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We measured extension rates across Lake Tahoe Basin for the last 60 ka. based on measured displacement of offset marker surfaces across three active faults beneath Lake Tahoe. Seismic chirp imaging with submeter accuracy, together with detailed multibeam and fight detection and ranging (LIDAR)--derived bathymetry, was used to measure fault offset, thickness of earthquake-derived colluvial wedges, depth of wave-cut paleo-terraces, and other geomorphic features. An analysis of these features provides refined estimates of extension rates and new information on Holocene faulting, and places Tahoe Basin deformation into the larger context of Walker Lane and Basin and Range tectonics. Measured offset marker surfaces include submerged wave-cut paleoterraces of Tioga age (19.2 [+ or -] 1.8 ka), McKinney Bay slide deposits (ca. 60 ka), and a winnowed boulder surface of Tahoe age (ca. 62 ka). Estimated vertical offset rates across submerged geomorphic surfaces are 0.43-0.81 mm/a for the West Tahoe fault, 0.35-0.60 mm/a for the Stateline-North Tahoe fault, and 0.12-0.30 mm/a for the Incline Village fault. These offset rates indicate a combined east-west extension rate across Lake Tahoe Basin, assuming 60[degrees] fault dips, of 0.52-0.99 mm/a. This estimate, when combined with the Genoa fault-slip rate, yields an extension rate consistent with the magnitude of the extension deficit across Carson Valley and Lake Tahoe Basin derived from global positioning system (GPS) velocities. The Stateline--North Tahoe, Incline Village, and West Tahoe faults all show evidence for individual Holocene earthquake events as recorded by either colluvial wedge deposits or offset fan-delta stratigraphy.

Maize (Zea mays L.) cultivars with improved N-use efficiency would be beneficial for low-input production systems. Our objective was to estimate quantitative genetic parameters to optimize breeding programs for improving productivity under low N levels. Results of 21 field experiments with European breeding materials belonging to the flint and dent gene pool are presented. The study was performed during 1989 and 1999 at several locations in typical maize growing regions of Germany and France. All experiments were conducted at high (HN) and low (LN, no N fertilizer applied) N levels. Average grain yield was reduced by 37% at LN compared with HN. Coefficients of genotypic correlation between HN and LN were variable with an average of [r.sub.G] = 0.74 for grain yield and generally high for grain dry matter content. For grain yield, analyses of variance were computed from relative data, where plot values were expressed as percentage of the trial mean. Variances caused by genotype (G), G x location (L) interaction, and error effects were higher at LN compared with HN, with similar heritabilities at both N levels. For the untransformed data, components of variance were higher at HN than at LN. Genotype x N as well as G x L x N level interaction variances were significant in most experiments. Efficiency of improvement of grain yield at LN through indirect selection at HN was 70% compared with direct selection at LN. A trend toward increased efficiency of direct selection under LN conditions was evident with decreasing grain yield at LN., FROM 1960 to 1990, the use of N fertilizer in modern agricultural systems has increased in parts of Asia, North America, and West Europe (Food and Agricultural Organization of the [...]

Byline: W. Geissdorfer (1), I. Wittmann (1), G. Seitz (2), R. Cesnjevar (3), M. Rollinghoff (1), C. Schoerner (1), C. Bogdan (1) Keywords: Key WordsTropheryma whippelii; Whipple's disease; Endocarditis; PCR Abstract: A case of endocarditis caused by Tropheryma whippelii is reported. The 69-year-old patient was diagnosed as suffering from severe aortic regurgitation requiring aortic valve replacement, but showed no other symptoms of Whipple's disease. T. whippelii was detected in the explanted aoritc valve by broad-range PCR amplification of the 16S rDNA and subsequent sequence analysis of the product. The etiologic agent was classified as a type 2A sequence variant based on the 16S-23S intergenic spacer and the 23S rDNA (domain III) sequences. The histological examination of the aortic valve was compatible with Whipple's disease. A duodenal biopsy revealed an infection with Giardia lamblia, but T. whippelii and histological signs of Whipple's disease were not detectable. Author Affiliation: (1) Institute of Clinical Microbiology, Immunology and Hygiene, Friedrich-Alexander University of Erlangen-Nurnberg, Wasserturmstr. 3, D-91054 Erlangen, Germany Phone: (+49/9131) 85-25744, Fax: -1001, e-mail: walter.geissdoerfer@mikrobio.med.uni-erlangen.de, DE (2) Institute of Pathology, Bamberg Clinic, D-96049 Bamberg, Germany, DE (3) Center for Cardiac Surgery Friedrich-Alexander University of Erlangen-Nurnberg, D-91054 Erlangen, Germany, DE Article note: Received: September 6, 2000 * Revision accepted: December 3, 2000