56,981 research outputs found
High Performance Turboalternator and Associated Hardware. 1 - Design of Turboalternator
Performance of two stage axial flow turbogenerator with gas bearing rotor support syste
Solar wind radiation damage effects in lunar material
The research on solar wind radiation damage and other effects in lunar samples which was conducted to understand the optical properties of lunar materials is reported. Papers presented include: solar radiation effects in lunar samples, albedo of the moon, radiation effects in lunar crystalline rocks, valence states of 3rd transition elements in Apollo 11 and 12 rocks, and trace ferric iron in lunar and meteoritic titanaugites
Research program of the Geodynamics Branch
This report is the Fourth Annual Summary of the Research Program of the Geodynamics Branch. The branch is located within the Laboratory for Terrestrial Physics of the Space and Earth Sciences Directorate of the Goddard Space Flight Center. The research activities of the branch staff cover a broad spectrum of geoscience disciplines including: tectonophysics, space geodesy, geopotential field modeling, and dynamic oceanography. The NASA programs which are supported by the work described in this document include the Geodynamics and Ocean Programs, the Crustal Dynamics Project and the proposed Ocean Topography Experiment (TOPEX). The reports highlight the investigations conducted by the Geodynamics Branch staff during calendar year 1985. The individual papers are grouped into chapters on Crustal Movements and Solid Earth Dynamics, Gravity Field Modeling and Sensing Techniques, and Sea Surface Topography. Further information on the activities of the branch or the particular research efforts described herein can be obtained through the branch office or from individual staff members
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Elevated fetal steroidogenic activity in autism
Autism affects males more than females, giving rise to the idea that the influence of steroid hormones on early fetal brain development may be one important early biological risk factor. Utilizing the Danish Historic Birth Cohort and Danish Psychiatric Central Register, we identified all amniotic fluid samples of males born between 1993 and 1999 who later received ICD-10 (International Classification of Diseases, 10th Revision) diagnoses of autism, Asperger syndrome or PDD-NOS (pervasive developmental disorder not otherwise specified) (n=128) compared with matched typically developing controls. Concentration levels of Δ4 sex steroids (progesterone, 17α-hydroxy-progesterone, androstenedione and testosterone) and cortisol were measured with liquid chromatography tandem mass spectrometry. All hormones were positively associated with each other and principal component analysis confirmed that one generalized latent steroidogenic factor was driving much of the variation in the data. The autism group showed elevations across all hormones on this latent generalized steroidogenic factor (Cohen's d=0.37, P=0.0009) and this elevation was uniform across ICD-10 diagnostic label. These results provide the first direct evidence of elevated fetal steroidogenic activity in autism. Such elevations may be important as epigenetic fetal programming mechanisms and may interact with other important pathophysiological factors in autism
Observation of the dielectric-waveguide mode of light propagation in p-n junctions
Theoretical considerations of the propagation of electromagnetic energy near a p-n junction (1) show that the “sandwich” formed by having a depletion layer bounded by the p and n regions can act as a dielectric waveguide. (1,2
Amplitudes Fitted to Experimental Data and to Roy's Equations
The scalar-isoscalar, scalar-isotensor and vector-isovector pi-pi amplitudes
are fitted simultaneously to experimental data and to Roy's equations. The
resulting amplitudes are compared with those fitted only to experimental data.
No additional constraints for the pi-pi threshold behaviour of the amplitudes
are imposed. Threshold parameters are calculated for the amplitudes in the
three waves. Spectrum of scalar mesons below 1.8 GeV is found from the analysis
of the analytical structure of the fitted amplitudes.Comment: 3 pages, 1 figure. Talk given at MESON 2004: 8th International
Workshop on Meson Production, Properties and Interactions, Cracow, Poland,
4-8 Jun 2004. Submitted to Int.J.Mod.Phys.
Parton-Hadron duality in event generators
The validity of local parton-hadron duality within the framework of HERWIG
and JETSET event generators is investigated. We concentrate on annihilations in LEP 2 energy range as these interactions provide
theoretically the cleanest condition for the discussion of this concept.Comment: PRA-HEP-92/14, 10 pages and 7 PS figures obtainable upon request,
LATEX. email transmission errors corrected. Requests for figures can be sent
on the above ID or to CHYLA@CSPGAS1
Dressed States of a two component Bose-Einstein Condensate
A condensate with two internal states coupled by external electromagnetic
radiation, is described by coupled Gross Pitaevskii equations, whose
eigenstates are analogous to the dressed states of quantum optics. We solve for
these eigenstates numerically in the case of one spatial dimension, and explore
their properties as a function of system parameters. In contrast to the quantum
optical case, the condensate dressed states exhibit spatial behaviour which
depends on the system parameters, and can be manipulated by changing the cw
external field.Comment: 6 pages, including 6 figures. This paper was presented at ACOLS98,
and is submitted to a special issue of J. Opt.
Additional time-dependent phase in the flavor-conversion formulas
In the framework of intermediate wave-packets for treating flavor
oscillations, we quantify the modifications which appear when we assume a
strictly peaked momentum distribution and consider the second-order corrections
in a power series expansion of the energy. By following a sequence of analytic
approximations, we point out that an extra time-dependent phase is merely the
residue of second-order corrections. Such phase effects are usually ignored in
the relativistic wave-packet treatment, but they do not vanish
non-relativistically and can introduce some small modifications to the
oscillation pattern even in the ultra-relativistic limit.Comment: 9 pages, 3 figure
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