1H and 19F ultra-fast MAS double-quantum single-quantum NMR correlation experiments using three-spin terms of the dipolar homonuclear Hamiltonian

Measuring internuclear distances through dipolar interaction is a major challenge for solid-state nuclear magnetic resonance (NMR) spectroscopy. Obtaining reliable interatomic distances provides an access to the local structure in ordered or disordered solids. We show that at magic angle spinning (MAS) frequencies larger than ca. 50 kHz, some of the three-spin terms of the homogeneous homonuclear dipolar Hamiltonian can be used to promote the creation of double-quantum coherences between neighbouring (1)H or (19)F spins without using dipolar recoupling pulse sequences in the Dipolar Homonuclear Homogeneous Hamiltonian (DH(3)) double-quantum/single-quantum correlation experiment. This makes it possible to probe inter-nuclear spatial proximity with limited risk of probe or sample damage from radio-frequency (RF) irradiation, and is fully appropriate for fast repetition rate offering sensitivity gains in favourable cases. Experimental demonstrations are supported by multi-spin numerical simulations, which points to new possibilities for the characterization of spin-system geometries.     

Virtual improvement of ice cream properties by computational homogenization of microstructures

Optimal shape design of microstructured materials has recently attracted a great deal of attention in materials science. The shape and the topology of the microstructure have a significant impact on the macroscopic properties. This paper presents different computational models of random microstructures, to virtually improve the physical properties of ice cream. Several sensory properties of this heterogeneous material issued from food industry are directly controlled by the elastic and thermal conducting ones. The material effective elastic and thermal conducting properties are obtained through direct large scale numerical simulations. The different formulations address the problem of finding the shape of the representative microstructural element for random heterogeneous media that increase the elastic moduli and thermal conductivity compared to existing products. The computational models are established using finite element method and images of virtual microstructures. In this paper we propose a new model of microstructures. This model is constructed with hexagonal prismatic rods and plates with volume fractions around 0.7 for the hard phase represented by hexagons of ice. A comparison between three two-phase elastic heterogeneous microstructures models is drawn. This illustrates the concept of design of microstructures using computational homogenization tools.     

Smart Digital Image Correlation Patterns via 3D Printing

Experimental Mechanics - Digital Image Correlation (DIC) is a popular experimental technique for measuring full-field deformations in materials. Accurate motion and displacement field...     

Determination of traces of heavy metals (Mn, Cu, Zn, Cd and Pb) in microsamples of teeth material by ETV-ICP-MS

Heavy metal levels in tooth compartments would appear to be a suitable indicator of long-term exposure. A method has been developed to assess the heavy metal levels (Mn, Cu, Zn, Cd and Pb) in tooth compartments like dentin and enamel. For the simultaneous determination of these elements in small dentin sample amounts (in some cases less than 1 mg) inductively coupled plasma mass spectrometry with electrothermal vaporization was the method of choice. Sample preparation, method development and first results of the application of the method for the analysis of tooth compartments have been described. Variation in the elemental concentrations depending on the kind of tooth and the sampling position have been observed. The method is useful for epidemiological studies of the heavy metal exposure of children.     

Experimental study of flame stabilization in low Reynolds and Dean number flows in curved mesoscale ducts

Flame stabilization during non-premixed combustion in curved ducts with a diameter of the order of magnitude of the premixed flame thickness of the reactants was investigated experimentally, since it has been established that this is a configuration with potential advantages in the context of “micro”-combustion. It was shown that, in such “mesoscale” tubes, a stable flame oscillation including extinction/re-ignition phenomena can be established for steady boundary conditions. These oscillations lead, under appropriate conditions, to sound emission in the 50–350 Hz range. This was a mode of stabilization in addition to the “classical” steady flamelet, stabilized through thermal losses to the duct walls at higher values of the Reynolds number. Curvature of the duct was shown to have minimal effect on reactant mixing, which was diffusion-controlled, but significantly affected flame thickness and stabilization. To probe the fuel-oxidizer mixing in the U-shaped, optically accessible tubes, laser induced fluorescence of acetone fuel dopant was used, and the flame structure was studied using OH PLIF. The various stabilization regimes are discussed in terms of the Reynolds and Dean numbers of the tube flow.     

Hydroxylamine-functionalised silica surfaces for biochip applications

The syntheses of triethoxy and trimethoxy silanes possessing an unprotected hydroxylamine group are described. The grafting of these coupling agents at the surface of oxidised silicon wafers was studied. Accessibility of the hydroxylamine group at the surface was demonstrated with chemical reagents, and the surface proved efficient for covalent immobilisation of peptides possessing the COCHO function.