West Virginia Space Grant Consortium

Abstract Symptoms of beech leaf disease (BLD), first reported in Ohio in 2012, include interveinal greening, thickening and often chlorosis in leaves, canopy thinning and mortality. Nematodes from diseased leaves of American beech ( Fagus grandifolia ) sent by the Ohio Department of Agriculture to the USDA, Beltsville, MD in autumn 2017 were identified as the first recorded North American population of Litylenchus crenatae ( Nematology , 21, 2019, 5), originally described from Japan. This and other populations from Ohio, Pennsylvania and the neighbouring province of Ontario, Canada showed some differences in morphometric averages among females compared to the Japanese population. Ribosomal DNA marker sequences were nearly identical to the population from Japan. A sequence for the COI marker was also generated, although it was not available from the Japanese population. The nematode was not encountered in Fagus crenata (its host in Japan) living among nematode‐infested Fagus grandifolia in the Holden Arboretum, nor has L. crenatae been reported in American beech in Japan. The morphological and host range differences in North American populations are nomenclaturally distinguished as L. crenatae mccannii ssp. n. from the population in Japan. Low‐temperature scanning electron microscopy (LT‐SEM) demonstrated five lip annules and a highly flexible cuticle. Females, juveniles and eggs were imaged within buds with a Hirox Digital microscope and an LT‐SEM. Nematodes swarmed to the tips of freshly cut beech buds, but explants could not be maintained. Inoculation of fresh nematodes from infested leaves or buds to buds or leaves of F. grandifolia seedlings resulted in BLD leaf symptoms. Injuring dormant buds prior to nematode application, in fall or spring, promoted the most reliable symptom expression. The biogeography and physiology of anguinid nematode leaf galling, and potential co‐factors and transmission are discussed.

Abstract The concept of effective stress, where the applied stress is reduced by a resisting or threshold stress, is often used in fatigue and creep strain rate models, but seldom in single-line equation creep life models. Recently, effective stress was used with single-line models to correlate creep life data of two low chromium creep-resistant steels (1Cr-1Mo-0.25V and 2.25Cr-1Mo), which have been used extensively in Rankine cycle power plants. In those models, the threshold stress was independent of applied stress, which causes a prediction of infinite time to rupture when applied stress equals the threshold stress. In this study, the overprediction of rupture time versus the experimental data of a power law model using a stress-independent threshold stress is quantified, and it is shown that other single line creep life models do not need a backstress term to provide equivalent or superior correlations of the same data sets. For the 1Cr-1Mo-0.25V steel, the coefficient of determinations of Larsen-Miller parameter and modified hyperbolic sine models were 13.8% and 6.9% better than the power law model with a backstress term, while the coefficient of determinations was essentially the same for the 2.25Cr-1Mo steel.

Abstract Mass transfer coefficients and film cooling effectiveness are measured downstream of a single row of holes (recovery region) inclined 30° with the surface and inline with the main turbulent boundary layer flow. The mass transfer coefficients are measured using a naphthalene sublimation technique. The effectiveness is determined through the injection of a trace gas into the secondary flow and measuring its concentration at the impermeable wall. Experiments are carried out in a subsonic, zero pressure gradient turbulent boundary layer, under isothermal conditions with three blowing ratios ( U j / U ∞ ): 0.4, 0.8, and 1.2. The data is collected in a region 7–80 jet diameters downstream of the injection location. From the data on mass transfer coefficients and effectiveness obtained under the same flow conditions a general mass transfer equation is derived. This paper presents extensive data and discussions; and is believed to be one of the few studies in which both of these variables are measured on the same surface and in a large area in the recovery region.