1,178 research outputs found
A Key to Container-Breeding Mosquitoes of Michigan (Diptera: Cllllcidae), With Notes on Their Biology
An illustrated key to larvae and notes on the biology of container-breeding mosquitoes of Michigan are presented. Two species included in the key. Aedes aegypti and Aedes albopictus. are not endemic in Michigan, but occasional introductions could occur with commercial shipments of scrap tires or other containers
Larval Ecology of Some Lower Michigan Black Flies (Diptera: Simuliidae) With Keys to the Immature Stages
The species composition, succession, and seasonal abundance of -immature simuliids ocmrrhg in the Rose Lake Wildlife Research Area in lower Michigan are presented. Selected physical and chemical characteristics of streams in the above area were examined and compared in relation to faunal distributions. Comparisons of species differences between permanent and temporary streams were made utilizing the functional group concept based on feeding mechanisms.
Keys and illustrations are presented for the identiiication of larvae and pupae of four genera (Prosimulium, Simulium, Stegopterna, Cnephia) and 19 species of Simuliidae known to occur in lower Michigan. Two species, Cnephia ornithophilia and Simulium vemum, were recorded for the first time in Michigan
Supermassive Black Holes in Active Galactic Nuclei. I. The Consistency of Black Hole Masses in Quiescent and Active Galaxies
We report the first results of a program to measure accurate stellar velocity
dispersions in the bulges of the host galaxies of active galactic nuclei (AGNs)
for which accurate black hole (BH) masses have been determined via
reverberation mapping. We find good agreement between BH masses obtained from
reverberation mapping, and from the M(BH) - sigma relation as defined by
quiescent galaxies, indicating a common relationship between active and
quiescent black holes and their large-scale environments.Comment: Submitted to ApJ
Crew Exploration Vehicle Ascent Abort Overview
One of the primary design drivers for NASA's Crew Exploration Vehicle (CEV) is to ensure crew safety. Aborts during the critical ascent flight phase require the design and operation of CEV systems to escape from the Crew Launch Vehicle and return the crew safely to the Earth. To accomplish this requirement of continuous abort coverage, CEV ascent abort modes are being designed and analyzed to accommodate the velocity, altitude, atmospheric, and vehicle configuration changes that occur during ascent. The analysis involves an evaluation of the feasibility and survivability of each abort mode and an assessment of the abort mode coverage. These studies and design trades are being conducted so that more informed decisions can be made regarding the vehicle abort requirements, design, and operation. This paper presents an overview of the CEV, driving requirements for abort scenarios, and an overview of current ascent abort modes. Example analysis results are then discussed. Finally, future areas for abort analysis are addressed
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Spatial and Temporal Variability of Macroinvertebrates in Spawning and Non-Spawning Habitats during a Salmon Run in Southeast Alaska
Spawning salmon create patches of disturbance through redd digging which can reduce macroinvertebrate abundance and biomass in spawning habitat. We asked whether displaced invertebrates use non-spawning habitats as refugia in streams. Our study explored how the spatial and temporal distribution of macroinvertebrates changed during a pink salmon (Oncorhynchus gorbuscha) spawning run and compared macroinvertebrates in spawning (riffle) and non-spawning (refugia) habitats in an Alaskan stream. Potential refugia included: pools, stream margins and the hyporheic zone, and we also sampled invertebrate drift. We predicted that macroinvertebrates would decline in riffles and increase in drift and refugia habitats during salmon spawning. We observed a reduction in the density, biomass and taxonomic richness of macroinvertebrates in riffles during spawning. There was no change in pool and margin invertebrate communities, except insect biomass declined in pools during the spawning period. Macroinvertebrate density was greater in the hyporheic zone and macroinvertebrate density and richness increased in the drift during spawning. We observed significant invertebrate declines within spawning habitat; however in non-spawning habitat, there were less pronounced changes in invertebrate density and richness. The results observed may be due to spawning-related disturbances, insect phenology, or other variables. We propose that certain in-stream habitats could be important for the persistence of macroinvertebrates during salmon spawning in a Southeast Alaskan stream
Supermassive Black Holes in Active Galactic Nuclei. II. Calibration of the M-sigma Relationship for AGNs
We calibrate reverberation-based black hole masses in active galactic nuclei
(AGNs) by using the correlation between black hole mass, M, and bulge/spheroid
stellar velocity dispersion, sigma. We use new measurements of sigma for 6 AGNs
and published velocity dispersions for 10 others, in conjunction with improved
reverberation mapping results, to determine the scaling factor required to
bring reverberation-based black hole masses into agreement with the quiescent
galaxy M-sigma relationship. The scatter in the AGN black hole masses is found
to be less than a factor of 3. The current observational uncertainties preclude
use of the scaling factor to discriminate between broad-line region models.Comment: 16 pages, including 3 figures. Accepted for publication in Ap
The Black Hole Mass of NGC 4151: Comparison of Reverberation Mapping and Stellar Dynamical Measurements
We present a stellar dynamical estimate of the black hole (BH) mass in the
Seyfert 1 galaxy, NGC 4151. We analyze ground-based spectroscopy as well as
imaging data from the ground and space, and we construct 3-integral
axisymmetric models in order to constrain the BH mass and mass-to-light ratio.
The dynamical models depend on the assumed inclination of the kinematic
symmetry axis of the stellar bulge. In the case where the bulge is assumed to
be viewed edge-on, the kinematical data give only an upper limit to the mass of
the BH of ~4e7 M_sun (1 sigma). If the bulge kinematic axis is assumed to have
the same inclination as the symmetry axis of the large-scale galaxy disk (i.e.,
23 degrees relative to the line of sight), a best-fit dynamical mass between
4-5e7 M_sun is obtained. However, because of the poor quality of the fit when
the bulge is assumed to be inclined (as determined by the noisiness of the
chi^2 surface and its minimum value), and because we lack spectroscopic data
that clearly resolves the BH sphere of influence, we consider our measurements
to be tentative estimates of the dynamical BH mass. With this preliminary
result, NGC 4151 is now among the small sample of galaxies in which the BH mass
has been constrained from two independent techniques, and the mass values we
find for both bulge inclinations are in reasonable agreement with the recent
estimate from reverberation mapping (4.57[+0.57/-0.47]e7 M_sun) published by
Bentz et al.Comment: 20 pages, including 11 low-res figures. Accepted for publication in
ApJ. High resolution version available upon reques
The nutritional ecology of larvae of Alsophila pometaria and Anisota senatoria feeding on early- and late-season oak foliage
The larvae of Alsophila pometaria (Harr.), feeding on the young foliage of oak, has a higher relative growth rate (RGR) and relative nitrogen accumulation rate (RNAR) than the larvae of Anisota senatoria (J. E. Smith), feeding on the mature foliage of oak. Although the young oak foliage is more efficiently digested by A. pometaria (higher AD's), it is not more efficiently assimilated and used for growth (no difference in ECI's). Thus, the higher growth rate of A. pometaria is due entirely to a higher consumption rate (RCR and RNCR). Young foliage is significantly higher in nitrogen and water than mature foliage, but phenol and tannin levels are comparable in young and old foliage. A. pometaria consumes the foliage of different oak species at the same rate, independent of nitrogen content, while A. senatoria increases its consumption rate in response to decreased nitrogen levels. As a result, the growth rate of A. pometaria is directly related to leaf nitrogen content, while the growth rate of A. senatoria is independent of leaf nitrogen. The two species of insects have digestive systems that are very similar biochemically, and that are well-designed for effective protein digestion. Tannins and phenols do not influence the nutrional indices of either species. We suggest that the major benefit of spring feeding is the availability of succulent, high-nitrogen foliage, and not the avoidance of high-tannin foliage. The spring feeder appears to have a feeding strategy that favors rapid growth at the expense of efficiency, while the late summer feeder has a strategy that favors efficiency over rate. Alimentées sur feuillage jeune de chêne, les chenilles d' Alsophila pometaria avaient un taux relatif de croissance (RGR) et un taux relatif d'accumulation d'azote (RNAR) plus élevés que les chenilles d' Anisota senatoria alimentées sur feuillage mûr de chêne. Bien que le jeune feuillage soit plus efficacement digéré par A. pometaria (AD plus élevé), il n'est pas assimilé et utilisé pour la croissance avec de meilleurs rendements (les ECI ne sont pas différents). Ainsi le taux de croissance plus élevé d' A. pometaria est dû entièrement à un taux de consommation plus important (RCR et RNCR). Le feuillage jeune est significativement plus riche en azote et en eau que le feuillage mûr, mais les niveaux de phénol et de tanins sont les mêmes. A pometaria consomme les feuilles de différentes espèces de chênes au même taux, indépendamment de la teneur en azote, tandis que A. senatoria accroît sa consommation en réponse à une diminution de la teneur en azote. Il en résulte que le taux de croissance d' A. pometaria dépend directement de la teneur en azote des feuilles, tandis que celui d' A. senatoria en est indépendant. Les systèmes digestifs des deux insectes sont biochimiquement semblables et sont efficaces pour la digestion des protéines. Les tanins et les phénols n'influent pas sur les indices nutritionnels de ces deux espèces. Nous estimons que le principal intérêt de l'alimentation printanière est la disponibilité en feuillage succulent, riche en azote, et non l'absence de feuilles à haute teneur en tanin. L'alimentation printanière semble correspondre à une strategie alimentaire qui favorise la croissance aux dépens de l'efficacité tandis que l'alimentation en fin d'été est une stratégie qui favorise l'efficacité sur la rapidité.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42708/1/10667_2004_Article_BF00217527.pd
The Dark Matter Distribution in the Central Regions of Galaxy Clusters: Implications for CDM
We have undertaken a spectroscopic survey of gravitational arcs in a
carefully chosen sample of six clusters each containing a dominant brightest
cluster galaxy. We use these systems to study the relative distributions of
dark and baryonic material in the central regions. Three clusters present both
radial and tangential arcs and provide particularly strong constraints on the
mass profiles, whereas the other three display only tangential arcs and act as
a control set. We analyze stellar velocity dispersion data for the brightest
cluster galaxies in conjunction with the arc redshifts and lens models to
constrain the dark and baryonic mass profiles jointly. For the systems
containing radial arcs we find that the inner dark matter density profile is
consistent with a 3-D distribution, rho_{DM} propto r^-beta, with logarithmic
slope =0.52^{+0.05}_{-0.05} (68% CL). Similarly, we find that the
tangential arc sample gives an upper limit, beta<0.57 (99% CL). Taking the 6
clusters together, the mean dark matter distribution is quite inconsistent with
the standard Navarro, Frenk & White (1997) value, beta=1.0, at >99% confidence.
In addition, we find considerable cosmic scatter in the beta (Delta beta ~0.3)
values of the radial arc sample. We find no evidence that systems with radial
arcs preferentially yield flatter dark matter profiles as might be expected if
they were a biased subset. We discuss the validity of our 1-D mass
reconstruction method and verify its conclusions by comparing with results of a
more rigorous ray-tracing lensing code. Our results extend and strengthen the
earlier conclusions presented by Sand et al. (2002) and suggest the
relationship between dark and visible matter in the cores of clusters is more
complex than anticipated from recent simulations. (abridged)Comment: 52 pages, 11 figures, preprint format, Accepted for publication in
Ap
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