Improvements in Air Intake on Frame 6 Gas Turbines

Työssä tarkastellaan kahta kaasuturbiinin imuilman sisäänottojärjestelmän kehitysmenetelmää, imuilman jäähdytystä ja sähköstaattista suodatusta. Imuilman jäähdytysmenetelmien tarkastelussa käytettiin kahta kaasuturbiinin tehonlisäystekniikoiden laskentatyökalua. Arviointi kohdistettiin Glanford Brigg Generating Station -voimalaitoksen kaasuturbiinityyppiin ja paikallisiin englantilaisiin ilmasto-olosuhteisiin. Tarkastelussa olivat kostutusjäähdytys ja overspray. Tuloksia vertailtiin keskenään ja näiden perusteella arvioitiin menetelmien vaikutuksia tehoon, hyötysuhteeseen sekä veden kulutukseen. Sähköstaattisen suodattimen prototyyppi oli rakennettu Briggin voimalaitokselle. Järjestelmää kehitetään kaupalliseksi tuotteeksi ja tätä varten kerättiin tekninen dokumentaatio kokonaisuudeksi, jota voitiin hyödyntää tuotteistusprosessissa. Imuilman jäähdyttämisellä voidaan saavuttaa merkittävä tehonlisäys ilmasto-olosuhteista riippuen. Menetelmällä voidaan myös tasata lämpötilan vuorokausi-vaihtelusta aiheutuvia tehoeroja. Sähköstaattisen suodattimen prototyyppi saavutti kehitysvaiheelle asetetut tavoitteet. Sähköstaattinen suodatus tarjoaa useita etuja perinteiseen mekaaniseen suodatukseen verrattuna.

Regime Switching Models for Electricity Time Series that Capture Fat Tailed Distributions

In the power market, electricity prices play an important role at the economic level. The behavior of a price trend usually known as a structural break may change over time in terms of its mean value, its volatility, or it may change for a period of time before reverting back to its original behavior or switching to another style of behavior, and the latter is typically termed a regime shift or regime switch. Our task in this thesis is to develop an electricity price time series model that captures fat tailed distributions which can explain this behavior and analyze it for better understanding. For NordPool data used, the obtained Markov Regime-Switching model operates on two regimes: regular and non-regular. Three criteria have been considered price difference criterion, capacity/flow difference criterion and spikes in Finland criterion. The suitability of GARCH modeling to simulate multi-regime modeling is also studied.

Berry polyphenol absorption and the effect of northern berries on metabolism, ectopic fat accumulation, and associated diseases

The prevalence of obesity and type 2 diabetes has increased at an alarming rate in developed countries. It seems in the light of current knowledge that metabolic syndrome may not develop at all without NAFLD, and NAFLD is estimated to be as common as metabolic syndrome in western population (23 % occurrence). Fat in the liver is called ectopic fat, which is triacylglycerols within the cells of non-adipose tissue. Serum alanine aminotransferase (ALT) values correlate positively with liver fat proportions, and increased activity of ALT predicts type 2 diabetes independently from obesity. Berries, high in natural bioactive compounds, have indicated the potential to reduce the risk of obesity-related diseases. Ectopic fat induces common endocrine excretion of adipose tissue resulting in the overproduction of inflammatory markers, which further induce insulin resistance by multiple mechanisms. Insulin resistance inducing hyperinsulinemia and lipolysis in adipocytes increases the concentration of free fatty acids and consequently causes further fat accumulation in hepatocytes. Polyphenolic fractions of berries have been shown to reverse inflammatory reaction cascades in in vitro and animal studies, and moreover to decrease ectopic fat accumulation. The aim of this thesis was to explore the role of northern berries in obesity-related diseases. The absorption and metabolism of selected berry polyphenols, flavonol glycosides and anthocyanins, was investigated in humans, and metabolites of the studied compounds were identified in plasma and urine samples (I, II). Further, the effects of berries on the risk factors of metabolic syndrome were studied in clinical intervention trials (III, IV), and the different fractions of sea buckthorn berry were tested for their ability to reduce postprandial glycemia and insulinemia after high-glucose meal in a postprandial study with humans (V). The marked impact of mixed berries on plasma ALT values (III), as well as indications of the positive effects of sea buckthorn, its fractions and bilberry on omental adiposity and adhesion molecules (IV) were observed. In study V, sea buckthorn and its polyphenol fractions had a promising effect on potprandial metabolism after high-glucose meal. In the literature review, the possible mechanisms behind the observed effects have been discussed with a special emphasis on ectopic fat accumulation. The literature review indicated that especially tannins and flavonoids have shown potential in suppressing diverse reaction cascades related to systemic inflammation, ectopic fat accumulation and insulin resistance development.

FAT-luokkien määritys hitsatuille levyliitoksille käyttämällä lineaarisen murtumismekaniikan särönkasvun simulointia

Työssä tutkittiin hitsattujen levyliitosten väsymiskestävyyden mitoitusarvoja. Hitsien väsymiskestävyyden mitoitusarvot määritettiin lineaarista murtumismekaniikkaa soveltavalla 2D FEM-laskentaohjelmalla. Murtumismekaanisen laskennan tuloksista määriteltiin, eri liitosgeometrioiden ja kuormitustyyppien mukaisia, nimellisen jännityksen väsymismitoitusmenetelmää vastaavia FAT-luokkia, joissa on huomioitu rakenteellinen jännitys hitsiä vastaan kohtisuorassa suunnassa. Tutkittujen liitosten geometriat olivat pääsääntöisesti poikkeavia mitoitusstandardien ja ohjeiden sisältämistä taulukkotapauksista. Laskennassa otettiin huomioon hitsien liittymiskulma perusaineeseen, rajaviivan pyöristykset ja vajaa hitsautumissyvyys. Kuormitustyyppien vaihtelua tutkittiin rakenteellisen jännityksen taivutusosuuden muutoksilla ja kuormaa kantavien X-liitosten risteävien kuormituksien suhteellisilla suuruuksilla. Väsymiskestävyydet määritettiin kuormituskohtaisille kalvo- ja taivutusjännityksille sekä näiden jännitysjakaumien keskiarvoille. Työssä saatuja FAT-luokkia voidaan hyödyntää vastaavien geometrioiden ja kuormitusten yhteydessä, sekä interpoloimalla myös tuloksien väliarvoissa. Työssä käytetyillä menetelmillä voidaan parantaa nimellisen jännityksen mitoitusmenetelmän tarkkuutta ja laajentaa sitä koskemaan myös taulukkotapausten ulkopuolisia liitoksia. Työn tuloksissa on esitetty FAT-luokkia T-, X- ja päittäisliitoksille ja näiden eri kuormitusyhdistelmille.

Alpha- and gamma-melanocyte stimulating hormones in obesity. A study of the key central areas of metabolic regulation

The melanocortin system is an important regulator of feeding, energy metabolism,and cardiovascular function and it consists of the pro-opiomelanocortin (POMC) derived melanocyte stimulating hormones (α-, β- and γ-MSH) and their endogenous melanocortin receptors, MC1R to MC5R. In the hypothalamus, α-MSH reduces food intake, and increases energy expenditure and sympathetic tone by binding to MC4R. Mutations affecting the MC4R gene lead to obesity in mammals. On the other hand, the metabolic effects of MC3R stimulation using agonists such as the endogenously expressed γ-MSH have been less extensively explored. The main objective of this study was to investigate the long-term effects of increased melanocortin tone in key areas of metabolic regulation in the central nervous system (CNS) in order to investigate the sitespecific roles of both α-MSH and γ-MSH. The aim was to stereotaxically induce local overexpression of single melanocortin peptides using lentiviral vectors expressing α-MSH (LVi-α-MSH-EGFP) and γ-MSH (LVi-γ-MSH-EGFP). The lentiviral vectors were shown to produce a long-term overexpression and biologically active peptides in cell-based assays. The LVi-α-MSHEGFP was targeted to the arcuate nucleus in the hypothalamus of diet induced obese mice where it reduced weight gain and adiposity independently of food intake. When the nucleus tractus solitarus in the brainstem was targeted, the LVi-α-MSH-EGFP treatment was shown to cause a small decrease in adiposity, which did not impact weight development. However, the α-MSH treatment increased heart rate, which was attenuated by adrenergic receptor blockade indicative of increased sympathetic activity. The LVi-γ-MSH-EGFP was targeted to the hypothalamus where it decreased fat mass in mice eating the standard diet, but the effect was abated if animals consumed a high-fat Western type diet. When the diet induced obese mice were subjected again to the standard diet, the LVi-γ-MSH-EGFP treated animals displayed increased weight loss and reduced adiposity. These results indicate that the long-term central anti-obesity effects of α-MSH are independent of food intake. In addition, overexpression of α-MSH in the brain stem efficiently blocked the development of adiposity, but increased sympathetic tone. The evidence presented in this thesis also indicates that selective MC3R agonists such as γ-MSH could be potential therapeutics in combination with low fat diets.

Pre- and postnatal nutrition – target for allergy risk reduction

A rapid increase in allergic diseases in Western societies has led to the conclusion that our modern lifestyle is a risk factor for immune dysregulation. Potential culprits and benefactors are searched among early dietary and microbial exposures, which may act to program later allergic disease. The aim of this thesis was to investigate the role of early maternal and child nutrition in reducing the risk of child allergy. The study population comprised of 256 mother – child pairs from families with a history of allergy participating in a randomized controlled dietary counseling and probiotic intervention (Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb12) study from early pregnancy onwards. The dietary counseling aimed for a diet complying with dietary recommendations for pregnant and lactating women, with special attention to fat quality. Maternal dietary counseling was reflected in cord blood fatty acids suggesting better essential fatty acid status in infants in the counseling group. Dietary counseling with probiotics or placebo had no effect on child allergy risk, but associations between maternal diet during pregnancy and breastfeeding and child allergic outcomes were found in secondary analyses. During pregnancy, milk intake was related to decreased and cheese intake to increased risk of child atopic eczema. During breastfeeding, intake of vitamin C was related to increased risk of asthma and intake of egg was related to decreased risk of atopic eczema. The timing of introduction of complementary foods to infant’s diet was not associated with risk of atopic eczema, when adjusted with parental opinion of child allergic symptoms (i.e., potential reverse causality). In conclusion, the results demonstrate that infant fatty acid supply can be modified via maternal dietary changes. In addition, interesting associations of maternal diet with child allergy risk were discovered. However, no difference in the incidence of allergic diseases with dietary counseling was observed. This suggests that more potent dietary interventions might be necessitated to induce clinical risk reduction of allergy. Highrisk families can safely adhere to dietary recommendations for pregnant and lactating women, and the results support the current conception that no additional benefit is gained with delaying introduction of complementary feeding.

Phenomena and mechanisms in purification of animal fat

Työn tarkoitus oli tutkia eläinrasvan puhdistusta biodieselin valmistusta varten. Eläinrasvaa syntyy elintarviketeollisuuden sivutuotteena ja sitä saadaan myös myymättä jääneistä elintarvikkeista. Rasva sisältää epäpuhtauksia, jotka on poistettava ennen biodieselprosessia. Tässä työssä tutkittavat epäpuhtaudet ovat typpi, fosfori, rauta, natrium, kalsium ja magnesium. Puhdistusmenetelminä käytettiin saostamista sitruunahapolla sekä adsorbointia kahdella eri adsorbentilla. Tavoitteena oli selvittää riittävä määrä happoa ja adsorbenttia sekä tutkia puhdistuksen mekanismia. Lisäksi tarkasteltiin lämpötilan vaikutusta adsorption aikana.

Natural born weight gainers: The mechanisms of obesity in transgenic mice overexpressing neuropeptide Y

Neuropeptide Y (NPY) is a neurotransmitter promoting energy storage by activating Y-receptors and thus affecting food intake, thermogenesis and adipose tissue metabolism. NPY is expressed both in the central and sympathetic nervous system. Hypothalamic NPY is known to stimulate feeding, but the effects of noradrenergic neuron NPY are more ambiguous. Chronic stress stimulates fat accumulation via NPY release from noradrenergic neurons. Furthermore, polymorphism in the human Npy gene has been associated with metabolic disturbances and increased NPY secretion after sympathetic stimulation. The main objective of this study was to clarify the mechanisms of noradrenergic neuron NPY in the development of obesity. The metabolic phenotype of a homozygous mouse overexpressing NPY in the brain noradrenergic neurons and sympathetic nervous system (OE-NPYDβH mouse) was characterized. OE-NPYDβH mice had an increased fat mass and body weight, which caused impairments of glucose metabolism and hyperinsulinaemia with age. There were no differences in energy intake or expenditure, but the sympathetic tone was down-regulated and the endocannabinoid system activated. Furthermore, peripheral Y2-receptors in energy-rich conditions played an important role in mediating the fat-accumulating effect of NPY. These results indicate that noradrenergic neuron NPY promotes obesity via direct effects in the periphery and by modulating the sympatho-adrenal and endocannabinoid systems. Additionally, NPY in the central noradrenergic neurons is believed to possess many important roles. The phenotype of the OE-NPYDβH mouse resembles the situations of chronic stress and Npy gene polymorphism and thus these mice may be exploited in testing novel drug candidates for the treatment of obesity.

Sedentary behaviour and health with special reference to obesity and fatty liver in early midlife. The Cardiovascular risk in Young Finns Study

Background: Physical inactivity and positive energy balance pose a risk to health. They increase the risk of obesity and associated non-communicable diseases. Recently, also sedentary behaviour has been associated with obesity and non-communicable diseases. Nevertheless, it has been unclear which type of sedentary behaviour is the most harmful. It is also unknown whether the relationship of sedentary behaviour with obesity is truly independent of other factors, for example physical activity and diet. Longitudinal data are limited, and the direction of causality and the mechanism of action are still unknown. Aims: The aim of this study was 1) to identify the type of sedentary behaviour having the strongest association with obesity, 2) to explore the causal relationship of sedentary behaviour and weight increase, and 3) to additionally, investigate the relationship of sedentary behaviour with fatty liver. These were studied in cross-sectional and/or longitudinal settings using data from the Cardiovascular Risk in Young Finns Study. Special emphasis was put on the evaluation of a wide range of other lifestyle factors and risks for obesity and fatty liver. Subjects: 2,060 subjects (aged 33-50 years in 2011, of which 55 % were female) from the Cardiovascular Risk in Young Finns Study participating in follow-ups in 2001, 2007, and 2011. Measures: Self-reported time spent in various types of sedentary behaviour (I), or TV viewing time (I-III). Measured body weight, height and waist circumference (I-III), and genetic variants for high BMI (I). Fasting plasma concentrations of gamma-glutamyltransferase enzyme and triglyceride, calculated Fatty Liver Index (based on gamma-glutamyltransferase and triglyceride concentration, BMI and waist circumference), and the amount of intrahepatic fat measured with ultrasound (III). Self-reported leisure-time physical activity and active commuting, occupational physical activity, energy intake, diet, alcohol consumption, smoking, socioeconomic status, and sleep duration as possible confounders were considered (I-III). Results: TV viewing is the sedentary behaviour type that has the strongest association with obesity. Sedentary behaviour (TV viewing) precedes weight increase, and not the other way around. Sedentary behaviour (TV viewing) is associated with increased risk of fatty liver. Conclusions: Sedentary behaviour (especially high TV viewing time) is associated with increased risks of obesity and fatty liver. Intervention studies are needed to assess whether reduction of TV time would prevent obesity and fatty liver.