MRI investigation of granular interface rheology using a new cylinder shear apparatus

The rheology of granular materials near an interface is investigated through proton magnetic resonance imaging. A new cylinder shear apparatus has been inserted in the magnetic resonance imaging device, which allows the control of the radial confining pressure exerted by the outer wall on the grains and the measurement of the torque on the inner shearing cylinder. A multi-layer velocimetry sequence has been developed for the simultaneous measurement of velocity profiles in different sample zones, while the measurement of the solid fraction profile is based on static imaging of the sample. This study describes the influence of the roughness of the shearing interface and of the transverse confining walls on the granular interface rheology.     

Nitrogen-Broadening Parameters for Atmospheric Spectra Modelling of the ν3 Band of SF6

The infrared absorption of the ν₃ band region of SF_6, at temperatures spanning the 130 to 297 K range, has been reexamined using improved instrumentation with one goal: to estimate the broadening of parameters by nitrogen gas. These parameters are compared to previous literature predictions and an extended set of IR cross-sections is proposed and compared to other existing datasets.     

Evaluation of Vetiver Volatile Compound Production under Aeroponic-Grown Conditions for the Perfume Industry

Vetiver (Chrysopogon zizanioides (L.) Roberty) is a major tropical perfume crop. Access to its essential oil (EO)-filled roots is nevertheless cumbersome and land-damaging. This study, therefore, evaluated the potential of vetiver cultivation under soilless high-pressure aeroponics (HPA) for volatile organic compound (VOC) production. The VOC accumulation in the roots was investigated by transmission electron microscopy, and the composition of these VOCs was analyzed by gas chromatography coupled with mass spectrometry (GC/MS) after sampling by headspace solid-phase microextraction (HS-SPME). The HPA-grown plants were compared to plants that had been grown in potting soil and under axenic conditions. The HPA-grown plants were stunted, demonstrating less root biomass than the plants that had been grown in potting soil. The roots were slender, thinner, more tapered, and lacked the typical vetiver fragrance. HPA cultivation massively impaired the accumulation of the less-volatile hydrocarbon and oxygenated sesquiterpenes that normally form most of the VOCs. The axenic, tissue-cultured plants followed a similar and more exacerbated trend. Ultrastructural analyses revealed that the HPA conditions altered root ontogeny, whereby the roots contained fewer EO-accumulating cells and hosted fewer and more immature intracellular EO droplets. These preliminary results allowed to conclude that HPA-cultivated vetiver suffers from altered development and root ontology disorders that prevent EO accumulation.     

Molecular view of copper deposition chemistry: (Hexafluoroacetylacetonate)Cu(vinyltrimethylsilane) on a Si(1 0 0)-2 × 1 surface

The chemistry of a common copper deposition precursor, (hexafluoroacetylacetonate)Cu(vinyltrimethylsilane), (hfac)Cu(VTMS), on a single crystal Si(1 0 0)-2 × 1 surface is described at the molecular level using a combination of experimental surface analytical techniques under ultra-high vacuum conditions with computational analysis. At a cryogenic temperature of 100 K, (hfac)Cu(VTMS) adsorbs on this surface molecularly, without noticeable decomposition. Upon surface annealing, VTMS is easily released into the gas phase below the room temperature, while the hfac ligand is bound to the surface through the copper atom. When (hfac)Cu(VTMS) is adsorbed at room temperature, VTMS is released into the gas phase immediately, leaving surface adsorbate analogous in structure to the one formed by adsorption at cryogenic temperature and a brief annealing to room temperature. Upon surface annealing, the hfac ligand decomposes and constitutes the main source of impurities in copper deposition process.     

Space averaging of vibration level differences measured in lightweight building structures

This paper examines space averaging methods applied to structural level differences measured in lightweight building structures (two beam junction and single plate and beam junction). The methods studied include the averaging assuming a constant input force, the averaging based on a constant vibration level across the source element, and the arithmetic averaging of level differences. Tests indicate that a fairly steady input force can be easily produced when using an impulsive source such as a hammer; the constant input force method is then appropriate and can be used to space average level differences (the two beam structure showing a standard deviation of 0.1 dB from the averaging based on levels normalised to the force). On the other hand, acceleration levels can exhibit significant variations with position due to the low mode count and modal overlap of some lightweight elements such as timber beams. Variations in the vibration level across the source element can then be responsible for large inaccuracies in the level difference calculated from the constant level assumption, the two beams’ results showing errors greater than 5 dB at several 1/3 octave band frequencies. The latter averaging method is then inappropriate and should not be used.     

Detection of susceptibility effects using simultaneous T(2)* and magnetic field mapping

Tracking susceptibility effects is a convenient way to detect small inclusions in a bulk tissue matrix by MRI. We propose a quantitative assessment of these susceptibility effects by simultaneously mapping T(2)* and magnetic field from the time course of magnitude and phase using a multiple GE sequence at 4.7 T. A high-pass scheme is also introduced to highlight the mesoscopic magnetic field variations due to local susceptibility differences specifically in the magnetic field map. Applying this method to muscle tissue, we demonstrate that connective tissue generates detectable susceptibility effects through concomitant local magnetic field variation and T(2)* shortening.     

Irrationalité de Valeurs Associées a l'Exponentielle de Carlitz

Lete and be the Carlitz-module analogues of their usual counterparts. We have proved in [4]-that these elements of are algebraically independent over whenq3. We study here the remaining caseq=2 and prove among other things that 1,e, are linearly independent over .