8,322 research outputs found
Isolated cold plasma regions: Observations and their relation to possible production mechanisms
Regions of enhanced cold plasma, isolated from the main plasmasphere along the Explorer 45 orbit on the equatorial plane, are reported using the sheath induced potentials seen by the electric field experiment. The occurrence of these regions has a strong correlation with negative enhancements of Dst, and their locations are primarily in the noon-dusk quadrant. The data support the concept that changes in large scale convection play a dominant role in the formation of these regions. Plasmatails that are predicted from enhancements of large scale convection electric fields in general define where these regions may be found. More localized processes are necessary to account for the exact configuration and structure seen in these regions and may eventually result in detachment from the main plasmasphere
Variational electric fields at low latitudes and their relation to spread F and plasma irregularities
Recordings from OGO 6 show that electric field irregularities are frequently present between + or - 35 deg geomagnetic latitude in the 2000 - 0600 local time sector. The signatures are very clear, and are easily distinguished from the normal AC background noise, and whistler and emission activity. The spectral appearance of the fields makes it meaningful to distinguish between 3 different types of irregularities: strong irregularities, weak irregularities, and weak irregularities with a rising spectrum. Strong irregularities seem most likely to occur in regions where gradients in ionization are present. Changes in plasma composition, resulting in an increase in the mean ion mass, are also often observed in the irregularity regions. Comparison with ground based ionosondes indicates a connection between strong irregularities and low latitude spread F. A good correlation is also present between strong fields and small scale fluctuations in ionization, delta N/N 1 percent. From the data it appears as if a gradient driven instability is the most likely source of the strong irregularities
Geologic considerations in underground coal mining system design
Geologic characteristics of coal resources which may impact new extraction technologies are identified and described to aid system designers and planners in their task of designing advanced coal extraction systems for the central Appalachian region. These geologic conditions are then organized into a matrix identified as the baseline mine concept. A sample region, eastern Kentucy is analyzed using both the developed baseline mine concept and the traditional geologic investigative approach
Prisoner's Dilemma cellular automata revisited: evolution of cooperation under environmental pressure
We propose an extension of the evolutionary Prisoner's Dilemma cellular
automata, introduced by Nowak and May \cite{nm92}, in which the pressure of the
environment is taken into account. This is implemented by requiring that
individuals need to collect a minimum score , representing
indispensable resources (nutrients, energy, money, etc.) to prosper in this
environment. So the agents, instead of evolving just by adopting the behaviour
of the most successful neighbour (who got ), also take into account if
is above or below the threshold . If an
individual has a probability of adopting the opposite behaviour from the one
used by its most successful neighbour. This modification allows the evolution
of cooperation for payoffs for which defection was the rule (as it happens, for
example, when the sucker's payoff is much worse than the punishment for mutual
defection). We also analyse a more sophisticated version of this model in which
the selective rule is supplemented with a "win-stay, lose-shift" criterion. The
cluster structure is analyzed and, for this more complex version we found
power-law scaling for a restricted region in the parameter space.Comment: 15 pages, 8 figures; added figures and revised tex
Chains of large gaps between primes
Let denote the -th prime, and for any and sufficiently
large , define the quantity which measures the occurrence of
chains of consecutive large gaps of primes. Recently, with Green and
Konyagin, the authors showed that for sufficiently large . In this
note, we combine the arguments in that paper with the Maier matrix method to
show that for any fixed and sufficiently large . The
implied constant is effective and independent of .Comment: 16 pages, no figure
UNDERSTANDING THE MARKET FOR HOLSTEIN STEERS
A semi-structured interview process was combined with an econometric analysis to document the newly changed structure of the Holstein sector, to evaluate existing quality perceptions, and to assess the impact that recent changes in production practices have had on prices of Holstein steers. Results suggest that finished Holstein steer prices are driven by many of the same market factors as native steers, overturning some common quality misconceptions. The shift towards the calf-fed production model appears to have greatly affected the market for backgrounded Holstein steers, but had little impact on the prices for light Holstein feeder steers.Livestock Production/Industries, Marketing,
Market Potential for Locally Produced Meat Products
The goal of this research was to guide livestock producers in marketing, product design and pricing decisions. Tools included a focus group, a consumer taste-testing and willingness-to-pay survey, and a restaurant survey. Experience attributes of locally produced ground beef were especially competitive, and demand for credence attributes packaged under the "local" label appears consistent with a niche market that could justify verification programs. Restaurants are a potentially receptive outlet for local meats, allowing producers to avoid the barriers to entry in mainstream grocery outlets.Agribusiness,
Understanding the Market for Holstein Steers
A semi-structured interview process was combined with an econometric analysis to document the newly changed structure of the Holstein sector, to evaluate existing quality perceptions, and to assess the impact that recent changes in production practices have had on prices of Holstein steers. Results suggest that finished Holstein steer prices are driven by many of the same market factors as native steers, overturning some common quality misconceptions. The shift towards the calf-fed production model appears to have greatly affected the market for backgrounded Holstein steers, but had little impact on the prices for light Holstein feeder steers.Marketing,
The synthesis of potential antimalarials. Derivatives of pantoyltaurine
The general hypothesis as to the mode of action of chemotherapeutic agents, which has been formulated by Fildes, Woods, McIlwain, and others (2), offers a rational and useful guide to the design of new drugs. Thus, bacteriostasis is pictured as caused by the blocking of reactions essential to growth by an inhibiting substance which has a structure similar to that of one of the normal enzymes or metabolites essential to the growth of the organism
Adsorption properties and third sound propagation in superfluid He films on carbon nanotubes
We consider the adsorption properties of superfluid He films on carbon
nanotubes. One major factor in the adsorption is the surface tension force
arising from the very small diameter of the nanotubes. Calculations show that
surface tension keeps the film thickness on the tubes very thin even when the
helium vapor is increased to the saturated pressure. The weakened Van der Waals
force due to the cylindrical geometry also contributes to this. Both of these
effects act to lower the predicted velocity of third sound propagation along
the tubes. It does not appear that superfluidity will be possible on
single-walled nanotubes of diameter about one nm, since the film thickness is
less than 3 atomic layers even at saturation. Superfluidity is possible on
larger-diameter nanotube bundles and multi-walled nanotubes, however. We have
observed third sound signals on nanotube bundles of average diameter 5 nm which
are sprayed onto a Plexiglass surface, forming a network of tubes.Comment: 4 pages, accepted for Journal of Physics: Conference Series
(Proceedings of LT25
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