10 research outputs found
Giant Planet Formation: A First Classification of Isothermal Protoplanetary Equilibria
We present a model for the equilibrium of solid planetary cores embedded in a
gaseous nebula. From this model we are able to extract an idealized roadmap of
all hydrostatic states of the isothermal protoplanets. The complete
classification of the isothermal protoplanetary equilibria should improve the
understanding of the general problem of giant planet formation, within the
framework of the nucleated instability hypothesis. We approximate the
protoplanet as a spherically symmetric, isothermal, self-gravitating classical
ideal gas envelope in equilibrium, around a rigid body of given mass and
density, with the gaseous envelope required to fill the Hill-sphere. Starting
only with a core of given mass and an envelope gas density at the core surface,
the equilibria are calculated without prescribing the total protoplanetary mass
or nebula density. The static critical core masses of the protoplanets for the
typical orbits of 1, 5.2, and 30 AU, around a parent star of 1 solar mass are
found to be 0.1524, 0.0948, and 0.0335 Earth masses, respectively, for standard
nebula conditions (Kusaka et al. 1970). These values are much lower than
currently admitted ones primarily because our model is isothermal and the
envelope is in thermal equilibrium with the nebula. For a given core, multiple
solutions (at least two) are found to fit into the same nebula. We extend the
concept of the static critical core mass to the local and global critical core
mass. We conclude that the 'global static critical core mass' marks the meeting
point of all four qualitatively different envelope regions.Comment: 13 pages, 15 figure
Stability of Terrestrial Planets in the Habitable Zone of Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208
We have undertaken a thorough dynamical investigation of five extrasolar
planetary systems using extensive numerical experiments. The systems Gl 777 A,
HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of
whether they could host terrestrial like planets in their habitable zones
(=HZ). First we investigated the mean motion resonances between fictitious
terrestrial planets and the existing gas giants in these five extrasolar
systems. Then a fine grid of initial conditions for a potential terrestrial
planet within the HZ was chosen for each system, from which the stability of
orbits was then assessed by direct integrations over a time interval of 1
million years. The computations were carried out using a Lie-series integration
method with an adaptive step size control. This integration method achieves
machine precision accuracy in a highly efficient and robust way, requiring no
special adjustments when the orbits have large eccentricities. The stability of
orbits was examined with a determination of the Renyi entropy, estimated from
recurrence plots, and with a more straight forward method based on the maximum
eccentricity achieved by the planet over the 1 million year integration.
Additionally, the eccentricity is an indication of the habitability of a
terrestrial planet in the HZ; any value of e>0.2 produces a significant
temperature difference on a planet's surface between apoapse and periapse. The
results for possible stable orbits for terrestrial planets in habitable zones
for the five systems are summarized as follows: for Gl 777 A nearly the entire
HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive
for a sufficiently long time, while for Gl 614 our results exclude terrestrial
planets moving in stable orbits within the HZ.Comment: 14 pages, 18 figures submitted to A&
Intestinal Metagenomes and Metabolomes in Healthy Young Males: Inactivity and Hypoxia Generated Negative Physiological Symptoms Precede Microbial Dysbiosis
We explored the metagenomic, metabolomic and trace metal makeup of intestinal microbiota and environment in healthy male participants during the run-in (5 day) and the following three 21-day interventions: normoxic bedrest (NBR), hypoxic bedrest (HBR) and hypoxic ambulation (HAmb) which were carried out within a controlled laboratory environment (circadian rhythm, fluid and dietary intakes, microbial bioburden, oxygen level, exercise). The fraction of inspired O2 (FiO2) and partial pressure of inspired O2 (PiO2) were 0.209 and 133.1 ± 0.3 mmHg for the NBR and 0.141 ± 0.004 and 90.0 ± 0.4 mmHg (~4,000 m simulated altitude) for HBR and HAmb interventions, respectively. Shotgun metagenomes were analyzed at various taxonomic and functional levels, 1H- and 13C -metabolomes were processed using standard quantitative and human expert approaches, whereas metals were assessed using X-ray fluorescence spectrometry. Inactivity and hypoxia resulted in a significant increase in the genus Bacteroides in HBR, in genes coding for proteins involved in iron acquisition and metabolism, cell wall, capsule, virulence, defense and mucin degradation, such as beta-galactosidase (EC3.2.1.23), α-L-fucosidase (EC3.2.1.51), Sialidase (EC3.2.1.18), and α-N-acetylglucosaminidase (EC3.2.1.50). In contrast, the microbial metabolomes, intestinal element and metal profiles, the diversity of bacterial, archaeal and fungal microbial communities were not significantly affected. The observed progressive decrease in defecation frequency and concomitant increase in the electrical conductivity (EC) preceded or took place in absence of significant changes at the taxonomic, functional gene, metabolome and intestinal metal profile levels. The fact that the genus Bacteroides and proteins involved in iron acquisition and metabolism, cell wall, capsule, virulence and mucin degradation were enriched at the end of HBR suggest that both constipation and EC decreased intestinal metal availability leading to modified expression of co-regulated genes in Bacteroides genomes. Bayesian network analysis was used to derive the first hierarchical model of initial inactivity mediated deconditioning steps over time. The PlanHab wash-out period corresponded to a profound life-style change (i.e., reintroduction of exercise) that resulted in stepwise amelioration of the negative physiological symptoms, indicating that exercise apparently prevented the crosstalk between the microbial physiology, mucin degradation and proinflammatory immune activities in the host
DataSheet1.pdf
<p>We explored the metagenomic, metabolomic and trace metal makeup of intestinal microbiota and environment in healthy male participants during the run-in (5 day) and the following three 21-day interventions: normoxic bedrest (NBR), hypoxic bedrest (HBR) and hypoxic ambulation (HAmb) which were carried out within a controlled laboratory environment (circadian rhythm, fluid and dietary intakes, microbial bioburden, oxygen level, exercise). The fraction of inspired O<sub>2</sub> (F<sub>i</sub>O<sub>2</sub>) and partial pressure of inspired O<sub>2</sub> (P<sub>i</sub>O<sub>2</sub>) were 0.209 and 133.1 ± 0.3 mmHg for the NBR and 0.141 ± 0.004 and 90.0 ± 0.4 mmHg (~4,000 m simulated altitude) for HBR and HAmb interventions, respectively. Shotgun metagenomes were analyzed at various taxonomic and functional levels, <sup>1</sup>H- and <sup>13</sup>C -metabolomes were processed using standard quantitative and human expert approaches, whereas metals were assessed using X-ray fluorescence spectrometry. Inactivity and hypoxia resulted in a significant increase in the genus Bacteroides in HBR, in genes coding for proteins involved in iron acquisition and metabolism, cell wall, capsule, virulence, defense and mucin degradation, such as beta-galactosidase (EC3.2.1.23), α-L-fucosidase (EC3.2.1.51), Sialidase (EC3.2.1.18), and α-N-acetylglucosaminidase (EC3.2.1.50). In contrast, the microbial metabolomes, intestinal element and metal profiles, the diversity of bacterial, archaeal and fungal microbial communities were not significantly affected. The observed progressive decrease in defecation frequency and concomitant increase in the electrical conductivity (EC) preceded or took place in absence of significant changes at the taxonomic, functional gene, metabolome and intestinal metal profile levels. The fact that the genus Bacteroides and proteins involved in iron acquisition and metabolism, cell wall, capsule, virulence and mucin degradation were enriched at the end of HBR suggest that both constipation and EC decreased intestinal metal availability leading to modified expression of co-regulated genes in Bacteroides genomes. Bayesian network analysis was used to derive the first hierarchical model of initial inactivity mediated deconditioning steps over time. The PlanHab wash-out period corresponded to a profound life-style change (i.e., reintroduction of exercise) that resulted in stepwise amelioration of the negative physiological symptoms, indicating that exercise apparently prevented the crosstalk between the microbial physiology, mucin degradation and proinflammatory immune activities in the host.</p