4,449 research outputs found
Political philosophy and political action: Science, social science and the American experience
[Δε διατίθεται περίληψη / no abstract available][Δε διατίθεται περίληψη / no abstract available
Populism and its perils: language and politics
Populism appeals to the masses, and against elites. To the extent that any successful democracy must respond to popular desires, democracies must incorporate some elements of populism. Nevertheless, for continued success a democratic polity also must ensure widespread education, including a concern for language and the ability to analyze and resist “mind manipulators”
Will the Three Gorges Dam affect the underwater light climate of Vallisneria spiralis L. and food habitat of Siberian crane in Poyang Lake?
Almost 95% of the entire population of the Siberian crane (Grus leucogeranus) winter in Poyang Lake, China, where they forage on the tubers of the submerged aquatic macrophyte Vallisneria spiralis. The Three Gorges Dam on the Yangtze River may possibly affect this food source of the Siberian crane by affecting the light intensity reaching the top of the V. spiralis canopy. In this study, the photosynthetically active radiation at the top of the V. spiralis canopy (PARtc) in Lake Dahuchi was modeled from 1998 to 2006, and the potential impacts of changes in water level and turbidity on the underwater light climate of V. spiralis were analyzed. PARtc was calculated from incident irradiance while the losses due to reflection at the water surface, absorption, and scattering within the water column were taken into consideration. The results indicated significant differences in PARtc between years. Six years of water level and Secchi disk depth records revealed a seasonal switching of the lake from a turbid state at low water levels in autumn, winter, and spring to a clear state at high water levels during the monsoon in summer. The highest PARtc occurred at intermediate water levels, which were reached when the Yangtze River forces Lake Dahuchi out of its turbid state in early summer and the water becomes clear. The intended operation of the Three Gorges Dam, which will increase water levels in May and June, may advance the moment when Lake Dahuchi switches from turbid to clear. We suggest that this might increase production of V. spiralis and possibly improve the food habitat conditions for wintering Siberian crane in Poyang Lake
Fireball Models for Flares in AE Aquarii
We examine the flaring behaviour of the cataclysmic variable AE~Aqr in the
context of the `magnetic propeller' model for this system. The flares are
thought to arise from collisions between high density regions in the material
expelled from the system after interaction with the rapidly rotating
magnetosphere of the white dwarf. We calculate the first quantitative models
for the flaring and calculate the time-dependent emergent optical spectra from
the resulting hot, expanding ball of gas. We compare the results under
different assumptions to observations and derive values for the mass,
lengthscale and temperature of the material involved in the flare. We see that
the fits suggest that the secondary star in this system has Population II
composition.Comment: 19 pages, 24 figure
- …