429 research outputs found
Ultracold atoms in multiple-radiofrequency dressed adiabatic potentials
We present the first experimental demonstration of a multiple-radiofrequency
dressed potential for the configurable magnetic confinement of ultracold atoms.
We load cold Rb atoms into a double well potential with an adjustable
barrier height, formed by three radiofrequencies applied to atoms in a static
quadrupole magnetic field. Our multiple-radiofrequency approach gives precise
control over the double well characteristics, including the depth of individual
wells and the height of the barrier, and enables reliable transfer of atoms
between the available trapping geometries. We have characterised the
multiple-radiofrequency dressed system using radiofrequency spectroscopy,
finding good agreement with the eigenvalues numerically calculated using
Floquet theory. This method creates trapping potentials that can be
reconfigured by changing the amplitudes, polarizations and frequencies of the
applied dressing fields, and easily extended with additional dressing
frequencies.Comment: 16 pages, 6 figure
Accuracy of averaged auditory brainstem response amplitude and latency estimates
<p><i>Objective</i>: The aims were to 1) establish which of the four algorithms for estimating residual noise level and signal-to-noise ratio (SNR) in auditory brainstem responses (ABRs) perform better in terms of post-average wave-V peak latency and amplitude errors and 2) determine whether SNR or noise floor is a better stop criterion where the outcome measure is peak latency or amplitude. <i>Design</i>: The performance of the algorithms was evaluated by numerical simulations using an ABR template combined with electroencephalographic (EEG) recordings obtained without sound stimulus. The suitability of a fixed SNR versus a fixed noise floor stop criterion was assessed when variations in the wave-V waveform shape reflecting inter-subject variation was introduced. <i>Study sample</i>: Over 100 hours of raw EEG noise was recorded from 17 adult subjects, under different conditions (e.g. sleep or movement). <i>Results</i>: ABR feature accuracy was similar for the four algorithms. However, it was shown that a fixed noise floor leads to higher ABR wave-V amplitude accuracy; conversely, a fixed SNR yields higher wave-V latency accuracy. <i>Conclusion</i>: Similar performance suggests the use of the less computationally complex algorithms. Different stop criteria are recommended if the ABR peak latency or the amplitude is the outcome measure of interest.</p
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