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Emerging noninfrastructure-based network types like mobile ad-hoc networks (MANETs) are becoming suitable platforms for exchanging/sharing real-time video streams, because of recent progress in routing algorithms, throughput and transmission bit-rate. MANETs are characterized by highly dynamic behavior of the transmission routes and path outage probabilities. In this article a multisource streaming approach is presented to increase the robustness of real-time video transmission in MANETs. For that, video coding as well as channel coding techniques on the application layer are introduced, exploiting the multisource representation of the transferred media. Source coding is based on the scalable video coding (SVC) extension of H.264/MPEG4-AVC with different layers for assigning importance for transmission. Channel coding is based on a novel unequal packet loss protection (UPLP) scheme, which is based on Raptor forward error correction (FEC) codes. While in the presented approach, the reception of a single stream guarantees base quality only, the combined reception enables playback of video at full quality and/or lower error rates. Furthermore, an application layer protocol is introduced for supporting peer-to-peer based multisource streaming in MANETs

In semi-arid regions, the effects of grazing or sparing management on natural communities of long-lived plants generally take decades to become evident. Event-driven dynamic behaviour, unpredictable and low rainfall, and complicated interactions between species make it difficult to gather sufficient understanding of vegetation dynamics to be able to develop guidelines for sustainable management. Simulation models that consider the essential processes that determine vegetation dynamics offer scope for quantitatively exploring long-term vegetation dynamics of arid and semi-arid rangelands. In this paper we review three models that were aimed to provide an understanding of the vegetation dynamics and management of different typical vegetation types in South Africa, including the Karoo shrubland, the shrub-grassland of the southern Kalahari, and pure semi-arid grasslands.

Tn5 is a composite transposon consisting of two IS50 sequences in inverted orientation with respect to a unique, central region encoding several antibiotic resistances. The IS50R element encodes two proteins in the same reading frame which regulate the transposition reaction: the transposase (Tnp), which is required for transposition, and an inhibitor of transposition (Inh). The inhibitor is a naturally occurring deletion variant of Tnp which lacks the N-terminal 55 amino acids. In this report, we present the purification of both the Tnp and Inh proteins and an analysis of their DNA binding properties. Purified Tnp, but not Inh, was found to bind specifically to the outside end of Tn5. Inh, however, stimulated the binding activity of Tnp to outside-end DNA and was shown to be present with Tnp in these bound complexes. Inh was also found to exist as a dimer in solution. These results indicate that the N-terminal 55 amino acids of Tnp are required for sequence-specific binding. They also suggest that Inh inhibits transposition by forming mixed oligomers with Tnp which still bind to the ends of the transposon but are defective for later stages of the transposition reaction.

Transposition of Tn5 in Escherichia coli is regulated by two transposon-encoded proteins: transposase (Tnp), promoting transposition preferentially in cis, and the trans-acting inhibitor (Inh). Two separate transposase mutants were isolated that replace glutamate with lysine at position 110 (EK110) and at position 345 (EK345). The EK transposase proteins increase the Tn5 transposition frequency 6- to 16-fold in cis and enhance the ability of transposase to act in trans. The purified mutant transposase proteins interact with transposon outside end DNA differently from the wild-type protein, resulting in the formation of a novel complex in gel retardation assays. During characterization of the transposase proteins in the absence of inhibitor, we found that wild-type transposase itself has a transposition-inhibiting function and that this inhibition is reduced for the mutant proteins. We present a model for the regulation of Tn5 transposition, which proposes the existence of two transposase species, one cis-activating and the other trans-inhibiting. The phenotype of the EK transposase mutants can be explained by a shift in the ratio of these two species.

In arid regions, the effects of grazing or sparing management on natural communities of long-lived plants generally take decades to become evident. Event-driven dynamic behavior, unpredictable and low rainfall and complicated interactions between species make it difficult to assess probabilities and time scales of vegetation change.