REGIONAL GAINS AND LOSSES FOR CONSUMERS AND PRODUCERS FROM CHANGES IN FLUID MILK PRICES

Agribusiness,

SIMULATING OZONE EFFECTS ON FOREST PRODUCTIVITY: INTERACTIONS AMONG LEAF‐, CANOPY‐, AND STAND‐LEVEL PROCESSES

Ozone pollution in the lower atmosphere is known to have adverse effects on forest vegetation, but the degree to which mature forests are impacted has been very difficult to assess directly. In this study, we combined leaf‐level ozone response data from independent ozone fumigation studies with a forest ecosystem model in order simulate the effects of ambient ozone on mature hardwood forests. Reductions in leaf carbon gain were determined as a linear function of ozone flux to the leaf interior, calculated as the product of ozone concentration and leaf stomatal conductance. This relationship was applied to individual canopy layers within the model in order to allow interaction with stand‐ and canopy‐level factors such as light attenuation, leaf morphology, soil water limitations, and vertical ozone gradients. The resulting model was applied to 64 locations across the northeastern United States using ambient ozone data from 1987 to 1992. Predicted declines in annual net primary production ranged from 3 to 16% with greatest reductions in southern portions of the region where ozone levels were highest, and on soils with high water‐holding capacity where drought stress was absent. Reductions in predicted wood growth were slightly greater (3–22%) because wood is a lower carbon allocation priority in the model than leaf and root growth. Interannual variation in predicted ozone effects was small due to concurrent fluctuations in ozone and climate. Periods of high ozone often coincided with hot, dry weather conditions, causing reduced stomatal conductance and ozone uptake. Within‐canopy ozone concentration gradients had little effect on predicted growth reductions because concentrations remained high through upper canopy layers where net carbon assimilation and ozone uptake were greatest. Sensitivity analyses indicate a trade‐off between model sensitivity to available soil water and foliar nitrogen and demonstrate uncertainties regarding several assumptions used in the model. Uncertainties surrounding ozone effects on stomatal function and plant water use efficiency were found to have important implications on current predictions. Field measurements of ozone effects on mature forests will be needed before the accuracy of model predictions can be fully assessed

Renormalization of the Vector Current in QED

It is commonly asserted that the electromagnetic current is conserved and therefore is not renormalized. Within QED we show (a) that this statement is false, (b) how to obtain the renormalization of the current to all orders of perturbation theory, and (c) how to correctly define an electron number operator. The current mixes with the four-divergence of the electromagnetic field-strength tensor. The true electron number operator is the integral of the time component of the electron number density, but only when the current differs from the MSbar-renormalized current by a definite finite renormalization. This happens in such a way that Gauss's law holds: the charge operator is the surface integral of the electric field at infinity. The theorem extends naturally to any gauge theory.Comment: 9 pages. Corresponds to published version (Phys. Rev. D), including appendix about Weeks's parado

Multiphoton localization and propagating quantum gap solitons in a frequency gap medium

The many-particle spectrum of an isotropic frequency gap medium doped with impurity resonance atoms is studied using the Bethe ansatz technique. The spectrum is shown to contain pairs of quantum correlated ``gap excitations'' and their heavy bound complexes (``gap solitons''), enabling the propagation of quantum information within the classically forbidden gap. In addition, multiparticle localization of the radiation and the medium polarization occurs when such a gap soliton is pinned to the impurity atom.Comment: 8 pages, RevTEX, to appear in Phys. Rev. Let

The application of low crude protein wheat-soyabean diets to growing and finishing pigs: 2. The effects on nutrient digestibility, nitrogen excretion, faecal volatile fatty acid concentration and ammonia emission from boars

peer-reviewedThis study received financial support from Telltech Ltd. (Wicklow, Ireland) and Enterprise Ireland (Dublin, Ireland).Diets containing 132, 152, 183 and 206 g/kg crude protein (CP) were fed to growing and finishing boars to evaluate the effect on nutrient digestibility, N balance, faecal volatile fatty acids (VFA) and ammonia-N (NH3–N) emission. Dietary CP concentration was adjusted by altering the ratio of wheat:soyabean meal. Lysine, threonine, tryptophan and total sulphur-containing amino acids were included in all diets at concentrations equivalent to that in the highest CP diet. All diets were formulated to provide 9.7 MJ/kg of net energy. Urine and faeces were collected from 16 boars (4 boars per treatment) housed in metabolism crates. Collections were performed at 72, 80 and 87 kg live weight. NH3–N emission was measured over 10 days using a laboratory scale procedure. Reducing the concentration of dietary CP decreased N intake (linear, P < 0.01), the excretion of urinary N, ammoniacal N and total N (linear, P < 0.001; cubic, P < 0.001) and the emission of NH3–N (linear, P < 0.001; cubic, P < 0.01). Total N excretion and NH3–N emission decreased 8.7% and 10.1% per 10 g/kg reduction in dietary CP concentration between 205.6 and 131.9 g/kg, respectively. There was no interaction between dietary CP concentration and collection period. N balance differed between the collection periods and less NH3–N was emitted at 87 kg than at 72 kg. Decreasing dietary CP reduced faecal VFA concentration (linear, P < 0.05) and the molar proportions of acetic and butyric acids (quadratic, P < 0.01).Enterprise Irelan

Spinor fields without Lorentz frames in curved spacetime using complexified quaternions

Using complexified quaternions, a formalism without Lorentz frames, and therefore also without vierbeins, for dealing with tensor and spinor fields in curved spacetime is presented. A local U(1) gauge symmetry, which, it is speculated, might be related to electromagnetism, emerges naturally.Comment: 14 pages; v2: minor corrections; v3: note added concerning unified treatment of local Lorentz transformations and local U(1) gauge transformations; v4: published in J. Math. Phys. 50 083507 (2009

M Theory from World-Sheet Defects in Liouville String

We have argued previously that black holes may be represented in a D-brane approach by monopole and vortex defects in a sine-Gordon field theory model of Liouville dynamics on the world sheet. Supersymmetrizing this sine-Gordon system, we find critical behaviour in 11 dimensions, due to defect condensation that is the world-sheet analogue of D-brane condensation around an extra space-time dimension in M theory. This supersymmetric description of Liouville dynamics has a natural embedding within a 12-dimensional framework suggestive of F theory.Comment: 17 pages LATEX, 1 epsf figure include