Mapping Resistance to Argentinean Fusarium (Graminearum) Head Blight Isolates in Wheat

Fusarium head blight (FHB) of wheat, caused by Fusarium graminearum (Schwabe), is a destructive disease worldwide, reducing wheat yield and quality. To accelerate the improvement of scab tolerance in wheat, we assessed the International Triticeae Mapping Initiative mapping population (ITMI/MP) for Type I and II resistance against a wide population of Argentinean isolates of F. graminearum. We discovered a total of 27 additive QTLs on ten different (2A, 2D, 3B, 3D, 4B, 4D, 5A, 5B, 5D and 6D) wheat chromosomes for Type I and Type II resistances explaining a maximum of 15.99% variation. Another four and two QTLs for thousand kernel weight in control and for Type II resistance, respectively, involved five different chromosomes (1B, 2D, 6A, 6D and 7D). Furthermore, three, three and five QTLs for kernel weight per spike in control, for Type I resistance and for Type II resistance, correspondingly, involved ten chromosomes (2A, 2D, 3B, 4A, 5A, 5B, 6B, 7A, 7B, 7D). We were also able to detect five and two epistasis pairs of QTLs for Type I and Type II resistance, respectively, in addition to additive QTLs that evidenced that FHB resistance in wheat is controlled by a complex network of additive and epistasis QTLs.     

Operational performance of grid‐connected PV systems on buildings in Germany

This paper presents operational performance results of grid‐connected PV systems in Germany, as collected and elaborated for the Photovoltaic Power Systems Programme (PVPS) of the International Energy Agency (IEA). Performance ratios obtained from 235 PV installations in Germany and from 133 PV plants in other countries are compared and discussed. For Germany, a significant rise in PV system performance and reliability was observed for new PV installations due to higher component efficiencies (e.g., inverter) and increased availabilities. There is a lack of long‐term experience in performance and reliability of PV systems, owing to the absence of monitoring programmes. As an outcome of IEA PVPS collaborative work, Task 2 provides reliable and worldwide monitoring performance data and results (www.task2.org). Technical and operational data is available for system planning and comparison, for teaching and training purposes as well as for future developments of financing schemes (e.g., feed‐in‐tariffs) in order to stimulate the PV market. Copyright © 2004 John Wiley & Sons, Ltd.     

Superior Mechanical and Magnetic Performance of Highly Anisotropic Sendust-Flake Composites Freeze Cast in a Uniform Magnetic Field

Despite extensive research, the manufacture in the bulk of high-performance flake-based magnetic composites with a highly aligned, nacre-like structure remains challenging. Many challenges can be overcome by freeze casting in an externally applied, uniform magnetic field, which causes both the flakes and the composite walls of the cellular solid to align parallel to the B-field lines. When appropriately sized, the flakes experience a second alignment parallel to the freezing direction because of a shear flow that occurs due to both the volumetric expansion of the ice phase and mold contraction during the directional solidification. The resulting orthotropic structure of the freeze-cast magnetic composite is reflected in orthotropic mechanical and magnetic properties of the material. The magnetic composites manufactured by magnetic-field assisted freeze casting outperform by a factor of 2–4 in terms of stiffness, strength, and toughness materials that are processed in the absence of a magnetic field and do not exhibit a monodomain architecture. Because of the highly aligned microstructure, it is possible to compact the initially lamellar composite with 90% porosity to at least 80% strain. The results presented in this study illustrate the tremendous potential for magnetic freeze casting of magnetic composites for use in power conversion.     

Roadmap to Gigahertz Organic Transistors

Despite the large body of research conducted on organic transistors, the transit frequency of organic field‐effect transistors has seen virtually no improvement for a decade and remains far below 1 GHz. One reason is that most of the research is still focused on improving the charge‐carrier mobility, a parameter that has little influence on the transit frequency of short‐channel transistors. By examining the fundamental equations for the transit frequency of field‐effect transistors and by extrapolating recent progress on the relevant device parameters, a roadmap to gigahertz organic transistors is derived.     

Explaining authors’ contribution to pivotal artifacts during mass collaboration in the Wikipedia’s knowledge base

This article discusses the relevance of large-scale mass collaboration for computer-supported collaborative learning (CSCL) research, adhering to a theoretical perspective that views collective knowledge both as substance and as participatory activity. In an empirical study using the German Wikipedia as a data source, we explored collective knowledge as manifested in the structure of artifacts that were created through the collaborative activity of authors with different levels of contribution experience. Wikipedia’s interconnected articles were considered at the macro level as a network and analyzed using a network analysis approach. The focus of this investigation was the relation between the authors’ experience and their contribution to two types of articles: central pivotal articles within the artifact network of a single knowledge domain and boundary-crossing pivotal articles within the artifact network of two adjacent knowledge domains. Both types of pivotal articles were identified by measuring the network position of artifacts based on network analysis indices of topological centrality. The results showed that authors with specialized contribution experience in one domain predominantly contributed to central pivotal articles within that domain. Authors with generalized contribution experience in two domains predominantly contributed to boundary-crossing pivotal articles between the knowledge domains. Moreover, article experience (i.e., the number of articles in both domains an author had contributed to) was positively related to the contribution to both types of pivotal articles, regardless of whether an author had specialized or generalized domain experience. We discuss the implications of our findings for future studies in the field of CSCL.