The Energy-Band Structure of Porous Silicon Studied with Photoluminescence Excitation and Photoacoustic Spectroscopy

Porous silicon has been studied with photoluminescence, photoluminescence excitation, and photoacoustic spectroscopy. From the luminescence data, an energy-level diagram related to the luminescence is constructed. The diagram is confirmed in detail by the photoacoustic spectra. The results are discussed with the conclusion that they are in good agreement with the surface-band oxyhydride-like emitter, which recently has been established as the source for the photoluminescence from porous silicon.     

Method development and validation for isoflavones quantification in coffee

This paper reports the development and validation of an analytical method to quantify three isoflavones (daidzein, genistein and formononetin) in coffee beans and coffee brews, by HPLC with diode-array detection. The aglycones were released by methanolic acid hydrolysis in the presence of the antioxidant BHT and the internal standard 2′-methoxyflavone. The method showed high correlation coefficients (r > 0.999) for standards subjected to the entire procedure. For samples, good intra- and inter-day precisions (<8%), and accuracies (recoveries of 95 ± 1% for ground coffee and 92 ± 2% for coffee brew) were achieved. Detection and quantification limits ranged from 5 to 8 ng/mL and from 14 and 25 ng/mL, respectively. The proposed method proved to be sensitive, precise and accurate.     

Flow Synthesis of a Thiazolidine Drug Intermediate in Capillary Microreactors

Microreactor technology can help to reduce the time to market new drugs. It was applied to produce (Z)‐5‐benzylidenethiazolidine‐2,4‐dione, a heterocyclic intermediate in the synthesis of various drugs. Ethanol was the optimum solvent and piperidine the best catalyst in the batch process. The continuous/microreactor process exhibited a much better performance than the batch process. The productivity, which was strongly influenced by solvent and temperature, reached a maximum at 160 °C using methanol as solvent. A kinetic/thermodynamic study indicated that the reaction followed the second‐order model and allowed estimating its main thermodynamic parameters. A product recovery protocol was finally proposed. The microreactor proved an efficient alternative to the batch reactor in scaling up the production of active pharmaceutical ingredients.     

Oral degradation of Y-TZP ceramics

The aim of this work was to study the degradation of yttria-stabilized tetragonal zirconia (Y-TZP) directly exposed to the oral environment. Four groups of Y-TZP were tested G1: TZ-PX-242A, Zpex^®; G2: TZ-PX-357, Zpex Yellow^®; G3: ProtMat^®, and G4: LAVA Frame^®. The samples were attached to the base of temporary full dentures of patients and aged for 100 days. In this way, one surface of the samples was exposed to the oral environment. The samples (25?×?2?×?1.5?mm) were cut from noncommercial (G1 and G2) and commercially available (G3 and G4) presintered zirconia blocks. Quantitative and qualitative analyses were performed by X-ray fluorescence (XRF). Microstructural characterization was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), 3D surface roughness measurements and grain size measurements. The mechanical properties were determined by a four-point bending test. The data were analyzed by one-way ANOVA (p?≤?0.05), Tukey's test and Weibull analysis. The results showed a tetragonal-monolithic transformation in the zirconia after oral aging. The surface roughness increased in all groups, and groups G3 and G4 showed increases in their flexural strengths.     

Joining sheets perpendicular to one other by sheet-bulk metal forming

This paper presents a variant of the traditional ‘mortise-and-tenon’ joint, which has been used for thousands of years by carpenters and blacksmiths to connect wood or metal parts. The new proposed joint is utilized to fix longitudinally in position two metal sheets (or plates) perpendicular to one other by sheet-bulk metal forming, at room temperature. The development is performed by means of a combined finite element and experimental investigation focused on the identification of the major process parameters and on the understanding of their influence on the overall joining feasibility. Destructive testing is carried out to characterize the performance of the new proposed joint, and an analytical expression is provided to determine the maximum tensile force that the joint can safely withstand.     

Use of Allyl Isothiocyanate‐containing Sachets to Reduce Aspergillus flavus Sporulation in Peanuts

Peanuts are oilseed crops that are frequently infected by fungi (including Aspergillus flavus) that may produce aflatoxin, a highly carcinogenic mycotoxin. Conventional food packaging techniques can only prevent aflatoxin production to a certain extent. Therefore, the development of novel active packaging strategies to control post‐harvest sporulation by A. flavus is important. Essential oils from plants have antimicrobial potential, and one of the most powerful components is allyl isothiocyanate (AITC), the major component of mustard essential oil. Here, we aimed to evaluate the antifungal effect of AITC against A. flavus, develop an AITC‐containing sachet to control A. flavus sporulation in peanuts and quantify residual AITC in grains and package headspaces during a 90 day period. Diffusion and volatile susceptibility tests showed the in vitro effectiveness of AITC at 0.215 ppb against A. flavus. Because in vitro and real food assays may provide distinct antimicrobial efficiencies due to different compositions, sachets incorporated with AITC were stored with peanuts for 90 days at 25°C. A 10‐fold reduction in A. flavus survival was observed in 1 week, and after 60 days, survival was reduced by 4.81 log cycles. No residual AITC was detected in grains throughout the storage period, whereas volatile AITC within the package headspaces decreased with time: 92.4% of volatile AITC was reduced within the first 15 days, and AITC was no longer detected after 30 days. We proved that AITC retards A. flavus sporulation and that sachets are a promising delivery system for AITC to act as an antimicrobial agent for peanuts. Copyright © 2014 John Wiley & Sons, Ltd.     

Assessment on the performance of distinct stress integration algorithms for complex non-quadratic anisotropic yield criteria

In this work, three distinct return mapping algorithms are presented and analyzed in detail: (i) a semi-explicit algorithm that accounts for the sub-incrementation technique, which reduces to (ii) a fully-explicit algorithm and, finally, (iii) a semi-implicit algorithm,. In order to describe the complex anisotropic behaviour of some metals, such as aluminium alloys, two non-quadratic anisotropic yield criteria were implemented: the Yld91 and Yld2004-18p. The performance of the developed algorithms is inferred in a series of sheet metal forming benchmarks and the quality of the results is assessed when compared to experimental results presented in the literature. The numerical simulations show that the semi-implicit algorithm is quite efficient with the von Mises yield criterion. However, when anisotropy is taken into account, the algorithm requires several iterations to return the stresses to the yield surface, particularly when the stresses are located at corner regions of that surface. The semi-explicit algorithm proved to be the most robust and efficient algorithm with anisotropic yield criteria. The good agreement between the experimental data and the obtained numerical results demonstrate the high efficiency of the presented algorithms and the ability of the anisotropic criteria to predict the material’s complex anisotropic behaviour.