44 research outputs found
Antineutrinos from Earth: A reference model and its uncertainties
We predict geoneutrino fluxes in a reference model based on a detailed
description of Earth's crust and mantle and using the best available
information on the abundances of uranium, thorium, and potassium inside Earth's
layers. We estimate the uncertainties of fluxes corresponding to the
uncertainties of the element abundances. In addition to distance integrated
fluxes, we also provide the differential fluxes as a function of distance from
several sites of experimental interest. Event yields at several locations are
estimated and their dependence on the neutrino oscillation parameters is
discussed. At Kamioka we predict N(U+Th)=35 +- 6 events for 10^{32} proton yr
and 100% efficiency assuming sin^2(2theta)=0.863 and delta m^2 = 7.3 X 10^{-5}
eV^2. The maximal prediction is 55 events, obtained in a model with fully
radiogenic production of the terrestrial heat flow.Comment: 24 pages, ReVTeX4, plus 7 postscript figures; minor formal changes to
match version to be published in PR
Abundances of the elements in the solar system
A review of the abundances and condensation temperatures of the elements and
their nuclides in the solar nebula and in chondritic meteorites. Abundances of
the elements in some neighboring stars are also discussed.Comment: 42 pages, 11 tables, 8 figures, chapter, In Landolt- B\"ornstein, New
Series, Vol. VI/4B, Chap. 4.4, J.E. Tr\"umper (ed.), Berlin, Heidelberg, New
York: Springer-Verlag, p. 560-63
Siliceous deep-sea sponge Monorhaphis chuni: A potential paleoclimate archive in ancient animals
The deep-sea sponge Monorhaphis chuni forms giant basal spicules, which
can reach lengths of 3 m; they represent the largest biogenic silica
structures on Earth that is formed from an individual metazoan. The
spicules offer a unique opportunity to record environmental change of
past oceanic and climatic conditions. A giant spicule collected in the
East China Sea in a depth of 1110 m was investigated. The oxygen
isotopic composition and Mg/Ca ratios determined along center-to-surface
segments are used as geochemical proxies for the assessment of seawater
paleotemperatures. Calculations are based on the assumption that the
calculated temperature near the surface of the spicule is identical with
the average ambient temperature of 4 degrees C. A seawater temperature
of 1.9 degrees C is inferred for the beginning of the lifespan of the
Monorhaphis specimen. The temperature increases smoothly to 2.3 degrees
C, to be followed by sharply increased and variable temperatures up to
6-10 degrees C. In the outer part of the spicule, the inferred seawater
temperature is about 4 degrees C. The lifespan of the spicule can be
estimated to 11,000 +/- 3000 years using the long-term trend of the
inferred temperatures fitted to the seawater temperature age
relationships since the Last Glacial Maximum. Specimens of Monorhaphis
therefore represents one the oldest living animals on Earth. The
remarkable temperature spikes of the ambient seawater occurring
9500-3100 years B.P. are explained by discharges of hydrothermal fluids
in the neighborhood of the spicule. The irregular lamellar organization
of the spicule and the elevated Mn concentrations during the
high-temperature growth are consistent with a hydrothermal fluid input.
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