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- Kristensson, Elias, et al.
(författare)
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Structured illumination for 3-D Mie imaging and 2-D attenuation measurements in optically dense sprays
- 2011
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 33, s. 855-861
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Tidskriftsartikel (refereegranskat)abstract
- Qualitative description of spray structure and geometry in the near-field region of atomizing sprays is particularly challenging due to the lack of visibility through such optically dense media. Similarly, quantitative determination of the optical depth can be particularly underestimated as a result of detecting photons which have experienced a number of scattering events. In this paper we demonstrate, based on average imaging, the possibility to reconstruct the "true" 3-D Mie representation of an aerated spray, where image artifacts introduced by multiple scattering have been suppressed by means of Structured Laser Illumination Planar Imaging (SLIPI). Here, six images were used, instead of three usually employed in structured illumination, to reconstruct a single SLIPI image. Based on a similar approach, a 2-D estimation of optical depth has been performed and compared with the conventional single-point attenuation measurement. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 2. |
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| 3. |
- Bylander, Anna, 1979, et al.
(författare)
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Rapid effects of progesterone on ciliary beat frequency in the mouse fallopian tube.
- 2010
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Ingår i: Reproductive biology and endocrinology : RB&E. - : Springer Science and Business Media LLC. - 1477-7827. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: The physiological regulation of ciliary beat frequency (CBF) within the fallopian tube is important for controlling the transport of gametes and the fertilized ovum. Progesterone influences gamete transport in the fallopian tube of several mammalian species. In fallopian tubes isolated from cows, treatment with 20 micromolar progesterone caused a rapid reduction of the tubal CBF. The aims of this study were to establish methodology for studying fallopian tube CBF in the mouse, as it is an important model species, and to investigate if progesterone rapidly affects the CBF of mice at nM concentrations. METHODS: A method to assess tubal CBF of mice was developed. Fallopian tubes were dissected and the tissue was cut in small pieces. Tissue samples with moving cilia were located under an inverted bright field microscope and held still against the bottom of a petri dish by a motorized needle system. Images were acquired over 90 minutes at 35 degrees C with a high-speed camera and used for assessing changes in the CBF in response to the addition of hormone. RESULTS: The baseline CBF of the mouse fallopian tube was 23.3 +/- 3.8 Hz. The CBF was stable over at least 90 minutes allowing establishment of a baseline frequency, addition of hormone and subsequent recordings. Progesterone at concentrations of 20 micromolar and 100 nM significantly reduced the CBF by 10% and 15% respectively after 30 minutes compared with controls. CONCLUSIONS: The present study demonstrates that the mouse, despite its small size, is a useful model for studying the fallopian tube CBF ex vivo. The rapid reduction in CBF by 100 nM progesterone suggests that gamete transport in the fallopian tube could be mediated by progesterone via a non-genomic receptor mechanism.
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| 5. |
- Duong, Jeudi, et al.
(författare)
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High Speed Combustion Imaging in a Large Bore Gas Engine: The Relationship Between Pre- and Main Chamber Heat Release
- 2014
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Ingår i: ASME 2013 International Mechanical Engineering Congress and Exposition Volume 8A: Heat Transfer and Thermal Engineering. - 9780791856345 ; 8A, s. 08-022
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Konferensbidrag (refereegranskat)abstract
- An experimental study is carried out to investigate the combustion process in a Wartsila 34SG spark-ignited lean burn four-stroke large bore engine (bore 340 mm) by means of optical diagnostics when operating on natural gas. The main focus of this work is to gain knowledge about in-cylinder combustion phenomena when igniting a lean air/fuel mixture with pre-combustion chamber induced jets. Especially the origin of cyclic variability is of interest. The flame propagation process in a single cycle was captured using a high speed video camera. The analysis is based on apparent heat release rates in the pre-combustion chamber and main chamber, in order to find correlations with the imaged phenomena. The results show that the flame propagation inside the main chamber starts at the end of the pre-chamber combustion heat release and that variation in main chamber heat release does not correlate with variations in the pre-combustion chamber.
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| 6. |
- Eriksson, Emma, 1980, et al.
(författare)
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Optical manipulation and microfluidics for studies of single cell dynamics
- 2007
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Ingår i: Journal of Optics. A, Pure and applied optics. - 1464-4258 .- 1741-3567 .- 1361-6617. ; 9:8, s. 113-121
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Tidskriftsartikel (refereegranskat)abstract
- Most research on optical manipulation aims towards investigation and development of the system itself. In this paper we show how optical manipulation, imaging and microfluidics can be combined for investigations of single cells. Microfluidic systems have been fabricated and are used, in combination with optical tweezers, to enable environmental changes for single cells. The environment within the microfluidic system has been modelled to ensure control of the process. Three biological model systems have been studied with different combinations of optical manipulation, imaging techniques and microfluidics. In Saccharomyces cerevisiae, environmentally induced size modulations and spatial localization of proteins have been studied to elucidate various signalling pathways. In a similar manner the oxygenation cycle of single red blood cells was triggered and mapped using Raman spectroscopy. In the third experiment the forces between the endoplasmic reticulum and chloroplasts were studied in Pisum sativum and Arabidopsis thaliana. By combining different techniques we make advanced biological research possible, revealing information on a cellular level that is impossible to obtain with traditional techniques.
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| 7. |
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| 8. |
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| 9. |
- Wellander, Rikard
(författare)
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Multi-Dimensional Quantitative Laser-based Diagnostics - Development and Practial Applications
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Laser based optical diagnostic methods are routinely used in combustion research. Many of the more common approaches are based on illuminating a cross-section of the sample with a thin laser sheet. For example, by targeting an electronic transition in a molecule, its concentration within the plane illuminated by the laser sheet can be deduced. By probing the relative occurrence of an atom or molecule in different rotational or vibrational states or by probing the Doppler shift in Rayleigh scattering, it is possible to extract the temperature. The flow field can be measured by seeding particles into the measurement volume and following them through multiple exposures. The work reported in the thesis concerns the development, improvement and applications of measurement techniques based on laser sheet illumination. The aforementioned techniques are most often employed on a single shot basis, providing independent snapshots of two-dimensional (2D) data. In some examples, the measurement techniques are extended to the third spatial dimension, and in recent years, studies employing high repetition rate measurements capable of resolving the dynamics in time have become more frequent. In the thesis, a method for simultaneously extending the measurements to the third spatial dimension and to the time dimension, is presented. A high repetition rate laser and detection system is combined with oscillating mirrors, the laser sheet being scanned back and forth throughout the measurement volume. The deflections from two mirrors operated at different frequencies are combined to obtain equidistant laser sheets in the measurement region. The method is demonstrated on the Mie-scattering from a flow of droplets and is used to probe the planar laser induced fluorescence (PLIF) from the OH in a flame. Post processing methods to calculate concentrations and flame-fronts from large data sets are demonstrated. Measurements of droplet concentration and size distribution in sprays, based on recording the light scattered from a laser sheet, suffer from uncertainties due to multiple scattering (MS) and attenuation of the illuminating and scattered light. A method is demonstrated here, that takes advantage of the ability to suppress the MS light by means of structured illumination. After MS suppression, the attenuation of the laser and signal light can be compensated for by comparing the transmission through the spray with the side-scattered signal. In the process, the local extinction coefficient is calculated from the Beer-Lambert law. Laser based optical diagnostic techniques are in general developed for atmospheric flames under ideal laboratory conditions. In the application of the same techniques in more realistic situations, such as internal combustion (IC) engines, the harsh conditions involving vibrations, varying pressure, moving parts, limited optical access and a sooty environment have to be taken into account. Several of the measurement campaigns reported in the thesis were conducted in IC engines. Although the main goals of these campaigns were to answer combustion or engine related questions, time has also been invested in improving and adopting the measurement techniques to the existing conditions. By following the spray propagation in a light duty-diesel engine over time, knowledge was gained regarding how early spray injections should be conducted to avoid wall wetting. From high speed laser induce incandescence (LII) measurements in a heavy-duty Diesel engine, conclusions regarding soot formation and oxidation were drawn. The implementation of LII at high repetition rates in IC engines was investigated here. Challenges associated with attenuation of the laser and signal light were also addressed. Visualization of the flame jet propagation in a large-bore gas engine was made possible by means of fuel tracer LIF. Apart from the combustion related conclusions, it was shown that the image quality could be improved substantially by the use of correction optics.
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| 10. |
- Wellander, Rikard, et al.
(författare)
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Study of the Early Flame Development in a Spark-Ignited Lean Burn Four-Stroke Large Bore Gas Engine by Fuel Tracer PLIF
- 2014
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Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944. ; 7:2, s. 928-936
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Tidskriftsartikel (refereegranskat)abstract
- In this work the pre- to main chamber ignition process is studied in a Wärtsilä 34SG spark-ignited lean burn four-stroke large bore optical engine (bore 340 mm) operating on natural gas. Unburnt and burnt gas regions in planar cross-sections of the combustion chamber are identified by means of planar laser induced fluorescence (PLIF) from acetone seeded to the fuel. The emerging jets from the pre-chamber, the ignition process and early flame propagation are studied. Measurements reveal the presence of a significant temporal delay between the occurrence of a pressure difference across the pre-chamber holes and the appearance of hot burnt/burning gases at the nozzle exit. Variations in the delay affect the combustion timing and duration. The combustion rate in the pre-chamber does not influence the jet propagation speed, although it still has an effect on the overall combustion duration. PLIF images also show that there is mainly lean unburnt gas, originating from the main-chamber, that exit the pre-chamber in the initial phase of ignition, indicating incomplete mixing of the gases in the pre-chamber prior ignition. These findings are also supported by CFD modeling performed on the Wärtsilä 34SG combustion system. Similar to the air entrainment in a diesel spray, the jets exiting the pre-chamber causes pronounced entrainment of compressed fresh charges into the burning jets, thus promoting heat transfer and subsequent ignition.
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