bluuebunny/crossref_metadata_2025_split huggingface dataset:
On uncertainty of Jupiter's core mass due to observational errors
Authors: Hori Yasunori , Sano Takayoshi , Ikoma Masahiro , Ida Shigeru 
Published: May 2008

AbstractThe origins of extrasolar gas giant planets have been discussed, based on our understanding of the gas giant planets in the solar system, Jupiter and Saturn. However, how Jupiter and Saturn formed is still uncertain because of the uncertainty in their interiors, especially the core mass (Mc). The uncertainty in Mc is partly due to those in observational data such as gravitational moments (J2n), equatorial radius (Req) and 1-bar temperatures (T1bar). New frontiers mission to Jupiter by NASA (JUNO) launched in 2011 is expected to reduce the observational errors. However, it is not necessarily clear yet which observational uncertainty dominates and how accurate observation is needed to constrain Mc enough to know the origin of Jupiter. Thus, modeling the interior of Jupiter, we evaluate each effect on Mc and required precision. We have found that the observational error of 5% in T1bar yields an error of several M⊕ in Mc. We have also found that the values of J6 of our successful models are confined in a narrow range compared to its observational error. This implies that comparison between the values of J6 of our successful models and the J6 value obtained from JUNO mission helps us to know whether the present theoretical model is valid.
Tidal evolution of close-in extra-solar planets
Authors: Jackson Brian , Greenberg Richard , Barnes Rory 
Published: May 2008

AbstractThe distribution of eccentricities e of extra-solar planets with semi-major axes a > 0.2 AU is very uniform, and values for e are generally large. For a < 0.2 AU, eccentricities are much smaller (most e < 0.2), a characteristic widely attributed to damping by tides after the planets formed and the protoplanetary gas disk dissipated. We have integrated the classical coupled tidal evolution equations for e and a backward in time over the estimated age of each planet, and confirmed that the distribution of initial e values of close-in planets matches that of the general population for reasonable tidal dissipation values Q, with the best fits for stellar and planetary Q being ∼ 105.5 and ∼ 106.5, respectively. The current small values of a were only reached gradually due to tides over the lifetimes of the planets, i.e., the earlier gas disk migration did not bring all planets to their current orbits. As the orbits tidally evolved, there was substantial tidal heating within the planets. The past tidal heating of each planet may have contributed significantly to the thermal budget that governed the planet's physical properties, including its radius, which in many cases may be measured by observing transit events. Here we also compute the plausible heating histories for a few planets with anomalously large measured radii, including HD 209458 b. We show that they may have undergone substantial tidal heating during the past billion years, perhaps enough to explain their large radii. Theoretical models of exoplanet interiors and the corresponding radii should include the role of large and time-variable tidal heating. Our results may have important implications for planet formation models, physical models of “hot Jupiters”, and the success of transit surveys.
SPH simulations of star/planet formation triggered by cloud-cloud collisions
Authors: Kitsionas Spyridon , Whitworth Anthony P. , Klessen Ralf S. 
Published: May 2008

AbstractWe present results of hydrodynamic simulations of star formation triggered by cloud-cloud collisions. During the early stages of star formation, low-mass objects form by gravitational instabilities in protostellar discs. A number of these low-mass objects are in the sub-stellar mass range, including a few objects of planetary mass. The disc instabilities that lead to the formation of low-mass objects in our simulations are the product of disc-disc interactions and/or interactions between the discs and their surrounding gas.
Planet formation around intermediate mass stars
Authors: Kretke Katherine A. , Lin D. N. C. , Turner Neal J. 
Published: May 2008

AbstractWe present a mechanism by which gas giants form efficiently around intermediate mass stars. MRI-driven turbulence effectively drives angular momentum transport in regions of the disk with sufficiently high ionization fraction. In the inner regions of the disk, where the midplane temperature is above ∼1000K, thermal ionization effectively couples the disk to the magnetic field, providing a relatively large viscosity. A pressure maximum will develop outside of this region as the gaseous disk approaches a steady-state surface density profile, trapping migrating solid material. This rocky material will coagulate into planetesimals which grow rapidly until they reach isolation mass. Around intermediate mass stars, viscous heating will push the critical radius for thermal ionization of the midplane out to around 1 AU. This will increase the isolation mass for solid cores. Planets formed here may migrate inwards due to type II migration, but they will induce the formation of subsequent giant planets at the outer edge of the gap they have opened. In this manner, gas giants can form around intermediate mass stars at a few AU.
Retention of protoplanetary cores near the snowline
Authors: Zhang Xiaojia , Kretke Katherine , Lin D. N. C. 
Published: May 2008

AbstractSuppression of type I migration is essential for the retention of protoplanetary cores which are sufficiently massive to accrete gas in their nascent disks and evolve into gas giant planets. We explore here the possibility that special disk properties at the snow line may be the dominant process which stalled the type I migration. We simply use a 1-D model to calculate the torque with linear formula and find that, if the surface density jump near snowline is great enough, the migration can be efficiently slowed down or even halted. This mechanism offers an explanation to the observed peak, at 2–3 AU, in the extra solar planets' semi major axis distribution.
Searching for H2 emission from protoplanetary disks using near- and mid-infrared high-resolution spectroscopy
Authors: Carmona A. , van den Ancker M. E. , Henning Th. , Pavlyuchenkov Ya. , Dullemond C. P. , Goto M. , Fedele D. , Stecklum B. , F-.Thi W. , Bouwman J. , Waters L. B. F. M. 
Published: May 2008

AbstractThe mass and dynamics of protoplanetary disks are dominated by molecular hydrogen (H2). However, observationally very little is known about the H2. In this paper, we discuss two projects aimed to constrain the properties of H2 in the disk's planet forming region (R<50AU). First, we present a sensitive survey for pure-rotational H2 emission at 12.278 and 17.035 μm in a sample of nearby Herbig Ae/Be and T Tauri stars using VISIR, ESO's VLT high-resolution mid-infrared spectrograph. Second, we report on a search for H2 ro-vibrational emission at 2.1228, 2.2233 and 2.2477 μm in the classical T Tauri star LkHα 264 and the debris disk 49 Cet employing CRIRES, ESO's VLT high-resolution near-infrared spectrograph.VISIR project: none of the sources show H2 mid-IR emission. The observed disks contain less than a few tenths of MJupiter of optically thin H2 at 150 K, and less than a few MEarth at T>300 K. % and higher T. Our non-detections are consistent with the low flux levels expected from the small amount of H2 gas in the surface layer of a Chiang and Goldreich (1997) Herbig Ae two-layer disk model. In our sources the H2 and dust in the surface layer have not significantly departed from thermal coupling (Tgas/Tdust<2) and the gas-to-dust ratio in the surface layer is very likely <1000.CRIRES project: The H2 lines at 2.1218 μm and 2.2233 μm are detected in LkHα 264. An upper limit on the 2.2477 μm H2 line flux in LkHα 264 is derived. 49 Cet does not exhibit H2 emission in any of observed lines. There are a few MMoon of optically thin hot H2 in the inner disk (∼0.1 AU) of LkHα 264, and less than a tenth of a MMoon of hot H2 in the inner disk of 49 Cet. The shape of the 1–0 S(0) line indicates that LkHα disk is close to face-on (i<35o). The measured 1–0 S(0)/1–0 S(1) and 2–1 S(1)/1–0 S(1) line ratios in LkHα 264 indicate that the H2 is thermally excited at T<1500 K. The lack of H2 emission in the NIR spectra of 49 Cet and the absence of Hα emission suggest that the gas in the inner disk of 49 Cet has dissipated.
Astromineralogy of protoplanetary disks
Authors: Schütz O. , Meeus G. , Sterzik M. F. , Peeters E. 
Published: May 2008

AbstractWe review mid-infrared N-band spectra (8–13 μm) for a sample of 28 targets, obtained with the TIMMI2 camera at La Silla Observatory. The sample contains 5 FU Orionis stars, 6 Herbig Ae/Be objects, 7 T Tauri stars and 10 Vega-type main sequence objects. All targets show infrared excess, but for several the proof of circumstellar matter was lacking up to our observations. We model the N-band emission features with a mixture of silicates consisting of different grain sizes and composition, and determine the status of dust processing in these disks. While for some targets the emission spectrum resembles those of known pre-main sequence stars of evolved dust, other objects show strong isolated PAH bands but no silicate emission. For the first time we find evidence of PAH processing occurring in a T Tauri star. The Vega-type object HD 113766 exhibits highly-processed secondary generation dust, likely released by the collision of planetesimal-sized bodies. The findings of our dust analysis are set in context to previous dust studies of young stellar objects.
Origin of the dusty disks around white dwarfs
Authors: Dong R. B. , Wang Y. , Lin D. N. C. , Liu X. W. 
Published: May 2008

AbstractSome circumstantial evidence for residual planetesimals is constructed based on the recent discovery of a dusty ring around a young white dwarf at the center of the Helix nebula (Suet al. 2007). This ring extends between about 35 and 150 AU from the nebula center, and have a total mass of about 0.13M⊕. In this paper we propose that this ring is the by-product of planets and planetesimals' orbital evolution during the epoch when the central star rapidly lost most of its mass. We examine the dynamical evolution of planetary systems similar to the solar system (i.e. with gas giant planets and residual planetesimals) as their host stars evolve off the main sequence. During the process, some planetesimals will be captured by the gas giants into mean motion resonances and their mutual collisions will form a dust ring similar to that observed at the center of the Helix nebula.
The effect of poloidal magnetic field on type I planetary migration
Authors: Muto Takayuki , Machida Masahiro N. , Inutsuka Shu-ichiro 
Published: May 2008

AbstractWe study the effect of poloidal magnetic field on type I planetary migration by linear perturbation analysis with the shearing-sheet approximation and the analytic results are compared with numerical calculation. We investigate the cases where magneto-rotational instability (MRI) does not occur: either the disk is two-dimensional, or a very strong field is exerted. We derive formulae for torque exerted on the planet for both cases. We find that two-dimensional torque is suppressed when plasma beta is less than 1 and three-dimensional modes dominate, in contrast to unmagnetized case.
Orbital determination and dynamics of resonant extrasolar planetary systems
Authors: Beaugé C. , Ferraz-Mello S. , Michtchenko T. A. , Giuppone C. A. 
Published: May 2008

AbstractIn this communication we review some properties and applications of mean-motion resonances in extrasolar planetary systems, with particular emphasis on the 2/1 commensurability. A first part is devoted to the dynamical structure of the 2/1 resonance, including (but not restricted to) the so-called apsidal corotations. In a second part we discuss the orbital evolution of resonant systems under the effects of non-conservative forces. Special attention is given to the use of apsidal corotations as markers of largescale orbital decay, possibly due to disk-planet interactions in primordial times. Finally, we analyze the interplay between dynamical analysis and orbital fitting. Using the HD82943 planetary system as an example, we discuss: (i) up to what point present orbital fits allow us to distinguish between different resonant configurations, and (ii) in what ways may the dynamical structure of resonances be used as a complementary part of the orbital fitting process.
Stability constraints in modeling of multi-planet extrasolar systems
Authors: Goździewski Krzysztof , Migaszewski Cezary , Musieliński Arek 
Published: May 2008

AbstractWe present an analysis of high precision radial velocity (RV) observations of stars hosting multi-planet systems with Jovian companions. We use dynamical stability constraints and quasi-global methods of optimization. As an illustration, we present new results derived for the RV data of the Sun-like dwarfs HD 155358 and τ1 Gruis.
Extrasolar planet interactions
Authors: Barnes Rory , Greenberg Richard 
Published: May 2008

AbstractThe dynamical interactions of planetary systems may be a clue to their formation histories. Therefore, the distribution of these interactions provides important constraints on models of planet formation. We focus on each system's apsidal motion and proximity to dynamical instability. Although only ∼25 multiple planet systems have been discovered to date, our analyses in these terms have revealed several important features of planetary interactions. 1) Many systems interact such that they are near the boundary between stability and instability. 2) Planets tend to form such that at least one planet's eccentricity periodically drops to near zero. 3) Mean-motion resonant pairs would be unstable if not for the resonance. 4) Scattering of approximately equal mass planets is unlikely to produce the observed distribution of apsidal behavior. 5) Resonant interactions may be identified through calculating a system's proximity to instability, regardless of knowledge of angles such as mean longitude and longitude of periastron (e.g. GJ 317 b and c are probably in a 4:1 resonance). These properties of planetary systems have been identified through calculation of two parameters that describe the interaction. The apsidal interaction can be quantified by determining how close a planet is to an apsidal separatrix (a boundary between qualitatively different types of apsidal oscillations, e.g. libration or circulation of the major axes). This value can be calculated through short numerical integrations. The proximity to instability can be measured by comparing the observed orbital elements to an analytic boundary that describes a type of stability known as Hill stability. We have set up a website dedicated to presenting the most up-to-date information on dynamical interactions: http://www.lpl.arizona.edu/~rory/research/xsp/dynamics.
Secular evolution of exoplanetary systems and close encounters
Authors: Šidlichovský M. , Gerlach E. 
Published: May 2008

AbstractWe investigate the secular evolution of non-resonant exoplanetary systems consisting of a central star and two co-planar planets using a semi-numerical averaging method of the first order in planetary masses (in this case equivalent to “averaging by scissors” or simply dropping the fast periodic terms). The resulting Hamiltonian level curves for different exoplanetary systems were compared to those obtained by direct numerical integration. Studying the dependence of the reliability of the averaging method (as well as chaoticity of numerically integrated trajectories) upon the initial conditions, we found that the averaging methods fails even for Hill stable systems. Based on the Hill stability criterion we introduced empirically a more restrictive stability condition, that enabled us to give an estimate for the region of validity of the averaging method in the plane of initial conditions.
Habitability of super-Earths: Gliese 581c & 581d
Authors: von Bloh W. , Bounama C. , Cuntz M. , Franck S. 
Published: May 2008

AbstractThe unexpected diversity of exoplanets includes a growing number of super-Earth planets, i.e., exoplanets with masses smaller than 10 Earth masses. Unlike the larger exoplanets previously found, these smaller planets are more likely to have similar chemical and mineralogical composition to the Earth. We present a thermal evolution model for super-Earth planets to identify the sources and sinks of atmospheric carbon dioxide. The photosynthesis-sustaining habitable zone (pHZ) is determined by the limits of biological productivity on the planetary surface. We apply our model to calculate the habitability of the two super-Earths in the Gliese 581 system. The super-Earth Gl 581c is clearly outside the pHZ, while Gl 581d is at the outer edge of the pHZ. Therefore, it could at least harbor some primitive forms of life.
The cannabinoid receptor‐1 antagonist rimonabant inhibits platelet activation and reduces pro‐inflammatory chemokines and leukocytes in Zucker rats
Authors: Schäfer A , Pfrang J , Neumüller J , Fiedler S , Ertl G , Bauersachs J 
Published: May 2008

Background and purpose:We investigated the effect of rimonabant on inflammation and enhanced platelet reactivity in type 2 diabetic Zucker rats, an experimental model of impaired glucose tolerance and the metabolic syndrome.Experimental approach:Rimonabant (10 mg kg−1 by gavage) was fed for 2 weeks to 3‐month‐old male obese Zucker rats as an impaired glucose tolerance model and for 10 weeks to 6‐month‐old male obese Zucker rats as a model of the metabolic syndrome. RANTES (Regulated upon Activation, Normal T cell Expressed, and Secreted) and MCP‐1 (monocyte chemotactic protein‐1) serum levels were determined by ELISA. Leukocyte populations were quantitatively assessed using a veterinary differential blood cell counter. Platelet activation was assessed by flow‐cytometry, platelet aggregation, and adhesion of isolated platelets to immobilized fibrinogen.Key results:RANTES and MCP‐1 serum levels were increased in obese vs lean Zucker rats and significantly reduced by long‐term treatment with rimonabant, which slowed weight gain in rats with the metabolic syndrome. Neutrophils and monocytes were significantly increased in young and old obese vs lean Zucker rats and lowered by rimonabant. Platelet‐bound fibrinogen was significantly enhanced in obese vs lean Zucker rats of both age, and was reduced by rimonabant. Platelets from obese rats were more sensitive to thrombin‐induced aggregation and adhesion to fibrinogen, which were both attenuated by rimonabant therapy.Conclusions and implications:We demonstrate positive modulation of circulating neutrophil and monocyte numbers, reduced platelet activation and lower RANTES and MCP‐1 levels by rimonabant in Zucker rats. This may potentially contribute to a reduction of cardiovascular risk.British Journal of Pharmacology (2008) 154, 1047–1054; doi:fn1; published online 12 May 2008
Characterization of heat‐labile uracil‐DNA glycosylase from Psychrobacter sp. HJ147 and its application to the polymerase chain reaction
Authors: Lee Mi Sun , Kim Gun A. , Seo Moo Seok , Lee Jung‐Hyun , Kwon Suk‐Tae 
Published: May 2008

The gene encoding Psp HJ147 UDG (Psychrobacter sp. HJ147 uracil‐DNA glycosylase) was cloned and sequenced. The gene consists of 735 bp for coding a protein with 244 amino acid residues. The deduced amino acid sequence of Psp HJ147 UDG showed a high similarity to that of Psychrobacter articus, Psychrobacter cryohalolentis K5 and Psychrobacter sp. PRwf‐1. The PCR‐amplified Psp HJ147 UDG gene was expressed under the control of the T7lac promoter on pTYB1 in Escherichia coli BL21(DE3). The expressed enzyme was purified with IMPACT™‐CN (intein‐mediated purification with an affinity chitin‐binding tag) system. The optimum pH and temperature of the purified enzyme were 7.0–7.5 and 20–25 °C respectively. The optimum NaCl and KCl concentrations for the activity of the purified enzyme ranged from 50 to75 mM. The half‐life of the enzyme at 50 °C was approx. 45 s. These heat‐labile characteristics enabled Psp HJ147 UDG to control carry‐over contamination in direct PCR without loss of the PCR product. Psp HJ147 UDG's contaminant control in both direct PCR and indirect PCR exhibited superiority over the UDG of the marine psychrophilic bacterium strain BMTU 3346 and that of E. coli.
Regulation of diacylglycerol production and protein kinase C stimulation during sperm‐ and PLCζ‐mediated mouse egg activation
Authors: Yu Yuansong , Halet Guillaume , Lai F. Anthony , Swann Karl 
Published: May 2008

Background information. At fertilization in mammalian eggs, the sperm induces a series of Ca2+ oscillations via the production of inositol 1,4,5‐trisphosphate. Increased inositol 1,4,5‐trisphosphate production appears to be triggered by a sperm‐derived PLCζ (phospholipase C‐ζ) that enters the egg after gamete fusion. The specific phosphatidylinositol 4,5‐bisphosphate hydrolytic activity of PLCζ implies that DAG (diacylglycerol) production, and hence PKC (protein kinase C) stimulation, also occurs during mammalian egg fertilization. Fertilization‐mediated increase in PKC activity has been demonstrated; however, its precise role is unclear.Results. We investigated PLCζ‐ and fertilization‐mediated generation of DAG in mouse eggs by monitoring plasma‐membrane translocation of a fluorescent DAG‐specific reporter. Consistent plasma‐membrane DAG formation at fertilization, or after injection of physiological concentrations of PLCζ, was barely detectable. However, when PLCζ is overexpressed in eggs, significant plasma‐membrane DAG production occurs in concert with a series of unexpected secondary high‐frequency Ca2+ oscillations. We show that these secondary Ca2+ oscillations can be mimicked in a variety of situations by the stimulation of PKC and that they can be prevented by PKC inhibition. The way PKC leads to secondary Ca2+ oscillations appears to involve Ca2+ influx and the loading of thapsigargin‐sensitive Ca2+ stores.Conclusions. Our results suggest that overproduction of DAG in PLCζ‐injected eggs can lead to PKC‐mediated Ca2+ influx and subsequent overloading of Ca2+ stores. These results suggest that DAG generation in the plasma membrane of fertilizing mouse eggs is minimized since it can perturb egg Ca2+ homoeostasis via excessive Ca2+ influx.
Hypovolaemia after glucose/insulin infusions in volunteers
Authors: Berndtson Dan , Olsson Joel , Hahn Robert G. 
Published: May 2008

High-dose intravenous infusion of 5% glucose promotes rebound hypoglycaemia and hypovolaemia in healthy volunteers. To study whether such effects occur in response to glucose/insulin, 12 healthy firemen (mean age, 39 years) received three infusions over 1–2 h that contained 20 ml of 2.5% glucose/kg of body weight, 5 ml of 10% glucose/kg of body weight with 0.05 unit of rapid-acting insulin/kg of body weight, and 4 ml of 50% glucose/kg of body weight with 1 unit of insulin/kg of body weight. The plasma glucose concentration and plasma dilution were compared at 5–10 min intervals over 4 h. Regardless of the amount of administered fluid and whether insulin was given, the plasma glucose concentration decreased to hypoglycaemic levels within 30 min of the infusion ending. The plasma dilution closely mirrored plasma glucose and became negative by approx. 5%, which indicates a reduction in the plasma volume. These alterations were only partially restored during the follow-up period. A linear relationship between plasma glucose and plasma dilution was most apparent when the infused glucose had been dissolved in only a small amount of fluid. For the strongest glucose/insulin solution, this linear relationship had a correlation coefficient of 0.77 (n=386, P&lt;0.0001). The findings of the present study indicate that a redistribution of water due to the osmotic strength of the glucose is the chief mechanism accounting for the hypovolaemia. It is concluded that infusions of 2.5%, 10% and 50% glucose, with and without insulin, in well-trained men were consistently followed by long-standing hypoglycaemia and also by hypovolaemia, which averaged 5%. These results emphasize the relationship between metabolism and fluid balance.