525 research outputs found
Models of helically symmetric binary systems
Results from helically symmetric scalar field models and first results from a
convergent helically symmetric binary neutron star code are reported here;
these are models stationary in the rotating frame of a source with constant
angular velocity omega. In the scalar field models and the neutron star code,
helical symmetry leads to a system of mixed elliptic-hyperbolic character. The
scalar field models involve nonlinear terms that mimic nonlinear terms of the
Einstein equation. Convergence is strikingly different for different signs of
each nonlinear term; it is typically insensitive to the iterative method used;
and it improves with an outer boundary in the near zone. In the neutron star
code, one has no control on the sign of the source, and convergence has been
achieved only for an outer boundary less than approximately 1 wavelength from
the source or for a code that imposes helical symmetry only inside a near zone
of that size. The inaccuracy of helically symmetric solutions with appropriate
boundary conditions should be comparable to the inaccuracy of a waveless
formalism that neglects gravitational waves; and the (near zone) solutions we
obtain for waveless and helically symmetric BNS codes with the same boundary
conditions nearly coincide.Comment: 19 pages, 7 figures. Expanded version of article to be published in
Class. Quantum Grav. special issue on Numerical Relativit
Centaurus A at Ultra-High Energies
We review the importance of Centaurus A in high energy astrophysics as a
nearby object with many of the properties expected of a major source of very
high energy cosmic rays and gamma-rays. We examine observational techniques and
the results so far obtained in the energy range from 200 GeV to above 100 EeV
and attempt to fit those data with expectations of Centaurus A as an
astrophysical source from VHE to UHE energies.Comment: 11 pages, 4 figures, accepted for publication in PAS
Dietary intake of inulin-type fructans in active and inactive Crohn’s disease and healthy controls: a case-control study
Background and Aims: Prebiotic inulin-type fructans are widely consumed in the diet and may have contrasting effects in Crohn’s disease by stimulating gut microbiota and/or by generating functional gastrointestinal symptoms. The aim of this study was to measure fructan and oligofructose intakes in patients with active and inactive Crohn’s disease compared with healthy controls. Methods: Patients with active Crohn’s disease (n=98), inactive Crohn’s (n=99) and healthy controls (n=106) were recruited to a case-control study. Dietary intake of inulin-type fructans was measured using a specific food frequency questionnaire and was compared between the three groups and between patients with different disease phenotypes (Montreal classification). Associations between intakes and disease activity (Harvey Bradshaw Index, HBI) were also undertaken. Results: Patients with active Crohn’s disease had lower fructan intakes (median 2.9 g/d, IQR 1.8) than those with inactive Crohn’s (3.6 g/d, 2.1, P=0.036) or controls (3.9 g/d, 2.1, P=0.003) and lower oligofructose intakes (2.8 g/d, 1.8) than inactive Crohn’s (3.5 g/d, 2.2, P=0.048) or controls (3.8 g/d, 2.1, P=0.003). There were no differences in intakes related to disease site or behaviour. There were negative correlations between HBI wellbeing score and fructan intake (ρ=-0.154, P=0.03) and oligofructose intake (ρ=-0.156, P=0.028) and for the HBI abdominal pain score and fructan (ρ=-0.164, P=0.021) and oligofructose intake (ρ=-0.157, P=0.027). Conclusions: Patients with active Crohn’s disease consume lower quantities of fructans and oligofructose than their inactive counterparts and healthy controls. The impact of lower intakes of prebiotic fructans on gut microbiota are unknown and warrant further research
Oligomerization of the vesicular stomatitis virus phosphoprotein is dispensable for mRNA synthesis but facilitates RNA replication
Nonsegmented negative-strand (NNS) RNA viruses possess a ribonucleoprotein template in which the genomic RNA is sequestered within a homopolymer of nucleocapsid protein (N). The viral RNA-dependent RNA polymerase (RdRP) resides within an approximately 250-kDa large protein (L), along with unconventional mRNA capping enzymes: a GDP:polyribonucleotidyltransferase (PRNT) and a dual-specificity mRNA cap methylase (MT). To gain access to the N-RNA template and orchestrate the
WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-10 2013 mooring turnaround cruise report
The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries Site (WHOTS),
100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a
part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a
coordinated part of the Hawaii Ocean Timeseries (HOT) program, contributing to the goals of
observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North
Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and
oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds.
These observations will be used to investigate air–sea interaction processes related to climate
variability.
This report documents recovery of the ninth WHOTS mooring (WHOTS-9) and
deployment of the tenth mooring (WHOTS-10). Both moorings used Surlyn foam buoys as the
surface element and were outfitted with two Air–Sea Interaction Meteorology (ASIMET)
systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface
meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum.
The upper 155 m of the moorings were outfitted with oceanographic sensors for the
measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of
the University of Hawaii. A pCO2 system and ancillary sensors were installed on the buoys in
cooperation with Chris Sabine at the Pacific Marine Environmental Laboratory. A set of
radiometers were installed in cooperation with Sam Laney at WHOI.
The WHOTS mooring turnaround was done on the NOAA ship Hi’ialakai by the Upper
Ocean Processes Group of the Woods Hole Oceanographic Institution. The cruise took place
between 9 and 16 July 2013. Operations began with deployment of the WHOTS-10 mooring on
10 July. This was followed by meteorological intercomparisons and CTDs. Recovery of the
WHOTS-9 mooring took place on 14 July. This report describes these cruise operations, as well
as some of the in-port operations and pre-cruise buoy preparations.Funding was provided by the National Oceanic and Atmospheric Administration under Grant. No.
NA090AR4320129 and the Cooperative Institute for the North Atlantic Region (CINAR
No Massive Companion to the Coherent Radio-Emitting M Dwarf GJ 1151
The recent detection of circularly polarized, long-duration (>8 hr)
low-frequency (~150 MHz) radio emission from the M4.5 dwarf GJ 1151 has been
interpreted as arising from a star-planet interaction via the electron
cyclotron maser instability. The existence or parameters of the proposed
planets have not been determined. Using 20 new HARPS-N observations, we put
99th-percentile upper limits on the mass of any close companion to GJ 1151 at
Msini < 5.6 M earth. With no stellar, brown dwarf, or giant planet companion
likely in a close orbit, our data are consistent with detected radio emission
emerging from a magnetic interaction between a short-period terrestrial-mass
planet and GJ 1151
WHOI Hawaii Ocean Timeseries Station (WHOTS): WHOTS-11 2014 mooring Turnaround Cruise Report
The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries Site (WHOTS),
100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a
part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a
coordinated part of the Hawaii Ocean Timeseries (HOT) program, contributing to the goals of
observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North
Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and
oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds.
These observations will be used to investigate air–sea interaction processes related to climate
variability.
This report documents recovery of the tenth WHOTS mooring (WHOTS-10) and
deployment of the eleventh mooring (WHOTS-11). Both moorings used Surlyn foam buoys as
the surface element and were outfitted with two Air–Sea Interaction Meteorology (ASIMET)
systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface
meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum.
The upper 155 m of the moorings were outfitted with oceanographic sensors for the
measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of
the University of Hawaii. A pCO2 system and ancillary sensors were installed on the buoys in
cooperation with Chris Sabine at the Pacific Marine Environmental Laboratory. A set of
radiometers were installed in cooperation with Sam Laney at WHOI.
The WHOTS mooring turnaround was done on the NOAA ship Hi’ialakai by the Upper
Ocean Processes Group of the Woods Hole Oceanographic Institution. The cruise took place
between 15 and 23 July 2014. Operations began with deployment of the WHOTS-11 mooring on
16 July. This was followed by meteorological intercomparisons and CTDs. Recovery of the
WHOTS-10 mooring took place on 20 July. This report describes these cruise operations, as well
as some of the in-port operations and pre-cruise buoy preparations.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No.
NA140AR4320158 and the Cooperative Institute for the North Atlantic Region (CINAR
WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-8 2011 mooring turnaround cruise report
Note: author "Ludovic Bariteau" is incorrectly listed as "Bariteau Ludovic" on the Cover and Title Page.The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site
(WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea
fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves
as a coordinated part of the HOT program, contributing to the goals of observing heat, fresh
water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The
approach is to maintain a surface mooring outfitted for meteorological and oceanographic
measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These
observations will be used to investigate air–sea interaction processes related to climate
variability.
This report documents recovery of the seventh WHOTS mooring (WHOTS-7) and deployment
of the eighth mooring (WHOTS-8). Both moorings used Surlyn foam buoys as the surface
element and were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each
ASIMET system measures, records, and transmits via Argos satellite the surface meteorological
variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 155
m of the moorings were outfitted with oceanographic sensors for the measurement of
temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of
Hawaii. A pCO2 system was installed on the WHOTS-8 buoy in a cooperative effort with Chris
Sabine at the Pacific Marine Environmental Laboratory. A set of radiometers were installed in
cooperation with Sam Laney at WHOI.
The WHOTS mooring turnaround was done on the NOAA ship Hi’ialakai by the Upper Ocean
Processes Group of the Woods Hole Oceanographic Institution. The cruise took place between 5
July and 13 July 2011. Operations began with deployment of the WHOTS-8 mooring on 6 July.
This was followed by meteorological intercomparisons and CTDs. Recovery of WHOTS-7 took
place on 11 July 2011. This report describes these cruise operations, as well as some of the in-port
operations and pre-cruise buoy preparations.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No.
NA090AR4320129 and the Cooperative Institute for the North Atlantic Region (CINAR)
Evolutionary distances in the twilight zone -- a rational kernel approach
Phylogenetic tree reconstruction is traditionally based on multiple sequence
alignments (MSAs) and heavily depends on the validity of this information
bottleneck. With increasing sequence divergence, the quality of MSAs decays
quickly. Alignment-free methods, on the other hand, are based on abstract
string comparisons and avoid potential alignment problems. However, in general
they are not biologically motivated and ignore our knowledge about the
evolution of sequences. Thus, it is still a major open question how to define
an evolutionary distance metric between divergent sequences that makes use of
indel information and known substitution models without the need for a multiple
alignment. Here we propose a new evolutionary distance metric to close this
gap. It uses finite-state transducers to create a biologically motivated
similarity score which models substitutions and indels, and does not depend on
a multiple sequence alignment. The sequence similarity score is defined in
analogy to pairwise alignments and additionally has the positive semi-definite
property. We describe its derivation and show in simulation studies and
real-world examples that it is more accurate in reconstructing phylogenies than
competing methods. The result is a new and accurate way of determining
evolutionary distances in and beyond the twilight zone of sequence alignments
that is suitable for large datasets.Comment: to appear in PLoS ON
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey : baryon acoustic oscillations in the Data Releases 10 and 11 Galaxy samples
We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations (BAO) in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey, which is part of the Sloan Digital Sky Survey III. Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately 8500 square degrees and the redshift range 0.2 < z < 0.7. We also compare these results with those from the publicly released DR9 and DR10 samples. Assuming a concordance Λ cold dark matter (ΛCDM) cosmological model, the DR11 sample covers a volume of 13 Gpc3 and is the largest region of the Universe ever surveyed at this density. We measure the correlation function and power spectrum, including density-field reconstruction of the BAO feature. The acoustic features are detected at a significance of over 7σ in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, rd, which has a value of rd,fid = 149.28 Mpc in our fiducial cosmology. We find DV = (1264 ± 25 Mpc)(rd/rd,fid) at z = 0.32 and DV = (2056 ± 20 Mpc)(rd/rd,fid) at z = 0.57. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line of sight yields measurements at z = 0.57 of DA = (1421 ± 20 Mpc)(rd/rd,fid) and H = (96.8 ± 3.4 km s−1 Mpc−1)(rd,fid/rd). Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat CDM model with a cosmological constant.Publisher PDFPeer reviewe
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