9,100 research outputs found
A human operator simulator model of the NASA Terminal Configured Vehicle (TCV)
A generic operator model called HOS was used to simulate the behavior and performance of a pilot flying a transport airplane during instrument approach and landing operations in order to demonstrate the applicability of the model to problems associated with interfacing a crew with a flight system. The model which was installed and operated on NASA Langley's central computing system is described. Preliminary results of its application to an investigation of an innovative display system under development in Langley's terminal configured vehicle program are considered
The Yersinia enterocolitica Ysa type III secretion system is expressed during infections both in vitro and in vivo.
Yersinia enterocolitica biovar 1B maintains two type III secretion systems (T3SS) that are involved in pathogenesis, the plasmid encoded Ysc T3SS and the chromosomally encoded Ysa T3SS. In vitro, the Ysa T3SS has been shown to be expressed only at 26°C in a high-nutrient medium containing an exceptionally high concentration of salt - an artificial condition that provides no clear insight on the nature of signal that Y. enterocolitica responds to in a host. However, previous research has indicated that the Ysa system plays a role in the colonization of gastrointestinal tissues of mice. In this study, a series of Ysa promoter fusions to green fluorescent protein gene (gfp) were created to analyze the expression of this T3SS during infection. Using reporter strains, infections were carried out in vitro using HeLa cells and in vivo using the mouse model of yersiniosis. Expression of green fluorescent protein (GFP) was measured from the promoters of yspP (encoding a secreted effector protein) and orf6 (encoding a structural component of the T3SS apparatus) in vitro and in vivo. During the infection of HeLa cells GFP intensity was measured by fluorescence microscopy, while during murine infections GFP expression in tissues was measured by flow cytometry. These approaches, combined with quantification of yspP mRNA transcripts by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), demonstrate that the Ysa system is expressed in vitro in a contact-dependent manner, and is expressed in vivo during infection of mice
Parameterization of Dark-Energy Properties: a Principal-Component Approach
Considerable work has been devoted to the question of how to best
parameterize the properties of dark energy, in particular its equation of state
w. We argue that, in the absence of a compelling model for dark energy, the
parameterizations of functions about which we have no prior knowledge, such as
w(z), should be determined by the data rather than by our ingrained beliefs or
familiar series expansions. We find the complete basis of orthonormal
eigenfunctions in which the principal components (weights of w(z)) that are
determined most accurately are separated from those determined most poorly.
Furthermore, we show that keeping a few of the best-measured modes can be an
effective way of obtaining information about w(z).Comment: Unfeasibility of a truly model-independent reconstruction of w at z>1
illustrated. f(z) left out, and w(z) discussed in more detail. Matches the
PRL versio
Femtoscopic results in Au+Au and p+p from PHENIX at RHIC
Ultra-relativistic gold-gold and proton-proton collisions are investigated in
the experiments of the Relativistic Heavy Ion Collider (RHIC). In the last
several years large amount of results were revealed about the matter created in
these collisions. The latest PHENIX results for femtoscopy and correlations are
reviewed in this paper. Bose-Einstein correlations of charged kaons in 200 GeV
Au+Au collisions and of charged pions in 200 GeV p+p collisions are shown. They
are both compatible with previous measurements of charged pions in gold-gold
collisions, with respect to transverse mass or number of participants scaling.Comment: Talk given at the VI Workshop on Particle Correlations and
Femtoscopy, Kiev, September 14-18, 2010. 6 pages, 4 figures. This work was
supported by the OTKA grant NK73143 and M. Csanad's Bolyai scholarshi
Georgia's Aging Population: What to Expect and How to Cope
This report analyzes the impacts of Georgia's aging population on state finances. FRC Report 11
Spatial Coherence of a Polariton Condensate
We perform Young's double-slit experiment to study the spatial coherence
properties of a two-dimensional dynamic condensate of semiconductor microcavity
polaritons. The coherence length of the system is measured as a function of the
pump rate, which confirms a spontaneous buildup of macroscopic coherence in the
condensed phase. An independent measurement reveals that the position and
momentum uncertainty product of the condensate is close to the Heisenberg
limit. An experimental realization of such a minimum uncertainty wave packet of
the polariton condensate opens a door to coherent matter-wave phenomena such as
Josephson oscillation, superfluidity, and solitons in solid state condensate
systems
Probing the Super Star Cluster Environment of NGC 1569 Using FISICA
We present near-IR JH spectra of the central regions of the dwarf starburst
galaxy NGC 1569 using the Florida Image Slicer for Infrared Cosmology and
Astrophysics (FISICA). The dust-penetrating properties and available spectral
features of the near-IR, combined with the integral field unit (IFU) capability
to take spectra of a field, make FISICA an ideal tool for this work. We use the
prominent [He I] (1.083\mu m) and Pa\beta (1.282 \mu m) lines to probe the
dense star forming regions as well as characterize the general star forming
environment around the super star clusters (SSCs) in NGC 1569. We find [He I]
coincident with CO clouds to the north and west of the SSCs, which provides the
first, conclusive evidence for embedded star clusters here.Comment: 6 pages, 3 figures, accepted for publication in the MNRA
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A submillimetre wavelength spectral line search of the Orion molecular cloud core
A submillimetre wavelength molecular line search of the Orion molecular cloud has been made covering a total of about 5 percent of the frequency range 342.8 - 358.6 GHz. This search, coupled with the authors' previous observations of submillimetre transitions in this cloud, has led to the detection of 22 transitions of 14 molecular species, of which 16 are reported here for the first time. No unidentified lines have been detected in the present search. Mapping observations have been obtained for several of the lines and, in the case of H2CO the authors have been able to compare the present data with that obtained from other telescopes, to estimate the density and abundance in the emitting region
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