6,268 research outputs found
Analytical studies of nuclear light bulb engine radiant heat transfer and performance characteristics
Analytical model of nuclear light bulb engine radiant heat transfer and engine performance, dynamics and control, heat loads and shutdown characteristic
A three stage model for adsorption of nonionic surfactants
Copyright @ 1993 American Institute of Physics.A three stage model for the adsorption of nonionic surfactants is proposed which makes use of existing theory from studies of random sequential adsorption. The model is simulated and the adsorption curves are found. The theory of random sequential adsorption is used to calculate the coverage exactly at the end of each of the three stages
Responses of Hyalella azteca and Ceridaphnia dubia to reservoir sediments following Chelated Copper Herbicide Applications
In response to nuisance growths of algae and vascular
plants, such as dioecious hydrilla (
Hydrilla verticillata
L.f.
Royle), copper formulations have been applied in lakes and
reservoirs for a number of years. Concerns have arisen regarding
the long-term consequences of copper applications
and those concerns have appropriately focused on sediment
residues. In this study, we evaluated the toxicity of sediments
from treated (for a decade) and untreated areas in Lake
Murray, South Carolina and estimated the capacity of those
sediments to bind additional copper. Two sentinel aquatic invertebrates,
Hyalella azteca
Saussure and
Ceriodaphnia dubia
Richard, were used to measure residual toxicity of treated
and untreated sediments from the field and after laboratory
amendments. (PDF has 5 pages.
Studies of nuclear light bulb start-up conditions and engine dynamics
Deep Space Network for two-way communications with unmanned spacecraft at planetary distances - Vol.
Synthetic 26Al emission from galactic-scale superbubble simulations
© 2019 The Author(s).Emission from the radioactive trace element 26Al has been observed throughout the Milky Way with the COMPTEL and INTEGRAL satellites. In particular the Doppler shifts measured with INTEGRAL connect 26Al with superbubbles, which may guide 26Al flows off spiral arms in the direction of Galactic rotation. In order to test this paradigm, we have performed galaxy-scale simulations of superbubbles with 26Al injection in a Milky Way-type galaxy. We produce all-sky synthetic ray emission maps of the simulated galaxies. We find that the 1809keV emission from the radioactive decay of 26Al is highly variable with time and the observer's position. This allows us to estimate an additional systematic variability of 0.2dex for a star formation rate derived from 26Al for different times and measurement locations in Milky Way-type galaxies. High-latitude morphological features indicate nearby emission with correspondingly high integrated gamma-ray intensities. We demonstrate that the 26Al scale height from our simulated galaxies depends on the assumed halo gas density. We present the first synthetic 1809keV longitude-velocity diagrams from 3D hydrodynamic simulations. The line-of-sight velocities for 26Al can be significantly different from the line-of-sight velocities associated with the cold gas. Over time, 26Al velocities consistent with the INTEGRAL observations, within uncertainties, appear at any given longitude, broadly supporting previous suggestions that 26Al injected into expanding superbubbles by massive stars may be responsible for the high velocities found in the INTEGRAL observations. We discuss the effect of systematically varying the location of the superbubbles relative to the spiral arms.Peer reviewedFinal Accepted Versio
H_2 Absorption and Fluorescence for Gamma Ray Bursts in Molecular Clouds
If a gamma ray burst with strong UV emission occurs in a molecular cloud,
there will be observable consequences resulting from excitation of the
surrounding H2. The UV pulse from the GRB will pump H2 into
vibrationally-excited levels which produce strong absorption at wavelengths <
1650 A. As a result, both the prompt flash and later afterglow will exhibit
strong absorption shortward of 1650 A, with specific spectroscopic features.
Such a cutoff in the emission from GRB 980329 may already have been observed by
Fruchter et al.; if so, GRB 980329 was at redshift 3.0 < z < 4.4 . BVRI
photometry of GRB 990510 could also be explained by H2 absorption if GRB 990510
is at redshift 1.6 < z < 2.3. The fluorescence accompanying the UV pumping of
the H2 will result in UV emission from the GRB which can extend over days or
months, depending on parameters of the ambient medium and beaming of the GRB
flash. The 7.5-13.6 eV fluorescent luminosity is \sim 10^{41.7} erg/s for
standard estimates of the parameters of the GRB and the ambient medium.
Spectroscopy can distinguish this fluorescent emission from other possible
sources of transient optical emission, such as a supernova.Comment: 13 pages, including 4 figures. submitted to Ap.J.(Letters
Land Applicaiton of Organic Manures and Silage Effluent
End of Project ReportIn recent times there is increasing interest in the hydraulic properties of
free-draining unsaturated soils and on the fate of slurries, sludges, effluents
and fertilisers applied to these soils. This is especially so where relatively
thin soils overlie bedrocks such as limestones with fissures and solution
channels (karstic aquifers). Irish soils are commonly gravelly and stony and
present special problems in determining their hydraulic properties. In this
project, various field and laboratory methods were employed to measure the
hydraulic conductivity of unsaturated gravelly and stony soils overlying
karstic limestone with a watertable 25 m below ground surface at the
Teagasc Centre at Athenry. In parallel with these measurements, cattle and
pig slurries and silage effluents were applied at normal and very heavy rates
in summer and in winter to a series of experimental plots. A chloride tracer
was also used. Rainfall and soil moisture contents and hydraulic potentials
of the soil of the various plots were measured. Samples of soil water were
collected in suction tubes and analysed for nitrate nitrogen (NO3-N). In
addition, samples of groundwater were taken from a nearby well and
analysed for NO3-N and a number of other parameters. Finally, a finite
difference computer model was used to predict contaminant transport to the
groundwater.European Union
Structural Funding (EAGGF
A molecular perspective on the limits of life: Enzymes under pressure
From a purely operational standpoint, the existence of microbes that can grow
under extreme conditions, or "extremophiles", leads to the question of how the
molecules making up these microbes can maintain both their structure and
function. While microbes that live under extremes of temperature have been
heavily studied, those that live under extremes of pressure have been
neglected, in part due to the difficulty of collecting samples and performing
experiments under the ambient conditions of the microbe. However, thermodynamic
arguments imply that the effects of pressure might lead to different organismal
solutions than from the effects of temperature. Observationally, some of these
solutions might be in the condensed matter properties of the intracellular
milieu in addition to genetic modifications of the macromolecules or repair
mechanisms for the macromolecules. Here, the effects of pressure on enzymes,
which are proteins essential for the growth and reproduction of an organism,
and some adaptations against these effects are reviewed and amplified by the
results from molecular dynamics simulations. The aim is to provide biological
background for soft matter studies of these systems under pressure.Comment: 16 pages, 8 figure
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