Designing for Irrelevance

My job title is ‘designer’ but I’m reluctant to describe myself as a designer for a number of reasons: first, because the practice has a lot to answer for; and second, because I don’t do a whole lot of design. I help groups of people to collaborate and converse their way through problems towards solutions—activating a latent capability for design in people as they think and work differently, together. The sense of agency that accompanies this is intoxicating. This work can produce strategies, systems, and services, as well as spaces, objects, and graphics. The awareness that design can shape both our (intangible) experiences and our (tangible) environments—and that, as a mode of thinking, it can be accessible, inclusive, and participatory—shifts it from a practice to a stance. In this sense, is design a choice that we make to perceive and move through the world in a contextual and intentional way? What does this mean for the practice of design?I respod to these question by reflecting on my experience of participating in the Indonesia Australia Design Futures project

Cause and Amelioration of MRI-Induced Heating Through Medical Implant Lead Wires

The RF fields present in magnetic resonance imaging (MRI) scanners can induce hazardous heating in patients wearing medical implants. The inherent design and locale of deep brain stimulators (DBS) and spinal cord stimulators (SCS) make them particularly susceptible. We apply antenna concepts and use electromagnetic (EM) simulation to explain the phenomenon and anticipate its sensitivity to lead wire length. We anticipate that a DC resistance of less than 50 Ω/m and an RF impedance of more than 1:23kΩ/m would be required for a safe electrode for SCS use. We investigate the possibility of manipulating wire conductivity and diameter in order to use the skin depth effect to achieve a safe electrode. The effect of the thickness and permittivity of insulation surrounding the wires is explored

Impulse TDR and its application to measurement of antennas

The traditional stimulus signal used in a time-domain reflectometer (TDR) is a voltage step. We propose an alternative technique, whereby an impulse generator is employed in place of the step generator in a TDR. The advantage conferred by “impulse TDR” is that more energy is available at higher frequencies than with conventional step TDR, and so a higher bandwidth and signal-to-noise ratio (SNR) is achieved. The theoretical result is compared with measurement

Measurement of antennas and microwave components using time-domain reflectometry of a voltage impulse

Band-pass microwave systems such as ultra-wideband antennas are traditionally characterized in the frequency-domain through a vector network analyzer in an anechoic chamber. A recent study proved antennas could be accurately measured in the time-domain using a step-function time-domain reflectometer (TDR), without the need for an anechoic chamber. We propose a new advance in the TDR characterization method. An impulse generator is employed in place of the step generator in a TDR set-up. The advantage conferred by this change is that more energy is available beyond a given frequency than with a step, and so a higher signal-to-noise ratio is achieved. The theoretical result is compared with measurement

Nonequilibrium electron rings for synchrotron radiation production

Electron storage rings used for the production of synchrotron radiation (SR) have an output photon brightness that is limited by the equilibrium beam emittance. By using interleaved injection and ejection of bunches from a source with repetition rate greater than 1 kHz, we show that it is practicable to overcome this limit in rings of energy ~1 GeV. Sufficiently short kicker pulse lengths enable effective currents of many milliamperes, which can deliver a significant flux of diffraction-limited soft X-ray photons. Thus, either existing SR facilities may be adapted for non-equilibrium operation, or the technique applied to construct SR rings smaller than their storage ring equivalent.Comment: 5 pages, 2 figures; accepted for publication in Physical Review Letter

Polyhedral computational geometry for averaging metric phylogenetic trees

This paper investigates the computational geometry relevant to calculations of the Frechet mean and variance for probability distributions on the phylogenetic tree space of Billera, Holmes and Vogtmann, using the theory of probability measures on spaces of nonpositive curvature developed by Sturm. We show that the combinatorics of geodesics with a specified fixed endpoint in tree space are determined by the location of the varying endpoint in a certain polyhedral subdivision of tree space. The variance function associated to a finite subset of tree space has a fixed $C^\infty$ algebraic formula within each cell of the corresponding subdivision, and is continuously differentiable in the interior of each orthant of tree space. We use this subdivision to establish two iterative methods for producing sequences that converge to the Frechet mean: one based on Sturm's Law of Large Numbers, and another based on descent algorithms for finding optima of smooth functions on convex polyhedra. We present properties and biological applications of Frechet means and extend our main results to more general globally nonpositively curved spaces composed of Euclidean orthants.Comment: 43 pages, 6 figures; v2: fixed typos, shortened Sections 1 and 5, added counter example for polyhedrality of vistal subdivision in general CAT(0) cubical complexes; v1: 43 pages, 5 figure

Thermal constraints on in vivo optogenetic manipulations.

A key assumption of optogenetics is that light only affects opsin-expressing neurons. However, illumination invariably heats tissue, and many physiological processes are temperature-sensitive. Commonly used illumination protocols increased the temperature by 0.2-2 °C and suppressed spiking in multiple brain regions. In the striatum, light delivery activated an inwardly rectifying potassium conductance and biased rotational behavior. Thus, careful consideration of light-delivery parameters is required, as even modest intracranial heating can confound interpretation of optogenetic experiments

Doctor of Philosophy

dissertationMicrofluidic methods were applied to nucleic acid mutation identification and quantification. DNA melting analysis interrogation volumes were reduced 4 orders of magnitude (down to 1 nL volumes) from commercial instrumentation, allowing less reagent consumption while yielding adequate signal for genotyping and scanning of polymerase chain reaction (PCR) products. A microfluidic instrument was developed for digital PCR applications, using a spinning plastic disk patterned by xurography. Theplatform offers faster thermocycling times (30 cycles in ~12 min), simplified fluid partitioning, and a less expensive disposable when compared to currently available digital PCR platforms. PCR within the disk was validated by quantifying plasmid DNA sample using "on/off" fluorescence interrogation across 1000 wells (30 nL/well) at varying template concentration. A 94% PCR efficiency and product amplification specificity were determined by aggregate real-time PCR and melting analysis. The technique of quasi-digital PCR was also applied within this platform, wherein a single mutation copy was preferentially amplified from a large background of wild-type DNA, to detect and quantify low levels of rare mutations. This method demonstrated a sensitivity of 0.01% (detecting a mutant to wild-type DNA ratio of 43:450000), by mixing known concentrations of an oncogene mutation with thousands of wild-type template copies. Statistic analysis tools were constructed in order to interpret digital PCR data, with results comparing well to DNA absorption measurements

Induced pi-facial discrimination in the alkylation of chiral derivatives of glycine.

Part A. The alkylation trans 2-arylcyclohexyl hippurates with a series of electrophiles was examined. The reaction stereoselectivity varied from 46 to 81% depending on the steric and electronic nature of the electrophile when (Ar = phenyl). Higher stereoselectivity was observed when reacting electrophiles of increasing pi-character. When the chiral auxiliary contained a naphthyl group the stereoselectivity was \u3e80% for every electrophile used. Part B. The alkylation of the trans 2-phenylcyclohexylamide of methyl glycinate with a series of electrophiles was examined. Incorporation of the chiral auxiliary on the amino terminus of the amino acid appears to induce good stereoselectivity only when the electrophiles contain a point of unsaturation. The reaction stereoselectivity ranged from 21 to 80% depending on the electronic nature of the electrophiles. It is proposed that a pi-stacking interaction between the aromatic group on the auxiliary and the unsaturated electrophiles was responsible for the high stereochemical excess observed. Source: Masters Abstracts International, Volume: 39-02, page: 0514. Adviser: John M. McIntosh. Thesis (M.Sc.)--University of Windsor (Canada), 1999