Binocular interactions

Contains fulltext : 62061.pdf (Publisher’s version ) (Open Access)RU Radboud Universiteit Nijmegen, 23 september 2002Promotor : Weert, C.M.M. de164 p

Delivering Live Multimedia Streams to Mobile Hosts in a Wireless Internet with Multiple Content Aggregators

We consider the distribution of channels of live multimedia content (e.g., radio or TV broadcasts) via multiple content aggregators. In our work, an aggregator receives channels from content sources and redistributes them to a potentially large number of mobile hosts. Each aggregator can offer a channel in various configurations to cater for different wireless links, mobile hosts, and user preferences. As a result, a mobile host can generally choose from different configurations of the same channel offered by multiple alternative aggregators, which may be available through different interfaces (e.g., in a hotspot). A mobile host may need to handoff to another aggregator once it receives a channel. To prevent service disruption, a mobile host may for instance need to handoff to another aggregator when it leaves the subnets that make up its current aggregator�s service area (e.g., a hotspot or a cellular network).\ud In this paper, we present the design of a system that enables (multi-homed) mobile hosts to seamlessly handoff from one aggregator to another so that they can continue to receive a channel wherever they go. We concentrate on handoffs between aggregators as a result of a mobile host crossing a subnet boundary. As part of the system, we discuss a lightweight application-level protocol that enables mobile hosts to select the aggregator that provides the �best� configuration of a channel. The protocol comes into play when a mobile host begins to receive a channel and when it crosses a subnet boundary while receiving the channel. We show how our protocol can be implemented using the standard IETF session control and description protocols SIP and SDP. The implementation combines SIP and SDP�s offer-answer model in a novel way

Herbivore-induced indirect defense of Arabidopsis : ecogenomic approach to the role of infochemicals in parasitoid attraction

Plants defend themselves against herbivorous insects with the induced production of volatiles that attract the enemies of the herbivores. In this thesis I used an ecogenomic approach to study the role of signal-transduction pathways that regulate the induction of herbivore-induced plant volatiles (HIPV) and the effects of HIPVs on parasitoid host-finding behavior. To this end, I have combined transcriptomics, metabolite analyses and insect behavioral analyses. Nine Arabidopsis thaliana accessions were screened for the emission of HIPVs. The accessions varied in the emission rate of Pieris rapae–induced volatiles after folivory or treatment with the herbivory-mimicking plant hormone jasmonic acid (JA). The relevance of this observed variation in the emission of JA-induced volatiles for host location was tested with Diadegma semiclausum parasitoids. Furthermore, the accessions also varied in transcript levels of genes that are (putatively) involved in the production of some of the recorded HIPV-compounds. The oxylipin JA is the key plant hormone involved in the induction of the HIPV-blend emitted in response to caterpillar folivory. Mutant plants affected in the oxylipin signal-transduction pathway were studied to assess the effects of JA and its oxylipin intermediates 12-oxo-phytodienoate (OPDA) and dinor-OPDA (dnOPDA) on HIPV emission and attraction of the parasitoid D. semiclausum. In contrast to the effect of JA on the induced production of HIPVs, dnOPDA and OPDA were found to have no and little effect, respectively. The HIPV-compound methyl salicylate was shown to be JA-regulated and its abundance in the headspace varied among accessions. The contribution of methyl salicylate to parasitoid attraction was investigated. Bioassays with P. rapae-infested transgenic plants, lacking MeSA production, showed that MeSA negatively influenced D. semiclausum host-finding behavior. Mutant plants were also studied to assess whether JA and its intermediates affected the induction of genes potentially involved in defense. The different oxylipins were shown to have distinct roles in induced defense signaling. Jasmonic acid had the strongest effect on transcript levels of defense-related genes from the oxylipin- and shikimate signal-transduction pathway. Minor roles were observed for OPDA and dnOPDA in the induction of one of these genes. Utilizing an ecogenomic approach has provided new insight into the mechanisms underlying insect-plant interactions and holds promising opportunities. <br/