TY - GEN
A1 - Hoppert, Michael
A1 - Reimer, Rudolph
A1 - Kemmling, Anne
A1 - Schröder, Annekatrin
A1 - Günzl, Bettina
A1 - Heinken, Thilo
T1 - Structure and reactivity of a biological soil crust from a xeric sandy soil in Central Europe
N2 - The investigation was designed to explore the structure, composition and activity of a biological soil crust on an acidic, sandy soil from a temperate climate. The crust covers several hundreds of square meters on the hilltop of a large terminal moraine. The conjugate alga Zygogonium ericetorum forms the essential matrix for the crust, a dense web of algal filaments with interspersed lichens and mosses. The crust is composed of three layers, with an uppermost layer consisting nearly entirely of a dense algal mat. In lower layers, a parasitic fungus, penetrating the algal cells, is another important component of the crust community. In this soil crust, photosynthetic and respiratory activity is stabilized at low water activities.
KW - biological soil crust
KW - desiccation tolerance
KW - electron microscopy
KW - Fusarium oxysporum
KW - Zygogonium ericetorum
Y1 - 2004
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5872
ER -
TY - GEN
A1 - Köchy, Martin
A1 - Wilson, Scott D.
T1 - Variation in nitrogen deposition and available soil nitrogen in a forest–grassland ecotone in Canada
N2 - Regional variation in nitrogen (N) deposition increases plant productivity and decreases species diversity, but landscape- or local-scale influences on N deposition are less well-known. Using ion-exchange resin, we measured variation of N deposition and soil N availability within Elk Island National Park in the ecotone between grassland and boreal forest in western Canada. The park receives regionally high amounts of atmospheric N deposition (22 kg ha⁻¹ yr⁻¹). N deposition was on average higher ton clayrich luvisols than on brunisols, and areas burned 1 – 15 years previously received more atmospheric N than unburned sites. We suggest that the effects of previous fires and soil type on deposition rate act through differences in canopy structure. The magnitude of these effects varied with the presence of ungulate grazers (bison, moose, elk) and vegetation type (forest, shrubland, grassland). Available soil N (ammonium and nitrate) was higher in burned than unburned sites in the absence of grazing, suggesting an effect of deposition. On grazed sites, differences between fire treatments were small, presumably because the removal of biomass by grazers reduced the effect of fire. Aspen invades native grassland in this region, and our results suggest that fire without grazing might reinforce the expansion of forest into grassland facilitated by N deposition.
KW - fire
KW - grazing
KW - vegetation type
KW - soil type
KW - shrubland
KW - forest invasion
KW - subboreal
KW - aspen parkland
KW - Canada
Y1 - 2004
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5768
ER -
TY - GEN
A1 - Ginoux, Nicolas
T1 - Une nouvelle estimation extrinsèque du spectre de l'opérateur de Dirac
T1 - A new extrinsic estimate for the spectrum of the Dirac operator
N2 - Nous établissons une nouvelle majoration optimale pour les plus petites valeurs propres de l'opérateur de Dirac sur une hypersurface compacte de l'espace hyperbolique.
N2 - We prove a new upper bound for the smallest eigenvalues of the Dirac operator on a compact hypersurface of the hyperbolic space.
KW - bounds
KW - Eigenvalues
Y1 - 2003
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5644
ER -
TY - GEN
A1 - Ginoux, Nicolas
T1 - Remarques sur le spectre de l'opérateur de Dirac
T1 - Remarks on the spectrum of the Dirac operator
N2 - Nous décrivons un nouvelle famille d'exemples d'hypersurfaces de la sphère satisfaisant le cas d'égalité de la majoration extrinsèque de C. Bär de la plus petite valeur propre de l'opérateur de Dirac.
N2 - We describe a new family of examples of hypersurfaces in the sphere satisfying the limitingcase in C. Bär's extrinsic upper bound for the smallest eigenvalue of the Dirac operator.
KW - 1st Eigenvalue
KW - Submanifolds
KW - Bounds
KW - Space
Y1 - 2003
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5630
ER -
TY - GEN
A1 - Ginoux, Nicolas
T1 - Dirac operators on Lagrangian submanifolds
N2 - We study a natural Dirac operator on a Lagrangian submanifold of a Kähler manifold. We first show that its square coincides with the Hodge - de Rham Laplacian provided the complex structure identifies the Spin structures of the tangent and normal bundles of the submanifold. We then give extrinsic estimates for the eigenvalues of that operator and discuss some examples.
KW - Dirac operators
KW - Global Analysis
KW - Spectral Geometry
KW - Spin Geometry
KW - Lagrangian submanifolds
Y1 - 2004
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5627
ER -
TY - GEN
A1 - Degkwitz, Andreas
A1 - Andermann, Heike
T1 - Angebots-, Nutzungs- und Bezugsstrukturen elektronischer Fachinformation in Deutschland
N2 - Mit dem Übergang zum digitalen Medium haben sich die Bezugsstrukturen und das Angebot an elektronischer Fachinformation in den Bibliotheken nachhaltig verändert. In den vorliegenden Untersuchungen wird das Angebot elektronischer Zeitschriften und Datenbanken und die Nutzung elektronischer Zeitschriften in fünf ausgewählten Fachgebieten und in unterschiedlichen Bibliothekstypen dargelegt. Darüber hinaus werden die derzeitigen Bezugsstrukturen beschrieben sowie die Ergebnisse einer Befragung der Konsortien zu Zielsetzungen, Vertragsformen und Geschäftsmodellen dargestellt. Chancen und Risiken der konsortialen Bezugsform werden erörtert.
N2 - With the transition to the digital medium the structures for purchasing digital information and the offer of scientific information in the libraries changed strongly. In the available examination the offer of electronic journals and databases and the usage of electronic journals in five selected disciplines and in different types of libraries is evaluated. Further more the current purchasing structures and the results of interviews with consortia in regard to objectives, forms of contracts and pricing models are described. Chances and risks of consortia purchasing are discussed.
KW - elektronische Zeitschriften
KW - Datenbanken
KW - Konsortien
KW - Bezugsstrukturen
KW - electronic journals
KW - databases
KW - consortia
KW - purchasing structures
Y1 - 2003
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-672
ER -