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  • Journal article
    Akilan AA, Kumar S, Shaikh MQ, Enneti RK, Atre SVet al., 2023,

    Effects of powder characteristics and chemical composition on the properties of 25Cr7Ni stainless steel fabricated by laser-powder bed fusion and evaluation of process simulation

    , Metals, Vol: 13, Pages: 1-18, ISSN: 2075-4701

    The 25Cr7Ni stainless steel alloy system is gaining increasing interest in the oil and gas industry because of its combination of high strength and corrosion resistance properties. However, very few studies on the effects of starting powder attributes and chemical composition on the as-printed properties of 25Cr7Ni stainless steel fabricated through laser-powder bed fusion (L-PBF) exist in the literature. This study examined the influence of powder attributes and chemical composition on the samples from gas atomized and water atomized 25Cr7Ni stainless steel powders, fabricated through L-PBF, on their as-printed microstructure and properties. The mechanical properties that were examined included ultimate tensile strength (UTS), elongation (%), and hardness. The corrosion behavior was also studied using linear sweep voltammetry in 3.5 wt.% NaCl solution. The evolved phases were characterized using optical and scanning electron microscopy, as well as through X-ray diffraction. The gas atomized powders, with their spherical and uniform morphology, yielded as-printed parts of higher relative densities when compared to water atomized powders, with irregular morphology due to better powder bed compaction. The higher densification obtained in the L-PBF samples from gas atomized powders translated into the highest UTS, hardness, and yield strength among the L-PBF samples from water atomized powders and wrought–annealed 25Cr7Ni stainless steel. The presence of higher amounts of N and Mn in the chemical composition of the gas atomized powders over water atomized powders promoted the presence of retained austenite in the corresponding L-PBF samples. Higher amounts of Mo, combined with austenite content, yielded a higher corrosion resistance in the L-PBF samples from the gas atomized powder than in the L-PBF samples from the water atomized powders. The latter part of the work is focused on the evaluation of simulation parameters for analyzing the fabrication procedure for

  • Journal article
    Vashist V, Banthia N, Kumar S, Agrawal Pet al., 2023,

    A systematic review on materials, design, and manufacturing of swabs

    , Annals of 3D Printed Medicine, Vol: 9, Pages: 1-14, ISSN: 2666-9641

    From simple cleaning to metagenomic studies and now the detection of the SARS-2 virus, swabs are absorbent pads with handles that hold significant promise in several applications and properties. Furthermore, the swab is now used for a wide range of medical purposes, such as the collection of bacteria and other pathogens such as influenza and H1N1. Various designs and materials used for the tip have led to a wide range of applications. In this review, we discuss the characteristics of essential tip materials such as rayon, polyester, nylon, and polyurethane in the context of specimen collection from various substrates. Further, this article reviews swab manufacturing techniques, including injection molding and calendar roll pressing, among others. In recent years, advances in additive manufacturing technology have made it possible to produce swabs in a fast and efficient manner. Furthermore, the design for additive manufacturing (DfAM) is given for the production of swabs. We also examine how 3-D printing of bio-resin swabs has revolutionized the manufacturing process, making it autonomous, quicker, more efficient, and environmentally friendly. Additionally, a shortage of medical devices for testing the SARS-2 virus has zealously motivated the medical industry to revolutionize through additive manufacturing of swabs, thus revolutionizing the medical industry. In conclusion, the limitations of the current techniques and future directions for swabs are discussed.

  • Journal article
    Muxworthy A, Lam C, Green D, Cowan A, Maher B, Gonet Tet al., 2022,

    Magnetic characterisation of London’s airborne nanoparticulate matter

    , Atmospheric Environment, Vol: 287, Pages: 1-8, ISSN: 1352-2310

    Iron-bearing particulate matter produced by vehicle emissions is known to be toxic. To better quantify potential health risks, we have conducted the first magnetic study of a time-series of London's inhalable particulate matter (<10 μm, PM10), captured by three monitoring stations in central London (Marylebone Road, Earl's Court Road and Oxford Street) through 2010 and 2012. We conducted room-temperature analysis on all the samples, and a limited number of samples were analysed at both high and low temperatures. The high-temperature measurements identified magnetite as the dominant magnetic phase. The low-temperature measurements revealed high numbers of nanoparticles, which, assuming magnetite, are in the grain-size range 1–4 nm. It is estimated that as much as ∼40% of the total magnetic signal at 10 K is from particles <4 nm, that are magnetically ‘invisible’ at room-temperature and are being routinely under-estimated in room temperature-based magnetic studies. From the low-temperature measurements, the total concentration of magnetite was estimated at ∼7.5%, significantly higher than previously reported. The room-temperature magnetic data were compared with other pollution data, e.g., NOX and PM10, and meteorological data. Mass-dependent terms like the saturation magnetisation were found to display a strong correlation with NOX and PM10, indicating a common source for these pollutants, i.e., vehicle emissions. Magnetic coercivity measurements, which are independent of abundance, and provide information on grain-size, were consistent across all three sampling localities, again suggesting a major dominant source. Relatively small variations in coercivity were correlated with meteorological events, e.g., temperature and precipitation, suggesting preferential removal of larger airborne grains, i.e., >50 nm.

  • Conference paper
    Kumar S, 2022,

    Design evaluation and performance optimization of an all-wheel drive miniature car capable of torque vectoring

    , ETH Research Symposium
  • Journal article
    Dechezleprêtre A, Gennaioli C, Martin R, Muûls M, Stoerk Tet al., 2021,

    Searching for carbon leaks in multinational companies

    , Journal of Environmental Economics and Management, Vol: 112, ISSN: 0095-0696

    Does a unilateral climate change policy cause companies to shift the location of production, thereby creating carbon leakage? In this paper, we analyze the effect of the European Union Emissions Trading System (EU ETS) on the geographic distribution of carbon emissions by multinational companies. The empirical evidence is based on unique data for the period 2007-2014 from the Carbon Disclosure Project, which tracks the emissions of multinational businesses by geographic region within each company. Because they already operate from multiple locations, multinational firms should be the most prone to carbon leakage. Our data includes the regional emissions of 1,122 companies, of which 261 are subject to EU ETS regulation. We find no evidence that the EU ETS has led to a displacement of carbon emissions from Europe toward the rest of the world, including to countries with lax climate policies and within energy-intensive companies. A large number of robustness checks confirm this finding. Overall, the paper suggests that modest differences in carbon prices between countries do not induce carbon leakage.

  • Journal article
    Price R, Ozkan Y, 2021,

    Characteristics of Imperial College London's COVID‐19 research outputs

    , Learned Publishing, Vol: 34, Pages: 358-369, ISSN: 0953-1513

    We identified 651 research outputs on the topic of COVID‐19 in the form of preprint, report, journal article, dataset, and software/code published by Imperial College London authors between January to September 2020. We sought to understand the distribution of outputs over time by output type, peer review status, publisher, and open access status. Search of Scopus, the institutional repositories, Github, and other databases identified relevant research outputs, which were then combined with Unpaywall open access data and manually‐verified associations between preprints and journal articles. Reports were the earliest output to emerge [median: 103 days, interquartile range (IQR): 57.5–129], but journal articles were the most commonly occurring output type over the entire period (60.8%, 396/651). Thirty preprints were identified as connected to a journal article within the set (15.8%, 30/189). A total of 52 publishers were identified, of which 4 publishers account for 59.6% of outputs (388/651). The majority of outputs were available open access through gold, hybrid, or green route (66.1%, 430/651). The presence of exclusively non‐peer reviewed material from January to March suggests that demand could not be met by journals in this period, and the sector supported this with enhanced preprint services for authors. Connections between preprints and published articles suggests that some authors chose to use both dissemination methods and that, as some publishers also serve across both models, traditional distinctions of output types might be changing. The bronze open access cohort brings widespread ‘free’ access but does not ensure true open access.

  • Journal article
    Brand C, Dons E, Anaya-Boig E, Avila-Palencia I, Clark A, de Nazelle A, Gascon M, Gaupp-Berghausen M, Gerike R, Gotschi T, Iacorossi F, Kahlmeier S, Laeremans M, Nieuwenhuijsen MJ, Orjuela JP, Racioppi F, Raser E, Rojas-Rueda D, Standaert A, Stigell E, Sulikova S, Wegener S, Panis LIet al., 2021,

    The climate change mitigation effects of daily active travel in cities

    , Transportation Research Part D: Transport and Environment, Vol: 93, Pages: 1-18, ISSN: 1361-9209

    Active travel (walking or cycling for transport) is considered the most sustainable form of personal transport. Yet its net effects on mobility-related CO2 emissions are complex and under-researched. Here we collected travel activity data in seven European cities and derived life cycle CO2 emissions across modes and purposes. Daily mobility-related life cycle CO2 emissions were 3.2 kgCO2 per person, with car travel contributing 70% and cycling 1%. Cyclists had 84% lower life cycle CO2 emissions than non-cyclists. Life cycle CO2 emissions decreased by −14% per additional cycling trip and decreased by −62% for each avoided car trip. An average person who ‘shifted travel modes’ from car to bike decreased life cycle CO2 emissions by 3.2 kgCO2/day. Promoting active travel should be a cornerstone of strategies to meet net zero carbon targets, particularly in urban areas, while also improving public health and quality of urban life.

  • Journal article
    Brand C, Gotschi T, Dons E, Gerike R, Anaya-Boig E, Avila-Palencia I, de Nazelle A, Gascon M, Gaupp-Berghausen M, Iacorossi F, Kahlmeier S, Panis LI, Racioppi F, Rojas-Rueda D, Standaert A, Stigell E, Sulikova S, Wegener S, Nieuwenhuijsen MJet al., 2021,

    The climate change mitigation impacts of active travel: Evidence from a longitudinal panel study in seven European cities

    , GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS, Vol: 67, Pages: 1-15, ISSN: 0959-3780

    Active travel (walking or cycling for transport) is considered the most sustainable and low carbon form of getting from A to B. Yet the net effects of changes in active travel on changes in mobility-related CO2 emissions are complex and under-researched. Here we collected longitudinal data on daily travel behavior, journey purpose, as well as personal and geospatial characteristics in seven European cities and derived mobility-related lifecycle CO2 emissions over time and space. Statistical modelling of longitudinal panel (n = 1849) data was performed to assess how changes in active travel, the ‘main mode’ of daily travel, and cycling frequency influenced changes in mobility-related lifecycle CO2 emissions.We found that changes in active travel have significant lifecycle carbon emissions benefits, even in European urban contexts with already high walking and cycling shares. An increase in cycling or walking consistently and independently decreased mobility-related lifecycle CO2 emissions, suggesting that active travel substituted for motorized travel – i.e. the increase was not just additional (induced) travel over and above motorized travel. To illustrate this, an average person cycling 1 trip/day more and driving 1 trip/day less for 200 days a year would decrease mobility-related lifecycle CO2 emissions by about 0.5 tonnes over a year, representing a substantial share of average per capita CO2 emissions from transport. The largest benefits from shifts from car to active travel were for business purposes, followed by social and recreational trips, and commuting to work or place of education. Changes to commuting emissions were more pronounced for those who were younger, lived closer to work and further to a public transport station.Even if not all car trips could be substituted by active travel the potential for decreasing emissions is considerable and significant. The study gives policy and practice the empirical evidence needed to assess climate

  • Journal article
    Corada K, Woodward H, Alaraj H, Collins CM, de Nazelle Aet al., 2021,

    A systematic review of the leaf traits considered to contribute to removal of airborne particulate matter pollution in urban areas

    , Environmental Pollution, Vol: 269, Pages: 1-13, ISSN: 0269-7491

    Global urban planning has promoted green infrastructure (GI) such as street trees, shrubs or other greenspace in order to mitigate air pollution. Although considerable attention has been paid to understanding particulate matter (PM) deposition on GI, there has been little focus on identifying which leaf traits might maximise airborne PM removal. This paper examines existing literature to synthesize the state of knowledge on leaf traits most relevant to PM removal. We systematically reviewed measurement studies that evaluated particulate matter accumulated on leaves on street trees, shrubs green roofs, and green walls, for a variety of leaf traits. Our final selection included 62 papers, most from field studies and a handful from wind tunnel studies. The following were variously promoted as useful traits: coniferous needle leaves; small, rough and textured broadleaves; lanceolate and ovate shapes; waxy coatings, and high-density trichomes. Consideration of these leaf traits, many of which are also associated with drought tolerance, may help to maximise PM capture. Although effective leaf traits were identified, there is no strong or consistent evidence to identify which is the most influential leaf trait in capturing PM. The diversity in sampling methods, wide comparison groups and lack of background PM concentration measures in many studies limited our ability to synthesize results. We found that several ancillary factors contribute to variations in the accumulation of PM on leaves, thus cannot recommend that selection of urban planting species be based primarily on leaf traits. Further research into the vegetation structural features and standardization of the method to measure PM on leaves is needed.

  • Journal article
    Kumar S, Bhattacharjee R, Jeyapandiarajan P, 2021,

    Design and development of longitudinal vehicle dynamics for an All-terrain vehicle

    , MATERIALS TODAY-PROCEEDINGS, Vol: 46, Pages: 8880-8886, ISSN: 2214-7853
  • Journal article
    Kumar S, Rajagopal TKR, 2021,

    Effect of Reynold's number on effective heat transfer dissipation of braking system

    , MATERIALS TODAY-PROCEEDINGS, Vol: 46, Pages: 8455-8460, ISSN: 2214-7853
  • Journal article
    Kia A, Wong H, Cheeseman C, 2019,

    High-strength clogging resistant permeable pavement

    , International Journal of Pavement Engineering, Vol: 22, Pages: 271-282, ISSN: 1029-8436

    Permeable pavement is utilised in order to alleviate flooding in towns, cities and other urban areas, but it is prone to clogging, has relatively low strength and requires regular maintenance. We have developed a novel permeable pavement with low tortuosity pore structure that can be cast on-site that is not only resistant to clogging, but also has high permeability and strength. This high strength clogging resistant permeable pavement (CRP) was prepared by introducing straight pore channels of varying size and number into self-compacting mortar. Samples with porosity ranging from 2 to 32% were tested. In all cases, permeability and compressive strength were substantially higher than conventional permeable concrete. More significantly, CRP can be engineered with low porosity (5%), high strength (> 50 MPa) and high permeability (> 2 cm/s), but does not clog despite extensive cyclic exposure to flow containing sand and clay. A simple method to model the permeability of CRP from the pore structure is described. We report for the first time a high strength clogging resistant permeable pavement capable of retaining sufficient porosity and permeability for storm-water infiltration without requiring frequent maintenance. This innovative system will help alleviate urban flooding and contribute towards a more sustainable urbanisation.

  • Journal article
    Gschwend F, Chambon C, Biedka M, Brandt-Talbot A, Fennell P, Hallett Jet al., 2019,

    Quantitative glucose release from softwood after pretreatment with low-cost ionic liquids

    , Green Chemistry, Vol: 21, Pages: 692-703, ISSN: 1463-9262

    Softwood is an abundantly available feedstock for the bio-based industry, however, achieving cost-effective sugar release is particularly challenging owing to its guaiacyl-only lignin. Here, we report the highly effective pretreatment of the softwood pine (Pinus sylvestris) using ionoSolv pretreatment, a novel ionic liquid-based lignocellulose fractionation technology. Three protic, low-cost ionic liquids, 1-butylimidazolium hydrogen sulfate, triethylammonium hydrogen sulfate and N,N-dimethylbutylammonium hydrogen sulfate, were used to fractionate the biomass into a carbohydrate-rich pulp and a lignin. The carbohydrate-rich pulp was hydrolysed into fermentable sugars by enzymatic saccharification. Under the most successful pretreatment conditions, quantitative glucose release from the pulp was achieved, which equates to a projected glucose release of 464 mg per gram of pine wood entering the process. We further intensified the process by increasing the solid to solvent ratio up to 1:2 g/g while maintaining saccharification yields of 75% of the theoretical maximum. We also demonstrate for the first time that N,N-dimethylbutylammonium hydrogen sulfate, [DMBA][HSO4] is an excellent low-cost pretreatment solvent, surpassing the pretreatment effectiveness of its symmetrically substituted analogue triethylammonium hydrogen sulfate. This shows that ionoSolv pretreatment with protic hydrogen sulfate ionic liquids is a truly feedstock-independent pretreatment option, further increasing the commercial potential of this pretreatment technology.

  • Journal article
    Vineis P, Fecht D, 2018,

    Environment, cancer and inequalities-The urgent need for prevention

    , European Journal of Cancer, Vol: 103, Pages: 317-326, ISSN: 0959-8049

    The proportion of total deaths attributable to environmental factors is estimated to be 23% of global deaths and 22% of global disability-adjusted life years (DALYs) according to one review. These estimates encompass all environmental agents including infectious agents but excluding behavioural factors. The authors of the review also estimated that 16% (95% CI: 7-41%) of cancer deaths are attributable to environmental risk factors (and 36% [95% CI: 17-52%] for lung cancer). In this article, we focus on the reasons why epidemiology is often unable to account for the whole burden of environmental carcinogens. The experience of air pollution is particularly instructive. While in the 1970s and early 1980s, air pollution was considered as a relatively marginal exposure in terms of attributable risks, the most recent estimate is that it accounts for 7.6% of global deaths and 4.2% of global DALYs world-wide (with East and South Asia accounting for 59% of the total). According to a review, ambient fine particulate matter air pollution contributed to 17.1% of ischaemic heart disease, 14.2% of cerebrovascular disease, 16.5% of lung cancer, 24.7% of low respiratory infections, and 27.1% of COPD mortality in 2015. Estimates for cancer as a whole are not available. The change in appreciation of the role of air pollution has been mainly due to the refinement of exposure assessment methods and the new generations of longitudinal studies. Mechanistic evidence via omic technologies is now rapidly increasing, thus lending credibility to previous epidemiological ('black box') associations. Much less is known about other environmental contaminants, some of which are widespread and pervasive, thus suggesting the need for the same rigourous methods as those applied to air pollution. Finally, a crucial issue remains inequality across different population groups, with uneven exposure to hazards and acquired susceptibilities due to multiple concomitant exposures and poorer health status.

  • Journal article
    Bull R, Romanowicz J, Jennings N, Laskari M, Stuart G, Everitt Det al., 2018,

    Competing priorities: lessons in engaging students to achieve energy savings in universities

    , International Journal of Sustainability in Higher Education, Vol: 19, ISSN: 1467-6370

    PurposeThis paper aims to present findings from an EU-funded international student-led energy saving competition (SAVES) on a scale previously unseen. There are multiple accounts of short-term projects and energy saving competitions encouraging pro-environmental behaviour change amongst students in university dormitories, but the purpose of this research is to provide evidence of consistent and sustained energy savings from student-led energy savings competitions, underpinned by practical action.Design/methodology/approachA mixed-methods approach (pre- and post-intervention surveys, focus groups and analysis of energy meter data) was used to determine the level of energy savings and quantifiable behaviour change delivered by students across participating university dormitories.FindingsThis research has provided further insight into the potential for savings and behaviour change in university dormitories through relatively simple actions. Whilst other interventions have shown greater savings, this project provided consistent savings over two years of 7 per cent across a large number of university dormitories in five countries through simple behaviour changes.Research limitations/implicationsAn energy dashboard displaying near a real-time leaderboard was added to the engagement in the second year of the project. Whilst students were optimistic about the role that energy dashboards could play, the evidence is not here to quantify the impact of dashboards. Further research is required to understand the potential of dashboards to contribute to behavioural change savings and in constructing competitions between people and dormitories that are known to each other.Social implicationsSAVES provided engagement with students, enabling, empowering and motivating them to save energy – focusing specifically on the last stage of the “Awareness, Interest, Desire, Action” framework. Automated meter reading data was used in the majority of participating dormitories

  • Journal article
    Chambon C, Mkhize T, Reddy P, Brandt-Talbot A, Deenadayalu N, Fennell P, Hallett Jet al., 2018,

    Pretreatment of South African sugarcane bagasse using a low-cost protic ionic liquid: a comparison of whole, depithed, fibrous and pith bagasse fractions

    , Biotechnology for Biofuels, Vol: 11, ISSN: 1754-6834

    BackgroundSugarcane bagasse is an abundant and geographically widespread agro-industrial residue with high carbohydrate content, making it a strong candidate feedstock for the bio-based economy. This study examines the use of the low-cost protic ionic liquid triethylammonium hydrogen sulfate ([TEA][HSO4]) to fractionate a range of South African sugarcane bagasse preparations into a cellulose-rich pulp and lignin. The study seeks to optimize pretreatment conditions and examine the necessity of applying a depithing step on bagasse prior to pretreatment.ResultsPretreatment of five bagasse preparations, namely whole, industrially depithed, laboratory depithed (short and long fiber) and pith bagasse with [TEA][HSO4]:[H2O] (4:1 w/w) solutions produced highly digestible cellulose-rich pulps, as assessed by residual lignin analysis and enzymatic hydrolysis. Pretreatment under the optimized condition of 120 °C for 4 h produced a pretreated cellulose pulp with up to 90% of the lignin removed and enabled the release of up to 69% glucose contained in the bagasse via enzymatic hydrolysis. Glucose yields from whole and depithed bagasse preparations were very similar. Significant differences in lignin recovery were obtained for laboratory depithed bagasse compared with whole and industrially depithed bagasse. The silica-rich ash components of bagasse were seen to partition mainly with the pulp, from where they could be easily recovered in the post-hydrolysis solids.ConclusionsThe five bagasse preparations were compared but did not show substantial differences in composition or cellulose digestibility after pretreatment. Evidence was presented that a depithing step appears to be unnecessary prior to ionoSolv fractionation, potentially affording significant cost and energy savings. Instead, lignin re-deposition onto the pulp surface (and, in turn, particle size and shape) appeared to be major factors affecting the conditioning of bagasse with the applied IL. We show that pith ba

  • Journal article
    Pierotti L, Schofield SJ, Collett D, Fecht D, De Hoogh K, Hansell AL, Dark J, Cullinan Pet al., 2018,

    Traffic-related air pollution and solid organ transplant failure in Great Britain: A retrospective cohort study

    , Journal of Transport and Health, Vol: 10, Pages: 124-131, ISSN: 2214-1405

    Background: Limited evidence suggests that exposure to traffic related air pollution is associated with graft failure among lung transplant recipients. We explored associations between pollution and transplant failure among lung and other solid organ transplant recipients in Great Britain through a retrospective cohort study. Methods: All patients who received a lung, heart, liver, or kidney transplant between 2000 and 2008 in Great Britain were included, as recorded in the National Health Service Blood and Transplant (NHSBT) register and followed to March 2015. Using residential addresses at time of transplant we calculated distance to nearest (major) road and modelled annual average exposures to airborne nitrogen oxides and particulate matter of diameter ≤10µm and ≤2.5µm for each transplant recipient. All-cause mortality or graft failure (kidney) during follow up was the main outcome; median follow-up was around 10 years for each organ type. We fitted Cox regression models with adjustment for age, sex, year of transplant and donor age/smoking status. Results: 780 lung, 1213 heart, 3650 liver and 11966 graft kidney transplant patients were analysed. We did not find any consistent associations between mortality or graft failure and any of the analysed air pollutants or road metrics. Although, exposure to particulate matter was associated with renal transplant failure in univariable analyses but not after adjustment for confounders. Conclusions: Our analysis does not confirm previously reported associations between traffic-related air pollution exposure and the risk of transplant failure.

  • Journal article
    Yunus IS, Wichmann J, Wördenweber R, Lauersen KJ, Kruse O, Jones PRet al., 2018,

    Synthetic metabolic pathways for photobiological conversion of CO2 into hydrocarbon fuel

    , Metabolic Engineering, Vol: 49, Pages: 201-211, ISSN: 1096-7176

    Liquid fuels sourced from fossil sources are the dominant energy form for mobile transport today. The consumption of fossil fuels is still increasing, resulting in a continued search for more sustainable methods to renew our supply of liquid fuel. Photosynthetic microorganisms naturally accumulate hydrocarbons that could serve as a replacement for fossil fuel, however productivities remain low. We report successful introduction of five synthetic metabolic pathways in two green cell factories, prokaryotic cyanobacteria and eukaryotic algae. Heterologous thioesterase expression enabled high-yield conversion of native fatty acyl-acyl carrier protein (ACP) into free fatty acids (FFA) in Synechocystis sp. PCC 6803 but not in Chlamydomonas reinhardtii where the polar lipid fraction instead was enhanced. Despite no increase in measurable FFA in Chlamydomonas, genetic recoding and over-production of the native fatty acid photodecarboxylase (FAP) resulted in increased accumulation of 7-heptadecene. Implementation of a carboxylic acid reductase (CAR) and aldehyde deformylating oxygenase (ADO) dependent synthetic pathway in Synechocystis resulted in the accumulation of fatty alcohols and a decrease in the native saturated alkanes. In contrast, the replacement of CAR and ADO with Pseudomonas mendocina UndB (so named as it is responsible for 1-undecene biosynthesis in Pseudomonas) or Chlorella variabilis FAP resulted in high-yield conversion of thioesterase-liberated FFAs into corresponding alkenes and alkanes, respectively. At best, the engineering resulted in an increase in hydrocarbon accumulation of 8- (from 1 to 8.5 mg/g cell dry weight) and 19-fold (from 4 to 77 mg/g cell dry weight) for Chlamydomonas and Synechocystis, respectively. In conclusion, reconstitution of the eukaryotic algae pathway in the prokaryotic cyanobacteria host generated the most effective system, highlighting opportunities for mix-and-match synthetic metabolism. These studies describe functioning synt

  • Journal article
    Yunus IS, Jones PR, 2018,

    Photosynthesis-dependent biosynthesis of medium chain-length fatty acids and alcohols

    , Metabolic Engineering, Vol: 49, Pages: 59-68, ISSN: 1096-7176

    Cyanobacteria can directly channel atmospheric CO2 into a wide range of versatile carbon products such as fatty acids and fatty alcohols with applications including fuel, cosmetics, and health products. Works on alcohol production in cyanobacteria have so far focused on either long (C12-C18) or short (C2-C4) chain-length products. In the present work, we report the first synthetic pathway for 1-octanol (C8) biosynthesis in Synechocystis sp. PCC 6803, employing a carboxylic acid reductase and C8-preferring fatty acyl-ACP thioesterase. The first engineered strain produced 1-octanol but exhibited poor productivity and cellular health issues. We therefore proceeded to systematically optimize the strain and cultivation conditions in order to understand what the limiting factors were. The identification of optimal promoters and ribosomal binding sites, in combination with isopropyl myristate solvent overlay, resulted in a combined (C8-OH and C10-OH) titer of more than 100 mg/L (a 25-fold improvement relative to the first engineered strain) and a restoration of cellular health. Additionally, more than 905 mg/L 1-octanol was produced when the strain expressing sfp (phosphopantetheinyl transferase) and car (carboxylic acid reductase) was fed with octanoic acid. A combination of feeding experiments and protein quantification indicated that the supply of octanoic acid from the introduced thioesterase, and possibly also native fatty acid synthesis pathway, were the main bottlenecks of the pathway.

  • Journal article
    Gschwend FJV, Brandt-Talbot A, Malaret FJ, Shinde S, Hallett JPet al., 2018,

    Rapid pretreatment of Miscanthus using the low-cost ionic liquid triethylammonium hydrogen sulfate at elevated temperatures

    , Green Chemistry, Vol: 20, Pages: 3486-3498, ISSN: 1463-9262

    Deconstruction with low-cost ionic liquids (ionoSolv) is a promising method to pre-condition lignocellulosic biomass for the production of renewable fuels, materials and chemicals. This study investigated process intensification strategies for the ionoSolv pretreatment of Miscanthus X giganteus using the low-cost ionic liquid triethylammonium hydrogen sulfate ([TEA][HSO4]) in the presence of 20 wt% water, using high temperatures and a high solid to solvent loading of 1:5 g/g. The temperatures investigated were 150, 160, 170 and 180°C. We discuss the effect of pretreatment temperature on lignin and hemicellulose removal, cellulose degradation and enzymatic saccharification yields. We report that very good fractionation can be achieved across all investigated temperatures, including an enzymatic saccharification yield exceeding 75% of the theoretical maximum after only 15 min of treatment at 180°C. We further characterised the recovered lignins which established some tunability of the hydroxyl group content, subunit composition, connectivity and molecular weight distribution in the isolated lignin while maintaining maximum saccharification yield. This drastic reduction of pretreatment time at increased biomass loading without a yield penalty is promising for the development of a commercial ionoSolv pretreatment process.

  • Journal article
    Tonne C, Milà C, Fecht D, Alvarez M, Gulliver J, Smith J, Beevers S, Ross Anderson H, Kelly Fet al., 2018,

    Socioeconomic and ethnic inequalities in exposure to air and noise pollution in London

    , Environment International, Vol: 115, Pages: 170-179, ISSN: 0160-4120

    BACKGROUND: Transport-related air and noise pollution, exposures linked to adverse health outcomes, varies within cities potentially resulting in exposure inequalities. Relatively little is known regarding inequalities in personal exposure to air pollution or transport-related noise. OBJECTIVES: Our objectives were to quantify socioeconomic and ethnic inequalities in London in 1) air pollution exposure at residence compared to personal exposure; and 2) transport-related noise at residence from different sources. METHODS: We used individual-level data from the London Travel Demand Survey (n = 45,079) between 2006 and 2010. We modeled residential (CMAQ-urban) and personal (London Hybrid Exposure Model) particulate matter <2.5 μm and nitrogen dioxide (NO2), road-traffic noise at residence (TRANEX) and identified those within 50 dB noise contours of railways and Heathrow airport. We analyzed relationships between household income, area-level income deprivation and ethnicity with air and noise pollution using quantile and logistic regression. RESULTS: We observed inverse patterns in inequalities in air pollution when estimated at residence versus personal exposure with respect to household income (categorical, 8 groups). Compared to the lowest income group (<£10,000), the highest group (>£75,000) had lower residential NO2 (-1.3 (95% CI -2.1, -0.6) μg/m3 in the 95th exposure quantile) but higher personal NO2 exposure (1.9 (95% CI 1.6, 2.3) μg/m3 in the 95th quantile), which was driven largely by transport mode and duration. Inequalities in residential exposure to NO2 with respect to area-level deprivation were larger at lower exposure quantiles (e.g. estimate for NO2 5.1 (95% CI 4.6, 5.5) at quantile 0.15 versus 1.9 (95% CI 1.1, 2.6) at quantile 0.95), reflecting low-deprivation, high residential NO2 areas in the city centre. Air pollution exposure at residence consistently overestimated personal exposure; this overestimation varied with age

  • Report
    Pimpin L, Retat L, Fecht D, de Preux LB, Sassi F, Gulliver J, Belloni A, Ferguson B, Corbould E, Jaccard A, Webber Let al., 2018,

    Estimation of costs to the NHS and social care due to the health impacts of air pollution

  • Journal article
    Fellenor JF, Barnett J, Potter C, Urquhart J, Mumford JD, Quine CPet al., 2018,

    The social amplification of risk on Twitter: the case of ash dieback disease in the United Kingdom

    , Journal of Risk Research, Vol: 21, Pages: 1163-1183, ISSN: 1466-4461

    It has long been recognised that the traditional media play a key role in representing risk and are a significant source of information which can shape how people perceive and respond to hazard events. Early work utilising the social amplification of risk framework (SARF) sought to understand the discrepancy between expert and lay perceptions of risk and patterns of risk intensification and attenuation with reference to the media. However, the advent of Web 2.0 challenges traditional models of communication. To date there has been limited consideration of social media within the SARF and its role in mediating processes of risk perception and communication. Against this backdrop, we focus on the social media platform Twitter to consider the social amplification of risk in relation to ash dieback disease (Hymenoscyphus fraxineus); a tree health issue that attracted intense media attention when it was first identified in the UK in 2012. We present an empirical analysis of 25,600 tweets in order to explore what people were saying about ash dieback on Twitter, who was talking about it and how they talked about it. Our discussion outlines the themes around which talk about ash dieback was orientated, the significance of users’ environmental ‘affiliations’ and the role of including links (URLs) to traditional media coverage. We utilise the notion of ‘piggybacking’ to demonstrate how information is customised in line with group/individual identities and interests and introduce the concept of the ‘frame fragment’ to illustrate how information is selected and moved around Twitter emphasising certain features of the messages. The paper affords a detailed consideration of the way in which people and organisations simultaneously appropriate, construct and pass on risk-relevant information. A conclusion is that social media has the potential to transform the media landscape within which the SARF was originally conceived, presenting renewe

  • Journal article
    Williams ML, Lott MC, Kitwiroon N, Dajnak D, Walton H, Holland M, Pye S, Fecht D, Toledano MB, Beevers SDet al., 2018,

    The Lancet Countdown on health benefits from the UK Climate Change Act

    , a modelling study for Great Britain, Vol: 2, Pages: e202-e213, ISSN: 2542-5196

    Background Climate change poses a dangerous and immediate threat to the health of populations in the UK and worldwide. We aimed to model different scenarios to assess the health co-benefits that result from mitigation actions. Methods In this modelling study, we combined a detailed techno-economic energy systems model (UK TIMES), air pollutant emission inventories, a sophisticated air pollution model (Community Multi-scale Air Quality), and previously published associations between concentrations and health outcomes. We used four scenarios and focused on the air pollution implications from fine particulate matter (PM2·5), nitrogen dioxide (NO2) and ozone. The four scenarios were baseline, which assumed no further climate actions beyond those already achieved and did not meet the UK's Climate Change Act (at least an 80% reduction in carbon dioxide equivalent emissions by 2050 compared with 1990) target; nuclear power, which met the Climate Change Act target with a limited increase in nuclear power; low-greenhouse gas, which met the Climate Change Act target without any policy constraint on nuclear build; and a constant scenario that held 2011 air pollutant concentrations constant until 2050. We predicted the health and economic impacts from air pollution for the scenarios until 2050, and the inequalities in exposure across different socioeconomic groups. Findings NO2 concentrations declined leading to 4 892 000 life-years saved for the nuclear power scenario and 7 178 000 life-years saved for the low-greenhouse gas scenario from 2011 to 2154. However, the associations that we used might overestimate the effects of NO2 itself. PM2·5 concentrations in Great Britain are predicted to decrease between 42% and 44% by 2050 compared with 2011 in the scenarios that met the Climate Change Act targets, especially those from road traffic and off-road machinery. These reductions in PM2·5 are tempered by a 2035 peak (and subsequent decline) in biomass (wood bu

  • Journal article
    Smith RB, Fecht D, Gulliver J, Beevers S, Dajnak D, Blangiardo M, Ghosh R, Hansell A, Kelly F, Anderson HR, Toledano MBet al., 2017,

    Impact of London's road traffic air and noise pollution on birth weight: retrospective population based cohort study

    , BMJ, Vol: 359, ISSN: 1756-1833

    Objective To investigate the relation between exposure to both air and noise pollution from road traffic and birth weight outcomes.Design Retrospective population based cohort study.Setting Greater London and surrounding counties up to the M25 motorway (2317 km2), UK, from 2006 to 2010.Participants 540 365 singleton term live births.Main outcome measures Term low birth weight (LBW), small for gestational age (SGA) at term, and term birth weight.Results Average air pollutant exposures across pregnancy were 41 μg/m3 nitrogen dioxide (NO2), 73 μg/m3 nitrogen oxides (NOx), 14 μg/m3 particulate matter with aerodynamic diameter <2.5 μm (PM2.5), 23 μg/m3 particulate matter with aerodynamic diameter <10 μm (PM10), and 32 μg/m3 ozone (O3). Average daytime (LAeq,16hr) and night-time (Lnight) road traffic A-weighted noise levels were 58 dB and 53 dB respectively. Interquartile range increases in NO2, NOx, PM2.5, PM10, and source specific PM2.5 from traffic exhaust (PM2.5 traffic exhaust) and traffic non-exhaust (brake or tyre wear and resuspension) (PM2.5 traffic non-exhaust) were associated with 2% to 6% increased odds of term LBW, and 1% to 3% increased odds of term SGA. Air pollutant associations were robust to adjustment for road traffic noise. Trends of decreasing birth weight across increasing road traffic noise categories were observed, but were strongly attenuated when adjusted for primary traffic related air pollutants. Only PM2.5 traffic exhaust and PM2.5 were consistently associated with increased risk of term LBW after adjustment for each of the other air pollutants. It was estimated that 3% of term LBW cases in London are directly attributable to residential exposure to PM2.5>13.8 μg/m3during pregnancy.Conclusions The findings suggest that air pollution from road traffic in London is adversely affecting fetal growth. The results suggest little evidence for an independent exposure-response effect of traffic related noise on b

  • Journal article
    Parrenin F, Cavitte MGP, Blankenship DD, Chappellaz J, Fischer H, Gagliardini O, Masson-Delmotte V, Passalacqua O, Ritz C, Siegert MJ, Roberts J, Young DAet al., 2017,

    Is there 1.5 million-year old ice near Dome C, Antarctica?

    , The Cryosphere, Vol: 11, Pages: 2427-2437, ISSN: 1994-0416

    Ice sheets provide exceptional archives of past changes in polar climate, regional environment and global atmospheric composition. The oldest dated deep ice core drilled in Antarctica has been retrieved at EPICA Dome C (EDC), reaching ∼ 800 000 years. Obtaining an older paleoclimatic record from Antarctica is one of the greatest challenges of the ice core community. Here, we use internal isochrones, identified from airborne radar coupled to ice-flow modelling to estimate the age of basal ice along transects in the Dome C area. Three glaciological properties are inferred from isochrones: surface accumulation rate, geothermal flux and the exponent of the Lliboutry velocity profile. We find that old ice (> 1.5 Myr, 1.5 million years) likely exists in two regions: one ∼ 40 km south-west of Dome C along the ice divide to Vostok, close to a secondary dome that we name Little Dome C (LDC), and a second region named North Patch (NP) located 10–30 km north-east of Dome C, in a region where the geothermal flux is apparently relatively low. Our work demonstrates the value of combining radar observations with ice flow modelling to accurately represent the true nature of ice flow, and understand the formation of ice-sheet architecture, in the centre of large ice sheets.

  • Book chapter
    Gschwend FJV, Brandt-Talbot A, Chambon CL, Hallett JPet al., 2017,

    Ultra-Low Cost Ionic Liquids for the Delignification of Biomass

    , Ionic Liquids: Current State and Future Directions, Editors: Shiflett, Scurto, Publisher: American Chemical Society, Pages: 209-223, ISBN: 9780841232136

    Low-cost pretreatment of lignocellulosic biomass is an essential next step toward large-scale deployment as renewable liquid fuels, materials or chemicals. Ionic liquids (ILs) are highly effective at pretreatment, but high IL cost has hindered commercial viability. We have recently developed low-cost (ca. $1/kg) ILs, such as triethylammonium hydrogen sulphate, for pretreatment. In this chapter we discuss the fractionation of the grass Miscanthus x giganteus, wherein we deconstruct the lignocellulosic matrix into a cellulose-rich pulp, a recovered lignin fraction and an organic distillate. More than 80% of the lignin and quantitative hemicelluloses are removed during extraction. This results in 70-90% glucose release during enzymatic saccharification. The IL can also be successfully recovered and reused, with >99% IL recovery and minimal effects on efficiency of extraction. A detailed mass balance of all components and subsequent economic analysis revealed this efficient pretreatment with an ultra-low cost IL could result in an economically viable pretreatment process.

  • Journal article
    Morlighem M, Williams C, Rignot E, An L, Bamber J, Chauche N, Dowdeswell J, Dorschel B, Holland DM, Holland D, Howat I, Hubbard A, Jordan T, Millan R, Mouginot J, Noel B, OCofaigh C, Seroussi H, Siegert M, Slabon P, van den Broeke M, Weinrebe Wet al., 2017,

    BedMachine v3: Complete bed topography and ocean bathymetry mapping of Greenland from multi-beam radar sounding combined with mass conservation

    , Geophysical Research Letters, Vol: 44, Pages: 11,051-11,061, ISSN: 0094-8276

    Greenland’s bed topography is a primary control on ice flow, grounding line migration,calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warmAtlantic water (AW) that rapidly melts and undercuts Greenland’s marine-terminating glaciers. Here wepresent a new compilation of Greenland bed topography that assimilates seafloor bathymetry and icethickness data through a mass conservation approach. A new 150 m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface, yieldingmajor improvements over previous data sets, particularly in the marine-terminating sectors of northwestand southeast Greenland. Our map reveals that the total sea level potential of the Greenland ice sheetis 7.42 ± 0.05 m, which is 7 cm greater than previous estimates. Furthermore, it explains recent calvingfront response of numerous outlet glaciers and reveals new pathways by which AW can access glacierswith marine-based basins, thereby highlighting sectors of Greenland that are most vulnerable to futureoceanic forcing.

  • Journal article
    Cai Y, Hodgson S, Blangiardo M, Gulliver J, Morley D, Vienneau D, de Hoogh K, Key T, Hveem K, Elliott P, Hansell Aet al., 2017,

    Road traffic noise and incident cardiovascular disease: a joint analysis of HUNT, EPIC-Oxford and UK Biobank

    , ICBEN 2017 Proceedings

    Aims: This study aimed to investigate the effects of long-term exposure to road traffic noise on incident CVD in three large cohorts: HUNT, EPIC-Oxford and UK Biobank. Methods: In a complete-case sample (N=361,699), 4,014 IHD and 2,109 cerebrovascular incident cases were ascertained between baseline (1993-2010) and end of follow-up (2008-2015) through medical record linkage. Annual mean road traffic noise exposure was modelled at baseline address. Individual-level covariate data were harmonised and data were pooled. Analyses used Cox proportional hazards model with adjustments for confounders, including air pollution. Results: For an interquartile range (IQR) (3.9 dBA) higher daytime noise, a non-significant association with incident IHD was seen (Hazard ratio (HR): 1.015, 95% Confidence Interval (CI): 0.989-1.042), fully adjusted. Statistically significant associations and interaction terms were seen in obese individuals (HR: 1.099, 95%CI: 1.029-1.174), and current-smokers (HR: 1.054, 95%CI: 1.007-1.103). No associations were found for ischemic or hemorrhagic stroke. Conclusions: Our study strengthens the evidence base for an effect of road traffic noise on incident IHD, whilst the association with incident stroke remains unclear.

  • Journal article
    Graham F, Roberts J, Galton-Fenzi B, Young D, Blankenship D, Siegert MJet al., 2017,

    A high-resolution synthetic bed elevation grid of the Antarctic continent

    , Earth System Science Data, Vol: 9, Pages: 267-279, ISSN: 1866-3516

    Digital elevation models of Antarctic bed topography are smoothed and interpolated onto low-resolution ( > 1 km) grids as current observed topography data are generally sparsely and unevenly sampled. This issue has potential implications for numerical simulations of ice-sheet dynamics, especially in regions prone to instability where detailed knowledge of the topography, including fine-scale roughness, is required. Here, we present a high-resolution (100 m) synthetic bed elevation terrain for Antarctica, encompassing the continent, continental shelf, and seas south of 60° S. Although not identically matching observations, the synthetic bed surface – denoted as HRES – preserves topographic roughness characteristics of airborne and ground-based ice-penetrating radar data measured by the ICECAP (Investigating the Cryospheric Evolution of the Central Antarctic Plate) consortium or used to create the Bedmap1 compilation. Broad-scale ( > 5 km resolution) features of the Antarctic landscape are incorporated using a low-pass filter of the Bedmap2 bed elevation data. HRES has applicability in high-resolution ice-sheet modelling studies, including investigations of the interaction between topography, ice-sheet dynamics, and hydrology, where processes are highly sensitive to bed elevations and fine-scale roughness. The data are available for download from the Australian Antarctic Data Centre (doi:10.4225/15/57464ADE22F50).

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