BCIT Citations Collection | BCIT Institutional Repository

BCIT Citations Collection

Description

Collection of published works from BCIT researchers, faculty, and instructors.

Pages

A functional task analysis and motion simulation for the development of a powered upper-limb orthosis
Describes research work directed towards the development and application of a design methodology to determine the optimal configuration of a powered upper-limb orthosis. The design objective was to minimize the orthosis complexity, defined as the number of degrees of freedom, while maintaining the ability to perform specific tasks. This objective was achieved in three stages. First, potential users of a powered orthosis were interviewed to determine their priority tasks. Secondly, the natural arm motions of able-bodied individuals performing the priority tasks were profiled using a video tracking system. Finally, a kinematic simulation algorithm was developed and employed in order to evaluate whether a proposed orthosis configuration could perform the priority tasks. The research results indicate that task functionality is overly compromised for orthosis configurations with less than five degrees of freedom, plus prehension. Acceptable task performance, based on the specific priority tasks considered, was achieved in the simulations of two different orthosis configurations with five degrees of freedom. In the first design option, elevation (rotation about a horizontal axis through the shoulder) and radial/ulnar deviation are fixed, while in the second option wrist flexion and radial/ulnar deviation are fixed. A prototype orthosis is currently being developed using the first design option., Peer-reviewed article, Published.
Gene expression noise in spatial patterning
Positional information in developing embryos is specified by spatial gradients of transcriptional regulators. One of the classic systems for studying this is the activation of the hunchback (hb) gene in early fruit fly (Drosophila) segmentation by the maternally-derived gradient of the Bicoid (Bcd) protein. Gene regulation is subject to intrinsic noise which can produce variable expression. This variability must be constrained in the highly reproducible and coordinated events of development. We identify means by which noise is controlled during gene expression by characterizing the dependence of hb mRNA and protein output noise on hb promoter structure and transcriptional dynamics. We use a stochastic model of the hb promoter in which the number and strength of Bcd and Hb (self-regulatory) binding sites can be varied. Model parameters are fit to data from WT embryos, the self-regulation mutant hb(14F), and lacZ reporter constructs using different portions of the hb promoter. We have corroborated model noise predictions experimentally. The results indicate that WT (self-regulatory) Hb output noise is predominantly dependent on the transcription and translation dynamics of its own expression, rather than on Bcd fluctuations. The constructs and mutant, which lack self-regulation, indicate that the multiple Bcd binding sites in the hb promoter (and their strengths) also play a role in buffering noise. The model is robust to the variation in Bcd binding site number across a number of fly species. This study identifies particular ways in which promoter structure and regulatory dynamics reduce hb output noise. Insofar as many of these are common features of genes (e.g. multiple regulatory sites, cooperativity, self-feedback), the current results contribute to the general understanding of the reproducibility and determinacy of spatial patterning in early development., Peer-reviewed article, Publisher. Received July 4, 2010; Accepted December 28, 2010; Published February 3, 2011.
A greenhouse gas emissions inventory and ecological footprint analysis of Metro Vancouver residents’ air travel
Ecological Footprint Analysis (EFA) at the city or regional scale does not typically include air travel due to a lack of readily available data. However, knowing the “load” placed on nature by various lifestyle choices, including air travel, is essential if we hope to enable society to live sustainably within ecological limits. This paper provides methods for including air travel in urban EFA, in a manner that is accessible to those that are interested in the complexities of urban sustainability. Our goal is to use the case of the Vancouver Metropolitan region to illustrate two methods in such a way that they can be replicated or adapted for use in other cities and regions. We found that the greenhouse gas emissions of air travel by Metro Vancouver residents for 2006 is between 1,191,070 and 1,402,420 tonnes of carbon dioxide equivalent (tCO2e). The resulting ecological footprint is between 287,030 and 337,980 global hectares (gha), or between 0.136 and 0.160 gha/capita. The dedicated carbon sink required to neutralize the carbon dioxide emissions from Metro Vancouver residents’ air travel alone is equivalent to twice the land area of the region (283,183 hectares)., Peer-reviewed article, Published. Received: July 15, 2013 ; Accepted: September 16, 2013 ; Online Published: September 27, 2013.
Heat, air and moisture transport properties of several North American bricks and mortar mixes
Hygrothermal models are emerging as practical building design tools. These models require a set of reliable inputs to provide results that are meaningful to the designers. One of these inputs is the set of heat, air and moisture transport properties of materials. For any given class of building materials the properties may vary within a broad range. This paper reports the porosity, density, matrix density, thermal conductivity, equilibrium moisture content, water vapor permeability, water absorption coefficient, liquid diffusivity and air permeability of six types of bricks and four mortar mixes that are commonly used in North America. The experimental and analytical procedures follow either international standards or well-established methodologies., Peer reviewed article, Published. Received 9 July 2003; accepted 17 March 2004.
Heat, air and moisture transport properties of three North American stuccos
Heat, air, and moisture transfer models that are used as practical building design tools require reliable inputs to provide meaningful results. One of these inputs is the set of heat, air, and moisture transport properties of materials. For any given class of building materials the properties may vary within a broad range. This paper reports the porosity, density, matrix density, thermal conductivity, equilibrium moisture content, water vapor permeability, water absorption coefficient, liquid diffusivity, and air permeability of regular lime stucco, regular Portland cement stucco, and acrylic stucco that are commonly used in North America. The experimental and analytical procedures follow either international standards or well-established methodologies., Peer reviewed article, Published. Received 9 January 2004; accepted 13 October 2005; published online 25 January 2006.
Identification of quantitative trait loci controlling fibre length and lignin content in Arabidopsis thaliana stems
Fibre properties and the biochemical composition of cell walls are important traits in many applications. For example, the lengths of fibres define the strength and quality of paper, and lignin content is a critical parameter for the use of biomass in biofuel production. Identifying genes controlling these traits is comparatively difficult in woody species, because of long generation times and limited amenability to high-resolution genetic mapping. To address this problem, this study mapped quantitative trait loci (QTLs) defining fibre length and lignin content in the Arabidopsis recombinant inbred line population Col-4×Ler-0. Adapting high-throughput phenotyping techniques for both traits for measurements in Arabidopsis inflorescence stems identified significant QTLs for fibre length on chromosomes 2 and 5, as well as one significant QTL affecting lignin content on chromosome 2. For fibre length, total variation within the population was 208% higher than between parental lines and the identified QTLs explained 50.58% of the observed variation. For lignin content, the values were 261 and 26.51%, respectively. Bioinformatics analysis of the associated intervals identified a number of candidate genes for fibre length and lignin content. This study demonstrates that molecular mapping of QTLs pertaining to wood and fibre properties is possible in Arabidopsis, which substantially broadens the use of Arabidopsis as a model species for the functional characterization of plant genes., Peer-reviewed article, Published. Received 3 April 2012; Revised 11 October 2012; Accepted 15 October 2012.
Impact of electrical intertie capacity on carbon policy effectiveness
This study investigates the potential cost and emissions reductions that result from an increase in electricity transmission capacity between Canada's two westernmost provinces: Alberta, a fossil fuel dominated jurisdiction, and British Columbia, a predominantly hydroelectric jurisdiction. A bottom-up model is used to find the least cost electricity generation mix in Alberta and British Columbia under different carbon policies. The long-term evolution of the electricity system is determined by minimizing net present cost of electricity generation for the time span of 2010–2060. Different levels of intertie capacity expansion are considered together with a variety of carbon tax and carbon cap scenarios. Results indicate that increased intertie capacity reduces the cost of electricity and emissions under carbon pricing policies. However, the expandable intertie does not encourage greater adoption of variable renewable generation. Instead, it is used to move low-cost energy from the United States to Alberta. The optimal intertie capacity and cost reduction of increased interconnectivity increases with more restrictive carbon policies., Peer-reviewed article, Published. Received 3 March 2016, Revised 23 September 2016, Accepted 12 October 2016, Available online 15 November 2016.
The importance of method selection in determining product integrity for nutrition research
The American Herbal Products Association estimates that there as many as 3000 plant species in commerce. The FDA estimates that there are about 85,000 dietary supplement products in the marketplace. The pace of product innovation far exceeds that of analytical methods development and validation, with new ingredients, matrixes, and combinations resulting in an analytical community that has been unable to keep up. This has led to a lack of validated analytical methods for dietary supplements and to inappropriate method selection where methods do exist. Only after rigorous validation procedures to ensure that methods are fit for purpose should they be used in a routine setting to verify product authenticity and quality. By following systematic procedures and establishing performance requirements for analytical methods before method development and validation, methods can be developed that are both valid and fit for purpose. This review summarizes advances in method selection, development, and validation regarding herbal supplement analysis and provides several documented examples of inappropriate method selection and application., Peer-reviewed article, Published.
In silico evolution of gene cooption in pattern-forming gene networks
Gene recruitment or cooption occurs when a gene, which may be part of an existing gene regulatory network (GRN), comes under the control of a new regulatory system. Such re-arrangement of pre-existing networks is likely more common for increasing genomic complexity than the creation of new genes. Using evolutionary computations (EC), we investigate how cooption affects the evolvability, outgrowth and robustness of GRNs. We use a data-driven model of insect segmentation, for the fruit fly Drosophila, and evaluate fitness by robustness to maternal variability—a major constraint in biological development. We compare two mechanisms of gene cooption: a simpler one with gene Introduction and Withdrawal operators; and one in which GRN elements can be altered by transposon infection. Starting from a minimal 2-gene network, insufficient for fitting the Drosophila gene expression patterns, we find a general trend of coopting available genes into the GRN, in order to better fit the data. With the transposon mechanism, we find co-evolutionary oscillations between genes and their transposons. These oscillations may offer a new technique in EC for overcoming premature convergence. Finally, we comment on how a differential equations (in contrast to Boolean) approach is necessary for addressing realistic continuous variation in biochemical parameters., Peer-reviewed article, Published. Received 29 September 2012; Accepted 13 November 2012.
In silico evolution of the hunchback gene indicates redundancy in cis-regulatory organization and spatial gene expression
Biological development depends on the coordinated expression of genes in time and space. Developmental genes have extensive cis-regulatory regions which control their expression. These regions are organized in a modular manner, with different modules controlling expression at different times and locations. Both how modularity evolved and what function it serves are open questions. We present a computational model for the cis-regulation of the hunchback (hb) gene in the fruit fly (Drosophila). We simulate evolution (using an evolutionary computation approach from computer science) to find the optimal cis-regulatory arrangements for fitting experimental hb expression patterns. We find that the cis-regulatory region tends to readily evolve modularity. These cis-regulatory modules (CRMs) do not tend to control single spatial domains, but show a multi-CRM/multi-domain correspondence. We find that the CRM-domain correspondence seen in Drosophila evolves with a high probability in our model, supporting the biological relevance of the approach. The partial redundancy resulting from multi-CRM control may confer some biological robustness against corruption of regulatory sequences. The technique developed on hb could readily be applied to other multi-CRM developmental genes., Peer-reviewed article, Published.
Increasing efficiency of enzymatic hemicellulose removal from bamboo for production of high-grade dissolving pulp
To improve the efficiency of enzymatic hemicellulose removal from bamboo pre-hydrolysis kraft pulp, mechanical refining was conducted prior to enzyme treatment. Refining significantly improved the subsequent hemicellulose removal efficiency by xylanase treatment. Results showed that when PFI refining was followed by 3 h xylanase treatment, the xylan content of the bamboo pre-hydrolysis kraft pulp (after first stage oxygen delignification) could be decreased to 2.72% (w/w). After bleaching of enzyme treated pulp, the alpha-cellulose content was 93.4% (w/w) while the xylan content was only 2.38%. The effect of refining on fibre properties was investigated in terms of freeness, water retention value, fibre length and fibrillation characteristics. The brightness, reactivity and viscosity were also determined to characterize the quality of final pulp. Results demonstrated the feasibility of combining refining and xylanase treatment to produce high quality bamboo dissolving pulp., Peer-reviewed article, Published. Received 1 September 2016; Revised 9 October 2016; Accepted 12 October 2016; Available online 24 October 2016.
Insight into the evolution of the proton concentration during autohydrolysis and dilute-acid hydrolysis of hemicellulose
Background: During pretreatment, hemicellulose is removed from biomass via proton-catalyzed hydrolysis to produce soluble poly- and mono-saccharides. Many kinetic models have been proposed but the dependence of rate on proton concentration is not well-defined; autohydrolysis and dilute-acid hydrolysis models apply very different treatments despite having similar chemistries. In this work, evolution of proton concentration is examined during both autohydrolysis and dilute-acid hydrolysis of hemicellulose from green bamboo. An approximate mathematical model, or “toy model”, to describe proton concentration based upon conservation of mass and charge during deacetylation and ash neutralization coupled with a number of competing equilibria, was derived. The model was qualitatively compared to experiments where pH was measured as a function of time, temperature, and initial acid level. Proton evolution was also examined at room temperature to decouple the effect of ash neutralization from deacetylation. Results: The toy model predicts the existence of a steady-state proton concentration dictated by equilibrium constants, initial acetyl groups, and initial added acid. At room temperature, it was found that pH remains essentially constant both at low initial pH and autohydrolysis conditions. Acid is likely in excess of the neutralization potential of the ash, in the former case, and the kinetics of neutralization become exceedingly small in the latter case due to the low proton concentration. Finally, when the hydrolysis reaction proceeded at elevated temperatures, one case of non-monotonic behavior in which the pH initially increased, and then decreased at longer times, was found. This is likely due to the difference in rates between neutralization and deacetylation. Conclusions: The model and experimental work demonstrate that the evolution of proton concentration during hydrolysis follows complex behavior that depends upon the acetyl group and ash content of biomass, initial acid levels and temperature. In the limit of excess added acid, pH varies very weakly with time. Below this limit, complex schemes are found primarily related to the selectivity of deacetylation in comparison to neutralization. These findings indicate that a more rigorous approach to models of hemicellulose hydrolysis is needed. Improved models will lead to more efficient acid utilization and facilitate process scale-up., Peer-reviewed article, Published. Received: 23 July 2016 ; Accepted: 22 September 2016 ; Published: 21 October 2016.
Integrated analysis of whole building heat, air and moisture transfer
There is a continuous dynamic heat, air and moisture (HAM) interaction between the indoor environment, building envelope and mechanical systems. In spite of these interdependences, the current indoor, building envelope and energy analysis tools are used independently. In this paper a holistic HAM model that integrates building envelope enclosures, indoor environment, HVAC systems, and indoor heat and moisture generation mechanisms, and solves simultaneously for the respective design parameters is developed. The model is benchmarked with internationally published test cases that require simultaneous prediction of indoor environmental conditions, building envelope moisture performance and energy efficiency of a building., Peer reviewed article, Published. Received 26 February 2009, Accepted 11 March 2010, Available online 16 April 2010.
Iterated belief change due to actions and observations
In action domains where agents may have erroneous beliefs, reasoning about the effects of actions involves reasoning about belief change. In this paper, we use a transition system approach to reason about the evolution of an agent's beliefs as actions are executed. Some actions cause an agent to perform belief revision while others cause an agent to perform belief update, but the interaction between revision and update can be non-elementary. We present a set of rationality properties describing the interaction between revision and update, and we introduce a new class of belief change operators for reasoning about alternating sequences of revisions and updates. Our belief change operators can be characterized in terms of a natural shifting operation on total pre-orderings over interpretations. We compare our approach with related work on iterated belief change due to action, and we conclude with some directions for future research., Peer-reviewed article, Published.
Lessons learnt from the shotcrete repair of the Powell River concrete hulks, and their applicability to other marine structures
Background : Concrete structures can be damaged by many chemical or physical processes. Where such damages affect appearance, serviceability or structural integrity, repair may be required. 10 decommissioned concrete ships form a massive floating breakwater on the Malaspina Strait in the City of Powell River in British Columbia, Canada. The ships are subjected to extremely onerous conditions, namely in the salt water splash zone under seasonal freeze-thaw cycling. This paper provides anecdotal evidence based on condition assessments after repairs were car-ried out, on how a well-matched repair concrete can significantly extend the service life of these and similar sorts of marine structures. Methods: Condition assessment was carried out using sounding, visual examination, photo and video documentation, compressive strength testing, splitting tensile strength testing, chloride ion concentration testing, and half-cell potential testing. Results: It was found that the areas which had been repaired had fared very well, with no observable de-terioration. The non-repaired areas of the structures had continued to deteriorate, particularly in non-submerged areas, close to the waterline, along with new impact damage. Conclusion: Durable concrete repairs can be achieved even for concrete exposed to extreme environ-mental conditions. Key conditions for such repairs are: complete removal of the deteriorated portions of the original concrete, removal of all loose corrosion products from exposed reinforcing steel, prepara-tion of a clean, firm, rough, surface dry but partially or fully water saturated, substrate surface, selection of a compatible repair material, use of an application technique which facilitates high bond strength between substrate and repair material, adequate curing, and protection of the repair material while immature., Peer-reviewed article, Published. Received: September 12, 2015; Revised: December 19, 2015; Accepted: June 28, 2016.
Limiting cases for spectrum closure results
The spectrum of a first-order sentence is the set of cardinalities of its finite models. Given a spectrum S and a function f, it is not always clear whether or not the image of S under f is also a spectrum. In this paper, we consider questions of this form for functions that increase very quickly and for functions that increase very slowly. Roughly speaking, we prove that the class of all spectra is closed under functions that increase arbitrarily quickly, but it is not closed under some natural slowly increasing functions., Peer-reviewed article, Published.

Pages