Sökning: "chemical abundances"

Visar resultat 1 - 5 av 45 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; [1985]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    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; Jürgen Schleucher; Farquhar Graham; [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; Johan Trygg; Tormod Naes; [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. On the Chemical Composition of Metal-Poor Stars Impact of Stellar Granulation and Departures from Local Thermodynamic Equilibrium on the Formation of Spectral Lines

    Detta är en avhandling från Uppsala : Acta Universitatis Upsaliensis

    Författare :Remo Collet; Bengt Gustafsson; Martin Asplund; Roger Cayrel; [2006]
    Nyckelord :Astronomy; late-type stars; stellar abundances; stellar atmospheres; spectral line formation; convection; hydrodynamics; Galactic chemical evolution; Astronomi;

    Sammanfattning : The information about the chemical compositions of stars is encoded in their spectra. Accurate determinations of these compositions are crucial for our understanding of stellar nucleosynthesis and Galactic chemical evolution. LÄS MER