Redundancy gain in the stop-signal paradigm: Implications for the locus of coactivation in simple reaction time.

The authors carried out 2 experiments designed to cast light on the locus of redundancy gain in simple visual reaction time by using a stop-signal paradigm. In Experiment 1, the authors found that single visual stimuli were more easily inhibited than double visual stimuli by an acoustic stop signal. This result is in keeping with the idea that redundancy gain occurs prior to the ballistic stage of the stop-signal task. In Experiment 2, the authors found that the response to an acoustic go signal was more easily inhibited by a double than by a single visual stop signal. This result provides conclusive evidence for a redundancy gain in the stop process—in a process that does not involve a motor response but rather its inhibition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fluorene–fullerene dyads: Modulation of interaction

Two new fullerene[C₆₀]–fluorene dyads, N-methyl-2-(9-fluorenyl)-3,4-fulleropyrrolydine and N-methyl-2-(2-fluorenyl)-3,4-fulleropyrrolydine, were synthesized and investigated. Cyclic voltammetry, fluorescence experiments, electronic spectra and Density Functional Theory (DFT) calculations, all indicate ground and excited state interactions when fluorene is linked at carbon 9, whereas linkage through position 2 does not affect the ground and excited state of the fulleropyrrolidine moiety. As a consequence, only changing the position of the fluorene chromophore linkage, opens the way to modulate interactions, choosing between a simple spacer and an active unit.     

Metal ion implantation in inert polymers for strain gauge applications

Metal ion implantation in inert polymers may produce ultra-thin conducting films below the polymer surface. These subsurface films are promising structures for strain gauge applications. To this purpose, polycarbonate substrates were irradiated at room temperature with low-energy metal ions (Cu⁺ and Ni⁺) and with fluences in the range between 1 × 10¹⁶ and 1 × 10¹⁷ ions/cm², in order to promote the precipitation of dispersed metal nanoparticles or the formation of a continuous thin film. The nanoparticle morphology and the microstructural properties of polymer nanocomposites were investigated by glancing-incidence X-ray diffraction and transmission electron microscopy (TEM) measurements. At lower fluences (<5 × 10¹⁶ ions/cm²) a spontaneous precipitation of spherical-shaped metal nanoparticles occurred below the polymer top-surface (∼50 nm), whereas at higher fluences the aggregation of metal nanoparticles produced the formation of a continuous polycrystalline nanofilm. Furthermore, a characteristic surface plasmon resonance peak was observed for nanocomposites produced at lower ion fluences, due to the presence of Cu nanoparticles. A reduced electrical resistance of the near-surface metal-polymer nanocomposite was measured. The variation of electrical conductivity as a function of the applied surface load was measured: we found a linear relationship and a very small hysteresis.     

An evaluation of the creep properties of two Al-Si alloys produced by rapid solidification processing

Tensile creep tests were conducted on two Al-Si alloys produced by rapid solidification: an Al-Si-Ni-Cr alloy and an Al-Si-Cu-Fe alloy, designated alloys A and B, respectively. The creep curves of these two alloys in the temperature range from 493 to 573 K were markedly different, with alloy A exhibiting a normal creep curve with a very short tertiary region and alloy B exhibiting an extended tertiary stage associated with strain localization. The minimum creep rates varied, with the applied stress raised to exponents of ∼9.0 and ∼8.5 for the two alloys, respectively. The hardness of alloy B decreased with time during the creep testing, but there was little or no change in the hardness of alloy A. These differences in the creep and hardness characteristics are attributed to the evolution of precipitates within the two alloys during creep testing. A detailed analysis shows that, over the temperature range examined experimentally, alloy A exhibits a creep strength that is superior to conventional Al-based alloys and comparable to, or even higher than, some SiC-reinforced Al composites.     

Effects of nano-scaled particles on endothelial cell function in vitro: Studies on viability, proliferation and inflammation

Recent studies give support for a connection between the presence of inorganic particles (of m and nm size) in different organs and tissues and the development of inflammatory foci, called granulomas. As the potential source of particles (e.g. porcelain dental bridges) and the location of particle detection were topographically far apart, a distribution via the blood stream appears highly probable. Thus, endothelial cells, which line the inner surface of blood vessels, would come into direct contact with these particles, making particle–endothelial interactions potentially pathogenically relevant. The objective of this study was to evaluate the effects that five different nano-scaled particles (PVC, TiO₂, SiO₂, Co, Ni) have on endothelial cell function and viability. Therefore, human endothelial cells were exposed to different amounts of the above-mentioned particles. Although most particle types are shown to be internalised (except Ni-particles), only Co-particles possessed cytotoxic effects. Furthermore, an impairment of the proliferative activity and a pro-inflammatory stimulation of endothelial cells were induced by exposure to Co- and, to a lesser extent, by SiO₂-particles. If a pro-inflammatory stimulation of endothelial cells occurs in vivo, a chronic inflammation could be a possible consequence.     

Role of hydroboron intermediates in the mechanism of chemical vapor generation in strongly acidic media

Unknown and controversial aspects related to the mechanisms of hydrolysis of borane complexes and to the mechanisms of chemical vapor generation for trace element determination in strongly acidic media (0.01-10 M HCl) have been investigated and clarified. The overall hydrolysis rates of borane complexes (BH(4)(-), H(3)N-BH(3)) in the acidity range of 0.2-10 M HCl were several orders of magnitude lower than those predicted by kinetics laws and obtained in the pH range of 3.8-14. The decomposition of the borane complexes takes place stepwise and proceeds through the formation of hydroboron intermediates, L(x)()BH(4)(-)(x)()(n)() (x = 1, 2, 3), where L could be one or more species among the donor groups H(2)O, NH(3), OH(-), and Cl(-) and n is the charge of the hydroboron species (n = 0, +1, -1, depending on L). Some intermediates present surprisingly long lifetimes at elevated acidities and play a key role in determining both the overall hydrolysis rates of borane complexes and the reactivity of Hg(II), As(III), Sb(III), Bi(III), Se(IV), Te(IV), and Sn(IV) in chemical vapor generation for trace element determination. Atomic absorption experiments demonstrated that almost all trihydroboron species (LBH(3)(n)()), dihydroboron species (L(2)BH(2)(n)()), and monohydroboron species (L(3)BH(n)()) play an active role in the generation of elemental mercury and stibine. Some of these intermediates are inactive or play a marginal role in the generation of arsine, bismuthine, and hydrogen selenide. Hydrogen telluride is preferentially formed by those hydroboron species, which are stable in strongly acidic conditions, while the same species are unreactive in the generation of stannane. The collected experimental evidence is in agreement with the general reactivity of the elements in chemical vapor generation techniques and, together with other literature data, definitely rule out the hypothesis of "nascent hydrogen" as a possible mechanism of chemical vapor generation by borane complex derivatization.     

Structural reliability analysis using a standard deterministic finite element code

A method for performing a reliability analysis of structural systems within a standard finite element code is presented. This numerical procedure can be implemented in any finite element (f.e.) code having an internal optimization routine. The design points of structural problems are determined by calculating the minimum distance from the origin to the failure surface in a set of normalized variables, by using the minimization routine of the f.e. code. In order to test the procedure, simple structural systems are solved and the results are compared with those obtained by using different approaches. Some examples of application of the procedure for the reliability analysis of real structures are presented.     

Development of nanocomposite based on hydroxyethylmethacrylate and functionalized fumed silica: mechanical, chemico-physical and biological characterization

In this research work organic/inorganic nano composites were synthesized from poly-2-hydroxyethylmethacrylate and properly modified silica nanoparticles by in situ polymerization. In particular, fumed nanosilica was functionalized with methacryloylpropyltrimetoxy silane (MPTMS) in order to obtain a more homogeneous, reliable and mechanically performing nano composite. For comparison, nano composites with non functionalised silica were also prepared. Scanning electron microscopy was performed in order to visualize the effects of functionalization on the mode and state of dispersion. This analysis demonstrated that MPTMS grafted onto silica surface acts as an effective coupling agent and assures a good dispersion and distribution of nanoparticles as well as a strong nano particle/matrix interfacial adhesion. As a result of strong interactions occurring between phases, a pronounced increase of the glass transition temperature and mechanical parameters were recorded. Finally, these novel nano composites were seeded with murine fibroblast and human mesenchymal stem cells, and observed in time-lapse experiments proving an effective biological response.     

Milk yield,quality, and coagulation properties of 6 breeds of goats: Environmental and individual variability

Goat milk and cheese production is continuously increasing and milk composition and coagulation properties (MCP) are useful tools to predict cheesemaking aptitude. The present study was planned to investigate the extension of lactodynamographic analysis up to 60 min in goat milk, to measure the farm and individual factors, and to investigate differences among 6 goat breeds. Daily milk yield (dMY) was recorded and milk samples collected from 1,272 goats reared in 35 farms. Goats were of 6 different breeds: Saanen and Camosciata delle Alpi for the Alpine type, and Murciano-Granadina, Maltese, Sarda, and Sarda Primitiva for the Mediterranean type. Milk composition (fat, protein, lactose, pH; somatic cell score; logarithmic bacterial count) and MCP [rennet coagulation time (RCT, min), curd-firming time (k₂₀, min), curd firmness at 30, 45, and 60 min after rennet addition (a₃₀, a₄₅, and a₆₀, mm)] were recorded, and daily fat and protein yield (dFPY g/d) was calculated as the sum of fat and protein concentration multiplied by the dMY. Data were analyzed using different statistical models to measure the effects of farm, parity_, stage of lactation and breed; lastly, the direct and the indirect effect of breed were quantified by comparing the variance of breed from models with or without the inclusion of linear regression of fat, protein, lactose, pH, bacterial, somatic cell counts, and dMY. Orthogonal contrasts were performed to compare least squares means. Almost all traits exhibited high variability, with coefficients of variation between 32 (for RCT) and 63% (for a₃₀). The proportion of variance regarding dMY, dFPY, and milk composition due to the farm was moderate, whereas for MCP it was low, except for a₆₀, at 69%. Parity affected both yield and quality traits of milk, with least squares means of dMY and dFPY showing an increase and RCT and curd firmness traits a decrease from the first to the last parity class. All milk quality traits, excluding fat, were affected by the stage of lactation; RCT and k₂₀ decreased rapidly and a₃₀ was higher from the first to the last part of lactation. Alpine breeds showed the highest dMY and dFPY but Mediterranean the best percentage of protein, fat, and lactose and a shorter k₂₀ and a greater a₃₀. Among the Mediterranean goats, Murciano-Granadina goats had the highest milk yield, fat, and protein contents, whereas Maltese, Sarda, and Sarda Primitiva were characterized by much more favorable technological properties in terms of k₂₀, a₃₀, and a₄₅. In conclusion, as both the farm and individual factors highly influenced milk composition and MCP traits, improvements of these traits should be based both on modifying management and individual goat factors. As expected, several differences were attributable to the breed effect, with the best milk production for the Alpines and milk quality and coagulation for the Mediterranean goats.