Shellfish Spotlight: 2008

Each year Granite State shellfishers search shallow briny waters in search of delicious mussels, clams, or oysters for the dinner table. Those who are skilled often are rewarded with full buckets, but few shellfishers realize that good harvests in New Hampshire’s Seacoast owe much to activities occurring far upstream. The quality of the water and amount of available nutrients that sustain a clam or oyster is directly related to the condition of the rivers and streams that drain the land. The Hampton-Seabrook Estuary is fed by approximately 46 square miles of surrounding land. An even larger system, the Piscataqua River Estuary that includes Great Bay, is supplied by a watershed that is 1,023 square miles. Development within the coastal watershed area has profound impacts on the amount of contaminants flowing to the sea. Sediment washed from roadways and bare soil flows downstream and collects in the estuary where it smothers shellfish beds in extreme cases. Nutrients, primarily nitrogen, are contributed by wastewater treatment plants, septic systems, and land use activities such as lawn fertilizing. Excessive nutrients threaten the ecological balance of the estuaries and thus the survival of shellfish populations. Finally, bacteria from failing septic systems, pet waste, or damaged sewer systems create a human health hazard in estuarine waters. Because shellfish filter great amounts of water to take in food and oxygen, they absorb contaminants from the water that accumulate in their flesh. Therefore, a watershed that flushes large amounts of contaminants downstream will deliver many of these contaminants to shellfish and reduce their numbers or often make them unsafe to eat. It is this close relationship between coastal watershed function and shellfish health that caused the New Hampshire Estuaries Project (NHEP), and many partnering agencies, to monitor shellfish in New Hampshire and make their restoration and maintenance a priority. The NHEP Manage- ment Plan includes many strategies that improve water quality throughout the watershed that will in turn improve shellfish populations and open more harvesting areas

Relativistic Effect on Low-Energy Nucleon-Deuteron Scattering

The relativistic effect on differential cross sections, nucleon-to-nucleon and nucleon-to-deuteron polarization transfer coefficients, and the spin correlation function, of nucleon-deuteron elastic scattering is investigated employing several three-dimensional relativistic three-body equations and several nucleon-nucleon potentials. The polarization transfer coefficients are found to be sensitive to the details of the nucleon-nucleon potentials and the relativistic dynamics employed, and prefer trinucleon models with the correct triton binding energy. (To appear in Phys. Rev. C)Comment: pages: 21, LaTex text + 7 ps-figures at the en

eta d scattering in the region of the S11 resonance

We have studied the reaction eta d -> eta d close to threshold within a nonrelativistic three-body formalism. We considered several eta N and NN models, in particular potentials with separable form, fitted to the low-energy eta N and NN data to represent the two-body interactions. We found that with realistic two-body interactions a quasibound state does not exist in this system, although there is an enhancement of the cross section by one order of magnitude, in the region near threshold, which is a genuine three-body effect not predicted within the impulse approximation.Comment: 18 pages Revtex, 2 figure

Determination of pi-N scattering lengths from pionic hydrogen and pionic deuterium data

The pi-N s-wave scattering lengths have been inferred from a joint analysis of the pionic hydrogen and the pionic deuterium x-ray data using a non-relativistic approach in which the pi-N interaction is simulated by a short-ranged potential. The pi-d scattering length has been calculated exactly by solving the Faddeev equations and also by using a static approximation. It has been shown that the same very accurate static formula for pi-d scattering length can be derived (i) from a set of boundary conditions; (ii) by a reduction of Faddeev equations; and (iii) through a summation of Feynman diagrams. By imposing the requirement that the pi-d scattering length, resulting from Faddeev-type calculation, be in agreement with pionic deuterium data, we obtain bounds on the pi-N scattering lengths. The dominant source of uncertainty on the deduced values of the pi-N scattering lengths are the experimental errors in the pionic hydrogen data.Comment: RevTeX, 20 pages,4 PostScript figure

Proton-Deuteron Elastic Scattering from 2.5 to 22.5 MeV

We present the results of a calculation of differential cross sections and polarization observables for proton-deuteron elastic scattering, for proton laboratory energies from 2.5 to 22.5 MeV. The Paris potential parametrisation of the nuclear force is used. As solution method for the charged-composite particle equations the 'screening and renormalisation approach' is adopted which allows to correctly take into account the Coulomb repulsion between the two protons. Comparison is made with the precise experimental data of Sagara et al. [Phys. Rev. C 50, 576 (1994)] and of Sperison et al. [Nucl. Phys. A422, 81 (1984)].Comment: 24 pages, 8 eps figures, uses REVTe

Symmetry and Coulomb corrections in light nuclear systems. [Below 20 MeV]

An approximation that describes the Coulomb-nuclear interference in a two-body manner is used to calculate vector analyzing powers in elastic p-d scattering and phase shifts for p-..cap alpha.. scattering. Comparison with experiments indicates that a good deal of the observed differences in charge-symmetric three- and five-nucleon reactions can be covered by Coulomb interference effects. Calculations for the four-nucleon system confirm this observation. It appears to be questionable that nuclear charge asymmetry has to be invoked to explain current experiments

PREDICTION OF N-HE-4 PHASE-SHIFTS FROM P-HE-4 DATA BETWEEN 20 AND 55 MEV

FROHLICH J, KRIESCHE H, Streit L, ZANKEL H. PREDICTION OF N-HE-4 PHASE-SHIFTS FROM P-HE-4 DATA BETWEEN 20 AND 55 MEV. NUCLEAR PHYSICS A. 1982;384(1-2):97-111