The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Joshua Tyler - One of the best experts on this subject based on the ideXlab platform.
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the mystery of the cosmic diffuse ultraviolet Background Radiation
The Astrophysical Journal, 2014Co-Authors: R C Henry, Jayant Murthy, James Overduin, Joshua TylerAbstract:The diffuse cosmic Background Radiation in the Galaxy Evolution Explorer far-ultraviolet (FUV, 1300-1700 ?) is deduced to originate only partially in the dust-scattered Radiation of FUV-emitting stars: the source of a substantial fraction of the FUV Background Radiation remains a mystery. The Radiation is remarkably uniform at both far northern and far southern Galactic latitudes and increases toward lower Galactic latitudes at all Galactic longitudes. We examine speculation that this might be due to interaction of the dark matter with the nuclei of the interstellar medium, but we are unable to point to a plausible mechanism for an effective interaction. We also explore the possibility that we are seeing Radiation from bright FUV-emitting stars scattering from a second population of interstellar grains?grains that are small compared with FUV wavelengths. Such grains are known to exist, and they scatter with very high albedo, with an isotropic scattering pattern. However, comparison with the observed distribution (deduced from their 100 ?m emission) of grains at high Galactic latitudes shows no correlation between the grains' location and the observed FUV emission. Our modeling of the FUV scattering by small grains also shows that there must be remarkably few such smaller grains at high Galactic latitudes, both north and south; this likely means simply that there is very little interstellar dust of any kind at the Galactic poles, in agreement with Perry and Johnston. We also review our limited knowledge of the cosmic diffuse Background at ultraviolet wavelengths shortward of Ly??it could be that our second component of the diffuse FUV Background persists shortward of the Lyman limit and is the cause of the reionization of the universe.
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the mystery of the cosmic diffuse ultraviolet Background Radiation
arXiv: Astrophysics of Galaxies, 2014Co-Authors: R C Henry, Jayant Murthy, James Overduin, Joshua TylerAbstract:The diffuse cosmic Background Radiation in the GALEX far ultraviolet (FUV, 1300 \AA\ - 1700 \AA) is deduced to originate only partially in the dust-scattered Radiation of FUV-emitting stars: the source of a substantial fraction of the FUV Background Radiation remains a mystery. The Radiation is remarkably uniform at both far northern and far southern Galactic latitudes, and it increases toward lower Galactic latitudes at all Galactic longitudes. We examine speculation that it might be due to interaction of the dark matter with the nuclei of the interstellar medium but we are unable to point to a plausible mechanism for an effective interaction. We also explore the possibility that we are seeing Radiation from bright FUV-emitting stars scattering from a "second population" of interstellar grains---grains that are small compared with FUV wavelengths. Such grains are known to exist (Draine 2011) and they scatter with very high albedo, with an isotropic scattering pattern. However, comparison with the observed distribution (deduced from their $100\ \mu$m emission) of grains at high Galactic latitudes shows no correlation between the grains' location and the observed FUV emission. Our modeling of the FUV scattering by small grains also shows that there must be remarkably few such "smaller" grains at high Galactic latitudes, both North and South; this likely means simply that there is very little interstellar dust of any kind at the Galactic poles, in agreement with Perry & Johnston (1982). We also review our limited knowledge of the cosmic diffuse Background at ultraviolet wavelengths shortward of Lyman $\alpha$---it could be that our "second component" of the diffuse far-ultraviolet Background persists shortward of the Lyman limit, and is the cause of the re-ionization of the Universe (Kollmeier et al. 2014).
Anilkumar Gopinathan - One of the best experts on this subject based on the ideXlab platform.
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Radionuclides and Radiation Indices of High Background Radiation Area in Chavara-Neendakara Placer Deposits (Kerala, India)
2016Co-Authors: Mary Thomas Derin, Perumal Vijayagopal, Balasubramaniam Venkatraman, Ra Chaubey, Anilkumar GopinathanAbstract:The present paper describes a detailed study on the distribution of radionuclides along Chavara – Neendakara placer deposit, a high Background Radiation area (HBRA) along the Southwest coast of India (Kerala). Judged from our studies using HPGe gamma spectrometric detector, it becomes evident that Uranium (238U), Thorium (232Th) and Potassium (40K) are the major sources for radioactivity prevailing in the area. Our statistical analyses reveal the existence of a high positive correlation between 238U and 232Th, implicating that the levels of these elements are interdependent. Our SEM-EDAX analyses reveal that titanium (Ti) and zircon (Zr) are the major trace elements in the sand samples, followed by aluminum, copper, iron, ruthenium, magnesium, calcium, sulphur and lead. This is first of its kind report on the Radiation hazard indices on this placer deposit. The average absorbed dose rates (9795 nGy h21) computed from the present study is comparable with the top-ranking HBRAs in the world, thus offering the Chavara-Neendakara placer the second position, after Brazil; pertinently, this value is much higher than the World average. The perceptibly high absorbed gamma dose rates, entrained with the high annual external effective dose rates (AEED) and average annual gonadal dose equivalent (AGDE) values existing in this HBRA, encourage us to suggest for a candid assessment of the impact of the Background Radiation, if any, on the organisms that inhabit along this placer deposit. Future research could effectively address the issue of the possibl
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Radionuclides and Radiation indices of high Background Radiation area in Chavara-Neendakara placer deposits (Kerala, India).
PloS one, 2012Co-Authors: Mary Thomas Derin, Perumal Vijayagopal, Balasubramaniam Venkatraman, R.c. Chaubey, Anilkumar GopinathanAbstract:The present paper describes a detailed study on the distribution of radionuclides along Chavara – Neendakara placer deposit, a high Background Radiation area (HBRA) along the Southwest coast of India (Kerala). Judged from our studies using HPGe gamma spectrometric detector, it becomes evident that Uranium (238U), Thorium (232Th) and Potassium (40K) are the major sources for radioactivity prevailing in the area. Our statistical analyses reveal the existence of a high positive correlation between 238U and 232Th, implicating that the levels of these elements are interdependent. Our SEM-EDAX analyses reveal that titanium (Ti) and zircon (Zr) are the major trace elements in the sand samples, followed by aluminum, copper, iron, ruthenium, magnesium, calcium, sulphur and lead. This is first of its kind report on the Radiation hazard indices on this placer deposit. The average absorbed dose rates (9795 nGy h−1) computed from the present study is comparable with the top-ranking HBRAs in the world, thus offering the Chavara-Neendakara placer the second position, after Brazil; pertinently, this value is much higher than the World average. The perceptibly high absorbed gamma dose rates, entrained with the high annual external effective dose rates (AEED) and average annual gonadal dose equivalent (AGDE) values existing in this HBRA, encourage us to suggest for a candid assessment of the impact of the Background Radiation, if any, on the organisms that inhabit along this placer deposit. Future research could effectively address the issue of the possible impact of natural Radiation on the biota inhabiting this HBRA.
Anssi Auvinen - One of the best experts on this subject based on the ideXlab platform.
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Background Radiation and childhood leukemia a nationwide register based case control study
International Journal of Cancer, 2016Co-Authors: Atte Nikkila, Sini Erme, H Arvela, Olli Holmgren, Jani Raitanen, Olli Lohi, Anssi AuvinenAbstract:High doses of ionizing Radiation are an established cause of childhood leukemia. However, substantial uncertainty remains about the effect of low doses of Radiation, including Background Radiation and potential differences between genetic subgroups of leukemia have rarely been explored. We investigated the effect of the Background gamma Radiation on childhood leukemia using a nationwide register-based case-control study. For each of the 1,093 cases, three age- and gender matched controls were selected (N = 3,279). Conditional logistic regression analyses were adjusted for confounding by Down syndrome, birth weight (large for gestational age), and maternal smoking. Complete residential histories and previously collected survey data of the Background gamma Radiation in Finland were used to assess the exposure of the study subjects to indoor and outdoor gamma Radiation. Overall, Background gamma Radiation showed a non-significant association with the OR of childhood leukemia (OR 1.01, 95% CI 0.97, 1.05 for 10 nSv/h increase in average equivalent dose rate to red bone marrow). In subgroup analyses, age group 2-<7 years displayed a larger effect (OR 1.27, 95% CI 1.01, 1.60 for 1 mSv increase in equivalent cumulative dose to red bone marrow). Suggestive difference in OR by genetic subtype was found. Our results provide further support to the notion that low doses of ionizing Radiation increase the risk for childhood leukemia, particularly at age 2-<7 years. Our findings suggest a larger effect of Radiation on leukemia with high hyperpdiploidy than other subgroups, but this result requires further confirmation.
Mary Thomas Derin - One of the best experts on this subject based on the ideXlab platform.
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Radionuclides and Radiation Indices of High Background Radiation Area in Chavara-Neendakara Placer Deposits (Kerala, India)
2016Co-Authors: Mary Thomas Derin, Perumal Vijayagopal, Balasubramaniam Venkatraman, Ra Chaubey, Anilkumar GopinathanAbstract:The present paper describes a detailed study on the distribution of radionuclides along Chavara – Neendakara placer deposit, a high Background Radiation area (HBRA) along the Southwest coast of India (Kerala). Judged from our studies using HPGe gamma spectrometric detector, it becomes evident that Uranium (238U), Thorium (232Th) and Potassium (40K) are the major sources for radioactivity prevailing in the area. Our statistical analyses reveal the existence of a high positive correlation between 238U and 232Th, implicating that the levels of these elements are interdependent. Our SEM-EDAX analyses reveal that titanium (Ti) and zircon (Zr) are the major trace elements in the sand samples, followed by aluminum, copper, iron, ruthenium, magnesium, calcium, sulphur and lead. This is first of its kind report on the Radiation hazard indices on this placer deposit. The average absorbed dose rates (9795 nGy h21) computed from the present study is comparable with the top-ranking HBRAs in the world, thus offering the Chavara-Neendakara placer the second position, after Brazil; pertinently, this value is much higher than the World average. The perceptibly high absorbed gamma dose rates, entrained with the high annual external effective dose rates (AEED) and average annual gonadal dose equivalent (AGDE) values existing in this HBRA, encourage us to suggest for a candid assessment of the impact of the Background Radiation, if any, on the organisms that inhabit along this placer deposit. Future research could effectively address the issue of the possibl
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Radionuclides and Radiation indices of high Background Radiation area in Chavara-Neendakara placer deposits (Kerala, India).
PloS one, 2012Co-Authors: Mary Thomas Derin, Perumal Vijayagopal, Balasubramaniam Venkatraman, R.c. Chaubey, Anilkumar GopinathanAbstract:The present paper describes a detailed study on the distribution of radionuclides along Chavara – Neendakara placer deposit, a high Background Radiation area (HBRA) along the Southwest coast of India (Kerala). Judged from our studies using HPGe gamma spectrometric detector, it becomes evident that Uranium (238U), Thorium (232Th) and Potassium (40K) are the major sources for radioactivity prevailing in the area. Our statistical analyses reveal the existence of a high positive correlation between 238U and 232Th, implicating that the levels of these elements are interdependent. Our SEM-EDAX analyses reveal that titanium (Ti) and zircon (Zr) are the major trace elements in the sand samples, followed by aluminum, copper, iron, ruthenium, magnesium, calcium, sulphur and lead. This is first of its kind report on the Radiation hazard indices on this placer deposit. The average absorbed dose rates (9795 nGy h−1) computed from the present study is comparable with the top-ranking HBRAs in the world, thus offering the Chavara-Neendakara placer the second position, after Brazil; pertinently, this value is much higher than the World average. The perceptibly high absorbed gamma dose rates, entrained with the high annual external effective dose rates (AEED) and average annual gonadal dose equivalent (AGDE) values existing in this HBRA, encourage us to suggest for a candid assessment of the impact of the Background Radiation, if any, on the organisms that inhabit along this placer deposit. Future research could effectively address the issue of the possible impact of natural Radiation on the biota inhabiting this HBRA.
F Hoyle - One of the best experts on this subject based on the ideXlab platform.
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inhomogeneities in the microwave Background Radiation interpreted within the framework of the quasi steady state cosmology
The Astrophysical Journal, 2003Co-Authors: J V Narlikar, R G Vishwakarma, Amir Hajian, T Souradeep, G R Burbidge, F HoyleAbstract:We calculate the expected angular power spectrum of the temperature fluctuations in the microwave Background Radiation (MBR) generated in the quasi-steady state cosmology (QSSC). The paper begins with a brief description of how the Background is produced and thermalized in the QSSC. We then discuss within the framework of a simple model the likely sources of fluctuations in the Background due to astrophysical and cosmological causes. Power spectrum peaks at l ≈ 6-10, 180-220, and 600-900 are shown to be respectively related in this cosmology to curvature effects at the last minimum of the scale factor, clusters, and groups of galaxies. The effect of clusters is shown to be related to their distribution in space as indicated by a toy model of structure formation in the QSSC. We derive and parameterize the angular power spectrum using six parameters related to the sources of temperature fluctuations at three characteristic scales. We are able to obtain a satisfactory fit to the observational band power estimates of the MBR temperature fluctuation spectrum. Moreover, the values of the best-fit parameters are consistent with the range of expected values.
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inhomogeneities in the microwave Background Radiation interpreted within the framework of the quasi steady state cosmology
arXiv: Astrophysics, 2002Co-Authors: J V Narlikar, R G Vishwakarma, Amir Hajian, T Souradeep, G R Burbidge, F HoyleAbstract:We calculate the expected angular power spectrum of the temperature fluctuations in the microwave Background Radiation (MBR) generated in the quasi-steady state cosmology (QSSC). The paper begins with a brief description of how the Background is produced and thermalized in the QSSC. We then discuss within the framework of a simple model, the likely sources of fluctuations in the Background due to astrophysical and cosmological causes. Power spectrum peaks at $l \approx 6-10$, 180-220 and 600-900 are shown to be related in this cosmology respectively to curvature effects at the last minimum of the scale factor, clusters and groups of galaxies. The effect of clusters is shown to be related to their distribution in space as indicated by a toy model of structure formation in the QSSC. We derive and parameterize the angular power spectrum using six parameters related to the sources of temperature fluctuations at three characteristic scales. We are able to obtain a satisfactory fit to the observational band power estimates of MBR temperature fluctuation spectrum. Moreover, the values of `best fit' parameters are consistent with the range of expected values.
