1,040 research outputs found
Using Full Information When Computing Modes of Post-Newtonian Waveforms From Inspiralling Compact Binaries in Circular Orbit
The increasing sophistication and accuracy of numerical simulations of
compact binaries (especially binary black holes) presents the opportunity to
test the regime in which post-Newtonian (PN) predictions for the emitted
gravitational waves are accurate. In order to confront numerical results with
those of post-Newtonian theory, it is convenient to compare multipolar
decompositions of the two waveforms. It is pointed out here that the individual
modes can be computed to higher post-Newtonian order by examining the radiative
multipole moments of the system, rather than by decomposing the 2.5PN
polarization waveforms. In particular, the dominant (l = 2, m = 2) mode can be
computed to 3PN order. Individual modes are computed to as high a
post-Newtonian order as possible given previous post-Newtonian results.Comment: 15 page
Suspensions of supracolloidal magnetic polymers: self-assembly properties from computer simulations
We study self-assembly in suspensions of supracolloidal polymer-like
structures made of crosslinked magnetic particles. Inspired by self-assembly
motifs observed for dipolar hard spheres, we focus on four different topologies
of the polymer-like structures: linear chains, rings, Y-shaped and X-shaped
polymers. We show how the presence of the crosslinkers, the number of beads in
the polymer and the magnetic interparticle interaction affect the structure of
the suspension. It turns out that for the same set of parameters, the rings are
the least active in assembling larger structures, whereas the system of Y- and
especially X-like magnetic polymers tend to form very large loose aggregates
Parameter estimation of compact binaries using the inspiral and ringdown waveforms
We analyze the problem of parameter estimation for compact binary systems
that could be detected by ground-based gravitational wave detectors.
So far this problem has only been dealt with for the inspiral and the
ringdown phases separately. In this paper, we combine the information from both
signals, and we study the improvement in parameter estimation, at a fixed
signal-to-noise ratio, by including the ringdown signal without making any
assumption on the merger phase. The study is performed for both initial and
advanced LIGO and VIRGO detectors.Comment: matching cqg versio
Infinite Kinematic Self-Similarity and Perfect Fluid Spacetimes
Perfect fluid spacetimes admitting a kinematic self-similarity of infinite
type are investigated. In the case of plane, spherically or hyperbolically
symmetric space-times the field equations reduce to a system of autonomous
ordinary differential equations. The qualitative properties of solutions of
this system of equations, and in particular their asymptotic behavior, are
studied. Special cases, including some of the invariant sets and the geodesic
case, are examined in detail and the exact solutions are provided. The class of
solutions exhibiting physical self-similarity are found to play an important
role in describing the asymptotic behavior of the infinite kinematic
self-similar models.Comment: 38 pages, 6 figures. Accepted for publication in General Relativity &
Gravitatio
Large-scale distribution of microbial and viral populations in the South Atlantic Ocean
Viruses are abundant, diverse and dynamic compo-nents of the marine environments and play a signi?-cant role in the ocean biogeochemical cycles. Toassess potential variations in the relation betweenviruses and microbes in different geographic regionsand depths, viral and microbial abundance and pro-duction were determined throughout the watercolumn along a latitudinal transect in the South Atlan-tic Ocean. Path analysis was used to examine therelationships between several abiotic and bioticparameters and the different microbial and viral popu-lations distinguished by ?ow cytometry.The depth-integrated contribution of microbial andviral abundance to the total microbial and viralbiomass differed signi?cantly among the differentprovinces. Additionally, the virus-to-microbe ratioincreased with depth and decreased laterally towardsthe more productive regions. Our data revealed thatthe abundance of phytoplankton and microbes is themain controlling factor of the viral populations in theeuphotic and mesopelagic layers, whereas in thebathypelagic realm, viral abundance was only weaklyrelated to the biotic and abiotic variables. The relativecontribution of the three viral populations distin-guished by ?ow cytometry showed a clear geographi-cal pattern throughout the water column, suggestingthat these populations are composed of distinct tax
Ice polyamorphism in the minimal Mercedes-Benz model of water
We investigate ice polyamorphism in the context of the two-dimensional Mercedes-Benz model of water. We find a first-order phase transition between a crystalline phase and a high-density amorphous phase. Furthermore, we find a reversible transformation between two amorphous structures of high and low density; however, we find this to be a continuous and not an abrupt transition, as the low-density amorphous phase does not show structural stability. We discuss the origin of this behavior and its implications with regard to the minimal generic modeling of polyamorphism. © 2012 American Institute of Physics.Simulations were performed at the IFISC’s Nuredduna highthroughput computing clusters, supported by the projects GRID-CSIC and FISICOS (FIS2007-60327, funded by the Spanish MINCNN and the ERDF). J.H.E.C. acknowledges MINCINN (Spain) Project No. FIS2010-22322-528C02-02. O.P. and P.A.S. acknowledge MINCINN (Spain) Project No. FIS2010-22322-528C02-01.Peer Reviewe
Dark CO2 fixation by chemolithoautotrophic prokaryotes in the deep-water masses of the north-west coast of the Iberian Peninsule
Recent studies suggest that the prokaryotes inhabiting the dark ocean present higher chemolithoautotrophic activity than assumed previously. These chemolithoautotrophic microbes incorporate dissolved inorganic carbon (DIC) as carbon source for biomass production and use reduced inorganic compound as an energy source. We have quantified DIC fixation in the meso- and bathypelagic waters of the northwestern coast of the Iberian Peninsula, ranging from 1.04 to 46.83 mmol C m-2 d-1. Combining microautoradiography and fluorescence in situ hybridization (MICRO-CARD-FISH), we confirmed that both Thaumarchaeota and some bacterial groups such as SAR-11, SAR-202, SAR-406, Alteromonas take up bicarbonate uptake, particularly in the mesopelagic waters. Quantitative PCR analyses clearly showed a higher abundance of thaumarchaeal 16S and low ammonia concentration (LAC)- amoA genes in meso- and lower bathypelagic waters than in surface waters. In contrast, high ammonia concentration (HAC)- amoA genes dominated the subsurface samples. Taken together, both genomic and physiological evidences indicate that some archaeal and bacterial groups may be significant contributors to dark ocean chemoautolithotrophy
Spectral Line Removal in the LIGO Data Analysis System (LDAS)
High power in narrow frequency bands, spectral lines, are a feature of an
interferometric gravitational wave detector's output. Some lines are coherent
between interferometers, in particular, the 2 km and 4 km LIGO Hanford
instruments. This is of concern to data analysis techniques, such as the
stochastic background search, that use correlations between instruments to
detect gravitational radiation. Several techniques of `line removal' have been
proposed. Where a line is attributable to a measurable environmental
disturbance, a simple linear model may be fitted to predict, and subsequently
subtract away, that line. This technique has been implemented (as the command
oelslr) in the LIGO Data Analysis System (LDAS). We demonstrate its application
to LIGO S1 data.Comment: 11 pages, 5 figures, to be published in CQG GWDAW02 proceeding
High dark CO2 fixation rates by active chemolithoautotrophic microbes along the water column (100-5000m) off Galicia (NW Iberian margin)
Poster communicationOur results provide evidence for the significant contribution to chemolithotrophy by specific archaeal and bacterial groups in the dark ocean
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