Erlangen-Nürnberg, Univ., Diss., 2010.

Universiẗat, Diss., 2003--Würzburg.

Invertasen spielen eine zentrale Rolle im Metabolismus der Pflanzen und werden über eine Vielzahl von Faktoren in ihrer Regulation beeinflusst. Invertasen mit pH-Optimum im sauren Bereich liegen dabei als vakuoläre und zellwandgebundene Isoformen einer Genfamilie in den Pflanzen vor. Im Rahmen dieser Arbeit wurden zum ersten Mal 9 putative Invertasen aus der Nutzpflanze Brassica napus, sowie 4 weitere putative Mitglieder der bereits bekannten Tabakinvertasenfamilie isoliert und Expressionsprofile für die neu klonierten Invertasen erstellt. Symplastisch isolierte Zellen, wie z. B. Pollen und Pollenschläuche, sind auf die Expression zellwandgebundener Invertasen besonders angewiesen, da sie Kohlen-hydrate primär in Form von Fructose und Glucose aufnehmen, die über die Invertasen-vermittelte Spaltung aus Saccharose gebildet werden. An Tabak hatten Goetz et al. (2001) gezeigt, dass eine Inhibierung dieser pollen¬spezi¬fischen Invertaseaktivität zu männlich sterilen Pflanzen führt. Im Rahmen dieser Arbeit wurde nachgewiesen, dass durch Inhibierung der Zellwandinvertase¬aktivität mittels Antisense-Technik oder Expression des proteinogenen Invertase-Inhbitors AtC/VIF2 auch männlich sterile Arabidopsis-Pflanzen generiert werden können. Ein Aktivitätsvergleich der Invertase-promotoren von Nin88 aus Tabak und AtcwINV2 aus Arabidopsis im jeweiligen homo- und heterologen System zeigte jedoch, dass der Einsatz dieser pollenspezifischen Promotoren zur Erzeugung männlich steriler Pflanzen über Familiengrenzen hinweg nicht möglich ist. Neben ihrer Funktion als Energieträger stellen Kohlenhydrate auch Signalmoleküle dar, die in die Regulation zentraler Prozesse der Pflanzen eingreifen. Anhand von Keimungsanalysen mit Arabidopsis-Pollen wurde festgestellt, dass Hexokinase-unabhängige Signalingwege involviert sein müssen, um ein Auskeimen der Pollen zu ermöglichen. Dabei kann die Hexokinase-vermittelte Inhibition der Pollenkeimung vermutlich durch die Beteiligung anderer Signaling-Wege aufgehoben werden. Es wurde außerdem die zuckerabhängige Ausbildung blasenartiger Strukturen an Arabidopsis-Pollen nachgewiesen, die vermutlich durch einen Zucker-spezifischen Abbruch des Pollenschlauchwachstums gebildet werden. / Invertases with acid pH-optimum play a central role in plant metabolism and are regulated by numerous biotic and abiotic factors. They consist of vacuolar and extracellular isoforms of a gene family in plants. For the first time 9 putative members of the invertase family of Brassica napus, as well as 4 additional putative tobacco acid invertases were cloned in this work and expression profiles were analysed. Symplastically isolated cells, like pollen and pollen tubes, in particular depend on the expression of extracellular invertases, since they prefer the uptake of glucose and fructose. These hexoses are generated by the invertase-mediated cleavage of sucrose. Goetz et al. (2001) have shown on tobacco that inhibition of the pollen specific invertase activity lead to male sterile plants. In this work it was shown that inhibition of cell wall invertase activity via antisense technology or expression of the proteinaceous invertase inhbitor AtC/VIF2 also causes male sterility in Arabidopsis thaliana. Comparison of the promoter activities of the invertases Nin88 (tobacco) and AtcwINV2 (Arabidopsis) in the corresponding homo- and heterologous systems revealed that the use of these pollen specific promoters for generating male sterile plants is not possible in diverse plant families. Besides their function as energy source, carbohydrates are signaling molecules that influcence regulation of central processes in the plants. On the basis of germination assays with Arabidopsis pollen, it was shown that hexokinase-independent signaling pathways must be involved to permit normal pollen germination. In this context, hexokinase-mediated inhibition of pollen germination might be overrode by the involvement of other signaling pathways. In addition, the sugar-dependent generation of bubble-like structures at Arabidopsis pollen was demonstrated, which might be caused by the sugar-specific interruption of pollen tube growth.

Previous studies have shown that football is getting more commercial and together with increased digital possibilities football clubs can bypass traditional media and attract audience via their own media channels. With strategic communication and agenda setting as a theoretic background I wanted to investigate how Swedish top football clubs used their own media channels, what affected the media strategy of the big clubs in Sweden and how sports journalists perceived the football club’s communicative development. I choose AIK as a case and I observed them and sports journalists before, during and after the local derby against Djurgården. Furthermore, I analyzed AIK´s content in their own media channels and media’s coverage of AIK-Djurgården. Finally, I conducted qualitative interviews with representatives from AIK and three sport journalists at three Swedish newspapers. My study revealed that the AIK significantly planned and applied strategic content and messaging across their media channels, consistent with the techniques used by more mature and traditional media organizations. When it comes to access to the club and players there are tendencies and signs of less accessibility, but in general Swedish sport journalists see the Swedish Allsvenskan as open and not as commercial and controlled as the major European football leagues. In the end journalists believe that the material which is produced by AIK and the other big Stockholm clubs (Djurgården and Hammarby) can be seen as a compliment, but also a competitor to the material that media produce.

Approximate query processing is an adequate technique to reduce response times and system load in cases where approximate results suffice. In database literature, sampling has been proposed to evaluate queries approximately by using only a subset of the original data. Unfortunately, most of these methods consider either only certain problems arising due to the use of samples in databases (e.g. data skew) or only join operations involving multiple relations. We describe how well-known sampling techniques dealing with group-by operations can be combined with foreign-key joins such that the join is computed after the generation of the sample. In detail, we show how senate sampling and small group sampling can be combined efficiently with the idea of join synopses. Additionally, we introduce different algorithms which maintain the sample if the underlying data changes. Finally, we prove the superiority of our method to the naive approach in an extensive set of experiments.