Comparing Al-SBA-15 Support and Pt/Al-SBA-15 Catalyst: Changes in Al Speciation and Acidic Properties Induced by the Introduction of Pt via Aqueous Medium

Differences between the acidic properties of silicoaluminic Pt-containing catalysts and those assessed on their parent supports have been reported in the literature and attributed to the presence of the metal nanoparticles and to their influence on the acid sites. It is shown here that for mesoporous materials containing various types of Al species, an alternative explanation can be proposed. ²⁷Al NMR spectroscopy, FTIR of adsorbed CO and probe catalytic tests suggest the redistribution of aluminium atoms upon contact of the parent support with the aqueous solution containing the Pt precursor. Upon contact with water and thermal treatment, strong and mild Brønsted sites (Si–O(H)–Al) transform into strong Lewis sites (isolated tetracoordinated Al atoms). As a consequence, it may not be straightforward to deduce the acidic properties of metal-containing catalysts supported on Al-containing mesoporous materials from those of the bare support, because the surface species may differ significantly.     

Microstructural characterization of creep anisotropy at 673 K in the M5® alloy

Zirconium alloy tubing is used in pressurized water nuclear reactors in order to prevent fissile material from leaking into the coolant. It can be the first safety wall of nuclear fuel, and is submitted to complex thermomechanical loadings. In consequence, new Nb-modified alloys, such as the M5® alloy, and fine numerical models are being developed to guarantee a better and longer mechanical integrity of these tubes. To identify the physical mechanisms that could be considered in such models, an experimental approach, combining creep tests with electron backscattered diffraction and Transmission electron microscopy investigations, was carried out.Tubular specimens were submitted to multiaxial creep tests at a temperature of 673 K. Seven ratios between the axial and hoop applied stresses were investigated. It enabled a macroscopic evidence of the creep anisotropy. Besides, EBSD analyses on a mesoscopic-sized non deformed area led to the characterization of the variation of the average Schmid factor with the direction of loading. Finally, TEM observations were done on seven crept samples, corresponding to the seven directions of loading tested mechanically. The variations of the different parameters investigated (activated slip systems, dislocation densities, curvatures of the dislocations) can be seen as the effects of the creep anisotropy at a microscopic scale. The correlation between results is then discussed in a multiscale frame.     

Estradiol Favors the Formation of Eicosapentaenoic Acid (20:5n-3) and n-3 Docosapentaenoic Acid (22:5n-3) from Alpha-Linolenic Acid (18:3n-3) in SH-SY5Y Neuroblastoma Cells

Whether neurosteroids regulate the synthesis of long chain polyunsaturated fatty acids in brain cells is unknown. We examined the influence of 17-β-estradiol (E2) on the capacity of SH-SY5Y cells supplemented with α-linolenic acid (ALA), to produce eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). Cells were incubated for 24 or 72 h with ALA added alone or in combination with E2 (ALA + E2). Fatty acids were analyzed by gas chromatography of ethanolamine glycerophospholipids (EtnGpl) and phosphatidylcholine (PtdCho). Incubation for 24 h with ALA alone increased EPA and DPA in EtnGpl, by 330 and 430% compared to controls (P < 0.001) and DHA by only 10% (P < 0.05). Although DHA increased by 30% (P < 0.001) in ALA + E2-treated cells, the difference between the ALA and ALA + E2 treatments were not significant after 24 h (Anova-1, Fisher’s test). After 72 h, EPA, DPA and DHA further increased in EtnGpl and PtdCho of cells supplemented with ALA or ALA + E2. Incubation for 72 h with ALA + E2 specifically increased EPA (+34% in EtnGpl, P < 0.001) and DPA (+15%, P < 0.001) compared to ALA alone. Thus, SH-SY5Y cells produced membrane EPA, DPA and DHA from supplemental ALA. The formation of DHA was limited, even in the presence of E2. E2 significantly favored EPA and DPA production in cells grown for 72 h. Enhanced synthesis of ALA-elongation products in neuroblastoma cells treated with E2 supports the hypothesis that neurosteroids could modulate the metabolism of PUFA.     

Semiclosed-Cell Mullite Foams: Preparation and Macro- and Micromechanical Characterization

The preparation and characterization of the properties of mullite ceramic foams suitable for diesel exhaust filtration systems are described. Two foams of different cell sizes, 32 and 61 ppi (pores per inch), were prepared from slurries by the replication process with polyurethane sponges as the templates. The microstructure and the dependence of the porosity and the mechanical properties on the preparation and resulting foam cell size and normalized density are discussed. In addition the micro- and macromechanical properties have been characterized using instrumented indentation techniques; with sharp (Berkovich) and small spherical-tipped indenters the hardness and modulus of the dense strut materials have been measured. The macroproperties have been measured with a large sapphire indenter, ∼5 mm radius using a load partial-unloading technique. The latter enables the modulus and the contact pressure versus penetration to be measured. These values are compared with traditional bulk measurements for crushing strength and elastic modulus. The results are discussed in terms of available theoretical treatments of the indentation of brittle porous materials.     

Modification of hydrophobic/hydrophilic properties of Vulcan XC72 carbon powder by grafting of trifluoromethylphenyl and phenylsulfonic acid groups

Carbon supports (glassy carbon and Vulcan XC72 powder) were modified by electrochemical and spontaneous grafting of phenylsulfonic acid (PSA) or trifluoromethylphenyl (TFMP) groups via diazonium ion reduction. The effectiveness of the grafting was confirmed electrochemically, by XPS measurements and elemental analyses. The hydrophobic or hydrophilic character of carbon surfaces was evidenced by measuring the contact angles of drops of different liquids (water, ethylene glycol and glycerol) in heptane. The surface energy was calculated and it was found, for example, that spontaneous grafting of a glassy carbon surface by PSA groups led to an increase by a factor 20 of the surface energy compared with an unmodified glassy carbon surface. The study of the grafting of such groups on XC72 carbon powder indicated that a very low grafting ratio (in wt%) led to a significant change in the macroscopic properties of the powder. Thermogravimetric analysis coupled with mass spectroscopy measurements (TGA-MS) showed that these grafted layers were thermally stable even in the presence of dispersed platinum nanoparticles. It was shown by cyclic voltammetry that the carbon substrate modification did not affect the electrochemical behavior of platinum catalyst, since the same active surface area was determined on Pt-XC72, Pt-PSA-XC72 and Pt-TFMP-XC72 catalysts.     

"Cognitive-neuropsychological function in chronic physical aggression and hyperactivity": Correction to Séguin et al. (2004).

Reports an error in "Cognitive-Neuropsychological Function in Chronic Physical Aggression and Hyperactivity" by Jean R. Séguin, Daniel Nagin, Jean-Marc Assaad and Richard E. Tremblay (Journal of Abnormal Psychology, 2004[Nov], Vol 113[4], 603-613). The use of a weighted procedure within SAS PROC GLM inflated F statistics and underestimated standard errors that affected only conclusions from secondary analyses that were drawn about the specificity of working memory effects to physical aggression and hyperactivity. The corrected conclusions are presented in the erratum. The last two sentences of the abstract also needed to be corrected in order to reflect the new conclusions. The corrected sentences appear in the erratum as well. (The following abstract of the original article appeared in record 2004-20178-011.) Histories of violence and of hyperactivity are both characterized by poor cognitive-neuropsychological function. However, researchers do not know whether these histories combine in additive or interactive ways. The authors tested 303 male young adults from a community sample whose trajectories of teacher-rated physical aggression and motoric hyperactivity from kindergarten to age 15 were well defined. No significant interaction was found. In a 1st model, both histories of problem behavior were independently associated with cognitive-neuropsychological function in most domains. In a 2nd model controlling for IQ, general memory, and test motivation, the 3 working-memory tests (relevant to executive function) remained associated with physical aggression, and 1 remained associated with hyperactivity. These results support an additive model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

HIx system thermodynamic model for hydrogen production by the Sulfur–Iodine cycle

The HI_x ternary system (H₂O–HI–I₂) is the latent source of hydrogen for the Sulfur–Iodine thermo-chemical cycle. After analysis of the literature data and models, a homogeneous approach with the Peng–Robinson equation of state used for both the vapor and liquid phase fugacity calculations is proposed for the first time to describe the phase equilibrium of this system. The MHV2 mixing rule is used, with UNIQUAC activity coefficient model combined with of hydrogen iodide solvation by water. This approach is theoretically consistent for HI_x separation processes operating above HI critical temperature. Model estimation is done on selected literature vapor–liquid, liquid–liquid, vapor–liquid–liquid and solid–liquid equilibrium data for the ternary system and the three binaries subsystems. Validation is done on the remaining literature data. Results agree well with the published data, but more experimental effort is needed to improve modeling of the HI_x system.     

Bunsen section thermodynamic model for hydrogen production by the sulfur–iodine cycle

A model for the Bunsen section of the Sulfur–Iodine thermo-chemical cycle is proposed, where sulfur dioxide reacts with excess water and iodine to produce two demixing liquid aqueous phases (H₂SO₄ rich and HI rich) in equilibrium. Considering the mild temperature and pressure conditions, the UNIQUAC activity coefficient model combined with Engels' solvation model is used. The complete model is discussed, with HI solvation by water and by iodine as well as H₂SO₄ solvation by water, leading to a very high complexity with almost hundred parameters to be estimated from experimental data. Taking into account the water excess, a successful reduced model with only 15 parameters is proposed after defining new apparent species. Acids total dissociation and total H⁺ solvation by water are the main assumptions. Results show a good agreement with published experimental data between 25 °C and 120 °C.