4,338 research outputs found
Propulsion systems dispersion analysis and optimum propellant management
Propulsion systems dispersion analysis and propellant optimization method for Apollo subsystem
Numerical Analyses of Weakly Nonlinear Velocity-Density Coupling
We study evolution of various statistical quantities of smoothed cosmic
density and velocity fields using N-body simulations. The parameter
characterizes nonlinear coupling of
these two fields and determines behavior of bulk velocity dispersion as a
function of local density contrast.
It is found that this parameter depends strongly on the smoothing scale even
in quasi-linear regimes where the skewness parameter
is nearly constant and close to the predicted value by the second-order
perturbation theory. We also analyze weakly nonlinear effects caused by an
adaptive smoothing known as the gather approach.Comment: 22 pages, 4 figures, to appear in ApJ (558, Sep 10
Apollo cryogenic integrated systems program
The integrated systems program is capable of simulating both nominal and anomalous operation of the Apollo cryogenics storage system (CSS). Two versions of the program exist; one for the Apollo 14 configuration and the other for J Type Mission configurations. The program consists of two mathematical models which are dynamically coupled. A model of the CSS components and lines determines the oxygen and hydrogen flowrate from each storage tank given the tank pressures and temperatures, and the electrical power subsystem and environmental control subsystem flow demands. Temperatures and pressures throughout the components and lines are also determined. A model of the CSS tankage determines the pressure and temperatures in the tanks given the flowrate from each tank and the thermal environment. The model accounts for tank stretch and includes simplified oxygen tank heater and stratification routines. The program is currently operational on the Univac 1108 computer
LISA Measurement of Gravitational Wave Background Anisotropy: Hexadecapole Moment via a Correlation Analysis
We discuss spatial fluctuations in the gravitational wave background arising
from unresolved Galactic binary sources, such as close white dwarf binaries,
due to the fact the galactic binary source distribution is anisotropic. We
introduce a correlation analysis of the two data streams of the Laser
Interferometer Space Antenna (LISA) to extract spherical harmonic coefficients,
in an independent manner, of the hexadecapole moment () related to the
projected two-dimensional density distribution of the binary source population.
The proposed technique complements and improves over previous suggestions in
the literature to measure the gravitational wave background anisotropy based on
the time modulation of data as LISA orbits around the Sun. Such techniques,
however, are restricted only to certain combinations of spherical harmonic
coefficients of the galaxy with no ability to separate them individually. With
LISA, and 4 coefficients of the hexadecapole () can be measured
with signal-to-noise ratios at the level of 10 and above in a certain
coordinate system. In addition to the hexadecapole coefficients, when combined
with the time modulation analysis, the correlation study can also be used, in
principle, to measure quadrupole coefficients of the binary distribution.Comment: 8 pages, 2 figure
Apollo mission J1, Csm 112 cryogenic storage system preflight performance report
Predicting flight performance of cryogenic storage system for Apollo 1
Gravitational Wave Astrometry for Rapidly Rotating Neutron Stars and Estimation of Their Distances
We discuss an astrometric timing effect on data analysis of continuous
gravitational waves from rapidly rotating isolated neutron stars. Special
attention is directed to the possibility of determining their distances by
measuring the curvature of the wave fronts. We predict that if continuous
gravitational waves from an unknown neutron star with a stable rotation are
detected around 1kHz within 1/3yr by initial LIGO detectors and the ellipticity
parameter epsilon is smaller than 10^{-6}, the distance r to the source can be
estimated with relative error \Delta r/r of \sim 10% by using the broad band
configuration of advanced LIGO detectors over 3 years. By combining the
observed amplitude of the waves with the estimated distance, information on the
parameter can be obtained purely through gravitational wave
measurements.Comment: 6 pages, 1 figure, to appear in PR
Modulation of hippocampal acetylcholine release - a potent central action of interleukin-2
The potential of the T-cell growth factor interleukin-2 (IL-2) to modulate the release of ACh from rat hippocampus was studied in vitro, as a means to investigate the possible functional significance of this cytokine in the CNS. Hippocampal slices were superfused with Krebs' buffer medium, and endogenous ACh released into the superfusate was measured using a radioenzymatic assay. Recombinant human IL-2 present during a stimulation with 25 mM KCl altered, in a concentration-dependent manner, the evoked transmitter release. At a concentration of 15 U/ml (< or = 1 nM), IL-2 inhibited ACh release by more than 50% of the control level (evoked ACh release from the untreated contralateral hemispheres). Inhibition was observed within 20 min of tissue exposure to IL-2 and lasted for up to 1 hr. The inhibitory effect of IL-2 was reversible since transient tissue exposure to IL-2 did not affect subsequent evoked ACh release. IL-2 at this concentration also significantly decreased evoked ACh in frontal cortical slices, but was ineffective in the parietal cortex and striatum, revealing that IL-2 selectively modulates the release of ACh from certain, but not all, cholinergic nerve terminals in the CNS. At very low concentrations (1.5 mU/ml, < or = 0.1 pM), IL-2 transiently increased hippocampal evoked ACh release, resulting in a biphasic dose-response profile with no significant effect observed at 0.015 mU/ml (< or = 1 fM). Other cytokines (IL-1 alpha, IL-3, IL-5, IL-6, interferon alpha), tested in hippocampal slice incubations, failed to modulate ACh release
An Experimental Overview of Results Presented at SQM 2006
I have been asked to give an critical overview on the experimental results
shown in the conference with a emphasis of what has been learned and the
challenges that are ahead in trying to understand the physics of the strongly
interacting quark-gluon plasma. I will not try to summarize all of the results
presented, rather I will concentrate primarily on RHIC data from this
conference. Throughout this summary, I will periodically review some of the
previous results for those not familiar with the present state of the field.Comment: 15 pages, 12 Figure
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