7,053 research outputs found
Yeah, Right, Uh-Huh: A Deep Learning Backchannel Predictor
Using supporting backchannel (BC) cues can make human-computer interaction
more social. BCs provide a feedback from the listener to the speaker indicating
to the speaker that he is still listened to. BCs can be expressed in different
ways, depending on the modality of the interaction, for example as gestures or
acoustic cues. In this work, we only considered acoustic cues. We are proposing
an approach towards detecting BC opportunities based on acoustic input features
like power and pitch. While other works in the field rely on the use of a
hand-written rule set or specialized features, we made use of artificial neural
networks. They are capable of deriving higher order features from input
features themselves. In our setup, we first used a fully connected feed-forward
network to establish an updated baseline in comparison to our previously
proposed setup. We also extended this setup by the use of Long Short-Term
Memory (LSTM) networks which have shown to outperform feed-forward based setups
on various tasks. Our best system achieved an F1-Score of 0.37 using power and
pitch features. Adding linguistic information using word2vec, the score
increased to 0.39
Time series of high resolution spectra of SN 2014J observed with the TIGRE telescope
We present a time series of high resolution spectra of the Type Ia supernova
2014J, which exploded in the nearby galaxy M82. The spectra were obtained with
the HEROS echelle spectrograph installed at the 1.2 m TIGRE telescope. We
present a series of 33 spectra with a resolution of R = 20, 000, which covers
the important bright phases in the evolution of SN 2014J during the period from
January 24 to April 1 of 2014. The spectral evolution of SN 2014J is derived
empirically. The expansion velocities of the Si II P-Cygni features were
measured and show the expected decreasing behaviour, beginning with a high
velocity of 14,000 km/s on January 24. The Ca II infrared triplet feature shows
a high velocity component with expansion velocities of > 20, 000 km/s during
the early evolution apart from the normal component showing similar velocities
as Si II. Further broad P-Cygni profiles are exhibited by the principal lines
of Ca II, Mg II and Fe II. The TIGRE SN 2014J spectra also resolve several very
sharp Na I D doublet absorption components. Our analysis suggests interesting
substructures in the interstellar medium of the host galaxy M82, as well as in
our Milky Way, confirming other work on this SN. We were able to identify the
interstellar absorption of M82 in the lines of Ca II H & K at 3933 and 3968 A
as well as K I at 7664 and 7698 A. Furthermore, we confirm several Diffuse
Interstellar Bands, at wavelengths of 6196, 6283, 6376, 6379 and 6613 A and
give their measured equivalent widths.Comment: 11 pages, 10 figures, accepted for publication in MNRA
Storage of correlated patterns in a perceptron
We calculate the storage capacity of a perceptron for correlated gaussian
patterns. We find that the storage capacity can be less than 2 if
similar patterns are mapped onto different outputs and vice versa. As long as
the patterns are in general position we obtain, in contrast to previous works,
that in agreement with Cover's theorem. Numerical simulations
confirm the results.Comment: 9 pages LaTeX ioplppt style, figures included using eps
Deep levels in a-plane, high Mg-content MgxZn1-xO epitaxial layers grown by molecular beam epitaxy
Deep level defects in n-type unintentionally doped a-plane MgxZn1−xO, grown by molecular beam epitaxy on r-plane sapphire were fully characterized using deep level optical spectroscopy (DLOS) and related methods. Four compositions of MgxZn1−xO were examined with x = 0.31, 0.44, 0.52, and 0.56 together with a control ZnO sample. DLOS measurements revealed the presence of five deep levels in each Mg-containing sample, having energy levels of Ec − 1.4 eV, 2.1 eV, 2.6 V, and Ev + 0.3 eV and 0.6 eV. For all Mg compositions, the activation energies of the first three states were constant with respect to the conduction band edge, whereas the latter two revealed constant activation energies with respect to the valence band edge. In contrast to the ternary materials, only three levels, at Ec − 2.1 eV, Ev + 0.3 eV, and 0.6 eV, were observed for the ZnO control sample in this systematically grown series of samples. Substantially higher concentrations of the deep levels at Ev + 0.3 eV and Ec − 2.1 eV were observed in ZnO compared to the Mg alloyed samples. Moreover, there is a general invariance of trap concentration of the Ev + 0.3 eV and 0.6 eV levels on Mg content, while at least and order of magnitude dependency of the Ec − 1.4 eV and Ec − 2.6 eV levels in Mg alloyed samples
Magnetic Flares on Asymptotic Giant Branch Stars
We investigate the consequences of magnetic flares on the surface of
asymptotic giant branch (AGB) and similar stars. In contrast to the solar wind,
in the winds of AGB stars the gas cooling time is much shorter than the outflow
time. As a result, we predict that energetic flaring will not inhibit, and may
even enhance, dust formation around AGB stars. If magnetic flares do occur
around such stars, we expect some AGB stars to exhibit X-ray emission; indeed
certain systems including AGB stars, such as Mira, have been detected in
X-rays. However, in these cases, it is difficult to distinguish between
potential AGB star X-ray emission and, e.g., X-ray emission from the vicinity
of a binary companion. Analysis of an archival ROSAT X-ray spectrum of the Mira
system suggests an intrinsic X-ray luminosity 2x10^{29} erg/sec and temperature
10^7 K. These modeling results suggest that magnetic activity, either on the
AGB star (Mira A) or on its nearby companion (Mira B), is the source of the
X-rays, but do not rule out the possibility that the X-rays are generated by an
accretion disk around Mira B.Comment: ApJ, Accepted; revised version of astro-ph/020923
Deconvolution of complex G protein-coupled receptor signaling in live cells using dynamic mass redistribution measurements
Label-free biosensor technology based on dynamic mass redistribution (DMR) of cellular constituents promises to translate GPCR signaling into complex optical 'fingerprints' in real time in living cells. Here we present a strategy to map cellular mechanisms that define label-free responses, and we compare DMR technology with traditional second-messenger assays that are currently the state of the art in GPCR drug discovery. The holistic nature of DMR measurements enabled us to (i) probe GPCR functionality along all four G-protein signaling pathways, something presently beyond reach of most other assay platforms; (ii) dissect complex GPCR signaling patterns even in primary human cells with unprecedented accuracy; (iii) define heterotrimeric G proteins as triggers for the complex optical fingerprints; and (iv) disclose previously undetected features of GPCR behavior. Our results suggest that DMR technology will have a substantial impact on systems biology and systems pharmacology as well as for the discovery of drugs with novel mechanisms
The stellar dynamics and mass of NGC 1316 using the radial velocities of planetary nebulae
We present a study of the kinematics of the outer regions of the early-type
galaxy NGC 1316, based on radial velocity measurements of 43 planetary nebulae
as well as deep integrated-light absorption line spectra. The smoothed velocity
field of NGC 1316 indicates fast rotation at a distance of 16 kpc, possibly
associated with an elongated feature orthogonal to the inner dust lanes. The
mean square stellar velocity is approximately independent of radius, and the
estimated total mass of the system is 2.6 x 10^11 M_sun within a radius of 16
kpc, implying an integrated mass-to-light ratio of M/L_B = 8.Comment: 39 pages, 14 figures, in press on The Astrophysical Journal n. 50
The Effects of Binary Evolution on the Dynamics of Core Collapse and Neutron-Star Kicks
We systematically examine how the presence in a binary affects the final core
structure of a massive star and its consequences for the subsequent supernova
explosion. Interactions with a companion star may change the final rate of
rotation, the size of the helium core, the strength of carbon burning and the
final iron core mass. Stars with initial masses larger than \sim 11\Ms that
experiece core collapse will generally have smaller iron cores at the time of
the explosion if they lost their envelopes due to a previous binary
interaction. Stars below \sim 11\Ms, on the other hand, can end up with larger
helium and metal cores if they have a close companion, since the second
dredge-up phase which reduces the helium core mass dramatically in single stars
does not occur once the hydrogen envelope is lost. We find that the initially
more massive stars in binary systems with masses in the range 8 - 11\Ms are
likely to undergo an electron-capture supernova, while single stars in the same
mass range would end as ONeMg white dwarfs. We suggest that the core collapse
in an electron-capture supernova (and possibly in the case of relatively small
iron cores) leads to a prompt explosion rather than a delayed neutrino-driven
explosion and that this naturally produces neutron stars with low-velocity
kicks. This leads to a dichotomous distribution of neutron star kicks, as
inferred previously, where neutron stars in relatively close binaries attain
low kick velocities. We illustrate the consequences of such a dichotomous kick
scenario using binary population synthesis simulations and discuss its
implications. This scenario has also important consequences for the minimum
initial mass of a massive star that becomes a neutron star. (Abbreviated.)Comment: 8 pages, 3 figures, submitted to ApJ, updated versio
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