11,594 research outputs found
THE EFFECTS OF ALTERNATIVE SEASONAL PRICE DIFFERENTIALS ON MILK PRODUCTION IN NEW YORK
Uneven monthly milk production (seasonality) is a major problem in the New York dairy industry. This article estimates expected monthly milk production response to a set of hypothetical seasonal price differentials designed to reduce the degree of seasonality. The analysis is based on a random mail survey and farm record data. The results indicate that a seasonal price differential of $1.12 per cwt. (over three times the current differential) would be necessary to completely balance spring and fall production in New York, based on the perceptions of farmers surveyed. Also, producers with better managerial skills are shown to be able to reduce their seasonality at a significantly lower price differential than less skilled farm managers.Livestock Production/Industries,
Internal wave pressure, velocity, and energy flux from density perturbations
Determination of energy transport is crucial for understanding the energy
budget and fluid circulation in density varying fluids such as the ocean and
the atmosphere. However, it is rarely possible to determine the energy flux
field , which requires simultaneous measurements of
the pressure and velocity perturbation fields, and . We present
a method for obtaining the instantaneous from density
perturbations alone: a Green's function-based calculation yields , and
is obtained by integrating the continuity equation and the
incompressibility condition. We validate our method with results from
Navier-Stokes simulations: the Green's function method is applied to the
density perturbation field from the simulations, and the result for
is found to agree typically to within with
computed directly using and from the Navier-Stokes
simulation. We also apply the Green's function method to density perturbation
data from laboratory schlieren measurements of internal waves in a stratified
fluid, and the result for agrees to within with results from
Navier-Stokes simulations. Our method for determining the instantaneous
velocity, pressure, and energy flux fields applies to any system described by a
linear approximation of the density perturbation field, e.g., to small
amplitude lee waves and propagating vertical modes. The method can be applied
using our Matlab graphical user interface EnergyFlux
A Spatial Cliff-Ord-type Model with Heteroskedastic Innovations: Small and Large Sample Results
In this paper we specify a linear Cliff and Ord-type spatial model. The model allows for spatial lags in the dependent variable, the exogenous variables, and disturbances. The innovations in the disturbance process are assumed to be heteroskedastic with an unknown form. We formulate a multi-step GMM/IV type estimation procedure for the parameters of the model. We then establish the limiting distribution of our suggested estimators, and give consistent estimators for their asymptotic variance covariance matrices, utilizing results given in Kelejian and Prucha (2007b). Monte Carlo results are given which suggest that the derived large sample distribution provides a good approximation to the actual small sample distribution of our estimators.
Galaxy Morphology from NICMOS Parallel Imaging
We present high resolution NICMOS images of random fields obtained in
parallel to other HST observations. We present galaxy number counts reaching
H=24. The H-band galaxy counts show good agreement with the deepest I- and
K-band counts obtained from ground-based data. We present the distribution of
galaxies with morphological type to H<23. We find relatively fewer irregular
galaxies compared to an I-band sample from the Hubble Deep Field, which we
attribute to their blue color, rather than to morphological K-corrections. We
conclude that the irregulars are intrinsically faint blue galaxies at z<1.Comment: 13 pages, including 4 figures. Accepted for publication in ApJ
Letter
EPR spectroscopy of iron- and nickel-doped [ZnAl]-layered double hydroxides: modeling active sites in heterogeneous water oxidation catalysts
Iron-doped nickel layered double hydroxides (LDHs) are among the most active heterogeneous water oxidation catalysts. Due to inter-spin interactions, however, the high density of magnetic centers results in line-broadening in magnetic resonance spectra. As a result, gaining atomic-level insight into the catalytic mechanism via electron paramagnetic resonance (EPR) is not generally possible. To circumvent spin-spin broadening, iron and nickel atoms were doped into non-magnetic [ZnAl]-LDH materials and the coordination environments of the isolated Fe(III) and Ni(II) sites were characterized. Multifrequency EPR spectroscopy identified two distinct Fe(III) sites (S = 5/2) in [Fe:ZnAl]-LDH. Changes in zero field splitting (ZFS) were induced by dehydration of the material, revealing that one of the Fe(III) sites is solvent-exposed (i.e. at an edge, corner, or defect site). These solvent-exposed sites feature an axial ZFS of 0.21 cm⁻¹ when hydrated. The ZFS increases dramatically upon dehydration (to -1.5 cm⁻¹), owing to lower symmetry and a decrease in the coordination number of iron. The ZFS of the other (“inert”) Fe(III) site maintains an axial ZFS of 0.19-0.20 cm⁻¹ under both hydrated and dehydrated conditions. We observed a similar effect in [Ni:ZnAl]-LDH materials; notably, Ni(II) (S = 1) atoms displayed a single, small ZFS (±0.30 cm⁻¹) in hydrated material, whereas two distinct Ni(II) ZFS values (±0.30 and ±1.1 cm⁻¹) were observed in the dehydrated samples. Although the magnetically-dilute materials were not active catalysts, the identification of model sites in which the coordination environments of iron and nickel were particularly labile (e.g. by simple vacuum drying) is an important step towards identifying sites in which the coordination number may drop spontaneously in water, a probable mechanism of water oxidation in functional materials
Two stage superconducting quantum interference device amplifier in a high-Q gravitational wave transducer
We report on the total noise from an inductive motion transducer for a
gravitational-wave antenna. The transducer uses a two-stage SQUID amplifier and
has a noise temperature of 1.1 mK, of which 0.70 mK is due to back-action noise
from the SQUID chip. The total noise includes thermal noise from the transducer
mass, which has a measured Q of 2.60 X 10^6. The noise temperature exceeds the
expected value of 3.5 \mu K by a factor of 200, primarily due to voltage noise
at the input of the SQUID. Noise from flux trapped on the chip is found to be
the most likely cause.Comment: Accepted by Applied Physics Letters tentatively scheduled for March
13, 200
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