Cache-Oblivious VAT-Algorithms

The VAT-model (virtual address translation model) extends the EM-model (external memory model) and takes the cost of address translation in virtual memories into account. In this model, the cost of a single memory access may be logarithmic in the largest address used. We show that the VAT-cost of cache-oblivious algorithms is only by a constant factor larger than their EM-cost; this requires a somewhat more stringent tall cache assumption as for the EM-model

Synthetic macrocyclic Ionophores

14-Crown-4 derivatives bearing either one or two oxymethyl, benzyl- oxymethyl, methoxycarbonylmethyl or carbamoylmethyl substituents have been prepared in an attempt to obtain selective ionophores for lithiumions. Complexation has been monitored by IR, (^13)C NMR, Fast Atom Bombardment Mass Spectrometry, and solvent polymeric membranes have been fabricated and evaluated using the fixed interference method. Improved lithium selectivities of the disubstituted 14-crown-4 ligands compared to the monosubstituted analogues in the potentiometric experiments, bears out the premise that there is a need to suppress competitive 2:1 complex formation with sodium. The most encouraging lithium selectivity was observed with an electrode based on trans- (2S,3S)(-)-2,3-bis(N,N'- dibutylcarbamoylmethyl)-1,4,8,11- tetraoxacyclo- tetradecane which vindicates the choice of axial amide donors to enhance the Li/Na selectivity of the 14-crown-4 skeleton. Triazacyclononane, triazacyclododecane and tetraazacyclododecane amide functionalised ligands were prepared in order to investigate the effect of donor number, macrocyclic ring size and chelate ring size on stability and selectivity of complexation with alkali and alkaline earth metal cations. Complexation has been monitored by IR, i3C NMR, Fast Atom Bombardment Mass Spectrometry and pH-metric titration experiments. The most stable complex was formed between calcium and N,N'-dimethyl- 1,4,7,10-tetraacetamido-1,4,7,10-tetraazacyclododecane, for which log K(CaL) =6.81 (H(_2)0). Once again, measurable log K values ≥ 3.9 in aqueous media for lithium, sodium and calcium complexation vindicate the choice of amide donors to ensure strong coordination with small cations of high charge density ratio

Ecology of the Cerulean Warbler in the Cumberland Mountains of East Tennessee

The objective of this study was to describe the distribution, local breeding densities and population trends, breeding biology, and habitat selection of the Cerulean Warbler (Dendroica cerulea) in the Cumberland Mountains of Morgan, Campbell, Scott, and Anderson Counties, Tennessee. Point counts were conducted during three years at six study sites. The Cerulean Warbler was detected at 50% of the point counts and was the sixth most frequently encountered bird. Spot-map censuses were conducted on five plots at three study sites. Cerulean Warblers occurred on all census plots at an average density of 84.9 pairs/100 ha. Average density on individual plots ranged from 21.3 to 137.6 pairs/100 ha. Although population trends on the census plots were not uniform, there was an overall decline during the late 1990s. The breeding biology of the Cerulean Warbler was studied by observing courtship behavior and nest-building, and monitoring a total of 52 nests. Female warblers built nests, incubated eggs, and brooded nestlings. Females fed nestlings more often than males; the rate at which males and females removed fecal sacs from the nest did not differ. Mean clutch size was 3.7 ± 0.13 SE. For the years 1996-1999, nest success, measured by the Mayfield method, averaged 0.3708; the daily nest success rate averaged 0.9685 ± 0.0057 SE. The major cause of nest failure appeared to be weather events, including presumed nestling starvation during unusually cool and wet weather. Nests were built in 12 taxa of deciduous trees. Although there were some plot-specific preferences, most tree taxa were selected in proportion to their availability. Nests averaged 15.9 m ± 0.81 SE (range 7.0 - 36.3m) above ground. Nest trees averaged 23.6 m ± 0.90 SE (range 10.2 - 42.2 m) tall and 39.6 cm± 2.53 SE (range 12.3 - 76.2 cm) in diameter at breast height. Habitat characteristics were sampled at nest sites, territory sites, and random sites on census plots, and at point count locations. Basal area was consistently greater, and both shrub cover and canopy cover consistently less, at nest sites than at random sites, at territory sites than at random sites, and at nest sites than at territory sites. Point count locations where Cerulean Warblers were present had larger diameter live trees and more sapling cover than locations where the warbler was absent. Logistic regression models successfully classified over 70% of sites on census plots but were less successful in predicting Cerulean Warbler presence at point count locations

Any-k: Anytime Top-k Tree Pattern Retrieval in Labeled Graphs

Many problems in areas as diverse as recommendation systems, social network analysis, semantic search, and distributed root cause analysis can be modeled as pattern search on labeled graphs (also called "heterogeneous information networks" or HINs). Given a large graph and a query pattern with node and edge label constraints, a fundamental challenge is to nd the top-k matches ac- cording to a ranking function over edge and node weights. For users, it is di cult to select value k . We therefore propose the novel notion of an any-k ranking algorithm: for a given time budget, re- turn as many of the top-ranked results as possible. Then, given additional time, produce the next lower-ranked results quickly as well. It can be stopped anytime, but may have to continues until all results are returned. This paper focuses on acyclic patterns over arbitrary labeled graphs. We are interested in practical algorithms that effectively exploit (1) properties of heterogeneous networks, in particular selective constraints on labels, and (2) that the users often explore only a fraction of the top-ranked results. Our solution, KARPET, carefully integrates aggressive pruning that leverages the acyclic nature of the query, and incremental guided search. It enables us to prove strong non-trivial time and space guarantees, which is generally considered very hard for this type of graph search problem. Through experimental studies we show that KARPET achieves running times in the order of milliseconds for tree patterns on large networks with millions of nodes and edges.Comment: To appear in WWW 201