Top program construction and reduction for polynomial time Meta-Interpretive learning

Meta-Interpretive Learners, like most ILP systems, learn by searching for a correct hypothesis in the hypothesis space, the powerset of all constructible clauses. We show how this exponentially-growing search can be replaced by the construction of a Top program: the set of clauses in all correct hypotheses that is itself a correct hypothesis. We give an algorithm for Top program construction and show that it constructs a correct Top program in polynomial time and from a finite number of examples. We implement our algorithm in Prolog as the basis of a new MIL system, Louise, that constructs a Top program and then reduces it by removing redundant clauses. We compare Louise to the state-of-the-art search-based MIL system Metagol in experiments on grid world navigation, graph connectedness and grammar learning datasets and find that Louise improves on Metagol’s predictive accuracy when the hypothesis space and the target theory are both large, or when the hypothesis space does not include a correct hypothesis because of “classification noise” in the form of mislabelled examples. When the hypothesis space or the target theory are small, Louise and Metagol perform equally well.

Review Of Quantitative Mechanistic Models Of Radiation-Induced Non-Targeted Effects (NTE)

Quantitative mechanistic modeling of the biological effects of ionizing radiation has a long rich history. Initially, it was dominated by target theory, which quantifies damage caused by traversal of cellular targets like DNA by ionizing tracks. The discovery that mutagenesis, death and/or altered behavior sometimes occur in cells that were not themselves traversed by any radiation tracks but merely interacted with traversed cells was initially seen as surprising. As more evidence of such ‘non-targeted’ or ‘bystander’ effects accumulated, the importance of their contribution to radiation-induced damage became more recognized. Understanding and modeling these processes is important for quantifying and predicting radiation-induced health risks. Here we review the variety of mechanistic mathematical models of nontargeted effects that emerged over the past 2–3 decades. This review is not intended to be exhaustive, but focuses on the main assumptions and approaches shared or distinct between models, and on identifying areas for future research.

A qualitative analysis to identify takeover target criteria

PurposeThis study proposes a qualitative analysis to identify takeover target criteria according to French Mergers and Acquisitions (M&A) practitioners.Design/methodology/approachA principal component factor analysis, applied to responses from 42 French M&A practitioners, highlighted four factors that summarize information about predictive variables and which explain the occurrence of takeover.FindingsAccording to the surveyed practitioners, four main axes explain 83% of the occurrence of takeover. These axes reflect motivations related to the undervalued target theory, synergy theory and agency theory. The first factor defined by the size of the company, its rate of return and turbulence in the sector. A second factor opposed market value and dividend payout ratio to the liquidity variable. The last two factors are called the debt factor, structured by the debt variable and the value creation factor, which opposed the value creation variable and transaction volume to the growth opportunities variable. The results therefore confirmed the importance of some predictor variables tested in previous studies and showed different results.Research limitations/implicationsThis study was limited in terms of sample size. The low number of responses obtained reflects the sensitivity of the subject, insofar as it highlights the predictive model used by M&A practitioners (professional secrecy). Future investigations will involve in extending the questionnaire approach to a larger sample of continental European M&A practitioners.Originality/valuePredicting takeover targets has been the subject of abundant literature. The results do not converge and are sometimes contradictory. This paper undertakes a field study conducted using a questionnaire survey to detect predictive variables used by M&A practitioners in their identification of a target firm. The authors aim to identify a relevant indicators favorable to the occurrence of a takeover bid and which are/or not handled by the literature.

Who are you, Professor N.W. Timofeeff-Ressovsky, – zoologist, genetics, radiobiologist, ecologist, evolutionist...?

To the 120th anniversary of the birth, information about the basic dates of life and creativity, as well as about the basic scientific achievements of the outstanding biologist Nikolay W. Timofeeff-Resovsky (1900–1981) is presented. The data on his contribution to genetics, radiation biology, ecology, the doctrine of microevolutionary processes are given. His works have played a major role in the development of molecular-physical approaches to the problems of genetics. He is regarded as one of the founders of radiation and population genetics. He is one of first who used the ionizing radiation, including a dense-ionizing radiation, for obtain of experimental mutations. He formulated a “hit-principle” and a “target theory” – the basis of modern quantitative radiobiology; a “principle of amplifier”, which explains how a single change, such as a gene mutation that can occur for energies of only a few electron-volts, activates forces that are several orders of magnitude larger and change the properties of the whole individual. He elaborated whole doctrine about microevolution – the emergence of new biological species, identified the elementary object of microevolution – population, elementary material – mutations, elementary factors – mutational process, elementary evolutionary phenomenon – stable change in the genotypic composition of the population. Based on the huge experimental material about migration of radionuclides in the environment and their uptake to living organisms, he formulated the main foundation of radiation ecology. The author summarizes the memories of meetings with scientist. Keywords: N.W. Timofeeff-Resovsky, radiation genetics, population genetics, radiation biology, radiation ecology, microevolution.

Combining Unmergeables: A Methodological Framework for Axiomatic Fusion of Qualitative Design Theories

The proposed methodological framework concerns axiomatic theory fusion (ATF) of non-additive engineering design theories. ATF includes seven steps: (i) semantic discretization of the composite theories, (ii) deriving epistemological entities by logical/semantic analysis, (iii) establishing and representation of relations among all relevant epistemological entities, (iv) combining the inter- theoretical epistemological entities of the component theories, (v) deriving propositions based on the combined set of epistemological entities, (vi) transcription of the epistemological entities and propositions into a textual/visual theory description, and (vii) validation of the resultant theory in application contexts. The proposed framework makes ATF an effective, content independent methodology for fusing component theories, no matter if they are descriptive, explanatory, predictive or controlling in nature. ATF methodology requires professional comprehension and rigor from the researchers. It is necessary to justify the logical correctness and practical validity of the target theory in the specific application context.

Was it you who died, or your brother?

This paper seeks to apply Christie Davies’ target theory to the classical jokebook Philogelos and more specifically, its most common protagonist, the scholastikos, whose central flaw is stupidity caused by his inability to interact with material reality, similar to modern “dotty professor” jokes. This paper seeks to build a model of how scholastikos jokes work, how the stereotype is constructed and perpetuated, how this differs from other “stupid” stereotypes used elsewhere in the Philogelos (largely ethnic-based stereotypes), and possible social and cultural anxieties bound up in the character of the scholastikos. It will explore the relationship between ancient and modern targets in light of Christie Davies’ target theory and extend this model of how humour functions to transhistorical case studies.

A RECOVERY OPERATOR FOR NONTRANSITIVE APPROACHES

In some recent articles, Cobreros, Egré, Ripley, & van Rooij have defended the idea that abandoning transitivity may lead to a solution to the trouble caused by semantic paradoxes. For that purpose, they develop the Strict-Tolerant approach, which leads them to entertain a nontransitive theory of truth, where the structural rule of Cut is not generally valid. However, that Cut fails in general in the target theory of truth does not mean that there are not certain safe instances of Cut involving semantic notions. In this article we intend to meet the challenge of answering how to regain all the safe instances of Cut, in the language of the theory, making essential use of a unary recovery operator. To fulfill this goal, we will work within the so-called Goodship Project, which suggests that in order to have nontrivial naïve theories it is sufficient to formulate the corresponding self-referential sentences with suitable biconditionals. Nevertheless, a secondary aim of this article is to propose a novel way to carry this project out, showing that the biconditionals in question can be totally classical. In the context of this article, these biconditionals will be essentially used in expressing the self-referential sentences and, thus, as a collateral result of our work we will prove that none of the recoveries expected of the target theory can be nontrivially achieved if self-reference is expressed through identities.