Impacts of Product Differentiation on the Crop Input Supply Industry

Agribusiness, Input Supply Industry, Seed, Pesticide, Farm Machinery, Structural Change, Porter’s Five Forces, Agribusiness, Crop Production/Industries, Q13, L10, L20, L80,

The White Dwarfs within 25 Parsecs of the Sun: Kinematics and Spectroscopic Subtypes

We present the fractional distribution of spectroscopic subtypes, range and distribution of surface temperatures, and kinematical properties of the white dwarfs within 25pc of the sun. There is no convincing evidence of halo white dwarfs in the total 25 pc sample of 224 white dwarfs. There is also little to suggest the presence of genuine thick disk subcomponent members within 25 parsecs. It appears that the entire 25 pc sample likely belong to the thin disk. We also find no significant kinematic differences with respect to spectroscopic subtypes. The total DA to non-DA ratio of the 25 pc sample is 1.8, a manifestation of deepening envelope convection which transforms DA stars with sufficiently thin H surface layers into non-DAs. We compare this ratio with the results of other studies. We find that at least 11% of the white dwarfs within 25 parsecs of the sun (the DAZ and DZ stars) have photospheric metals that likely originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, then it suggests the possibility that a similar percentage have planets, asteroid-like bodies or debris disks orbiting them. Our volume-limited sample reveals a pileup of DC white dwarfs at the well-known cutoff in DQ white dwarfs at Tef about 6000K. Mindful of small number statistics, we speculate on its possible evolutionary significance. We find that the incidence of magnetic white dwarfs in the 25 pc sample is at least 8%, in our volume-limited sample, dominated by cool white dwarfs. We derive approximate formation rates of DB and DQ degenerates and present a preliminary test of the evolutionary scenario that all cooling DB stars become DQ white dwarfs via helium convective dredge-up with the diffusion tail of carbon extending upward from their cores.Comment: Accepted for publication in The Astronomical Journa

Integrable Hamiltonian systems related to the Hilbert--Schmidt ideal

By application of the coinduction method as well as Magri method to the ideal of real Hilbert-Schmidt operators we construct the hierarchies of integrable Hamiltonian systems on the Banach Lie-Poisson spaces which consist of these type of operators. We also discuss their algebraic and analytic properties as well as solve them in dimensions N=2,3,4.Comment: 36 page

The Magnetosphere and Us

In this activity, students explore the size and shape of the magnetosphere and how long it takes various forms of particles and radiation to reach Earth from the sun. They will discover that the solar wind causes distortions in the magnetosphere, altering its shape and orientation in space. During this activity, students will label and describe the parts of the magretosphere and determine a scale based on the distances given in the accompanying figure. Educational levels: High school, Middle school