[en] The half removal time (t/sub c/) of Th from the surface waters of the New York Bight was almost independent of season suggesting that variable biological activity does not affect the removal rate of Th. The decreasing trend of t/sub c/ from the continental slope (t/sub c/ = 70 +/- 10 days) toward the shelf (t/sub c/ = 20 +/- 10 days) correlated with the general trend of increasing concentrations of suspended non-living particles toward the shore throughout the year. Incorporation in zooplankton fecal pellets was not a significant removal mechanism of Th in the surface waters of the continental shelf of the New York Bight. The same conclusion was reached for Pu whose removal was related to that of Th. The most important process affecting the removal of Th in the ocean is the total particle flux through the system

[en] The authors study the properties of a vortex-line liquid, within a uniformly frustrated 3d XY model for a type-II high-T_c superconductor. The helicity modulus, 4- and 6-fold orientational order parameter, and vortex structure function S(k_{perpendicular},k_z) are computed with Monte Carlo simulation. In the dense vortex-liquid, only one transition is found. S(k_{perpendicular},k_z) compares with the hydrodynamic and 2d boson approximation. In the dilute system, they found the vortex-line lattice melts at a temperature much below the temperature at which helicity modulus along the magnetic field vanishes

[en] Progress is reported on studies of geochemistry, marine biology, and physical oceanography. Detailed, quantitative data on the rates of mixing within coastal waters of the New York Bight and across the continental slope and the exchange of water masses and species transported within them between shelf and ocean waters are presented. This research is aimed at understanding the chemical, physical, and biological processes which control the origin, dispersal and fate of particulate matter, and to ultimately model the impact of energy-related pollutants on the continental shelf

[en] Radionuclide concentrations of a number of elements (Am, Pu, U, Pa, Th, Ac, Ra, Po, Pb, Cs, and Sr) have been measured in the water and sediments of a group of alkaline lakes in the western USA. These data demonstrate greatly enhanced soluble phase concentrations of elements with oxidation states of III, IV, V, and VI as the result of carbonate complexing. Dissolved concentrations of isotopes of U, Pa, and Th in a lake with pH = 10 and a total inorganic carbon concentration of 4 x 10^-1 moles/1 were greater than those in sea water (pH = 8, ΣCO₂ = 2 x 10^-3 moles/1) by order of magnitude for ²³³U, ²³⁸U (--10²), ²³¹Pa, ²²⁸Th, ²³⁰Th (--10³) and ²²Th (--10⁵). Concentrations of fallout /sup 239,240/Pu in the more alkaline lakes were equivalent to effective distribution coefficients of --10³, about a factor of 10² lower than in most other natural lakes, rivers, estuaries and coastal marine waters. Measurements of radionuclides in natural systems are essential for assessment of the likely fate of radionuclides which may be released from high level waste repositories to ground water. Laboratory-scale experiments using tracer additions of radionuclides to mixtures of water and sediment yielded distribution coefficients which were significantly different from those derived from field measurements (10¹-10² lower for Po and Pu). Order of magnitude calculations from thermodynamic data of expected maximum U and Th concentrations, limited by pure phase solubilities, suggest that carbonate complexing can enhance solubility by many orders of magnitude in natural waters, even at relatively low carbonate ion concentrations

No abstract available

[en] The operating plan for HT-7 Superconducting tokamak considers the staging of its hardware capabilities after finished its construction. Superconducting magnet of toroidal coils enters upon the superconducting phase after cooling down in 4 days, and then it is charged to 2.4 tesla., but it is reduced to 1.4 tesla or so when operation of ohmic discharge. Two experimental items, in this operation, are performed as following. A) increasing flux swing by bias-magnetism for getting longer pulses ohmic plasma is conducted. A 1s flat-top duration discharge is achieved with a lower safety factor q_a (∼2). Plasma current is up to 0.16 MA, loop voltage ∼1V, chord-average density 1.3 x 10¹⁹ m^-3, Te(0) > 1 keV and Ti = 0.3 keV without any auxiliary heating; B) plasma current modulation for investigations both of plasma current feedback controlling and plasma current profile with LHCD and ICRF which will be preformed in the next experiment. The details physical investigation, in this operation, is less because of some technological troubles. (author)

[en] Apparent sorption rate constants on oceanic particles were measured in batch experiments for a series of soluble and particle-reactive radionuclides. The authors have found that radionuclide uptake by natural particles is slow compared to adsorption rates onto defined oxide surfaces. Equilibrium is attained only at time scales of days. One reason for slow scavenging reactions is the coagulation of radioactively tagged colloidal particles onto larger (filterable) particles. This interpretation explains both the slow sorption (scavenging) kinetics and the dependence of the sorption rate and the distribution ratio (K/sub d/) on the particle concentration. The sorption rate constants for Th isotopes calculated by this method are in good agreement with the rates determined by in situ measurements of the U/Th disequilibrium. In areas where particle residence times are shorter than the time scales of the sorption reactions, such as in shallow coastal marine ecosystems, radioisotope removal from the water column can become limited by the kinetics of sorption onto resuspended particles. If the authors use a simple box model, typical particle residence times, and rate constants for the sorption reactions of Th isotopes that depend on the particle concentration, they can predict residence times of Th isotopes for environments with particle fluxes varying over six orders of magnitude. The fact that these estimates are consistent with those measured directly by the U/Th disequilibrium method implies that Th isotopes might be natural coagulometers; that is, they might be good indicators of coagulation reactions of colloidal-sized particles in natural waters

[en] The uptake of radioactive trace metals by suspended particles in natural aquatic systems is often slow and the time constants for scavenging are of the same order of magnitude as the residence times of particles in the water column. Therefore, models simulating removal of radioactive trace metals from water to sediments in shallow aquatic systems with short particle residence times need to include sorption (i.e. scavenging) kinetics. The authors present a numerical kinetic transport model designed to simulate tracer movements from a well mixed water column where particles are generated by both primary production and sediment resuspension processes. Tracers are allowed to penetrate into underlying sediments by diffusion and particle and pore water mixing. All model parameters can be experimentally determined either in the ecosystem itself or in separate laboratory experiments. Limited sensitivity analyses and simulations of actual experiments indicate that under conditions of particle cycling in the sediments and the water, tracer removal can be affected and even be limited by the slow kinetics of tracer uptake by suspended particles. The model is also useful in identifying and quantifying critical pathways in the complicated web of interrelated processes of an aquatic ecosystem

[en] This paper presents the results obtained from a comparative study of ion implanted Gallium (Ga) into (100), n type Silicon. A comparison is made between long time (≥ 30 mins) furnace annealed and Rapid Thermally Processed (RTP), 100keV implants of 1 and 3x10/sup 15//cm/sup 2/ doses of Ga. The results show that for RTP an extremely high substitutional concentration of Gallium, in excess of 3x10/sup 20//cm/sup 3/ can be obtained with approximately 100% electrical activation, resulting in highly conductive very shallow p type layers

[en] A pronounced desorption phenomenon of ²²⁶Ra from sediment was observed in the Hudson River estuary. Mass balance calculations indicate that the desorption of ²²⁶Ra from the river-borne sediment in estuarine environment is an important source of ²²⁶Ra to the oceans. (Auth.)