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Environmental trade-offs associated with bioenergy from agri-residues in sub-tropical regions: A case study of the Colombian coffee sector
No full textThe coffee sector generates vast amounts of residues along its value chain. Crop residues, like coffee stems, are burned in the field, used for domestic cooking or coffee drying in processing plants having significant environmental and health implication to rural communities. This research investigated the environmental impacts of replacing current practices with modern bioenergy applications in the Colombian coffee sector. A biomass gasification system to produce decentralised energy from coffee stems was considered, and the environmental impacts of such bioenergy implementation were evaluated. A lifecycle assessment was conducted to quantify the environmental performance of this bioenergy system and compare it to current residues uses and energy needs that feature small- to large-scale coffee farms. The results show that deploying modern bioenergy could result in reductions in 48-86% greenhouse gas (GHG) emissions and up to 98% less particulate matter formation when current practices and fossil-based energy are replaced. However, negative impacts should be considered as substituting grid electricity, largely generated from hydro-electricity, could increase GHGs by 68% and fossil fuel consumption by 73%. The results also show the relevance of understanding the environmental performance of bioenergy systems compared to reference scenarios; this allowed to evaluate and identify environmental trade-offs from modern bioenergy implementations. To maximise benefits and minimise the limitations of these systems, it is important to conduct whole-system assessments that inform on the wider environmental impacts of using agri-residues for bioenergy generation in a region- and system-specific context
The PLANES Study: A protocol for a randomised controlled feasibility study of the placental growth factor (PlGF) blood test informed care versus standard care alone for women with a small for gestational age fetus at or after 32+0 weeks’ gestation
No full textBackgroundStillbirth remains a major concern across the globe and in some high-resource countries,such as the UK, efforts to reduce the rate have achieved only modest reductions. One thirdof stillborn babies are small for gestational age (SGA) and these pregnancies are also at riskof neonatal adverse outcomes and lifelong health problems, especially when deliveredpreterm. Current UK clinical guidance advocates regular monitoring and early term deliveryof the SGA fetus however; the most appropriate regimen for surveillance of these babiesremains unclear and often leads to increased intervention for a large number of thesewomen. This pilot trial will determine the feasibility of a large-scale trial refining the risk ofadverse pregnancy outcome in SGA pregnancies using biomarkers of placental functionsFlt-1/PlGF, identifying and intervening in only those deemed at highest risk of stillbirth.MethodsPLANES is a randomised controlled feasibility study of women with an SGA fetus that will beconducted at two tertiary care hospitals in the UK. Once identified on ultrasound, women willbe randomised into two groups in a 3:1 ratio in favour of sFlt-1/PlGF ratio led managementvs standard care. Women with an SGA fetus and a normal sFlt-1/PlGF ratio will have arepeat ultrasound and sFlt-1/PlGF ratio every 2 weeks with planned birth delayed until 40weeks. In those women with an SGA fetus and an abnormal sFlt-1/PlGF ratio we will offerbirth from 37 weeks, or sooner if there are other concerning features on ultrasound. Womenassigned to standard care will have an sFlt-1/PlGF ratio taken but the results will beconcealed from the clinical team and the woman’s pregnancy will be managed as per thelocal NHS hospital policy. This integrated mixed method study will also involve a healtheconomic analysis and a perspectives work package exploring trial feasibility throughinterviews and questionnaires with participants, their partners and clinicians.DiscussionOur aim is to determine feasibility through the assessment of our ability to recruit and retainparticipants to the study. Results from this pilot study will inform the design of a future largerandomised controlled trial that will be adequately powered for adverse pregnancy outcome.Such a study would provide the evidence needed to guide future management of the SGAfetus
Quantum rescaling, domain metastability and hybrid domain-walls in two-dimensional CrI3 magnets
No full textHigher-order exchange interactions and quantum effects are widely known to play an importantrole in describing the properties of low-dimensional magnetic compounds. Here we identifythe recently discovered two-dimensional (2D) van der Waals (vdW) CrI3 as a quantumnon-Heisenberg material with properties far beyond an Ising magnet as initially assumed.We find that biquadratic exchange interactions are essential to quantitatively describe themagnetism of CrI3 but requiring quantum rescaling corrections to reproduce its thermalproperties. The quantum nature of the heat bath represented by discrete electron-spin andphonon-spin scattering processes induced the formation of spin fluctuations in the low temperatureregime. These fluctuations induce the formation of metastable magnetic domainsevolving into a single macroscopic magnetization or even a monodomain over surface areasof a few micrometers. Such domains display hybrid characteristics of N´eel and Bloch typeswith a narrow domain wall width in the range of 3-5 nm. Similar behaviour is expected forthe majority of 2D vdW magnets where higher-order exchange interactions are appreciable
Effects of Age on Electrophysiological Measures of Cochlear Synaptopathy in Humans
No full textAge-related cochlear synaptopathy (CS) has been shown to occur in rodents with minimal noise exposure, and has been hypothesized to play a crucial role in age-related hearing declines in humans. Because CS affects mainly low-spontaneous rate auditory nerve fibers, differential electrophysiological measures such as the ratio of the amplitude of wave I of the auditory brainstem response (ABR) at high to low click levels (WIH/WIL), and the difference between frequency following response (FFR) levels to shallow and deep amplitude modulated tones (FFRS-FFRD), have been proposed as CS markers. However, age-related audiometric threshold shifts, particularly prominent at high frequencies, may confound the interpretation of these measures in cross-sectional studies of age-related CS. To address this issue, we measured WIH/WIL and FFRS-FFRD using highpass masking (HP) noise to eliminate the contribution of high-frequency cochlear regions to the responses in a crosssectional sample of 102 subjects (34 young, 34 middle-aged, 34 elderly). WIH/WIL in the presence of the HP noise did not decrease as a function of age. However, in the absence of HP noise, WIH/WIL showed credible age-related decreases even after partialing out the effects of audiometric threshold shifts. No credible age-related decreases of FFRS-FFRD were found. Overall, the results do not provide evidence of age-related CS in the low-frequency region where the responses were restricted by the HP noise, but are consistent with the presence of age-related CS in higher frequency regions
Tail asymptotics for the area under the excursion of a random walk with heavy-tailed increments
No full textWe study the tail behaviour of the distribution of the area under the positive excursion of a random walk which has negative drift and heavy-tailed increments. We determine the asymptotics for tail probabilities for the area.</p
Robust Formation Control of Train Platoons for Interval Maintaining
No full textTrain coordination technology in moving block signaling (MBS) systems has a huge potential in maximizing line utilization and railways safe operation [1]. However, the realization of reliable cooperative control is a nontrivial task, facing challenges such as environmental uncertainties, unpredictable and time-varying disturbances. This paper investigates the robust cooperative control problem of networked homogeneous trains with physically connected carriages using the cooperative control theories for Negative Imaginary (NI) systems. The coupling between trains within the overall system is described by a network topology. A local robust Strictly Negative Imaginary (SNI) controller is designed to track a prescribed reference and maintain a pre-defined formation. Numerical simulations are provided to demonstrate the effectiveness of the proposed controller
Characterisation of deuterium distributions in corroded zirconium alloys using high-resolution SIMS imaging
No full textHydrogen diffusion through the oxide grown on Zr alloys by aqueous corrosion processes plays a critical role in determining the rate of hydrogen pickup (HPU) which can result in embrittlement of fuel cladding and limit the burnup of the nuclear fuel it encapsulates. Mapping the hydrogen/deuterium distributions in these oxide layers, especially in the barrier layer close to the metal/oxide interface, is a powerful way to understand the mechanism of both oxidation and hydrogen pickup. Here we have characterised by high-resolution SIMS analysis the deuterium distribution in oxide layers on a series of Zr alloys, including autoclave-oxidised Zircaloy-4, Zr-1Nb and Zr-2.5Nb alloys, and in-flux and out-of-flux corroded Zr-2.5Nb samples. Pre-transition Zircaloy-4 samples show a high deuterium trapping ratio in the oxide and a higher diffusion coefficient than in oxides on the Nb-containing samples. Neutron irradiation increases the deuterium diffusion coefficient, the deuterium concentration in the oxide and the pickup fraction in Zr-2.5 Nb samples. Comparative NanoSIMS and EDX/SEM analysis demonstrates that the deuterium is not preferentially trapped at second phase particles in the oxides on any of the alloys studied, but there is direct evidence for trapping at the surfaces of small oxide cracks especially in Zircaloy-4 samples. The high resolution mapping of these hot-spots in 3D can provide unique information on the mechanisms of hydrogen uptake, and suggests that the development of interconnected porosity in the oxide may be the critical rate-determining mechanism that controls HPU in the aqueous corrosion of zirconium alloys in water-cooled reactors
The Impact of Oil Polarity on the Mixing Time at Pore-Scale in Low Salinity Waterflooding
No full textThe efficiency of low salinity waterflooding (LSWF), particularly during tertiary mode injection, is highly controlled by in-situ mixing between the stagnant regions holding high salinity water (HSW) and the flowing regions containing low salinity water (LSW), because it impacts directly the electrokinetics of wettability alteration and the time-scale of the low salinity effect (LSE). This study aims to address the effect of oil polarity and charged rock surfaces on the time-scale of mixing and transport under two-phase flow conditions. A systematic series of micromodel experiments were performed. The micromodels were first saturated with high salinity formation brine and oil (both model and crude oil), thereafter HSW and LSW were injected sequentially and the mixing time was carefully monitored. Besides, the polarity of model oils was manipulated by adding oleic acid as representative for the acidic functional groups of crude oil. In addition to the experimental work, conceptual computational fluid dynamics (CFD) simulations were performed to get further insights into the experimental observations and to identify the dominant parameters on the time-scale of mixing in stagnant regions. The experimental results show that the time-scale of ionic transport in stagnant regions can be slowed down 10-16 times by increase of the polar fractions of the oil, where the time-scale cannot be simply described by the Fickian diffusion. It is postulated that the stronger electrical field established in the water film by the increase of oil polarity lowers the solute transport rate according to the Poisson-Nernst-Planck theory. The results were further verified by using crude oil which is highly polar and contains complex types of polar components such as resins/asphaltenes. Experimental results clearly indicated the electrokinetics effect during wettability alteration process as the time-scale was increased further. Nevertheless, the mixing time does not vary linearly with the polar group fraction and follows a rather logarithmic trend. The CFD simulation confirms that the effective diffusion coefficient (which is influenced by the oil polarity and the induced electric field) is the predominant parameter determining the time-scale of mixing. Other parameters such as film thickness/film length and salinity gradient have comparatively a lesser effect on the time-scale of mixing in the stagnant regions. <br/