48,551 research outputs found
Observations of the Gallery Habits of \u3ci\u3eTrypodendron Retusum\u3c/i\u3e (Coleoptera: Scolytidae) Infesting Aspen in Central Michigan
A monogamous pair of adult Trypodendron retusum construct a gallery system consisting of an entrance tunnel and from two to five lateral tunnels into the sapwood of aspen. Inoculation of the mutualistic fungus Ambrosiella ferruginea by the female beetle, was followed by oviposition in shallow egg cradles. Two instars were observed as the larvae enlarged their cradles. The number of cradles per gallery system was correlated to the length of the gallery system. Progeny adults with a sex ratio of approximately 1:1 emerged from late June to early August to overwinter in the litter
Study reveals effect of aluminum on saturation moment of Fe-Ni alloys
Study of saturation magnetization, important in the investigation of the electronic structure of alloys, reveals the effect of aluminum on the saturation moments of iron-nickel alloys. The saturation magnetizations were extrapolated to the absolute zero of temperature for calculating average atomic moments
Magnetic fields near the peripheries of galactic discs
Magnetic fields are observed beyond the peripheries of optically detected
galactic discs, while numerical models of their origin and the typical
magnitudes are still absent. Previously, studies of galactic dynamo have
avoided considering the peripheries of galactic discs because of the very
limited (though gradually growing) knowledge about the local properties of the
interstellar medium. Here we investigate the possibility that magnetic fields
can be generated in the outskirts of discs, taking the Milky Way as an example.
We consider a simple evolving galactic dynamo model in the "no-z" formulation,
applicable to peripheral regions of galaxies, for various assumptions about the
radial and vertical profiles of the ionized gas disc. The magnetic field may
grow as galaxies evolve, even in the more remote parts of the galactic disc,
out to radii of 15 to 30 kpc, becoming substantial after times of about 10 Gyr.
This result depends weakly on the adopted distributions of the half thickness
and surface density of the ionized gas component. The model is robust to
changes in the amplitude of the initial field and the position of its maximum
strength. The magnetic field in the remote parts of the galactic disc could be
generated in situ from a seed field by local dynamo action. Another possibility
is field production in the central regions of a galaxy, followed by transport
to the disc's periphery by the joint action of the dynamo and turbulent
diffusivity. Our results demonstrate the possibilities for the appearance and
strengthening of magnetic fields at the peripheries of disc galaxies and
emphasize the need for observational tests with new and anticipated radio
telescopes (LOFAR, MWA, and SKA).Comment: 8 pages, 5 figure
The CF6 Jet Engine Performance Improvement - Low Pressure Turbine Active Clearance Control
A low pressure turbine (LPT) active clearance control (ACC) cooling system was developed to reduce the fuel consumption of current CF6-50 turbofan engines for wide bodied commercial aircraft. The program performance improvement goal of 0.3% delta sfc was determined to be achievable with an improved impingement cooling system. The technology enables the design of an optimized manifold and piping system which is capable of a performance gain of 0.45% delta sfc
Aphidophagous Coccinellids in Alfalfa, Small Grains, and Maize in Eastern South Dakota
In a 13-year study of aphidophagous coccinellids associated with alfalfa (Medicago sativa), maize (Zea mays), and small grain crops in eastern South Dakota, the following species were consistently associated with the crops: Hippodamia convergens, H. tredecimpunctata tibialis, H. parenthesis, Coleomegilla maculata lengi, Coccinella transversoguttata richardsoni, Cycloneda munda, and Adalia bipunctata. All species except A. bipunctata were associated with each of the three crops, while A. bipunctata occurred only in maize. Relative abundances of each species varied among crops and among years. Although only seven species were associated with the crops, additional species were captured on sticky traps stationed adjacent to sampled fields. The species diversity of immature coccinellids did not differ among crops but did differ among years. The diversity of adults differed among crops and years. The site from which samples were taken had no influence on the diversity of immatures or adults. Species relative abundances in alfalfa and small grains were more similar to each other than they were to relative abundances in maize
Magnetic field reversals and galactic dynamos
We argue that global magnetic field reversals similar to those observed in
the Milky Way occur quite frequently in mean-field galactic dynamo models that
have relatively strong, random, seed magnetic fields that are localized in
discrete regions. The number of reversals decreases to zero with reduction of
the seed strength, efficiency of the galactic dynamo and size of the spots of
the seed field. A systematic observational search for magnetic field reversals
in a representative sample of spiral galaxies promises to give valuable
information concerning seed magnetic fields and, in this way, to clarify the
initial stages of galactic magnetic field evolution
Hybrid Atom--Photon Quantum Gate in a Superconducting Microwave Resonator
We propose a novel hybrid quantum gate between an atom and a microwave photon
in a superconducting coplanar waveguide cavity by exploiting the strong
resonant microwave coupling between adjacent Rydberg states. Using
experimentally achievable parameters gate fidelities are possible on
sub-s timescales for waveguide temperatures below 40 mK. This provides a
mechanism for generating entanglement between two disparate quantum systems and
represents an important step in the creation of a hybrid quantum interface
applicable for both quantum simulation and quantum information processing.Comment: 4 pages, 4 figure
In good company: risk, security and choice in young people's drug decisions
This article draws on original empirical research with young people to question the degree to which 'individualisation of risk', as developed in the work of Beck and Giddens, adequately explains the risks young people bear and take. It draws on alternative understandings and critiques of 'risk' not to refute the notion of the reflexive individual upon which 'individualisation of risk' is based but to re-read that reflexivity in a more hermeneutic way. It explores specific risk-laden moments â young people's drug use decisions â in their natural social and cultural context of the friendship group. Studying these decisions in context, it suggests, reveals the meaning of 'risk' to be not given, but constructed through group discussion, disagreement and consensus and decisions taken to be rooted in emotional relations of trust, mutual accountability and common security. The article concludes that 'the individualisation of risk' fails to take adequate account of the significance of intersubjectivity in risk-decisions. It argues also that addressing the theoretical overemphasis on the individual bearer of risk requires not only further empirical testing of the theory but appropriate methodological reflection
Prospective cognitions in anxiety and depression: Replication and methodological extension
The present study presents a replication and methodological extension of MacLeod, Tata, Kentish, and Jacobsen (1997) with a nonclinical sample, using future-directed imagery to assess prospective cognitions. Results showed that only anxiety (but not depression) was related to enhanced imagery for future negative events. Both anxiety and depression showed significant zero-order correlations with reduced imagery for future positive events. However, when the overlap between anxiety and depression was controlled for, only depression (but not anxiety) showed a unique association with reduced imagery for positive events. Implications of these findings for cognitive models of anxiety and depression are discussed
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