Choosing Breeds and Crossbreeding Systems by Computer

A computer program called Simumate has been developed that will allow a producer to evaluate crossbreeding systems for his particular nutrition and management situation using the breeds of his choice. This program, based on a method suggested by Dearborn (1970), takes into account energy requirements for maintenance of the cow, for milk production and for gain required during the gestation period (Neville and McCullough, 1969). It also takes into account the reproductive rate, growth rate, selling prices at several stages and the costs of production both feed and fixed in arriving at a net return for all straightbreds, all possible two breed rotation, three breed rotation and specialized crosses. In order to acquaint the producer with the program, the following example has been calculated. This example is intended only to acquaint the producer with what the program can do for him and should not be used for planning a program. The cost situation should be tailored to the individual ranch unit and the breed estimates will vary with the nutrition and management levels of different operations

Choosing Breeds and Crossbreeding Systems by Computer

The first report dealing with this project appeared in the Cow-Calf Field Day bulletin, August, 1972. That report presented an example to demonstrate the utility of the program for the cow-calf man. The example was based on estimates of performance traits for specific breeds under a particular environment and management situation and on market conditions existing at that time. The management system basic to the program took the weaning calf to 700 pounds in a backgrounding phase and then through a 140-day feedlot phase which was split into a 50-day growing period and a 90-day finishing period. The purpose of this report is to investigate varying certain of the marketing conditions, specifically selling on a retail cut basis rather than a carcass weight basis, and, secondly, eliminating the carcass quality grade as a basis for pricing the carcass. The results should assist the producer in evaluating breeds and crossbreeding systems for the marketing system he thinks will be most commonly used in the future

Application of the Cubed-Sphere Grid to Tilted Black-Hole Accretion Disks

In recent work we presented the first results of global general relativistic magnetohydrodynamic (GRMHD) simulations of tilted (or misaligned) accretion disks around rotating black holes. The simulated tilted disks showed dramatic differences from comparable untilted disks, such as asymmetrical accretion onto the hole through opposing "plunging streams" and global precession of the disk powered by a torque provided by the black hole. However, those simulations used a traditional spherical-polar grid that was purposefully underresolved along the pole, which prevented us from assessing the behavior of any jets that may have been associated with the tilted disks. To address this shortcoming we have added a block-structured "cubed-sphere" grid option to the Cosmos++ GRMHD code, which will allow us to simultaneously resolve the disk and polar regions. Here we present our implementation of this grid and the results of a small suite of validation tests intended to demonstrate that the new grid performs as expected. The most important test in this work is a comparison of identical tilted disks, one evolved using our spherical-polar grid and the other with the cubed-sphere grid. We also demonstrate an interesting dependence of the early-time evolution of our disks on their orientation with respect to the grid alignment. This dependence arises from the differing treatment of current sheets within the disks, especially whether they are aligned with symmetry planes of the grid or not.Comment: 15 pages, 11 figures, submitted to Ap

Vascular uptake of rehydration fluids in hypohydrated men at rest and exercise

The purpose of this study was to formulate and to evaluate rehydration drinks, which would restore total body water and plasma volume (PV), for astronauts to consume before and during extravehicular activity, a few hours before reentry, and immediately after landing. In the first experiment (rest, sitting), five healthy men (23-41 yr), previously dehydrated for 24 hr., drank six (1a, 2, 4, 5, 6, 7) fluid formulations (one each at weekly intervals) and then sat for 70 min. Pre-test PV were measured with Evans blue dye and changes in PV were calculated with the hematocrit-hemoglobin transformation equation. This rest experiment simulated hypohydrated astronauts preparing for reentry. The second experiment (exercise, supine) followed the same protocol except four healthy men (30-46 yr) worked for 70 min. in the supine position on a cycle ergometer at a mean load of 71+/-1 percent of their peak aerobic work capacity. This exercise experiment simulated conditions for astronauts with reduced total body water engaging in extravehicular activity

3D Numerical Experimentation on the Core Helium Flash of Low-mass Red Giants

We model the core helium flash in a low-mass red giant using Djehuty, a fully three-dimensional (3D) code. The 3D structures were generated from converged models obtained during the 1D evolutionary calculation of a 1\Msun star. Independently of which starting point we adopted, we found that after some transient relaxation the 3D model settled down with a briskly convecting He-burning shell that was not very different from what the 1D model predicted.Comment: 32 pages, 13 figures, accepted by ApJ. Figures reduced from high-res eps to low-res gif for rapid download. Contact Lattanzio for a copy of the higher res images (included, inplace, in the manuscript

Origin and evolution of the light nuclides

After a short historical (and highly subjective) introduction to the field, I discuss our current understanding of the origin and evolution of the light nuclides D, He-3, He-4, Li-6, Li-7, Be-9, B-10 and B-11. Despite considerable observational and theoretical progress, important uncertainties still persist for each and every one of those nuclides. The present-day abundance of D in the local interstellar medium is currently uncertain, making it difficult to infer the recent chemical evolution of the solar neighborhood. To account for the observed quasi-constancy of He-3 abundance from the Big Bang to our days, the stellar production of that nuclide must be negligible; however, the scarce observations of its abundance in planetary nebulae seem to contradict this idea. The observed Be and B evolution as primaries suggests that the source composition of cosmic rays has remained quasi-constant since the early days of the Galaxy, a suggestion with far reaching implications for the origin of cosmic rays; however, the main idea proposed to account for that constancy, namely that superbubbles are at the source of cosmic rays, encounters some serious difficulties. The best explanation for the mismatch between primordial Li and the observed "Spite-plateau" in halo stars appears to be depletion of Li in stellar envelopes, by some yet poorly understood mechanism. But this explanation impacts on the level of the recently discovered early ``Li-6 plateau'', which (if confirmed), seriously challenges current ideas of cosmic ray nucleosynthesis.Comment: 18 pages, 9 figs. Invited Review in "Symposium on the Composition of Matter", honoring Johannes Geiss on the occasion of his 80th birthday (Grindelwald, Switzerland, Sept. 2006), to be published in Space Science Series of ISS

The N Enrichment and Supernova Ejection of the Runaway Microquasar LS 5039

We present an investigation of new optical and ultraviolet spectra of the mass donor star in the massive X-ray binary LS 5039. The optical band spectral line strengths indicate that the atmosphere is N-rich and C-poor, and we classify the stellar spectrum as type ON6.5 V((f)). The N-strong and C-weak pattern is also found in the stellar wind P Cygni lines of N V 1240 and C IV 1550. We suggest that the N-enrichment may result from internal mixing if the O-star was born as a rapid rotator, or the O-star may have accreted N-rich gas prior to a common-envelope interaction with the progenitor of the supernova. We re-evaluated the orbital elements to find an orbital period of P=4.4267 +/- 0.0010 d. We compared the spectral line profiles with new non-LTE, line-blanketed model spectra, from which we derive an effective temperature T_eff = 37.5 +/- 1.7 kK, gravity log g = 4.0 +/- 0.1, and projected rotational velocity V sin i = 140 +/- 8 km/s. We fit the UV, optical, and IR flux distribution using a model spectrum and extinction law with parameters E(B-V)= 1.28 +/- 0.02 and R= 3.18 +/- 0.07. We confirm the co-variability of the observed X-ray flux and stellar wind mass loss rate derived from the H-alpha profile, which supports the wind accretion scenario for the X-ray production in LS 5039. Wind accretion models indicate that the compact companion has a mass M_X/M_sun = 1.4 +/- 0.4, consistent with its identification as a neutron star. The observed eccentricity and runaway velocity of the binary can only be reconciled if the neutron star received a modest kick velocity due to a slight asymmetry in the supernova explosion (during which >5 solar masses was ejected).Comment: 38 pages, 9 figures; 2004, ApJ, 600, Jan. 10 issue, in press Discussion revised thanks to comments from P. Podsiadlowsk

Cool bottom processes on the thermally-pulsing AGB and the isotopic composition of circumstellar dust grains

(Abridged) We examine the effects of cool bottom processing (CBP) on several isotopic ratios in the convective envelope during the TP-AGB phase of evolution in a 1.5 M_sun initial-mass star of solar initial composition. We use a parametric model which treats extra mixing by introducing mass flow between the convective envelope and the underlying radiative zone. The parameters of this model are the mass circulation rate (Mdot) and the maximum temperature (T_P) experienced by the circulating material. The effects of nuclear reactions in the flowing matter were calculated using a set of structures of the radiative zone selected from a complete stellar evolution calculation. The compositions of the flowing material were obtained and the resulting changes in the envelope determined. Abundant ^26Al was produced by CBP for log T_P > 7.65. While ^26Al/^27Al depends on T_P, the isotopic ratios in CNO elements depend dominantly on the circulation rate. The correspondence is shown between models of CBP as parameterized by a diffusion formalism within the stellar evolution model and those using the mass-flow formalism employed here. The isotopic ratios are compared with the data on circumstellar dust grains. It is found that the ratios ^{18}O/^{16}O, ^{17}O/^{16}O, and ^26Al/^27Al observed for oxide grains formed at C/O < 1 are reasonably well-understood. However, the ^15N/^14N, ^12C/^13C, and ^26Al/^27Al in carbide grains (C/O > 1) require many stellar sources with ^14N/^15N at least a factor of 4 below solar. The rare grains with ^12C/^13C < 10 cannot be produced by any red-giant or AGB source.Comment: 35 pages, plus 18 included figures. Scheduled for January 10, 2003 issue of Ap

Effect of Neutrino Heating on Primordial Nucleosynthesis

We have modified the standard code for primordial nucleosynthesis to include the effect of the slight heating of neutrinos by $e^\pm$ annihilations. There is a small, systematic change in the $^4$He yield, $\Delta Y \simeq +1.5\times 10^{-4}$, which is insensitive to the value of the baryon-to-photon ratio $\eta$ for 10^{-10}\la \eta \la 10^{-9}. We also find that the baryon-to-photon ratio decreases by about 0.5\% less than the canonical factor of 4/11 because some of the entropy in $e^\pm$ pairs is transferred to neutrinos. These results are in accord with recent analytical estimates.Comment: 14 pages/4 Figs (upon request