5,434 research outputs found
Alien Registration Card- Dreyer, Klaus I. (Readfield, Kennebec County)
https://digitalmaine.com/alien_cards/1023/thumbnail.jp
Alien Registration- Dreyer, Klaus I. (Readfield, Kennebec County)
https://digitalmaine.com/alien_docs/17234/thumbnail.jp
Adjustment of interaural-time-difference analysis to sound level
To localize low-frequency sound sources in azimuth, the binaural system compares the timing of sound waves at the two ears with microsecond precision. A similarly high precision is also seen in the binaural processing of the envelopes of high-frequency complex sounds. Both for low- and high-frequency sounds, interaural time difference (ITD) acuity is to a large extent independent of sound level. The mechanisms underlying this level-invariant extraction of ITDs by the binaural system are, however, only poorly understood. We use high-frequency pip trains with asymmetric and dichotic pip envelopes in a combined psychophysical, electrophysiological, and modeling approach. Although the dichotic envelopes cannot be physically matched in terms of ITD, the match produced perceptually by humans is very reliable, and it depends systematically on the overall sound level. These data are reflected in neural responses from the gerbil lateral superior olive and lateral lemniscus. The results are predicted in an existing temporal-integration model extended with a level-dependent threshold criterion. These data provide a very sensitive quantification of how the peripheral temporal code is conditioned for binaural analysis
Evolutionary Inference via the Poisson Indel Process
We address the problem of the joint statistical inference of phylogenetic
trees and multiple sequence alignments from unaligned molecular sequences. This
problem is generally formulated in terms of string-valued evolutionary
processes along the branches of a phylogenetic tree. The classical evolutionary
process, the TKF91 model, is a continuous-time Markov chain model comprised of
insertion, deletion and substitution events. Unfortunately this model gives
rise to an intractable computational problem---the computation of the marginal
likelihood under the TKF91 model is exponential in the number of taxa. In this
work, we present a new stochastic process, the Poisson Indel Process (PIP), in
which the complexity of this computation is reduced to linear. The new model is
closely related to the TKF91 model, differing only in its treatment of
insertions, but the new model has a global characterization as a Poisson
process on the phylogeny. Standard results for Poisson processes allow key
computations to be decoupled, which yields the favorable computational profile
of inference under the PIP model. We present illustrative experiments in which
Bayesian inference under the PIP model is compared to separate inference of
phylogenies and alignments.Comment: 33 pages, 6 figure
Modelling the unfolding pathway of biomolecules: theoretical approach and experimental prospect
We analyse the unfolding pathway of biomolecules comprising several
independent modules in pulling experiments. In a recently proposed model, a
critical velocity has been predicted, such that for pulling speeds
it is the module at the pulled end that opens first, whereas for
it is the weakest. Here, we introduce a variant of the model that is
closer to the experimental setup, and discuss the robustness of the emergence
of the critical velocity and of its dependence on the model parameters. We also
propose a possible experiment to test the theoretical predictions of the model,
which seems feasible with state-of-art molecular engineering techniques.Comment: Accepted contribution for the Springer Book "Coupled Mathematical
Models for Physical and Biological Nanoscale Systems and Their Applications"
(proceedings of the BIRS CMM16 Workshop held in Banff, Canada, August 2016),
16 pages, 6 figure
Convex Independence in Permutation Graphs
A set C of vertices of a graph is P_3-convex if every vertex outside C has at
most one neighbor in C. The convex hull \sigma(A) of a set A is the smallest
P_3-convex set that contains A. A set M is convexly independent if for every
vertex x \in M, x \notin \sigma(M-x). We show that the maximal number of
vertices that a convexly independent set in a permutation graph can have, can
be computed in polynomial time
Two physical characteristics of numerical apparent horizons
This article translates some recent results on quasilocal horizons into the
language of general relativity so as to make them more useful to
numerical relativists. In particular quantities are described which
characterize how quickly an apparent horizon is evolving and how close it is to
either equilibrium or extremality.Comment: 6 pages, 2 figures, conference proceedings loosely based on talk
given at Theory Canada III (Edmonton, Alberta, 2007). V2: Minor changes in
response to referees comments to improve clarity and fix typos. One reference
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Experimental harvesting of fish populations drives genetically based shifts in body size and maturation
Size-selective harvesting in commercial fisheries can induce rapid changes in biological traits. While experimental and wild harvested populations often exhibit clear shifts in body size and maturation associated with fishing pressure, the relative contributions of genetic and environmental factors to these shifts remain uncertain and have been much debated. To date, observations of so-called fisheries-induced evolution (FIE) have been based solely on phenotypic measures, such as size data. Genetic data are hitherto lacking. Here, we quantify genetic versus environmental change in response to size-selective harvesting for small and large body size in guppies (Poecilia reticulata) across three generations of selection. We document for the first time significant changes at individual genetic loci, some of which have previously been associated with body size. In contrast, variation at neutral microsatellite markers was unaffected by selection, providing direct genetic evidence for rapid evolution induced by size-selective harvesting. These findings demonstrate FIE in an experimental system, with major implications for the sustainability of harvested populations, as well as impacts on size-structured communities and ecosystem processes. These findings highlight the need for scientists and managers to reconsider the capacity of harvested stocks to adapt to, and recover from, harvesting and predation. © 2013 The Ecological Society of America
Symmetries at stationary Killing horizons
It has often been suggested (especially by Carlip) that spacetime symmetries
in the neighborhood of a black hole horizon may be relevant to a statistical
understanding of the Bekenstein-Hawking entropy. A prime candidate for this
type of symmetry is that which is exhibited by the Einstein tensor. More
precisely, it is now known that this tensor takes on a strongly constrained
(block-diagonal) form as it approaches any stationary, non-extremal Killing
horizon. Presently, exploiting the geometrical properties of such horizons, we
provide a particularly elegant argument that substantiates this highly
symmetric form for the Einstein tensor. It is, however, duly noted that, on
account of a "loophole", the argument does fall just short of attaining the
status of a rigorous proof.Comment: 11 pages, Revte
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