5,475 research outputs found
The Impact of Recent Extradition Cases Involving Canada and the United States: A Canadian Perspective
extradition in Canada and the United State
Gravitational Interactions in a General Multibrane Model
The gravitational interactions of the four-dimensional effective theory
describing a general -brane model in five dimensions without radion
stabilization are analyzed. Both uncompactified and orbifolded models are
considered. The parameter space is constrained by requiring that there be no
ghost modes in the theory, and that the Eddington parameterized post-Newtonian
parameter be consistent with observations. We show that we must reside
on the brane on which the warp factor is maximized. The resultant theory
contains radion modes in a nonlinear sigma model, with the target space
being a subset of hyperbolic space. Imposing observational constraints on the
relative strengths of gravitational interactions of dark and visible matter
shows that at least 99.8% of the dark matter must live on our brane in this
model.Comment: 18 pages, 4 figures. Version 2 (submitted to PRD) adds analysis on
orbifold
Trade studies for nuclear space power systems
As human visions of space applications expand and as we probe further out into the universe, our needs for power will also expand, and missions will evolve which are enabled by nuclear power. A broad spectrum of missions which are enhanced or enabled by nuclear power sources have been defined. These include Earth orbital platforms, deep space platforms, planetary exploration, and terrestrial resource exploration. The recently proposed Space Exploration Initiative (SEI) to the Moon and Mars has more clearly defined these missions and their power requirements. Presented here are results of recent studies of radioisotope and nuclear reactor energy sources, combined with various energy conversion devices for Earth orbital applications, SEI lunar/Mars rovers, surface power, and planetary exploration
Validating performance of automotive materials at high strain rate for improved crash design
This paper investigates sources of performance variability in high velocity testing of automotive crash structures. Sources of variability, or so called noise factors, present in a testing environment, arise from uncertainty in structural properties, joints, boundary conditions and measurement system. A box structure, which is representative of a crash component, is designed and fabricated from a high strength Dual Phase sheet steel. Crush tests are conducted at low and high speed. Such tests intend to validate a component model and material strain rate sensitivity data determined from high speed tensile testing. To support experimental investigations, stochastic modeling is used to investigate the effect of noise factors on crash structure performance variability, and to identify suitable performance measures to validate a component model and material strain rate sensitivity data. The results of the project will enable the measurement of more reliable strain rate sensitivity data for improved crashworthiness predictions of automotive structures
Coupled quintessence and vacuum decay
We discuss observational consequences of a class of cosmological models
characterized by the dilution of pressureless matter attenuated with respect to
the usual scaling due to the decay of vacuum energy. We carry out a
joint statistical analysis of observational data from the new \emph{gold}
sample of 182 SNe Ia, recent estimates of the CMB shift parameter, and BAO
measurements from the SDSS to show that such models favor the decay of vacuum
only into the dark matter sector, and that the separately conserved baryons
cannot be neglected. In order to explore ways to more fundamentally motivated
models, we also derive a coupled scalar field version for this general class of
vacuum decay scenarios.Comment: 6 pages, 3 figures, LaTe
An investigation of Fe XV emission lines in solar flare spectra
Previously, large discrepancies have been found between theory and
observation for Fe XV emission line ratios in solar flare spectra covering the
224-327 A wavelength range, obtained by the Naval Research Laboratory's S082A
instrument on board Skylab. These discrepancies have been attributed to either
errors in the adopted atomic data or the presence of additional atomic
processes not included in the modelling, such as fluorescence. However our
analysis of these plus other S082A flare observations (the latter containing Fe
XV transitions between 321-482 A), performed using the most recent Fe XV atomic
physics calculations in conjunction with a CHIANTI synthetic flare spectrum,
indicate that blending of the lines is primarily responsible for the
discrepancies. As a result, most Fe XV lines cannot be employed as electron
density diagnostics for solar flares, at least at the spectral resolution of
S082A and similar instruments (i.e. ~ 0.1 A). An exception is the intensity
ratio I(321.8 A)/I(327.0 A), which appears to provide good estimates of the
electron density at this spectral resolution.Comment: 6 pages, 3 figures, Astronomy & Astrophysics, in pres
Effects of Sex and Gender on Adaptation to Space: Musculoskeletal Health
There is considerable variability among individuals in musculoskeletal response to long-duration spaceflight. The specific origin of the individual variability is unknown but is almost certainly influenced by the details of other mission conditions such as individual differences in exercise countermeasures, particularly intensity of exercise, dietary intake, medication use, stress, sleep, psychological profiles, and actual mission task demands. In addition to variations in mission conditions, genetic differences may account for some aspect of individual variability. Generally, this individual variability exceeds the variability between sexes that adds to the complexity of understanding sex differences alone. Research specifically related to sex differences of the musculoskeletal system during unloading is presented and discussed
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