Critical core mass for enriched envelopes: the role of H2O condensation

Context. Within the core accretion scenario of planetary formation, most simulations performed so far always assume the accreting envelope to have a solar composition. From the study of meteorite showers on Earth and numerical simulations, we know that planetesimals must undergo thermal ablation and disruption when crossing a protoplanetary envelope. Once the protoplanet has acquired an atmosphere, the primordial envelope gets enriched in volatiles and silicates from the planetesimals. This change of envelope composition during the formation can have a significant effect in the final atmospheric composition and on the formation timescale of giant planets. Aims. To investigate the physical implications of considering the envelope enrichment of protoplanets due to the disruption of icy planetesimals during their way to the core. Particular focus is placed on the effect on the critical core mass for envelopes where condensation of water can occur. Methods. Internal structure models are numerically solved with the implementation of updated opacities for all ranges of metallicities and the software CEA to compute the equation of state. CEA computes the chemical equilibrium for an arbitrary mixture of gases and allows the condensation of some species, including water. This means that the latent heat of phase transitions is consistently incorporated in the total energy budget. Results. The critical core mass is found to decrease significantly when an enriched envelope composition is considered in the internal structure equations. A particular strong reduction of the critical core mass is obtained for planets whose envelope metallicity is larger than Z=0.45 when the outer boundary conditions are suitable for condensation of water to occur in the top layers of the atmosphere. We show that this effect is qualitatively preserved when the atmosphere is out of chemical equilibrium.Comment: Accepted for publication in A&

Orbital Evolution of Planets around Intermediate-Mass Giants

Around low- and intermediate-mass (1.5-3 M_sun) red giants, no planets have been found inside 0.6 AU. Such a paucity is not seen in the case of 1 M_sun main sequence stars. In this study, we examine the possibility that short-period planets were engulfed by their host star evolving off the main sequence. To do so, we have simulated the orbital evolution of planets, including the effects of stellar tide and mass loss, to determine the critical semimajor axis, a_crit, beyond which planets survive the RGB expansion of their host star. We have found that a_crit changes drastically around 2 M_sun: In the lower-mass range, a_crit is more than 1 AU, while a_crit is as small as about 0.2 AU in the higher-mass range. Comparison with measured semimajor axes of known planets suggests that there is a lack of planets that only planet engulfment never accounts for in the higher-mass range. Whether the lack is real affects our understanding of planet formation. Therefore, increasing the number of planet samples around evolved intermediate-mass stars is quite meaningful to confirm robustness of the lack of planets.Comment: 4 pages, 3 figures, Part of PlanetsbeyondMS/2010 proceedings http://arxiv.org/html/1011.660

Ductal-cutaneous fistula secondary to recurrent Bartholin’s cysts: a case report

Background: Disorders of the Bartholin’s duct and gland, including cyst and abscess formation, account for 2% of gynecologic visits annually. An uncommon complication of a Bartholin’s duct or gland abscess is fistula formation. Literature has described cases of recto-Bartholin’s and recto-vaginal fistulas. Case: We present a case of fistula development between the perineum and the Bartholin’s duct and gland. The patient was successfully managed with fistulectomy and Bartholin’s gland excision. Conclusion: Though fistula formation is a rare complication of Bartholin’s duct and gland pathology, investigation is warranted. A ductal-cutaneous fistula is possible in the setting of recurrent cysts located beyond the vaginal introitus. The best method of prevention is appropriate execution of a marsupialization. Complete removal of the fistulous tract and Bartholin’s duct and/or gland can result in resolution of symptoms

The naked planet Earth: Most essential pre-requisite for the origin and evolution of life

AbstractOur blue planet Earth has long been regarded to carry full of nutrients for hosting life since the birth of the planet. Here we speculate the processes that led to the birth of early life on Earth and its aftermath, finally leading to the evolution of metazoans. We evaluate: (1) the source of nutrients, (2) the chemistry of primordial ocean, (3) the initial mass of ocean, and (4) the size of planet. Among the life-building nutrients, phosphorus and potassium play a key role. Only three types of rocks can serve as an adequate source of nutrients: (a) continent-forming TTG (granite), enabling the evolution of primitive life to metazoans; (b) primordial continents carrying anorthosite with KREEP (Potassium, Rare Earth Elements, and Phosphorus) basalts, which is a key to bear life; (c) carbonatite magma, enriched in radiogenic elements such as U and Th, which can cause mutation to speed up evolution and promote the birth of new species in continental rift settings. The second important factor is ocean chemistry. The primordial ocean was extremely acidic (pH = 1–2) and enriched in halogens (Cl, F and others), S, N and metallic elements (Cd, Cu, Zn, and others), inhibiting the birth of life. Plate tectonics cleaned up these elements which interfered with RNA. Blue ocean finally appeared in the Phanerozoic with pH = 7 through extensive interaction with surface continental crust by weathering, erosion and transportation into ocean. The initial ocean mass was also important. The birth of life and aftermath of evolution was possible in the habitable zone with 3–5 km deep ocean which was able to supply sufficient nutrients. Without a huge landmass, nutrients cannot be supplied into the ocean only by ridge-hydrothermal circulation in the Hadean. Finally, the size of the planet plays a crucial role. Cooling of massive planets is less efficient than smaller ones, so that return-flow of seawater into mantle does not occur until central stars finish their main sequence. Due to the suitable size of Earth, the dawn of Phanerozoic witnessed the initiation of return-flow of seawater into the mantle, leading to the emergence of huge landmass above sea-level, and the distribution of nutrients on a global scale. Oxygen pump also played a critical role to keep high-PO2 in atmosphere since then, leading to the emergence of ozone layer and enabling animals and plants to invade the land.To satisfy the tight conditions to make the Earth habitable, the formation mechanism of primordial Earth is an important factor. At first, a ‘dry Earth’ must be made through giant impact, followed by magma ocean to float nutrient-enriched primordial continents (anorthosite + KREEP). Late bombardment from asteroid belt supplied water to make 3–5 km thick ocean, and not from icy meteorites from Kuiper belt beyond cool Jupiter. It was essential to meet the above conditions that enabled the Earth as a habitable planet with evolved life forms. The tight constraints that we evaluate for birth and evolution of life on Earth would provide important guidelines for planetary scientists hunting for life in the exo-solar planets

Comparison of Reliable Change Indices of CNS Vital Signs for Different Ranges of Baseline Scores

Computerized neurocognitive tests are widely used in the management of sport-related concussion. Many of these assessments use reliable change confidence intervals—computed as baseline score ± reliable change index (RCI)—to classify an individual as impaired or unimpaired at a follow-up test point. If an individual’s retest score falls outside of the reliable change confidence interval on a given domain, he or she is classified as impaired on that domain. The purpose of this study was to compare RCIs for three different ranges of CNS Vital Signs baseline scores: the lowest quintile (0-20th percentile), middle quintile (40-60th percentile), and highest quintile (80-100th percentile). One-hundred seven Division I student-athletes completed baseline and follow-up computerized neurocognitive testing on CNS Vital Signs and were divided into quintile groups based on their baseline score for each clinical domain. RCIs were computed for the lowest, middle, and highest quintiles for each domain. Overall group RCIs were also computed. The RCIs varied considerably across the quintile groups, with average and high baseline performers tending to have smaller RCIs than low baseline performers and the full group in each domain. In addition, significant interaction effects of time and quintile group were found for several domains as well as for Neurocognition Index. These results suggest that it is important for clinicians to consider an individual’s baseline performance level when interpreting CNS Vital Signs neurocognitive test results using a baseline/post-injury comparison model.Bachelor of Scienc

Detectability of Rocky-Vapour atmospheres on super-Earths with Ariel

Ariel will mark the dawn of a new era as the first large-scale survey characterising exoplanetary atmospheres with science objectives to address fundamental questions about planetary composition, evolution and formation. In this study, we explore the detectability of atmospheres vaporised from magma oceans on dry, rocky Super-Earths orbiting very close to their host stars. The detection of such atmospheres would provide a definitive piece of evidence for rocky planets but are challenging measurements with currently available instruments due to their small spectral signatures. However, some of the hottest planets are believed to have atmospheres composed of vaporised rock, such as Na and SiO, with spectral signatures bright enough to be detected through eclipse observations with planned space-based telescopes. In this study, we find that rocky super-Earths with a irradiation temperature of 3000 K and a distance from Earth of up to 20 pc, as well as planets hotter than 3500 K and closer than 50 pc, have SiO features which are potentially detectable in eclipse spectra observed with Ariel

Formation of giant planets around stars with various masses

We examine the predictions of the core accretion - gas capture model concerning the efficiency of planet formation around stars with various masses. First, we follow the evolution of gas and solids from the moment when all solids are in the form of small grains to the stage when most of them are in the form of planetesimals. We show that the surface density of the planetesimal swarm tends to be higher around less massive stars. Then, we derive the minimum surface density of the planetesimal swarm required for the formation of a giant planet both in a numerical and in an approximate analytical approach. We combine these results by calculating a set of representative disk models characterized by different masses, sizes, and metallicities, and by estimating their capability of forming giant planets. Our results show that the set of protoplanetary disks capable of giant planet formation is larger for less massive stars. Provided that the distribution of initial disk parameters does not depend too strongly on the mass of the central star, we predict that the percentage of stars with giant planets should increase with decreasing stellar mass. Furthermore, we identify the radial redistribution of solids during the formation of planetesimal swarms as the key element in explaining these effects.Comment: Accepted for publication in A&A. 9 pages, 9 figure

TRPV1-expressing primary afferents generate behavioral responses to pruritogens via multiple mechanisms

The mechanisms that generate itch are poorly understood at both the molecular and cellular levels despite its clinical importance. To explore the peripheral neuronal mechanisms underlying itch, we assessed the behavioral responses (scratching) produced by s.c. injection of various pruritogens in PLCβ3- or TRPV1-deficient mice. We provide evidence that at least 3 different molecular pathways contribute to the transduction of itch responses to different pruritogens: 1) histamine requires the function of both PLCβ3 and the TRPV1 channel; 2) serotonin, or a selective agonist, α-methyl-serotonin (α-Me-5-HT), requires the presence of PLCβ3 but not TRPV1, and 3) endothelin-1 (ET-1) does not require either PLCβ3 or TRPV1. To determine whether the activity of these molecules is represented in a particular subpopulation of sensory neurons, we examined the behavioral consequences of selectively eliminating 2 nonoverlapping subsets of nociceptors. The genetic ablation of MrgprD^+ neurons that represent ≈90% of cutaneous nonpeptidergic neurons did not affect the scratching responses to a number of pruritogens. In contrast, chemical ablation of the central branch of TRPV1+ nociceptors led to a significant behavioral deficit for pruritogens, including α-Me-5-HT and ET-1, that is, the TRPV1-expressing nociceptor was required, whether or not TRPV1 itself was essential. Thus, TRPV1 neurons are equipped with multiple signaling mechanisms that respond to different pruritogens. Some of these require TRPV1 function; others use alternate signal transduction pathways

Migration then assembly: Formation of Neptune mass planets inside 1 AU

We demonstrate that the observed distribution of `Hot Neptune'/`Super-Earth' systems is well reproduced by a model in which planet assembly occurs in situ, with no significant migration post-assembly. This is achieved only if the amount of mass in rocky material is $\sim 50$--$100 M_{\oplus}$ interior to 1 AU. Such a reservoir of material implies that significant radial migration of solid material takes place, and that it occur before the stage of final planet assembly. The model not only reproduces the general distribution of mass versus period, but also the detailed statistics of multiple planet systems in the sample. We furthermore demonstrate that cores of this size are also likely to meet the criterion to gravitationally capture gas from the nebula, although accretion is rapidly limited by the opening of gaps in the gas disk. If the mass growth is limited by this tidal truncation, then the scenario sketched here naturally produces Neptune-mass objects with substantial components of both rock and gas, as is observed. The quantitative expectations of this scenario are that most planets in the `Hot Neptune/Super-Earth' class inhabit multiple-planet systems, with characteristic orbital spacings. The model also provides a natural division into gas-rich (Hot Neptune) and gas-poor (Super-Earth) classes at fixed period. The dividing mass ranges from $\sim 3 M_{\oplus}$ at 10 day orbital periods to $\sim 10 M_{\oplus}$ at 100 day orbital periods. For orbital periods $< 10$ days, the division is less clear because a gas atmosphere may be significantly eroded by stellar radiation.Comment: 41 pages in preprint style, 15 figures, final version accepted to Ap