[1] The Los Alamos Sferic Array (LASA) recorded VLF/LF electric-field-change signals from over ten million lightning discharges during the period from 1998 to 2001. Using the differential-times-of-arrival of lightning sferics recorded by three or more stations, the latitudes and longitudes of the source discharges were determined. Under conditions of favorable geometry and ionospheric propagation, sensors obtained ionospherically reflected skywave signals from the lightning discharges in addition to the standard groundwave sferics. In approximately 1% of all waveforms, automated processing identified two 1-hop skywave reflection paths with delays indicative of an intracloud (height greater than 5 km) lightning source origin. For these events it was possible to determine both the height of the source above ground and the virtual reflection height of the ionosphere. Ionosphere heights agreed well with published values of 60 to 95 km with an expected diurnal variation. Source height determinations for 100,000+ intracloud lightning events ranged from 7 to 20 km AGL with negative-polarity events occurring above $15 km and positive-polarity events occurring below $15 km. The negativepolarity events are at a suprisingly high altitude and may be associated with discharges between the upper charge layer of a storm and a screening layer of charge above the storm. Approximately 100 of the intracloud events with LASA height determinations were also recorded by VHF receivers on the FORTE satellite. Independent FORTE source height estimates based on delays between direct and ground-reflected radio emissions showed excellent correlation with the VLF/LF estimates, but with a +1 km bias for the VLF/LF height determinations.

A rapid and specific technique to detect polyriboadenylic acid sequences in RNA is described. The method depends upon the ability of RNAs that contain poly(A) sequences to associate specifically with poly(U) that has been immobilized on fiberglass filters by ultraviolet irradiation. A high proportion of the transcripts synthesized in vivo and in vitro from the vaccinia virus genome contain poly(A) sequences and bind to the poly(U) filters. Similarly, DNA-like RNA from the nucleus and from the cytoplasmic polyribosomes of HeLa cells is rich in species that bind to poly(U) filters. Poly(U) immobilized on cellulose powder is useful to make columns with a high capacity for the binding and purification of poly(A)-containing RNAs.

Using optically stimulated luminescence (OSL) analysis we obtained depositional ages ranging from 25 ± ± ± ± ± 10 to 928 ± ± ± ± ± 144 years before present for sediments deposited in oxbow lakes along three lowland river systems. The dated sediments were collected from the banks of tie channels along the Lower Mississippi River, the Fly River in Papua New Guinea, and Birch Creek along the Yukon River in Alaska. Tie channels connect the oxbow lakes to the main stem river and allow the exchange of water and suspended sediment between the two. The banks consist of fine sand and sandy silt beds interlayered with silt and clay. OSL samples were collected both horizontally from exposed banks and vertically by coring through levee crests; sample collection was targeted at beds containing appreciable quantities of fine sand. OSL ages were determined using single-grain or in some cases single-aliquot techniques and dose distribution analysis. Samples were first collected along the Lower Mississippi tie channel to compare OSL dates with historical data sources and test the applicability of OSL in these settings; the OSL dates agreed closely with historical data. In all three river systems, OSL dating allowed the determination of vertical accretion rates, tie channel advancement rates, and oxbow lake ages. In Papua New Guinea, OSL sampling also provides an estimate of lateral migration rates of the Fly River and allows a comparison of modern mineinfluenced deposition rates with natural background rates over the last 1000 years. Results from Papua New Guinea and the Mississippi River suggest that the advancement rate of tie channels responds directly to changes in the sediment load of the main stem river.

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Neutron diffractometry and X-ray diffractometry were used to characterize the cation disorder and vacancy distribution in nonstoichiometric spinel, MgOؒxAl 2 O 3 , where x ≥ 1.0. Both synthetic and natural samples were examined. Least-squares refinements of integrated intensities for single crystals and Rietveld profile refinements for powders yielded the average scattering "power" from tetrahedral and octahedral sites within the almost-perfect cubic closepacked oxygen sublattice. The cation disorder was calculated assuming models in which the vacancies resided on tetrahedral, octahedral, or both types of sites. No degree of cation disorder was consistent with the tetrahedral vacancy model, and vacancies most likely resided on octahedral sites.