François-Xavier Simon

Self-assembling properties of a series of homologous ester-diamides – from ribbons to nanotubes

We have studied the aggregation properties of a series of compounds BHPB-n bearing two amide groups and an ester alkyl chain. The number (n) of carbon atoms in this alkyl chain has been varied from 5 to 16. These compounds form gels at low concentration in alkanes. The gel concentrations and the heats of formation of the gels, measured by DSC, are divided into three different regimes: n ≤ 7, 8 ≤ n ≤ 12 and n ≥ 13. Freeze fracture TEM shows that all the compounds self-assemble into high aspect ratio objects, i.e. flat ribbons for n ≤ 7 and irregular helical ribbons for n ≥ 13. For 8 ≤ n ≤ 12, the compounds form tubes (except BHPB-11) and were studied by SANS. The outer and inner diameter distributions of the tubes were determined from the scattered intensities with a model of paired tubes. The diameters are controlled by the length of the ester chain (n) and vary from 21 for BHPB-8 to 32 nm for BHPB-12 (outer diameters). The SANS measurements also provide an estimate of the ratio of paired tubes and the proportion of non-tubular objects that eventually co-exist with these tubes. Variable temperature FTIR and DSC proved that H-bonds between the amide groups are involved in all types of self-assemblies. In addition, FTIR spectra of helical tapes and nanotubes exhibit a double ester νCO band whereas flat tapes display a single band, which confirms the involvement of the ester in the self-assemblies.

1D sequential inversion of portable multi-configuration electromagnetic induction data

We present an algorithm that performs sequentially one-dimensional inversion of subsurface magnetic npermeability and electrical conductivity by using multi-configuration electromagnetic induction nsensor data. The presented method is based on the conversion of the in-phase and out-of-phase ndata into effective magnetic permeability and electrical conductivity of the equivalent homogeneous nhalf-space. In the case of small-offset systems, such as portable electromagnetic induction sensors, nfor which in-phase and out-of-phase data are moderately coupled, the effective half-space magnetic npermeability and electrical conductivity can be inverted sequentially within an iterative scheme. We ntest and evaluate the proposed inversion strategy using synthetic and field examples. First, we apply nit to synthetic data for some highly magnetic environments. Then, the method is tested on real field ndata acquired in a basaltic environment to image a formation of archaeological interest. These nexamples demonstrate that a joint interpretation of in-phase and out-of-phase data leads to a better ncharacterisation of the subsurface in magnetic environments such as volcanic areas.

The Highest Gradient Model: A New Method for Analytical Assessment of the Efficiency of LiDAR-Derived Visualization Techniques for Landform Detection and Mapping

ALS-derived raster visualization techniques have become common in recent years, opening up new possibilities for subtle landform detection in earth sciences and archaeology, but they have also introduced confusion for users. As a consequence, the choice between these visualization techniques is still mostly supported by empirical knowledge. Some attempts have been made to compare these techniques, but there is still a lack of analytical data. This work proposes a new method, based on gradient modelling and spatial statistics, to analytically assess the efficacy of these visualization techniques. A selected panel of outstanding visualization techniques was assessed first by a classic non-analytical approach, and secondly by the proposed new analytical approach. The comparison of results showed that the latter provided more detailed and objective data, not always consistent with previous empirical knowledge. These data allowed us to characterize with precision the terrain for which each visualization technique performs best. A combination of visualization techniques based on DEM manipulation (Slope and Local Relief Model) appeared to be the best choice for normal terrain morphometry, occasionally supported by illumination techniques such as Sky-View Factor or Negative Openness as a function of terrain characteristics.

How efficient is an integrative approach in archaeological geophysics? Comparative case studies from Neolithic settlements in Thessaly (Central Greece)

The geophysical prospection of Neolithic tells imposes specific challenges due to the preservation nand nature of the architectural context and the multiple, usually disturbed, soil strata. Contrary to nthe usual application of a single method, this paper deals with the advantages of using an integrated ngeophysical approach through the employment of various methodologies to map the Neolithic cultural nand environmental landscape of Thessalian tells (magoules) in Central Greece. The success nand failure of each method in resolving the various features of the magoules are discussed in detail, nand as a whole, they demonstrate the benefits of a manifold geophysical prospection of the sites.