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E Grun - One of the best experts on this subject based on the ideXlab platform.

  • a homogeneous nucleus for comet 67p churyumov gerasimenko from its gravity field
    Nature, 2016
    Co-Authors: M Patzold, T Andert, Matthias Hahn, S W Asmar, J P Barriot, M K Bird, B Hausler, Kerstin Peter, Silvia Tellmann, E Grun
    Abstract:

    Cometary nuclei consist mostly of dust and water ice(1). Previous observations have found nuclei to be low-density and highly porous bodies(2-4), but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kiloMetres. The gravitational point mass is GM = 666.2 +/- 0.2 Cubic Metres per second squared, giving a mass M = (9,982 +/- 3) x 10(9) kilograms. Together with the current estimate of the volume of the nucleus(5), the average bulk density of the nucleus is 533 +/- 6 kilograms per Cubic Metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1(2,3). The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.

E. Gruen - One of the best experts on this subject based on the ideXlab platform.

  • A homogeneous nucleus for comet 67P/Churyumov-Gerasimenko from its gravity field
    Nature, 2016
    Co-Authors: M. Paetzold, T Andert, Matthias Hahn, S W Asmar, J P Barriot, M K Bird, Kerstin Peter, Silvia Tellmann, B. Haeusler, E. Gruen
    Abstract:

    Cometary nuclei consist mostly of dust and water ice(1). Previous observations have found nuclei to be low-density and highly porous bodies(2-4), but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kiloMetres. The gravitational point mass is GM = 666.2 +/- 0.2 Cubic Metres per second squared, giving a mass M = (9,982 +/- 3) x 10(9) kilograms. Together with the current estimate of the volume of the nucleus(5), the average bulk density of the nucleus is 533 +/- 6 kilograms per Cubic Metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1(2,3). The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.

Michael J Abramson - One of the best experts on this subject based on the ideXlab platform.

  • outdoor pollen is a trigger of child and adolescent asthma emergency department presentations a systematic review and meta analysis
    Allergy, 2018
    Co-Authors: Bircan Erbas, Mitra Jazayeri, Katrina A Lambert, C Katelaris, Luke A Prendergast, Rachel Tham, M J Parrodi, Janet M Davies, Ed Newbigin, Michael J Abramson
    Abstract:

    Article is free to read on publisher website Abstract Background In the context of increased asthma exacerbations associated with climatic changes such as thunderstorm asthma, interest in establishing the link between pollen exposure and asthma hospital admissions has intensified. Here, we systematically reviewed and performed a meta‐analysis of studies on pollen and emergency department (ED) attendance. Methods A search for studies with appropriate search strategy in MEDLINE, EMBASE, Web of Science and CINAHL was conducted. Each study was assessed for quality and risk of bias. The available evidence was summarized both qualitatively and meta‐analysed using random‐effects models when moderate heterogeneity was observed. Results Fourteen studies were included. The pollen taxa investigated differed between studies, allowing meta‐analysis only of the effect of grass pollen. A statistically significant increase in the percentage change in the mean number of asthma ED presentations (MPC) (pooled results from 3 studies) was observed for an increase in 10 grass pollen grains per Cubic Metre of exposure 1.88% (95% CI = 0.94%, 2.82%). Time series studies showed positive correlations between pollen concentrations and ED presentations. Age‐stratified studies found strongest associations in children aged 5‐17 years old. Conclusion Exposure to ambient grass pollen is an important trigger for childhood asthma exacerbations requiring ED attendance. As pollen exposure is increasingly a problem especially in relation to thunderstorm asthma, studies with uniform measures of pollen and similar analytical methods are necessary to fully understand its impact on human health.

Matthias Hahn - One of the best experts on this subject based on the ideXlab platform.

  • a homogeneous nucleus for comet 67p churyumov gerasimenko from its gravity field
    Nature, 2016
    Co-Authors: M Patzold, T Andert, Matthias Hahn, S W Asmar, J P Barriot, M K Bird, B Hausler, Kerstin Peter, Silvia Tellmann, E Grun
    Abstract:

    Cometary nuclei consist mostly of dust and water ice(1). Previous observations have found nuclei to be low-density and highly porous bodies(2-4), but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kiloMetres. The gravitational point mass is GM = 666.2 +/- 0.2 Cubic Metres per second squared, giving a mass M = (9,982 +/- 3) x 10(9) kilograms. Together with the current estimate of the volume of the nucleus(5), the average bulk density of the nucleus is 533 +/- 6 kilograms per Cubic Metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1(2,3). The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.

  • A homogeneous nucleus for comet 67P/Churyumov-Gerasimenko from its gravity field
    Nature, 2016
    Co-Authors: M. Paetzold, T Andert, Matthias Hahn, S W Asmar, J P Barriot, M K Bird, Kerstin Peter, Silvia Tellmann, B. Haeusler, E. Gruen
    Abstract:

    Cometary nuclei consist mostly of dust and water ice(1). Previous observations have found nuclei to be low-density and highly porous bodies(2-4), but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kiloMetres. The gravitational point mass is GM = 666.2 +/- 0.2 Cubic Metres per second squared, giving a mass M = (9,982 +/- 3) x 10(9) kilograms. Together with the current estimate of the volume of the nucleus(5), the average bulk density of the nucleus is 533 +/- 6 kilograms per Cubic Metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1(2,3). The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.

Silvia Tellmann - One of the best experts on this subject based on the ideXlab platform.

  • a homogeneous nucleus for comet 67p churyumov gerasimenko from its gravity field
    Nature, 2016
    Co-Authors: M Patzold, T Andert, Matthias Hahn, S W Asmar, J P Barriot, M K Bird, B Hausler, Kerstin Peter, Silvia Tellmann, E Grun
    Abstract:

    Cometary nuclei consist mostly of dust and water ice(1). Previous observations have found nuclei to be low-density and highly porous bodies(2-4), but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kiloMetres. The gravitational point mass is GM = 666.2 +/- 0.2 Cubic Metres per second squared, giving a mass M = (9,982 +/- 3) x 10(9) kilograms. Together with the current estimate of the volume of the nucleus(5), the average bulk density of the nucleus is 533 +/- 6 kilograms per Cubic Metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1(2,3). The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.

  • A homogeneous nucleus for comet 67P/Churyumov-Gerasimenko from its gravity field
    Nature, 2016
    Co-Authors: M. Paetzold, T Andert, Matthias Hahn, S W Asmar, J P Barriot, M K Bird, Kerstin Peter, Silvia Tellmann, B. Haeusler, E. Gruen
    Abstract:

    Cometary nuclei consist mostly of dust and water ice(1). Previous observations have found nuclei to be low-density and highly porous bodies(2-4), but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kiloMetres. The gravitational point mass is GM = 666.2 +/- 0.2 Cubic Metres per second squared, giving a mass M = (9,982 +/- 3) x 10(9) kilograms. Together with the current estimate of the volume of the nucleus(5), the average bulk density of the nucleus is 533 +/- 6 kilograms per Cubic Metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1(2,3). The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.