On the Cost of Negation for Dynamic Pruning

Negated query terms allow documents containing such terms to be filtered out of a search results list, supporting disambiguation. In this work, the effect of negation on the efficiency of disjunctive, top-k retrieval is examined. First, we show how negation can be integrated efficiently into two popular dynamic pruning algorithms. Then, we explore the efficiency of our approach, and show that while often efficient, negation can negatively impact the dynamic pruning effectiveness for certain queries

A comparison of evaluation measures given how users perform on search tasks

Information retrieval has a strong foundation of empirical investigation: based on the position of relevant resources in a ranked answer list, a variety of system performance metrics can be calculated. One of the most widely reported measures, mean average precision (MAP), provides a single numerical value that aims to capture the overall performance of a retrieval system. However, recent work has suggested that broad measures such as MAP do not relate to actual user performance on a number of search tasks. In this paper, we investigate the relationship between various retrieval metrics, and consider how these reflect user search performance. Our results suggest that there are two distinct categories of measures: those that focus on high precision in an answer list, and those that attempt to capture a broader summary, for example by including a recall component. Analysis of runs submitted to the TREC terabyte track in 2006 suggests that the relative performance of systems can differ significantly depending on which group of measures is being used

MeV magnetosheath ions energized at the bow shock

A causal relationship between midlatitude magnetosheath energetic ions and bow shock magnetic geometry was previously established for ion energy up to 200 keV e−1 for the May 4, 1998, storm event. This study demonstrates that magnetosheath ions with energies above 200 keV up to 1 MeV simply extend the ion spectrum to form a power law tail. Results of cross-correlation analysis suggest that these ions also come directly from the quasi-parallel bow shock, not the magnetosphere. This is confirmed by a comparison of energetic ion fluxes simultaneously measured in the magnetosheath and at the quasi-parallel bow shock when both regions are likely connected by the magnetic field lines. We suggest that ions are accelerated at the quasi-parallel bow shock to energies as high as 1 MeV and subsequently transported into the magnetosheath during this event

Bayesian Markov-chain-Monte-Carlo inversion of time-lapse cross hole ground-penetrating radar data to characterize the vadose zone at the Arrenaes field site, Denmark

The ground-penetrating radar (GPR) geophysical method has the potential to provide valuable information on the hydraulic properties of the vadose zone because of its strong sensitivity to soil water content. In particular, recent evidence has suggested that the stochastic inversion of crosshole GPR traveltime data can allow for a significant reduction in uncertainty regarding subsurface van Genuchten-Mualem (VGM) parameters. Much of the previous work on the stochastic estimation of VGM parameters from crosshole GPR data has considered the case of steady-state infiltration conditions, which represent only a small fraction of practically relevant scenarios. We explored in detail the dynamic infiltration case, specifically examining to what extent time-lapse crosshole GPR traveltimes, measured during a forced infiltration experiment at the Arreneas field site in Denmark, could help to quantify VGM parameters and their uncertainties in a layered medium, as well as the corresponding soil hydraulic properties. We used a Bayesian Markov-chain-Monte-Carlo inversion approach. We first explored the advantages and limitations of this approach with regard to a realistic synthetic example before applying it to field measurements. In our analysis, we also considered different degrees of prior information. Our findings indicate that the stochastic inversion of the time-lapse GPR data does indeed allow for a substantial refinement in the inferred posterior VGM parameter distributions compared with the corresponding priors, which in turn significantly improves knowledge of soil hydraulic properties. Overall, the results obtained clearly demonstrate the value of the information contained in time-lapse GPR data for characterizing vadose zone dynamics

MOLT PATTERNS AND SEXING AND AGING CRITERIA FOR TEN SPECIES OF HIGH ELEVATION LANDBIRDS FROM SOUTHEASTERN PERU

Abstract ∙ Knowledge of molt patterns and their resulting plumages is useful for aging and sexing birds and, in mono‐ chromatic species, morphometric measurements can help to discern males from females. However, these data are largely undescribed for the majority of the world’s bird species, especially in the tropics. We sought to classify the molt strategy for 10 species of Neotropical passerines during their breeding seasons and considered whether a combination of wing chord, tail length and mass could be used to determine their sex. We used banding data from three years of mark‐recapture study at Wayqecha Biological Station (2900 m a.s.l.) along the east slope of the Andes in southeastern Peru to characterize molt and estimate morphological measurements. Each of the species exhibited a complete definitive prebasic molt and either a partial (nine species) or partial‐incomplete (one species) preformative molt, which we interpreted to be consistent with a complex basic molt strategy. For five of the 10 species, we found that wing, tail, and body mass measurements were useful in distinguishing between males and females. This study contributes to our understanding of tropical bird molt by providing previously undescribed aging and sexing criteria for some tropical landbirds common to high elevations of southern Peru.Resumen ∙ Patrones de muda y criterios para categorizar sexo y edad en diez especies de aves altoandinas en el sureste de Perú Los patrones de muda en la mayoría de las aves Neotropicales son poco conocidos y en especial se desconoce si las medidas corporales pueden ser usadas para determinar el sexo en especies sin dimorfismo sexual. En este trabajo clasificamos la estrategia de muda para 10 especies de paserinos Neotropicales y también exploramos si una combi‐ nación de medidas de longitud del ala, longitud de la cola y masa corporal pueden ser usadas para la determinación del sexo. Usamos datos de anillamiento de tres años de un estudio de recaptura en la Estación Biológica Wayqecha (2900 m s.n.m.) en el flanco oriental de los Andes al sureste de Perú. Cada especie exhibió una estrategia básica compleja de muda con una muda prebásica definitiva compleja, y una muda preformativa parcial (nueve especies) o parcial‐incompleta (uno especie). Para cinco de cada 10 especies, la combinación de medidas de la longitud del ala, la cola, y la masa corporal sirvieron para distinguir entre machos y hembras. Este estudio contribuye a la creciente literatura sobre los patrones de muda en aves tropicales y provee herramientas para clasificar la edad y el sexo de aves con plumaje sexualmente monocromático

When threat matters: Self-regulation, threat salience, and stereotyping

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.jesp.2015.03.003 © 2015. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Four experiments examined whether information implying imminent threat to safety would interact with regulatory focus (Higgins, 1997) to affect the utilization of threat-relevant stereotypes. Because information suggesting imminent danger is more relevant to the safety goals of prevention-focused individuals than the advancement goals of promotion-focused individuals, utilization of threat-relevant stereotypes was expected to increase under such conditions only under prevention focus. Support for this prediction was obtained in four distinct and socially important domains. Using scenarios describing a violent crime committed by an African-American male (Experiment 1) or a petty crime committed by an undocumented immigrant (Experiment 2), prevention-focused individuals made judgments consistent with stereotypes when threat was perceived to be high rather than low. In studies that manipulated the stereotypicality of the target in a terrorism scenario (Experiments 3 & 4), prevention-focused individuals were more likely to endorse scrutinizing a stereotypical compared with a non-stereotypical target when terrorism was described as an increasing problem. Implications for models of stereotyping, self-regulation, and responding to threat are discussed.NSF Grant [1147779

Estimation of the correlation structure of crustal velocity heterogeneity from seismic reflection data

Numerous sources of evidence point to the fact that heterogeneity within the Earth's deep crystalline crust is complex and hence may be best described through stochastic rather than deterministic approaches. As seismic reflection imaging arguably offers the best means of sampling deep crustal rocks in situ, much interest has been expressed in using such data to characterize the stochastic nature of crustal heterogeneity. Previous work on this problem has shown that the spatial statistics of seismic reflection data are indeed related to those of the underlying heterogeneous seismic velocity distribution. As of yet, however, the nature of this relationship has remained elusive due to the fact that most of the work was either strictly empirical or based on incorrect methodological approaches. Here, we introduce a conceptual model, based on the assumption of weak scattering, that allows us to quantitatively link the second-order statistics of a 2-D seismic velocity distribution with those of the corresponding processed and depth-migrated seismic reflection image. We then perform a sensitivity study in order to investigate what information regarding the stochastic model parameters describing crustal velocity heterogeneity might potentially be recovered from the statistics of a seismic reflection image using this model. Finally, we present a Monte Carlo inversion strategy to estimate these parameters and we show examples of its application at two different source frequencies and using two different sets of prior information. Our results indicate that the inverse problem is inherently non-unique and that many different combinations of the vertical and lateral correlation lengths describing the velocity heterogeneity can yield seismic images with the same 2-D autocorrelation structure. The ratio of all of these possible combinations of vertical and lateral correlation lengths, however, remains roughly constant which indicates that, without additional prior information, the aspect ratio is the only parameter describing the stochastic seismic velocity structure that can be reliably recovered