202 research outputs found
Mixing of ultracold atomic clouds by merging of two magnetic traps
We demonstrate a method to make mixtures of ultracold atoms that does not
make use of a two-species magneto-optical trap. We prepare two clouds of 87Rb
atoms in distinct magnetic quadrupole traps and mix the two clouds by merging
the traps. For correctly chosen parameters the mixing can be done essentially
without loss of atoms and with only minor heating. The basic features of the
process can be accounted for by a classical simulation of particle
trajectories. Such calculations indicate that mixing of different mass species
is also feasible, opening the way for using the method as a starting point for
making quantum gas mixtures.Comment: 12 pages, 13 figures. Fig. 10 corrected. Fig. 13 updated with more
points and better statistics. A couple of paragraphs rephrased and typos
corrected. References update
Robust Bayesian Pitch Tracking Based on the Harmonic Model
Fundamental frequency is one of the most important characteristics of speech and audio signals. Harmonic model-based fundamental frequency estimators offer a higher estimation accuracy and robustness against noise than the widely used autocorrelation-based methods. However, the traditional harmonic model-based estimators do not take the temporal smoothness of the fundamental frequency, the model order, and the voicing into account as they process each data segment independently. In this paper, a fully Bayesian fundamental frequency tracking algorithm based on the harmonic model and a first-order Markov process model is proposed. Smoothness priors are imposed on the fundamental frequencies, model orders, and voicing using first-order Markov process models. Using these Markov models, fundamental frequency estimation and voicing detection errors can be reduced. Using the harmonic model, the proposed fundamental frequency tracker has an improved robustness to noise. An analytical form of the likelihood function, which can be computed efficiently, is derived. Compared to the state-of-the-art neural network and nonparametric approaches, the proposed fundamental frequency tracking algorithm has superior performance in almost all investigated scenarios, especially in noisy conditions. For example, under 0 dB white Gaussian noise, the proposed algorithm reduces the mean absolute errors and gross errors by 15% and 20% on the Keele pitch database and 36% and 26% on sustained /a/ sounds from a database of Parkinson's disease voices. A MATLAB version of the proposed algorithm is made freely available for reproduction of the results. 1 1An implementation of the proposed algorithm using MATLAB may be found in https://tinyurl.com/yxn4a543
Decreased Heart Rate Variability in HIV Positive Patients Receiving Antiretroviral Therapy: Importance of Blood Glucose and Cholesterol
The presence of autonomic dysfunction in HIV patients is largely unknown. Early studies found autonomic dysfunction in patients with AIDS. Antiretroviral combination therapy (ART) has dramatically changed the course of the disease and improved prognosis and decreased morbidity
The morphology of the ejecta in Supernova 1987A: a study over time and wavelength
We present a study of the morphology of the ejecta in Supernova 1987A based
on images and spectra from the HST as well as integral field spectroscopy from
VLT/SINFONI. The HST observations were obtained between 1994 - 2011 and
primarily probe the outer hydrogen-rich zones of the ejecta. The SINFONI
observations were obtained in 2005 and 2011 and instead probe the [Si I]/[Fe
II] emission from the inner regions. We find a strong temporal evolution of the
morphology in the HST images, from a roughly elliptical shape before ~5,000
days, to a more irregular, edge-brightened morphology thereafter. This
transition is a natural consequence of the change in the dominant energy source
powering the ejecta, from radioactive decay before ~5,000 days to X-ray input
from the circumstellar interaction thereafter. The [Si I]/[Fe II] images
display a more uniform morphology, which may be due to a remaining significant
contribution from radioactivity in the inner ejecta and the higher abundance of
these elements in the core. Both the H-alpha and the [Si I]/[Fe II] line
profiles show that the ejecta are distributed fairly close to the plane of the
inner circumstellar ring, which is assumed to define the rotational axis of the
progenitor. The H-alpha emission extends to higher velocities than [Si I]/[Fe
II] as expected. There is no clear symmetry axis for all the emission and we
are unable to model the ejecta distribution with a simple ellipsoid model with
a uniform distribution of dust. Instead, we find that the emission is
concentrated to clumps and that the emission is distributed somewhat closer to
the ring in the north than in the south. This north-south asymmetry may be
partially explained by dust absorption. We compare our results with explosion
models and find some qualitative agreement, but note that the observations show
a higher degree of large-scale asymmetry.Comment: Accepted for publication in Ap
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