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  • American Physical Society  (100)
  • Springer  (44)
  • Blackwell Science Ltd  (3)
  • 2000-2004  (114)
  • 1980-1984  (33)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 55 (2004), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Analysis of soil lipids may contribute to an improved understanding of atmosphere to soil carbon fluxes, soil organic matter source differentiation and pollutant accumulation. Soil lipids, mostly originating from plants and microorganisms, have traditionally been analysed by non-automated extraction and separation methods, which produce several lipid fractions, operationally defined by polarity. Here we present a combination of fast, automated and reproducible techniques, adopted from organic geochemical studies, for preparative separation of individual soil lipid fractions with increasing polarity. These techniques involve commercially available instruments, including accelerated solvent extraction and a two-step automated medium-pressure liquid chromatography procedure. The method yields eight lipid fractions consisting of five fractions fully amenable to gas chromatography/mass spectrometry (GC/MS) (aliphatic hydrocarbons, aromatic hydrocarbons, ketones, alcohols, carboxylic acids), and three fractions of highly polar or high molecular weight compounds (bases, very long-chain wax esters (C40+), high polarity compounds) that were not measurable with GC/MS under standard conditions. We tested the method on five agricultural soils. Results show that (i) mass recoveries for the individual fractions are reproducible, (ii) within individual fractions compound distribution patterns are reproducible, as demonstrated for alkanes and carboxylic acids, and (iii) individual fractions represent distinct and clean compound classes, free of interfering substances detectable by GC/MS. Thus, automated separation can be a fast, effective and reproducible procedure for fractionation of complex mixtures of soil lipids into clean compound classes, directly suitable for a variety of molecular (e.g. GC/MS) and isotopic characterizations (e.g. gas chromatography coupled with isotope ratio monitoring mass spectrometry or accelerator mass spectrometry).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 53 (2002), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The organic matter in soils may be stabilized by its interactions with minerals. We have studied such interactions in a Haplic Alisol under forest in which clay and organic matter have migrated from an eluvial A horizon to accumulate in an illuvial B horizon. We have tried to trace the fate of organic matter in these horizons (Ah and Bvt) by determining clay mineralogy, carbon and nitrogen content, hydrolysable amino acids, lignin signature by alkaline CuO oxidation and carbon species by 13C CPMAS NMR of bulk soils and particle-size fractions. In both horizons, most of the organic matter was present in O–alkyl and methylene structures, each contributing one-third to the bulk organic matter. In the Ah horizon the ratios of carbon-to-nitrogen, and yields for lignin and hydrolysable amino acids decreased as the particle-size class decreased, but side-chain oxidation of lignin compounds increased with decreasing particle size. In contrast to previous observations, the proportions of O–alkyl carbon increased as particle size decreased, constituting a major proportion of the organic carbon in the clay-size fractions from both the Ah and Bvt horizons (≥ 38%), while proportions of methylene carbon decreased. Illite was the dominant mineral in the fraction ≤ 6 μm, whereas the mobile fine clay fraction (〈0.2 μm) was rich in smectites – minerals with large surface areas. Our results support the hypothesis that potentially labile organic matter, such as O–alkyl carbon typically present in polysaccharides, may be stabilized against further degradation in organomineral complexes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 45 (2002), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In recent years, accumulating evidence for glycosylated bacterial proteins has overthrown an almost dogmatic belief that prokaryotes are not able to synthesize glycoproteins. Now it is widely accepted that eubacteria express glycoproteins. Although, at present, detailed information about glycosylation and structure–function relationships is available for only few eubacterial proteins, the variety of different components and structures observed already indicates that the variations in bacterial glycoproteins seem to exceed the rather limited display found in eukaryotes. Numerous virulence factors of bacterial pathogens have been found to be covalently modified with carbohydrate residues, thereby identifying these factors as true glycoproteins. In several bacterial species, gene clusters suggested to represent a general pro-tein glycosylation system have been identified. In other cases, genes encoding highly specific glycosyltransferases have been found to be directly linked with virulence genes. These findings raise interesting questions concerning a potential role of glycosylation in pathogenesis. In this review, we will therefore focus on protein glycosylation in Gram-negative bacterial pathogens.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 313 (1983), S. 369-370 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown how for temperatures below the critical one (Tc≈20 MeV) the phase diagram of hot nuclear matter may be reconstructed by using experimentally determined cluster abundances from nucleus-nucleus collisions.
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  • 5
    ISSN: 1434-6036
    Keywords: PACS. 74.72.Jt Other cuprates – 79.60.-i Photoemission and photoelectron spectra – 74.25.Jb Electronic structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In recent years insight has been gained into the electronic structure of layered cuprates using angle-resolved photoelectron spectroscopy. In many of these studies it is assumed that the electron-photon matrix element follows the trends set by the atomic photoionization cross sections and does not influence lineshape, dispersion and the k-dependence of the spectral intensity. In this study using Sr2CuO2Cl2 as an example it will be shown that the electron-photon matrix element can have a strong impact on both strength and shape of a feature in an angle-resolved photoelectron spectrum of a layered cuprate which can strongly affect information on character and the momentum-dependence of the energy and spectral weight of a state deduced from the spectra. The results of this study put an emphasis on the need to employ the whole parameter range of the ARPES method to get reliable information on the spectral function of cuprates for which purpose synchrotron radiation is an uniquely suited tool.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 16 (1983), S. 347-352 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The extended technicolor modelSU(8) ⊃SU(5)×SU(3) c ×U(1)⊃SU TC(3)×SU w(2)×SU c(3) ×U(1) with fermion representations containing three quark lepton families attracts attention because of its unique technicolor coupling: it increases in the infrared circumventing a no-go theorem and further-more stays big over the whole technicolor range. Hence an enhancement of fermion and pseudogoldstone masses proposed by Holdom might happen, allowing for a large sideways scale. A scalar field in the 1015 GeV range introduced in order to break an exact global flavour symmetry of the model is argued to influence strongly the vacuum alignment in the technicolor sector. It permits an explanation of the quark lepton mass pattern even with-out a detailed fit.
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  • 7
    ISSN: 1432-0649
    Keywords: 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
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  • 8
    ISSN: 1432-0630
    Keywords: PACS: 61.80.Fe; 61.82.Fk; 84.60.Jt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. We investigate the degradation of ZnO/CdS/ Cu(In,Ga)Se2 heterojunction solar cells for space applications and the defect generation in polycrystalline Cu(In,Ga)Se2 thin films by irradiation with 1-MeV electrons with fluences φe up to φe=5×1018 cm-2. Notable degradation of the solar cell performance starts at fluences of φe=1017 cm-2 where the open circuit voltage decreases by about 5% while short circuit current and fill factor remain essentially unaffected. Thus, Cu(In,Ga)Se2 solar cells withstand electron fluences which are higher by one order of magnitude or more when compared to other technologies. A model describes the absolute open circuit voltage loss considering the increase of space charge recombination by electron irradiation-induced defects. Defect analysis by admittance spectroscopy shows that acceptor defects with an energy distance of approximately 300 meV from the valence band are generated at a rate γ=0.017 (±0.01) cm-1.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 28 (1982), S. 211-214 
    ISSN: 1432-0630
    Keywords: 78.35 ; 68.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In the experiments reported here we observed the generation of non-thermal, large amplitude acoustic surface waves at GHz frequencies on the surface of a GaAs crystal under intense illumination with 514.5 nm radiation from an Ar+ laser at room temperature. The acoustic surface waves were detected by optical Brillouin spectroscopy.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 8 (1982), S. 206-211 
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract By means of paramagnetic Mössbauer spectra the cation distribution of the solid solution CoFe x Al2−x O4 with 0≦x≦1.5 has been determined. The existence of high field magnetic susceptibility at low temperature for samples with x≧0.4 has been interpreted in terms of non-collinear ferrimagnetic arrangements. Below the Neel temperature the spinel CoAl2O4 has a complex antiferromagnetic behavior.
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