8,321 research outputs found
Connecting the discrete and continuous-time quantum walks
Recently, quantized versions of random walks have been explored as effective
elements for quantum algorithms. In the simplest case of one dimension, the
theory has remained divided into the discrete-time quantum walk and the
continuous-time quantum walk. Though the properties of these two walks have
shown similarities, it has remained an open problem to find the exact relation
between the two. The precise connection of these two processes, both quantally
and classically, is presented. Extension to higher dimensions is also
discussed.Comment: 5 pages, 1 figur
Earth orbital teleoperator visual system evaluation program
Visual system parameters and stereoptic television component geometries were evaluated for optimum viewing. The accuracy of operator range estimation using a Fresnell stereo television system with a three dimensional cursor was examined. An operator's ability to align three dimensional targets using vidicon tube and solid state television cameras as part of a Fresnell stereoptic system was evaluated. An operator's ability to discriminate between varied color samples viewed with a color television system was determined
Alcohol Interventions for Trauma Patients Treated in Emergency Departments and Hospitals: A Cost Benefit Analysis
Summarizes a study of whether screening for problem drinking and interventions to reduce alcohol intake in hospital trauma centers reduce the direct cost of injury-related health care. Compares the costs of injury recidivism with and without intervention
Mesoscopic Transport: The Electron-Gas Sum Rules in a Driven Quantum Point Contact
The nature of the electron gas is characterized, above all, by its
multi-particle correlations. The conserving sum rules for the electron gas have
been thoroughly studied for many years, and their centrality to the physics of
metallic conduction is widely understood (at least in the many-body community).
We review the role of the conserving sum rules in mesoscopic transport, as
normative criteria for assessing the conserving status of mesoscopic models. In
themselves, the sum rules are specific enough to rule out any such theory if it
fails to respect the conservation laws. Of greater interest is the capacity of
the compressibility sum rule, in particular, to reveal unexpected fluctuation
effects in nonuniform mesoscopic structures.Comment: TeX, 11pp, no fi
Doppler Probe of Accretion onto a T Tauri star
The YY Ori stars are T Tauri stars with prominent time-variable redshifted
absorption components that flank certain emission lines. One of the brightest
in this class is S CrA, a visual double star. We have obtained a series of
high-resolution spectra of the two components during four nights with the UVES
spectrograph at the Very Large Telescope. We followed the spectral changes
occurring in S CrA to derive the physical structure of the accreting gas.
We found that both stars are very similar with regard to surface temperature,
radius, and mass. Variable redshifted absorption components are particularly
prominent in the SE component. During one night, this star developed a spectrum
unique among the T Tauri stars: extremely strong and broad redshifted
absorption components appeared in many lines of neutral and ionized metals, in
addition to those of hydrogen and helium. The absorption depths of cooler, low
ionization lines peak at low velocities - while more highly ionized lines have
peak absorption depths at high velocities. The different line profiles indicate
that the temperature and density of the accretion stream increase as material
approaches the star. We derive the physical conditions of the flow at several
points along the accretion funnel directly from the spectrum of the infalling
gas. We estimated mass accretion rates of about 10^(-7) solar masses per year,
which is similar to that derived from the relation based on the strength of H
alpha emission line.
This is the first time the density and temperature distributions in accretion
flows around a T Tauri star have been inferred from observations. Compared with
predictions from standard models of accretion in T Tauri stars, which assume a
dipole stellar magnetic field, we obtained higher densities and a steeper
temperature rise toward the star.Comment: Replaces 1408.1846 4 pages, 4 figures. Appears in Astronomy and
Astrophysics, 201
Laser induced breakdown spectroscopy for heavy metal detection in a sand matrix
© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Spectrochimica Acta Part B: Atomic Spectroscopy 125 (2016):177-183, doi:10.1016/j.sab.2016.10.001.Sediments in many locations, including harbors and coastal areas, can become
contaminated and polluted, for example, from anthropogenic inputs,
shipping, human activities, and poor waste management. Sampling followed
by laboratory analysis has been the traditional methodology for such analysis.
In order to develop rapid methodologies for eld analysis of sediment
samples, especially for metals analyses, we look to Laser Induced Breakdown
Spectroscopy as an option. Here through laboratory experiments, we demonstrate
that dry sand samples can be rapidly analyzed for the detection of the
heavy metals chromium, zinc, lead, and copper. We also demonstrate that
cadmium and nickel are detectable in sand matrices at high concentrations.This work is supported by funding from the National Science Foundation
(OCE-RIG: 1322704) and the Woods Hole Oceanographic Institution
by The Penzance Endowed Fund in Support of Assistant Scientists and The
Reuben F. and Elizabeth B. Richards Endowed Fund in Support of Scienti c
Sta .2018-10-0
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