3,214 research outputs found
Hybrid Search: Effectively Combining Keywords and Semantic Searches
This paper describes hybrid search, a search method supporting both document and knowledge retrieval via the flexible combination of ontologybased search and keyword-based matching. Hybrid search smoothly copes with
lack of semantic coverage of document content, which is one of the main limitations of current semantic search methods. In this paper we define hybrid search formally, discuss its compatibility with the current semantic trends and present a reference implementation: K-Search. We then show how the method outperforms both keyword-based search and pure semantic search in terms of precision and recall in a set of experiments performed on a collection of about 18.000 technical documents. Experiments carried out with professional users show that users understand the paradigm and consider it very powerful and reliable. K-Search has been ported to two applications released at Rolls-Royce
plc for searching technical documentation about jet engines
Les remaniements de sols pendant le Quaternaire supérieur au Congo : évolution des paysages dans la région de la Sangha
The ionization mechanism of NGC 185: how to fake a Seyfert galaxy?
NGC 185 is a dwarf spheroidal satellite of the Andromeda galaxy. From
mid-1990s onwards it was revealed that dwarf spheroidals often display a varied
and in some cases complex star formation history. In an optical survey of
bright nearby galaxies, NGC 185 was classified as a Seyfert galaxy based on its
emission line ratios. However, although the emission lines in this object
formally place it in the category of Seyferts, it is probable that this galaxy
does not contain a genuine active nucleus. NGC 185 was not detected in radio
surveys either in 6 or 20 cm, or X-ray observations, which means that the
Seyfert-like line ratios may be produced by stellar processes. In this work, we
try to identify the possible ionization mechanisms for this galaxy. We
discussed the possibility of the line emissions being produced by planetary
nebulae (PNe), using deep spectroscopy observations obtained with GMOS-N, at
Gemini. Although the fluxes of the PNe are high enough to explain the
integrated spectrum, the line ratios are very far from the values for the
Seyfert classification. We then proposed that a mixture of supernova remnants
and PNe could be the source of the ionization, and we show that a composition
of these two objects do mimic Seyfert-like line ratios. We used chemical
evolution models to predict the supernova rates and to support the idea that
these supernova remnants should be present in the galaxy.Comment: 9 pages, 7 figures, accepted for publication in MNRA
The Future of Stellar Populations Studies in the Milky Way and the Local Group
The last decade has seen enormous progress in understanding the structure of
the Milky Way and neighboring galaxies via the production of large-scale
digital surveys of the sky like 2MASS and SDSS, as well as specialized,
counterpart imaging surveys of other Local Group systems. Apart from providing
snaphots of galaxy structure, these "cartographic" surveys lend insights into
the formation and evolution of galaxies when supplemented with additional data
(e.g., spectroscopy, astrometry) and when referenced to theoretical models and
simulations of galaxy evolution. These increasingly sophisticated simulations
are making ever more specific predictions about the detailed chemistry and
dynamics of stellar populations in galaxies. To fully exploit, test and
constrain these theoretical ventures demands similar commitments of
observational effort as has been plied into the previous imaging surveys to
fill out other dimensions of parameter space with statistically significant
intensity. Fortunately the future of large-scale stellar population studies is
bright with a number of grand projects on the horizon that collectively will
contribute a breathtaking volume of information on individual stars in Local
Group galaxies.Comment: 12 pages, 0 figures, IAU Symposium No. 262, Stellar Populations -
Planning for the Next Decad
A wide angle view of the Sagittarius dwarf Spheroidal Galaxy. I: VIMOS photometry and radial velocities across Sgr dSph major and minor axis
The Sagittarius dwarf Spheroidal Galaxy (Sgr dSph) provides us with a unique
possibility of studying a dwarf galaxy merging event while still in progress.
Due to its low distance (25 kpc), the main body of Sgr dSph covers a vast area
in the sky (roughly 15 x 7 degrees). Available photometric and spectroscopic
studies have concentrated either on the central part of the galaxy or on the
stellar stream, but the overwhelming majority of the galaxy body has never been
probed. The aim of the present study is twofold. On the one hand, to produce
color magnitude diagrams across the extension of Sgr dSph to study its stellar
populations, searching for age and/or composition gradients (or lack thereof).
On the other hand, to derive spectroscopic low-resolution radial velocities for
a subsample of stars to determine membership to Sgr dSph for the purpose of
high resolution spectroscopic follow-up. We used VIMOS-VLT to produce V and I
photometry and spectroscopy on 7 fields across the Sgr dSph minor and major
axis, plus 3 more centered on the associated globular clusters Terzan 7, Terzan
8 and Arp 2. A last field has been centered on M 54, lying in the center of Sgr
dSph. We present photometry for 320,000 stars across the main body of Sgr dSph,
one of the richest, and safely the most wide-angle sampling ever produced for
this fundamental object. We also provide robust memberships for more than one
hundred stars, whose high resolution spectroscopic analysis will be the object
of forthcoming papers. Sgr dSph appears remarkably uniform among the observed
fields. We confirm the presence of a main Sgr dSph population characterized
roughly by the same metallicity of 47 Tuc, but we also found the presence of
multiple populations on the peripheral fields of the galaxy, with a metallicity
spanning from [Fe/H]=-2.3 to a nearly solar value.Comment: 10 pages, 12 figures, accepted for publication in A&
Glutathione reductase-catalyzed cascade of redox reactions to bioactivate potent antimalarial 1,4-naphthoquinones--a new strategy to combat malarial parasites.
Our work on targeting redox equilibria of malarial parasites propagating in red blood cells has led to the selection of six 1,4-naphthoquinones, which are active at nanomolar concentrations against the human pathogen Plasmodium falciparum in culture and against Plasmodium berghei in infected mice. With respect to safety, the compounds do not trigger hemolysis or other signs of toxicity in mice. Concerning the antimalarial mode of action, we propose that the lead benzyl naphthoquinones are initially oxidized at the benzylic chain to benzoyl naphthoquinones in a heme-catalyzed reaction within the digestive acidic vesicles of the parasite. The major putative benzoyl metabolites were then found to function as redox cyclers: (i) in their oxidized form, the benzoyl metabolites are reduced by NADPH in glutathione reductase-catalyzed reactions within the cytosols of infected red blood cells; (ii) in their reduced forms, these benzoyl metabolites can convert methemoglobin, the major nutrient of the parasite, to indigestible hemoglobin. Studies on a fluorinated suicide-substrate indicate as well that the glutathione reductase-catalyzed bioactivation of naphthoquinones is essential for the observed antimalarial activity. In conclusion, the antimalarial naphthoquinones are suggested to perturb the major redox equilibria of the targeted infected red blood cells, which might be removed by macrophages. This results in development arrest and death of the malaria parasite at the trophozoite stage
A new species of Dichelyne (Nematoda, Cucullanidae) parasitizing siaenid fishes from off the South American Atlantic coast
Anew nematode species Dichelyne (Cucullanellus) sciaenidicola sp. nov. is described based on specimens collected from the Whitemouth croaker Micropogonias furnieri (Desmarest) and the Argentine croaker Umbrina canosai Berg, from coastal waters of Argentina and Brazil. These nematodes were firstly identified as D. (C.) elongatus (Törnquist, 1931), a commonly reported species from M. furnieri in South American Atlantic waters. However, other species of Dichelyne have so far been reported from this host in the same area, namely D. (C.) rodriguesi (Pinto, Fábio et Noronha, 1970), D. (C.) amaruincai (Freitas, Vicente et Ibañez, 1969) and D. (Dichelyne) micropogonii Pereira et Costa, 1996. A careful re-examination of these parasites, as well as of type specimens of all species reported from M. furnieri, revealed that these nematodes represented a new species. The new species is distinguished from most of its congeners by having papillae 5-7 and 9 forming a subventral line close to cloaca, this feature is shared with other 6 species [D. (C.) dichelyneformis (Szidat, 1950), D. (C.) fraseri (Baylis, 1929), D. (C.) abbreviatus (Rudolphi, 1819), D. (C.) adriaticus (Törnquist, 1931), D. (C.) minutus (Rudolphi, 1819) and D. (C.) mariajuliae Alarcos, Timi, Etchegoin et Sardella, 2006)], which are readily distinguished by their body size, spicules length, distribution patterns of other papillae and position of the excretory pore and deirids. Also, D. (C.) elongatus from Umbrina canariensis (Valenciennes) from West Africa is established as a new species Dichelyne (Cucullanellus) yvonnecampanae sp. nov.; D. (C.) amaruincai from Pacific waters is considered as a valid species, D. (D.) micropogonii is regarded as species inquirendae and D. (C.) rodriguesi is identified as Cucullanus sp.Fil: Timi, Juan Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Lanfranchi, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Tavares, Luiz E. R.. Universidade Federal Rural do Rio de Janeiro; BrasilFil: Luque, José L.. Universidade Federal Rural do Rio de Janeiro; Brasi
Solar and Atmospheric Neutrinos: Background Sources for the Direct Dark Matter Searches
In experiments for direct dark matter searches, neutrinos coherently
scattering off nuclei can produce similar events as Weakly Interacting Massive
Particles (WIMPs). The calculated count rate for solar neutrinos in such
experiments is a few events per ton-year. This count rate strongly depends on
the nuclear recoil energy threshold achieved in the experiments for the WIMP
search. We show that solar neutrinos can be a serious background source for
direct dark matter search experiments using Ge, Ar, Xe and CaWO_4 as target
materials. To reach sensitivities better than approximatly 10^-10 pb for the
elastic WIMP nucleon spin-independent cross section in the zero-background
limit, energy thresholds for nuclear recoils should be approximatly >2.05 keV
for CaWO_4, >4.91 keV for Ge, >2.89 keV for Xe, and >8.62 keV for Ar as target
material. Next-generation experiments should not only strive for a reduction of
the present energy thresholds but mainly focus on an increase of the target
mass. Atmospheric neutrinos limit the achievable sensitivity for the
background-free direct dark matter search to approximatly >10^-12 pb.Comment: accepted by Astroparticle Physic
Increased hormonal stress response of Apennine chamois induced by interspecific interactions and anthropogenic disturbance
Responses of animals to environmental changes and their interactions with other species play an important role in conservation. Sharing a common habitat may lead to interspecific competition for resources, but field assessment of these biological events is not always easily accomplished. By using a non-invasive method, we evaluated the physiological stress responses of Apennine chamois (Rupicapra pyrenaica ornata) to the presence of cattle, sheep and goat, red deer (Cervus elaphus), people (hikers), and predators to identify which factors may affect this endangered species. During September 2012, November 2012, and July 2013, a total of 318 faecal samples were collected in representative sites and analysed for faecal cortisol metabolites (FCM). FCM concentration was analysed through linear mixed-effect models. A significant increase in FCM values in Apennine chamois sharing their habitat with domestic animals was recorded during all study periods. On the contrary, stress responses to red deer and people were limited in time and emerged only during summer months, when hikers are more frequent and red deer extend their altitudinal range reaching chamois\u2019 habitat. The observed effects of domestic animals, red deer, and hikers should be considered in future Apennine chamois management plans, which should include the regulation of pastured domestic livestock, anthropogenic disturbances, and possible interferences with other wild species within parks
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