2,402 research outputs found
Low Frequency Tilt Seismology with a Precision Ground Rotation Sensor
We describe measurements of the rotational component of teleseismic surface
waves using an inertial high-precision ground-rotation-sensor installed at the
LIGO Hanford Observatory (LHO). The sensor has a noise floor of 0.4 nrad at 50 mHz and a translational coupling of less than 1 rad/m
enabling translation-free measurement of small rotations. We present
observations of the rotational motion from Rayleigh waves of six teleseismic
events from varied locations and with magnitudes ranging from M6.7 to M7.9.
These events were used to estimate phase dispersion curves which shows
agreement with a similar analysis done with an array of three STS-2
seismometers also located at LHO
Seismic topographic scattering in the context of GW detector site selection
In this paper, we present a calculation of seismic scattering from irregular
surface topography in the Born approximation. Based on US-wide topographic
data, we investigate topographic scattering at specific sites to demonstrate
its impact on Newtonian-noise estimation and subtraction for future
gravitational-wave detectors. We find that topographic scattering at a
comparatively flat site in Oregon would not pose any problems, whereas
scattering at a second site in Montana leads to significant broadening of wave
amplitudes in wavenumber space that would make Newtonian-noise subtraction very
challenging. Therefore, it is shown that topographic scattering should be
included as criterion in the site-selection process of future low-frequency
gravitational-wave detectors.Comment: 16 pages, 7 figure
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Innovations in Wind and Solar PV Financing
There is growing national interest in renewable energy development based on the economic, environmental, and security benefits that these resources provide. Historically, greater development of our domestic renewable energy resources has faced a number of hurdles, primarily related to cost, regulation, and financing. With the recent sustained increase in the costs and associated volatility of fossil fuels, the economics of renewable energy technologies have become increasingly attractive to investors, both large and small. As a result, new entrants are investing in renewable energy and new business models are emerging. This study surveys some of the current issues related to wind and solar photovoltaic (PV) energy project financing in the electric power industry, and identifies both barriers to and opportunities for increased investment
Observations of the GRB afterglow ATLAS17aeu and its possible association with GW170104
We report the discovery and multi-wavelength data analysis of the peculiar
optical transient, ATLAS17aeu. This transient was identified in the skymap of
the LIGO gravitational wave event GW170104 by our ATLAS and Pan-STARRS
coverage. ATLAS17aeu was discovered 23.1hrs after GW170104 and rapidly faded
over the next 3 nights, with a spectrum revealing a blue featureless continuum.
The transient was also detected as a fading x-ray source by Swift and in the
radio at 6 and 15 GHz. A gamma ray burst GRB170105A was detected by 3
satellites 19.04hrs after GW170104 and 4.10hrs before our first optical
detection. We analyse the multi-wavelength fluxes in the context of the known
GRB population and discuss the observed sky rates of GRBs and their afterglows.
We find it statistically likely that ATLAS17aeu is an afterglow associated with
GRB170105A, with a chance coincidence ruled out at the 99\% confidence or
2.6. A long, soft GRB within a redshift range of would be consistent with all the observed multi-wavelength data. The
Poisson probability of a chance occurrence of GW170104 and ATLAS17aeu is
. This is the probability of a chance coincidence in 2D sky location
and in time. These observations indicate that ATLAS17aeu is plausibly a normal
GRB afterglow at significantly higher redshift than the distance constraint for
GW170104 and therefore a chance coincidence. However if a redshift of the faint
host were to place it within the GW170104 distance range, then physical
association with GW170104 should be considered.Comment: 16 pages, 6 figures, accepted to Ap
Identification of long-duration noise transients in LIGO and Virgo
The LIGO and Virgo detectors are sensitive to a variety of noise sources,
such as instrumental artifacts and environmental disturbances. The Stochastic
Transient Analysis Multi-detector Pipeline (STAMP) has been developed to search
for long-duration (t1s) gravitational-wave (GW) signals. This pipeline
can also be used to identify environmental noise transients. Here we present an
algorithm to determine when long-duration noise sources couple into the
interferometers, as well as identify what these noise sources are. We analyze
the cross-power between a GW strain channel and an environmental sensor, using
pattern recognition tools to identify statistically significant structure in
cross-power time-frequency maps. We identify interferometer noise from
airplanes, helicopters, thunderstorms and other sources. Examples from LIGO's
sixth science run, S6, and Virgo's third scientific run, VSR3, are presented.Comment: 10 pages, 7 figures, Gravitational-wave Physics & Astronomy Worksho
The nucleotide and partial amino acid sequences of rat fetuin
Fetuins are among the major plasma proteins, yet their biological role has remained elusive. Here we report the molecular cloning of rat fetuin and the sequence analysis of a full-length clone, RF619 of 1456 bp with an open reading frame of 1056 bp encoding 352 amino acid residues. The coding part of RF619 was identical with the cDNA sequence of the natural inhibitor of the insulin receptor tyrosine kinase from rat (pp63) except for four substitutions and a single base insertion causing divergence of the predicted protein sequences. Partial amino acid sequences of rat plasma fetuin were in agreement with the predictions based on the RF619 cDNA. Purified rat fetuin inhibited the insulin receptor tyrosine kinase in vitro. Therefore, we conclude that RF619 and pp63 cDNA encode the same protein, i.e. authentic rat fetuin which is a functional tyrosine kinase inhibitor
Constraining Neutron-Star Matter with Microscopic and Macroscopic Collisions
Interpreting high-energy, astrophysical phenomena, such as supernova explosions or neutron-star collisions, requires a robust understanding of matter at supranuclear densities. However, our knowledge about dense matter explored in the cores of neutron stars remains limited. Fortunately, dense matter is not only probed in astrophysical observations, but also in terrestrial heavy-ion collision experiments. In this work, we use Bayesian inference to combine data from astrophysical multi-messenger observations of neutron stars and from heavy-ion collisions of gold nuclei at relativistic energies with microscopic nuclear theory calculations to improve our understanding of dense matter. We find that the inclusion of heavy-ion collision data indicates an increase in the pressure in dense matter relative to previous analyses, shifting neutron-star radii towards larger values, consistent with recent NICER observations. Our findings show that constraints from heavy-ion collision experiments show a remarkable consistency with multi-messenger observations and provide complementary information on nuclear matter at intermediate densities. This work combines nuclear theory, nuclear experiment, and astrophysical observations, and shows how joint analyses can shed light on the properties of neutron-rich supranuclear matter over the density range probed in neutron stars
Securing combined Fog-to-Cloud systems: challenges and directions
Nowadays, fog computing is emerged for providing computational power closer to the users. Fog computing brings real-time processing, lowlatency, geo-distributed and etc. Although, fog computing do not come to compete cloud computing, it comes to collaborate. Recently, Fog-To-Cloud (F2C) continuum system is introduced to provide hierarchical computing system and facilitates fog-cloud collaboration. This F2C continuum system might encounter security issues and challenges due to their hierarchical and distributed nature. In this paper, we analyze attacks in different layer of F2C system and identify most potential security requirements and challenges for the F2C continuum system. Finally, we introduce the most remarkable efforts and trends for bringing secure F2C system.This work is supported by the H2020 projects mF2C (730929). It is also supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund both under contract RTI2018-094532-B-100.Peer ReviewedPostprint (author's final draft
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