Hemiballismus, Hyperphagia, and Behavioral Changes following Subthalamic Infarct

The function of subthalamic nucleus (STN) which is a part of the basal ganglia system is not clear, but it is hypothesized that this component might be involved in action selection. Unilateral damage to STN, which can commonly occur due to the small vessel stroke mainly, causes hemiballismus and sometimes hemichorea-hemiballismus. This paper deals with a 60-year-old patient with sudden onset of abnormal movements in his right limbs. He had increased appetite and hyperphagia and also developed mood and behavioral changes (aggressiveness, irritability, anxiety, and sometimes obscene speech). The magnetic resonance imaging revealed infarct area in left subthalamus. In our case, hemiballismus is caused by infarction in left subthalamic area. Occurrence of irritability, anxiety, and some behavioral changes such as aggressiveness and obscene speech can be explained by impairment of STN role in nonmotor behavior and cognitive function as a result of infarct

Effets de l'environnement sur les propriétés physico-chimiques des atomes d'argent et des nanoparticules mono-et bimétalliques à base d'or (étude par radiolyse pulsée et stationnaire)

Le travail présenté dans ce manuscrit de thèse concerne la synthèse radiolytique et l'étude des propriétés physico-chimiques des atomes d argent et de nanoparticules mono- et bimétalliques à base d or. Dans la première partie de cette thèse, l effet de ligand Br- sur les propriétés cinétiques et spectrales des atomes d argent complexés a été étudié. La constante de vitesse de la réduction du complexe d argent en présence de bromure a été déterminée par radiolyse impulsionnelle et le potentiel de réduction du couple AgBr43-/Ag0Br44- a été estimé à l aide de cycles thermodynamiques. La comparaison de la valeur obtenue avec celle du couple AgBr43-/Ag0 + 4Br-, indique que la réaction de formation de l atome d argent complexé est plus favorable que celle de l atome d argent libre. Dans la seconde partie, l effet d'agents stabilisants sur les propriétés structurales et électro-catalytiques de nanoparticules monométalliques d or et de fer et bimétalliques à base d or (Au/Fe et Au/Pt) induites par radiolyse stationnaire a été étudié. Nous avons confirmé le rôle important de l agent stabilisant sur le processus de réduction d ions métalliques, sur la morphologie des nanoparticules (forme et taille) ainsi que sur la composition élémentaire des nanoparticules formées en utilisant un mélange d'ions métalliques comme précurseurs. L adjonction du fer à l or permet pour différentes réactions impliquées dans les piles à combustible (réduction du proton, réduction de l oxygène et oxydation du méthanol) d obtenir des réponses électro-catalytiques importantes qui sont proches de celles du platine, actuellement le meilleur électro-catalyseur. Nous avons montré que les systèmes bimétalliques obtenus à base d or présentent une forte activité bifonctionnelle et peuvent être utilisés tant à l anode qu à la cathode dans des piles à combustible.The aim of the present work was to study the physico-chemical properties of silver atoms, monometallic and gold-based bimetallic nanoparticles synthesized by the radiation chemical reduction method. In the first part of thesis, we studied the effects of bromide ligands on the kinetics and spectral properties of the silver atom complex. The rate constant for the reduction of AgIBr43- in aqueous solution was determined by pulse radiolysis and the redox potential of the couples AgIBr43-/Ag0Br44- and AgIBr43-/ Ag0 + Br44- were estimated with the help of thermodynamic cycles. Comparison of the obtained values indicates that the redox potential of the silver atom couple is lowered by bromide ligands and the formation of Ag0Br44- is more favourable than a free silver atom. In the second part, the effects of stabilizing agents on optical, structural and electrocatalytic properties of monometallic nanoparticles, such as gold and iron and bimetallic nanoparticles systems, Au/Fe and Au/Pt, prepared by gamma-radiolysis were studied. Our results offer a new strategy to present the effectiveness of the stabilizing agents in the process of metal ion reduction, in the nanoparticles morphology (shape and size) as well as in the elementary composition of bimetallic nanoparticles. This study indicates that the radiolysis method, which we used for the nanoparticles synthesis, allow us to obtain gold based bimetallic nanoparticles that showed an excellent electrocatalytic activity toward reduction of oxygen and proton as well as oxidation of methanol. Our results show that these systems are very promising for application in fuel cells.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

N-Methyl-2-pyrrolidone as a Reaction Medium for Gold(III)-Ion Reduction and Star-like Gold Nanostructure Formation

The efficiency of a wet chemical route to synthesize gold nanostructures with tunable size and shape significantly depends on the applied solvent and the interaction of solvent molecules with other species such as gold ions. The ability of the organic solvent N-methyl-2-pyrrolidone (NMP) as a suitable medium for application in star-like gold nanostructure (AuNS) synthesis with a tunable morphology at ambient conditions has been investigated. The time-dependent analysis of the UV–vis absorption spectra of AuIIICl₄– in a pure NMP solution illustrates the role of NMP as simultaneous complexing and reducing agents. Kinetic studies indicate that AuIIICl₄– in NMP solution is reduced to AuICl₂–, with no need to use another reducing agent, any external energy sources, or solvent pretreatment. This is because AuI species stay stable in this solution unless poly(vinylpyrrolidone) (PVP) catalyzes their disproportionation. Morphological studies by transmission electron microscopy (TEM) specify the high-yield synthesis of AuNS with monocrystalline spikes in a concentrated NMP solution by PVP. This study illustrates that the presence of seeds, as another agent to catalyze the disproportionation of AuI species, makes it possible to synthesize AuNS in varying concentrations of PVP in this medium. The role of PVP concentration and the presence of seeds in the formation kinetics, morphology, and optical properties is systematically discussed. The results achieved through this study develop a straightforward and safe procedure for AuNS synthesis in high yield in a water-miscible organic polar solvent with tunable morphology and optical properties. Considering the high capability of NMP to dissolve various types of polymers and hydrophobic ligands, synthesizing AuNS in this solvent opens a window to a practical and easy way to fabricate gold-based nanomaterials with fascinating optical properties

Oxidation of Bromide Ions by Hydroxyl Radicals: Spectral Characterization of the Intermediate BrOH^•–

The reaction of ^•OH with Br^– has been reinvestigated by picosecond pulse radiolysis combined with streak camera absorption detection and the obtained spectro-kinetics data have been globally analyzed using Bayesian data analysis. For the first time, the absorption spectrum of the intermediate species BrOH^•– has been determined. This species absorbs in the same spectral domain as Br₂^•–: the band maximum is roughly at the same wavelength (λ_max = 352 nm instead of 354 nm) but the extinction coefficient is smaller (ε_max = 7800 ± 400 dm³ mol^–1 cm^–1 compared with 9600 ± 300 dm³ mol^–1 cm^–1) and the band is broader (88 nm versus 76 nm). Quantum chemical calculations have also been performed and corroborate the experimental results. In contrast to Br₂^•–, the existence of several water–BrOH^•– configurations leading to different transition energies may account for the broadening of the absorption spectrum in addition to the higher number of degrees of freedom