Типоморфизм хлоритов Сухаринского рудного поля

Изучены хлориты из руд и метасоматитов скарново-магнетитового, с наложенной золото-сульфидной минерализацией, Сухаринского рудного поля (Горная Шория). Выделены две разновидности хлоритов: метасоматические и прожилковые, приведены данные об их типоморфных особенностях; установлена зависимость железистости метасоматического хлорита от состава замещаемых минералов; установлено возрастание железистости всех типов хлоритов по мере удаления от Тельбесского гранитоидного массива, что указывает на парагенетическую связь гидротермальной минерализации с гранитоидным магматизмом

Проблема социальных коммуникаций в контексте современных международных отношений

Исследована роль технологического аспекта социальных коммуникаций в современных международных отношениях. Показано, что информационные технологии, устранив барьеры коммуникаций, как во внутренней, так и международной жизни, сделали внешнюю политику крупных государств более сдержанной и ответственной

Влияние высокодисперсных наполнителей на термические и механические характеристики эпоксидных композитов

Исследование термической стабильности, горючести и механической прочности эпоксидных композитов при введении в эпоксидную смолу замедлителей горения в качестве наполнителей в высокодисперсном состоянии.Investigation of the thermal stability, flammability and mechanical strength of epoxy composites when flame retardants are added to the epoxy resin as fillers in a highly dispersed state

High and Low Molecular Weight Fluorescein Isothiocyanate (FITC)–Dextrans to Assess Blood-Brain Barrier Disruption: Technical Considerations

This note is to report how histological preparation techniques influence the extravasation pattern of the different molecular sizes of fluorescein isothiocyanate (FITC)–dextrans, typically used as markers for blood-brain barrier leakage. By using appropriate preparation methods, false negative results can be minimized. Wistar rats underwent a 2-h middle cerebral artery occlusion and magnetic resonance imaging. After the last imaging scan, Evans blue and FITC–dextrans of 4, 40, and 70 kDa molecular weight were injected. Different histological preparation methods were used. Sites of blood-brain barrier leakage were analyzed by fluorescence microscopy. Extravasation of Evans blue and high molecular FITC–dextrans (40 and 70 kDa) in the infarcted region could be detected with all preparation methods used. If exposed directly to saline, the signal intensity of these FITC–dextrans decreased. Extravasation of the 4-kDa low molecular weight FITC–dextran could only be detected using freshly frozen tissue sections. Preparations involving paraformaldehyde and sucrose resulted in the 4-kDa FITC–dextran dissolving in these reactants and being washed out, giving the false negative result of no extravasation. FITC–dextrans represent a valuable tool to characterize altered blood-brain barrier permeability in animal models. Diffusion and washout of low molecular weight FITC–dextran can be avoided by direct immobilization through immediate freezing of the tissue. This pitfall needs to be known to avoid the false impression that there was no extravasation of low molecular weight FITC–dextrans

Höherdimensionale Modelle zur Segmentierung biologischer Strukturen

Many tasks in medical image processing require the robust segmentation of images. Information on the position and contour of objects allows the subsequent extraction of relevant quantitative information. This task is difficult due to actual imaging modalities that provide multi-dimensional (volumetric, time-variable, and multichannel) images. A newly formulated model is able to segment objects with arbitrary occurrence in images of any dimension. Model based segmentation methods are categorized. Subsequently, it is possible to formulate specifications that a model must meet for the robust segmentation of medical images. According to these specifications, a balloon-model is introduced. Objects are represented by a simplicial complex. Using mechanic simulations, this model is deformed to adapt to significant structures in an image. For the computation of image influences in single- and multichannel images, subsets of the same dimension as the image space itself are taken into account. The balloon-model is combined with a shape-based model. Shape knowledge from an automatically generated point distribution model is used to compute directed shape forces. The combination of all forces results in a segmentation result even if an initial contour is not given. The intersection of simplexes forms an inconsistency of the contour. This frequent problem for active contours is solved by methods that detect and correct such intersections. If necessary, these methods adaptively change the topology of objects. Further methods were developed to allow the transfer into clinical routine. The required parameter setting can be trained based on an exemplary segmentation. For heterogeneous image sets, more than one exemplary segmentation can be given. Then, an individual parameter set is computed for each image using global texture features and their similarity to prototype images. Non-contextual experiments on synthetic image material quantify the quality of segmentations for varying image properties and the dependency of the model on parameter choices. For contextual tests on medical images, usually no valid reference segmentation is known. Therefore, a silver-standard method to create synthetic images with realistic textures and contours was developed. The model was exemplary applied to immunohistochemically stained micrographs of neurons, CTs of vertebrae following prolaps of intervertebral discs, a MR of the beating heart, and laryngoscopic color video sequences. The robustness of segmentations was quantified in all applications

<title>Automatic parameter setting for balloon models</title>

We describe a &quot;learning-from-examples&quot;-method to automatically adjust parameters for a balloon model. Our goal is to segment arbitrarily shaped objects in medical images with as little human interaction as possible. For our model, we identified six significant parameters that are adjusted with respect to certain applications. These parameters are computed from one manual segmentation drawn by a physician. (1) The maximal edge length is derived from a polygon-approximation of the manual segmentation. (2) The size of the image subset that exerts external influences on edges is set according to the scale of gradients normal to the contour. (3) The offset of the assignment from greylevels to image potentials is adjusted such that the propulsive pressure overcomes image potentials in homogeneous parts of the image. (4) The gain of this assignment is tuned to stop the contour at the border of objects of interest. (5) The strength of deformation force is computed to balance the contour at edges with ambiguous image information. (6) These parameters are computed for both, positive and negative pressure. The variation that gives the best segmentation result is chosen. The analytically derived adjustments are optimized with a genetic algorithm that evolutionarily reduces the number of misdetected pixels. The method is used on a series of histochemically stained cells. Similar segmentation quality is obtained applying both, manual and automatic parameter setting. We further use the method on laryngoscopic color image sequences, where, even for experts, the manual adjustment of parameters is not applicable