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  • Journal article
    Zhu Z, Piao S, Myneni RB, Huang M, Zeng Z, Canadell JG, Ciais P, Sitch S, Friedlingstein P, Arneth A, Cao C, Cheng L, Kato E, Koven C, Li Y, Lian X, Liu Y, Liu R, Mao J, Pan Y, Peng S, Peñuelas J, Poulter B, Pugh TAM, Stocker BD, Viovy N, Wang X, Wang Y, Xiao Z, Yang H, Zaehle S, Zeng Net al., 2016,

    Greening of the Earth and its drivers

    , Nature Climate Change, Vol: 6, Pages: 791-795, ISSN: 1758-678X

    Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning of the Earth system and provision of ecosystem services1, 2. Yet how global vegetation is responding to the changing environment is not well established. Here we use three long-term satellite leaf area index (LAI) records and ten global ecosystem models to investigate four key drivers of LAI trends during 1982–2009. We show a persistent and widespread increase of growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows decreasing LAI (browning). Factorial simulations with multiple global ecosystem models suggest that CO2 fertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition (9%), climate change (8%) and land cover change (LCC) (4%). CO2 fertilization effects explain most of the greening trends in the tropics, whereas climate change resulted in greening of the high latitudes and the Tibetan Plateau. LCC contributed most to the regional greening observed in southeast China and the eastern United States. The regional effects of unexplained factors suggest that the next generation of ecosystem models will need to explore the impacts of forest demography, differences in regional management intensities for cropland and pastures, and other emerging productivity constraints such as phosphorus availability.

  • Journal article
    Ruenraromgsak P, Chen S, Hu S, Melbourne J, Sweeney S, Thorley AJ, Skepper JN, Shaffer MSP, Tetley TD, Porter AEet al., 2016,

    Translocation of functionalized multi-walled carbon nanotubes across human pulmonary alveolar epithelium: dominant role of epithelial type 1 cells

    , ACS Nano, Vol: 10, Pages: 5070-5085, ISSN: 1936-086X

    Uptake and translocation of short functionalized multi-walled carbon nanotubes (short-fMWCNTs) through the pulmonary respiratory epithelial barrier depend on physicochemical property and cell type. Two monoculture models, immortalized human alveolar epithelial type 1 (TT1) cells and primary human alveolar epithelial type 2 cells (AT2), which constitute the alveolar epithelial barrier, were employed to investigate the uptake and transport of 300 and 700 nm in length, poly(4-vinylpyridine)-functionalized, multi-walled carbon nanotubes (p(4VP)-MWCNTs) using quantitative imaging and spectroscopy techniques. The p(4VP)-MWCNT exhibited no toxicity on TT1 and AT2 cells, but significantly decreased barrier integrity (*p < 0.01). Uptake of p(4VP)-MWCNTs was observed in 70% of TT1 cells, correlating with compromised barrier integrity and basolateral p(4VP)-MWCNT translocation. There was a small but significantly greater uptake of 300 nm p(4VP)-MWCNTs than 700 nm p(4VP)-MWCNTs by TT1 cells. Up to 3% of both the 300 and 700 nm p(4VP)-MWCNTs reach the basal chamber; this relatively low amount arose because the supporting transwell membrane minimized the amount of p(4VP)-MWCNT translocating to the basal chamber, seen trapped between the basolateral cell membrane and the membrane. Only 8% of AT2 cells internalized p(4VP)-MWCNT, accounting for 17% of applied p(4VP)-MWCNT), with transient effects on barrier function, which initially fell then returned to normal; there was no MWCNT basolateral translocation. The transport rate was MWCNT length modulated. The comparatively lower p(4VP)-MWCNT uptake by AT2 cells is proposed to reflect a primary barrier effect of type 2 cell secretions and the functional differences between the type 1 and type 2 alveolar epithelial cells.

  • Journal article
    Gulliver J, de Hoogh K, Hoek G, Vienneau D, Fecht D, Hansell Aet al., 2016,

    Back-extrapolated and year-specific NO2 land use regression models for Great Britain - Do they yield different exposure assessment?

    , Environment International, Vol: 92-93, Pages: 202-209, ISSN: 1873-6750

    Robust methods to estimate historic population air pollution exposures are important tools for epidemiological studies evaluating long-term health effects. We developed land use regression (LUR) models for NO2 exposure in Great Britain for 1991 and explored whether the choice of year-specific or back-extrapolated LUR yields 1) similar LUR variables and model performance, and 2) similar national and regional address-level and small-area concentrations. We constructed two LUR models for 1991using NO2 concentrations from the diffusion tube monitoring network, one using 75% of all available measurement sites (that over-represent industrial areas), and the other using 75% of a subset of sites proportionate to population by region to study the effects of monitoring site selection bias. We compared, using the remaining (hold-out) 25% of monitoring sites, the performance of the two 1991 models with back-extrapolation of a previously published 2009 model, developed using NO2 concentrations from automatic chemiluminescence monitoring sites and predictor variables from 2006/2007. The 2009 model was back-extrapolated to 1991 using the same predictors (1990 & 1995) used to develop 1991 models. The 1991 models included industrial land use variables, not present for 2009. The hold-out performance of 1991 models (mean-squared-error-based-R2: 0.62–0.64) was up to 8% higher and ~ 1 μg/m3 lower in root mean squared error than the back-extrapolated 2009 model, with best performance from the subset of sites representing population exposures. Year-specific and back-extrapolated exposures for residential addresses (n = 1.338,399) and small areas (n = 10.518) were very highly linearly correlated for Great Britain (r > 0.83). This study suggests that year-specific model for 1991 and back-extrapolation of the 2009 LUR yield similar exposure assessment.

  • Journal article
    Siegert MJ, 2016,

    A wide variety of unique environments beneath the Antarcticice sheet

    , Geology, Vol: 44, Pages: 399-400, ISSN: 0091-7613

    It is 20 years since subglacial Lake Vostok in central East Antarcticawas found to be one of the world’s largest freshwater bodies (Kapitsa et al.,1996). It was hypothesized to be both an ancient, extreme yet viable environmentfor microbial life, and a recorder of past climate change. Testingthese hypotheses is possible with direct measurement and sampling, butin-situ examination is challenging because of the thick ice to drill through,the necessary cleanliness required of the experiment, and the extremepolar conditions in which to operate. In this issue of Geology, Michaudet al. (2016, p. 347) report on water and sedimentary material collectedin January 2013 from Lake Whillans, a component of the hydrologicalsystem beneath Whillans ice stream in West Antarctica. They reveal thewater comprises melted basal ice and a small proportion of seawater, theconcentration of which increases with sediment depth, making it uniqueamong known subglacial environments within and outside of Antarctica.Here, to place the Lake Whillans work in context, I discuss the range ofAntarctic subglacial lake environments, showing the continent to containan assortment of systems in which novel physical, chemical, and biologicalprocesses may take place.

  • Journal article
    Green RJ, Staffell, 2016,

    Electricity in Europe: exiting fossil fuels?

    , Oxford Review of Economic Policy, Vol: 32, Pages: 282-303, ISSN: 1460-2121

    There are many options for generating electricity with low carbon emissions, and the electrification of heatand transport can decarbonise energy use across the economy. This places the power sector at the forefrontof any move away from fossil fuels, even though fossil-fuelled generators are more dependable and flexiblethan nuclear reactors or intermittent renewables, and vital for the second-by-second balancing of supply anddemand. Renewables tend to supplement, rather than replace, fossil capacity, although output from fossilfuelledstations will fall and some will have to retire to avoid depressing wholesale power prices. At times oflow demand and high renewable output prices can turn negative, but electricity storage, long-distanceinterconnection and flexible demand may develop to absorb any excess generation. Simulations for GreatBritain show that while coal may be eliminated from the mix within a decade, natural gas has a long-termrole in stations with or without carbon capture and storage, depending on its cost and the price of carbon.

  • Journal article
    Prat-Guitart N, Rein G, Hadden RM, Belcher CM, Yearsley JMet al., 2016,

    Effects of spatial heterogeneity in moisture content on the horizontal spread of peat fires

    , Science of the Total Environment, Vol: 572, Pages: 1422-1430, ISSN: 0048-9697

    The gravimetric moisture content of peat is the main factor limiting the ignition and spread propagation of smouldering fires. Our aim is to use controlled laboratory experiments to better understand how the spread of smouldering fires is influenced in natural landscape conditions where the moisture content of the top peat layer is not homogeneous. In this paper, we study for the first time the spread of peat fires across a spatial matrix of two moisture contents (dry/wet) in the laboratory. The experiments were undertaken using an open-top insulated box (22. ×. 18. ×. 6. cm) filled with milled peat. The peat was ignited at one side of the box initiating smouldering and horizontal spread. Measurements of the peak temperature inside the peat, fire duration and longwave thermal radiation from the burning samples revealed important local changes of the smouldering behaviour in response to sharp gradients in moisture content. Both, peak temperatures and radiation in wetter peat (after the moisture gradient) were sensitive to the drier moisture condition (preceding the moisture gradient).Drier peat conditions before the moisture gradient led to higher temperatures and higher radiation flux from the fire during the first 6. cm of horizontal spread into a wet peat patch. The total spread distance into a wet peat patch was affected by the moisture content gradient. We predicted that in most peat moisture gradients of relevance to natural ecosystems the fire self-extinguishes within the first 10. cm of horizontal spread into a wet peat patch. Spread distances of more than 10. cm are limited to wet peat patches below 160% moisture content (mass of water per mass of dry peat). We found that spatial gradients of moisture content have important local effects on the horizontal spread and should be considered in field and modelling studies.

  • Journal article
    Shevchenko I, Berloff P, Guerrero-López D, Roman Jet al., 2016,

    On low-frequency variability of the midlatitude ocean gyres

    , Journal of Fluid Mechanics, Vol: 795, Pages: 423-442, ISSN: 1469-7645

    This paper studies the large-scale low-frequency variability of the wind-driven midlatitude ocean gyres and their western boundary currents, such as the Gulf Stream or Kuroshio, simulated with the eddy-resolving quasi-geostrophic model. We applied empirical orthogonal functions analysis to turbulent flow solutions and statistically extracted robust and significant large-scale decadal variability modes concentrated around the eastward jet extension of the western boundary currents. In order to interpret these statistical modes dynamically, we linearized the governing quasi-geostrophic equations around the time-mean circulation and solved for the corresponding full set of linear eigenmodes with their eigenfrequencies. We then projected the extracted decadal variability on the eigenmodes and found that this variability is a multimodal coherent pattern phenomenon rather than a single mode or a combination of several modes as in the flow regimes preceding developed turbulence.

  • Journal article
    Mawhood RK, Gazis E, de Jong S, Hoefnagels R, Slade Ret al., 2016,

    Production pathways for renewable jet fuel: a review of commercialisation status and future prospects

    , Biofuels, Bioproducts and Biorefining, Vol: 10, Pages: 462-484, ISSN: 1932-1031

    Aviation is responsible for an increasing share of anthropogenic CO2 emissions.Decarbonisation to 2050 is expected to rely on renewable jet fuel (RJF) derived frombiomass, but this represents a radical departure from the existing regime of petroleumbasedfuels. Increased market deployment will require significant cost reductions, alongsideadaptation of existing supply chains and infrastructure.This article maps development and manufacturing efforts for six RJF production pathwaysexpected to reach commercialisation in the next 5-10 years. A Rapid Evidence Assessmentwas conducted to evaluate the technological and commercial maturity of each pathway andprogress towards international certification, using the Commercial Aviation Alternative FuelsInitiative’s Fuel Readiness Level (FRL) framework. Planned and operational facilities havebeen catalogued alongside partnerships with the aviation industry. Policy and economicfactors likely to affect future development and deployment are considered.Hydroprocessed Esters and Fatty Acids (FRL 9) is the most developed pathway. It is ASTMcertified, has fuelled the majority of RJF flights to date, and is produced at threecommercial-scale facilities. Fischer-Tropsch derived fuels are moving towards the start-up offirst commercial facilities (FRL 7-8), although widespread deployment seems unlikely undercurrent market conditions. The Direct Sugars to Hydrocarbons conversion pathway (FRL 5-7)is being championed by Amyris and Total in Brazil, but has yet to be demonstrated at scale.Other pathways are in the demonstration and pilot phases (FRL 4-6).Despite growing interest in RJF, demand and production volumes remain negligible.Development of supportive policy is likely to be critical to future deployment.

  • Journal article
    Alonso Alvarez D, Ekins-Daukes N, 2016,

    Photoluminescence-Based Current-Voltage Characterisation Of Individual Subcells In Multi-Junction Devices

    , IEEE Journal of Photovoltaics, Vol: 6, Pages: 1004-1011, ISSN: 2156-3381

    We demonstrate a photoluminescence based,contactless method to determine the current-voltagecharacteristics of the individual subcells in a multi-junctionsolar cell. The method relies upon the reciprocity relationbetween the absorption and emission properties on a solarcell. Laser light with a suitable energy is used to excitecarriers selectively in one junction and the internal voltagesare deduced from the intensity of the resultingluminescence. The IV curves obtained this way on 1J, 2Jand 6J devices are compared to those obtained usingelectroluminescence. Good agreement is obtained at highinjection conditions while discrepancies at low injection areattributed to in-plane carrier transport.

  • Journal article
    Scheelbeek PFD, Chowdhury MAH, Haines A, Alam A, Hoque MA, Butler AP, Khan AE, Mojumder SK, Blangiardo MAG, Elliott P, Vineis Pet al., 2016,

    High concentrations of sodium in drinking water and raised blood pressure in coastal deltas affected by episodic seawater inundations

    , Lancet Global Health, Vol: 4, ISSN: 2214-109X

    Background In times of seawater inundation in coastal deltas, unprotected drinking water sources, such as ponds andshallow tube wells, take on salt water with each inundation. Daily consumption of these saline sources contributes tooverall sodium intake. Although there is evidence that a high dietary salt intake is an important risk factor forhypertension, little is known about the eff ect of high concentrations of sodium in drinking water on populationhealth. In this longitudinal study, we aimed to measure the eff ect of high concentrations of sodium in drinking wateron blood pressure and to assess the reversibility of raised blood pressure when conventional drinking water sourceswere replaced by low-saline water.Methods We used a multistage sampling process to recruit participants aged 18 years or older from the salinityaffectedsub-districts of Dacope, Batiagatha, and Paikgatchha in coastal Bangladesh. Most participants consumeddrinking water from highly saline sources, such as ponds and tube-wells, while a small percentage had access torainwater. In March, 2013, we recorded: baseline concentrations of sodium in drinking water; participants’ bloodpressure; and personal, lifestyle, and environmental characteristics. During the study period, some study participantsgained access to low-saline drinking water alternatives that were installed for use in the dry season, when water fromponds becomes more saline. In March, 2014, and May, 2014, we made follow-up assessments of drinking watersodium, blood pressure, and repeated the questionnaire about personal, lifestyle, and environmental characteristics.We used generalised linear mixed methods to model the eff ect of drinking water sodium on blood pressure andassess reversibility of raised blood pressure when participants switched from conventional drinking water sources tolow-saline alternatives.Findings We included data from 581 participants in analysis, of which 277 (48%) were male. Median age was 38 years(IQR 30&

  • Journal article
    Curtin OJ, Yoshida M, Pusch A, Hylton NP, Ekins-Daukes NJ, Phillips CC, Hess Oet al., 2016,

    Quantum cascade photon ratchets for intermediate band solar cells

    , IEEE Journal of Photovoltaics, Vol: 6, Pages: 673-678, ISSN: 2156-3381

    We propose an antimonide-based quantum cascade design to demonstrate the ratchet mechanism for incorporation into the recently suggested photon ratchet intermediate-band solar cell. We realize the photon ratchet as a semiconductor heterostructure in which electrons are optically excited into an intermediate band and spatially decoupled from the valence band through a type-II quantum cascade. This process reduces both radiative and nonradiative recombination and can thereby increase the solar cell efficiency over intermediate-band solar cells. Our design method uses an adaptive simulated annealing genetic algorithm to determine the optimum thicknesses of semiconductor layers in the quantum cascade, allowing efficient transport (via phonon emission) of the electrons away from the interband active region.

  • Journal article
    Leese HS, Govada L, Saridakis E, Khurshid S, Menzel R, Morishita T, Clancy ARJ, White E, Chayen NE, Shaffer MSPet al., 2016,

    Reductively PEGylated carbon nanomaterials andtheir use to nucleate 3D protein crystals:a comparison of dimensionality

    , Chemical Science, Vol: 7, Pages: 2916-2923, ISSN: 2041-6539

    A range of carbon nanomaterials, with varying dimensionality, were dispersed by a non-damaging and versatile chemical reduction route, and subsequently grafted by reaction with methoxy polyethylene glycol (mPEG) monobromides. The use of carbon nanomaterials with different geometries provides both a systematic comparison of surface modification chemistry and the opportunity to study factors affecting specific applications. Multi-walled carbon nanotubes, single-walled carbon nanotubes, graphite nanoplatelets, exfoliated few layer graphite and carbon black were functionalized with mPEG-Br, yielding grafting ratios relative to the nanocarbon framework between ca. 7 and 135 wt%; the products were characterised by Raman spectroscopy, TGA-MS, and electron microscopy. The functionalized materials were tested as nucleants by subjecting them to rigorous protein crystallization studies. Sparsely functionalized flat sheet geometries proved exceptionally effective at inducing crystallization of six proteins. This new class of nucleant, based on PEG grafted graphene-related materials, can be widely applied to promote the growth of 3D crystals suitable for X-ray crystallography. The association of the protein ferritin with functionalized exfoliated few layer graphite was directly visualized by transmission electron microscopy, illustrating the formation of ordered clusters of protein molecules critical to successful nucleation.

  • Journal article
    Mac Dowell N, 2016,

    About the size of it

    , TCE The Chemical Engineer, Pages: 27-30, ISSN: 0302-0797

    Global anthropogenic CO2 production is vast, currently on the order of 35.5 Gt/yr or slightly > 910 million bbl/day of CO2. Due to serious environmental issues, the world has agreed to mitigate global warming and limit it to no more than 1.5°C above pre-industrial levels by the end of the century. One solution is the conversion of CO2 to useful products, e.g., fuels or plastics or otherwise use the CO2 in processes, e.g., CO2-EOR. This is broadly referred to as carbon capture utilization (CCU). The current scale of global CO2 utilization and the role of CCU option might play in mitigating climate change are discussed.

  • Conference paper
    Strapasson A, Woods J, Mbuk K, 2016,

    Land Use Futures in Europe: How changes in diet, agricultural practices and forestlands could help reduce greenhouse gas emissions

    , Vienna, 23rd European Meetings on Cybernetics and Systems Research (EMCSR), Publisher: Bertalanffy Center for the Study of Systems Science (BCSSS), Pages: 106-109
  • Journal article
    Lambert RSC, Polak JW, Maier S, Shah Net al., 2016,

    Optimal phasing of district heating network investments using multi-stage stochastic programming

    , International journal of sustainable energy planning and management, Vol: 09, Pages: 57-57
  • Journal article
    Cavitte M, Blankenship D, Young D, Schroeder D, Parrenin F, LeMeur E, MacGregor J, Siegert MJet al., 2016,

    Deep radiostratigraphy of the East Antarctic plateau: connectingthe Dome C and Vostok ice core sites

    , Journal of Glaciology, Vol: 62, Pages: 323-334, ISSN: 1727-5652

    Several airborne radar-sounding surveys are used to trace internal reflections around theEuropean Project for Ice Coring in Antarctica Dome C and Vostok ice core sites. Thirteen reflections,spanning the last two glacial cycles, are traced within 200 km of Dome C, a promising region formillion-year-old ice, using the University of Texas Institute for Geophysics High-Capacity RadarSounder. This provides a dated stratigraphy to 2318 m depth at Dome C. Reflection age uncertaintiesare calculated from the radar range precision and signal-to-noise ratio of the internal reflections. Theradar stratigraphy matches well with the Multichannel Coherent Radar Depth Sounder (MCoRDS)radar stratigraphy obtained independently. We show that radar sounding enables the extension of icecore ages through the ice sheet with an additional radar-related age uncertainty of ∼1/3–1/2 that ofthe ice cores. Reflections are extended along the Byrd-Totten Glacier divide, using University ofTexas/Technical University of Denmark and MCoRDS surveys. However, core-to-core connection isimpeded by pervasive aeolian terranes, and Lake Vostok’s influence on reflection geometry. Poorradar connection of the two ice cores is attributed to these effects and suboptimal survey design inaffected areas. We demonstrate that, while ice sheet internal radar reflections are generally isochronaland can be mapped over large distances, careful survey planning is necessary to extend ice core chronologiesto distant regions of the East Antarctic ice sheet.

  • Conference paper
    Alonso Alvarez D, Ekins-Daukes N,

    Quantum wells for high-efficiency photovoltaics

    , SPIE OPTO 2016: Physics, Simulation, and Photonic Engineering of Photovoltaic Devices V
  • Journal article
    Ferguson A, Khan U, Walsh M, Lee KY, Bismarck A, Shaffer MS, Coleman JN, Bergin SDet al., 2016,

    Understanding the dispersion and assembly of bacterial cellulose in organic solvents

    , Biomacromolecules, Vol: 17, Pages: 1845-1853, ISSN: 1526-4602

    The constituent nanofibrils of bacterial cellulose are of interest to many researchers because of their purity and excellent mechanical properties. Mechanisms to disrupt the network structure of bacterial cellulose (BC) to isolate bacterial cellulose nanofibrils (BCN) are limited. This work focuses on liquid-phase dispersions of BCN in a range of organic solvents. It builds on work to disperse similarly intractable nanomaterials, such as single-walled carbon nanotubes, where optimum dispersion is seen for solvents whose surface energies are close to the surface energy of the nanomaterial; bacterial cellulose is shown to disperse in a similar fashion. Inverse gas chromatography was used to determine the surface energy of bacterial cellulose, under relevant conditions, by quantifying the surface heterogeneity of the material as a function of coverage. Films of pure BCN were prepared from dispersions in a range of solvents; the extent of BCN exfoliation is shown to have a strong effect on the mechanical properties of BC films and to fit models based on the volumetric density of nanofibril junctions. Such control offers new routes to producing robust cellulose films of bacterial cellulose nanofibrils.

  • Journal article
    Nixon CW, McNeill LC, Bull JM, Bell RE, Gawthorpe RL, Henstock TJ, Christodoulou, Ford M, Taylor B, Sakellariou D, Ferentinos G, Papatheodorou G, Leeder M, Collier RELI, Goodliffe A, Sachpazi M, Kranis Het al.,

    Rapid spatio-temporal variations in rift structure during development of the Corinth Rift, central Greece

    , Tectonics, ISSN: 1944-9194
  • Journal article
    Marsham JH, Parker DJ, Todd MC, Banks JR, Brindley HE, Garcia-Carreras L, Roberts AJ, Ryder CLet al., 2016,

    The contrasting roles of water and dust in controlling daily variations in radiative heating of the summertime Saharan heat low

    , Atmospheric Chemistry and Physics, Vol: 16, Pages: 3563-3575, ISSN: 1680-7324

    The summertime Sahara heat low (SHL) is a key component of the West African monsoon (WAM) system. Considerable uncertainty remains over the relative roles of water vapour and dust aerosols in controlling the radiation budget over the Sahara and therefore our ability to explain variability and trends in the SHL, and in turn, the WAM. Here, new observations from Fennec supersite-1 in the central Sahara during June 2011 and June 2012, together with satellite retrievals from GERB, are used to quantify how total column water vapour (TCWV) and dust aerosols (from aerosol optical depth, AOD) control day-to-day variations in energy balance in both observations and ECWMF reanalyses (ERA-I). The data show that the earth-atmosphere system is radiatively heated in June 2011 and 2012. Although the empirical analysis of observational data cannot completely disentangle the roles of water vapour, clouds and dust, the analysis demonstrates that TCWV provides a far stronger control on TOA net radiation, and so the net heating of the earth-atmosphere system, than AOD does. In contrast, variations in dust provide a much stronger control on surface heating, but the decreased surface heating associated with dust is largely compensated by increased atmospheric heating, and so dust control on net TOA radiation is weak. Dust and TCWV are both important for direct atmospheric heating. ERA-I, which assimilated radiosondes from the Fennec campaign, captures the control of TOA net flux by TCWV, with a positive correlation (r = 0.6) between observed and modelled TOA net radiation, despite the use of a monthly dust climatology in ERA-I that cannot capture the daily variations in dustiness. Variations in surface net radiation, and so the vertical profile of radiative heating, are not captured in ERA-I, since it does not capture variations in dust. Results show that ventilation of the SHL by cool moist air leads to a radiative warming, stabilising the SHL with respect to such perturbations. It is k

  • Journal article
    Shaffer MSP, Diba M, Fam DWH, Boccaccini Aet al., 2016,

    Electrophoretic deposition of graphene-related materials: A review of the fundamentals

    , Progress in Materials Science, Vol: 82, Pages: 83-117, ISSN: 1873-2208

    The Electrophoretic Deposition (EPD) of graphene-related materials (GRMs) is an attractive strategy for a wide range of applications. This review paper provides an overview of the fundamentals and specific technical aspects of this approach, highlighting its advantages and limitations, in particular considering the issues that arise specifically from the behaviour and dimensionality of GRMs. Since obtaining a stable dispersion of charged particles is a pre-requisite for successful EPD, the strategies for suspending GRMs in different media are discussed, along with the resulting influence on the deposited film. Most importantly, the kinetics involved in the EPD of GRMs and the factors that cause deviation from linearity in Hamaker’s Law are reviewed. Side reactions often influence both the efficiency of deposition and the nature of the deposited material; examples include the reduction of graphene oxide (GO) and related materials, as well as the decomposition of the suspension medium at high potentials. The microstructural characteristics of GRM deposits, including their degree of reduction and orientation, strongly influence their performance in their intended function. These factors will also determine, to a large extent, the commercial potential of this technique for applications involving GRMs, and are therefore discussed here.

  • Journal article
    Brogan AP, Hallett JP, 2016,

    Solubilizing and stabilizing proteins in anhydrous lonic liquids through formation of protein-polymer surfactant nanoconstructs

    , Journal of the American Chemical Society, Vol: 138, Pages: 4494-4501, ISSN: 1520-5126

    Nonaqueous biocatalysis is rapidly becoming a desirable tool for chemical and fuel synthesis in both the laboratory and industry. Similarly, ionic liquids are increasingly popular anhydrous reaction media for a number of industrial processes. Consequently, the use of enzymes in ionic liquids as efficient, environment-friendly, commercial biocatalysts is highly attractive. However, issues surrounding the poor solubility and low stability of enzymes in truly anhydrous media remain a significant challenge. Here, we demonstrate for the first time that engineering the surface of a protein to yield protein-polymer surfactant nanoconstructs allows for dissolution of dry protein into dry ionic liquids. Using myoglobin as a model protein, we show that this method can deliver protein molecules with near native structure into both hydrophilic and hydrophobic anhydrous ionic liquids. Remarkably, using temperature-dependent synchrotron radiation circular dichroism spectroscopy to measure half-denaturation temperatures, our results show that protein stability increases by 55 °C in the ionic liquid as compared to aqueous solution, pushing the solution thermal denaturation beyond the boiling point of water. Therefore, the work presented herein could provide a platform for the realization of biocatalysis at high temperatures or in anhydrous solvent systems.

  • Journal article
    Menke R, Abraham E, Parpas P, Stoianov Iet al., 2016,

    Demonstrating demand response from water distribution system through pump scheduling

    , Applied Energy, Vol: 170, Pages: 377-387, ISSN: 1872-9118

    Significant changes in the power generation mix are posing new challenges for the balancing systems of the grid. Many of thesechallenges are in the secondary electricity grid regulation services and could be met through demand response (DR) services. Weexplore the opportunities for a water distribution system (WDS) to provide balancing services with demand response through pumpscheduling and evaluate the associated benefits. Using a benchmark network and demand response mechanisms available in theUK, these benefits are assessed in terms of reduced green house gas (GHG) emissions from the grid due to the displacement ofmore polluting power sources and additional revenues for water utilities. The optimal pump scheduling problem is formulated as amixed-integer optimization problem and solved using a branch and bound algorithm. This new formulation finds the optimal levelof power capacity to commit to the provision of demand response for a range of reserve energy provision and frequency responseschemes offered in the UK. For the first time we show that DR from WDS can offer financial benefits to WDS operators whileproviding response energy to the grid with less greenhouse gas emissions than competing reserve energy technologies. Using aMonte Carlo simulation based on data from 2014, we demonstrate that the cost of providing the storage energy is less than thefinancial compensation available for the equivalent energy supply. The GHG emissions from the demand response provision froma WDS are also shown to be smaller than those of contemporary competing technologies such as open cycle gas turbines. Thedemand response services considered vary in their response time and duration as well as commitment requirements. The financialviability of a demand response service committed continuously is shown to be strongly dependent on the utilisation of the pumpsand the electricity tariffs used by water utilities. Through the analysis of range of water demand scenarios and financial in

  • Journal article
    Siegert MJ, 2016,

    Environmental Sciences in the Twenty-First Century

    , Frontiers in Environmental Science, Vol: 4, ISSN: 2296-665X
  • Journal article
    Vance T, Roberts J, Moy A, Curran M, Tozer A, Gallant A, Abram T, van Ommen T, Young D, Blankenship D, Siegert MJet al., 2016,

    Optimal site selection for a high-resolution ice core record in East Antarctica

    , Climate of the Past, Vol: 12, Pages: 595-610, ISSN: 1814-9332

    Ice cores provide some of the best-dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection for a new East Antarctic high-resolution ice core record. Specifically, seven criteria are considered: (1) 2000-year-old ice at 300 m depth; (2) above 1000 m elevation; (3) a minimum accumulation rate of 250 mm years−1 IE (ice equivalent); (4) minimal surface reworking to preserve the deposited climate signal; (5) a site with minimal displacement or elevation change in ice at 300 m depth; (6) a strong teleconnection to midlatitude climate; and (7) an appropriately complementary relationship to the existing Law Dome record (a high-resolution record in East Antarctica). Once assessment of these physical characteristics identified promising regions, logistical considerations (for site access and ice core retrieval) were briefly considered. We use Antarctic surface mass balance syntheses, along with ground-truthing of satellite data by airborne radar surveys to produce all-of-Antarctica maps of surface roughness, age at specified depth, elevation and displacement change, and surface air temperature correlations to pinpoint promising locations. We also use the European Centre for Medium-Range Weather Forecast ERA 20th Century reanalysis (ERA-20C) to ensure that a site complementary to the Law Dome record is selected. We find three promising sites in the Indian Ocean sector of East Antarctica in the coastal zone from Enderby Land to the Ingrid Christensen Coast (50–100° E). Although we focus on East Antarctica for a new ice core site, the methodology is more generally applicable, and we include key parameters for all of Antarctica which may be useful for ice core site selection elsewhere and/or for other purposes.

  • Journal article
    Kline KL, Msangi S, Dale VH, Woods J, Souza GM, Osseweijer P, Clancy JS, Hilbert JA, Mugera HK, McDonnell PC, Johnson FXet al.,

    Reconciling biofuels and food security: priorities for action

    , Global Change Biology Bioenergy, ISSN: 1757-1693

    Addressing the challenges of understanding and managing complex interactions among food security, biofuels, and resource management requires a focus on specific contextual problems and opportunities. The United Nations’ 2030 Sustainable Development Goals prioritize food and energy security; bioenergy plays an important role in achieving both goals. Effective food security programs begin by clearly defining the problem and asking, “What can be done to effectively assist people at high risk?” Headlines and cartoons that blame biofuels for food insecurity may reflect good intentions but mislead the public and policy makers because they obscure the main drivers of local food insecurity and ignore opportunities for biofuels to contribute to solutions. Applying sustainability guidelines to bioenergy will help achieve near- and long- term goals to eradicate hunger. Priorities for achieving successful synergies between bioenergy and food security include (1) clarifying communications with clear and consistent terms, (2) recognizing that food and bioenergy need not compete for land and instead, need to be integrated with improved resource management, (3) investing in innovations to build capacity and infrastructure such as rural agricultural extension and technology, (4) promoting stable prices that incentivize local production, (5) adopting flex crops that can provide food along with other products and services to society, and (6) engaging stakeholders in identifying and assessing specific opportunities for biofuels to improve food security. Systematic monitoring and analysis to support adaptive management and continual improvement are essential elements to build synergies and help society equitably meet growing demands for both food and energy.

  • Journal article
    Huck CE, van de Flierdt T, Jimenez-Espejo FJ, Bohaty SM, Rohl U, Hammond SJet al., 2016,

    Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting

    , Geochemistry, Geophysics, Geosystems, Vol: 17, Pages: 679-698, ISSN: 1525-2027

    Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation.However, combined studies on sediments, pore waters, fish teeth and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources.

  • Journal article
    Guarracino I, Mellor A, Ekins-Daukes N, Markides CNet al., 2016,

    Dynamic coupled thermal-and-electrical modelling of sheet-and-tube hybrid photovoltaic/thermal (PVT) collectors

    , Applied Thermal Engineering, Vol: 101, Pages: 778-795, ISSN: 1873-5606

    In this paper we present a dynamic model of a hybrid photovoltaic/thermal (PVT) collector with a sheet-and-tube thermal absorber. The model is used in order to evaluate the annual generation of electrical energy along with the provision of domestic hot-water (DHW) from the thermal energy output, by using real climate-data at high temporal resolution. The model considers the effect of a non-uniform temperature distribution on the surface of the solar cell on its electrical power output. An unsteady 3-dimensional numerical model is developed to estimate the performance of such a collector. The model allows key design parameters of the PVT collector to vary so that the influence of each parameter on the system performance can be studied at steady state and at varying operating and atmospheric conditions. A key parameter considered in this paper is the number of glass covers used in the PVT collector. The results show that while the thermal efficiency increases with the additional glazing, the electrical efficiency deteriorates due to the higher temperature of the fluid and increased optical losses, as expected. This paper also shows that the use of a dynamic model and of real climate-data at high resolution is of fundamental importance when evaluating the yearly performance of the system. The results of the dynamic simulation with 1-min input data show that the thermal output of the system is highly dependent on the choice of the control parameters (pump operation, differential thermostat controller, choice of flow rate etc.) in response to the varying weather conditions. The effect of the control parameters on the system's annual performance can be captured and understood only if a dynamic modelling approach is used. The paper also discusses the use of solar cells with modified optical properties (reduced absorptivity/emissivity) in the infrared spectrum, which would reduce the thermal losses of the PVT collector at the cost of only a small loss in electrical output

  • Journal article
    De Marco MDM, Markoulidis F, Menzel R, Bawaked S, Mokhtar M, Al-Thabaiti S, Basahel S, Shaffer Met al., 2016,

    Cross-linked single-walled carbon nanotube aerogel electrodes via reductive coupling chemistry

    , Journal of Materials Chemistry A, Vol: 4, Pages: 5385-5389, ISSN: 2050-7496

    Single-walled carbon nanotube (SWCNT) anions can be cross-linked by a dielectrophile to form covalent, carbon-bonded organogels. Freeze-drying produces cryogels with low density (2.3 mg cm−3), high surface area (766 m2 g−1), and high conductivity (9.4 S m−1), showing promise as supercapacitor electrodes. Counterion concentration controls debundling, grafting ratio, as well as all the resulting properties.

  • Journal article
    O'Gorman EJ, Ólafsson Ó, Demars BOL, Friberg N, Guðbergsson G, Hannesdóttir ER, Jackson MC, Johansson LS, McLaughlin Ó, Ólafsson JS, Woodward G, Gíslason GMet al., 2016,

    Temperature effects on fish production across a natural thermal gradient

    , Global Change Biology, Vol: 22, Pages: 3206-3220, ISSN: 1365-2486

    Global warming is widely predicted to reduce the biomass production of top predators, or even result in species loss. Several exceptions to this expectation have been identified, however, and it is vital that we understand the underlying mechanisms if we are to improve our ability to predict future trends. Here, we used a natural warming experiment in Iceland and quantitative theoretical predictions to investigate the success of brown trout as top predators across a stream temperature gradient (4–25 °C). Brown trout are at the northern limit of their geographic distribution in this system, with ambient stream temperatures below their optimum for maximal growth, and above it in the warmest streams. A five-month mark-recapture study revealed that population abundance, biomass, growth rate, and production of trout all increased with stream temperature. We identified two mechanisms that contributed to these responses: (1) trout became more selective in their diet as stream temperature increased, feeding higher in the food web and increasing in trophic position; and (2) trophic transfer through the food web was more efficient in the warmer streams. We found little evidence to support a third potential mechanism: that external subsidies would play a more important role in the diet of trout with increasing stream temperature. Resource availability was also amplified through the trophic levels with warming, as predicted by metabolic theory in nutrient-replete systems. These results highlight circumstances in which top predators can thrive in warmer environments and contribute to our knowledge of warming impacts on natural communities and ecosystem functioning.

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