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| 2. |
- Walker, Anthony P, et al.
(författare)
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Horizon 2020 EuPRAXIA design study
- 2017
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 874:1
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Tidskriftsartikel (refereegranskat)abstract
- The Horizon 2020 Project EuPRAXIA ("European Plasma Research Accelerator with eXcellence In Applications") is preparing a conceptual design report of a highly compact and cost-effective European facility with multi-GeV electron beams using plasma as the acceleration medium. The accelerator facility will be based on a laser and/or a beam driven plasma acceleration approach and will be used for photon science, high-energy physics (HEP) detector tests, and other applications such as compact X-ray sources for medical imaging or material processing. EuPRAXIA started in November 2015 and will deliver the design report in October 2019. EuPRAXIA aims to be included on the ESFRI roadmap in 2020.
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| 3. |
- Audet, J., et al.
(författare)
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Forest streams are important sources for nitrous oxide emissions
- 2020
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26:2, s. 629-641
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Tidskriftsartikel (refereegranskat)abstract
- Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2O). N2O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2O concentration data from low-order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2O concentrations of 1.6±2.1 and 1.3±1.8µgN/L, respectively (mean±SD) despite higher total N (TN) concentrations in agricultural streams (1,520±1,640 vs. 780±600µgN/L). Although clear patterns linking N2O concentrations and environmental variables were difficult to discern, the percent saturation of N2O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2O emissions. An estimate of the N2O emission from low-order streams at the national scale revealed that ~1.8×109g N2O-N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2O sources in the landscape with 800×109gCO2-eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector. © 2019 The Authors. Global Change Biology published by John Wiley & Sons Ltd
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| 4. |
- Audet, T. L., et al.
(författare)
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Electron injector for compact staged high energy accelerator
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 829, s. 304-308
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Tidskriftsartikel (refereegranskat)abstract
- An electron injector for multi-stage laser wakefield experiments is presented. It consists of a variable length gas cell of small longitudinal dimension (⩽10mm). The gas filling process in this cell was characterized both experimentally and with fluid simulation. Electron acceleration experiments were performed at two different laser facilities. Results show low divergence and low pointing fluctuation electron bunches suitable for transport to a second stage, and a peaked energy distribution suitable for injection into the second stage wakefield accelerator.
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| 5. |
- Peacock, M., et al.
(författare)
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Global importance of methane emissions from drainage ditches and canals
- 2021
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Ingår i: Environmental Research Letters. - : IOP Publishing Ltd. - 1748-9326. ; 16:4
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Tidskriftsartikel (refereegranskat)abstract
- Globally, there are millions of kilometres of drainage ditches which have the potential to emit the powerful greenhouse gas methane (CH4), but these emissions are not reported in budgets of inland waters or drained lands. Here, we synthesise data to show that ditches spanning a global latitudinal gradient and across different land uses emit large quantities of CH4 to the atmosphere. Area-specific emissions are comparable to those from lakes, streams, reservoirs, and wetlands. While it is generally assumed that drainage negates terrestrial CH4 emissions, we find that CH4 emissions from ditches can, on average, offset similar to 10% of this reduction. Using global areas of drained land we show that ditches contribute 3.5 Tg CH4 yr(-1) (0.6-10.5 Tg CH4 yr(-1)); equivalent to 0.2%-3% of global anthropogenic CH4 emissions. A positive relationship between CH4 emissions and temperature was found, and emissions were highest from eutrophic ditches. We advocate the inclusion of ditch emissions in national GHG inventories, as neglecting them can lead to incorrect conclusions concerning the impact of drainage-based land management on CH4 budgets.
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| 6. |
- Peacock, M., et al.
(författare)
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Small artificial waterbodies are widespread and persistent emitters of methane and carbon dioxide
- 2021
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 27:20, s. 5109-5123
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Tidskriftsartikel (refereegranskat)abstract
- Inland waters play an active role in the global carbon cycle and emit large volumes of the greenhouse gases (GHGs), methane (CH4) and carbon dioxide (CO2). A considerable body of research has improved emissions estimates from lakes, reservoirs and rivers but recent attention has been drawn to the importance of small, artificial waterbodies as poorly quantified but potentially important emission hotspots. Of particular interest are emissions from drainage ditches and constructed ponds. These waterbody types are prevalent in many landscapes and their cumulative surface areas can be substantial. Furthermore, GHG emissions from constructed waterbodies are anthropogenic in origin and form part of national emissions reporting, whereas emissions from natural waterbodies do not (according to Intergovernmental Panel on Climate Change guidelines). Here, we present GHG data from two complementary studies covering a range of land uses. In the first, we measured emissions from nine ponds and seven ditches over a full year. Annual emissions varied considerably: 0.1-44.3 g CH4 m(-2) year(-1) and -36-4421 g CO2 m(-2) year(-1). In the second, we measured GHG concentrations in 96 ponds and 64 ditches across seven countries, covering subtropical, temperate and sub-arctic biomes. When CH4 emissions were converted to CO2 equivalents, 93% of waterbodies were GHG sources. In both studies, GHGs were positively related to nutrient status (C, N, P), and pond GHG concentrations were highest in smallest waterbodies. Ditch and pond emissions were larger per unit area when compared to equivalent natural systems (streams, natural ponds). We show that GHG emissions from natural systems should not be used as proxies for those from artificial waterbodies, and that artificial waterbodies have the potential to make a substantial but largely unquantified contribution to emissions from the Agriculture, Forestry and Other Land Use sector, and the global carbon cycle.
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| 7. |
- Audet, Carolyn M., et al.
(författare)
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An unrecognized key population? : Traditional treatment practices associated with HIV risk among traditional healers in rural South Africa
- 2020
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Ingår i: AIDS. - : Lippincott Williams & Wilkins. - 0269-9370 .- 1473-5571. ; 34:15, s. 2313-2317
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To understand the risk of HIV acquisition through occupational exposure among rural South African traditional healers, notably via the practice of traditional skin incisions with razors.Design: A random sample of traditional healers living in South Africa participated in a cross-sectional survey that included a rapid HIV test.Setting: Rural Bushbuckridge district of Mpumalanga, South Africa.Participants: Traditional healers.Intervention: Pretest counseling, posttest counseling, and referral to care if HIV seropositive.Main outcome measure(s): HIV infection.Results: Among healers who reported a previous positive test result or accepted an HIV test (96%), HIV prevalence was 30% (95% confidence interval: 23–37%). During their careers, 98% of healers reported conducting at least one ‘vaccination’ (as traditional incisions are called), 32% reported always using gloves when conducting these procedures, 29 (14%) reported patient blood touching their bare skin. Healers who reported exposure to patient blood had a higher HIV prevalence than their nonexposed colleagues (adjusted risk ratio: 2.35, 95% confidence interval: 1.55–3.56, P = 0.001).Conclusion: Nearly all traditional healers are routinely performing minimally invasive skin incisions that could expose them to patient blood. The lack of training and access to personal protective equipment increase their risk of acquisition of blood–borne pathogens, including HIV. Given the widespread practice of traditional skin incisions across southern Africa, and the higher levels of HIV among traditional healers exposed to patient blood, it is likely that traditional healers are a hitherto unrecognized key population at disproportionate risk of acquiring HIV.
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| 8. |
- Audet, Carolyn M., et al.
(författare)
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Mixed methods inquiry into traditional healers' treatment of mental, neurological and substance abuse disorders in rural South Africa
- 2017
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Ingår i: PLOS ONE. - : Public library science. - 1932-6203. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Traditional healers are acceptable and highly accessible health practitioners throughout sub-Saharan Africa. Patients in South Africa often seek concurrent traditional and allopathic treatment leading to medical pluralism. Methods & findings: We studied the cause of five traditional illnesses known locally as "Mavabyi ya nhloko" (sickness of the head), by conducting 27 in-depth interviews and 133 surveys with a randomly selected sample of traditional healers living and working in rural, northeastern South Africa. These interviews were carried out to identify treatment practices of mental, neurological, and substance abuse (MNS) disorders. Participating healers were primarily female (77%), older in age (median: 58.0 years; interquartile range [IQR]: 50-67), had very little formal education (median: 3.7 years; IQR: 3.2-4.2), and had practiced traditional medicine for many years (median: 17 years; IQR: 9.5-30). Healers reported having the ability to successfully treat: seizure disorders (47%), patients who have lost touch with reality (47%), paralysis on one side of the body (59%), and substance abuse (21%). Female healers reported a lower odds of treating seizure disorders (Odds Ratio (OR): 0.47), patients who had lost touch with reality (OR: 0.26; p-value<0.05), paralysis of one side of the body (OR: 0.36), and substance abuse (OR: 0.36) versus males. Each additional year of education received was found to be associated with lower odds, ranging from 0.13-0.27, of treating these symptoms. Each additional patient seen by healers in the past week was associated with roughly 1.10 higher odds of treating seizure disorders, patients who have lost touch with reality, paralysis of one side of the body, and substance abuse. Healers charged a median of 500 South African Rand (similar to US$35) to treat substance abuse, 1000 Rand (similar to US$70) for seizure disorders or paralysis of one side of the body, and 1500 Rand (similar to US$105) for patients who have lost touch with reality. Conclusions: While not all healers elect to treat MNS disorders, many continue to do so, delaying allopathic health services to acutely ill patients.
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| 9. |
- Audet, T. L., et al.
(författare)
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Investigation of ionization-induced electron injection in a wakefield driven by laser inside a gas cell
- 2016
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 23:2
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Tidskriftsartikel (refereegranskat)abstract
- Ionization-induced electron injection was investigated experimentally by focusing a driving laser pulse with a maximum normalized potential of 1.2 at different positions along the plasma density profile inside a gas cell, filled with a gas mixture composed of 99%H2+1%N2. Changing the laser focus position relative to the gas cell entrance controls the accelerated electron bunch properties, such as the spectrum width, maximum energy, and accelerated charge. Simulations performed using the 3D particle-in-cell code WARP with a realistic density profile give results that are in good agreement with the experimental ones. The interest of this regime for optimizing the bunch charge in a selected energy window is discussed.
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| 10. |
- Gallardo González, I., et al.
(författare)
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Effects of the dopant concentration in laser wakefield and direct laser acceleration of electrons
- 2018
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 20:5
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we experimentally study the effects of the nitrogen concentration in laser wakefield acceleration of electrons in a gas mixture of hydrogen and nitrogen. A 15 TW peak power laser pulse is focused to ionize the gas, excite a plasma wave and accelerate electrons up to 230 MeV. We find that at dopant concentrations above 2% the total divergence of the electrons is increased and the high energy electrons are emitted preferentially with an angle of ±6 mrad, leading to a forked spatio-spectral distribution associated to direct laser acceleration (DLA). However, electrons can gain more energy and have a divergence lower than 4 mrad for concentrations below 0.5% and the same laser and plasma conditions. Particle-in-cell simulations show that for dopant concentrations above 2%, the amount of trapped charge is large enough to significantly perturb the plasma wave, reducing the amplitude of the longitudinal wakefield and suppressing other trapping mechanisms. At high concentrations the number of trapped electrons overlapping with the laser fields is increased, which rises the amount of charge affected by DLA. We conclude that the dopant concentration affects the quantity of electrons that experience significant DLA and the beam loading of the plasma wave driven by the laser pulse. These two mechanisms influence the electrons final energy, and thus the dopant concentration should be considered as a factor for the optimization of the electron beam parameters.
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