245 research outputs found
Strain-induced partially flat band, helical snake states, and interface superconductivity in topological crystalline insulators
Topological crystalline insulators in IV-VI compounds host novel topological
surface states consisting of multi-valley massless Dirac fermions at low
energy. Here we show that strain generically acts as an effective gauge field
on these Dirac fermions and creates pseudo-Landau orbitals without breaking
time-reversal symmetry. We predict the realization of this phenomenon in IV-VI
semiconductor heterostructures, due to a naturally occurring misfit dislocation
array at the interface that produces a periodically varying strain field.
Remarkably, the zero-energy Landau orbitals form a flat band in the vicinity of
the Dirac point, and coexist with a network of snake states at higher energy.
We propose that the high density of states of this flat band gives rise to
interface superconductivity observed in IV-VI semiconductor multilayers at
unusually high temperatures, with non-BCS behavior. Our work demonstrates a new
route to altering macroscopic electronic properties to achieve a partially flat
band, and paves the way for realizing novel correlated states of matter.Comment: Accepted by Nature Physic
COVNET : A cooperative coevolutionary model for evolving artificial neural networks
This paper presents COVNET, a new cooperative coevolutionary model for evolving artificial neural networks. This model is based on the idea of coevolving subnetworks. that must cooperate to form a solution for a specific problem, instead of evolving complete networks. The combination of this subnetwork is part of a coevolutionary process. The best combinations of subnetworks must be evolved together with the coevolution of the subnetworks. Several subpopulations of subnetworks coevolve cooperatively and genetically isolated. The individual of every subpopulation are combined to form whole networks. This is a different approach from most current models of evolutionary neural networks which try to develop whole networks. COVNET places as few restrictions as possible over the network structure, allowing the model to reach a wide variety of architectures during the evolution and to be easily extensible to other kind of neural networks. The performance of the model in solving three real problems of classification is compared with a modular network, the adaptive mixture of experts and with the results presented in the bibliography. COVNET has shown better generalization and produced smaller networks than the adaptive mixture of experts and has also achieved results, at least, comparable with the results in the bibliography
Virtual Immortality: Reanimating Characters from TV Shows.
The objective of this work is to build virtual talking avatars of characters fully automatically from TV shows. From this unconstrained data, we show how to capture a character's style of speech, visual appearance and language in an e ort to construct an interactive avatar of the person and e ectively immortalize them in a computational model. We make three contributions (i) a complete framework for producing a generative model of the audiovisual and language of characters from TV shows; (ii) a novel method for aligning transcripts to video using the audio; and (iii) a fast audio segmentation system for silencing nonspoken audio from TV shows. Our framework is demonstrated using all 236 episodes from the TV series Friends [34] ( 97hrs of video) and shown to generate novel sentences as well as character specific speech and video
Adequacy of Therapy for People with Both COPD and Heart Failure in the UK: Historical Cohort Study
Purpose: Chronic obstructive pulmonary disease (COPD) and heart failure (HF) often occur concomitantly, presenting diagnostic and therapeutic challenges for clinicians. We examined the characteristics of patients prescribed adequate versus inadequate therapy within 3 months after newly diagnosed comorbid COPD or HF.
Patients and Methods: Eligible patients in longitudinal UK electronic medical record databases had pre-existing HF and newly diagnosed COPD (2017 GOLD groups B/C/D) or pre-existing COPD and newly diagnosed HF. Adequate COPD therapy was defined as long-acting bronchodilator(s) with/without inhaled corticosteroid; adequate HF therapy was defined as beta-blocker plus angiotensin-converting enzyme inhibitor and/or angiotensin receptor blocker.
Results: Of 2439 patients with HF and newly diagnosed COPD (mean 75 years, 61% men), adequate COPD therapy was prescribed for 726 (30%) and inadequate for 1031 (42%); 682 (28%) remained untreated for COPD. Adequate (vs inadequate) COPD therapy was less likely for women (35%) than men (45%), smokers (36%) than ex-/non-smokers (45%), and non-obese (41%) than obese (47%); spirometry was recorded for 57% prescribed adequate versus 35% inadequate COPD therapy. Of 12,587 patients with COPD and newly diagnosed HF (mean 75 years, 60% men), adequate HF therapy was prescribed for 2251 (18%) and inadequate for 5332 (42%); 5004 (40%) remained untreated for HF. Adequate (vs inadequate) HF therapy was less likely for smokers (27%) than ex-/non-smokers (32%) and non-obese (30%) than obese (35%); spirometry was recorded for 65% prescribed adequate versus 39% inadequate HF therapy.
Conclusion: Many patients with comorbid COPD/HF receive inadequate therapy after new diagnosis. Improved equity of access to integrated care is needed for all patient subgroups
The Missing Link! A New Skeleton for Evolutionary Multi-agent Systems in Erlang
Evolutionary multi-agent systems (EMAS) play a critical role in many artificial intelligence applications that are in use today. In this paper, we present a new generic skeleton in Erlang for parallel EMAS computations. The skeleton enables us to capture a wide variety of concrete evolutionary computations that can exploit the same underlying parallel implementation. We demonstrate the use of our skeleton on two different evolutionary computing applications: (1) computing the minimum of the Rastrigin function; and (2) solving an urban traffic optimisation problem. We show that we can obtain very good speedups (up to 142.44 ΓΓ the sequential performance) on a variety of different parallel hardware, while requiring very little parallelisation effort.Publisher PDFPeer reviewe
Implications of Behavioral Architecture for the Evolution of Self-Organized Division of Labor
Division of labor has been studied separately from a proximate self-organization and an ultimate evolutionary perspective. We aim to bring together these two perspectives. So far this has been done by choosing a behavioral mechanism a priori and considering the evolution of the properties of this mechanism. Here we use artificial neural networks to allow for a more open architecture. We study whether emergent division of labor can evolve in two different network architectures; a simple feedforward network, and a more complex network that includes the possibility of self-feedback from previous experiences. We focus on two aspects of division of labor; worker specialization and the ratio of work performed for each task. Colony fitness is maximized by both reducing idleness and achieving a predefined optimal work ratio. Our results indicate that architectural constraints play an important role for the outcome of evolution. With the simplest network, only genetically determined specialization is possible. This imposes several limitations on worker specialization. Moreover, in order to minimize idleness, networks evolve a biased work ratio, even when an unbiased work ratio would be optimal. By adding self-feedback to the network we increase the network's flexibility and worker specialization evolves under a wider parameter range. Optimal work ratios are more easily achieved with the self-feedback network, but still provide a challenge when combined with worker specialization
Variations in Stress Sensitivity and Genomic Expression in Diverse S. cerevisiae Isolates
Interactions between an organism and its environment can significantly influence
phenotypic evolution. A first step toward understanding this process is to
characterize phenotypic diversity within and between populations. We explored
the phenotypic variation in stress sensitivity and genomic expression in a large
panel of Saccharomyces strains collected from diverse
environments. We measured the sensitivity of 52 strains to 14 environmental
conditions, compared genomic expression in 18 strains, and identified gene
copy-number variations in six of these isolates. Our results demonstrate a large
degree of phenotypic variation in stress sensitivity and gene expression.
Analysis of these datasets reveals relationships between strains from similar
niches, suggests common and unique features of yeast habitats, and implicates
genes whose variable expression is linked to stress resistance. Using a simple
metric to suggest cases of selection, we found that strains collected from oak
exudates are phenotypically more similar than expected based on their genetic
diversity, while sake and vineyard isolates display more diverse phenotypes than
expected under a neutral model. We also show that the laboratory strain S288c is
phenotypically distinct from all of the other strains studied here, in terms of
stress sensitivity, gene expression, Ty copy number, mitochondrial content, and
gene-dosage control. These results highlight the value of understanding the
genetic basis of phenotypic variation and raise caution about using laboratory
strains for comparative genomics
From evolutionary computation to the evolution of things
Evolution has provided a source of inspiration for algorithm designers since the birth of computers. The resulting field, evolutionary computation, has been successful in solving engineering tasks ranging in outlook from the molecular to the astronomical. Today, the field is entering a new phase as evolutionary algorithms that take place in hardware are developed, opening up new avenues towards autonomous machines that can adapt to their environment. We discuss how evolutionary computation compares with natural evolution and what its benefits are relative to other computing approaches, and we introduce the emerging area of artificial evolution in physical systems
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