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  • 2005-2009  (1)
  • 2000-2004  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 36 (2005), S. 643-689 
    ISSN: 1543-592X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Oysters have been introduced worldwide to 73 countries, but the ecological consequences of the introductions are not fully understood. Economically, introduced oysters compose a majority of oyster harvests in many areas. Oysters are ecosystem engineers that influence many ecological processes, such as maintenance of biodiversity, population and food web dynamics, and nutrient cycling. Consequently, both their loss, through interaction of overharvest, habitat degradation, disease, poor water quality, and detrimental species interactions, and their gain, through introductions, can cause complex changes in coastal ecosystems. Introductions can greatly enhance oyster population abundance and production, as well as populations of associated native species. However, introduced oysters are also vectors for non-native species, including disease-causing organisms. Thus, substantial population, community, and habitat changes have accompanied new oysters. In contrast, ecosystem-level consequences of oyster introductions, such as impacts on flow patterns, sediment and nutrient dynamics, and native bioengineering species, are not well understood. Ecological risk assessments for future introductions must emphasize probabilities of establishment, spread, and impacts on vulnerable species, communities, and ecosystem properties. Many characteristics of oysters lead to predictions that they would be successful, high-impact members of recipient ecosystems. This conclusion leaves open the discussion of whether such impacts are desirable in terms of restoration of coastal ecosystems, especially where restoration of native oysters is possible.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Graphs and combinatorics 16 (2000), S. 231-244 
    ISSN: 1435-5914
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract.  The pebbling number of a graph G, f(G), is the least m such that, however m pebbles are placed on the vertices of G, we can move a pebble to any vertex by a sequence of moves, each move taking two pebbles off one vertex and placing one on an adjacent vertex. It is conjectured that for all graphs G and H, f(G×H)≤f(G)f(H).¶Let C m and C n be cycles. We prove that f(C m×C n)≤f(C m) f(C n) for all but a finite number of possible cases. We also prove that f(G×T)≤f(G) f(T) when G has the 2-pebbling property and T is any tree.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0533
    Keywords: Key words Ki-67 labeling index ; Magnetic resonance imaging ; Optic nerve glioma ; p53 ; Pilocytic ¶astrocytoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Gliomas of the optic nerve, although typically of pilocytic (WHO grade I) histology, can present within the spectrum of astrocytic neoplasia including glioblastoma (WHO grade IV). In certain cases, histologic features alone make the distinction between pilocytic and diffuse astrocytomas difficult. We reviewed 22 cases of optic nerve gliomas, 19 of which were pilocytic astrocytomas (PA), and 3 of which were diffuse, non-pilocytic astrocytomas. The cases were evaluated for their clinical course, radiographic appearance, histologic grade, and proliferation indices as detected by MIB-1 (Ki-67) and p53 antibodies. Of the 19 PA, 14 showed no tumor growth by magnetic resonance imaging, and had Ki-67 and p53 labeling indices (LI) of 〈 1%. The other 5 PA exhibited aggressive behavior manifest by marked diffuse infiltrative tumor growth causing death in 2 patients, 1 of whom was diagnosed with neurofibromatosis type 1 (immunoperoxidase and radiographs not available), and marked local growth with an average time to growth of 39.3 months, a Ki-67 LI of 2–3%, and a p53 LI of 〈 1% in three others. Three of the five aggressive PA histologically demonstrated a finely reticulated pattern, a pattern that appears as an exaggeration or expansion of the normal neuroglia of the optic nerve, and may simulate a diffuse low-grade astrocytoma. Two demonstrated the coarsely reticulated pattern, with the biphasic and microcystic pattern typical of PA. Three diffuse astrocytomas (2 anaplastic astrocytomas and 1 glioblastoma) originated clinically and radiographically from the optic nerve, and revealed a Ki-67 LI of 2–12%, a p53 LI of 2–8%, and an average time to growth of 8 months. We conclude that the majority of PA of the optic nerve are non-aggressive, stabilize radiographically, and have Ki-67 and p53 LI 〈 1%. However, a subpopulation of PA has a propensity for aggressive behavior, and are identified by a Ki-67 LI of 2–3% and a p53 LI of 〈 1%. Diffuse astrocytomas have both Ki-67 and p53 LI 〉 2%. Thus, in cases of aggressive optic nerve tumors in which the histologic review of biopsy material cannot confidently confirm the diagnosis of pilocytic or diffuse fibrillary glioma, a p53 LI of 〉 1% appears to favor the diagnosis of diffuse astrocytoma.
    Type of Medium: Electronic Resource
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