Entity Ranking on Graphs: Studies on Expert Finding

Todays web search engines try to offer services for finding various information in addition to simple web pages, like showing locations or answering simple fact queries. Understanding the association of named entities and documents is one of the key steps towards such semantic search tasks. This paper addresses the ranking of entities and models it in a graph-based relevance propagation framework. In particular we study the problem of expert finding as an example of an entity ranking task. Entity containment graphs are introduced that represent the relationship between text fragments on the one hand and their contained entities on the other hand. The paper shows how these graphs can be used to propagate relevance information from the pre-ranked text fragments to their entities. We use this propagation framework to model existing approaches to expert finding based on the entity's indegree and extend them by recursive relevance propagation based on a probabilistic random walk over the entity containment graphs. Experiments on the TREC expert search task compare the retrieval performance of the different graph and propagation models

PFTijah: text search in an XML database system

This paper introduces the PFTijah system, a text search system that is integrated with an XML/XQuery database management system. We present examples of its use, we explain some of the system internals, and discuss plans for future work. PFTijah is part of the open source release of MonetDB/XQuery

Expansion-limited aggregation of nanoclusters in a single-pulse laser-produced plume

Formation of carbon nanoclusters in a single-laser-pulse created ablation plume was studied both in vacuum and in a noble gas environment at various pressures. The developed theory provides cluster radius dependence on combination of laser parameters, properties of ablated material, and type and pressure of an ambient gas in agreement with experiments. The experiments were performed on carbon nanoclusters formed by laser ablation of graphite targets with 12 picosecond 532 nm laser pulses at MHz-range repetition rate in a broad range of ambient He, Ar, Kr, and Xe gas pressures from 2× 10-2 to 1500 Torr. The experimental results confirmed our theoretical prediction that the average size of the nanoparticles depends weakly on the type of the ambient gas used, and is determined exclusively by the single laser pulse parameters even at the repetition rate as high as 28 MHz with the time gap 36 ns between the pulses. The most important finding relates to the fact that in vacuum the cluster size is mainly determined by hydrodynamic expansion of the plume while in the ambient gas it is controlled by atomic diffusion in the gas. We demonstrate that the ultrashort pulses can be used for production of clusters with the size less than the critical value, which separates the particles with properties drastically different from those of a material in a bulk. The presented results of experiments on formation of carbon nanoclusters are in close agreement with the theoretical scaling. The developed theory is applicable for cluster formation from any monatomic material, such as silicon for example

Sound ranking algorithms for XML search

Ranking algorithms for XML should reflect the actual combined content and structure constraints of queries, while at the same time producing equal rankings for queries that are semantically equal. Ranking algorithms that produce different rankings for queries that are semantically equal are easily detected by tests on large databases: We call such algorithms not sound. We report the behavior of different approaches to ranking content-and-structure queries on pairs of queries for which we expect equal ranking results from the query semantics. We show that most of these approaches are not sound. Of the remaining approaches, only 3 adhere to the W3C XQuery Full-Text standard

Polar Bear Distribution and Habitat Association Reflect Long-term Changes in Fall Sea Ice Conditions in the Alaskan Beaufort Sea

The polar bear (Ursus maritimus) is considered an indicator species of ecosystem health because of its longevity, life-history requirements, reliance on sea ice (i.e., sea ice obligate), and position in the Arctic food web. Polar bear distribution and habitat association should both be reliable signals for environmental perturbation, as the bears respond behaviorally to changes in sea ice extent, the timing and duration of ice formation, and ablation. Polar bears and sea ice conditions were monitored as part of the annual fall bowhead whale (Balaena mysticetus) aerial survey in the Alaskan Beaufort Sea between 1979 and 2005. Habitats associated with polar bear sightings changed during the study, with fewer bears associated with ice (irrespective of ice type and percent) and more bears associated with land and open water. Large-scale differences were documented for both ice type and percent ice cover, particularly in September. In general, the pattern in September (and to a lesser extent in October) included a reduction in old ice and a concomitant increase in open water. In addition, there was an eastward and landward shift in polar bear sightings. From 1979 to 1987, polar bears were observed primarily on ice along the shelf break near Barrow, whereas from 1997 to 2005, polar bears were observed on barrier islands or along the mainland coast near Kaktovik. The changes in polar bear distribution and habitat association appear to reflect a behavioral response by polar bears to changes in ice (type and percent cover) and in the timing of ice formation and ablation.L’ours polaire (Ursus maritimus) est considéré comme une espèce indicatrice de la santé de l’écosystème en raison de sa longévité, des besoins de son cycle biologique, de sa dépendance de la glace de mer (c’est-à-dire la glace de mer obligatoire) et de la position qu’il occupe dans le réseau alimentaire de l’Arctique. La répartition de l’ours polaire et son association à un habitat devraient tous deux constituer des signaux fiables en matière de perturbation de l’environnement car le comportement des ours varie en fonction des changements caractérisant l’étendue de glace de mer, la synchronisation et la durée de la formation de la glace, de même que l’ablation. Les ours polaires et les conditions de la glace de mer ont fait l’objet d’une surveillance dans le cadre du levé aérien annuel de la baleine boréale (Balaena mysticetus) effectué à l’automne dans la mer de Beaufort alaskienne entre 1979 et 2005. Au cours de l’étude, les habitats liés aux observations d’ours polaires ont évolué, un moins grand nombre d’ours étant associés à la glace (sans égard au type et au pourcentage de glace) et un plus grand nombre d’ours étant associés à la terre et à l’eau libre. Les différences à grande échelle ont été répertoriées tant pour le type de glace que pour le pourcentage de couche de glace, particulièrement en septembre. En général, la tendance en septembre (et en octobre, dans une moindre mesure) comprenait une réduction de l’ancienne glace de même qu’une augmentation concomitante dans l’eau libre. De plus, on a enregistré un décalage vers l’est et vers l’intérieur des terres en ce qui a trait aux observations d’ours polaires. De 1979 à 1987, les ours polaires ont surtout été observés sur la glace le long du rebord continental près de Barrow, tandis que de 1997 à 2005, les ours polaires ont été observés sur les îles-barrières ou le long de la côte continentale près de Kaktovik. Les changements caractérisant la répartition des ours polaires et l’association à un habitat semblent refléter une réaction comportementale des ours polaires vis-à-vis des changements relatifs à la glace (le type et le pourcentage de la couche) ainsi que de la synchronisation de la formation et de l’ablation de la glace

The Introduction of a Protocol for the Use of Biobrane for Facial Burns in Children

Biobrane has become an indispensible dressing with three established indications in acute burns care at our institution: (1) as the definitive dressing of superficial partial thickness facial burns, (2) after tangential excision of deep burns when autograft or cadaver skin is unavailable, and (3) for graft reduction. This paper details our initial experience of Biobrane for the management of superficial partial thickness facial burns in children and the protocol that was compiled for its optimal use. A retrospective analysis of theatre records, case notes and photographs was performed to evaluate our experience with Biobrane over a one-year period. Endpoints included length of stay, analgesic requirements, time to application of Biobrane, healing times, and aesthetic results. Historical controls were used to compare the results with our previous standard of care. 87 patients with superficial partial thickness burns of the face had Biobrane applied during this period. By adhering to the protocol we were able to demonstrate significant reductions in hospital stay, healing time, analgesic requirements, nursing care, with excellent cosmetic results. The protocol is widely accepted by all involved in the optimal management of these patients, including parents, anaesthetists, and nursing staff

Unconventional magnetism in all-carbon nanofoam

We report production of nanostructured carbon foam by a high-repetition-rate, high-power laser ablation of glassy carbon in Ar atmosphere. A combination of characterization techniques revealed that the system contains both sp2 and sp3 bonded carbon atoms. The material is a novel form of carbon in which graphite-like sheets fill space at very low density due to strong hyperbolic curvature, as proposed for ?schwarzite?. The foam exhibits ferromagnetic-like behaviour up to 90 K, with a narrow hysteresis curve and a high saturation magnetization. Such magnetic properties are very unusual for a carbon allotrope. Detailed analysis excludes impurities as the origin of the magnetic signal. We postulate that localized unpaired spins occur because of topological and bonding defects associated with the sheet curvature, and that these spins are stabilized due to the steric protection offered by the convoluted sheets.Comment: 14 pages, including 2 tables and 7 figs. Submitted to Phys Rev B 10 September 200