52 research outputs found
Non-collinear magnetism in iron at high pressures
Using a first principles based, magnetic tight-binding total energy model,
the magnetization energy and moments are computed for various ordered spin
configurations in the high pressure polymorphs of iron (fcc, or -Fe,
and hcp, or -Fe), as well ferromagnetic bcc iron (-Fe). For
hcp, a non-collinear, antiferromagnetic, spin configuration that minimizes
unfavorable ferromagnetic nearest neighbor ordering is the lowest energy state
and is more stable than non-magnetic iron up to about 75 GPa.
Accounting for non-collinear magnetism yields better agreement with the
experimental equation of state, in contrast to the non-magnetic equation of
state, which is in poor agreement with experiment below 50 GPa
Stellar structure and compact objects before 1940: Towards relativistic astrophysics
Since the mid-1920s, different strands of research used stars as "physics
laboratories" for investigating the nature of matter under extreme densities
and pressures, impossible to realize on Earth. To trace this process this paper
is following the evolution of the concept of a dense core in stars, which was
important both for an understanding of stellar evolution and as a testing
ground for the fast-evolving field of nuclear physics. In spite of the divide
between physicists and astrophysicists, some key actors working in the
cross-fertilized soil of overlapping but different scientific cultures
formulated models and tentative theories that gradually evolved into more
realistic and structured astrophysical objects. These investigations culminated
in the first contact with general relativity in 1939, when J. Robert
Oppenheimer and his students George Volkoff and Hartland Snyder systematically
applied the theory to the dense core of a collapsing neutron star. This
pioneering application of Einstein's theory to an astrophysical compact object
can be regarded as a milestone in the path eventually leading to the emergence
of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal
Evaluation of a Screening Procedure for Basic and Neutral Drugs: N-Butyl Chloride Extraction and Megabore Capillary Gas Chromatography
Studies of Long-term Continuous Irradiations Using Daily Doses Ranging From 0.07 To 0.30 Gy On the B-lymphoid System of the Rat
The Effect of Low Exposure-rate Gamma Irradiation on T and B Lymphocyte Function in the Mouse
Studies of Long-term Continuous Irradiations Using Daily Doses Ranging from 0·07 to 0·30 Gy on the B lymphoid System of the Rat
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