Modellqualität als Indikator für Softwarequalität: eine Taxonomie

Zusammenfassung  Komplexit?t, Anforderungsmanagement und Variantenvielfalt sind zentrale Herausforderungen bei der Entwicklung und Evolution heutiger softwaregesteuerter Systeme. Diesen wird zunehmend durch den Einsatz modellbasierter Entwicklungsmethoden begegnet. Dadurch wird das Modell zum zentralen Artefakt und die Erstellung und Nutzung von Modellen zu einer zentralen T?tigkeit in der Softwareentwicklung. Mit der Bedeutung der Modelle steigen auch die Ansprüche an ihre Qualit?t. Dieser Beitrag untersucht die Implikationen, die daraus entstehen, insbesondere werden sinnvolle Qualit?tsmerkmale für softwarebeschreibende Modelle identifiziert und diskutiert.     

Thermodynamics and Single Particle Spectra of the Kondo Insulator by the Variational Self-Energy Method

The variational self-energy method is applied to a study of the half-filled periodic Anderson model. Trial-self-energies and the numerical value of the Luttinger–Ward functional are obtained by diagonalization of a single c – f dimer. The dependence of the zero-temperature single-particle gap on the c – f-hybridization is found in qualitative agreement with mean-field theory for the Kondo-lattice, the specific heat agrees well with numerical results from density-matrix-renormalization group calculations. The single particle spectral function at finite-temperature shows marked deviations from a hybridization picture which agree well with quantum Monte–Carlo results.     

An analysis method for atomistic abrasion simulations featuring rough surfaces and multiple abrasive particles

We present a molecular dynamics (MD) model system to quantitatively study nanoscopic wear of rough surfaces under two-body and three-body contact conditions with multiple abrasive particles. We describe how to generate a surface with a pseudo-random Gaussian topography which is periodically replicable, and we discuss the constraints on the abrasive particles that lead to certain wear conditions. We propose a post-processing scheme which, based on advection velocity, dynamically identifies the atoms in the simulation as either part of a wear particle, the substrate, or the sheared zone in-between. This scheme is then justified from a crystallographic order point of view. We apply a distance-based contact zone identification scheme and outline a clustering algorithm which can associate each contact atom with the abrasive particle causing the respective contact zone. Finally, we show how the knowledge of each atom’s zone affiliation and a time-resolved evaluation of the substrate topography leads to a break-down of the asperity volume reduction into its components: the pit fill-up volume, the individual wear particles, the shear zone, and the sub-surface substrate compression. As an example, we analyze the time and pressure dependence of the wear volume contributions for two-body and three-body wear processes of a rough iron surface with rigid spherical and cubic abrasive particles.     

Heavy metals contribution of non-aqueous fluids used in offshore oil drilling

A monitoring program was performed to investigate heavy metal content alteration due to exploratory drilling for oil using non-aqueous fluids (NAFs) in Brazilian offshore, 900 m deep. Fourteen elements were monitored in 54 sites and it was verified that after drilling activities the average Ba concentration was remarkably increased with respect to background level, even 1 year after the activity. A minor increase in Mn and a moderate increase in Al concentrations were verified. The Cd, Cr, Ni, As, Co, Cu, Pb, V, and Zn concentrations were at the background levels, ca. 1 year after the NAFs drilling materials deposition on the seafloor. The Al, Ba, Cd, Cr, Cu, Ni and Zn mean concentrations were significantly different (P<0.05) between the three sampling operations (cruises) performed, while As, Cd, Fe and Pb presented different mean values according to the distance of the oil well, independent of the sampling operation. Interaction between sampling operation and distance was observed for Mn. In all sediment samples the Hg concentration was below the detection limit (0.07 μg g⁻¹).     

Glyphosate Adsorption from Water Using Hierarchically Porous Metal–Organic Frameworks

The selective removal of one ligand in mixed-ligand MOFs upon thermolysis provides a powerful strategy to introduce additional mesopores without affecting the overall MOF structure. By varying the initial ligand ratio, MOFs of the MIL-125-Ti family with two distinct hierarchical pore architectures are synthesized, resembling either large cavities or branching fractures. The performance of the resulting hierarchically porous MOFs is evaluated toward the adsorptive removal of glyphosate (N-(phosphonomethyl)glycine) from water, and the adsorption kinetics and mechanism are examined. Due to their strong affinity for phosphoric groups, the numerous Ti–OH groups resulting from the selective ligand removal act as natural anchor points for effective glyphosate uptake. The relationships between contact duration, glyphosate concentration, and adsorbent dosage are investigated, and the impact of these parameters on the effectiveness of glyphosate removal from contaminated water samples is examined. The introduction of additional mesopores has increased the adsorption capacities by nearly 3 times with record values exceeding 440.9 mg g⁻¹, which ranks these MOFs among the best-reported adsorbents.     

The Formation of Calcified Nanospherites during Micropetrosis Represents a Unique Mineralization Mechanism in Aged Human Bone

Osteocytes—the central regulators of bone remodeling—are enclosed in a network of microcavities (lacunae) and nanocanals (canaliculi) pervading the mineralized bone. In a hitherto obscure process related to aging and disease, local plugs in the lacuno‐canalicular network disrupt cellular communication and impede bone homeostasis. By utilizing a suite of high‐resolution imaging and physics‐based techniques, it is shown here that the local plugs develop by accumulation and fusion of calcified nanospherites in lacunae and canaliculi (micropetrosis). Two distinctive nanospherites phenotypes are found to originate from different osteocytic elements. A substantial deviation in the spherites' composition in comparison to mineralized bone further suggests a mineralization process unlike regular bone mineralization. Clearly, mineralization of osteocyte lacunae qualifies as a strong marker for degrading bone material quality in skeletal aging. The understanding of micropetrosis may guide future therapeutics toward preserving osteocyte viability to maintain mechanical competence and fracture resistance of bone in elderly individuals.     

The Donauspital-Stolzalpe concept (Danube Hospital, Vienna, Austria). Corrective osteotomy with selective labrum surgery following preoperative MRI arthrography

Concomitant pathologies (labral lesions, intra-/extra-osseous ganglia and stress bone marrow edema) in adult residual hip dysplasia (RHD) might influence the outcome of conservative hip surgery. The aim of our prospective clinical study was to assess the value of preoperative MR arthrography in diagnosing concomitant lesions and in making surgical decisions in RHD. The first 37 consecutive patients with a minimum follow-up of 18 months have been analysed. All 37 patients presented RHD with the clinical symptomatology of labral lesions and underwent routine preoperative MRA. According to clinical, radiological and MR arthrographical criteria, these 37 patients were subdivided into four therapeutic subgroups: (1) reorientation of the acetabulum using the T?nnis triple pelvic osteotomy (TPO); (2) intertrochanteric varisation osteotomy (IVO); (3) palliative decompression with only symptomatic partial resection of the torn labrum (PALL); (4) primary total hip replacement (TEP). Based on the preliminary clinical and radiological outcomes of these four subgroups, the following conclusions can be drawn: labral lesions are considered to be a sign of chronic joint instability. Therefore, acetabular malorientation should be corrected by redirectional osteotomy of the acetabulum (TPO-subgroup) even in low grades of RHD if labral lesions are present. "Palliative" labral resections without corrective osteotomy (PALL subgroup) in secondary osteoarthritis due to RHD are definitively obsolete, because they rapidly progress to severe osteoarthritis due to surgically accelerated joint instability. In RHD with highly osteoarthritic hip joints and concomitant lesions, one should not hesitate to perform primary THR even in young patients.