10 research outputs found
Accretion, Outflows, and Winds of Magnetized Stars
Many types of stars have strong magnetic fields that can dynamically
influence the flow of circumstellar matter. In stars with accretion disks, the
stellar magnetic field can truncate the inner disk and determine the paths that
matter can take to flow onto the star. These paths are different in stars with
different magnetospheres and periods of rotation. External field lines of the
magnetosphere may inflate and produce favorable conditions for outflows from
the disk-magnetosphere boundary. Outflows can be particularly strong in the
propeller regime, wherein a star rotates more rapidly than the inner disk.
Outflows may also form at the disk-magnetosphere boundary of slowly rotating
stars, if the magnetosphere is compressed by the accreting matter. In isolated,
strongly magnetized stars, the magnetic field can influence formation and/or
propagation of stellar wind outflows. Winds from low-mass, solar-type stars may
be either thermally or magnetically driven, while winds from massive, luminous
O and B type stars are radiatively driven. In all of these cases, the magnetic
field influences matter flow from the stars and determines many observational
properties. In this chapter we review recent studies of accretion, outflows,
and winds of magnetized stars with a focus on three main topics: (1) accretion
onto magnetized stars; (2) outflows from the disk-magnetosphere boundary; and
(3) winds from isolated massive magnetized stars. We show results obtained from
global magnetohydrodynamic simulations and, in a number of cases compare global
simulations with observations.Comment: 60 pages, 44 figure
Historical Analysis of the U.S. Oyster Market with Emphasis on the Role of Imports
The U.S. oyster supply has experienced a substantial change in
its composition. Since 1950 total'oyster imports have more. than
tripled, with most of this increase coming from Japan. Imports now
account for 23 percent of total U.S. supply. The Pacific Coast
receives nearly 60 percent of all U.S. imports and the Atlantic and
Gulf Coasts receive approximately 18 percent each.
The U.S. oyster industry has been beset by a number of problems.
These problems include an antiquated regulatory structure, competition
for the resource base, pollution, MSX disease, stagnant technology,
declining consumption and imports. As a result the trend in annual
harvests has shown a considerable decrease since 1950, particularly
in middle Atlantic States where it decreased from 18 to 2 million
pounds in only 19 years. Harvesting techniques and ownership patterns
are also examined and decreased use of dredges and private oyster
grounds are noted.
All of these problems affecting the oyster industry have affected
profits. To fully understand the role of imports in their effect on
profits other determinants of profitability must also be measured. Independent of these other problems, however, imports are shown
to have had a measurable impact in some instances in the Gulf and the
Pacific region
Discussions and Research on Ocean Fishery Management: A Summary of U.S. Workshop
In November of 1970 the U.S. National Marine Fisheries Service, its Division of Economic Research, held a subject workshop which was attended by 60 persons from broad research backgrounds, including representatives from the British Whitefish Authority, the ORganization fro Economic Co-operation and Development, and Food and Agricultural Fisheries and Forestry, as well as representatives of U.S. government agencies and universities. Research topics ranged from production economics and bio-economic models to general discussions of management for both conservation and economic purposes, the political framework involved. This paper summarizes the key issues in the 16 papers presented at that Workshop and the discussions that resulted. The highlights of these issues are presented to this symposium in the form of suggested critical problems which must urgently be faced by the professionals gathered here
The Domain of Population Dynamics and Production Economcis in Fisheries Management Research
With growing conceptual acceptability of fishery management techniques which advocate the reduction in the number of units of effort applied to overexploited and/or overcapitalized fisheries it is increasingly necessary that some readily usable measures be developed whihc may serve all those involved in fishery management and supporting research. Toward this end this paper examines the foundations of measures of fishing effort and fishing power as conceived within the domains of population dynamics and production economics. The degree to whiche ach discipline generates different and mutually exclusive measures is examined, along with an attempt to delineate a separate and distinct role for each discipline within the overall process of generating supporting information needed in all generalized fishery management plan
A Price Incentive Plan for Distressed Fisheries
Many regional fisheries have reached crossroads and decisions
must be made. Vast untapped resources exist as a potential foundation
for a revitalized fishery. In addition, there exists available
unemployed labor and capital in harvesting, processing, and marketing.
As many of the traditional fisheries must continue at a low level due
to an array of circumstances, we propose to encourage the transfer
of effort to underutilized resources by paeans of price incentives.
This will complement existing programs concerned primarily.with the
acquisition of basic technical and biological data or long run
improvements in harvesting efficiency as provided in part by the
Fishing Fleet Improvement Act