10,518 research outputs found
Six Peaks Visible in the Redshift Distribution of 46,400 SDSS Quasars Agree with the Preferred Redshifts Predicted by the Decreasing Intrinsic Redshift Model
The redshift distribution of all 46,400 quasars in the Sloan Digital Sky
Survey (SDSS) Quasar Catalog III, Third Data Release, is examined. Six Peaks
that fall within the redshift window below z = 4, are visible. Their positions
agree with the preferred redshift values predicted by the decreasing intrinsic
redshift (DIR) model, even though this model was derived using completely
independent evidence. A power spectrum analysis of the full dataset confirms
the presence of a single, significant power peak at the expected redshift
period. Power peaks with the predicted period are also obtained when the upper
and lower halves of the redshift distribution are examined separately. The
periodicity detected is in linear z, as opposed to log(1+z). Because the peaks
in the SDSS quasar redshift distribution agree well with the preferred
redshifts predicted by the intrinsic redshift relation, we conclude that this
relation, and the peaks in the redshift distribution, likely both have the same
origin, and this may be intrinsic redshifts, or a common selection effect.
However, because of the way the intrinsic redshift relation was determined it
seems unlikely that one selection effect could have been responsible for both.Comment: 12 pages, 12 figure, accepted for publication in the Astrophysical
Journa
The Distribution of Redshifts in New Samples of Quasi-stellar Objects
Two new samples of QSOs have been constructed from recent surveys to test the
hypothesis that the redshift distribution of bright QSOs is periodic in
. The first of these comprises 57 different redshifts among all
known close pairs or multiple QSOs, with image separations 10\arcsec,
and the second consists of 39 QSOs selected through their X-ray emission and
their proximity to bright comparatively nearby active galaxies. The redshift
distributions of the samples are found to exhibit distinct peaks with a
periodic separation of in identical to that claimed
in earlier samples but now extended out to higher redshift peaks and 4.47, predicted by the formula but never seen before. The periodicity
is also seen in a third sample, the 78 QSOs of the 3C and 3CR catalogues. It is
present in these three datasets at an overall significance level -
, and appears not to be explicable by spectroscopic or similar
selection effects. Possible interpretations are briefly discussed.Comment: submitted for publication in the Astronomical Journal, 15 figure
The increase in physical performance and gain in lean and fat mass occur in pre-pubertal children independent of mode of school transportation - one year - data from the prospective Pediatric Osteoporosis Prevention (POP)
A Quantum solution to the Byzantine agreement problem
We present a solution to an old and timely problem in distributed computing.
Like Quantum Key Distribution (QKD), quantum channels make it possible to
achieve taks classically impossible. However, unlike QKD, here the goal is not
secrecy but agreement, and the adversary is not outside but inside the game,
and the resources require qutrits.Comment: 4 pages, 1 figur
An Inexpensive Electronic Viewbox
An electronic viewbox is described that has been designed to meet the demand for a modestly priced soft-copy display for radiology. Issues associated with spatial resolution, intensity resolution, image magnification, user interface, digital communications and possible applications are discussed
Measurement of Interfacial Shear Mechanical Properties in Thermal Barrier Coating Systems by a Barb Pullout Method
A test technique has been developed to facilitate evaluation of the fracture characteristics of coatings and interfaces in thermal barrier coating (TBC) systems. The methodology has particular application in analyzing delamination crack growth, where crack propagation occurs under predominantly mode II loading. The technique has been demonstrated by quantitatively measuring the effective delamination fracture resistance of an electron-beam physical vapor deposition TBC
Nerve growth factor is expressed by postmitotic avian retinal horizontal cells and supports their survival during development in an autocrine mode of action.
Cell death in the developing retina is regulated, but so far little is known about what factors regulate the cell death. Several neurotrophic factors and receptors, including the neurotrophins and Trk receptors, are expressed during the critical time. We have studied the developing avian retina with respect to the role of nerve growth factor (NGF) in these processes. Our starting point for the work was that NGF and its receptor TrkA are expressed in a partially overlapping pattern in the inner nuclear layer of the developing retina. Our results show that TrkA and NGF-expressing cells are postmitotic. The first NGF-expressing cells were found on the vitreal side of the central region of E5.5–E6 retina. This pattern changed and NGF-expressing cells identified as horizontal cells were later confined to the external inner nuclear layer. We show that these horizontal cells co-express TrkA and NGF, unlike a subpopulation of amacrine cells that only expresses TrkA. In contrast to the horizontal cells, which survive, the majority of the TrkA-expressing amacrine cells die during a period of cell death in the inner nuclear layer. Intraocular injections of NGF protein rescued the dying amacrine cells and injection of antisense oligonucleotides for NGF that block its synthesis, caused death among the TrkA-expressing horizontal cells, which normally would survive. Our results suggest that NGF supports the survival of TrkA expressing avian horizontal cells in an autocrine mode of action in the retina of E10-E12 chicks. The cells co-express TrkA and NGF and the role for NGF is to maintain the TrkA-expressing horizontal cells. The TrkA-expressing amacrine cells are not supported by NGF and subsequently die. In addition to the effect on survival, our results suggest that NGF plays a role in horizontal cell plasticity
Interaction-free measurement and forward scattering
Interaction-free measurement is shown to arise from the forward-scattered
wave accompanying absorption: a "quantum silhouette" of the absorber.
Accordingly, the process is not free of interaction. For a perfect absorber the
forward-scattered wave is locked both in amplitude and in phase. For an
imperfect one it has a nontrivial phase of dynamical origin (``colored
silhouette"), measurable by interferometry. Other examples of quantum
silhouettes, all controlled by unitarity, are briefly discussed.Comment: 4 pages in RevTex + 1 figure in eps; submitted to Phys. Rev. A since
09Jan98; now update
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