The Role of Contract in Quality Assurance

In recent years a debate has raged about the accuracy of the cost-of-living index. A major bone of contention regards capturing the changes in the quality of goods. Were it easy to measure quality, disputes about the magnitude of the change would have not arisen. The difficulty in pinpointing quality is not merely an academic or policy question; it also poses a major problem for exchange. When the quality of the exchanged commodities is uncertain, costly disputes about what one gives and the other receives are bound to arise. Such disputes are a matter of property rights, of who owns what.Contracts and Vertical Integration, Agricultural and Food Policy,

"Offener Unterricht? Rechner?... Dafür bleibt keine Zeit...."

Der Titel drückt die Befürchtung vieler Lehrpersonen aus, dass mit neuen Unterrichtsmethoden, die dem Schüler und der Schülerin mehr Raum zur Eigenaktivität lassen, sowie der Integration von Rechnern in den Unterricht curriculare Vorgaben noch schwerer zu erreichen sind als ohne diese Innovationen. Verändern der Unterrichtsmethode und Rechnereinsatz werden als zeitliches Additivum empfunden, das zusätzlich belastet. Dagegen steht die Erfahrung von Lehrpersonen, die offenen Unterricht mit integriertem Rechnereinsatz nicht als Hürde sondern als besondere Chance erleben, inhaltliche und prozessuale Ziele gleichermaßen und gemeinsam in den Blick zu nehmen. Aufgrund dieser Erfahrungen ist im Rahmen des Lehrerfortbildungsprojekets T³ (Teachers Teaching with Technology) die Idee entstanden, Unterrichtsmaterial zu entwickeln, das exemplarisch für eine veränderte Unterrichtskultur mit integriertem Einsatz von Computeralgebrasystemen (CAS) stehen kann. Damit sollte an einem Beispiel ein Weg aufgezeigt werden, Öffnen von Unterricht und Medieneinsatz als Einheit zu begreifen mit dem Ziel, Mathematik und mathematische Tätigkeiten gleichermaßen im Unterricht erlebbar zu machen. So entstand Unterrichtmaterial zur Untersuchung ganzrationaler Funktionen (11. Jg), an dem Schülerinnen und Schüler sich über mehrere Wochen vielfältige Aspekte einer Funktionsuntersuchung selbstständig erarbeiten. Dies geschieht in Form einer "Lernwerkstatt", die im Rahmen des Forschungsprojektes MUKI (Mathematikunterricht zwischen Konstruktion und Instruktion) an der Universität Duisburg-Essen theoretisch reflektiert, weiterentwickelt und evaluiert wurde

A hybrid moment equation approach to gas-grain chemical modeling

[Context] The stochasticity of grain chemistry requires special care in modeling. Previously methods based on the modified rate equation, the master equation, the moment equation, and Monte Carlo simulations have been used. [Aims] We attempt to develop a systematic and efficient way to model the gas-grain chemistry with a large reaction network as accurately as possible. [Methods] We present a hybrid moment equation approach which is a general and automatic method where the generating function is used to generate the moment equations. For large reaction networks, the moment equation is cut off at the second order, and a switch scheme is used when the average population of certain species reaches 1. For small networks, the third order moments can also be utilized to achieve a higher accuracy. [Results] For physical conditions in which the surface reactions are important, our method provides a major improvement over the rate equation approach, when benchmarked against the rigorous Monte Carlo results. For either very low or very high temperatures, or large grain radii, results from the rate equation are similar to those from our new approach. Our method is faster than the Monte Carlo approach, but slower than the rate equation approach. [Conclusions] The hybrid moment equation approach with a cutoff and switch scheme is applicable to large gas-grain networks, and is accurate enough to be used for astrochemistry studies. The layered structure of the grain mantle could also be incorporated into this approach, although a full implementation of the grain micro-physics appears to be difficult.Comment: 11 pages, 4 figures. Accepted for publication in Astronomy and Astrophysic

Molecular Determinants of Tumor Re-Initiation in Breast Cancer

Cancer progression is characterized by the formation of tumors in primary organs and the subsequent re-formation of tumors in distant metastatic sites. The tumorigenic, or tumor-forming, capacity of cancer cells drives cancer along a continuum that includes primary tumor formation, metastatic re-initiation, and macroscopic relapse. As such, a greater understanding of the biological features and molecular determinants that govern tumor-forming capacity in the primary and metastatic site is of great importance to the scientific and biomedical communities. This thesis presents an unbiased approach to systematically select and characterize breast cancer cells with enhanced tumorigenic capacity in order to elucidate genes and cell biological features that are important to tumor-forming potential in primary and metastatic sites. The first part of this thesis describes a method to select for populations of cells with enhanced tumor-forming capacity from heterogeneous breast cancer populations. Two human Estrogen Receptor-negative (ER-negative) breast cancer cell lines, MDA-231 and CN34, were subjected to in vivo selection to yield ‘tumorigenic-enriched’ (TE) derivatives, which demonstrated enhanced tumor re-initiation capacity in multiple organ sites in a xenograft model. In the second part of this study, a systematic approach was employed to identify genes that promote tumor re-initiation. Transcriptomic profiling revealed a set of genes–LAMA4, FOXQ1, and NAP1L3–that were expressed at greater levels in tumorigenic-enriched derivatives relative to their parental populations. These genes were also expressed at greater levels in independently derived metastatic populations. All three of these genes were found to promote metastatic efficiency, and one of these genes, LAMA4, was subjected to further characterization. Functional studies revealed LAMA4 to promote clonal expansion during substratum-detachment in vitro, tumor re-initiation in multiple organ microenvironments, the proliferation of disseminated metastatic cells, and the formation of incipient micro-metastatic colonies in vivo. The final phase of this study revealed the association of LAMA4 expression with human breast cancer progression and clinical outcome in multiple patient datasets. In support of the role of LAMA4 in promoting early tumor formation, malignant breast cancer cells isolated from incipient breast cancer lesions were found to express higher levels of LAMA4 relative to pre-malignant cells from matched patient lesions. In addition, consistent with functional studies demonstrating the role of LAMA4 in driving primary and metastatic tumor re-initiation, higher levels of LAMA4 expression in ER-negative primary tumors correlated with worse relapse-free survival in multiple patient clinical cohorts