“Biological Geometry Perception”: Visual Discrimination of Eccentricity Is Related to Individual Motor Preferences

In the continuum between a stroke and a circle including all possible ellipses, some eccentricities seem more “biologically preferred” than others by the motor system, probably because they imply less demanding coordination patterns. Based on the idea that biological motion perception relies on knowledge of the laws that govern the motor system, we investigated whether motorically preferential and non-preferential eccentricities are visually discriminated differently. In contrast with previous studies that were interested in the effect of kinematic/time features of movements on their visual perception, we focused on geometric/spatial features, and therefore used a static visual display.In a dual-task paradigm, participants visually discriminated 13 static ellipses of various eccentricities while performing a finger-thumb opposition sequence with either the dominant or the non-dominant hand. Our assumption was that because the movements used to trace ellipses are strongly lateralized, a motor task performed with the dominant hand should affect the simultaneous visual discrimination more strongly. We found that visual discrimination was not affected when the motor task was performed by the non-dominant hand. Conversely, it was impaired when the motor task was performed with the dominant hand, but only for the ellipses that we defined as preferred by the motor system, based on an assessment of individual preferences during an independent graphomotor task.Visual discrimination of ellipses depends on the state of the motor neural networks controlling the dominant hand, but only when their eccentricity is “biologically preferred”. Importantly, this effect emerges on the basis of a static display, suggesting that what we call “biological geometry”, i.e., geometric features resulting from preferential movements is relevant information for the visual processing of bidimensional shapes

On the Anomalous Magnetic Behavior and the Multiferroic Properties in BiMn₂O₅

Sealed-tube synthesis of BiMn₂O₅ materials and their physical properties have rationally been reinvestigated depending on the reactants. The aim of the study was to characterize its potential multiferroic properties and to investigate the anomalous magnetic properties in relation to the expected ferroelectric properties. Rietveld refinement of the room temperature X-ray diffraction data shows the stability of the crystallographic structure with a Mn³⁺/Mn⁴⁺ ratio far from 1 because of bismuth and oxygen deficiencies despite the sealed-tube synthesis. Our detailed magnetic susceptibility and specific heat data analysis unambiguously support an intrinsic anomalous magnetic behavior in relation to the establishment of a magnetic short-range ordering far from the Néel temperature. Around room temperature, oxygen vacancies are responsible for supporting the dielectric loss peak measured, and, interestingly, the so-called <i>T</i>*, which was underlined in relation to an anomalous phonon shift (García-Flores, A. F.; et al. <i>Phys. Rev. B</i> <b>2006</b>, <i>73</i>, 104411), is not a characteristic temperature in relation to the multiferroic properties because no ferroelectric transition was detected

Simple synthesis and characterization of vertically aligned Ba0.7Sr0.3TiO3 –CoFe2O4 multiferroic nanocomposites from CoFe2 nanopillar arrays

A new strategy to elaborate (1-3) type multiferroic nanocomposites with controlled dimensions and vertical alignment is presented. The process involves a supported nanoporous alumina layer as a template for growth of free-standing and vertically aligned CoFe2 nanopillars using a room temperature pulsed electrodeposition process. Ba0.70Sr0.30TiO3–CoFe2O4 multiferroic nanocomposites were grown through direct deposition of Ba0.7Sr0.3TiO3 films by radio-frequency sputtering on the top surface of the pillar structure, with in situ simultaneous oxidation of CoFe2 nanopillars. The vertically aligned multiferroic nanocomposites were characterized using various techniques for their structural and physical properties. The large interfacial area between the ferrimagnetic and ferroelectric phases leads to a magnetoelectric voltage coefficient as large as ~320 mV cm−1 Oe−1 at room temperature, reaching the highest values reported so far for vertically architectured nanocomposite systems. This simple method has great potential for large-scale synthesis of many other hybrid vertically aligned multiferroic heterostructures