4,569 research outputs found
Measuring the U.S. Health Care System: A Cross-National Comparison
Compares U.S. healthcare data including hospital beds and physicians, hospital and physician visits, healthcare spending, and high-tech procedures per capita, as well as life expectancy with those of twenty-nine other industrialized countries
Atom chips on direct bonded copper substrates
We present the use of direct bonded copper (DBC) for the straightforward
fabrication of high power atom chips. Atom chips using DBC have several
benefits: excellent copper/substrate adhesion, high purity, thick (> 100
microns) copper layers, high substrate thermal conductivity, high aspect ratio
wires, the potential for rapid (< 8 hr) fabrication, and three dimensional atom
chip structures. Two mask options for DBC atom chip fabrication are presented,
as well as two methods for etching wire patterns into the copper layer. The
wire aspect ratio that optimizes the magnetic field gradient as a function of
power dissipation is determined to be 0.84:1 (height:width). The optimal wire
thickness as a function of magnetic trapping height is also determined. A test
chip, able to support 100 A of current for 2 s without failing, is used to
determine the thermal impedance of the DBC. An assembly using two DBC atom
chips to provide magnetic confinement is also shown.Comment: 8 pages, 5 figure
Fluctuating magnetic moments in liquid metals
We re-analyze literature data on neutron scattering by liquid metals to show
that non-magnetic liquid metals possess a magnetic moment that fluctuates on a
picosecond time scale. This time scale follows the motion of the cage-diffusion
process in which an ion rattles around in the cage formed by its neighbors. We
find that these fluctuating magnetic moments are present in liquid Hg, Al, Ga
and Pb, and possibly also in the alkali metals.Comment: 17 pages, 5 figures, submitted to PR
The Host Galaxy of GRB 990123
We present deep images of the field of gamma-ray burst (GRB) 990123 obtained
in a broad-band UV/visible bandpass with the Hubble Space Telescope, and deep
near-infrared images obtained with the Keck-I 10-m telescope. Both the HST and
Keck images show that the optical transient (OT) is clearly offset by 0.6
arcsec from an extended object, presumably the host galaxy. This galaxy is the
most likely source of the metallic-line absorption at z = 1.6004 seen in the
spectrum of the OT. With magnitudes V_{C} ~ 24.6 +/- 0.2 and K = 21.65 +/- 0.30
mag this corresponds to an L ~ 0.7 L_* galaxy, assuming that it is located at z
= 1.6. The estimated unobscured star formation rate is SFR ~ 6 M_sun/yr, which
is not unusually high for normal galaxies at comparable redshifts. The strength
of the observed metallic absorption lines is suggestive of a relatively high
metallicity of the gas, and thus of a chemically evolved system which may be
associated with a massive galaxy. It is also indicative of a high column
density of the gas, typical of damped Ly-alpha systems at high redshifts. We
conclude that this is the host galaxy of GRB 990123. No other obvious galaxies
are detected within the same projected radius from the OT. There is thus no
evidence for strong gravitational lensing magnification of this burst, and some
alternative explanation for its remarkable energetics may be required. The
observed offset of the OT from the center of its apparent host galaxy, 5.5 +/-
0.9 proper kpc (projected) in the galaxy's rest-frame, both refutes the
possibility that GRBs are related to galactic nuclear activity and supports
models of GRBs which involve the death and/or merger of massive stars. Further,
the HST image suggests an intimate connection of GRB 990123 and a star-forming
region.Comment: Updated references. 12 pages including 3 Postscript figures. Camera-
ready reproductions of the figures can be found at
http://astro.caltech.edu/~jsb/GRB/grb990123.htm
Infrared Properties of Radio-Selected Submillimeter Galaxies in the Spitzer First Look Survey Verification Field
We report on submillimeter and infrared observations of 28 radio-selected
galaxies in the Spitzer First Look Survey Verification field (FLSV). All of the
radio-selected galaxies that show evidence for emission at 850um with SCUBA
have Spitzer counterparts at 24um, while only half of the radio-selected
galaxies without 850um emission have detectable counterparts at 24um. The data
show a wide range of infrared colors (S70/S24 < 5--30, S8/S3.6 < 0.3--4),
indicative of a mixture of infrared-warm AGN and cooler starburst dominated
sources. The galaxies showing 850um emission have Spitzer flux densities and
flux density ratios consistent with the range of values expected for
high-redshift (z=1--4) ultraluminous infrared galaxies.Comment: Accepted for Spitzer ApJS Special Edition, 12 pages including 4
figures and 1 tabl
Deep Imaging of AXJ2019+112: The Luminosity of a ``Dark Cluster''
We detect a distant cluster of galaxies centered on the QSO lens and luminous
X-ray source AXJ2019+112, a.k.a. ``The Dark Cluster'' (Hattori et al 1997).
Using deep V,I Keck images and wide-field K_s imaging from the NTT, a tight red
sequence of galaxies is identified within a radius of 0.2 h^{-1} Mpc of the
known z=1.01 elliptical lensing galaxy. The sequence, which includes the
central elliptical galaxy, has a slope in good agreement with the model
predictions of Kodama et al (1998) for z~1. We estimate the integrated
rest-frame luminosity of the cluster to be L_V > 3.2 x 10^{11}h^{-2}L_{\sun}
(after accounting for significant extinction at the low latitude of this
field), more than an order of magnitude higher than previous estimates. The
central region of the cluster is deconvolved using the technique of Magain,
Courbin & Sohy (1998), revealing a thick central arc coincident with an
extended radio source. All the observed lensing features are readily explained
by differential magnification of a radio loud AGN by a shallow elliptical
potential. The QSO must lie just outside the diamond caustic, producing two
images, and the arc is a highly magnified image formed from a region close to
the center of the host galaxy, projecting inside the caustic. The
mass--to--light ratio within an aperture of 0.4 h ^{-1} Mpc is M_x/L_V=
224^{+112}_{-78}h(M/L_V)_{\sun}, using the X-ray temperature. The strong lens
model yields a compatible value, M/L_V= 372^{+94}_{-94}h(M/L_V)_{\sun}, whereas
an independent weak lensing analysis sets an upper limit of M/L_V <520
h(M/L_V)_{\sun}, typical of massive clusters.Comment: AAS Latex format, 24 pages, 9 figures. Fig 1a,b available at
http://astro.berkeley.edu/~benitezn/cluster.html . Submitted to ApJ on August
15t
Neutron Scattering and the B_{1g} Phonon in the Cuprates
The momentum dependent lineshape of the out-of-phase oxygen vibration as
measured in recent neutron scattering measurements is investigated. Starting
from a microscopic coupling of the phonon vibration to a local crystal field,
the phonon lineshift and broadening is calculated as a function of transfered
momentum in the superconducting state of YBaCuO. It is shown
that the anisotropy of the density of states, superconducting energy gap, and
the electron-phonon coupling are all crucial in order to explain these
experiments.Comment: new figures and discussio
The magnetic neutron scattering resonance of high-T_c superconductors in external magnetic fields: an SO(5) study
The magnetic resonance at 41 meV observed in neutron scattering studies of Y
Ba_2 Cu_3 O_7 holds a key position in the understanding of high-T_c
superconductivity. Within the SO(5) model for superconductivity and
antiferromagnetism, we have calculated the effect of an applied magnetic field
on the neutron scattering cross-section of the magnetic resonance. In the
presence of vortices, the neutron scattering cross-section shows clear
signatures of not only the fluctuations in the superconducting order parameter
\psi, but also the modulation of the phase of \psi due to vortices. In
reciprocal space we find that i) the scattering amplitude is zero at
(pi/a,pi/a), ii) the resonance peak is split into a ring with radius pi/d
centered at (pi/a,pi/a), d being the vortex lattice constant, and consequently,
iii) the splitting pi/d scales with the magnetic field as sqrt{B}.Comment: 4 pages including 3 eps-figures - minor changes and one reference
added. Accepted for publication in Phys. Rev.
Trypanosomes of some sub-Saharan birds
Linear measurements and derived indices from striated trypanosomes in nine species of sub-Saharan
birds representing seven families of the Passeriformes, were compared. The dimensions of the striated
trypomastigotes from the Carduelinae, Estrildidae, Nectarinidae, Passeridae, Pycnonotidae, Turdinae
and Zosteropidae were similar to each other as well as to those of the striated trypanosomes from the
boreal owl (Strigidae). All these trypanosomes were considered to be Trypanosoma avium Danilewsky,
1885. A further 20 avian species were considered to harbour T. avium, thus greatly extending the
reported host range of this trypanosome. Non-striated trypanosomes from the estrildid Uraeginthus
angolensis closely resembled Trypanosoma bouffardi Leger & Blanchard, 1911 in appearance and
dimensions, and were considered to be of this species. Additional host records for T. bouffardi from an
additional nine avian species have been reported. The uniquely small and stumpy Trypanosoma everetti
Molyneux, 1973 was reported from an additional 18 avian species. A large non-striated trypanosome
from the laughing dove, Streptopelia senegalensis, was identified as Trypanosoma hannae Pittaluga,
1905 and this species was re-described. An infection of this parasite was also found in a single
Streptopelia capicola and a single Streptopelia semitorquata. Two trypanosomes seen in the francolin,
Francolinus natalensis, were identified as Trypanosoma calmettei Mathis & Leger, 1909.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.Natural Sciences and Engineering
Research Council of Canada.mn201
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