321 research outputs found
A Bayesian method to estimate the depth and the range of phonating sperm whales using a single hydrophone
Some bioacousticians have used a single hydrophone to calculate the depth/range of phonating diving animals. The standard one-hydrophone localization method uses multipath transmissions (direct path, sea surface, and seafloor reflections) of the animal phonations as a substitute for a vertical hydrophone array. The standard method requires three multipath transmissions per phonation. Bioacousticians who study foraging sperm whales usually do not have the required amount of multipath transmissions. However, they usually detect accurately (using shallow hydrophones towed by research vessels) direct path transmissions and sea surface reflections of sperm whale phonations (clicks). Sperm whales emit a few thousand clicks per foraging dive, therefore researchers have this number of direct path transmissions and this number of sea surface reflections per dive. The author describes a Bayesian method to combine the information contained in those acoustic data plus visual observations. The author’s tests using synthetic data show that the accurate estimation of the depth/range of sperm whales is possible using a single hydrophone and without using any seafloor reflections. This method could be used to study the behavior of sperm whales using a single hydrophone in any location no matter what the depth, the relief, or the constitution of the seafloor might be
The processes of sound scattering at the ocean surface and bottom
In order to have a firm basis for the prediction of reverberation or back-scattering of sound in the sea, field measurements leading to values for a back-scattering coefficient of the sea surface and bottom have been made. Variation of this coefficient with angle of incidence of the sound beam provides some interesting clues as to the back-scattering processes which operate...
Upwelling regime off the Cabo Frio region in Brazil and impact on acoustic propagation
This work introduces a description of the complex upwelling regime off the Cabo Frio region in Brazil and shows that ocean modeling, based on the feature-oriented regional modeling system (FORMS) technique, can produce reliable predictions of sound speed fields for the corresponding shallow water environment. This work also shows, through the development of simulations, that the upwelling regime can be responsible for the creation of shadow coastal zones, in which the detection probability is too low for an acoustic source to be detected. The development of the FORMS technique and its validation with real data, for the particular region of coastal upwelling off Cabo Frio, reveals the possibility of a sustainable and reliable forecast system for the corresponding (variable in space and time) underwater acoustic environment. (C) 2018 Acoustical Society of AmericaBrazilian Navy; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)/Ciencias Sem Fronteiras [400671/2014-0]; European Union [OAEX-230855]; Fundacao de Amparo a Pesquisa (FAPERJ) [E-26/110.327/2012
Oceanic Ambient Noise as a Background to Acoustic Neutrino Detection
Ambient noise measured in the deep ocean is studied in the context of a
search for signals from ultra-high energy cosmic ray neutrinos. The spectral
shape of the noise at the relevant high frequencies is found to be very stable
for an extensive data set collected over several months from 49 hydrophones
mounted near the bottom of the ocean at ~1600 m depth. The slopes of the
ambient noise spectra above 15 kHz are found to roll-off faster than the -6
dB/octave seen in Knudsen spectra. A model attributing the source to an uniform
distribution of surface noise that includes frequency-dependent absorption at
large depth is found to fit the data well up to 25 kHz. This depth dependent
model should therefore be used in analysis methods of acoustic neutrino pulse
detection that require the expected noise spectra.Comment: Minor changes. Submitted to PRD. 5 pages, 7 figure
Development of Acoustic Sensors for the ANTARES Experiment
In order to study the possibility of acoustic detection of ultra-high energy
neutrinos in water, our group is planning to deploy and operate an array of
acoustic sensors using the ANTARES Neutrino telescope in the Mediterranean Sea.
Therefore, acoustic sensor hardware has to be developed which is both capable
of operation under the hostile conditions of the deep sea and at the same time
provides the high sensitivity necessary to detect the weak pressure signals
resulting from the neutrino's interaction in water. In this paper, two
different approaches to building such sensors, as well as performance studies
in the laboratory and in situ, are presented.Comment: 5 pages, 3 figures. Proceedings of the ARENA 2005 Worksho
Embryonic Stem Cell-Derived Cardiomyocyte Heterogeneity and the Isolation of Immature and Committed Cells for Cardiac Remodeling and Regeneration
Pluripotent stem cells represent one promising source for cell replacement therapy in heart, but differentiating embryonic stem cell-derived cardiomyocytes (ESC-CMs) are highly heterogeneous and show a variety of maturation states. In this study, we employed an ESC clonal line that contains a cardiac-restricted ncx1 promoter-driven puromycin resistance cassette together with a mass culture system to isolate ESC-CMs that display traits characteristic of very immature CMs. The cells display properties of proliferation, CM-restricted markers, reduced mitochondrial mass, and hypoxia-resistance. Following transplantation into rodent hearts, bioluminescence imaging revealed that immature cells, but not more mature CMs, survived for at least one month following injection. These data and comparisons with more mature cells lead us to conclude that immature hypoxia resistant ESC-CMs can be isolated in mass in vitro and, following injection into heart, form grafts that may mediate long-term recovery of global and regional myocardial contractile function following infarction
A Very Sensitive 21cm Survey for Galactic High-Velocity HI
Very sensitive HI 21cm observations have been made in 860 directions at dec
>= -43deg in search of weak, Galactic, high-velocity HI emission lines at
moderate and high Galactic latitudes. One-third of the observations were made
toward extragalactic objects. The median 4-sigma detection level is NHI =
8x10^{17} cm^-2 over the 21' telescope beam. High-velocity HI emission is
detected in 37% of the directions; about half of the lines could not have been
seen in previous surveys. The median FWHM of detected lines is 30.3 km/s. High-
velocity HI lines are seen down to the sensitivity limit of the survey implying
that there are likely lines at still lower values of NHI. The weakest lines
have a kinematics and distribution on the sky similar to that of the strong
lines, and thus do not appear to be a new population. Most of the emission
originates from objects which are extended over several degrees; few appear to
be compact sources. At least 75%, and possibly as many as 90%, of the lines are
associated with one of the major high-velocity complexes. The Magellanic Stream
extends at least 10 deg to higher Galactic latitude than previously thought and
is more extended in longitude as well. Although there are many lines with low
column density, their numbers do not increase as rapidly as NHI^-1, so most of
the HI mass in the high-velocity cloud phenomenon likely resides in the more
prominent clouds. The bright HI features may be mere clumps within larger
structures, and not independent objects.Comment: 88 pages includes 22 figures Accepted for Publication in ApJ Suppl.
June 200
Integration of Acoustic Neutrino Detection Methods into ANTARES
The ANTARES Neutrino Telescope is a water Cherenkov detector currently under
construction in the Mediterranean Sea. It is also designed to serve as a
platform for investigations of the deep-sea environment. In this context, the
ANTARES group at the University of Erlangen will integrate acoustic sensors
within the infrastructure of the experiment. With this dedicated setup, tests
of acoustic particle detection methods and deep-sea acoustic background studies
shall be performed. The aim of this project is to evaluate the feasibility of a
future acoustic neutrino telescope in the deep sea operating in the ultra-high
energy regime. In these proceedings, the implementation of the project is
described in the context of the premises and challenges set by the physics of
acoustic particle detection and the integration into an existing
infrastructure.Comment: 6 pages, 5 figures, to appear in the proceedings of the International
ARENA Workshop, May 28-30th, 2006, University of Northumbri
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