Polymerization of Ethene and Branched α-olefins with Group IV Metal Complexes Bearing Nitrogen- and Oxygen-Based Ligands

The commodity plastics that are used in our everyday lives are based on polyolefin resins and they find wide variety of applications in several areas. Most of the production is carried out in catalyzed low pressure processes. As a consequence polymerization of ethene and α-olefins has been one of the focus areas for catalyst research both in industry and academia. Enormous amount of effort have been dedicated to fine tune the processes and to obtain better control of the polymerization and to produce tailored polymer structures The literature review of the thesis concentrates on the use of Group IV metal complexes as catalysts for polymerization of ethene and branched α-olefins. More precisely the review is focused on the use of complexes bearing [O,O] and [O,N] type ligands which have gained considerable interest. Effects of the ligand framework as well as mechanical and fluxional behaviour of the complexes are discussed. The experimental part consists mainly of development of new Group IV metal complexes bearing [O,O] and [O,N] ligands and their use as catalysts precursors in ethene polymerization. Part of the experimental work deals with usage of high-throughput techniques in tailoring properties of new polymer materials which are synthesized using Group IV complexes as catalysts. It is known that the by changing the steric and electronic properties of the ligand framework it is possible to fine tune the catalyst and to gain control over the polymerization reaction. This is why in this thesis the complex structures were designed so that the ligand frameworks could be fairly easily modified. All together 14 complexes were synthesised and used as catalysts in ethene polymerizations. It was found that the ligand framework did have an impact within the studied catalyst families. The activities of the catalysts were affected by the changes in complex structure and also effects on the produced polymers were observed: molecular weights and molecular weight distributions were depended on the used catalyst structure. Some catalysts also produced bi- or multi-modal polymers. During last decade high-throughput techniques developed in pharmaceutical industries have been adopted into polyolefin research in order to speed-up and optimize the catalyst candidates. These methods can now be regarded as established method suitable for both academia and industry alike. These high-throughput techniques were used in tailoring poly(4-methyl-1-pentene) polymers which were synthesized using Group IV metal complexes as catalysts. This work done in this thesis represents the first successful example where the high-throughput synthesis techniques are combined with high-throughput mechanical testing techniques to speed-up the discovery process for new polymer materials.

The effect of structure on the dilute solution properties of branched polysaccharides studied with SEC and AsFlFFF

Cereal arabinoxylans, guar galactomannans, and dextrans produced by lactic acid bacteria(LAB) are a structurally diverse group of branched polysaccharides with nutritional and industrial functions. In this thesis, the effect of the chemical structure on the dilute solution properties of these polysaccharides was investigated using size-exclusion chromatography(SEC) and asymmetric flow field-flow fractionation (AsFlFFF) with multiple-detection. The chemical structures of arabinoxylans were determined, whereas galactomannan and dextran structures were studied in previous investigations. Characterization of arabinoxylans revealed differences in the chemical structures of cereal arabinoxylans. Although arabinoxylans from wheat, rye, and barley fiber contained similar amounts of arabinose side units, the substitution pattern of arabinoxylans from different cereals varied. Arabinoxylans from barley husks and commercial low-viscosity wheat arabinoxylan contained a lower number of arabinose side units. Structurally different dextrans were obtained from different LAB. The structural effects on the solution properties could be studied in detail by modifying pure wheat and rye arabinoxylans and guar galactomannan with specific enzymes. The solution characterization of arabinoxylans, enzymatically modified galactomannans, and dextrans revealed the presence of aggregates in aqueous polysaccharide solutions. In the case of arabinoxylans and dextrans, the comparison of molar mass data from aqueous and organic SEC analyses was essential in confirming aggregation, which could not be observed only from the peak or molar mass distribution shapes obtained with aqueous SEC. The AsFlFFF analyses gave further evidence of aggregation. Comparison of molar mass and intrinsic viscosity data of unmodified and partially debranched guar galactomannan, on the other hand, revealed the aggregation of native galactomannan. The arabinoxylan and galactomannan samples with low or enzymatically extensively decreased side unit content behaved similarly in aqueous solution: lower molar mass samples stayed in solution but formed large aggregates, whereas the water solubility of the higher-molar-mass samples decreased significantly. Due to the restricted solubility of galactomannans in organic solvents, only aqueous galactomannan solutions were studied. The SEC and AsFlFFF results differed for the wheat arabinoxylan and dextran samples. Column matrix effects and possible differences in the separation parameters are discussed, and a problem related to the non-established relationship between the separation parameters of the two separation techniques is highlighted. This thesis shows that complementary approaches in the solution characterization of chemically heterogeneous polysaccharides are needed to comprehensively investigate macromolecular behavior in solution. These results may also be valuable when characterizing other branched polysaccharides.

Molecular Background of Common Dyslipidemias

The leading cause of death in the Western world continues to be coronary heart disease (CHD). At the root of the disease process is dyslipidemia an aberration in the relevant amounts of circulating blood lipids. Cholesterol builds up in the arterial wall and following rupture of these plaques, myocardial infarction or stroke can occur. Heart disease runs in families and a number of hereditary forms are known. The leading cause of adult dyslipidemia presently however is overweight and obesity. This thesis work presents an investigation of the molecular genetics of common, hereditary dyslipidemia and the tightly related condition of obesity. Familial combined hyperlipidemia (FCHL) is the most common hereditary dyslipidemia in man with an estimated population prevalence of 1-6%. This complex disease is characterized by elevated levels of serum total cholesterol, triglycerides or both and is observed in about 20% of individuals with premature CHD. Our group identified the disease to be associated with genetic variation in the USF1 transcription factor gene. USF1 has a key role in regulating other genes that control lipid and glucose metabolism as well as the inflammatory response all central processes in the progression of atherosclerosis and CHD. The first two works of this thesis aimed at understanding how these USF1 variants result in increased disease risk. Among the many, non-coding single-nucleotide polymorphisms (SNPs) that associated with the disease, one was found to have a functional effect. The risk-enhancing allele of this SNP seems to eradicate the ability of the important hormone insulin to induce the expression of USF1 in peripheral tissues. The resultant changes in the expression of numerous USF1 target genes over time probably enhance and accelerate the atherogenic processes. Dyslipidemias often represent an outcome of obesity and in the final work of this thesis we wanted to address the metabolic pathways related to acquired obesity. It is recognized that active processes in adipose tissue play an important role in the development of dyslipidemia, insulin resistance and other pathological conditions associated with obesity. To minimize the confounding effects of genetic differences present in most human studies, we investigated a rare collection of identical twins that differed significantly in the amount of body fat. In the obese, but otherwise healthy young adults, several notable changes were observed. In addition to chronic inflammation, the adipose tissue of the obese co-twins was characterized by a marked (47%) decrease in amount of mitochondrial DNA (mtDNA) a change associated with mitochondrial dysfunction. The catabolism of branched chain amino acids (BCAAs) was identified as the most down-regulated process in the obese co-twins. A concordant increase in the serum level of these insulin secretagogues was identified. This hyperaminoacidemia may provide the feed-back signal from insulin resistant adipose tissue to the pancreas to ensure an appropriately augmented secretory response. The down regulation of BCAA catabolism correlated closely with liver fat accumulation and insulin. The single most up-regulated gene (5.9 fold) in the obese co-twins was osteopontin (SPP1) a cytokine involved in macrophage recruitment to adipose tissue. SPP1 is here implicated as an important player in the development of insulin resistance. These studies of exceptional study samples provide better understanding of the underlying pathology in common dyslipidemias and other obesity associated diseases important for future improvement of intervention strategies and treatments to combat atherosclerosis and coronary heart disease.

Mannans as film formers and emulsion stabilizers

Mannans are abundant plant polysaccharides found in the endosperm of certain leguminous seeds (guar gum galactomannan, GG; locust bean gum galactomannan, LBG), in the tuber of the konjac plant (konjac glucomannan, KGM), and in softwoods (galactoglucomannan, GGM). This study focused on the effects of the chemical structure of mannans on their film-forming and emulsion-stabilizing properties. Special focus was on spruce GGM, which is an interesting new product from forest biorefineries. A plasticizer was needed for the formation of films from mannans other than KGM and the optimal proportion was 40% (w/w of polymers) glycerol or sorbitol. Galactomannans with lower galactose content (LBG, modified GG) produced films with higher elongation at break and tensile strength. The mechanical properties of GG-based films were improved by decreasing the degree of polymerization of the polysaccharide with moderate mannanase treatments. The improvement of mechanical properties of GGM-based films was sought by blending GGM with each of poly(vinyl alcohol) (PVOH), corn arabinoxylan (cAX), and KGM. Adding other polymers increased the elongation at break of GGM blend films. The tensile strength of films increased with increasing amounts of PVOH and KGM, but the effect of cAX was the opposite. Dynamic mechanical analysis showed two separate loss modulus peaks for blends of GGM and PVOH, but a single peak for all other films. Optical and scanning electron microscopy confirmed good miscibility of GGM with cAX and KGM. In contrast, films blended from GGM and PVOH showed phase separation. GGM and KGM were mixed with cellulose nanowhiskers (CNW) to form composite films. Addition of CNW to KGM-based films induced the formation of fiberlike structures with lengths of several millimeters. In GGM-based films, rodlike structures with lengths of tens of micrometers were formed. Interestingly, the notable differences in the film structure did not appear to be related to the mechanical and thermal properties of the films. Permeability properties of GGM-based films were compared to those of films from commercial mannans KGM, GG, and LBG. GGM-based films had the lowest water vapor permeability when compared to films from other mannans. The oxygen permeability of GGM films was of the same magnitude as that of commercial polyethylene / ethylene vinyl alcohol / polyethylene laminate film. The aroma permeability of GGM films was low. All films were transparent in the visible region, but GGM films blocked the light transmission in the ultraviolet region of the spectra. The stabilizing effect of GGM on a model beverage emulsion system was studied and compared to that of GG, LBG, KGM, and cAX. In addition, GG was enzymatically modified in order to examine the effect of the degree of polymerization and the degree of substitution of galactomannans on emulsion stability. Use of GGM increased the turbidity of emulsions both immediately after preparation and after storage of up to 14 days at room temperature. GGM emulsions had higher turbidity than the emulsions containing other mannans. Increasing the storage temperature to +45 ºC led to rapid emulsion breakdown, but a decrease in storage temperature increased emulsion stability after 14 days. A low degree of polymerization and a high degree of substitution of the modified galactomannans were associated with a decrease in emulsion turbidity.

Stabilization of Phospholipid Coatings in Capillary Electrophoresis

The development of a simple method of coating a semi-permanent phospholipid layer onto a capillary for electrochromatography use was the focus of this study. The work involved finding good coating conditions, stabilizing the phospholipid coating, and examining the effect of adding divalent cations, cetyltrimethylammonium bromide, and polyethylene glycol (PEG)-lipids on the stability of the coating. Since a further purpose was to move toward more biological membrane coatings, the capillaries were also coated with cholesterol-containing liposomes and liposomes of red blood cell ghost lipids. Liposomes were prepared by extrusion, and large unilamellar vesicles with a diameter of about 100 nm were obtained. Zwitterionic phosphatidylcholine (PC) was used as a basic component, mainly 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine (POPC) but also eggPC and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Different amounts of sphingomyelin, bovine brain phosphatidylserine, and cholesterol were added to the PC. The stability of the coating in 40 mM N-(2-hydroxyethyl)piperazine-N’-(2-ethanesulfonic acid) (HEPES) solution at pH 7.4 was studied by measuring the electroosmotic flow and by separating neutral steroids, basic proteins, and low-molar-mass drugs. The presence of PC in the coating solution was found to be essential to achieving a coating. The stability of the coating was improved by the addition of negative phosphatidylserine, cholesterol, divalent cations, or PEGylated lipids, and by working in the gel-state region of the phospholipid. Study of the effect on the PC coating of divalent metal ions calcium, magnesium, and zinc showed a molar ratio of 1:3 PC/Ca2+ or PC/Mg2+ to give increased rigidity to the membrane and the best coating stability. The PEGylated lipids used in the study were sterically stabilized commercial lipids with covalently attached PEG chains. The vesicle size generally decreased when PEGylated lipids of higher molar mass were present in the vesicle. The predominance of discoidal micelles over liposomes increased PEG chain length and the average size of the vesicles thus decreased. In the capillary electrophoresis (CE) measurements a highly stable electroosmotic flow was achieved with 20% PEGylated lipid in the POPC coating dispersion, the best results being obtained for disteroyl PEG (3000) conjugates. The results suggest that smaller particles (discoidal micelles) result in tighter packing and better shielding of silanol groups on the silica wall. The effect of temperature on the coating stability was investigated by using DPPC liposomes at temperatures above (45 C) and below (25 C) the main phase transition temperature. Better results were obtained with DPPC in the more rigid gel state than in the fluid state: the electroosmotic flow was heavily suppressed and the PC coating was stabilized. Also dispersions of DPPC with 0−30 mol% of cholesterol and sphingomyelin in different ratios, which more closely resemble natural membranes, resulted in stable coatings. Finally, the CE measurements revealed that a stable coating is formed when capillaries are coated with liposomes of red blood cell ghost lipids.

Aminopyridinato Complexes as Possible Alternatives for Metallocenes in Ethylene Polymerization

Polyethylene is the most widely used synthetic polymer in the world. Most polyethylene is made with Ziegler-Natta catalysts. Polyethylenes for special applications are made with metallocenes, which are nowadays heavily patented. It is laborious therefore, to develop new metallocenes. The aim of this work was to investigate the feasibility of replacing the cyclopentadienyl ligands of metallocenes by aminopyridinato ligands without losing the good properties of the metallocenes, such as high activity and formation of linear polymer. The subject was approached by studying what kind of catalysts the metallocenes are and how they catalyze polyethylene. The polymerization behavior of metallocenes was examined by synthesizing a piperazino substituted indenyl zirconocene catalyst and comparing its polymerization data with that of the indenyl zirconocene catalyst. On the basis of their isolobality, it was thought that aminopyridinato ligands might replace cyclopentadienyl ligands. It was presumed that the polymerization mechanism and the active center in ethylene polymerization would be similar for aminopyridinato and metallocene catalysts. Titanium aminopyridinato complexes were prepared and their structures determined to clarify the relationship between structure of the catalyst precursor and polymerization results. The ethylene polymerization results for titanium 2-phenylaminopyridinato catalysts and titanocene catalysts were compared.

Primary total hip arthroplasty for primary osteoarthritis in Finland : A national register based analysis

The first aim of the current study was to evaluate the survival of total hip arthroplasty (THA) in patients aged 55 years and older on a nation-wide level. The second aim was to evaluate, on a nation wide-basis, the geographical variation of the incidence of primary THA for primary OA and also to identify those variables that are possibly associated with this variation. The third aim was to evaluate the effects of hospital volume: on the length of stay, on the numbers of re-admissions and on the numbers of complications of THR on population-based level in Finland. The survival of implants was analysed based on data from the Finnish Arthroplasty Register. The incidence and hospital volume data were obtained from the Hospital Discharge Register. Cementless total hip replacements had a significantly reduced risk of revision for aseptic loosening compared with cemented hip replacements. When revision for any reason was the end point in the survival analyses, there were no significant differences found between the groups. Adjusted incidence ratios of THA varied from 1.9- to 3.0-fold during the study period. Neither the average income within a region nor the morbidity index was associated with the incidence of THA. For the four categories of volume of total hip replacements performed per hospital, the length of the surgical treatment period was shorter for the highest volume group than for the lowest volume group. The odds ratio for dislocations was significantly lower in the high volume group than in the low volume group. In patients who were 55 years of age or older, the survival of cementless total hip replacements was as good as that of the cemented replacements. However, multiple wear-related revisions of the cementless cups indicate that excessive polyethylene wear was a major clinical problem with modular cementless cups. The variation in the long-term rates of survival for different cemented stems was considerable. Cementless proximal porous-coated stems were found to be a good option for elderly patients. When hip surgery was performed on with a large repertoire, the indications to perform THAs due to primary OA were tight. Socio-economic status of the patient had no apparent effect on THA rate. Specialization of hip replacements in high volume hospitals should reduce costs by significantly shortening the length of stay, and may reduce the dislocation rate.

Sociolinguistic Implications of Narratology: Focalization and ‘Double Deixis’ in Conversational Storytelling

Over the last few decades, literary narratology has branched out into a wide array of ‘post-classical’ narratologies that have borrowed concepts from cognitive psychology, sociology, anthropology, history, linguistics, and other disciplines. The question arises to what extent ‘classical’ narratological concepts can also be successfully exported to other disciplines which have an interest in narrative. In this article, I apply the concept of ‘focalization’ as well as David Herman’s insights into doubly-deictic ‘you’ in second-person narratives to an interview narrative and further materials from my empirical sociolinguistic study on general practitioners’ narrative discourse on intimate partner abuse. I consider how the narrative positioning of the GP as storyteller and ‘protagonist’ of his story corresponds with his social and professional positioning with regard to his patients in the context of intimate partner violence cases and vis-à-vis the interviewer during the research interview. Focalization and double deixis are shown to become part of a narrative strategy whereby the narrator distances himself from his own personal self in the narrative and at the same time tries to align the interviewer with his viewpoint.

Disordered matter studied by x-ray Raman scattering

Spectroscopy can provide valuable information on the structure of disordered matter beyond that which is available through e.g. x-ray and neutron diffraction. X-ray Raman scattering is a non-resonant element-sensitive process which allows bulk-sensitive measurements of core-excited spectra from light-element samples. In this thesis, x-ray Raman scattering is used to study the local structure of hydrogen-bonded liquids and solids, including liquid water, a series of linear and branched alcohols, and high-pressure ice phases. Connecting the spectral features to the local atomic-scale structure involves theoretical references, and in the case of hydrogen-bonded systems the interpretation of the spectra is currently actively debated. The systematic studies of the intra- and intermolecular effects in alcohols, non-hydrogen-bonded neighbors in high-pressure ices, and the effect of temperature in liquid water are used to demonstrate different aspects of the local structure that can influence the near-edge spectra. Additionally, the determination of the extended x-ray absorption fine structure is addressed in a momentum-transfer dependent study. This work demonstrates the potential of x-ray Raman scattering for unique studies of the local structure of a variety of disordered light-element systems.