1,721,025 research outputs found
Why should we abandon the mental logic hypothesis?
No full textTwo hypotheses on deductive reasoning are under development: mental logic and mental models. It is often accepted that there are overwhelming arguments to reject the mental logic hypothesis. I revise these arguments and claim that they are either not conclusive, or point at problems which are troublesome for the mental model hypothesis as well. © 1994
Modeling nanoplasmonics from an atomistic point of view: from theory to applications
Full text linkThe theoretical modeling of plasmonics is challenging due to the complex interplay between electromagnetic waves, the electronic properties of the material, and the geometrical arrangement of the substrate. In the last decades, the comprehension of plasmons related phenomena arising in noble metal nanostructures and in graphene has benefited from the development of several theoretical methods, which can be divided into two main categories: continuum and ab initio methods respectively. The first are based on classical electrodynamics principles and are limited to the study of systems with a simple shape only, because otherwise the resolution of Maxwell’s equation would be impossible.In addition, they may fail when quantum effects have a predominant role on the optical properties of the system, such as in the case of complex-shape structures and nanojunctions.On the contrary, ab initio methods are able to overcome such limitations and return a precise description of plasmonic substrates. However, due to their high computational cost, such methods are constrained to systems of a few thousand of atoms. In this context, classical, yet atomistic models can predict results close to ab initio methods, while being computationally efficient such as continuum models. In this thesis, the optical properties of plasmonic nanostructures are investigated by using a classic, atomistic model called ωFQ, which has been developed by the research group I joined during my Ph.D. internship. In ωFQ, the charge interaction between the atoms of the nanostructure is modeled in terms of electric conduction between nearest neighbors via a simple Drude mechanism, which is modulated by a Fermi-like step function that mimics quantum tunneling effects. In this way, ωFQ is able to take into account quantum effects and returns results in agreement with ab initio references. In particular, the Thesis discusses the developments performed during my Ph.D. research activity to the initial formulation of the ωFQ model. Attention is firstly paid to the extension of ωFQ to model the optical properties of noble metal NPs which are characterized by interband effects. Then, the coupling between a molecular system, treated at the quantum mechanical level, and a plasmonic substrate, described by means of the ωFQ model, is presented and analysed. In this way, the modeling of the enhanced Raman spectrum of target molecules adsorbed on a plasmonic substrate becomes possible.<br /
Infants anticipate probabilistic but not deterministic outcomes
No full textInfants look at physically impossible events longer than at physically possible events, and at improbable events longer than at probable events. Such behaviors are generally interpreted as showing that infants have expectations about future events and are surprised to see them violated. It is unknown, however, whether and under what conditions infants form proactive expectations about the future, as opposed to realizing post hoc that outcomes do not comply with their previous knowledge or experience.Here we investigate the relation between expectation and surprise at probabilistic or deterministic events in preverbal infants. When a situation is uncertain, 12-month-olds anticipate probable outcomes and are surprised at improbable continuations of the scene. However, they do not anticipate the only possible outcome of a physically deterministic situation, although they are surprised when it does not occur. The results suggest that infants are sensitive to the tradeoff between information gain and programming efforts, showing higher propensity to anticipate those future events that carry novel knowledge. (C) 2016 Elsevier B.V. All rights reserved
Words and possible words in early language acquisition
No full textIn order to acquire language, infants must extract its building blocks words and master the rules governing their legal combinations from speech. These two problems are not independent, however: words also have internal structure. Thus, infants must extract two kinds of information from the same speech input. They must find the actual words of their language. Furthermore, they must identify its possible words, that is, the sequences of sounds that, being morphologically well formed, could be words. Here, we show that infants' sensitivity to possible words appears to be more primitive and fundamental than their ability to find actual words. We expose 12- and 18-month-old infants to an artificial language containing a conflict between statistically coherent and structurally coherent items. We show that 18-month-olds can extract possible words when the familiarization stream contains marks of segmentation, but cannot do so when the stream is continuous. Yet, they can find actual words from a continuous stream by computing statistical relationships among syllables. By contrast, 12-month-olds can find possible words when familiarized with a segmented stream, but seem unable to extract statistically coherent items from a continuous stream that contains minimal conflicts between statistical and structural information. These results suggest that sensitivity to word structure is in place earlier than the ability to analyze distributional information. The ability to compute nontrivial statistical relationships becomes fully effective relatively late in development, when infants have already acquired a considerable amount of linguistic knowledge. Thus, mechanisms for structure extraction that do not rely on extensive sampling of the input are likely to have a much larger role in language acquisition than general-purpose statistical abilities. (C) 2013 Published by Elsevier Inc
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