Ultrafast nonlinear sub-wavelength solid immersion spectroscopy at T = 8 K: an alternative to nonlinear scanning near-field optical microscopy

Pump–probe measurements were performed with a sub-wavelength spatial resolution of 355 nm and a temporal resolution of 130 fs in a multiple quantum well sample at T  = 8 K. A solid immersion lens was used to increase the spatial resolution to 0.41 λ, demonstrating that the limit of conventional microscopy was surpassed.     

The influence of formulation and processing parameters on the thermal properties of a chitosan–epoxy prepolymer system

Waterborne epoxy dispersions have been employed effectively for many years in response to environmental regulations aimed at reducing solvent levels in coatings. Very few non‐toxic bio‐based polyamines have been reported in the literature as curing agents for epoxy‐functional waterborne dispersions. Currently to our knowledge the only bio‐based amino hardener used to cure a waterborne epoxy prepolymer is ?‐polylysine. Being one of the rare primary amine‐containing polymers of natural origin, chitosan is produced commercially by the deacetylation of chitin. In the work reported here, chitosan and oligochitosan were evaluated as curing agents for diepoxy prepolymers. A solvent‐free prepolymer (Epotec) and a waterborne prepolymer dispersion (Epirez) were both used. A crosslinked network was obtained when the reaction was performed with the waterborne epoxy dispersion. The influence of the hardener‐to‐epoxy prepolymer ratio on the crosslinking density was investigated. The thermal properties of networks were measured using differential scanning calorimetry and thermogravimetric analysis. © 2013 Society of Chemical Industry     

Modeling of Ethylene Glycol Production from Glucose in a Semi-Continuous Reactor

A numerical study describes the catalytic conversion of glucose into ethylene glycol (EG) in a semi-batch reactor. This analysis couples a set of power law models (homogeneous reactions) and Langmuir-Hinshelwood-Hougen-Watson (LHHW) equations (hydrogenations). For this purpose, the kinetic parameters of the LHHW expressions are estimated for the reaction conditions. Then, the kinetic model evaluates the influence of the H₂ pressure and the catalyst concentrations on the selectivity. The results indicate that the EG yield is increased by setting the temperature and the H₂ pressure. In this manner, the process reduces the hexitols and methane production and increases the EG yield. The originality of the work is based on the influence of the H₂ pressure and the catalyst concentrations in the model.     

Low-temperature, mineral-catalyzed air oxidation: a possible new pathway for PAH stabilization in sediments and soils

Reactivity of polycyclic aromatic hydrocarbons (PAHs) in the subsurface is of importance to environmental assessment, as they constitute a highly toxic hazard. Understanding their reactivity in the long term in natural recovering systems is thus a key issue. This article describes an experimental investigation on the air oxidation of fluoranthene (a PAH abundant in natural systems polluted by industrial coal use) at 100°C on different mineral substrates commonly found in soils and sediments (quartz sand, limestone, and clay). Results demonstrate that fluoranthene is readily oxidized in the presence of limestone and clay, leading to the formation of high molecular weight compounds and a carbonaceous residue as end product especially for clay experiments. As demonstrated elsewhere, the experimental conditions used permitted the reproduction of the geochemical pathway of organic matter observed under natural conditions. It is therefore suggested that low-temperature, mineral-catalyzed air oxidation is a mechanism relevant to the stabilization of PAHs in sediments and soils.     

Scaling laws for a buoyant release used to simulate fire-induced smoke in laboratory experiments

This paper presents and discusses some scaling laws which have to be considered within the framework of fire-induced smoke simulation using a buoyant release at lower scale. The correspondences between the fire and the buoyant release are supposed known and then, for a size reduction, dimensionless numbers are obtained from the buoyant jet momentum equation. It then appears, theoretically, that the single Froude similitude used in many laboratory experiments is inadequate for fire problems when the Boussinesq approximation cannot be considered. Indeed, in that case, the density difference between the released fluid and the ambient fluid has to be the same for both full and reduced scales. An alternative theoretical justification is also proposed from considerations on the source parameter Γ_i.     

Architecture and phases composition of suspension plasma sprayed alumina-titania sub-micrometer-sized coatings

Sub-micrometer-sized Al₂O₃-TiO₂ plasma-sprayed coatings exhibit superior performances compared to micrometer-sized ones. Two routes can be implemented to manufacture such finely structured coatings: i) spraying micrometer-sized agglomerates of nanometer-sized particles which results in a two-scale coating architecture and ii) spraying a suspension of sub-micrometer-sized particles (suspension plasma spraying, SPS). SPS was implemented in this study and Al₂O₃-base coatings with 13 and 60 wt.% of titania, respectively, were manufactured by spraying a suspension made of a mixture of Al₂O₃ and TiO₂ particles both of 300 nm, average diameter. Coating structural features and phase contents were studied. Results show that the coatings exhibit a very fine lamellar structure with a homogeneous repartition of Al and Ti. Complex phases, made of intermediate Al, Ti, and O oxides, have been also identified. Indeed, coatings formation results from rapid solidification rates and high transient thermal fluxes imparted by the plasma flow to the substrate due to the short spray distance encountered in SPS (in the order of 30 mm) requested by the small kinetics and thermal inertia of sub-micrometer-sized particles.     

Light and heavy water dynamic structure factor for neutron transport codes

In this study, we report on recent neutron inelastic scattering experiments performed at the Institut Laue-Langevin (ILL) for H₂O and D₂O. The measured dynamic structure factors S(q, ω) have been reduced, normalised and transformed into the S(α, β) formalism, where α and β stand for the unit-less momentum and energy transfers, respectively. The measurements were complemented with molecular dynamics simulations. After processing with NJOY, new water neutron scattering cross-sections have been generated for use with e.g. the Monte Carlo N-Particle (MCNP) software in view to improve the accuracy of the nuclear facility models. As an example, we present improved accuracy calculations for the safety rod insertion impact on the criticality factor k_eff for the ILL high flux research reactor.     

Binding of Cdc48p to a ubiquitin-related UBX domain from novel yeast proteins involved in intracellular proteolysis and sporulation

The Cdc48/p97 AAA-ATPase functions in membrane fusion and ubiquitin-dependent protein degradation. Here, we show that, in yeast, Cdc48p interacts with three novel proteins, Cuil-3p, which contain a conserved ubiquitin-related (UBX) domain. Cui2p and Cui3p are closely related, interact with each other, and are localized at the perinuclear membrane. Cdc48p binds directly the UBX domain of Cui3p in vitro. Multiple deletions of the CUI1, CUI2 and CUI3 genes confer deficiency in sporulation and degradation of model ubiquitin-protein fusions. The Cuil-3 proteins were also found to interact with Ufd3p, a WD repeat protein known to associate with Cdc48p. Together, these results indicate that the Cuil-3 proteins form complexes that are components of the ubiquitin-proteasome system.     

Low temperature oxidation of a coking plant soil organic matter and its major constituents: an experimental approach to simulate a long term evolution

In contaminated soils, several natural processes (biodegradation, oxidation, etc.) can induce degradation of organic pollutants. The aim of this work was to evaluate the impact of an abiotic low-temperature oxidation on a coking plant soil and its main organic constituents (coal, coke, coal tar and road asphalts) in order to understand its long term evolution. This natural process was experimentally reproduced by oxidizing the soil and isolated organic matrices at 100 °C during 180 days. The samples were analyzed by total organic carbon measurements and elemental analyses, and the solvent-extractable organic matter was quantified by GC-MS (gas chromatography-mass spectrometry). Oxidation experiments on coal, coal tar and coking plant soil samples lead to the decrease in polycyclic aromatic hydrocarbon (PAH) concentrations correlated to an incorporation of oxygen evidenced by the production of oxygenated PAHs. The increasing amount of polar macromolecules and the decrease in solvent-extractable organic matter suggest a molecular growth through ether/ester cross-linking. The chemical environment of organic compounds and the presence of a reactive mineral fraction are important parameters that improve the efficiency of oxidation. This work reveals that abiotic low temperature oxidation, can strongly contribute to pollutant removal especially by a stabilization process and should be considered in the long term evolution of a soil.