Spallation model

Harper C. L., Wiesmann H., Nyquist L. E., Howard W. M., Meyer B., Yokoyama Y., Rayet M., Amould M., Palme H., Spettel B., and Jochum K. P. (1991b) Nb/ Nb and Nb/ Sm ratios of the early solar system observations and comparison of p-process and spallation models. In Lunar Planet. Sci. XXII. The Lunar and Planetary Institute, Houston, pp. 519-520. 

The relative abundances of the various isotopes of the light elements Li, Be and B therefore depend to some extent on which detailed model of the big bang is adopted, and experimentally determined abundances may in time permit conclusions to be drawn as to the relative importance of these processes as compared to x-process spallation reactions. 

The above models are all rather unsatisfactory, because they involve somewhat arbitrary assumptions about the time-dependence of the cosmic-ray flux and spectrum and because they predict a secondary-like behaviour for Be and B abundances, whereas the overall trend indicated by the data is more like a primary one and there are the energetic difficulties pointed out above. In the case of nB, there is a possible primary mechanism for stellar production in supemovae by neutrino spallation processes (Woosley et al. 1990 Woosley Weaver 1995), but the primary-like behaviour of beryllium in metal-poor stars, combined with a constant B/Be ratio of about 20 fully consistent with cosmic-ray spallation (Garcia Lopez et al. 1998) in the absence of any known similar process for Be, indicates that this does not solve the problem unless a primary process can be found for Be as well. Indeed,... 

The discussion of the GCE of light elements formed by cosmic-ray spallation is based on Pagel (1994) and has a somewhat different outlook from many other treatments in the literature, e.g. Fields, Olive and Schramm (1995), which should be consulted to get another viewpoint. A numerical treatment of the Simple model by Vangioni-Flam et al. (1990) gave similar results to the ones derived more simply here, as did the discussion of inflow models by Prantzos (1994). 

First, the role of rubber modification in high rate impact is to suppress spallation by inducing the material to yield in the presence of dynamic tensile stresses arising from impact. Second, this yield-spall transition occurs at different strain rates for different rubber contents and may be predictable using quasistatic, low temperature tests of this type. These tests can also provide information concerning the basic nature of the yield process in these materials through the activation parameters which are obtained. Third, the Bauwens-Crowet equation seems to be a good model for the rate and temperature sensitive behavior of the American Cyanamid materials and is therefore a likely candidate for a yield criterion to use in the analytical code work on these materials which we hope to perform as a continuation of this work. 

At present, the Be versus O and the Be versus Mg relations for metal-poor stars appear to be quasi-linear King (2002) gives indices of about 1.1 for both Be and B when Mg is adopted. Recent determinations of the O abundance seem likely to confirm this near-linear trend. All interpretations assume that spallation processes are the sole source of the Be but not necessarily of the B (see below). Ingredients of the modelling other than the mode of synthesis are varied to fit the Be vs O (or Mg) relations. 

Timmes, Woosley Weaver (1995) developed a chemical evolution model of the solar neighbourhood in an attempt to account for the observed abundances of elements from H to Zn in metal-rich and metal-poor stars. The (/-process contributions were included. With their predicted yields of nB and excluding 10B and nB from cosmic ray driven spallation, they were able to reproduce the then fragmentary data on the run of the boron abundance with metallicity (see their Fig. 9) from [Fe/H] —2.5 to [Fe/H] cz 0 and including a fit to the meteoritic abundance. Newer data on the B abundances is equally... 

Finite element model analysis simulating the thermal cycle tests demonstrated that the top coat spallation of both types of coating is caused by the buckling driven by delamination due to the transient large in-plane compressive stress development immediately after initiate heating. 

Note that the above considerations concern only thermonuclear modes of p-nuclide synthesis. Some non-thermonuclear scenarios have in fact been proposed, like production by spallation reactions in the interstellar medium [71,72], or photonuclear reactions triggered by non-thermalized photons [73]. These models suffer from either too low efficiencies, or from constraints that limit their astro-physical plausibility. They are not discussed further here. 

Figure 1. Depth profiles of °Be, and produetion in quartz by spallation reaetions, eapture of stopped negative muons, and fast muon interaetions, respeetively. The data are based on both experimental determinations and model eal-eulations (Heisinger and Nolle...

The slope of the spallation line depends on the relative production ratios of cosmogenic e, Ne, and Ne and, therefore, on the mineral composition. It has been determined experimentally for quartz and pyroxene (Niedermann et al. 1993 Bruno et al. 1997 Phillips et al. 1998 Schafer et al. 1999). The relevant data are compiled in Table 8. The values for ( Ne/ %e)c were assumed based on observations in well-shielded lunar samples and meteorites and model calculations (Hohenberg et al. 1978 Schafer et al. 

Nuclear level schemes and resonance parameters are of great interest for nuelear spectroseopy, for astrophysical models, thermonuelear ealeulations and for other applieations. Parameters for nuelear levels of stable nuclei have been published in the Volumes I/16B, I/18A, B, C, andinI/19Al, A2. In the Volumes I/19A, B further data obtained from transfer reaetions are presented. Volume I/19C eontains the data of unstable nuclei far from the stability region whieh have been dedueed from reactions oflier than transfer reactions (e.g. beta deeay, spallation reactions, or inverse reactions). The data in these volumes should be considered as the most complete data collection for nuclear levels. 

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