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  • 2000-2004  (18)
  • 1995-1999  (18)
  • 1985-1989  (16)
  • 1975-1979  (13)
  • 1945-1949  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Reflectance anisotropy spectroscopy study of the surface reconstructions of decapped InP(001) (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 480-485 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A reflectance anisotropy spectroscopy (RAS) and low-energy electron diffraction study of the InP(001) surface is presented. The surface was prepared by thermal desorption of an As-P capped epilayer grown by molecular beam epitaxy. RA spectra have been monitored over a spectral range of 1.5–5.5 eV at regular intervals during thermal decapping and annealing up to the point of decomposition (553–973 K). Each of the RA spectra of the surface reconstructions comprise positive (at 2.9 eV) and negative (at 1.8 eV) anisotropies which have been previously associated with P- and In-related bonding, respectively. Unlike other III-V (001) semiconductor surfaces, the evolution of different reconstructions cannot be explained in terms of a change in surface stoichiometry which involves loss of the anion species. In the case of InP(001) the P species contributes to the clean surface reconstruction from the early stages of decapping to the point of decomposition. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.366718
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  • 2
    Digitale Medien
    Digitale Medien
    Letters. Power Plants (1976)
    s.l. : American Chemical Society
    Environmental science & technology 10 (1976), S. 964-964 
    Details
    ISSN: 1520-5851
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Energietechnik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/es60121a601
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  • 3
    Digitale Medien
    Digitale Medien
    Trimorphic incompatibility in Eichhornia azurea (Pontederiaceae) (2000)
    Springer
    Sexual plant reproduction 12 (2000), S. 203-208 
    Details
    ISSN: 1432-2145
    Schlagwort(e): Key words Tristyly ; Trimorphic incompatibility ; Pollen trimorphism ; Partial incompatibility ; Clonal aquatic plant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Eichhornia azurea (Pontederiaceae) is a mat-forming, clonal aquatic that inhabits lakes, marshes and river systems in many parts of the Neotropics. The species is tristylous with long-, mid-, and short-styled morphs commonly represented in natural populations. To investigate whether E. azurea possesses a trimorphic incompatibility system typical of tristylous species, we conducted a controlled pollination experiment on 15 clones representing the three style morphs from a natural population near Rosario, Argentina. Comparisons of fruit and seed set following self-, illegitimate, and legitimate pollinations clearly demonstrated the presence of trimorphic incompatibility in E. azurea. Self- and illegitimate pollinations produced significantly less fruit and seed than legitimate pollinations in all three style morphs. Pollen from the two anther levels within a flower exhibited contrasting compatibility relations in self-pollinations. In common with several other tristylous species in Pontederiaceae, the expression of self-incompatibility was weakest in the mid-styled morph and strongest in the short-styled morph. We discuss the ecological and evolutionary significance of the partial expression of trimorphic incompatibility in E. azurea.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004970050001
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  • 4
    Digitale Medien
    Digitale Medien
    Variation of pollen limitation in the early flowering Mediterranean geophyte Narcissus assoanus (Amaryllidaceae) (2000)
    Springer
    Oecologia 124 (2000), S. 529-535 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Key words Fruit and seed set ; Narcissus assoanus ; Pollen limitation ; Reproductive ecology ; Seed:ovule ratios
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  A recent literature review indicates that pollen limitation of female fertility is a common feature of flowering plants. Despite the ecological and evolutionary significance of pollen limitation, most studies have only examined fertility in a single population at one time. Here we investigate pollen limitation of fruit and seed set in five populations of Narcissus assoanus, a self- sterile, insect-pollinated geophyte, over 2–3 years in southern France. In common with many early spring flowering plants, pollinator visitation to N. assoanus is often infrequent. Supplemental hand-pollination of flowers with outcross pollen significantly increased overall fruit and seed set by 11% and 19%, respectively. Four of the five populations experienced some pollen limitation during the study. For a given year, there was significant variation in pollen limitation among populations. Two of the populations were pollen limited in one year but not in other years in which they were studied. Seed:ovule ratios for open- and hand-pollinated flowers averaged 0.29 and 0.33, respectively. While hand pollination significantly increased the seed:ovule ratio, the low value obtained indicates that the majority of ovules in flowers do not mature seeds despite hand pollination. The role of genetic and environmental factors governing low seed:ovule ratios in N. assoanus is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004420000417
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  • 5
    Digitale Medien
    Digitale Medien
    Pollinator foraging behavior and pollen collection on the floral morphs of tristylous Pontederia cordata L. (1987)
    Springer
    Oecologia 74 (1987), S. 347-351 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Pontederia cordata ; Bombus ; Tristyly ; Pollination ; Behavior
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The foraging behavior of the pollinators of tristylous Pontederia cordata was studied to determine if differences in floral morphology would lead to preferential visitation of the floral morphs. Although nectar production is not different in the three floral morphs, differences in the production and size of pollen grains produced by the three anther levels results in the morphs offering variable amounts of resources to pollen-collecting insects. Bumblebees (Bombus spp.) and the solitary bee Melissodes apicata used P. cordata primarily as a nectar source and therefore did not seem to exhibit any morph preference. In contrast, honeybees visited flowers mainly for pollen and preferred to forage on long-level anthers of the short-and mid-styled morphs. An analysis of the composition of corbicular pollen loads indicated that, relative to the frequency of production in the population: 1) honeybees collected an excess of pollen from long-level anthers; 2) bumblebees collected the three types of pollen without any apparent preference; and 3) M. apicata preferentially collected pollen from the short-level anthers — presumably because their proboscides are modified by the presence of tiny hairs. The results suggest that P. cordata in Ontario is serviced by a diverse, unspecialized pollinator fauna which is not co-adapted to the tristylous floral polymorphism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00378928
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  • 6
    Digitale Medien
    Digitale Medien
    Utilization of Photoemission Cross-Section Effects for Monitoring Thin-Film Growth in UHV (1995)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 2 (1995), S. 252-255 
    Details
    ISSN: 1600-5775
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Given the tunability of synchrotron radiation, photoemission spectroscopy can be used to monitor the growth modes of thin films in UHV. Cross-section effects such as Cooper minima and resonant photoemission can be exploited to maximize the adsorbate signal and minimize that from the substrate. Under favourable circumstances growth can be monitored in real time at coverages of 〈1%. As an example the growth of Gd on W(110) is investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0909049595008697
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  • 7
    Digitale Medien
    Digitale Medien
    Gd/W(110) Interface Formation Studied by W 4f Surface Core-Level Spectroscopy (1995)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 2 (1995), S. 261-263 
    Details
    ISSN: 1600-5775
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: W 4f core-level spectra of Gd films on W(110) show components which can be identified as being due to bulk and interface W. The results suggest that the W/Gd interface is abrupt, i.e. no interface alloying occurs. At submonolayer coverages a further component is seen which is attributable to intermediate (n × 2) phases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S090904959500954X
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  • 8
    Digitale Medien
    Digitale Medien
    Photoemission Study of CO Adsorption on Gd (1995)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 2 (1995), S. 312-315 
    Details
    ISSN: 1600-5775
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: Angle-resolved UV photoemission spectroscopy has been used to investigate the interaction of CO with Gd films, grown on W(110). The results suggest the CO absorbs dissociatively, initially forming Gd2O3, with subsequent catalytic oxidation of CO to form carbonate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S090904959501137X
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  • 9
    Digitale Medien
    Digitale Medien
    Variation in expression of trimorphic incompatibility in Pontederia cordata L. (Pontederiaceae) (1985)
    Springer
    Theoretical and applied genetics 70 (1985), S. 355-362 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Trimorphic incompatibility ; Pontederia cordata L.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Pontederia cordata L. (Pontederiaceae), a perennial diploid, possesses the rare genetic polymorphism tristyly. A controlled pollination programme was conducted over a three year period, under glasshouse conditions, on 36 clones of P. cordata var. cordata to examine the nature of the self-incompatibility system. The three major findings of the pollination study were: (1) the three floral morphs display different levels of self-incompatibility, (2) pollen from the two anther levels within a flower exhibits different compatibility behaviour in self-pollinations, (3) considerable individual genetic variation in the expression of self-incompatibility is evident among clones within floral morphs. Similar results were also obtained from a smaller study on 15 clones of P. cordata var. lancifolia conducted over a 6 month period. In common with other Pontederia species the mid-styled morph (M) of P. cordata produces large amounts of seed when self-pollinated with pollen from long-level anthers. A developmental model is proposed to explain the high level of self-compatibility of the M morph in Pontederia species. Self-pollination of segregating progenies from M and S morphs of known incompatibility status demonstrated that the expression of incompatibility is closely associated with style length. It is suggested that overall differences in incompatibility behaviour among the floral morphs may be due to the pleiotropic effects of major genes controlling sub-characters of the tristylous syndrome, rather than linked modifier genes. However, the variable expression of trimorphic incompatibility within floral morphs suggests that this variation may be polygenic in origin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00273739
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  • 10
    Digitale Medien
    Digitale Medien
    Comments on the uv photoelectron spectra of yttrium (1989)
    Springer
    The European physical journal 76 (1989), S. 137-138 
    Details
    ISSN: 1434-6036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Peaks in the uv photoelectron spectra from single crystal surfaces of yttrium which cannot be ascribed to the one-electron states in band structure calculations have been recently interpreted as due to hydrogen contamination. The evidence for this suggestion, however, is based on an erroneous comparison between the results of UPS experiments on polycrystalline samples exposed to hydrogen and previously published spectra from single crystal samples. In this paper we show how the spectra have been misinterpreted and comment on the consequences concerning the origin of the peaks.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01323495
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