48,002 research outputs found
Review of: Sharon M. Friedman et al. eds., Communicating Uncertainty
A review of the book Communicating Uncertainty: Media Coverage of New and Controversial Science (Sharon M. Friedman, Sharon Dunwoody & Carol L. Rogers, eds.; Lawrence Erlbaum Associates 1999). Preface, introduction. ISBN 0-8058-2728-5 [261 pp. $32.50. Paperback, 10 Industrial Avenue, Mahwah, NJ 07430-2262]
On the Origin of Narrow, Very Long, Straight Jets from Some Newly Forming Stars
Observations have shown the existence of narrow, very long, straight jets
emitted by some newly forming stars (1). It is highly likely that stars forming
in the plane of a spiral galaxy do so in the presence of an almost uniform
magnetic field. In the Strong Magnetic Field model (SMF), gravitational
collapse of a highly conducting plasma in the presence of such a field will
result in the formation of a stable, highly relativistic current loop (storage
ring) around the central object. The concept was first described by Greyber
(2-14). In the figures in Mestel & Strittmatter (15), one can see such a
storage ring beginning to form. Such an increasing dipole magnetic field
(formed temporarily for 10 to 10 years) will produce, accelerate and
confine a narrow, very long, straight jet. When the density becomes too high,
either the loop is destroyed, or the current-carrying plasma ring is buried
inside the newly forming star and is the source of primordial stellar
magnetism.Comment: 6 pages, LaTeX-AAS styl
Modelling and directionally encoding the acoustics of a room
Geometrical methods are often used to model the acoustic properties of a room, but are valid only for high frequencies. At low frequencies. diffraction and the effects of room modes cannot be neglected. A method for modelling the two-dimensional propagation of sound within an enclosed room is presented which encompasses both of these particular properties by making use of a digital waveguide model
Orderly Marketing in Agriculture Revisited
This paper presents a model of economic behavior that explicates the phenomenon known as “orderly marketing,†which was a main objective of the Marketing Orders agricultural program introduced early in the New Deal. Recent analyses of marketing orders start with an implicit assumption that there is no market failure—thus, that price regulation can cause only deviations from the first-best market solution. However, historical evidence suggests that disorderly marketing might refer to a kind of market imperfection. In the model presented here, a monopsonist processor sets a price to be paid, and an aggregate quantity to be purchased. In some states of the world, some farmers are excluded from the market. In other words, nonprice rationing can occur, and changes in consumer expenditure for the final product are absorbed by the processor rather than passed along to the farmer. The classified price and pooling provisions of federal orders can lead to a Pareto improvement in welfare.disorderly marketing, market orders, Marketing,
A Martian global groundwater model
A global groundwater flow model was constructed for Mars to study hydrologic response under a variety of scenarios, improving and extending earlier simple cross sectional models. The model is capable of treating both steady state and transient flow as well as permeability that is anisotropic in the horizontal dimensions. A single near surface confining layer may be included (representing in these simulations a coherent permafrost layer). Furthermore, in unconfined flow, locations of complete saturation and seepage are determined. The flow model assumes that groundwater gradients are sufficiently low that DuPuit conditions are satisfied and the flow component perpendicular to the ground surface is negligible. The flow equations were solved using a finite difference method employing 10 deg spacing of latitude and longitude
- …