Visuomotor transformation for interception:catching while fixating

Catching a ball involves a dynamic transformation of visual information about ball motion into motor commands for moving the hand to the right place at the right time. We previously formulated a neural model for this transformation to account for the consistent leftward movement biases observed in our catching experiments. According to the model, these biases arise within the representation of target motion as well as within the transformation from a gaze-centered to a body-centered movement command. Here, we examine the validity of the latter aspect of our model in a catching task involving gaze fixation. Gaze fixation should systematically influence biases in catching movements, because in the model movement commands are only generated in the direction perpendicular to the gaze direction. Twelve participants caught balls while gazing at a fixation point positioned either straight ahead or 14 degrees to the right. Four participants were excluded because they could not adequately maintain fixation. We again observed a consistent leftward movement bias, but the catching movements were unaffected by fixation direction. This result refutes our proposal that the leftward bias partly arises within the visuomotor transformation, and suggests instead that the bias predominantly arises within the early representation of target motion, specifically through an imbalance in the represented radial and azimuthal target motion.

Uptake, translocation and transformation of arsenate and arsenite in sunflower (Helianthus annuus):formation of arsenic-phytochelatin complexes during exposure to high arsenic concentrations

The aim of the study was to determine the time-dependent formation of arsenic-phytochelatin (As-PC) complexes in the roots, stems and leaves of an arsenic-nontolerant plant (Helianthus annuus) during exposure to 66 mol l(-1) arsenite (As(III)) or arsenate (As(V)). We used our previously developed method of simultaneous element-specific (inductively coupled plasma mass spectrometry, ICP-MS) and molecular-specific (electrospray-ionization mass spectrometry, ES-MS) detection systems interfaced with a suitable chromatographic column and eluent conditions, which enabled us to identify and quantify As-PC complexes directly. Roots of As-exposed H. annuus contained up to 14 different arsenic species, including the complex of arsenite with two (gamma-Glu-Cys)(2)-Gly molecules [As((III))-(PC(2))(2)], the newly identified monomethylarsonic phytochelatin-2 or (gamma-Glu-Cys)(2)-Gly CH(3)As (MA((III))-PC(2)) and at least eight not yet identified species. The complex of arsenite with (gamma-Glu-Cys)(3)-Gly (As((III))-PC(3)) and the complex of arsenite with glutathione (GSH) and (gamma-Glu-Cys)(2)-Gly (GS-As((III))-PC(2)) were present in all samples (roots, stems and leaves) taken from plants exposed to As. The GS-As((III))-PC(2) complex was the dominant complex after 1 h of exposure. As((III))-PC(3) became the predominant As-PC complex after 3 h, binding up to 40% of the As present in the exposed plants. No As-PC complexes were found in sap (mainly xylem sap from the root system), in contrast to roots, stems and leaves, which is unequivocal evidence that As-PC complexes are not involved in the translocation of As from root to leaves of H. annuus.

Ethnic Competition and the logic of party system transformation

This article adapts and expands a recent model of ethnic competition by exploring its implications over a long period spanning crucial stages in the modernisation of the political system. It illustrates the model by reference to developments in Northern Ireland since its modern party system was launched in the 1880s. This offers an exceptionally clear example of the interaction of central elements of the model: the initial bedding down of a system of bipartisan ethnic competition, with two parties having a remarkable capacity to resist ethnic outbidding; the fragmentation of this system following the introduction of a set of major institutional forms that facilitated ethnic outbidding; and the continuing resilience of ethnically based parties in warding off challenges from groups seeking to prioritise other political dimensions. The model's implications are tested against a comprehensive collection of ecological and survey data.

Chemically blockable transformation and ultraselective low-pressure gas adsorption in a non-porous metal organic framework

Metal organic frameworks (MOFs) are among the most exciting materials discovered recently, attracting particular attention for their gas-adsorption and -storage properties. Certain MOFs show considerable structural flexibility in response to various stimuli. Although there are several examples of 'breathing' MOFs, in which structural changes occur without any bond breaking, examples of transformations in which several bonds are broken and made are much rarer. In this paper we demonstrate how a flexible MOF, Cu-2(OH)(C8H3O7S)(H2O)center dot 2H(2)O, can be synthesized by careful choice of the organic linker ligand. The flexibility can be controlled by addition of a supplementary coordinating molecule, which increases the thermal stability of the solid sufficiently for direct imaging with electron microscopy to be possible. We also demonstrate that the MOF shows unprecedented low-pressure selectivity towards nitric oxide through a coordination-driven gating mechanism. The chemical control over these behaviours offers new possibilities for the synthesis of MOFs with unusual and potentially exploitable properties.