Deep Mixing of He-3: Reconciling Big Bang and Stellar Nucleosynthesis

Low-mass stars, ~1-2 solar masses, near the Main Sequence are efficient at producing He-3, which they mix into the convective envelope on the giant branch and should distribute into the Galaxy by way of envelope loss. This process is so efficient that it is difficult to reconcile the low observed cosmic abundance of He-3 with the predictions of both stellar and Big Bang nucleosynthesis. In this paper we find, by modeling a red giant with a fully three-dimensional hydrodynamic code and a full nucleosynthetic network, that mixing arises in the supposedly stable and radiative zone between the hydrogen-burning shell and the base of the convective envelope. This mixing is due to Rayleigh-Taylor instability within a zone just above the hydrogen-burning shell, where a nuclear reaction lowers the mean molecular weight slightly. Thus we are able to remove the threat that He-3 production in low-mass stars poses to the Big Bang nucleosynthesis of He-3.Comment: Accepted by Science, and available from Science Express onlin

Exploiting lattice potentials for sorting chiral particles

Several ways are demonstrated of how periodic potentials can be exploited for sorting molecules or other small objects which only differ by their chirality. With the help of a static bias force, the two chiral partners can be made to move along orthogonal directions. Time-periodic external forces even lead to motion into exactly opposite directions.Comment: 4 pages, 4 figure

Compulsory Deep Mixing of 3He and CNO Isotopes in the Envelopes of low-mass Red Giants

Three-dimensional stellar modeling has enabled us to identify a deep-mixing mechanism that must operate in all low mass giants. This mixing process is not optional, and is driven by a molecular weight inversion created by the 3He(3He,2p)4He reaction. In this paper we characterize the behavior of this mixing, and study its impact on the envelope abundances. It not only eliminates the problem of 3He overproduction, reconciling stellar and big bang nucleosynthesis with observations, but solves the discrepancy between observed and calculated CNO isotope ratios in low mass giants, a problem of more than 3 decades' standing. This mixing mechanism, which we call `$\delta\mu$-mixing', operates rapidly (relative to the nuclear timescale of overall evolution, ~ 10^8 yrs) once the hydrogen burning shell approaches the material homogenized by the surface convection zone. In agreement with observations, Pop I stars between 0.8 and 2.0\Msun develop 12C/13C ratios of 14.5 +/- 1.5, while Pop II stars process the carbon to ratios of 4.0 +/- 0.5. In stars less than 1.25\Msun, this mechanism also destroys 90% to 95% of the 3He produced on the main sequence.Comment: Final accepted version (submitted to Astrophys J in Jan 2007...

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For cooperation and assistance in the work reported here, we gratefully acknowledge Dr. William Burgoyne, State of Alaska Division of Environmental Conservation and Mr. Delon Brown, USDA, Alaska Crop and Livestock Reporting Service. We especially appreciate the efforts of numerous pesticide manufacturers, distributors, dealers, and users who took the necessary time to provide information essential for this compilation. Richard Maxwell, Agricultural Chemicals Specialist, Cooperative Extension Service, Washington State University, provided difficult to locate pesticide label information. The editors of Farm Chemicals Handbook, 1980, provided the list of preferred names as well as information regarding general application of pesticide products.Acknowledgments -- Introduction -- Reference -- Pesticide Use in Alaska, 197

The Revived Bretton Woods System: The Effects of Periphery Intervention and Reserve Management on Interest Rates & Exchange Rates in Center Countries

In this paper we explore some implications of the revived' Bretton Woods system for exchange market intervention and reserve management in periphery countries. Financial policies in these countries are seen as a component of a more general portfolio management policy in which the formation of an efficient domestic capital stock is a key objective. Because intervention in financial markets is an important part of their development strategy, intervention in exchange and financial markets has, and we argue will continue to be, large and persistent enough to generate predictable deviations of exchange rates and relative yields in industrial country financial markets from normal cyclical patterns. We argue that management of the currency composition of international reserves by emerging market governments and central banks is unlikely to alter these conclusions.

Evidence for a Spectroscopic Sequence Among SNe Ia

In this Letter we present evidence for a spectral sequence among Type Ia supernovae (SNe Ia). The sequence is based on the systematic variation of several features seen in the near-maximum light spectrum. This sequence is analogous to the recently noted photometric sequence among SNe Ia which shows a relationship between the peak brightness of a SN Ia and the shape of its light curve. In addition to the observational evidence we present a partial theoretical explanation for the sequence. This has been achieved by producing a series of non-LTE synthetic spectra in which only the effective temperature is varied. The synthetic sequence nicely reproduces most of the differences seen in the observed one and presumably corresponds to the amount of 56Ni produced in the explosion.Comment: To appear in Astrophysical Journal Letters, uuencoded, gzipped postscript file, also available from http://www.nhn.uoknor.edu/~baron