22,939 research outputs found
A pilot program for selecting, editing, and disseminating engineering and scientific educational subject matter from NASA technical reports Quarterly report, Mar. 1 - May 31, 1968
Statistics on NASA program of disseminating educational monographs and visual briefs to industries and universitie
Multi-channel GaAs-based planar gunn diodes
We present a multi-channel GaAs-based planar Gunn
diode. By introducing extra channels, the output RF power has
been significantly improved compared to single-channel GaAsbased
planar Gunn diodes. For a 1.14 μm length and 60 μm wide
device, the highest power achieved was approximately -4 dBm
operating in fundamental mode at 109 GHz, and -26.6 dBm at its
second-harmonic at 218 GHz
Experimentally estimated dead space for GaAs and InP based planar Gunn diodes
The authors would like to thank the staff of the James Watt Nanofabrication Centre at the University of Glasgow for help in fabricating the devices which is reported in this paper. ‘Part of this work was supported by ESPRC through EP/H011862/ 1, and EP/H012966/1.Peer reviewedPublisher PD
Spin Torque Dynamics with Noise in Magnetic Nano-System
We investigate the role of equilibrium and nonequilibrium noise in the
magnetization dynamics on mono-domain ferromagnets. Starting from a microscopic
model we present a detailed derivation of the spin shot noise correlator. We
investigate the ramifications of the nonequilibrium noise on the spin torque
dynamics, both in the steady state precessional regime and the spin switching
regime. In the latter case we apply a generalized Fokker-Planck approach to
spin switching, which models the switching by an Arrhenius law with an
effective elevated temperature. We calculate the renormalization of the
effective temperature due to spin shot noise and show that the nonequilibrium
noise leads to the creation of cold and hot spot with respect to the noise
intensity.Comment: 10 pages, 7 figure
Long-duration exercise at moderate work loads
Metabolic effects of long duration exercise at moderate work loads including tables of heart rate, rectal temperature, minute volume, water balance, and respiratory quotien
Sonic levitation apparatus
A sonic levitation apparatus is disclosed which includes a sonic transducer which generates acoustical energy responsive to the level of an electrical amplifier. A duct communicates with an acoustical chamber to deliver an oscillatory motion of air to a plenum section which contains a collimated hole structure having a plurality of parallel orifices. The collimated hole structure converts the motion of the air to a pulsed. Unidirectional stream providing enough force to levitate a material specimen. Particular application to the production of microballoons in low gravity environment is discussed
A 10 kpc Scale Seyfert Galaxy Outflow: HST/COS Observations of IRAS F22456-5125
We present analysis of the UV-spectrum of the low-z AGN IRAS-F22456-5125
obtained with the Cosmic Origins Spectrograph on board the Hubble Space
Telescope. The spectrum reveals six main kinematic components, spanning a range
of velocities of up to 800 km s-1, which for the first time are observed in
troughs associated with CII, CIV, NV, SiII, SiIII, SiIV and SIV. We also obtain
data on the OVI troughs, which we compare to those available from an earlier
FUSE epoch. Column densities measured from these ions allow us to derive a
well-constrained photoionization solution for each outflow component. Two of
these kinematic components show troughs associated with transitions from
excited states of SiII\ and CII. The number density inferred from these
troughs, in combination with the deduced ioinization parameter, allows us to
determine the distance to these outflow components from the central source. We
find these components to be at a distance of ~ 10 kpc. The distances and the
number densities derived are consistent with the outflow being part of a
galactic wind.Comment: 52 pages, 15 figures, accepted for publication in ApJ March 25, 201
Investigating Heating and Cooling in the BCS & B55 Cluster Samples
We study clusters in the BCS cluster sample which are observed by Chandra and
are more distant than redshift, z>0.1. We select from this subsample the
clusters which have both a short central cooling time and a central temperature
drop, and also those with a central radio source. Six of the clusters have
clear bubbles near the centre. We calculate the heating by these bubbles and
express it as the ratio r_heat/r_cool=1.34+/-0.20. This result is used to
calculate the average size of bubbles expected in all clusters with central
radio sources. In three cases the predicted bubble sizes approximately match
the observed radio lobe dimensions.
We combine this cluster sample with the B55 sample studied in earlier work to
increase the total sample size and redshift range. This extended sample
contains 71 clusters in the redshift range 0<z<0.4. The average distance out to
which the bubbles offset the X-ray cooling in the combined sample is at least
r_heat/r_cool=0.92+/-0.11. The distribution of central cooling times for the
combined sample shows no clusters with clear bubbles and t_cool>1.2Gyr. An
investigation of the evolution of cluster parameters within the redshift range
of the combined samples does not show any clear variation with redshift.Comment: 12 pages, 9 figures, accepted for publication in MNRA
A QTL for osteoporosis detected in an F2 population derived from White Leghorn chicken lines divergently selected for bone index
Osteoporosis, resulting from progressive loss of structural bone during the period of egg-laying in hens, is associated with an increased susceptibility to bone breakage. To study the genetic basis of bone strength, an F cross was produced from lines of hens that had been divergently selected for bone index from a commercial pedigreed White Leghorn population. Quantitative trait loci (QTL) affecting the bone index and component traits of the index (tibiotarsal and humeral strength and keel radiographic density) were mapped using phenotypic data from 372 F individuals in 32 F families. Genotypes for 136 microsatellite markers in 27 linkage groups covering ∼80% of the genome were analysed for association with phenotypes using within-family regression analyses. There was one significant QTL on chromosome 1 for bone index and the component traits of tibiotarsal and humeral breaking strength. Additive effects for tibiotarsal breaking strength represented 34% of the trait standard deviation and 7.6% of the phenotypic variance of the trait. These QTL for bone quality in poultry are directly relevant to commercial populations
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