18,383 research outputs found
Effects of space environment on composites: An analytical study of critical experimental parameters
A generalized methodology currently employed at JPL, was used to develop an analytical model for effects of high-energy electrons and interactions between electron and ultraviolet effects. Chemical kinetic concepts were applied in defining quantifiable parameters; the need for determining short-lived transient species and their concentration was demonstrated. The results demonstrates a systematic and cost-effective means of addressing the issues and show qualitative and quantitative, applicable relationships between space radiation and simulation parameters. An equally important result is identification of critical initial experiments necessary to further clarify the relationships. Topics discussed include facility and test design; rastered vs. diffuse continuous e-beam; valid acceleration level; simultaneous vs. sequential exposure to different types of radiation; and interruption of test continuity
The Radius of the Proton: Size Does Matter
The measurement by Pohl et al. [1] of the 2S_1/2^F=1 to 2P_3/2^F=2 transition
in muonic hydrogen and the subsequent analysis has led to a conclusion that the
rms charge radius of the proton differs from the accepted (CODATA [2]) value by
approximately 4%, leading to a 4.9 s.d. discrepancy. We investigate the muonic
hydrogen spectrum relevant to this transition using bound-state QED with Dirac
wave-functions and comment on the extent to which the perturbation-theory
analysis which leads to the above conclusion can be confirmed.Comment: Delayed arXiv submission. To appear in 'Proceedings of T(R)OPICALQCD
2010' (September 26 - October 1, 2010). 7 pages, 1 figure. Superseded by
arXiv:1104.297
A head restraint device for vestibular studies
Head restraint device based on vacuum bladder technique for use in vestibular studie
Ground-based measurements of O3, NO2, OClO, and BrO during the 1987 Antarctic ozone depletion event
Near-ultraviolet absorption spectroscopy in the wavelength range from 330 to 370 nm was used to measure O3, NO2, OClO, and BrO at McMurdo Station (78S) during 1987. Visible absorption measurements of O3, NO2, and OClO were also obtained using the wavelength range from about 403 to 453 nm. These data are described and compared to observations obtained in 1986. It is shown that comparisons of observations in the two wavelength ranges provide a sensitive measure of the altitude where the bulk of atmospheric absorption takes place
Light Deflection, Lensing, and Time Delays from Gravitational Potentials and Fermat's Principle in the Presence of a Cosmological Constant
The contribution of the cosmological constant to the deflection angle and the
time delays are derived from the integration of the gravitational potential as
well as from Fermat's Principle. The findings are in agreement with recent
results using exact solutions to Einstein's equations and reproduce precisely
the new -term in the bending angle and the lens equation. The
consequences on time delay expressions are explored. While it is known that
contributes to the gravitational time delay, it is shown here that a
new -term appears in the geometrical time delay as well. Although
these newly derived terms are perhaps small for current observations, they do
not cancel out as previously claimed. Moreover, as shown before, at galaxy
cluster scale, the contribution can be larger than the second-order
term in the Einstein deflection angle for several cluster lens systems.Comment: 6 pages, 1 figure, matches version published in PR
Nuclear Quasi-Elastic Electron Scattering Limits Nucleon Off-Mass Shell Properties
The use of quasi-elastic electron nucleus scattering is shown to provide
significant constraints on models of the proton electromagnetic form factor of
off-shell nucleons. Such models can be constructed to be consistent with
constraints from current conservation and low-energy theorems, while also
providing a contribution to the Lamb shift that might potentially resolve the
proton radius puzzle in muonic hydrogen. However, observations of quasi-elastic
scattering limit the overall strength of the off-shell form factors to values
that correspond to small contributions to the Lamb shift.Comment: 11 pages, 2 figures. Resubmission to improve the clarity, and correct
possible misconception
Photovoltaic module encapsulation design and materials selection, volume 1
Encapsulation material system requirements, material selection criteria, and the status and properties of encapsulation materials and processes available are presented. Technical and economic goals established for photovoltaic modules and encapsulation systems and their status are described. Available encapsulation technology and data are presented to facilitate design and material selection for silicon flat plate photovoltaic modules, using the best materials available and processes optimized for specific power applications and geographic sites. The operational and environmental loads that encapsulation system functional requirements and candidate design concepts and materials that are identified to have the best potential to meet the cost and performance goals for the flat plate solar array project are described. Available data on encapsulant material properties, fabrication processing, and module life and durability characteristics are presented
Neutron Star Properties with Hyperons
In the light of the recent discovery of a neutron star with a mass accurately
determined to be almost two solar masses, it has been suggested that hyperons
cannot play a role in the equation of state of dense matter in
-equilibrium. We re-examine this issue in the most recent development of
the quark-meson coupling model. Within a relativistic Hartree-Fock approach and
including the full tensor structure at the vector-meson-baryon vertices, we
find that not only must hyperons appear in matter at the densities relevant to
such a massive star but that the maximum mass predicted is completely
consistent with the observation.Comment: Minor correction
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