1,281 research outputs found
Progress Toward an Unthinkable Consummation: Sin and the Evolution of Human Consciousness
Michael Polanyi has argued that tacit knowing—the consolidation and integration of earlier achievements from which to launch further advances— plays an essential role in evolution. Tacit knowledge is often transmitted by observation and imitation—what anthropologist Rene Girard calls mimesis. Girard suggests that this mimetic tendency has had both beneficial and negative effects: violent outbreaks of mimetic rivalry among early hominids necessitated the development of ritual controls, representing the beginning of culture. Beneath all culture, a universal scapegoating mechanism—humankind\'s \"original sin\"—remains hidden. Jewish and Christian scriptures present a countervailing cultural force, challenging human beings to develop in directions not dependent on rivalry and violence
Electronic theory for superconductivity in SrRuO: triplet pairing due to spin-fluctuation exchange
Using a two-dimensional Hubbard Hamiltonian for the three electronic bands
crossing the Fermi level in SrRuO we calculate the band structure and
spin susceptibility in quantitative agreement with
nuclear magnetic resonance (NMR) and inelastic neutron scattering (INS)
experiments. The susceptibility has two peaks at {\bf Q}
due to the nesting Fermi surface properties and at {\bf q}
due to the tendency towards ferromagnetism. Applying spin-fluctuation exchange
theory as in layered cuprates we determine from ,
electronic dispersions, and Fermi surface topology that superconductivity in
SrRuO consists of triplet pairing. Combining the Fermi surface topology
and the results for we can exclude and wave
symmetry for the superconducting order parameter. Furthermore, within our
analysis and approximations we find that -wave symmetry is slightly favored
over p-wave symmetry due to the nesting properties of the Fermi surface.Comment: 5 pages, 5 figures, misprints correcte
Spin-triplet superconductivity due to antiferromagnetic spin-fluctuation in Sr_2RuO_4
A mechanism leading to the spin-triplet superconductivity is proposed based
on the antiferromagnetic spin fluctuation. The effects of anisotropy in spin
fluctuation on the Cooper pairing and on the direction of d vector are examined
in the one-band Hubbard model with RPA approximation. The gap equations for the
anisotropic case are derived and applied to Sr_2RuO_4. It is found that a
nesting property of the Fermi surface together with the anisotropy leads to the
triplet superconductivity with the d=z(sin{k_x}\pm isin{k_y}), which is
consistent with experiments.Comment: 4 pages, 3 eps figures, revte
Contribution of Freshwater Bivalves to Muskrat Diets in the Green River, Mammoth Cave National Park, Kentucky
Muskrats (Ondatra zibethicus) are known to prey on freshwater bivalves (mussels and clams) and can negatively impact imperiled mussel species. However, factors that infl uence muskrat predation on bivalves are poorly understood. We evaluated the feeding ecology of muskrats at Mammoth Cave National Park, Kentucky by using stable isotope analysis of muskrat hair samples and by monitoring bivalve shell deposition at muskrat middens. Bayesian mixing-model analysis of stable isotope δ15N and δ13C ratios revealed that the median muskrat biomass derived from bivalves was 51.4% (5th and 95th percentiles were 39.1 to 63.4%, respectively), a much higher dietary proportion than previously reported. Shell depositions by muskrats at middens decreased with the availability of seasonal emergent vegetation, suggesting that the consumption of animal matter is in response to a scarcity of plant foods. Our results add to the growing body of evidence that muskrats have the potential to impact mussel population growth and recovery in some environments
The evolution of galaxy formation
Our history of understanding galaxy formation could be traced through the
development of individual ideas. A cynic might be tempted to suggest that new
catchphrases are developed at a faster rate than genuine progress is made.Comment: 10 pages, Plain TeX, no figures. A slightly abbreviated version of
this article appears in the December issue of Astronomy & Geophysic
Resource Partitioning among Young-of-year Sunfish (Lepomis Spp.), And Phenotypic Variation of Bluegills (L. Macrochirus)
Zoolog
The Structure and Interpretation of Cosmology: Part I - General Relativistic Cosmology
The purpose of this work is to review, clarify, and critically analyse modern
mathematical cosmology. The emphasis is upon mathematical objects and
structures, rather than numerical computations. This paper concentrates on
general relativistic cosmology. The opening section reviews and clarifies the
Friedmann-Robertson-Walker models of general relativistic cosmology, while
Section 2 deals with the spatially homogeneous models. Particular attention is
paid in these opening sections to the topological and geometrical aspects of
cosmological models. Section 3 explains how the mathematical formalism can be
linked with astronomical observation. In particular, the informal,
observational notion of the celestial sphere is given a rigorous mathematical
implementation. Part II of this work will concentrate on inflationary cosmology
and quantum cosmology
Clausius' Virial vs. Total Potential Energy in the dynamics of a two-component system
In a gravitational virialized bound system built up of two components, one of
which is embedded in the other, the Clausius' virial energy of one subcomponent
is not, in general, equal to its total potential energy, as occurs in a single
system without external forces. This is the main reason for the presence, in
the case of two non-coinciding concentric spheroidal subsystems, of a minimum
(in absolute value) in the Clausius' virial of the inner component B, when it
assumes a special configuration characterized by a value of its semi-major axis
we have named "tidal radius". The physical meaning, connected with its
appearance, is to introduce a scale length on the gravity field of the inner
subsystem, which is induced from the outer one. Its relevance in the galaxy
dynamics has been stressed by demonstrating that some of the main features of
the Fundamental Plane may follow as consequence of its existence. More physical
insight into the dynamics of a two component system may be got by looking at
the location of this scale length inside the plots of the potential energies of
each subsystem and of the whole system and by also taking into account the
trend of the anti-symmetric residual-energy, that is the difference between the
tidal and the interaction-energy of each component. Some thermodynamical
arguments related to the inner component are also added to prove as special is
the "tidal radius configuration". Moreover the role of the divergency at the
center of the two subsystems in obtaining this scale length is considered. For
the sake of simplicity the analysis has been performed in the case of a frozen
external component even if this constraint does not appear to be too relevant
in order to preserve the main results.Comment: New Astronomy, accepte
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