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Showing papers by "Chalk River Laboratories published in 1991"


Journal ArticleDOI
TL;DR: The recently developed approach to deriving genetic markers via amplification of random DNA segments with single primers of arbitrary nucleotide sequence was tested for its utility in genetic linkage mapping studies with conifers.
Abstract: The recently developed approach to deriving genetic markers via amplification of random DNA segments with single primers of arbitrary nucleotide sequence was tested for its utility in genetic linkage mapping studies with conifers. Reaction conditions were optimized to reproducibly yield clean and specific amplification products. Template DNA from several genotypes of Douglas-fir (Pseudotsuga menziesii) and white spruce (Picea glauca) were tested against eight ten-base oligonucleotide primers. Most of the tested primer/parent tree combinations yielded polymorphic PCR products ("RAPD" markers). Selected primers were then used in PCR reactions with template DNA isolated from offspring in Douglas-fir and black spruce diallel crosses among the same parental lines. The diallel study confirmed the appropriate inheritance of RAPD markers in the F1 generation. The value of these dominant RAPD markers for genetic linkage mapping in trees was established from both theoretical and applied perspectives.

342 citations


Journal ArticleDOI
TL;DR: Simulated high-burnup nuclear fuel (SIMFUEL) replicates the chemical state and microstructure of irradiated fuel so that detailed experiments on fission gas release, thermal conductivity and leaching can be undertaken in the laboratory.

189 citations



Journal ArticleDOI
TL;DR: In this article, a simple high-current low-emittance dc ECR proton source was developed for a cw RFQ accelerator injector, and the normalized rms emittance of a 25 mA beam from a single 4.0 mm diameter extraction aperture was 0.07 π mm mrad corresponding to a brightness of 5 A/(π mm mdr)2.
Abstract: A simple high-current low-emittance dc ECR proton source has been developed for a cw RFQ accelerator injector. Proton fractions of up to 90% have been obtained at beam current densities as high as 350 mA/cm2. The normalized rms emittance of a 25 mA beam from a single 4.0 mm diameter extraction aperture was 0.07 π mm mrad corresponding to a brightness of 5 A/(π mm mrad)2. Similar results were obtained with multiple aperture extraction systems.

80 citations


Journal ArticleDOI
TL;DR: In this article, the authors report that fluidelastic instability is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to cross-flow and that fluid damping is important and should be considered in the formulation of fluid instability.
Abstract: This paper reports that fluidelastic instability is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to cross-flow. Most of the available data on this topic have been reviewed from the perspective of the designer. Uniform definitions of critical flow velocity for instability, damping, natural frequency and hydrodynamic mass were used. Nearly 300 data points were assembled. The authors found that only data from experiments where all tubes are free to vibrate are valid form a design point of view. In liquids, fluid damping is important and should be considered in the formulation of fluidelastic instability. From a practical design point of view, we conclude that fluidelastic instability may be expressed simply in term of dimensionless flow velocity and dimensionless mass-damping. There is no advantage in considering more sophisticated models at this time. Practical design guidelines are discussed.

80 citations


Journal ArticleDOI
TL;DR: Zygotic embryos from open-pollinated seeds of 20 black spruce families were used to investigate the proportion of genotypes that would give rise to embryogenic tissue (ET) and mature somatic embryos, indicating the additive nature of the genetic variation.
Abstract: Zygotic embryos from open-pollinated seeds of 20 black spruce (Picea mariana) families were used to investigate the proportion of genotypes that would give rise to embryogenic tissue (ET) and mature somatic embryos. Eighty-five percent of the maternal genotypes gave rise to embryogenic tissue. Within-family rates of ET induction ranged from 0 to 17%, with an average of 8%. The largest proportion of variation was among families, indicating the additive nature of the genetic variation. On a medium with 6% sucrose and 3.7 μM ABA, 90% of the embryogenic lines gave rise to abundant (>100/100 mg of ET), well-formed, mature somatic embryos. A medium with 2% sucrose, without 2,4-D, was used to germinate the mature somatic embryos. These were grown in the greenhouse and have now been established in field trials.

77 citations


Journal ArticleDOI
TL;DR: No significant difference was observed in the number of embryos produced with 6% sucrose or 3% Sucrose plus an equimolar concentration of either mannitol, sorbitol, or myo-inositol in the maturation medium, suggesting that the effect of the carbohydrate on the m maturity was partly osmotic.
Abstract: Different carbohydrates were investigated for somatic embryo development of black spruce and red spruce. They were tested in a basal maturation medium consisting of Litvay's salts at half-strength containing 1 g l-1 glutamine, 1 g l-1 casein hydrolysate, 7.5 μM abscisic acid, and 0.9% Difco Bacto-agar. A comparison of different sucrose concentrations showed that 6% was optimal for embryo development. Among the nine carbohydrates tested, sucrose, fructose, glucose, maltose, and cellobiose supported embryo development while arabinose, mannitol, myo-inositol, and sorbitol did not. A comparison of sucrose, glucose, and fructose at three concentrations showed that the general pattern of response for both species followed concentration expressed as a percentage, independent of the molarity of carbohydrate in the medium. Interspecific differences were observed concerning carbohydrate requirements. For red spruce, 6% fructose was found best for embryo development, while no such preference was observed for black spruce. No significant difference was observed in the number of embryos produced with 6% sucrose or 3% sucrose plus an equimolar concentration of either mannitol, sorbitol, or myo-inositol in the maturation medium, suggesting that the effect of the carbohydrate on the maturation was partly osmotic.

76 citations


Journal ArticleDOI
TL;DR: The number of somatic embryos produced was significantly higher on medium solidified with Gelrite gellan gum than with Difco Bacto-agar, and the number of germinating embryos was produced when the embryogenic tissue was maintained in darkness, followed by a maturation stage in light.

72 citations


Journal ArticleDOI
TL;DR: In this paper, the authors considered the nature of the Fe-enhancement mechanism in terms of vacancies strongly bound to either substitutional or interstitial Fe atoms and concluded that the experimentally observed substitutional diffusion enhancements are most readily interpreted as transport via an inter-stitial Fe/vacancy pair.

67 citations


Journal ArticleDOI
TL;DR: In this paper, isotopic and chemical hydrograph separation indicated three runoff components: pre-melt subsurface flow, new (event) water, and direct precipitation on to saturated areas (DPS) during spring runoff in a small headwater basin using field mapping and direct tracing of saturated areas.
Abstract: Current conceptual runoff models hypothesize that stormflow generation on the Canadian Shield is a combination of subsurface stormflow and saturation overland flow. This concept was tested during spring runoff in a small (3.3 ha) headwater basin using: (1) isotopic and chemical hydrograph separation and (2) field mapping and direct tracing of saturated areas. Isotopic and chemical hydrograph separation indicated three runoff components: (1) pre-melt subsurface flow; (2) subsurface flow of new (event) water; and (3) direct precipitation on to saturated areas (DPS). During early thaw-freeze cycles, their relative contributions to total flow remained constant (65 per cent, 30 per cent, and 5 per cent respectively). It is hypothesized that lateral flow along the bedrock/mineral soil interface, possibly through macropores, supplied large volumes of subsurface flow (of both old and new water) rapidly to the stream channel. Much higher contributions of DPS were observed during an intensive rain-on-snow event (15 per cent of total flow). Mapping and direct tracing of saturated areas using lithium bromide, suggested that saturated area size was positively correlated to stream discharge but its response lagged behind that of discharge. These observations suggest that the runoff mechanisms, and hence the sources of stream flow, will vary depending on storm characteristics.

56 citations


Journal ArticleDOI
TL;DR: The embryogenic cultures initiated from interior spruce embryos show a high degree of genetic stability in that the morphological behavior and isozyme phenotype were always consistent with that of the explant genotype.
Abstract: Somaclonal variation during interior spruce (Picea glauca engelmannii complex) somatic embryogenesis was evaluated using culture morphology and isozyme analysis. Genotype-specific abscisic acid-dependent developmental profiles and isozyme patterns were similar for subclone and parent line embryogenic cultures and cotyledonary somatic embryos. Extensive analysis of fifteen hundred subclone embryos of one genotype revealed no isozyme pattern variation. Initiation of embryogenic cultures was dependent on the developmental stage of the explant although cultures derived from different stages were morphologically similar. The embryogenic cultures initiated from interior spruce embryos show a high degree of genetic stability in that the morphological behavior and isozyme phenotype were always consistent with that of the explant genotype. These results support the conclusion that this culture system is appropriate for clonal propagation of interior spruce.

Journal ArticleDOI
TL;DR: In this paper, state-of-the-art technologies in the related areas of thermal-hydraulic analysis, flow-induced vibration and mechanical damage prediction are outlined. But, the authors do not discuss the impact of these technologies on the performance of nuclear components.

Journal ArticleDOI
TL;DR: A microprojection protocol using the DuPont Biolistic™ particle delivery system and the β-glucuronidase (GUS) reporter gene fused with the 35S promoter of Cauliflower mosaic virus (CaMV) was developed for Picea mariana callus, and transient GUS gene expression was highest when cells were treated 5 and 6 days after subculturing to fresh media.
Abstract: A microprojection protocol using the DuPont Biolistic™ particle delivery system and the β-glucuronidase (GUS) reporter gene fused with the 35S promoter of Cauliflower mosaic virus (CaMV) was developed for Picea mariana callus. Comparison of four tungsten microprojectile sizes showed the highest transient gene expression with 1.11μm diameter particles. Adsorption of DNA on the microcarriers using calcium chloride led to higher GUS gene activity than using polyethylene glycol. GUS gene activity in P. mariana was the highest when cells were treated 5 and 6 days after subculturing to fresh media. The wheat ABA-inducible Em gene promoter yielded 4.5 times higher GUS gene activity than the 35S CaMV promoter. Comparison of transient GUS gene expression among 10 P. mariana embryogenic cell lines from six different open-pollinated families showed comparable gene activity, with the exception of one family showing no GUS gene activity.

Journal ArticleDOI
TL;DR: Mandelic acid was investigated as an eluent for the determination of inorganic cations via dynamic ion-exchange and "hydrophobic interaction" chromatography as discussed by the authors, and the retention behavior of transition metals, lanthanides and actinides was studied.


Journal ArticleDOI
TL;DR: In this paper, a level scheme organized into fifteen rotational bands is proposed on the basis on the γγ-coincidence and γ-ray angular correlation data.

Journal ArticleDOI
TL;DR: In this article, self-diffusion in α-Zr single crystals has been measured in the temperature interval 871-1074 K, with the effective activation enthalpy increasing with decreasing temperature.

Journal ArticleDOI
TL;DR: It is shown by inelastic neutron scattering that dynamic spin correlations coexist with superconductivity in YBa{sub 2}Cu{sub 3}O{sub 6+{ital x}} and is approximately constant from 250 to 10 K, in contrast to earlier data on superconducting La{sub 1.85}Sr{sub 0.15}CuO ({ital T}{sub {ital c}}=35 K) which showed a decrease of the integrated intensity at a
Abstract: We show by inelastic neutron scattering that dynamic spin correlations coexist with superconductivity in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathit{x}}$ (x=0.4,0.45,0.5). For the x=0.5, ${\mathit{T}}_{\mathit{c}}$=50 K sample, the inelastic magnetic intensity at \ensuremath{\Delta}E=6 meV does not show any change near ${\mathit{T}}_{\mathit{c}}$ and is approximately constant from 250 to 10 K, in contrast to earlier data on superconducting ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_{4}$ (${\mathit{T}}_{\mathit{c}}$=35 K) which showed a decrease of the integrated intensity at a temperature well above ${\mathit{T}}_{\mathit{c}}$. The inelastic magnetic cross section observed here can be consistently modeled as two-dimensional spin waves overdamped by short correlation lengths. The correlation length in the x=0.5 sample is an order of magnitude smaller than in the x=0.40 and x=0.45 samples, indicating a drastic disruption of planar copper spin-spin correlation upon hole doping. The present results are compared with recent NMR studies of ${\mathit{T}}_{\mathit{c}}$=60 K material.

Journal ArticleDOI
TL;DR: In this paper, a 0.06 pct C-0.3 pct Mn and a 3.5 pct Nb steel were deformed in torsion at a constant strain rate of 2/s.
Abstract: A 0.06 pct C-0.3 pct Mn and a 0.07 pct C-0.6 pct Mn-0.028 pct Nb steel were deformed in torsion at a constant strain rate of 2/s. Two schedules were used. In schedule A, seven roughing passes executed between 1260°C and 1130°C were followed by a single large finishing pass with a strain of 3.5 at constant temperatures between 1010°C and 840°C. The time between roughing and finishing was 200 seconds. In schedule B, the seven roughing passes were followed by 10 finishing passes, again applied isothermally, with strains of 0.3 and interpass times of 0.6, 2, and 10 seconds. The results indicate that for the Nb steel, low rolling temperatures (870°C) and strains above 2 are required for complete dynamic recrystallization, which results in austenite grain sizes under 6μm. Cooled at a rate of 10°C/s, the dynamically recrystallized austenite grain structures transform into ferrite with grain sizes under 4 μ. Extrapolations from the present data suggest that at industrial strain rates and cooling rates, ferrite grain sizes under 2 μm should be achieved.

Journal ArticleDOI
TL;DR: Detailed calculations are presented using BCS theory and its dynamic extension, Eliashberg theory, for the ac conductivity in a superconductor, for arbitrary impurity content and in the clean limit, no peak is predicted to be present.
Abstract: BCS theory predicts that coherence peaks should occur in both the nuclear-magnetic-resonance (NMR) relaxation rate and the electromagnetic absorption rate as the temperature is lowered below ${\mathit{T}}_{\mathit{c}}$. The former peak has not been observed in the high-${\mathit{T}}_{\mathit{c}}$ oxides while the latter has. We present detailed calculations using BCS theory and its dynamic extension, Eliashberg theory, for the ac conductivity in a superconductor, for arbitrary impurity content. The peak in the conductivity, and hence in the electromagnetic absorption rate, is reduced by damping effects just as in the case of NMR. Furthermore, in the clean limit, no peak is predicted to be present. The observation of a coherence peak in the high-${\mathit{T}}_{\mathit{c}}$ oxides thus places important restrictions on the parameters of any BCS-like theory.

Journal ArticleDOI
TL;DR: Instrumental Neutron Activation Analysis (INAA) was used to determine the amount of sodium present in NASICON powders (x=1.5) as a function of the extent of ion exchange in 0.2 molar HCl solutions.

Journal ArticleDOI
TL;DR: In this paper, the general properties of sphere-pac beds for application in fusion breeder blankets are examined and the design correlations are compared against available fusion ceramic data, and it is concluded that ternary (three-size) beds are not attractive for fusion blankets, and that the fusion spheres should be as large as possible subject primarily to packing constraints.

Journal ArticleDOI
TL;DR: Sphere-pac ceramic breeders have been under development in Canada for several years as discussed by the authors, with the future development of binary beds planned for use in engineering test reactors and subsequent fusion power reactors.


Journal ArticleDOI
TL;DR: L'application de la theorie du champ de Affleck a RbNiCl 3 montre que cette theorie est a mesure d'expliquer la dispersion du mode du gap et son intensite relative au voisinage du vecteur d'onde de la mise en ordre tridimensionnelle.
Abstract: The Haldane gap is observed by neutron scattering in ${\mathrm{RbNiCl}}_{3}$. The three-dimensional-phase magnetic spectrum of ${\mathrm{RbNiCl}}_{3}$ is found to be very similar to that of ${\mathrm{CsNiCl}}_{3}$, even though the two materials differ significantly in the exchange parameters. Application of Affleck's field theory to ${\mathrm{RbNiCl}}_{3}$ shows that the theory is capable of explaining the dispersion of the gap mode and its relative intensity near the three-dimensional ordering wave vector (1/3,1/3,1). However, the theory does not provide a satisfactory explanation for the nearly degenerate magnon frequencies at (0,0,1). We argue that the degeneracy at (0,0,1) may not be related to the existence of the Haldane gap in integer-spin systems. Rather, it could be a general feature of certain antiferromagnetic materials.

Journal ArticleDOI
TL;DR: In this paper, the radiotracers were measured down to 5 cm in inner core sections and up to 10 cm in outer core sections in a laboratory experiment with soft, highly porous gyttja.
Abstract: Gravity coring of soft sediments can result in smearing of sediment between adjacent vertical sections in a core. We have quantified this artifact in a laboratory experiment with soft, highly porous gyttja using radiotracers to label the surface of the sediments. After coring, extrusion, and sectioning, the radiotracers were measured down to 5 cm in inner core sections and to 10 cm in outer core sections. We have estimated the impact of smearing on the interpretation of concentration-depth profiles, and gradients calculated from smeared profiles can be less than those occurring in situ in the sediments. This effect seems most pronounced near the mud— water interface. We have simulated radionuclide profiles in sediments from Chernobyl fallout (e.g. 134Cs) and natural emissions (e.g. 210Pb) to examine this problem. Concentration gradients of these radionuclides and of other contaminants used to establish geochronologies can be altered significantly depending on sediment type. A tracer layered on the surface of the sediments can be used to quantitate smearing effects, and corrections can then be made to concentration-depth profiles.

Journal ArticleDOI
TL;DR: In this article, a theory of vacancy formation in ordered Cu3Au-type ordered fcc alloys is presented, which is based on the pairwise bonding model, and is found to be in good agreement with the experimentally observed vacancy properties in ordered Ni3Al.
Abstract: A theory of vacancy formation in Cu3Au-type ordered fcc alloys is presented. The present theory, which is based on the pairwise bonding model, is found to be in good agreement with the experimentally observed vacancy properties in ordered Cu3Au and Ni3Al. Various shortcomings in the previous theoretical calculations have also been identified.

Journal ArticleDOI
TL;DR: In this paper, the reaction energies of 25Mg(n, γ)26Mg and 25mg(p, ǫ)26Alm have been measured as Q = 11093.24 6 and 6078.09 8 keV, respectively, which yields Q = 4232.81 10 keV for the 26Alm(β+ + EC) 26Mg decay energy.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the diffusion coefficients of Hf, Ta and Pb at 1000 and 1100 K, respectively, and reported that D(Ta)>D(Hf) >D(Pb) with respect to the decrease in Fe concentration.
Abstract: Substitutional diffusion coefficients D of Hf, Ta and Pb have been measured α- Zr single crystals and the diffusion profiles analysed by Rutherford backscattering (Hf, Ta and Pb) and secondary-ion mass spectrometry (Hf). Measurements were made either parallel (D ‖) or perpendicular (D‖ ) to the specimen c axis. Although the main study is concerned with the influence of Fe on the diffusion of Hf, Ta and Pb at 1100 K, some preliminary data are also reported for Pb and Ta at 872 and 1000 K. The initial measurements at 1100 K show that D(Ta)>D(Hf)>D(Pb); the Zr specimens used for these measurements were then treated to reduce the Fe content (65–30 at.p.p.m.) and the diffusion coefficients remeasured. With one exception, D‖ for Hf, the diffusion coefficients fell by a factor of about two with the decrease in Fe concentration; D‖ for Hf fell by about an order of magnitude. All the D values measured at 1100 K for Hf, Ta and Pb lie in the range 4 × 10−19-3 × 10−17m2s: those for Hf, and their dependence o...