Arable weeds in alley cropping agroforestry systems - results of a first year survey

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Using Eye Movements to Develop an Ecologically-valid AI Measure of Reading Comprehension

The ability to understand written information is a critical skill for surviving and thriving in a literate society. As such, reliable and accurate measures of reading comprehension ability are necessary to ensure that readers with difficulties understanding texts can be identified and provided with adequate help as early as possible. However, in recent years the validity of reading comprehension assessments used in clinics and schools has been brought into question.This thesis examines the validity of existing measures of reading comprehension ability typically used by schools, clinics, and research. Specifically, it examines the influence of the way reading comprehension tests are designed on the skills they measure, and readers’ performance on the test. In addition, the thesis examines the possibility of using eye-movement behaviour during reading as an alternative to standard measures of reading comprehension ability. The results contribute to our understanding of reading comprehension as a cognitive skill, and suggest that reading comprehension measures should be chosen with caution as they do not always measure the same aspects of reading comprehension. The results also provide support for the potential of using eye-movement behaviour as an alternative to standard measures of reading comprehension ability. The current thesis, together with future research on the relationship between eye-movement behaviour and reading comprehension ability provide a strong basis for the development of a reading comprehension assessment based on eye-movement behaviour during reading

Spin dynamics in S = 1/2 antiferromagnetic chain compounds delta-(EDT-TTF-CONMe_2)_2X (X=AsF_6, Br): a multi-frequency Electron Spin Resonance study

We present a multi-frequency Electron Spin Resonance (ESR) study in the range of 4 GHz to 420 GHz of the quasi-one-dimensional, non-dimerized, quarter-filled Mott insulators, delta-(EDT-TTF-CONMe_2)_2X (X=AsF_6, Br). In the high temperature orthorhombic phase above T~190 K, the magnitude and the temperature dependence of the high temperature spin susceptibility are described by a S = 1/2 Heisenberg antiferromagnetic chain with J_AsF6=298 K and J_Br=474 K coupling constants for X=AsF_6 and Br respectively. We estimate from the temperature dependence of the line width an exchange anisotropy, J'/J of ~2 * 10^{-3}. The frequency dependence of the line width and the g-shift have an unusual quadratic dependence in all crystallographic orientations that we attribute to an antisymmetric exchange (Dzyaloshinskii--Moriya) interaction.Comment: 6 pages, 6 figure

1,4-Bis(carboxylatoethynyl)bicyclo[2.2.2]octane : un rotor ultra-rapide dans un cristal de sel dilué est freiné au sein d’un métal multifonctionnel

1,4-Bis(carboxylatoethynyl)bicyclo[2.2.2]octane : un rotor ultra-rapide dans un sel dilué est freiné au sein d’un métal multifonctionnel1 L’objectif de ce travail est la conception de systèmes dans lesquels les propriétés dynamiques d’une machine moléculaire seraient corrélées aux propriétés électroniques que l’on rencontre habituellement dans les matériaux conçus au laboratoire par la technique d’électrocristallisation. Pour cela un sel dilué de formulation [nBu4N+]2[BABCO][BABCO–]2 a été préparé à partir du 1,4-di(ethynyl)bicyclo[2.2.2]octane synthétisé en neuf étapes2. Des expériences de temps de relaxation spin-réseau du 1H sur cristal statique montrent que deux environnements différents des rotors sont associés à des énergies d’activation et des fréquences de rotation différentes. Ce sel a été engagé dans un processus d’électrocristallisation avec le donneur d’électrons de type π EDT-TTF-CONH2 pour donner un nouveau métal organique cristallin : (EDT-TTF-CONH2)2[BABCO–], pour la première fois avec une fonctionnalité dynamique. Une seule position d’équilibre est observée pour le rotor dont on observe que l’énergie d’activation est grandement augmentée : ceci pourrait être attribué à des contraintes à la rotation accrues, expression d’un réseau dense d’interactions non covalentes (liaisons hydrogènes et interactions dihydrogène attractives3).  Ce matériau organique métallique ouvre la voie à d’autres systèmes multifonctionnels amphidynamiques. 1C. Lemouchi, C. Mézière, L. Zorina, E. Canadell, P. Wzietek, P. Auban-Senzier, C. Pasquier, P. Batail, soumis 2C. Lemouchi, C. Vogelsberg, S. Simonov, L. Zorina, P. Batail, S. Brown, M. A. Garcia-Garibay, J. Am. Chem. Soc., 133, 6371-6379 (2011). 3J. Echeverrıa, G. Aullon, D. Danovich, S. Shaik, S. Alvarez, Nature Chem., 2011, DOI: 10.1038/nchem.100

Evidence for the coexistence of Dirac and massive carriers in a-(BEDT-TTF)2I3 under hydrostatic pressure

Transport measurements were performed on the organic layered compound \aI3 under hydrostatic pressure. The carrier types, densities and mobilities are determined from the magneto-conductance of \aI3 . While evidence of high-mobility massless Dirac carriers has already been given, we report here, their coexistence with low-mobility massive holes. This coexistence seems robust as it has been found up to the highest studied pressure. Our results are in agreement with recent DFT calculations of the band structure of this system under hydrostatic pressure. A comparison with graphene Dirac carriers has also been done.Comment: 5 pages 5 figure

Functional materials based on TTF amino-acids/peptides

We report the synthesis and crystal chemistry of a series of TTF derivatives bearing simple amino acids such as the achiral Glycine or the chiral Alanine or Valine. The amino acids are linked to the TTF cores via the amino group and the acid functionality is further deprotonated to yield a TTF-carboxylate anion. The latter acts as both a pi-donor and electrolyte in the electrocristallisation experiments which deliver unprecedented zwitterionic (neutral) radicals. Their X-ray structures is analyzed and discussed in relation with their electronic and magnetic properties. This work is further extended to engage simple oligopeptides that can easily be linked to the TTF moiety. The preparation and the X-ray structures of both TTF-peptides and/or their zwitterionic radicals prepared by chemical or electrochemical methods will also be reported with an eye on how self-assembly via peptidic intermolecular interactions may be rationalized to direct the construction of novel pi-functional peptidic architectures

Croissance de matériaux moléculaires monocristallins par électrocristallisation

L\u27électrocristallisation est devenue à ce jour une technique incontournable pour la préparation de cristaux moléculaires d\u27espèces radicalaires, obtenus sur l\u27électrode par oxydation ou réduction électrochimique de précurseurs moléculaires. C’est un outil à fort potentiel car il n\u27est pas limité à la seule préparation de cristaux conducteurs mais peut être mis en œuvre facilement pour différents types de cristaux isolants de molécules électro-actives [1]. Une collaboration active entre les laboratoires de Rennes et Angers s’est développée autour de cette technique d’élaboration de monocristaux qui ont l’avantage d’être très purs. Les études physiques sont actuellement menées au niveau international entre différents partenaires, notamment dans le cadre de l’ANR blanche intitulée « ¾-Filled » coordonnée par le Laboratoire de Physique des Solides d’Orsay. Cette activité commune a été soutenue par le réseau CRISTECH avec un financement de 4000 € qui a permis l’achat de deux générateurs de micro-courant pour renouveler et étoffer le parc à Angers ainsi qu’une enceinte thermostatée à Rennes pour équiper le service installé plus récemment. L’affiche présente le principe sur lequel repose cette technique particulière de cristallogénèse, les molécules type qui peuvent être engagées, le matériel nécessaire ainsi que les paramètres qui influent sur la croissance. Deux exemples d’études récentes qui ont pu voir le jour grâce à cette technique sont également mis en exergue. L’une sur le système δ-(EDT-TTF-CONMe2)2X avec X = AsF6– ou Br–, un isolant de Mott à bande ¾ remplie [2] et [3]. L’autre concerne des sels d\u27un autre tétrathiafulvalène dissymétrique, à savoir o-DMTTF qui cristallise dans une structure quadratique très originale avec des anions halogénures comme Cl–, Br– et I– [4]. En particulier, nous avons pu accéder à deux séries de solutions solides [(o-DMTTF)2(X)x(Y)1–x] avec X, Y = Cl–/Br– ou Br–/I–, dans lesquelles des phénomènes d\u27insertion préférentielle de Br– ont été mis en évidence [1] P. Batail et al., Chem. Mater., 10, 3005 (1998). [2] L. Zorina et al., J. of Mater. Chem., 19, 6980 (2009) [3] P. Auban-Senzier et al., Phys. Rev. Lett., 102, 257001 (2009) [4] M. Fourmigué et al., Dalton Trans, 4652 (2008

Dry granular flows: rheological measurements of the μ(I)\mu(I)-Rheology

Granular materials do not flow homogeneously like fluids when submitted to external stress,but often form rigid regions that are separated by narrow shear bands where the material yields and flows. This shear localization impacts their apparent rheology, which makes it difficult to infer a constitutive behaviour from conventional rheometric measurements. Moreover, they present a dilatant behaviour, which makes their study in classical fixedvolume geometries difficult. These features led to perform extensive studies with inclined plane flows, which were of crucial importance for the development and the validation of the $\mu(I)$ rheology. Our aim is to develop a method to characterize granular materials with rheometrical tools. Using unusual rheometry measurements in an annular shear cell adapted from Boyer et al. (2011), dense granular flows are studied. A focus is placed on the comparison between the present results and the $\mu(I)$-rheology

Photoluminescence properties of 4,5-dimethyl-4′,5′-di(methylamido) tetrathiafulvalene thin film grown by thermal evaporation

In this paper, a temperature dependence study of photoluminescence spectra of vacuum-deposited organic donor tetrathiafulvalene: 4,5-dimethyl-4′,5′-di(methylamido) tetrathiafulvalene thin layers is presented. The investigated layers were deposited in a high vacuum (2 × 10−6 Torr) using molecular beam deposition (MBD) technique on n-doped (1 1 1) oriented silicon substrates. The photoluminescence studies were carried out in the temperatures range [13 K–325 K]. Under a 325 nm wavelength light excitation and at low-temperature a broad luminescence emission peak was observed in the UV–Visible and 2 peaks in the near infrared region. The photoluminescence spectra exhibit temperature dependence with a maximum emission at 180 K. Furthermore, an enhancement of the photoluminescence signal under a continuous excitation was observed at room temperature

Wild herbaceous vegetation in agroforestry systems: an asset that should not be overlooked

Thanks to agroforestry, trees and hedgerows are back in numbers in agricultural landscapes, where they provide many services. Agroforestry also gives pride of place to wild herbaceous vegetation, often perceived as a constraint or neglected by humans. Omnipresent when the soil is not tilled, herbaceous vegetation grows spontaneously at the foot of trees. From alley-cropping agroforestry to bocage landscapes, these 'little' plants are proving to be a major asset for the agroecological transition. Through the presentation of key results, this article explains how to take advantage of the wild herbaceous vegetation in agroforestry systems, in order to conserve biodiversity and promote sustainable agricultural productio