Laser surface nanostructuring for reliable Si3N4/Si3N4 and Si3N4/Invar joined components

IR pulsed laser radiation in air was applied to Si₃N₄ and Invar to obtain reliable Si₃N₄/Si₃N₄ and Si₃N₄/Invar adhesive bonded components. The laser pre-treatment produced a homogeneous nanostructured oxide layer on the surfaces, which effectively increased the adhesion at the adhesive/adherends interface and led to cohesive failure in the joining material. The mechanical strength of Si₃N₄/ Si₃N₄ and Si₃N₄/Invar joined components was measured, with and without laser nanostructuring, before and after thermal cycling from room temperature to 50?K, and it resulted that the exposure to extremely low temperatures did not affect the mechanical integrity of the joints. It was also demonstrated that this laser pre-treatment did not alter the mechanical properties of the ceramic substrate.     

Plant-Growth Inhibitory Activity of Cedrelanolide from Cedrela salvadorensis

The effect of cedrelanolide, the most abundant limonoid isolated from Cedrela salvadorensis (Meliaceae), was assayed as a plant-growth inhibitory compound against monocotyledonous and dicotyledonous seeds. This compound inhibited germination, seed respiration, and seedling dry weights of some plant species (Lolium multiflorum, var. Hercules, Triticum vulgare, var. Salamanca, Physalis ixocarpa, and Trifolium alexandrinum). Our results indicate that cedrelanolide interferes with monocot preemergence properties, mainly energy metabolism of the seeds at the level of respiration. In addition, the compound inhibits photophosphorylation, H⁺ uptake, and noncyclic electron flow. This behavior might be responsible for its plant-growth inhibitory properties and its possible role as an allelopathic agent.     

An octaethylene glycol monododecyl ether-based mixed micellar assay for determining the lipid acyl hydrolase activity of patatin

Patatin was extracted from potato tubers (Solanum tuberosum L. cv. Spunta) and purified to homogeneity by ammonium sulfate salt fractionation and one sole chromatographic step. A spectrophotometric mixed micellar assay for patatin lipid acyl hydrolase (LAH) activity was designed with the detergent octaethylene glycol monododecyl ether (C₁₂E₈). Patatin LAH used p-nitrophenyl butyrate (PNP-butyrate) as substrate when solubilized in (C₁₂E₈) micelles. In the mixed micellar system, patatin LAH responds to the PNP-butyrate surface concentration expressed as mol% (=[PNP-butyrate]·100/([detergent]-critical micellar concentration)) and not to the molarity of PNP-butyrate. The kinetic parameters were determinined; V _max was independent of the mixed micelle concentration, as was K _m, when expressed as mol%. However, K _m was dependent on C₁₂E₈ concentration when expressed in molar concentration. C₁₂E₈/PNP-butyrate proved to be a reliable system for assaying patatin LAH activity and is superior to the commonly used Triton X-100 and SDS methods. It permits investigation of the substrate requirements of patatin LAH activity because the concentration-independent K _m can be determined both in mol% and as the absolute number of substrate molecules per micelle. In addition, the detergent did not affect the enzyme activity.     

Functionalized polyglycidol-CuCl-complexes as catalysts in the oxidative coupling reaction of terminal acetylenes

Summary Novel hyperbranched amino-terminated polyglycidoles have been synthesized and tested as macromolecular ligands in the oxidative coupling reaction of phenylacetylene. Amino-terminated polyglycidoles-CuCl complexes showed to be more effective catalysts than the reference monomeric tertiary amines-CuCl ones, but less effective than the most efficient N,N,N'N'-tetramethylethylenediamine-(TMDA) CuCl complex. The difference in performance of monomeric and hyperbranched ligands is probably due to two factors. The first one is better complexation abilities and the second is the local increase of reagent concentration. Received: 28 April 2001/Revised version: 29 August 2001/Accepted: 5 September 2001     

Benzodioxoles as alternative coinitiators for radical polymerization in a model‐dental adhesive resin

This study evaluated the effectiveness of benzodioxole derivatives as coinitiators of radical polymerization in a model‐dental adhesive resin. To compose the adhesive resin, a monomer mixture based on 50 wt % of Bis‐GMA, 25 wt % of TEGDMA, and 25 wt % of HEMA was used. Camphorquinone (CQ) 1 mol % was used as a photoinitiator to initiate polymerization. 1,3‐Benzodioxole (BDO) and piperonyl alcohol (PA) were used as coinitiators at 0.25, 0.5, 1, 2, 4, 8, and 16 mol % level. In addition, tertiary amine, ethyl 4‐dimethylamino benzoate (EDAB) was used as coinitiator in the control group. Some physical, chemical, and mechanical properties of the polymer formed in the experimental adhesives were evaluated using the kinetics of polymerization, sorption and solubility, flexural strength, and elastic modulus tests. The results indicated that BDO and PA were effective coinitiators in the photoinitiator system based on CQ. Comparisons between the benzodioxoles derivative coinitiators and EDAB showed similar performance in the kinetics of polymerization and flexural strength. For water sorption and solubility evaluation, BDO and PA demonstrated significantly more sorption of water and less solubility than the EDAB control group. The findings suggest that BDO and PA were feasible alternatives to conventional amine as coinitiator. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Anti-fog chitosan/sodium lauryl ether sulfate films

The aim of this study was the preparation and characterization of hydrophobic–hydrophilic chitosan films obtained through interaction between the cationic biopolymer, chitosan (CH), with sodium lauryl ether sulfate (SLES), an anionic surfactant, which has also nonionic surfactant properties. The chitosan flat films were obtained at different concentrations of SLES, in the range of 0.02–0.1 M, where spherical capsules were also obtained. The wettability, quantified by the values of contact angle, indicated the hydrophobic character of the films. The significant values of swelling capacity in water, and in 1 % acetic acid solution confirmed the hydrophilic character of the obtained films. Weight loss of CH/SLES films after 24 h, in water and 1 % acetic acid solution was less than 3 % for the all samples. The structure of CH/SLES complex was determined by FTIR spectroscopy method. The morphology of CH/SLES film surfaces determined by atomic force microscopy showed a film surface with nanoroughness structure, determined by the SLES self-assembled nanostructures. The obtained CH/SLES films are transparent and have anti-fogging properties, compared with CH/sodium lauryl sulfate film, which is also transparent but, it gets fogged when coming in contact with warm air.     

Hybrid MCM-41 grafted by a general microwave-assisted procedure: a characterization study

Hybrid materials obtained through a Microwave-assisted grafting of organic functional groups on mesoporous silica (MCM-41 type) have been characterized by X-ray powder diffraction, TG-DSC, N₂ adsorption, solid state ¹³C- and ²⁹Si-NMR, TEM and SEM. The studied grafting procedure is effective in the preparation of hybrid organosilicas under solvent-free conditions. Microwaves allows an ultra-fast and clean functionalization of the mesoporous materials and the method has been applied to produce a wide series of functional materials. The hybrid materials maintain the original mesoporous structure when the loading of linked organic groups does not exceed 10 %. In this cases, the slight pore volume reduction is linearly correlated to the organic amount in the product. If functional groups able to interact among them through hydrogen bond are used, hybrid materials exhibit high Organic/SiO₂ ratios and low pore volumes due to the formation of a network occluding the pores, where functional groups of free organosilane molecules interacts with the functional groups of molecules linked to the matrix. NMR data confirm that the network is composed by organosilane molecules linked or not to the framework. Acid washing is able to labilize hydrogen bond and open the network. In the case of bulky but chemically inert functionalising agents the network is not produced.     

Viability of a native isolate of Lactobacillus brevis in a fermented milky drink

The objective of this research was to test the viability of a native isolate of Lactobacillus brevis in two fermented milky drinks: a drink without prebiotic ingredient and another drink with oat flour (0.5%, p/v) as prebiotic ingredient. The viability of L. brevis was tested at 7, 14, and 21 after inoculation. Drink pH and lactic acid concentration was measured as a function of time (2, 7, 14, and 21 days after inoculation). The isolate was viable in both drinks because its counting plates was higher than 10(6) CFU/mL until day 21st. Between the 7th and 14th day, the rate of growth was higher in the drink that included oat flour, however, at the day 21st the colony density was similar in both drinks.     

Impact of tire debris on in vitro and in vivo systems

Background  

It is estimated that over 80% of respirable particulate matter (PM₁₀) in cities comes from road transport and that tire and brake wear are responsible for the 3–7% emission of it. Data on the indicators of environmental impact of tire debris (TD), originated from the tire abrasion on roads, are extremely scarce, even though TD contains chemicals (zinc and organic compounds) which can be released in the environment.     

Optical,Morphological, and Structural Properties of Tablets Obtained from Porous Silicon

Silicon - Porous silicon (PS) is a material with a great interest due to its optical (photoluminescent) and chemical (reactive surface) properties, for this reason, it is important to find new ways...