1,038 research outputs found
Summer Institute in Biomedical Engineering, 1973
Bioengineering of medical equipment is detailed. Equipment described includes: an environmental control system for a surgical suite; surface potential mapping for an electrode system; the use of speech-modulated-white-noise to differentiate hearers and feelers among the profoundly deaf; the design of an automatic weight scale for an isolette; and an internal tibial torsion correction study. Graphs and charts are included with design specifications of this equipment
Open access in humanities and social sciences: visions for the future of publishing
For this month's column, the editors are gearing up for the Library Publishing Forum, which will be held March 29?30, 2015, at Portland State University in Portland, Oregon. We have interviewed the forum's keynote speakers, Martin Paul Eve and John Willinsky, who will share their vision of open access in the humanities and social sciences as well as their thoughts on future developments
Expansion, Geometry, and Gravity
In general-relativistic cosmological models, the expansion history, matter
content, and geometry are closely intertwined. In this brief paper, we clarify
the distinction between the effects of geometry and expansion history on the
luminosity distance. We show that the cubic correction to the Hubble law,
measured recently with high-redshift supernovae, is the first cosmological
measurement, apart from the cosmic microwave background, that probes directly
the effects of spatial curvature. We illustrate the distinction between
geometry and expansion with a toy model for which the supernova results already
indicate a curvature radius larger than the Hubble distance.Comment: 4 pages, 1 color figur
New CMB Power Spectrum Constraints from MSAMI
We present new cosmic microwave background (CMB) anisotropy results from the
combined analysis of the three flights of the first Medium Scale Anisotropy
Measurement (MSAM1). This balloon-borne bolometric instrument measured about 10
square degrees of sky at half-degree resolution in 4 frequency bands from 5.2
icm to 20 icm with a high signal-to-noise ratio. Here we present an overview of
our analysis methods, compare the results from the three flights, derive new
constraints on the CMB power spectrum from the combined data and reduce the
data to total-power Wiener-filtered maps of the CMB. A key feature of this new
analysis is a determination of the amplitude of CMB fluctuations at . The analysis technique is described in a companion paper by Knox.Comment: 9 pages, 6 included figure
Provenance, protolith and metamorphic ages of jadeite-bearing orthogneiss and host paragneiss at Tavagnasco, the Sesia Zone, Lower Aosta Valley, Italy
An eclogite-facies orthogneiss and host paragneiss from a quarry
near Tavagnasco in the Lower Aosta Valley were studied in order to refine
the protolith, provenance and metamorphic ages of the Eclogitic Micaschist
Complex of the Sesia Zone. The orthogneiss contains jadeite with quartz + phengite + K-feldspar ± garnet + rutile + zircon, whereas the
paragneiss hosts garnet + jadeite + phengite ± glaucophane + epidote + rutile + quartz. Phase diagram modeling of two representative
samples yields minimum equilibration conditions of 550 ± 50 ∘C and 18 ± 2 kbar. Cathodoluminescence images of zircon from the
orthogneiss show oscillatory-zoned cores that are embayed and overgrown by
complex, oscillatory-zoned rims. Four concordant secondary ion mass
spectrometry analyses from the cores give a weighted mean
206Pb / 238U age of 457 ± 5 Ma. The cores have Th/U = 0.1
and negative Eu anomalies indicative of an igneous protolith, which we
interpret to have crystallized in the Ordovician at 780 ∘C, based
on Ti-in-zircon measurements. Zircon rims yield a range of
206Pb / 238U dates from 74 to 86 Ma, and four concordant analyses
define a weighted mean 206Pb / 238U age of 78 ± 2 Ma. The rims
are interpreted to have grown in the eclogite facies based on their lower
Th/U (0.01), less negative Eu anomalies and steeper heavy rare
earth element (HREE) patterns at <600 ∘C. The paragneiss yielded a detrital zircon population with
major peaks at 575–600, 655 and 765 Ma; minor older components; and a
maximum depositional age of approximately 570 Ma. The prominent
Neoproterozoic zircon population and Ediacaran depositional age suggest
derivation from the Gondwana margin. The metamorphic zircon is consistent
with the oldest eclogite-facies event in the Sesia Zone; it does not show
evidence of multiple periods of rim growth or any pre-Alpine (e.g.,
Variscan) metamorphism.</p
Observations of the Cosmic Microwave Background and Implications for Cosmology and Large Scale Structure
Observations of the Cosmic Microwave Background (CMB) are discussed, with
particular emphasis on current ground-based experiments and on future
satellite, balloon and interferometer experiments. Observational techniques and
the effects of contaminating foregrounds are highlighted. Recent CMB data is
used with large scale structure (LSS) data to constrain cosmological parameters
and the complementary nature of CMB, LSS and supernova distance data is
emphasized.Comment: 23 pages, 10 figures. Phil. Trans. R. Soc. Lond. A., 1998, in pres
Cosmological dynamics of scalar fields with O(N) symmetry
In this paper, we study the cosmological dynamics of scalar fields with O(N)
symmetry in general potentials. We compare the phase space of the dynamical
systems of the quintessence and phantom and give the conditions for the
existence of various attractors as well as their cosmological implications. We
also show that the existence of tracking attractor in O(N) phantom models
require the potential with , which makes the models with
exponential potential possess no tracking attractor.Comment: 9 pages, 4 figures; Replaced with the version to be published in
Classical and Quantum Gravity. Reference adde
First Estimations of Cosmological Parameters From BOOMERANG
The anisotropy of the cosmic microwave background radiation contains
information about the contents and history of the universe. We report new
limits on cosmological parameters derived from the angular power spectrum
measured in the first Antarctic flight of the BOOMERANG experiment. Within the
framework of inflation-motivated adiabatic cold dark matter models, and using
only weakly restrictive prior probabilites on the age of the universe and the
Hubble expansion parameter , we find that the curvature is consistent with
flat and that the primordial fluctuation spectrum is consistent with scale
invariant, in agreement with the basic inflation paradigm. We find that the
data prefer a baryon density above, though similar to, the
estimates from light element abundances and big bang nucleosynthesis. When
combined with large scale structure observations, the BOOMERANG data provide
clear detections of both dark matter and dark energy contributions to the total
energy density , independent of data from high redshift
supernovae.Comment: As submitted to PRD, revised longer version with an additional figur
Cosmological models from quintessence
A generalized quintessence model is presented which corresponds to a richer
vacuum structure that, besides a time-dependent, slowly varying scalar field,
contains a varying cosmological term. From first principles we determine a
number of scalar-field potentials that satisfy the constraints imposed by the
field equations and conservations laws, both in the conventional and
generalized quintessence models. Besides inverse-power law solutions, these
potentials are given in terms of hyperbolic functions or the twelve Jacobian
elliptic functions, and are all related to the luminosity distance by means of
an integral equation. Integration of this equation for the different solutions
leads to a large family of cosmological models characterized by luminosity
distance-redshift relations. Out of such models, only four appear to be able to
predict a required accelerating universe conforming to observations on
supernova Ia, at large or moderate redshifts.Comment: 9 pages, RevTex, to appear in Phys. Rev.
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