761 research outputs found
Trajectories of Quality of Life after Hematopoietic Cell Transplantation: Secondary Analysis of BMT CTN 0902 Data
Quality of life is increasingly recognized as an important secondary endpoint of hematopoietic cell transplantation (HCT). The current study examined the extent to which attrition results in biased estimates of patient quality of life. The study also examined whether patients differ in terms of trajectories of quality of life in the first six months post-transplant. A secondary data analysis was conducted of 701 participants who enrolled in the Blood and Marrow Transplantation Clinical Trials Network (BMT CTN) 0902 trial. Participants completed the SF-36, a measure of quality of life, prior to transplant and 100 and 180 days post-transplant. Results indicated that attrition resulted in slightly biased overestimates of quality of life but the amount of overestimation remained stable over time. Patients could be grouped into three distinct classes based on physical quality of life: 1) low and stable; 2) average and declining, then stable; and 3) average and stable. Four classes of patients emerged for mental quality of life: 1) low and stable; 2) average, improving, then stable; 3) higher than average (by almost 1 SD) and stable; and 4) average and stable. Taken together, these data provide a more comprehensive understanding of quality of life that can be used to educate HCT recipients and their caregivers
New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation
(abridged) The heating mechanism at high densities during M dwarf flares is
poorly understood. Spectra of M dwarf flares in the optical and
near-ultraviolet wavelength regimes have revealed three continuum components
during the impulsive phase: 1) an energetically dominant blackbody component
with a color temperature of T 10,000 K in the blue-optical, 2) a smaller
amount of Balmer continuum emission in the near-ultraviolet at lambda 3646
Angstroms and 3) an apparent pseudo-continuum of blended high-order Balmer
lines. These properties are not reproduced by models that employ a typical
"solar-type" flare heating level in nonthermal electrons, and therefore our
understanding of these spectra is limited to a phenomenological interpretation.
We present a new 1D radiative-hydrodynamic model of an M dwarf flare from
precipitating nonthermal electrons with a large energy flux of erg
cm s. The simulation produces bright continuum emission from a
dense, hot chromospheric condensation. For the first time, the observed color
temperature and Balmer jump ratio are produced self-consistently in a
radiative-hydrodynamic flare model. We find that a T 10,000 K
blackbody-like continuum component and a small Balmer jump ratio result from
optically thick Balmer and Paschen recombination radiation, and thus the
properties of the flux spectrum are caused by blue light escaping over a larger
physical depth range compared to red and near-ultraviolet light. To model the
near-ultraviolet pseudo-continuum previously attributed to overlapping Balmer
lines, we include the extra Balmer continuum opacity from Landau-Zener
transitions that result from merged, high order energy levels of hydrogen in a
dense, partially ionized atmosphere. This reveals a new diagnostic of ambient
charge density in the densest regions of the atmosphere that are heated during
dMe and solar flares.Comment: 50 pages, 2 tables, 13 figures. Accepted for publication in the Solar
Physics Topical Issue, "Solar and Stellar Flares". Version 2 (June 22, 2015):
updated to include comments by Guest Editor. The final publication is
available at Springer via http://dx.doi.org/10.1007/s11207-015-0708-
Spectral quark model and low-energy hadron phenomenology
We propose a spectral quark model which can be applied to low energy hadronic
physics. The approach is based on a generalization of the Lehmann
representation of the quark propagator. We work at the one-quark-loop level.
Electromagnetic and chiral invariance are ensured with help of the gauge
technique which provides particular solutions to the Ward-Takahashi identities.
General conditions on the quark spectral function follow from natural physical
requirements. In particular, the function is normalized, its all positive
moments must vanish, while the physical observables depend on negative moments
and the so-called log-moments. As a consequence, the model is made finite,
dispersion relations hold, chiral anomalies are preserved, and the twist
expansion is free from logarithmic scaling violations, as requested of a
low-energy model. We study a variety of processes and show that the framework
is very simple and practical. Finally, incorporating the idea of vector-meson
dominance, we present an explicit construction of the quark spectral function
which satisfies all the requirements. The corresponding momentum representation
of the resulting quark propagator exhibits only cuts on the physical axis, with
no poles present anywhere in the complex momentum space. The momentum-dependent
quark mass compares very well to recent lattice calculations. A large number of
predictions and relations can be deduced from our approach for such quantities
as the pion light-cone wave function, non-local quark condensate, pion
transition form factor, pion valence parton distribution function, etc.Comment: revtex, 24 pages, 3 figure
Graviton Mass from Close White Dwarf Binaries Detectable with LISA
The arrival times of gravitational waves and optical light from orbiting
binaries provide a mechanism to understand the propagation speed of gravity
when compared to that of light or electromagnetic radiation. This is achieved
with a measurement of any offset between optically derived orbital phase
related to that derived from gravitational wave data, at a specified location
of one binary component with respect to the other. Using a sample of close
white dwarf binaries (CWDBs) detectable with the Laser Interferometer Space
Antenna (LISA) and optical light curve data related to binary eclipses from
meter-class telescopes for the same sample, we determine the accuracy to which
orbital phase differences can be extracted. We consider an application of these
measurements involving a variation to the speed of gravity, when compared to
the speed of light, due to a massive graviton. For a subsample of 400
CWDBs with high signal-to-noise gravitational wave and optical data with
magnitudes brighter than 25, the combined upper limit on the graviton mass is
at the level of eV. This limit is two orders of
magnitude better than the present limit derived by Yukawa-correction arguments
related to the Newtonian potential and applied to the Solar-system.Comment: revised version, 8 pages, 5 figures, to appear in PR
Ethnic and gender differences in applicants' decision-making processes: An application of the theory of reasoned action
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