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Optimization and single-laboratory validation of a method for the determination of flavonolignans in milk thistle seeds by high-performance liquid chromatography with ultraviolet detection
Seeds of milk thistle, Silybum marianum (L.) Gaertn., are used for treatment and prevention of liver disorders and were identified as a high priority ingredient requiring a validated analytical method. An AOAC International expert panel reviewed existing methods and made recommendations concerning method optimization prior to validation. A series of extraction and separation studies were undertaken on the selected method for determining flavonolignans from milk thistle seeds and finished products to address the review panel recommendations. Once optimized, a single-laboratory validation study was conducted. The method was assessed for repeatability, accuracy, selectivity, LOD, LOQ, analyte stability, and linearity. Flavonolignan content ranged from 1.40 to 52.86 % in raw materials and dry finished products and ranged from 36.16 to 1570.7 μg/mL in liquid tinctures. Repeatability for the individual flavonolignans in raw materials and finished products ranged from 1.03 to 9.88 % RSD, with HorRat values between 0.21 and 1.55. Calibration curves for all flavonolignan concentrations had correlation coefficients of >99.8 %. The LODs for the flavonolignans ranged from 0.20 to 0.48 μg/mL at 288 nm. Based on the results of this single-laboratory validation, this method is suitable for the quantitation of the six major flavonolignans in milk thistle raw materials and finished products, as well as multicomponent products containing dandelion, schizandra berry, and artichoke extracts. It is recommended that this method be adopted as First Action Official Method status by AOAC International., Peer-reviewed article, Published. Received 1 June 2015; Revised 14 July 2015; Accepted 16 July 2015; Published online 31 July 2015.
Ordinal conditional functions for nearly counterfactual revision
Proceedings of the 16th International Workshop on Non-Monotonic Reasoning (NMR 2016), Cape Town, South Africa; April 22-24, 2016. We are interested in belief revision involving conditional statements where the antecedent is almost certainly false. To represent such problems, we use Ordinal Conditional Functions that may take infinite values. We model belief change in this context through simple arithmetical operations that allow us to capture the intuition that certain antecedents can not be validated by any number of observations. We frame our approach as a form of finite belief improvement, and we propose a model of conditional belief revision in which only the "right" hypothetical levels of implausibility are revised., Conference paper, Published.
Osmoregulation in the halophilic bacterium halomonas elongata
Halophilic bacteria use a variety of osmoregulatory methods, such as the accumulation of one or more compatible solutes. The wide diversity of compounds that can act as compatible solute complicates the task of understanding the different strategies that halophilic bacteria use to cope with salt. This is specially challenging when attempting to go beyond the pathway that produces a certain compatible solute towards an understanding of how the metabolic network as a whole addresses the problem. Metabolic reconstruction based on genomic data together with Flux Balance Analysis (FBA) is a promising tool to gain insight into this problem. However, as more of these reconstructions become available, it becomes clear that processes predicted by genome annotation may not reflect the processes that are active in vivo. As a case in point, E. coli is unable to grow aerobically on citrate in spite of having all the necessary genes to do it. It has also been shown that the realization of this genetic potential into an actual capability to metabolize citrate is an extremely unlikely event under normal evolutionary conditions. Moreover, many marine bacteria seem to have the same pathways to metabolize glucose but each species uses a different one. In this work, a metabolic network inferred from genomic annotation of the halophilic bacterium Halomonas elongata and proteomic profiling experiments are used as a starting point to motivate targeted experiments in order to find out some of the defining features of the osmoregulatory strategies of this bacterium. This new information is then used to refine the network in order to describe the actual capabilities of H. elongata, rather than its genetic potential., Peer-reviewed article, Published. Received: September 20, 2016; Accepted: November 17, 2016; Published: January 12, 2017.
Pattern selection in plants
Background and Aims A study is made by computation of the interplay between the pattern formation of growth catalysts on a plant surface and the expansion of the surface to generate organismal shape. Consideration is made of the localization of morphogenetically active regions, and the occurrence within them of symmetry-breaking processes such as branching from an initially dome-shaped tip or meristem. Representation of a changing and growing three-dimensional shape is necessary, as two-dimensional work cannot distinguish, for example, formation of an annulus from dichotomous branching. Methods For the formation of patterns of chemical concentrations, the Brusselator reaction-diffusion model is used, applied on a hemispherical shell and generating patterns that initiate as surface spherical harmonics. The initial shape is hemispherical, represented as a mesh of triangles. These are combined into finite elements, each made up of all the triangles surrounding each node. Chemical pattern is converted into shape change by moving nodes outwards according to the concentration of growth catalyst at each, to relieve misfits caused by area increase of the finite element. New triangles are added to restore the refinement of the mesh in rapidly growing regions. Key Results The postulated mechanism successfully generates: tip growth (or stalk extension by an apical meristem) to ten times original hemisphere height; tip flattening and resumption of apical advance; and dichotomous branching and higher-order branching to make whorled structures. Control of the branching plane in successive dichotomous branchings is tackled with partial success and clarification of the issues. Conclusions The representation of a growing plant surface in computations by an expanding mesh that has no artefacts constraining changes of shape and symmetry has been achieved. It is shown that one type of pattern-forming mechanism, Turing-type reaction-diffusion, acting within a surface to pattern a growth catalyst, can generate some of the most important types of morphogenesis in plant development., Peer-reviewed article, Published. Received: 26 July 2007; Returned for revision: 5 October 2007; Accepted: 15 October 2007; Published electronically: 28 November 2007.
A performance comparison between FRC and WWM reinforced slabs on grade
Proceedings of 4th International Conference on Structural Health Monitoring of Intelligent Infrastructure (SHMII-4) 2009, 22-24 July 2009, Zurich, Switzerland. A comparative experimental study was conducted to investigate the effectiveness of fiber reinforcement as a non-corrosive alternative for welded-wire reinforcement in slabs on grade. Six full-scale slabs-on-grade, reinforced with various combinations of WWM (Welded Wire Mesh), polymeric macro-synthetic fibers (PMF) and cellulose fibers were tested under a centrally concentrated load. Their ductility and load carrying capacity were evaluated and compared. Based on the results of this study, it seems that high dosages of polymeric macrofibers can be used to successfully reinforce concrete slabs. Given that the use of PMF eliminates the possibility of corrosion of reinforcement, this may be a superior option. Furthermore, it seems low dosages of fibers act as an ineffective replacement for WWM. Low dosages of PMF and cellulose fiber when added on their own, or in combination with each other were found to be insufficient in providing sufficient ductility or load carrying capacity compared to the control slab when subjected to the load test. Slabs reinforced with cellulose fiber had a poor mechanical response in comparison to WWM and therefore cellulose fiber on its own is not recommended., Conference paper, Published.
Performance of sprayed fiber reinforced polymer strengthened timber beams
A study was carried out to investigate the use of Sprayed Fiber Reinforced Polymer (SFRP) for retrofit of timber beams. A total of 10-full scale specimens were tested. Two different timber preservatives and two different bonding agents were investigated. Strengthening was characterized using load deflection diagrams. Results indicate that it is possible to enhance load-carrying capacity and energy absorption characteristics using the technique of SFRP. Of the two types of preservatives investigated, the technique appears to be more effective for the case of creosote-treated specimens, where up to a 51% improvement in load-carrying capacity and a 460% increase in the energy absorption capacity were noted. Effectiveness of the bonding agent used was dependent on the type of preservative the specimen had been treated with., Peer-reviewed article, Published. Received 26 July 2010; Revised 8 October 2010; Accepted 12 October 2010.
Performance-risk analysis for the design of high-performance affordable homes
Proceedings of the 3rd Building Enclosure Science & Technology (BEST3) Conference, Atlanta, USA, April 2-4, 2014. Net-zero energy, emissions, and carbon sustainability targets for buildings are becoming achievable with the use of renewable energy technologies and high-performance construction, equipment, and appliances. Methodologies and tools have also been developed and tested to help design teams search for viable strategies for net-zero buildings during the early stages of design. However, the risks for underperformance of high-performance technologies, systems, and whole buildings are usually not assessed methodically. The negative consequences have been, often reluctantly, reported. This paper presents a methodology for explicitly considering and assessing underperformance risks during the design of high-performance buildings. The methodology is a first attempt to formalize extensive applied research and industry experiences in the quest for net-zero energy homes in the U.S., and build on existing tools and methods from performance-based design, as well as optimization, decision, and risk analysis. The methodology is knowledge driven and iterative in order to facilitate new knowledge acquired to be incorporated in the decision making. As a point of departure in the process, a clear definition of the project vision and a two-level organization of the corresponding building function performance objectives are laid out, with objectives further elaborated into high-performance targets and viable alternatives selected from the knowledge-base to meet these. Then, a knowledge guided search for optimized design strategies to meet the performance targets takes place, followed by a selection of optimized strategies to meet the objectives and the identification of associated risks from the knowledge-base. These risks are then evaluated, leading either to mitigation strategies or to changing targets and alternatives, and feeding back to the knowledge-base. A case study of affordable homes in hot humid climate is used to test the methodology and demonstrate its application. The case study clearly illustrates the advantages of using the methodology to minimize under performance risks. Further work will follow to develop the underpinning mathematical formalisms of the knowledge base and the risk evaluation procedure., Conference paper, Published.
Phase change material's (PCM) impacts on the energy performance and thermal comfort of buildings in a mild climate
The current residential buildings are of light weight construction. As such, they tend to frequent indoor air temperatures fluctuations and have been proven detrimental for thermal comfort and mechanical system energy consumption. This is reflected in the energy consumption statistics for residential buildings. More than 62% of the building energy use is towards maintaining comfortable indoor conditions. Phase change materials (PCM); a latent heat thermal storage material, have the potential to increase the thermal mass of these buildings without drastically affecting the current construction techniques. In this paper, the potential of phase change materials is investigated through numerical and experimental studies. The field experimental study is conducted using twin side-by-side buildings exposed to the same interior and exterior boundary conditions, and EnergyPlus, after being benchmarked with the experimental results, is used for the numerical study. The numerical study is carried out for an existing residential apartment unit with particular emphasis on the effects of different design parameters such as orientation and window to wall ratio. Preliminary analyses of experimental data show that phase change materials are effective in stabilizing the indoor air by reversing the heat flow direction. In fact, the indoor air and wall temperature fluctuations are reduced by 1.4 °C and 2.7 °C respectively. Following, benchmarking of the numerical simulation shows confidence levels in predicting the interior conditions since discrepancies between experimental data and numerical data are within tolerance limits of the measuring device. Further, from the analysis of the numerical data, phase change material is effective in moderating the operative temperature but does not translate to significant thermal comfort improvement when evaluated over a night time occupancy regime in the summer. On the contrary, PCM is effective in lowering the heating energy demand by up to 57% during the winter condition., Peer reviewed article, Published. Received 1 October 2015, Revised 22 January 2016, Accepted 23 January 2016, Available online 29 January 2016.
A pilot scale comparison of the effects of chemical pre-treatments of wood chips on the properties of low consistency refined TMP
Proceedings of the International Mechanical Pulping Conference 2016, IMPC 2016. After decades of research and development, the technology of thermomechanical pulping (TMP) has dramatically improved resulting in higher pulp quality, especially strength. However, the TMP industry is still faced with the challenge of continually increasing energy costs. One approach to reducing the energy costs is to replace the second-stage high consistency (HC) refiner with several low consistency (LC) refiners. This is based on the observation that low consistency refining is more energy efficient than high consistency refining. The limitation of LC refining is loss of paper strength due to the high frequency of fibre cutting especially at high refining intensity. Chemical treatment combined with low consistency refining provides opportunity for even further energy savings. The chemical treatment could improve pulp properties allowing for further energy reduction in the HC refining stage or reduced intensity during LC refining resulting in less fibre cutting. Indeed, it is also possible that the chemical treatment itself will improve the resistance of the fibre to the cutting during LC refining., Conference paper, Published.
Planning for climate action in British Columbia, Canada
Significant greenhouse gas (GHG) reductions from all sectors of human enterprise are necessary to avoid further effects and reduce the current effects of climate change. Agriculture and the global food system are estimated to contribute to one-third of all anthropogenic GHGs. In British Columbia, Canada, mandated GHG reduction targets and voluntary climate action programs are challenging local governments to include emission reduction targets, policies, and actions within official planning documents. At this early stage of GHG reductions, local government attention does not yet include agriculture but is directed toward the transportation, buildings, and waste management sectors. Given agriculture's contribution to GHG emissions and local government's engagement with GHG mitigation and food system planning, it seems reasonable to anticipate that over time, local governments should and will engage increasingly in reducing GHGs from agriculture. With the goal of advancing agriculture GHG mitigation by local governments, this paper reviews the jurisdictional powers governing agriculture and climate change within British Columbia. It examines how local governments can support mitigation within the sector through their roles in planning, policy, programming, and public engagement, and identifies potential research agenda items., Peer-reviewed article, Published. Submitted 18 April 2011 ; Revised 4 July 2011 and 1 August 2011 ; Accepted 2 September 2011 ; Published online 20 March 2012.
Precision of non-invasive temperature measurement by diffuse reflectance spectroscopy
Diffuse reflectance spectroscopy can be used as a noninvasive probe for measurement of temperature in real time. We have measured the precision of this technique to determine the temperature of Si and GaAs substrates during semiconductor processing. Our results show that the standard deviation of the noninvasive optical technique is less than 1.5 °C for GaAs and less than 2.0 °C for Si over the temperature range 25 °C≪T≪600 °C. This standard deviation compares favorably to that for a type‐K thermocouple used in the same measurements: s.d.≪1.5 °C. These results support the notion that noninvasive optical temperature measurement can be used in semiconductor processing with a precision approaching that of a thermocouple., Peer-reviewed article, Published.
Predicting academic performance
Proceedings of the 23rd Annual ACM Conference on Innovation and Technology in Computer Science Education. The ability to predict student performance in a course or program creates opportunities to improve educational outcomes. With effective performance prediction approaches, instructors can allocate resources and instruction more accurately. Research in this area seeks to identify features that can be used to make predictions, to identify algorithms that can improve predictions, and to quantify aspects of student performance. Moreover, research in predicting student performance seeks to determine interrelated features and to identify the underlying reasons why certain features work better than others. This working group report presents a systematic literature review of work in the area of predicting student performance. Our analysis shows a clearly increasing amount of research in this area, as well as an increasing variety of techniques used. At the same time, the review uncovered a number of issues with research quality that drives a need for the community to provide more detailed reporting of methods and results and to increase efforts to validate and replicate work., Peer reviewed, Conference paper, Published.

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