10,490 research outputs found
On the mechanism of response latencies in auditory nerve fibers
Despite the structural differences of the middle and inner ears, the latency pattern in auditory nerve fibers to an identical sound has been found similar across numerous species. Studies have shown the similarity in remarkable species with distinct cochleae or even without a basilar membrane. This stimulus-, neuron-, and species- independent similarity of latency cannot be simply explained by the concept of cochlear traveling waves that is generally accepted as the main cause of the neural latency pattern.
An original concept of Fourier pattern is defined, intended to characterize a feature of temporal processing—specifically phase encoding—that is not readily apparent in more conventional analyses. The pattern is created by marking the first amplitude maximum for each sinusoid component of the stimulus, to encode phase information. The hypothesis is that the hearing organ serves as a running analyzer whose output reflects synchronization of auditory neural activity consistent with the Fourier pattern.
A combined research of experimental, correlational and meta-analysis approaches is used to test the hypothesis. Manipulations included phase encoding and stimuli to test their effects on the predicted latency pattern. Animal studies in the literature using the same stimulus were then compared to determine the degree of relationship.
The results show that each marking accounts for a large percentage of a corresponding peak latency in the peristimulus-time histogram. For each of the stimuli considered, the latency predicted by the Fourier pattern is highly correlated with the observed latency in the auditory nerve fiber of representative species.
The results suggest that the hearing organ analyzes not only amplitude spectrum but also phase information in Fourier analysis, to distribute the specific spikes among auditory nerve fibers and within a single unit.
This phase-encoding mechanism in Fourier analysis is proposed to be the common mechanism that, in the face of species differences in peripheral auditory hardware, accounts for the considerable similarities across species in their latency-by-frequency functions, in turn assuring optimal phase encoding across species. Also, the mechanism has the potential to improve phase encoding of cochlear implants
Alternative Measures of State UI Systems
Comparisons among state unemployment insurance (UI) systems can be misleading. Frequently quoted indicators of benefit generosity, tax cost, and adherence to the experience-rating principle are influenced by the relative economic conditions of states. Such comparisons thereby obscure underlying structural differences in state UI systems. A business considering alternative states in which to locate a production facility should be cautious when interpreting UI information in an economic developer's marketing pitch. This paper offers alternative indicators based on how representative firms, with a well specified unemployment experience, would fare in different states. The authors use a micro-simulation approach to model the experiences of representative workers and firms to compare 28 states and contrast the results with those obtained from more conventional indicators. In closing, the authors consider whether a business location decision would be influenced differently by the alternative measures of state UI systems.unemployment, insurance, state, O'Leary, Tannenwald
Use of multiple singular value decompositions to analyze complex intracellular calcium ion signals
We compare calcium ion signaling () between two exposures;
the data are present as movies, or, more prosaically, time series of images.
This paper describes novel uses of singular value decompositions (SVD) and
weighted versions of them (WSVD) to extract the signals from such movies, in a
way that is semi-automatic and tuned closely to the actual data and their many
complexities. These complexities include the following. First, the images
themselves are of no interest: all interest focuses on the behavior of
individual cells across time, and thus, the cells need to be segmented in an
automated manner. Second, the cells themselves have 100 pixels, so that they
form 100 curves measured over time, so that data compression is required to
extract the features of these curves. Third, some of the pixels in some of the
cells are subject to image saturation due to bit depth limits, and this
saturation needs to be accounted for if one is to normalize the images in a
reasonably unbiased manner. Finally, the signals have
oscillations or waves that vary with time and these signals need to be
extracted. Thus, our aim is to show how to use multiple weighted and standard
singular value decompositions to detect, extract and clarify the signals. Our signal extraction methods then lead to simple although
finely focused statistical methods to compare signals
across experimental conditions.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS253 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone
M-stars comprise 80% of main-sequence stars, and so their planetary systems
provide the best chance for finding habitable planets, i.e.: those with surface
liquid water. We have modelled the broadband albedo or reflectivity of water
ice and snow for simulated planetary surfaces orbiting two observed red dwarf
stars (or M-stars) using spectrally resolved data of the Earth's cryosphere.
The gradual reduction of the albedos of snow and ice at wavelengths greater
than 1 ?m, combined with M-stars emitting a significant fraction of their
radiation at these same longer wavelengths, mean that the albedos of ice and
snow on planets orbiting M-stars are much lower than their values on Earth. Our
results imply that the ice/snow albedo climate feedback is significantly weaker
for planets orbiting M-stars than for planets orbiting G-type stars such as the
Sun. In addition, planets with significant ice and snow cover will have
significantly higher surface temperatures for a given stellar flux if the
spectral variation of cryospheric albedo is considered, which in turn implies
that the outer edge of the habitable zone around M-stars may be 10-30% further
away from the parent star than previously thought.Comment: Final accepted by Astrobiology, 20 pages (double spaced), 3 figures
include
Prediction of Nontrivial Band Topology and Superconductivity in MgPb
The interplay of BCS superconductivity and nontrivial band topology is
expected to give rise to opportunities for creating topological
superconductors, achieved through pairing spin-filtered boundary modes via
superconducting proximity effects. The thus-engineered topological
superconductivity can, for example, facilitate the search for Majorana fermion
quasiparticles in condensed matter systems. Here we report a first-principles
study of MgPb and predict that it should be a superconducting topological
material. The band topology of MgPb is identical to that of the archetypal
quantum spin Hall insulator HgTe, while isostructural and isoelectronic
MgSn is topologically trivial; a trivial to topological transition is
predicted for MgSnPb for x~0.77. We propose that
MgPb-MgSn quantum wells should generate robust spin-filtered edge
currents in analogy to HgTe/CdTe quantum wells. In addition, our calculations
predict that MgPb should become superconducting upon electron doping.
Therefore, MgPb is expected to provide a practical material platform for
studying emergent phenomena arising from the interplay of superconductivity and
band topology.Comment: 5 figure
Multiple Scattering Theory for Two-dimensional Electron Gases in the Presence of Spin-Orbit Coupling
In order to model the phase-coherent scattering of electrons in
two-dimensional electron gases in the presence of Rashba spin-orbit coupling, a
general partial-wave expansion is developed for scattering from a cylindrically
symmetric potential. The theory is applied to possible electron flow imaging
experiments using a moveable scanning probe microscope tip. In such
experiments, it is demonstrated theoretically that the Rashba spin-orbit
coupling can give rise to spin interference effects, even for unpolarized
electrons at nonzero temperature and no magnetic field.Comment: 34 pages, 7 figure
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