Determining crystal structures through crowdsourcing and coursework

We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality

Improved Performance of Bluetooth with Focus on Ad-Hoc Applications

The number of devices making use of Bluetooth cable-replacement technology has rapidly increased in numbers thanks to the amount of implementations in cellular telephones, Personal Digital Assistants (PDAs), etc. Instead of the point-to-point technique used today the wireless community demands more sophisticated solutions to transmit information between two devices, e.g. using a chat program within an ad-hoc network. However, Bluetooth provides neither a routing protocol, nor is the slave/slave bridge, which is an important enabler for point-to-multipoint communication in so-called scatternets, implemented in hardware. Another issue relates to the time-to-connect which determines the usability of Bluetooth in scenarios where the units move around. In order to build research on these topics on trustworthy ground, we first address the validation of a Bluetooth simulation model, implementing the Frequency Hopping Spread Spectrum (FHSS) technique of Bluetooth version 1.1 in a correct way. A potential source of problems in reference simulation models has been identified and corrections are described. Next, an improvement is presented for the pseudo random hop sequence regarding the distribution of frequencies used in the Adapted Channel Hopping (ACH) scheme for Bluetooth version 1.2. Further, the impact of the random backoff boundary, which determines the duration of the inquiry procedure and thus of the time-to-connect, is studied by simulation. Obviously, the settings of this parameter contained in the specification leads to suboptimal behaviour. In this thesis, a lower random backoff boundary parameter is suggested, which yields much faster time-to-connect. Finally, the Modified Reverse Path Forwarding (MRPF) routing algorithm for Bluetooth is proposed. This algorithm reduces the amount of connections needed to transmit Asynchronous Connection Less (ACL) data packets as compared to the standard RPF, at the cost of additional overhead. Altogether, especially with the proposed improvements of Bluetooth performance, this technology can be considered to be well suited for nomadic scenarios

Seamless Communications

The evolution of today’s wireless technologies and small hand-held devices has enabled the handling of the trade-off between mobility and performance. Things have, however, become more complex. Users demand high performance when using small and resource-efficient devices. Users also demand high-performance connectivity anywhere and anytime without having to care about transitions between different access networks. As of today, the absence of Mobile IP (MIP) support in most networks implies the need for a reconnection of the service as soon as the access network changes. That is why a new seamless communication concept is required. In the thesis, a new seamless communication concept is proposed. The goal is to be Always Best Connected (ABC) even if the conditions change. Initially, a network link has to be selected and a connection has to be established. The service used should be maintained as long as the conditions are fulfilled. First, a set of Generic Services (GSs), each related to a specific communication task, is defined. Furthermore, a deep performance investigation of some of the wireless technologies available is summarized and used. Based on the combination of a GS and a wireless technology selected criteria are used. The data extracted from our measurements have the option of later being fed into statistical algorithms. The translation of the extracted information through the statistical methods could be non-linear and for that reason the Fuzzy Set Theory (FST) is used. The FST provides us with the tool needed for the next step, the decision aiming at ABC. To be able to handle the large amount of data, the Multi-Criteria Decision Making (MCDM) is used. This decision model requires a linguistic 9-point scale which suits the FST tool perfectly. A judgment between different criteria can then be made. Moreover, the thesis describes a couple of important issues regarding the Internet protocol address problem. Each problem is discussed and solutions are presented in the context of having seamless communication without today’s constraints. The result is a seamless communication concept that is more flexible than other solutions. Both the FST and the MCDM tools have been successfully implemented into a running prototype

Seamless Communications

The evolution of today’s wireless technologies and small hand-held devices has enabled the handling of the trade-off between mobility and performance. Things have, however, become more complex. Users demand high performance when using small and resource-efficient devices. Users also demand high-performance connectivity anywhere and anytime without having to care about transitions between different access networks. As of today, the absence of Mobile IP (MIP) support in most networks implies the need for a reconnection of the service as soon as the access network changes. That is why a new seamless communication concept is required. In the thesis, a new seamless communication concept is proposed. The goal is to be Always Best Connected (ABC) even if the conditions change. Initially, a network link has to be selected and a connection has to be established. The service used should be maintained as long as the conditions are fulfilled. First, a set of Generic Services (GSs), each related to a specific communication task, is defined. Furthermore, a deep performance investigation of some of the wireless technologies available is summarized and used. Based on the combination of a GS and a wireless technology selected criteria are used. The data extracted from our measurements have the option of later being fed into statistical algorithms. The translation of the extracted information through the statistical methods could be non-linear and for that reason the Fuzzy Set Theory (FST) is used. The FST provides us with the tool needed for the next step, the decision aiming at ABC. To be able to handle the large amount of data, the Multi-Criteria Decision Making (MCDM) is used. This decision model requires a linguistic 9-point scale which suits the FST tool perfectly. A judgment between different criteria can then be made. Moreover, the thesis describes a couple of important issues regarding the Internet protocol address problem. Each problem is discussed and solutions are presented in the context of having seamless communication without today’s constraints. The result is a seamless communication concept that is more flexible than other solutions. Both the FST and the MCDM tools have been successfully implemented into a running prototype