ALBERT

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  • clustering  (2)
  • Al3+  (1)
  • Springer  (3)
  • National Academy of Sciences
  • Oxford University Press
  • 2005-2009
  • 1990-1994  (3)
  • 1930-1934
  • 1990  (3)
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Publisher
  • Springer  (3)
  • National Academy of Sciences
  • Oxford University Press
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  • 2005-2009
  • 1990-1994  (3)
  • 1930-1934
Year
  • 1990  (3)
  • 1
    ISSN: 1572-9125
    Keywords: D.4.3 ; E.2 ; H.3.2 ; partial-match retrieval ; multi-attribute hashing ; multi-key hashing ; clustering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The average cost for answering partial-match queries can be dramatically reduced by storing multiple copies of the data, each with a different clustering. We analyse the cost benefits (in terms of page accesses) of this arrangement and present heuristic algorithms for determining a near-minimal-cost file organisation for a given probability distribution of queries. We also show how constraining the range of values for specific attributes affects the usefulness of maintaining multiple copies.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1420-9136
    Keywords: Earthquake precursors ; clustering ; quiescence ; earthquake statistics ; seismicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This paper describes a new method, single-link cluster analysis (SLC), to evaluate percursory quiescence for shallow earthquakes in sixteen subduction zones, using data from the ISC catalog. To define quiescent regions, we divided the catalog into time intervals with a durationT, overlapping byT/2. We considered all earthquakes having magnitudes larger than some magnitudeM min, lying within a specified distance of a great circle which is approximately coincident with the trench near a subduction zone. Within each time interval we connected or ‘linked’ all earthquakes lying within some cutoff distanced of one another. We then projected all these links onto the great circle, and defined a region to be quiescent if it was not covered by the projection of any links. For this study,T was two years,M min wasm b =4.9, and we variedd from 100 to 400 km. We defined an earthquake as ‘following quiescence’ if it occurred within two years following, and within 75 km of a quiescent zone as defined above. The primary conclusion of this study was that earthquakes with surface wave magnitudes 7.2 and greater were about 5–15% more likely to follow quiescence than were the smaller background earthquakes withm b 〉-4.9. A chi-squared analysis shows that this result is significant at the 99% level. In contrast, earthquakes with surface wave magnitude of 6.7 to 7.1 were no more likely to follow quiescence than were background earthquakes. Of sixteen individual regions, Central America, Japan, and Peru-Chile were the only regions where large earthquakes were more likely to occur following quiescence than were background earthquakes. For a cutoff link length of 300 km, only in Central America was the difference between large earthquakes and background earthquakes significant at the 95% level of significance. For a cutoff link length of 250 km, the significance level exceeded 95% only in Japan. The SLC method is an objective, quantitative method for evaluating large data catalogs, or for monitoring quiescence in regions where quiescence is conjectured to precede large earthquakes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 126 (1990), S. 237-246 
    ISSN: 1573-5036
    Keywords: Al3+ ; Ca2+ ; Mg2+ ; NH4 + ; NO3 − ; SO4 2− ; Al toxicity ; forest dieback ; Fagus sylvatica ; Nothofagus ; pH ; Picea abies ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Concentrations of ions were measured in soil solutions from beech (Nothofagus) forests in remote areas of New Zealand and in solutions from beech (Fagus sylvatica) and Norway spruce (Picea abies) forests in North-East Bavaria, West Germany, to compare the chemistry of soil solutions which are unaffected by acid deposition (New Zealand) with those that are affected (West Germany). In New Zealand, soil solution SO4 2− concentrations ranged between 〈2 and 58 μmol L−1, and NO3 − concentrations ranged between 〈1 and 3 μmol L−1. In West Germany, SO4 2− concentrations ranged between 80 and 700 μmol L−1, and NO3 − concentrations at three of six sites ranged between 39 and 3750 μmol L−1, but was not detected at the remaining three sites. At all sites in New Zealand, and at sites where the soil base status was moderately high in West Germany, pH levels increased, and total Al (Alt) and inorganic monomeric Al (Ali) levels decreased rapidly with increasing soil depth. In contrast, at sites on soils of low base status in West Germany, pH levels increased only slightly, and Al levels did not decline with increasing soil depth. Under a high-elevation Norway spruce stand showing severe Mg deficiency and dieback symptoms in West Germany, soil solution Mg2+ levels ranged between 20 and 60 μmol L−, and were only half those under a healthy stand. Alt and Ali levels were substantially higher the healthy stand than under the unhealthy stand, indicating that Al toxicity was not the main cause of spruce decline.
    Type of Medium: Electronic Resource
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