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  • Articles: DFG German National Licenses  (17)
  • 2000-2004  (2)
  • 1995-1999  (15)
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  • Articles: DFG German National Licenses  (17)
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  • 1
    Electronic Resource
    Electronic Resource
    Microscopic structure and optical properties of GaAs1−xNx/GaAs(001) interface grown by metalorganic vapor phase epitaxy (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2460-2462 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the structure and optical properties of GaAs0.97N0.03/GaAs produced by metalorganic vapor phase epitaxy grown on GaAs surface at 520–550 °C. Using cross-sectional transmission electron microscopy and photoluminescence spectroscopy (PL), we show the presence of a 5–6-nm-thick nitrogen-rich interfacial region. The nitrogen composition near the interface is twice higher (x=0.038) than that of the bulk epilayer (x=0.016). PL data shows two peaks located at 1.05 and 1.18 eV associated to the interfacial region and the bulk layer, respectively. We discuss several mechanisms of surface enrichment of nitrogen that occurred during the first stage of GaAsN growth. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1468272
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Strain-induced surface morphology of slightly mismatched InxGa1−xAs films grown on vicinal (100) InP substrates (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7185-7190 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A surface investigation by atomic force microscope of InP and slightly lattice-mismatched InGaAs epilayers grown by metalorganic vapor phase epitaxy shows the effect of strain on InGaAs/InP surface morphology. Epilayers were grown at 600 °C with arsine at 760 Torr. We could clearly observe the regular step/terrace-like feature of the vicinal surface morphology for InP and InGaAs lattice-matched epilayers. It is shown that the step flow mode appears with a step edge with regular spacing for lattice-matched epilayers. A crosshatch pattern, i.e., an array of perpendicular lines visible at the surface, were obtained for strain-relaxed InGaAs epilayers (|(Δa/a)⊥|〉10−3) with an average separation of 1000–1500 nm. The detailed surface structure of the step edge presents a specific bending of terraces. The influence of step kinetics on the morphological stability of the surface will be illustrated. The relationship between the misfit dislocation network and anisotropic growth rate of the front step will be discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370530
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Passivation and depassivation of Monel electrodes in KF.2HF melts in comparison with the behaviour of nickel (1997)
    Springer
    Journal of applied electrochemistry 27 (1997), S. 1245-1253 
    Details
    ISSN: 1572-8838
    Keywords: fluorine production ; monel alloy ; corrosion ; passive films ; KF.2HF melts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Commercial fluorine production is conducted from KF.2HF melts at 85∘C in Monel cells that are subject to corrosion. Here we report studies of passivation and depassivation of the Monel in relation to that of Ni, its principal (65 wt % ) constituent, by means of cyclic voltammetry and recording of open-circuit potential-relaxation transients. The latter exhibit arrests at characteristic Flade-type potentials and lead to information on the kinetics of passive film breakdown. The role of diffusion processes in such breakdown and film dissolution is evaluated using the rotating disc electrode technique which enables comparisons to be made with the passivation behaviour of the separate main components of Monel, viz. Ni and Cu.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018436004516
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  • 4
    Electronic Resource
    Electronic Resource
    Dissolution and passivation processes in the corrosion of copper and nickel in KF.2HF at 85 °C (1997)
    Springer
    Journal of applied electrochemistry 27 (1997), S. 267-279 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The process of electrolytic production of fluorine is conducted in a melt of KF.2HF at about 85°C. The metallic cell materials, copper and copper–nickel alloys (Monel), and the steel electrodes that are used as the cathode, are subject to substantial corrosion in the liquid electrolyte. Comparative studies are reported on the relative extent of corrosion of copper and nickel in the above melt, and the respective passivation behaviours of these two metals. The formation of fluoride films on the two metals is examined by means of cyclic voltammetry and complementarily through recording of open-circuit potential-decay transients, following passivation. Flade behaviour is observed and the role of diffusion-controlled processes in depassivation is quantitatively evaluated. Weight-change measurements also support the electrochemically derived results. The passive film at Ni is much less easily reducible than at Cu.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018424628739
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    102+ rotifer species (Rotifera: Monogononta) in Broa reservoir (SP., Brazil) on 26 August 1994, with the description of three new species (1995)
    Springer
    Hydrobiologia 316 (1995), S. 183-197 
    Details
    ISSN: 1573-5117
    Keywords: Rotifera ; Broa reservoir ; new species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The monogonont Rotifera fauna of Lobo (Broa) reservoir (SP., Brazil), present in 12 samples collected on a single date during the cool season (26 August 1994), is listed and commented upon. In total, 102 species could be identified, three of which, Ascomorpha tundisii n.sp., Lecane broaensis n.sp. and Lepadella neglecta n.sp. are new to science. Lecane mitis Harring & Myers and Lepadella elongata Koste are redescribed. A note on the taxonomy of the Ascomorpha saltans-group is added.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017436
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of zooplankton type and abundance on prey consumption by the fairy shrimp, Streptocephalus proboscideus (Anostraca: Crustacea) (1996)
    Springer
    Hydrobiologia 319 (1996), S. 191-202 
    Details
    ISSN: 1573-5117
    Keywords: fairy shrimp ; zooplankton ; prey size ; prey density ; electivity index ; filtration rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Laboratory cultured Streptocephalus proboscideus (three sizes (mm), viz. 8.44 ± 0.95 (virgin), 14.18 ± 1.49 (adult I) and 19.24 ± 1.52 (adult II)) were offered (separately for males and females) field collected zooplankton (12 prey types) at three levels of abundance (1.0 ml−1, 2.0 ml−1 and 4.1 ind. ml−1 in 30-minute feeding experiments. Gut contents, analyzed for abundance and diversity of prey type, showed that predator size, sex and their interaction had strong effects on prey consumption. Regardless of their size, and of prey density, S. proboscideus females consumed 25–90% more prey than males. Their filtration rates (adult II) were higher (125 ml ind.−1 h.−1) than those of males (30 ml ind.−1 h.−1) too. Rotifers had the highest numerical percentage in the gut, regardless of predator size or sex. Cladocerans were only consumed by adults I and II. Adult II females consumed 28.5–43.3 µg zooplankton dry weight ind.−1 h.−1. Size distribution of B. longirostris in the field and in the gut were closely similar. This study confirms S. proboscideus as a non-selective filter feeder. Since it did not eat jumping rotifers, copepod nauplii and copepodites, it may contribute to structuring its prey communities, because good escapers will be enriched in the medium, while poor escapers will be depleted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00013732
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of light, DMSO and glycerol on the hatchability ofThamnocephalus platyurus Packard cysts (1995)
    Springer
    Hydrobiologia 298 (1995), S. 175-178 
    Details
    ISSN: 1573-5117
    Keywords: Thamnocephalus ; light ; cyst hatching ; dimethyl sulfoxide ; glycerol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of two light intensities and different concentration of dimethyl sulfoxide (DMSO) and glycerol on hydrated cyst hatching inThamnocephalus platyurus were studied. A maximum of 65±6% hatching was recorded within seven days at 2500 lux continuous light regime. Hatching was at a minimum during the first two days, peaked between the third and fourth days, decreased thereafter. Hatching success was a function of duration of light exposure. Eight percent of cysts hatched in the dark, while cysts exposed to 24h light and subsequently incubated in the dark showed 27±2% hatching. Hatchability was significantly increased (23%) in 0.0375% DMSO and 0.0125% glycerol. Concentration above 0.05% DMSO and 0.025% glycerol had no or a negative influence on hatching. Since low concentrations of DMSO were non-toxic, apolar compounds like Ca2+ ionophore can be dissolved in DMSO to study the role of Calcium in cyst hatching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033812
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  • 8
    Electronic Resource
    Electronic Resource
    Competitive interactions between herbivorous rotifers: importance of food concentration and initial population density (1996)
    Springer
    Hydrobiologia 331 (1996), S. 1-7 
    Details
    ISSN: 1573-5117
    Keywords: Rotifer ; Brachionus ; Anuraeopsis ; initial population density ; competition ; food level ; population growth rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the outcome of competition between a large (Brachionus calyciflorus) and a small (Anuraeopsis fissa) rotifer species at five algal (Scenedesmus acutus) concentrations (0.5 × 106 to 40.5 × 106 cells ml−1) and with varying initial densities in mixed populations (100 to 0% of B. calcyciflorus or A. fissa), the combined initial biomass being 0.2 µg ml−1 in all test jars. Experiments were conducted at 28 ± 1 °C. Regardless of food concentration, B. calcyciflorus showed a greater increase in biomass than A. fissa, peak densities (mean ± standard error) at the lowest food concentration in the controls being 1.34 ± 0.31 µg dry weight ml−1 and 0.82 ± 0.08 dry weight ml−1, respectively. At the lower food concentrations, A. fissa displaced B. calyciflorus and vice versa at the higher food concentrations. At the intermediate food concentrations of 4.5 × 106 cells ml−1, B. calyciflorus outcompeted A. fissa only if its initial population density was three times higher. The rates of population growth in controls varied from 0.792 ± 0.06 d−1 to 1.492 ± 0.13 d−1 for B. calyciflorus and 0.445 ± 0.04 to 0.885 ± 0.01 for A. fissa depending on food level. When both species were introduced together, low food levels favoured higher abundance of A. fissa than B. calyciflorus, suggesting, in nature, it is likely that small Anuraeopsis colonize oligotrophic water bodies more successfully than larger Brachionus. The results also suggest that the outcome of competition depends not only on the size of the competing species and food availability but also on their colonizing density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025402
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  • 9
    Electronic Resource
    Electronic Resource
    Feeding preference and population growth of Asplanchna brightwelli (Rotifera) offered two non-evasive prey rotifers (1997)
    Springer
    Hydrobiologia 361 (1997), S. 77-88 
    Details
    ISSN: 1573-5117
    Keywords: Rotifer ; biomass ; predation ; population growth ; handlingtime
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Population growth rates of the predatory rotifer Asplanchna brightwelli were determined at 25 °C using a large (Brachionus calyciflorus) and a small (Anuraeopsis fissa) rotifer prey species in three concentrations (0.5, 0.1 and 2.0 μg dry weight ml-1) and in five combinations. The prey ingestion time by the predator was also measured. For B. calyciflorus the ingestion time (22.97–8.95 s) was more than six times that of A. fissa (3.68 ± 0.93). Regardless of prey type, the population growth of Asplanchna increased with increasing food density. There was a direct correlation between densities of amictic and mictic fernales. The maximum rate of population growth (1.01 ± 0.10 d-1) was higher at high density of A. fissa prey than that at the same density of B. calyciflorus. Progressive increase of A. fissa density in the offered food combination resulted in a corresponding increase of the predator's number. Gut content analysis of A. brightwelli revealed that the number of prey ingested increased with increasing prey densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003189312452
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    ERRATUM: A note on the Diaptomidae of Thailand, including redescription of three species and description of a new species (Copepoda, Calanoida) (1998)
    Springer
    Hydrobiologia 377 (1998), S. 217-218 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hydrobiologia 361: 201–223, 1998. Due to technical problems, Figures 91–94 on page 217 of the above volume were poorly reproduced. We now present the correct figures with their captions, on page 218 of this volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003474411353
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