| 1. |
- Andersson, Martin
(author)
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Churning losses and efficiency in gearboxes
- 2014
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Licentiate thesis (other academic/artistic)abstract
- Efficient transmissions systems are key to producing competitive motor vehicles that have a smaller environmental impact. Gears are the main components in vehicle transmissions and although they are already highly efficient, there is still room for improvement. In this study, the focus falls on the lubricant used to create separating films between gears and todissipate heat. When driving, the gears churn this lubricant, giving rise to power losses that are related to the amount and properties of the lubricant. However, any attempt to reduce these losses must not compromise the required lubrication and heat dissipation. Paper A reports on the use of an FZG gear test rig to investigate power losses and heat generation for different gear immersion depths, surface roughness and coatings. The results show that lower gear roughness reduces gear mesh losses and heat generation. A polishing affect was obtained when a non-coated gear ran against a coated gear.The aim of the research reported in paper B was to increase the accuracy of efficiency testing. It investigated how and whether repeated disassembly and re-assembly of the same test equipment, as well as test performance and rig conditions, affect the measured torque loss in an FZG gear test rig. It was shown that the measured torque loss changes between one assembly and another. Repeatability between tests is crucial for accurate conclusions.The aim of the research reported in paper C was to study whether gear efficiency could be increased by a running-in procedure, which would reduce the need for a coolant. A back-to-back gear test rig was used to test two running-in loads. Higher gear mesh efficiency was seen when a higher running-in load was used.
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| 2. |
- Levin, Malin, 1973, et al.
(author)
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Evaluation of macrophage-specific promoters using lentiviral delivery in mice.
- 2012
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In: Gene therapy. - : Springer Science and Business Media LLC. - 1476-5462 .- 0969-7128. ; 19:11, s. 1041-7
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Journal article (peer-reviewed)abstract
- In gene therapy, tissue-specific promoters are useful tools to direct transgene expression and improve efficiency and safety. Macrophage-specific promoters (MSPs) have previously been published using different delivery systems. In this study, we evaluated five different MSPs fused with green fluorescent protein (GFP) to delineate the one with highest specificity using lentiviral delivery. We compared three variants of the CD68 promoter (full length, the 343-bp proximal part and the 150-bp proximal part) and two variants (in forward and reverse orientation) of a previously characterized synthetic promoter derived from elements of transcription factor genes. We transduced a number of cell lines and primary cells in vitro. In addition, hematopoietic stem cells were transduced with MSPs and transferred into lethally irradiated recipient mice. Fluorescence activated cell sorting analysis was performed to determine the GFP expression in different cell populations both in vitro and in vivo. We showed that MSPs can efficiently be used for lentiviral gene delivery and that the 150-bp proximal part of the CD68 promoter provides primarily macrophage-specific expression of GFP. We propose that this is the best currently available MSP to use for directing transgene expression to macrophage populations in vivo using lentiviral vectors.
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| 3. |
- Perman, Jeanna, 1981, et al.
(author)
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The VLDL receptor promotes lipotoxicity and increases mortality in mice following an acute myocardial infarction.
- 2011
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In: The Journal of clinical investigation. - : American Society for Clinical Investigation. - 1558-8238 .- 0021-9738. ; 121:7, s. 2625-40
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Journal article (peer-reviewed)abstract
- Impaired cardiac function is associated with myocardial triglyceride accumulation, but it is not clear how the lipids accumulate or whether this accumulation is detrimental. Here we show that hypoxia/ischemia-induced accumulation of lipids in HL-1 cardiomyocytes and mouse hearts is dependent on expression of the VLDL receptor (VLDLR). Hypoxia-induced VLDLR expression in HL-1 cells was dependent on HIF-1α through its interaction with a hypoxia-responsive element in the Vldlr promoter, and VLDLR promoted the endocytosis of lipoproteins. Furthermore, VLDLR expression was higher in ischemic compared with nonischemic left ventricles from human hearts and was correlated with the total lipid droplet area in the cardiomyocytes. Importantly, Vldlr-/- mice showed improved survival and decreased infarct area following an induced myocardial infarction. ER stress, which leads to apoptosis, is known to be involved in ischemic heart disease. We found that ischemia-induced ER stress and apoptosis in mouse hearts were reduced in Vldlr-/- mice and in mice treated with antibodies specific for VLDLR. These findings suggest that VLDLR-induced lipid accumulation in the ischemic heart worsens survival by increasing ER stress and apoptosis.
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| 4. |
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| 5. |
- Perricone, Guido, 1973-, et al.
(author)
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A proposed dyno bench test cycle to study particle emissions from disc brakes
- 2014
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Conference paper (peer-reviewed)abstract
- In urban areas, the impact of on-road vehicles on particulate matter is well acknowledged. Particulates originating from vehicles come not only from the engine exhaust emissions, but also from wear processes in brakes and between tires and road surface. In the EU, these non-exhaust vehicle emissions equal approximately 50 % of the exhaust emissions of PM10 (particles with aerodynamic diameters smaller than 10 μm).To reduce the air pollution, tail pipe emissions are today regulated. Detailed test protocols for engine exhaust verification and certification, using different driving cycles, are available. However, there are no formal test protocols for particulate emissions from disc brakes.Here a test cycle for disc brakes is proposed considering a typical European car usage. It consists of nine different braking blocks, starting from a burning-in and involving town, country road, highway and hill descend conditions.To evaluate the test cycle, a front brake assembly was set-up in a shaft-type inertia dynamometer. Particle emissions were continuously registered using a particle counter, which can measure particulate matter from ultrafine to coarse sizeThe conclusion is that the proposed test cycle can be used to evaluate particulate emissions from disc brakes, and the next step towards a test protocol should be to improve the measurements using a clean environment around the brake assembly and isokinetic sampling.
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| 6. |
- Zhu, Yi, et al.
(author)
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A field test study of leaf contamination on railhead surfaces
- 2012
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In: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 98
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Journal article (peer-reviewed)abstract
- Leaves on train tracks cause low adhesion between wheels and rails, especially in the autumn. A Stockholm local traffic track with a long history of adhesion problems was subject to field tests of railhead contamination. Over a year, on five occasions under different conditions, the friction coefficient was measured using a hand-push tribometer and rail samples were taken. ESCA and GD-OES analyses were conducted to determine the composition of the top layer of rail contaminants. The blackish layer contains much higher contents of calcium, carbon, and nitrogen than other samples indicating a chemical reaction occurring from the surface to a depth of several microns. The thickness of the friction-reducing oxide layer predicts the friction coefficient and leaf contamination extent.
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