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cited By 6; International audience; Strain mapping is an active area of research in transmission electron microscopy. Here we introduce a dark-field electron holographic technique that shares several aspects in common with both off-axis and in-line holography. Two incident and convergent plane waves are produced in front of the specimen thanks to an electrostatic biprism in the condenser system of a transmission electron microscope. The interference of electron beams diffracted by the illuminated crystal is then recorded in a defocused plane. The differential phase recovered from the hologram is directly proportional to the strain in the sample. The strain can be quantified if the separation of the images due to the defocus is precisely determined. The present technique has the advantage that the derivative of the phase is measured directly which allows us to avoid numerical differentiation. The distribution of the noise in the reconstructed strain maps is isotropic and more homogeneous. This technique was used to investigate different samples: a Si/SiGe superlattice, transistors with SiGe source/drain and epitaxial PZT thin films. © 2015 Elsevier B.V.

Monodispersed Fe3O4 nanoparticles with comparable size distributions have been synthesized by two different synthesis routes, co-precipitation and thermal decomposition. Thanks to the different steric stabilizations, the described samples can be considered as a model system to investigate the effects of magnetic dipolar interactions on the aggregation states of the nanoparticles. Moreover, the presence of magnetic dipolar interactions can strongly affect the nanoparticle efficiency as a hyperthermic mediator. In this paper, we present a novel way to visualize and map the magnetic dipolar interactions in different kinds of nanoparticle aggregates by the use of Lorentz microscopy, an easy and reliable in-line electron holographic technique. By exploiting Lorentz microscopy, which is complementary to the magnetic measurements, it is possible to correlate the interaction degrees of magnetic nanoparticles with their magnetic behaviors. In particular, we demonstrate that Lorentz microscopy is successful in visualizing the magnetic configurations stabilized by dipolar interactions, thus paving the way to the comprehension of the power loss mechanisms for different nanoparticle aggregates.

Après avoir analysé les différents modes d'action des lasers sur la matière vivante, l'auteur passe en revue les différentes spécialités médicales et chirurgicales utilisant, ou susceptibles d'utiliser, le laser. En ophtalmologie son utilisation bien qu'habituelle n'est pas encore optimisée. En otorhinolaryngologie les premiers résultats sont extrêmement encourageants. En dermatologie on note un état de stagnation dû à l'absence d'appareillage adapté. En chirurgie et en endoscopie le choix de la meilleure longueur d'onde n'est pas encore fait, surtout si on se réfère à l'action hémostatique et à l'effet de coupe. En odontologie les lasers pulsés semblent exclus de la thérapeutique, mais les techniques holographiques semblent prometteuses pour la réalisation des prothèses. L'auteur conclut à la nécessité de développer une recherche sur les problèmes fondamentaux posés par les applications biomédicales des lasers.

Basalt fibre reinforced epoxy laminates were obtained by overlapping plain woven fabrics by resin infusion. Rectangular specimens cut from the panels were impacted at penetration and at increasing energy values, to investigate the damage onset and propagation. Two non-destructive techniques, namely Ultrasound testing (UT) and Electronic Speckle Pattern Interferometry (ESPI), were adopted to investigate the internal damage. It was difficult to obtain information by using the most common UT method, since the high amount of signal absorbed. The ESPI technique proved to be, on the contrary, very useful in providing information about the presence, the shape and the extent of the delaminatio.