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Andrew Collins - One of the best experts on this subject based on the ideXlab platform.
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the next three decades of the Comet assay a report of the 11th international Comet assay workshop
Mutagenesis, 2017Co-Authors: Gudrun Koppen, Bertrand Pourrut, Gunnar Brunborg, Amaya Azqueta, Andrew Collins, Sabine A S LangieAbstract:: The International Comet Assay Workshops are a series of scientific conferences dealing with practical and theoretical aspects of the Comet Assay (single-cell gel electrophoresis)-a simple method for detecting DNA strand breaks. The first paper describing such an assay was published over 30 years ago in 1984 by Swedish researchers O. Ostling and K. J. Johanson. Appropriately, the theme for the 2015 meeting was looking to the future: 'The Next 3 Decades of the Comet Assay'. The programme included 25 oral and 43 poster presentations depicting the latest advances in technical developments as well as applications of the Comet assay in genotoxicity testing (in vitro and in vivo) and biomonitoring of both humans and the environment. Open discussion sessions based on questions from the participants allowed exchange of practical details on current Comet assay protocols. This report summarises technical issues of high importance which were discussed during the sessions. We provide information on ways to improve the assay performance, by testing for cytotoxicity, by using reference samples to reduce or allow for inter-experimental variation, and by standardising quantification of the damage, including replicates and scoring enough Comets to ensure statistical validity. After 30 years of experimentation with the Comet assay, we are in a position to control the important experimental parameters and make the Comet assay a truly reliable method with a wealth of possible applications.
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can the Comet assay be used reliably to detect nanoparticle induced genotoxicity
Environmental and Molecular Mutagenesis, 2015Co-Authors: Hanna L Karlsson, Sebastiano Di Bucchianico, Andrew Collins, Maria DusinskaAbstract:The Comet assay is a sensitive method to detect DNA strand breaks as well as oxidatively damaged DNA at the level of single cells. Today the assay is commonly used in nano-genotoxicology. In this review we critically discuss possible interactions between nanoparticles (NPs) and the Comet assay. Concerns for such interactions have arisen from the occasional observation of NPs in the “Comet head”, which implies that NPs may be present while the assay is being performed. This could give rise to false positive or false negative results, depending on the type of Comet assay endpoint and NP. For most NPs, an interaction that substantially impacts the Comet assay results is unlikely. For photocatalytically active NPs such as TiO2, on the other hand, exposure to light containing UV can lead to increased DNA damage. Samples should therefore not be exposed to such light. By comparing studies in which both the Comet assay and the micronucleus assay have been used, a good consistency between the assays was found in general (69%); consistency was even higher when excluding studies on TiO2 NPs (81%). The strong consistency between the Comet and micronucleus assays for a range of different NPs—even though the two tests measure different endpoints—implies that both can be trusted in assessing the genotoxicity of NPs, and that both could be useful in a standard battery of test methods. Environ. Mol. Mutagen. 56:82–96, 2015. © 2014 Wiley Periodicals, Inc.
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the Comet assay as a tool for human biomonitoring studies the comnet project
Mutation Research-reviews in Mutation Research, 2014Co-Authors: Andrew Collins, Gudrun Koppen, Vanessa Valdiglesias, Emilio Rojas, Iris F. F. Benzie, Marcin Kruszewski, Peter Möller, Maria Dusinska, Alok Dhawan, Erdem CoskunAbstract:The Comet assay is widely used in human biomonitoring to measure DNA damage as a marker of exposure to genotoxic agents or to investigate genoprotective effects. Studies often involve small numbers of subjects, and design may be sub-optimal in other respects. In addition, Comet assay protocols in use in different laboratories vary significantly. In spite of these difficulties, it is appropriate to carry out a pooled analysis of all available Comet assay biomonitoring data, in order to establish baseline parameters of DNA damage, and to investigate associations between Comet assay measurements and factors such as sex, age, smoking status, nutrition, lifestyle, etc. With this as its major objective, the ComNet project has recruited almost 100 research groups willing to share datasets. Here we provide a background to this project, discussing the history of the Comet assay and practical issues that can critically affect its performance. We survey its diverse applications in biomonitoring studies, including environmental and occupational exposure to genotoxic agents, genoprotection by dietary and other factors, DNA damage associated with various diseases, and intrinsic factors that affect DNA damage levels in humans. We examine in depth the quality of data from a random selection of studies, from an epidemiological and statistical point of view.
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launch of the comnet Comet network project on the Comet assay in human population studies during the international Comet assay workshop meeting in kusadasi turkey september 13 16 2011
Mutagenesis, 2012Co-Authors: Andrew Collins, Erdem Coskun, Gudrun Koppen, Marcin Kruszewski, Maria Dusinska, Alok Dhawan, Diana Anderson, Massimo Moretti, Emilio RojasAbstract:To whom correspondence should be addressed. Clinical and MolecularEpidemiology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) SanRaffaele Pisana, Via di Val Cannuta, 247, 00166 Rome, Italy. Tel: þ39 0652253418; Fax: þ39 06 52255668; Email: stefano.bonassi@sanraffaele.itReceived on December 27, 2011; revised on February 22, 2012;accepted on February 23, 2012
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recommendations for conducting the in vivo alkaline Comet assay
Mutagenesis, 2003Co-Authors: Andreas Hartmann, E Agurell, Carol Beevers, Susanne Brendlerschwaab, Brian Burlinson, P. Clay, Gunter Speit, Andrew Collins, A. Smith, Veronique ThybaudAbstract:: The in vivo alkaline single cell gel electrophoresis assay, hereafter the Comet assay, can be used to investigate the genotoxicity of industrial chemicals, biocides, agrochemicals and pharmaceuticals. The major advantages of this assay include the relative ease of application to any tissue of interest, the detection of multiple classes of DNA damage and the generation of data at the level of the single cell. These features give the Comet assay potential advantages over other in vivo test methods, which are limited largely to proliferating cells and/or a single tissue. The Comet assay has demonstrated its reliability in many testing circumstances and is, in general, considered to be acceptable for regulatory purposes. However, despite the considerable data published on the in vivo Comet assay and the general agreement within the international scientific community over many protocol-related issues, it was felt that a document giving detailed practical guidance on the protocol required for regulatory acceptance of the assay was required. In a recent meeting held in conjunction with the 4th International Comet Assay Workshop (Ulm, Germany, 22-25 July 2001) an expert panel reviewed existing data and recent developments of the Comet assay with a view to developing such a document. This paper is intended to act as an update to the more general guidelines which were published as a result of the International Workshop on Genotoxicity Test Procedures. The recommendations are also seen as a major step towards gaining more formal regulatory acceptance of the Comet assay.
Andreas Hartmann - One of the best experts on this subject based on the ideXlab platform.
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the in vivo Comet assay use and status in genotoxicity testing
Mutagenesis, 2005Co-Authors: Susanne Brendlerschwaab, Stefan Pfuhler, Andreas Hartmann, Gunter SpeitAbstract:The in vivo Comet assay (single cell gel electrophoresisassay) in itsalkaline version (pH 413) is being increasinglyused in genotoxicity testing of substances such as industrialchemicals, biocides, agrochemicals, food additives andpharmaceuticals. Recommendations for an appropriateperformance of the test using OECD guidelines for otherin vivo genotoxicity tests have been published. In thisreview, we critically discuss the biological significance ofComet assay effects in general and the status of the test incurrent strategies for genotoxicity testing. Examples forpractical applications of the in vivo Comet assay and poten-tial consequences of positive and negative test results aregiven. The significance of Comet assay results for hazardidentification and risk assessment is discussed. In accord-ance with international guidelines for genotoxicity testingthe in vivo Comet assay is recommended for follow-up test-ing of positive in vitro findings. It is particularly useful asa tool for the evaluation of local genotoxicity, especially fororgans/cell types which cannot easily be evaluated withother standard tests. A positive result in an appropriatelyperformed in vivo Comet assay indicates genotoxicity ofthe test compound in the tissue tested and gains particularsignificance when a mutagenic potential of the test com-pound has already been demonstrated in vitro. Such find-ings will have practical consequences in the risk assessmentprocesses and further development of substances.IntroductionThe in vivo Comet assay (single cell gel electrophoresis) isincreasingly being used in genotoxicity testing. The advantagesof the in vivo Comet assay include its applicability to varioustissues and/or special cell types, its sensitivity for detecting lowlevels of DNA damage, its requirement for small numbers ofcells per sample, general ease of test performance, the shorttime needed to complete a study and its relatively low cost (1).Following current OECD guidelines for other in vivo geno-toxicity tests, international expert groups have publishedrecommendations describing standards aiming at high qualityprotocols in order to obtain valid and reliable data (1,2).Therefore, aspects of the Comet assay protocol will not be dis-cussed here. However, it has to be emphasized that the qualityof the study protocol and the experimental performance is ofcrucial importance for the scientific and regulatory acceptanceof Comet assay results.In this paper, the biological significance of Comet assayresults is discussed, the status of the in vivo Comet assay incurrent strategies for genotoxicity testing is described andexamples of current applications of the in vivo Comet assay inindustrial genotoxicity testing are given. Using these examples,possible consequences of invivoComet assay results for hazardidentification and risk assessment are discussed.DNA damage detected by the Comet assayThe alkaline version (pH 413), which is exclusively discussedhere, can be used to detect DNA damage such as strand breaks,alkali-labile sites (ALS), DNA-- DNA and DNA-- protein cross-links. In contrast to other DNA alterations, cross-links maystabilize chromosomal DNA and inhibit DNA migration (3,4).Thus, reduced DNA migration in comparison to the negativecontrol (which should show some degree of DNA migration)may indicate the induction of crosslinks, which are relevantlesions with regard to mutagenesis and should be further invest-igated. Increased DNA migration indicates the induction ofDNAstrandbreaksand/orALS.Furthermore,enhancedactivityofexcisionrepairmayresultinincreasedDNA migration.DNAexcision repair can influence Comet assay effects in a complexway (5). While DNA repair generally reduces DNA migrationby eliminating DNA lesions, ongoing excision repair mayincrease DNA migration due to incision-related DNA strandbreaks. Thus, the contribution of excision repair to the DNAeffects seen in the Comet assay depends on the types of inducedprimary DNA damage and the time point of analysis (6).DNA lesions leading to effects in the Comet assay can notonly be strand breaks, which may be relevant for the formationof chromosome aberrations, but also DNA modifications suchas abasic sites (AP sites) with relevance for the induction ofgene mutations. However, it has to be recognized that the prim-ary lesions detected by the Comet assay may also be correctlyrepaired without resulting in permanent genetic alterations.Neither the extent of DNA migration in the Comet assay northe shape of the Comet can reveal the mode of action or themutagenic potential of a test substance.There are only few limitations of the Comet assay withregard to its application and interpretation. Short-lived primaryDNA lesions such as single strand breaks, which may undergorapid DNA repair, could be missed when using inadequatesampling times. However, an appropriate study design includ-ing one early preparation time point (i.e. at 2-- 6 h) shouldensure that these lesions are captured. A general issue with‘DNA strand break assays’ such as the Comet assay is thatindirect mechanisms related to cytotoxicity can lead to positiveeffects. However, an advantage of the Comet assay comparedwith other techniques analysing DNA damage in tissues (suchas the alkaline elution method) is that DNA damage is assessedon the level of individual cells. Thus, dead or dying cells may
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comparative study with the alkaline Comet assay and the chromosome aberration test
Mutation Research-genetic Toxicology and Environmental Mutagenesis, 2003Co-Authors: Andreas Hartmann, U Plappert, Franziska Poetter, Willi SuterAbstract:The alkaline Comet assay is becoming a useful tool for early genotoxicity testing of new pharmaceutical drug candidates. The aim of this study was to elucidate the predictive value of Comet assay results for the outcome of the chromosome aberration (CA) test. For this purpose, a validation exercise with 13 drug candidates was carried out utilizing V79 Chinese hamster cells and human lymphocytes. The study demonstrates that results of the Comet assay and the chromosome aberration test show a high degree of agreement, irrespective of the cell type used. In the Comet assay, seven compounds were positive and six were negative, while in the CA test, six were positive and seven were negative. The only discrepancy was found with one compound that was positive in the Comet assay with V79 cells, negative in the Comet assay with human lymphocytes and clearly negative in the CA test with human lymphocytes. For the selection of concentrations for testing in the Comet assay, cytotoxicity by means of cell count after incubation or viability by means of Trypan-blue dye exclusion (TBDE) were used. The results show that either parameter led to analysis of a concentration range in the Comet assay similar to that chosen in the CA test, in which cell count (when using V79 cells) or mitotic index (in case of lymphocytes) were used. However, since cell count after incubation of cells is much more labour-intensive, viability was preferred as the parameter to assess cytotoxicity and for selecting concentrations for analysis in the Comet assay. The data presented in this study may contribute the regulatory acceptance of the Comet assay, e.g. for mechanistic studies.
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recommendations for conducting the in vivo alkaline Comet assay
Mutagenesis, 2003Co-Authors: Andreas Hartmann, E Agurell, Carol Beevers, Susanne Brendlerschwaab, Brian Burlinson, P. Clay, Gunter Speit, Andrew Collins, A. Smith, Veronique ThybaudAbstract:: The in vivo alkaline single cell gel electrophoresis assay, hereafter the Comet assay, can be used to investigate the genotoxicity of industrial chemicals, biocides, agrochemicals and pharmaceuticals. The major advantages of this assay include the relative ease of application to any tissue of interest, the detection of multiple classes of DNA damage and the generation of data at the level of the single cell. These features give the Comet assay potential advantages over other in vivo test methods, which are limited largely to proliferating cells and/or a single tissue. The Comet assay has demonstrated its reliability in many testing circumstances and is, in general, considered to be acceptable for regulatory purposes. However, despite the considerable data published on the in vivo Comet assay and the general agreement within the international scientific community over many protocol-related issues, it was felt that a document giving detailed practical guidance on the protocol required for regulatory acceptance of the assay was required. In a recent meeting held in conjunction with the 4th International Comet Assay Workshop (Ulm, Germany, 22-25 July 2001) an expert panel reviewed existing data and recent developments of the Comet assay with a view to developing such a document. This paper is intended to act as an update to the more general guidelines which were published as a result of the International Workshop on Genotoxicity Test Procedures. The recommendations are also seen as a major step towards gaining more formal regulatory acceptance of the Comet assay.
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Use of the alkaline Comet assay for industrial genotoxicity screening: comparative investigation with the micronucleus test.
Food and Chemical Toxicology, 2001Co-Authors: Andreas Hartmann, Franziska Poetter, Wilfried Frieauff, Azeddine Elhajouji, Evangelos Kiskinis, Hans-jörg Martus, A Fjällman, Willi SuterAbstract:We evaluated the suitability of the alkaline Comet assay as a screening test in industrial routine testing of new chemicals. Thirty-six pharmaceutical compounds with unknown genotoxic potential were tested comparatively in the Comet assay and micronucleus test (MNT) using V79 Chinese hamster cells. The comparison of results is generally based on at least two independent experiments, each with two replicate cultures at a minimum of three concentrations. We found a high degree of concordance between results of the Comet assay and MNT. All compounds with negative MNT results were also negative in the Comet assay. All positive compounds in the Comet assay were also positive in the MNT. However, 16 of 38 positive MNT results were negative in the Comet assay. Some of the contrary findings may be due to aneugenic effects, which are detected in the MNT but not in the Comet assay. However, the majority of the contrary results may be a consequence of cytotoxicity, which can induce elevated micronucleus frequencies but may not lead to positive effects in the Comet assay. Additional data of 39 compounds tested in the Ames test and the Comet assay were compared. Four of these compounds that were Ames positive were also positive in the Comet assay. However, the Comet assay also detected 16 compounds that were negative in the Ames test. We believe that the Comet assay in vitro is a useful, fast screening system in mammalian cells that can be used in a test battery during drug development.
Coronel R. - One of the best experts on this subject based on the ideXlab platform.
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Comet 21P/Giacobini-Zinner: Water production activity over 20 years with SOHO/SWAN
'Elsevier BV', 2021Co-Authors: Combi M.r., Mäkinen T., Bertaux Jean-loup, Quémerais Eric, Ferron Stéphane, Coronel R.Abstract:International audienceIn 1985 Comet 21P/Giacobini-Zinner was the first Comet visited by a spacecraft, the International Cometary Explorer (ICE) satellite, several months before the armada of Halley spacecraft had their encounters in 1986. ICE was originally the ISEE-3 satellite, designed for magnetospheric measurements near the Earth, and was diverted via a lunar gravity assist to pass through the plasma tail of the Comet. The Comet has been observed by the all-sky hydrogen Lyman-alpha Solar Wind Anisotropies (SWAN) camera on the SOlar and Heliospheric Observatory satellite during its last four apparitions in 1998, 2005, 2012 and 2018. This paper compares water production rates calculated from the hydrogen images from the 1998 and 2005 results, published by Combi et al. (2011), with new observations from 2012 and 2018. Unlike some Comets that have faded over time, except for 2 outbursts seen in the 2012 results, the activity levels for Comet 21P have not changed consistently over time
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Comet 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova, and 46P/Wirtanen: Water Production Activity over 21 Years with SOHO/SWAN
IOP Science, 2020Co-Authors: Combi, Michael R., Mäkinen T., Bertaux Jean-loup, Quémerais Eric, Ferron Stéphane, Coronel R.Abstract:International audienceIn 2017, 2018 and 2019, Comets 46P/Wirtanen, 45P/Honda-Mrkos-Pajdusakova, and 41P/Tuttle-Giacobini-Kresak all had perihelion passages. Their hydrogen comae were observed by the Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha Camera on the SOlar and Heliospheric Observer (SOHO) satellite: Comet 46P for the fourth time and Comets 45P and 41P for the third time each since 1997. Comet 46P/Wirtanen is one of a small class of so-called hyperactive Comets whose gas production rates belie their small size. This Comet was the original target Comet of the Rosetta mission. The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the SOlar and Heliospheric Observer (SOHO) satellite observed the hydrogen coma of Comet 46P/Wirtanen during the apparitions of 1997, 2002, 2008 and 2018. Over the 22 years, the activity decreased and its variation with heliocentric distance has changed markedly in a way very similar to that of another hyperactive Comet, 103P/Hartley 2. Comet 45P/Honda-Mrkos-Pajdusakova was observed by SWAN during its perihelion apparitions of 2001, 2011 and 2017. Over this time period the activity level has remained remarkably similar, with no long-term fading or abrupt decreases. Comet 41P/Tuttle-Giacobini-Kresak was observed by SWAN in its perihelion apparitions of 2001, 2006 and 2017 and has decreased in activity markedly over the same time period. In 1973 it was known for large outbursts, which continued during the 2001 (2 outbursts) and 2006 (1 outburst) apparitions. However, over the 2001 to 2017 time period covered by the SOHO/SWAN observations the water production rates have greatly decreased by factors of 10-30 over corresponding times during its orbit
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Comet 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova, and 46P/Wirtanen: Water Production Activity over 21 Years with SOHO/SWAN
2020Co-Authors: Combi M. R., Mäkinen T., Bertaux J. -l., Quémerais E., Ferron S., Coronel R.Abstract:In 2017, 2018 and 2019, Comets 46P/Wirtanen, 45P/Honda-Mrkos-Pajdusakova, and 41P/Tuttle-Giacobini-Kresak all had perihelion passages. Their hydrogen comae were observed by the Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha Camera on the SOlar and Heliospheric Observer (SOHO) satellite: Comet 46P for the fourth time and Comets 45P and 41P for the third time each since 1997. Comet 46P/Wirtanen is one of a small class of so-called hyperactive Comets whose gas production rates belie their small size. This Comet was the original target Comet of the Rosetta mission. The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the SOlar and Heliospheric Observer (SOHO) satellite observed the hydrogen coma of Comet 46P/Wirtanen during the apparitions of 1997, 2002, 2008 and 2018. Over the 22 years, the activity decreased and its variation with heliocentric distance has changed markedly in a way very similar to that of another hyperactive Comet, 103P/Hartley 2. Comet 45P/Honda-Mrkos-Pajdusakova was observed by SWAN during its perihelion apparitions of 2001, 2011 and 2017. Over this time period the activity level has remained remarkably similar, with no long-term fading or abrupt decreases. Comet 41P/Tuttle-Giacobini-Kresak was observed by SWAN in its perihelion apparitions of 2001, 2006 and 2017 and has decreased in activity markedly over the same time period. In 1973 it was known for large outbursts, which continued during the 2001 (2 outbursts) and 2006 (1 outburst) apparitions. However, over the 2001 to 2017 time period covered by the SOHO/SWAN observations the water production rates have greatly decreased by factors of 10-30 over corresponding times during its orbit.Comment: 17 Pages, 6 Figures, 4 Tables, accepted by Planetary Science Journa
K J Meech - One of the best experts on this subject based on the ideXlab platform.
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the similarity of the interstellar Comet 2i borisov to solar system Comets from high resolution optical spectroscopy
Astronomy and Astrophysics, 2021Co-Authors: Cyrielle Opitom, Emmanuel Jehin, Damien Hutsemekers, Yoshiharu Shinnaka, Jean Manfroid, Philippe Rousselot, Susarla Raghuram, Hideyo Kawakita, A Fitzsimmons, K J MeechAbstract:2I/Borisov - hereafter 2I - is the first visibly active interstellar Comet observed in the solar system, allowing us for the first time to sample the composition of a building block from another system. We report on the monitoring of 2I with UVES, the high resolution optical spectrograph of the ESO Very Large Telescope at Paranal, during four months from November 15, 2019 to March 16, 2020. Our goal is to characterize the activity and composition of 2I with respect to solar system Comets. We collected high resolution spectra at 12 different epochs from 2.1 au pre-perihelion to 2.6 au post perihelion. On December 24 and 26, 2019, close to perihelion, we detected several OH lines of the 309 nm (0-0) band and derived a water production rate of $2.2\pm0.2 \times 10^{26}$ molecules/s. The three [OI] forbidden oxygen lines were detected at different epochs and we derive a green-to-red doublet intensity ratio (G/R) of $0.31\pm0.05$ close to perihelion. NH$_2$ ortho and para lines from various bands were measured and allowed us to derive an ortho-to-para ratio (OPR) of $3.21\pm0.15$, corresponding to an OPR and spin temperature of ammonia of $1.11\pm0.08$ and $31^{+10}_{-5}$ K, respectively. These values are consistent with the values usually measured for solar system Comets. Emission lines of the radicals NH (336 nm), CN (388 nm), CH (431 nm), and C$_2$ (517 nm) were also detected. Several FeI and NiI lines were identified and their intensities were measured to provide a ratio of log (NiI/FeI) = $0.21\pm0.18$ in agreement with the value recently found in solar system Comets. Our high spectral resolution observations of 2I/Borisov and the associated measurements of the NH$_2$ OPR and the Ni/Fe abundance ratio are remarkably similar to solar system Comets. Only the G/R ratio is unusually high but consistent with the high abundance ratio of CO/H$_2$O found by other investigators.
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pre discovery activity of new interstellar Comet 2i borisov beyond 5 au
The Astronomical Journal, 2020Co-Authors: Michael S P Kelley, K J Meech, Bryce Bolin, Dennis Bodewits, Davide Farnocchia, Frank J Masci, M Micheli, R J Weryk, Eric C Bellm, E ChristensenAbstract:Comet 2I/Borisov, the first unambiguous interstellar Comet ever found, was discovered in 2019 August at ~3 au from the Sun on its inbound leg. No pre-discovery detection beyond 3 au has yet been reported, mostly due to the Comet's proximity to the Sun as seen from the Earth. Here we present a search for pre-discovery detections of Comet Borisov using images taken by the Catalina Sky Survey, Pan-STARRS, and the Zwicky Transient Facility (ZTF), with a further comprehensive follow-up campaign being presented in Bolin et al. We identified Comet Borisov in ZTF images taken in 2019 May and use these data to update its orbit. This allowed us to identify the Comet in images acquired as far back as 2018 December, when it was 7.8 au from the Sun. The Comet was not detected in 2018 November when it was 8.6 au from the Sun, possibly implying an onset of activity around this time. This suggests that the activity of the Comet is either driven by a more volatile species other than H₂O, such as CO or CO₂, or by exothermic crystallization of amorphous ice. We derive the radius of the nucleus to be <7 km using the non-detection in 2018 November, and estimate an area of ~0.5–10 km² has been active between 2018 December and 2019 September, though this number is model-dependent and is highly uncertain. The behavior of Comet Borisov during its inbound leg is observationally consistent with dynamically new Comets observed in our solar system, suggesting some similarities between the two.
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pre discovery activity of new interstellar Comet 2i borisov beyond 5 au
arXiv: Earth and Planetary Astrophysics, 2019Co-Authors: Michael S P Kelley, K J Meech, Bryce Bolin, Dennis Bodewits, Davide Farnocchia, Frank J Masci, M Micheli, R J Weryk, Eric C Bellm, E ChristensenAbstract:Comet 2I/Borisov, the first unambiguous interstellar Comet ever found, was discovered in August 2019 at $\sim3$ au from the Sun on its inbound leg. No pre-discovery detection beyond 3 au has yet been reported, mostly due to the Comet's proximity to the Sun as seen from the Earth. Here we present a search for pre-discovery detections of Comet Borisov using images taken by the Catalina Sky Survey (CSS), Pan-STARRS and Zwicky Transient Facility (ZTF), with a further comprehensive follow-up campaign being presented in \citet{Bolin2019}. We identified Comet Borisov in ZTF images taken in May 2019 and use these data to update its orbit. This allowed us to identify the Comet in images acquired as far back as December 2018, when it was 7.8 au from the Sun. The Comet was not detected in November 2018 when it was 8.6 au from the Sun, possibly implying an onset of activity around this time. This suggests that the activity of the Comet is either driven by a more volatile species other than H$_2$O, such as CO or CO$_2$, or by exothermic crystallization of amorphous ice. We derive the radius of the nucleus to be $<7$ km using the non-detection in November 2018, and estimate an area of $\sim0.5$---$10 \mathrm{km^2}$ has been active between December 2018 and September 2019, though this number is model-dependent and is highly uncertain. The behavior of Comet Borisov during its inbound leg is observationally consistent with dynamically new Comets observed in our solar system, suggesting some similarities between the two.
Eugenio Picano - One of the best experts on this subject based on the ideXlab platform.
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ultrasound Comet tail images a marker of pulmonary edema a comparative study with wedge pressure and extravascular lung water
Chest, 2005Co-Authors: Eustachio Agricola, Tiziana Bove, Michele Oppizzi, Giovanni Marino, Alberto Zangrillo, Alberto Margonato, Eugenio PicanoAbstract:Background: Echographic examination of the lung surface may reveal multiple “Comet-tail images” originating from water-thickened interlobular septa. These images could be useful for noninvasive assessment of interstitial pulmonary edema. Study objective: The purpose of this study was to assess the diagnostic accuracy of lung Comet-tail images compared with chest radiography, wedge pressure, and extravascular lung water (EVLW) quantified by the indicator dilution method (PiCCO System, version 4.1; Pulsion Medical Systems; Munich, Germany). Methods and patients: We enrolled 20 patients (mean age, 62.6 11.5 years [ SD]). Patients were studied before, immediately after, and 24 h following cardiac surgery with chest ultrasound, chest radiography, pulmonary artery catheterization, and the PiCCO system. Performing echo scanning (right and left hemithorax, from second to fourth intercostal space, from parasternal to midaxillary line), an individual patient Comet score was obtained by summing the number of Comets in each scanned space. Results: A total of 60 comparisons were obtained. Significant positive linear correlations were found between Comet score and EVLW determined by the PiCCO System (r 0.42, p 0.001), between Comet score and wedge pressure (r 0.48, p 0.01), and between Comet score and radiologic lung water score (r 0.60, p 0.0001). Conclusions: The presence and the number of Comet-tail images provide reliable information on interstitial pulmonary edema. Therefore, ultrasonography represent an attractive, easy-to-use, bedside diagnostic tool for assessing cardiac function and pulmonary congestion. (CHEST 2005; 127:1690–1695)
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usefulness of ultrasound lung Comets as a nonradiologic sign of extravascular lung water
American Journal of Cardiology, 2004Co-Authors: Zoltan Jambrik, Eustachio Agricola, Simonetta Monti, Vincenzo Coppola, G Mottola, Massimo Miniati, Eugenio PicanoAbstract:The "Comet-tail" is an ultrasound sign detectable with ultrasound chest instruments; this sign consists of multiple Comet-tails fanning out from the lung surface. They originate from water-thickened interlobular septa and would be ideal for nonradiologic bedside assessment of extravascular lung water. To assess the feasibility and value of ultrasonic Comet signs, we studied 121 consecutive hospitalized patients (43 women and 78 men; aged 67 +/- 12 years) admitted to our combined cardiology-pneumology department (including cardiac intensive care unit); the study was conducted with commercially available echocardiographic systems including a portable unit. Transducer frequencies (range 2.5 to 3.5 MHz) were used. In each patient, the right and left chest was scanned by examining predefined locations in multiple intercostal spaces. Examiners blinded to clinical diagnoses noted the presence and numbers of lung Comets at each examining site. A patient lung Comet score was obtained by summing the number of Comets in each of the scanning spaces. Within a few minutes, patients underwent chest x-ray, with specific assessment of extravascular lung water score by 2 pneumologist-radiologists blinded to clinical and echo findings. The chest ultrasound scan was obtained in all patients (feasibility 100%). The imaging time per examination was always <3 minutes. There was a linear correlation between echocardiographic Comet score and radiologic lung water score (r = 0.78, p <0.01). Intrapatient variations (n = 15) showed an even stronger correlation between changes in echocardiographic lung Comet and radiologic lung water scores (r = 0.89; p <0.01). In 121 consecutive hospitalized patients, we found a linear correlation between echocardiographic Comet scores and radiologic extravascular lung water scores. Thus, the Comet-tail is a simple, non-time-consuming, and reasonably accurate chest ultrasound sign of extravascular lung water that can be obtained at bedside (also with portable echocardiographic equipment) and is not restricted by cardiac acoustic window limitations.
