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  • 61.70  (1)
  • 72.20  (1)
  • Key Words: Variscan basement, 3-D wide-angle data, DEKORP, deep seismic sounding, crustal structure, prestack-migration.  (1)
  • Key words Evergreen  (1)
  • Springer  (3)
  • 1995-1999  (3)
  • 1975-1979
Collection
Keywords
Publisher
  • Springer  (3)
Years
  • 1995-1999  (3)
  • 1975-1979
Year
  • 1
    ISSN: 1432-1939
    Keywords: Key words Evergreen ; Light and temperature response ; Physiology ; Summergreen ; Understory herbs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal differences in photosynthesis and stomatal conductance of four herbaceous perennials from beneath a deciduous canopy was assessed at two light levels (60 and 400 μmol m−2 s−1 photosynthetic photon flux density, PPFD) and two leaf temperatures (7 and 20°C). Leaves of an evergreen, Pyrola asarifolia Michx., a wintergreen, Cornus canadensis L., and two summergreen species, Rubus pubescens Raf. and Aralia nudicaulis L., were collected at four times during the growing season. In addition, midsummer light response curves were obtained for one summergreen (A. nudicaulis) and one evergreen species (P. asarifolia) at both 7 and 20°C. Gas exchange measurements were made in the laboratory under controlled environmental conditions. For leaves collected in April, when insolation was high due to the leafless overstory, only P. asarifolia had green leaves, and there was no effect of temperature or light on this species' photosynthesis. P. asarifolia's net assimilation rate (NA) in April was about 30% of it's maximum in late summer. In early summer (June), A. nudicaulis and R. pubescens had higher NA at the higher temperature; at this time, these summergreen species also reached their maximum NA. Midsummer photosynthetic light response curves showed that the light-saturation point was higher and more responsive to leaf temperature in the summergreen A. nudicaulis than in the evergreen P. asarifolia. The summergreen species appear to have a photosystem which performs at high rates during early- and mid-summer, as well as a taller stature which allows them to intercept more light. The photosynthetic system of the ever/wintergreen species is adapted to the low ground-level light conditions in the summer and there does not appear to be an adjustment to take further advantage of the higher light in the spring and fall period. The adaptation of the evergreen and wintergreen understory species is tolerance to low temperatures, enabling them to photosynthesize into the fall till the first continuous frosts occur in the understory and also permitting the evergreen species to begin photosynthesis early in the spring.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1420-9136
    Keywords: Key Words: Variscan basement, 3-D wide-angle data, DEKORP, deep seismic sounding, crustal structure, prestack-migration.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —In addition to the near normal-incidence observations within the German DEKORP 2 project in 1984, wide-angle observations have been carried out on a parallel profile across the boundary between the Saxothuringian and Moldanubian crust, approximately 50 km NE of the main transect to control three-dimensional variations. Explosion sources have been used for the entire survey, providing excellent conditions for wide-angle registrations. A velocity model has been derived on the basis of in- and off-line refraction measurements using a kinematic raytracer which was extended to three dimensions by interpolation of 2-D velocity fields between parallel sections. Although prestack-migration of the data led to aliasing effects due to large shot and geophone spacing, stable results were obtained by forming envelopes after single-shot migration. The migrated sections reveal a strongly reflective Moho at about 31 km depth and a steeply (50°) dipping intracrustal reflector, which seems to be related to the border between the two Variscan units.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 61 (1995), S. 89-93 
    ISSN: 1432-0649
    Keywords: 61.70 ; 72.20 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In LiNbO3:Fe,Me crystals (Me = K, Mg, Zn) elementary holograms are recorded and erased with frequency-doubled, ordinarily polarized pulses of a Q-switched Nd:YAG laser. At high light intensities (I 〉 109 Wm−2) holographic sensitivities and saturation values of refractive index changes grow with increasing intensity and a contribution to photo-conductivity appears increasing quadratically withI. The intensity-dependent parts of the holographic quantities are diminished by increasing the lithium content of the samples or by doping the crystals with magnesium or zinc. Experimental results can be described by a two-center charge transport model, which is the Fe2+/3+ model supplemented by shallow traps, namely niobium ions occupying lithium sites.
    Type of Medium: Electronic Resource
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