Spherical harmonic coefficients for the potential of a constant-density polyhedron

Recurrent relationships for the definitions of fully normalized spherical harmonic coefficients C?_n,m and S?_n,m are derived and integrated analytically to yield the gravitational potential of a constant-density polyhedron. The algorithm is expressed in a C language computer program.     

Software quality management in turbulent times – are there alternatives to process oriented software quality management?

Software Quality Journal - There is a widely accepted paradigm of successful software development, called process oriented software quality management (PSQM). The proponents of PSQM claim that it...     

Ortselektive laserchemische Oberflächenfunktionalisierung von Polymeren im Mikrometerbereich. Selective laser‐chemical micro surface modification of polymers

Polymeric substrate materials like polystyrene (PS), polycarbonate (PC) or cyclic olefins (COC) are getting more attention besides silica, glass and ceramic for the preparation of reaction vessels, optical slides, microfluidic components or microtiterplates in applications like medical diagnostics and pharmaceutical drug screening. Actually, the market of transparent polymeric chips is demanding the availability of modified surfaces with well defined arrays of wettable areas or special chemical functionalities. The modified areas are starting point to graft bioactive molecules, for instance proteins or DNA‐oligomers. Another application is pretreatment of adhesive bonded joints. Presently surface modifications are performed chemically and physically by plasma surface interaction. IWS has developed a new technique for dry chemical structuring of polymeric surfaces based on the principle of excimer laser irradiation in reactive gas atmosphere. This technique is characterized by a high resolution and a negligible amount of chemicals. The procedure consists of only a few processing steps, in contrast to conventional lithographic structuring methods. Also wetting problems do not play a role as they do in printing techniques. The technology provides the possibility of tailoring the chemical and topographical surface properties from ultrahydrophobic to hydrophilic or to functionalize areas of choice in the μm range with a chemical group of defined density. Using an excimer‐laser to induce reactions, mask imaging can be applied for microstructuring the surface with new properties, e. g. for microarrays. In addition, the laser allows defined amount of energy into the elementary reaction, according to the wavelength applied, which opens the possibility of replacing atoms in the polymer molecules by other atoms or molecules taken from an agent in the environment, in a selective way. The precondition is that both the polymer and the agent absorb the same wavelength. For instance 193 nm radiation (ArF excimer laser) is absorbed by polyolefines and by ammonia allowing an exchange of H atoms for amino groups by which the surface is changed to starting point to graft bioactive molecules. Chemical microstructures for instance amino group arrays have been realized on a variety of polymeric materials like cyclic olefin foil. This array of monofunctionality is the starting point for the preparation of parallel microreactors. These samples of topographical and chemical microstructures are the first step for biochemical preparations in medical diagnostic kits, DNA‐, protein‐ or cell biochips. The upscaling of the laser modification process in a multi‐chamber reactor offers the semicontinuous functionalization of polymers in pilot scale or in batch processing. On this basis the surface modification step can be adapted into a mass production line of “Lab‐on‐a‐chip” systems.     

An ADI-based adaptive mesh Poisson solver for the MHD code NIRVANA

I describe a Poisson solver for the adaptive mesh magnetohydrodynamics (MHD) code NIRVANA using ADI techniques (ADI: Alternative Direction Implicit). The solver is fit to the mesh refinement framework of the code and utilizes its special block-structured design. The key part of the method is an algorithm for the intelligent clustering of subgrids which permits the application of numerical methods based on dimensional operator splitting like ADI. Test problems show the convergence of this ansatz.     

Oligodendrogliomas. Part II: A new grading system based on morphological and imaging criteria

Myocardial perfusion scintigraphy is a noninvasive diagnostic method for the evaluation of patients with suspected or proven coronary artery disease (CAD). We utilized case-based reasoning (CBR) methods to develop the computer-based image interpretation system SCINA which automatically derives from a scintigraphic image data set an assessment concerning the presence of CAD. We compiled a case library of 100 patients who underwent both perfusion scintigraphy and coronary angiography to document or exclude the presence of CAD. The angiographic diagnosis of the retrieved nearest neighbor match of a scintigraphic input case was selected as the CBR diagnosis. We examined the effects of input data granularity, case indexing, similarity metric, and adaptation on the diagnostic accuracy of the CBR application SCINA. For the final prototype, sensitivity and specificity for detection of coronary heart disease were 98% and 70% suggesting that CBR systems may achieve a diagnostic accuracy that appears feasible for clinical use.     

Incident Light Metering in Computer Graphics

Every rendering process consists of two steps. The first is the computing of luminance values by methods like ray tracing or radiosity, and the second step is the mapping of the computed values to values appropriate for displaying. In the last years, as alternative to simple linear scaling which maps the average value to the medium luminance, some new ways of mapping were introduced. These new methods are based on photography analogies and on human vision models. All existing methods follow, implicitly or explicitly, the reflected light metering principle. The method introduced in this paper is the first that follows the incident light metering used in professional photography and in the movie industry. Actually the irradiances are measured using a set of diffusors, which are placed automatically in the scene, and a linear scale factor based on these measurements is used to map the computed radiances to the display device. The diffusors act as half space integrators, they collect the light energy from all half space directions. The light comes from the primary light sources, or it is the result of various interreflections. The newly introduced method reproduces original colors faithfully even for scenes with very low or very high average reflectivity.