Sökning: "sub-zero temperatures"

Visar resultat 1 - 5 av 15 avhandlingar innehållade orden sub-zero temperatures.

  1. 1. The fracture mechanisms in duplex stainless steels at sub-zero temperatures

    Författare :Johan Pilhagen; Pavel Korzhavy; Rolf Sandström; Kim Wallin; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Duplex stainless steel; Weldments; Delamination; Fracture toughness; Impact toughness; Cleavage fracture; Nickel;

    Sammanfattning : The aim of the thesis was to study the susceptibility for brittle failures and the fracture process of duplex stainless steels at sub-zero temperatures (°C). In the first part of the thesis plates of hot-rolled duplex stainless steel with various thicknesses were used to study the influence of delamination (also known as splits) on the fracture toughness. LÄS MER

  3. 2. The influence of temperature on enzyme selectivity in organic media

    Författare :Åsa Jönsson; Bioteknik; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; water activity; sub-zero temperatures; enantioselectivity; peptide yields; asymmetric reductions of ketones; peptide synthesis; ADH from Thermoanaerobium brockii; subtilisin; Enzyme catalysis; a-chymotrypsin; organic solvent; aqueous media; Biotechnology; Bioteknik;

    Sammanfattning : The influence of different reaction parameters on enzyme selectivity was investigated. The reaction conditions studied were solvent dependence, water activity and reaction temperature. LÄS MER

  4. 3. Cold air, physical activity, and the airways : epidemiological and experimental studies

    Författare :Linda Eklund; Nikolai Stenfors; Anne Lindberg; Thomas Sandström; Rita Sjöström; Leif Bjermer; Umeå universitet; []
    Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; asthma; asthma medication; athletes; cold temperature; environmental chamber; epidemiology; healthy; orienteers; physical activity; respiratory symptoms; risk factors; skiers; lungmedicin; Lung Medicine;

    Sammanfattning : Background: Cold exposure is associated with increased morbidity and mortality. Elite cross-country skiers are regularly exposed to cold, dry air and have a high prevalence of asthma compared to the Swedish population. LÄS MER

  5. 4. Lateral movements versus stationarity : adaptive alternatives in benthic invertebrates to the seasonal environment in a boreal river

    Författare :Tommy I. Olsson; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Benthic invertebrates; cold-hardiness; ice; migrations; overwintering; river; seasonal variations; spatial distribution; spring flood; water level;

    Sammanfattning : Benthic invertebrates inhabiting boreal rivers are exposed to very large seasonal variations in their physical environment. The extremes are in winter when the littoral area freezes solid and in spring when water flow increases rapidly. LÄS MER

  7. 5. Lipase-Mediated Syntheses of Trimethylolpropane-Based Biolubricant and Cyclic Carbonate

    Författare :Amin Bornadel; Bioteknik; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

    Sammanfattning : Abstract Biocatalysis is considered as benign and efficient alternative to chemical catalysis for organic syntheses. Lipases are the most versatile biological catalysts implemented so far with great potential for production of different chemicals and materials in non-conventional reaction media. LÄS MER