Neptune
Minor Planets
Uranus
Evolution, Planetary
Dissociation of CH4 at high pressures and temperatures: diamond formation in giant planet interiors? (1/10)
Experiments using laser-heated diamond anvil cells show that methane (CH4) breaks down to form diamond at pressures between 10 and 50 gigapascals and temperatures of about 2000 to 3000 kelvin. Infrared absorption and Raman spectroscopy, along with x-ray diffraction, indicate the presence of polymeric hydrocarbons in addition to the diamond, which is in agreement with theoretical predictions. Dissociation of CH4 at high pressures and temperatures can influence the energy budgets of planets containing substantial amounts of CH4, water, and ammonia, such as Uranus and Neptune. (+info)Inhibition of glycogen synthesis by increased lipid availability is associated with subcellular redistribution of glycogen synthase. (2/10)
Increased lipid availability is associated with diminished insulin-stimulated glucose uptake and glycogen synthesis in muscle, but it is not clear whether alterations in glycogen synthase activity itself play a direct role. Because intracellular localization of this enzyme is involved in its regulation, we investigated whether fat oversupply causes an inhibitory redistribution. We examined the recovery of glycogen synthase in subcellular fractions from muscle of insulin-resistant, fat-fed rats and chow-fed controls, either maintained in the basal state or after a euglycaemic-hyperinsulinaemic clamp. Although glycogen synthase protein and activity were mostly recovered in an insoluble fraction, insulin caused translocation of activity from the smaller soluble pool to the insoluble fraction. Fat-feeding, which led to a reduction in glycogen synthesis during the clamp, was associated with a depletion in the soluble pool, consistent with an important role for this component. A similar depletion was also observed in cytosolic fractions of muscles from obese db/db mice, another model of lipid-induced insulin resistance. To investigate this in more detail, we employed lipid-pretreated L6 myotubes, which exhibited a reduction in insulin-stimulated glycogen synthesis independently of alterations in glucose flux or insulin signalling through protein kinase B. In control cells, insulin caused redistribution of a minor cytosolic pool of glycogen synthase to an insoluble fraction, which was again forestalled by lipid pretreatment. Glycogen synthase recovered in the insoluble fraction from pre-treated cells exhibited a low fractional velocity that was not increased in response to insulin. Our results suggest that the initial localization of glycogen synthase in a soluble pool plays an important role in glycogen synthesis, and that its sequestration in an insulin-resistant insoluble pool may explain in part the reduced glycogen synthesis caused by lipid oversupply. (+info)Grain size-sensitive creep in ice II. (3/10)
Rheological experiments on fine-grained water ice II at low strain rates reveal a creep mechanism that dominates at conditions of low stress. Using cryogenic scanning electron microscopy, we observed that a change in stress exponent from 5 to 2.5 correlates strongly with a decrease in grain size from about 40 to 6 micrometers. The grain size-sensitive creep of ice II demonstrated here plausibly dominates plastic strain at the low-stress conditions in the interior of medium- to large-sized icy moons of the outer solar system. (+info)A thick cloud of Neptune Trojans and their colors. (4/10)
The dynamical and physical properties of asteroids offer one of the few constraints on the formation, evolution, and migration of the giant planets. Trojan asteroids share a planet's semimajor axis but lead or follow it by about 60 degrees near the two triangular Lagrangian points of gravitational equilibrium. Here we report the discovery of a high-inclination Neptune Trojan, 2005 TN(53). This discovery demonstrates that the Neptune Trojan population occupies a thick disk, which is indicative of "freeze-in" capture instead of in situ or collisional formation. The Neptune Trojans appear to have a population that is several times larger than the Jupiter Trojans. Our color measurements show that Neptune Trojans have statistically indistinguishable slightly red colors, which suggests that they had a common formation and evolutionary history and are distinct from the classical Kuiper Belt objects. (+info)Kepler constraints on planets near hot Jupiters. (5/10)
(+info)Dissociation of methane into hydrocarbons at extreme (planetary) pressure and temperature. (6/10)
Constant-pressure, first-principles molecular dynamic simulations were used to investigate the behavior of methane at high pressure and temperature. Contrary to the current interpretation of shock-wave experiments, the simulations suggest that, below 100 gigapascals, methane dissociates into a mixture of hydrocarbons, and it separates into hydrogen and carbon only above 300 gigapascals. The simulation conditions (100 to 300 gigapascals; 4000 to 5000 kelvin) were chosen to follow the isentrope in the middle ice layers of Neptune and Uranus. Implications on the physics of these planets are discussed. (+info)Surface composition of Kuiper belt object 1993SC. (7/10)
The 1.42- to 2.40-micrometer spectrum of Kuiper belt object 1993SC was measured at the Keck Observatory in October 1996. It shows a strongly red continuum reflectance and several prominent infrared absorption features. The strongest absorptions in 1993SC's spectrum occur near 1.62, 1.79, 1.95, 2.20, and 2.32 micrometers in wavelength. Features near the same wavelengths in the spectra of Pluto and Neptune's satellite Triton are due to CH4 on their surfaces, suggesting the presence of a simple hydrocarbon ice such as CH4, C2H6, C2H4, or C2H2 on 1993SC. In addition, the red continuum reflectance of 1993SC suggests the presence of more complex hydrocarbons. (+info)A disk of scattered icy objects and the origin of Jupiter-family comets. (8/10)
Orbital integrations carried out for 4 billion years produced a disk of scattered objects beyond the orbit of Neptune. Objects in this disk can be distinguished from Kuiper belt objects by a greater range of eccentricities and inclinations. This disk was formed in the simulations by encounters with Neptune during the early evolution of the outer solar system. After particles first encountered Neptune, the simulations show that about 1 percent of the particles survive in this disk for the age of the solar system. A disk currently containing as few as approximately 6 x 10(8) objects could supply all of the observed Jupiter-family comets. Two recently discovered objects, 1996 RQ20 and 1996 TL66, have orbital elements similar to those predicted for objects in this disk, suggesting that they are thus far the only members of this disk to be identified. (+info)I'm sorry for any confusion, but "Neptune" is not a term commonly used in medical definitions. Neptune is the eighth and farthest known planet from the Sun in the Solar System. It is the fourth-largest planet by diameter and the third-largest by mass.
If you have any questions related to medical terminology or health concerns, I'd be happy to help with those instead!
I'm sorry for any confusion, but the term "minor planets" is not typically used in medical definitions. It is a term from astronomy that refers to small celestial bodies orbiting the Sun, which are smaller than planets and dwarf planets. They are also commonly known as asteroids. If you have any questions related to medical terminology or health concerns, I would be happy to help with those instead!
I'm sorry for any confusion, but the term 'Uranus' is not a medical concept or condition. It is the seventh planet from the Sun in our solar system. If you have any medical questions or terms you would like defined, I'd be happy to help!
Planetary evolution is a field of study that focuses on the processes that have shaped the formation, development, and changes of planets and other celestial bodies over time. This encompasses various scientific disciplines, including astronomy, astrobiology, geology, and atmospheric science. The study of planetary evolution helps scientists understand how planets form, how they change over time, and the conditions that allow for the development of life.
The process of planetary evolution can be driven by a variety of factors, including:
1. Formation: Planets form from a protoplanetary disk, a rotating disk of gas and dust surrounding a young star. Over time, solid particles in the disk collide and stick together to form larger and larger bodies, eventually leading to the formation of planets.
2. Internal differentiation: As planets grow, their interiors differentiate into layers based on density, with heavier materials sinking towards the center and lighter materials rising towards the surface. This process can lead to the formation of a core, mantle, and crust.
3. Geological activity: Planetary evolution is also influenced by geological processes such as volcanism, tectonics, and erosion. These processes can shape the planet's surface, create mountain ranges, and carve out valleys and basins.
4. Atmospheric evolution: The evolution of a planet's atmosphere is closely tied to its geological activity and the presence of volatiles (gases that easily vaporize). Over time, the composition of a planet's atmosphere can change due to processes such as outgassing from the interior, chemical reactions, and interactions with the solar wind.
5. Climate evolution: The climate of a planet can also evolve over time due to changes in its orbit, axial tilt, and atmospheric composition. These factors can influence the amount of sunlight a planet receives and the greenhouse effect, which can lead to global warming or cooling.
6. Impact events: Collisions with other celestial bodies, such as asteroids and comets, can significantly impact a planet's evolution by causing large-scale changes to its surface and atmosphere.
7. Life: On planets where life emerges, biological processes can also play a role in shaping the planet's environment and influencing its evolution. For example, photosynthetic organisms can produce oxygen, which can alter the composition of a planet's atmosphere.
Understanding the various factors that contribute to a planet's evolution is crucial for understanding the formation and development of planetary systems and searching for potentially habitable exoplanets.
Euphausiacea is a taxonomic category, specifically an order, that includes various types of planktonic crustaceans commonly known as krill. These small, shrimp-like animals are found in oceans all over the world and play a crucial role in marine ecosystems as a key food source for many larger animals, including whales, seals, and fish.
Euphausiids, as they are sometimes called, have a transparent exoskeleton and a distinctive bioluminescent ability that they use for communication, attracting prey, and evading predators. They are filter feeders, consuming large quantities of phytoplankton and other small organisms.
Euphausiacea is part of the larger decapod group, which also includes crabs, lobsters, and shrimp. The study of these animals and their role in marine ecosystems is important for understanding ocean health and biodiversity.