Automated identification of Fos expression

The concentration of Fos, a protein encoded by the immediate-early gene c-fos, provides a measure of synaptic activity that may not parallel the electrical activity of neurons. Such a measure is important for the difficult problem of identifying dynamic properties of neuronal circuitries activated by a variety of stimuli and behaviours. We employ two-stage statistical pattern recognition to identify cellular nuclei that express Fos in two-dimensional sections of rat forebrain after administration of antipsychotic drugs. In stage one, we distinguish dark-stained candidate nuclei from image background by a thresholding algorithm and record size and shape measurements of these objects. In stage two, we compare performance of linear and quadratic discriminants, nearest-neighbour and artificial neural network classifiers that employ functions of these measurements to label candidate objects as either Fos nuclei, two touching Fos nuclei or irrelevant background material. New images of neighbouring brain tissue serve as test sets to assess generalizability of the best derived classification rule, as determined by lowest cross-validation misclassification rate. Three experts, two internal and one external, compare manual and automated results for accuracy assessment. Analyses of a subset of images on two separate occasions provide quantitative measures of inter- and intra-expert consistency. We conclude that our automated procedure yields results that compare favourably with those of the experts and thus has potential to remove much of the tedium, subjectivity and irreproducibility of current Fos identification methods in digital microscopy

Thermal imaging with pyroelectric vidicons

This paper reviews the major problems plaguing the pyroelectric vidicon from its inception: short tube life, low responsivity and spatial resolution, ineffective temporal modulation of the radiation. The tube life was extended from a few hundred to over two thousand operating hours by abandoning the gassy tube approach, in which negative charges are eliminated by positive ions1 and going to hard vacuum tubes. The latter required a new readout method to reset the target potential by secondary electron emission.2 Special coatings protect the targets against erosion by the electron beam and impose a responsivity that is uniform within about 5 %. The tube performance was increased by reducing the electron beam discharge lag. This was achieved by using a laminar flow electron gun to lower the beam impedance and by replacing the triglycine sulfate target by deuterated triglycine fluoroberyllate to reduce the capacitance.3 These measures improved the performance of the panning camera with a T/1 optics from a minimum detectable temperature difference of 0.5°C at 100 TV lines to 0.5°C at 250 TV lines. Temporal modulation of the input radiation, required to generate video signals in pyroelectric vidicons, restricts the camera operation either to imaging of moving objects or to panning or chopping. These modes will be discussed, and it will be shown that chopping and proper signal processing4 remove the thermal streaking characteristic of the panning mode without introducing objectionable flicker. As a result pyroelectric vidicon cameras approach the image quality of a well designed infrared scanner having the equivalent performance.</jats:p

Altlastenbericht 1. Fortschreibung

With 1 mapTIB Hannover RO 8421(1989,1) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman