Historian rumuus

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Perinteitä luomassa ja jatkamassa

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Kattava yleisesitys Suomen väestön tilasta ja sen kehityksestä

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Arvio Ilpo Ojalan väitöskirjasta

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Hallintolainkäytön tehostaminen

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Kirja-arvio

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Dewatering of hard-to-dewater pulps

Nanocellulose has much potential for enhancing the tensile strength of paper but it slows down significantly drainage, restricting its use in industrial scale. Main objective of the work was to find ways to improve the dewatering of nanocellulose-containing papers. The effects of cationic potato starch, microparticle system and filler addition on dewatering and such key properties as formation, tensile strength and air permeance of manufactured paper were studied. Test points had 0, 4 or 8 % CNF and 0, 15 or 30 % PCC content. Based on earlier studies, 25 mg/g starch dosage was added to some test points. Modern microparticle system, consisted of cationic polyacrylamide and amorphous silica, was used in few test points. Dosages for both components were 0.3 and 0.6 mg/g, following the recommendations of the supplier. Also, the influences of CNF and filler on drying behaviour after different stages (drainage, wet pressing and cylinder drying) were estimated. Following trends were observed. Starch does not have unambiguous influence on dewatering. In some cases, it improved drainage slightly but effects on the properties of end product were discovered small. Filler quickened dewatering but large proportions were noticed to be detrimental for the drainage, air permeance and tensile strength. Microparticle system improved drainage notably, especially if CNF dosage was high. In addition, microparticle system increased tensile strength and decreased air permeance. However, its effects on formation were detrimental. Dewatering of nanocellulose-containing furnishes is treatable up to a certain point. In the end, such drainage times that were measured from test points which consisted only of pure kraft pulps are awkward to reach.

Molecular Evolution of Metazoan Hypoxia-inducing Factors

Most metazoans rely on aerobic energy production, which is dependent on adequate oxygen supply. In the case of reduced oxygen supply (hypoxia), the most profound changes in gene expression are mediated by transcription factors named hypoxia-inducible factors (HIF alpha). These proteins are post-translationally regulated by prolyl-4-hydroxylase (PHD) enzymes that are direct “sensors” of cellular oxygen levels. This thesis examines the molecular evolution of metazoan HIF systems. In early metazoans the HIF system emerged from pre-existing PHD oxygen sensors and early bHLH-PAS transcription factors. In invertebrates our analysis revealed an unexpected diversity of PHD genes and HIF alpha sequence characteristics. An early branching vertebrate, the epaulette shark (Hemiscyllium ocellatum) was chosen for sequencing and hypoxia preconditioning studies of HIF alpha and PHD genes. As no quantitative PCR reference genes were available, this thesis includes the first study of reference genes in cartilaginous fish species. Applying multiple statistical analysis we also discoveredthat commonly used reference gene software may perform poorly with some data sets. Novel reference genes allowed accurate measurements of the mRNAlevels of the studied target genes. Cartilaginous fishes have three genomic duplicates of both HIF alpha and PHD genes like mammals and teleost fishes. Combining functional divergence and selection analyses it was possible to describe how sequence changes in both HIF alpha and PHD duplicates may have contributed to the differential oxygen sensitivityof HIF alphas. Additionally, novel teleost HIF-1 alpha sequences were produced and used to reveal the molecular evolution of HIF-1 alpha in this lineage rich with hypoxia tolerant species.

Komea kansallislintumme

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Hopeinen Kairamo-mitali FT Ilkka Koivistolle

Kairamo-mitalit 2008.

Ideoita opetukseen hyvien käytäntöjen avulla

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