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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 15 (1980), S. 231-238 
    ISSN: 1432-1432
    Keywords: β-structure ; Poly-DL-peptides ; Kinetics of hydrolysis ; Enantiomer enrichment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It was previously shown that nuclei ofβ-sheets surrounded by unordered segments are formed in polypeptide chains built up with alternating hydrophobic and hydrophilic residues and containing both L- and D-enantiomers. It was also established that segments of residues having the same configuration tend to segregate in these nuclei when the starting composition of stereomonomers departs from the racemic mixture. Soft acidic hydrolysis of these polymers has been studied. Kinetic measurements show two pseudo first order rate constants, in agreement with the existence of two conformational species. The unordered part of the chains is hydrolyzed more rapidly, allowing the isolation of aβ-fraction enriched in one enantiomer. Thus, a plausible process of enrichment in enantiomer during prebiotic evolution has been described, which however does not explain the preference of one enantiomer over the other one.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2021-10-22
    Description: Abstract
    Description: This data publication contains global maps of the vertical total electron content (VTEC) of the Earth's ionosphere. They are computed at GFZ from ground GNSS data and provided on an operational basis. The dataset covers the period since the beginning of 2000 and is published in daily files.
    Description: Methods
    Description: Based on a network of around 250 GNSS stations of the tracking network of the International GNSS Service (IGS), the GFZ generates global VTEC solutions using the latest development version of the EPOS.P8 Software. Observation data from GPS, GLONASS (from 2012), and Galileo (from 2014) satellites are used. The processing is based on a rigorous least-squares approach using uncombined code and phase observations, and does not entail leveling techniques. A single-layer ionospheric model with a spherical harmonic VTEC representation is applied. VTEC values are provided with a temporal resolution of 2 hours and a spatial resolution of 2.5 degrees in latitude and 5 degrees in longitude. The processing is described in detail in Brack et al. (2021). The solution series contains daily files (〈YYYY〉 and 〈DDD〉 refer to the year and day of year) in the ionex data format (https://files.igs.org/pub/data/format/ionex1.pdf): - GFZ0OPSRAP_〈YYYY〉〈DDD〉0000_01D_02H_ION.IOX.gz: rapid solution published with a delay of one day - GFZ0OPSFIN_〈YYYY〉〈DDD〉0000_01D_02H_ION.IOX.gz: final solution containing the middle day of a combination of the rapid solutions of three consecutive days The file naming follows the IGS Long Product Filename (http://acc.igs.org/repro3/Long_Product_Filenames_v1.0.pdf). All files are .gz compressed.
    Keywords: Ionosphere ; Total electron content (TEC) ; Atmosphere ; GPS ; GLONASS ; Galileo ; atmosphere 〉 atmospheric structure 〉 ionosphere ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 Galileo ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GLONASS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GNSS ; Earth Remote Sensing Instruments 〉 Passive Remote Sensing 〉 Positioning/Navigation 〉 GPS ; EARTH SCIENCE 〉 ATMOSPHERE ; EARTH SCIENCE 〉 SUN-EARTH INTERACTIONS 〉 SOLAR ENERGETIC PARTICLE PROPERTIES 〉 TOTAL ELECTRON CONTENT
    Type: Dataset , Dataset
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