Dr. Eddy Lelievre-Berna Profile

Dr. Eddy Lelievre-Berna

at Institut Laue-Langevin

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Proceedings Article | 18 November 2002 Paper

Novel polarized neutron tools

Eddy Lelievre-Berna

Proceedings Volume 4785, (2002) https://doi.org/10.1117/12.455781

KEYWORDS: Polarization, Magnetism, Scattering, Polarization analysis, Laser scattering, Crystals, Optical pumping, Polarimetry, Sensors, Optical filters

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³He neutron spin filters and zero-field polarimeters are being intensively developed in order to better investigate exotic magnetic systems and prepare the construction of polarized neutron instruments at spallation neutron sources. There are several incentives for using ³He spin filters. They are simple transmission devices having minimal impact on the optics of the neutron beam and they are broadband with properties that vary only weakly with neutron energy. However, a very homogeneous magnetic field is required for long relaxation time of the ³He polarization. We will present devices which remove this difficulty, even in front of a cryomagnet producing a large inhomogeneous stray field. With a zero-field polarimeter Cryopad, the three components of the scattered spin-polarization vector are measured, which is not possible by standard uniaxial polarization analysis. In the case of magnetic structures, Cryopad allows the direct determination of the direction and phase of the magnetic interaction vector. Hence, it is the most powerful tool for solving non-trivial antiferromagnetic structures. In recent years, the technique has been used to correct major errors in magnetic structures previously determined with other techniques. Efforts are being made to adapt this technique to the case of a spallation neutron source.

Proceedings Article | 29 April 1998 Paper

Image analysis applied to luminescence microscopy

Eric Maire, Eddy Lelievre-Berna, Veronique Fafeur, Bernard Vandenbunder

Proceedings Volume 3260, (1998) https://doi.org/10.1117/12.307084

KEYWORDS: Luminescence, Cameras, Image segmentation, Image analysis, Microscopy, Image acquisition, Microscopes, Light emitting diodes, Mathematical morphology, Image processing

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We have developed a novel approach to study luminescent light emission during migration of living cells by low-light imaging techniques. The equipment consists in an anti-vibration table with a hole for a direct output under the frame of an inverted microscope. The image is directly captured by an ultra low- light level photon-counting camera equipped with an image intensifier coupled by an optical fiber to a CCD sensor. This installation is dedicated to measure in a dynamic manner the effect of SF/HGF (Scatter Factor/Hepatocyte Growth Factor) both on activation of gene promoter elements and on cell motility. Epithelial cells were stably transfected with promoter elements containing Ets transcription factor-binding sites driving a luciferase reporter gene. Luminescent light emitted by individual cells was measured by image analysis. Images of luminescent spots were acquired with a high aperture objective and time exposure of 10 - 30 min in photon-counting mode. The sensitivity of the camera was adjusted to a high value which required the use of a segmentation algorithm dedicated to eliminate the background noise. Hence, image segmentation and treatments by mathematical morphology were particularly indicated in these experimental conditions. In order to estimate the orientation of cells during their migration, we used a dedicated skeleton algorithm applied to the oblong spots of variable intensities emitted by the cells. Kinetic changes of luminescent sources, distance and speed of migration were recorded and then correlated with cellular morphological changes for each spot. Our results highlight the usefulness of the mathematical morphology to quantify kinetic changes in luminescence microscopy.

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