ALBERT

Description: The evolution of a tandem accelerator 14C dating system at Chalk River is recounted. Background problems and sources of instability are discussed and solutions are described. Details of sample chemistry and source preparation are presented.

Description: Canadian deuterium uranium (CANDU) pressurized heavy-water reactors produce 14C by neutron activation of trace quantities of nitrogen in annular gas and reactor components (14N(n,p)14C), and from 17O in the heavy water moderator by (17O(n,α)14C). The radiocarbon produced in the moderator is removed on ion exchange resins incorporated in the water purification systems; however, a much smaller gaseous portion is vented from reactor stacks at activity levels considerably below 1% of permissible derived emission limits. Early measurements of the carbon speciation indicated that 〉90% of the 14C emitted was in the form of CO2. We conducted surveys of the atmospheric dispersion of 14CO2 at the Chalk River Laboratories and at the Pickering Nuclear Generating Station. We analyzed air, vegetation, soils and tree rings to add to the historical record of 14C emissions at these sites, and to gain an understanding of the relative importance of the various carbon pools that act as sources/sinks within the total 14C budget. Better model parameters than those currently available for calculating the dose to the critical group can be obtained in this manner. Global dose estimates may require the development of techniques for estimating emissions occurring outside the growing season.

Description: The Chalk River Tandem Accelerator Mass Spectrometry System has reached a state of reliable measurement of 14C using 2 to 5mg elemental carbon prepared by Mg reduction of CO2. For two comparisons of a near-modern unknown with the NBS oxalic acid standard we obtain a total error of ∼±4.5%, consisting of a random system error of about ±3.5% combined with the statistical counting error. Measurements have been made on 70 samples in 30 days of running time during the past year. Samples included deep rock carbonates, cosmogenic 14C in meteorites, charcoal from earthquake fault zones, collagen of bone artifacts and fossil beetle-fragments.

Description: A solid sphere falling through a Bingham plastic moves in a small envelope of fluid with shape that depends on the yield stress. A finite-element/Newton method is presented for solving the free-boundary problem composed of the velocity and pressure fields and the yield surfaces for creeping flow. Besides the outer surface, solid occurs as caps at the front and back of the sphere because of the stagnation points in the flow. The accuracy of solutions is ascertained by mesh refinement and by calculation of the integrals corresponding to the maximum and minimum variational principles for the problem. Large differences from the Newtonian values in the flow pattern around the sphere and in the drag coefficient are predicted, depending on the dimensionless value of the critical yield stress Ygbelow which the material acts as a solid. The computed flow fields differ appreciably from Stokes’ solution. The sphere will fall only when Yg is below 0.143. For yield stresses near this value, a plastic boundary layer forms next to the sphere. Boundary-layer scalings give the correct forms of the dependence of the drag coefficient and mass-transfer coefficient on yield stress for values near the critical one. The Stokes limit of zero yield stress is singular in the sense that for any small value of Ygthere is a region of the flow away from the sphere where the plastic portion of the viscosity is at least as important as the Newtonian part. Calculations for the approach of the flow field to the Stokes result are in good agreement with the scalings derived from the matched asymptotic expansion valid in this limit. © 1985, Cambridge University Press. All rights reserved.

Description: Experimental results for a reactive non-buoyant plume of nitric oxide (NO) in a turbulent grid flow doped with ozone (O3) are presented. The Damköhler number (ND) for the experiment is of order unity indicating the turbulence and chemistry have similar timescales and both affect the chemical reaction rate. Continuous measurements of two components of velocity using hot-wire anemometry and the two reactants using chemiluminescent analysers have been made. A spatial resolution for the reactants of four Kolmogorov scales has been possible because of the novel design of the experiment. Measurements at this resolution for a reactive plume are not found in the literature. The experiment has been conducted relatively close to the grid in the region where self-similarity of the plume has not yet developed. Statistics of a conserved scalar, deduced from both reactive and non-reactive scalars by conserved scalar theory, are used to establish the mixing field of the plume, which is found to be consistent with theoretical considerations and with those found by other investigators in non-reactive flows. Where appropriate the reactive species means and higher moments, probability density functions, joint statistics and spectra are compared with their respective frozen, equilibrium and reaction-dominated limits deduced from conserved scalar theory. The theoretical limits bracket reactive scalar statistics where this should be so according to conserved scalar theory. Both reactants approach their equilibrium limits with greater distance downstream. In the region of measurement, the plume reactant behaves as the reactant not in excess and the ambient reactant behaves as the reactant in excess. The reactant covariance lies outside its frozen and equilibrium limits for this value of ND. The reaction rate closure of Toor (1969) is compared with the measured reaction rate. The gradient model is used to obtain turbulent diffusivities from turbulent fluxes. Diffusivity of a non-reactive scalar is found to be close to that measured in non-reactive flows by others.

Description: Canada and the USSR together possess most of the territory in the Northern Hemisphere underlain by permafrost or perennially frozen ground. As about one half of the land area of each country is affected, the permafrost region of the Soviet Union is 2½ times larger than that of Canada. Outside mountainous regions, permafrost extends southward in Canada to the southern tip of James Bay at lat 51° N (Brown, in press). Permafrost extends farther south in eastern Asia, however, and occurs in Outer Mongolia and Manchuria to about lat 47° N Fig 1) (Baranov, 1959; Nekrasov, 1962).

Description: Beachcombers usually are associated with tropical islands, with hot sandy foreshores and coral reefs, backed by waving palms and jungle-clad slopes. They conjure up an atmosphere of dusky maidens and pearls and the other features of a lazy lotus land. But wherever ordered life frays out on the edges of civilization, the beachcomber makes his appearance. He likes comfort, but cheerfully accepts inconvenience provided only that he can escape a life of rules and ordered conventions: he seeks a measure of freedom far beyond the dreams of the noisy democrat. The untrammelled life that the unsocial beachcomber seeks is not impossible in Spitsbergen: true, conditions are not such as would attract lovers of warmth and comfort in every hour of existence, but a nomad's life in the Arctic has not all the discomforts that the inexperienced might believe.

Description: The following place-names in the South Orkney Islands and the Antarctic Continent were proposed by Dr W. S. Bruce; they were first published in the maps accompanying his paper in the Scottish Geographical Magazine for June 1905, and in the Reports on the Scientific Results of the Voyage of S.Y. Scotia, 1902–04 (Edinburgh, 1907–).

Description: Since the publication of the classical report of Lawes, Gilbert and Pugh (15), it has been generally accepted that the Gramineae obtain all the nitrogen they require in the combined form from the soil solution. The results of recent investigations on the relation between the fungus endophyte and the host have suggested the possibility of an atmospheric origin for part of the nitrogen present in the host. Hannig(10) isolated fungus-free races of Lolium temulentum, and showed that the infected plants had a slight power of assimilating molecular nitrogen. Hiltner(11) grew plants of Lolium temulentum under culture conditions with, and without, nitrate nitrogen, and he found that those without did as well as those with nitrate nitrogen, from which he concluded that plants grown without nitrate nitrogen must be meeting their nitrogen requirements from atmospheric sources. It appears, however, that Hiltner's cultures were not sterile, and no special precautions were taken to ensure that the sand and water were nitrogen free. McLennan(20) repeated Hiltner's work using Lolium perenne, but great care was taken to ensure that all ingredients of the cultures were nitrogen free, and that the cultures were sterile. Under these conditions the results were negative, pointing to an absence of fixation. McLennan, however, states that her results do not preclude the possibility of fixation when small quantities of combined nitrogen are available in the medium.