Numerical Verification of the Weak Turbulent Model for Swell Evolution

The purpose of this article is numerical verification of the theory of weak turbulence. We performed numerical simulation of an ensemble of nonlinearly interacting free gravity waves (swell) by two different methods: solution of primordial dynamical equations describing potential flow of the ideal fluid with a free surface and, solution of the kinetic Hasselmann equation, describing the wave ensemble in the framework of the theory of weak turbulence. In both cases we observed effects predicted by this theory: frequency downshift, angular spreading and formation of Zakharov-Filonenko spectrum $I_{\omega} \sim \omega^{-4}$. To achieve quantitative coincidence of the results obtained by different methods, one has to supply the Hasselmann kinetic equation by an empirical dissipation term $S_{diss}$ modeling the coherent effects of white-capping. Using of the standard dissipation terms from operational wave predicting model ({\it WAM}) leads to significant improvement on short times, but not resolve the discrepancy completely, leaving the question about optimal choice of $S_{diss}$ open. In a long run {\it WAM} dissipative terms overestimate dissipation essentially.Comment: 41 pages, 37 figures, 1 table. Submitted in European Journal of Mechanics B/Fluid

Identification of a major QTL for Xanthomonas arboricola pv. pruni resistance in apricot

Xanthomonas arboricola pv. pruni causes bacterial spot of stone fruit resulting in severe yield losses in apricot production systems. Present on all continents, the pathogen is regulated in Europe as a quarantine organism. Host resistance is an important component of integrated pest management; however, little work has been done describing resistance against X. arboricola pv. pruni. In this study, an apricot population derived from the cross “Harostar” × “Rouge de Mauves” was used to construct two parental genetic maps and to perform a quantitative trait locus analysis of resistance to X. arboricola pv. pruni. A population of 101 F1 individuals was inoculated twice for two consecutive years in a quarantine greenhouse with a mixture of bacterial strains, and disease incidence and resistance index data were collected. A major QTL for disease incidence and resistance index accounting respectively for 53 % (LOD score of 15.43) and 46 % (LOD score of 12.26) of the phenotypic variation was identified at the same position on linkage group 5 of “Rouge de Mauves.” Microsatellite marker UDAp-452 co-segregated with the resistance, and two flanking microsatellites, namely BPPCT037 and BPPCT038A, were identified. When dividing the population according to the alleles of UDAp-452, the subgroup with unfavorable allele had a disease incidence of 32.6 % whereas the group with favorable allele had a disease incidence of 21 %, leading to a reduction of 35.6 % in disease incidence. This study is a first step towards the marker-assisted breeding of new apricot varieties with an increased tolerance to X. arboricola pv. pruni

The BELT and phenoSEED platforms: shape and colour phenotyping of seed samples

Abstract Background Quantitative and qualitative assessment of visual and morphological traits of seed is slow and imprecise with potential for bias to be introduced when gathered with handheld tools. Colour, size and shape traits can be acquired from properly calibrated seed images. New automated tools were requested to improve data acquisition efficacy with an emphasis on developing research workflows. Results A portable imaging system (BELT) supported by image acquisition and analysis software (phenoSEED) was created for small-seed optical analysis. Lentil (Lens culinaris L.) phenotyping was used as the primary test case. Seeds were loaded into the system and all seeds in a sample were automatically individually imaged to acquire top and side views as they passed through an imaging chamber. A Python analysis script applied a colour calibration and extracted quantifiable traits of seed colour, size and shape. Extraction of lentil seed coat patterning was implemented to further describe the seed coat. The use of this device was forecasted to eliminate operator biases, increase the rate of acquisition of traits, and capture qualitative information about traits that have been historically analyzed by eye. Conclusions Increased precision and higher rates of data acquisition compared to traditional techniques will help to extract larger datasets and explore more research questions. The system presented is available as an open-source project for academic and non-commercial use. </jats:sec

The BELT and phenoSEED platforms: shape and colour phenotyping of seed samples

AbstractBackgroundSeed analysis is currently a bottleneck in phenotypic analysis of seeds. Measurements are slow and imprecise with potential for bias to be introduced when gathered manually. New acquisition tools were requested to improve phenotyping efficacy with an emphasis on obtaining colour information.ResultsA portable imaging system (BELT) supported by image acquisition and analysis software (phenoSEED) was created for small-seed optical analysis. Lentil (Lens culinaris L.) phenotyping was used as the primary test case. Seeds were loaded into the system and all seeds in a sample were automatically and individually imaged to acquire top and side views as they passed through an imaging chamber. A Python analysis script applied a colour calibration and extracted quantifiable traits of seed colour, size and shape. Extraction of lentil seed coat patterning was implemented to further describe the seed coat. The use of this device was forecasted to eliminate operator biases, increase the rate of acquisition of traits, and capture qualitative information about traits that have been historically analyzed by eye.ConclusionsIncreased precision and higher rates of data acquisition compared to traditional techniques will help breeders to develop more productive cultivars. The system presented is available as an open-source project for academic and non-commercial use.</jats:sec

Freak waves in crossing seas

We consider the modulational instability in crossing seas as a potential mechanism for the formation of freak waves. The problem is discussed in terms of a system of two coupled Nonlinear Schröedinger equations. The asymptotic validity of such system is discussed. For some specific angles between the two wave trains, the equations reduce to an integrable system. A stability analysis of these equations is discussed. Furthermore, we present an analytical study of the maximum amplification factor for an unstable plane wave solution. Results indicate that angles between 10° and 30° are the most probable for establishing a freak wave sea. We show that the theoretical expectations are consistent with numerical simulations of the Euler equations

Freak waves in crossing seas

We consider the modulational instability in crossing seas as a potential mechanism for the formation of freak waves. The problem is discussed in terms of a system of two coupled Nonlinear Schröedinger equations. The asymptotic validity of such system is discussed. For some specific angles between the two wave trains, the equations reduce to an integrable system. A stability analysis of these equations is discussed. Furthermore, we present an analytical study of the maximum amplification factor for an unstable plane wave solution. Results indicate that angles between 10° and 30° are the most probable for establishing a freak wave sea. We show that the theoretical expectations are consistent with numerical simulations of the Euler equations