19,482 research outputs found
The Anisoplanatic Point Spread Function in Adaptive Optics
The effects of anisoplanatism on the adaptive optics point spread function
are investigated. A model is derived that combines observations of the guide
star with an analytic formulation of anisoplanatism to generate predictions for
the adaptive optics point spread function at arbitrary locations within the
field of view. The analytic formulation captures the dependencies of
anisoplanatism on aperture diameter, observing wavelength, angular offset,
zenith angle and turbulence profile. The predictions of this model are compared
to narrowband 2.12 um and 1.65 um images of a 21 arcsec binary (mV=7.3, 7.6)
acquired with the Palomar Adaptive Optics System on the Hale 5 meter telescope.
Contemporaneous measurements of the turbulence profile made with a DIMM/MASS
unit are used together with images of the primary to predict the point spread
function of the binary companion. Predicted companion Strehl ratios are shown
to match measurements to within a few percent, whereas predictions based on the
isoplanatic angle approximation are highly discrepant. The predicted companion
point spread functions are shown to agree with observations to 10%. These
predictions are used to measure the differential photometry between binary
members to an accuracy of 1 part in 10^{3}, and the differential astrometry to
an accuracy of 1 mas. Errors in the differential astrometry are shown to be
dominated by differential atmospheric tilt jitter. These results are compared
to other techniques that have been employed for photometry, astrometry, and
high contrast imaging.Comment: 26 pages, 7 figure
The one-loop effective potential of the Wess-Zumino model revisited
The full one-loop supersymmetric effective potential for the Wess-Zumino
model is calculated using superfield techniques. This includes the K\"ahler
potential and the auxiliary field potential, of which the former was originally
computed in 1993 while the latter is derived for the first time. In the purely
bosonic sector our results match those of older component field calculations.
In light of prior contradictory results found in the literature, the
calculation of the leading term in the auxiliary field potential is approached
in a variety of ways. Issues related to conditional convergence that occur
during these calculations and their possible consequences are discussed.Comment: 32 page
How to allocate scarce health resources without discriminating against people with disabilities
One widely used method for allocating health care resources involves the use of cost-effectiveness analysis (CEA) to rank treatments in terms of quality-adjusted life-years (QALYs) gained. CEA has been criticized for discriminating against people with disabilities by valuing their lives less than those of non-disabled people. Avoiding discrimination seems to lead to the ’QALY trap’: we cannot value saving lives equally and still value raising quality of life. This paper reviews existing responses to the QALY trap and argues that all are problematic. Instead, we argue that adopting a moderate form of prioritarianism avoids the QALY trap and disability discrimination
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