33(d/7.1 kpc)^2 ergs/s is a large fraction of E-dot, which challenges the
rotation-powered assumption. Instead, its high blackbody temperature,
0.46+/-0.04 keV, small blackbody radius ~ 0.8 km, and large pulsed fraction, ~
80%, may be evidence of accretion onto a polar cap, possibly from a fallback
disk made of supernova debris. If B_p < 1e10 G, an accretion disk can penetrate
the light cylinder and interact with the magnetosphere while resulting torques
on the neutron star remain within the observed limits. A weak B-field is also
inferred in another CCO, the 424-ms pulsar 1E 1207.4-5209, from its steady spin
and soft X-ray absorption lines. We propose this origin of radio-quiet CCOs:
the B-field, derived from a turbulent dynamo, is weaker if the NS is formed
spinning slowly, which enables it to accrete SN debris. Accretion excludes
neutron stars born with both B_p 0.1 s from radio pulsar
surveys, where B_p
40 Myr) or recycled pulsars. Finally, such a CCO, if born in SN 1987A, could
explain the non-detection of a pulsar there.Comment: 8 pages, 3 figures, to appear in The Astrophysical Journa
The Next Geminga: Deep Multiwavelength Observations of a Neutron Star Identified with 3EG J1835+5918
We describe Chandra, HST, and radio observations that reveal a radio-quiet
but magnetospherically active neutron star in the error circle of the
high-energy gamma-ray source 3EG J1835+5918, the brightest of the unidentified
EGRET sources at high Galactic latitude. A Chandra ACIS-S spectrum of the
ultrasoft X-ray source RX J1836.2+5925, suggested by Mirabal & Halpern as the
neutron star counterpart of 3EG J1835+5918, requires two components: a
blackbody of T~3x10^5 K and a hard tail that can be parameterized as a power
law of photon index Gamma~2. An upper limit of d < 800 pc can be derived from
the blackbody fit under an assumption of R = 10 km. Deep optical imaging with
the HST STIS CCD failed to detect this source to a limit of V > 28.5, thus
f_X/f_V > 6000 and d > 250 pc assuming the X-ray fitted temperature for the
full surface. Repeated observations with the 76 m Lovell telescope at Jodrell
Bank place an upper limit of < 0.1 mJy on the flux density at 1400 MHz for a
pulsar with P > 0.1 s, and < 0.25 mJy for a ~10 ms pulsar at the location of RX
J1836.2+5925. All of this evidence points to an older, possibly more distant
version of the highly efficient gamma-ray pulsar Geminga, as the origin of the
gamma-rays from 3EG J1835+5918.Comment: 4 pages, 4 figures, accepted for publication in ApJ Letter
Discovery of the Putative Pulsar and Wind Nebula Associated with the TeV Gamma-ray Source HESS J1813-178
We present a Chandra X-ray observation of G12.82-0.02, a shell-like radio
supernova remnant coincident with the TeV gamma-ray source HESS J1813-178. We
resolve the X-ray emission from the co-located ASCA source into a point source
surrounded by structured diffuse emission that fills the interior of the radio
shell. The morphology of the diffuse emission strongly resembles that of a
pulsar wind nebula. The spectrum of the compact source is well-characterized by
a power-law with index Gamma approx 1.3, typical of young and energetic
rotation-powered pulsars. For a distance of 4.5 kpc, consistent with the X-ray
absorption and an association with the nearby star formation region W33, the
2-10 keV X-ray luminosities of the putative pulsar and nebula are L(PSR) =
3.2E33 ergs/s and L(PWN) = 1.4E34 ergs/s, respectively. Both the flux ratio of
L(PWN)/L(PSR) = 4.3 and the total luminosity of this system predict a pulsar
spin-down power of Edot > 1E37 ergs/s, placing it within the ten most energetic
young pulsars in the Galaxy. A deep search for radio pulsations using the
Parkes telescope sets an upper-limit of approx 0.07 mJy at 1.4 GHz for periods
>~ 50 ms. We discuss the energetics of this source, and consider briefly the
proximity of bright H2 regions to this and several other HESS sources, which
may produce their TeV emission via inverse Compton scattering.Comment: 7 pages, 6 figure, Latex, emulateapj style. To appear in the
Astrophysical Journa
VLBA measurement of the transverse velocity of the magnetar XTE J1810-197
We have obtained observations of the magnetar XTE J1810-197 with the Very
Long Baseline Array at two epochs separated by 106 days, at wavelengths of 6 cm
and 3.6 cm. Comparison of the positions yields a proper motion value of
13.5+-1.0 mas/yr at an equatorial position angle of 209.4+-2.4 deg (east of
north). This value is consistent with a lower-significance proper motion value
derived from infrared observations of the source over the past three years,
also reported here. Given its distance of 3.5+-0.5 kpc, the implied transverse
velocity corrected to the local standard of rest is 212+-35 km/s (1 sigma). The
measured velocity is slightly below the average for normal young neutron stars,
indicating that the mechanism(s) of magnetar birth need not lead to high
neutron star velocities. We also use Australia Telescope Compact Array, Very
Large Array, and these VLBA observations to set limits on any diffuse emission
associated with the source on a variety of spatial scales, concluding that the
radio emission from XTE J1810-197 is >96% pulsed.Comment: Accepted for publication in The Astrophysical Journal. Six pages, 2
figure
An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1990
The following monthly mean global distributions for 1990 are proposed with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States (US) Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the advanced very high resolution radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) spacecraft; Cartesian components of free drifting buoys which are tracked by the ARGOS navigation system on NOAA satellites; and Cartesian components on the 10-m height wind vector computed by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of monthly mean value, sampling distribution, and standard deviation values are displayed. Annual mean distributions are displayed
An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1991
The following monthly mean global distributions for 1991 are presented with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the advanced very high resolution radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) spacecraft; Cartesian components of free-drifting buoys which are tracked by the ARGOS navigation system on NOAA satellites; and Cartesian components of the 10-m height wind vector computed by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of monthly mean value, sampling distribution, and standard deviation value are displayed. Annual mean distributions are displayed
PSR J2229+6114: Discovery of an Energetic Young Pulsar in the Error Box of the EGRET Source 3EG J2227+6122
We report the detection of radio and X-ray pulsations at a period of 51.6 ms
from the X-ray source RX/AX J2229.0+6114 in the error box of the EGRET source
3EG J2227+6122. An ephemeris derived from a single ASCA observation and
multiple epochs at 1412 MHz from Jodrell Bank indicates steady spin-down with
P-dot = 7.83 x 10^(-14) s/s. From the measured P and P-dot we derive spin-down
power E-dot = 2.2 x 10^(37) erg/s, magnetic field B = 2.0 x 10^(12) G, and
characteristic age P/2P-dot = 10,460 yr. An image from the Chandra X-ray
Observatory reveals a point source surrounded by centrally peaked diffuse
emission that is contained within an incomplete radio shell. We assign the name
G106.6+2.9 to this new supernova remnant, which is evidently a pulsar wind
nebula. For a distance of 3 kpc estimated from X-ray absorption, the ratio of
X-ray luminosity to spin-down power is ~8 x 10^(-5), smaller than that of most
pulsars, but similar to the Vela pulsar. If PSR J2229+6114 is the counterpart
of 3EG J2227+6122 then its efficiency of gamma-ray production, if isotropic, is
0.016 (d/3 kpc)^2. It obeys an established trend of gamma-ray efficiency among
known gamma-ray pulsars which, in combination with the demonstrated absence of
any other plausible counterpart for 3EG J2227+6122, makes the identification
compelling. If confirmed, this identification bolsters the pulsar model for
unidentified Galactic EGRET sources.Comment: 5 pages, 4 figures, accepted by The Astrophysical Journal Letter
Discovery of a Hard X-Ray Source, SAX J0635+0533, in the Error Box of the Gamma-Ray Source 2EG 0635+0521
We have discovered an x-ray source, SAX J0635+0533, with a hard spectrum
within the error box of the GeV gamma-ray source in Monoceros, 2EG J0635+0521.
The unabsorbed x-ray flux is 1.2*10^-11 erg cm^-2 s^-1 in the 2-10 keV band.
The x-ray spectrum is consistent with a simple powerlaw model with absorption.
The photon index is 1.50 +/- 0.08 and we detect emission out to 40 keV. Optical
observations identify a counterpart with a V-magnitude of 12.8. The counterpart
has broad emission lines and the colors of an early B type star. If the
identification of the x-ray/optical source with the gamma-ray source is
correct, then the source would be a gamma-ray emitting x-ray binary.Comment: Accepted to the Astrophysical Journal, 8 page
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