The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
Ralph E. Pudritz - One of the best experts on this subject based on the ideXlab platform.
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Planetary Populations in the Mass-Period Diagram: A Statistical Treatment of Exoplanet Formation and the Role of Planet Traps
The Astrophysical Journal, 2013Co-Authors: Yasuhiro Hasegawa, Ralph E. PudritzAbstract:The rapid growth in the number of known exoplanets has revealed the existence of several distinct planetary populations in the observed mass-period diagram. Two of the most surprising are, (1) the concentration of gas giants around 1AU and (2) the accumulation of a large number of low-mass planets with tight orbits, also known as super-Earths and hot Neptunes. We have recently shown that protoplanetary disks have multiple planet traps that are characterized by orbital radii in the disks and halt rapid type I planetary migration. By coupling planet traps with the standard core accretion scenario, we showed that one can account for the positions of planets in the mass-period diagram. In this paper, we demonstrate quantitatively that most gas giants formed at planet traps tend to end up around 1 AU with most of these being contributed by dead zones and ice lines. In addition, we show that a large fraction of super-Earths and hot Neptunes are formed as "failed" cores of gas giants - this population being constituted by comparable contributions from dead zone and heat transition traps. Our results are based on the evolution of forming planets in an ensemble of disks where we vary only the lifetimes of disks as well as their mass accretion rates onto the host star. We show that a Statistical Treatment of the evolution of a large population of planetary cores initially caught in planet traps accounts for the existence of three distinct exoplantary populations - the hot Jupiters, the more massive planets at roughly orbital radii around 1 AU orbital, and the short period SuperEarths and hot Neptunes. There are very few evolutionary tracks that feed into the large orbital radii characteristic of the imaged Jovian planet, which agrees with recent surveys. Finally, we find that low-mass planets in tight orbits become the dominant planetary population for low mass stars ($M_* \le 0.7 M_{\odot}$).
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planetary populations in the mass period diagram a Statistical Treatment of exoplanet formation and the role of planet traps
The Astrophysical Journal, 2013Co-Authors: Yasuhiro Hasegawa, Ralph E. PudritzAbstract:The rapid growth in the number of known exoplanets has revealed the existence of several distinct planetary populations in the observed mass-period diagram. Two of the most surprising are, (1) the concentration of gas giants around 1AU and (2) the accumulation of a large number of low-mass planets with tight orbits, also known as super-Earths and hot Neptunes. We have recently shown that protoplanetary disks have multiple planet traps that are characterized by orbital radii in the disks and halt rapid type I planetary migration. By coupling planet traps with the standard core accretion scenario, we showed that one can account for the positions of planets in the mass-period diagram. In this paper, we demonstrate quantitatively that most gas giants formed at planet traps tend to end up around 1 AU with most of these being contributed by dead zones and ice lines. In addition, we show that a large fraction of super-Earths and hot Neptunes are formed as ”failed” cores of gas giants - this population being constituted by comparable contributions from dead zone and heat transition traps. Our results are based on the evolution of forming planets in an ensemble of disks where we vary only the lifetimes of disks as well as their mass accretion rates onto the host star. We show that a Statistical Treatment of the evolution of a large population of planetary cores initially caught in planet traps accounts for the existence of three distinct exoplantary populations - the hot Jupiters, the more massive planets at roughly orbital radii around 1 AU orbital, and the short period SuperEarths and hot Neptunes. There are very few evolutionary tracks that feed into the large orbital radii characteristic of the imaged Jovian planet and this is in accord with the result of recent surveys that find a paucity of Jovian planets beyond 10 AU. Finally, we find that low-mass planets in tight orbits become the dominant planetary population for low mass stars (M∗ ≤ 0.7M⊙), in agreement with the previous studies which show that the formation of gas giants is preferred for massive stars.
Yasuhiro Hasegawa - One of the best experts on this subject based on the ideXlab platform.
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Planetary Populations in the Mass-Period Diagram: A Statistical Treatment of Exoplanet Formation and the Role of Planet Traps
The Astrophysical Journal, 2013Co-Authors: Yasuhiro Hasegawa, Ralph E. PudritzAbstract:The rapid growth in the number of known exoplanets has revealed the existence of several distinct planetary populations in the observed mass-period diagram. Two of the most surprising are, (1) the concentration of gas giants around 1AU and (2) the accumulation of a large number of low-mass planets with tight orbits, also known as super-Earths and hot Neptunes. We have recently shown that protoplanetary disks have multiple planet traps that are characterized by orbital radii in the disks and halt rapid type I planetary migration. By coupling planet traps with the standard core accretion scenario, we showed that one can account for the positions of planets in the mass-period diagram. In this paper, we demonstrate quantitatively that most gas giants formed at planet traps tend to end up around 1 AU with most of these being contributed by dead zones and ice lines. In addition, we show that a large fraction of super-Earths and hot Neptunes are formed as "failed" cores of gas giants - this population being constituted by comparable contributions from dead zone and heat transition traps. Our results are based on the evolution of forming planets in an ensemble of disks where we vary only the lifetimes of disks as well as their mass accretion rates onto the host star. We show that a Statistical Treatment of the evolution of a large population of planetary cores initially caught in planet traps accounts for the existence of three distinct exoplantary populations - the hot Jupiters, the more massive planets at roughly orbital radii around 1 AU orbital, and the short period SuperEarths and hot Neptunes. There are very few evolutionary tracks that feed into the large orbital radii characteristic of the imaged Jovian planet, which agrees with recent surveys. Finally, we find that low-mass planets in tight orbits become the dominant planetary population for low mass stars ($M_* \le 0.7 M_{\odot}$).
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planetary populations in the mass period diagram a Statistical Treatment of exoplanet formation and the role of planet traps
The Astrophysical Journal, 2013Co-Authors: Yasuhiro Hasegawa, Ralph E. PudritzAbstract:The rapid growth in the number of known exoplanets has revealed the existence of several distinct planetary populations in the observed mass-period diagram. Two of the most surprising are, (1) the concentration of gas giants around 1AU and (2) the accumulation of a large number of low-mass planets with tight orbits, also known as super-Earths and hot Neptunes. We have recently shown that protoplanetary disks have multiple planet traps that are characterized by orbital radii in the disks and halt rapid type I planetary migration. By coupling planet traps with the standard core accretion scenario, we showed that one can account for the positions of planets in the mass-period diagram. In this paper, we demonstrate quantitatively that most gas giants formed at planet traps tend to end up around 1 AU with most of these being contributed by dead zones and ice lines. In addition, we show that a large fraction of super-Earths and hot Neptunes are formed as ”failed” cores of gas giants - this population being constituted by comparable contributions from dead zone and heat transition traps. Our results are based on the evolution of forming planets in an ensemble of disks where we vary only the lifetimes of disks as well as their mass accretion rates onto the host star. We show that a Statistical Treatment of the evolution of a large population of planetary cores initially caught in planet traps accounts for the existence of three distinct exoplantary populations - the hot Jupiters, the more massive planets at roughly orbital radii around 1 AU orbital, and the short period SuperEarths and hot Neptunes. There are very few evolutionary tracks that feed into the large orbital radii characteristic of the imaged Jovian planet and this is in accord with the result of recent surveys that find a paucity of Jovian planets beyond 10 AU. Finally, we find that low-mass planets in tight orbits become the dominant planetary population for low mass stars (M∗ ≤ 0.7M⊙), in agreement with the previous studies which show that the formation of gas giants is preferred for massive stars.
Helge Erik Solberg - One of the best experts on this subject based on the ideXlab platform.
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RefVal: a program implementing the recommendations of the International Federation of Clinical Chemistry on the Statistical Treatment of reference values
Computer methods and programs in biomedicine, 1995Co-Authors: Helge Erik SolbergAbstract:RefVal is a computer program that implements the recommendations of the International Federation of Clinical Chemistry on the Statistical Treatment of reference values. The program performs the following main tasks: graphical display of the distribution of reference values, identification or elimination of outliers, testing of the fit of the distribution to Gaussian shape (coefficients of skewness and kurtosis, Anderson-Darling's test, Cramer-von Mises' test, Kolmogorov-Smirnov's test), non-parametric and parametric estimation of reference limits (fractiles, percentiles). The parametric estimation method is based on a two-stage mathematical transformation of data: (1) Manly's exponential transformation (to remove skewness) and (2) John and Draper's modulus transformation (to adjust for remaining kurtosis). The program exists in different versions. The paper describes two of these: (1) a library of FORTRAN functions and subroutines and (2) a Pascal PC program that runs under MS-DOS.
J. Ross - One of the best experts on this subject based on the ideXlab platform.
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Statistical Treatment of umbra length inside willow coppice.
Agricultural and Forest Meteorology, 2000Co-Authors: J. Ross, Matti MõttusAbstract:Abstract Measurements of the Statistical characteristics of umbra and sunflecks at different depths inside a willow coppice — Salix viminalis and Salix dasyclados — were carried out at Tartu Observatory, Toravere, Estonia, in 1997. A new instrument, the sunfleck indicator, constructed by M. Sulev, was used. This instrument, moving perpendicularly to rows in the horizontal direction , counts the number and length of sunflecks and umbrae at a level where downward cumulative leaf area index is L . During Statistical data processing, several umbra characteristics — umbra length distribution function, mean number of umbrae, mean umbra length, fractional area of umbra, etc. — were calculated at different measurement heights as the functions of the optical path length τ = L/ sin h , where h is the solar elevation. The number of umbrae N U increases rapidly at small τ , has a maximum at τ ≈ 3–4 and decreases slowly with further increase in τ . This interrelationship was fitted by an exponential function. Umbra length distribution function can be divided into three regions: small umbrae (0–10 cm in length), medium-length umbrae (10–20 cm) and long umbrae (up to 100 cm). At all depths the number of small umbrae exceeds the number of medium-length and long umbrae by 3–10 times. The fractional area of umbra k U ( τ ) increases with τ and was approximated by a rectangular hyperbola. In lower layers ( τ = 8–12) k U ( τ ) reaches 0.85–0.90 and these layers are dominated by umbra.
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Statistical Treatment of the PAR variability and its application to willow coppice.
Agricultural and Forest Meteorology, 1998Co-Authors: J. Ross, M Sulev, P SaarelaidAbstract:Abstract For characterization of spatial variability of the global photosynthetically active radiation (PAR) Q at different depths in a plant canopy a new Statistical Treatment has been developed. It is based on the use of the irradiance probability density function (IPDF) which is divided into three parts: IPDF for umbra fuQ, for penumbra fpQ and for sunflecks fsQ. In umbra, IPDF was approximated by a normal distribution, in penumbra by the Beta-distribution, and in sunflecks, by a normal distribution. Statistical Treatment has been applied for the fast growing willow coppice. In the umbra area the mean value QI of global PAR decreases exponentially with the optical path length of the direct solar radiation inside the canopy τ=L/sinh with small values of the standard deviation σu. In the sunfleck area the mean value QII decreases linearly with τ with small values of the standard deviation. In the penumbra area agreement with experimental data is inferior to that in umbra and sunfleck areas. Inside the canopy, the sunfleck fractional area ks, fitted by a second order polynomial, decreases with τ up to τ=3.3. The umbra fractional area ku increases nearly linearly with depth τ starting from τ=0.8. The fractional area of the penumbra kp increases rapidly with τ, reaches the maximum value (kp=0.6–0.8) at τ=3 and then decreases nearly linearly.
Martin Wolkewitz - One of the best experts on this subject based on the ideXlab platform.
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hospital acquired infections appropriate Statistical Treatment is urgently needed
International Journal of Epidemiology, 2013Co-Authors: Martin Schumacher, Arthur Allignol, Jan Beyersmann, Nadine Binder, Martin WolkewitzAbstract:Research on hospital-acquired infections (HAIs) requires the highest methodological standards to minimize the risk of bias and to avoid misleading interpretation. There are two major issues related specifically to studies in this area, namely the timing of infection and the occurrence of so-called competing risks, which deserve special attention. Just as a patient who acquires a serious infection during hospital admission needs appropriate antibiotic Treatment, data being collected in studies on hospital-acquired infections need appropriate Statistical analysis. We illustrate the urgent need for appropriate Statistical Treatment of hospital-acquired infections with some examples from recently conducted studies.The considerations presented are relevant for investigations on risk factors for HAIs as well as for outcome studies.
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Hospital-acquired infections—appropriate Statistical Treatment is urgently needed!
International journal of epidemiology, 2013Co-Authors: Martin Schumacher, Arthur Allignol, Jan Beyersmann, Nadine Binder, Martin WolkewitzAbstract:Research on hospital-acquired infections (HAIs) requires the highest methodological standards to minimize the risk of bias and to avoid misleading interpretation. There are two major issues related specifically to studies in this area, namely the timing of infection and the occurrence of so-called competing risks, which deserve special attention. Just as a patient who acquires a serious infection during hospital admission needs appropriate antibiotic Treatment, data being collected in studies on hospital-acquired infections need appropriate Statistical analysis. We illustrate the urgent need for appropriate Statistical Treatment of hospital-acquired infections with some examples from recently conducted studies.The considerations presented are relevant for investigations on risk factors for HAIs as well as for outcome studies.
