1,333 research outputs found

    Diet, microhabitat and time of activity in a Pristimantis (Anura, Strabomantidae) assemblage

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    We tested if the richness and abundance of six closely related species of Pristimantis significantly varied among three transects located at different distances from a creek in an Andean cloud forest. We found that richness and abundance of frogs varied significantly among transects, being the transect located at the forest interior the richest in frog species and number of individuals. We chose these more crowded sites to evaluate resource use differences among the species. We evaluated ecological variables such as microhabitat, diet, and time of activity in these species that are similar in morphology and body size, to determine whether they have differences in the use of these resources. Most specimens perch on leaves at heights within 1.5 and 2.0 m of the ground and are nocturnal; only P. douglasi was found with diurnal and nocturnal activity. The species had similar diets, they ingested a wide spectrum of prey sizes that are similar among species, months, and between transects. Almost all collected frogs were juveniles and were found during every single month of sampling suggesting continuous reproduction; however, adults and juveniles of P. douglasi were absent during some of the drier months, indicating seasonality. Thus, we found that most of these Pristimantis species occupy the forest interior and that there is no a strong segregation in the use of the evaluated resources, only one species had a slight difference in activity and reproductive time

    Characterisation of candidate members of (136108) Haumea's family

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    Ragozzine & Brown [2007] presented a list of candidate members of the first collisional family to be found among the trans-Neptunian Objects (TNOs), the one associated with (136108) Haumea (2003 EL61). We aim to identify which of the candidate members of the Haumea collisional family are true members, by searching for water ice on their surfaces. We also attempt to test the theory that the family members are made of almost pure water ice by using optical light-curves to constrain their densities. We use optical and near-infrared photometry to identify water ice, in particular using the (J - H_S) colour as a sensitive measure of the absorption feature at 1.6 micron. We use the CH_4 filter of the new Hawk-I instrument at the VLT as a short H-band (H_S) for this as it is more sensitive to the water ice feature than the usual H filter. We report colours for 22 candidate family members, including NIR colours for 15. We confirm that 2003 SQ317 and 2005 CB79 are family members, bringing the total number of confirmed family members to 10. We reject 8 candidates as having no water ice absorption based on our Hawk-I measurements, and 5 more based on their optical colours. The combination of the large proportion of rejected candidates and time lost to weather prevent us from putting strong constraints on the density of the family members based on the light-curves obtained so far; we can still say that none of the family members (except Haumea) require a large density to explain their light-curve.Comment: 9 pages, 5 figures, accepted for publication in A&

    Methane, ammonia, and their irradiation products at the surface of an intermediate-size KBO? A portrait of Plutino (90482) Orcus

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    Orcus is an intermediate-size 1000km-scale Kuiper Belt Object in 3:2 mean-motion resonance with Neptune, in an orbit very similar to that of Pluto. We present visible and near-infrared photometry and spectroscopy obtained with the Keck 10m-telescope and the Gemini 8m-telescope . We confirm the unambiguous detection of crystalline water ice as well as absorption in the 2.2\mu m region. Both in the visible and near-infrared Orcus' spectral properties appear to be homogeneous over time (and probably rotation) at the resolution available. From Hapke radiative transfer models involving intimate mixtures of various ices we find for the first time that ammonium (NH+4) and traces of ethane (C2 H6), which are most probably solar irradiation products of ammonia and methane, and a mixture of methane and ammonia (diluted or not) are the best candidates to improve the description of the data with respect to a simple water ice mixture (Haumea type surface). The possible more subtle structure of the 2.2\mu m band(s) should be investigated thoroughly in the future for Orcus and other intermediate size Plutinos to better understand the methane and ammonia chemistry at work, if any. We investigated the thermal history of Orcus with a new 3D thermal evolution model. Simulations over 4.5 x109 yrs with an input 10% porosity, bulk composition of 23% amorphous water ice and 77% dust, and cold accretion show that even with the action of long-lived radiogenic elements only, Orcus should have a melted core and most probably suffered a cryovolcanic event in its history which brought large amounts of crystalline ice to the surface. The presence of ammonia in the interior would strengthen the melting process. The crystalline water ice possibly brought to the surface by a past cryovolcanic event sbe detectable after several billion years despite the irradiation eects, as demonstrated by recent laboratory experiments.Comment: 15 pages, 9 figure

    Garnet-clinopyroxene bearing assemblages in the 'upper catazonal unit' of the Cabo Ortega! Complex (NW Spain)

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    [Resumen] Se han estudiado los siguientes materiales de la 'unidad catazonal superior' del Complejo del Cabo Ortegal conteniendo asociaciones con granate-clinopiroxeno: eclogitas, granulitas básicas, intercalaciones gneísicas en las granulitas, piroxenitas con granate, gneises de la aureola de contacto de las rocas ultramáficas, metabasitas de la 'formación Candelaria' y 'carbonatitas'. Los datos termobarométricos obtenidos sugieren que, mientras que los minerales de algunos de estos materiales han sufrido importantes reajustes composicionales durante los procesos de retromorfosis (e. g. granulitas con distena, intercalaciones gneísicas en granulitas, -intercalaciones u1tramáficas en gneises, etc.), otros han conservado elementos mineralógicos con la composición alcanzada durante el episodio metamórfico que originó la formación de las asociaciones con granate-clinopiroxeno. Este segundo grupo de materiales puede subdividirse en dos categorías: 1) aquellos materiales en los que la asociación granate-clinopiroxeno se formó en torno a los 800 oC y 15 ± 1. 5 kbar (eclogitas 'tipo-I', granulitas de la 'formación Bracariza', piroxenitas con granate de los macizos de rocas u1tramáficas 'carbonatitas'), y, 11) aquellos en los que dicha asociaci6n se formó a unos 700 oC y la misma P aproximadamente (eclogitas y granulitas intercaladas en las formaciones gneísicas). Aunque las diferencias no son muy importantes, es posible que los dos conjuntos litológicos representen dos gradientes metamórficos distintos y, por tanto, la existencia en dicha 'unidad' de materiales con diferentes historias tectono-metamórficas.[Abstract] The following materials from the 'uper' catazonal unit' of the Cabo Ortegal Complex, containing garnet-clinopyroxene assemblages, have been studied: eclogites, basic granulites, gneissic intercalations within granulites, garnetbearing pyroxenites, gneisses from the contact aureole of the ultramafic rocks, metabasites from the 'Candelaria formation' and 'carbonatites'. The thermobarometric data obtained from this study suggest that the minerals from several of those materials underwent strong compositional readjustements during the subsequent retromorphic events (e. g. the kyanite-bearing granulites, the gneissic intercalations in granulites, the u1tramafic intercalations in gneisses, etc.). The remaining materials have preserved mineral compositions attained during the metamorphic episode that produced the garnetclinopyroxene assemblages; these materials may be classified as follows: 1) those in which the garnet-clinopyroxene assemblage formed at ca. 800 oC and 15 ± ± 1,5 kbar ('type-I' eclogites, granulites from the 'Bacariza formation', garnetbearing pyroxenites from the ultramafic massifs and 'carbonatites'), and, 11) those where the same association developed at ca 700 oC and more or less the same P conditions (eclogites and granulites intercaled in gneisses). Although these differences in P and Tare not very important, it is possible that these two groups represent two different metamorphic gradients, and therefore the existence in this 'unit' of the Complex of two lithological sub-units with different tectono-metamorphic histories

    Linfoma angiocéntrico centrofacial

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    El linfoma angiocéntrico centrofacial es una neoplasia linfoide rara, con un diagnóstico a menudo difícil, debido al cuadro clínico inespecífico y a que muchas veces son necesarias varias biopsias para llegar a un diagnóstico correcto. Se trata de un linfoma no Hodgkin(LNH) agresivo, de localización preferente en el tracto respiratorio superior (sobre todo en cavidad nasal), y con un pronóstico ominoso, ya que la supervivencia media es de 12-18 meses aproximadamente(1). Predomina en orientales y sudamericanos, entre los 50-60 años de edad, y con ligera preferencia por el sexo masculino (2:1). Se presenta el caso de una paciente ecuatoriana que acude a nuestro servicio con edema hemifacial, rinorrea achocolatada y obstrucción respiratoria nasal de 1 mes de evolución, sin respuesta al tratamiento antibiótico y antiinflamatorio, que tras realizar varias pruebas diagnósticas se evidenció histológicamente la presencia de un linfoma T extranodal de tipo nasal (también llamado linfoma de células T angiocéntrico).The centrofacial angiocentric lymphoma is a rare lymphoid neoplasm, with an often-difficult diagnosis due to the non-specific clinical picture. On many occasions it is necessary to perform various biopsies to reach the correct diagnosis. This lymphoma is an aggressive Non-Hodgkin's (NHL) type, which is normally found in the upper respiratory tract (predominantly in the nasal cavity), and has an ominous prognosis, as the average survival rate is between 12 and 18 months (1). It is predominantly found in subjects of oriental and South American extraction, who are between the ages of 50 and 60 years and with a slight tendency towards males (2:1). This is the case study of a female Ecuadorian patient who was referred to our department with a hemifacial edema, chocolate- like rhinorrhea and nasal respiratory obstruction, which had been treated with antibiotics and anti-inflammatories for a month without success. After performing a number of diagnostic tests, it was found histologically that the patient had an extranodal T-cell lymphoma of the nasal type (also known as T-cell angiocentric lymphoma)

    Characterisation of candidate members of (136108) Haumea's family: II. Follow-up observations

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    From a dynamical analysis of the orbital elements of transneptunian objects (TNOs), Ragozzine & Brown reported a list of candidate members of the first collisional family found among this population, associated with (136108) Haumea (a.k.a. 2003 EL61). We aim to distinguish the true members of the Haumea collisional family from interlopers. We search for water ice on their surfaces, which is a common characteristic of the known family members. The properties of the confirmed family are used to constrain the formation mechanism of Haumea, its satellites, and its family. Optical and near-infrared photometry is used to identify water ice. We use in particular the CH4 filter of the Hawk-I instrument at the European Southern Observatory Very Large Telescope as a short H-band (Hs), the (J-Hs) colour being a sensitive measure of the water ice absorption band at 1.6 {\mu}m. Continuing our previous study headed by Snodgrass, we report colours for 8 candidate family members, including near-infrared colours for 5. We confirm one object as a genuine member of the collisional family (2003 UZ117), and reject 5 others. The lack of infrared data for the two remaining objects prevent any conclusion from being drawn. The total number of rejected members is therefore 17. The 11 confirmed members represent only a third of the 36 candidates. The origin of Haumea's family is likely to be related to an impact event. However, a scenario explaining all the peculiarities of Haumea itself and its family remains elusive.Comment: 8 pages, 4 figures, accepted for publication in A&

    Homocysteine and cognition: A systematic review of 111 studies

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    Background Elevated plasma homocysteine ​​(Hcy) levels have been associated with cognitive dysfunction in a wide range of conditions. The aim of this review is to establish which cognitive domains and populations are the most affected. Methods We systematically review the literature and consider all articles that showed any relationship between plasma Hcy levels and scores achieved on cognitive performance tests in both, the general population and patients suffering from central nervous system disorders and other diseases. When effect sizes were available and combinable, several meta-analyses were performed. Results We found 111 pertinent articles. There were 24 cohort studies, 18 randomized trials, 21 case-control studies, and 48 cross-sectional studies. This review reveals a positive trend between cognitive decline and increased plasma Hcy concentrations in general population and in patients with cognitive impairments. Results from the meta-analyses also confirm this trend. Treatment with vitamin supplementation fails to show a reduction in cognitive decline. Discussion Further investigations are warranted to clarify this relationship. Earlier detection of the elevated Hcy levels may be an effective intervention to prevent cognitive impairment and dementia
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