Papers by Nigel Livingston
This paper describes some of the basic principles and motivations underlying our brain-computer i... more This paper describes some of the basic principles and motivations underlying our brain-computer interface design. Our intent is to abstractly describe multi-rate filtering and orthogonal subspace decomposition appropriate for processing electroencephalographic data and identify some of the constraints imposed on the interface when considering a user with amyotrophic lateral sclerosis . Using an additive Gaussian noise model, orthogonal filter bank decomposition using a custom basis vector is demonstrated as an effective means for identification of events in an electroencephalogram. INTRODUCTION The University of Victoria Assistive Technology Team, (UVATT) is developing a non-invasive brain-computer interface, (BCI) to provide persons with a means to communicate when all other conventional methods have failed. More broadly, the technology under development may also be used to detect and characterize electrical parameters within the human brain associated with specific behavioural fun...
Panel discussion recorded at Critical Conversations: The Art and Science of Diversity - Provost&#... more Panel discussion recorded at Critical Conversations: The Art and Science of Diversity - Provost's Diversity Research Forum Feb 9-11, 2011
Design and Use of Assistive Technology, 2010
CanAssist is a university-based program at the University of Victoria that is dedicated to develo... more CanAssist is a university-based program at the University of Victoria that is dedicated to developing and providing services and technologies to those with disabilities. All of CanAssist’s activities are in response to requests from the community. The program has engaged many thousands of students (from a broad range of disciplines), faculty and staff, as well as many hundreds of community volunteers. The CanAssist model extends the traditional mandate of universities, to undertake research and education, by adding a third core pillar of activity – community service. This additional task is highly augmentative in that it creates outstanding new research avenues and provides students with a myriad of extraordinarily challenging and rewarding experiential learning opportunities.
Design and Use of Assistive Technology, 2010
ABSTRACT Unfortunately, device abandonment (by clients or caregivers) is a pervasive problem in t... more ABSTRACT Unfortunately, device abandonment (by clients or caregivers) is a pervasive problem in the provision of assistive technology. This is not necessarily the result of poor design of the technology, but rather a failure to account for other factors or determinants. This issue can be successfully addressed by employing the human activity assistive technology (HAAT) model when considering potential solutions for clients. The model conceptualizes the consumer, their activities, environment, and assistive technology as an integrated system in which changing one element affects all other elements in the system. The model can be applied in the design, selection, and evaluation of technology for use by an individual, or as a conceptual model for exploring the influence of assistive technology on participation in daily activities. In this chapter, examples and explanations are given for both “successful” and “failed” technologies with specific reference to the HAAT model.
2012 Seventh International Conference on P2P, Parallel, Grid, Cloud and Internet Computing, 2012
Tree Physiology, 2004
The temporal distribution of soil nutrients is heterogeneous, and thus the uptake, storage and la... more The temporal distribution of soil nutrients is heterogeneous, and thus the uptake, storage and later remobilization of brief nutrient pulses may be critical for growth in nutrient-limited habitats. We investigated the response of photosynthesis and the major nitrogen (N) fractions in needles of 2-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings to a 15-day nutrient pulse (containing 250 ppm N). The nutrient pulse (N pulse) was imposed in late July, toward the end of the seedlings'third growing season, and subsequent changes in photosynthesis and needle N fractions were examined over the following 3 months. Needles are sites of photosynthesis and putative storage organs. Thus we tested two hypotheses: (1) N from the N pulse is quickly synthesized from soluble non-protein N into soluble proteins, especially Rubisco, and (2) the N pulse increases photosynthetic rates and thus growth. We also examined an alternative hypothesis that Rubisco functions also as a storage protein, in which case we would predict increases in amount of Rubisco in response to the N pulse without concomitant increases in photosynthesis. Soluble non-protein N was the most dynamic N pool and may have constituted a temporary storage reservoir; however, the quantitative significance of soluble non-protein N is questionable because this pool was at most only 7% of total N. Concentrations of Rubisco were unaffected by the N-pulse treatment and there was little evidence that Rubisco served as a storage protein. Nutrient-pulse seedlings added twice as much dry mass as controls during the 3 months post-treatment (Warren et al. 2003a). Over the same period, the maximum rate of light-saturated photosynthesis (A max) declined to low rates in control seedlings, whereas A max increased in N-pulse seedlings. Nevertheless, treatment and temporal trends in N and Rubisco content per unit area were poorly related to A max , and it seems likely that photosynthesis was limited by additional factors, perhaps thylakoid proteins or an inadequate supply of other nutrients.
Soil Science Society of America Journal, 1992
ABSTRACT We describe a new time domain reflectometry (TDK) technique that increases the reliabili... more ABSTRACT We describe a new time domain reflectometry (TDK) technique that increases the reliability of soil water content measurements. Remotely switched shorting diodes in combination with differential detection techniques greatly increase the effective amplitude ...
Soil Science Society of America Journal, 1995
The determination of soil water content by time domain reflectometry (TDK) involves two steps: th... more The determination of soil water content by time domain reflectometry (TDK) involves two steps: the measurement of the propagation velocity of an electromagnetic pulse along a transmission line and the conversion of this measurement to an estimate of soil water content. The objective of this study was to identify and quantify errors associated with propagation velocity measurements. We developed new TDR techniques, involving the use of remotely switched diodes and differential wave form detection, that can be used to quantify and minimize propagation velocity errors. These errors are presented in terms of time interval errors. We show that the dominant time interval error term relates to the transition time of reflected pulses and that absolute time interval errors cannot be assumed to be <200 ps. We identify the presence of dissolved ions and the use of long cables as major sources of additional transition time errors. For transition times >2 ns, the time interval error caused by transition time effects can be estimated as the root mean square sum of the basic 200-ps error and an error equal to 10% of the transition time. We show that
Plant, Cell and Environment, 1996
... Correspondence: NJ LIVINGSTON,. *Correspondence: NJ Livingston, Department of Biology, Univer... more ... Correspondence: NJ LIVINGSTON,. *Correspondence: NJ Livingston, Department of Biology, University of Victoria, Victoria, British Columbia V8R 2Y2, Canada. Publication History. ... Soil Science Society of America Journal 60, 3541. ...
Plant, Cell and Environment, 1997
Experiments were conducted on well watered 1-year-old Douglas fir [Pseudotsuga menziesii (Mirb.) ... more Experiments were conducted on well watered 1-year-old Douglas fir [Pseudotsuga menziesii (Mirb.) Franco], western hemlock [Tsuga heterophylla (Raf.) Sarg.] and western redcedar (Thuja plicata Donn) seedlings to determine the effects of temperature on whole-plant photosynthetic and stomatal responses to short-term fluctuations in irradiance (Q). Following a step change in Q, time constants (τ, the period over which 63% of the total change occurs) for stomatal conductance (gs) and assimilation rate (A) decreased linearly with increasing air temperature (Tair). For example, in western redcedar τA decreased from 30 ± 4 min at 5 °C to 10 ± 1 min at 25 °C. In all cases, τA was within 10–15% of τgs. There was considerable variation in τ among individuals within a given species. Differences between species became more pronounced with decreasing temperature. Multiplicative models that included functions for τ accounted for 99% of the diurnal variability in A and gs for seedlings exposed to varying air temperature, irradiance and vapour pressure deficit. Estimates of daily A were within 2% of those measured. Intermittent cloud cover and understory shading were approximated by exposing seedlings to 3–4 episodes (≥1 h) of shade (200 or 500 μmol m−2 s−1) or complete darkness during the day. In such cases, daily A was overestimated by up to 4 and 21%, respectively, if a function for τ was excluded from the models. Our results suggest that there is scope for selecting seedling stock for increased carbon assimilation on the basis of reduced time constants. For example, in western redcedar, a 40% reduction in τ could lead to increases in daily carbon gains of almost 5% depending on the frequency and degree of shading. If these daily gains were translated into increased dry matter production and compounded, seasonal gains would be even larger.
Plant, Cell and Environment, 1994
ABSTRACT ABSTRACTA simple and inexpensive feedback control system that provides continuous and pr... more ABSTRACT ABSTRACTA simple and inexpensive feedback control system that provides continuous and precise control of photosynthetic photon flux density (PPFD) in a whole plant cuvette is described. A ‘Plexiglass’ tank is interposed between a light source and cuvette and PPFD changed by varying the level of dyed liquid in the tank. The amount of liquid pumped into or drained from the tank is a function of the difference (error) between a defined set point value of PPFD and that measured in the cuvette. The set point can be varied as a function of time, can follow the output of a quantum sensor measuring ambient PPFD or can be driven by values of PPFD read from a data file. Within the 0.4 to 0.64 μm waveband, the dye acts as a neutral density filter so that there is no change in spectral distribution with PPFD. Photosynthetic photon flux density in the cuvette was controlled to better than 20 μmol m−2s−1 when the set point was varied from 200 to 1100 μmol m−2s−1 over 3 min. When the set point was held constant or changed less rapidly, errors did not exceed 5 μmol m−2s−1. Net photosynthesis of Western redcedar (Thuja plicata Donn.) seedlings held at 18 °C closely followed rapid changes in PPFD.
Physiologia Plantarum, 1999
ABA were also determined. Analog activity was re-ABA analog structure-function relationships were... more ABA were also determined. Analog activity was re-ABA analog structure-function relationships were determined duced by changing the oxidation level at C-1 from the car-by testing an array of 19 different ABA analogs on 1-year-old clonal white spruce (Picea glauca [Moench.] Voss) raised from boxylic acid. The ring C-2%, C-3% double bond was important somatic embryos. The contribution of specific structural fea-but not essential to activity. The activity lost through changes tures to analog activity was determined from the relative in ring structure and C-1 oxidation level was, in many cases, effect of aeroponically applied analog solutions (10 − 3 M) on almost fully restored by replacing the C-4, C-5 double bond with a triple bond. Therefore, analogs with a triple bond at seedling gas exchange. Seedling transpiration rate (E) and carbon assimilation rate (A) were measured continuously dur-C-4 were more active than their equivalents with a dienoic side ing treatment by means of a whole plant cuvette system. The chain. Fluorination of the C-7% methyl caused a relatively analogs were racemic about the C-1% chiral center and were moderate reduction in analog activity. Truncation of C-1 and C-2 from the side chain reduced activity to near zero. The derived from changes imposed on six regions of the ABA molecule. The activity of optically pure (+)-S-ABA and unnatural (−)-ABA enantiomer was inactive.
Canadian Journal of Forest Research, 1988
Container-grown 1-0 seedlings of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlo... more Container-grown 1-0 seedlings of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), and Pacific silver fir (Abiesamabilis (Dougl.) Forbes) were spring planted on a south-facing high-elevation clearcut located on Mount Arrowsmith, Vancouver Island, British Columbia, and their growth and development was measured over three successive growing seasons. Treatments designed to modify seedling microclimate, including provision of shade cards, irrigation, and irrigation and shade cards combined, had a marked effect on the extent and type of growth in all species. Irrigated seedlings had the largest shoot dry masses and the highest shoot to root dry mass ratios. Shaded seedlings had larger shoots than untreated seedlings, which had the lowest shoot to root dry mass ratios. All seedlings showed a pronounced decline in seasonal growth 1 year after planting. Douglas-fir seedlings exhibited a high degree of drought tolerance; in the driest year t...
Canadian Journal of Forest Research, 1991
Reversible changes in cell wall water content, elasticity, and osmotic adjustment are all importa... more Reversible changes in cell wall water content, elasticity, and osmotic adjustment are all important drought tolerance mechanisms. Pressure chambers have been used extensively to generate water-release curves from which these basic water relations parameters are derived. Major limitations of this technique include the considerable time required to generate water-release curves and the difficulty in avoiding damage to tissue during the process. A simple and practical technique is descried that overcomes these limitations and allows the routine and rapid generation of water-release curves. Needles were removed from hydrated black spruce (Piceamariana (Mill.) B.S.P.) shoots, weighed on a precision balance, and suspended above unsaturated salt solutions of known molality in sealed test tubes held at 5 °C. Eighteen solutions were used with water potentials ranging from −0.09 to −4.67 MPa. Once needles had equilibrated with air above the salt solution (8–30 h depending on needle age), they...
Canadian Journal of Forest Research, 1987
Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg... more Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), and Pacific silver fir (Abiesamabilis (Dougl.) Forbes) container-grown 1-0 seedlings were spring planted on a south-facing high elevation clear-cut located on Mount Arrowsmith, Vancouver Island, British Columbia. Treatments, which included inclining seedlings to the southwest, provision of shade cards, irrigation, and irrigation and shade cards combined, were applied to determine whether modification of seedling microclimate would increase survival. Highest survival rates, regardless of treatment, were shown by Douglas-fir. By April 1984, 72 and 82% of untreated Douglas-fir seedlings planted in 1981 and 1982, respectively, survived, whereas survival of treated seedlings ranged from 81 to 95%. The high survival rate in Douglas-fir appeared to be due to their high drought tolerance. The osmotic potential of unirrigated Douglas-fir seedlings declined by over 1.1 MPa during the course of...
Behavioural Brain Research, 2011
We present a novel method of combining eye tracking with specially designed virtual environments ... more We present a novel method of combining eye tracking with specially designed virtual environments to provide objective evidence of navigational strategy selection. A simple, inexpensive video camera with an easily built infrared LED array is used to capture eye movements at 60 Hz. Simple algorithms analyze gaze position at the start of each virtual maze trial to identify stimuli used for navigational orientation. To validate the methodology, human participants were tested in two virtual environments which differed with respect to features usable for navigation and which forced participants to use one or another of two well-known navigational strategies. Because the environmental features for the two kinds of navigation were clustered in different regions of the environment (and the video display), a simple analysis of gazeposition during the first (i.e., orienting) second of each trial revealed which features were being attended to, and therefore, which navigational strategy was about to be employed on the upcoming trial.
Agronomy Journal, 1988
Osmotic adjustment and changes in cell wall elastic modulus are important processes that enable p... more Osmotic adjustment and changes in cell wall elastic modulus are important processes that enable plants to maintain physiological activity and prolong leaf survival as plant water deficits increase. This paper describes a simple and practical technique to produce tissue water-release curves that allows many measurements of osmotic potential (P) , elastic modulus (e), and apoplastic water fraction (A) to be made both rapidly and routinely. Discs, 6 mm in diameter, were punched out of hydrated leaves of wheat (Trificum aesfivum L.), barley (Hordeum distichon L.), and oilseed rape (Brussicu nupus and B. cumpesfris) and weighed immediately on a precision balance. Each disc was then suspended above an unsaturated salt solution of known molality in a sealed test tube held at 5°C in a stirred water bath. Eighteen salt solutions were used whose water potentials ranged from-0.09 to-4.67 MPa. After 12 h the discs were reweighed and then oven dried at 65°C for 24 h. Water-release curves were obtained by plotting paired values of disc relative water content and salt solution water potential. Using leaves from the same stem, P, at full and zero turgor, E, and A determined from the water-release curves were compared with pressure chamber measurements made on the next lower leaf. Measurements of wheat, barley, and oilseed rape P, e, and A obtained from water release curves generated using salt solutions were within 0.2 MPa for P, 3.0 MPa for e, and 0.07 for A, of those obtained using a pressure chamber over a wide range of P and e. More than 40 water-release curves could be generated over 2 d.
Agronomy Journal, 1990
Crop seeds and seedlings are exposed to drought, salinity and/or low soil temperatures in some ar... more Crop seeds and seedlings are exposed to drought, salinity and/or low soil temperatures in some areas. Therefore, the combined effects of these stresses on germination and emergence is of considerable interest. A growth room study was conducted to determine the effects of matric and osmotic potential at different temperatures on the rate and total number of seedling emergence for wheat (Triticum aestivum L. cv. Neepawa) and two rapeseed species, Polish type (Brassica campestris var. Tobin) and Argentinean type (B. napus var. Westar). Twenty-four treatments [3 species X 2 matric potentials (-0.02 and-0.2 MPa) X 4 osmotic potentials (-0.03,-0.3,-0.6 and-1.2 MPa)], each replicated four times, were arranged in a completely randomized design in two insulated tanks through which water from a temperature regulated water bath was calculated. Temperature at seed depth (IS mm) was maintained at 3, 6, 12, and IS °C in four separate experiments. In each treatment ten seeds were planted in a 300-mL container packed with a sandy loam soil (Entic Haploborall) to give a density of 1.2S g cm" 3. For all species time to 50% emergence (f TO) increased with decreasing temperature. Polish rape (the smallest seed) emerged fastest at all temperatures and soil water potentials followed by Argentinean rape and then wheat (the largest seed). Differences between species generally became less pronounced with increasing temperature at all soil water potentials. For soils with the lowest matric potentials the relationship between fg, and total potential (* T) was linear and almost all the variability in fa, could be explained by changes in osmotic potential. Effects of * T
The WISP is a novel wireless sensor that uses 3 axis magnetometers, accelerometers, and rate gyro... more The WISP is a novel wireless sensor that uses 3 axis magnetometers, accelerometers, and rate gyroscopes to provide a real-time measurement of its own orientation in space. Orientation data are transmitted via the Open Sound Control protocol (OSC) to a synthesis engine for interactive live dance performance.
International Journal of Healthcare, 2020
The elderly are the fastest growing portion of the world population. The majority of elderly want... more The elderly are the fastest growing portion of the world population. The majority of elderly want to remain independent as long as possible, with responsibility for their care often falling to family or caregivers. Assistive robots could help maintain independence in the elderly while relieving the burden of care on families and healthcare professionals. This scoping review seeks to examine the type and scope of global policies on the use of robotic technology for care of the elderly in international jurisdictions and to assess how they align with current Canadian policies. This review also seeks to determine current perceptions on the use of robotics in care of the elderly and potential barriers to their use that policy makers could encounter. A comprehensive literature search was conducted for articles related to robotic care of the elderly, perceptions of robotic care of the elderly and related policies, using a global lens. A three-step strategy was used to review and identify a...
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Papers by Nigel Livingston