| 1. |
- Wallén-Mackenzie, Åsa, et al.
(författare)
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Restricted cortical and amygdaloid removal of vesicular glutamate transporter 2 in preadolescent mice impacts dopaminergic activity and neuronal circuitry of higher brain function.
- 2009
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Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401 .- 0270-6474. ; 29:7, s. 2238-51
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Tidskriftsartikel (refereegranskat)abstract
- A major challenge in neuroscience is to resolve the connection between gene functionality, neuronal circuits, and behavior. Most, if not all, neuronal circuits of the adult brain contain a glutamatergic component, the nature of which has been difficult to assess because of the vast cellular abundance of glutamate. In this study, we wanted to determine the role of a restricted subpopulation of glutamatergic neurons within the forebrain, the Vglut2-expressing neurons, in neuronal circuitry of higher brain function. Vglut2 expression was selectively deleted in the cortex, hippocampus, and amygdala of preadolescent mice, which resulted in increased locomotor activity, altered social dominance and risk assessment, decreased sensorimotor gating, and impaired long-term spatial memory. Presynaptic VGLUT2-positive terminals were lost in the cortex, striatum, nucleus accumbens, and hippocampus, and a downstream effect on dopamine binding site availability in the striatum was evident. A connection between the induced late-onset, chronic reduction of glutamatergic neurotransmission and dopamine signaling within the circuitry was further substantiated by a partial attenuation of the deficits in sensorimotor gating by the dopamine-stabilizing antipsychotic drug aripiprazole and an increased sensitivity to amphetamine. Somewhat surprisingly, given the restricted expression of Vglut2 in regions responsible for higher brain function, our analyses show that VGLUT2-mediated neurotransmission is required for certain aspects of cognitive, emotional, and social behavior. The present study provides support for the existence of a neurocircuitry that connects changes in VGLUT2-mediated neurotransmission to alterations in the dopaminergic system with schizophrenia-like behavioral deficits as a major outcome.
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| 2. |
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| 3. |
- Birgner, Carolina, et al.
(författare)
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VGLUT2 in dopamine neurons is required for psychostimulant-induced behavioural activation
- 2010
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 107:1, s. 389-394
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Tidskriftsartikel (refereegranskat)abstract
- The “One neuron-one neurotransmitter” concept has been challenged frequently during the last three decades, and the coexistence of neurotransmitters in individual neurons is now regarded as a common phenomenon. The functional significance of neurotransmitter coexistence is, however, less well understood. Several studies have shown that a subpopulation of dopamine (DA) neurons in the ventral tegmental area (VTA) expresses the vesicular glutamate transporter 2 (VGLUT2) and has been suggested to use glutamate as a cotransmitter. The VTA dopamine neurons project to limbic structures including the nucleus accumbens, and are involved in mediating the motivational and locomotor activating effects of psychostimulants. To determine the functional role of glutamate cotransmission by these neurons, we deleted VGLUT2 in DA neurons by using a conditional gene-targeting approach in mice. A DAT-Cre/Vglut2Lox mouse line (Vglut2f/f;DAT-Cre mice) was produced and analyzed by in vivo amperometry as well as by several behavioral paradigms. Although basal motor function was normal in the Vglut2f/f;DAT-Cre mice, their risk-taking behavior was altered. Interestingly, in both home-cage and novel environments, the gene targeted mice showed a greatly blunted locomotor response to the psychostimulant amphetamine, which acts via the midbrain DA system. Our results show that VGLUT2 expression in DA neurons is required for normal emotional reactivity as well as for psychostimulant-mediated behavioral activation.
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| 4. |
- Bäckström, Daniel, 1985, et al.
(författare)
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On the use of alternative fuels in rotary kiln burners - An experimental and modelling study of the effect on the radiative heat transfer conditions
- 2015
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Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 138, s. 210-220
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Tidskriftsartikel (refereegranskat)abstract
- Abstract In this work, the radiative heat transfer conditions in a 400 kWfuel test furnace were studied. The test furnace is a scaled pilot of a rotary kiln furnace used in iron ore pellet production. In particular, the study focuses on the choice of fuel and the subsequent effect on temperature and radiative conditions in the flame. Several co-firing flames of coal and biomass were investigated and also other fuels such as heavy fuel oil and natural gas. The test furnace was used in the experiments, and radiative intensity was measured with a narrow angle radiometer. Detailed radiation modelling was performed using spectral models for gas and particle properties. The results show that all co-firing flames give a shorter radiating flame length. Based on the radiation modelling, it was also shown that the particle radiation dominates the heat transfer from the flames. Due to the high pre-heating temperature of the combustion air (1100°C), the flame temperatures were generally very high. The flame temperature in the natural gas flame was likely around 2000°C while the coal flame temperatures were estimated to 1500-1600°C. The two coals tested, having almost identical fuel specifications, resulted in a substantial difference in the radiation intensity emitted by the flame. This emphasizes the need of direct radiation measurements to evaluate fuel changes in industrial processes that are highly dependent on the heat transfer conditions.
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| 5. |
- Colin, Samuel, et al.
(författare)
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Flame Characterization of Cofiring Gaseous and Solid Fuels in Suspensions
- 2024
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Ingår i: ACS Omega. - 2470-1343. ; 9:26, s. 28268 -28282
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Tidskriftsartikel (refereegranskat)abstract
- This work characterizes technical scale flames of suspension firing of gaseous and solid fuel mixtures through in-flame measurements with focus on nitrogen oxide (NOx) formation. The aims are to investigate the impacts of substituting a solid fuel with a gaseous fuel on the important mechanisms for NOx formation and to highlight important considerations for burner design. The investigation was performed in a 100 kW test unit that fires mixtures of propane and lignite. The global emissions levels and in-flame compositions were measured. A detailed reaction model was used to interpret the experimental results. The study highlights the importance of the early release of volatile nitrogen to reduce the levels of NOx. The findings indicate that substituting lignite by propane is advantageous in terms of reducing NO emissions, primarily due to the diminished input of fuel-bound nitrogen to the flame. However, this holds true only if the flame temperature of the gaseous fuel does not increase excessively. Finally, introducing a relatively small quantity of solid fuel to a propane flame appears to alter the flame behavior to resembles that of the “solid fuel,” with a longer and wider flame. Despite this, carbon monoxide and nitrogen oxide concentrations remain like gas combustion but more dispersed.
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| 6. |
- Edland, Rikard, 1990, et al.
(författare)
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Evaluation of NOx-Reduction Measures for Iron-Ore Rotary Kilns
- 2020
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 34:4, s. 4934-4948
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Tidskriftsartikel (refereegranskat)abstract
- The grate-kiln process is employed for sintering and oxidation of iron-ore pellets. In this process, a fuel (typically coal) is combusted with a large amount of excess air in a rotary kiln, and the high air-to-fuel ratio leads to significant NOx formation. The current Article is an assessment of NOx reduction measures that have been tested in pilot-scale and in full-scale by the Swedish iron-ore company Luossavaara-Kiirunavaara Aktiebolag (LKAB). The results show that the scaling between the full-scale kiln and the pilot-scale kiln is crucial, and several primary measures that reduce NOx significantly in pilot-scale achieve negligible reduction in full-scale. In the investigated full-scale kiln, thermal NOx formation is efficiently suppressed and low compared with the NO formation from the fuel-bound nitrogen (especially char-bound nitrogen). Suppressing the NO formation from the char-bound nitrogen is difficult due to the high amounts of excess air, and all measures tested to alter mixing patterns have shown limited effect. Switching to a fuel with a lower nitrogen content is efficient and probably necessary to achieve low NOx emissions without secondary measures. Simulations show that replacing the reference coal with a biomass that contains 0.1% nitrogen can reduce NOx emissions by 90%.
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| 7. |
- Edland, Rikard, 1990, et al.
(författare)
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Formation of nitrogen oxides in rotary kiln burners: an assessment of pilot scale experiments using gaseous, liquid and solid fuels
- 2015
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Ingår i: INFUB 2015.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The combustion process in rotary kilns for iron ore production is associated with high temperatures and large amounts of highly preheated air (λ=5-6). These conditions are favourable for NOx formation. Further, coal is typically the main fuel in the process and the CO2 emissions need to be reduced. Thus, emission control strategies are becoming of increasing importance for this type of industrial processes. The present work studies the formation of NOx during combustion of oil, gas, two coals and different blends of coal and biomass. The paper includes both experimental and modelling work. The experiments were performed in co-operation with LKAB using their pilot scale burner test facility (400 kWfuel), which is able to simulate the conditions of the full-scale process. The model, which is used to interpret the experimental results, is based on detailed reaction kinetics with simplified descriptions of temperature and mixing profiles. The results show that oil and gas flames lead to significantly higher NOx formation than solid fuel flames. In general, the thermal formation route is shown to be an important contributor to NOx formation, i.e. also for the solid fuels.
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| 8. |
- Edland, Rikard, 1990, et al.
(författare)
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Implications of Fuel Choice and Burner Settings for Combustion Efficiency and NOx Formation in PF-Fired Iron Ore Rotary Kilns
- 2017
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 31:3, s. 3253-3261
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Tidskriftsartikel (refereegranskat)abstract
- The combustion process applied in the grate-kiln process for iron ore pellet production employs air-to-fuel equivalence ratios in the range of 4-6, typically with coal as fuel and high-temperature air (>1000 degrees C) as oxidant. The NOx emissions from these units are in general significantly higher than those in other combustion systems, and the large flows of flue gases make the implementation of secondary measures for NOx control costly. Therefore, it is of importance to investigate NOx. formation under combustion conditions relevant for iron ore production, in order to control the emissions from these units. The present work examines NO formation during the combustion of four pulverized coals, as well as during cofiring with biomass in a pilot-scale kiln (580 kWfuel) based on a two-week experimental campaign. The influence of burner settings was also included in the investigation. Based on the presented experimental results and the results of previous modeling and experimental studies, we suggest that the NOx emissions are mainly the result of a high conversion of fuel-bound nitrogen (fuel-N) to NO. In particular, char-bound nitrogen (char-N) conversion appears to be higher than in conventional pulverized fuel flames, presumably due to the high levels of oxygen present in the char-burnout region. The temperatures in the kiln varied between the test cases, but thermal NO formation is estimated to be of low importance.
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| 9. |
- Edland, Rikard, 1990, et al.
(författare)
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Scaling of Pulverized-Fuel Jet Flames That Apply Large Amounts of Excess Air - Implications for NOx Formation
- 2019
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 12:14
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Tidskriftsartikel (refereegranskat)abstract
- Measures to reduce nitrogen oxides (NOx) formation in industrial combustion processes often require up-scaling through pilot-scale facilities prior to being implemented in commercial scale, and scaling is therefore an important aspect of achieving lower NOx emissions. The current paper is a combined experimental and modelling study that aims to expand the understanding of constant velocity scaling for industrial jet flames applying high amounts of excess air. These types of flames are found in e.g., rotary kilns for production of iron ore pellets. The results show that, even if the combustion settings, velocity, and temperature profiles are correctly scaled, the concentration of oxygen experienced by the fuel during char combustion will scale differently. As the NO formation from the char combustion is important in these flames, the differences induced by the scaling has important impacts on the efficiencies of the applied primary measures. Increasing the rate of char combustion (to increase the Damköhler number), by using, for example, smaller-sized particles, in the pilot-scale is recommended to improve scaling.
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| 10. |
- Fredriksson, Robert, et al.
(författare)
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The polyamine transporter Slc18b1(VPAT) is important for both short and long time memory and for regulation of polyamine content in the brain.
- 2019
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Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 15:12
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Tidskriftsartikel (refereegranskat)abstract
- SLC18B1 is a sister gene to the vesicular monoamine and acetylcholine transporters, and the only known polyamine transporter, with unknown physiological role. We reveal that Slc18b1 knock out mice has significantly reduced polyamine content in the brain providing the first evidence that Slc18b1 is functionally required for regulating polyamine levels. We found that this mouse has impaired short and long term memory in novel object recognition, radial arm maze and self-administration paradigms. We also show that Slc18b1 KO mice have altered expression of genes involved in Long Term Potentiation, plasticity, calcium signalling and synaptic functions and that expression of components of GABA and glutamate signalling are changed. We further observe a partial resistance to diazepam, manifested as significantly lowered reduction in locomotion after diazepam treatment. We suggest that removal of Slc18b1 leads to reduction of polyamine contents in neurons, resulting in reduced GABA signalling due to long-term reduction in glutamatergic signalling.
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