Optimal Concentration of Information Content For Log-Concave Densities

An elementary proof is provided of sharp bounds for the varentropy of random vectors with log-concave densities, as well as for deviations of the information content from its mean. These bounds significantly improve on the bounds obtained by Bobkov and Madiman ({\it Ann. Probab.}, 39(4):1528--1543, 2011).Comment: 15 pages. Changes in v2: Remark 2.5 (due to C. Saroglou) added with more general sufficient conditions for equality in Theorem 2.3. Also some minor corrections and added reference

Estimation in high dimensions: a geometric perspective

This tutorial provides an exposition of a flexible geometric framework for high dimensional estimation problems with constraints. The tutorial develops geometric intuition about high dimensional sets, justifies it with some results of asymptotic convex geometry, and demonstrates connections between geometric results and estimation problems. The theory is illustrated with applications to sparse recovery, matrix completion, quantization, linear and logistic regression and generalized linear models.Comment: 56 pages, 9 figures. Multiple minor change

Differences in proleptic and epicormic shoot structures in relation to water deficit and growth rate in almond trees (Prunus dulcis)

UMR 1334 AGAP : Equipe AFEF "Architecture et Fonctionnement des Espèces fruitières" ; Team AFFS "Architecture and Functioning of Fruit Species"International audienceBackground and Aims Shoot characteristics differ depending on the meristem tissue that they originate from and environmental conditions during their development. This study focused on the effects of plant water status on axillary meristem fate and flowering patterns along proleptic and epicormic shoots, as well as on shoot growth rates on 'Nonpareil' almond trees (Prunus dulcis). The aims were (1) to characterize the structural differences between pro-leptic and epicormic shoots, (2) to determine whether water deficits modify shoot structures differently depending on shoot type, and (3) to determine whether shoot structures are related to shoot growth rates. Methods A hidden semi-Markov model of the axillary meristem fate and number of flower buds per node was built for two shoot types growing on trees exposed to three plant water status treatments. The models segmented observed shoots into successive homogeneous zones, which were compared between treatments. Shoot growth rates were cal-culated from shoot extension measurements made during the growing season. Key Results Proleptic shoots had seven successive homogeneous zones while epicormic shoots had five zones. Shoot structures were associated with changes in growth rate over the season. Water deficit (1) affected the occurrence and lengths of the first zones of proleptic shoots, but only the occurrence of the third zone was reduced in epicormic shoots; (2) had a minor effect on zone flowering patterns and did not modify shoot or zone composition of axillary meristem fates; and (3) reduced growth rates, although patterns over the season were similar among treatments. Conclusions Two meristem types, with different latency durations, produced shoots with different growth rates and distinct structures. Differences between shoot type structure responses to water deficit appeared to reflect their onto-genetic characteristics and/or resource availability for their development. Tree water deficit appeared to stimulate a more rapid progression through ontogenetic states

Sustainable development and African local government: can electronic training help build capacities?

A recent study carried out by European and African organizations into the potential for electronic distance training (EDT) on sustainability in African local governments concluded that EDT was both 'useful and feasible'. This article reflects on some of the theoretical and practical implications of that study. It focuses on the connection between learning and sustainability and how EDT programmes might be designed and promoted. The paper argues that, while resource issues and poor access to Information and Communication Technologies (ICTs) create considerable constraints and point to the need for policies to improve access, in general the most important factors for successful capacity building relate to the design of learning programmes that take account of the work contexts and skill and capability requirements of those targeted as learners. 'Useful' and 'feasible' depend on (i) how work-based and work-related learning processes are understood and (ii) the conditions to promote learning within African local government. Keywords: Africa; Electronic distance training; Local government; Sustainability; Workplace learnin

Observation of Quantum Interference in Molecular Charge Transport

As the dimensions of a conductor approach the nano-scale, quantum effects will begin to dominate its behavior. This entails the exciting possibility of controlling the conductance of a device by direct manipulation of the electron wave function. Such control has been most clearly demonstrated in mesoscopic semiconductor structures at low temperatures. Indeed, the Aharanov-Bohm effect, conductance quantization and universal conductance fluctuations are direct manifestations of the electron wave nature. However, an extension of this concept to more practical emperatures has not been achieved so far. As molecules are nano-scale objects with typical energy level spacings (~eV) much larger than the thermal energy at 300 K (~25 meV), they are natural candidates to enable such a break-through. Fascinating phenomena including giant magnetoresistance, Kondo effects and conductance switching, have previously been demonstrated at the molecular level. Here, we report direct evidence for destructive quantum interference in charge transport through two-terminal molecular junctions at room temperature. Furthermore, we show that the degree of interference can be controlled by simple chemical modifications of the molecule. Not only does this provide the experimental demonstration of a new phenomenon in quantum charge transport, it also opens the road for a new type of molecular devices based on chemical or electrostatic control of quantum interference

Analysis and modelling of fruit tree axillary shoot and flowering distribution.

International audienceIntroduction. Pour caractériser le comportement de diverses variétés d'arbres fruitiers à partir de caractères morphologiques, la distribution des productions axillaires le long de rameaux de pommiers a été comparée. Des rameaux végétatifs répartis le long des troncs et des associations de bourgeons végétatifs et floraux sur des rameaux de pêchers d'un an ont été étudiés. Aspects méthodologiques. Les unités de croissance sont représentées par des séquences dont l'index est le rang du nœud. Le type de production axillaire et d'autres variables qualitatives ou quantitatives ont été considérées à chaque nœud successif. Le calcul d'une distance entre séquences est proposé; il permet d'analyser la variabilité des séquences d'un même échantillon. Par ailleurs, sur la base d'une analyse exploratoire des séquences observées, la construction de modèles permet de synthétiser et de caractériser l'organisation interne des unités de croissance. Applications. L'homogénéité et la séparabilité du comportement de ramification de sept variétés de pommier ont été étudiées à partir de la comparaison des séquences deux à deux, en tenant compte de leur appartenance à une variété donnée. Les résultats de cette comparaison sont donnés. Par ailleurs, la répartition des floraisons sur différents types de rameaux de pêcher est analysée à l'aide de modèles. Conclusion. Appliquée à la ramification de jeunes scions, la démarche présentée permet de caractériser les zones où les nœuds portent des rameaux longs. Il est alors possible d'évaluer, dès la pépinière, le potentiel de croissance et de ramification des scions et donc de préciser les interventions nécessaires à une formation des plants. Dans le second exemple, les rameaux fructifères de pêchers diffèrent par les caractéristiques du modèle. Une analyse de l'effet de vigueur sur la structure du rameau est proposée à partir de l'occurrence de zones particulièrement florifères