Recent Submissions

  • Green Lean Six Sigma for Improving Manufacturing Sustainability: Framework Development and Validation

    Garza-Reyes, Jose Arturo; University of Derby (Elsevier, 2022-02)
    In the past few decades, a competitive landscape, learned customers and rigorous regulations have forced manufacturing industries to focus on sustainability alongside operational efficiency. The main objective of the present study is to develop a systematic Green Lean Six Sigma (GLSS) framework for improvement in operational efficiency together with environmental and social sustainability. Further, the proposed framework was tested in a leading manufacturing company. The framework was designed with insights gained from the literature and industrial personnel and encompasses the systematic application of different tools of the Green paradigm, Lean, and Six Sigma, from the identification and assessment of the problem to the sustainment of the adopted measures. A systematic application of lifecycle assessment and social lifecycle assessment was used to assess environmental and societal performance. The sustainability focused GLSS framework enhances the environmental capability, process performance and provides a new perspective for researchers and practitioners to support GLSS projects to achieving higher sustainability dynamics.
  • Power Management and Control of a Hybrid Electric Vehicle Based on Photovoltaic, Fuel Cells, and Battery Energy Sources

    Mohamed, Naoui; Aymen, Flah; Altamimi, Abdullah; Khan, Zafar A.; Lassaad, Sbita; University of Gabès, Gabès 6072, Tunisia; University, Al-Majmaah 11952, Saudi Arabia; Mirpur University of Science and Technology, Mirpur 10250, Pakistan; University of Derby (MDPI AG, 2022-02-23)
    This paper deals with an energy management problem to ensure the best performance of the recharging tools used in electric vehicles. The main objective of this work is to find the optimal condition for controlling a hybrid recharging system by regrouping the photovoltaic cells and fuel cells. The photovoltaic and fuel cell systems were connected in parallel via two converters to feed either a lithium battery bank or the main traction motor. This combination of energy sources resulted in a hybrid recharging system. The mathematical model of the overall recharging system and the designed power management loop was developed, taking into account multiple aspects, including vehicle loading, the stepwise mathematical modelling of each component, and a detailed discussion of the required electronic equipment. Finally, a simplistic management loop was designed and implemented. Multiple case studies were simulated, statistical approaches were used to quantify the contribution of each recharging method, and the benefits of the combination of the two sources were evaluated. The energetic performance of an electric vehicle with the proposed hybrid recharging tool under various conditions, including static and dynamic modes, was simulated using the MATLAB/Simulink tool. The results suggest that despite the additional weight of PV panels, the combination of the PV and FC systems improves the vehicle’s energetic performance and provides a higher charging capacity instead of using an FC alone. A comparison with similar studies revealed that the proposed model has a higher efficiency. Finally, the benefits and drawbacks of each solution are discussed to emphasise the significance of the hybrid recharging system.
  • Hierarchical Energy Management System With a Local Competitive Power Market for Inter-Connected Multi-Smart Buildings

    Hussain, Mirza Shehbaz; Kazmi, Syed Ali Abbas; Khan, Zafar A.; Alghassab, Mohammed; Altamimi, Abdullah; National University of Sciences and Technology (NUST), Islamabad, Pakistan; Mirpur University of Science and Technology, Mirpur AJK, Pakistan; University of Derby; Shaqra University, Riyadh, Saudi Arabia; Majmaah University, Al-Majmaah, Saudi Arabia (Institute of Electrical and Electronics Engineers (IEEE), 2022-02-09)
    The energy management in new distribution paradigms are amongst one of core research dimension, particularly in smart grids. This paper proposes a hierarchical energy management system for inter-connected multi-smart buildings with an inclusion of local Power Market. As home appliances have huge contribution in load of buildings, the appliances are scheduled in order to minimize operational cost while taking into account the user comfort and other system constraints. The objectives of this paper aim to minimize operational cost, CO 2 emissions, grid dependency while maximize user comfort and revenue. The proposed technique enables a prosumer with two options, either they can sell excess energy to the utility or can bid and sell in market with high price compare to utility. Besides increase in revenue, the consumer is enabled to buy electricity from utility or from local market with low prices compare to utility grid aiming at reducing operational cost. The proposed framework is evaluated across three algorithms namely, JAYA, teacher learning based optimization (TLBO) and Rao1, respectively. As per comparative analysis, the JAYA algorithm outperforms the others in achieving the aimed objectives in-terms of favorable achieved numerical values. Different cases are created in order to test the effectiveness of proposed system. The overall simulation results validate the proposed approach with highest operational cost reduction of 151.48%, peak load reduction 76.76%, grid dependency reduction 95.61%, and minimum emission of CO 2 is 3.70 Kg/Day as compare to base case.
  • Techno-Economic and Environmental Impact Analysis of Large-Scale Wind Farms Integration in Weak Transmission Grid from Mid-Career Repowering Perspective

    Butt, Rohan Zafar; Kazmi, Syed Ali Abbas; Alghassab, Mohammed; Khan, Zafar A.; Altamimi, Abdullah; Imran, Muhammad; Alruwaili, Fahad F.; National University of Sciences and Technology (NUST), Islamabad, Pakistan; Shaqra University, Riyadh, Saudi Arabia; Mirpur University of Science and Technology, Mirpur AJK, Pakistan; et al. (MDPI AG, 2022-02-22)
    Repowering a wind farm enhances its ability to generate electricity, allowing it to better utilize areas with high mean wind speeds. Pakistan’s present energy dilemma is a serious impediment to its economic development. The usage of a diesel generator as a dependable backup power source raises the cost of energy per kWh and increases environmental emissions. To minimize environmental emissions, grid-connected wind farms enhance the percentage of wind energy in the electricity system. These wind generators’ effects, on the other hand, are augmented by the absorption of greater quantities of reactive electricity from the grid. According to respective grid codes, integration of commercial onshore Large-Scale Wind Farms (LSWF) into a national grid is fraught with technical problems and inter-farm wake effects, which primarily ensure power quality while degrading overall system operation and limiting the optimal use of attainable wind resources. The goal of this study is to examine and estimate the techno-economic influence of large-scale wind farms linked to poor transmission systems in Pakistan, contemplating the inter-farm wake effect and reactive power diminution and compensating using a range of voltage-ampere reactive (VAR) devices. This study presents a partial repowering technique to address active power deficits produced by the wake effect by raising hub height by 20 m, which contributed to recovering the active power deficit to 48% and so reduced the effects of upstream wind farms. Simulations were conducted for several scenarios on an actual test system modeled in MATLAB for comparative study using capacitor banks and different flexible alternating current transmission system (FACTS) devices. Using the SAM (System Advisor Model) and RETscreen, a complete technical, economic, and environmental study was done based on energy fed into the grid, payback time, net present value (NPV), and greenhouse gases (GHG) emission reduction. The studies suggest that the unified power flow controller (UPFC) is the optimum compensating device via comparison analysis as it improved the power handling capabilities of the power system. Our best-case scenario includes UPFC with hub height augmentation, demonstrating that it is technically, fiscally, and environmentally viable. Over the course of its lifespan, the planned system has the potential to save 1,011,957 tCO2, resulting in a greener environment. When the energy generated annually by a current wake-affected system is compared to our best-recommended scenario, a recovered shortfall of 4.851% is seen, with improved system stability. This modest investment in repowering boosts energy production due to wake effects, resulting in increased NPV, revenue, and fewer CO2 footprints.
  • Effects of mental fatigue on static upright stance and functional balance in older adults

    Fletcher, Lucy J.; Osler, Callum J.; University of Derby (Elsevier, 2021-11-16)
    Cognitive influences on balance control may contribute to greater instability and falls in older adults. In support of this, old age exacerbates the effects of a concurrent cognitive task on balance. Mental fatigue is a psychobiological state experienced following prolonged demanding cognitive activity. However, its effects on static upright stance and functional balance in older adults is unclear. It is also unclear how the effects of mental fatigue and a concurrent task interact. Balance was assessed in ten younger and ten older participants before and immediately after 25 min of the incongruent Stroop colour-word test (mental fatigue) and leisurely reading (control), presented in a randomized counterbalanced order on separate days. Static and functional balance was assessed using the centre of pressure path length when standing still and the ‘Timed Up & Go’ test, respectively. These balance assessments were completed with and without a concurrent backward counting task (i.e. dual-task and single-task, respectively). Under subjectively-confirmed conditions of mental fatigue, sway path length when standing still was 32% greater than the control condition in older adults but unchanged in younger adults. This age-dependant effect of mental fatigue on static balance was similar in single-task and dual-task trials. Mental fatigue did not significantly affect functional balance performance in either age group. These findings are the first to show mental fatigue to impair static balance control in older adults. Therefore, whether due to everyday activities or a symptom of disease, mental fatigue may contribute to poor balance in older adults.
  • Melt Percolation, Melt-Rock Reaction and Oxygen Fugacity in Supra-Subduction Zone Mantle and Lower Crust from the Leka Ophiolite Complex, Norway

    O’Driscoll, Brian; Leuthold, Julien; Lenaz, Davide; Skogby, Henrik; Day, James, M.; Adetunji, Jacob; University of Manchester; Institute of Geochemistry and Petrology, Zürich, Switzerland; Università degli Studi di Trieste, Trieste, Italy; Swedish Museum of Natural History, Stockholm, Sweden; et al. (Oxford University Press, 2021-09-17)
    Samples of peridotites and pyroxenites from the mantle and lower crustal sections of the Leka Ophiolite Complex (LOC; Norway) are examined to investigate the effects of melt-rock reaction and oxygen fugacity variations in the sub-arc oceanic lithosphere. The LOC is considered to represent supra-subduction zone (SSZ) oceanic lithosphere, but also preserves evidence of pre-SSZ magmatic processes. Here we combine field and microstructural observations with mineral chemical and structural analyses of different minerals from the major lithologies of the LOC. Wehrlite and websterite bodies in both the mantle and lower crust contain clinopyroxene likely formed at a pre-SSZ stage, characterised by high Al, high Cr, low Mg crystal cores. These clinopyroxenes also exhibit low Al, low Cr, high Mg outer rims and intracrystalline dissolution surfaces, indicative of reactive melt percolation during intrusion and disruption of these lithologies by later, SSZ-related, dunite-forming magmas. Chromian-spinel compositional variations correlate with lithology; dunite-chromitite Cr-spinels are characterised by relatively uniform and high TiO2 and Al2O3, indicating formation by melt-rock reaction associated with SSZ processes. Harzburgite Cr-spinel compositions are more variable but preserve a relatively high Al2O3, low TiO2 endmember that may reflect crystallisation in a pre-SSZ oceanic spreading centre setting. An important finding of this study is that the LOC potentially preserves the petrological signature of a transition between oceanic spreading centre processes and subsequent SSZ magmatism. Single crystal Cr-spinel Fe3+/ΣFe ratios calculated on the basis of stoichiometry (from electron microprobe [EPMA] and crystal structural [X-ray diffraction; XRD] measurements) correlate variably with those calculated by point-source (single crystal) Mössbauer spectroscopy. Average sample EPMA Fe3+/ΣFe ratios overestimate or underestimate the Mössbauer-derived values for harzburgites, and always overestimate the Mössbauer Fe3+/ΣFe ratios for dunites and chromitites. The highest Fe3+/ΣFe ratios, irrespective of method of measurement, are therefore generally associated with dunites and chromitites, and yield calculated log(fO2)FMQ values of up to ~ + 1.8. While this lends support to the formation of the dunites and chromitites during SSZ-related melt percolation in the lower part of the LOC, it also suggests that these melts were not highly oxidised, compared to typical arc basalts (fO2FMQ of > + 2). This may in turn reflect the early (forearc) stage of subduction zone activity preserved by the LOC and implies that some of the arc tholeiitic and boninitic lava compositions preserved in the upper portion of the ophiolite are not genetically related to the mantle and lower crustal rocks, against which they exhibit tectonic contacts. Our new data also have implications for the use of ophiolite chromitites as recorders of mantle oxidation state through time; a global comparison suggests that the Fe3+/ΣFe signatures of ophiolite chromitites are likely to have more to do with local environmental petrogenetic conditions in sub-arc systems than large length-scale mantle chemical evolution
  • Paying for end of life in care homes in the UK

    Stubbs, John; Adetunji, Jacob; University of Derby (Cambridge University Press, 2020-10-08)
    To live to a ripe old age, untroubled by health problems, physical or mental, is an almost universal aspiration. But most people are not so lucky and will likely be in care homes for their final years, with varying levels of disease, disability and dementia. Kinley et al [1] maintain that over a fifth of the population of developed countries die in care homes. Moreover, the financial cost of this end of life care, which is the focus of this paper, can be daunting and require much planning [2]. It was reported in 2017 that, in the UK, care home costs are rising up to twice as fast as inflation [3]. Consequently the question arises about the long term affordability of such care to those having to fund it, a question that ever more people both nationally and globally are having to confront.
  • Impact of the COVID-19 Pandemic on Manufacturing Operations and Supply Chain Resilience: Effects and Response Strategies

    Bastas, A; Garza-Reyes, Jose Arturo; University of Derby (Emerald, 2022-02)
    Manufacturing organisations are striving towards adapting and responding to the unprecedented challenges posed by the COVID-19 pandemic, along with the operations research streams endeavouring to support their recovery. With a view to bridging our knowledge gap on the impact of the COVID-19 pandemic on manufacturing operations, this paper investigates the key challenges and strategies formulated by manufacturing organisations operating in the Northern region of Cyprus. The research was conducted through 10 in-depth interviews that analyzed the effects of the pandemic, the associated causes, and the response strategies implemented. The effects of the pandemic on the manufacturing organisations investigated are identified, along with the associated causes, and the response strategies deployed. Learnings and countermeasures implemented to date are established in light of the insights captured from the practitioners. Learnings and countermeasures implemented to date are established in light of the insights captured from the practitioners. Contributions are made to the body of knowledge on manufacturing management and manufacturing supply chain resilience (SCR) through fostering our understanding of the impacts that the pandemic had on manufacturing organisations, and practical contributions are presented through evidencing and transferring of the operations management knowledge and solutions devised in various sectors to date.
  • A Framework for the Systematic Implementation of Green-Lean and Sustainability in SMEs

    Siegel, R; Antony, J; Govindan, K; Garza-Reyes, Jose Arturo; Lameijer, B; Samadhiya, A; University of Derby (Taylor&Francis, 2022-03)
    Evidence suggests that smaller organisations find the implementation of combined operations- and environmental Sustainability improvement initiatives such as Green-Lean and Sustainability (GLS) challenging. This paper, therefore, develops a framework for the systematic implementation of Green-Lean and Sustainability in small and medium-sized enterprises (SMEs) to achieve long-term improvement of environmental, social and economic processes and performance. A literature assessment of theories, frameworks, and concepts was employed in the study to better comprehend the difficulties confronting the modern business world. In addition, the research employed expert perspectives from the lean, green-lean, and sustainability fields to propose, develop, test, and validate a framework for addressing business concerns. The research uncovers considerable implementation problems, such as employee motivation and integration, responsibilities, and measurements. It also underlines the success factors for the implementation process, such as management, firm- goals and strategy, reviews and audits, vision, and guidance by lean, green and sustainability frameworks. The novelty in this research lies in the approach where Green-Lean and Sustainability are combined and applied in an SME context. The presented framework offers the potential to be implemented in SMEs that operate in different sectors and contexts and are affected by different environmental and social considerations.
  • Effects of Caffeine Ingestion on Human Standing Balance: A Systematic Review of Placebo-Controlled Trials.

    Briggs, Isobel; Chidley, Joel; Chidley, Corinna; Osler, Callum; University of Derby (MDPI, 2021-10-08)
    Caffeine ingestion may influence balance control via numerous mechanisms. Although previously investigated using various study designs and methods, here we aimed to create the first evidence-based consensus regarding the effects of caffeine on the control of upright stance via systematic review (PROSPERO registration CRD42021226939). Embase, PubMed/MEDLINE, SPORTDiscus and Web of Science databases were searched on 27 January 2021 to identify placebo-controlled trials investigating caffeine-induced changes in human standing balance. Reference lists of eligible studies were also searched. Overall, nine studies involving a total of 290 participants were included. All studies were moderate to strong in quality according to the QualSyst tool. Balance-related outcome measures were collected across a range of different participant ages, stances and sensory conditions. The results show that younger participants' balance was generally unaffected by caffeine ingestion. However, a significant balance impairment was observed following caffeine ingestion in all studies involving older participants (average age >65 years). Our results therefore suggest an age-dependent effect of caffeine ingestion on human standing. Further research into this effect is warranted as only one study has directly compared younger and older adults. Nonetheless, an important implication of our findings is that caffeine ingestion may increase fall risk in older adults. Furthermore, based on our findings, caffeine ingestion should be considered as a potential confounding factor when assessing human standing balance, particularly in older adults.
  • It pays to quit: a review of evidence about how financial incentives may improve smoking cessation during pregnancy

    Wyke, Eleanor; Elander, James; University of Derby (British Psychological Society, 2022-03-03)
    Helping women to stop smoking during pregnancy is a major priority for health professionals and evidence suggests that financial incentives can be effective. With the aim of maximising the benefits and minimising unintended negative consequences, this paper gives a brief review of evidence about using financial incentives for smoking cessation during pregnancy, with a special emphasis on how financial incentives work. The review showed that financial incentives can increase pregnant women’s capability, opportunity and motivation to stop smoking. The evidence supports five specific recommendations about how financial incentives should be used in future to reduce smoking during pregnancy, including measures to increase public acceptability. These recommendations can contribute to updating published UK policy for smoking cessation during pregnancy, including the National Institute for Health and Care Excellence (NICE) guideline on stopping smoking in pregnancy and after childbirth (PH26).
  • Education, Skills and Social Justice in a Polarising World

    Esmond, Bill; Atkins, Liz; University of Derby (Routledge, 2022-01-13)
    This book explains how education policies offering improved transitions to work and higher-level study can widen the gaps between successful and disadvantaged groups of young people. Centred on an original study of ongoing further education and apprenticeship reforms in England, the book traces the emergence of distinctive patterns of transition that magnify existing societal inequalities. It illustrates the distinction between mainly male ‘technical elites’ on STEM-based courses and the preparation for low-level service roles described as ‘welfare vocationalism’, whilst digital and creative fields ill-suited to industry learning head for a ‘new economy precariat’. Yet the authors argue that social justice can nevertheless be advanced in the spaces between learning and work. The book provides essential insights for academics and postgraduate students researching technical, vocational and higher education. It will also appeal to professionals with interests in contemporary educational policy and emerging practice.
  • Analysing the Barriers to Sustainable Sourcing in the Apparel and Fashion-Luxury Industry

    Bhandari, N; Garza-Reyes, Jose Arturo; Rocha-Lona, L; Kumar, F; Naz, F; Joshi, R; University of Warwick; University of Derby; ESCA Santo Tomás, Instituto Politécnico Nacional, Mexico City, Mexico; London Metropolitan University; et al. (Elsevier, 2022-02-19)
    The fashion industry’s transition to Sustainable Sourcing (SS) is crucial to address some of the social and environmental problems faced by societies. While previous research has identified SS implementation barriers in the mainstream fashion industry, this article provides a methodical identification, validation, and prioritization of the 20 key SS implementation barriers for the global apparel and fashion-luxury sector. The paper employs a multi-phase research methodology to benchmark the SS implementation barriers in the apparel and fashion-luxury sector. These barriers were analysed through 154 responses received from global SS professionals by employing a survey questionnaire. Through an Exploratory Factor Analysis (EFA), the barriers were categorized into six unique dimensions. To establish their importance, an analytical hierarchy process (AHP) analysis further provided a global ranking of the identified barriers. The results of the study revealed that ‘Management, Government Support, and Infrastructure Barriers’ hold the most significant importance among all barrier dimensions, followed by ‘Material Barriers’, ‘Finance Barriers’, ‘Supplier Barriers’, ‘Certificates and Customer Perceptions’, and ‘Sustainable Packaging and Human Resource Barriers’. Furthermore, the results showed that specific barriers such as ‘Undersupply of Sustainable Raw Materials’, ‘Insufficient Commitment from Top Management’, and ‘Inadequate Awareness’ are the top three barriers according to global ranking. The research theoretically contributes by identifying and ranking the SS barriers that may hinder the efforts of the fashion sector to become more sustainable. This will facilitate researchers, sourcing professionals, fashion retailers, policymakers, and governing bodies in the formulation and deployment of dynamic strategies to overcome them and successfully implement SS practices.
  • Florence Nightingale, the Colossus: Was She a Feminist?

    Hogan, Susan; University of Derby (Bridgewater State University, 2022)
    Nightingale displayed a particular brand of feminism that reflected the circumstances of her era. The question of women’s involvement in healthcare is addressed through an analysis of Nightingale’s most famous work, Notes on Nursing. What it is, and what it is not (1859/60). Then other key works are scrutinised with reference to ideas about female involvement in healthcare and how she addresses the position of women in general terms.2 Nightingale’s works, Notes on Hospitals (1859); Suggestions for Thought to the Searchers after Truth among the Artisans of England (1860); Introductory Notes on Lying-In Institutions (1871) are focussed upon illustrating her views on women’s involvement in healthcare and answering the overarching question: was and how was she feminist?
  • Redesigning Traditional Linear Supply Chains into Circular Supply Chains – A Study into its Challenges

    Tarun, Roy; Garza-Reyes, Jose Arturo; Kumar, Vikas; Kumar, Anil; Agrawal, Rohit; University of Warwick; University of Derby; University of the West of England; London Metropolitan University; Indian Institute of Technology, Delhi (Elsevier, 2022-02-12)
    Transitioning to a Circular Economy (CE) is considered the most promising way to achieve economic and environmental sustainability. However, companies and governments are faced with challenges in redesigning existing linear supply chains (SCs) into circular supply chains (CSCs). Although previous research has tried to identify challenges in the implementation of CE in their own specific contexts, the literature lacks a systematic identification and validation of challenges to transition to circular supply chain management (CSCM). This study identifies the key barriers to the redesign of SCs into CSCs in the global manufacturing sector and develops a broad classification to facilitate their mitigation. An extensive review of the state-of-the-art literature on CSCM identified a list of 20 barriers plaguing manufacturing firms and impeding the transition of their linear SCs into CSCs. The barriers were analysed through 200 responses received from experts in the fields of CE and supply chain management using a questionnaire-based survey. The findings of the study suggest significant restraints towards CSCs implementation owing to the lack of incentives and policies, and product complexity. Moreover, the study of the broadly classified barriers such as standardisation and legal barriers, and financial and economic barriers indicate substantial similarities between the results and findings of the extant literature thereby implying significant alignment between the industry and the academia regarding the subject. This work is useful in formulating strategies to redesign CSCs, and helps researchers and practitioners to understand the challenges in implementing CSCs.
  • Chromite chemistry of a massive chromitite seam in the northern limb of the Bushveld Igneous Complex, South Africa: correlation with the UG-2 in the eastern and western limbs and evidence of variable assimilation of footwall rocks

    Langa, Malose M.; Jugo, Pedro J.; Leybourne, Matthew I.; Grobler, Danie F.; Adetunji, Jacob; Skogby, Henrik; Laurentian University, Sudbury, Canada; Queen’s University, Kingston, Ontario, Canada; Ivanplats (Pty) Ltd., Mokopane, South Africa; University of Derby; et al. (Springer, 2020-02-03)
    The Bushveld Igneous Complex (BIC) is known for its laterally extensive platinum group element–bearing layers, the most famous being the Merensky Reef and the UG-2 chromitite in the eastern and western limbs of the complex. In the northern limb, the Plat-reef mineralization and a thick chromitite seam below it (referred to as the “UG-2 equivalent” or UG-2E) have been proposed to be the stratigraphic equivalents of the Merensky Reef and the UG-2, respectively. In this study, we compare a suite ofUG-2E samples from the Turfspruit project with a UG-2 reference suite from the western limb using petrography, electron probe microanalysis, laser ablation-inductively coupled plasma-mass spectrometry, and Mössbauer spectroscopy. The results show that(a) in Mg# vs. Cr# diagrams, UG-2E chromites have a distinct compositional field; however, when samples of similar chromite modal abundance (≥80%) are used, the UG-2E chromites overlap the field that characterizes UG-2 chromites; (b) the UG-2E is more variable in chromite modal abundance than the UG-2; and (c) variations in Mg# and Fe3+/ΣFe in the UG-2E indicate contamination of the magma by metasedimentary rocks of the Duitschland Formation (Transvaal Supergroup) during emplace-ment, followed by partial re-equilibration of chromite grains with a trapped melt. Thus, we conclude that for chromite modes higher than 80%, the chromite composition retains enough information to allow correlation and that the UG-2E in the northern limb is very likely the UG-2 chromitite
  • Dense melt residues drive mid-ocean-ridge “hotspots”

    Phethean, Jordan; Papadopoulou, Martha; Peace, Alexander L.; University of Derby; University of Leicester; McMaster University, Hamilton, Ontario L8S 4K1, Canada (Geological Society of America, 2022-01-27)
    The geodynamic origin of melting anomalies found at the surface, often referred to as “hotspots,” is classically attributed to a mantle plume process. The distribu- tion of hotspots along mid-ocean-ridge spreading systems around the globe, however, questions the universal validity of this concept. Here, the preferential association of hotspots with slow- to intermediate-spreading centers and not fast-spreading centers, an observation contrary to the expected effect of ridge suction forces on upwelling mantle plumes, is explained by a new mechanism for producing melting anomalies at shallow (<2.3 GPa) depths. By combining the effects of both chemical and ther- mal density changes during partial melting of the mantle (using appropriate latent heat and depth-dependent thermal expansivity parameters), we find that mantle resi- dues experience an overall instantaneous increase in density when melting occurs at <2.3 GPa. This controversial finding is due to thermal contraction of material during melting, which outweighs the chemical buoyancy due to melting at shallow pressures (where thermal expansivities are highest). These dense mantle residues are likely to locally sink beneath spreading centers if ridge suction forces are modest, thus driving an increase in the flow of fertile mantle through the melting window and increasing magmatic production. This leads us to question our understanding of sub–spreading center dynamics, where we now suggest a portion of locally inverted mantle flow results in hotspots. Such inverted flow presents an alternative mecha- nism to upwelling hot mantle plumes for the generation of excess melt at near-ridge hotspots, i.e., dense downwelling of mantle residue locally increasing the flow of fertile mantle through the melting window. Near-ridge hotspots, therefore, may not require the elevated temperatures commonly invoked to account for excess melting. The pro- posed mechanism also satisfies counterintuitive observations of ridge-bound hotspots at slow- to intermediate-spreading centers, yet not at fast-spreading centers, where large dynamic ridge suction forces likely overwhelm density-driven downwelling.
  • #52etc - 52 Engaging Toolkit Cards for enhancing student engagement

    Turner, Ian, J.; Norton, Stuart; Moody, Jasmine; University of Derby (Advance HE, 2020-12-01)
  • Characterization of a newly fallen Nigerian meteorite

    Gismelssed, Abbasher; Okunola, Olugbenga; Al-Rawas, Ahmed; Yousif, Ali; Oyedokun, Matthew; Adetunji, Jacob; Widatallah, Hisham; Elzai, Mohammed; Sultan Qaboos University, Muscat, Oman; University of Ibadan, Nigeria; et al. (Springer, 2019-12-19)
    X-ray diffraction (XRD), Fields Emission Scanning Electron Microscope (FE-SEM) with EDS and Mössbauer Spectroscopy (MS), were applied to investigate a newly fallen solid piece of debris named the Aba Panu meteorite, after a city in south western Nigeria (Lat: N 08° 14′ 25.7″ and Long: E 003° 33′ 47.0″). Matching X-ray diffraction results, together with the FE-SEM analysis confirms the presence of four kinds of iron-bearing minerals, namely olivine, pyroxene, kamacite (Fe-Ni alloys) and troilite (FeS). The Mössbauer spectra recorded at 295 K and 78 K consist of two strong paramagnetic doublets emanating from olivine of quadrupole splitting 2.9 mm/s and pyroxene of quadrupole splitting 2.1 mm/s. These are superimposed on two magnetic sub-spectra attributed to kamacite and troilite phases. From the Mössbauer sub-spectra absorption area, the ratio of the olivine absorption area to the pyroxene absorption area indicates that the meteorite can be classified as an L-ordinary chondrite. The mole fraction of the Fe end-member of olivine (fayalite) and the orthopyroxene (ferrosilite) calculated from the EDS data will be used to identify the petrographic type of the meteorite.
  • The Effects of High-Grade Metamorphism on Cr-Spinel from the Archean Sittampundi Complex, South India

    Lenaz, Davide; Bidyananda, Maibam; Adetunji, Jacob; Skogby, Henrik; Università degli Studi di Trieste, Trieste, I-34127, Italy; Manipur University, Imphal 795003, India; University of Derby; Swedish Museum of Natural History, SE-10405 Stockholm, Sweden (MDPI AG, 2021-12-03)
    We investigated the crystal and structural behavior of Cr‐bearing spinels from the Ar‐ chean chromitites of Sittampundi (India), which had been subjected to very high‐grade metamor‐ phism. The structural data show that their oxygen positional parameters are among the highest ever recorded for Cr‐bearing spinels with similar Cr# and Mg# and very similar to those found for other Archean occurrences. The general agreement between electron microprobe and Mössbauer data in‐ dicates that the analyzed spinels are stoichiometric. It is therefore most likely that the PH2O and Ptotal values as well as both the oxygen fugacity and the temperature reached during high‐grade meta‐ morphism inhibited the possibility of the non‐stoichiometry of chromites, contrary to what can hap‐ pen in ophiolites, where non‐stoichiometry has recently been documented.

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