293 research outputs found
Dual-barrel conductance micropipet as a new approach to the study of ionic crystal dissolution kinetics
A new approach to the study of ionic crystal dissolution kinetics is described, based on the use of a dual-barrel theta conductance micropipet. The solution in the pipet is undersaturated with respect to the crystal of interest, and when the meniscus at the end of the micropipet makes contact with a selected region of the crystal surface, dissolution occurs causing the solution composition to change. This is observed, with better than 1 ms time resolution, as a change in the ion conductance current, measured across a potential bias between an electrode in each barrel of the pipet. Key attributes of this new technique are: (i) dissolution can be targeted at a single crystal surface; (ii) multiple measurements can be made quickly and easily by moving the pipet to a new location on the surface; (iii) materials with a wide range of kinetics and solubilities are open to study because the duration of dissolution is controlled by the meniscus contact time; (iv) fast kinetics are readily amenable to study because of the intrinsically high mass transport rates within tapered micropipets; (v) the experimental geometry is well-defined, permitting finite element method modeling to allow quantitative analysis of experimental data. Herein, we study the dissolution of NaCl as an example system, with dissolution induced for just a few milliseconds, and estimate a first-order heterogeneous rate constant of 7.5 (±2.5) × 10–5 cm s–1 (equivalent surface dissolution flux ca. 0.5 μmol cm–2 s–1 into a completely undersaturated solution). Ionic crystals form a huge class of materials whose dissolution properties are of considerable interest, and we thus anticipate that this new localized microscale surface approach will have considerable applicability in the future
Search for gravitational waves from binary inspirals in S3 and S4 LIGO data
We report on a search for gravitational waves from the coalescence of compact
binaries during the third and fourth LIGO science runs. The search focused on
gravitational waves generated during the inspiral phase of the binary
evolution. In our analysis, we considered three categories of compact binary
systems, ordered by mass: (i) primordial black hole binaries with masses in the
range 0.35 M(sun) < m1, m2 < 1.0 M(sun), (ii) binary neutron stars with masses
in the range 1.0 M(sun) < m1, m2 < 3.0 M(sun), and (iii) binary black holes
with masses in the range 3.0 M(sun)< m1, m2 < m_(max) with the additional
constraint m1+ m2 < m_(max), where m_(max) was set to 40.0 M(sun) and 80.0
M(sun) in the third and fourth science runs, respectively. Although the
detectors could probe to distances as far as tens of Mpc, no gravitational-wave
signals were identified in the 1364 hours of data we analyzed. Assuming a
binary population with a Gaussian distribution around 0.75-0.75 M(sun), 1.4-1.4
M(sun), and 5.0-5.0 M(sun), we derived 90%-confidence upper limit rates of 4.9
yr^(-1) L10^(-1) for primordial black hole binaries, 1.2 yr^(-1) L10^(-1) for
binary neutron stars, and 0.5 yr^(-1) L10^(-1) for stellar mass binary black
holes, where L10 is 10^(10) times the blue light luminosity of the Sun.Comment: 12 pages, 11 figure
First LIGO search for gravitational wave bursts from cosmic (super)strings
We report on a matched-filter search for gravitational wave bursts from
cosmic string cusps using LIGO data from the fourth science run (S4) which took
place in February and March 2005. No gravitational waves were detected in 14.9
days of data from times when all three LIGO detectors were operating. We
interpret the result in terms of a frequentist upper limit on the rate of
gravitational wave bursts and use the limits on the rate to constrain the
parameter space (string tension, reconnection probability, and loop sizes) of
cosmic string models.Comment: 11 pages, 3 figures. Replaced with version submitted to PR
Search for Gravitational Waves Associated with 39 Gamma-Ray Bursts Using Data from the Second, Third, and Fourth LIGO Runs
We present the results of a search for short-duration gravitational-wave
bursts associated with 39 gamma-ray bursts (GRBs) detected by gamma-ray
satellite experiments during LIGO's S2, S3, and S4 science runs. The search
involves calculating the crosscorrelation between two interferometer data
streams surrounding the GRB trigger time. We search for associated
gravitational radiation from single GRBs, and also apply statistical tests to
search for a gravitational-wave signature associated with the whole sample. For
the sample examined, we find no evidence for the association of gravitational
radiation with GRBs, either on a single-GRB basis or on a statistical basis.
Simulating gravitational-wave bursts with sine-gaussian waveforms, we set upper
limits on the root-sum-square of the gravitational-wave strain amplitude of
such waveforms at the times of the GRB triggers. We also demonstrate how a
sample of several GRBs can be used collectively to set constraints on
population models. The small number of GRBs and the significant change in
sensitivity of the detectors over the three runs, however, limits the
usefulness of a population study for the S2, S3, and S4 runs. Finally, we
discuss prospects for the search sensitivity for the ongoing S5 run, and beyond
for the next generation of detectors.Comment: 24 pages, 10 figures, 14 tables; minor changes to text and Fig. 2;
accepted by Phys. Rev.
All-sky search for periodic gravitational waves in LIGO S4 data
We report on an all-sky search with the LIGO detectors for periodic
gravitational waves in the frequency range 50-1000 Hz and with the frequency's
time derivative in the range -1.0E-8 Hz/s to zero. Data from the fourth LIGO
science run (S4) have been used in this search. Three different semi-coherent
methods of transforming and summing strain power from Short Fourier Transforms
(SFTs) of the calibrated data have been used. The first, known as "StackSlide",
averages normalized power from each SFT. A "weighted Hough" scheme is also
developed and used, and which also allows for a multi-interferometer search.
The third method, known as "PowerFlux", is a variant of the StackSlide method
in which the power is weighted before summing. In both the weighted Hough and
PowerFlux methods, the weights are chosen according to the noise and detector
antenna-pattern to maximize the signal-to-noise ratio. The respective
advantages and disadvantages of these methods are discussed. Observing no
evidence of periodic gravitational radiation, we report upper limits; we
interpret these as limits on this radiation from isolated rotating neutron
stars. The best population-based upper limit with 95% confidence on the
gravitational-wave strain amplitude, found for simulated sources distributed
isotropically across the sky and with isotropically distributed spin-axes, is
4.28E-24 (near 140 Hz). Strict upper limits are also obtained for small patches
on the sky for best-case and worst-case inclinations of the spin axes.Comment: 39 pages, 41 figures An error was found in the computation of the C
parameter defined in equation 44 which led to its overestimate by 2^(1/4).
The correct values for the multi-interferometer, H1 and L1 analyses are 9.2,
9.7, and 9.3, respectively. Figure 32 has been updated accordingly. None of
the upper limits presented in the paper were affecte
Astrophysically Triggered Searches for Gravitational Waves: Status and Prospects
In gravitational-wave detection, special emphasis is put onto searches that
focus on cosmic events detected by other types of astrophysical observatories.
The astrophysical triggers, e.g. from gamma-ray and X-ray satellites, optical
telescopes and neutrino observatories, provide a trigger time for analyzing
gravitational wave data coincident with the event. In certain cases the
expected frequency range, source energetics, directional and progenitor
information is also available. Beyond allowing the recognition of gravitational
waveforms with amplitudes closer to the noise floor of the detector, these
triggered searches should also lead to rich science results even before the
onset of Advanced LIGO. In this paper we provide a broad review of LIGO's
astrophysically triggered searches and the sources they target
A Joint Search for Gravitational Wave Bursts with AURIGA and LIGO
The first simultaneous operation of the AURIGA detector and the LIGO
observatory was an opportunity to explore real data, joint analysis methods
between two very different types of gravitational wave detectors: resonant bars
and interferometers. This paper describes a coincident gravitational wave burst
search, where data from the LIGO interferometers are cross-correlated at the
time of AURIGA candidate events to identify coherent transients. The analysis
pipeline is tuned with two thresholds, on the signal-to-noise ratio of AURIGA
candidate events and on the significance of the cross-correlation test in LIGO.
The false alarm rate is estimated by introducing time shifts between data sets
and the network detection efficiency is measured with simulated signals with
power in the narrower AURIGA band. In the absence of a detection, we discuss
how to set an upper limit on the rate of gravitational waves and to interpret
it according to different source models. Due to the short amount of analyzed
data and to the high rate of non-Gaussian transients in the detectors noise at
the time, the relevance of this study is methodological: this was the first
joint search for gravitational wave bursts among detectors with such different
spectral sensitivity and the first opportunity for the resonant and
interferometric communities to unify languages and techniques in the pursuit of
their common goal.Comment: 18 pages, IOP, 12 EPS figure
All-sky LIGO Search for Periodic Gravitational Waves in the Early S5 Data
We report on an all-sky search with the LIGO detectors for periodic
gravitational waves in the frequency range 50--1100 Hz and with the frequency's
time derivative in the range -5.0E-9 Hz/s to zero. Data from the first eight
months of the fifth LIGO science run (S5) have been used in this search, which
is based on a semi-coherent method (PowerFlux) of summing strain power.
Observing no evidence of periodic gravitational radiation, we report 95%
confidence-level upper limits on radiation emitted by any unknown isolated
rotating neutron stars within the search range. Strain limits below 1.E-24 are
obtained over a 200-Hz band, and the sensitivity improvement over previous
searches increases the spatial volume sampled by an average factor of about 100
over the entire search band. For a neutron star with nominal equatorial
ellipticity of 1.0E-6, the search is sensitive to distances as great as 500
pc--a range that could encompass many undiscovered neutron stars, albeit only a
tiny fraction of which would likely be rotating fast enough to be accessible to
LIGO. This ellipticity is at the upper range thought to be sustainable by
conventional neutron stars and well below the maximum sustainable by a strange
quark star.Comment: 6 pages, 1 figur
Search for gravitational-wave bursts in LIGO data from the fourth science run
The fourth science run of the LIGO and GEO 600 gravitational-wave detectors,
carried out in early 2005, collected data with significantly lower noise than
previous science runs. We report on a search for short-duration
gravitational-wave bursts with arbitrary waveform in the 64-1600 Hz frequency
range appearing in all three LIGO interferometers. Signal consistency tests,
data quality cuts, and auxiliary-channel vetoes are applied to reduce the rate
of spurious triggers. No gravitational-wave signals are detected in 15.5 days
of live observation time; we set a frequentist upper limit of 0.15 per day (at
90% confidence level) on the rate of bursts with large enough amplitudes to be
detected reliably. The amplitude sensitivity of the search, characterized using
Monte Carlo simulations, is several times better than that of previous
searches. We also provide rough estimates of the distances at which
representative supernova and binary black hole merger signals could be detected
with 50% efficiency by this analysis.Comment: Corrected amplitude sensitivities (7% change on average); 30 pages,
submitted to Classical and Quantum Gravit
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