Gelcasting of alumina suspensions containing nanoparticles with glycerol monoacrylate

An acrylic monomer of low toxicity containing two hydroxyl groups has been synthesized and used for gelcasting in water. The results have been compared to those achieved with the use of a commercially available monomer (2-hydroxyethyl acrylate). Due to the chemical structure of the synthesized monomer, no addition of the crosslinking agent was necessary for gelation and similar results in terms of rheology of suspensions, density and microstructure of the bodies were obtained with respect to those obtained with the commercial monomer. However, higher time for gelation was observed.Two alumina powders with very different particle sizes were used in this study: a commercial submicron-sized powder (d₅₀ = 0.35 μm) and a nanometer-sized alumina obtained by freeze-drying from aluminum sulphate solutions. The rheological behavior of concentrated suspensions was studied in order to establish their stability and to analyse the effect of the different monomers used in the process. Once the suspensions were optimized, the influence of the size of the powder on the gelation process was studied. The sintered density of submicrometer-sized alumina was higher (99%) than that measured when the bimodal suspension was used due to the difficulty to obtain highly concentrated suspensions from nanometric powder.     

UV spectrophotometry method for the monitoring of galacto-oligosaccharides production

Monitoring the industrial production of galacto-oligosaccharides (GOS) requires a fast and accurate methodology able to quantify, in real time, the substrate level and the product yield. In this work, a simple, fast and inexpensive UV spectrophotometric method, together with partial least squares regression (PLS) and artificial neural networks (ANN), was applied to simultaneously estimate the products (GOS) and the substrate (lactose) concentrations in fermentation samples. The selected multiple models were trained and their prediction abilities evaluated by cross-validation and external validation being the results obtained compared with HPLC measurements. ANN models, generated from absorbance spectra data of the fermentation samples, gave, in general, the best performance being able to accurately and precisely predict lactose and total GOS levels, with standard error of prediction lower than 13 g kg⁻¹ and coefficient of determination for the external validation set of 0.93–0.94, showing residual predictive deviations higher than five, whereas lower precision was obtained with the multiple model generated with PLS. The results obtained show that UV spectrophotometry allowed an accurate and non-destructive determination of sugars in fermentation samples and could be used as a fast alternative method for monitoring GOS production.     

Tape-Casting Performance of Ethanol Slurries for the Processing of Textured PMN–PT Ceramics from Nanocrystalline Powder

The rheological behavior and tape-casting performance of ethanol-based Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PMN–PT) slurries is studied. A nanocrystalline powder obtained by mechanochemical activation was used. Suspensions were prepared up to solid contents of 32 vol%, significantly higher than those usually reported for nonaqueous systems. The feasibility of replacing toxic solvents commonly used for tape casting of functional ferroelectric materials, often toluene, with ethanol is demonstrated. The density, phases and microstructure of the green tapes and sintered ceramics are presented. Cube-shaped templates were successfully aligned during the tape casting for the processing of 〈001〉-textured PMN–PT ceramics by templated grain growth. An effect of the lamination of tape stacks on the template orientation is described.     

Determination of the surface area and porosity of carbon nanotube bundles from a Langmuirian analysis of sub- and supercritical adsorption data

In this paper we revisit the problem of how to obtain reliable information on the porosity and surface area of single-walled carbon nanotube (SWCNT) bundles from adsorption data. We report on adsorption measurements obtained on bundles of high-purity electric-arc nanotubes, with various gases (methane, ethane, ethylene, propane, and propylene) spanning reduced temperatures between 0.8 and 1.6, and pressures from 200 Pa up to 8 MPa, exploring low uptakes as well as multilayering conditions. Using these data we demonstrate the applicability of an analytical procedure for interpreting adsorption isotherms of light alkanes and alkenes on SWCNT bundles in quantitative terms. In particular, its use for the reliable assessment of the surface area and accessible pore volume of the bundles is demonstrated. Our results show that the same set of endohedral sites, as well as the same set of external sites, is available on our sample to all adsorbates investigated. We also show a crossover behavior in endohedral adsorption between the alkene and its saturated counterpart when moving from low pressure to near saturation conditions.     

Signal Integrity Enhancement in Digital Circuits

This article proposes a new methodology for enhancing SoC signal integrity without degrading performance in the presence of power-ground voltage transients. The underlying principle is the dynamic adaptation of the clock duty cycle to propagation delay variation along disturbed logic paths. This methodology makes digital circuits more robust to power line fluctuations while maintaining the at-speed clock rate.     

Monitoring genetically modified soybean along the industrial soybean oil extraction and refining processes by polymerase chain reaction techniques

In the present work, the extraction and detection of DNA along a complete industrial soybean oil processing chain was described to monitor the presence of Roundup Ready^® (RR) soybean. The analysed samples comprised all the steps prior to industrial oil extraction, namely, raw, cracked, laminated and expanded seeds, and the defatted flour as a sub-product. The samples collected at the refining unit included the crude oil, degummed/neutralised, washed, bleached and deodorised oil, as final product. The amplification of soybean lectin gene by end-point polymerase chain reaction (PCR) was successfully achieved in all the steps of extraction and refining processes, until the fully refined soybean oil. The amplification of RR soybean by PCR assays using event-specific primers was also achieved for all the extraction and refining steps, except for the intermediate steps of refining (neutralisation, washing and bleaching) possibly due to sample instability. The real-time PCR assays using specific probes confirmed all the results and proved that it is possible to detect and quantify genetically modified organisms in the fully refined soybean oil. To our knowledge, this has never been reported before and represents an important accomplishment regarding the traceability of genetically modified organisms in refined oils.     

Ochratoxin A removal in synthetic media by living and heat-inactivated cells of Oenococcus oeni isolated from wines

The capacity of Oenococcus oeni to eliminate ochratoxin A (OTA) from synthetic media in different conditions was studied. Ten tested O. oeni strains removed OTA from the medium but with significant differences depending on the strain, incubation period, and initial OTA level in the medium. Mycotoxin reductions higher than 60% were recorded in 14-day cultures spiked with 2 μg OTA/l. Toxin removal was independent of bacterial viability and culture medium composition. This is the first study carried out to study OTA removal dynamics by living and heat-inactivated cells of O. oeni. The results aim that this bacterium may be a very useful tool to control OTA in food and beverages.     

Is ionic dialysance useful for early detection of vascular access dysfunction? Six illustrative cases

Continuous ionic dialysance monitoring is a useful clinical tool to determine the dialysis dose in real time in each hemodialysis session. We followed up 49 patients for 16 months. Six patients with a Kt reduction of ≥20% in >3 consecutive hemodialysis sessions were identified. Fistulography demonstrated significant stenosis in all 6 patients. Angioplasty was performed in 5 with an excellent angiographic result and optimal Kt levels were restored. Unexplained and persistent Kt reduction in patients with stable chronic kidney disease under hemodialysis could represent, together with an accurate vascular access examination, a practical and additional indirect method for the early detection of vascular access dysfunction.     

Phenolic profile of seventeen Portuguese wild mushrooms

Analysis of phenolic compounds in seventeen Portuguese wild mushroom species was carried out by high-performance liquid chromatography coupled to photodiode array detection (HPLC-DAD). Protocatechuic, p-hydroxybenzoic, p-coumaric and cinnamic acid were found and quantified. Fistulina hepatica showed the highest phenolic acids concentration (111.72 mg/Kg, dw) due to the significant contribution of protocatechuic (67.62 mg/Kg) and p-hydroxybenzoic (41.92 mg/kg) acids. The edible mushrooms analysed could be directly used in the human diet to combat oxidative stress, while inedible species could represent a source of extractable phenolic compounds to be used as additives in the food industry or as components in pharmaceutical and cosmetic formulations, due to their well-known antioxidant properties.     

Comparative studies on parametric sensitivity analyses using conventional and factorial design methodologies: mathematical modelling of clavulanic acid adsorption on zeolites

BACKGROUND: The main objective of this work was to evaluate the parametric sensitivity of model parameters of clavulanic acid (CA) adsorption in a stirred‐tank reactor using zeolites. The system sensitivity was evaluated in terms of mass transfer and hydrodynamic parameters using two methodologies. First, the sensitivity factors of input variables were evaluated according to a disturbance of ± 20% in the nominal parameter values; second, the factorial design methodology was employed. In both cases, the responses were obtained by means of model simulations. RESULTS: From the sensitivity analysis by experimental design, the best operational conditions for adsorption of CA on zeolites were solid to liquid percentage 7.0%, initial CA concentration 300 mg L^?1 and particle diameter 0.100 mm, which led to a reduction of 25 min in the adsorption time and 9% in the adsorption capacity, increasing the process productivity. CONCLUSION: The use of the factorial design had advantages compared with the conventional method because it provided information regarding the possibility of simultaneous changes in the factors investigated, enabling analyses of system sensitivity regarding operational parameters, as well as the choice of more suitable parameters. Copyright © 2012 Society of Chemical Industry