CRSR 462

From the unrelated facts that Mars is subjected to a flux of asteroidal projectiles and that it has two very small satellites, an elementary analysis leads to the proposition that the planet possesses an orbiting dust belt system, previously unsuspected. Furthermore the satellites themselves should have surfaces resembling that of the Moon. Factors bearing on the evolution of an orbiting debris system are discussed, leading to some speculations concerning the origin and structure of the rings of Saturn.Cornell University, Center for Radiophysics and Space Research

What is a planet?

A planet is an end product of disk accretion around a primary star or substar. I quantify this definition by the degree to which a body dominates the other masses that share its orbital zone. Theoretical and observational measures of dynamical dominance reveal a gap of four to five orders of magnitude separating the eight planets of our solar system from the populations of asteroids and comets. The proposed definition dispenses with upper and lower mass limits for a planet. It reflects the tendency of disk evolution in a mature system to produce a small number of relatively large bodies (planets) in non-intersecting or resonant orbits, which prevent collisions between them.Comment: 22 pages, 3 tables, 4 figures, published in Astronomical Journal 132, 2513-1519 (2006

Radiocarbon Anomalies from Old CO2 in the Soil and Canopy Air

The canopies of forests and cultivated fields can retard the ventilation of CO2 respired from the soil. The plants in dense canopies can then acquire a small fraction of their carbon by recycling some of the respired CO2. Furthermore, some plants can assimilate a small fraction of their carbon by uptake of CO2 in the soil via their roots. In tectonically active areas, the diffuse flux of CO2 from geological sources may be comparable to that from normal soil respiration. In such areas, both the canopy and root uptake effects may allow plants to acquire a measurable fraction of their carbon from geological sources. Because this "old" carbon lacks radiocarbon, its assimilation would increase the apparent 14C ages of the plants. These effects may account for some of the discrepancies between archaeological and 14C dates.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Locating Archaeological Horizons with 14C Sediment Dating: The Case of the Lost City of Helike

From the 15th International Radiocarbon Conference held in Glasgow, Scotland, August 15-19, 1994.In 373 BC a catastrophic earthquake and seismic sea wave destroyed Helike, a Greek city near Aigion on the southern shore of the Gulf of Corinth. The ruins were buried by sediments of unknown depth, leaving no trace of the city. We here discuss the radiocarbon dating of organic sediment samples recovered from seven boreholes drilled on the coastal plain in the area where ancient sources located Helike. Most of the samples apparently acquired a substantial addition of older carbon from natural sources, and hence their apparent ages are older than the true ages of sedimentation. However, if we assume that the addition is systematic, we can use the apparent ages to show that the sedimentation rate was initially rapid (about 1 cm yr-1) for the strata between 40 and 10 m below the surface, and then decreased by an order of magnitude about 6500 yr ago. A related change in the sediment deposition at about the same time has been found in many other marine deltas throughout the world, probably due to the deceleration of the global sea-level rise. We conclude that in the boreholes sampled by the present data, the horizon corresponding to ancient Helike is less than 8 m deep.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Locating Archaeological Horizons with 14

From the 15th International Radiocarbon Conference held in Glasgow, Scotland, August 15-19, 1994.In 373 BC a catastrophic earthquake and seismic sea wave destroyed Helike, a Greek city near Aigion on the southern shore of the Gulf of Corinth. The ruins were buried by sediments of unknown depth, leaving no trace of the city. We here discuss the radiocarbon dating of organic sediment samples recovered from seven boreholes drilled on the coastal plain in the area where ancient sources located Helike. Most of the samples apparently acquired a substantial addition of older carbon from natural sources, and hence their apparent ages are older than the true ages of sedimentation. However, if we assume that the addition is systematic, we can use the apparent ages to show that the sedimentation rate was initially rapid (about 1 cm yr-1) for the strata between 40 and 10 m below the surface, and then decreased by an order of magnitude about 6500 yr ago. A related change in the sediment deposition at about the same time has been found in many other marine deltas throughout the world, probably due to the deceleration of the global sea-level rise. We conclude that in the boreholes sampled by the present data, the horizon corresponding to ancient Helike is less than 8 m deep.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

TNF-α and Th2 Cytokines Induce Atopic Dermatitis–Like Features on Epidermal Differentiation Proteins and Stratum Corneum Lipids in Human Skin Equivalents

Dermatology and Venereolog