Increasing the efficiency and performance of internal combustion engines is always of interest in the automotive industry. One limiting factor to achieve this in gasoline combustion engines is the ignition timing which can not always be set where optimal ignition efficiency and performance is obtained. This is due to the knock phenomenon which is an abnormal combustion process that can damage the engine. Due to knock, a feedback controller which sets the ignition timing at the best possible value without the risk of harming the engine is required. In this thesis, a statistically driven knock intensity simulation environment based on the Burr Type XII distribution model was set up. In the simulation environment, different stochastic knock feedback controllers were implemented along with background noise estimation techniques used in the knock detection system. The feedback controllers were evaluated against the conventional knock controller commonly used in today’s engines in terms of ignition angle and transient response. The results from the simulation environment showed that a more advanced mean ignition angle can be achieved with stochastic based knock control strategies with the same knock-rate and without lessening the fast transient response achieved from the conventional strategy. To evaluate the results, some of the controllers were implemented in a four cylinder two-liter four stroke Volvo engine with similar results.

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Abstract Although the genetic sex of an embryo is determined at conception by the presence or absence of the Y chromosome, both females and males have bipotential, undifferentiated gonads early in their development. Genes and testicular hormones direct differentiation into either testes or ovaries. The first relevant gene to be identified was the Y-linked master regulatory gene, SRY, since when several other genes have been found to be of importance for sex determination. The primary aim here was to identify the role of Wnt-4 in the development of the gonad and adrenal gland. Wnt-4 was found to be expressed in the developing gonad, the Müllerian duct and the adrenal gland, in addition to the kidney, pituitary gland and mammary gland as observed earlier. Expression in the gonad was found to be regulated in a sex-specific manner. After sex determination Wnt-4 was downregulated in the testis, but the expression persisted until birth in the ovary. Wnt-4-deficient female mice demonstrated a partial female-to-male sex reversal and a reduction in the number of oocytes, while the Müllerian duct was absent from both sexes. Lack of Wnt-4 in the adrenal gland led to reduced aldosterone production, indicating abnormal development of the zona glomerulosa. Flutamide administration to pregnant Wnt-4 heterozygote females was shown to partially restore the sex reversal. The results suggest that female development is not a default pathway but needs active signalling, in which Wnt-4 plays an essential role.

In this thesis the possibility of using knock sensors for misfire detection in heavy duty diesel engines is investigated. This is of great interest due to many emission legislations getting stricter, especially in the US where robust misfire detection is mandatory for these types of engines. In order to capture the relevant vibra- tions on the engine a pre-study is made where the resonance frequencies in the cylinders are calculated which can be used for bandpass filtering the knock sen- sor signal. These bandpass filters are used to run tests where the engine is run with normal combustion and misfire on individual cylinders. The tests are made using a straight six cylinder diesel engine with a displacement of 12.7 litres. The test data is used to create threshold maps that can be used for misfire detection and for sensitivity analysis. Thereafter a detection algorithm is developed in MATLAB which involves integrating the knock sensor signal between two prede- fined crank angle degrees and then comparing it with a threshold value that can be interpolated from the threshold map. The test results show that this type of detection algorithm with these types of sensors is possible. There are also some areas of improvements presented that can make the misfire detection even more robust. / I denna rapport undersöks möjligheten att använda knackgivare för misständ- ningsdetektion i dieselmotorer för kommersiellt bruk. Bakgrunden är allt sträng- are lagstiftning i framförallt USA där det ställs krav på robust detektion av miss- tändningar i motorer för kommersiellt bruk. För att fånga de relevanta frekven- serna i cylindrarna som kan användas för detektion av misständning görs en för- studie där resonansfrekvenser beräknas och sedan används för att skapa band- passfilter. Filterna kan i sin tur användas för att filtrera knackgivarsignalerna. De framtagna bandpassfilterna används sedan för omfattande testning av miss- tändning i testcell. Motorn som används i testningen är en rak sexcylindrig die- selmotor med 12.7 liters slagvolym. Med den insamlade datan görs en känslig- hetsanalys samt gränsvärdesmappar som kan användas för misständsdetektion. Därefter utvecklas en detektionsalgoritm i MATLAB som går ut på att integrera knackgivarsignalen mellan två vevaxelvinklar och sedan jämföra med ett gräns- värde som kan interpoleras fram från gränsvärdesmappen. Testdatan visar att detektion med denna typ av system och med denna typ av algoritm är möjlig. I rapporten föreslås också ett antal områden som skulle kunna göra systemet ännu mer robust.

<p>Zebrafish regenerate amputated caudal fins, restoring the size and shape of the original appendage. Regeneration requires generation of diverse cell types comprising the adult fin tissue. Knowledge of the cellular source of new cells and the molecules involved is fundamental to our understanding of regenerative responses. In this dissertation, the contribution made by the bone cells towards fin regeneration is investigated. Fate mapping of osteoblasts revealed that spared osteoblasts contribute only to regenerating osteoblasts and not to other cell types, thereby suggesting lineage restriction during fin regeneration. The functional significance of osteoblast contribution to fin regeneration is tested by developing an osteoblast ablation tool capable of drug induced loss of bone cells. Normal fin regeneration in the absence of resident osteoblast population suggests that the osteoblast contribution is dispensable and provides evidence for cellular plasticity during fin regeneration. To uncover the genes involved in proliferation of osteoblasts within the fin regenerate, a candidate in-situ screen was carried out and revealed bone specific expression of fgfr4 and twist3. Transgenic tools for visualization of gene expression confirmed the screen results. Knockdown of twist3 by morpholino antisense technology impedes fin regeneration. Mutant heterozygotes for twist3 were generated using genome editing reagents, which will enable loss-of-function study in future.</p> / Dissertation

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As powertrains and IC engines continue to grow in complexity, many vehicle manufacturers (OEMs) are turning to simulation in an effort to reduce design validation and calibration costs. Ultimately, their aim is to complete this process entirely within the virtual domain, without the need for any physical testing. Practical simulation techniques for the prediction of knock in spark ignition (SI) engines rely on empirical ignition delay correlations (IDCs). These IDCs are used to approximate the complex ignition delay characteristics of real and surrogate fuel compositions with respect to temperature, pressure and mixture composition. Over the last 40 years, a large number of IDCs have been put forward in the literature, spanning a broad range of fuels, operating conditions and calibration methods. However, the applicability of these tools has yet to be verified at the high brake mean effective pressure (BMEP) operating conditions relevant to highly boosted, downsized engines. Here, the applicability of 16 gasoline-relevant IDCs for predicting knock onset at high loads (BMEP > 30bar) has been investigated by comparing the knock predictions from each IDC against experimentally measured knock onset times. Firstly, a detailed investigation into cylinder pressure data processing techniques was performed to determine which knock detection and angle of knock onset (aKO) measurement methods were most appropriate at high loads. A method based on the maximum amplitude pressure oscillation (MAPO) during knock-free operation best estimated cycle classifications, whilst Shahlari’s Signal Energy Ratio technique [1] most accurately predicted knock onset. To the author’s knowledge, this is the first time that such a comprehensive study on the accuracy of these techniques at such high loads has been conducted. Importantly, these findings represent a valuable framework to inform other researchers in the field of knocking combustion on which techniques are needed to extract accurate and relevant information from measured cylinder pressure records. Secondly, the data processing techniques derived were applied to experimental data collected across a wide range of high BMEP operating conditions (up to a maximum of 32 bar) using a 1.6 litre, 4-cylinder SI engine. Trapped charge composition and temperature were predicted using a calibrated 1D model of the engine, whilst the temperature of a hypothetical hotspot in the unburned zone was estimated separately by assuming adiabatic compression from a point after intake valve closing and by mapping γ (the ratio of specific heat capacities) as a function of temperature. This revealed that none of the IDCs tested performed well at conditions relevant to modern, downsized engines. The IDC that achieved the best overall balance between aKO accuracy and cycle-classification agreement was the “cool-flame” correlation for iso-octane proposed by Ma [2]. However, this had an unacceptably high average aKO error of ±3.5° compared to the ±2°CA limit observed within the literature, and its average cycle-classification accuracy was below 60%. The main reason for this relatively modest accuracy was a large number of false-positive cycle classifications, which mainly occurred in slow or late burning cycles. Further work should therefore focus on methods to reduce the number of false positive classifications obtained with this correlation, which could be achieved using empirical correlations to describe the latest point in the cycle for which knock would be permitted to occur in terms other measureable combustion parameters. Overall, this research has generated a unique insight into combustion at very high loads, as well as an extensive dataset that can be used for future research to improve the accuracy of empirical knock modelling techniques. Furthermore, this work has demonstrated that for the purposes of virtual spark timing calibration and the avoidance of knock, the current crop of practical simulation tools is not accurate enough at the conditions relevant to modern SI engines and has provided a better understanding of their limitations. These findings represent a major contribution to the field from both a research perspective and for industrial applications.

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In this study the importance of prohibitin1 and prohibitin2 genes for Trypanosoma brucei was examined. RNA interference showed both of them essential for parasites to survive. Knocking down of these genes resulted in altered morphology of the mitochondrion, changes in membrane potential and shut down of mitochondrial translation. No changes were observed in levels of Reactive Oxygen Species and respiration. Both prohibitines are part of big complex present in the mitochondrion.

Advanced combustion concepts are required to meet the increasing global energy demand and stringent emission regulations imposed by the governments on automobile manufacturers. Improvement in efficiency and reduction in emissions can be achieved by downsizing the Spark Ignition (SI) engines. The operating range of SI engine is limited by occurrence of knock, pre-ignition and the following super-knock due to boosting of intake pressure, to account for the reduction of power, as a result of downsizing the engine. Super-knock, which represents high momentary pressure accompanied with pressure oscillations, is known to permanently damage the moving component of the engines. Therefore fundamental comprehensive understanding of the mechanism involved in pre-ignition and super-knock are required to design highly efficient spark ignition engines with lower emissions that can meet the increasing government regulations. \nThe thesis focuses on auto-ignition characteristics of endgas and the bulk mixture properties that favor transition of pre-ignition to super-knock. Direct numerical studies indicate that super-knock occurs to due to initiation of premature flame front that transition into detonation. In literature, many sources are reported to trigger pre-ignition. Due to the uncertainty of the information on the sources that trigger pre-ignition, it is extremely difficult to predict and control pre-ignition event in SI engines. Since the information on the source of pre-ignition is not available, the main focus of this work is to understand the physical and chemical mechanisms involved in super-knock, factors that influence super-knock and methods to predict super-knock. \n
Pre-ignition was initiated at known locations and crank angle using a hotspot of known size and strength. Different parametric cases were studied and the location and timing of pre-ignition initiation is found to be extremely important in determining the transition of pre-ignition event to super-knock. Pre-ignition increases the temperature of the endgas and the overall bulk mixture, that transitions the pre-ignition flame front to a detonation. The transition of the flame propagation mode from deflagration to detonation was investigated with different type of analysis methods and all results confirmed the transition of pre-ignition flame front to detonation that results in super- knock.