1,661 research outputs found
Gladys-on-the-Prairie: The effect of social and environmental forces on the identity and life of Dr. Gladys C. Galligar
Twentieth century Americans recognized problems created by both the subjected status women held by society and the harmful impact humanity had on natural resources and domains. Americaâs search for realization and solutions for the inherent problems associated with the devaluation of women and nature did not come quickly or easily; it took a path that wound around both traditional concepts and progressive insights. I argue in this thesis that the biography of Dr. Gladys C. Galligar demonstrates, on an intimate level, Americaâs dawning awareness of the necessity of a healthier environment and a more egalitarian society. As a biology researcher and educator, she participated in the development of the school of American ecology; as a professional and empowered woman, she was both benefactor and survivor of societyâs struggle with gender. Her self-identity was the product of both the natural world and society, and as such she lived in the epicenter of the debate between tradition and progress
Photoelasticity as a Research Technique for Analyzing Stresses in Dental Structures
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67063/2/10.1177_00220345550340060601.pd
First-principles study of stability and vibrational properties of tetragonal PbTiO_3
A first-principles study of the vibrational modes of PbTiO_3 in the
ferroelectric tetragonal phase has been performed at all the main symmetry
points of the Brillouin zone (BZ). The calculations use the local-density
approximation and ultrasoft pseudopotentials with a plane-wave basis, and
reproduce well the available experimental information on the modes at the Gamma
point, including the LO-TO splittings. The work was motivated in part by a
previously reported transition to an orthorhombic phase at low temperatures
[(J. Kobayashi, Y. Uesu, and Y. Sakemi, Phys. Rev. B {\bf 28}, 3866 (1983)]. We
show that a linear coupling of orthorhombic strain to one of the modes at Gamma
plays a role in the discussion of the possibility of this phase transition.
However, no mechanical instabilities (soft modes) are found, either at Gamma or
at any of the other high-symmetry points of the BZ.Comment: 8 pages, two-column style with 3 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#ag_pbt
Phase transitions in BaTiO from first principles
We develop a first-principles scheme to study ferroelectric phase transitions
for perovskite compounds. We obtain an effective Hamiltonian which is fully
specified by first-principles ultra-soft pseudopotential calculations. This
approach is applied to BaTiO, and the resulting Hamiltonian is studied
using Monte Carlo simulations. The calculated phase sequence, transition
temperatures, latent heats, and spontaneous polarizations are all in good
agreement with experiment. The order-disorder vs.\ displacive character of the
transitions and the roles played by different interactions are discussed.Comment: 13 page
Flavour Universal Dynamical Electroweak Symmetry Breaking
The top condensate see-saw mechanism of Dobrescu and Hill allows electroweak
symmetry to be broken while deferring the problem of flavour to an electroweak
singlet, massive sector. We provide an extended version of the singlet sector
that naturally accommodates realistic masses for all the standard model
fermions, which play an equal role in breaking electroweak symmetry. The models
result in a relatively light composite Higgs sector with masses typically in
the range of (400-700)~GeV. In more complete models the dynamics will
presumably be driven by a broken gauged family or flavour symmetry group. As an
example of the higher scale dynamics a fully dynamical model of the quark
sector with a GIM mechanism is presented, based on an earlier top condensation
model of King using broken family gauge symmetry interactions (that model was
itself based on a technicolour model of Georgi). The crucial extra ingredient
is a reinterpretation of the condensates that form when several gauge groups
become strong close to the same scale. A related technicolour model of Randall
which naturally includes the leptons too may also be adapted to this scenario.
We discuss the low energy constraints on the massive gauge bosons and scalars
of these models as well as their phenomenology at the TeV scale.Comment: 22 pages, 3 fig
Search for Small Trans-Neptunian Objects by the TAOS Project
The Taiwan-America Occultation Survey (TAOS) aims to determine the number of
small icy bodies in the outer reach of the Solar System by means of stellar
occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9)
telescopes have been installed at Lulin Observatory in Taiwan to simultaneously
monitor some thousand of stars for such rare occultation events. Because a
typical occultation event by a TNO a few km across will last for only a
fraction of a second, fast photometry is necessary. A special CCD readout
scheme has been devised to allow for stellar photometry taken a few times per
second. Effective analysis pipelines have been developed to process stellar
light curves and to correlate any possible flux changes among all telescopes. A
few billion photometric measurements have been collected since the routine
survey began in early 2005. Our preliminary result of a very low detection rate
suggests a deficit of small TNOs down to a few km size, consistent with the
extrapolation of some recent studies of larger (30--100 km) TNOs.Comment: 4 pages, 3 figures, IAU Symposium 23
On Yukawa quasi-unification with mu<0
Although recent data on the muon anomalous magnetic moment strongly disfavor
the constrained minimal supersymmetric standard model with mu<0, they cannot
exclude it because of theoretical ambiguities. We consider this model
supplemented by a Yukawa quasi-unification condition which allows an acceptable
b-quark mass. We find that the cosmological upper bound on the lightest
sparticle relic abundance is incompatible with the data on the branching ratio
of b-->s gamma, which is evaluated by including all the next-to-leading order
corrections. Thus, this scheme is not viable.Comment: 4 pages including 3 figures, Revte
Constraints on Masses of Charged PGBs in Technicolor Model from Decay
In this paper we calculate the contributions to the branching ratio of from the charged Pseudo-Goldstone bosons appeared in one generation
Technicolor model. The current experimental results can eliminate large
part of the parameter space in the plane, and
specifically, one can put a strong lower bound on the masses of color octet
charged PGBs : at for free
.Comment: 9 pages, 3 figures(uuencoded), Minor changes(Type error), to appear
in Phys. Rev.
Book Reviews
Review of Prehistory, by Derek Roe; Aspects of Prehistory, by Grahame Clark; World Prehistory, by Grahame Clark; Introductory Readings in Archaeology, by Brian M. Fagan, ed.; The Origins of Civilization, by Carroll L. Riley; The Archaeology of Early Man, by J. M. Coles and E. S. Higgs; Shipwrecks and Archaeology, by Peter Throckmorton; A History of Dyed Textiles, by Stuart Robinson; Food in Antiquity, by Don and Patricia Brothwell; World Archaeology, Vol. 1, nos. 1, 2, 3, by Roy Hodson and Colin Platt, eds.; The Structure and Growth of Australia's Aboriginal Population, by F. Lancaster Jones; Attitudes and Social Conditions, by Ronald Taft, John L. M. Dawson, and Pamela Beasley; Aboriginal Settlements, by J. P. M. Long; The Destruction of Aboriginal Society, by C. D. Rowley; Aboriginal Advancement to Integration, by H. P. Schapper
Ab-initio study of BaTiO3 surfaces
We have carried out first-principles total-energy calculations of (001)
surfaces of the tetragonal and cubic phases of BaTiO3. Both BaO-terminated
(type I) and TiO2-terminated (type II) surfaces are considered, and the atomic
configurations have been fully relaxed. We found no deep-gap surface states for
any of the surfaces, in agreement with previous theoretical studies. However,
the gap is reduced for the type-II surface, especially in the cubic phase. The
surface relaxation energies are found to be substantial, i.e., many times
larger than the bulk ferroelectric well depth. Nevertheless, the influence of
the surface upon the ferroelectric order parameter is modest; we find only a
small enhancement of the ferroelectricity near the surface.Comment: 8 pages, two-column style with 4 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#pad_sur
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