Energy required to pinch a DNA plectoneme

DNA supercoiling plays an important role on a biological point of view. One of its consequences at the supra-molecular level is the formation of DNA superhelices named plectonemes. Normally separated by a distance on the order of 10 nm, the two opposite double-strands of a DNA plectoneme must be brought closer if a protein or protein complex implicated in genetic regulation is to be bound simultaneously to both strands, as if the plectoneme was locally pinched. We propose an analytic calculation of the energetic barrier, of elastic nature, required to bring closer the two loci situated on the opposed double-strands. We examine how this energy barrier scales with the DNA supercoiling. For physically relevant values of elastic parameters and of supercoiling density, we show that the energy barrier is in the $k_{\rm B} T$ range under physiological conditions, thus demonstrating that the limiting step to loci encounter is more likely the preceding plectoneme slithering bringing the two loci side by side.Comment: Published version (new title to conform to editorial policy

What differences exist between Lavaux’s perception and its promoted image, and how can the promotion be adjusted to ensure consistency and improve the knowledge of the area?

Lavaux, the Swiss vineyard which has been part of the UNESCO World Heritage List since 2007, is renowned for its terrace vineyards, its traditions, its breath-taking views on the Geneva Lake, and its unique landscape configuration. The purpose of this report is to provide an in-depth analysis of the perception and behaviour of the public towards Lavaux, and to compare them with the promotion of the area. The field research, which is based on a survey and interviews, aims at analysing the mental representation of the public, the places visited and activities performed, the wine-consumption habits and the public’s UNESCO’s definition. In parallel, the interviews of different economic actors in the vineyard allow a deep understanding of the promotion done for Lavaux. The findings suggest that the public’s perception and behaviour are aligned with the promotion of the area. Wine, landscape and UNESCO are shared values and are fully part of the promotion. Though, more implicit values, such as traditions, culture, local products are not enough highlighted. Also, no influence on Lavaux’s wine consumption has happened after the UNESCO’s nomination as far as the opinion of the public and of economic actors is concerned. Globally, the current strategy is relevant and adapts to the market needs to some extent. In order to improve the efficiency of the promotion and fill the existing gaps, recommendations include four main dimensions that can be developed. Firstly, the traditions and local products should be fully part of the promotion strategy, through quality products, service and wide opening hours. Then, the visit of the vineyard in winter could be promoted, with the creation of events to attract visitors at that period of the year. Also, the creation of a Vine and Wine Museum would enable the education of visitors about the heritage, traditions and the cultural background, while being a family activity. Finally, the creation of a global image through branding could improve the consistency of the promotion strategy. The branding should be decided amongst the promotion actors and should represent a first image to attract visitors in the area. The individualities and diversity of the economic activity should be kept within the vineyard, as they are part of the richness of the area. To summarize, unity and coordination amongst actors, the sustainability of traditions and heritage, the orientation towards preferred tourism and the promotion of experiences are key to the development of the promotion of Lavaux in the coming years

Structured Cooperative Learning as a Means for Improving Average Achievers' Mathematical Learning in Fractions

International audienceIn primary school, learning fractions is a central mathematical objective. However, the mastery of basic procedures involving fractions presents a difficulty for many students. The aim of the current intervention is to introduce structured cooperative learning as means to improve students' learning, particularly for average achievers. Previous research has underscored that heterogeneous groups might be deleterious for average achievers because they are excluded by the teacher learner relationships that is likely to take place between low and high achievers students. This intervention proposes structuring interactions in order to boost the learning of average achievers in heterogeneous groups. We hypothesize that highly structured cooperative learning should improve average achievers' understanding of the content-targeted in group work as well as progress in terms of fractions learning, when compared to low-structured cooperative learning. In this intervention, 108 fifth graders worked cooperatively in heterogeneous triads (a low, average, and high achiever). The triads had to express the length of one segment using three rulers with different sub-units and respecting three mathematical skills regarding fractions. Triads were randomly assigned to a low-structured or high-structured cooperative learning condition. In the low-structured condition, no specific structure was provided. (i.e., they organized their cooperative work as they wished). In the high-structured condition, each student became an expert for one part before working in the triad and endorsed different responsibilities. The results indicated that highly structured cooperative learning favors the understanding of the targeted task, especially for average-ability students. Moreover, students at all levels progressed from the baseline test to the post-test. Indeed, low and high achievers had the same progression in both conditions, whereas average achievers progressed more in the highly structured condition. Results are discussed in terms of new teaching methods that could efficiently increase average achievers’ performances

On the Testing of Ground--Motion Prediction Equations against Small--Magnitude Data

Ground-motion prediction equations (GMPE) are essential in probabilistic seismic hazard studies for estimating the ground motions generated by the seismic sources. In low seismicity regions, only weak motions are available in the lifetime of accelerometric networks, and the equations selected for the probabilistic studies are usually models established from foreign data. Although most ground-motion prediction equations have been developed for magnitudes 5 and above, the minimum magnitude often used in probabilistic studies in low seismicity regions is smaller. Desaggregations have shown that, at return periods of engineering interest, magnitudes lower than 5 can be contributing to the hazard. This paper presents the testing of several GMPEs selected in current international and national probabilistic projects against weak motions recorded in France (191 recordings with source-site distances up to 300km, 3.8\leqMw\leq4.5). The method is based on the loglikelihood value proposed by Scherbaum et al. (2009). The best fitting models (approximately 2.5\leqLLH\leq3.5) over the whole frequency range are the Cauzzi and Faccioli (2008), Akkar and Bommer (2010) and Abrahamson and Silva (2008) models. No significant regional variation of ground motions is highlighted, and the magnitude scaling could be predominant in the control of ground-motion amplitudes. Furthermore, we take advantage of a rich Japanese dataset to run tests on randomly selected low-magnitude subsets, and check that a dataset of ~190 observations, same size as the French dataset, is large enough to obtain stable LLH estimates. Additionally we perform the tests against larger magnitudes (5-7) from the Japanese dataset. The ranking of models is partially modified, indicating a magnitude scaling effect for some of the models, and showing that extrapolating testing results obtained from low magnitude ranges to higher magnitude ranges is not straightforward

Multimedia ontology matching by using visual and textual modalities

International audienceOntologies have been intensively applied for improving multimedia search and retrieval by providing explicit meaning to visual content. Several multimedia ontologies have been recently proposed as knowledge models suitable for narrowing the well known semantic gap and for enabling the semantic interpretation of images. Since these ontologies have been created in different application contexts, establishing links between them, a task known as ontology matching, promises to fully unlock their potential in support of multimedia search and retrieval. This paper proposes and compares empirically two extensional ontology matching techniques applied to an important semantic image retrieval issue: automatically associating common-sense knowledge to multimedia concepts. First, we extend a previously introduced textual concept matching approach to use both textual and visual representation of images. In addition, a novel matching technique based on a multi-modal graph is proposed. We argue that the textual and visual modalities have to be seen as complementary rather than as exclusive sources of extensional information in order to improve the efficiency of the application of an ontology matching approach in the multimedia domain. An experimental evaluation is included in the paper

Comment mesurer la précarité énergétique en matière de transport

National audienceSi des indicateurs existent pour quantifier la précarité énergétique dans le logement, leur simple transposition au domaine du transport n’est pas satisfaisante. Afin de mieux identifier les ménages vulnérables à une hausse des prix des carburants, un « indicateur Composite » est proposé. Il permet de mieux refléter les différents facteurs qui contraignent la mobilité des ménages et leurs possibilités d’adaptation

Investigating fuel poverty in the transport sector: toward a composite indicator of vulnerability

International audienceThis paper investigates the issue of fuel poverty and of its measurement in the transport sector. We seek to identify households who run the risk of facing difficulties if fuel prices increase. We show that fuel poverty indicators from the domestic sector are not satisfactory in this regard. They fail to take into account three specificities of the transport sector: (1) the diversity of travel needs, (2) restriction behaviours, and (3) variable capacities to adapt. We propose a composite indicator that targets factors of vulnerabilities. In contrast to the previous indicators, it does not solely focus on budgetary aspects but also reflects conditions of mobility. Three levels of exposition to rising fuel prices are considered, depending on the combinations of factors. We test this indicator on French data and find that 7,8% of French households are identified fuel poor, a further 7,4% fuel vulnerable and a further 3,7% fuel dependent