Distributed Hash Tables (DHTs) have proven to be a novel and efficient platform for building a variety of scalable and robust distributed applications like content sharing and location in the Internet. Similar to those in the Internet, distributed applications and network services in mobile ad hoc networks (MANETs) can potentially benefit from the deployment of a DHT. However, bandwidth limitations, node mobility, and multi access interference pose unique challenges to deploying such DHTs in MANETs.In this paper, we first study how to efficiently implement DHTs in MANETs. We explore two disparate design options: the simple approach of directly overlaying a DHT on top of a MANET multi-hop routing protocol, and Ekta which integrates a DHT with a multi-hop routing protocol at the network layer. Second, we examine the efficiency of DHT substrates in supporting applications in MANETs by examining the performance of a resource discovery application built on top of Ekta with one that directly uses physical layer broadcast. Such a study answers the fundamental question of whether a DHT substrate can be more efficient in supporting applications than a physical layer broadcast-based protocol, since in MANETs, DHT protocols effectively rely on physical layer broadcast to discover and maintain routes.

In order to provide information for the development of molecular selection markers for drought tolerance improvement, the methods of prometric analysis, quantitative real-time PCR and field evaluation were employed for the identification of the differential expression of candidate genes under drought stress in maize. At seventeen, twenty-four and forty-eight hours of polyethylene glycol-simulated drought stress at the seventh leaf stage, leaf samples were collected from two drought-tolerant inbred lines for prometric analysis by two-dimensional electrophoresis and peptide mass fingerprinting. Fifty-eight proteins out of more than 500 were found in response to drought stress. Three drought-induced spots 2506, 3507 and 4506 showed sequence similarity with cinnamyl alcohol dehydrogenase, cytochrome protein 96A8 and S-adenosyl-L-methionine synthase, respectively. The expression of two key enzymes to lignin biosynthesis was quantified by quantitative real-time PCR among three drought-tolerant and one drought-sensitive inbred lines under drought stress and well-watered control conditions. After a decrease at the beginning of drought stress, the expression of cinnamyl alcohol dehydrogenase and caffeate O-methyltransferase recovered at twenty-four hours of the drought stress in the three drought-tolerant lines, but not in the drought-sensitive lines. Leaf lignin content, anthesis-silking interval and grain weight per plant were investigated with six inbred lines of varying drought tolerance under drought stress and well-watered control. Drought tolerance coefficients of these three characters were calculated and the correlation coefficients among these drought tolerance coefficients were estimated. Significant difference in leaf lignin content was found among the inbred lines and in response to drought stress. Close correlations were observed between the drought tolerant coefficients for leaf lignin content and grain weight per plant, and between the drought tolerant coefficients for leaf lignin content and anthesis-silking interval. These results indicate that leaf lignin content is a useful index for evaluation of drought tolerance in maize. Molecular selection markers can be developed on the basis of differential expression of the candidate genes and applied to maize improvement for drought tolerance.

Structured peer-to-peer overlay networks provide a substrate for the construction of large-scale, decentralized applications, including distributed storage, group communication, and content distribution. These overlays are highly resilient; they can route messages correctly even when a large fraction of the nodes crash or the network partitions. But current overlays are not secure; even a small fraction of malicious nodes can prevent correct message delivery throughout the overlay. This problem is particularly serious in open peer-to-peer systems, where many diverse, autonomous parties without preexisting trust relationships wish to pool their resources. This paper studies attacks aimed at preventing correct message delivery in structured peer-to-peer overlays and presents defenses to these attacks. We describe and evaluate techniques that allow nodes to join the overlay, to maintain routing state, and to forward messages securely in the presence of malicious nodes.

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