148,475 research outputs found
Forced flexural motion of a rocket-boosted vehicle
Bending vibration equations for rocket boosted vehicle controlled by vectored thrust - structural dynamic
Gravitational waveforms from the evaporating ACO cosmic string loop
The linearly polarized gravitational waveforms from a certain type of
rotating, evaporating cosmic string - the Allen-Casper-Ottewill loop - are
constructed and plotted over the lifetime of the loop. The formulas for the
waveforms are simple and exact, and describe waves which attenuate
self-similarly, with the amplitude and period of the waves falling off linearly
with time.Comment: 30 pages, 16 figure
The evolution of carrying capacity in constrained and expanding tumour cell populations
Cancer cells are known to modify their micro-environment such that it can
sustain a larger population, or, in ecological terms, they construct a niche
which increases the carrying capacity of the population. It has however been
argued that niche construction, which benefits all cells in the tumour, would
be selected against since cheaters could reap the benefits without paying the
cost. We have investigated the impact of niche specificity on tumour evolution
using an individual based model of breast tumour growth, in which the carrying
capacity of each cell consists of two components: an intrinsic,
subclone-specific part and a contribution from all neighbouring cells. Analysis
of the model shows that the ability of a mutant to invade a resident population
depends strongly on the specificity. When specificity is low selection is
mostly on growth rate, while high specificity shifts selection towards
increased carrying capacity. Further, we show that the long-term evolution of
the system can be predicted using adaptive dynamics. By comparing the results
from a spatially structured vs.\ well-mixed population we show that spatial
structure restores selection for carrying capacity even at zero specificity,
which a poses solution to the niche construction dilemma. Lastly, we show that
an expanding population exhibits spatially variable selection pressure, where
cells at the leading edge exhibit higher growth rate and lower carrying
capacity than those at the centre of the tumour.Comment: Major revisions compared to previous version. The paper is now aimed
at tumour modelling. We now start out with an agent-based model for which we
derive a mean-field ODE-model. The ODE-model is further analysed using the
theory of adaptive dynamic
Reduction and analysis of data from the plasma wave instruments on the IMP-6 and IMP-8 spacecraft
The primary data reduction effort during the reporting period was to process summary plots of the IMP 8 plasma wave data and to submit these data to the National Space Science Data Center. Features of the electrostatic noise are compared with simultaneous observations of the magnetic field, plasma and energetic electrons. Spectral characteristics of the noise and the results of this comparison both suggest that in its high frequency part at least the noise does not belong to normal modes of plasma waves but represents either quasi-thermal noise in the non-Maxwellian plasma or artificial noise generated by spacecraft interaction with the medium
Study plasma interactions in the auroral ionosphere
Analyzed data from rocket flight, 29.007UE is presented. In a discrete electron arc the measured upward moving electrons are well accounted for by secondaries produced in collisional scattering of the measured downcoming electrons. No collective mechanisms need to invoke. The low energy downcoming electrons are accounted for by thermal plasma accelerated through a potential drop of a few kV that specularly reflects upward-moving lower energy electrons. No low altitude collective effects need to invoke in the arc. Simultaneous measurements of electric field by double probes on 29.007 and the Chatanika Radar allow one to infer that there are upward drifting ions above the discrete electron arc, and there is a westward neutral wind in the discrete arc. Two rocket payloads were built to investigate plasma effects in the pulsating aurora
Holographic entanglement entropy under the minimal geometric deformation and extensions
The holographic entanglement entropy (HEE) of the minimal geometrical
deformation (MGD) procedure and extensions (EMGD), is scrutinized within the
membrane paradigm of AdS/CFT. The HEE corrections of the Schwarzschild and
Reissner--Nordstr\"om solutions, due to a finite fluid brane tension, are then
derived and discussed in the context of the MGD and the EMGD.Comment: 31 pages and 23 figure
Plasma wave observations near the plasmapause with the S3-A satellite
The electric field noise phenomena is described which was observed by the S3-A spacecraft near the plasmapause during the magnetic storm of 16 to 17 December, 1971. The occurrence is noted of a region of intense, low frequency (20 Hz to 500 Hz) electrostatic noise bursts just outside the plasmapause boundary. These noise bursts occurred concurrent with the rapid decrease in 24.3 or = E or = 35.1 keV ring current protons mirroring near the equator during this storm and may be responsible for the pitch angle diffusion and loss of these particles. The characteristics of other phenomena, such as whistlers, ELF hiss, and banded chorus, observed near the plasmapause during this period are also discussed
Automatic transponder
A method and apparatus for the automatic, remote measurement of the internal delay time of a transponder at the time of operation is provided. A small portion of the transmitted signal of the transponder is converted to the receive signal frequency of the transponder and supplied to the input of the transponder. The elapsed time between the receive signal locally generated and the receive signal causing the transmission of the transmitted signal is measured, said time being representative of or equal to the internal delay time of the transponder at the time of operation
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