19,019 research outputs found
Reproductive strategies of two similar Daphnia species
Cladocerans, like many other invertebrates, continue to grow after beginning to reproduce, and their reproductive capability increases with size. What are the demographic consequences of this strategy of indeterminate growth? Here we present results of laboratory experiments in which we measured reproductive strategies of two large, similar cladoceran species, Daphnia pulex and D. pulicaria under high and moderately limiting food conditions. From the experimental data, we calculated the intrinsic rates of increase r for each reproductive strategy. We also estimated the effect on r of changing the pattern of allocation of biomass to reproduction. The results suggest that the daphnid strategy may represent an evolutionary compromise between strategies that maximize r and strategies that maximize total reproductive output
Preliminary antenna design considerations for a STADAN relay satellite system
Antenna design for multiple-beam, wide angle scanning phased array relay satellite syste
Tunnel diode low-level detection
Tunnel diode low level detection analysis for characteristics occurring under bias condition
Peaks and Troughs in Helioseismology: The Power Spectrum of Solar Oscillations
I present a matched-wave asymptotic analysis of the driving of solar
oscillations by a general localised source. The analysis provides a simple
mathematical description of the asymmetric peaks in the power spectrum in terms
of the relative locations of eigenmodes and troughs in the spectral response.
It is suggested that the difference in measured phase function between the
modes and the troughs in the spectrum will provide a key diagnostic of the
source of the oscillations. I also suggest a form for the asymmetric line
profiles to be used in the fitting of solar power spectra.
Finally I present a comparison between the numerical and asymptotic
descriptions of the oscillations. The numerical results bear out the
qualitative features suggested by the asymptotic analysis but suggest that
numerical calculations of the locations of the troughs will be necessary for a
quantitative comparison with the observations.Comment: 18 pages + 8 separate figures. To appear in Ap
The late merging phase of a galaxy cluster : XMM EPIC Observations of A3266
We present a mosaic of five XMM-Newton observations of the nearby
() merging galaxy cluster Abell 3266. We use the spectro-imaging
capabilities of \xmm to build precise (projected) temperature, entropy,
pressure and Fe abundance maps. The temperature map exhibits a curved,
large-scale hot region, associated with elevated entropy levels, very similar
to that foreseen in numerical simulations. The pressure distribution is
disturbed in the central region but is remarkably regular on large scales. The
Fe abundance map indicates that metals are inhomogeneously distributed across
the cluster. Using simple physical calculations and comparison with numerical
simulations, we discuss in detail merging scenarios that can reconcile the
observed gas density, temperature and entropy structure, and the galaxy density
distribution
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