1,145 research outputs found
Host Galaxy Contribution to the Colours of `Red' Quasars
We describe an algorithm that measures self-consistently the relative galaxy
contribution in a sample of radio-quasars from their optical spectra alone.
This is based on a spectral fitting method which uses the size of the
characteristic 4000\AA~ feature of elliptical galaxy SEDs. We apply this method
to the Parkes Half-Jansky Flat Spectrum sample of Drinkwater et al. (1997) to
determine whether emission from the host galaxy can significantly contribute to
the very red optical-to-near-infrared colours observed. We find that at around
confidence, most of the reddening in unresolved (mostly quasar-like)
sources is unlikely to be due to contamination by a red stellar component.Comment: 11 pages, 11 figures. Accepted for Publication in Monthly Notices of
the Royal Astronomical Societ
Liquid and vapour phase of lavandin (Lavandula × intermedia) essential oil: chemical composition and antimicrobial activity
Essential oils from Lavandula genus and the obtained hybrids are widely used for different purposes such as perfume production in the cosmetic field and for its biological properties. This is the first study on the liquid and vapour phase of Lavandula × intermedia “Grosso” essential oil grown in the Lazio Region, Italy, investigated using headspace coupled to gas chromatography and mass spectrometry (HS-GC/MS). The results showed the most abundant components were linalool and linalyl acetate, followed by 1,8-cineole and terpinen-4-ol, while lavandulyl acetate and borneol were identified as minor compounds, maintaining the same proportion in both the liquid and vapour phase. Furthermore, we tested lavandin liquid and vapour phase essential oil on gram-negative bacteria (Escherichia coli, Acinetobacter bohemicus, and Pseudomonas fluorescens) and gram-positive bacteria (Bacillus cereus and Kocuria marina)
Chemical investigation of a biologically active schinus molle L. leaf extract
The pepper tree Schinus molle L. is an evergreen ornamental plant belonging to the Anacardiaceae family, native to South America and widespread throughout the world. It has biological activities and is used in folk medicine. This paper aims to contribute to a deeper knowledge of its chemical composition and biological properties. S. molle leaf extracts were obtained by sequential extraction with solvents of different polarities and subsequently tested on the HL-60 human leukaemia cell line to define a possible cytotoxic activity. Among the investigated extracts, the petroleum ether extract revealed a high cytotoxic activity, and its chemical composition was further investigated. By a silica column chromatography, eight fractions were obtained, and their compositions were determined by GC-MS analysis. Compounds and relative abundance differed widely among the fractions; sesquiterpenes resulted the main component and alcoholic sesquiterpenes the most abundant
Cosmological Obscuration by Galactic Dust: Effects of Dust Evolution
We explore the effects of dust in cosmologically distributed intervening
galaxies on the high redshift universe using a generalised model where dust
content evolves with cosmic time. The absorbing galaxies are modelled as
exponential disks which form coevally, maintain a constant space density and
evolve in dust content at a rate that is uniform throughout. We find that the
inclusion of moderate to moderately weak amounts of evolution consistent with
other studies can reduce the mean observed -band optical depth to redshifts
z \simgt 1 by at least 60% relative to non-evolving models. Our predictions
imply that intervening galactic dust is unlikely to bias the optical counts of
quasars at high redshifts and their evolution in space density derived
therefrom.Comment: 10 pages, 6 figures, Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Prediction of hearing recovery in sudden deafness treated with intratympanic steroids
The present study aims to obtain a probability model allowing the prediction of the auditory recovery in patients affected by sudden sensorineural hearing loss treated exclusively with intratympanic steroids. A monocentric retrospective chart review of three-hundred eighty-one patients has been performed. A Probit model was used to investigate the correlation between the success of the treatment (marked or total recovery according to Furuashi's criteria), and the delay between the onset of disease and the beginning of therapy. The age of the patients and the audiometric curve shapes were included in the analysis. Results show that delay is negatively correlated with the variable success. Considering the entire sample, each day of delay decreases by 3% the probability of success. The prediction model shows that for every day that passes from the onset of the disease the probability of success declines in absence of the medical treatment, hence we conclude that early treatment is strongly recommended
An Optical and Infrared Time-Domain Study of the Supergiant Fast X-ray Transient Candidate IC 10 X-2
We present an optical and infrared (IR) study of IC 10 X-2, a high-mass X-ray
binary in the galaxy IC 10. Previous optical and X-ray studies suggest X-2 is a
Supergiant Fast X-ray Transient: a large-amplitude (factor of 100),
short-duration (hours to weeks) X-ray outburst on 2010 May 21. We analyze R-
and g-band light curves of X-2 from the intermediate Palomar Transient Factory
taken between 2013 July 15 and 2017 Feb 14 show high-amplitude ( 1
mag), short-duration ( d) flares and dips ( 0.5 mag).
Near-IR spectroscopy of X-2 from Palomar/TripleSpec show He I,
Paschen-, and Paschen- emission lines with similar shapes and
amplitudes as those of luminous blue variables (LBVs) and LBV candidates
(LBVc). Mid-IR colors and magnitudes from Spitzer/IRAC photometry of X-2
resemble those of known LBV/LBVcs. We suggest that the stellar companion in X-2
is an LBV/LBVc and discuss possible origins of the optical flares. Dips in the
optical light curve are indicative of eclipses from optically thick clumps
formed in the winds of the stellar counterpart. Given the constraints on the
flare duration ( d) and the time between flares ( d),
we estimate the clump volume filling factor in the stellar winds, , to be
, which overlaps with values measured from massive star
winds. In X-2, we interpret the origin of the optical flares as the accretion
of clumps formed in the winds of an LBV/LBVc onto the compact object.Comment: 15 pages, 4 figures. Submitted to ApJ on Sep 26 201
Unravelling Active Galactic Nuclei
A complete flat-spectrum radio-loud sample of AGN includes a significant
fraction of Seyfert-like AGN including a NLS1. Analysis of their optical
spectra suggests that the reddest continuum colours are either associated with
AGN in nearby resolved galaxies, or distant quasars showing relatively narrow
permitted emission lines.Comment: Poster contribution presented at the Joint MPE,AIP,ESO workshop on
NLS1s, Bad Honnef, Dec. 1999, to appear in New Astronomy Reviews; also
available at http://wave.xray.mpe.mpg.de/conferences/nls1-worksho
A hazard analysis method for systematic identification of safety requirements for user interface software in medical devices
© Springer International Publishing AG (outside the US) 2017. Formal methods technologies have the potential to verify the usability and safety of user interface (UI) software design in medical devices, enabling significant reductions in use errors and consequential safety incidents with such devices. This however depends on comprehensive and verifiable safety requirements to leverage these techniques for detecting and preventing flaws in UI software that can induce use errors. This paper presents a hazard analysis method that extends Leveson’s System Theoretic Process Analysis (STPA) with a comprehensive set of causal factor categories, so as to provide developers with clear guidelines for systematic identification of use-related hazards associated with medical devices, their causes embedded in UI software design, and safety requirements for mitigating such hazards. The method is evaluated with a case study on the Gantry-2 radiation therapy system, which demonstrates that (1) as compared to standard STPA, our method allowed us to identify more UI software design issues likely to cause use-related hazards; and (2) the identified UI software design issues facilitated the definition of precise, verifiable safety requirements for UI software, which could be readily formalized in verification tools such as Prototype Verification System (PVS).- U.S. Food and Drug Administration(NORTE-01-0145-FEDER-000016)Sandy Weininger (FDA), Scott Thiel (Navigant Consulting, Inc.), Michelle Jump (Stryker), Stefania Gnesi (ISTI/CNR) and the CHI+MED team (www.chi-med.ac.uk) provided useful feedback and inputs. Paolo Masci’s work is supported by the North Portugal Regional Operational Programme (NORTE 2020) under the PORTUGAL 2020 Partnership Agreement, and by the European Regional Development Fund (ERDF) within Project “NORTE-01-0145-FEDER-000016”.info:eu-repo/semantics/publishedVersio
The Population of Tiny Near-Earth Objects Observed by NEOWISE
Only a very small fraction of the asteroid population at size scales
comparable to the object that exploded over Chelyabinsk, Russia has been
discovered to date, and physical properties are poorly characterized. We
present previously unreported detections of 106 close approaching near-Earth
objects (NEOs) by the Wide-field Infrared Survey Explorer mission's NEOWISE
project. These infrared observations constrain physical properties such as
diameter and albedo for these objects, many of which are found to be smaller
than 100 m. Because these objects are intrinsically faint, they were detected
by WISE during very close approaches to the Earth, often at large apparent
on-sky velocities. We observe a trend of increasing albedo with decreasing
size, but as this sample of NEOs was discovered by visible light surveys, it is
likely that selection biases against finding small, dark NEOs influence this
finding.Comment: Accepted to Ap
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