24,477 research outputs found
Travelling waves in wound healing
We illustrate the role of travelling waves in wound healing by considering three different cases. Firstly, we review a model for surface wound healing in the cornea and focus on the speed of healing as a function of the application of growth factors. Secondly, we present a model for scar tissue formation in deep wounds and focus on the role of key chemicals in determining the quality of healing. Thirdly, we propose a model for excessive healing disorders and investigate how abnormal healing may be controlled
Quantum field effects in coupled atomic and molecular Bose-Einstein condensates
This paper examines the parameter regimes in which coupled atomic and
molecular Bose-Einstein condensates do not obey the Gross-Pitaevskii equation.
Stochastic field equations for coupled atomic and molecular condensates are
derived using the functional positive-P representation. These equations
describe the full quantum state of the coupled condensates and include the
commonly used Gross-Pitaevskii equation as the noiseless limit. The model
includes all interactions between the particles, background gas losses,
two-body losses and the numerical simulations are performed in three
dimensions. It is found that it is possible to differentiate the quantum and
semiclassical behaviour when the particle density is sufficiently low and the
coupling is sufficiently strong.Comment: 4 postscript figure
Development of a second generation prototype reflectometer for reflectance measurement in space Final technical report
Prototype reflectometer development for reflection measurements in spac
Airloads research study. Volume 2: Airload coefficients derived from wind tunnel data
The development of B-1 aircraft rigid wind tunnel data for use in subsequent tasks of the Airloads Research Study is described. Data from the Rockwell International external structural loads data bank were used to generate coefficients of rigid airload shear, bending moment, and torsion at specific component reference stations or both symmetric and asymmetric loadings. Component stations include the movable wing, horizontal and vertical stabilizers, and forward and aft fuselages. The coefficient data cover a Mach number range from 0.7 to 2.2 for a wing sweep position of 67.5 degree
Airloads research study. Volume 1: Flight test loads acquisition
The acquisition of B-1 aircraft flight loads data for use in subsequent tasks of the Airloads Research Study is described. The basic intent is to utilize data acquired during B-1 aircraft tests, analyze these data beyond the scope of Air Force requirements, and prepare research reports that will add to the technology base for future large flexible aircraft. Flight test data obtained during the airloads survey program included condition-describing parameters, surface pressures, strain gage outputs, and loads derived from pressure and strain gauges. Descriptions of the instrumentation, data processing, and flight load survey program are included. Data from windup-turn and steady yaw maneuvers cover a Mach number range from 0.7 to 2.0 for a wing sweep position of 67.5 deg
Neutron activation analysis traces copper artifacts to geographical point of origin
Impurities remaining in the metallic copper are identified and quantified by spectrographic and neutron activation analysis. Determination of the type of ore used for the copper artifact places the geographic point of origin of the artifact
Einstein-Podolsky-Rosen correlations via dissociation of a molecular Bose-Einstein condensate
Recent experimental measurements of atomic intensity correlations through
atom shot noise suggest that atomic quadrature phase correlations may soon be
measured with a similar precision. We propose a test of local realism with
mesoscopic numbers of massive particles based on such measurements. Using
dissociation of a Bose-Einstein condensate of diatomic molecules into bosonic
atoms, we demonstrate that strongly entangled atomic beams may be produced
which possess Einstein-Podolsky-Rosen (EPR) correlations in field quadratures,
in direct analogy to the position and momentum correlations originally
considered by EPR.Comment: Final published version (corrections in Ref. [32], updated
references
The problem of the Pleiades distance. Constraints from Stromgren photometry of nearby field stars
The discrepancy between the Pleiades cluster distance based on Hipparcos
parallaxes and main sequence fitting is investigated on the basis of Stromgren
photometry of F-type stars. Field stars with the same metallicity as the
Pleiades have been selected from the m1 index and a technique has been
developed to locate the ZAMS of these field stars in color-magnitude diagrams
based on the color/temperature indices b-y, v-y, and beta. Fitting the Pleiades
to these ZAMS relations results in a distance modulus of 5.61+/-0.03 mag in
contrast to the Hipparcos modulus of 5.36+/-0.06 mag. Hence, we cannot confirm
the recent claim by Grenon (1999) that the distance problem is solved by
adopting a low metallicity of the Pleiades ([Fe/H]=-0.11) as determined from
Geneva photometry. The metallicity sensitivity of the ZAMS determined by the
field stars is investigated, and by combining this sensitivity in all three
color/temperature indices b-y, v-y, and beta we get a independent test of the
Pleiades distance modulus which support our value of 5.61 mag. Furthermore, the
field star sample used for the comparison is tested against theoretical
isochrones of different ages to show that evolutionary effects in the field
star sample are not biasing our distance modulus estimate significantly.
Possible explanations of the Pleiades distance problem are discussed and it is
suggested that the discrepancy in the derived moduli may be linked to a
non-spherical shape of the cluster.Comment: 11 pages, 5 figures, accepted for publication in A&
Asynchronous displays for multi-UV search tasks
Synchronous video has long been the preferred mode for controlling remote robots with other modes such as asynchronous control only used when unavoidable as in the case of interplanetary robotics. We identify two basic problems for controlling multiple robots using synchronous displays: operator overload and information fusion. Synchronous displays from multiple robots can easily overwhelm an operator who must search video for targets. If targets are plentiful, the operator will likely miss targets that enter and leave unattended views while dealing with others that were noticed. The related fusion problem arises because robots' multiple fields of view may overlap forcing the operator to reconcile different views from different perspectives and form an awareness of the environment by "piecing them together". We have conducted a series of experiments investigating the suitability of asynchronous displays for multi-UV search. Our first experiments involved static panoramas in which operators selected locations at which robots halted and panned their camera to capture a record of what could be seen from that location. A subsequent experiment investigated the hypothesis that the relative performance of the panoramic display would improve as the number of robots was increased causing greater overload and fusion problems. In a subsequent Image Queue system we used automated path planning and also automated the selection of imagery for presentation by choosing a greedy selection of non-overlapping views. A fourth set of experiments used the SUAVE display, an asynchronous variant of the picture-in-picture technique for video from multiple UAVs. The panoramic displays which addressed only the overload problem led to performance similar to synchronous video while the Image Queue and SUAVE displays which addressed fusion as well led to improved performance on a number of measures. In this paper we will review our experiences in designing and testing asynchronous displays and discuss challenges to their use including tracking dynamic targets. © 2012 by the American Institute of Aeronautics and Astronautics, Inc
SIGAME simulations of the [CII], [OI] and [OIII] line emission from star forming galaxies at z ~ 6
Of the almost 40 star forming galaxies at z>~5 (not counting QSOs) observed
in [CII] to date, nearly half are either very faint in [CII], or not detected
at all, and fall well below expectations based on locally derived relations
between star formation rate (SFR) and [CII] luminosity. Combining cosmological
zoom simulations of galaxies with SIGAME (SImulator of GAlaxy
Millimeter/submillimeter Emission) we have modeled the multi-phased
interstellar medium (ISM) and its emission in [CII], [OI] and [OIII], from 30
main sequence galaxies at z~6 with star formation rates ~3-23Msun/yr, stellar
masses ~(0.7-8)x10^9Msun, and metallicities ~(0.1-0.4)xZsun. The simulations
are able to reproduce the aforementioned [CII]-faintness at z>5, match two of
the three existing z>~5 detections of [OIII], and are furthermore roughly
consistent with the [OI] and [OIII] luminosity relations with SFR observed for
local starburst galaxies. We find that the [CII] emission is dominated by the
diffuse ionized gas phase and molecular clouds, which on average contribute
~66% and ~27%, respectively. The molecular gas, which constitutes only ~10% of
the total gas mass is thus a more efficient emitter of [CII] than the ionized
gas making up ~85% of the total gas mass. A principal component analysis shows
that the [CII] luminosity correlates with the star formation activity as well
as average metallicity. The low metallicities of our simulations together with
their low molecular gas mass fractions can account for their [CII]-faintness,
and we suggest these factors may also be responsible for the [CII]-faint normal
galaxies observed at these early epochs.Comment: 24 pages, 14 figures. Accepted for publication in the Astrophysical
Journa
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