3,506 research outputs found
The Ecological And Economic Failures Of Florida\u27s Mangrove Regulatory Scheme
The mangrove ecosystem is one of the most productive and biologically diverse wetlands on Earth, providing habitats worldwide for thousands of species, including both threatened and endangered species. Although the mangroves of Florida are concurrently governed by federal, state and, often, local regulations, they are still subject to depletion through dredging and filling, and are sacrificed for private riparian rights of view. At the foundation6 of mangrove depletion is the failure of the Florida Legislature and the Florida Department of Environmental Protection (DEP) to fully account for the values served by the mangrove ecosystem in dredge and fill permitting and under the Mangrove Trimming and Preservation Act ( Mangrove Act ). This article will briefly identify the use and nonuse values served by the mangrove ecosystem, examine the real societal cost of dredging or trimming a mangrove under the current legal structure in Florida, and propose adjustments to account for the loss incurred by society when a mangrove is dredged or trimmed
The Ecological And Economic Failures Of Florida\u27s Mangrove Regulatory Scheme
The mangrove ecosystem is one of the most productive and biologically diverse wetlands on Earth, providing habitats worldwide for thousands of species, including both threatened and endangered species. Although the mangroves of Florida are concurrently governed by federal, state and, often, local regulations, they are still subject to depletion through dredging and filling, and are sacrificed for private riparian rights of view. At the foundation6 of mangrove depletion is the failure of the Florida Legislature and the Florida Department of Environmental Protection (DEP) to fully account for the values served by the mangrove ecosystem in dredge and fill permitting and under the Mangrove Trimming and Preservation Act ( Mangrove Act ). This article will briefly identify the use and nonuse values served by the mangrove ecosystem, examine the real societal cost of dredging or trimming a mangrove under the current legal structure in Florida, and propose adjustments to account for the loss incurred by society when a mangrove is dredged or trimmed
Unusual statistics of interference effects in neutron scattering from compound nuclei
We consider interference effects between p-wave resonance scattering
amplitude and background s-wave amplitude in low-energy neutron scattering from
a heavy nucleus which goes through the compound nucleus stage. The first effect
is in the difference between the forward and backward scattering cross
sections. Because of the chaotic nature of the compound states, this effect is
a random variable with zero mean. However, a statistical consideration shows
that the probability distribution of this effect does not obey the standard
central limit theorem. That is, the probability density for the effect averaged
over n resonances does not become a Gaussian distribution with the variance
decreasing as 1/sqrt(n) (``violation'' of the theorem!). We derive the
probability distribution of the effect and the limit distribution of the
average. It is found that the width of this distribution does not decrease with
the increase of n, i.e., fluctuations are not suppressed by averaging.
Furthermore, we consider the correlation between the neutron spin and the
scattering plane and find that this effect, although much smaller, shows
fluctuations which actually increase upon averaging over many measurements.
Limits of the effects due to finite resonance widths are also considered. In
the appendix we present a simple derivation of the limit theorem for the
average of random variables with infinite variances.Comment: 15 pages, RevTeX, submitted to Phys. Rev.
Future impacts of fresh water resource management: sensitivity of coastal deltas
We present an assessment of contemporary and future effective sealevel rise (ESLR) using a sample of 40 deltas distributed worldwide. For any delta, ESLR is a net rate defined by eustatic sea-level rise, natural gross rates of fluvial sediment deposition and subsidence, and accelerated subsidence due to groundwater and hydrocarbon extraction. Present-day ESLR, estimated from geospatial data and a simple model of deltaic dynamics, ranges from 0.5 to 12.5 mm year-1. Reduced accretion of fluvial sediment from upstream siltation of reservoirs and freshwater consumptive irrigation losses are primary determinants of ESLR in nearly 70% of the deltas, while for only 12% eustatic sea-level rise predominates. Future scenarios indicate a much larger impact on deltas than previously estimated. Serious challenges to human occupancy of deltas worldwide are conveyed by upland watershed factors, which have been studied less comprehensively than the climate change and sea-level rise question
Forward analysis of N scattering with an expansion method
The N forward scattering data are analyzed using an expansion method,
where the invariant amplitudes are represented by expansions satisfying the
forward dispersion relations. The experimental errors of the data are taken
into account through the covariance matrix of the coefficients of the
expansions in a careful error analysis. From the results, some coefficients,
, of the subthreshold expansions have been calculated with proper
error bars.Comment: 5 pages, 4 figures. v2: Added some references. v3: Corrected
hyphenatio
Weak Pion Production off the Nucleon
We develop a model for the weak pion production off the nucleon, which
besides the Delta pole mechanism (weak excitation of the
resonance and its subsequent decay into ), includes also some background
terms required by chiral symmetry. We re-fit the form factor to
the flux averaged ANL differential cross
section data, finding a substantially smaller contribution of the Delta pole
mechanism than traditionally assumed in the literature. Within this scheme, we
calculate several differential and integrated cross sections, including pion
angular distributions, induced by neutrinos and antineutrinos and driven both
by charged and neutral currents. In all cases we find that the background terms
produce quite significant effects and that they lead to an overall improved
description of the data, as compared to the case where only the Delta pole
mechanism is considered. We also show that the interference between the Delta
pole and the background terms produces parity-violating contributions to the
pion angular differential cross section, which are intimately linked to odd
correlations in the contraction between the leptonic and hadronic tensors.
However, these latter correlations do not imply a genuine violation of time
reversal invariance because of the existence of strong final state interaction
effects.Comment: Typos corrected; comments adde
The Goldberger-Miyazawa-Oehme sum rule revisited
The Goldberger-Miyazawa-Oehme sum rule is used to extract the pion-nucleon
coupling constant from experimental N information. Chiral perturbation
theory is exploited in relating the pionic hydrogen s-wave level shift and
width results to the appropriate scattering lengths. The deduced value for the
coupling is , where the largest source of uncertainty is
the determination of the s-wave scattering length from the atomic
level shift measurement.Comment: 4 pages, 1 figure. v2: Revised the second last paragraph of 5th
section and clarified the electromagnetic corrections (Tromborg vs.
PT). Also removed the KH80 slope from the fig.
A Perturbative Calculation of the Electromagnetic Form Factors of the Deuteron
Making use of the effective field theory expansion recently developed by the
authors, we compute the electromagnetic form factors of the deuteron
analytically to next-to-leading order (NLO). The computation is rather simple,
and involves calculating several Feynman diagrams, using dimensional
regularization. The results agree well with data and indicate that the
expansion is converging. They do not suffer from any ambiguities arising from
off-shell versus on-shell amplitudes.Comment: 22 pages, 8 figures. Discussion of effective range theory added,
typos correcte
Regge phenomenology of pion photoproduction off the nucleon at forward angles
We present a Regge model for pion photoproduction which is basically free of
parameters within the framework of the s-channel helicity amplitude. We use
coupling constants of all exchanged mesons determined from empirical decay
widths or from the SU(3) relations together with consistency check with
existing estimates that are widely accepted in other reaction processes. Cross
sections and spin polarization asymmetries at various photon energies are
analyzed and results are obtained in better agreement with experimental data
without referring to any fitting procedure.Comment: 19 pages, 20 figures, two column, revtex
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