A LINEAR APPROXIMATE ACREAGE ALLOCATION MODEL

It is shown that the first-order differential acreage allocation model developed by Bettendorf an Bloome and by Barten and Vanloot, and based on certainty equivalent profit maximization, may be extended to a levels version. The levels model, referred to as a linear approximate acreage allocation model, is potentially useful when panel or cross-sectional data are employed. An empirical application with U.S. state-level corn flex acreage data for the period 1991-95 indicates the feasibility of the approach. Estimated price and scale elasticities are generally larger than previous estimates, and are perhaps indicative of acreage response under the provisions of the 1996 Farm Act.Crop Production/Industries,

Microscopic Restoration of Proton-Neutron Mixed Symmetry in Weakly Collective Nuclei

Starting from the microscopic low-momentum nucleon-nucleon interaction V{low k}, we present the first systematic shell model study of magnetic moments and magnetic dipole transition strengths of the basic low-energy one-quadrupole phonon excitations in nearly-spherical nuclei. Studying in particular the even-even N=52 isotones from 92Zr to 100Cd, we find the predicted evolution of the predominantly proton-neutron non-symmetric state reveals a restoration of collective proton-neutron mixed-symmetry structure near mid-shell. This provides the first explanation for the existence of pronounced collective mixed-symmetry structures in weakly-collective nuclei.Comment: 5 Pages, 3 figure

Prediction and analysis of long-term variability of temperature and salinity in the Irish Sea

The variability of temperature and salinity in the Irish Sea over the 40 year period 1960 - 1999 is investigated using a free-running fine-resolution local area model. The skill of the model to represent observed temperature and salinity variability is assessed using conductivity-temperature-depth survey data ( 3397 profiles) and a long time series of measurements from Cypris station (southwest of Isle of Man). This clearly demonstrates that the model can reproduce the observed seasonal and longer-term cycles in temperature, with mean and RMS errors of - 0.01 degrees C and 0.78 degrees C. Particularly apparent is the long-term warming trend at Cypris station and throughout the model domain. Model estimates of salinity are less accurate and are generally too saline (mean and RMS errors are 0.79 and 0.98 practical salinity units). Inaccuracies are likely to arise from boundary conditions and forcing (riverine and surface). However, while absolute values are not particularly well represented, the model reproduces many of the trends in the salinity variability observed at Cypris station, suggesting that the dominant physical processes in the Irish Sea, with timescales up to similar to 3 years, are well represented. The model is also used to investigate the variability in temperature stratification. While stratification is confined to approximately the same geographical area in each year of the simulation, there is significant variability in the timing of the onset and breakdown of stratification and in the peak surface to bed temperature difference. Together, these results suggest that a local area model with limited boundary conditions may be sufficiently accurate for climatic investigation of some (locally forced) parameter

Breaks, bubbles, booms, and busts: the evolution of primary commodity price fundamentals

This paper explores the behavior of real commodity prices over a 50–year period. Attention is given to how the fundamentals for various commodity prices have changed with a special emphasis on behavior since the mid 2000s. To identify changing commodity price fundamentals we estimate shifting–mean autoregressions by using: the Bai and Perron (1998) procedure for estimating structural breaks; a SlowShift procedure that specifies intercepts to be nonlinear, potentially smooth functions of time; and low frequency Fourier functions. We find that the pattern in the timing of the various shifts is suggestive of the causal fundamentals underlying the recent boom.Commodity Prices, Fundamentals, Nonlinear Trends, Shifting--Mean Autoregression

EFFICIENCY OF FOREST COMMODITY FUTURES MARKETS

Market efficiency and unbiasedness tests are performed for the first time for three forest commodity futures markets: softwood lumber, oriented strand board (OSB), and northern bleached softwood kraft pulp (NBSK). The Johansen cointegration procedure is applied to test long-term market efficiency, while the standard error correction models (ECM) and ECM with GQARCH-in-mean process are also used to examine short-term market efficiency and unbiasedness. Results show that these markets are inefficient and biased in both the long-term and short-term. Results also indicate that no short-term time-varying risk premiums are found in these commodity futures markets.Marketing,

PRICE UNCERTAINTY AND AGRICULTURAL PRODUCTIVITY

This paper examines the effects of price uncertainty on agricultural productivity. Appelbaum(1991) provided an empirical framework to analyze the effects of uncertainty on firm behavior. We apply the model to the U.S. agricultural sector, using a parametric rather than a nonparametric approach to obtain the measurement of price uncertainty and risk. Keywords: risk, uncertainty, productivityrisk, uncertainty, productivity, Productivity Analysis,

Shell model description of the 14C dating beta decay with Brown-Rho-scaled NN interactions

We present shell model calculations for the beta-decay of the 14C ground state to the 14N ground state, treating the states of the A=14 multiplet as two 0p holes in an 16O core. We employ low-momentum nucleon-nucleon (NN) interactions derived from the realistic Bonn-B potential and find that the Gamow-Teller matrix element is too large to describe the known lifetime. By using a modified version of this potential that incorporates the effects of Brown-Rho scaling medium modifications, we find that the GT matrix element vanishes for a nuclear density around 85% that of nuclear matter. We find that the splitting between the (J,T)=(1+,0) and (J,T)=(0+,1) states in 14N is improved using the medium-modified Bonn-B potential and that the transition strengths from excited states of 14C to the 14N ground state are compatible with recent experiments.Comment: 4 pages, 5 figures Updated to include referee comments/suggestion