Simple nitric acid leaching and alkali fusion techniques for the determination of the total content of fallout239,240Pu in deep-sea sediment were compared. Leaching neither with boiling conc. HNO3 nor with boiling conc. HNO3+H2O2 was found to be sufficient. The sodium hydroxide fusion technique yielded reproducible analytical results and is proposed
as an optimum dissolution method for quantitative determination of the total content of fallout239,240Pu in deep-sea sediment.
Host phases of fallout239,240Pu and241Am were studied in the surface sediments obtained in 1994 from abyssal basins of relatively small area of the western North
Pacific. An analytical procedure involving sequential chemical extraction was employed for partitioning the host phases of
the nuclides in sediment into five fractions: (1) exchangeable (2) bound to carbonate, (3) bound to hydrous Fe-Mn oxides,
(4) bound to organic matter and (5) residual. Decrease of total239,240Pu concentration with decreasing association of239,240Pu with organic matter, high241Am/239,240Pu activity ratio in carbonate phase and somewhat high proportion of oxidized239,240Pu in leachable phases suggest a possibility of post-depositional diagenetic remobilization of Pu from sediment to water column.
Authors:Hsiao-Fang Lee, Benedict Samuel, and M. Haque
We present a new analytical model for thermal conductivity measurement of one-dimensional nanostructures on substrates. The model expands the capability of the conventional 3ω technique, to make it versatile with both in and out of plane thermal conductivity measurement on specimens either freestanding or attached to substrates. We demonstrate the model on both conducting (aluminum) and semi-conducting (focused ion beam deposited platinum) specimens. The agreement with the established values in the literature suggests the superiority of this technique in terms of convenience and robustness of measurement.
Authors:M. Haque, P. Martinek, N. Watanabe, and T. Kuboyama
Semi-dwarf varieties in wheat associated with gibberellic acid (GA3)-insensitive height reducing genes have led to significant increases in yield but often fall below this potential because of poor seedling emergence after deep showing. Alternative semi-dwarf genes may have the potential to reduce plant height without compromising early plant growth. In durum wheat, bulk segregant analysis was used to screen microsatellite markers linked with the GA3-sensitive genes Rht14 in cv. Castelporziano, Rht16 in cv. Edmore M1 and Rht18 in cv. Icaro. Molecular marker Xbarc3-6A for Rht14, Rht16 and Rht18 showed significant polymorphic differences among DNA bulks for height classes. The genes Rht14, Rht16 and Rht18 were linked with Xbarc3 (11.7–28.0 cM) on the short arm of chromosome 6A and they appear to be allelic. Semi-dwarf genes on chromosome 6AS may potentially be used in breeding for improved establishment.