This study explains processes for the characterization by acoustic microscopy of materials presenting, along a thickness d close to the surface, agradient in elastic properties in direction perpendicular to the surface. The method,modelling the non-homogeneous area by a finite number of layers of the same thickness,is sensitive to the factor fd (f is the working frequency) and to the natureof the gradient profile. The study of the dispersion of the Rayleigh velocity as afunction of frequency shows that the shape of the curve Maynly depends on the gradientprofile and on the structure (surface material and bulk material). When the numericalderivative of the dispersion curves presents inflexion points, they can be linked tothe depth and to the nature of the profile. Modelling of the materials displaying agradient shows that, in some cases, the plot of the curvature of the dispersion curvesas a function of frequency is a useful means of characterization.

Recently a new nematic bistable pixel, using simple monostable planar anchorings, has beenproposed [4−6]. This pixel can be switched between two textures, having the same boundary conditionsbut different optical properties: one texture (U) is undistorted, whereas the other one (T) ischaracterized by the presence of a half-turn twist. The U → T switching was obtained by abruptlydropping the driving electric field. A slow decrease of the driving electric field favors the T → Utransition. The electric field fall rate discriminates the kind of coupling between the boundary surfaces,hydrodynamic or elastic. Here we show the same behavior of this system by using square electric fieldpulses. We present experimental results concerning the critical values (amplitude and duration) of thedriving signals, for which the elastic and the hydrodynamic effects are balanced and we measure theiroptimized values. Our results are in reasonable agreement with the theoretical predictions obtained by asimplified model.

Slip patterning is influenced by both the distribution of Frank-Read sources in the bulk crystal and the dislocation interactions before emerging at the surface. The fine structure of slip lines is also highly dependent on the intrinsic nature of Frank-Read sources and particularly on their pinning points and external dislocation network, which is often not considered.In this paper, different types of Frank-Read sources are reviewed and the direct effects are described and discussed of these dislocation multiplication mechanisms on the step fine structure at the surface.

Electron mean free path (λa) has been investigated using BallisticElectron Emission Microscopy (BEEM). Using the average collector current computed fromlarge scale BEEM images and a model in which the current exponentially decreases interms of metal thickness, a constant value of λa = 11 nm has been calculatedin the 1–1.8 eV electron energy range. On small scale images, the study ofwell-defined BEEM doMayns shows that either λa or the interface transmissionfactor (or both) may differ from their average values. These local variations from onegrain to another are interpreted as interface defects and channeling of the electronbeam due to the electronic and crystallographic of the gold layer.

A linear transformation f(S) of configurational entropy with length scale dependent coefficients as a measure of spatial inhomogeneity is considered. When a final pattern is formed with periodically repeated initial arrangement of point objects the value of the measure is conserved. This property allows for computation of the measure at every length scale. Its remarkable sensitivity to the deviation (per cell) from a possible maximally uniform object distribution for the length scale considered is comparable to behaviour of strictly mathematical measure h introduced by Garncarek et al. in [2]. Computer generated object distributions reveal a correlation between the two measures at a given length scale for all configurations as well as at all length scales for a given configuration. Some examples of complementary behaviour of the two measures are indicated.

The high intensity of concentrated solar radiation obtained with the Odeillo (France) solar furnace facilities can be used to produce carbon nanotubes by direct vaporization of carbon bi-metal targets under inert gas atmosphere. Electron microscope pictures and Raman spectra show that the structure of the produced carbon nanotubes is likely to depend on experimental conditions and that the growth of single-wall or multi-walled carbon nanotubes can be favored.

In this paper, finite element method is used to compute inductance parameters of asquirrel cage induction machine. To take into account saturation effect, saturatedequivalent parameters are introduced, which depend on the instantaneous value of themagnetising current. For a balanced induction machine, the particular inductance behaviors allow straightforward flux expressions without any cross saturation effect.Moreover, these expressions are explained thanks to an extended analytical approachconsidering a magnetic saliency phenomenon by a second order air-gap permeance. Asimple way of transformation ratio and leakage inductance computation is also deduced.The numerical results show the compatibility between finite element approach and extended analytical Park's method. Besides, two operating points (at no load and for nominal speed) studied by the both methods give very closed results.

We report the local study of an operating double hetero-junction GaAs/GaAlAs laser diode by apertureless Scanning Near-field Optical Microscopy (SNOM). This study allows the characterization of the spatial properties of the light emitted by the laser source. The optical probe used is a tungsten tip vibrating (at frequency f) perpendicularly to theemitting surface. Suitable experimental parameters permitting us to accede tonear-field information have been defined. This has leaded to an experimentalconfiguration in which the probe vibration amplitude is "optimal". A far-fielddetection at grazing angle is used and a second harmonic (at frequency 2f) lock-indetection is performed. This configuration has permitted us to obtain SNOM images instimulated emission as well as in spontaneous emission. Above the threshold current,information concerning the emitted laser mode are obtained, whereas in spontaneousemission the SNOM images are linked to the index contrast of the laser diode frontfacet.

Gratings can be considered as resonant structures in near-field.The enhancement of the intensity recorded by Scanning Near-FieldOptical Microscopes (SNOM) is due to interferences in relation with the ratio ofthe wavelength to the product of the optical index by the period of thegrating. We discuss the effect of this ratio (in the range 0.9, 1.1) on theintensity patterns. The influence of the polarization on near-field data isanalyzed in both theoretical computations and experimental result.

This contribution presents an application of scanningnear-field optical microscopy to the characterization of semi-conductors.It is based on the photocurrent mapping of a patterned Au/GaAs structure(Schottky barrier) under local illumination by the nanosource. The resultsobtained with different wavelengths, metallized or dielectric probes anddifferent bias voltages exhibit photocurrent variations independent of the topography and induced by interface defects. Finally, from this study ofa patterned planar structure, we propose a method to determine the meanfree path of the charge carriers in the volume.

We have developed an apertureless Scanning Near field Optical Microscope (SNOM) in transmission, devoted to near field magneto-optics. Our apertureless SNOM combines an inverted optical microscope, which has been adapted to Faraday effect imaging, with a commercial stand-alone Scanning Probe Microscope, used in Atomic Force Microscope (AFM) mode. Two different probes are validated as apertureless SNOM tips: a home-made etched tungsten wire and a commercial AFM silicon probe. We present and analyze preliminary images of the doMayn structure in iron garnets. They indicate a SNOM resolution clearly in the sub-micrometric range. Besides, the near field magneto-optical image presents some unexpected features, not revealed in far field images.

In Near-Field Optical microscopy, the resolution isdirectly related to the experimental conditions of illuminationand separation between tip and sample. In general, there is nowell-defined linear transfer function of the measurement system.The local resolution can be described by the signal-to-noiseratio, by the separation of individual objects or in terms of datashape sharpness. In this paper we use wavelet analysis todetermine local resolution. We deduce the resolution from thecharacteristics of the wavelet and with the help of the localenergy in the decomposition.

The plasma plume created during photoablation of various targets by an excimer KrF laser beam is studied in typical conditions of pulsed laser film deposition. For the examination of transport phenomena of ejected species, the space and time resolved evolution of the luminous plume is investigated by fast imaging as a function of laser fluence (from 7 to $200~\mathrm{J/cm}^{2}$ ) and nitrogen background pressure (from 5 × 10−3 to 500 Pa) for five different target materials (boron nitride, graphite, alumina, molybdenum, a superconducting oxide YBCO). Under "vacuum" (5 × 10−3 Pa and for nitrogen background pressures up to 10−1−1 Pa, the plume expands freely. For higher background pressures $(\geq 10~\mathrm{Pa})$ , three successive regions above the target can be distinguished: at first the expansion is free, then the plume expands according to a shock wave-like behaviour, and lastly a drag force model correctly describes the plume shape evolution. Velocities of the luminous plasma front and of the "mass center" of the plume are determined versus laser fluence and background nitrogen gas pressure.

Detailed derivations and further analysis are presented of a recent conceptfor a plasma-based accelerator scheme incorporating a strong circularly polarisedmagnetic wiggler field producing relativistic-strength diamagnetic transverse plasmacurrents. The increase in the plasma Lorentz factor leads to a substantial increase inthe longitudinal component of the wave electric field and therefore of theacceleration rate. It is also found that ultra-high acceleration gradients are possible with relatively low plasma densities and long wave lengths. It also appearspossible that the transverse wiggling motion of the electrons of the beam is able todelay the dephasing with the accelerating wave leading to much higher values of theenergy gained by the beam at saturation and even electron bunches that have beeninjected with the "wrong" phase seem to be able to reverse their motion and accelerateto very high energies in short distances.

Ferrofluids are colloidal solutions of iron oxide magnetic nanoparticles in either a polar or no polar liquid. We present here two biological applications using maghemite (γFe2O3) ferrofluids: magnetic cell sorting and magnetocytolysis.The first application employs magnetic particles binding a biological effector, which is capable to recognize the target cells specifically. These cells become magnetic and can be sorted in a gradient of magnetic field. We describe first the various steps of the synthesis of a biocompatible ferrofluid and the grafting an effector protein onto the particles. We then describe the use of particles carrying annexin V in the separation and quantification of damaged erythrocytes in blood samples. This very sensitive technique can be used to follow the erythrocytes ageing of normal blood samples during their storage under blood bank conditions or to detect the membrane modifications that are associated with some pathologies such as malaria or Alzheimer's disease.The dependence of the magnetic susceptibility versus the frequency is a way to transform magnetic energy into thermal energy. Magnetocytolysis is the destruction of cells, carrying magnetic particles, through the action of an alternating magnetic field (about 1 MHz). We present here preliminary experiments with macrophages, which demonstrate the method's feasibility and the formation of the non-specific interactions between the cells and the magnetic particles.