198 research outputs found
Towards a FPGA-controlled deep phase modulation interferometer
Deep phase modulation interferometry was proposed as a method to enhance
homodyne interferometers to work over many fringes. In this scheme, a
sinusoidal phase modulation is applied in one arm while the demodulation takes
place as a post-processing step. In this contribution we report on the
development to implement this scheme in a fiber coupled interferometer
controlled by means of a FPGA, which includes a LEON3 soft-core processor. The
latter acts as a CPU and executes a custom made application to communicate with
a host PC. In contrast to usual FPGA-based designs, this implementation allows
a real-time fine tuning of the parameters involved in the setup, from the
control to the post-processing parameters.Comment: Proceedings of the X LISA Symposium, Gainesville, May 18-23, 201
LISA and LISA PathFinder, the endeavour to detect low frequency GWs
This is a review about LISA and its technology demonstrator, LISA PathFinder.
We first describe the conceptual problems which need to be overcome in order to
set up a working interferometric detector of low frequency Gravitational Waves
(GW), then summarise the solutions to them as currently conceived by the LISA
mission team. This will show that some of these solutions require new
technological abilities which are still under development, and which need
proper test before being fully implemented. LISA PathFinder (LPF) is the the
testbed for such technologies. The final part of the paper will address the
ideas and concepts behind the PathFinder as well as their impact on LISA.Comment: 25 pages, 21 figures, presented at the Spanish Relativity Meeting,
Mallorca September 2006. Will be published in Journal of Physics: Conference
Series, IOP. To be published in Journal of Physics: Conference Series, IO
Calibrating spectral estimation for the LISA Technology Package with multichannel synthetic noise generation
The scientific objectives of the Lisa Technology Package (LTP) experiment, on
board of the LISA Pathfinder mission, demand for an accurate calibration and
validation of the data analysis tools in advance of the mission launch. The
levels of confidence required on the mission outcomes can be reached only with
an intense activity on synthetically generated data. A flexible procedure
allowing the generation of cross-correlated stationary noise time series was
set-up. Multi-channel time series with the desired cross correlation behavior
can be generated once a model for a multichannel cross-spectral matrix is
provided. The core of the procedure is the synthesis of a noise coloring
multichannel filter through a frequency-by-frequency eigendecomposition of the
model cross-spectral matrix and a Z-domain fit. The common problem of initial
transients in noise time series is solved with a proper initialization of the
filter recursive equations. The noise generator performances were tested in a
two dimensional case study of the LTP dynamics along the two principal channels
of the sensing interferometer.Comment: Accepted for publication in Physical Review D (http://prd.aps.org/
Bayesian parameter estimation in the second LISA Pathfinder Mock Data Challenge
A main scientific output of the LISA Pathfinder mission is to provide a noise
model that can be extended to the future gravitational wave observatory, LISA.
The success of the mission depends thus upon a deep understanding of the
instrument, especially the ability to correctly determine the parameters of the
underlying noise model. In this work we estimate the parameters of a simplified
model of the LISA Technology Package (LTP) instrument. We describe the LTP by
means of a closed-loop model that is used to generate the data, both injected
signals and noise. Then, parameters are estimated using a Bayesian framework
and it is shown that this method reaches the optimal attainable error, the
Cramer-Rao bound. We also address an important issue for the mission: how to
efficiently combine the results of different experiments to obtain a unique set
of parameters describing the instrument.Comment: 14 pages, 4 figures, submitted to PR
Establishing the Tolerability to Turkeys of Nonanoic Acid at Practical Levels of Use as a Feed Flavoring
Objective: Nonanoic acid (NA) is one of a series of straight-chain aliphatic alcohols, aldehydes, acids and their derivatives with a well-documented history of use as a synthetic flavoring in human food. As part of a safety evaluation of NA for use as a flavoring in animal feed, an experiment was conducted to evaluate the ability of turkeys to tolerate NA at levels relevant to practical feeding practices. Materials and Methods: A total of 594-day-old BUT Premium turkeys (300 males and 294 females) were allocated at random to 40
floor pens containing either 15 males or 13 to 15 females. Poults were fed one
of 4 treatment diets in crumble (0 to 14 days) or pellet (15 to 59 days) form
containing 0 (control), 100, 300 or 1000 mg NA/kg complete feed for 59 days.
General health and performance were monitored for the duration of the
study. At days 57 and 59 of age, blood samples were taken and birds were sacrificed and necropsied for histopathological examination of the digestive tract. Significant differences were considered at P ≤ 0.05 and near-significant trends at P ≤ 0.10. Results: NA had no effect on mortality (Pχ2 = 0.54), average daily feed intake (ADFI) (P = 0.11), average daily gain (ADG) (P = 0.12) or feed conversion ratio (FCR) (P = 0.45) in poults over the 56-day feeding period. No treatment-related effects on blood parameters or tissue pathology were observed. Conclusion: The results of the study support the safety and tolerance of NA to turkeys at dietary levels of up to 1000 mg/kg which will provide a considerable margin of safety compared to anticipated practical conditions of use as a feed flavoring.info:eu-repo/semantics/publishedVersio
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