Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Genetic variation in somatic embryogenic response in open-pollinated families of black spruce

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.

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...

Phase decomposition and chemical inhomogeneity in Nd 2 − x Ce x CuO 4 ± δ

Abstract: Extensive x-ray and neutron scattering experiments and additional transmission electron microscopy results reveal the partial decomposition of ${\mathrm{Nd}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4\ifmmode\pm\else\textpm\fi{}\ensuremath{\delta}}$ (NCCO) in a low-oxygen-fugacity environment such as that typically realized during the annealing process required to create a superconducting state. Unlike a typical situation in which a disordered secondary phase results in diffuse powder scattering, a serendipitous match between the in-plane lattice constant of NCCO and the lattice constant of one of the decomposition products, ${(\mathrm{Nd},\mathrm{Ce})}_{2}{\mathrm{O}}_{3}$, causes the secondary phase to form an oriented, quasi-two-dimensional epitaxial structure. Consequently, diffraction peaks from the secondary phase appear at rational positions $(H,K,0)$ in the reciprocal space of NCCO. Additionally, because of neodymium paramagnetism, the application of a magnetic field increases the low-temperature intensity observed at these positions via neutron scattering. Such effects may mimic the formation of a structural superlattice or the strengthening of antiferromagnetic order of NCCO, but the intrinsic mechanism may be identified through careful and systematic experimentation. For typical reduction conditions, the ${(\mathrm{Nd},\mathrm{Ce})}_{2}{\mathrm{O}}_{3}$ volume fraction is approximately 1%, and the secondary-phase layers exhibit long-range order parallel to the NCCO ${\mathrm{CuO}}_{2}$ sheets and have a typical thickness of approximately $100\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. The presence of the secondary phase should also be taken into account in the analysis of other experiments on NCCO, such as transport measurements.