Some aspects of radical chemistry in the assembly of complex molecular architectures

International audienceThis review article describes briefly some of the radical processes developed in the authors' laboratory as they pertain to the concise assembly of complex molecular scaffolds. The emphasis is placed on the use of nitrogen-centred radicals, on the degenerate addition-transfer of xanthates, especially on its potential for intermolecular carbon-carbon bond formation, and on the generation and capture of radicals through electron transfer processes

Fun with radicals: Some new perspectives for organic synthesis

International audienceThe degenerative radical addition-transfer of xanthates onto alkenes allows the rapid assembly of richly functionalized structures. Various families of open-chain, cyclic, and polycyclic compounds can thus be readily accessed. Furthermore, the process can be extended to the synthesis or modification of aromatic and heteroaromatic derivatives by exploiting the possibility of using peroxides both as initiators and stoichiometric oxidants. The modification of existing polymers and the controlled synthesis of block polymers by what is now known as the RAFT/MADIX (reversible addition-fragmentation transfer/ macromolecular design by interchange of xanthate) process is described briefly. © 2010 IUPAC

A convergent, modular access to α-chloro-trifluoromethyl derivatives and to 1,1-difluoroalkenes

International audienceAn efficient protocol for the preparation of S-(1-chloro-2,2,2-trifluoroethyl)-O-ethyl xanthate is reported. This reagent serves as a versatile precursor of highly functionalized gem-difluoroalkenes through various inter- and intramolecular radical reactions and subsequent reduction with activated magnesium metal. (C) 2014 Elsevier Ltd. All rights reserved

A flexible radical approach to 5-substituted 4,5-dihydro-3H-pyrido[4,3-b]azepin-2-ones. Some mechanistic observations on the radical cyclisation-aromatisation process

International audienceVariously substituted novel dihydropyridoazepinones have been prepared by an intermolecular radical addition followed by a radical cyclisation on a pyridine ring. The latter process involved the use of a combination of two different peroxides, an experimental contrivance resulting from a careful product analysis and a better understanding of the cyclisation step. © 2012 Elsevier Ltd. All rights reserved

Rapid assembly of polycyclic structures via sigmatropic rearrangement of s-propargyl xanthates

International audienceUpon heating in chlorobenzene, propargyl xanthates yield the corresponding 4,5-bis(alkylidene)-1,3-dithiolan-2-ones which are trapped by unactivated olefins in an intramolecular Diels-Alder cycloaddition yielding interesting polycyclic structures

Aging without disorder on long time scales

We study the Metropolis dynamics of a simple spin system without disorder, which exhibits glassy dynamics at low temperatures. We use an implementation of the algorithm of Bortz, Kalos and Lebowitz \cite{bortz}. This method turns out to be very efficient for the study of glassy systems, which get trapped in local minima on many different time scales. We find strong evidence of aging effects at low temperatures. We relate these effects to the distribution function of the trapping times of single configurations.Comment: 8 pages Revtex, 7 figures uuencoded (Revised version: the figures are now present

Low-temperature properties of some disordered systems from the statistical properties of nearly degenerate two-level excitations

The thermal fluctuations that exist at very low temperature in disordered systems are often attributed to the existence of some two-level excitations. In this paper, we revisit this question via the explicit studies of the following 1D models (i) a particle in 1D random potentials (ii) the random field Ising chain with continuous disorder distribution. In both cases, we define precisely the `two-level' excitations and their statistical properties, and we show that their contributions to various observables are in full agreement at low temperature with the the rigorous results obtained independently. The statistical properties of these two-level excitations moreover yield simple identities at order $T$ in temperature for some generating functions of thermal cumulants. For the random-field Ising chain, in the regime where the Imry-Ma length is large, we obtain that the specific heat is dominated by small non-universal excitations, that depend on the details of the disorder distribution, whereas the magnetic susceptibility and the Edwards-Anderson order parameter are dominated by universal large excitations, whose statistical properties only depend on the variance of the initial disorder via the Imry-Ma length.Comment: 19 pages, 4 figure

Replica Symmetry Breaking in Attractor Neural Network Models

The phenomenon of replica symmetry breaking is investigated for the retrieval phases of Hopfield-type network models. The basic calculation is done for the generalized version of the standard model introduced by Horner [1] and by Perez-Vicente and Amit [2] which can exhibit low mean levels of neural activity. For a mean activity $\bar a =1/2$ the Hopfield model is recovered. In this case, surprisingly enough, we cannot confirm the well known one step replica symmetry breaking (1RSB) result for the storage capacity which was presented by Crisanti, Amit and Gutfreund [3] (\alpha_c^{\hbox{\mf 1RSB}}\simeq 0.144). Rather, we find that 1RSB- and 2RSB-Ans\"atze yield only slightly increased capacities as compared to the replica symmetric value (\alpha_c^{\hbox{\mf 1RSB}}\simeq 0.138\,186 and \alpha_c^{\hbox{\mf 2RSB}}\simeq 0.138\,187 compared to \alpha_c^{\hbox{\mf RS}}\simeq 0.137\,905), significantly smaller also than the value \alpha_c^{\hbox{\mf sim}} = 0.145\pm 0.009 reported from simulation studies. These values still lie within the recently discovered reentrant phase [4]. We conjecture that in the infinite Parisi-scheme the reentrant behaviour disappears as is the case in the SK-spin-glass model (Parisi--Toulouse-hypothesis). The same qualitative results are obtained in the low activity range.Comment: Latex file, 20 pages, 8 Figures available from the authors upon request, HD-TVP-94-

Consumer Manipulation via Online Behavioral Advertising

Online behavioral advertising (OBA) has a significant role in the digital economy. It allows advertisers to target consumers categorized according to their algorithmically inferred interests based on their behavioral data. As Alphabet and Meta gatekeep the Internet with their digital platforms and channel most of the consumer attention online, they are best placed to execute OBA and earn profits far exceeding fair estimations. There are increasing concerns that gatekeepers achieve such profitability at the expense of consumers, advertisers, and publishers who are dependent on their services to access the Internet. In particular, some claim that OBA systematically exploits consumers' decision-making vulnerabilities, creating internet infrastructure and relevant markets that optimize for consumer manipulation. Intuitively, consumer manipulation via OBA comes in tension with the ideal of consumer autonomy in liberal democracies. Nevertheless, academia has largely overlooked this phenomenon and instead has primarily focused on privacy and discrimination concerns of OBA. This article redirects academic discourse and regulatory focus on consumer manipulation via OBA. In doing so, first, this article elaborates on how OBA works. Second, it constructs an analytic framework for understanding manipulation. Third, it applies the theory of manipulation to OBA. As a result, this article illustrates the extent to which OBA leads to consumer manipulation. Crucially, this article is purely analytic and avoids normative evaluation of consumer manipulation via OBA. Evaluating consumer manipulation harms of OBA is an equally important but separate task and is pursued in another publication

Digitale Spill og Språkferdigheter i Engelsk Språklæring

Title: Video Games and Language Skills in English Language Learning. The purpose of this systematic literature review is to review studies that research video games and English language acquisition when English is the second language or foreign language. By studying their results, I wish to uncover what effects video games have on the language skills and the English language learning with our students. The methodological approach of this research closely follows the guidelines for a systematic literature review presented by Xiao and Watson (2019). The search was done through ORIA and ERIC and the inclusion criteria were limited to English as L2 and the students in the study had to be non-native English speakers. The chosen articles were limited to peer-reviewed articles published in the year 2010 and forward, as well as studies specifically on the primary school, meaning children aged 6 – 13. This encompasses the primary school grade system in Norway and includes some countries where 8th grade is a part of the primary school. The results of the reviewed studies show a correlation of increased academic performance in the experimental groups who were exposed to video games. All studies applied a pre-test-post-test process as to increase reliability and secure validity. The students in the experimental groups showed great interest in the subject of learning the English language through video games as well as a motivation for continued learning. The video games had a positive effect overall on their language skills as evident by the results of the studies and the student’s own input. Research shows a mainly positive relationship between using video games as a tool for English language learning and development of student’s language skills. By including the students’ pastime activities, which in this case was video games, the students showed a more eager approach and a willingness to use the English language unsolicited. This could potentially point in the direction of using video games as medium to further help learning and teaching in the English language. However, not all studies show a positive outcome, as students who have no previous interest in video games scored the same or lower on tests done in some of these studies. The necessity for more research in the field of video games and English language learning is clear. There is far too little research on video games in relationship with English language learning and language skills, especially since video games have become a major part of many students lives