Efficient 550-600-nm tunable laser based on noncritically phase-matched frequency doubling of room-temperature LiF:F2- in lithium triborate

We report on efficient conversion of a 1064-nm Nd:YAG laser to tunable visible light. The conversion scheme uses noncritically phase-matched second-harmonic generation of a pulsed Nd:YAG-pumped LiF:F2- laser in lithium triborate. Optimization yields 42% LiF:F2- laser efficiency and 56% frequency-doubling efficiency, providing >20% conversion from 1064 nm to broadly tunable visible output. A dramatic sensitivity of laser efficiency to pump pulse duration is recorded, with a fundamental efficiency improvement of over 30-fold measured for an increase in pump pulse duration from 5 to 34 ns.     

Dithiopheneindenofluorene (TIF) Semiconducting Polymers with Very High Mobility in Field‐Effect Transistors

The charge‐carrier mobility of organic semiconducting polymers is known to be enhanced when the energetic disorder of the polymer is minimized. Fused, planar aromatic ring structures contribute to reducing the polymer conformational disorder, as demonstrated by polymers containing the indacenodithiophene ( IDT ) repeat unit, which have both a low Urbach energy and a high mobility in thin‐film‐transistor (TFT) devices. Expanding on this design motif, copolymers containing the dithiopheneindenofluorene repeat unit are synthesized, which extends the fused aromatic structure with two additional phenyl rings, further rigidifying the polymer backbone. A range of copolymers are prepared and their electrical properties and thin‐film morphology evaluated, with the co ‐benzothiadiazole polymer having a twofold increase in hole mobility when compared to the IDT analog, reaching values of almost 3 cm² V^?1 s^?1 in bottom‐gate top‐contact organic field‐effect transistors.     

Going into the wild in child–robot interaction studies: issues in social robotic development

As robots move into more human centric environments we require methods to develop robots that can naturally interact with humans. Doing so requires testing in the real-world and addressing multidisciplinary challenges. Our research is focused on child–robot interaction which includes very young children, for example toddlers, and children diagnosed with autism. More traditional forms of human–robot communication, such as speech or gesture recognition, may not be appropriate with these users, where as touch may help to provide a more natural and appropriate means of communication for such instances. In this paper, we present our findings on these topics obtained from a project involving a spherical robot that acquires information regarding natural touch from analysing sensory patterns over-time to characterize the information. More specifically, from this project we have derived important factors for future consideration, we describe our iterative experimental methodology of testing in and out of the ‘wild’ (lab based and real world), and outline discoveries that were made by doing so.     

An Organic Electrochemical Transistor Integrated Photodetector for High Quality Photoplethysmogram Signal Acquisition

The organic photodiode (OPD) is a promising building block for solution-processable, flexible, lightweight, and miniaturized photodetectors, ideal for wearable applications. Despite the advances in materials used in OPDs, their photocurrent and light responsivity are limited, and alternative methods are required to boost the signal response. Herein, a miniaturized organic electrochemical transistor (OECT) is integrated with an OPD module to unlock the potential of OPDs to acquire physiological signals. In this integrated photodetector (IPD) system, the light intensity regulates the OPD voltage output that modulates the OECT channel current. The high transconductance of the OECT provides efficient voltage-to-current conversion, enhancing the signal-to-noise ratio on the sensing site. A microscale, p-type enhancement-mode OECT with high g_m and fast switching speed performs better in this application than depletion-mode OECT of the same geometry. The IPD achieves a photocurrent and responsivity 318 and 140 times higher than the standalone OPD, respectively. It is shown that with the IPD, the amplitude of the photoplethysmogram signals detected by the OPD is enhanced by a factor of 2.9 × 10³, highlighting its potential as a wearable biosensor and to detect weak, often uncaptured, light-based signals from living systems.     

Malware and steganography in hard disk firmware

The hard disk drive remains the most commonly used form of storage media in both commercial and domestic computer systems. These drives can contain a vast range of data both of personal value and commercial significance. This paper focuses on two key areas; the potential for the drive operation to be impacted by malicious software and the possibility for the drive firmware to be manipulated to enable a form of steganography. Hard drive firmware is required for the correct operation of the disk drive in particular for dealing with errors arising due to natural wear as the drive ages. Where an area of the drive becomes unreliable due to wear and tear, the disk firmware which monitors the reliability of data access will copy the data from the failing area to a specially designated reserved area. The firmware remaps this data shift so the old data area and the original copy of the data are no longer accessible by the computer operating system. There are now a small number of commercially available devices, intended for data recovery, which can be used to modify the hard drive firmware components. This functionality can be used to conceal code on the disk drive, either as a form of steganography or to potentially include malicious code with the intention to infect or damage software or possibly system hardware. This paper discusses the potential problem generated by firmware being manipulated for malicious purposes.     

Degradative proteomics and disease mechanisms

Protein degradation is a fundamental biological process, which is essential for the maintenance and regulation of normal cellular function. In humans and animals, proteins can be degraded by a number of mechanisms: the ubiquitin-proteasome system, autophagy and intracellular proteases. The advances in contemporary protein analysis means that proteomics is increasingly being used to explore these key pathways and as a means of monitoring protein degradation. The dysfunction of protein degradative pathways has been associated with the development of a number of important diseases including cancer, muscle wasting disorders and neurodegenerative diseases. This review will focus on the role of proteomics to study cellular degradative processes and how these strategies are being applied to understand the molecular basis of diseases arising from disturbances in protein degradation.     

The Web in education

The Web has spurred our imagination as to how education could be radically transformed and enhanced through the adoption of Information and Communication Technologies (ICTs). While there have been many significant innovations and successes over the last decade there have also been many unrealised aims. Beliefs in technology-driven change for education have been countered by shortcomings in technological understanding by educationalists and in turn by shortcomings in the understanding of educational theories and learning concepts by technologists. The use of the Web in education has revealed issues such as the distinction between formal and informal learning; the packaging and formatting of learning materials for online distribution and use; the management of learning materials and processes in virtual and managed learning environments; solutions offered by the semantic Web; and how the quality of experience in interactive learning environments relates to the quality of the Internet infrastructure. A comparison between the performance of early and current Web technologies from a user perspective is given for an interactive learning environment which has been in use for over a decade. Client, server, network and protocol components which contribute to the quality of experience for the end user are presented and analysed. In summary, this paper examines the use of the Web in education to date and looks forward to new challenges and aspirations such as MOOCs (massively online open coursewares) and the immersive 3D Web as the basis for the next generation of learning environments.     

CASSM and cognitive walkthrough: usability issues with ticket vending machines

We focus on the ability of two analytical usability evaluation methods (UEMs), namely CASSM (Concept-based Analysis for Surface and Structural Misfits) and Cognitive Walkthrough, to identify usability issues underlying the use made of two London Underground ticket vending machines. By setting both sets of issues against the observed interactions with the machines, we assess the similarities and differences between the issues depicted by the two methods. In so doing we de-emphasise the mainly quantitative approach which is typical of the comparative UEM literature. However, by accounting for the likely consequences of the issues in behavioural terms, we reduced the proportion of issues which were anticipated but not observed (the false positives), compared with that achieved by other UEM studies. We assess these results in terms of the limitations of problem count as a measure of UEM effectiveness. We also discuss the likely trade-offs between field studies and laboratory testing.