Plants are integral to our lives, providing food, shelter and the air we breathe. The shapes that plants take are central to their functionality, tailoring each for its particular place in the ecosystem. Given the relatively large and static forms of plants, it may not be immediately apparent that chemical kinetics is involved in, for example, distinguishing the form of a spruce tree from that of a fern. But plants share the common feature that their shapes are continuously being generated, and this largely occurs in localized regions of cell division and expansion, such as the shoot and root apical meristems at either end of a plant’s main axis; these regions remain essentially embryonic throughout the life cycle. The final regular structure of a plant, such as the arrangement of leaves along the main stalk, may seem to follow an overall spatial template; but in reality the spatial patterning is occurring at relatively short range, and it is the temporal unfolding of this small scale patterning which generates the plant’s form. A key part of understanding plant morphogenesis, or shape generation, therefore, is to understand how the molecular determinants of cell type, cell division and cell expansion are localized to and patterned within the actively growing regions. At this scale, transport processes such as diffusion and convection are obvious components of localization, for moving molecules to the correct places; but the reaction kinetics for molecular creation, destruction and interaction are also critical to maintaining the molecular identity and the size regulation of the active regions., Book chapter, Published. Submission date: 04. October, 2011; Review date: 13. November, 2011; Published online: 29. February, 2012.
There is a nearly unanimous consensus among scientists that increasing greenhouse gas emissions, primarily carbon dioxide generated by human activity, are effecting the Earth's climate. For many key parameters, the climate system is already moving beyond the patterns of natural variability within which our societies and economies have developed and thrived. These parameters include global mean surface temperature, sea-level, ocean and ice sheet dynamics, and extreme climatic events. There is a significant risk that many of the trends will accelerate, leading to an increasing risk of abrupt or irreversible climatic shifts. One overlooked area of research is the impact of climate change on concrete infrastructure. Concrete structures form an essential part of the world. Climate change could potentially affect the durability of concrete infrastructure. In this paper, the findings of a study at the University of British Columbia which demonstrate a long-term risk to the durability of steel-reinforced concrete structures in some parts of the world via accelerated carbonation-induced corrosion are presented. Research demonstrates that service lifespans of structures will be affected in the long term, with the need for earlier repairs unless the adverse effects of climate change are taken into account at the time of design., Peer-reviewed article, Published.
Direct brain interface (BI) systems provide an alternative communication and control solution for individuals with severe motor disabilities, bypassing impaired interface pathways. Most BI systems are aimed to be operated by individuals with severe disabilities. With these individuals, there is no observable indicator of their intent to control or communicate with the BI system. In contrast, able-bodied subjects can perform the desired physical movements such as finger flexion and one can observe the movement as the indicator of intent. Since no external knowledge of intention is available for individuals with severe motor disabilities, generating the data for system training is problematic. This paper introduces three methods for generating training-data for self-paced BI systems and compares their performances with four alternative methods of training-data generation. Results of the offline analysis on the electroencephalogram data of eight subjects during self-paced BI experiments show that two of the proposed methods increase true positive rates (at fixed false positive rate of 2%) over that of the four alternative methods from 50.8%-58.4% to about 62% which corresponds to 3.6%-11.2% improvement., Peer-reviewed article, Published. Manuscript received June 26, 2006; Revised October 27, 2006; Accepted December 6, 2006.
As part of a program to reduce electrical energy consumption in the refining process, the effects of the ozone and alkaline peroxide treatments on fibre and handsheet properties, prior and subsequent to low consistency (LC) refining, were assessed and compared by applying different levels of ozone and a range of peroxide and alkali charges to a primary stage hemlock thermomechanical pulp (TMP). Both highly alkaline peroxide treatments and ozone treatments decreased the specific energy required for strong mechanical pulp. The improvement in pulp strength through alkaline peroxide treatment mainly resulted from pulp surface changes caused by generation of acid groups. The highly alkaline peroxide treatments significantly increased pulp brightness but did not promote the further fibrillation during the subsequent LC refining. On the other hand, ozone treatments provided tensile strength increases, along with small brightness enhancements for the dark hemlock TMP, and increased the tensile gains obtained through LC refining. The effects of ozone treatments on tensile strength before and after LC refining were the result of pulp surface modifications, fibre swelling, and loss of fibre wall integrity due to non-selective chemical attack. High levels of ozone treatment caused tear strength to decrease during subsequent LC refining., Peer-reviewed article, Published.
There is a long history of use and modern commercial importance of large and small cranberries in North America. The central objective of the current research was to characterize and compare the chemical composition of 2 west coast small cranberry species traditionally used (Vaccinium oxycoccos L. and Vaccinium vitis-idaea L.) with the commercially cultivated large cranberry (Vaccinium macrocarpon Ait.) indigenous to the east coast of North America. V. oxycoccos and V. macrocarpon contained the 5 major anthocyanins known in cranberry; however, the ratio of glycosylated peonidins to cyanidins varied, and V. vitis-idaea did not contain measurable amounts of glycosylated peonidins. Extracts of all three berries were found to contain serotonin, melatonin, and ascorbic acid. Antioxidant activity was not found to correlate with indolamine levels while anthocyanin content showed a negative correlation, and vitamin C content positively correlated. From the metabolomics profiles, 4624 compounds were found conserved across V. macrocarpon, V. oxycoccos, and V. vitis-idaea with a total of approximately 8000–10 000 phytochemicals detected in each species. From significance analysis, it was found that 2 compounds in V. macrocarpon, 3 in V. oxycoccos, and 5 in V. vitis-idaea were key to the characterization and differentiation of these cranberry metabolomes. Through multivariate modeling, differentiation of the species was observed, and univariate statistical analysis was employed to provide a quality assessment of the models developed for the metabolomics data., Peer-reviewed article, Published.
The overall U-factor values for an attic assembly are usually computed with the ANSI/ASHRAE/IES based R-value (thermal resistance) conversion. In the ANSI/ASHRAE/IES Standard 90.1 (2010), the effects of attic air resistance, roof pitch and attic width are not taken into account while calculating the U-Factor values. In addition, the R-value is estimated using a one dimensional thermal resistance model. In ventilated attics, where the insulation near the roof sheathing is tapered, it is difficult to find the correct R-value of the attic system as the heat transfer becomes two dimensional. In this paper, a 2-dimensional CFD model is developed for various insulation R-values and insulation taper angles near roof decks. COMSOL Multiphysics 4.4 is used to model and analyse the attic structure. Results show that a discrepancy in overall U-factor for entire attic assembly between the developed model and the existing standard estimation. These results are pronounced for lower slope roofs with high insulation thickness., Peer-reviewed article, Published. Available online 30 December 2015.
This paper reports modelling of heart localization in the axolotl (Ambystoma mexicanum). The region of heart specification in the mesoderm defined by classical induction from the endoderm is larger than the area of final myocardial differentiation. For localizing the area of differentiation within the area of specification, we postulate a mesoderm in response to induction from the endoderm. This mechanism generates a spatial pattern for two chemicals, an activator and an inhibitor, corresponding to the area of myocardial differentiation. We postulate a diffusible chemical rescuer, which is absent in the cardiac lethal mutant, and which is a precursor to the reaction-diffusion mechanism. The activator, inhibitor, rescuer, and product of endodermal induction are presented in an enzyme mechanism with rate equations similar to the Gierer-Meinhardt equations. These equations were solved numerically in both one and two spatial dimensions. We have attained quantitative agreement with the experimental data for sizes of tissue regions and for times to heartbeat. Experiments modelled include wild-type heart localization as well as both in vitro and in vivo rescue of cardiac lethal mesoderm with wild-type mesoderm. Based upon the parameters necessary to model heart localization, we make a series of predictions. We predict: a specific profile for the endodermal inducer gradient; the possibility of producing multiple hearts in vivo; and a greater contribution to the heart from the wild-type mesoderm for in vivo transplants with cardiac lethal mesoderm. We make some suggestions as to the possible chemical nature of the substances in the model. We indicate that the inhibitory field and mechanochemical theories are probably not as promising as reaction-diffusion for the mechanism of heart localization., Peer-reviewed article, Published. Received January 24, 1994; accepted April 7, 1994.
Computer support for conceptual design of building structures is still ineffective, mainly because existing structural engineering applications fail to recognize that structural design and architectural design are highly interdependent processes. This paper describes a computer representation called StAr (structure-architecture), aimed to act as a common basis for collaboration between architects and engineers during conceptual structural design. The StAr representation describes the structural system as a hierarchy of entities with architectural counterparts, which enables the direct integration of the structural system to the building architecture as well as engineering feedbacks to the architect at various abstraction levels. The hierarchical structural description implements a top-down design approach where high-level structural entities, which are defined first, facilitate the configuration of lower-level entities whose functions in turn contribute to those of the higher-level wholes that they belong to. The representation has been built on top of a geometric modeling kernel that allows reasoning based on the geometry and topology of the design model, which is paramount during early design stages. A proof-of-concept software prototype, called StAr prototype, has been developed and a test example demonstrates how the representation can support the different activities that take place during the conceptual design of building structures., Peer reviewed, Technical paper, Received: September 16, 2004 ; Accepted: October 27, 2004 ; Published online: March 01, 2006, StAr, Conceptual design
In northern coastal climates, surface condensation often occurs in fenestration systems during winter. The most common contributors of this phenomenon are air leakage, thermal bridging, local convection and radiation. (i.e. boundary conditions). Researchers and industry experts typically focus on improving designs of fenestration and developing different strategies to deal with air leakage and thermal bridging. However, the effects of local convection and radiation on window condensation are often overlooked. This project focuses on investigating the ways different heating systems internet with window-wall systems via convection and radiation heat exchanges, and their effects on surface condensation. The three most common heating systems for multi-unit residential building (MURB) arc considered: electric baseboard, hydronic radiant floor and forced air system. Each heating system provides vastly different indoor conditions due to differences in thermal stratification, room air distribution and location of heat sources. These differences have direct impacts on window performance and potentially increase risk of condensation. In this project, the following questions are investigated: How significant is impact of room air flow on condensation risk in window-wall systems? Are empirical film coefficients sufficient for predicting condensation risk of window-wall units' What are the differences between each of the heating systems on condensation risk? This project designed a methodology in an attempt to better understand and predict these physical phenomena and will hopefully guide further efforts to better characterize the effect of different heating systems in window condensation risk analysis., Peer reviewed, Peer reviewed article, Published.
Curcuma longa L. rhizomes are used extensively as a spice in food preparations and dietary supplements for their anti-inflammatory and antioxidant properties. An expert review panel (ERP) evaluated analytical methods for the quantitation of individual curcuminoids for the purpose of identifying a method for official method status. It was requested that several modifications be undertaken to improve method performance prior to subjecting the chosen method to a single-laboratory validation. Two separate Plackett-Burman factorial studies were used to identify factors that contributed to the chromatographic separation and extraction of curcuminoids. Significant factors were further optimized to produce the improved HPLC method for curcuminoid separation. This method was then subjected to a single-laboratory validation according to the AOAC International guidelines for linearity, detection limits, precision, and accuracy. The two most significant factors impacting the quantitation of curcuminoids were column temperature and extraction solvent, which were optimized to 55 °C and 100 % methanol, respectively. The validation was performed on 12 raw materials and finished products containing turmeric roots. The method precision was reported using HorRat values which were within recommended ranges of the AOAC guidelines. Overall accuracy of the method was accessed at three separate levels for each analyte and ranged from 99.3–100.9 %. The validated method is suitable for quantitation of individual curcuminoids in turmeric raw materials and finished products and is recommended for consideration as an official method by the AOAC International., Peer-reviewed article, Published. Received 13 July 2015; Accepted 21 September 2015; Published online 29 September 2015.
The demand for validated analytical methods for botanicals has grown in response to the increasing consumer market for botanical supplements. Government initiatives to increase the availability of validated analytical methods and botanical reference material have led to the publication of numerous validation studies in scientific journals. Single laboratory validation and collaborative validation studies are structured to confirm a method's ruggedness and fit for purpose. The performance characteristics and statistical protocols followed throughout a validation study vary with the source of guidelines. Analytical techniques and priority methods are influenced by the need for fast-screening techniques, the limited availability of reference material, market value, and the prevalence of contaminants in botanical supplements., Peer-reviewed article, Published.
The Neil Squire Foundation (NSF) is a Canadian nonprofit organization whose purpose is to create opportunities for independence for individuals who have significant physical disabilities. Over the last ten years, our team in partnership with researchers at the Electrical and Computer Engineering Department, the University of British Columbia, has been working to develop a direct brain-controlled switch for individuals with significant physical disabilities. The NSF Brain Interface Project primarily focuses on the development of brain-computer interface switch technologies for intermittent (or asynchronous) control in natural environments. That is, technologies that will work when the user intends control but also remains in a stable off state when there is no intent to control. A prototype of such a switch has successfully been developed. This switch has demonstrated classification accuracies greater than 94%. The initial results are promising, but further research is required to improve switch accuracies and reliability and to test these switch technologies over a larger population of users and operating conditions. This paper provides an overview of the NSF brain-switch technologies and details our approach to future work in this area., Peer-reviewed article, Published. Manuscript received June 20, 2002; revised January 22, 2003.