Inhomogeneous Magnetism in La-doped CaMnO3. (II) Mesoscopic Phase Separation due to Lattice-coupled FM Interactions

A detailed investigation of mesoscopic magnetic and crystallographic phase separation in Ca(1-x)La(x)MnO3, 0.00<=x<=0.20, is reported. Neutron powder diffraction and DC-magnetization techniques have been used to isolate the different roles played by electrons doped into the eg level as a function of their concentration x. The presence of multiple low-temperature magnetic and crystallographic phases within individual polycrystalline samples is argued to be an intrinsic feature of the system that follows from the shifting balance between competing FM and AFM interactions as a function of temperature. FM double-exchange interactions associated with doped eg electrons are favored over competing AFM interactions at higher temperatures, and couple more strongly with the lattice via orbital polarization. These FM interactions thereby play a privileged role, even at low eg electron concentrations, by virtue of structural modifications induced above the AFM transition temperatures.Comment: 8 pages, 7 figure

Anxiety Disorders and Sensory Over-Responsivity in Children with Autism Spectrum Disorders: Is There a Causal Relationship?

Anxiety disorders and sensory over-responsivity (SOR) are common in children with autism spectrum disorders (ASD), and there is evidence for an association between these two conditions. Currently, it is unclear what causal mechanisms may exist between SOR and anxiety. We propose three possible theories to explain the association between anxiety and SOR: (a) SOR is caused by anxiety; (b) Anxiety is caused by SOR; or (c) SOR and anxiety are causally unrelated but are associated through a common risk factor or diagnostic overlap. In this paper, we examine support for each theory in the existing anxiety, autism, and neuroscience literature, and discuss how each theory informs choice of interventions and implications for future studies

Evaluating MRI biomarkers of tumour hypoxia

Tumour hypoxia is associated with resistance to radiotherapy and chemotherapy, and represents a major challenge in the treatment of head and neck squamous cell carcinoma (HNSCC). Non-invasive imaging methods to repeatedly and rapidly quantify the degree and spatial distribution of hypoxia would offer clinical benefit. This thesis focusses on the evaluation of oxygen-enhanced magnetic resonance imaging (OE-MRI) for mapping and quantifying hypoxia in HNSCC xenografts in vivo. OE-MRI relies on the quantification of changes in the longitudinal MRI relaxation rate R1, induced by excess paramagnetic oxygen molecules dissolved in blood plasma and interstitial fluid with inhalation of oxygen. A refined OE-MRI protocol was first developed, designed to incorporate susceptibility MRI in the same imaging session, thereby providing measurements of tumour R1 and R2 during air and 100% O2 breathing, and fractional blood volume (fBV) using ultrasmall superparamagnetic iron oxide particles. MRI biomarkers were validated through comparison with image-aligned tissue sections stained for the hypoxia marker pimonidazole, and the perfusion marker Hoechst 33342. Susceptibility MRI revealed that hyperoxia-induced DR2*O2-air inversely correlated with pimonidazole-derived hypoxic fraction, and fBV positively correlated with Hoechst 33342 uptake. Parcellation of the voxelwise DR2*O2-air identified voxels non-responsive to hyperoxia that may inform on cycling hypoxia. OE-MRI showed that both tumour sub-volumes refractory to hyperoxia induced changes in R1 (OxyR), and perfused OxyR (pOxyR) were associated with an extensive and heterogeneous distribution of hypoxia across the HNSCC xenografts. Both OxyR positively correlated with pimonidazole-derived hypoxic fraction, suggesting that binerisation of hyperoxia-induced DR1 data with a perfusion mask may not be necessary in strongly hypoxic tumours such as HNSCC. Finally, the potential utility of OE-MRI for monitoring tumour response to the hypoxia-alleviating drug atovaquone was investigated. OE-MRI can identify and quantify hypoxia in HNSCC and could provide an easily translatable imaging tool for patient stratification and treatment management

Influence of visual features on the ability to locate information on a screen: recommendations for seniors.

International audienceAs part of a project to design more ergonomic web-application portals for older users, we established recommendations on color choices and the level of detail needed to make it easier for seniors to locate icons and lexical labels. The experimental protocol featured an original combination of eye tracking and an ecological environment (participants’ homes). Participants had to locate different targets in different color and detail conditions. Results showed that the combination of a figurative target with an incongruent color increased target location times, but only if there was a strong target concept congruent color link. Furthermore, a high level of detail for figurative targets improved reaction times, but only when there was a weak concept congruent color link. These effects were linked to the implementation of top down processes.Keywords: Eye Tracking, Information Location Task, Older Adult, Color, Level of Detail, Top-Down ProcessesL’étude qui est décrite dans cet article s’inscrit dans un projet de conception du système de télésanté et de maintien à domicile, dit HADAGIO, qui est essentiellement destiné à un public âgé. Cette étude vise à contribuer à la définition de l’ergonomie des interfaces du portail d’applications Web qui va permettre aux utilisateurs séniors d’accéder aux services proposés par ce système. Plus précisément, un objectif appliqué consistera à proposer des recommandations concernant d’une part les couleurs des icônes et des libellés lexicaux présents sur le portail, et d’autre part le niveau de détails à préconiser pour ces icônes, afin de faciliter la tâche de localisation de ces cibles sur le portail par des séniors. Après avoir présenté des hypothèses concernant le rôle de ces éléments de surface sur les performances de localisation de cibles, nous avons donc mis en place un protocole expérimental dont la particularité est de reposer sur l’utilisation d’un dispositif d’oculométrie dans un environnement écologique (au domicile des personnes âgées). Les participants devaient localiser des cibles dans différentes modalités de couleur et de niveau de détails. Les résultats obtenus montrent que l’association d’une cible figurative avec une couleur qui lui est non congruente dégrade les performances de temps de localisation de cette cible du fait d’un nombre de distracteurs fixés avant la cible plus élevé, mais uniquement si le lien cible-couleur congruente est fort. Ces résultats ne sont pas retrouvés lors de la localisation de cibles lexicales. Par ailleurs, un niveau de détails élevé des cibles figuratives permet d’améliorer les performances de temps de localisation, du fait d’une moindre latence saccadique, mais uniquement lorsque le lien cible-couleur congruente est faible. Ces effets de la couleur et du niveau de détails des cibles figuratives seraient liés à la mise en œuvre de processus de type Top-Down lors de la tâche de localisation des cibles

Un modelo animal para el estudio de las bases genéticas del comportamiento en los seres humanos: las cepas con marcadores múltiples (CMM)

ResumenLos modelos animales se utilizan a menudo para la investigación preclínica en la neurobiología de los trastornos psiquiátricos. Mientras que muchos se emplean para la detección selectiva de nue-vos agentes terapéuticos, algunos de ellos se usan para estudiar las bases genéticas de las enfermedades psiquiátricas, probablemente a causa del complejo determinismo genético que subyace a rasgos cuanti-tativos del comportamiento como el estado de ánimo, la personalidad o la inteligencia. El presente artículo presenta una breve revisión que introduce un modelo de análisis que usa ratones: el modelo de cepas con marcadores. Utilizando este modelo es posible mostrar datos de determinismo genético y localizar algunos de los fragmentos cromosómicos implicados en la regulación de los procesos ansiogénicos. El modelo no puede determinar con precisión la posición de uno o más genes en la actualidad, pero proporciona un medio valioso de explorar el genoma de modo aproximado. Por medio del análisis genético, se intentarán identificar utilizando el modelo fragmentos autosómicos que pueden estar implicados en dos rasgos del comportamiento: la ansiedad y las crisis inducidas por productos químicos. En este artículo, después de revisar los aspectos teóricos de la búsqueda de los genes implicados en el comportamiento, introduciremos sucesivamente estudios en materias genéticas en trabajos de psiquiatna humana, y además estudios de comportamiento animal apropiados. Luego presentaremos un modelo genético en ratones, las cepas con marcadores múltiples, que nos permite localizar fragmentos cromosómicos asociados con un rasgo del comportamiento.</jats:p