112 research outputs found
Cellular decision making at the nanoscale
No full textThe well-established dependence of cell traction forces on the compliance of supporting matrices has been attributed to levels of force exerted on components in focal contacts. Here, use of novel, force-limited nanoscale tension gauges revealed that both force and substrate deformations govern cell decision-making during initial attachment to compliant substrates. We propose a mechanical model consistent with observed behavior. Upon formation of stable cell contacts, bond tension and tether rupture govern cell attachment, spreading, and focal adhesion maturation at force levels on individual receptors predicted by prior studies.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2019-08-01The student, Zainab Rahil, accepted the attached license on 2016-04-27 at 06:49.The student, Zainab Rahil, submitted this Thesis for approval on 2016-04-27 at 06:55.This Thesis was approved for publication on 2016-04-29 at 14:30.DSpace SAF Submission Ingestion Package generated from Vireo submission #9538 on 2017-09-29 at 11:12:58Made available in DSpace on 2017-09-29T17:52:42Z (GMT). No. of bitstreams: 2
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Previous issue date: 2016-04-29Embargo set by: Colleen Fallaw for item 103531
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Cells and force transduction
No full textThis thesis studies mechanism involved in propagating force generated at cadherin complexes. The first part of this thesis demonstrates that mechanotransduction at classical cadherin complexes is not only ligand-dependent but also dependent on the respective receptor tyrosine kinase (RTK) binding partner of cadherin. This involvement of RTKs at cadherin complexes is important in propagating force transduction globally, implying that force transduction at cadherin complexes is not restricted to cell-cell junctions but is also propagated globally via the mediation of its respective RTK binding partner. These results suggest that homophilic ligation in trans- and cadherin association with cognate receptor tyrosine kinase in cis comprises a combinatorial, mechano-chemical switch. That is, specific combinations of cadherin, ligand, and RTK is required for force-activated RTK-dependent signaling, activation of cell contractility, and cytoskeletal remodeling at perturbed cadherin adhesions. These findings confirm that cadherins form both homophilic and heterophilic bonds, but homophilic cadherin ligation selectively triggers cadherin-associated RTK signals that mechanically reinforce homophilic, but not heterophilic cadherin adhesions, thereby stabilizing homophilic adhesions and amplifying binding differences. This study demonstrates that this mechano-chemical switch is not governed by cadherin adhesion differences, but requires a specific combination of cadherin ligand in trans- and RTK expression in cis to actuate force transduction signaling on rigid surfaces to propagate force transduction at a global level.
For the second part of this study used novel, force-limited nanoscale tension gauges to investigate how force and substrate stiffness guide cellular decision-making during initial cell attachment and spreading on deformable substrates. The well-established dependence of cell traction and spreading on substrate stiffness has been attributed to levels of force exerted on molecular components in focal contacts. The molecular tension gauges used in this study enabled direct estimates of the threshold, pico Newton forces that instructed decision-making at different stages of cell attachment, spreading, and adhesion maturation. These results further confirm that the force thresholds controlling adhesion and spreading transitions depend on substrate stiffness. Reported findings agree semi-quantitatively with a proposed model that attributes rigidity-dependent differences in cell spreading to stiffness-dependent rates of competing biochemical processesSubmission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2020-12-01The student, Zainab Rahil, accepted the attached license on 2018-11-08 at 12:34.The student, Zainab Rahil, submitted this Dissertation for approval on 2018-11-08 at 12:48.This Dissertation was approved for publication on 2018-11-13 at 10:27.DSpace SAF Submission Ingestion Package generated from Vireo submission #13072 on 2019-02-08 at 11:38:31Made available in DSpace on 2019-02-08T18:39:44Z (GMT). No. of bitstreams: 2
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Previous issue date: 2018-11-13Embargo set by: Seth Robbins for item 109931
Lift date: 2021-02-08T18:40:00Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 109931
Lift date: 2021-02-08T18:42:23Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 109931
Lift date: 2021-02-08T18:43:54Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 109931
Lift date: 2021-02-08T18:44:50Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 109931 on 2021-02-09T10:15:38Z
The synthesis and alkaline hydrolysis of alkyl dialkylthionphosphinates - by Jubrail F. Rahil
No full textThesis (M.S.)--Dept. of Chemistry, A.U.B.Includes bibliographical references
Mechanism and performance evaluation of spent-coffee grounds-derived nanocomposite materials for highly efficient photocatalytic degradation of organic pollutant
No full textThe study demonstrates a facile and environmentally friendly method for synthesizing crystalline TiO2 nanoparticles on the surface of hydrochar generated from readily available biomass waste, i.e., spent coffee grounds (SCGs), using a simple sol–gel process. The hydrochar served as a support for TiO2, reducing the rate at which electrons and holes recombine during photocatalysis, thereby facilitating the effective binding of TiO2, enhancing its adsorption capacity, and the convenient separation of the photocatalyst after usage. The materials were tested in the photocatalytic degradation of an organic pollutant, methylene blue (MB) dye. TiO2-hydrochar obtained at 210 ⁰C has the best performance, giving a degradation efficiency of 98.5 % and a mineralization efficiency of 87.1 % in 90 min at neutral pH. Radical trapping experiments showed
being the dominant species, followed by
. Besides, it showed superior stability with an activity loss of ∼ 9.2 % after five runs. The superior performance of the HCT210 was ascribed to the enhanced interfacial charge transfer kinetics between the TiO2 and hydrochar through
bond formation, better light absorption, and the high surface area of the materials. Performance metrics show that synthesized nanocomposites are promising photocatalysts, providing a biomass-assisted method for robust photocatalytic wastewater treatment.Killam TrustsNatural Science and Engineering Research Council (NSERC
House of Music : Festivity from city to seat
No full textHouse of Music : Festivity from city to seat.Concert HallArchitecture, Urbanism and Building Sciences | Interiors Buildings Citie
Assessment of Various Natural Pozzolans, Recycled Glass Powder, and Reclaimed Fly Ash as Supplementary Cementitious Materials for Concrete Mixtures
No full textThe increasing demand for reducing the CO2 emissions associated with Portland cement production in the concrete industry has increased the need for the use of supplementary cementitious materials (SCMs) to partially replace the Portland cement. Such a demand, in addition to the decline in the availability of Class F fly ash, necessitates exploring alternative SCMs. This study aimed to fill this gap by assessing the performance of different natural pozzolans and industrial wastes/by-products as SCMs for concrete mixtures. The SCMs included a medium- and a high-grade metakaolin (MMK and HMK), diatomaceous earth (DE), pumice, wollastonite, recycled glass powder (RGP), and reclaimed fly ash (RFA), all sourced from North America. The research first explored the effect of these SCMs in cement paste and mortar, when used at 20% by weight of cement, with DE at 10%. The rheology and heat of reaction were measured in cement paste, and the flow table and compressive strength were assessed in mortar. Reactivity of these SCMs was also tested according to RILEM TC 267-TRM. The SCMs that met the threshold for the 7-day heat release and bound water content were then used in concrete at the same content as that used in cement paste and mortar. The concretes were tested for fresh properties, compressive strength, and durability parameters, including depth of water penetration, water sorptivity, chloride penetrability, and bulk and surface electrical resistivity. The results showed that the selected natural pozzolans (MMK, HMK, and DE) had similar or improved compressive strengths over the reference concrete with no SCMs at all testing ages (3 to 91 days), however, they reduced the workability of the concrete. Concretes with these natural pozzolans also had the highest resistance to water and chloride penetration out of all the concretes tested, indicating improved durability. Concretes with RFA and RGP had reduced early-age strength, however, achieved comparable late-age strengths to the reference concrete and the concrete containing Class F fly ash, with improved or similar workability to the reference concrete. The concrete with RGP did not perform as well as the concretes with the natural pozzolans, however, it provided enhanced strength and durability compared to the concretes with RFA and Class F fly ash. The findings from this research contribute to a deeper understanding of the effectiveness of these SCMs across various applications in the concrete industry
Towards High-Strength and Low-Carbon Concrete Masonry Blocks Using Locally Available Materials
No full textHigh-strength concrete masonry blocks are attracting attention to be used for loadbearing applications, such as tall walls. Such blocks can be achieved via modification of the dry mixture design and production methods. These modifications, however, may increase the carbon footprint of the concrete masonry blocks upon manufacturing. Careful selection of the mixture parameters is, therefore, necessary for the production of concrete blocks that have higher compressive strengths yet low carbon footprints. This study explored the effectiveness of using locally available materials for the production of dry concrete mixtures that can be used for the masonry block manufacturing. First, the suitability of utilizing pumice, sourced in British Columbia, as an alternative for Class F fly ash to partially replace the Portland cement in the concrete mixtures was studied. That was important as the availability of Class F fly ash is declining in Alberta and finding alternative replacements is imperative. To overcome the lower reactivity and strength development of pumice, a performance enhancing chemical admixture was used. Finally, recycled aggregates were obtained by crushing and pulverizing concrete masonry blocks that were used for structural testing in the laboratory. The so-produced aggregates were used as a replacement for the natural aggregates in the production of the dry concrete mixtures without and with pumice and chemical admixture. The resulting dry concrete mixtures were categorized into different classes of 30, 35, 40, and 50 MPa based on their average compressive strength at the age of 28 days in the laboratory conditions. Their mixture proportion with respect to their cement intensity (cement content per unit of strength) and application was discussed, and recommendations for future research were made. It is worth noting that although the results of this study were obtained for producing dry concrete mixtures, they can be extended for other concrete applications
Self-assembled 3D hierarchical Mo2S3 flowers from wrinkled sheets for enhanced electrochemical energy storage performanc
No full textIn this study, wrinkled sheets of molybdenum sulfide Mo2S3 were self-assembled into 3D hierarchical flowers via a simple hydrothermal technique. Additionally, binary (Mo2S3/CNTs) and ternary (Mo2S3/CNTs/gCN) composites were synthesized through ultrasonication route. Synergistic effect of 3D Mo2S3 flowers with 1D CNTs and gCN strengthen and heighten electrochemical properties of Mo2S3/CNTs/gCN composite. The GCD graph of Mo2S3/CNTs/gCN composite endorsed greatest specific capacitance 1309 F/g at 1 A/g with highest discharge time period
(1414 s). Though, the discharge time for Mo2S3/CNTs and Mo2S3 was 495 s and 330 s with specific capacitance 458 F/g and 306 F/g respectively. The significantly improved electrochemical properties of Mo2S3/CNTs/gCN composite professed via CV curves and GCD data are authorized to the outstanding architecture of the material. TheMo2S3/CNTs/gCN composite also shows greater ion diffusion and outstanding capacitive behavior. In composite electrode, Mo2S3 flowers with CNTs and gCN organize a unique architecture which improves the ionic movement in all the three directions due to 3D hierarchical structure. In conclusion, the advanced proficiency of our as-designed working electrode (Mo2S3/CNTs/gCN composite) is a promising choice for energy storage systems.This is a manuscript of an article published as Katubi, Khadijah MohammedSaleh, Nusrat Shaheen, Eric W. Cochran, Tahani Rahil Aldhafeeri, Z. A. Alrowaili, M. S. Al-Buriahi, Muhammad Farooq Warsi, and Sonia Zulfiqar. "Self-Assembled 3D Hierarchical Mo2S3 Flowers from Wrinkled Sheets for Enhanced Electrochemical Energy Storage Performance." Journal of the Indian Chemical Society (2025): 101645. doi: https://doi.org/10.1016/j.jics.2025.101645
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