32,499 research outputs found
Video photographic considerations for measuring the proximity of a probe aircraft with a smoke seeded trailing vortex
Considerations for acquiring and analyzing 30 Hz video frames from charge coupled device (CCD) cameras mounted in the wing tips of a Beech T-34 aircraft are described. Particular attention is given to the characterization and correction of optical distortions inherent in the data
Stink Bugs (Hemiptera: Heteroptera: Pentatomidae) of Minnesota: An Annotated Checklist and New State Records
Pentatomidae have been relatively poorly documented in Minnesota. Based on literature and museum records, an annotated checklist of the Pentatomidae of Minnesota was created. State-level and county-level records for Minnesota and the distribution of each species in North America are provided. Fifty-one species of Pentatomidae (12 Asopinae, 37 Pentatominae, and 2 Podopinae) are recorded for Minnesota. Of this total, 15 species are newly recorded for the state. Knowledge of the fauna of Pentatomidae in Minnesota will be important for providing baseline data for monitoring of potential shifts in the fauna resulting from the invasions of exotic Pentatomidae. Furthermore, a list of native Pentatomidae will be necessary for monitoring non-target impacts, if classical biological control is implemented for management of exotic Pentatomidae
Continuity properties of a factor of Markov chains
Starting from a Markov chain with a finite alphabet, we consider the chain
obtained when all but one symbol are undistinguishable for the practitioner. We
study necessary and sufficient conditions for this chain to have continuous
transition probabilities with respect to the past
Finite-Temperature Properties of Ba(Zr,Ti)O Relaxors From First Principles
A first-principles-based technique is developed to investigate properties of
Ba(Zr,Ti)O relaxor ferroelectrics as a function of temperature. The use of
this scheme provides answers to important, unresolved and/or controversial
questions, such as: what do the different critical temperatures usually found
in relaxors correspond to? Do polar nanoregions really exist in relaxors? If
yes, do they only form inside chemically-ordered regions? Is it necessary that
antiferroelectricity develops in order for the relaxor behavior to occur? Are
random fields and random strains really the mechanisms responsible for relaxor
behavior? If not, what are these mechanisms? These {\it ab-initio-based}
calculations also leads to a deep microscopic insight into relaxors.Comment: 3 figures + Supplemen
Unequal incomes, unequal outcomes? Economic inequality and measures of well-being: summary of observations and recommendations
This is a summary of the proceedings of the conference "Unequal incomes, unequal outcomes? Economic inequality and measures of well-being." The conference was held at the Federal Reserve Bank of New York on May 7, 1999. The conference was organized to focus on the evolution of more direct measures of the material well-being of Americans. Of particular concern was the impact of income inequality on trends in health, housing, and crime victimization. Conference participants also examined some of the changes in policymakers' responses to these trends, especially in the areas of education financing and local governance. Finally, the participants discussed efforts to evaluate the social consequences of policy reforms and offered some guidelines on the best direction for future research and policy initiatives.Income distribution ; Public policy
An ellipsometer with variable angle of incidence for studies in ultrahigh vacuum
The windows for the vacuum chamber are incorporated into the optical bench system by means of flexible bellows which allow measurements to be made over a large range of angle of incidence, one of which is chosen so that maximum sensitivity is obtained. The principal angle of incidence was determined, and straightforward corrections for strain birefringence of vacuum chamber windows were made. Atomically clean surfaces of sodium chloride and lithium fluoride were investigated to verify the performance of the system. Submonolayer and monolayer coverage of water on these surfaces could be detected. On cleavage planes of NaCl, a first monolayer of adsorbed water is complete at about one torr only
Imaging the Molecular Gas in A z=3.9 Quasar Host Galaxy at 0\farcs3 Resolution: A Central, Sub-Kilparsex Scale Star Formation Reservoir in APM 08279+5255
We have mapped the molecular gas content in the host galaxy of the strongly lensed high-redshift quasar APM 08279+5255 (z = 3.911) with the Very Large Array at 0\farcs3 resolution. The CO(J = 1➝0) emission is clearly resolved in our maps. The CO(J = 1➝0) line luminosity derived from these maps is in good agreement with a previous single-dish measurement. In contrast to previous interferometer-based studies, we find that the full molecular gas reservoir is situated in two compact peaks separated by ≲0\farcs4. Our observations reveal, for the first time, that the emission from cold molecular gas is virtually co-spatial with the optical/near-infrared continuum emission of the central active galactic nucleus (AGN) in this source. This striking similarity in morphology indicates that the molecular gas is situated in a compact region close to the AGN. Based on the high-resolution CO maps, we present a revised model for the gravitational lensing in this system, which indicates that the molecular gas emission is magnified by only a factor of 4 (in contrast to previously suggested factors of 100). This model suggests that the CO is situated in a circumnuclear disk of ~550 pc radius that is possibly seen at an inclination of ≲25°, i.e., relatively close to face-on. From the CO luminosity, we derive a molecular gas mass of Mgas = 1.3x10^11 M☉ for this galaxy. From the CO structure and linewidth, we derive a dynamical mass of M dyn sin^2 i = 4.0x10^10 M☉. Based on a revised mass estimate for the central black hole of Mbh = 2.3x10^10 M☉ and the results of our molecular line study, we find that the mass of the stellar bulge of APM 08279+5255 falls short of the local M BH-σbulge relationship of nearby galaxies by more than an order of magnitude, lending support to recent suggestions that this relation may evolve with cosmic time and/or change toward the high-mass end
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