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  • Springer  (65)
  • 2005-2009  (31)
  • 1985-1989  (32)
  • 1950-1954  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Social competition among gynes in halictine bees: The influence of bee size and pheromones on behavior (1989)
    Springer
    Journal of insect behavior 2 (1989), S. 397-411 
    Details
    ISSN: 1572-8889
    Keywords: social competition ; solitary gynes ; Halictidae ; size ; pheromones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Solitary gynes of two species of social bees, Lasioglossum (Evylaeus) malachurumand L. (E.) pauxillum(Hymenoptera: Halictidae), were observed in the field and in the laboratory during the solitary (spring) phase of their life cycles. Fighting over nests among gynes of the former species is common when nests are being provisioned and can result in serious injury or even death to one or both interactants. The payoff is occasional acquisition of a nest. In contrast, fighting was never observed in the field among gynes of L. pauxillum.Several factors determine the outcome of such fights in L. malachuram,these include relative sizes of the two opponents as well as nest ownership. Dyadic interactions in the laboratory reveal that size influences the behavioral strategies of the gynes of both species, with the larger of two individuals in a dyadic interaction being on average more aggressive. Furthermore, in a second experimental series with L. malachurum,application to the smaller gyne of synthetically derived macrocyclic lactones found in the species' Dufour's gland pheromone mixture significantly decreased the aggressive tendencies of the larger such that its behavior was no longer significantly different from that for the smaller gyne. Therefore, among gynes, aggressive pheromonal signaling, coupled with other possible signal modalities, is probably an integral part in the communication system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01068064
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  • 2
    Electronic Resource
    Electronic Resource
    Rotational distribution of nascent OH radicals after H2O2 photolysis at 193 nm (1987)
    Springer
    Applied physics 42 (1987), S. 173-179 
    Details
    ISSN: 1432-0649
    Keywords: 82.50 ; 33.50 ; 06.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The rotational distribution of OH(X 2Π,v″=0) radicals was investigated by resonant laser-induced fluorescence (LIF) after photolysis of H2O2 at 193 nm. A microcomputer equipped LIF arrangement allowed special shot-by-shot normalization of the fluorescence signal for noise reduction. Using a least-squares procedure we were able to account for all measured line intensities including overlapping lines (blends) and obtain a complete rotational state distribution of the OH(X 2Π,v″=0) state. The rotational excitation shows a Gaussian-like distribution with a maximum atK″=12 and with 16% of the total available energy (17,400 cm−1) appearing in rotation. Only 1% of the available energy is converted into vibration, leaving over 83% for translational excitation. The measured rotational distribution appears to fit a semiclassical theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693881
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  • 3
    Electronic Resource
    Electronic Resource
    Model calculations of diffusion limited trapping dynamics in quantum well laser structures (1989)
    Springer
    Applied physics 48 (1989), S. 509-515 
    Details
    ISSN: 1432-0630
    Keywords: 73.20.Dx ; 78.55.Cr ; 78.47.+p
    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 present a phenomenological theoretical model to treat the trapping of carriers into quantum wells of semiconductor laser structures. We consider explicitely the transport within the barrier layers by solving the continuity equation with the appropriate boundary conditions taking into account surface recombination, radiative and nonradiative recombination in the barrier layers and trapping of carriers into the quantum wells. The experimental findings for the trapping dynamics in GaAs/AlGaAs quantum well structures can be consistently interpreted by the model calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617851
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  • 4
    Electronic Resource
    Electronic Resource
    Spectroscopic study of potential magneto-optic storage layers (1989)
    Springer
    Applied physics 49 (1989), S. 599-618 
    Details
    ISSN: 1432-0630
    Keywords: 75.70 ; 78.20L
    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 present an experimental investigation of magneto-optic (MO) thin film materials of interest in optical storage. XPS valence band spectra of ultrahigh vacuum deposited rare earth — Fe50Co50 alloys are correlated to magneto-optic and reflectivity spectra measured ex-situ in the photon energy range 0.5 ≦E ph ≦ 5.5 eV. It is found that 4f n →4f n−15d 1 optical transitions contribute to room temperature Kerr spectra in Pr-FeCo and Nd-FeCo, but only in the UV spectral region (λ≦300 nm). Eu is found to enter Eu-FeCo intermetallic alloys with a 4f 7 ground state at −2 eV binding energy. However, no substantial contribution to the Kerr effect from excitations of this electronic state has been observed n either at room temperaturen or at 100 K. We present a general argument that 4f excitations of RE ions in typical intermetallic alloys can never be expected to contribute more than some tenths of a degree toθ k in contrast to the well known huge rotations in RE-chalcogenides. For Yb-FeCo we have observed in XPS a mixed valence behavior of Yb showing a discontinuous transition from divalent Yb2+ in the pure metal to mixed valent Yb2.55+ in amorphous Yb-FeCo films. Nof→d contributions to the room temperature MO spectra have been detected. Strong optical enhancement effects are presented for metallic bilayer and multilayer structures of the type MO-layer/reflector. The total thickness of an optimized structure corresponds to about two times the penetration depth of light. Enhancement occurs predominantly at photon energies below the plasma frequency of the reflector material and is caused by low values of the optical constantsn andk of the reflector. In storage materials like Tb-FeCo the read-out performance can be improved by about a factor of 2 with a bilayer of 30 nm Tb-FeCo on Cu. Quantitative modelling of the optical and magneto-optic properties of these films is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616985
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  • 5
    Electronic Resource
    Electronic Resource
    Applicability of the transfer function approach to forecasting employment levels in small regions (1987)
    Springer
    The annals of regional science 21 (1987), S. 34-43 
    Details
    ISSN: 1432-0592
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography , Economics
    Notes: Abstract The problem investigated in this paper is that of forecasting employment levels (both raw and seasonally adjusted) in small regions, regions typically lacking data sufficient for the construction of simultaneous equation econometric models. The method employed is transfer function analysis using readily available national variables as drivers. The results suggest that the transfer function approach is capable of providing accurate forecasts of employment levels in small regions, forecast accuracy being measured in terms of mean absolute percentage errors and root mean squared errors. We conclude on the basis of this demonstrated accuracy that this approach is a viable method for forecasting selected variables in a small region context.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01540230
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  • 6
    Electronic Resource
    Electronic Resource
    Issues and approaches in assessing cumulative impacts on waterbird habitat in wetlands (1988)
    Springer
    Environmental management 12 (1988), S. 695-701 
    Details
    ISSN: 1432-1009
    Keywords: Wetlands ; Wildlife ; Habitat ; Cumulative impacts ; Losses ; Perturbations ; Waterbirds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Wetlands are attractive to vertebrates because of their abundant nutrient resources and habitat diversity. Because they are conspicuous, vertebrates commonly are used as indicators of changes in wetlands produced by environmental impacts. Such impacts take place at the landscape level where extensive areas are lost; at the wetland complex level where some (usually small) units of a closely spaced group of wetlands are drained or modified; or at the level of the individual wetland through modification or fragmentation that impacts its habitat value. Vertebrates utilize habitats differently according to age, sex, geographic location, and season, and habitat evaluations based on isolated observations can be biased. Current wetland evaluation systems incorporate wildlife habitat as a major feature, and the habitat evaluation procedure focuses only on habitat. Several approaches for estimating bird habitat losses are derived from population curves based on natural and experimentally induced population fluctuations. Additional research needs and experimental approaches are identified for addressing cumulative impacts on wildlife habitat values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01867546
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  • 7
    Electronic Resource
    Electronic Resource
    The fragile site (17)(p12): induction by AT-specific DNA-ligands and population cytogenetics (1987)
    Springer
    Human genetics 〈Berlin〉 77 (1987), S. 118-121 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The rare fragile site at 17p12 can be induced in lymphocyte cultures with the AT-specific DNA-ligands distamycin A, DAPI, Hoechst 33258 and berenil. The optimum culture conditions for the experimental induction of fra(17)(p12) were studied. There are indications that fra(17)(p12) is a latereplicating chromosome region in which AT-rich DNA is located. The fragile site also occurs spontaneously in cell cultures of most fra(17)(p12) carriers. A population screening of 250 unselected individuals showed that the frequency of carriers heterozygous for fra(17)(p12) is 2%. The results are compatible with a population being in Hardy-Weinberg equilibrium with respect to fra(17)(p12) and its non-fragile allelomorph. Neither the heterozygous nor the homozygous condition of fra(17)(p12) have any deleterious effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00272376
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  • 8
    Electronic Resource
    Electronic Resource
    Brechungsindex von Dipolgasgemischen bei Dezimeferwellen (1953)
    Springer
    Naturwissenschaften 40 (1953), S. 17-18 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00595716
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  • 9
    Electronic Resource
    Electronic Resource
    A note on the effect of observations with missing data on genetic correlation estimates (1987)
    Springer
    Theoretical and applied genetics 74 (1987), S. 549-553 
    Details
    ISSN: 1432-2242
    Keywords: Covariance components ; Genetic correlations ; Unbalanced data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Various studies have estimated covariance components as half the difference between the variance component of the sum of the variable values, for each observation, and the sum of the corresponding variable variance components. Although the variance components for the separate variables can be computed using all available data, the variance components of the sum can be computed only from those observations with records for both variables. Previous studies have suggested eliminating observations with missing data, because of possible selection bias. The effect of missing data on estimates of covariance components and genetic correlations was tested on sample beef cattle data and simulated data by randomly deleting differing proportions of records of one variable for each pair of variables analyzed. Estimates of genetic correlations computed with observations with missing data eliminated, were more accurate than estimates computed using all available data. Furthermore, when observations with missing data were included, estimates of genetic correlation far outside the parameter space were common. Therefore, this method should be used only if observations with missing data have been eliminated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288850
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  • 10
    Electronic Resource
    Electronic Resource
    A novel class of unstable 6-thioguanine-resistant cells from dog and human kidneys (1988)
    Springer
    Cell biology and toxicology 4 (1988), S. 211-223 
    Details
    ISSN: 1573-6822
    Keywords: hypoxanthine phosphoribosyltransferase ; kidney primary clones ; purine analogue resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Thioguanine-resistant primary clones were grown from single cell suspensions obtained from dog and human kidneys by enzymatic digestion. In medium containing a relatively high concentration (10μg/ ml) of thioguanine, thioguanine-resistant primary clones arose from each source at frequencies ranging from 10−4 to 10−5. A reduction in total hypoxanthine uptake was found in the thioguanine-resistant primary clones which had developed in thioguanine medium, consistent with a reduction in hypoxanthine phosphoribosyltransferase activity. When these thioguanine-resistant primary clones were subsequently grown in the absence of thioguanine and assayed for the thioguanine-resistant phenotype and hypoxanthine phosphoribosyltransferase activity, it was found that most were now thioguanine-sensitive and yielded cell free extracts with substantial amounts of hypoxanthine phosphoribosyltransferase activity. In contrast, thioguanine-resistant human clones grown continuously in the presence of thioguanine yielded cell free extracts with little or no detectable hypoxanthine phosphoribosyltransferase activity. Southern blot analysis demonstrated no structural alterations in the hypoxanthine phosphoribosyltransferase gene in thioguanine-resistant primary human kidney clones. These results suggest that a novel mechanism(s) for thioguanine resistance and the control of hypoxanth phosphoribosyltransferase expression may occur in dog and human kidney cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119247
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