8,507 research outputs found
Human-chimpanzee alignment: Ortholog Exponentials and Paralog Power Laws
Genomic subsequences conserved between closely related species such as human
and chimpanzee exhibit an exponential length distribution, in contrast to the
algebraic length distribution observed for sequences shared between distantly
related genomes. We find that the former exponential can be further decomposed
into an exponential component primarily composed of orthologous sequences, and
a truncated algebraic component primarily composed of paralogous sequences.Comment: Main text: 31 pages, 13 figures, 1 table; Supplementary materials: 9
pages, 9 figures, 1 tabl
Globally Normalized Reader
Rapid progress has been made towards question answering (QA) systems that can
extract answers from text. Existing neural approaches make use of expensive
bi-directional attention mechanisms or score all possible answer spans,
limiting scalability. We propose instead to cast extractive QA as an iterative
search problem: select the answer's sentence, start word, and end word. This
representation reduces the space of each search step and allows computation to
be conditionally allocated to promising search paths. We show that globally
normalizing the decision process and back-propagating through beam search makes
this representation viable and learning efficient. We empirically demonstrate
the benefits of this approach using our model, Globally Normalized Reader
(GNR), which achieves the second highest single model performance on the
Stanford Question Answering Dataset (68.4 EM, 76.21 F1 dev) and is 24.7x faster
than bi-attention-flow. We also introduce a data-augmentation method to produce
semantically valid examples by aligning named entities to a knowledge base and
swapping them with new entities of the same type. This method improves the
performance of all models considered in this work and is of independent
interest for a variety of NLP tasks.Comment: Presented at EMNLP 201
Quasi-classical Gravity effect on neutrino oscillations in a gravitational field of an heavy astrophysical object
In the framework of quantum field theory, a graviton interacts locally with a
quantum state having definite mass, i.e. the gravitational mass eigenstate,
while a weak boson interacts with a state having definite flavor, i.e. the
flavor eigenstate. An interaction of a neutrino with an energetic graviton may
trigger the collapse of the neutrino to a definite mass eigenstate with
probability expressed in terms of PMNS mixing matrix elements. Thus, gravitons
would induce quantum decoherence of a coherent neutrino flavor state similarly
to how weak bosons induce quantum decoherence of a neutrino in a definite mass
state. We demonstrate that such an essentially quantum gravity effect may have
strong consequences for neutrino oscillation phenomena in astrophysics due to
relatively large scattering cross sections of relativistic neutrinos undergoing
large-angle radiation of energetic gravitons in gravitational field of a
classical massive source (i.e. the quasi-classical case of gravitational
Bethe-Heitler scattering). This graviton-induced {\it decoherence} is compared
to {\it decoherence} due to propagation in the presence of the Earth matter
effect. Based on this study, we propose a new technique for the indirect
detection of energetic gravitons by measuring the flavor composition of
astrophysical neutrinos.Comment: 25 pages, 4 figures, minor revision with clarifications, main
conclusions are unchange
Evolution of the Potential Energy Surface with Size for Lennard-Jones Clusters
Disconnectivity graphs are used to characterize the potential energy surfaces
of Lennard-Jones clusters containing 13, 19, 31, 38, 55 and 75 atoms. This set
includes members which exhibit either one or two `funnels' whose low-energy
regions may be dominated by a single deep minimum or contain a number of
competing structures. The graphs evolve in size due to these specific size
effects and an exponential increase in the number of local minima with the
number of atoms. To combat the vast number of minima we investigate the use of
monotonic sequence basins as the fundamental topographical unit. Finally, we
examine disconnectivity graphs for a transformed energy landscape to explain
why the transformation provides a useful approach to the global optimization
problem.Comment: 13 pages, 8 figures, revte
Faster Approximate Multicommodity Flow Using Quadratically Coupled Flows
The maximum multicommodity flow problem is a natural generalization of the
maximum flow problem to route multiple distinct flows. Obtaining a
approximation to the multicommodity flow problem on graphs is a well-studied
problem. In this paper we present an adaptation of recent advances in
single-commodity flow algorithms to this problem. As the underlying linear
systems in the electrical problems of multicommodity flow problems are no
longer Laplacians, our approach is tailored to generate specialized systems
which can be preconditioned and solved efficiently using Laplacians. Given an
undirected graph with m edges and k commodities, we give algorithms that find
approximate solutions to the maximum concurrent flow problem and
the maximum weighted multicommodity flow problem in time
\tilde{O}(m^{4/3}\poly(k,\epsilon^{-1}))
Your turn: experiments in narrative and play
Carson and Miller’s artists’ book, 'The Exquisite Fold', utilises the book as a site for play and storytelling. Both acts are interpretative; they are ways through which both child and adult attempt to understand the world that surrounds them.
In 'Your Turn' the process of making 'The Exquisite Fold' is explored in terms of both its content and its very particular physical construction. Through this examination the ideas that underpin the book are drawn out; the potential for the book to be played with (particularly as a place to play with narrative) and, in turn, the impulse to uncover meaning through narrative and play
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