AN ANALYSIS OF U.S. DAIRY POLICY DEREGULATION USING AN IMPERFECT COMPETITION MODEL

An imperfect competition model of the U.S. milk market is developed for analyzing the impacts of dairy policy deregulation. Estimated degree-of-competition parameters indicate that the U.S. milk market has become more competitive over time. The usefulness of the model is demonstrated by showing the relative differences of dynamic simulation results of the imperfect competition model with the results of a conventional exogenous fluid differential model.Agricultural and Food Policy,

MODELING THE U.S. DAIRY SECTOR WITH GOVERNMENT INTERVENTION

An econometric framework for estimating a two-regime dairy structural system is presented. Failure to account for switching between regimes due to government price intervention raises the problem of selectivity bias. Further, since a structural system of equations is involved, the problem is not limited to the market associated with the intervention. Rather, bias from a single source can distort all equations in the system. The ramifications of not correcting for the bias in policy analyses are investigated.Agricultural and Food Policy, Industrial Organization,

GENERIC ADVERTISING WEAROUT: THE CASE OF THE NEW YORK CITY FLUID MILK CAMPAIGN

This article examines two major generic fluid milk advertising campaigns in New York City during the 1986-92 period. Estimates from a time-varying parameter model show that the evolution of the impact of generic advertising on fluid milk sales over each campaign followed a bell-shaped pattern. Results also show that the first campaign was effective for twice as long as the second campaign and that it has a higher peak and higher average advertising elasticity. These findings may reflect long-term generic milk advertising wearout in the New York City market.Marketing,

AN ECONOMIC ANALYSIS OF THE U.S. GENERIC DAIRY ADVERTISING PROGRAM USING AN INDUSTRY MODEL

The market impacts of generic dairy advertising are assessed using an industry model which encompasses supply and demand conditions at the retail, wholesale, and farm levels, and government intervention under the dairy price support program. The estimated model is used to simulate price and quantity values for four advertising scenarios: (1) no advertising, (2) historical fluid advertising, (3) historical manufactured advertising, and (4) historical fluid and manufactured advertising. Compared to previous studies, the dairy-industry model provides additional insights into the way generic dairy advertising influences prices and quantities at the retail, wholesale, and farm levels.Livestock Production/Industries, Marketing,

Perturbed-angular-correlation study of phase transformations in nanoscaled Al₂O₃-coated and noncoated ZrO₂ particles synthesized in a microwave plasma

The phase transformations of nanoscaled (n-) Al$_{2}$O$_{3}$-coated and noncoated ZrO$_{2}$ particles synthesized in a microwave plasma have been investigated by perturbed-angular-correlation (PAC) measurements of the electric quadrupole interaction (QI) of $^{181}$Ta on Zr sites between 290 and 1600 K. For the phase identification and structural characterization the QI parameters of the nanoscaled particles are compared to those of coarsegrained ZrO$_{2}$ which were measured between 290 and 2160 K. The PAC spectra of the nanoscaled particles in the as-prepared state are characterized by a broad distribution of strong, axially asymmetric QI’s, which reflects a highly disordered oxygen environment of the Zr sites. Upon annealing, the tetragonal phase is the first well-crystallized structure to emerge at about 500 K, both in coated and noncoated n-ZrO2, in contrast to the previously reported annealing reaction of n-ZrO$_{2}$ synthesized by gas-phase condensation in which the tetragonal phase has not been observed. This disorder-order transformation is partially reversible upon cooling. In n-ZrO$_{2}$ /Al$_{2}$O$_{3}$ synthesized in a microwave plasma the monoclinic phase can be completely suppressed up to 1600 K. In the noncoated particles monoclinic ZrO$_{2}$ starts to appear at 600 K. At 1400 K the transformation from the monoclinic to the tetragonal phase of noncoated n-ZrO2 was observed to occur with a transformation rate of $\lambda$=6.9(1.2)x10$^{-5}$ s$^{-1}$. In nanoscaled coated and noncoated tetragonal ZrO$_{2}$ the T$^{3/2}$-temperature dependence of the quadrupole frequency v$_{q}$ is weaker than in the same phase of the coarse-grained compound, suggesting a decrease of the mean-square vibrational amplitudes with decreasing particle size

Comment on “Nature and entropy content of the ordering transitions in RCo₂”

In their analysis of our perturbed angular correlation (PAC) study of the magnetic phase transitions of RCo₂ [Phys. Rev. B 68, 014409 (2003)], Herrero-Albillos [Phys. Rev. B 73, 134410 (2006)] come to the conclusion that it is very difficult for PAC spectroscopy to distinguish a first-order from a second-order phase transition. The statement is incorrect and does not resolve the conflict between the conclusion drawn from the PAC data and the differential scanning calorimetry data of Herrero- Albillos on the order of the magnetic phase transitions of PrCo₂ and NdCo₂. In this Comment we show that measurements of hyperfine interactions by PAC and other microscopic techniques are a very powerful tool for the investigation of phase transitions which may provide details on the transition not accessible to macroscopic methods. We explain why the PAC data leave no alternative to the conclusion that the spontaneous magnetization of PrCo₂ and NdCo₂ undergoes a discontinuous, first-order phase transition at T_(C)

Perturbed angular correlation study of the magnetic phase transitions in the rare-earth cobalt Laves phases RCo₂

The order and other properties of the magnetic phase transitions in the rare-earth (R)-cobalt Laves phases RCo2 have been studied for R=Gd, Tb, Dy, Ho, Er, Sm, Nd, and Pr by measuring the temperature dependence of the magnetic hyperfine interaction of the nuclear probe ^111Cdon the cubic R sites using the perturbed angular correlation technique. Both for heavy and light R constituents the transitions change from second order (Gd, Tb, Sm) to first order (Dy, Ho, Er, Nd, Pr) at order temperatures of 150-200 K. For heavy R constituents, the order deduced from the hyperfine interaction is in agreement with previous investigations. The observation of first order transitions in NdCo₂ and PrCo₂, however, is unexpected. In earlier studies the transitions in these compounds are usually classified as second order transitions. Both in the heavy and the light RCo₂ the discontinuous jump of the hyperfine interaction at the first order transitions increases with decreasing order temperature. This trend implies that the Co magnetization at the transition increases with decreasing T_C which can be related to the temperature dependence of the coefficient of the M^(4) term of the free energy in the Wohlfarth-Rhodes-Shimizu theory of itinerant electron magnetism. All compounds investigated presented a spread of the order temperature of similar to1-2 K which results in a coexistence of the paramagnetic and the magnetically ordered phase near the transition and causes a critical increase of the relative linewidth of the hyperfine frequency diverging as δ ∞ [(1-T/T_(C)]^ε with ε =-1.0(1)

Perturbed angular correlation study of the magnetic phase transitions in the rare-earth cobalt Laves phases RCo₂

The order and other properties of the magnetic phase transitions in the rare-earth (R)-cobalt Laves phases RCo₂ have been studied for R=Gd, Tb, Dy, Ho, Er, Sm, Nd, and Pr by measuring the temperature dependence of the magnetic hyperfine interaction of the nuclear probe ¹¹¹Cd on the cubic R sites using the perturbed angular correlation technique. Both for heavy and light R constituents the transitions change from second order (Gd, Tb, Sm) to first order (Dy, Ho, Er, Nd, Pr) at order temperatures of 150‐200 K. For heavy R constituents, the order deduced from the hyperfine interaction is in agreement with previous investigations. The observation of first order transitions in NdCo₂ and PrCo₂, however, is unexpected. In earlier studies the transitions in these compounds are usually classified as second order transitions. Both in the heavy and the light RCo₂ the discontinuous jump of the hyperfine interaction at the first order transitions increases with decreasing order temperature. This trend implies that the Co magnetization at the transition increases with decreasing TC which can be related to the temperature dependence of the coefficient of the M⁴ term of the free energy in the Wohlfarth-Rhodes-Shimizu theory of itinerant electron magnetism. All compounds investigated presented a spread of the order temperature of ∼ 1–2 K which results in a coexistence of the paramagnetic and the magnetically ordered phase near the transition and causes a critical increase of the relative linewidth of the hyperfine frequency diverging as δ∝(1–T/TC)ε with ε = –1.0(1).Facultad de Ciencias Exacta

Spectrum of magnetic hyperfine fields at ^111 C probe nuclei in the pseudobinary rare-earth Laves-phase compounds R_(1-x)Y_xCo₂

The spectrum of the magnetic hyperfine fields at the closed-shell probe nucleus ^111 Cd on the rare earth (R) site of the pseudobinary Laves-phase compounds R_81-x)Y_xCo₂ has been investigated by perturbed angular correlation (PAC) spectroscopy at 10 K for the rare earth R=Tb and Ho at various Y concentrations x ≤ 0.8 and for R=Gd, Dy, Er at the concentration x=0.3. Up to four components with different magnetic interaction frequencies ν^(i) _(M) could be resolved from the PAC spectra. The relative intensities of these components are in fair agreement with those of a binomial distribution of Y atoms on the four nearest neighbor (NN) R sites of the probe nucleus. For all R constituents, one finds a strictly linear relation between the number n_(R) of NN R atoms and the magnetic hyperfine frequencies: ν^(i) _(M) =ν_(M)(4Y)+∆ ν(M) Xn_(R).The frequency ν_(M)(4Y)=35(2) MHz is independent of the R constituent and of the Y concentration up to x ≤ 0.6. These properties identify ν_(M)(4Y) as the contribution of the Co 3d moments to the hyperfine interaction at the ^111 Cdsite. The frequency steps ∆ ν_(M)[≤ 0.1 ν_(M)(4Y)] reflect the spin polarization directly induced by the 4f spins at the probe nucleus. From Gd to Er, the spin polarization decreases much stronger than expected from the linear variation of the 4f spin in the heavy R series. An indirect 4f contribution caused by a dependence of the Co 3d moment on the number of R neighbors can be excluded. The relation ν_(M)^(i) = ν_(M)(4Y) + ∆ν_(M) X n_(R) then implies that the contributions of the 3d and 4f spins to the magnetic hyperfine field in RCo₂ have the same relative sign