11,701 research outputs found
Salt-gradient Solar Ponds: Summary of US Department of Energy Sponsored Research
The solar pond research program conducted by the United States Department of Energy was discontinued after 1983. This document summarizes the results of the program, reviews the state of the art, and identifies the remaining outstanding issues. Solar ponds is a generic term but, in the context of this report, the term solar pond refers specifically to saltgradient solar pond. Several small research solar ponds have been built and successfully tested. Procedures for filling the pond, maintaining the gradient, adjusting the zone boundaries, and extracting heat were developed. Theories and models were developed and verified. The major remaining unknowns or issues involve the physical behavior of large ponds; i.e., wind mixing of the surface, lateral range or reach of horizontally injected fluids, ground thermal losses, and gradient zone boundary erosion caused by pumping fluid for heat extraction. These issues cannot be scaled and must be studied in a large outdoor solar pond
Cofactor regeneration by a soluble pyridine nucleotide transhydrogenase for biological production of hydromorphone
We have applied the soluble pyridine nucleotide transhydrogenase of Pseudomonas fluorescens to a cell-free system for the regeneration of the nicotinamide cofactors NAD and NADP in the biological production of the important semisynthetic opiate drug hydromorphone. The original recombinant whole-cell system suffered from cofactor depletion resulting from the action of an NADP(+)-dependent morphine dehydrogenase and an NADH-dependent morphinone reductase. By applying a soluble pyridine nucleotide transhydrogenase, which can transfer reducing equivalents between NAD and NADP, we demonstrate with a cell-free system that efficient cofactor cycling in the presence of catalytic amounts of cofactors occurs, resulting in high yields of hydromorphone. The ratio of morphine dehydrogenase, morphinone reductase, and soluble pyridine nucleotide transhydrogenase is critical for diminishing the production of the unwanted by-product dihydromorphine and for optimum hydromorphone yields. Application of the soluble pyridine nucleotide transhydrogenase to the whole-cell system resulted in an improved biocatalyst with an extended lifetime. These results demonstrate the usefulness of the soluble pyridine nucleotide transhydrogenase and its wider application as a tool in metabolic engineering and biocatalysis
Duality Between the Weak and Strong Interaction Limits for Randomly Interacting Fermions
We establish the existence of a duality transformation for generic models of
interacting fermions with two-body interactions. The eigenstates at weak and
strong interaction U possess similar statistical properties when expressed in
the U=0 and U=infinity eigenstates bases respectively. This implies the
existence of a duality point U_d where the eigenstates have the same spreading
in both bases. U_d is surrounded by an interval of finite width which is
characterized by a non Lorentzian spreading of the strength function in both
bases. Scaling arguments predict the survival of this intermediate regime as
the number of particles is increased.Comment: RevTex4, 4 pages, 4 figures. Accepted for publication at Phys. Rev.
Let
Evaluation of Aerodynamic and Propulsive Terminal Phase Systems for an Unmanned Mars Soft Lander
The terminal phase of an unmanned Mars soft lander is defined as that portion of the descent trajectory bridging the gap between the high speed entry trajectory and the very low speed soft landing. This paper presents the results of a parametric analysis comparing the performance and capability of several candidate deceleration systems considered for use during the terminal phase. System comparison is made on the basis of total decelerator system weight requirements and system capability to cope with the mission uncertainties. The mission mode is entry from orbit.
Two general types of terminal phase decelerator systems are analyzed; aerodynamic and allretro systems. The aerodynamic decelerators considered include both subsonic type parachutes and (supersonic) ballutes. Subsonic type parachutes are limited to a maximum deployment Mach No. of 1.6. Supersonic ballutes are assumed deployed at Mach Nos. from 3.0 to 5.0. Both groups use a propulsive retro vernier system for final deceleration and landing. The all-retro system analysis assumes a rocket propulsion system with two phases - initial braking followed by a vertical descent
Dwarf Mistletoe Parasite in Spruce
Locations of all known major infection centers of dwarf mistletoe (Arceuthobium pusillum) in Minnesota are presented and compared to botanical ranges of important hosts. A brief summary of disease symptoms and identification of the parasite are included
Dynamics of Perfectly Wetting Drops under Gravity
We study the dynamics of small droplets of polydimethylsiloxane (PDMS)
silicone oil on a vertical, perfectly-wetting, silicon wafer. Interference
videomicroscopy allows us to capture the dynamics of these droplets. We use
droplets with a volumes typically ranging from 100 to 500 nanolitres
(viscosities from 10 to 1000 centistokes) to understand long time derivations
from classical solutions. Past researchers used one dimensional theory to
understand the typical scaling for the position of the tip of the
droplet in time . We observe this regime in experiment for intermediate
times and discover a two-dimensional, similarity solution of the shape of the
droplet. However, at long times our droplets start to move more slowly down the
plane than the scaling suggests and we observe deviations in droplet
shape from the similarity solution. We match experimental data with simulations
to show these deviations are consistent with retarded van der Waals forcing
which should become significant at the small heights observed
Drying and cracking mechanisms in a starch slurry
Starch-water slurries are commonly used to study fracture dynamics. Drying
starch-cakes benefit from being simple, economical, and reproducible systems,
and have been used to model desiccation fracture in soils, thin film fracture
in paint, and columnar joints in lava. In this paper, the physical properties
of starch-water mixtures are studied, and used to interpret and develop a
multiphase transport model of drying. Starch-cakes are observed to have a
nonlinear elastic modulus, and a desiccation strain that is comparable to that
generated by their maximum achievable capillary pressure. It is shown that a
large material porosity is divided between pore spaces between starch grains,
and pores within starch grains. This division of pore space leads to two
distinct drying regimes, controlled by liquid and vapor transport of water,
respectively. The relatively unique ability for drying starch to generate
columnar fracture patterns is shown to be linked to the unusually strong
separation of these two transport mechanisms.Comment: 9 pages, 8 figures [revised in response to reviewer comments
Drying and cracking mechanisms in a starch slurry
Starch-water slurries are commonly used to study fracture dynamics. Drying
starch-cakes benefit from being simple, economical, and reproducible systems,
and have been used to model desiccation fracture in soils, thin film fracture
in paint, and columnar joints in lava. In this paper, the physical properties
of starch-water mixtures are studied, and used to interpret and develop a
multiphase transport model of drying. Starch-cakes are observed to have a
nonlinear elastic modulus, and a desiccation strain that is comparable to that
generated by their maximum achievable capillary pressure. It is shown that a
large material porosity is divided between pore spaces between starch grains,
and pores within starch grains. This division of pore space leads to two
distinct drying regimes, controlled by liquid and vapor transport of water,
respectively. The relatively unique ability for drying starch to generate
columnar fracture patterns is shown to be linked to the unusually strong
separation of these two transport mechanisms.Comment: 9 pages, 8 figures [revised in response to reviewer comments
Special Theory of Relativity through the Doppler Effect
We present the special theory of relativity taking the Doppler effect as the
starting point, and derive several of its main effects, such as time dilation,
length contraction, addition of velocities, and the mass-energy relation, and
assuming energy and momentum conservation, we discuss how to introduce the
4-momentum in a natural way. We also use the Doppler effect to explain the
"twin paradox", and its version on a cylinder. As a by-product we discuss
Bell's spaceship paradox, and the Lorentz transformation for arbitrary
velocities in one dimension.Comment: 20 pages, 1 figur
Crushed Stone Aggregate Resources of Indiana
Indiana Geological Survey Bulletin 42-HMineral aggregate is an aggregation of mineral material, such as
crushed rock, expanded shale, perlite, sand and gravel, shells, or slag.
It is sometimes bound with such material as cement or asphalt or is
sometimes not bound for use as filter stone, flux stone, railroad
ballast, riprap, or road metal. Crushed limestone and dolomite, sand
and gravel, slag, perlite, and expanded shale are the main natural and
fabricated aggregates currently used in Indiana. Some aggregate, such
as sand and gravel, requires little or no processing and can be used
almost as it is mined, but rock must be crushed and sorted into
various desired sizes before it can be used. Many types of rocks can
be used for crushed stone aggregate, but limestone and dolomite are
used exclusively in Indiana (pl. 1). In this report crushed stone is
synonymous with crushed limestone and dolomite.
Each type of aggregate has a distinct advantage with respect to
cost and availability or to a specific use for which one type is more
suited than another. The advantages of crushed limestone and
dolomite are that they can be crushed and sized to meet most specifications,
the materials are clean and angular and bind well with
cementing mixtures, a uniform lithologic composition can be maintained
with little or no selective quarrying in many areas, and they
are available at low cost in most counties in Indiana. Crushed stone
is one of Indiana’s most important mineral commodities, ranking
third in annual value behind coal and cement. During 1969 crushed
stone production in Indiana totaled 25, 516,000 tons and was valued
at $34,418,000.Indiana Department of Natural Resource
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