33 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
Dispatchable Operation of Multiple Electrolysers for Demand Side Response and the Production of Hydrogen Fuel-Libyan Case Study
No full textConcerns over both environmental issues and about the depletion of fossil fuels have acted as twin driving forces to the development of renewable energy and its integration into existing electricity grids. The variable nature of RE generators assessment affects the ability to balance supply and demand across electricity networks; however, the use of energy storage and demand-side response techniques is expected to help relieve this situation. One possibility in this regard might be the use of water electrolysis to produce hydrogen while producing industrial-scale DSR services. This would be facilitated by the use of tariff structures that incentive the operation of electrolysers as dispatchable loads. This research has been carried out to answer the following question: What is the feasibility of using electrolysers to provide industrial-scale of Demand-side Response for grid balancing while producing hydrogen at a competitive price? The hydrogen thus produced can then be used, and indeed sold, as a clean automotive fuel. To these ends, two common types of electrolyser, alkaline and PEM, are examined in considerable detail. In particular, two cost scenarios for system components are considered, namely those for 2015 and 2030. The coastal city of Darnah in Libya was chosen as the basis
for this case study, where renewable energy can be produced via wind turbines and photovoltaics (PVs), and where there are currently six petrol stations serving the city that can be converted to hydrogen refuelling stations (HRSs). In 2015 all scenarios for both PEM and alkaline electrolysers were considered and were found to be able to partly meet the project aims but with high cost of hydrogen due to the high cost of system capital costs, low price of social carbon cost and less government support. However, by 2030 the price of hydrogen price will make it a good option as energy storage and clean fuel for many reasons such as the expected drop in capital cost, improvement in the efficiency of the equipment, and the expectation of high price of social carbon cost. Penetration of hydrogen into the energy sector requires strong governmental support by either establishing or modifying policies and energy laws to increasingly support renewable energy usage. Government support could effectively bring forward the date at which hydrogen becomes techno-economically viable (i.e. sooner than 2030).Ministry of Education- Liby
Dispatchable Hydrogen Production at the Forecourt for Electricity Demand Shaping
No full textEnvironmental issues and concerns about depletion of fossil fuels have driven rapid growth in the generation of renewable energy (RE) and its use in electricity grids. Similarly, the need for an alternative to hydrocarbon fuels means that the number of fuel cell vehicles is also expected to increase. The ability of electricity networks to balance supply and demand is greatly affected by the variable, intermittent output of RE generators; however, this could be relieved using energy storage and demand-side response (DSR) techniques. One option would be production of hydrogen by electrolysis powered from wind and solar sources. The use of tariff structures would provide an incentive to operate electrolysers as dispatchable loads. The aim of this paper is to compare the cost of hydrogen production by electrolysis at garage forecourts in Libya, for both dispatchable and continuous operation, without interruption of fuel supply to vehicles. The coastal city of Derna was chosen as a case study, with the renewable energy being produced via a wind turbine farm. Wind speed was analysed in order to determine a suitable turbine, then the capacity was calculated to estimate how many turbines would be needed to meet demand. Finally, the excess power was calculated, based on the discrepancy between supply and demand. The study looked at a hydrogen refueling station in both dispatchable and continuous operation, using an optimisation algorithm. The following three scenarios were considered to determine whether the cost of electrolytic hydrogen could be reduced by a lower off-peak electricity price. These scenarios are: Standard Continuous, in which the electrolyser operates continuously on a standard tariff of 12 p/kWh; Off-peak Only, in which the electrolyser operates only during off-peak periods at the lower price of 5 p/kWh; and 2-Tier Continuous, in which the electrolyser operates continuously on a low tariff at off-peak times and a high tariff at other times. The results indicate that Scenario 2 produced the cheapest electricity at £2.90 per kg of hydrogen, followed by Scenario 3 at £3.80 per kg, and the most expensive was Scenario 1 at £6.90 per kg.</jats:p
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
Dispatchable hydrogen production by multiple electrolysers to provide clean fuel and responsive demand in Libya
No full textThe Publisher's final version can be found by following the DOI link.The use of hydrogen as a fuel carries major environmental advantages because there are a number of ways of producing it by low-carbon methods. When electrolysis is used, additional benefits are obtained by flexible operation that offers the opportunity to reduce the cost of hydrogen production by absorbing electricity during off-peak hours, and stopping operation during peak hours. This can also act as a tool in support of balancing electrical systems. In this research, off-peak electricity is used to produce hydrogen via electrolysis, which is sold as a fuel at six garage forecourts in Darna, a small city on
the east coast of Libya. In addition to the six forecourt electrolysers, a centralised electrolyser plant will be included in the system to consume the surplus energy and to satisfy any deficiency in hydrogen production at the forecourt. The capital cost of both forecourt and centralised electrolyser systems, plus fixed costs, were financed by bank loans at a 5% rate of interest over seven years. A MATLAB model with optimisation tools was used to formulate this problem. This research shows that forecourt hydrogen production at off-peak times (and without the centralised electrolyser) can satisfy nearly 53.93% of the fuel demand. This represents 59.82% of the total surplus renewable
energy. The average hydrogen sale price at the forecourts is between £10.82-11.71/kg. After adding the centralised electrolyser, nearly 78.83 % of the total surplus power was
absorbed and the average hydrogen selling prices were between £15.04-19.80/kg The centralised electrolyser can meet 43%, 49%, 50%, 42%, 57% and 53% of the deficit in consumption for stations 1, 2, 3, 4, 5 and 6, respectively
Flexible operation of electrolyser at the garage forecourt to support grid balancing and exploitation of hydrogen as a clean fuel
No full textThe file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Rapid growth in the generation of renewable energy (RE) and its integration with electricity grids has been driven by concerns about both the climate impacts and the depletion of fossil fuels. Moreover, these concerns have prompted the need to develop alternatives to hydrocarbon fuels, leading to the expectation that fuel cell vehicle numbers will similarly increase. However, the variable and intermittent output of RE generators significantly affects the capability for electricity networks to balance supply and demand, although this may be addressed through energy storage and demand-side response (DSR) technologies. One potential DSR technique that can be implemented at industrial scale is water electrolysis, which is used for hydrogen production. When electrolyser operation is modulated, for example, to respond to the variable output of wind and solar power sources, it can be exploited as a dispatchable demand load. Naturally, this would need to be incentivized by electricity tariff structures that reflect the dynamics of RE availability. This paper aims to compare the economics of continuous and dispatchable electrolyser operation for producing affordable hydrogen at garage forecourts in Libya, while ensuring no interruption in the fuel supply to vehicles. Using the coastal city of Derna as a case study, with renewable energy generated by a wind farm, a suitable turbine specification and the number of turbines needed to meet demand was determined through an analysis of wind speeds. The constantly varying difference between RE power supply and electricity demand on the grinded the surplus power at any given time. Using a linear programming algorithm to optimize the hydrogen cost, based on the current price of electricity, this study examines a hydrogen refuelling station in both dispatchable and continuous operation. As the capital cost is already known, the optimisation focuses on the variable cost in order to reduce the price of hydrogen, which means using the cheaper of two electricity tariffs. Three scenarios were considered to evaluate whether the cost of electrolytic hydrogen could be reduced through using lower-cost off-peak electricity supplies:
1- Standard Continuous, in which the electrolyser operates continuously on a standard tariff of 7/kWh.
3- 2-Tier Continuous, in which the electrolyser operates continuously on a low tariff at off-peak times and a high tariff at other times.
The results indicate that Scenario 2 produced the cheapest electricity at 5.10 per kg, and the most expensive was Scenario 1 at $9.26 per kg
Techno-economic assessment of dispatchable hydrogen production by multiple electrolysers in Libya
No full textThe file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI linkWith the worldwide growth of renewable energy generation, the value of hydrogen production by electrolysis as a demand management tool for electricity networks is likely to increase. Electrolytic hydrogen can be sold as a fuel, chemical feedstock or injected into pipelines to lower the carbon content of natural gas. The main obstacle to hydrogen’s use as a fuel or energy storage method is the price. The highest costs are in the capital expenditure and the consumption of feedstock (electricity and water). In this paper, three major techno-economic aspects of the system are investigated, including technical analyses of both the energy absorbed by the process in the provision of electricity demand management services and in its meeting of fuel demand, plus an economic assessment of the hydrogen price at the at the point of sale. Thus, the study investigates how only off-peak electricity is used to produce hydrogen via onsite electrolysis at a number of garage forecourts. In a simulated case study, six garage forecourts are assumed to be sited in Darnah, a small city on the east coast of Libya. An electricity pricing mechanism is devised to allow the energy producer (utility company) and energy consumer (garage forecourt operator) to make a profit. Short term (2015) and long term (2030) cost scenarios are applied. Matlab software was used to simulate this process. Without any government support or changes in regulation and policy, hydrogen prices were £10.00/kg, £9.80/kg, £9.60/kg, £10.00/kg, £9.40/kg and £10.30/kg for forecourts 1–6 respectively under the 2015 cost scenario. The electricity price represents around 17% of the total hydrogen cost, whereas, due to the investment cost reduction in 2030, the average prices of hydrogen dropped to £6.50/kg, £6.60/kg, £6.30/kg, £6.40/kg, £6.20/kg and £6.50/kg for stations 1–6 respectively. The feedstock cost share became 44% in the 2030 cost scenario. Nearly 53.91% and 53.77% of available energy is absorbed in short and long term scenarios respectively. Under the long term cost scenario, 65% of hydrogen demand can be met, whereas less than 60% of hydrogen demand is met under the short term scenario. The system reliability (i.e. the meeting of hydrogen fuel demand) is quite low due to the operational mode of the system. Increasing the system size (mainly electrolyser production capacity) can clearly improve the system reliability
