22,218 research outputs found
Cryopreservation of slime mutants of Neurospora crassa
Cryopreservation of slime mutants of Neurospora crass
Towards an ecological index for tropical soil quality based on soil macrofauna
The objective of this work was to construct a simple index based on the presence/absence of different groups of soil macrofauna to determine the ecological quality of soils. The index was tested with data from 20 sites in South and Central Tabasco, Mexico, and a positive relation between the model and the field observations was detected. The index showed that diverse agroforestry systems had the highest soil quality index (1.00), and monocrops without trees, such as pineapple, showed the lowest soil quality index (0.08). Further research is required to improve this model for natural systems that have very low earthworm biomass
The Central Region in M100: Observations and Modeling
We present new high-resolution observations of the center of the late-type
spiral M100 (NGC 4321) supplemented by 3D numerical modeling of stellar and gas
dynamics, including star formation (SF). NIR imaging has revealed a stellar
bar, previously inferred from optical and 21 cm observations, and an
ovally-shaped ring-like structure in the plane of the disk. The K isophotes
become progressively elongated and skewed to the position angle of the bar
(outside and inside the `ring') forming an inner bar-like region. The galaxy
exhibits a circumnuclear starburst in the inner part of the K `ring'. Two
maxima of the K emission have been observed to lie symmetrically with respect
to the nucleus and equidistant from it slightly leading the stellar bar. We
interpret the twists in the K isophotes as being indicative of the presence of
a double inner Lindblad resonance (ILR) and test this hypothesis by modeling
the gas flow in a self-consistent gas + stars disk embedded in a halo, with an
overall NGC4321-like mass distribution. We have reproduced the basic morphology
of the region (the bar, the large scale trailing shocks, two symmetric K peaks
corresponding to gas compression maxima which lie at the caustic formed by the
interaction of a pair of trailing and leading shocks in the vicinity of the
inner ILR, both peaks being sites of SF, and two additional zones of SF
corresponding to the gas compression maxima, referred usually as `twin peaks').Comment: 31 pages, postscript, compressed, uuencoded. 21 figures available in
postscript, compressed form by anonymous ftp from
ftp://asta.pa.uky.edu/shlosman/main100 , mget *.ps.Z. To appear in Ap.
Simulations of Dust in Interacting Galaxies I: Dust Attenuation
A new Monte-Carlo radiative-transfer code, Sunrise, is used in conjunction
with hydrodynamic simulations of major galaxy mergers to calculate the effects
of dust in such systems. The simulations are in good agreement with
observations of dust absorption in starburst galaxies, and the dust has a
profound effect on their appearance. The dust attenuation increases with
luminosity such that at peak luminosities ~90% of the bolometric luminosity is
absorbed by dust. In general, the detailed appearance of the merging event
depends on the stage of the merger and the geometry of the encounter. The
fraction of bolometric energy absorbed by the dust, however, is a robust
quantity that can be predicted from the intrinsic properties bolometric
luminosity, baryonic mass, star-formation rate, and metallicity of the system.
This paper presents fitting formulae, valid over a wide range of masses and
metallicities, from which the absorbed fraction of luminosity (and consequently
also the infrared dust luminosity) can be predicted. The attenuation of the
luminosity at specific wavelengths can also be predicted, albeit with a larger
scatter due to the variation with viewing angle. These formulae for dust
attenuation appear to be valid for both isolated and interacting galaxies, are
consistent with earlier studies, and would be suitable for inclusion in
theoretical models, e.g. semi-analytic models of galaxy formation.Comment: 12 pages, 10 figures, submitted to Ap
Two small-volume electrochemical cells for the measurement of surface enhanced Raman scattering
Two electrochemical cells, for performing surface enhanced Raman scattering (SERS), with submillilitre volumes are presented. One of the cells is especially developed for use in a Raman microspectrometer. The smallest cell uses only 80 mu l of sample. SER measurements are performed on 2*10-3 M adenine
X-Ray and Infrared Enhancement of Anomalous X-ray Pulsar 1E 2259+58
The long term (~1.5 years) X-ray enhancement and the accompanying infrared
enhancement light curves of the anomalous X-ray pulsar 1E 2259+58 following the
major bursting epoch can be accounted for by the relaxation of a fall back disk
that has been pushed back by a gamma-ray flare. The required burst energy
estimated from the results of our model fits is low enough for such a burst to
have remained below the detection limits. We find that an irradiated disk model
with a low irradiation efficiency is in good agreement with both X-ray and
infrared data. Non-irradiated disk models also give a good fit to the X-ray
light curve, but are not consistent with the infrared data for the first week
of the enhancement.Comment: 17 pages, 3 figures, accepted for publication in Ap
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