72 research outputs found
Experimental demonstration of a classical analog to quantum noise cancellation for use in gravitational wave detection
We present results that are a classical analog to quantum noise cancellation. It is possible to breach the standard quantum limit in an interferometer by the use of squeezing to correlate orthogonal quadratures of quantum noise, causing their effects on the resulting sensitivity to cancel. A laser beam incident on a Fabry-Perot cavity was imprinted with classical, correlated noise in the same quadratures that cause shot noise and radiation pressure noise. Couplings between these quadratures due to a movable mirror, sensitive to radiation pressure, cause the excess classical noise to cancel. This cancellation was shown to improve the signal to noise ratio of an injected signal by approximately a factor of 10
Cooling of a gram-scale cantilever flexure to 70 mK with a servo-modified optical spring
A series of recent articles have presented results demonstrating optical cooling of macroscopic objects,
highlighting the importance of this phenomenon for investigations of macroscopic quantum mechanics
and its implications for thermal noise in gravitational wave detectors. In this Letter, we present a
measurement of the off-resonance suspension thermal noise of a 1 g oscillator, and we show that it
can be cooled to just 70 mK. The cooling is achieved by using a servo to impose a phase delay between
oscillator motion and optical force. A model is developed to show how optical rigidity and optical cooling
can be interchangeable using this technique
Coating-free mirrors for high precision interferometric experiments
Thermal noise in mirror optical coatings may not only limit the sensitivity of future gravitational-wave
detectors in their most sensitive frequency band but is also a major impediment for experiments that aim to
reach the standard quantum limit or cool mechanical systems to their quantum ground state. We present the
design and experimental characterization of a highly reflecting mirror without any optical coating. This
coating-free mirror is based on total internal reflection and Brewster-angle coupling. In order to characterize its
performance, the coating-free mirror was incorporated into a triangular ring cavity together with a high quality
conventional mirror. The finesse of this cavity was measured using an amplitude transfer function to be about
F 4000. This finesse corresponds to a reflectivity of the coating-free mirror of about R 99.89%. In addition,
the dependence of the reflectivity on rotation was mapped out
Sensing and control in dual-recycling laser interferometer gravitational-wave detectors
We introduce length-sensing and control schemes for the dual-recycled cavity-enhanced Michelson interferometer configuration proposed for the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO). We discuss the principles of this scheme and show methods that allow sensing and control signals to be derived. Experimental verification was carried out in three benchtop experiments that are introduced. We present the implications of the results from these experiments for Advanced LIGO and other future interferometric gravitational-wave detectors
Report on an all-sky LIGO search for periodic gravitational waves in the 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 having a negative
frequency time derivative with magnitude between zero and Hz/s. Data
from the fourth LIGO science run have been used in this search. Three different
semi-coherent methods of summing strain power were applied. Observing no
evidence for periodic gravitational radiation, we report upper limits on strain
amplitude and interpret these limits to constrain radiation from rotating
neutron stars.Comment: 5 pages, 1 figure, presented at Amaldi7, Sydney (July 2007
Searching for stochastic gravitational-wave background with the co-located LIGO interferometers
This paper presents techniques developed by the LIGO Scientific Collaboration
to search for the stochastic gravitational-wave background using the co-located
pair of LIGO interferometers at Hanford, WA. We use correlations between
interferometers and environment monitoring instruments, as well as time-shifts
between two interferometers (described here for the first time) to identify
correlated noise from non-gravitational sources. We veto particularly noisy
frequency bands and assess the level of residual non-gravitational coupling
that exists in the surviving data.Comment: Proceedings paper from the 7th Edoardo Amaldi Conference on
Gravitational Waves, held in Sydney, Australia from 8-14 July 2007. Accepted
to J. Phys.: Conf. Se
Growth Hormone Regulates the Balance Between Bone Formation and Bone Marrow Adiposity
Cancellous bone decreases and bone marrow fat content increases with age. Osteoblasts and adipocytes are derived from a common precursor, and growth hormone (GH), a key hormone in integration of energy metabolism, regulates the differentiation and function of both cell lineages. Since an age-related decline in GH is associated with bone loss, we investigated the relationship between GH and bone marrow adiposity in hypophysectomized (HYPOX) rats and in mice with defects in GH signaling. HYPOX dramatically reduced body weight gain, bone growth and mineralizing perimeter, serum insulin-like growth factor 1 (IGF-1) levels, and mRNA levels for IGF-1 in liver and bone. Despite reduced body mass and adipocyte precursor pool size, HYPOX resulted in a dramatic increase in bone lipid levels, as reflected by increased bone marrow adiposity and bone triglyceride and cholesterol content. GH replacement normalized bone marrow adiposity and precursor pool size, as well as mineralizing perimeter in HYPOX rats. In contrast, 17β -estradiol, IGF-1, thyroxine, and cortisone were ineffective. Parathyroid hormone (PTH) reversed the inhibitory effects of HYPOX on mineralizing perimeter but had no effect on adiposity. Finally, bone marrow adiposity was increased in mice deficient in GH and IGF-1 but not in mice deficient in serum IGF-1. Taken together, our findings indicate that the reciprocal changes in bone and fat mass in GH signaling-deficient rodents are not directly coupled with one another. Rather, GH enhances adipocyte as well as osteoblast precursor pool size. However, GH increases osteoblast differentiation while suppressing bone marrow lipid accumulation. © 2010 American Society for Bone and Mineral Researc
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Curcumin induces human cathelicidin antimicrobial peptide gene expression through a vitamin D receptor-independent pathway
The vitamin D receptor (VDR) mediates the pleiotropic biologic effects of 1alpha,25
dihydroxy-vitamin D3. Recent in vitro studies suggested that curcumin and poly-unsaturated fatty
acids (PUFAs) also bind to VDR with low affinity. As potential ligands for the VDR, we hypothesized
that curcumin and PUFAs would induce expression of known VDR target genes in cells. In this study,
we tested whether these compounds regulated two important VDR target genes - human cathelicidin
antimicrobial peptide (CAMP) and 1,25-dihydroxyvitamin D3 24-hydroxylase (CYP24A1)- in human
monocytic cell line U937, colon cancer cell line HT-29 and keratinocyte cell line HaCaT. We
demonstrated that PUFAs failed to induce CAMP or CYP24A1 mRNA expression in all three cell lines,
but curcumin up-regulated CAMP mRNA and protein levels in U937 cells. Curcumin treatment induced
CAMP promoter activity from a luciferase reporter construct lacking the VDR binding site and did not
increase binding of the VDR to the CAMP promoter as determined by chromatin immunoprecipitation
assays. These findings indicate that induction of CAMP by curcumin occurs through a vitamin D
receptor-independent manner. We conclude that PUFAs and curcumin do not function as ligands for
the VDR.This is the authors' peer-reviewed accepted manuscript. The version of record is published and copyrighted by Elsevier and can be found at: http://www.elsevier.com/wps/find/journaldescription.cws_home/525013/description#descriptionKeywords: curcumin, vitamin D receptor, cathelicidin, poly-unsaturated fatty acid, innate immunit
Hierarchical Hough all-sky search for periodic gravitational waves in LIGO S5 data
We describe a new pipeline used to analyze the data from the fifth science
run (S5) of the LIGO detectors to search for continuous gravitational waves
from isolated spinning neutron stars. The method employed is based on the Hough
transform, which is a semi-coherent, computationally efficient, and robust
pattern recognition technique. The Hough transform is used to find signals in
the time-frequency plane of the data whose frequency evolution fits the pattern
produced by the Doppler shift imposed on the signal by the Earth's motion and
the pulsar's spin-down during the observation period. The main differences with
respect to previous Hough all-sky searches are described. These differences
include the use of a two-step hierarchical Hough search, analysis of
coincidences among the candidates produced in the first and second year of S5,
and veto strategies based on a test.Comment: 7 pages, 2 figures, Amaldi08 proceedings, submitted to JPC
Detection Confidence Tests for Burst and Inspiral Candidate Events
The LIGO Scientific Collaboration (LSC) is developing and running analysis
pipelines to search for gravitational-wave transients emitted by astrophysical
events such as compact binary mergers or core-collapse supernovae. However,
because of the non-Gaussian, non-stationary nature of the noise exhibited by
the LIGO detectors, residual false alarms might be found at the end of the
pipelines. A critical aspect of the search is then to assess our confidence for
gravitational waves and to distinguish them from those false alarms. Both the
'Compact Binary Coalescence' and the 'Burst' working groups have been
developing a detection checklist for the validation of candidate-events,
consisting of a series of tests which aim to corroborate a detection or to
eliminate a false alarm. These tests include for example data quality checks,
analysis of the candidate appearance, parameter consistency studies and
coherent analysis. In this paper, the general methodology used for candidate
validation is presented. The method is illustrated with an example of simulated
gravitational-wave signal and a false alarm.Comment: 15 pages, 8 figures, Contribution to 12th Gravitational Wave Data
Analysis Workshop. Version sent to Classical and Quantum Gravity immediately
before publication. It addresses the CQG referee's comment
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