REGIONAL ACREAGE RESPONSE FOR U.S. CORN AND WHEAT: THE EFFECTS OF GOVERNMENT PROGRAMS

This paper presents findings from an analytical scheme that offers a promising alternative to traditional procedures of modeling acreage response. The scheme addresses the two-step decision process in which program and nonprogram planting decisions are modeled separately, conditional on the decision to participate. This provides a more realistic and intuitive portrayal of producersÂ’ decision making process. The model is applied at the regional level to assess the impact of farm programs on acreage response for corn in the Cornbelt and Lake States, and for wheat in the Northern Plains. The impacts of policy variable changes on participation and planted acreage are also analyzed.Agricultural and Food Policy,

Ionosphere/microwave beam interaction study

A solar power satellite microwave power density of 20mw sq cm was confirmed as the level where nonlinear interactions may occur in the ionosphere, particularly at 100 km altitude. Radio wave heating at this altitude, produced at the Arecibo Observatory, yielded negative results for radio wave heating of an underdense ionosphere. Overdense heating produced striations in the ionosphere which may cause severe radio frequency interference problems under certain conditions. The effects of thermal self-focusing are shown to be limited severely geographically. The aspect sensitivity of field-aligned striations makes interference-free regions above magnetic latitude about 60 deg. A test program is proposed to simulate the interaction of the SPS beam with the ionosphere, to measure the effects of the interaction on the ionosphere and on communication and navigation systems, and to interpret the results

Aspects of the biology of the herring gull (larus atgentatus pont.)

A study of the herring gull Larus argentatus emphasising interrelationships of population ecology, social behaviour and breeding biology was undertaken on the Isle of May, Scotland, with some comparative work in a moorland gull colony on Mallowdale Fell in the Pennines. A cull of the herring gull population, which had hitherto been increasing at 13% per annum, has been practised by the Nature Conservancy Council on the Isle of May yearly since 1972, and special attention was given in this study to the biological effects of culling. The population trends were followed in detail up to 1977, and it was shown that the annual, recruitment rate has been very variable since 1972 and there has been a shortfall in the number of young gulls predicted to join the breeding population. These have presumably moved and some ringed gulls were located breeding in other colonies. The population has been held at about 20-25% of its 1972 level since 1975. With many of the older gulls having been culled, the average age of the population had been reduced, so that by 1977 about 50% of the population was breeding for the first time. Despite a strong correlation between parental age and percentage breeding success, the average number of chicks fledged per pair in control areas was 0.82, which was as high as that recorded in a previous study by Parsons (1971, unpublished Ph.D. thesis, Durham University) on the Isle of May in the late 1960s. In addition, it was found that the median date of laying was the same as that estimated by Parsons, and that egg size (positively correlated with chick survival) had increased significantly. Experiments on recruitment by manipulating breeding density showed that at the highest densities recorded the annual recruitment rate was close to the average annual mortality rate. In areas where density had been greatly reduced, the recruitment rate was insufficient to replace annual adult mortality, and in some areas no recruitment was recorded. There was a broad, optimal breeding density of between 2 and 10 nests/l00m(^2) where highest recruitment rates took place. Much of the Isle of May was found to be at this density as a result of culling. Birds which spread their nests most uniformly were the most successful breeders, and the majority of nests were thus spaced. Aggression was found to increase with density. The rationale of gull culling has been discussed for the Isle of May, together with recommendations for future culls on the island and elsewhere

The Populations of Comet-Like Bodies in the Solar system

A new classification scheme is introduced for comet-like bodies in the Solar system. It covers the traditional comets as well as the Centaurs and Edgeworth-Kuiper belt objects. At low inclinations, close encounters with planets often result in near-constant perihelion or aphelion distances, or in perihelion-aphelion interchanges, so the minor bodies can be labelled according to the planets predominantly controlling them at perihelion and aphelion. For example, a JN object has a perihelion under the control of Jupiter and aphelion under the control of Neptune, and so on. This provides 20 dynamically distinct categories of outer Solar system objects in the Jovian and trans-Jovian regions. The Tisserand parameter with respect to the planet controlling perihelion is also often roughly constant under orbital evolution. So, each category can be further sub-divided according to the Tisserand parameter. The dynamical evolution of comets, however, is dominated not by the planets nearest at perihelion or aphelion, but by the more massive Jupiter. The comets are separated into four categories -- Encke-type, short-period, intermediate and long-period -- according to aphelion distance. The Tisserand parameter categories now roughly correspond to the well-known Jupiter-family comets, transition-types and Halley-types. In this way, the nomenclature for the Centaurs and Edgeworth-Kuiper belt objects is based on, and consistent with, that for comets.Comment: MNRAS, in press, 11 pages, 6 figures (1 available as postscript, 5 as gif). Higher resolution figures available at http://www-thphys.physics.ox.ac.uk/users/WynEvans/preprints.pd

Unquenched QCD with Light Quarks

We present recent results in unquenched lattice QCD with two degenerate light sea quarks using the truncated determinant approximation (TDA). In the TDA the infrared modes contributing to the quark determinant are computed exactly up to some cutoff in quark off-shellness (typically 2$\Lambda_{QCD}$). This approach allows simulations to be performed at much lighter quark masses than possible with conventional hybrid MonteCarlo techniques. Results for the static energy and topological charge distributions are presented using a large ensemble generated on very coarse (6$^4$) but physically large lattices. Preliminary results are also reported for the static energy and meson spectrum on 10$^3$x20 lattices (lattice scale $a^{-1}$=1.15 GeV) at quark masses corresponding to pions of mass $\leq$ 200 MeV. Using multiboson simulation to compute the ultraviolet part of the quark determinant the TDA approach becomes an exact with essentially no increase in computational effort. Some preliminary results using this fully unquenched algorithm are presented.Comment: LateX, 39 pages, 16 eps figures, 1 ps figur

ECONOMIC FEASIBILITY OF THE CATTLE FEEDING INDUSTRY IN THE NORTHERN PLAINS AND WESTERN LAKES STATES - SUMMARY

The five-state study area of the Northern Plains and Western Lakes States, Minnesota, Montana, North Dakota, South Dakota, and Wisconsin, has adequate feed supplies and feeder cattle to markedly increase cattle feeding. Feed costs in these states have historically been lower than in the Southern Plains States. However, higher transportation costs appear to offset that advantage. Close access to slaughter plants in these states could offset that transportation disadvantage. Backgrounding of cattle appears to be quite profitable and cattle feeding, especially in larger sized feedlots, can be profitable. However, the cattle feeding industry has an increasing level of excess capacity. To be successful, new feedlots in the Northern Plains and Western Lakes States would need cost efficiencies to offset higher production costs, compared to Nebraska and Kansas, or would need to produce for a niche market unaffected by the lower operating costs of already established feedlots in the Central and Southern Plains States. Finally, a range of strategies are available in developing value-added cattle production in the Northern Plains and Western Lakes States. These strategies embody differing levels of capital investment, and involve different levels of risk and profitability.cattle feeding, Northern Plains, economies of scale, cooperative ownership, entrance strategies, Production Economics,

Triton's surface age and impactor population revisited in light of Kuiper Belt fluxes: Evidence for small Kuiper Belt objects and recent geological activity

Neptune's largest satellite, Triton, is one of the most fascinating and enigmatic bodies in the solar system. Among its numerous interesting traits, Triton appears to have far fewer craters than would be expected if its surface was primordial. Here we combine the best available crater count data for Triton with improved estimates of impact rates by including the Kuiper Belt as a source of impactors. We find that the population of impactors creating the smallest observed craters on Triton must be sub-km in scale, and that this small-impactor population can be best fit by a differential power-law size index near -3. Such results provide interesting, indirect probes of the unseen small body population of the Kuiper Belt. Based on the modern, Kuiper Belt and Oort Cloud impactor flux estimates, we also recalculate estimated ages for several regions of Triton's surface imaged by Voyager 2, and find that Triton was probably active on a time scale no greater than 0.1-0.3 Gyr ago (indicating Triton was still active after some 90% to 98% of the age of the solar system), and perhaps even more recently. The time-averaged volumetric resurfacing rate on Triton implied by these results, 0.01 km$^3$ yr$^{-1}$ or more, is likely second only to Io and Europa in the outer solar system, and is within an order of magnitude of estimates for Venus and for the Earth's intraplate zones. This finding indicates that Triton likely remains a highly geologically active world at present, some 4.5 Gyr after its formation. We briefly speculate on how such a situation might obtain.Comment: 14 pages (TeX), plus 2 postscript figures Stern & McKinnon, 2000, AJ, in pres