28,276 research outputs found
Reflective Ghost Imaging through Turbulence
Recent work has indicated that ghost imaging may have applications in
standoff sensing. However, most theoretical work has addressed
transmission-based ghost imaging. To be a viable remote-sensing system, the
ghost imager needs to image rough-surfaced targets in reflection through long,
turbulent optical paths. We develop, within a Gaussian-state framework,
expressions for the spatial resolution, image contrast, and signal-to-noise
ratio of such a system. We consider rough-surfaced targets that create fully
developed speckle in their returns, and Kolmogorov-spectrum turbulence that is
uniformly distributed along all propagation paths. We address both classical
and nonclassical optical sources, as well as a computational ghost imager.Comment: 13 pages, 3 figure
Nonlinearity and pixel shifting effects in HXRG infrared detectors
We study the nonlinearity (NL) in the conversion from charge to voltage in
infrared detectors (HXRG) for use in precision astronomy. We present laboratory
measurements of the NL function of a H2RG detector and discuss the accuracy to
which it would need to be calibrated in future space missions to perform
cosmological measurements through the weak gravitational lensing technique. In
addition, we present an analysis of archival data from the infrared H1RG
detector of the Wide Field Camera 3 in the Hubble Space Telescope that provides
evidence consistent with the existence of a sensor effect analogous to the
brighter-fatter effect found in Charge-Coupled Devices. We propose a model in
which this effect could be understood as shifts in the effective pixel
boundaries, and discuss prospects of laboratory measurements to fully
characterize this effect.Comment: Accepted for publication in the Journal of Instrumentation (JINST).
Part of "Precision Astronomy with Fully Depleted CCDs" (Dec 1-2, 2016),
Brookhaven National Laboratory, Upton, NY, US
Vacuum effective action and inflation
We consider vacuum quantum effects in the Early Universe, which may lead to
inflation. The inflation is a direct consequence of the supposition that, at
high energies, all the particles can be described by the weakly interacting,
massless, conformally invariant fields. We discuss, from the effective field
theory point of view, the stability of inflation, transition to the FRW
solution, and also possibility to study metric and density perturbations.Comment: 6 pages, LaTeX, no figures. Contribution to the Proceedings of the X
Jorge Andre Swieca school in Particles and Fields. To be published in World
Scientifi
Pilot trial of fk 506 in the management of steroid-resistant nephrotic syndrome
Seven patients with steroid-resistant nephrotic syndrome were treated with FK 506 monotherapy. Four patients were children with focal sclerosing glomerulonephritis (FSGS). Three of these had evldence for chronic progressive renal disease consisting of interstitial fibrosis and tubular atrophy on pretreatment renal biopsies. Two patients had also failed cyclosporin A (CsA), two cyclophosphamide, and one chlorambucil prior to treatment with FK 506. Three patients were adults wlth mesangial proliferative. membranoproliferative, and membranous glomerulonephritis. Three patterns of response were noted: (1) a reduction in proteinuria to normal levels, (2) partial response (50% reduction) or; (3) no improvement. All patients except one experienced at least a 50% reduction in protein excretion at some time during FK 506 therapy. Two of the children and one adult reduced protein excretion to essentially normal values. One patient had no sustained reduction In Droteln excretion and is considered to be a treatment fallure, although her protein excretion was approximately 50% of pretreatment values intermittently. The drug was generally well tolerated. The most common side-effect was nephrotoxlclty, whlch was reversible. These encouraging results suggest that FK 506 monotherapy may be effective in controlling the proteinuria of somc patlents with steroid-resistant nephrotic syndrome The use of this drug may extend our understanding of the role of T lymphocytes and cytokines in the pathogenesls of glomerulonephritis. Further study of this agent In a larger population of patlents is warranted. © 1993 European Dialysis and Transplant Assoiation-European Renal Association
Quantum corrections to gravity and their implications for cosmology and astrophysics
The quantum contributions to the gravitational action are relatively easy to
calculate in the higher derivative sector of the theory. However, the
applications to the post-inflationary cosmology and astrophysics require the
corrections to the Einstein-Hilbert action and to the cosmological constant,
and those we can not derive yet in a consistent and safe way. At the same time,
if we assume that these quantum terms are covariant and that they have relevant
magnitude, their functional form can be defined up to a single free parameter,
which can be defined on the phenomenological basis. It turns out that the
quantum correction may lead, in principle, to surprisingly strong and
interesting effects in astrophysics and cosmology.Comment: 15 pages, LaTeX, WS style, contribution to the Proceedings of the
QFEXT-2011 conference in the Centro de Ciencias de Benasque Pedro Pasqual,
Spai
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