A Centralized Energy Management System for Wireless Sensor Networks

This document presents the Centralized Energy Management System (CEMS), a dynamic fault-tolerant reclustering protocol for wireless sensor networks. CEMS reconfigures a homogeneous network both periodically and in response to critical events (e.g. cluster head death). A global TDMA schedule prevents costly retransmissions due to collision, and a genetic algorithm running on the base station computes cluster assignments in concert with a head selection algorithm. CEMS\u27 performance is compared to the LEACH-C protocol in both normal and failure-prone conditions, with an emphasis on each protocol\u27s ability to recover from unexpected loss of cluster heads

Verificare: a platform for composable verification with application to SDN-Enabled systems

Software-Defined Networking (SDN) has become increasing prevalent in both the academic and industrial communities. A new class of system built on SDNs, which we refer to as SDN-Enabled, provide programmatic interfaces between the SDN controller and the larger distributed system. Existing tools for SDN verification and analysis are insufficiently expressive to capture this composition of a network and a larger distributed system. Generic verification systems are an infeasible solution, due to their monolithic approach to modeling and rapid state-space explosion. In this thesis we present a new compositional approach to system modeling and verification that is particularly appropriate for SDN-Enabled systems. Compositional models may have sub-components (such as switches and end-hosts) modified, added, or removed with only minimal, isolated changes. Furthermore, invariants may be defined over the composed system that restrict its behavior, allowing assumptions to be added or removed and for components to be abstracted away into the service guarantee that they provide (such as guaranteed packet arrival). Finally, compositional modeling can minimize the size of the state space to be verified by taking advantage of known model structure. We also present the Verificare platform, a tool chain for building compositional models in our modeling language and automatically compiling them to multiple off-the-shelf verification tools. The compiler outputs a minimal, calculus-oblivious formalism, which is accessed by plugins via a translation API. This enables a wide variety of requirements to be verified. As new tools become available, the translator can easily be extended with plugins to support them

Using alloy to formally model and reason about an OpenFlow network switch

Openflow provides a standard interface for separating a network into a data plane and a programmatic control plane. This enables easy network reconfiguration, but introduces the potential for programming bugs to cause network effects. To study OpenFlow switch behavior, we used Alloy to create a software abstraction describing the internal state of a network and its OpenFlow switches. This work is an attempt to model the static and dynamic behaviour a network built using OpenFlow switches

Grid Portal Application

This project concerns EMMIL (E-Marketplace Model Integrated with Logistics) and its viability as a grid application. The model was evaluated on a single processor and on the SEEGRID network using MTA-SZTAKI\u27s P-GRADE Portal. A granularity heuristic was developed to guide the mapping of EMMIL datasets to processes. A portlet for P-GRADE Portal was also created to aid in data entry. Finally, pre-processing filters were added. These were designed to discard useless combinations and reduce overall computing time

Mapping Building Characteristics In Mitcham

The London Borough of Merton has begun the development of a district heat and power system. In order to financially model the feasibility of this scheme, energy consumption data for borough buildings must be known. The objective of this project was to investigate and apply methods for mapping the energy use of buildings within the borough of Merton. Difficulties encountered in data collection led to a revision of our project to include the drafting of sustainable information gathering mechanisms. With these in place the Merton Council will be able to base future plans on an accurate and thorough knowledge base

The Zenith attack: vulnerabilities and countermeasures

In this paper we identify and define Zenith attacks, a new class of attacks on content-distribution systems, which seek to expose the popularity (i.e. access frequency) of individual items of content. As the access pattern to most real-world content exhibits Zipf-like characteristics, there is a small set of dominating items which account for the majority of accesses. Identifying such items enables an adversary to perform follow up adversarial actions targeting these items, including mounting denial of service attacks, deploying censorship mechanisms, and eavesdropping on or prosecution of the host or recipient. We instantiate a Zenith attack on the Kademlia and Chord structured overlay networks and quantify the cost of such an attack. As a countermeasure to these attacks we propose Crypsis, a system to conceal the lookup frequency of individual keys through aggregation over ranges of the keyspace. Crypsis provides provable security guarantees for concealment of lookup frequency while maintaining logarithmic routing and state bounds.National Science Foundation (0735974, 0820138, 0952145, 1012798

Identification of essential and non-essential single-stranded DNA-binding proteins in a model archaeal organism

Single-stranded DNA-binding proteins (SSBs) play vital roles in all aspects of DNA metabolism in all three domains of life and are characterized by the presence of one or more OB fold ssDNA-binding domains. Here, using the genetically tractable euryarchaeon Haloferax volcanii as a model, we present the first genetic analysis of SSB function in the archaea. We show that genes encoding the OB fold and zinc finger-containing RpaA1 and RpaB1 proteins are individually non-essential for cell viability but share an essential function, whereas the gene encoding the triple OB fold RpaC protein is essential. Loss of RpaC function can however be rescued by elevated expression of RpaB, indicative of functional overlap between the two classes of haloarchaeal SSB. Deletion analysis is used to demonstrate important roles for individual OB folds in RpaC and to show that conserved N- and C-terminal domains are required for efficient repair of DNA damage. Consistent with a role for RpaC in DNA repair, elevated expression of this protein leads to enhanced resistance to DNA damage. Taken together, our results offer important insights into archaeal SSB function and establish the haloarchaea as a valuable model for further studies

The ubiquitin-conjugating enzyme CDC34 is essential for cytokinesis in contrast to putative subunits of a SCF complex in Trypanosoma brucei

The ubiquitin-proteasome system is a post-translational regulatory pathway for controlling protein stability and activity that underlies many fundamental cellular processes, including cell cycle progression. Target proteins are tagged with ubiquitin molecules through the action of an enzymatic cascade composed of E1 ubiquitin activating enzymes, E2 ubiquitin conjugating enzymes, and E3 ubiquitin ligases. One of the E3 ligases known to be responsible for the ubiquitination of cell cycle regulators in eukaryotes is the SKP1-CUL1-F-box complex (SCFC). In this work, we identified and studied the function of homologue proteins of the SCFC in the life cycle of Trypanosoma brucei, the causal agent of the African sleeping sickness. Depletion of trypanosomal SCFC components TbRBX1, TbSKP1, and TbCDC34 by RNAi resulted in decreased growth rate and contrasting cell cycle abnormalities for both procyclic (PCF) and bloodstream (BSF) forms. Depletion of TbRBX1 in PCF cells interfered with kinetoplast replication, whilst depletion of TbSKP1 arrested PCF and BSF cells in the G1/S transition. Silencing of TbCDC34 in BSF cells resulted in a block in cytokinesis and caused rapid clearance of parasites from infected mice. We also show that TbCDC34 is able to conjugate ubiquitin in vitro and in vivo, and that its activity is necessary for T. brucei infection progression in mice. This study reveals that different components of a putative SCFC have contrasting phenotypes once depleted from the cells, and that TbCDC34 is essential for trypanosome replication, making it a potential target for therapeutic intervention