2,459 research outputs found
Rates of Relative Sea Level Rise Along the United States East Coast
Recent studies have indicated that some coastal areas, including the East Coast of the United States, are experiencing higher rates of sea level rise than the global average. Rates of relative sea level rise are affected by changes in ocean dynamics, as well as by surface elevation fluctuations due to local land subsidence or uplift. In this study, we derived long-term trends in annual mean relative sea level using tide gauge data obtained from the Permanent Service for Mean Sea Level for stations along the United States East Coast. Stations were grouped by location into the Northeast, Mid-Atlantic, and Southeast regions of the United States East Coast, with the intent of investigating relative sea level rise variability between the three regions. Trends for each region were calculated using stations with a minimum record length of at least 30 years; the longest record began in 1856. Records that were less than 70 percent complete were rejected. For the three-year moving averages, Northeast trends were calculated to be 2.79 mm/yr, Mid-Atlantic trends were calculated to be 4.02 mm/yr, and Southeast trends were calculated to be 2.92 mm/yr. For the five-year moving averages, Northeast trends were calculated to be 2.81 mm/yr, Mid-Atlantic trends were calculated to be 4.04 mm/yr, and Southeast trends were calculated to be 2.91 mm/yr. The Mid-Atlantic region of the United States East Coast was determined to be experiencing significantly higher rates of relative sea level rise than the other regions
Fabrication of Conducting Si Nanowire Arrays
The recent development of the superlattice nanowire pattern transfer (SNAP)
technique allows for the fabrication of arrays of nanowires at a diameter,
pitch, aspect ratio, and regularity beyond competing approaches. Here, we
report the fabrication of conducting Si nanowire arrays with wire widths and
pitches of 10-20 nm and 40-50 nm, respectively, and resistivity values
comparable to the bulk through the selection of appropriate
silicon-on-insulator substrates, careful reactive-ion etching, and spin-on
glass doping. These results promise the realization of interesting
nano-electronic circuits and devices, including chemical and biological
sensors, nano-scale mosaics for molecular electronics, and ultra-dense
field-effect transistor (FET) arrays.Comment: 10 pages, 3 figures, submitted to APL Mar '0
When Is a Bulge Not a Bulge? Inner Disks Masquerading as Bulges in NGC 2787 and NGC 3945
We present a detailed morphological, photometric, and kinematic analysis of
two barred S0 galaxies with large, luminous inner disks inside their bars. We
show that these structures, in addition to being geometrically disk-like, have
exponential profiles (scale lengths 300--500 pc) distinct from the
central, non-exponential bulges. We also find them to be kinematically
disk-like. The inner disk in NGC 2787 has a luminosity roughly twice that of
the bulge; but in NGC 3945, the inner disk is almost ten times more luminous
than the bulge, which itself is extremely small (half-light radius
100 pc, in a galaxy with an outer ring of radius 14 kpc) and only
5% of the total luminosity -- a bulge/total ratio much more typical of
an Sc galaxy. We estimate that at least 20% of (barred) S0 galaxies may have
similar structures, which means that their bulge/disk ratios may be
significantly overestimated. These inner disks dominate the central light of
their galaxies; they are at least an order of magnitude larger than typical
``nuclear disks'' found in ellipticals and early-type spirals. Consequently,
they must affect the dynamics of the bars in which they reside.Comment: LaTeX, 37 pages, 14 EPS figures. To appear in The Astrophysical
Journal (November 10, 2003 issue). Version with full-resolution figures
available at http://www.iac.es/galeria/erwin/research
Spiral inflow feeding the nuclear starburst in M83, observed in H-alpha emission with the GHAFAS Fabry-Perot interferometer
We present observations of the nearby barred starburst galaxy, M83 (NGC5236),
with the new Fabry-Perot interferometer GHAFAS mounted on the 4.2 meter William
Herschel Telescope on La Palma. The unprecedented high resolution observations,
of 16 pc/FWHM, of the H-alpha-emitting gas cover the central two kpc of the
galaxy. The velocity field displays the dominant disk rotation with signatures
of gas inflow from kpc scales down to the nuclear regions. At the inner Inner
Lindblad Resonance radius of the main bar and centerd at the dynamical center
of the main galaxy disk, a nuclear rapidly
rotating disk with scale length of pc has formed. The nuclear
starburst is found in the vicinity as well as inside this nuclear disk, and our
observations confirm that gas spirals in from the outer parts to feed the
nuclear starburst, giving rise to several star formation events at different
epochs, within the central 100 pc radius of M83.Comment: Accepted for publication in ApJ Letters. High-resolution version can
be found at http://www.astro.su.se/~kambiz/DOC/paper-M83.pd
A new chemo-evolutionary population synthesis model for early-type galaxies. II: Observations and Results
We present here the results of applying a new chemo-evolutionary stellar
population model developed by ourselves in a previous paper (Vazdekis et al.
1996) to new high quality observational data of the nuclear regions of two
representative elliptical galaxies and the bulge of the Sombrero galaxy. Here
we fit in detail about 20 absorption lines and 6 optical and near-infrared
colors following two approaches: fitting a single-age single-metallicity model
and fitting our full chemical evolutionary model. We find that all of the iron
lines are weaker than the best fitting models predict, indicating that the
iron-abundance is anomalous and deficient. We also find that the Ca_I index at
4227 A is much lower than predicted by the models. We can obtain good fits for
all the other lines and observed colors with models of old and metal-rich
stellar populations, and can show that the observed radial gradients are due to
metallicity decreasing outward. We find that good fits are obtained both with
fully evolutionary models and with single-age single-metallicity models. This
is due to the fact that in the evolutionary model more than 80% of stars form
with in 1.5 Gyr after the formation of the galaxies. The fact that slightly
better fits are obtained with evolutionary models indicates these galaxies
contain a small spread in metallicity.Comment: 29 pages, Latex with 22 figures and 2 landscape tables in ps-format.
Paper to be published in the Ap. J. Suppl., June 199
Computing prime factors with a Josephson phase qubit quantum processor
A quantum processor (QuP) can be used to exploit quantum mechanics to find
the prime factors of composite numbers[1]. Compiled versions of Shor's
algorithm have been demonstrated on ensemble quantum systems[2] and photonic
systems[3-5], however this has yet to be shown using solid state quantum bits
(qubits). Two advantages of superconducting qubit architectures are the use of
conventional microfabrication techniques, which allow straightforward scaling
to large numbers of qubits, and a toolkit of circuit elements that can be used
to engineer a variety of qubit types and interactions[6, 7]. Using a number of
recent qubit control and hardware advances [7-13], here we demonstrate a
nine-quantum-element solid-state QuP and show three experiments to highlight
its capabilities. We begin by characterizing the device with spectroscopy.
Next, we produces coherent interactions between five qubits and verify bi- and
tripartite entanglement via quantum state tomography (QST) [8, 12, 14, 15]. In
the final experiment, we run a three-qubit compiled version of Shor's algorithm
to factor the number 15, and successfully find the prime factors 48% of the
time. Improvements in the superconducting qubit coherence times and more
complex circuits should provide the resources necessary to factor larger
composite numbers and run more intricate quantum algorithms.Comment: 5 pages, 3 figure
Association of Lower Plasma Fetuin-A Levels With Peripheral Arterial Disease in Type 2 Diabetes
Causal and localizable quantum operations
We examine constraints on quantum operations imposed by relativistic
causality. A bipartite superoperator is said to be localizable if it can be
implemented by two parties (Alice and Bob) who share entanglement but do not
communicate; it is causal if the superoperator does not convey information from
Alice to Bob or from Bob to Alice. We characterize the general structure of
causal complete measurement superoperators, and exhibit examples that are
causal but not localizable. We construct another class of causal bipartite
superoperators that are not localizable by invoking bounds on the strength of
correlations among the parts of a quantum system. A bipartite superoperator is
said to be semilocalizable if it can be implemented with one-way quantum
communication from Alice to Bob, and it is semicausal if it conveys no
information from Bob to Alice. We show that all semicausal complete measurement
superoperators are semilocalizable, and we establish a general criterion for
semicausality. In the multipartite case, we observe that a measurement
superoperator that projects onto the eigenspaces of a stabilizer code is
localizable.Comment: 23 pages, 7 figures, REVTeX, minor changes and references adde
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