4,032 research outputs found
Wetlands in the Northern Great Plains: A Guide to Values and Management
At a glance⊠This booklet helps you to understand: the biological, and soil factors that define a wetland the habitat management practices landowners and engineers can use to create or improve wetlands the economic values wetlands can provide landowners and the public the locations of additional help and information, including wetland map
Robust Stability Analysis Using the Small Gain, Circle, Positivity, and Popov Theorems: A Comparative Study
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57852/1/SmallGainTCST1993.pd
Biological control of the vernal population increase of \u3cem\u3eCalanus finmarchicus\u3c/em\u3e on Georges Bank
An adjoint data assimilation approach was used to quantify the physical and biological controls on Calanus finmarchicus N3âC6 stages on Georges Bank and its nearby environs. The mean seasonal cycle of vertically averaged distributions, from 5 years of the GLOBEC Georges Bank Broad-Scale Surveys between January and June, was assimilated into a physicalâbiological model based on the climatological circulation. Large seasonal and spatial variability is present in the inferred supply sources, mortality rates, computed molting fluxes, and physical transports. Estimated mortalities fall within the range of observed rates, and exhibit stage structure that is consistent with earlier findings. Inferred off-bank initial conditions indicate that the deep basins in the Gulf of Maine are source regions of early stage nauplii and late-stage copepodids in January. However, the population increase on Georges Bank from January to April is controlled mostly by local biological processes. Magnitudes of the physical transport terms are nearly as large as the mortality and molting fluxes, but their bank-wide averages are small in comparison to the biological terms. The hypothesis of local biological control is tested in a sensitivity experiment in which upstream sources are set to zero. In that solution, the lack of upstream sources is compensated by a decrease in mortality that is much smaller than the uncertainty in observational estimates
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Beagle 2: Seeking the signatures of life on Mars
ESA's Beagle 2 lander will land on Mars to search for signatures of present and past life. A Gas Analysis Package (GAP) with a mass spectrometer, XRF, Mossbauer, stereo cameras, microscope, environmental sensors, rock corer/grinder, and a Mole attachment are on the lander
Fast Ensemble Smoothing
Smoothing is essential to many oceanographic, meteorological and hydrological
applications. The interval smoothing problem updates all desired states within
a time interval using all available observations. The fixed-lag smoothing
problem updates only a fixed number of states prior to the observation at
current time. The fixed-lag smoothing problem is, in general, thought to be
computationally faster than a fixed-interval smoother, and can be an
appropriate approximation for long interval-smoothing problems. In this paper,
we use an ensemble-based approach to fixed-interval and fixed-lag smoothing,
and synthesize two algorithms. The first algorithm produces a linear time
solution to the interval smoothing problem with a fixed factor, and the second
one produces a fixed-lag solution that is independent of the lag length.
Identical-twin experiments conducted with the Lorenz-95 model show that for lag
lengths approximately equal to the error doubling time, or for long intervals
the proposed methods can provide significant computational savings. These
results suggest that ensemble methods yield both fixed-interval and fixed-lag
smoothing solutions that cost little additional effort over filtering and model
propagation, in the sense that in practical ensemble application the additional
increment is a small fraction of either filtering or model propagation costs.
We also show that fixed-interval smoothing can perform as fast as fixed-lag
smoothing and may be advantageous when memory is not an issue
Halpha-Derived Star-Formation Rates For Three z ~ 0.75 EDisCS Galaxy Clusters
We present Halpha-derived star-formation rates (SFRs) for three z ~ 0.75
galaxy clusters. Our 1 sigma flux limit corresponds to a star-formation rate of
0.10-0.24 solar mass per year, and our minimum reliable Halpha + [N II]
rest-frame equivalent width is 10\AA. We show that Halpha narrowband imaging is
an efficient method for measuring star formation in distant clusters. In two
out of three clusters, we find that the fraction of star-forming galaxies
increases with projected distance from the cluster center. We also find that
the fraction of star-forming galaxies decreases with increasing local galaxy
surface density in the same two clusters. We compare the median rate of star
formation among star-forming cluster galaxies to a small sample of star-forming
field galaxies from the literature and find that the median cluster SFRs are
\~50% less than the median field SFR. We characterize cluster evolution in
terms of the mass-normalized integrated cluster SFR and find that the z ~ 0.75
clusters have more SFR per cluster mass on average than the z <= 0.4 clusters
from the literature. The interpretation of this result is complicated by the
dependence of the mass-normalized SFR on cluster mass and the lack of
sufficient overlap in the mass ranges covered by the low and high redshift
samples. We find that the fraction and luminosities of the brightest starburst
galaxies at z ~ 0.75 are consistent with their being progenitors of the
post-starburst galaxies at z ~ 0.45 if the post-starburst phase lasts several
(~5) times longer than the starburst phase.Comment: Accepted for publication in ApJ, 20 pages, 24 figure
Heat-flux footprints for I-mode and EDA H-mode plasmas on Alcator C-Mod
IR thermography is used to measure the heat flux footprints on C-Modâs outer target in I-mode and EDA H-mode plasmas. The footprint profiles are fit to a function with a simple physical interpretation. The fit parameter that is sensitive to the power decay length into the SOL, λ[subscript SOL], is ~1â3Ă larger in I-modes than in H-modes at similar plasma current, which is the dominant dependence for the H-mode λ[subscript SOL]. In contrast, the fit parameter sensitive to transport into the private-flux-zone along the divertor leg is somewhat smaller in I-mode than in H-mode, but otherwise displays no obvious dependence on I[subscript p], B[subscript t], or stored energy. A third measure of the footprint width, the âintegral widthâ, is not significantly different between H- and I-modes. Also discussed are significant differences in the global power flows of the H-modes with âfavorableâ âB drift direction and those of the I-modes with âunfavorableâ âB drift direction.United States. Dept. of Energy (Cooperative Agreement DE-FC02-99-ER54512
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