• Benchmarking of a micro gas turbine model integrated with post-combustion CO2 capture

      Usman, Ali; Font Palma, Carolina; Nikpey Somehsaraei, Homam; Mansouri Majoumerd, Mohammad; Akram, Muhammad; Finney, Karen N.; Best, Thom; Mohd Said, Nassya B.; Assadi, Mohsen; Pourkashanian, Mohamed; et al. (Elsevier, 2017-03-19)
      The deployment of post-combustion CO2 capture on large-scale gas-fired power plants is currently progressing, hence the integration of the power and capture plants requires a good understanding of operational requirements and limitations to support this effort. This article aims to assist research in this area, by studying a micro gas turbine (MGT) integrated with an amine-based post-combustion CO2 capture unit. Both processes were simulated using two different software tools –IPSEpro and Aspen Hysys, and validated against experimental tests. The two MGT models were benchmarked at the nominal condition, and then extended to part-loads (50 and 80 kWe), prior to their integration with the capture plant at flue gas CO2 concentrations between 5 and 10 mol%. Further, the performance of the MGT and capture plant when gas turbine exhaust gases were recirculated was assessed. Exhaust gas recirculation increases the CO2 concentration, and reduces the exhaust gas flowrate and specific reboiler duty. The benchmarking of the two models revealed that the IPSEpro model can be easily adapted to new MGT cycle modifications since turbine temperatures and rotational speeds respond to reaching temperature limits; whilst a detailed rate-based approach for the capture plant in Hysys resulted in closely aligned simulation results with experimental data.
    • Modelling the molecular mechanisms of ageing

      Mc Auley, Mark T.; Martinez Guimera, Alvaro; Hodgson, David; McDonald, Neil; Mooney, Kathleen M.; Morgan, Amy; Proctor, Carole; University of Chester; Edgehill University; Newcastle University (Portland Press, 2017-02-23)
      The ageing process is driven at the cellular level by random molecular damage which slowly accumulates with age. Although cells possess mechanisms to repair or remove damage, they are not 100% efficient and their efficiency declines with age. There are many molecular mechanisms involved and exogenous factors such as stress also contribute to the ageing process. The complexity of the ageing process has stimulated the use of computational modelling in order to increase our understanding of the system, test hypotheses and make testable predictions. As many different mechanisms are involved, a wide range of models have been developed. This paper gives an overview of the types of models that have been developed, the range of tools used, modelling standards, and discusses many specific examples of models which have been grouped according to the main mechanisms that they address. We conclude by discussing the opportunities and challenges for future modelling in this field.
    • Investigating Cholesterol Metabolism and Ageing Using a Systems Biology Approach

      Morgan, Amy; Mooney, Kathleen M.; Wilkinson, Stephen J.; Pickles, Neil; Mc Auley, Mark T.; University of Chester (Cambridge University Press, 2016-11-02)
      CVD accounted for 27 % of all deaths in the UK in 2014, and was responsible for 1·7 million hospital admissions in 2013/2014. This condition becomes increasingly prevalent with age, affecting 34·1 and 29·8 % of males and females over 75 years of age respectively in 2011. The dysregulation of cholesterol metabolism with age, often observed as a rise in LDL-cholesterol, has been associated with the pathogenesis of CVD. To compound this problem, it is estimated by 2050, 22 % of the world's population will be over 60 years of age, in culmination with a growing resistance and intolerance to pre-existing cholesterol regulating drugs such as statins. Therefore, it is apparent research into additional therapies for hypercholesterolaemia and CVD prevention is a growing necessity. However, it is also imperative to recognise this complex biological system cannot be studied using a reductionist approach; rather its biological uniqueness necessitates a more integrated methodology, such as that offered by systems biology. In this review, we firstly discuss cholesterol metabolism and how it is affected by diet and the ageing process. Next, we describe therapeutic strategies for hypercholesterolaemia, and finally how the systems biology paradigm can be utilised to investigate how ageing interacts with complex systems such as cholesterol metabolism. We conclude by emphasising the need for nutritionists to work in parallel with the systems biology community, to develop novel approaches to studying cholesterol metabolism and its interaction with ageing.
    • Computational Modelling Folate Metabolism and DNA Methylation: Implications for Understanding Health and Ageing

      Mc Auley, Mark T.; Mooney, Kathleen M.; Salcedo-Sora, J. Enrique; University of Chester; Edge Hill University; Liverpool Hope University (Oxford University Press, 2016-12-21)
      Dietary folates have a key role to play in health as deficiencies in the intake of these B vitamins have been implicated in a wide variety of clinical conditions. The reason for this is folates function as single carbon donors in the synthesis of methionine and nucleotides. Moreover, folates have a vital role to play in the epigenetics of mammalian cells by supplying methyl groups for DNA methylation reactions. Intriguingly, a growing body of experimental evidence suggests DNA methylation status could be a central modulator of the ageing process. This has important health implications because the methylation status of the human genome could be used to infer age-related disease risk. Thus, it is imperative we further our understanding of the processes which underpin DNA methylation and how these intersect with folate metabolism and ageing. The biochemical and molecular mechanisms which underpin these processes are complex. However, computational modelling offers an ideal framework for handling this complexity. A number of computational models have been assembled over the years, but to date no model has represented the full scope of the interaction between the folate cycle and the reactions which govern the DNA methylation cycle. In this review we will discuss several of the models which have been developed to represent these systems. In addition we will present a rationale for developing a combined model of folate metabolism and the DNA methylation cycle.
    • Carbon dioxide rich microbubble acceleration of biogas production in anaerobic digestion

      Al-Mashhadani, Mahmood K. H.; Wilkinson, Stephen J.; Zimmerman, William B. (2016-12-15)
      This paper addresses the use of anaerobic bacteria to convert carbon dioxide to biomethane as part of the biodegradation process of organic waste. The current study utilises gaslift bioreactors with microbubbles generated by fluidic oscillation to strip the methane produced in the gaslift bioreactor. Removal of methane makes its formation thermodynamically more favourable. In addition, intermittent sparging of microbubbles can prevent thermal stratification, maintain uniformity of the pH and increase the intimate contact between the feed and microbial culture with lower energy requirements than traditional mixing. A gaslift bioreactor with microbubble sparging has been implemented experimentally, using a range of carrier gas, culminating in pure carbon dioxide, in the anaerobic digestion process. The results obtained from the experiments show that the methane production rate is approximately doubled with pure carbon dioxide as the carrier gas for intermittent microbubble sparging.
    • Obesity and the Dysregulation of Fatty Acid Metabolism: Implications for Healthy Aging

      Morgan, Amy; Mooney, Kathleen M.; Mc Auley, Mark T.; University of Chester; Edge Hill University (Taylor & Francis, 2016-10-17)
      The population of the world is aging. In 2010, an estimated 524 million people were aged 65 years or older presenting eight percent of the global population. By 2050, this number is expected to nearly triple to approximately 1.5 billion, 16 percent of the world’s population. Although people are living longer, the quality of their lives are often compromised due to ill-health. Areas covered. Of the conditions which compromise health as we age, obesity is at the forefront. Over half of the global older population were overweight or obese in 2010, significantly increasing the risk of a range of metabolic diseases. Although, it is well recognised excessive calorie intake is a fundamental driver of adipose tissue dysfunction, the relationship between obesity; intrinsic aging; and fat metabolism is less understood. In this review we discuss the intersection between obesity, aging and the factors which contribute to the dysregulation of whole-body fat metabolism. Expert Commentary. Being obese disrupts an array of physiological systems and there is significant crosstalk among these. Moreover it is imperative to acknowledge the contribution intrinsic aging makes to the dysregulation of these systems and the onset of disease.
    • A deterministic oscillatory model of microtubule growth and shrinkage for differential actions of short chain fatty acids

      Kilner, Josephine; Corfe, Bernard M.; Mc Auley, Mark T.; Wilkinson, Stephen J.; University of Sheffield; University of Chester (Royal Society of Chemistry, 2015-11-09)
      Short chain fatty acids (SCFA), principally acetate, propionate, butyrate and valerate, are produced in pharmacologically relevant concentrations by the gut microbiome. Investigations indicate that they exert beneficial effects on colon epithelia. There is increasing interest in whether different SCFAs have distinct functions which may be exploited for prevention or treatment of colonic diseases including colorectal cancer (CRC), inflammatory bowel disease and obesity. Based on experimental evidence, we hypothe-sised that odd-chain SCFAs may possess anti-mitotic capabilities in colon cancer cells by disrupting microtubule (MT) structural integrity via dysregulation of b-tubulin isotypes. MT dynamic instability is an essential characteristic of MT cellular activity. We report a minimal deterministic model that takes a novel approach to explore the hypothesised pathway by triggering spontaneous oscillations to represent MT dynamic behaviour. The dynamicity parameters in silico were compared to those reported in vitro.Simulations of untreated and butyrate (even-chain length) treated cells reflected MT behaviour in interphase or untreated control cells. The propionate and valerate (odd-chain length) simulations displayed increased catastrophe frequencies and longer periods of MT-fibre shrinkage. Their enhanced dynamicity wasdissimilar to that observed in mitotic cells, but parallel to that induced by MT-destabilisation treatments.Antimicrotubule drugs act through upward or downward modulation of MT dynamic instability. Our computational modelling suggests that metabolic engineering of the microbiome may facilitate managing CRC risk by predicting outcomes of SCFA treatments in combination with AMDs
    • Trion formation in a two-dimensional hole-doped electron gas

      Spink, Graham G.; López Ríos, Pablo; Drummond, Neil D.; Needs, Richard J.; University of Cambridge; University of Chester; Lancaster University (American Physical Society, 2016-07-22)
      The interaction between a single hole and a two-dimensional, paramagnetic, homogeneous electron gas is studied using diffusion quantum Monte Carlo simulations. Electron-hole relaxation energies, pair-correlation functions, and electron-hole center-of-mass momentum densities are reported for a range of electron-hole mass ratios and electron densities. We find numerical evidence of a crossover from a collective excitonic state to a trion-dominated state in a density range in agreement with that found in recent experiments on quantum-well heterostructures.
    • Mathematically modelling the dynamics of cholesterol metabolism and ageing

      Morgan, Amy; Mooney, Kathleen M.; Wilkinson, Stephen J.; Pickles, Neil; Mc Auley, Mark T.; University of Chester, Edgehill University (Elsevier, 2016-07-30)
      Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the UK. This conditionbecomes increasingly prevalent during ageing; 34.1% and 29.8% of males and females respectively, over 75years of age have an underlying cardiovascular problem. The dysregulation of cholesterol metabolism isinextricably correlated with cardiovascular health and for this reason low density lipoprotein cholesterol(LDL-C) and high density lipoprotein cholesterol (HDL-C) are routinely used as biomarkers of CVD risk. Theaim of this work was to use mathematical modelling to explore how cholesterol metabolism is affectedby the ageing process. To do this we updated a previously published whole-body mathematical model ofcholesterol metabolism to include an additional 96 mechanisms that are fundamental to this biologicalsystem. Additional mechanisms were added to cholesterol absorption, cholesterol synthesis, reversecholesterol transport (RCT), bile acid synthesis, and their enterohepatic circulation. The sensitivity of themodel was explored by the use of both local and global parameter scans. In addition, acute cholesterolfeeding was used to explore the effectiveness of the regulatory mechanisms which are responsible formaintaining whole-body cholesterol balance. It was found that our model behaves as a hypo-responderto cholesterol feeding, while both the hepatic and intestinal pools of cholesterol increased significantly.The model was also used to explore the effects of ageing in tandem with three different cholesterolester transfer protein (CETP) genotypes. Ageing in the presence of an atheroprotective CETP genotype,conferring low CETP activity, resulted in a 0.6% increase in LDL-C. In comparison, ageing with a genotypereflective of high CETP activity, resulted in a 1.6% increase in LDL-C. Thus, the model has illustrated theimportance of CETP genotypes such as I405V, and their potential role in healthy ageing.
    • Cardiovascular disease and healthy ageing

      Mooney, Kathleen M.; Mc Auley, Mark T.; University of Chester, Edgehill University (Open Access Text, 2016-06-16)
      Cardiovascular diseases are main cause of morbidity and mortality in the Western World. Cardiovascular disease increases in its prevalence with age and the burden of this condition is set to increase with an Ageing global population. There are many factors that impact cardiovascular disease risk. The aim of this brief commentary is to explore some of these factors; specifically, we will examine the role of social status, nutrition and, psychological stress in modulating cardiovascular disease risk. Our aim is to emphasise the multidimensional nature of this condition and to stress that a more complete understanding of the mechanisms which underpin its pathology can only be achieved by adopting an integrated approach which treats the progression of this disease in a more holistic fashion.
    • A mathematical model of microbial folate biosynthesis and utilisation: implications for antifolate development

      Salcedo-Sora, J. Enrique; Mc Auley, Mark T.; Liverpool Hope University, University of Chester (Royal Society of Chemistry, 2016-01-15)
      The metabolic biochemistry of folate biosynthesis and utilisation has evolved into a complex network of reactions. Although this complexity represents challenges to the field of folate research it has also provided a renewed source for antimetabolite targets. A range of improved folate chemotherapy continues to be developed and applied particularly to cancer and chronic inflammatory diseases. However, new or better antifolates against infectious diseases remain much more elusive. In this paper we describe the assembly of a generic deterministic mathematical model of microbial folate metabolism. Our aim is to explore how a mathematical model could be used to explore the dynamics of this inherently complex set of biochemical reactions. Using the model it was found that: (1) a particular small set of folate intermediates are overrepresented, (2) inhibitory profiles can be quantified by the level of key folate products, (3) using the model to scan for the most effective combinatorial inhibitions of folate enzymes we identified specific targets which could complement current antifolates, and (4) the model substantiates the case for a substrate cycle in the folinic acid biosynthesis reaction. Our model is coded in the systems biology markup language and has been deposited in the BioModels Database (MODEL1511020000), this makes it accessible to the community as a whole.
    • Aging and computational systems biology

      Mooney, Kathleen M.; Morgan, Amy; Mc Auley, Mark T.; Edgehill University, University of Chester (John Wiley & Sons, 2016-01-29)
      Aging research is undergoing a paradigm shift, which has led to new and innovative methods of exploring this complex phenomenon. The systems biology approach endeavors to understand biological systems in a holistic manner, by taking account of intrinsic interactions, while also attempting to account for the impact of external inputs, such as diet. A key technique employed in systems biology is computational modeling, which involves mathematically describing and simulating the dynamics of biological systems. Although a large number of computational models have been developed in recent years, these models have focused on various discrete components of the aging process, and to date no model has succeeded in completely representing the full scope of aging. Combining existing models or developing new models may help to address this need and in so doing could help achieve an improved understanding of the intrinsic mechanisms which underpin aging.
    • Cholesterol metabolism: A review of how ageing disrupts the biological mechanisms responsible for its regulation

      Morgan, Amy; Mooney, Kathleen M.; Wilkinson, Stephen J.; Pickles, Neil; Mc Auley, Mark T.; University of Chester, Edgehill University (Elsevier, 2016-04-01)
      Cholesterol plays a vital role in the human body as a precursor of steroid hormones and bile acids, in addition to providing structure to cell membranes. Whole body cholesterol metabolism is maintained by a highly coordinated balancing act between cholesterol ingestion, synthesis, absorption, and excretion. The aim of this review is to discuss how ageing interacts with these processes. Firstly, we will present an overview of cholesterol metabolism. Following this, we discuss how the biological mechanisms which underpin cholesterol metabolism are effected by ageing. Included in this discussion are lipoprotein dynamics, cholesterol absorption/synthesis and the enterohepatic circulation/synthesis of bile acids. Moreover, we discuss the role of oxidative stress in the pathological progression of atherosclerosis and also discuss how cholesterol biosynthesis is effected by both the mammalian target of rapamycin and sirtuin pathways. Next, we examine how diet and alterations to the gut microbiome can be used to mitigate the impact ageing has on cholesterol metabolism. We conclude by discussing how mathematical models of cholesterol metabolism can be used to identify therapeutic interventions.
    • Integrated Oxyfuel Power Plant with Improved CO2 Separation and Compression Technology for EOR application

      Font Palma, Carolina; Errey, Olivia; Corden, Caroline; Chalmers, Hannah; Lucquiaud, Mathieu; Sanchez del Rio, Maria; Jackson, Steve; Medcalf, Daniel; Livesey, Bryony; Gibbins, Jon; et al. (Elsevier, 2016-06-25)
      An integrated advanced supercritical coal-fired oxyfuel power plant with a novel cryogenic CO2 separation and compression technology for high purity CO2 to suit injection for enhanced oil recovery purposes is investigated. The full process is modelled in Aspen Plus® consisting of: an Air Separation Unit (ASU), an Advanced Supercritical Pulverised Fuel (ASC PF) power plant with a bituminous coal as feedstock, a steam cycle, and a Carbon dioxide Purification Unit (CPU). The proposed CPU process accommodates a distillation column with an integrated reboiler duty to achieve a very high purity CO2 product (99.9%) with constrained oxygen levels (100 ppm). This work presents a detailed analysis of the CO2 separation and compression process within the full power plant, including effective heat integration to reduce the electricity output penalty associated with oxyfuel CO2 capture. The results of this analysis are compared with previous studies and indicate that the combined application of process optimisation in the CPU and advanced heat integration with the power plant offer promising results: In this work a high purity CO2 product was achieved while maintaining 90% capture for a net plant efficiency of 38.02% (LHV), compared with a thermal efficiency of 37.76% (LHV) for a reference simulation of an ASC PF oxy-fired plant with advanced heat integration, providing a lower purity CO2 product.
    • Thermodynamic Analysis and Process System Comparison of the Exhaust Gas Recirculated, Steam Injected and Humidified Micro Gas Turbine

      Ali, Usman; Font Palma, Carolina; Hughes, Kevin J.; Ingham, Derek B.; Ma, Lin; Pourkashanian, Mohamed; University of Leeds (ASME Proceedings, 2015-08-12)
      Stringent environmental emission regulations and continuing efforts to reduce carbon dioxide (CO2) from the energy sector, in the context of global warming, have promoted interest to improve the efficiency of power generation systems whilst reducing emissions. Further, this has led to the development of innovative gas turbine systems which either result in higher electrical efficiency or the reduction of CO2 emissions. Micro gas turbines are one of the secure, economical and environmentally viable options for power and heat generation. Here, a Turbec T100 micro gas turbine (MGT) is simulated using Aspen HYSYS® V8.4 and validated through experimental data. Due to the consistency and robustness of the steady state model developed, it is further extended to three different innovative cycles: (i) an exhaust gas recirculated (EGR) cycle, in which part of the exhaust gas is dried and re-circulated to the MGT inlet; (ii) a steam injected (STIG) cycle, and (iii) a humid air turbine (HAT) cycle. The steam and hot water are generated through the exhaust of the recuperator for the STIG and HAT cycle, respectively. Further, the steam is directly injected into the recuperator for power augmentation, while for the HAT cycle; the compressed air is saturated with water in the humid tower before entering the recuperator. This study evaluates the impact of the EGR ratio, steam to air ratio, and water to air ratio on the performance and efficiency of the system. The comparative potential for each innovative cycle is assessed by thermodynamic properties estimation of process parameters through the models developed to better understand the behavior of each cycle. The thermodynamic assessment indicates that CO2 enrichment occurs for the three innovative cycles. Further, the results indicate that the electrical efficiency increases for the STIG and HAT cycle while it decreases for the EGR cycle. In conclusion, the innovative cycles indicates the possibilities to improve the system performance and efficiency.
    • Impact of the operating conditions and position of exhaust gas recirculation on the performance of a micro gas turbine

      Ali, Usman; Font Palma, Carolina; Hughes, Kevin J.; Ingham, Derek B.; Ma, Lin; Pourkashanian, Mohamed; University of Chester/University of Leeds (Elsevier, 2015-06-10)
      Gas turbines are a viable and secure option both economically and environmentally for power and heat generation. The process simulation of the micro gas turbine with exhaust gas recirculation (EGR) and its impact on performance is evaluated. This study is further extended to evaluate the effect of the operating conditions and position of the EGR on the performance of the micro gas turbine. The performance analysis for different configurations of the EGR cycle, as well as flue gas condensation temperature, results in the optimized position of EGR at the compressor inlet with partial condensation resulting in the CO2 enhancement to 3.7 mol%.
    • Airlift Bioreactor for Biological Applications with Microbubble Mediated Transport Processes

      Al-Mashhadani, Mahmood K. H.; Wilkinson, Stephen J.; Zimmerman, William B.; University of Chester (Elsevier, 2015-12-01)
      Airlift bioreactors can provide an attractive alternative to stirred tanks, particularly for bioprocesses with gaseous reactants or products. Frequently, however, they are susceptible to being limited by gas-liquid mass transfer and by poor mixing of the liquid phase, particularly when they are operating at high cell densities. In this work we use CFD modelling to show that microbubbles generated by fluidic oscillation can provide an effective, low energy means of achieving high interfacial area for mass transfer and improved liquid circulation for mixing. The results show that when the diameter of the microbubbles exceeded 200 μm, the “downcomer” region, which is equivalent to about 60 % of overall volume of the reactor, is free from gas bubbles. The results also demonstrate that the use of microbubbles not only increases surface area to volume ratio, but also increases mixing efficiency through increasing the liquid velocity circulation around the draft tube. In addition, the depth of downward penetration of the microbubbles into the downcomer increases with decreasing bubbles size due to a greater downward drag force compared to the buoyancy force. The simulated results indicate that the volume of dead zone increases as the height of diffuser location is increased. We therefore hypothesise that poor gas bubble distribution due to the improper location of the diffuser may have a markedly deleterious effect on the performance of the bioreactor used in this work.
    • Synergistic carbon metabolism in a fast growing mixotrophic freshwater microalgal species Micractinium inermum

      Smith, Richard T.; Bangert, Krys; Wilkinson, Stephen J.; Gilmour, D. James; University of Sheffield ; University of Sheffield ; University of Sheffield/University of Chester ; University of Sheffield (Elsevier, 2015-05-11)
      In recent years microalgae have attracted significant interest as a potential source of sustainable biofuel. Mixotrophic microalgae are able to simultaneously photosynthesise while assimilating and metabolising organic carbon. By combining autotrophic and heterotrophic metabolic pathways biomass productivity can be significantly increased. In this study, acetate-fed mixotrophic Micractinium inermum cultures were found to have a specific growth rate 1.74 times the sum of autotrophic and heterotrophic growth. It was hypothesised that gas exchange between the two metabolic pathways within mixotrophic cultures may have prevented growth limitation and enhanced growth. To determine the extent of synergistic gas exchange and its influence on metabolic activity, dissolved inorganic carbon (DIC), dissolved oxygen (DO) and photosynthesis and respiration rates were measured under different trophic conditions. A 32.7 fold and 2.4 fold increase in DIC and DO concentrations, relative to autotrophic and heterotrophic cultures respectively, were coupled with significant increases in rates of photosynthesis and respiration. These data strongly support the hypothesis of mixotrophic gas exchange within M. inermum cultures. In addition to enhanced growth, this phenomenon may provide reductions in aeration and oxygen stripping costs related to microalgae production.
    • Experimental and process modelling study of integration of a micro-turbine with an amine plant

      Agbonghae, Elvis O.; Best, Thom; Finney, Karen N.; Font Palma, Carolina; Hughes, Kevin J.; Pourkashanian, Mohamed; University of Leeds (Elsevier, 2014-12-31)
      An integrated model of a micro-turbine coupled to a CO2 capture plant has been developed with Aspen Plus, and validated with experimental data obtained from a Turbec T100 microturbine at the PACT facilities in the UKCCS Research Centre, Beighton, UK. Monoethanolamine (MEA) was used as solvent and experimental measurements from the CO2 capture plant have been used to validate the steady-state model developed with Aspen Plus®. The optimum liquid/gas ratio and the lean CO2 loading for 90% CO2 capture has been quantified for flue gases with CO2 concentrations ranging from 3 to 8 mol%.
    • Oxyfuel power plant with novel CO2 separation and compression technology

      Font Palma, Carolina; University of Leeds (2014-04-03)