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Peter C Burns

Publications and source records attributed to Peter C Burns.

16 recordsLinked to original sources
PubMed2006

Cation-cation interactions in Sr5(UO2)20(UO6)2O16(OH)6(H2O)6 and Cs(UO2)9U3O16(OH)5.

Two novel U6+ compounds, Sr5(UO2)20(UO6)2O16(OH)6(H2O)6 (SrFm) and Cs(UO2)9U3O16(OH)5 (CsFm), have been synthesized by mild hydrothermal reactions. The structures of SrFm (orthorhombic, C2221, a = 11.668(1), b = 21.065 (3), c = 13.273 A, V = 3532.5(1) A3, Z = 2) and CsFm (trigonal, R3c, a = 11.395(2), c = 43.722(7) A, V = 4916.7(1) A3, Z = 6) are rare examples of uranyl compounds that contain cation-cation interactions where an O atom of one uranyl ion is directly linked to another uranyl ion. Both structures are complex frameworks. SrFm contains sheets of polyhedra that are linked through cation-cation interactions with uranyl ions located between the sheets. CsFm possesses an unusually complex framework of vertex- and edge-sharing U6+ polyhedra that incorporates cation-cation interactions.

Journal Article↗
PubMed2006

The structure and synthesis of plutonium(III) chlorides from aqueous solution.

The preparation and structure of three trivalent plutonium chloride compounds from aqueous solution is reported. Two of the three are plutonium tetraaquatetrachloro complexes exhibiting a cis and a trans arrangement of Cl about the Pu. The identification of the coordination number of 4 with respect to Cl and the isomerism are both unprecedented in actinide solution chemistry. The third complex is a hexaaquadichloro complex of Pu(III), predicted by available thermodynamic data.

Journal Article↗
PubMed2006

Expanding the crystal chemistry of actinyl peroxides: open sheets of uranyl polyhedra in Na5[(UO2)3(O2)4(OH)3](H2O)13.

A uranyl peroxide, Na5[(UO2)3(O2)4(OH)3](H2O)13, with an open sheet of uranyl polyhedra has been synthesized under ambient conditions and structurally characterized. The structure (orthorombic, Cmca, a = 23.632(1) A, b = 15.886(1) A, c = 13.952(1) A, V = 5237.7 A(3), and Z = 8) consists of sheets composed of two symmetrically unique uranyl (UO2)2+ ions that are coordinated equatorially by two peroxide groups and two OH(-) groups, forming distorted uranyl hexagonal bipyramids of composition (UO2)(O2)2(OH)2(4-). The uranyl bipyramids are connected into sheets with openings with dimensions 13.7 A along [010] and 15.9 A along [100]. The shortest dimension of the cavity is 8.08 A. Sheets of two-dimensionally polymerized uranyl polyhedra are the most common structural type of inorganic uranyl phases; however, such an open topology has never been observed.

Journal Article↗
PubMed2006

Particular topological complexity of lead oxide blocks in Pb31O22X18 (X = Br, Cl).

Dark-green platy crystals of the new compound Pb31O22Br10Cl8 (1) have been obtained by rapid quenching of a lead oxide halide melt. The structure of 1 (triclinic, P1, a = 12.1192(7) angstroms, b = 16.2489(10) angstroms, c = 18.3007(11) angstroms, alpha = 93.104(2) degrees, beta = 95.809(2) degrees, gamma = 111.252(1) degrees, V = 3325.4(3) angstroms3, Z = 2) can be viewed as incorporation of [PbX6]4- halide units (X = Br, Cl) into the defect PbO matrix. The latter represents a two-dimensional [O22Pb30]16+ cationic layer of OPb4 tetrahedra that can be derived from the [OPb] tetrahedral layer observed in tetragonal PbO. The layer consists of 22 symmetrically inequivalent OPb4 tetrahedra and represents the topologically most complicated arrangement of tetrahedra known to date.

Journal Article↗
PubMed2004

Investigations into the vertical distribution of PCDDs and mineralogy in three ball clay cores from the United States exhibiting the natural formation pattern.

In this study, we report the PCDD and mineralogical results from the analyses of 27 different samples from three ball clay cores from different locations in Kentucky and Tennessee. One goal of this study was to determine if there is a correlation between the mineralogy of the ball clay samples and the PCDD concentrations and/or homologue profiles in each sample. Samples from each of the three cores exhibited the natural formation profile with extremely high PCDD concentrations with low and mostly undetectable levels of polychlorinated dibenzofurans (PCDFs). The maximum toxic equivalents (TEQs) for Cores C-E were 2500, 440, and 15,000 pg WHO-TEQ/g, respectively. Although there does not seem to be a direct correlation between mineralogy and PCDD concentrations or homologue profiles, the mineralogy of Core C is substantially different than that of Cores D and E, which may in part explain the differences in congener patterns we observed among the three cores.

Aluminum Silicates↗
PubMed2004

An unprecedented uranyl phosphate framework in the structure of [(UO2)3(PO4)O(OH)(H2O)2](H2O).

The new uranyl phosphate [(UO2)3(PO4)O(OH)(H2O)2](H2O) (1) with an unprecedented framework structure has been synthesized at 150 and 185 degrees C. The structure (tetragonal, P4(2)/mbc, a = 14.015(1) A, c = 13.083(2) A, V = 2575.6(4) A(3), Z = 8) contains uranyl phosphate chains composed of uranyl pentagonal and hexagonal bipyramids and phosphate tetrahedra linked by sharing of polyhedral edges. The uranyl phosphate chains are aligned both along [100] and [010] and are linked into a novel framework structure involving channels along [001]. Topologically identical chains occur linked into sheets in more than a dozen uranyl phosphate minerals, but these chains have never been observed in opposing orientations and linked into a framework as in 1.

Journal Article↗
PubMed2004

The Rb analogue of grimselite, Rb6Na2[(UO2)(CO3)3]2(H2O).

The crystal structure of the Rb analogue of grimselite, rubidium sodium uranyl tricarbonate hydrate, Rb6Na2[(UO2)(CO3)3]2(H2O), consists of a uranyl hexagonal bipyramid that shares three non-adjacent equatorial edges with carbonate triangles, resulting in a uranyl tricarbonate cluster of composition [(UO2)(CO3)3)]. These uranyl tricarbonate clusters form layers perpendicular to [001] and are interconnected by NaO8 polyhedra. The title compound is isostructural with grimselite, with a reduced occupancy of the H2O site (25% versus 50% in grimselite).

Journal Article↗
PubMed2004

Task interruptability and duration as measures of visual distraction.

Tasks that are easily interrupted under intermittent viewing conditions may be less distracting while driving because they allow drivers greater control over task sharing decisions. This paper investigates the reliability and sensitivity of the occlusion paradigm as a potential means of measuring task interruptability and distraction. Twenty-four participants, between the ages of 21 and 34, completed two separate experimental sessions. In one session they performed three in-vehicle tasks (a radio-tuning task and two simulated visual search tasks) under occlusion and while unoccluded. In another session, participants completed the same in-vehicle tasks while driving in a simulator, without occlusion. The tasks did not differ in terms of total task time, yet significant differences were found using the occlusion paradigm and subjective workload ratings. Task interruptability and task duration both need to be considered when assessing the suitability of tasks for time-sharing with driving.

Adult↗
PubMed2004

Perspectives on occlusion and requirements for validation.

This paper discusses the limitations and potential of using an occlusion test to assess visual distraction and the suitability of an in-vehicle information system (IVIS) task for driving. This discussion was expanded from issues raised during a UK workshop on occlusion. The paper describes the research history and empirical foundations of occlusion. It describes some of the occlusion technology and applications for this procedure. Issues concerning the occlusion tasks and the duration and timing of occlusion are presented. The main part of this paper focuses on the priority research considerations for occlusion. The paper concludes with a description of some alternatives to occlusion and future research needs. It is concluded that the occlusion test has some promise, however the empirical basis for occlusion is lacking. If occlusion is to be developed as a metric to determine maximal safe visual distraction, substantial barriers remain.

Automobile Driving↗
PubMed2003

Stability of peroxide-containing uranyl minerals.

Minerals containing peroxide are limited to studtite, (UO2)O2(H2O)4, and metastudtite, (UO2)O2(H2O)2. High-temperature oxide-melt solution calorimetry and solubility measurements for studtite (standard enthalpy of formation at 298 kelvin is -2344.7 +/- 4.0 kilojoules per mole from the elements) establishes that these phases are stable in peroxide-bearing environments, even at low H2O2 concentrations. Natural radioactivity in a uranium deposit, or the radioactivity of nuclear waste, can create sufficient H2O2 by alpha radiolysis of water for studtite formation. Studtite and metastudtite may be important alteration phases of nuclear waste in a geological repository and of spent fuel under any long-term storage, possibly at the expense of the commonly expected uranyl oxide hydrates and uranyl silicates.

Journal Article↗
PubMed2003

A monoclinic polymorph of uranyl dinitrate trihydrate, [UO2(NO3)2(H2O)2].H2O.

Diaquadinitratouranyl(VI) monohydrate is monoclinic (space group P2(1)/c), in contrast to its triclinic polymorph. The main building block of the structure is the finite non-centrosymmetric [UO(2)(NO(3))(2)(H(2)O)(2)] cluster, which is a uranyl hexagonal bipyramid that shares two non-opposite equatorial edges with the nitrate triangles, such that the two water molecules are at neighbouring equatorial vertices. There is an interstitial water site in the structure, which is located between adjacent [UO(2)(NO(3))(2)(H(2)O)(2)] clusters.

Journal Article↗
PubMed2003

A new polytype of orthoboric acid, H(3)BO(3)-3T.

The crystal structure of H(3)BO(3)-3T, a new trigonal polytype of orthoboric acid, consists of sheets of hydrogen-bonded B(OH)(3) molecules similar to those found in the triclinic structure of orthoboric acid, H(3)BO(3)-2A. In each case, van der Waals forces connect the sheets. However, the stacking sequences of the sheets differ between the two polymorphs. In H(3)BO(3)-3T (space group P3(2)), the sheets are stacked in the repeating sequence ABC em leader, whereas in H(3)BO(3)-2A (space group P-1, the sheets are stacked in the repeating sequence AB em leader.

Journal Article↗
PubMed2002

Uranyl dinitrate trihydrate, UO2(NO3)2(H2O)3.

The structure of the title compound, which has been synthesized by evaporation at 294 K, consists of centrosymmetric uranyl hexagonal bipyramids that share opposite equatorial edges with two nitrate triangles, resulting in two distinct finite clusters of composition [(UO(2))(H(2)O)(2)(NO(3))(2)]. There are two unique symmetrically independent U(VI) positions and two unique nitrate groups.

Journal Article↗
PubMed2002

Synthesis and structure of Ag(6)[(UO(2))(3)O(MoO(4))(5)]: a novel sheet of triuranyl clusters and MoO(4) tetrahedra.

The new uranyl molybdate Ag(6)[(UO(2))(3)O(MoO(4))(5)] (1) with an unprecedented uranyl molybdate sheet has been synthesized at 650 degrees C. The structure (monoclinic, C2/c, a = 16.4508(14) A, b = 11.3236(14) A, c = 12.4718(13) A, beta = 100.014(4)(o), V = 2337.4(4) A(3), Z = 4) contains [(UO(2))(3)O(MoO(4))(5)] sheets composed of triuranyl [(UO(2))(3)O] clusters that are connected by MoO(4) tetrahedra. The topology of the uranyl molybdate sheet in 1 represents a major departure from sheets observed in other uranyl compounds. Of the approximately 120 known inorganic uranyl compounds containing sheets of polyhedra, 1 is the only structure that contains trimers of uranyl pentagonal bipyramids that are connected only by the sharing of vertexes with other polyhedra. The sheets are parallel to (001) and are linked by Ag cations.

Journal Article↗
PubMed2002

A uranyl sulfate cluster in Na10[(UO2)(SO4)4](SO4)2.3H2O.

Decasodium uranyl hexasulfate trihydrate, Na(10)[(UO(2))(SO(4))(4)](SO(4))(2).3H(2)O, contains an unusual uranyl sulfate cluster with the composition [(UO(2))(SO(4))(4)](6-). The cluster is composed of a uranyl pentagonal bipyramid and four sulfate tetrahedra. Three sulfate tetrahedra are linked to the uranyl pentagonal bipyramid by the sharing of vertices, and the other shares an equatorial edge of the uranyl pentagonal bipyramid. The uranyl sulfate clusters occur in layers parallel to (010). The structure also contains two isolated symmetrically distinct sulfate tetrahedra, which also occur in layers parallel to (010). The uranyl sulfate clusters and isolated sulfate tetrahedra are linked through bonds to Na(+) cations, and by hydrogen bonding involving the water molecules.

Journal Article↗