70,937 research outputs found
Stocking, Enhancement, and Mariculture of Penaeus orientalis and Other Species in Shanghai and Zhejiang Provinces, China
China's marine aquaculture landings provide only 18% of its combined freshwater and amrine capture and culture landings, at a per-capita consumption of only 3.2 kg/yr out of a total of 18.1 kg/yr. We described development and some of the results of long-term mariculture and stocking/enhancement projects that have been underway for up to 20 years in the Hangzhou Bay area. Penaeus orientalis (also referred to as P. chinensis) stocking provided up to 400 t/yr, at a total cost-benefit ratio of up to 8 Yuan of landed shrimp per Yuan invested in shrimp stocking. Over 40 t of Penaeus orientalis were produced commercially in 1993, with proceeds being used to fund mariculture and fisheries research. Large scale edible jellyfish restocking is also underway, while semicommercial culture of abalone, Haliotis diversicolor, has been successful. Technical problems limitig mariculture have been solved successfully for some species
Analytical models for quark stars
We find two new classes of exact solutions to the Einstein-Maxwell system of
equations. The matter content satisfies a linear equation of state consistent
with quark matter; a particular form of one of the gravitational potentials is
specified to generate solutions. The exact solutions can be written in terms of
elementary functions, and these can be related to quark matter in the presence
of an electromagnetic field. The first class of solutions generalises the Mak
and Harko model. The second class of solutions does not admit any singularities
in the matter and gravitational potentials at the centre.Comment: 10 pages, To appear in Int. J. Mod. Phys.
The gravitational field of a global monopole
We present an exact solution to the non-linear equation which describes a
global monopole in the flat space. We re-examine the metric and the geodesics
outside the global monopole. We will see that a global monopole produces a
repulsive gravitational field outside the core in addition to a solid angular
deficit. The lensing property of the global monopole and the global
monopole-antimonopole annihilation mechanism are studied.Comment: 8 pages, no figure
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