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  • 1
    ISSN: 1612-1112
    Keywords: Enantiomeric purity ; α-Amino acids ; Oxfenicine ; High-performance liquid chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reaction of the methyl esters of the α-amino acids, R-(−)-, and S-(+)-4-hydroxyphenylglycine (oxfenicine) with the enantiomerically pure acid anhydride of R-(+)-1-methoxy-1-trifluoromethyl-phenylacetic acid (i.e. R-(+)-MTPA) yields diastereoisomeric amides which are separable by high-performance liquid chromatography (HPLC). The ratios of the diastereoisomeric amides may be measured chromatographically and are shown to correspond to the enantiomeric purities of the amino acids. This method is particularly well suited for detecting low levels of an enantiomeric impurity in α-amino acids which possess a base labile α-methine hydrogen atom.
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  • 2
    ISSN: 1573-8590
    Keywords: Artemia ; divergence ; DNA ; haemoglobin ; Parartemia ; protein sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Parartemia is a genus of brine shrimp endemic to Australia which is related to the more widespread and economically important Artemia sp. The expression of a multimeric haemoglobin molecule in Artemia is well documented but in Parartemia only trace levels of a possible haemoglobin have been observed. In this paper we describe the DNA sequence of a domain of a haemoglobin molecule in Parartemia. The derived amino acid sequence suggests that the possible date of divergence about 85 million years ago of the two genera predates the divergence of the C and T polymers of Artemia haemoglobin. This date would correlate with the physical and temporal isolation of Australia in the late Mesozoic.
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  • 3
    ISSN: 1573-8590
    Keywords: Artemia ; divergence ; DNA ; haemoglobin ; Parartemia ; protein sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Parartemia is a genus of brine shrimp endemic to Australia which is related to the more widespread and economically importantArtemia sp. The expression of a multimeric haemoglobin molecule inArtemia is well documented but inParartemia only trace levels of a possible haemoglobin have been observed. In this paper we describe the DNA sequence of a domain of a haemoglobin molecule inParartemia. The derived amino acid sequence suggests that the possible date of divergence about 85 million years ago of the two genera predates the divergence of the C and T polymers ofArtemia haemoglobin. This date would correlate with the physical and temporal isolation of Australia in the late Mesozoic.
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  • 4
    ISSN: 1573-5036
    Keywords: fine-root turnover ; hybrid poplar ; minirhizotron ; red pine ; soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tree root activity, including fine-root production, turnover and metabolic activity are significant components of forest productivity and nutrient cycling. Differences in root activity among forest types are not well known. A 3-year study was undertaken in red pine (Pinus resinosa Ait.) and hybrid poplar (Populus tristis X P. balsamifera cv `Tristis no. 1') plantations to compare belowground root dynamics. We measured fine-root production, mortality and standing crop, as well as soil CO2 efflux. Pine fine-root production was only 2.9% of that of poplar during three years; 85 pine roots were observed in minirhizotron tubes compared with 4088 poplar roots. Live-root density oscillated seasonally for both species with late winter minimum and autumn maximum. Poplar reached constant maximum live-root length within the first growing season, but pine continued to increase observed fine-root length for three growing seasons. Within the first 100 days following initial appearance, 22% of the pine roots disappeared and 38% of the poplar roots disappeared. Median fine-root longevity of pine was 291 days compared with 149 days for poplar roots. Fine-root longevity increased with depth in the soil, and was greater for roots with initial diameter 〉0.5 mm. The probability of poplar root death from late February to May was more than three times that in any other season, regardless of root age. Despite the greater poplar root production and live-root length, fine-root biomass and soil CO2 efflux was greater in pine. Greater metabolic activity in the pine stand may be due to greater fine-root biomass or greater heterotrophic respiration.
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  • 5
    ISSN: 1573-5044
    Keywords: frequency distribution ; haploids ; multiplicative binomial ; poisson ; Solanum tuberosum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methods for the production and utilisation of haploids have been developed for a range of crop plants. Genetical and environmental factors are known to influence both the rate of haploid induction and the mode of regeneration. Investigations designed to examine the parameters that influence haploid production from anthers are usually based on the overall percentage of responding anthers. Previous studies have rarely taken into account the frequency or distribution of anther culture response within a potato flower. In this paper the binomial, poisson and multiplicative binomial distributions are used for the first time to describe the distribution of anther culture response within a Solanum tuberosum flower.
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  • 6
    ISSN: 1573-5044
    Keywords: heritability ; protoplasts ; RFLPs ; Solanum tuberosum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genetics of tissue culture response in potato has been examined by analysing a sample of dihaploids (2n=2x=24) extracted from tetraploid parents (4n=4x=48). The genotypes were screened for rate of nodal multiplication, in vitro tuberisation, regeneration from leaf discs and protoplast plating efficiency. Significant differences were detected between dihaploids for the traits measured and this indicates that tissue culture response in the tetraploid parents must be in the heterozygous condition. Estimates of the broad sense heritabilities were calculated together with the number of genes or effective factors involved in the control of the traits. These estimates indicate that tissue culture response in potato is under relatively simple genetic control and “blocks of genes” may be located on specific chromosomes. The inheritance of RFLP markers in the segregating dihaploid population was also monitored and the potential of using molecular markers linked to gene(s) controlling tissue culture response is discussed.
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  • 7
    ISSN: 1573-1561
    Keywords: Antarctica ; marine benthos ; Tritoniella belli ; Mollusca ; nudibranch ; Clavularia frankliniana ; Cnidaria ; chemical defense ; predator ; prey ; chimyl alcohol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Extracts of the dorid nudibranchTritoniella belli and stoloniferan coralClavularia frankliniana were chromatographed and analyzed by1H NMR and thin-layer chromatography. Three glycerol ethers were detected inT. belli, primarily 1-O-hexadecyl glycerol (chimyl alcohol). Chimyl alcohol was also detected after gradient flash chromatography and reverse-phase HPLC purification in the tissues ofC. frankliniana. The common omnivorous predatory Antarctic sea starOdontaster validus, a likely predator of benthic invertebrates, showed feeding deterrence to small cubes ofT. belli mantle tissue placed on the tube feet along the ambulacral feeding groove, while always extruding the cardiac stomach when presented with cubes of shrimp tissue of similar size. Filter-paper disks soaked in an aqueous shrimp solution and then dried were found to elicit a broad range of feeding behaviors inO. validus, including movement of the shrimp disk to the mouth, extrusion of the cardiac stomach, and the assumption of a humped feeding posture. Chimyl alcohol-treated shrimp disks caused significant feeding deterrence in sea stars when compared with control disks (solvent plus shrimp treated disks alone).T. belli andC. frankliniana appear to employ a defensive compound that has been found in a variety of temperate and tropical mollusks, where it has been demonstrated to deter fish predators. We provide evidence for further deterrent capabilities of chimyl alcohol and of its trophic relationship in the polar ecosystem of McMurdo Sound, Antarctica.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1627-1629 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrostatic potential profile in the accelerating gap in a plasma-prefilled magnetically insulated intense pulsed ion beam diode has been determined using laser-induced fluorescence spectroscopy. Results for a 300–400 kV planar diode are presented, both with and without an electron emitting vane protruding from the cathode. In both cases, a 5–6 mm accelerating gap forms in the 1012–1013/cm3 plasma in a few nanoseconds. The experimental potential profiles are not consistent with electrons confined to a sheath near the cathode. Rather, electrons are required throughout the gap to explain the observations.
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  • 9
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fundamental vibrational frequencies of an isolated chain of cis-1,4-polybutadiene have been calculated. Infrared and polarized Raman data are used in the force constant refinement routine. The assignments of the vibrational frequencies are discussed in terms of the potential energy distribution.
    Additional Material: 5 Ill.
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  • 10
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra have been obtained for the crystalline regions of samples of predominantly trans-1,4-polychloroprenes polymerized at -20, 0, and 40°C. Spectral differences among the polychloroprenes are interpreted in terms of the increase in structural irregularities that occur as the polymerization temperature is increased. Results of this study indicate that crystallization occurs with random inclusion of these structural irregularities into the crystalline domains. The conclusion is supported by the spectra of the crystalline regions of a chloroprene copolymer containing known impurities in the form of 2,3-dichloro-2-butenylene units in addition to the normal 2-chloro-2-butenylene units.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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