Showing papers by "Chalk River Laboratories published in 1985"

Automated measurements of terrain reflection and height variations using an airborne infrared laser system

Abstract: A pulsed near-infrared laser system was converted to determine laser height and reflection values in airborne operations. The laser produces precise traces of the terrain and vegetation canopy and tree measurements can readily be made in open forests since the laser beam frequently penetrates openings in the canopy cover. The reflection measurements were useful in discriminating between vegetation type and density. Using the combined laser height, laser reflection and reflection variability parameters, it was possible to arrive at a simple semiautomated terrain classification which allowed a distinction between conifer and broadleaf forests and terrain with low-growing vegetation cover. The classification of individual trees into coniferous and broadleaf of different height classes is demonstrated. The data is in digital form and can be incorporated into geographic information systems. Considering that these measurements were made at a single wavelength (904 nm), it is clearly evident that high-r...

Heat Exchanger Tube Fretting Wear: Review and Application to Design

Abstract: Flow-induced vibration in steam generators and heat exchangers can cause dynamic interactions between tubes and tube supports resulting in fretting-wear. The effects on tube wear of various parameters, such as tube/support interactions, materials, and tube/support clearances have been studied. Techniques to predict the dynamic tube/support interaction and analyze the impact force at the support have been developed. The results of this work are reviewed and discussed in the context of how best they may be applied in the assessment of heat exchanger designs. A new design criterion based on support impact force is also discussed. Finally, a technique to predict long-term tube life is outlined. 15 references, 13 figures, 1 table.

Methods to extract NAD+-malate dehydrogenase efficiently from white spruce needles

Abstract: The spectrophotometrically-determined activity of NAD+-malate dehydrogenase (MDH, EC 1.1.1.37) from white spruce [Picea glauca (Moench) Voss] needles was assayed with NADH and oxaloacetate. Activity was very low when extracted with only acetate buffer (pH 5.4), phosphate buffer (pH 6.8), or Tris-HCl buffer (pH 8.0). However, activity increased from 1 to over 200 μmol (g dry weight)-1 min-1 with the addition of polymers such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) and the detergents, Tween 80, Tergitol 15-S-9 and Triton X-100. Best activity was observed when extracted in a buffer at pH 6.8 and with 1% (v/v) for the three detergents and PEG, and 6% (w/v) for PVP. MDH activity decreased with age of the needles on the tree. Six-year-old needles contained only about one-fifth of the activity of current year, fully-expanded needles. The main decrease in enzyme activity was observed in one-year-old needles. Protein content obtained from needles extracted with just phosphate buffer (pH 6.8) was very low, but increased greatly when the above chemicals were added to the buffer. In contrast with needles, extracts of vegetative buds contained much higher levels of MDH and protein when extracted with only phosphate buffer (pH 6.8). Although MDH activity in needle extracts declined with storage of the extracts at 4°C in the dark for 6 days, the decrease was least for buffers containing a combination of different protective agents.

Hereditary and Familial Disorders Linking Cancer Proneness with Abnormal Carcinogen Response and Faulty DNA Metabolism

Abstract: Insight into cancer, one of the principal scourges of modern man, has increased slowly but steadily over the years. Epidemiologists concur that most human malignancies are caused, at least in part, by environmental determinants over which an individual can exercise some control; in principle then, the disease is preventable to some extent (Doll and Peto, 1981). In practice, however, the goal of cancer prevention by large-scale efforts to minimize exposure to the causal agents would seem to be unattainable, as judged by societal experience with two major ‘life-style’ factors, habitual tobacco usage and sunbathing. Although an ultimate aim is to develop other more socially acceptable prevention strategies, there exists in the interim a requirement for improved diagnostic techniques and more rational treatment protocols. Each of these approaches to cancer control will almost certainly necessitate clearer understanding of the fundamental mechanisms underlying the etiology and pathogenesis of the disease.

General numerical solutions of the Friedberg-Lee soliton model for ground and excited states

Abstract: A new numerical method is applied to solving the equations of motion of the Friedberg-Lee soliton model for both ground and spherically symmetric excited states. General results have been obtained over a wide range of parameters. Critical coupling constants and particle numbers have been determined below which soliton solutions cease to exist. The static properties of the proton are considered to show that as currently formulated the model fails to fit all experimental data for any set of parameters.

On the interpretation of In-vacancy complexes observed by PAC

Abstract: Using PAC we studied the annealing of defects in quenched Al samples doped with111In. The experiments show that two In-vacancy complexes are formed in recovery stage III, characterized by their hyperfine parameters ω=3π·eQVZZ/10 h=64 Mrad/s and 123 Mrad/s. We conclude that the first complex consists of fewer vacancies than the second one, in contradiction to the interpretation given by Pleiter and Prasad in a recent article.

Parity nonconservation in proton-water scattering at 1.5 GeV/c

Abstract: A search has been made for parity nonconservation in the scattering of 1.5-GeV/c (800-MeV) polarized protons from an unpolarized water target. The result for the longitudinal asymmetry is A/sub L/ = (1.7 +- 3.3 +- 1.4) x 10/sup -7/, where the second uncertainty is an estimate of systematic effects. This result is significantly smaller than the value of A/sub L/ for H/sub 2/O reported at 6 GeV/c.

Defect production by light-ion, low-energy irradiations of aluminum

Abstract: Measurements of the production of free interstitials due to 15 and 20 keV D + and 30 keV He + irradiations of Al containing 0.05–0.1 at.% Ag have been carried out. The interstitials escaping vacancy capture are trapped by silver atoms, creating Al Ag 〈100〉 mixed dumbbells that are detected by means of the channeling technique. The irradiations and subsequent channeling analysis are performed at 100 K, i.e., at a temperature where interstitials are freely migrating but vacancies are not. The measured interstitial production is much lower than theoretical estimates of the number of produced Frenkel pairs, neglecting the recombinations in the calculations. In addition to measuring the interstitial-production rate, we observe extremely high defect concentrations at higher irradiation doses. In contrast to the annealing of the dumbbells, these structures anneal out above room temperature.