Phasenkonjugation. Grundlagen fuer die Phasenkonjugation durch stimulierte Streuprozesse Abschlussbericht

With increasing pump power there are thermally induced aberrations in solid state lasers, having direct consequences for the beam quality and efficiency of the laser. Therefore the aim of the project was to carry out preparatory research for compensating aberrations by means of phase conjugation through stimulated Brillouin-scattering, and adaptive optics. In order to determine the most favourable parameters for this kind of phase conjugation there were carried out investigations, which showed the effect of laser output energy, pulse behaviour, pulse duration, beam quality and coherence length on the efficiency and quality of the phase conjugation process. An optimally designed system resulted in a threshold energy of about 4 mJ and a reflection coefficient up to 40% at 8 - 10 mJ laser energy. As adaptive optical elements a deformable mirror on the one hand and a liquid crystal cell with spatial resolved, variable phase shift on the other hand was investigated. The deformable mirror is assembled with one actuator and allows radii of curvature from 1 m to infinity, allowing to compensate the focal part of the thermal lens. The attained prototype however shows relatively high portions of astigmatism and coma. Further there were carried out investigations on liquid crystal cells with structured electrodes (68 #mu#m width, 1.5 #mu#m distance). These cells were used as phase shifting elements (#approx# 7 #pi#) at wavelengths of 632 and 1064 nm. Only very little diffraction appeared as a result of the discrete electrode structure. Contrary to the stimulated Brillouin-scattering, which is a threshold process, the both adaptive methods are also applicable for lasers in the lower and medium power range, that means also for continuous wave lasers. (orig.)SIGLEAvailable from TIB Hannover: F94B1498+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Mass Spectrometry Imaging visualization tools developed during the Computis European project

International audienceThe Computis European project (2006-2009) was aimed at developing innovative experimental mass spectrometry imaging (MSI) techniques and software tools for data treatment and visualization, and at validating them in key biological applications (neurobiology, pharmaceutical drug development). The project succeeded in defining a specific standard format for MSI, imzML, in collaboration with the HUPO consortium. The four main MSI software tools developed by the project all handle the imzML format.Data Cube Explorer provides an easy spectral and spatial exploration of MS images: spectrum zooming, scrolling through the dataset masses with a manual contrast tuning for images, selection of Regions Of Interest with the display of the associated spectra. The self-organizing map functionality classifies images according to the intensity of all pixel places and automatically selects images as different as possible. Mirion is a simple visualization module displaying spectra by pixel and for the total image, with zooming and scrolling functions. Histogram of the total ion count of each pixel can be calculated, using different input parameters. Images are displayed for each peak of the total spectrum, with a manual intensity tuning and a comparison of the intensity distributions by pixel between several images.EasyMSI enables spatial and spectral visualization of mass spectrometry imaging datasets (spectrum and image display, peak and pixel picking, zooming on spectra and images, ROI selection), as well as an assistance for the interpretation of data: This assistance includes indicators (relative variance, Moran index, m/z correlation) to highlight peaks that bring interesting information, peak list for molecule identification, spectrum denoising or structure analysis by clustering methods (K-means, fuzzy, hierarchical clustering, diffusion map). EasyMSI offers the advantage of processing and displaying the original data (i.e. without binning).BioMap is an image analysis platform for MSI and Magnetic Resonance Imaging. It includes viewing functions (spectrum and image display, intensity adjustment, zoom, treatment of multiple ROIs, geometrical transformations and operations), and spectrum treatment (spatial or temporal filtering, baseline correction, detrending). More elaborated functions enable a simultaneous view of all dataset images, creation of a movie, statistical and histogram analysis, co-registration of images of one or two dataset(s), and realignment of images. The use and capacities of these tools are presented through a comparative analysis of a rodent urinary bladder dataset in imzML format

Mass Spectrometry Imaging of the Hypoxia Marker Pimonidazole in a Breast Tumor Model

Although tumor hypoxia is associated with tumor aggressiveness and resistance to cancer treatment, many details of hypoxia-induced changes in tumors remain to be elucidated. Mass spectrometry imaging (MSI) is a technique that is well suited to study the biomolecular composition of specific tissue regions, such as hypoxic tumor regions. Here, we investigate the use of pimonidazole as an exogenous hypoxia marker for matrix-assisted laser desorption/ionization (MALDI) MSI. In hypoxic cells, pimonidazole is reduced and forms reactive products that bind to thiol groups in proteins, peptides, and amino acids. We show that a reductively activated pimonidazole metabolite can be imaged by MALDI-MSI in a breast tumor xenograft model. Immunohistochemical detection of pimonidazole adducts on adjacent tissue sections confirmed that this metabolite is localized to hypoxic tissue regions. We used this metabolite to image hypoxic tissue regions and their associated lipid and small molecule distributions with MALDI-MSI. We identified a heterogeneous distribution of 1-methylnicotinamide and acetylcarnitine, which mostly colocalized with hypoxic tumor regions. As pimonidazole is a widely used immunohistochemical marker of tissue hypoxia, it is likely that the presented direct MALDI-MSI approach is also applicable to other tissues from pimonidazole-injected animals or humans

Software tools of the Computis European project to process mass spectrometry images

Among the needs usually expressed by teams using mass spectrometry imaging, often arise user-friendly software able to quickly manage huge data volume and to provide efficient assistance for the interpretation of data. To answer this need, the Computis European project developed several complementary software tools to process mass spectrometry imaging data. Data Cube Explorer provides a simple spatial and spectral exploration for MALDI-ToF and ToF-SIMS data. SpectViewer offers visualization functions, assistance to the interpretation of data, classification functionalities, peak list extraction to interrogate biological database, image overlay and can process data issued from MALDI-ToF, ToF-SIMS and DESI equipments. EasyReg2D is able to register two images, in ASCII format, issued from different technologies. The collaboration between teams being hampered by the multiplicity of equipments and data formats, the project also developed a common data format (imzML) to facilitate the exchange of experimental data and their interpretation by the different software tools. The BioMap platform for visualization and exploration of MALDI-ToF and DESI images was adapted to parse imzML files, enabling its access to all project partners and more globally to a larger community of users. Considering the huge advantages brought by the imzML standard format, a specific editor (vBrowser) for imzML files and converters from proprietary formats to imzML were developed to enable the use of imzML format by a broad scientific community. This initiative is paving the way towards the development of a large panel of software tools able to process mass spectrometry imaging datasets in the future