Behavior of Paramagnetic Iron during the Thermal Transformations of Kaolinite

Kaolinites with various degrees of structural order and iron content were heated and subsequently analyzed via electron paramagnetic resonance. Iron was present in two different states in the heated materials, either as dilute structural Fe³⁺ ions or in concentrated Fe³⁺ phases. During metakaolinization, the environment of dilute Fe³⁺ ions changed, following modifications of the Al³⁺ coordination, and the Fe³⁺ concentration increased. With the breakdown of metakaolinite, the diffusion of Fe³⁺ ions induced their exsolution in superparamagnetic iron-rich domains (Fe³⁺ clusters in γ-Al₂O₃ and/or Fe³⁺ oxide nanophases), which produced a decrease in the dilute Fe³⁺ concentration. The subsequent breakdown of γ-Al₂O₃ and the formation of mullite made the dilute Fe³⁺ concentration increase again, because of the incorporation of Fe³⁺ ions in the mullite structure.     

Photoclickable Surfaces for Profluorescent Covalent Polymer Coatings

The nitrile imine‐mediated tetrazole‐ene cycloaddition reaction (NITEC) is introduced as a powerful and versatile conjugation tool to covalently ligate macromolecules onto variable (bio)surfaces. The NITEC approach is initiated by UV irradiation and proceeds rapidly at ambient temperature yielding a highly fluorescent linkage. Initially, the formation of block copolymers by the NITEC methodology is studied to evidence its efficacy as a macromolecular conjugation tool. The grafting of polymers onto inorganic (silicon) and bioorganic (cellulose) surfaces is subsequently carried out employing the optimized reaction conditions obtained from the macromolecular ligation experiments and evidenced by surface characterization techniques, including X‐ray photoelectron spectroscopy and FT‐IR microscopy. In addition, the patterned immobilization of variable polymer chains onto profluorescent cellulose is achieved through a simple masking process during the irradiation.     

Thermo-mechanical characteristics of concrete at elevated temperatures up to 310 °C

Both, the normal strength concretes (NSC) and high strength concretes (HSC) have been used in structures which may be exposed to elevated temperatures. Concretes have also been used in the construction of radiation shielding structures. Data on the behaviour of concrete at high temperature is of prime concern in predicting the constructions and safety of buildings in response to certain accidents or particular service conditions. Prediction of mechanical behaviour, thermo-mechanical deformations and moisture migration in non-uniformly heated concrete is important for safe operation of concrete containment.This paper presents the results of an experimental investigation carried out to predict the behaviour of concrete intended for nuclear applications. For this purpose, normal concrete having compressive strength of 40 MPa was designed using limestone aggregates. Cylindrical specimens (110 mm × 22 mm) were made and subjected to heating-cooling cycles at 110, 210 and 310 °C. Measurements were taken for thermal gradient, mass loss, deformations, residual mechanical properties, thermal conductivity, and porosity. This investigation developed some important data on the properties of concrete exposed to elevated temperatures up to 310 °C. Comparisons and interesting conclusions were drawn about the thermal stability at high temperature and the residual mechanical properties of the tested concrete.     

Modelling mechanical properties of spruce and Douglas fir timber by means of X-ray and grain angle measurements for strength grading purpose

This study proposes a model using data from a scanner (X-ray and grain angle measurements) to perform strength grading. The research also includes global measurements of modulus of elasticity (obtained by vibrations and ultrasound methods), static bending stiffness and bending strength of 805 boards of Douglas fir and 437 boards of spruce. This model can be used in an industrial context since it requires low computational time. The results of this study show that the developed model gives better results than the global non-destructive measurements of the elastic modulus commonly used in the industry. It also shows that this improvement is particularly higher in the case of Douglas fir than for spruce. The comparison has been made on both the quality of the mechanical properties assessment and on the improvement of the grading process according to the European standards by using different index.     

Physical market determinants of the price of crude oil and the market premium

We analyze the determinants of the real price of crude oil by means of an equilibrium correction model over the last two decades where we focus on the aspects of the physical market that impact on the clearing price. We find that two cointegrating relations affect the changes in prices: one refers to OPEC's behavior, attempting to control prices using its market power and quotas; the other to the coverage rate of OECD expected future demand using inventory behaviors. We derive a forecasting equation for the change in oil prices which we use to assess the speculative elements of the price increases of the period 2000–05. We show that worries alien to the physical markets were the causes of the increase in oil prices and we quantify their overall impact.     

Elimination protocols in atopic dermatitis

Both dacryocystography and dacryoscintigraphy are well established in the evaluation of stenoses of the lacrimal drainage system. They provide limited information about the ductal anatomy itself and about periductal structures. MR imaging was evaluated for its capability to directly visualize the lacrimal drainage system in detail and simultaneously provide functional characterization of dacryostenosis. SUBJECTS AND METHODS: Twenty-seven lacrimal drainage systems of 23 patients suffering from epiphora were examined in an MR unit before and after conjunctival and intravenous application of Gd-DTPA using a surface coil. RESULTS: Dacryostenosis was found in 23 of 27 lacrimal systems. Stenoses were localized to the canalicular (n = 3), saccular (n = 8), and ductal (n = 12) level, and were classified as stenosis or occlusion. CONCLUSION: MR imaging with conjunctival contrast application allows within one examination both detailed morphological and functional assessment of the lacrimal drainage system with depiction of surrounding structures. Limitations arise mainly from demands on technical and patient-related preconditions.     

Characterisation of electrodeposited nanocrystalline Ni–Mo alloys

Ni–Mo nanocrystalline layers were electrodeposited using direct current from citrate–ammonia solutions. The quartz crystal microbalance investigation confirms that the discharge process starts with hydrogen evolution before the onset of the alloy deposition. The grain size was estimated from X-ray line broadening. It decreases when the molybdenum content is increased. It is smaller for layers deposited at pH 9.5 than 8.5. The microhardness exhibits a maximum close to 800 Vickers for _Mo around 17 wt%. For higher _Mo a softening is observed showing a deviation from Hall-Petch behaviour due to small grain size. In deaerated hydrochloric solutions, the layers show a large passivation domain without any pitting. The corrosion currents as well as the passivation currents, higher than for the bulk Hastelloy B alloy, decrease when _Mo is increased.     

Self-assembling of atomic vacancies at an oxide/intermetallic alloy interface

Oxide layers grown on the surface provide an effective way of protecting metallic materials against corrosion for sustainable use in a broad range of applications. However, the growth of cavities at the metal/oxide interface weakens the adherence of the protective layer and can promote its spallation under service conditions, as observed for alumina layers formed by selective oxidation of aluminide intermetallic alloys used in high-temperature applications. Here we show that direct atomic-scale observations of the interface between an ultrathin protective oxide layer (alumina) grown on an intermetallic titanium aluminide substrate (TiAl) can be performed with techniques sensitive to the topmost atomic layers at the surface. Nanocavities resulting from the self-assembling of atomic vacancies injected at the interface by the growth mechanism of the protective oxide are observed for the first time, bringing new insight into the understanding of the fate of injected cavities in oxidation processes.     

Generalized diffusion model in optical tomography with clear layers

We introduce a generalized diffusion equation that models the propagation of photons in highly scattering domains with thin nonscattering clear layers. Classical diffusion models break down in the presence of clear layers. The model that we propose accurately accounts for the clear-layer effects and has a computational cost comparable to that of classical diffusion. It is based on modeling the propagation in the clear layer as a local tangential diffusion process. It can be justified mathematically in the limit of small mean free paths and is shown numerically to be very accurate in two- and three-dimensional idealized cases. We believe that this model can be used as an accurate forward model in optical tomography.