The aim of the present work is to study by means of thermodynamic measurements, i.e. isotherms of adsorption and desorption of water and Infrared (IR) spectroscopy, the effect of the interlayer cations on the mechanism of adsorption-desorption of water in the case of a montmorillonite exchanged with alkaline-earth metals. For the first time, the net isosteric heat of water adsorption and desorption is determined from isotherms recorded at three temperatures. The net isosteric heat is a very useful parameter for getting more insights into the sorption mechanism since it provides information about the sorption energy evolution which can be complementary to that obtained from structural or gravimetric measurements. The homoionic montmorillonite samples are prepared from purification and cationic exchanged in aqueous solution of the raw material, i.e the reference SWy-2 Wyoming material. XRD at the dry state and elemental chemical analysis confirm that the treatment does not deteriorate the clay structure and yield the expected homoionic composition. The adsorption and desorption isotherms measured at various temperatures show that the nature of the interlayer, i.e. exchangeable, cation changes the adsorbed/desorbed amount of water molecules for a given water relative pressure. The total amount of water adsorbed at = 0.5 follows the cation sequence Ca>Mg>Ba. Although the adsorption isosteric heat also follows the cation sequence Ca>Mg>Ba, that of desorption obeys a slightly different sequence Ca~Mg>Ba. This discrepancy between the adsorption and desorption heat is due to the higher irreversibility of water sorption process in the Ca exchanged montmorillonite. Finally, analysis of the IR spectra recorded at room temperature and under a primary vacuum reveals that the amount of adsorbed water follows the same sequence as that of the isosteric heat of adsorption and shows the coexistence of liquid-like and solid-like water confined in the interlayer space.

New GaN and silicon juncionless field effect transistor THz detectors

ATRC is a new ligth scattering technique that measures by holography the field amplitude scattered by a sample, and analyze its spatial correlations. ATRC outperforms other light scattering techniques like DLS, DWS and TRC. Dynamic light scattering (DLS) [1], diffusing wave spectroscopy (DWS) [2] and time resolved correlation (TRC) [3] are well-established techniques for investigating the dynamics of a wide variety of systems in physics, chemistry, biology , and medicine. DLS and DWS consider the intensity time fluctuations of the scattered light, and study samples, whose dynamics are homogeneous in time. TRC considers the spatial fluctuations, and is able to study slow or temporally heterogeneous dynamics. We propose, in this work, to replace the TRC multi pixel detector by an holographic one, and to consider the spatial fluctuations of the field complex amplitude E as a new quantity of interest. We introduce thus a new tool called ATRC for Amplitude Time Resolved Correlation, which outperforms TRC and open new perspectives. Fig. 1. (a) TRCA typical setup. (b) Reconstructed image of a nanocomposite sample. Fig.1 (a) shows a simplified diagram of the TRCA setup. The sample S is illuminated by the laser beam L1. The light scattered by the sample is split by the beam splitter BS into two imaging paths, corresponding to cameras C1 and C2. Lens L made the image of the sample S on C1, which records the light intensity image I of S. On the other hand, the camera C2 records the interference pattern (i.e. the hologram) of the scattered light with the reference laser light L2, and the complex amplitude image E of S is calculated by holographic reconstruction. The optimize the detection sensitivity [4], holography is heterodyne [5] and off-axis. Fig.1 (b) shows the intensity reconstructed image (I = |E| 2) of a 30 × 10 mm 2 Styrene-Butadiene/Silica nanocom-posite sample, which is observed in reflection. Because 2 phase detection is used, both the +1 and-1 image of the sample are seen (right and left hand side images of Fig.1 (b)). To analyze the dynamic of the sample, TRC considers

A microscopic technique based on digital holography is proposed to investigate blood microcirculation and vascular development in model organisms such as zebrafish larvae. Recent achievements in 3D imaging of blood flow in vessels are presented.