Sökning: "chemical abundances"

Visar resultat 1 - 5 av 43 avhandlingar innehållade orden chemical abundances.

  1. 1. Stochastic Chemical Evolution A Study of Scatter in Relative Elemental Abundances in Extremely Metal-poor Stars

    Detta är en avhandling från Uppsala : Acta Universitatis Upsaliensis

    Författare :Torgny Karlsson; Uppsala universitet.; [2004]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; nucleosynthesis; chemical evolution; Galactic evolution; supernovae; chemical abundances; Population II stars; Astronomi; NATURAL SCIENCES Physics Astronomy and astrophysics; NATURVETENSKAP Fysik Astronomi och astrofysik;

    Sammanfattning : Chemical evolution addresses the problem of the formation of the chemical elements and their evolution throughout the history of the universe. This thesis discusses in particular the chemical evolution in the young universe and what we may learn from the observations of the oldest stars. LÄS MER

  2. 2. Optical lifetime studies using time-resolved spectroscopy with applications to the solar chemical composition

    Detta är en avhandling från Stockholm : Stockholm University

    Författare :Bertel Engman; Stockholms universitet.; [1985]

    Sammanfattning : This survey presents six previously published papers dealing with time-resolved atomic and molecular spectroscopy with applications to the chemical composition of the solar atmosphere. Three methods of measuring mean lives of excited states have been used:Beam-foil spectroscopy Beam-laser spectroscopy High-frequency deflectionThe methods used to estimate the abundances of the chemical elements in the sun will also be outlined. LÄS MER

  3. 3. NMR studies of metabolites and xenobiotics: From time-points to long-term metabolic regulation

    Detta är en avhandling från Umeå : Umeå universitet

    Författare :Ina Ehlers; Umeå universitet.; [2015]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NMR spectroscopy; isotopomer; phospholipid; persistent organic pollutant; CO2 fertilization; photorespiration;

    Sammanfattning : Chemical species carry information in two dimensions, in their concentrations and their isotopic signatures. The concentrations of metabolites or synthetic compounds describe the composition of a chemical or biological system, while isotopic signatures describe processes in the system by their reaction pathways, regulation, and responses to external stimuli. LÄS MER

  4. 4. Latent variable based computational methods for applications in life sciences Analysis and integration of omics data sets

    Detta är en avhandling från Umeå : Kemi

    Författare :Max Bylesjö; Umeå universitet.; [2008]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Chemometrics; orthogonal projections to latent structures; OPLS; O2PLS; K-OPLS; kernel-based; non-linear; regression; classification; Populus; NATURAL SCIENCES Chemistry; NATURVETENSKAP Kemi;

    Sammanfattning : With the increasing availability of high-throughput systems for parallel monitoring of multiple variables, e.g. levels of large numbers of transcripts in functional genomics experiments, massive amounts of data are being collected even from single experiments. LÄS MER

  5. 5. Hydrothermal alteration of organic matter at spreading centers

    Detta är en avhandling från Stockholm : Department of Geology and Geochemistry, Stockholm University

    Författare :Eva Andersson; Stockholms universitet.; [1998]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURAL SCIENCES Chemistry; NATURVETENSKAP Kemi; Biogeochemistry; biogeokemi;

    Sammanfattning : Alteration of organic matter, mainly amino acids, at sub-seafloor hydrothermal conditions has been investigated by performing laboratory experiments and by studying deep-sea sediments from hydrothermally active areas on the northern Juan de Fuca Ridge, northeast Pacific Ocean.Quaternary sediments from Middle Valley and the eastern flank of the Juan de Fuca Ridge recovered during the Ocean Drilling Program Legs 139 and 168 have been analyzed for total hydrolyzable amino acid concentrations, individual amino acid abundances and stereochemistry in order to evaluate the effects of hydrothermal stress on the decomposition of sedimentary amino acids. LÄS MER