105 research outputs found
An interim report on the NTS-2 solar cell experiment
Data obtained from the fourteen solar cell modules on the NTS-2 satellite are presented together with a record of panel temperature and sun inclination. The following flight data are discussed: (1) state of the art solar cell configurations which embody improvements in solar cell efficiency through new silicon surface and bulk technology, (2) improved coverslip materials and coverslip bonding techniques, (3) short and long term effects of ultraviolet rejection filters vs. no filters on the cells, (4) degradation on a developmental type of liquid epitaxy gallium-aluminum-arsenide solar cell, and (5) space radiation effects
Solar cell research, phase 2 Semiannual report
Radiation effects on properties of lithium solar cell
Effects of impurities on radiation damage of silicon solar cells
Impurities effects on radiation damage of silicon solar cell
Chaos and Elliptical Galaxies
Recent results on chaos in triaxial galaxy models are reviewed. Central mass
concentrations like those observed in early-type galaxies -- either stellar
cusps, or massive black holes -- render most of the box orbits in a triaxial
potential stochastic. Typical Liapunov times are 3-5 crossing times, and
ensembles of stochastic orbits undergo mixing on time scales that are roughly
an order of magnitude longer. The replacement of the regular orbits by
stochastic orbits reduces the freedom to construct self-consistent equilibria,
and strong triaxiality can be ruled out for galaxies with sufficiently high
central mass concentrations.Comment: uuencoded gziped PostScript, 12 pages including figure
The intrinsic shape of galaxy bulges
The knowledge of the intrinsic three-dimensional (3D) structure of galaxy
components provides crucial information about the physical processes driving
their formation and evolution. In this paper I discuss the main developments
and results in the quest to better understand the 3D shape of galaxy bulges. I
start by establishing the basic geometrical description of the problem. Our
understanding of the intrinsic shape of elliptical galaxies and galaxy discs is
then presented in a historical context, in order to place the role that the 3D
structure of bulges play in the broader picture of galaxy evolution. Our
current view on the 3D shape of the Milky Way bulge and future prospects in the
field are also depicted.Comment: Invited Review to appear in "Galactic Bulges" Editors: Laurikainen
E., Peletier R., Gadotti D. Springer Publishing. 24 pages, 7 figure
Recommended from our members
Translocating Adult Pacific Lamprey within the Columbia River Basin: State of the Science
The Pacific lamprey (Entosphenus tridentatus) is in decline in the Columbia River Basin, and translocating adult lamprey to bypass difficult migration corridors has been implemented since 2000. We describe and report results from two current translocation programs, provide context for use of translocation, and discuss potential benefits, risks, and uncertainties. Both translocation programs appear to have increased the number of spawning adults and the presence of larvae and juveniles; however, any subsequent increase in naturally spawning adults will require at least one, and likely more, generations to be realized. It was seen that the number of adults entering the Umatilla River increased beginning four years after the first translocations. Potential benefits of translocation programs are increased pheromone production by ammocoetes to attract adults, increased lamprey distribution and abundance in target areas, increased marine-derived nutrients, and promotion of tribal culture. Potential risks include disruption of population structure and associated genetic adaptations, disease transmission, and depletion of donor stocks.This is the publisher’s final pdf. The article is copyrighted by the American Fisheries Society and published by Taylor & Francis. It can be found at: http://www.tandfonline.com/toc/ufsh20/curren
Self-Consistent Gravitational Chaos
The motion of stars in the gravitational potential of a triaxial galaxy is
generically chaotic. However, the timescale over which the chaos manifests
itself in the orbital motion is a strong function of the degree of central
concentration of the galaxy. Here, chaotic diffusion rates are presented for
orbits in triaxial models with a range of central density slopes and nuclear
black-hole masses. Typical diffusion times are found to be less than a galaxy
lifetime in triaxial models where the density increases more rapidly than 1/r
at the center, or which contain black holes with masses that exceed roughly
0.1% of the galaxy mass. When the mass of a central black hole exceeds roughly
0.02 times the mass of the galaxy, there is a transition to global
stochasticity and the galaxy evolves to an axisymmetric shape in little more
than a crossing time. This rapid evolution may provide a negative feedback
mechanism that limits the mass of nuclear black holes to a few percent of the
stellar mass of a galaxy.Comment: 15 Tex pages, 7 Postscript figures. To appear in the Twelfth Annual
Florida Workshop in Nonlinear Astronomy and Physics: Long Range Correlations
in Astrophysical and Other Systems, eds. J. R. Buchler, J. Dufty and H.
Kandru
Young Nuclei in Dwarf Elliptical Galaxies
We report discovery of young embedded structures in three diffuse elliptical
galaxies (dE) in the Virgo cluster: IC 783, IC 3468, and IC 3509. We performed
3D spectroscopic observations of these galaxies using the MPFS spectrograph at
the Russian 6-m telescope, and obtained spatially resolved distributions of
kinematical and stellar population parameters by fitting high-resolution
PEGASE.HR synthetic single stellar populations (SSP) in the pixel space. In all
three galaxies, the luminosity weighted age of the nuclei, about 4 Gyr, is
considerably younger than population in the outer regions of the galaxies. We
discuss two possibilities to acquire the observed structures -- dissipative
merger event and different ram pressure stripping efficiency during two
consequent crossings of the Virgo cluster centre.Comment: accepted to "Astronomy Letters". Version for astro-ph with colour
figures. 14 pages, 3 figures, 2 table
Twisting of X-ray isophotes in triaxial galaxies
We investigate X-ray isophote twists created by triaxiality differences
between the luminous stellar distributions and the dark halos in elliptical
galaxies. For a typically oblate luminous galaxy embedded in a more prolate
halo formed by dissipationless collapse, the triaxiality difference of \Delta T
= ~0.7 leads to typical isophote twists of = ~16 deg +/- 19 deg
at 3 stellar effective radii. In a model which includes baryonic dissipation
the effect is smaller, with \Delta T = ~0.3 and = ~5 deg +/- 8
deg. Thus, accurate measurements of X-ray isophote twists may be able to set
constraints on the interactions between baryons and dissipationless dark matter
during galaxy formation. The 30-deg X-ray isophote twist in the E4 galaxy NGC
720 cannot be reproduced by our model, suggesting an intrinsic misalignment
between the halo and the stars rather than a projection effect.Comment: 18 pages, with 9 inline Postscript figures, LaTeX, aaspp4.sty,
submitted to ApJ; postscript paper w/figs (200 kb) also avaliable at
http://cfa-www.harvard.edu/~romanow/int.email.v2.ps.g
Information Display System for Atypical Flight Phase
Method and system for displaying information on one or more aircraft flights, where at least one flight is determined to have at least one atypical flight phase according to specified criteria. A flight parameter trace for an atypical phase is displayed and compared graphically with a group of traces, for the corresponding flight phase and corresponding flight parameter, for flights that do not manifest atypicality in that phase
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