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  • 1995-1999  (139)
  • 1945-1949  (4)
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  • 1
    Digitale Medien
    Digitale Medien
    The Edible Plant Dichelostemma capitatum: Its Vegetative Reproduction Response to Different Indigenous Harvesting Regimes in California (1999)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 7 (1999), S. 0 
    Details
    ISSN: 1526-100X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: To more thoroughly understand the ecological effects of harvesting geophytes for food by American Indians, an investigation of the ethnobotany and population dynamics of Dichelostemma capitatum (blue dicks), an attractive source of nutrition to many California Indian groups was undertaken. Some cultural groups harvest the corms and replant the cormlets, spare plants, and harvest after seeding to ensure replenishment of seed. Some Indian elders equate judicious harvesting with the maintenance and enhancement of field populations of this geophyte. A field experiment was conducted to determine the degree to which differences in intensity and timing of harvest, with and without replanting of cormlets, have any effect on corm and cormlet production. We found that harvesting at 100% intensity, through digging up all plants and corms, and without replanting cormlets at the seed stage, significantly reduces numbers of corms and cormlets compared to the controls (no harvest). However, harvesting at 50% intensity, through digging up half of all plants and corms at the flowering or seed stages, without replanting cormlets, was not significantly different from the controls (no harvest). The results suggest that harvesting blue dicks corms with a digging stick in the latter way could yield a sustainable level of harvest. Indigenous harvesting and management regimes may offer some of the best examples of long-term uses and management of the regional flora without detriment to its biodiversity. Restorationists are urged to study and experimentally mimic indigenous disturbance regimes and their ecological effects known to occur historically in various ecosystems. In some cases, areas will greatly benefit from the reintroduction of management and harvesting regimes that authentically simulate ancient indigenous interactions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1526-100X.1999.72016.x
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  • 2
    Digitale Medien
    Digitale Medien
    Electronic states of vapor deposited electron and hole transport agents and luminescent materials for light-emitting diodes (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5619-5625 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The electronic states of vapor-deposited materials used in electroluminescent devices were measured by ultraviolet and x-ray photoelectron spectroscopy, UV-visible absorbance, and photoluminescence spectroscopy. The combination of these measurements on ultrathin films of these materials allows (1) the determination of the energy (with respect to vacuum) of the highest occupied molecular orbital (HO) and the ionization potential (IP), and (2) the estimation of the lowest unoccupied molecular orbital (LU) energy and an approximation of the electron affinity, (EA). The knowledge of the binding energies of these states is important for the understanding of light-emitting diode properties and the potential optimization of such devices. The luminescent material tris(8-hydroxy-quinoline) aluminum has an IP of 5.9 eV and an apparent EA smaller than 3.5 eV. The IP of both hole transport agents, tri-p-tolylamine and 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane, is 5.4 eV and their EA is estimated to be smaller than 1.8 eV. The electron transport agents 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, 2-t-butyl-9,10-n,n'-dicyano-anthraquinonediimine and dicyano-diphenylsulfone differ in IP from 7.1 to 7.6 eV and the EA for these materials are estimated to be smaller than 3.5, 4.9 and 5.5 eV, respectively. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.359685
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  • 3
    Digitale Medien
    Digitale Medien
    Millimeter-wave spectroscopy of vibrationally excited ground state alkaline-earth hydroxide radicals (X 2Σ+) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4334-4339 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Pure rotational spectra of the alkaline-earth monohydroxides have been recorded for vibrationally excited states (0 1 0), (0 2 0), (0 3 0), and (1 0 0) of the ground electronic state (X 2Σ+) using millimeter-wave absorption spectroscopy. The radicals MgOH, CaOH, SrOH, and BaOH were studied. The data for CaOH, SrOH, and BaOH were analyzed with a linear 2Σ+ model, but with the addition of two terms to account for contamination of the v2=1 2Π and v2=2 2Δ vibronic levels with 2Π and 2Δ electronic states. The data for MgOH, however, did not fit well to this linear model and is additional evidence that this species is quasilinear. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.469482
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  • 4
    Digitale Medien
    Digitale Medien
    High resolution spectroscopy of MgOH (X 2Σ+) in its V2 mode: Further evidence for quasilinearity (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 10919-10925 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Pure rotational spectra of the MgOH and MgOD radicals have been recorded in the v2 bending vibration of their X 2Σ+ ground electronic states using millimeter-wave direct absorption spectroscopy. Multiple rotational transitions arising from the v2l=11, 22, 20, 31, 33, 42, and 44 substates have been measured in the frequency range 240–520 GHz for these species. Both the spin-rotation and l-type doubling interactions have been resolved in the spectra. The complete data sets for MgOH and MgOD have been analyzed using a linear model for the Hamiltonian which takes into account higher order (l=±4) l-type interactions. The global analyses were adequate, but anomalous behavior was apparent in both molecules. In particular, the Bv vs v2 relation was found to be highly nonlinear, large variations in the l-type doubling constant q were observed with vibrational level, and r0, rs, and r˜e structures determined differed substantially. Such findings suggest that MgOH is highly quasilinear, comparable to HNCO. The competition between ionic and covalent bonding is therefore becoming apparent in the lighter alkaline earth hydroxide species. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.480455
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  • 5
    Digitale Medien
    Digitale Medien
    Factors affecting ovipositor probing in Trybliographa rapae, a parasitoid of the cabbage root fly (1999)
    Springer
    Entomologia experimentalis et applicata 93 (1999), S. 217-225 
    Details
    ISSN: 1570-7458
    Schlagwort(e): parasitoid ; Hymenoptera ; Cynipidae ; ovipositor probing ; cabbage root fly ; host location ; contact chemoreception ; synomones ; kairomones
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of allelochemicals from its host, the larva of the cabbage root fly, Delia radicum (L.) (Diptera: Anthomyiidae), and the host's food plant on the ovipositor probing response of the parasitoid Trybliographa rapae (Westw.) (Hymenoptera: Cynipidae) were investigated. Trybliographa rapae probed both cabbage root fly infested and uninfested swede (Brassica napus var. napobrassica), although significantly more wasps responded to infested swede. Antennal sensilla are likely to be the mediators of this response. The synomones and kairomones involved are extractable in water, diethyl ether and methanol. No response was observed to washed, starved cabbage root fly larvae. Wasps spent significantly longer searching infested swede than uninfested, although probing frequency remained constant. It is suggested that the initiation of probing in T. rapae is dependent on a threshold concentration of general synomones or host related synomones and kairomones, whereas time spent searching a particular area is dependent on the environment perceived by sensilla on the ovipositor.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003804609482
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  • 6
    Digitale Medien
    Digitale Medien
    Spectral efficiency of the glasshouse whitefly Trialeurodes vaporariorum and Encarsia formosa its hymenopteran parasitoid (1997)
    Springer
    Entomologia experimentalis et applicata 83 (1997), S. 11-20 
    Details
    ISSN: 1570-7458
    Schlagwort(e): electroretinogram ; vision ; wavelength discrimination ; Homoptera: Aleyrodidae ; Aphelinidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Using the electroretinogram (ERG) technique the spectral efficiency of the compound eye of the glasshouse whitefly Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae) and its main parasitoid Encarsia formosa (Gahan) (Hymenoptera: Aphelinidae) was measured at selected wavelengths between 340 nm and 670 nm. The form of the ERG for both T. vaporariorum and E. formosa was found to be monophasic in nature. For both male and female T. vaporariorum and female E. formosa a primary peak of efficiency occurred in the blue-green-yellow region, peak 520 nm and a secondary peak in the ultraviolet (UV) region. The compound eye of female E. formosa gave a significantly greater response in the UV region than either the dorsal or ventral regions of the compound eye of T. vaporariorum relative to the responses in the blue-green-yellow region. T. vaporariorum has divided compound eyes with distinct dorsal and ventral regions. In this study it was found that the percentage response in the UV, of the dorsal region of the eye, is significantly greater than that of the ventral region of the eye relative to the percentage response in the blue-green-yellow region and there is a significant shift in the blue-green yellow peak towards the right of the spectrum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1002940410960
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  • 7
    Digitale Medien
    Digitale Medien
    Scalar Curvature, Metric Degenerations and the Static Vacuum Einstein Equations on 3-manifolds, I (1999)
    Springer
    Geometric and functional analysis 9 (1999), S. 855-967 
    Details
    ISSN: 1420-8970
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract. ((Without Abstract)).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000390050104
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  • 8
    Digitale Medien
    Digitale Medien
    Temperature/magnetization-induced distortions in the local structure of substituted LaMnO3 (1999)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 6 (1999), S. 543-545 
    Details
    ISSN: 1600-5775
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0909049598016008
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  • 9
    Digitale Medien
    Digitale Medien
    Interface phenomena and optical properties of structurally confined InP quantum wire ensembles (1997)
    Springer
    Physics of the solid state 39 (1997), S. 641-648 
    Details
    ISSN: 1063-7834
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Three-dimensional regular ensembles of InP quantum wires have been produced in channels of porous dielectric matrices by metal-organic chemical vapor deposition. These matrices differ both in the diameter of the channels (0.7, 3, and 8 nm) and in their spatial arrangement. The InP layer thickness does not exceed two-three monolayers. A comparative study of Raman, optical absorption, and photoluminescence spectra revealed the dependence of the optical properties of these quantum wires on interface effects, namely, atomic interaction in the wires, wire-matrix, and wire-wire interactions. It is shown that the wire-matrix interaction distorts the InP lattice, broadens the wire electronic density-of-states spectrum in the vicinity of the fundamental gap, and redistributes the relaxation of photoinduced excitations among states belonging to the wire itself and to defects in the matrix bound to the wire.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1134/1.1129945
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  • 10
    Digitale Medien
    Digitale Medien
    Effects of gastropod grazers on recruitment and succession of an estuarine assemblage: a multivariate and univariate approach (1997)
    Springer
    Oecologia 109 (1997), S. 442-453 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Key words Assemblage structure ; Gastropods ; Grazing ; Oysters ; Multivariate effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Grazers have been shown to affect assemblages of species in many habitats. Here we studied the effects of the gastropod grazers, Austrocochlea porcata and Bembicium auratum, on intertidal estuarine assemblages in a sheltered bay in New South Wales, Australia. We examined the effects of gastropods on individual species and on the assemblage as a whole. The multivariate response was compared with data on succession in these assemblages to estimate potential effects of grazers on succession. The experiment was repeated several times to determine the generality of grazer effects in the light of possible variation in the timing or intensity of recruitment. There were different responses of individual species to the presence of grazers. Grazers reduced the abundance of ephemeral algal species, bryozoans, copepods, insect larvae and Balanus spp. barnacles. They had a positive effect on oysters and spirorbids and no effect on the barnacles Elminius covertus and Hexaminius spp. These effects were consistent through time. Multivariate analyses confirmed that grazers caused significant changes to whole assemblages and that these effects were far-reaching and not only caused by changes to algal species. The removal of grazers appeared to neither speed up nor slow down succession, but rather caused a completely different assemblage to develop. Apparent important mechanisms affecting the composition of animal species when grazers were removed included accumulation of sediments and detritus and pre-emption of space by algae.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004420050104
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