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- Ghajeri, Farnaz
(author)
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Characterization of a silica based nano/mesoporous material for adsorption application : A study of the relation between synthesis, structure and adsorption efficiency
- 2019
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Licentiate thesis (other academic/artistic)abstract
- During last years the interest in large scale production of nano/mesoporous materials has increased in the industry due to benefits that these materials can provide. Silica based nanomaterials are examples of such materials with large specific surface area and pore volume where the porous structure is the key for the resulting properties leading to efficiency in e.g. filtration applications.The aim of this research was to contribute knowledge on understanding the porous structure and its relation to the efficiency. For this approach, the porous structure of a nano/mesoporous silica-based material is characterized. The analysis of this material is a challenge as it has a wide range of pores in the structure from a few nanometres to several micrometres. Electron microscopy (EM) methods are used for the structural analysis of the materials as a complementary method to nitrogen adsorption (NA). The samples are analysed as powders and the relation between the structure and efficiency in the application is discussed.Through this research different synthesis pathways have been studied under the family name of Quartzene®, and the differences in the resulting structure is discussed. The synthesis and storage conditions have been varied in order to study the effect on the porous structure.
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| 2. |
- Larsson, Anders
(author)
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High frequency distortion in power grids due to electronic equipment
- 2006
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Licentiate thesis (other academic/artistic)abstract
- Power quality is a subject that has received a lot of attention during the last 10 to 20 years, both in industry and in academia. Power quality concerns interaction between the power grid and its customers and between the power grid and equipment connected to it, reflected in voltages and currents. Research and other developments in this area have to a great extent concentrated on relatively slow and low-frequency phenomena, with the main emphasis being on voltage dips (reductions in voltage magnitude with duration between about 50 ms and several seconds) and low-frequency harmonics (waveform distortion by frequency components up to about 2 kHz). These phenomena are reasonably well understood. For higher-frequency phenomena there is no such general understanding. There are a number of reasons for looking closer into this frequency range, including increased distortion by energy-efficient equipment, interference with equipment such as that used for communications, reduced service life of equipment, the availability of measurement and analysis tools, and pure scientific curiosity. This licentiate thesis addresses voltage and current distortion in low- voltage networks in the frequency range between 2 kHz and 1 MHz. The report starts with a general overview of power quality and power-quality disturbances. This part is mainly a review of existing knowledge. The report continues with a philosophical discussion of measurement and analysis of power-quality disturbances. The objectiveness of the analysis methods is especially addressed. The importance of understanding the limitations posed by measurement standards and commonly used analysis methods is emphasized. The choice of measurement and analysis tool has the potential to influence the conclusions drawn from a study. Different analysis and presentation tools are discussed for disturbances in the frequency band of interest. Where possible, a range of methods should be used. Next to the commonly used time- and frequency-domain presentations, the spectrogram or time-frequency-domain is introduced as a useful tool. The measurement technology used for obtaining sampled voltage and current waveforms is discussed. Measurements have been performed on the current drawn by individual devices and by groups of devices. These measurements have been performed mainly in a controlled laboratory environment. Voltage measurements have mainly been performed at a number of locations in the field. Both current and voltage measurements are described in detail in this report, together with the measurement results. The main contribution of this licentiate report is in the systematic analysis of disturbances in the frequency range between 2 kHz and 1 MHz. The spectrogram has proven a suitable tool for analyzing and visualizing these disturbances. Further knowledge is obtained on the disturbances arising from fluorescent lamps with high-frequency ballasts. Contrary to conventional knowledge, the main concern is in the so-called zero-crossing distortion. The level of this distortion component demonstrates a linear increase with the number of devices.
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| 3. |
- Larsson, Anders, 1977-
(author)
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System-on-Chip Test Scheduling and Test Infrastructure Design
- 2005
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Licentiate thesis (other academic/artistic)abstract
- There are several challenges that have to be considered in order to reduce the cost of System-on-Chip (SoC) testing, such as test application time, chip area overhead due to hardware introduced to enhance the testing, and the price of the test equipment. In this thesis the test application time and the test infrastructure hardware overhead of multiple-core SoCs are considered and two different problems are addressed. First, a technique that makes use of the existing bus structure on the chip for transporting test data is proposed. Additional buffers are inserted at each core to allow test application to the cores and test data transportation over the bus to be performed asynchronously. The non-synchronization of test data transportation and test application makes it possible to perform concurrent testing of cores while test data is transported in a sequence. A test controller is introduced, which is responsible for the invocation of test transportations on the bus. The hardware cost, introduced by the buffers and test controller, is minimized under a designer-specified test time constraint. This problem has been solved optimally by using a Constraint Logic Programming formulation, and a tabu search based heuristic has also been implemented to generate quickly near-optimal solutions. Second, a technique to broadcast tests to several cores is proposed, and the possibility to use overlapping test vectors from different tests in a SoC is explored. The overlapping tests serve as alternatives to the original, dedicated, tests for the individual cores and, if selected, they are broadcasted to the cores so that several cores are tested concurrently. This technique allows the existing bus structure to be reused; however, dedicated test buses can also be introduced in order to reduce the test time. Our objective is to minimize the test application time while a designer-specified hardware constraint is satisfied. Again Constraint Logic Programming has been used to solve the problem optimally. Experiments using benchmark designs have been carried out to demonstrate the usefulness and efficiency of the proposed techniques.
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| 4. |
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| 5. |
- Marchesi, Silvia, MD, 1985-
(author)
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The effect of mechanical ventilation on abdominal organs : Analysing the role of PEEP and perfusion.
- 2019
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Licentiate thesis (other academic/artistic)abstract
- Background: The effect of mechanical ventilation on abdominal organs is not well understood and investigated yet. Previous studies, using an animal sepsis-like model, found an association between mechanical ventilation (MV) and abdominal edema and inflammation.The presented thesis was aimed to investigate the role of perfusion in edema formation and inflammation, and to study the abdomen during mechanical ventilation in an ARDS model to reduce the confounding effect of inflammation related to sepsis.Methods: In the first paper presented, inflammation and edema in the abdomen were investigated in an endotoxin model. The study subjects were divided into two groups with different mean arterial pressures (MAP), another small group of healthy controls were studied as well. MRI analyses were used to measure perfusion in the different abdominal organs. In the second paper presented, differences in abdominal edema and inflammation were assessed in two groups of subjects, one group underwent MV and one group had spontaneously breathing.Results: In the first study, MRI analyses confirm that the group with higher MAP had better perfusion than the low MAP group. In the liver, perfusion was lower in LowMAP group compared to HighMAP group, but the HighMAP group had lower perfusion than the healthy controls. However, in the other studied organs HighMAP group and healthy controls had similar perfusion.Edema did not differ between the groups. Inflammation was globally higher in LowMAP group and correlated with hemodynamics. TNFα in liver tissue and portal vein serum correlated with intra-abdominal pressure (IAP).In the second study, the cytokine concentration was higher in serum in the MV group. MV did not increase abdominal edema or inflammation, compared to spontaneous breathing. Discussion and conclusion: Abdominal edema and inflammation are multifactorial phenomena, and many elements have to be included in the analysis. Perfusion plays an important role in determining inflammation and IAP. MV per se was not found to be related to increased edema and inflammation. In a previous study, the role of different levels of PEEP and different respiratory rate between mechanically ventilated and spontaneously breathing animals were not analyzed, but could have contributed to the results. The efforts made in this study to maintain similar respiratory rate and PEEP in both groups, could have contributed to the presented results.It is important to underline that, even if MV was not related to inflammation in abdomen, it was related to an increase in systemic inflammation, most probably because of an enhanced lung production of inflammatory mediators.Further studies, focusing on the role of respiratory rate and PEEP on abdomen, as well as the analysis of the inter-relations among inflammation, perfusion and edema, are needed to increase the pathophysiological understanding of these phenomena.
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| 6. |
- Olausson, Johan, 1980-
(author)
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Studies of recombinant forms of Aleuria aurantia lectin
- 2009
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Licentiate thesis (other academic/artistic)abstract
- The presented work describes construction and analysis of recombinantly produced forms of Aleuria aurantia lectin (AAL). The binding properties of the produced AAL forms were studied using techniques such as tryptophan fluorescence, hemagglutination analysis, ELISA and surface plasmon resonance analysis.Lectins are proteins that are ubiquitous in nature with the ability to bind specifically to different types of carbohydrates. The physiological function of different lectins is not always known, but they are involved in many recognition events at molecular and cellular levels. In research, lectins are widely used for structural and functional studies of complex carbohydrates, and they are also used to detect changes in the carbohydrate pattern on glycoproteins in different diseases.With the use of recombinant technology it is now possible to refine properties of lectins such as decreasing the valency and alter specificity and affinity. This may be a way of constructing more suitable reagents for use in diagnostic glycosylation analysis assays.AAL has been extensively used in different types of research for its ability to bind the monosaccharide fucose and to fucose-containing oligosaccharides. It is composed of two identical subunits where each subunit contains five binding sites for fucose. AAL was expressed recombinantly (rAAL) and its properties was investigated. These studies reveled that one of the binding sites in rAAL had unusually high affinities towards fucose and fucosecontaining oligosaccharides with Kd-values in the nanomolar range. This binding site is not detected in AAL that have been exposed to fucose during its purification, and therefore we proposed that this site may be blocked with free fucose in commercial preparations of AAL.Normally lectin-oligosaccharide interactions are considered to be of weak affinity, so the finding of a high affinity site was interesting for the future study of recombinant forms of AAL. The next step was to produce recombinant AAL forms with decreased valency. This was done using site-directed mutagenesis. First a monomeric form of AAL (mAAL) was constructed and then a monovalent form of AAL, containing only one fucose-binding site (S2-AAL) was constructed. Both of these forms had retained ability to bind fucose. The binding characteristics of mAAL were similar to that of rAAL, but mAAL showed decreased hemagglutinating activity. S2-AAL showed a lower binding affinity to fucosylated oligosaccharides and did not bind to sialylated fuco-oligosaccharides such as sialyl-LewisX. This study shows that molecular engineering techniques could be important tools for development of reliable and specific diagnostic and biological assays for carbohydrate analysis.
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