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.

An approach to high-density polyethylene (HDPE) geomembrane selection for challenging design requirements

Abstract: An approach for selecting a geomembrane (GMB) for a long design-life is described and illustrated for five 2 mm-thick textured GMBs when immersed in a simulated municipal solid waste leachate (L3) ...

Molecular Evidence for Cleavage of Intradimer Phosphodiester Linkage as a Novel Step in Excision Repair of Cyclobutyl Pyrimidine Photodimers in Cultured Human Cells

Abstract: SUMMARY A re-analysis of the metabolic fate of ultraviolet light (u.v.)-induced cyclobutyl pyrimidine dimers in the DNA of dermal fibroblasts from patients with different genetic forms of xeroderma pigmentosum (XP), a rare cancer-prone skin disorder, has provided new insight into the mode of dimer repair in normal human cells. When DNA isolated from post-u.v. incubated cultures was subjected to enzymic photoreactivation (PR) to probe dimer authenticity, single-strand scissions were produced in the damaged DNA of incubated XP group A and D cells, but not in DNA from XP group C cells or normal controls. Since enzymic PR treatment ruptures only the cyclobutane ring, these results suggested that in dimer excision-defective XP group A and D strains, the intradimer phosphodiester bond may have been cleaved without site restoration. Such a cleavage event had not previously been detected; the possibility that this reaction may be an early step in the normal excision-repair process is supported by the observed release of free thymidine (dThd) and its monophosphate (TMP), but not of thymine, upon photochemical reversal of the dimer-containing excision fragments isolated from post-u.v. incubated normal cells. The combined number of dThd and TMP molecules released was equal to ≈80% of the number of dimers photoreversed; for such release to occur, the dimer must both be at one end of an excised fragment and contain an internal phosphodiester break. Taken together, these data lead us to propose a novel model for dimer repair in human cells in which hydrolysis of the intradimer phosphodiester linkage precedes the concerted action of a generalized ‘bulky lesion-repair complex’ involving conventional strand incision/lesion excision/repair resynthesis/strand ligation reactions.

Rotational bands near the Z=50 closed shell: 51111Sb.

Abstract: Rotational states have been identified in $_{51}^{111}\mathrm{Sb}$ for the first time. Three decoupled (\ensuremath{\Delta}I=2) bands extending to over 1 MeV in rotational frequency have been observed. At the highest frequencies, the ${\mathit{scrJ}}^{(2)}$ moments of inertia for these three bands are seen to decrease steadily to unexpectedly low values; this is interpreted as evidence for a novel form of band termination. One of these bands is interpreted as being based on the \ensuremath{\pi}${\mathit{h}}_{11/2}$ orbital coupled to a deformed [(\ensuremath{\pi}${\mathit{g}}_{9/2}$${)}^{\mathrm{\ensuremath{-}}2}$\ensuremath{\bigotimes}(\ensuremath{\pi}${\mathit{g}}_{7/2}$)${]}_{0+}$ state of the $_{50}^{110}\mathrm{Sn}$ core. The interaction strength for the alignment of a pair of ${\mathit{h}}_{11/2}$ neutrons has been extracted and compared with calculations. Two possible quasiparticle configurations are discussed for the other decoupled bands. Two strongly coupled (\ensuremath{\Delta}I=1) bands have been identified and both shown to involve the [(\ensuremath{\pi}${\mathit{g}}_{9/2}$${)}^{\mathrm{\ensuremath{-}}1}$\ensuremath{\bigotimes}(\ensuremath{\pi}${\mathit{g}}_{7/2}$${)}^{2}$] configuration. A large number of spherical states have also been observed, which can be explained on the basis of valence protons coupled to spherical states in the $^{110}\mathrm{Sn}$ core.

Neutron scattering investigation of the d - d excitations below the Mott gap of CoO

Abstract: Neutron scattering is used to investigate the single-ion spin and orbital excitations below the Mott-Hubbard gap in CoO Three excitations are reported at $0870\ifmmode\pm\else\textpm\fi{}0009$ eV, $184\ifmmode\pm\else\textpm\fi{}003$, and $230\ifmmode\pm\else\textpm\fi{}015$ eV These were parametrized within a weak crystal field scheme with an intraorbital exchange of $J(dd)=13\ifmmode\pm\else\textpm\fi{}02$ eV and a crystal field splitting $10Dq=094\ifmmode\pm\else\textpm\fi{}010$ eV A reduced spin-orbit coupling of $\ensuremath{\lambda}=\ensuremath{-}0016\ifmmode\pm\else\textpm\fi{}0003$ eV is derived from dilute samples of Mg${}_{097}$Co${}_{003}$O, measured to remove effects due to spin exchange and structural distortion parameters which break the cubic phase degeneracy of the orbital excitations complicating the inelastic spectrum The peak at 184 eV, while reported using resonant x-ray and optical techniques, was absent or weak for nonresonant x-ray experiments and overlaps with the expected position of a ${}^{4}{A}_{2}$ level This transition is absent in the dipolar approximation but expected to have a finite quadrupolar matrix element that can be observed with neutron scattering techniques at larger momentum transfers Our results agree with a crystal field analysis (in terms of Racah parameters and Tanabe-Sugano diagrams) and with previous calculations performed using local-density band theory for Mott insulating transition metal oxides The results also demonstrate the use of neutron scattering for measuring dipole forbidden transitions in transition metal oxide systems