Formation of silicon nanodots via ion beam sputtering of ultrathin gold thin film coatings on Si

Ion beam sputtering of ultrathin film Au coatings used as a physical catalyst for self-organization of Si nanostructures has been achieved by tuning the incident particle energy. This approach holds promise as a scalable nanomanufacturing parallel processing alternative to candidate nanolithography techniques. Structures of 11- to 14-nm Si nanodots are formed with normal incidence low-energy Ar ions of 200 eV and fluences above 2 × 1017 cm-2. In situ surface characterization during ion irradiation elucidates early stage ion mixing migration mechanism for nanodot self-organization. In particular, the evolution from gold film islands to the formation of ion-induced metastable gold silicide followed by pure Si nanodots formed with no need for impurity seeding

The relationship between joint mobility and motor performance in children with and without the diagnosis of developmental coordination disorder

<p>Background: The purpose of this study was to determine whether joint mobility is associated with motor performance in children referred for Developmental Coordination Disorder (DCD-group) in contrast to a randomly selected group of children between 3-16 years of age (Random-Group).</p><p>Methods: 36 children with DCD and 352 typically developing children (Random-Group) participated. Hypermobility was classified based on the Beighton score (cut-off >= 5 for 3-9 years and >= 4 for 10-16 years) using goniometry. Motor performance was assessed with the Movement Assessment Battery for Children (MABC).</p><p>Results: The mean Beighton score in the DCD-group was 5.0 versus 2.6 in the Random group. Prevalence of hypermobility was higher in the DCD-group than in the Random Group (64% and 33% respectively; X-2 = 16.09, p <.001). There was a significant [negative] correlation (r(p) = -.38, p = .02) between Beighton score and total MABC scores within the DCD group, but not in the Random Group (r(p) = -0.07, p = .20). More specifically, in the DCD group we found a significant negative correlation between the MABC total score and the degree of hyperextension of the knees.</p><p>Conclusion: The extremely high prevalence of hypermobility when applying the recommended cut-off scores stresses the need for an international agreement on firm cut-off points and the use of standardized measurement of Beighton mobility manoeuvres. The results of this study show that a cut-off of 7 is more appropriate, resulting in a prevalence of 6% in children aged 3-16 years. Although in the general population motor performance and joint mobility are not related, this is the case in children referred for DCD. We argue that more mobility of the joints may be a disadvantage when motor coordination is poorly developed.</p>

XPS–SIMS Surface Characterization of Aluminovanadate Oxide Catalyst Precursors Co-Precipitated at Different pH: Effect of Calcination

X-ray photoelectron spectroscopy and time-offlight secondary ion mass spectrometry were employed in a comparative study of the surface physical and chemical state of aluminovanadate oxide catalyst precursors (V-Al- O), which were precipitated in the range of pH from 5.5 to 10, after drying and calcination. Core-level photoelectron spectra, X-ray induced Auger and valence band spectra of the samples were measured so as to quantitatively evaluate the surface concentrations of the catalyst components. The binding energy shifts of the respective O 1s, V 2p and Al 2p lines were determined as a function of pH and analyzed in terms of the initial state effect related to the atomic charge and Madelung potential. The surface of the catalysts was composed of aluminum hydroxide/oxyhydroxide and of dispersed vanadium oxide species. Increasing pH was found to result in a monotonic variation of the elemental surface composition, modification of the valence band, progressive hydroxylation of the surface and increasing dispersion of vanadium oxide species. Increasing pH was also accompanied by an increase in the abundance of V4? species, specific surface area and reducibility. Calcination in air at 500 °C gave rise to surface segregation of vanadium, changes in the valence band and partial dehydroxylation. The structural transformations in vanadium oxide species and aluminium hydroxide support and their interaction were accompanied by an increasing abundance of V-O-Al bonds. The net result of the restructuring was a decrease in the specific surface area and reducibility of the calcined catalysts. The enhancement of the catalytic activity in propane oxidative dehydrogenation demonstrated by V-Al-O samples with increasing precipitation pH and after calcination was in good correlation with a growing population of the V4? states and increasing nucleophilicity of oxygen sites. © Springer Science+Business Media, LLC 2012.SCOPUS: ar.jinfo:eu-repo/semantics/publishe