102,013 research outputs found
Bridging the Gap between Probabilistic and Deterministic Models: A Simulation Study on a Variational Bayes Predictive Coding Recurrent Neural Network Model
The current paper proposes a novel variational Bayes predictive coding RNN
model, which can learn to generate fluctuated temporal patterns from exemplars.
The model learns to maximize the lower bound of the weighted sum of the
regularization and reconstruction error terms. We examined how this weighting
can affect development of different types of information processing while
learning fluctuated temporal patterns. Simulation results show that strong
weighting of the reconstruction term causes the development of deterministic
chaos for imitating the randomness observed in target sequences, while strong
weighting of the regularization term causes the development of stochastic
dynamics imitating probabilistic processes observed in targets. Moreover,
results indicate that the most generalized learning emerges between these two
extremes. The paper concludes with implications in terms of the underlying
neuronal mechanisms for autism spectrum disorder and for free action.Comment: This paper is accepted the 24th International Conference On Neural
Information Processing (ICONIP 2017). The previous submission to arXiv is
replaced by this version because there was an error in Equation
Inception and propagation of positive streamers in high-purity nitrogen: effects of the voltage rise-rate
Controlling streamer morphology is important for numerous applications. Up to
now, the effect of the voltage rise rate was only studied across a wide range.
Here we show that even slight variations in the voltage rise can have
significant effects. We have studied positive streamer discharges in a 16 cm
point-plane gap in high-purity nitrogen 6.0, created by 25 kV pulses with a
duration of 130 ns. The voltage rise varies by a rise rate from 1.9 kV/ns to
2.7 kV/ns and by the first peak voltage of 22 to 28 kV. A structural link is
found between smaller discharges with a larger inception cloud caused by a
faster rising voltage. This relation is explained by the greater stability of
the inception cloud due to a faster voltage rise, causing a delay in the
destabilisation. Time-resolved measurements show that the inception cloud
propagates slower than an earlier destabilised, more filamentary discharge.
This explains that the discharge with a faster rising voltage pulse ends up to
be shorter. Furthermore, the effect of remaining background ionisation in a
pulse sequence has been studied, showing that channel thickness and branching
rate are locally affected, depending on the covered volume of the previous
discharge.Comment: 16 pages, 9 figure
A Stochastic Approach to Shortcut Bridging in Programmable Matter
In a self-organizing particle system, an abstraction of programmable matter,
simple computational elements called particles with limited memory and
communication self-organize to solve system-wide problems of movement,
coordination, and configuration. In this paper, we consider a stochastic,
distributed, local, asynchronous algorithm for "shortcut bridging", in which
particles self-assemble bridges over gaps that simultaneously balance
minimizing the length and cost of the bridge. Army ants of the genus Eciton
have been observed exhibiting a similar behavior in their foraging trails,
dynamically adjusting their bridges to satisfy an efficiency trade-off using
local interactions. Using techniques from Markov chain analysis, we rigorously
analyze our algorithm, show it achieves a near-optimal balance between the
competing factors of path length and bridge cost, and prove that it exhibits a
dependence on the angle of the gap being "shortcut" similar to that of the ant
bridges. We also present simulation results that qualitatively compare our
algorithm with the army ant bridging behavior. Our work gives a plausible
explanation of how convergence to globally optimal configurations can be
achieved via local interactions by simple organisms (e.g., ants) with some
limited computational power and access to random bits. The proposed algorithm
also demonstrates the robustness of the stochastic approach to algorithms for
programmable matter, as it is a surprisingly simple extension of our previous
stochastic algorithm for compression.Comment: Published in Proc. of DNA23: DNA Computing and Molecular Programming
- 23rd International Conference, 2017. An updated journal version will appear
in the DNA23 Special Issue of Natural Computin
Cerulean: A hybrid assembly using high throughput short and long reads
Genome assembly using high throughput data with short reads, arguably,
remains an unresolvable task in repetitive genomes, since when the length of a
repeat exceeds the read length, it becomes difficult to unambiguously connect
the flanking regions. The emergence of third generation sequencing (Pacific
Biosciences) with long reads enables the opportunity to resolve complicated
repeats that could not be resolved by the short read data. However, these long
reads have high error rate and it is an uphill task to assemble the genome
without using additional high quality short reads. Recently, Koren et al. 2012
proposed an approach to use high quality short reads data to correct these long
reads and, thus, make the assembly from long reads possible. However, due to
the large size of both dataset (short and long reads), error-correction of
these long reads requires excessively high computational resources, even on
small bacterial genomes. In this work, instead of error correction of long
reads, we first assemble the short reads and later map these long reads on the
assembly graph to resolve repeats.
Contribution: We present a hybrid assembly approach that is both
computationally effective and produces high quality assemblies. Our algorithm
first operates with a simplified version of the assembly graph consisting only
of long contigs and gradually improves the assembly by adding smaller contigs
in each iteration. In contrast to the state-of-the-art long reads error
correction technique, which requires high computational resources and long
running time on a supercomputer even for bacterial genome datasets, our
software can produce comparable assembly using only a standard desktop in a
short running time.Comment: Peer-reviewed and presented as part of the 13th Workshop on
Algorithms in Bioinformatics (WABI2013
Bridging the gap between design and implementation of components libraries
Object-oriented design is usually driven by three main reusability principles:
step-by-step design, design for reuse and design with reuse. However, these
principles are just partially
applied to the subsequent object-oriented implementation, often due to efficienc
y
constraints, yielding to a gap between design and implementation. In this paper
we provide a solution for bridging this gap for a concrete framework, the one of
designing and implementing container-like component libraries, such as STL, Booc
h
Components, etc. Our approach is based on a new design pattern together with its
corresponding implementation. The proposal enhances the same principles that
drive the design process: step-by--step implementation (adding just what is
needed in every step), implementation with reuse (component implementations are
reused while library implementation
progresses and component hierarchies grow) and implementation for reuse
(intermediate component implementations can be reused in many different points o
f
the hierarchy). We use our approach in two different manners: for building a
brand-new container-like
component library, and for reengineering an existing one, Booch Components in
Ada95.Postprint (published version
Structure and Function of a Mycobacterial NHEJ DNA Repair Polymerase
Non homologous end-joining (NHEJ)-mediated repair of DNA double-strand breaks in prokaryotes requires Ku and a specific multidomain DNA ligase (LigD). We present crystal structures of the primase/polymerisation domain (PolDom) of Mycobacterium tuberculosis LigD, alone and complexed with nucleotides. The PolDom structure combines the general fold of the archaeo-eukaryotic primase (AEP) superfamily with additional loops and domains that together form a deep cleft on the surface, likely used for DNA binding. Enzymatic analysis indicates that the PolDom of LigD, even in the absence of accessory domains and Ku proteins, has the potential to recognise DNA end-joining intermediates. Strikingly, one of the main signals for the specific and efficient binding of PolDom to DNA is the presence of a 5'-phosphate group, located at the single/double-stranded junction at both gapped and 3'-protruding DNA molecules. Although structurally unrelated, Pol lambda and Pol mu, the two eukaryotic DNA polymerases involved in NHEJ, are endowed with a similar capacity to bind a 5'-phosphate group. Other properties that are beneficial for NHEJ, such as the ability to generate template distortions and realignments of the primer, displayed by Pol lambda and Pol mu, are shared by the PolDom of bacterial LigD. In addition, PolDom can perform non-mutagenic translesion synthesis on termini containing modified bases. Significantly, ribonucleotide insertion appears to be a recurrent theme associated with NHEJ, maximised in this case by the deployment of a dedicated primase, although its in vivo relevance is unknown
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