Comparison of three vertical search spiders

The Web's dynamic,.unstructured nature makes locating resources difficult. Vertical search engines solve part of the problem by keeping indexes only in specific domains. They also offer more opportunity to apply domain knowledge in the spider applications that collect content for their databases. The authors used three approaches to investigate algorithms for improving the performance of vertical search engine spiders: a breadth-first graph-traversal algorithm with no heuristics to refine the search process, a best-first traversal algorithm that uses a hyperlink-analysis heuristic, and a spreading-activation algorithm based on modeling the Web as a neural network.published_or_final_versio

SPIDERS: Selection of spectroscopic targets using AGN candidates detected in all-sky X-ray surveys

SPIDERS (SPectroscopic IDentification of eROSITA Sources) is an SDSS-IV survey running in parallel to the eBOSS cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected AGN and galaxy cluster members detected in wide area eROSITA, XMM-Newton and ROSAT surveys. We describe the methods used to choose spectroscopic targets for two sub-programmes of SPIDERS: X-ray selected AGN candidates detected in the ROSAT All Sky and the XMM-Newton Slew surveys. We have exploited a Bayesian cross-matching algorithm, guided by priors based on mid-IR colour-magnitude information from the WISE survey, to select the most probable optical counterpart to each X-ray detection. We empirically demonstrate the high fidelity of our counterpart selection method using a reference sample of bright well-localised X-ray sources collated from XMM-Newton, Chandra and Swift-XRT serendipitous catalogues, and also by examining blank-sky locations. We describe the down-selection steps which resulted in the final set of SPIDERS-AGN targets put forward for spectroscopy within the eBOSS/TDSS/SPIDERS survey, and present catalogues of these targets. We also present catalogues of ~12000 ROSAT and ~1500 XMM-Newton Slew survey sources which have existing optical spectroscopy from SDSS-DR12, including the results of our visual inspections. On completion of the SPIDERS program, we expect to have collected homogeneous spectroscopic redshift information over a footprint of ~7500 deg$^2$ for >85 percent of the ROSAT and XMM-Newton Slew survey sources having optical counterparts in the magnitude range 17<r<22.5, producing a large and highly complete sample of bright X-ray-selected AGN suitable for statistical studies of AGN evolution and clustering.Comment: MNRAS, accepte

Studies in Liocranidae (Araneae): a new afrotropical genus featuring a synapomorphy for the Cybaeodinae

Cteniogaster, a new genus of small ground spiders is described from Kenya and Tanzania. It encompasses seven new species, three of which are known from both sexes: C. toxarchus sp. nov., the type species, C. conviva sp. nov. and C. hexomma sp. nov. Three species are known from females only: C. lampropus sp. nov., C. sangarawe sp. nov. and C. taxorchis sp. nov. and one only from males: C. nana sp. nov. The new genus can be recognised by the presence of a posterior ventral abdominal f eld of strong setae and anterior lateral spinnerets with enlarged piriform gland spigots in males. A cladistic analysis attributes the genus to Liocranidae, Cybaeodinae. The results of the analysis performed do not produce an unequivocal autapomorphy for Liocranidae, but provide a combination of non-homoplasious character changes that offers significant potential for recognising genera as Liocranidae. Moreover, robust apomorphies are determined within Liocranidae for the subfamilies Liocraninae and Cybaeodinae. Based on these fi ndings Toxoniella Warui & Jocqué, 2002 is transferred from Gallieniellidae to Liocranidae, Cybaeodinae. Jacaena Thorell, 1897, Plynnon Deeleman-Reinhold, 2001 and Teutamus Thorell, 1890 are transferred to Corinnidae, Phrurolithinae and Montebello Hogg, 1914 to Gnaphosidae. Itatsina Kishida, 1930 is synonymised with Prochora Simon, 1886

Vertical stratification of selected Hymenoptera in a remnant forest of the Po Plain (Italy, Lombardy) (Hymenoptera: Ampulicidae, Crabronidae, Sphecidae)

Communities of the canopy of temperate forests are still relatively unexplored. Furthermore, very little is known on how vertical stratification for some insect groups is related to biological strategies. In this study, we investigated the community composition of both canopy and understory of the families Ampulicidae, Crabronidae and Sphecidae (Hymenoptera) of the Natural Reserve of "Bosco della Fontana", a remnant lowland forest in northeastern Italy. Observed patterns in vertical stratification have been related to species foraging habits. Our study reveals that the bulk of the community of Spheciformes of the understory consists of species predating dipterans and spiders, while species associated with the canopy are mainly predators of sap-sucking honeydew producers and epiphyte grazers, like aphids, thrips, and barkflies. Comparing the communities of canopy and understory may lead to a better understanding of species ecology and provides useful information to forest managers

Do functional traits improve prediction of predation rates for a disparate group of aphid predators?

Aphid predators are a systematically disparate group of arthropods united on the basis that they consume aphids as part of their diet. In Europe, this group includes Araneae, Opiliones, Heteroptera, chrysopids, Forficulina, syrphid larvae, carabids, staphylinids, cantharids and coccinellids. This functional group has no phylogenetic meaning but was created by ecologists as a way of understanding predation, particularly for conservation biological control. We investigated whether trait-based approaches could bring some cohesion and structure to this predator group. A taxonomic hierarchy-based null model was created from taxonomic distances in which a simple multiplicative relationship described the Linnaean hierarchies (species, genera, etc.) of fifty common aphid predators. Using the same fifty species, a functional groups model was developed using ten behavioural traits (e.g. polyphagy, dispersal, activity, etc.) to describe the way in which aphids were predated in the field. The interrelationships between species were then expressed as dissimilarities within each model and separately analysed using PROXSCAL, a multidimensional scaling (MDS) program. When ordinated using PROXSCAL and then statistically compared using Procrustes analysis, we found that only 17% of information was shared between the two configurations. Polyphagy across kingdoms (i.e. predatory behaviour across animal, plant and fungi kingdoms) and the ability to withstand starvation over days, weeks and months were particularly divisive within the functional groups model. Confirmatory MDS indicated poor prediction of aphid predation rates by the configurations derived from either model. The counterintuitive conclusion was that the inclusion of functional traits, pertinent to the way in which predators fed on aphids, did not lead to a large improvement in the prediction of predation rate when compared to the standard taxonomic approach

Ground-Based Coronagraphy with High Order Adaptive Optics

We summarize the theory of coronagraphic optics, and identify a dimensionless fine-tuning parameter, F, which we use to describe the Lyot stop size in the natural units of the coronagraphic optical train and the observing wavelength. We then present simulations of coronagraphs matched to adaptive optics (AO) systems on the Calypso 1.2m, Palomar Hale 5m and Gemini 8m telescopes under various atmospheric conditions, and identify useful parameter ranges for AO coronagraphy on these telescopes. Our simulations employ a tapered, high-pass filter in spatial frequency space to mimic the action of adaptive wavefront correction. We test the validity of this representation of AO correction by comparing our simulations with recent K-band data from the 241-channel Palomar Hale AO system and its dedicated PHARO science camera in coronagraphic mode.Comment: To appear in ApJ, May 2001 (28 pages, 10 figs

Apodized pupil Lyot coronagraphs for arbitrary apertures. V. Hybrid Shaped Pupil designs for imaging Earth-like planets with future space observatories

We introduce a new class of solutions for Apodized Pupil Lyot Coronagraphs (APLC) with segmented aperture telescopes to remove broadband diffracted light from a star with a contrast level of $10^{10}$. These new coronagraphs provide a key advance to enabling direct imaging and spectroscopy of Earth twins with future large space missions. Building on shaped pupil (SP) apodization optimizations, our approach enables two-dimensional optimizations of the system to address any aperture features such as central obstruction, support structures or segment gaps. We illustrate the technique with a design that could reach $10^{10}$ contrast level at 34\,mas for a 12\,m segmented telescope over a 10\% bandpass centered at a wavelength $\lambda_0=$500\,nm. These designs can be optimized specifically for the presence of a resolved star, and in our example, for stellar angular size up to 1.1\,mas. This would allow probing the vicinity of Sun-like stars located beyond 4.4\,pc, therefore fully retiring this concern. If the fraction of stars with Earth-like planets is \eta_{\Earth}=0.1, with 18\% throughput, assuming a perfect, stable wavefront and considering photon noise only, 12.5 exo-Earth candidates could be detected around nearby stars with this design and a 12\,m space telescope during a five-year mission with two years dedicated to exo-Earth detection (one total year of exposure time and another year of overheads). Our new hybrid APLC/SP solutions represent the first numerical solution of a coronagraph based on existing mask technologies and compatible with segmented apertures, and that can provide contrast compatible with detecting and studying Earth-like planets around nearby stars. They represent an important step forward towards enabling these science goals with future large space missions.Comment: 9 pages, 6 figures, ApJ accepted on 01/04/201