Application of ATR-FTIR for a rapid and simultaneous determination of sugars and organic acids in apricot fruit

A simple, fast and accurate Fourier transform mid-infrared spectroscopy method was developed for simultaneously determining sugar and organic acid contents in apricot fruit slurries using the attenuated total reflectance. The potential of this method coupled with chemometric techniques based on partial least squares was assessed by comparison with currently used enzymatic determination of sucrose, glucose, fructose, malic acid and citric acid. Fruits of eight contrasted cultivars harvested at different ripening stages were used in this study and randomly divided in a calibration set (505 apricots) and in a validation set (252 apricots). The most suitable region was found in the range between 1500 and 900 cm⁻¹. Good prediction performances were obtained (R² ? 0.74 and RMSEP ? 18%). Results concerning the prediction of other quality traits such as firmness, skin colour, ethylene production, soluble solids content and titratable acidity were discussed.     

Neutronic characterization of the MEGAPIE target

The MEGAPIE project aimed to design, build and operate a liquid metal spallation neutron target of about 1 MW beam power in the SINQ facility at the Paul Scherrer Institut (Villigen, Switzerland). This project is an important step in the roadmap towards the demonstration of the accelerator driven system (ADS) concept and high power liquid metal targets in general. Following the design phase, an experimental program was defined to provide a complete characterization of the facility by performing a “mapping” of the neutron flux at different points, from the center of the target to the beam lines. The neutronic performance of the target was studied using different experimental techniques with the goals of validating the Monte Carlo codes used in the design of the target; additionally, the performance was compared with the solid lead targets used before and after the MEGAPIE experiment.     

Comprehensive study of the influence of total pressure on products yields in fluidized bed gasification of wood sawdust

Wood sawdust gasification experiments were performed in a steam fluidized bed at 800 °C between 2 and 10 bar. An evolution of gas yields with time was measured during the tests, and especially an increase of hydrogen and carbon dioxide yields. This test duration effect was ascribed to char build-up in the bed. As tests proceed, the contribution of char steam gasification to gas yield increases, and the catalytic effect of char on hydrocarbons and tar conversion and on water-gas shift reaction is enhanced.As total pressure increases from 2 to 10 bar, hydrogen, carbon dioxide and methane yields increase by 16%, 53% and 38% respectively, whereas carbon monoxide yield decreases by 33%. The changes in gaseous yields with pressure can be partly explained by the influence of pressure on gas phase reactions (acceleration of water-gas shift kinetics and change in hydrocarbon reactions). The increase of methane yield with pressure is rather suggested to be linked to a change in secondary pyrolysis reactions scheme under high pressure.     

Influence of H2/NH3 mixtures on the composition of SiCNYO and SiCNAl(O) nanopowders

We performed pyrolysis of SiCNAlH and SiCNYOH nanopowder precursors under a reactive atmosphere (Ar/NH₃/H₂) with various compositions of ammonia (NH₃) and dihydrogen (H₂) to diminish C content, which is deleterious for thermal stability and sintering of the powders. This paper continues a previous work on the fabrication of an Si₃N₄/SiC composite without free C by studying the effect of H₂ on the C/N atomic ratio of the powder. We studied the influence of the nature of the gaseous mixture (Ar/NH₃/H₂) on the powder composition. Elemental analysis showed that the introduction of H₂ in the pyrolysis atmosphere limited the decomposition of NH₃ and allowed for control of the C/N ratio. This behaviour can be explained by the structural evolution observed by ²⁹Si NMR spectrometry but also by Fourier transform infrared and Raman spectroscopy. An Si₃N₄/SiC composite, with traces of free C, was obtained after post-pyrolysis heat treatment of the powders synthesized with 10 wt.% of H₂ and 25 wt.% NH₃.     

Iron oxide magnetic nanoparticles used as probing agents to study the nanostructure of mixed self-assembled monolayers

Self-assembled monolayers (SAMs) of organic molecules are of exceptional technological importance since they represent a convenient, flexible, and simple system for tuning the chemical and physical properties of surfaces. The fine control of surface properties is directly dependent on the structure of mixed SAMs which is difficult to characterize at the nanoscale with usual techniques such as scanning probe microscopies. In this study, we report on a general method to investigate at the nanoscale the structure of molecular patterns which consist in SAMs of two components. Iron oxide nanoparticles (NPs) have been used as probing agents to study indirectly the structure of mixed SAMs. Mixed SAMs were prepared by the replacement of mercaptododecane (MDD) adsorbed by mercaptoundecanoic acid (MUA) molecules on gold substrates. Therefore, the SAM surface displays both chelating carboxylic terminal groups and non-chelating methylene terminal groups. As NPs have been previously demonstrated to specifically interact with carboxylic acid groups, the increasing density in NPs was correlated with the evolution of the COOH/CH(3) terminal groups ratio. Therefore the structure of mixed SAMs was studied indirectly as well as the kinetic of the replacement reaction and its mechanism. With this aim, we took advantage of the SPR properties of the gold substrate and of the high refractive index of iron oxide nanoparticles to follow their assembling on mixed SAMs as a time resolved study. The high sensitivity and tuning of the SPR signal over a wide range of wavelengths are correlated with the NP density. Furthermore, SEM combined with image analysis has allowed studying the replacement rate of MDD by MUA in SAMs. We took also advantages of the magnetic properties of NPs to evaluate qualitatively the replacement of thiol molecules.     

Insight into β-Carotene Thermal Degradation in Oils with Multiresponse Modeling

The aim of this study was to gain further insight into β-carotene thermal degradation in oils. Multiresponse modeling was applied to experimental high-performance liquid chromatography–diode array detection (HPLC–DAD) data (trans-, 13-cis-, and 9-cis-β-carotene concentrations) during the heat treatments (120–180 °C) of two β-carotene-enriched oils, i.e., palm olein and copra. The test of different reaction schemes showed that β-carotene isomerization reactions were dominant and reversible. The resulting cis isomers and trans-β-carotene simultaneously underwent oxidation and cleavage reactions at the same rate constant. From the kinetic analysis, it appeared that—contrary to oxidation and cleavage reactions—isomerization rate constants did not follow the Arrhenius law. However, the isomerization equilibrium constant increased with temperature, favoring isomer production, particularly 9-cis-β-carotene. Its production was shown to be concomitant with oxidation and cleavage reactions, indicating that 9-cis-β-carotene could be a good degradation indicator during oil storage or processing.     

Gas environment effect on cavitation damage in stretched polyvinylidene fluoride

The influence of gas sorption on damage nucleation of a semicrystalline polymer during coupled diffuso‐mechanical monotonic loading in tension was investigated for the first time. Alpha‐poly(vinylidene fluoride) was mechanically strained under the presence of two chemically different gases, hydrogen and carbon dioxide, at a temperature of 30°C and a pressure up to 120 bar. The cavitation damage at the microstructure scale after gas decompression was assessed from a careful SEM and TEM micrographs analysis. Compared with SEM, TEM allowed quantifying the smallest cavities (ten‐nanometer size). If decompression in hydrogen appeared to have only a slight effect on cavitation however, carbon dioxide showed a detrimental effect on damage nucleation with the exhibition of a significant population of small cavities. On the other hand, tension under gas pressure is more sensitive to hydrogen than to carbon dioxide. Once interaction with gaseous carbon dioxide takes place the plasticizing effect is in competition with damage by cavitation. POLYM. ENG. SCI., 54:2139–2146, 2014. © 2013 Society of Plastics Engineers     

Phase structure and mechanical properties of PP/EPR/CaCO3 nanocomposites: Effect of particle's size and treatment

Calcium carbonate (CaCO₃) reinforced polypropylene/ethylene propylene rubber (PP/EPR) copolymer composites for automotive use were developed by means of extrusion and injection molding process. Three kinds of CaCO₃ (stearic acid treated and untreated) nanoparticles and microparticles were used as fillers. The influence of stearic acid, particle size, and filler content on the state distribution and morphology were investigated by SEM and rheological measurements. Two different morphologies were observed: EPR and CaCO₃ dispersed in the PP matrix and a core shell structure, depending on the interactions between EPR and CaCO₃. Toughening mechanisms and mechanical properties of the different systems were investigated. Significant improvement in tensile modulus is observed in all composites, depending on filler content. Elongation and notched impact strength were drastically decreased, especially for composites with nano CaCO₃. Better impact properties were obtained with low content of treated particles, showing the importance of filler treatment. POLYM. ENG. SCI., 55:2859–2868, 2015. © 2015 Society of Plastics Engineers