221 research outputs found

    Towards new insights in the phylogeny of the Spermacoce clade: an integrative taxonomic approach using morphology, anatomy, ecology and phylogenetics reveáis the new genus Leonoria

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    Phylogenetic inference analyses o f two nuclear and four plastid DNA markers from 82 accessions representing 19 genera o f the Spermacoce clade (Spermacoceae-Rubiaceae) confirm that the Brazilian genus Denscantia is biphyletic. By the analyses o f reproductive morphological characters, foliar morpho-anatomy and histochemical, geographical distribution ranges, and ecological niche derived from climatic space, Denscantia caldcóla is shown as a distinct lineage from the other Denscantia species, indicating its taxonomic segregation into a new monospecific genus Leonoria. Significant morphological diíferences o f Leonoria with Denscantia were found in inflorescence organization, stigma shape, fruit dehiscence, and pollen morphology. Morphoanatomical variation among leaf traits were found in epidemial cells, occurrence o f trichomes, mesophyll histochemical, and vascular organization. Analysis o f occurrence records o f 205 specimens demonstrates a clear ecological distinction between o f Denscantia s.s. and Leonoria, which is ecologically confined to limestone outcrops associated with seasonally dry forests. The current study demonstrates the importance of an integrative taxonomic approach - in which múltiple disciplines are combined - to the unravel complex taxonomic pattems within Rubiaceae. The genus Leonoria, to be newly described, is dedicated to Professor Elsa Leonor Cabral

    A Large Brightness Enhancement of the QSO 0957+561 A Component

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    We report an increase of more than 0.2 mag in the optical brightness of the leading image (A) of the gravitational lens Q0957+561, detected during the 09/2000 -- 06/2001 monitoring campaign (2001 observing season). The brightening is similar to or even greater than the largest change ever detected during the 20 years of monitoring of this system. We discuss two different provisional explanations to this event: intrinsic source variability or microlensing (either short timescale microlensing or cessation of the historical microlensing). An exhaustive photometric monitoring of Q0957+561 is needed until summer of 2002 and during 2003 to discriminate between these possibilities.Comment: 13 pages including 3 figures and 1 table. Accepted for publication in ApJ Let

    Brorfelde Schmidt CCD Catalog (BSCC)

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    The Brorfelde Schmidt CCD Catalog (BSCC) contains about 13.7 million stars, north of +49 deg Declination with precise positions and V, R photometry. The catalog has been constructed from the reductions of 18,667 CCD frames observed with the Brorfelde Schmidt Telescope between 2000 and 2007. The Tycho-2 catalog was used for astrometric and photometric reference stars. Errors of individual positions are about 20 to 200 mas for stars in the R = 10 to 18 mag range. External comparisons with 2MASS and SDSS reveal possible small systematic errors in the BSCC of up to about 30 mas. The catalog is supplemented with J, H, and K_s magnitudes from the 2MASS catalog. The catalog data file (about 550 MB ASCII, compressed) will be made available at the Strasbourg Data Center (CDS).Comment: 16 pages, 22 figures, 2 tables, accepted by A

    Does the current taxonomic delimitation of Galianthe find support in phylogenetic perspective?

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    Galianthe Griseb. is a neotropical genus comprising 50 species divided into two subgenera: G. subgen. Galianthe (41 spp.), characterized by homogeneous morphological traits, with species further divided into two sections (G. secc. Galianthe and G. secc. Laxae); and G. subgen. Ebelia (14 spp.) with more heterogeneous morphological characteristics. Due to its morphological similarity with other genera, Galianthe has historically been associated with Borreria, Spermacoce, Diodia (based on fruit type), as well as Denscantia and Emmeorhiza (based on inflorescence type). In recent years, molecular studies have established Galianthe as a basal genus within the Spermacoce clade, closely related to other genera such as Carajasia and Schwendenera. Despite the progress made in recent molecular studies, the studies have focused on a limited number of species within the genus, failing to encompass all infrageneric categories. Questioning of the current taxonomic delimitation of the genus, this study aims to test the monophyly of Galianthe and explore its infrageneric and interspecific phylogenetic relationships. Three markers (two nuclear: ITS, ETS, and one plastid: rps16) were utilized, encompassing 107 entities, including 42 Galianthe species, thereby representing 76% of the current genus diversity, as well as 17 closely related genera within the Spermacoce clade. The phylogenetic results confirm the monophyly of Galianthe, revealing the presence of three major subclades. Subclades I and II comprise several G. subgen. Ebelia species, whereas subclade III consists of all G. subgen. Galianthe species plus G. angulata. Regarding the sections, monophyly was not supported. Based on these findings, it can be concluded that G. subgen. Ebelia is paraphyletic, G. subgen. Galianthe is potentially paraphyletic due to G. angulata, and there is no clear distinction between the sections

    A Robust Determination of the Time Delay in 0957+561A,B and a Measurement of the Global Value of Hubble's Constant

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    Photometric monitoring of the gravitational lens system 0957+561A,B in the g and r bands with the Apache Point Observatory (APO) 3.5 m telescope during 1996 shows a sharp g band event in the trailing (B) image light curve at the precise time predicted from the observation of an event during 1995 in the leading (A) image with a delay of 415 days. This success confirms the "short delay," and the lack of any feature at a delay near 540 days rejects the "long delay" for this system, resolving a long-standing controversy. A series of statistical analyses of our light curve data yield a best fit delay of 417 +/- 3 days (95% confidence interval). Recent improvements in the modeling of the lens system (consisting of a galaxy and cluster) allow us to derive a value of the global (at z = 0.36) value of Hubble's constant H_0 using Refsdal's method, a simple and direct distance determination based on securely understood physics and geometry. The result is H_0 = 63 +/- 12 km/s/Mpc (for Omega = 1) where this 95% confidence interval is dominated by remaining lens model uncertainties.Comment: accepted by ApJ, AASTeX 4.0 preprint, 4 PostScript figure

    Further Investigation of the Time Delay, Magnification Ratios, and Variability in the Gravitational Lens 0218+357

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    High precision VLA flux density measurements for the lensed images of 0218+357 yield a time delay of 10.1(+1.5-1.6)days (95% confidence). This is consistent with independent measurements carried out at the same epoch (Biggs et al. 1999), lending confidence in the robustness of the time delay measurement. However, since both measurements make use of the same features in the light curves, it is possible that the effects of unmodelled processes, such as scintillation or microlensing, are biasing both time delay measurements in the same way. Our time delay estimates result in confidence intervals that are somewhat larger than those of Biggs et al., probably because we adopt a more general model of the source variability, allowing for constant and variable components. When considered in relation to the lens mass model of Biggs et al., our best-fit time delay implies a Hubble constant of H_o = 71(+17-23) km/s-Mpc for Omega_o=1 and lambda_o=0 (95% confidence; filled beam). This confidence interval for H_o does not reflect systematic error, which may be substantial, due to uncertainty in the position of the lens galaxy. We also measure the flux ratio of the variable components of 0218+357, a measurement of a small region that should more closely represent the true lens magnification ratio. We find ratios of 3.2(+0.3-0.4) (95% confidence; 8 GHz) and 4.3(+0.5-0.8) (15 GHz). Unlike the reported flux ratios on scales of 0.1", these ratios are not strongly significantly different. We investigate the significance of apparent differences in the variability properties of the two images of the background active galactic nucleus. We conclude that the differences are not significant, and that time series much longer than our 100-day time series will be required to investigate propagation effects in this way.Comment: 33 pages, 9 figures. Accepted for publication in ApJ. Light curve data may be found at http://space.mit.edu/RADIO/papers.htm

    A Sharp Event in the Image a Light Curve of the Double Quasar 0957+561 and Prediction of the 1996 Image B Light Curve

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    CCD photometry of the gravitational lens system 0957+561A,B in the g and r bands was obtained on alternate nights, weather permitting, from December 1994 through May 1995 using the Double Imaging Spectrograph (DIS) on the Apache Point Observatory (APO) 3.5-meter telescope. The remote observing and fast instrument change capabilities of this facility allowed accumulation of light curves sampled frequently and consistently. The Honeycutt ensemble photometry algorithm was applied to the data set and yielded typical relative photometric errors of approximately 0.01 magnitudes. Image A exhibited a sharp drop of about 0.1 magnitudes in late December 1994; no other strong features were recorded in either image. This event displays none of the expected generic features of a microlensing-induced flux variation and is likely to be intrinsic to the quasar; if so, it should also be seen in the B image with the lensing differential time delay. We give the expected 1996 image B light curves based on two values of the time delay and brightness ratio which have been proposed and debated in the literature. Continued monitoring of the system in the first half of 1996 should easily detect the image B event and thus resolve the time-delay controversy.Comment: submitted to ApJ Letters, 15 pages, uuencoded PostScript with figures included; also available through WWW at http://www.astro.princeton.edu/~library/prep.htm

    Antimicrobial use in European acute care hospitals: results from the second point prevalence survey (PPS) of healthcare-associated infections and antimicrobial use, 2016 to 2017

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    Antimicrobial agents used to treat infections are life-saving. Overuse may result in more frequent adverse effects and emergence of multidrug-resistant microorganisms. In 2016-17, we performed the second point-prevalence survey (PPS) of healthcare-associated infections (HAIs) and antimicrobial use in European acute care hospitals. We included 1,209 hospitals and 310,755 patients in 28 of 31 European Union/European Economic Area (EU/EEA) countries. The weighted prevalence of antimicrobial use in the EU/EEA was 30.5% (95% CI: 29.2-31.9%). The most common indication for prescribing antimicrobials was treatment of a community-acquired infection, followed by treatment of HAI and surgical prophylaxis. Over half (54.2%) of antimicrobials for surgical prophylaxis were prescribed for more than 1 day. The most common infections treated by antimicrobials were respiratory tract infections and the most commonly prescribed antimicrobial agents were penicillins with beta-lactamase inhibitors. There was wide variation of patients on antimicrobials, in the selection of antimicrobial agents and in antimicrobial stewardship resources and activities across the participating countries. The results of the PPS provide detailed information on antimicrobial use in European acute care hospitals, enable comparisons between countries and hospitals, and highlight key areas for national and European action that will support efforts towards prudent use of antimicrobials

    Odor supported place cell model and goal navigation in rodents

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    Experiments with rodents demonstrate that visual cues play an important role in the control of hippocampal place cells and spatial navigation. Nevertheless, rats may also rely on auditory, olfactory and somatosensory stimuli for orientation. It is also known that rats can track odors or self-generated scent marks to find a food source. Here we model odor supported place cells by using a simple feed-forward network and analyze the impact of olfactory cues on place cell formation and spatial navigation. The obtained place cells are used to solve a goal navigation task by a novel mechanism based on self-marking by odor patches combined with a Q-learning algorithm. We also analyze the impact of place cell remapping on goal directed behavior when switching between two environments. We emphasize the importance of olfactory cues in place cell formation and show that the utility of environmental and self-generated olfactory cues, together with a mixed navigation strategy, improves goal directed navigation
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