Waves propagating on the surface of a three–dimensional ideal fluid of arbitrary depth bounded above by an elastic sheet that resists flexing are considered in the small amplitude modulational asymptotic limit. A Benney–Roskes–Davey–Stewartson model is derived, and we find that fully localized wavepacket solitary waves (or lumps) may bifurcate from the trivial state at the minimum of the phase speed of the problem for a range of depths. Results using a linear and two nonlinear elastic models are compared. The stability of these solitary wave solutions and the application of the BRDS equation to unsteady wave packets is also considered. The results presented may have applications to the dynamics of continuous ice sheets and their breakup.

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Compliance (C ) and resistance (R ) maintain a unique, inverse relationship in the pulmonary circulation, resulting in a constant characteristic time τ ¼ RC that has been observed in healthy subjects as well as patients with pulmonary arterial hypertension (PAH). However, little is known about the dependence of right ventricular (RV) function on the coupled changes in R and C in the context of this inverse relationship. We hypothesized three simple dependencies of RV ejection fraction (RVEF) on R and C. The first model (linear-R ) assumes a linear RVEF-R relation; the second (linear-C ) assumes a linear RVEF-C relation; and the third one combines the former two in a mixed linear model. We found that the linear-R model and the mixed linear model are in good agreement with clinical evidence. A conclusive validation of these models will require more clinical data. Longitudinal data in particular are needed to identify the time course of ventricular-vascular impairment in PAH. Simple models like the ones we present here, once validated, will advance our understanding of the mechanisms of RV failure, which could improve strategies to manage RV dysfunction in PAH. In understanding the progression of right ventricular (RV) failure in pulmonary arterial hypertension (PAH), a key knowledge gap is the mechanisms that underlie the transition from normal RV function to RV dysfunction and failure and how these transitions are dependent on changes in pulmonary vascular function as the disease progresses. Clinical studies have shown that the mechanical properties of the pulmonary vasculature (i.e., resistance [R] and compliance [C ]) correlate with mortality in PAH. [1][2][3] In addition, an inverse relationship exists between C and R in the pulmonary circulation. 4 The time constant τ ¼ RC has been found to be equal to ∼0.5 s in a large clinical population, including patients with and without PAH, patients with different types of PAH, and patients before and after treatment. 4-7 However, it is unclear how pathological changes in vascular R and C mediate RV dysfunction.Here we formulate three hypothetical models to describe the dependence of RV function on the metrics of pulmonary vascular function R and C. We hypothesize that RV function, expressed as RV ejection fraction (RVEF), depends linearly on R or C or on a combination of both. The results from the three models are evaluated on the basis of relevant clinical evidence. METHODSTo describe the dependence of RV function on R and C, we chose a single metric of RV function. Under normal physiological conditions, known mechanisms of RV autoregulation preserve stroke volume (SV ) and cardiac output (CO) in the face of increased afterload. 8 The maintenance of SV or CO may persist in the adaptively functioning RV in mild or moderate PAH; thus, it would be difficult to correlate these parameters with the early phase of disease. RVEF may be a more sensitive metric of PAH progression than SV and CO. 9 RVEF correlates with mean pulmonary artery pressure 10 and pulmonary...

Creeping bentgrass (Agrostis stolonifera L.) is currently the most desirable grass for golf courses in temperate climates. In temperate climates, creeping bentgrass is highly susceptible to snow mold fungi which can cause significant injury and mortality. The objectives of this study were to survey a collection of creeping bentgrass clones for reaction to snow mold fungi (Typhula spp.), to identify clones with potential resistance to snow mold fungi, and to identify ecological factors related to necrotic reactions of creeping bentgrass clones to snow mold fungi. Three hundred sixty creeping bentgrass clones, selected from old golf courses in Wisconsin, were evaluated for necrosis reaction during incubation and recovery periods following inoculation with Typhula ishikariensis Imai or as noninoculated controls. Genotypic variation was observed for tolerance to snow mold and cold, dark (noninoculated) conditions but the two tolerances were uncorrelated with each other. Clones from fairways were more tolerant of snow mold, most likely due to long‐term natural selection in the absence of fungicide applications. In a second experiment involving 72 selected clones, selection was successful in identifying divergent groups of clones, although differences between experiments indicated that future selection and breeding should make use of multiple inoculation runs. Resistance to snow mold in creeping bentgrass appears to be nonspecific with respect to race and species of snow mold isolates.