2,535 research outputs found
Relatedness Measures to Aid the Transfer of Building Blocks among Multiple Tasks
Multitask Learning is a learning paradigm that deals with multiple different
tasks in parallel and transfers knowledge among them. XOF, a Learning
Classifier System using tree-based programs to encode building blocks
(meta-features), constructs and collects features with rich discriminative
information for classification tasks in an observed list. This paper seeks to
facilitate the automation of feature transferring in between tasks by utilising
the observed list. We hypothesise that the best discriminative features of a
classification task carry its characteristics. Therefore, the relatedness
between any two tasks can be estimated by comparing their most appropriate
patterns. We propose a multiple-XOF system, called mXOF, that can dynamically
adapt feature transfer among XOFs. This system utilises the observed list to
estimate the task relatedness. This method enables the automation of
transferring features. In terms of knowledge discovery, the resemblance
estimation provides insightful relations among multiple data. We experimented
mXOF on various scenarios, e.g. representative Hierarchical Boolean problems,
classification of distinct classes in the UCI Zoo dataset, and unrelated tasks,
to validate its abilities of automatic knowledge-transfer and estimating task
relatedness. Results show that mXOF can estimate the relatedness reasonably
between multiple tasks to aid the learning performance with the dynamic feature
transferring.Comment: accepted by The Genetic and Evolutionary Computation Conference
(GECCO 2020
Elastic properties of hydrogenated graphene
There exist three conformers of hydrogenated graphene, referred to as chair-,
boat-, or washboard-graphane. These systems have a perfect two-dimensional
periodicity mapped onto the graphene scaffold, but they are characterized by a
orbital hybridization, have different crystal symmetry, and otherwise
behave upon loading. By first principles calculations we determine their
structural and phonon properties, as well as we establish their relative
stability. Through continuum elasticity we define a simulation protocol
addressed to measure by a computer experiment their linear and nonlinear
elastic moduli and we actually compute them by first principles. We argue that
all graphane conformers respond to any arbitrarily-oriented extention with a
much smaller lateral contraction than the one calculated for graphene.
Furthermore, we provide evidence that boat-graphane has a small and negative
Poisson ratio along the armchair and zigzag principal directions of the carbon
honeycomb lattice (axially auxetic elastic behavior). Moreover, we show that
chair-graphane admits both softening and hardening hyperelasticity, depending
on the direction of applied load.Comment: submitted on Phys.Rev.
Spontaneous onset of homochirality in oligopeptide chains generated in the polymerization of N-carboxyanhydride amino acids in water
ISSN:0169-6149ISSN:1573-087
Constraining planet formation around 6M⊙-8M⊙ stars
Identifying planets around O-type and B-type stars is inherently difficult; the most massive known planet host has a mass of only about 3M⊙. However, planetary systems which survive the transformation of their host stars into white dwarfs can be detected via photospheric trace metals, circumstellar dusty and gaseous discs, and transits of planetary debris crossing our line-of-sight. These signatures offer the potential to explore the efficiency of planet formation for host stars with masses up to the core-collapse boundary at ≈8M⊙, a mass regime rarely investigated in planet formation theory. Here, we establish limits on where both major and minor planets must reside around ≈6M⊙ − 8M⊙ stars in order to survive into the white dwarf phase. For this mass range, we find that intact terrestrial or giant planets need to leave the main sequence beyond approximate minimum star-planet separations of respectively about 3 and 6 au. In these systems, rubble pile minor planets of radii 10, 1.0, and 0.1 km would have been shorn apart by giant branch radiative YORP spin-up if they formed and remained within, respectively, tens, hundreds and thousands of au. These boundary values would help distinguish the nature of the progenitor of metal-pollution in white dwarf atmospheres. We find that planet formation around the highest mass white dwarf progenitors may be feasible, and hence encourage both dedicated planet formation investigations for these systems and spectroscopic analyses of the highest mass white dwarfs
Nonlinear elasticity of monolayer graphene
By combining continuum elasticity theory and tight-binding atomistic
simulations, we work out the constitutive nonlinear stress-strain relation for
graphene stretching elasticity and we calculate all the corresponding nonlinear
elastic moduli. Present results represent a robust picture on elastic behavior
of one-atom thick carbon sheets and provide the proper interpretation of recent
experiments. In particular, we discuss the physical meaning of the effective
nonlinear elastic modulus there introduced and we predict its value in good
agreement with available data. Finally, a hyperelastic softening behavior is
observed and discussed, so determining the failure properties of graphene.Comment: 4 page
Regulation of NF-κB by PML and PML-RARα
Promyelocytic Leukemia (PML) is a nuclear protein that forms sub-nuclear structures termed nuclear bodies associated with transcriptionally active genomic regions. PML is a tumour suppressor and regulator of cell differentiation. We demonstrate that PML promotes TNFα-induced transcriptional responses by promoting NF-κB activity. TNFα-treated PML−/− cells show normal IκBα degradation and NF-κB nuclear translocation but significantly reduced NF-κB DNA binding and phosphorylation of NF-κB p65. We also demonstrate that the PML retinoic acid receptor-α (PML-RARα) oncofusion protein, which causes acute promyelocytic leukemia, inhibits TNFα induced gene expression and phosphorylation of NF-κB. This study establishes PML as an important regulator of NF-κB and demonstrates that PML-RARα dysregulates NF-κB
Neuronal Chains for Actions in the Parietal Lobe: A Computational Model
The inferior part of the parietal lobe (IPL) is known to play a very important role in sensorimotor integration. Neurons in this region code goal-related motor acts performed with the mouth, with the hand and with the arm. It has been demonstrated that most IPL motor neurons coding a specific motor act (e.g., grasping) show markedly different activation patterns according to the final goal of the action sequence in which the act is embedded (grasping for eating or grasping for placing). Some of these neurons (parietal mirror neurons) show a similar selectivity also during the observation of the same action sequences when executed by others. Thus, it appears that the neuronal response occurring during the execution and the observation of a specific grasping act codes not only the executed motor act, but also the agent's final goal (intention)
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