6,323 research outputs found
An RF-Driven Josephson Bifurcation Amplifier for Quantum Measurements
We have constructed a new type of amplifier whose primary purpose is the
readout of superconducting quantum bits. It is based on the transition of an
RF-driven Josephson junction between two distinct oscillation states near a
dynamical bifurcation point. The main advantages of this new amplifier are
speed, high-sensitivity, low back-action, and the absence of on-chip
dissipation. Pulsed microwave reflection measurements on nanofabricated Al
junctions show that actual devices attain the performance predicted by theory.Comment: 5 Figure
Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids
Existing determinations show that n(C)/n(Fe) is more than a factor of 10
below solar in the atmospheres of three white dwarfs that appear to be
externally-polluted. These results are not easily explained if the stars have
accreted interstellar matter, and we re-interpret these measurements as
evidence that these stars have accreted asteroids of a chrondritic composition.Comment: 23 pages, 6 figures, accepted for Ap
A planet-sized transiting star around OGLE-TR-122 - Accurate mass and radius near the Hydrogen-burning limit
We report the discovery and characterisation of OGLE-TR-122b, the smallest
main-sequence star to date with a direct radius determination. OGLE-TR-122b
transits around its solar-type primary every 7.3-days. With M=0.092+-0.009 Mo
and R=0.120 +0.024-0.013 Ro, it is by far the smallest known eclipsing M-dwarf.
The derived mass and radius for OGLE-TR-122b are in agreement with the
theoretical expectations. OGLE-TR-122b is the first observational evidence that
stars can indeed have radii comparable or even smaller than giant planets. In
such cases, the photometric signal is exactly that of a transiting planet and
the true nature of the companion can only be determined with high-resolution
spectroscopy.Comment: 4 pages, 3 figures, A&A letters, in Press. Revise
Sounding stellar cycles with Kepler - preliminary results from ground-based chromospheric activity measurements
Due to its unique long-term coverage and high photometric precision,
observations from the Kepler asteroseismic investigation will provide us with
the possibility to sound stellar cycles in a number of solar-type stars with
asteroseismology. By comparing these measurements with conventional
ground-based chromospheric activity measurements we might be able to increase
our understanding of the relation between the chromospheric changes and the
changes in the eigenmodes.
In parallel with the Kepler observations we have therefore started a
programme at the Nordic Optical Telescope to observe and monitor chromospheric
activity in the stars that are most likely to be selected for observations for
the whole satellite mission. The ground-based observations presented here can
be used both to guide the selection of the special Kepler targets and as the
first step in a monitoring programme for stellar cycles. Also, the
chromospheric activity measurements obtained from the ground-based observations
can be compared with stellar parameters such as ages and rotation in order to
improve stellar evolution models.Comment: submitted to the proceedings of the IAU symposium No. 264, 200
Arithmetic Of Love
Photo of woman wearing bonnethttps://scholarsjunction.msstate.edu/cht-sheet-music/1571/thumbnail.jp
New Chemicals May Help Trefoil Seed Harvest
Though birdsfoot trefoil sets between 200 and 300 pounds of seed per acre in Iowa, harvested yields are commonly only 40 to 60 pounds. Use of chemical desicants followed by direct combining offers a possible solution
Evidence of Substructure in the Cluster of Galaxies A3558
We investigate the dynamical properties of the cluster of galaxies A3558
(Shapley 8). Studying a region of one square degree ( 3 Mpc) centered
on the cluster cD galaxy, we have obtained a statistically complete photometric
catalog with positions and magnitudes of 1421 galaxies (down to a limiting
magnitude of ). This catalog has been matched to the recent velocity
data obtained by Mazure et al. (1997) and from the literature, yielding a
radial velocity catalog containing 322 galaxies. Our analysis shows that the
position/velocity space distribution of galaxies shows significant
substructure. A central bimodal core detected previously in preliminary studies
is confirmed by using the Adaptive Kernel Technique and Wavelet Analysis. We
show that this central bimodal subtructure is nevertheless composed of a
projected feature, kinematically unrelated to the cluster, plus a group of
galaxies probably in its initial merging phase into a relaxed core. The cD
velocity offset with respect to the average cluster redshift, reported earlier
by several authors, is completely eliminated as a result of our dynamical
analysis. The untangling of the relaxed core component also allows a better,
more reliable determination of the central velocity dispersion, which in turn
eliminates the ``-problem'' for A3558. The cluster also shows a
``preferential'' distribution of subclumps coinciding with the direction of the
major axis position angle of the cD galaxy and of the central X-ray emission
ellipsoidal distribution, in agreement with an anisotropic merger scenario.Comment: 35 pages in latex, 17 figures in Postscript, accepted for publication
in the Astrophysical Journa
Concerning the Wave equation on Asymptotically Euclidean Manifolds
We obtain KSS, Strichartz and certain weighted Strichartz estimate for the
wave equation on , , when metric
is non-trapping and approaches the Euclidean metric like with
. Using the KSS estimate, we prove almost global existence for
quadratically semilinear wave equations with small initial data for
and . Also, we establish the Strauss conjecture when the metric is radial
with for .Comment: Final version. To appear in Journal d'Analyse Mathematiqu
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