Electrochemical characterization of 8-hydroxyquinoline-5-sulphonate/aluminium(III) aqueous solutions

8-Hydroxyquinoline-5-sulphonate/Al(III) aqueous solutions were studied both by potentiometric titrations and voltammetric measurements, in order to obtain the number, the stoichiometry and the stability constants of the complexes formed at equilibrium, and to evaluate the redox and (electro)kinetic properties of the free ligand and of the metal/ligand complexes. The complexes formed in 0.2 m (Na)Cl aqueous solution (stability log beta values ± standard deviation) are AlL⁺ (8.95 ± 0.05), AlL₂⁻ (17.43 ± 0.03) and AlL₃³⁻ (24.58 ± 0.05), where “L” denotes the free ligand in the completely deprotonated form (L²⁻, pK_a1 = 3.910 ± 0.008, pK_a2 = 8.319 ± 0.004). AlL₃³⁻ is the predominant Al(III) species in a very wide range of pH, metal and ligand concentrations and metal-to-ligand ratios. The free ligand shows an oxidation wave at 0.62 V versus SCE. The proposed oxidation mechanism includes a first reversible one-electron oxidation of the ligand, followed by a coupling reaction and by a second reversible one-electron oxidation, and finally by a decomposition reaction. The addition of Al(III) lowers the intensity of the oxidation wave due to the formation of the redox-inactive complex AlL₃³⁻. A residual low signal was attributed to the free ligand produced by the complex dissociation, AlL₃³⁻ = AlL₂⁻ + L²⁻. All the kinetic parameters involved in the ligand oxidation and in the complex disruption were calculated on the basis of the agreement between experimental and simulated linear sweep and cyclic voltammetries. Correctness of the mechanisms proposed was further confirmed “a posteriori” by the agreement between potentiometric and linear sweep voltammetric results. The low residual signal observed in the presence of fully formed complex was attributed to the free ligand produced by the complex dissociation, having a kinetic constant estimated 0.2 s⁻¹.     

Heat Induced Structure Modifications in Polymer‐Layered Silicate Nanocomposites

Summary: The success of the use of layered silicates in polymer nanocomposites, to improve physical and chemical properties is strictly related to a deeper knowledge of the mechanistic aspects on which the final features are grounded. This work shows the temperature induced structural rearrangements of nanocomposites based on poly[ethylene‐co‐(vinyl acetate)] (EVA) intercalated‐organomodified clay (at 3–30 wt.‐% silicate addition) which occur in the range between 75 and 350 °C. In situ high temperature X‐ray diffraction (HT‐XRD) studies have been performed under both nitrogen and air to monitor the modifications of the nanocomposite structure at increasing temperatures under inert/oxidative atmosphere. Heating between 75 and 225 °C, under nitrogen or air, causes the layered silicate to migrate towards the nanocomposite surface and to increase its interlayer distance. The degradation of both the clay organomodifier and the VA units of the EVA polymer seems to play a key role in driving the evolution of the silicate phase in the low temperature range. The structural modifications of the nanocomposites in the high temperature range (250–350 °C), depended on the atmosphere, either inert or oxidizing, in which the samples were heated. Heating under nitrogen led to deintercalation and thus a decrease of the silicate interlayer space, whereas exfoliation was the main process under air leading to an increase of the silicate interlayer space.

Heat induced structural modification of EVA‐clay nanocomposite under nitrogen and air.     

The effects of time-compressed instruction and redundancy on learning and learners’ perceptions of cognitive load

Can increasing the speed of audio narration in multimedia instruction decrease training time and still maintain learning? The purpose of this study was to examine the effects of time-compressed instruction and redundancy on learning and learners’ perceptions of cognitive load. 154 university students were placed into conditions that consisted of time-compression (0%, 25%, or 50%) and redundancy (redundant text and narration or narration only). Participants were presented with multimedia instruction on the human heart and its parts then given factual and problem solving knowledge tests, a cognitive load measure, and a review behavior (back and replay buttons) measure. Results of the study indicated that participants who were presented 0% and 25% compression obtained similar scores on both the factual and problem solving measures. Additionally, they indicated similar levels of cognitive load. Participants who were presented redundant instruction were not able to perform as well as participants presented non-redundant instruction.     

Evaluation of the corrosion inhibition of salts of organic acids in alkaline solutions and chloride contaminated concrete

This paper summarizes the results of testing on salts of organic acids for evaluating their use as inhibitors of rebar corrosion in chloride‐contaminated concrete. Initially a screening based on electrochemical tests in alkalinized calcium hydroxide solutions was performed on a number of carboxylic acid salts with different number of carbon atoms in the chain and carboxylic groups, also covering substances with hydroxyl and amine group substituents. The screening was completed by testing on carbon steel rebars in concretes with chlorides and substances added at 1:1 molar ratio, focused on sodium lactate, sodium oxalate and sodium borate for comparison. The monitoring of free corrosion potential and linear polarization resistance of steel bars have confirmed significant inhibition only for lactate. Corrosion was only restricted to occluded zones where the access of substance was limited by disadvantageous geometry, producing shallow attacks. Results of further tests in saturated calcium hydroxide solution are reported in order to assess the inhibition ability of lactate as a function of its content, chloride content and pH.     

Dual-Function Semaphorin 4D Released by Platelets: Suppression of Osteoblastogenesis and Promotion of Osteoclastogenesis

Effects of the antiosteoblastogenesis factor Semaphorin 4D (Sema4D), expressed by thrombin-activated platelets (TPs), on osteoblastogenesis, as well as osteoclastogenesis, were investigated in vitro. Intact platelets released both Sema4D and IGF-1. However, in response to stimulation with thrombin, platelets upregulated the release of Sema4D, but not IGF-1. Anti-Sema4D-neutralizing monoclonal antibody (mAb) upregulated TP-mediated osteoblastogenesis in MC3T3-E1 osteoblast precursors. MC3T3-E1 cells exposed to TPs induced phosphorylation of Akt and ERK further upregulated by the addition of anti-sema4D-mAb, suggesting the suppressive effects of TP-expressing Sema4D on osteoblastogenesis. On the other hand, TPs promoted RANKL-mediated osteoclastogenesis in the primary culture of bone-marrow-derived mononuclear cells (BMMCs). Among the known three receptors of Sema4D, including Plexin B1, Plexin B2 and CD72, little Plexin B2 was detected, and no Plexin B1 was detected, but a high level of CD72 mRNA was detected in RANKL-stimulated BMMCs by qPCR. Both anti-Sema4D-mAb and anti-CD72-mAb suppressed RANKL-induced osteoclast formation and bone resorptive activity, suggesting that Sema4D released by TPs promotes osteoclastogenesis via ligation to a CD72 receptor. This study demonstrated that Sema4D released by TPs suppresses osteogenic activity and promotes osteoclastogenesis, suggesting the novel property of platelets in bone-remodeling processes.     

Contribution of Response Surface Design to the Synthesis of Monoacylglycerols Catalyzed by Rhizopus sp. lipase

The partially purified lipase from Rhizopus sp was tested as a biocatalyst for the synthesis of monolaurin from lauric acid and glycerol. A central composite rotatable design was applied to optimize the substrate molar ratio and the percentage of molecular sieve for achieving maximum monolaurin yield. The best results were obtained when the molar ratio of substrates was 1:1, the medium contained 100% (w/w) molecular sieve, and the reaction was conducted at 50 °C and 200 rpm applying 2 mg of the partially purified lipase. The maximum yield in monolaurin (17.52%) was achieved after a 72‐h reaction.     

Cellular distribution of pulmonary Mn and CuZn superoxide dismutase: effect of hyperoxia and interleukin-1

Pulmonary superoxide dismutase (SOD) plays an important role in the lung defense against O2 toxicity. We have previously demonstrated that tracheal insufflation of interleukin-1 alpha (IL-1) selectively enhances pulmonary MnSOD and protects rats against O2 toxicity. However, little is known about the cellular distribution of pulmonary MnSOD- and CuZnSOD-specific proteins. We performed immunohistochemistry in plastic sections (2 microns thick) to determine the effects of hyperoxia and IL-1 on the cellular distribution of pulmonary MnSOD and CuZnSOD in rats. MnSOD and CuZnSOD were present in all lung cells. Smooth muscle and endothelial cells appeared to contain higher immunoreactive MnSOD and CuZnSOD proteins than other lung cell types. Exposure of rats to 100% O2 for 24 hr had no effect on the cellular distribution and intensity of pulmonary MnSOD. However, at 50 hr after O2 exposure the intensity of pulmonary MnSOD was reduced. In contrast, tracheal insufflation of IL-1 markedly enhanced the intensity of pulmonary MnSOD in rats exposed to O2 for 50 hr. Neither O2 exposure nor IL-1 insufflation had any apparent effect on the distribution and intensity of pulmonary CuZnSOD. We conclude that IL-1 selectively enhances pulmonary MnSOD and that this effect is manifested in most lung cells, particularly smooth muscle and endothelial cells.     

Surface acidity of novel mesostructured silicas with framework aluminum obtained by SBA-16 related synthesis

A novel SBA-16-related synthesis of mesostructured silica containing framework aluminum is reported here. This material was successfully synthesized using aluminum sulphate and the pH-adjusting method. The structural and porosity properties of this novel material were studied by X-ray diffraction and N₂ adsorption at 77 K. The Al insertion was determined by ²⁷Al-MAS-NMR and the acidity was monitored by infrared spectroscopy of CO adsorption at 100 K.