185 research outputs found
Clinical trial of FK 506 immunosuppression in adult cardiac transplantation
The new immunosuppressive agent FK 506 was used as primary immunotherapy in conjunction with low-dose steroids and azathioprine in 72 patients subsequent to orthotopic cardiac transplantation. Overall patient survival at a mean follow-up of 360 days was 92%. The number of episodes of cardiac rejection (grade 3A or greater) within 90 days of transplantation was 0.95 per patient. The actuarial freedom from rejection at 90 days was 41%. Achievement of this level of immunosuppression is comparable with that of cyclosporine-based triple-drug therapy with OKT3 immunoprophylaxis. Thirty percent of patients were tapered off all steroids, and the average steroid dose in the group who received steroids was 8.6 mg of prednisone per day. The incidence of infection reflected the diminished necessity for steroids: seven major infections (10%) and 11 minor infections (16%). Renal dysfunction occurred during the perioperative period in most patients in this trial. However, the incidence of hypertension was 54% compared with 70% during the cyclosporine era. Ten adults underwent successful rescue therapy with FK 506 after cardiac rejection refractory to conventional immunotherapy. Side effects of FK 506 were notably few, and the results of the trial are encouraging for the future of the cardiac transplant recipient. © 1992
Sagittarius A* Accretion Flow and Black Hole Parameters from General Relativistic Dynamical and Polarized Radiative Modeling
We obtain estimates of Sgr A* accretion flow and black hole parameters by
fitting polarized sub-mm observations with spectra computed using
three-dimensional (3D) general relativistic (GR) magnetohydrodynamical (MHD)
(GRMHD) simulations. Observations are compiled from averages over many epochs
from reports in 29 papers for estimating the mean fluxes Fnu, linear
polarization (LP) fractions, circular polarization (CP) fractions, and electric
vector position angles (EVPAs). GRMHD simulations are computed with
dimensionless spins a_*=0,0.5,0.7,0.9,0.98 over a 20,000M time interval. We
perform fully self-consistent GR polarized radiative transfer using our new
code to explore the effects of spin a_*, inclination angle \theta, position
angle (PA), accretion rate Mdot, and electron temperature Te (Te is reported
for radius 6M). By fitting the mean sub-mm fluxes and LP/CP fractions, we
obtain estimates for these model parameters and determine the physical effects
that could produce polarization signatures. Our best bet model has a_*=0.5,
\theta=75deg, PA=115deg, Mdot=4.6*10^{-8}M_Sun/year, and Te=3.1*10^10K at 6M.
The sub-mm CP is mainly produced by Faraday conversion as modified by Faraday
rotation, and the emission region size at 230GHz is consistent with the VLBI
size of 37microas. Across all spins, model parameters are in the ranges
\theta=42deg-75deg, Mdot=(1.4-7.0)*10^{-8}M_Sun/year, and Te=(3-4)*10^10K.
Polarization is found both to help differentiate models and to introduce new
observational constraints on the effects of the magnetic field that might not
be fit by accretion models so-far considered.Comment: 19 pages, 11 figures, accepted to Ap
Resolving the inner jet structure of 1924-292 with the EVENT HORIZON TELESCOPE
We present the first 1.3 mm (230 GHz) very long baseline interferometry model
image of an AGN jet using closure phase techniques with a four-element array.
The model image of the quasar 1924-292 was obtained with four telescopes at
three observatories: the James Clerk Maxwell Telescope (JCMT) on Mauna Kea in
Hawaii, the Arizona Radio Observatory's Submillimeter Telescope (SMT) in
Arizona, and two telescopes of the Combined Array for Research in
Millimeterwave Astronomy (CARMA) in California in April 2009. With the greatly
improved resolution compared with previous observations and robust closure
phase measurement, the inner jet structure of 1924-292 was spatially resolved.
The inner jet extends to the northwest along a position angle of at
a distance of 0.38\,mas from the tentatively identified core, in agreement with
the inner jet structure inferred from lower frequencies, and making a position
angle difference of with respect to the cm-jet. The size of
the compact core is 0.15\,pc with a brightness temperature of
\,K. Compared with those measured at lower frequencies, the
low brightness temperature may argue in favor of the decelerating jet model or
particle-cascade models. The successful measurement of closure phase paves the
way for imaging and time resolving Sgr A* and nearby AGN with the Event Horizon
Telescope.Comment: 6 pages, 4 figures, accepted for publication in ApJ
1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales
Sagittarius A*, the ~4 x 10^6 solar mass black hole candidate at the Galactic
Center, can be studied on Schwarzschild radius scales with (sub)millimeter
wavelength Very Long Baseline Interferometry (VLBI). We report on 1.3 mm
wavelength observations of Sgr A* using a VLBI array consisting of the JCMT on
Mauna Kea, the ARO/SMT on Mt. Graham in Arizona, and two telescopes of the
CARMA array at Cedar Flat in California. Both Sgr A* and the quasar calibrator
1924-292 were observed over three consecutive nights, and both sources were
clearly detected on all baselines. For the first time, we are able to extract
1.3 mm VLBI interferometer phase information on Sgr A* through measurement of
closure phase on the triangle of baselines. On the third night of observing,
the correlated flux density of Sgr A* on all VLBI baselines increased relative
to the first two nights, providing strong evidence for time-variable change on
scales of a few Schwarzschild radii. These results suggest that future VLBI
observations with greater sensitivity and additional baselines will play a
valuable role in determining the structure of emission near the event horizon
of Sgr A*.Comment: 8 pages, submitted to ApJ
Pleistocene allopatric differentiation followed by recent range expansion explains the distribution and molecular diversity of two congeneric crustacean species in the Palaearctic
Pleistocene glaciations had a tremendous impact on the biota across the Palaearctic, resulting
in strong phylogeographic signals of range contraction and rapid postglacial recolonization of
the deglaciated areas. Here, we explore the diversity patterns and history of two sibling species
of passively dispersing taxa typical of temporary ponds, fairy shrimps (Anostraca). We combine
mitochondrial (COI) and nuclear (ITS2 and 18S) markers to conduct a range-wide phylogeographic
study including 56 populations of Branchinecta ferox and Branchinecta orientalis in the Palaearctic.
Specifically, we investigate whether their largely overlapping ranges in Europe resulted from allopatric
differentiation in separate glacial refugia followed by a secondary contact and reconstruct their
postglacial recolonization from the inhabited refugia. Our results suggest the existence of distinct
refugia for the two species, with genetic divergence among intraspecific lineages consistent with late
Pleistocene glacial cycles. While B. ferox lineages originated from Mediterranean refugia, the origin
of B. orientalis lineages was possibly located on the Pannonian Plain. We showed that most dispersal
events predominantly happened within 100 km, coupled with several recent long-distance events
(> 1000 km). Hence the regional habitat density of suitable habitats in Central Europe is possibly a
key to the co-existence of the two species. Overall, our study illustrates how isolation in combination
with stochastic effects linked to glacial periods are important drivers of the allopatric differentiation of
Palaearctic taxa
The Atacama Cosmology Telescope: Dynamical Masses and Scaling Relations for a Sample of Massive Sunyaev-Zel'dovich Effect Selected Galaxy Clusters
We present the first dynamical mass estimates and scaling relations for a
sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample
consists of 16 massive clusters detected with the Atacama Cosmology Telescope
(ACT) over a 455 sq. deg. area of the southern sky. Deep multi-object
spectroscopic observations were taken to secure intermediate-resolution
(R~700-800) spectra and redshifts for ~60 member galaxies on average per
cluster. The dynamical masses M_200c of the clusters have been calculated using
simulation-based scaling relations between velocity dispersion and mass. The
sample has a median redshift z=0.50 and a median mass M_200c~12e14 Msun/h70
with a lower limit M_200c~6e14 Msun/h70, consistent with the expectations for
the ACT southern sky survey. These masses are compared to the ACT SZE
properties of the sample, specifically, the match-filtered central SZE
amplitude y, the central Compton parameter y0, and the integrated Compton
signal Y_200c, which we use to derive SZE-Mass scaling relations. All SZE
estimators correlate with dynamical mass with low intrinsic scatter (<~20%), in
agreement with numerical simulations. We explore the effects of various
systematic effects on these scaling relations, including the correlation
between observables and the influence of dynamically disturbed clusters. Using
the 3-dimensional information available, we divide the sample into relaxed and
disturbed clusters and find that ~50% of the clusters are disturbed. There are
hints that disturbed systems might bias the scaling relations but given the
current sample sizes these differences are not significant; further studies
including more clusters are required to assess the impact of these clusters on
the scaling relations.Comment: 15 pages, 4 figures. Accepted for publication in The Astrophysical
Journal; matches published version. Full Table 8 with complete spectroscopic
member sample available in machine-readable form in the journal site and upon
request to C. Sif\'o
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