Portugal and the Anglo-Russian Naval Crisis (1808)

During the Napoleonic period several critical decisions had a major influence on the future of the French Empire. Unquestionably, one of the most catastrophic decisions centered around Napoleon\u27s efforts to subjugate Portugal and Spain. This in turn, forced Great Britain to commit its wealth, man­power, and ultimately its future to the struggle for control of the Peninsula. ln the initial stages of this conflict, the Royal Navy became the cutting edge of Britain\u27s new offensive

EFFECTS OF RISK ON OPTIMAL NITROGEN FERTILIZATION DATES IN WINTER WHEAT PRODUCTION AS AFFECTED BY DISEASE AND NITROGEN SOURCE

Optimal fertilization dates were found for two nitrogen sources in the presence of two diseases for wheat farmers with different risk preferences. Risk was independent of fertilization date. Ammonium Nitrate and Urea-Ammonium Nitrate did not affect risk differently. Ammonium Nitrate applied on March 9 was optimal regardless of risk preferences.Crop Production/Industries,

EFFECTS OF RISK, DISEASE, AND NITROGEN SOURCE ON OPTIMAL NITROGEN FERTILIZATION RATES IN WINTER WHEAT PRODUCTION

Interactions among nitrogen (N) fertilization rate, N source, and disease severity can affect mean yield and yield variance in conservation tillage wheat production. A Just-Pope model was used to evaluate the effects of N rate, N source, and disease on the spring N-fertilization decision. Ammonium nitrate (AN) was the utility-maximizing N source regardless of risk preferences. The net-return-maximizing AN rate was 92 lb N/acre, providing $0.52/acre higher net returns than the best alternative N source (urea). If a farmer could anticipate a higher than average Take-All infection, the difference in optimal net-returns between AN and urea would increase to$35.11/acre.Crop Production/Industries,

Explosive Nucleosynthesis in Helium Zones

We study by numerical integration the network of nuclear reactions that are expected to occur when the helium zones of a star are instantaneously heated and allowed to expand adiabatically. The dependence of the results on nuclear cross-sections, on the peak temperature, and on the time scale of the hydrodynamic expansion are discussed. Of particular interest is the result that the nucleus `4N, constituting about 2 percent by mass following the earlier operation of the CNO cycle, is substantially converted into 150, 15F, 15Ne, and 21Ne in ratios close to the solar abundances of 55N, 80, 55F, and 21Ne. It is very likely that these nuclei are synthesized in such zones. The nucleus 22Ne, on the other hand, is apparently not produced in the explosion in sufficient amounts relative to 21Ne, which indicates that 22Ne is probably synthesized in hydrostatic helium burning and survives the ejection

Heavy-Element Abundances from a Neutron Burst that Produces Xe-H

We examine quantitatively the suggestion that the heavy anomalous isotopes of Xe-HL found in meteoritic diamonds were produced by a short intense neutron burst and then implanted into the diamonds. Using a large nuclear reaction network we establish one (out of many) neutron irradiation histories that successfully reproduces the heavy isotopes of Xe-HL, and then evaluate what that same history would produce in every heavy element. This has become more relevant following recent measurement of anomalous Ba and Sr in those same diamond samples. Therefore we offer these calculations as a guide to the anomalies to be expected in all elements if this scenario is correct. We also discuss several other aspects of the problem, especially the established contradictions for Ba, the observed Kr pattern, the near normalcy of 129Xe, and some related astrophysical ideas. In particular we argue from p-process theory that the observed deficit of 78Kr in correlation with 124–126Xe excess implicates Type II supernovae as the diamond sources. However, our more complete astrophysical conclusions will be published elsewhere. This present work is offered as computational expectation for this class of models and as a guide to considerations that may accelerate the digestion of new experimental results in the diamonds

Thermonuclear Origin of Rare Neutron-Rich Isotopes

Many rare neutron-rich isotopes in the range 16\u3c~Z≲34 can be synthesized from seed nuclei exposed to explosive carbon burning. This process, which involves no new astrophysical parameters, can solve most of the outstanding problems in the thermonuclear synthesis of elements in the range Z≲34

Nucelosynthesis of Rare Nuclei from Seed Nuclei in Explosive Carbon Burning

We demonstrate that a Population I concentration of primordial heavy seed nuclei, when present in the carbon- and oxygewrich core of the presupernova star and exposed to the temperature and free nucleon densities of explosive carbon burning, is efficiently transmuted into the rare species 365, 40K, 43Ar, 43Ca, 46Ca, 48Ca, 405c, 45Ti, 0Ti, 50V, 62Ni, 64Ni, 68Zn, 70Zn, and 76Ge in approximately their solar-system abundance ratios. If the temperature is high enough (T0 2.1) that at least 10 percent of the Fe and Ni seed nuclei undergo (p, ) reactions during the explosion, the nuclei 60Cu, 63Zn, 71Ga, 73Ce, and perhaps 75As can also be synthesized. These nuclei comprise virtually all of the relatively rare neutron-rich nuclei in the range 36 \u3c A \u3c 76 except 04Cr and 50Fe. We emphasize the dependence of the results upon the rates of important nuclear reactions, most of which are unknown. The temperature, density, and timescale of the carbon explosion all have a strong influence on the results as well. We therefore regard this paper as an exploratory survey of a very difficult problem that will give increasing information about nucleosynthesis as nuclear facts and models of nuclear explosions become more secure

Hubble Space Telescope Astrometry of the Procyon System

The nearby star Procyon is a visual binary containing the F5 IV-V subgiant Procyon A, orbited in a 40.84 yr period by the faint DQZ white dwarf Procyon B. Using images obtained over two decades with the Hubble Space Telescope, and historical measurements back to the 19th century, we have determined precise orbital elements. Combined with measurements of the parallax and the motion of the A component, these elements yield dynamical masses of 1.478 +/- 0.012 Msun and 0.592 +/- 0.006 Msun for A and B, respectively. The mass of Procyon A agrees well with theoretical predictions based on asteroseismology and its temperature and luminosity. Use of a standard core-overshoot model agrees best for a surprisingly high amount of core overshoot. Under these modeling assumptions, Procyon A's age is ~2.7 Gyr. Procyon B's location in the H-R diagram is in excellent agreement with theoretical cooling tracks for white dwarfs of its dynamical mass. Its position in the mass-radius plane is also consistent with theory, assuming a carbon-oxygen core and a helium-dominated atmosphere. Its progenitor's mass was 1.9-2.2 Msun, depending on its amount of core overshoot. Several astrophysical puzzles remain. In the progenitor system, the stars at periastron were separated by only ~5 AU, which might have led to tidal interactions and even mass transfer; yet there is no direct evidence that these have occurred. Moreover the orbital eccentricity has remained high (~0.40). The mass of Procyon B is somewhat lower than anticipated from the initial-to-final-mass relation seen in open clusters. The presence of heavy elements in its atmosphere requires ongoing accretion, but the place of origin is uncertain.Comment: Accepted by Astrophysical Journa