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Tntroduction. The [alpha]-subunit (KCNQl) and auxiliary [beta]-subunit (KCNEl) form the slow delayed rectifier potassium channel (IKs)' Although the IKs current is considered to be involved in repolarisation of the cardiac action potential the exact role of IKs in cardiac physiology is still unclear. Recent studies have suggested that IKs is involved as a repolarisation reserve. However, inherited mutations in KCNQl and KCNEI genes suggest that IKs has a prominent role in normal cardiac repolarisation. Understanding the role of IKs in human cardiac physiology may lead to improvements in the treatment of arrhythmias. The aim of this project was to assess the extent to which the cardiac IKs current is involved in excitation-contraction coupling and whether modification of the IKs CUlTent can be of therapeutic benefit in treatment of ventricular arrhythmias.

Distributed storage systems provide reliable storage of data by dispersing redundancy across multiple nodes. As individual nodes are unreliable this protects the integrity of the data against the failure of nodes. In order to maintain this reliability new nodes must be introduced into the system whenever nodes are lost which restore the redundancy. This process involves having a new node download information from remaining nodes and is known as the repair problem. In this thesis, we consider networks with communication costs associated to each link and explore means to minimize the cost of performing these repairs. We do this by considering a generalized method of repair wherein the amount of information downloaded to a new node varies amongst the other nodes in the network. We find that when nodes store the minimum amount of data that the minimum cost can be achieved by quasi-uniform repair, where the same amount of data is downloaded from each node communicated with. We also consider systems with the additional freedom that the amount of storage is allowed to vary from node to node and look at repair cost minimization there as well