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We derive a simple formula for the lowest natural frequencies of an infinitely long bubble plume with arbitrary cross section. Expressions are derived in terms of bubble volume fraction and equivalent radius of the plume, and a criterion for the existence of collective modes is established. For the plume with the circular cross section, our analytical approach is validated with the results of previous studies and numerical solution. [ABSTRACT FROM AUTHOR]

Experiments were undertaken to develop a relationship between bubble size and acoustic-emission amplitude for a vertical stream of water impacting a water pool. A particular focus is the formation of the discrete bubbles. Although the relationship between bubble diameter and the natural frequency of sound emissions has been established through Minnaert's work, a comprehensive investigation into the amplitude of sound emissions is missing. Air bubbles were generated from the impact of falling-water streams of varying diameters on an underlying water pool and their acoustic emissions were recorded using a nearby hydrophone. Sound amplitude was found to increase monotonically with bubble size. A second-order polynomial relationship between logarithmic acoustic sound pressure level (L) and bubble diameter ( D b ) was found, L = − 0.0401 D b 2 + 1.5781 D b + 110.7225 within the ±3 dB margin of error. The relationship between linear sound pressure level (P) and bubble diameter ( D b ) is expressed by the equation P = 0.0059 D b 2 + 0.0505 D b + 0.3591 , within the ±3 dB margin of error. Results demonstrate that larger bubbles (D > 4 mm) exhibit noise emissions similar to bubbles produced by other mechanisms, such as the underwater nozzle, while smaller diameters tend to produce higher noise levels compared to the same mechanism. [ABSTRACT FROM AUTHOR]

Introduction: Potato (Solanum tuberosum L.), the fourth most important food crop in the world, is affected by several viral pathogens with potato virus Y (PVY) having the greatest economic impact. At least nine biologically distinct variants of PVY are known to infect potato. These include the relatively new recombinant types named PVY-NTN and PVYN-Wi, which induce tuber necrosis in susceptible cultivars. To date, the molecular plant-virus interactions underlying this pathogenicity have not been fully characterized. We hypothesized that this necrotic behavior is supported by transcriptional and functional signatures that are unique to PVY-NTN and PVYN-Wi. Methods: To test this hypothesis, transcriptional responses of cv. Russet Burbank, a PVY susceptible cultivar, to three PVY strains PVY-O, PVY-NTN, and PVYN-Wi were studied using mRNA-Seq. A haploid-resolved genome assembly for tetraploid potato was used for bioinformatics analysis. Results: The study revealed 36 GO terms and nine KEGG 24 pathways that overlapped across the three PVY strains, making them generic features of PVY susceptibility in potato. Ten GO terms and three KEGG pathways enriched for PVY-NTN and PVYN-Wi only, which made them candidate functional signatures associated with PVY-induced tuber necrosis in potato. In addition, five other pathways were enriched for PVYNTN or PVYN-Wi. One carbon pool by folate was enriched exclusively in response to PVY-NTN infection; PVYN-Wi infection specifically impacted cutin, suberine and wax biosynthesis, phenylalanine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, and monoterpenoid biosynthesis. Discussion: Results suggest that PVYN-Wi-induced necrosis may be mechanistically distinguishable from that of PVY-NTN. Our study provides a basis for understanding the mechanism underlying the development of PVYinduced tuber necrosis in potato. [ABSTRACT FROM AUTHOR]

Oscillating water column (OWC) devices with Helmholtz resonator features are analyzed with semi-analytical, numerical, and experimental techniques. Conventionally, an OWC is a type of wave energy converter that consists of a duct with one end submerged, where the device's peak frequency is tuned by the length of the submerged duct. This leads to large devices when the desired peak frequency is low. The size of a conventional OWC can be reduced significantly by synthesizing features of Helmholtz resonators into it, such as using a narrow entrance. When integrated with a breakwater, it has been shown that the Helmholtz-type OWC can generate power while protecting the coastline from low-frequency ocean waves, making them dual-purpose. A systematic study of dual-purpose offshore Helmholtz-type OWC is still wanting. This study considers offshore "buoy-like" Helmholtz-type OWCs by a fast and heuristic semi-analytical model, which incorporated viscosity-related damping by empirical terms. The model shows that the Helmholtz-type OWCs have the potential to protect the coastline from low-frequency (long wavelength) waves, by producing a wide wave shadow behind them. The semi-analytical model is validated against the boundary element method (BEM), as well as experiments. The first experiment compares a Helmholtz-type OWC and a conventional OWC of the same size but different peak frequencies; the second compares a larger conventional OWC with a smaller Helmholtz OWC, which is tuned to have the same peak frequency as the former. In both cases, the semi-analytical model and the results from BEM agree well with the experiments. [ABSTRACT FROM AUTHOR]