The increasing performance of high resolution surface analytical instruments, in the nanometer range, requires suitable site conditions, in order to achieve the design performance specifications. Due to our practical experience in selling these instruments over the last twenty years we have established a well defined procedure, which is used for the characterisation of new instruments, as well as for the assessment of customer site conditions.
KEYWORDS: Sensors, Foam, Digital signal processing, Signal processing, Quality measurement, Field programmable gate arrays, CCD image sensors, Microcontrollers, CCD cameras, Data processing
With this publication an automatic measurement equipment for quality control in the loop slitting department is presented. The sensor is a stand-alone system. A digital signal processor, a field programmable gate array, and a microcontroller collect and process the data of the linear CCD-sensors.
The elongation curve of RBC as determined by rheoscopy or ektacytometry (laser diffraction) resembles a rectangular hyperbola. The experimental data obtained so far included too large errors of measurement to allow precise mathematical description. The combination of laser diffraction with image analysis has improved ektacytometry considerably, such that the error of measurement is reduced to less than 0.5%. In laminar flow RBC of healthy donors are elongated elliptically (p <EQ 0.001). Using the precise data of elliptical deformation, the elongation curve can be described to be hyperbolic. Hence, the double reciprocal plot gives a linear curve which -- over a wide range of shear stress (15 to 500 dyn/cm2) -- fits well the experimental data (r >= 0.99: p <EQ 0.001). The stress strain characteristics (i.e. elongation curve) can be described by two parameters: maximum elongation (Emax) and the shear stress needed for half-maximum elongation (KE).
In quite a large number of disorders, reduced flexibility of red blood cells (RBC) can be detected. In cardiovascular diseases it is supposed that rigidification of RBC may be regarded as a pathogenetic factor aggravating ischemia by disturbing capillary perfusion. Most methods established so far to estimate RBC deformability are hard to standardize and include large measurement errors. We present a low-cost system to determine RBC shape and flexibility. It combines laser diffraction of RBC in Couette flow with automated computer assisted image analysis. Effortless handling allows the system to be used for RBC elongation measurements even in routine diagnostics. Analysis of the whole information content of diffraction patterns reduces errors due to noisy diffraction patterns of working a little off axis. The system allows detection of very small changes in flexibility (less than 5%). The accuracy of measurement is not affected by variation of hematocrit or the intensity of transmitted light. Using the newly developed system it is demonstrated (1) that mechanically induced RBC rigidification may occur without hemolysis; (2) that in photodynamic therapy (e.g., pheophorbide A) RBC rigidification occurs during irridation; and (3) that in-vitro aging of conserved blood may partly be inhibited by calmodulin antagonists (e.g., fendiline).
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