6,569 research outputs found
Evaluation of range and distortion tolerance for high Mach number transonic fan stages. Task 2: Performance of a 1500-foot-per-second tip speed transonic fan stage with variable geometry inlet guide vanes and stator
A 0.5 hub/tip radius ratio compressor stage consisting of a 1500 ft/sec tip speed rotor, a variable camber inlet guide vane and a variable stagger stator was designed and tested with undistorted inlet flow, flow with tip radial distortion, and flow with 90 degrees, one-per-rev, circumferential distortion. At the design speed and design IGV and stator setting the design stage pressure ratio was achieved at a weight within 1% of the design flow. Analytical results on rotor tip shock structure, deviation angle and part-span shroud losses at different operating conditions are presented. The variable geometry blading enabled efficient operation with adequate stall margin at the design condition and at 70% speed. Closing the inlet guide vanes to 40 degrees changed the speed-versus-weight flow relationship along the stall line and thus provided the flexibility of operation at off-design conditions. Inlet flow distortion caused considerable losses in peak efficiency, efficiency on a constant throttle line through design pressure ratio at design speed, stall pressure ratio, and stall margin at the 0 degrees IGV setting and high rotative speeds. The use of the 40 degrees inlet guide vane setting enabled partial recovery of the stall margin over the standard constant throttle line
Bumpy Black Holes in Alternate Theories of Gravity
We generalize the bumpy black hole framework to allow for alternative theory
deformations. We construct two model-independent parametric deviations from the
Kerr metric: one built from a generalization of the quasi-Kerr and bumpy
metrics and one built directly from perturbations of the Kerr spacetime in
Lewis-Papapetrou form. We find the conditions that these "bumps" must satisfy
for there to exist an approximate second-order Killing tensor so that the
perturbed spacetime still possesses three constants of the motion (a deformed
energy, angular momentum and Carter constant) and the geodesic equations can be
written in first-order form. We map these parameterized metrics to each other
via a diffeomorphism and to known analytical black hole solutions in
alternative theories of gravity. The parameterized metrics presented here serve
as frameworks for the systematic calculation of extreme-mass ratio inspiral
waveforms in parameterized non-GR theories and the investigation of the
accuracy to which space-borne gravitational wave detectors can constrain such
deviations.Comment: 17 pages, replaced with version published in Phys. Rev.
A strong immune response in young adult honeybees masks their increased susceptibility to infection compared to older bees
Honeybees, Apis mellifera, show age-related division of labor in which young adults perform maintenance ("housekeeping") tasks inside the colony before switching to outside foraging at approximately 23 days old. Disease resistance is an important feature of honeybee biology, but little is known about the interaction of pathogens and age-related division of labor. We tested a hypothesis that older forager bees and younger "house" bees differ in susceptibility to infection. We coupled an infection bioassay with a functional analysis of gene expression in individual bees using a whole genome microarray. Forager bees treated with the entomopathogenic fungus Metarhizium anisopliae s.l. survived for significantly longer than house bees. This was concomitant with substantial differences in gene expression including genes associated with immune function. In house bees, infection was associated with differential expression of 35 candidate immune genes contrasted with differential expression of only two candidate immune genes in forager bees. For control bees (i.e. not treated with M. anisopliae) the development from the house to the forager stage was associated with differential expression of 49 candidate immune genes, including up-regulation of the antimicrobial peptide gene abaecin, plus major components of the Toll pathway, serine proteases, and serpins. We infer that reduced pathogen susceptibility in forager bees was associated with age-related activation of specific immune system pathways. Our findings contrast with the view that the immunocompetence in social insects declines with the onset of foraging as a result of a trade-off in the allocation of resources for foraging. The up-regulation of immune-related genes in young adult bees in response to M. anisopliae infection was an indicator of disease susceptibility; this also challenges previous research in social insects, in which an elevated immune status has been used as a marker of increased disease resistance and fitness without considering the effects of age-related development
Electronic structure study by means of X-ray spectroscopy and theoretical calculations of the "ferric star" single molecule magnet
The electronic structure of the single molecule magnet system
M[Fe(L)2]3*4CHCl3 (M=Fe,Cr; L=CH3N(CH2CH2O)2) has been studied using X-ray
photoelectron spectroscopy, X-ray absorption spectroscopy, soft X-ray emission
spectroscopy, and density functional calculations. There is good agreement
between theoretical calculations and experimental data. The valence band mainly
consists of three bands between 2 eV and 30 eV. Both theory and experiments
show that the top of the valence band is dominated by the hybridization between
Fe 3d and O 2p bands. From the shape of the Fe 2p spectra it is argued that Fe
in the molecule is most likely in the 2+ charge state. Its neighboring atoms
(O,N) exhibit a magnetic polarisation yielding effective spin S=5/2 per iron
atom, giving a high spin state molecule with a total S=5 effective spin for the
case of M = Fe.Comment: Fig.2 replaced as it will appear in J. Chem. Phy
A method for measuring acid mucopolysaccharides in serum-containing tissue culture media
The details of a simple, relatively rapid method for measuring uronic acid-containing acid mucopolysaccharides in protein-rich tissue culture media are presented. The procedure would appear to be most useful in those situations where hyaluronic acid and chondroitin sulfate are the primary mucopolysaccharides present.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32374/1/0000449.pd
EUV ionization of pure He nanodroplets: Mass-correlated photoelectron imaging, Penning ionization and electron energy-loss spectra
The ionization dynamics of pure He nanodroplets irradiated by EUV radiation
is studied using Velocity-Map Imaging PhotoElectron-PhotoIon COincidence
(VMI-PEPICO) spectroscopy. We present photoelectron energy spectra and angular
distributions measured in coincidence with the most abundant ions He+, He2+,
and He3+. Surprisingly, below the autoionization threshold of He droplets we
find indications for multiple excitation and subsequent ionization of the
droplets by a Penning-like process. At high photon energies we evidence
inelastic collisions of photoelectrons with the surrounding He atoms in the
droplets
Penning ionization of doped helium nanodroplets following EUV excitation
Helium nanodroplets are widely used as a cold, weakly interacting matrix for
spectroscopy of embedded species. In this work we excite or ionize doped He
droplets using synchrotron radiation and study the effect onto the dopant atoms
depending on their location inside the droplets (rare gases) or outside at the
droplet surface (alkali metals). Using photoelectron-photoion coincidence
imaging spectroscopy at variable photon energies (20-25 eV), we compare the
rates of charge-transfer to Penning ionization of the dopants in the two cases.
The surprising finding is that alkali metals, in contrast to the rare gases,
are efficiently Penning ionized upon excitation of the (n=2)-bands of the host
droplets. This indicates rapid migration of the excitation to the droplet
surface, followed by relaxation, and eventually energy transfer to the alkali
dopants
Rapid response to abalone virus depletion in western Victoria: information acquisition and reef code assessment
Future management of disease-affected abalone must adapt to the changing circumstances, and adopting a precautionary approach will allow maximum potential for stock recovery. This approach is mandated by the observation that no documented examples are known of abalone populations recovering from catastrophic impacts such as have occurred in the abalone fisheries of Victoria's Western and Central zones. Indeed the balance of international evidence points towards the contrary, so these fisheries are in dangerous territory. This need not mean that recovery cannot occur.
However, the modelling results from this project confirm the above precautionary view and suggest that unless it is known with certainty that disease-induced mortalities have been moderate (less than 40%), then any resumption of fishing in the near term risks the future of the fishery. Acquisition of accurate mortality data is the only basis upon which fishing can recommence in the short term (within 5 years) and in many instances, such as for some among those reefs considered in our study, the opportunity has passed. The simulation results provide guidance, but their validity is conditional on myriad assumptions as well as on the accuracy of data employed. We already know that catches early in the fishery’s history were higher than reported officially, but how much higher is conjecture. Growth is highly variable over small spatial scales and feedback effects from reduced abundance together with changed size structure and persistence of habitat will play roles in determining the rate, if any, of recovery. The extent of the contemporary illegal catch is uncertain, particularly given the unprecedented closure of the fisheries. The results show that even small illegal catches can significantly degrade recovery where the viral impact is high, with clear implications for the enforcement aspects of managing these fisheries
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