J. Scott Bechtold

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This review article describes vectors for nitrogen and phosphorus delivery to riparian zones in semiarid African savannas, the processing of nutrients in the riparian zone and the effect of disturbance on these processes. Semiarid savannas exhibit sharp seasonality, complex hillslope hydrology and high spatial heterogeneity, all of which ultimately impact(More)
We analyze a sample of optical light curves for 100 quasars, 70 of which have black hole mass estimates. Our sample is the largest and broadest used yet for modeling quasar variability. The sources in our sample have z < 2.8, 10 . λLλ(5100Å) . 10 , and 10 . MBH/M⊙ . 10 . We model the light curves as a continuous time stochastic process, providing a natural(More)
Floodplains in the Pacific Coastal Ecoregion (PCE) stem from steep eroding mountain landscapes in a rain forest environment, and sustain a rich array of natural resources. Like floodplains elsewhere, many of the approximately 200 coastal river valleys are profoundly altered by flow regulation and land conversion for agriculture and urban development, and(More)
In this work we use a sample of 318 radio-quiet quasars (RQQ) to investigate the dependence of the ratio of optical/UV flux to X-ray flux, αox, and the X-ray photon index, ΓX , on black hole mass, UV luminosity relative to Eddington, and X-ray luminosity relative to Eddington. Our sample is drawn from the literature, with X-ray data from ROSAT and Chandra,(More)
Moderate resolution data for 40 QSOs at z ≈ 2 were combined with spectra of comparable resolution of 59 QSOs with redshifts greater than 1.7 found in the literature to form a large, homogeneous sample of moderate resolution (∼1 Å) QSO spectra. These spectra were presented and the statistics of the Lyman α forest were discussed in Paper I. In this analysis,(More)
A protogalaxy candidate at z = 2:72 has been discovered serendipitously by the CNOC cluster redshift survey. The candidate is an extremely luminous (V = 20:5 mag, absolute mag {26) and well resolved (2 00 300) disk-like galaxy. The redshift is identi ed from a dozen strong UV absorption lines, including lines with P-Cygni pro les, which are indicative of(More)
We introduced an 15N-NH4+ tracer to the riparian forest of a salmon-bearing stream (Kennedy Creek, Washington, USA) to quantify the cycling and fate of a late-season pulse of salmon N and, ultimately, mechanisms regulating potential links between salmon abundance and tree growth. The 15N tracer simulated deposition of 7.25 kg of salmon (fresh) to four 50-m2(More)
We present detections of absorption from the ground state and excited states of C I in the z = 1.9731 damped Lyα system of the QSO 0013−004. The excitation temperature between the J = 0 and J = 1 fine-structure levels of C I is 11.6 ± 1.0 K. We estimate other contributions to the excitation of the C I fine-structure levels, and use the population ratio of(More)
Texture is an important influence on organic matter (SOM) dynamics in upland soils but little is known about its role in riverine soils. We hypothesized that texture might be especially important to SOM accumulation in young alluvial soils. We combined the soil component of the CENTURY ecosystem model, which uses sand, silt, and clay concentration as(More)
This paper presents an empirical study comparing the effectiveness of four different versions of an on-line database tutorial, each of which calls upon the student to perform a different kind of inference. The general-to-specific version presents instructions in the form of general rules, from which the students expected to infer how to apply the rule in(More)