| 1. |
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| 2. |
- ter Veer, Emil, et al.
(författare)
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Consensus statement on mandatory measurements in pancreatic cancer trials (COMM-PACT) for systemic treatment of unresectable disease
- 2018
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Ingår i: The Lancet Oncology. - 1470-2045 .- 1474-5488. ; 19:3, s. E151-E160
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Forskningsöversikt (refereegranskat)abstract
- Variations in the reporting of potentially confounding variables in studies investigating systemic treatments for unresectable pancreatic cancer pose challenges in drawing accurate comparisons between findings. In this Review, we establish the first international consensus on mandatory baseline and prognostic characteristics in future trials for the treatment of unresectable pancreatic cancer. We did a systematic literature search to find phase 3 trials investigating first-line systemic treatment for locally advanced or metastatic pancreatic cancer to identify baseline characteristics and prognostic variables. We created a structured overview showing the reporting frequencies of baseline characteristics and the prognostic relevance of identified variables. We used a modified Delphi panel of two rounds involving an international panel of 23 leading medical oncologists in the field of pancreatic cancer to develop a consensus on the various variables identified. In total, 39 randomised controlled trials that had data on 15 863 patients were included, of which 32 baseline characteristics and 26 prognostic characteristics were identified. After two consensus rounds, 23 baseline characteristics and 12 prognostic characteristics were designated as mandatory for future pancreatic cancer trials. The COnsensus statement on Mandatory Measurements in unresectable PAncreatic Cancer Trials (COMM-PACT) identifies a mandatory set of baseline and prognostic characteristics to allow adequate comparison of outcomes between pancreatic cancer studies.
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| 3. |
- Goey, Kaitlyn K. H., et al.
(författare)
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Consensus statement on essential patient characteristics in systemic treatment trials for metastatic colorectal cancer : Supported by the ARCAD Group
- 2018
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Ingår i: European Journal of Cancer. - : ELSEVIER SCI LTD. - 0959-8049 .- 1879-0852. ; 100, s. 35-45
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Tidskriftsartikel (refereegranskat)abstract
- Background: Patient characteristics and stratification factors are key features influencing trial outcomes. However, there is substantial heterogeneity in reporting of patient characteristics and use of stratification factors in phase 3 trials investigating systemic treatment of metastatic colorectal cancer (mCRC). We aimed to develop a minimum set of essential baseline characteristics and stratification factors to include in such trials. Methods: We performed a modified, two-round Delphi survey among international experts with wide experience in the conduct and methodology of phase 3 trials of systemic treatment of mCRC. Results: Thirty mCRC experts from 15 different countries completed both consensus rounds. A total of 14 patient characteristics were included in the recommended set: age, performance status, primary tumour location, primary tumour resection, prior chemotherapy, number of metastatic sites, liver-only disease, liver involvement, surgical resection of metastases, synchronous versus metachronous metastases, (K)RAS and BRAF mutation status, microsatellite instability/mismatch repair status and number of prior treatment lines. A total of five patient characteristics were considered the most relevant stratification factors: RAS/BRAF mutation status, performance status, primary tumour sidedness and liver-only disease. Conclusions: This survey provides a minimum set of essential baseline patient characteristics and stratification factors to include in phase 3 trials of systemic treatment of mCRC. Inclusion of these patient characteristics and strata in study protocols and final study reports will improve interpretation of trial results and facilitate cross-study comparisons.
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| 4. |
- Flechard, Chris R., et al.
(författare)
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Carbon-nitrogen interactions in European forests and semi-natural vegetation - Part 1: Fluxes and budgets of carbon, nitrogen and greenhouse gases from ecosystem monitoring and modelling
- 2020
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 17:6, s. 1583-1620
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Tidskriftsartikel (refereegranskat)abstract
- The impact of atmospheric reactive nitrogen (N-r) deposition on carbon (C) sequestration in soils and biomass of unfertilized, natural, semi-natural and forest ecosystems has been much debated. Many previous results of this dC/dN response were based on changes in carbon stocks from periodical soil and ecosystem inventories, associated with estimates of N-r deposition obtained from large-scale chemical transport models. This study and a companion paper (Flechard et al., 2020) strive to reduce uncertainties of N effects on C sequestration by linking multi-annual gross and net ecosystem productivity estimates from 40 eddy covariance flux towers across Europe to local measurement-based estimates of dry and wet N-r deposition from a dedicated collocated monitoring network. To identify possible ecological drivers and processes affecting the interplay between C and N-r inputs and losses, these data were also combined with in situ flux measurements of NO, N2O and CH4 fluxes; soil NO3- leaching sampling; and results of soil incubation experiments for N and greenhouse gas (GHG) emissions, as well as surveys of available data from online databases and from the literature, together with forest ecosystem (BAS-FOR) modelling. Multi-year averages of net ecosystem productivity (NEP) in forests ranged from -70 to 826 gCm(-2) yr(-1) at total wet + dry inorganic N-r deposition rates (N-dep) of 0.3 to 4.3 gNm(-2) yr(-1) and from -4 to 361 g Cm-2 yr(-1) at N-dep rates of 0.1 to 3.1 gNm(-2) yr(-1) in short semi-natural vegetation (moorlands, wetlands and unfertilized extensively managed grasslands). The GHG budgets of the forests were strongly dominated by CO2 exchange, while CH4 and N2O exchange comprised a larger proportion of the GHG balance in short semi-natural vegetation. Uncertainties in elemental budgets were much larger for nitrogen than carbon, especially at sites with elevated N-dep where N-r leaching losses were also very large, and compounded by the lack of reliable data on organic nitrogen and N-2 losses by denitrification. Nitrogen losses in the form of NO, N2O and especially NO3- were on average 27%(range 6 %-54 %) of N-dep at sites with N-dep < 1 gNm(-2) yr(-1) versus 65% (range 35 %-85 %) for N-dep > 3 gNm(-2) yr(-1). Such large levels of N-r loss likely indicate that different stages of N saturation occurred at a number of sites. The joint analysis of the C and N budgets provided further hints that N saturation could be detected in altered patterns of forest growth. Net ecosystem productivity increased with N-r deposition up to 2-2.5 gNm(-2) yr(-1), with large scatter associated with a wide range in carbon sequestration efficiency (CSE, defined as the NEP/GPP ratio). At elevated N-dep levels (> 2.5 gNm(-2) yr(-1)), where inorganic N-r losses were also increasingly large, NEP levelled off and then decreased. The apparent increase in NEP at low to intermediate N-dep levels was partly the result of geographical cross-correlations between N-dep and climate, indicating that the actual mean dC/dN response at individual sites was significantly lower than would be suggested by a simple, straightforward regression of NEP vs. N-dep.
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| 5. |
- Prins, A. J., et al.
(författare)
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Visualization of Biomass Pyrolysis and Temperature Imaging in a Heated-Grid Reactor
- 2009
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 23:1, s. 993-1006
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Tidskriftsartikel (refereegranskat)abstract
- The main advantage of a heated-grid reactor for studying pyrolysis kinetics of solid fuel samples is that high heating rates of up to 1000 K/s can be obtained. However, one of the concerns is whether the temperature distribution over the grid material is uniform and whether the presence of a thermocouple welded to the grid causes any measurement errors. Biomass samples were placed on the heated-grid reactor, and the volatiles, emitted in the biomass pyrolysis process as hot gas plumes, were imaged with an infrared camera with a high framing speed. The temporal resolved infrared images indicate that the pyrolysis process does not take place at the same rate everywhere on the grid. Two-dimensional temperature images of a heated grid made of stainless steel were recorded using the method of laser-induced thermometry with thermographic phosphors. As expected from a heat-transfer model, measured temperatures were found to be significantly higher than temperatures indicated by a thermocouple welded to the bottom of the grid. It was also observed that there is a large temperature gradient between the two electrodes on which the grid is connected. It is shown that replacing a wire mesh by a foil as a grid material may lead to more homogeneous temperature distribution. The paper recommends additional research to demonstrate the suitability of the heated-grid reactor for carrying out accurate measurements.
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| 6. |
- Raida, M. B., et al.
(författare)
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Laminar burning velocity measurements of ethanol+air and methanol+air flames at atmospheric and elevated pressures using a new Heat Flux setup
- 2021
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 230
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Tidskriftsartikel (refereegranskat)abstract
- A new setup for burning velocity measurements of liquid fuels at elevated pressures using the Heat Flux method has been constructed. The burner design has been improved comparing to previous studies in this and other laboratories. Laminar burning velocities were determined experimentally for ethanol+air and methanol+air mixtures over a range of conditions including equivalence ratio (0.8 to 1.3), inlet gas temperature (318–338 K), and pressure (1–5 bar). Experimental uncertainties have been determined and analyzed. The overall accuracy of the burning velocity, SL, was evaluated to be better than ±1 cm/s for atmospheric pressure and ±1.5 cm/s at elevated pressure conditions. Experimental results at 1 atm are in good agreement with recent literature data. To compare the present measurements with the literature data often obtained at other initial temperatures and pressures, an empirical expression SL = SL0 (T/T0)α (p/p0)β, which correlates the burning velocity at a specific temperature, T, and pressure, p, with that at standard conditions indicated by superscripts 0, was implemented. At a fixed temperature, pressure dependence at each equivalence ratio can be analyzed. It was found that power exponents β derived in the present work and from the literature data possess large scattering. The best agreement was found between the present results and experimental literature data from spherical flames using non-linear stretch correction models. Burning velocities at atmospheric as well as elevated pressures and power exponents β have been also compared with kinetic modeling results using several detailed kinetic mechanisms, showing a fair to a good agreement. As the new results are accurate and free from stretch effects, they form a new source of reliable data for validation of the reaction mechanisms.
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| 7. |
- Franklin, Oskar, et al.
(författare)
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Organizing principles for vegetation dynamics
- 2020
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Ingår i: Nature plants. - : Springer Science and Business Media LLC. - 2055-026X .- 2055-0278. ; 6:5, s. 444-453
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Tidskriftsartikel (refereegranskat)abstract
- Plants and vegetation play a critical-but largely unpredictable-role in global environmental changes due to the multitude of contributing processes at widely different spatial and temporal scales. In this Perspective, we explore approaches to master this complexity and improve our ability to predict vegetation dynamics by explicitly taking account of principles that constrain plant and ecosystem behaviour: natural selection, self-organization and entropy maximization. These ideas are increasingly being used in vegetation models, but we argue that their full potential has yet to be realized. We demonstrate the power of natural selection-based optimality principles to predict photosynthetic and carbon allocation responses to multiple environmental drivers, as well as how individual plasticity leads to the predictable self-organization of forest canopies. We show how models of natural selection acting on a few key traits can generate realistic plant communities and how entropy maximization can identify the most probable outcomes of community dynamics in space- and time-varying environments. Finally, we present a roadmap indicating how these principles could be combined in a new generation of models with stronger theoretical foundations and an improved capacity to predict complex vegetation responses to environmental change. Integrating natural selection and other organizing principles into next-generation vegetation models could render them more theoretically sound and useful for earth system applications and modelling climate impacts.
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| 8. |
- Prins, M. J., et al.
(författare)
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Biomass pyrolysis in a heated-grid reactor: Visualization of carbon monoxide and formaldehyde using Laser-Induced Fluorescence
- 2011
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 1873-250X .- 0165-2370. ; 92:2, s. 280-286
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Tidskriftsartikel (refereegranskat)abstract
- The development of improved biomass pyrolysis models is vital for more accurate modelling and design of biomass conversion equipment. Such improved models must be based on reliable experimental data: biomass should be pyrolyzed at high heating rates and the reaction products should be measured using an on-line, non-intrusive method. Therefore, a heated grid reactor with heating rate of 300-600 K/s was used to study pyrolysis of biomass at temperatures in the range of 500-700 degrees C. The formation of formaldehyde and carbon monoxide from wood at high heating rates was successfully visualized using Laser-Induced Fluorescence (LIF). A thin vertical laser line or sheet was present directly above the biomass lying on the heated grid. Two-photon excitation at 230 nm was applied to induce fluorescence of carbon monoxide present in the volatiles, whereas excitation of formaldehyde was done at 355 nm. Visualization of these compounds shows that the release rises strongly with temperature; this typically happens on a timescale in the order of seconds. In principle, the method described allows for the determination of truly primary products. Future research is recommended, aimed at quantifying the concentrations measured by LIE. Care must be taken to calibrate for quenching of the fluorescence signal. Avoiding secondary reactions taking place in the gas phase is another experimental challenge. (C) 2011 Elsevier B.V. All rights reserved.
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| 9. |
- Van Oijen, M., et al.
(författare)
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Impact of droughts on the carbon cycle in European vegetation : a probabilistic risk analysis using six vegetation models
- 2014
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 11:22, s. 6357-6375
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Tidskriftsartikel (refereegranskat)abstract
- We analyse how climate change may alter risks posed by droughts to carbon fluxes in European ecosystems. The approach follows a recently proposed framework for risk analysis based on probability theory. In this approach, risk is quantified as the product of hazard probability and ecosystem vulnerability. The probability of a drought hazard is calculated here from the Standardized Precipitation-Evapotranspiration Index (SPEI). Vulnerability is calculated from the response to drought simulated by process-based vegetation models. We use six different models: three for generic vegetation (JSBACH, LPJmL, ORCHIDEE) and three for specific ecosystems (Scots pine forests: BASFOR; winter wheat fields: EPIC; grasslands: PASIM). The periods 1971-2000 and 2071-2100 are compared. Climate data are based on gridded observations and on output from the regional climate model REMO using the SRES A1B scenario. The risk analysis is carried out for similar to 18 000 grid cells of 0.25 x 0.25 degrees across Europe. For each grid cell, drought vulnerability and risk are quantified for five seasonal variables: net primary and ecosystem productivity (NPP, NEP), heterotrophic respiration (Rh), soil water content and evapotranspiration. In this analysis, climate change leads to increased drought risks for net primary productivity in the Mediterranean area: five of the models estimate that risk will exceed 15 %. The risks increase mainly because of greater drought probability; ecosystem vulnerability will increase to a lesser extent. Because NPP will be affected more than Rh, future carbon sequestration (NEP) will also be at risk predominantly in southern Europe, with risks exceeding 0.25 g Cm-2 d(-1) according to most models, amounting to reductions in carbon sequestration of 20 to 80 %.
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| 10. |
- Yu, J. F., et al.
(författare)
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Heat transfer and flame stabilization of laminar premixed flames anchored to a heat-flux burner
- 2016
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 41:3, s. 2037-2051
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Tidskriftsartikel (refereegranskat)abstract
- Measurement of the burning velocity of unstretched laminar hydrogen/air premixed flames suffers from large uncertainties owing to the highly diffusive nature of hydrogen that can give rise to flame instability. This paper reports on a numerical study of the structures and stability of laminar premixed CH4/O2/CO2 flames and H2/O2/N2 flames anchored to a heat-flux burner using a high-order numerical method with detailed chemical kinetic mechanisms and detailed transport properties. The aim is to elucidate the effect of the flow and temperature inhomogeneity generated by the burner plate holes on flame structures and burning velocity. Heat transfer flux between the burner plate and the surrounding gaseous mixture is investigated under various standoff distances and burner plate temperatures. The burning velocity and the detailed flow, temperature and species distributions in flames with a zero net heat flux between the flames and the burner plate are analyzed. It is found that for the methane flames, when the standoff distance is sufficiently small, the burner can essentially suppress the intrinsic flame instability, but the plate holes can give rise to flame wrinkles of the size of the holes. At high standoff distances, the non-uniformity of the flow from the burner plate holes has a minor effect on the flame surface wrinkling; however, large-scale cellular structures can appear on the flame surface due to intrinsic flame instability. For the studied methane flames the effect of non-uniformity of the flow from the burner plate holes on the burning velocity is fairly small. For the studied hydrogen flames the burner plate could not totally suppress the intrinsic flame instability. The intrinsic flame instability can give rise to a significant increase in the flame surface area and mean burning velocity, with more than 25% increase in the burning velocity.
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| 11. |
- Akkerman, V., et al.
(författare)
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Flow-flame interaction in a closed chamber
- 2008
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Ingår i: Physics of Fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 20:5, s. 21-
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Tidskriftsartikel (refereegranskat)abstract
- Numerous studies of flame interaction with a single vortex and recent simulations of burning in vortex arrays in open tubes demonstrated the same tendency for the turbulent burning rate proportional to U-rms lambda(2/3), where U-rms is the root-mean-square velocity and lambda is the vortex size. Here, it is demonstrated that this tendency is not universal for turbulent burning. Flame interaction with vortex arrays is investigated for the geometry of a closed burning chamber by using direct numerical simulations of the complete set of gas-dynamic combustion equations. Various initial conditions in the chamber are considered, including gas at rest and several systems of vortices of different intensities and sizes. It is found that the burning rate in a closed chamber (inverse burning time) depends strongly on the vortex intensity; at sufficiently high intensities it increases with U-rms approximately linearly in agreement with the above tendency. On the contrary, dependence of the burning rate on the vortex size is nonmonotonic and qualitatively different from the law lambda(2/3). It is shown that there is an optimal vortex size in a closed chamber, which provides the fastest total burning rate. In the present work, the optimal size is six times smaller than the chamber height.
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| 12. |
- Goey, Kaitlyn K. H., et al.
(författare)
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Reporting of patient characteristics and stratification factors in phase 3 trials investigating first-line systemic treatment of metastatic colorectal cancer : A systematic review
- 2018
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Ingår i: European Journal of Cancer. - : Elsevier BV. - 0959-8049 .- 1879-0852. ; 96, s. 115-124
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Forskningsöversikt (refereegranskat)abstract
- Background: Patient characteristics and stratification factors are important factors influencing trial outcomes. Uniform reporting on these parameters would facilitate cross-study comparisons and extrapolation of trial results to clinical practice. In 2007, standardisation on patient characteristics reporting and stratification in metastatic colorectal cancer (mCRC) trials was proposed. We investigated the reporting of prognostic factors and implementation of this proposal in mCRC trials published from 2005 to 2016.Methods: We searched PubMed and Embase (January 2005 – June 2016) for first-line phase 3 mCRC trials. Patient characteristics reporting and use of stratification factors were extracted and analysed for adherence to the proposal from 2007.Results: Sixty-seven trials (35,315 patients) were identified, reporting 48 different patient characteristics (median: 9 [range: 5–18] per study). Age, gender, performance status (PS), primary tumour site and adjuvant chemotherapy were frequently reported (87%–100%), in contrast to laboratory values, such as alkaline phosphatase, lactate dehydrogenase and white blood cell count (10%–25%). We identified 29 different stratification factors (median: 3 [range: 1–9] per study). The most common strata were PS and treatment centre (>60%). A median of 8/12 (range: 4–11) of the proposed parameters was reported. Although the percentage of studies reporting each factor slightly increased over time, there was no significant correlation between publication year and adherence to the proposal from 2007.Conclusions: We observed persistent heterogeneity in the reporting of patient characteristics and use of stratification factors in first-line mCRC trials. The proposal from 2007 has not led to increased uniformity of patient characteristics reporting and use of stratification over time. There is an urgent need to address this issue to improve the interpretation of trial results.
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| 13. |
- Hyvonen, R., et al.
(författare)
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The likely impact of elevated [CO2], nitrogen deposition, increased temperature and management on carbon sequestration in temperate and boreal forest ecosystems: a literature review
- 2007
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Ingår i: New Phytologist. - Cambridge : Wiley. - 0028-646X .- 1469-8137. ; 173:3, s. 463-480
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Forskningsöversikt (refereegranskat)abstract
- Temperate and boreal forest ecosystems contain a large part of the carbon stored on land, in the form of both biomass and soil organic matter. Increasing atmospheric [CO2], increasing temperature, elevated nitrogen deposition and intensified management will change this C store. Well documented single-factor responses of net primary production are: higher photosynthetic rate (the main [CO2] response); increasing length of growing season (the main temperature response); and higher leaf-area index (the main N deposition and partly [CO2] response). Soil organic matter will increase with increasing litter input, although priming may decrease the soil C stock initially, but litter quality effects should be minimal (response to [CO2], N deposition, and temperature); will decrease because of increasing temperature; and will increase because of retardation of decomposition with N deposition, although the rate of decomposition of high-quality litter can be increased and that of low-quality litter decreased. Single-factor responses can be misleading because of interactions between factors, in particular those between N and other factors, and indirect effects such as increased N availability from temperature-induced decomposition. In the long term the strength of feedbacks, for example the increasing demand for N from increased growth, will dominate over short-term responses to single factors. However, management has considerable potential for controlling the C store.
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| 14. |
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| 15. |
- Verhoeven, L. M., et al.
(författare)
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A numerical and experimental study of Polycyclic Aromatic Hydrocarbons in a laminar diffusion flame
- 2013
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 34, s. 1819-1826
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Tidskriftsartikel (refereegranskat)abstract
- During the process of biomass gasification tars are formed which exit the gasifier in vapor phase. Tar condensation creates problems like fouling and plugging of after-treatment, conversion and end-use equipment. Gasification tars consist mainly of Polycyclic Aromatic Hydrocarbons (PAHs). Former research has shown the possibilities and difficulties of tar conversion by partial combustion. Basic studies to investigate the oxidation of tars in non-premixed combustion processes are expected to give more insight in this problem. In this paper the ability of the flamelet-generated manifold (FGM) approach to numerically model multi-dimensional, laminar, non-premixed flames with the inclusion of PAH chemistry is investigated. Modeling detailed PAH chemistry requires the employment of large reaction mechanisms which lead to expensive numerical calculations. The application of a reduction technique like FGM leads to a considerable decrease (up to two orders) in the required computation time. A 1D numerical validation shows that the improvements achieved by implementing a varying Lewis number for the progress variable Y are significant for PAH species with a large Lewis number, such as C10H8. Considerable improvements are found near the flame front and on the fuel side of the flame. A comparison has been made of FGM results with qualitative Planar Laser Induced Fluorescence (PLIF) measurements. A laminar CH4/N-2-air co-flow flame has been doped with two dopants, benzene and toluene, at three different concentrations. A set of filters was used in order to qualitatively distinguish the small (1-2 rings) and large (3 or more rings) aromatic species. The results show that the model is able to capture the major flame characteristics typical for PAH formation in multi-dimensional laminar non-premixed flames. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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