32,443 research outputs found
Improved sampling of compressed gases for condensable hydrocarbon content
Sampling process was developed which uses commercially available high pressure filters and provides measurements in fraction of time required by older methods. Measurements show no significant difference in results between low pressure and high pressure samples. Filter method is slightly more accurate than scrubber technique
Avatars:the other side of Proteus's mirror : a study into avatar choice regarding perception
The trend for online interactions, can be regarded as being âanti-so-cially socialâ, meaning that a great deal of time is spent playing, working and socializing with the internet serving as the communication conduit. Within that Virtual Social Environment very deep relationships are formed and maintained without the parties ever having met each other face-to-face. Raising the question how much does the physical appearance of an avatar influence the perception of the person behind it? Are relationships informed by appearance even in the vir-tual world and what implications does that have for second language acquisition? This paper leads to a small-scale research project where a selection of avatars with various racially identifiable characteristics were used to identify which av-atars a second language speaker would feel more at ease interacting with in the target language. The resultant research aims to test three hypotheses regarding preferred avatar choice for second language users based solely on perceptions
Surrogate-assisted network analysis of nonlinear time series
The performance of recurrence networks and symbolic networks to detect weak
nonlinearities in time series is compared to the nonlinear prediction error.
For the synthetic data of the Lorenz system, the network measures show a
comparable performance. In the case of relatively short and noisy real-world
data from active galactic nuclei, the nonlinear prediction error yields more
robust results than the network measures. The tests are based on surrogate data
sets. The correlations in the Fourier phases of data sets from some surrogate
generating algorithms are also examined. The phase correlations are shown to
have an impact on the performance of the tests for nonlinearity.Comment: 9 pages, 5 figures, Chaos
(http://scitation.aip.org/content/aip/journal/chaos), corrected typo
Parsec-scale radio morphology and variability of a changing-look AGN: the case of Mrk 590
We investigate the origin of the parsec-scale radio emission from the
changing-look active galactic nucleus (AGN) of Mrk 590, and examine whether the
radio power has faded concurrently with the dramatic decrease in accretion
rates observed between the 1990s and the present. We detect a compact core at
1.6 GHz and 8.4 GHz using new Very Long Baseline Array observations, finding no
significant extended, jet-like features down to 1 pc scales. The flat
spectral index () and high brightness temperature
() indicate self-absorbed synchrotron emission
from the AGN. The radio to X-ray luminosity ratio of , similar to that in coronally active stars, suggests
emission from magnetized coronal winds, although unresolved radio jets are also
consistent with the data. Comparing new Karl G. Jansky Very Large Array
measurements with archival and published radio flux densities, we find ,
, and (insignificantly) flux density decreases between the 1990s
and the year 2015 at 1.4 GHz, 5 GHz and 8.4 GHz respectively. This trend,
possibly due to the expansion and fading of internal shocks within the
radio-emitting outflow after a recent outburst, is consistent with the decline
of the optical-UV and X-ray luminosities over the same period. Such correlated
variability demonstrates the AGN accretion-outflow connection, confirming that
the changing-look behaviour in Mrk 590 originates from variable accretion rates
rather than dust obscuration. The present radio and X-ray luminosity
correlation, consistent with low/hard state accretion, suggests that the black
hole may now be accreting in a radiatively inefficient mode.Comment: 14 pages, 5 tables, 5 figures, accepted for publication in MNRA
Implementable Quantum Bit-String Commitment Protocol
Quantum bit-string commitment[A.Kent, Phys.Rev.Lett., 90, 237901 (2003)] or
QBSC is a variant of bit commitment (BC). In this paper, we propose a new QBSC
protocol that can be implemented using currently available technology, and
prove its security under the same security criteria as discussed by Kent. QBSC
is a generalization of BC, but has slightly weaker requirements, and our
proposed protocol is not intended to break the no-go theorem of quantum BC.Comment: To appear in Phys. Rev. A., 9 pages, 2 figure
Optical Continuum and Emission-Line Variability of Seyfert 1 Galaxies
We present the light curves obtained during an eight-year program of optical
spectroscopic monitoring of nine Seyfert 1 galaxies: 3C 120, Akn 120, Mrk 79,
Mrk 110, Mrk 335, Mrk 509, Mrk 590, Mrk 704, and Mrk 817. All objects show
significant variability in both the continuum and emission-line fluxes. We use
cross-correlation analysis to derive the sizes of the broad Hbeta-emitting
regions based on emission-line time delays, or lags. We successfully measure
time delays for eight of the nine sources, and find values ranging from about
two weeks to a little over two months. Combining the measured lags and widths
of the variable parts of the emission lines allows us to make virial mass
estimates for the active nucleus in each galaxy. The virial masses are in the
range 10^{7-8} solar masses.Comment: 24 pages, 16 figures. Accepted for publication in Ap
A Variational Approach for Minimizing Lennard-Jones Energies
A variational method for computing conformational properties of molecules
with Lennard-Jones potentials for the monomer-monomer interactions is
presented. The approach is tailored to deal with angular degrees of freedom,
{\it rotors}, and consists in the iterative solution of a set of deterministic
equations with annealing in temperature. The singular short-distance behaviour
of the Lennard-Jones potential is adiabatically switched on in order to obtain
stable convergence. As testbeds for the approach two distinct ensembles of
molecules are used, characterized by a roughly dense-packed ore a more
elongated ground state. For the latter, problems are generated from natural
frequencies of occurrence of amino acids and phenomenologically determined
potential parameters; they seem to represent less disorder than was previously
assumed in synthetic protein studies. For the dense-packed problems in
particular, the variational algorithm clearly outperforms a gradient descent
method in terms of minimal energies. Although it cannot compete with a careful
simulating annealing algorithm, the variational approach requires only a tiny
fraction of the computer time. Issues and results when applying the method to
polyelectrolytes at a finite temperature are also briefly discussed.Comment: 14 pages, uuencoded compressed postscript fil
Reverberation Mapping and the Physics of Active Galactic Nuclei
Reverberation-mapping campaigns have revolutionized our understanding of AGN.
They have allowed the direct determination of the broad-line region size,
enabled mapping of the gas distribution around the central black hole, and are
starting to resolve the continuum source structure. This review describes the
recent and successful campaigns of the International AGN Watch consortium,
outlines the theoretical background of reverberation mapping and the
calculation of transfer functions, and addresses the fundamental difficulties
of such experiments. It shows that such large-scale experiments have resulted
in a ``new BLR'' which is considerably different from the one we knew just ten
years ago. We discuss in some detail the more important new results, including
the luminosity-size-mass relationship for AGN, and suggest ways to proceed in
the near future.Comment: Review article to appear in Astronomical Time Series, Proceedings of
the Wise Observatory 25th Ann. Symposium. 24 pages including 7 figure
Building Better Pastures
Pastures and hay lands were plowed up during the war to make room for more corn and soybeans. On many farms itâs time to get land back into clover and grass, to meet the needs for pasture and hay and to help build up depleted soils. On many farms it is a matter of making the land now in pasture carry more livestock than it has been. What should we be planning now to get better pastures in the season ahead
Reducing Civil Disabilities for Convicted Felons in North Dakota: A Step in the Right Direction
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