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Abstract: Accumulating evidence suggests that oxidative stress induced mechanisms are believed to be associated with the pathophysiology of autism. In this study, we recruited 19 Omani autistic children with age-matched controls to analyze their plasma and serum redox status and the levels of ATP, NAD+ and NADH using well established spectrophotometric assays. A significant decrease was observed in the levels of plasma total antioxidants (TA), reduced glutathione (GSH), superoxide and catalase activity in Omani autistic children as compared to their age-matched controls. In contrary, the level of plasma glutathione peroxidase (GSH-Px) was significantly increased in autistic children. Reduced serum NAD+ and ATP levels and lower NAD+:NADH ratio were observedin patients with autism compared to controls. Finally, a significant inverse correlation was observed between plasma GSH, SOD, catalase activity, and serum NAD+ and ATP levels, and autism severity using Childhood Autism Rating Scale (CARS) scores. The levels of plasma GSH-Px and serum NADH correlated strongly with autism severity whilst no significant correlation was observed for plasma TA. Our data suggests that increased vulnerability to oxidative stress in autism may occur as a consequence of alterations in antioxidant enzymes leading to mitochondrial dysfunction. [Copyright &y& Elsevier]

Abstract: This paper reports on the TEM characterization of the surface oxide layer forming on Co nanocrystals (NCs) prepared using a standard method [Puntes, V.F., Krishnan, K.M., Alivisatos, P., 2001. Synthesis, self-assembly, and magnetic behavior of a two-dimensional superlattice of single-crystal epsilon-Co nanoparticles. Appl. Phys. Lett. 78 (15), 2187–2189]. Complementary transmission electron microscopy (TEM)-related techniques presented direct evidence of a 1.5–3nm CoO shell forming on ɛ-Co NCs. The crystalline structure of the Co NCs was confirmed by selected area diffraction study while the nature of the shell was probed by energy-loss near-edge spectroscopy and energy-filtered TEM. Based on these results, we comment on the detection of nanoscale feature with energy-filtered imaging. [Copyright &y& Elsevier]

We report on the effect of the Nd:YAG laser intensity on diameter distribution, yield and physical characteristics of single-wall carbon nanotubes (SWNTs) while comparing three different laser configurations (namely: (i) single 532 nm pulse; (ii) single 1064 nm pulse; and (iii) 532 nm followed by the 1064 nm double pulse). The carbon SWNTs were synthesized at a furnace temperature of 1150 °C and characterized by means of laser micro-Raman spectroscopy and high resolution transmission electron microscopy (HRTEM). Regardless of the laser configuration used, it is found that both the yield and the structural characteristics of the SWNTs are highly sensitive to the laser intensity. Indeed, by combining Raman analyses together with HRTEM observations we were able to point out the existence of an optimal laser intensity which leads not only to the highest yield of SWNTs and the largest bundles but also to the lowest level of amorphous and, or disordered sp2 carbon in the deposits. While the optimal laser intensity was found to increase from 1.7 to 2.9×109 W/cm2 when the laser wavelength is changed from 1064 to 532 nm, the double pulse configuration offered a larger process latitude since high yield of SWNTs was obtained over the (0.8–3.5)×109 W/cm2 laser intensity range centered around the optimal value of 2.3×109 W/cm2. Moreover, it is shown that the increase of the laser intensity (from ∼0.5 to 5.6×109 W/cm2) favors the growth of large nanotubes (1.4 nm-diam.) to the detriment of smaller ones (1.1 nm-diam.). A tendency to form larger nanotubes was also observed when increasing the furnace temperature from 1000 to 1150 °C. Finally, the laser intensity effect is interpreted in terms of near-surface or deep laser energy absorption in the graphite target. [Copyright &y& Elsevier]

We report on the synthesis of carbon single-wall nanotubes (SWNTs) produced for the first time by means of pulsed UV laser vaporization. High resolution transmission electron microscopy (HRTEM) and Raman spectroscopy have revealed that the produced nanotubes have a narrow diameter distribution and are self-organized into bundles having diameters in the (15–20) nm range. It is also shown that carbon SWNTs can be grown at a furnace temperature as low as 550 °C. At this latter temperature, the SWNTs yield is lower than at 1150 °C and the nanotubes were found to be characterized by a broader diameter distribution and a smaller bundle diameter. Finally, the increase of the laser repetition rate from 30 to 150 Hz was found to lead to a higher yield of SWNTs and larger bundles. [Copyright &y& Elsevier]

Tungsten carbide powders are extensively used to provide wear-resistance properties to metal-matrix coatings. Here, we propose a simple and efficient route for the production of WC powders from elemental W and C by room-temperature high-energy ball milling (HEBM) and subsequent annealing. WC powders were obtained, with a minor (<4%wt.) iron contamination, with only 4 h of milling of a W/C atomic mixture of 42/58 and 90min anneal at 1000 °C. This innovative and simple route to produce WC powders can be used to produce feedstock of reinforcing particles intended for wear resistant coatings. We explored the impact of the milling times (from 6min to 96 h), compositions (W:C ratio of 1, 1.17 and 1.38) and annealing conditions ranging from 4 h at 850 °C to 90 min at 1000 °C. The samples were analyzed for phase distribution and composition using XRD, SEM with EDX mapping, XRF and TGA. As expected, milling induces amorphization and introduces iron from the milling media. We show that an excess of C can efficiently suppress the formation of deleterious tungsten carbides. [ABSTRACT FROM AUTHOR]