A comparison of systems of developing beef bulls to about twenty months of age

Performance testing is important in the beef cattle industry as an aid to selection for improvement. It is an excellent means for evaluating the genotypic and phenotypic worth of an animal. Since the sire transmits one-half of the genetic material of each calf, an estimate of the genetic potential of each sirs should be made prior to selection if optimum genetic progress is to be accomplished. Despite the need for choosing a herd sire with a reliable performance record, there is still little information in the literature relating to methods of developing beef breeding bulls. Most per-formance testing programs for beef bulls have been progeny tests. These are useful in predicting a bull\u27s prepotency but are time con-suming and expensive. Most post-weaning performance tests for beef cattle have emphasized that the best way to evaluate the gaining and feed utilizing ability of an animal is to feed a maximum of concentrate for a period of 140 days or some similar period. This type of test has been used as one of the criteria for the selection of breeding stock. Ruminant animals have the unique ability of converting low cost roughages, with the assistance of rumen microorganisms, into a wholesome, nutritious human food. Since roughages are a natural food for beef cattle, it is more economical and practical to feed high levels of roughages to beef animals for development and maintenance. There may be times when high levels of concentrates are desirable, such as a finishing period for slaughter animals, yet this is only a short span in the lifetime of an animal. To obtain more data on methods of developing bulls and consider-ing the foregoing facts, a comparison of methods of developing bulls was initiated by the Animal Husbandry-Veterinary Science Department at the University of Tennessee. In an earlier report, Anderson (1962) concluded that the most desirable program of those tested for developing bulls was: 1. A 140-day wintering period in which the basic ration con-sisted of a full feed of corn silage, 2 lb. of alfalfa hay and 5.5 lb. of concentrate per head per day. 2. A pasture period of approximately 90 days during which time the bulls were allowed to consume an average of approximately 1 lb. of concentrate per 100 lb. of body weight daily in addition to pasture. 3. A 98-day full-feed period. This was designated as the BA system of developing bulls. In a later report, Knapka (1963) compared the BA system with one designated as the CA system. The CA system differed from the BA system only in that during the 140-day wintering period 2.5 lb. of concentrates were fed instead of 5.5 lb. Throughout the three periods the bulls on the BA system had an average daily gain of 1.92 lb. as compared to 1.82 lb. for the bulls on the CA system. The lifetime average daily gain, type grade and con-dition grade were slightly higher for the bulls on the BA system, but there was no significant difference between treatment groups for the entire test period. Because the bulls on the CA system obtained a greater percentage of their nutrients from less expensive roughages during the winter period, the feed cost per head was $11.40 less for the bulls on the CA system than for those on the BA system. The main disadvantage of these two systems compared to a 140-day full-feed test is the higher feed, labor and handling cost resulting from the extended length of time on test. Also, there is some delay in obtaining the complete data on a bull, which could result in consid-erable retardation of genetic progress. The objectives of this thesis are to compare bulls developed on the BA system with those developed on the CA system and to relate their performance from birth to weaning with their post-weaning per-formance

Towards New Comet Missions

The Rosetta observations have greatly advanced our knowledge of the cometary nucleus and its immediate environment. However, constraints on the mission (both planned and unplanned), the only partially successful Philae lander, and other instrumental issues have inevitably resulted in open questions. Surprising results from the many successful Rosetta observations have also opened new questions, unimagined when Rosetta was first planned. We discuss these and introduce several mission concepts that might address these issues. It is apparent that a sample return mission as originally conceived in the 1980s during the genesis of Rosetta would provide many answers but it is arguable whether it is technically feasible even with today’s technology and knowledge. Less ambitious mission concepts are described to address the suggested main outstanding scientific goals

Implications of the Small Spin Changes Measured for Large Jupiter-Family Comet Nuclei

Rotational spin-up due to outgassing of comet nuclei has been identified as a possible mechanism for considerable mass-loss and splitting. We report a search for spin changes for three large Jupiter-family comets (JFCs): 14P/Wolf, 143P/Kowal-Mrkos, and 162P/Siding Spring. None of the three comets has detectable period changes, and we set conservative upper limits of 4.2 (14P), 6.6 (143P) and 25 (162P) minutes per orbit. Comparing these results with all eight other JFCs with measured rotational changes, we deduce that none of the observed large JFCs experiences significant spin changes. This suggests that large comet nuclei are less likely to undergo rotationally-driven splitting, and therefore more likely to survive more perihelion passages than smaller nuclei. We find supporting evidence for this hypothesis in the cumulative size distributions of JFCs and dormant comets, as well as in recent numerical studies of cometary orbital dynamics. We added 143P to the sample of 13 other JFCs with known albedos and phase-function slopes. This sample shows a possible correlation of increasing phase-function slopes for larger geometric albedos. Partly based on findings from recent space missions to JFCs, we hypothesise that this correlation corresponds to an evolutionary trend for JFCs. We propose that newly activated JFCs have larger albedos and steeper phase functions, which gradually decrease due to sublimation-driven erosion. If confirmed, this could be used to analyse surface erosion from ground and to distinguish between dormant comets and asteroids

Pre-Impact Thermophysical Properties and the Yarkovsky Effect of NASA DART Target (65803) Didymos

The NASA DART (Double Asteroid Redirection Test) spacecraft impacted the secondary body of the binary asteroid (65803) Didymos on 2022 September 26and altered its orbit about the primary body. Before the DART impact, we performed visible and mid-infrared observations to constrain the pre-impact thermophysical properties of the Didymos system and to model its Yarkovsky effect. Analysis of the photometric phase curve derives a Bond albedo of 0.07 ± 0.01, and a thermophysical analysis of the mid-infrared observations derives a thermal inertia of 320 ± 70 J m-2 K-1 s-1/2 and a thermal roughness of 40° ± 3° RMS (root-mean-square) slope. These properties are compatible with the ranges derived for other S-type near-Earth asteroids. Model-to-measurement comparisons of the Yarkovsky orbital drift for Didymos derives a bulk density of 2750 ± 350 kg m-3, which agrees with other independent measures based on the binary mutual orbit. This bulk density indicates that Didymos is spinning at or near its critical spin-limit at which self-gravity balances equatorial centrifugal forces. Furthermore, comparisons with the post-impact infrared observations presented in Rivkin et al. (2023) indicate no change in the thermal inertia of the Didymos system following the DART impact. Finally, orbital temperature simulations indicate that sub-surface water ice is stable over geologic timescales in the polar regions if present. These findings will be investigated in more detail by the upcoming ESA Hera mission.<br/

Pre-impact Thermophysical Properties and the Yarkovsky Effect of NASA DART Target (65803) Didymos

The NASA Double Asteroid Redirection Test (DART) spacecraft impacted the secondary body of the binary asteroid (65803) Didymos on 2022 September 26 and altered its orbit about the primary body. Before the DART impact, we performed visible and mid-infrared observations to constrain the pre-impact thermophysical properties of the Didymos system and to model its Yarkovsky effect. Analysis of the photometric phase curve derives a Bond albedo of 0.07 ± 0.01, and a thermophysical analysis of the mid-infrared observations derives a thermal inertia of 320 ± 70 J m−2 K−1 s−1/2 and a thermal roughness of 40° ± 3° rms slope. These properties are compatible with the ranges derived for other S-type near-Earth asteroids. Model-to-measurement comparisons of the Yarkovsky orbital drift for Didymos derives a bulk density of 2750 ± 350 kg m−3, which agrees with other independent measures based on the binary mutual orbit. This bulk density indicates that Didymos is spinning at or near its critical spin-limit at which self-gravity balances equatorial centrifugal forces. Furthermore, comparisons with the post-impact infrared observations presented in Rivkin et al. indicate no change in the thermal inertia of the Didymos system following the DART impact. Finally, orbital temperature simulations indicate that subsurface water ice is stable over geologic timescales in the polar regions if present. These findings will be investigated in more detail by the upcoming ESA Hera mission

The Main Belt Comets and ice in the Solar System

We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies

Enveloping Sophisticated Tools into Process-Centered Environments

We present a tool integration strategy based on enveloping pre-existing tools without source code modifications or recompilation, and without assuming an extension language, application programming interface, or any other special capabilities on the part of the tool. This Black Box enveloping (or wrapping) idea has existed for a long time, but was previously restricted to relatively simple tools. We describe the design and implementation of, and experimentation with, a new Black Box enveloping facility intended for sophisticated tools --- with particular concern for the emerging class of groupware applications

A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2

The peculiar object P/2010 A2 was discovered by the LINEAR near-Earth asteroid survey in January 2010 and given a cometary designation due to the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized class of 'Main Belt Comets' (MBCs). If confirmed, this new object would greatly expand the range in heliocentric distance over which MBCs are found. Here we present observations taken from the unique viewing geometry provided by ESA's Rosetta spacecraft, far from the Earth, that demonstrate that the trail is due to a single event rather than a period of cometary activity, in agreement with independent results from the Hubble Space Telescope (HST). The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around February 10, 2009.Comment: Published in Nature on 14/10/2010. 25 pages, includes supplementary materia

The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos

Hera is a planetary defense mission under development in the Space Safety and Security Program of the European Space Agency for launch in 2024 October. It will rendezvous in late 2026 December with the binary asteroid (65803) Didymos and in particular its moon, Dimorphos, which will be impacted by NASA’s DART spacecraft on 2022 September 26 as the first asteroid deflection test. The main goals of Hera are the detailed characterization of the physical properties of Didymos and Dimorphos and of the crater made by the DART mission, as well as measurement of the momentum transfer efficiency resulting from DART’s impact. The data from the Hera spacecraft and its two CubeSats will also provide significant insights into asteroid science and the evolutionary history of our solar system. Hera will perform the first rendezvous with a binary asteroid and provide new measurements, such as radar sounding of an asteroid interior, which will allow models in planetary science to be tested. Hera will thus provide a crucial element in the global effort to avert future asteroid impacts at the same time as providing world-leading science