Clinical potential and design of programmable mechanical impedances for orthotic applications

A person with a moderate or severe motor disability will often use specialised or adapted tools to assist their interaction with a general environment. Such tools can assist with the movement of a person's arms so as to facilitate manipulation, can provide postural supports, or interface to computers, wheelchairs or similar assistive technologies. Designing such devices with programmable stiffness and damping may offer a better means for the person to have effective control of their surroundings. This paper addresses the possibility of designing some assistive technologies using impedance elements that can adapt to the user and the circumstances. Two impedance elements are proposed. The first, based on magnetic particle brakes, allows control of the damping coefficient in a passive element. The second, based on detuning the P-D controller in a servo-motor mechanism, allows control of both stiffness and damping. Such a mechanical impedance can be modulated to the conditions imposed by the task in hand. The limits of linear theory are explored and possible uses of programmable impedance elements are proposed.

Investigating a robot as a therapy partner for children with autism

The aurora project is investigating the possibility of using a robotic platform as a therapy aid for--children with autism. Because of the nature of this disability, the robot could be beneficial in its ability--to present the children with a safe and comfortable environment and allow them to explore and learn--about the interaction space involved in social situations. The robotic platform is able to present--information along a limited number of channels and in a manner which the children are familiar with--from television and cartoons. Also, the robot is potentially able to adapt its behaviour and to allow the--children to develop at their own rates. Initial trial results are presented and discussed, along with the--rationale behind the project and its goals and motivations. The trial procedure and methodology are--explained and future work is highlighted.

Generating virtual environments to allow increased access to the built environment

The problems encountered by individuals with disabilities when accessing large public buildings is described and a solution based on the generation of virtual models of the built environment is proposed. These models are superimposed on a control network infrastructure, currently utilised in intelligent building applications such as lighting, heating and access control. The use of control network architectures facilitates the creation of distributed models that closely mirror both the physical and control properties of the environment. The model of the environment is kept local to the installation which allows the virtual representation of a large building to be decomposed into an interconnecting series of smaller models. This paper describes two methods of interacting with the virtual model, firstly a two dimensional aural representation that can be used as the basis of a portable navigational device. Secondly an augmented reality called DAMOCLES that overlays additional information on a user’s normal field of view. The provision of virtual environments offers new possibilities in the man-machine interface so that intuitive access to network based services and control functions can be given to a user.

Head-controlled assistive telerobot with extended physiological proprioception capability

People with disabilities such as quadriplegia can use mouth-sticks and head-sticks as extension devices to perform desired manipulations. These extensions provide extended proprioception which allows users to directly feel forces and other perceptual cues such as texture present at the tip of the mouth-stick. Such devices are effective for two principle reasons: because of their close contact with the user's tactile and proprioceptive sensing abilities; and because they tend to be lightweight and very stiff, and can thus convey tactile and kinesthetic information with high-bandwidth. Unfortunately, traditional mouth-sticks and head-sticks are limited in workspace and in the mechanical power that can be transferred because of user mobility and strength limitations. We describe an alternative implementation of the head-stick device using the idea of a virtual head-stick: a head-controlled bilateral force-reflecting telerobot. In this system the end-effector of the slave robot moves as if it were at the tip of an imaginary extension of the user's head. The design goal is for the system is to have the same intuitive operation and extended proprioception as a regular mouth-stick effector but with augmentation of workspace volume and mechanical power. The input is through a specially modified six DOF master robot (a PerForceTM hand-controller) whose joints can be back-driven to apply forces at the user's head. The manipulation tasks in the environment are performed by a six degree-of-freedom slave robot (the Zebra-ZEROTM) with a built-in force sensor. We describe the prototype hardware/software implementation of the system, control system design, safety/disability issues, and initial evaluation tasks.

Letterforms for handwriting and reading: print script and sanserifs in early twentieth-century England

This essay is about letterforms and typography in reading books for young children and how they were influenced by the teaching of handwriting in the early decades of the twentieth century. I examine the contributions made by infant teachers to typography and book design and draw particular attention to the print script movement and the gradual introduction of sanserif typefaces in reading books. I suggest that the use of sanserifs in reading books for young children is one of their first appearances for continuous text. Although the influence of print script on the teaching of handwriting may have had some undesirable effects, I suggest that it indirectly contributed to some innovations in book design.

Replication enhancer elements within the open reading frame of tick-borne encephalitis virus and their evolution within the Flavivirus genus

We provide experimental evidence of a replication enhancer element (REE) within the capsid gene of tick-borne encephalitis virus (TBEV, genus Flavivirus). Thermodynamic and phylogenetic analyses predicted that the REE folds as a long stable stem–loop (designated SL6), conserved among all tick-borne flaviviruses (TBFV). Homologous sequences and potential base pairing were found in the corresponding regions of mosquito-borne flaviviruses, but not in more genetically distant flaviviruses. To investigate the role of SL6, nucleotide substitutions were introduced which changed a conserved hexanucleotide motif, the conformation of the terminal loop and the base-paired dsRNA stacking. Substitutions were made within a TBEV reverse genetic system and recovered mutants were compared for plaque morphology, single-step replication kinetics and cytopathic effect. The greatest phenotypic changes were observed in mutants with a destabilized stem. Point mutations in the conserved hexanucleotide motif of the terminal loop caused moderate virus attenuation. However, all mutants eventually reached the titre of wild-type virus late post-infection. Thus, although not essential for growth in tissue culture, the SL6 REE acts to up-regulate virus replication. We hypothesize that this modulatory role may be important for TBEV survival in nature, where the virus circulates by non-viraemic transmission between infected and non-infected ticks, during co-feeding on local rodents.

Reading Derrida on mathematics

This article engages with the claims of Anne Brubaker that “[n]ow that the dust has settled after the so-called ‘Science Wars’ […] it is an opportune time to reassess the ways in which poststructural theory both argues persuasively for mathematics as a culturally embedded practice – a method as opposed to a metaphysics – and, at the same time, reinscribes realist notions of mathematics as a noise-free description of a mind independent reality.” Through a close re-reading of Jacques Derrida’s work I argue, in alliance with Vicki Kirby’s critique of the work of Brian Rotman, not only that Brubaker misunderstands Derrida’s “writing” but also that her argument constitutes a typical instance of much wider misreadings of Derrida and “poststructuralism” across a range of disciplines in terms of the ways in which her text re-institutes the very stabilities it itself attributes to Derrida’s texts.