New charge-transport materials for OLED applications

Novel fluorene-1 ,3,4-oxadiazole and spirobifluorene-1 ,3,4-oxadiazole compounds 202 and 211, respectively, have been synthesised. Compound 202 was blended with MEHPPV in various ratios and incorporated into organic light-emitting diodes (OLEDs).The devices were found to emit light purely from MEH-PPV up to very high doping levels. When the device architecture ITO/PEDOT:PSS/MEH-PPV :202/Ca:Al was used it was found that increasing the amount of202 increases the lifetime of the device. Novel bipolar fluorene- I ,3 ,4-oxadiazole-triphenylamine molecules 237 and 240 were synthesised using silicon protecting groups. When incorporated into devices with architecture ITO/PEDOT:PSS/237 or 240/Ca:Al it was found that the materials facilitated the transport of electrons and holes as well as acting as blue-green emitters with efficiencies of up to 0.26%/0.6 cd A-1. Compound 237 also performed well when blended with MEH-PPV giving rise to efficiencies two orders of magnitude greater than for pure MEH -PPV devices

Implementation of functional safety in a robotic manufacturing cell using iec 61508 standard and siemens technology

The past 50 years have seen a staggering amount of change in the technology and the business of process automation. The programmable logic controller (PLC) based control and monitoring system is a proven technology used to not only control processes but also to perform safety functions for processes in many industrial applications. There are many opportunities for improvements in any process or manufacturing system. One of the opportunities is achieving accurate safety function for measurement and process control to prevent human injury or death. The programmable electronic systems (PES) such as PLC systems are increasingly being used to perform safety functions as an integral part of the process or plant control system. A Robotic Manufacturing Cell is an example of a PES system and is used as an experimental setup for this work. The IEC 61508 standard defines various phases involved in the overall safety lifecycle for the PES system. This thesis study concentrates on such phases that include safety analysis methods, selection of an appropriate safety control system, implementation of safety as per the standard and safety validation. In this study four test cases are selected to perform safety analysis and implementation. It is verified how the conventional safety analysis method (FMEA) can be used to estimate the risk associated with each test case. As recommended by IEC 61508, a Risk-Graph method is used to calculate the Safety Integrity Level (SIL) requirement for each test case. A number of factors are required to be considered for selecting the appropriate safety control system architecture. After studying these factors and the safety analysis results, the Siemens safety PLC-based control system with SIL 3 configuration is selected for this application. IEC 61508 also recommends implementation of independent control systems for normal operation and safety. This study demonstrates how two independent PLC based control systems, one for normal operations and other for safety-related functions, are implemented to offer the most effective solution for this application. This is achieved by using PLCs from two different manufacturers, a non-safety PLC for normal operations and a Siemens safety PLC for safety-related functions. This study focuses on Machine Safety, and it can be used as a guideline for implementation of functional safety in real-life manufacturing environment

Law in Plato's Late Politics

Throughout his political works, Plato takes the aim of politics to be the virtue and happiness of the citizens and the unity of the city. This paper examines the roles played by law in promoting individual virtue and civic unity in the Republic, Statesman, and Laws. Section 1 argues that in the Republic, laws regulate important institutions, such as education, property, and family, and thereby creating a way of life that conduces to virtue and unity. Section 2 argues that in the Statesman, the political expert determines the mean between extremes and communicates it to citizens through laws that guide their judgment and conduct, so that they become virtuous themselves and the city is unified; this account of the role of law suggest how even non-expert legislation can contribute to virtue and unity. Section 3 argues that the Laws affirms and develops the idea that citizens should know and accept the laws to become virtuous themselves and to unify the city, and explains how the persuasive preludes and the sanction for violation attached to laws contribute to citizen virtue and civic unity

A Hierarchical Approach to Protein Molecular Evolution

Biological diversity has evolved despite the essentially infinite complexity of protein sequence space. We present a hierarchical approach to the efficient searching of this space and quantify the evolutionary potential of our approach with Monte Carlo simulations. These simulations demonstrate that non-homologous juxtaposition of encoded structure is the rate-limiting step in the production of new tertiary protein folds. Non-homologous ``swapping'' of low energy secondary structures increased the binding constant of a simulated protein by $\approx10^7$ relative to base substitution alone. Applications of our approach include the generation of new protein folds and modeling the molecular evolution of disease.Comment: 15 pages. 2 figures. LaTeX styl

Designability of alpha-helical Proteins

A typical protein structure is a compact packing of connected alpha-helices and/or beta-strands. We have developed a method for generating the ensemble of compact structures a given set of helices and strands can form. The method is tested on structures composed of four alpha-helices connected by short turns. All such natural four-helix bundles that are connected by short turns seen in nature are reproduced to closer than 3.6 Angstroms per residue within the ensemble. Since structures with no natural counterpart may be targets for ab initio structure design, the designability of each structure in the ensemble -- defined as the number of sequences with that structure as their lowest energy state -- is evaluated using a hydrophobic energy. For the case of four alpha-helices, a small set of highly designable structures emerges, most of which have an analog among the known four-helix fold families, however several novel packings and topologies are identified.Comment: 21 pages, 6 figures, to appear in PNA

Crystal Structures of the HslVU Peptidase–ATPase Complex Reveal an ATP-Dependent Proteolysis Mechanism

AbstractBackground: The bacterial heat shock locus HslU ATPase and HslV peptidase together form an ATP-dependent HslVU protease. Bacterial HslVU is a homolog of the eukaryotic 26S proteasome. Crystallographic studies of HslVU should provide an understanding of ATP-dependent protein unfolding, translocation, and proteolysis by this and other ATP-dependent proteases.Results: We present a 3.0 Å resolution crystal structure of HslVU with an HslU hexamer bound at one end of an HslV dodecamer. The structure shows that the central pores of the ATPase and peptidase are next to each other and aligned. The central pore of HslU consists of a GYVG motif, which is conserved among protease-associated ATPases. The binding of one HslU hexamer to one end of an HslV dodecamer in the 3.0 Å resolution structure opens both HslV central pores and induces asymmetric changes in HslV.Conclusions: Analysis of nucleotide binding induced conformational changes in the current and previous HslU structures suggests a protein unfolding–coupled translocation mechanism. In this mechanism, unfolded polypeptides are threaded through the aligned pores of the ATPase and peptidase and translocated into the peptidase central chamber

Involvement of the TPR2 subdomain movement in the activities of ϕ29 DNA polymerase

The polymerization domain of ϕ29 DNA polymerase acquires a toroidal shape by means of an arch-like structure formed by the specific insertion TPR2 (Terminal Protein Region 2) and the thumb subdomain. TPR2 is connected to the fingers and palm subdomains through flexible regions, suggesting that it can undergo conformational changes. To examine whether such changes take place, we have constructed a ϕ29 DNA polymerase mutant able to form a disulfide bond between the apexes of TPR2 and thumb to limit the mobility of TPR2. Biochemical analysis of the mutant led us to conclude that TPR2 moves away from the thumb to allow the DNA polymerase to replicate circular ssDNA. Despite the fact that no TPR2 motion is needed to allow the polymerase to use the terminal protein (TP) as primer during the initiation of ϕ29 TP–DNA replication, the disulfide bond prevents the DNA polymerase from entering the elongation phase, suggesting that TPR2 movements are necessary to allow the TP priming domain to move out from the polymerase during transition from initiation to elongation. Furthermore, the TPR2-thumb bond does not affect the equilibrium between the polymerization and exonuclease activities, leading us to propose a primer-terminus transference model between both active sites