Analyzing the Mass-Rearing System of the California Red Scale Parasitoid Aphytis melinus (Hymenoptera: Aphelinidae)

Results from studies to improve mass rearing production of the parasitoid Aphytis melinus De Bach (Hymenoptera: Aphelinidae) are presented. Parasitoid production was carried out following standard commercial procedures using an alternative host, Aspidiotus nerii Bouché (Hemiptera: Diaspididae), infesting Cucurbita moschata (Duchesne) (Cucurbitaceae), butternut squash. We found that the initial number of A. melinus adults introduced into rearing cages to start production and the scale/parasitoid ratio in those cages profoundly influenced future parasitoid production. We also observed that scale parasitism was positively correlated with the production of parasitoid adults, but this relationship was negatively correlated if > 2.6 parasitoids per d, per cm2, were used in the cages to start parasitism. Supplemental honey (provided on the squash surface) had no clear impact on parasitoid production or survival, but improved host parasitism. Approximately 47% of the host scale population on squash was parasitized, with another 43.1% of the population recorded as dead. We found that ≤ 10 host scales per cm2 on squash was an adequate density for mass production purposes

Supernova Feedback in Molecular Clouds: Global Evolution and Dynamics

We use magnetohydrodynamical simulations of converging warm neutral medium flows to analyse the formation and global evolution of magnetised and turbulent molecular clouds subject to supernova feedback from massive stars. We show that supernova feedback alone fails to disrupt entire, gravitationally bound, molecular clouds, but is able to disperse small--sized (~10 pc) regions on timescales of less than 1 Myr. Efficient radiative cooling of the supernova remnant as well as strong compression of the surrounding gas result in non-persistent energy and momentum input from the supernovae. However, if the time between subsequent supernovae is short and they are clustered, large hot bubbles form that disperse larger regions of the parental cloud. On longer timescales, supernova feedback increases the amount of gas with moderate temperatures (T~300-3000 K). Despite its inability to disrupt molecular clouds, supernova feedback leaves a strong imprint on the star formation process. We find an overall reduction of the star formation efficiency by a factor of 2 and of the star formation rate by roughly factors of 2-4.Comment: 16 pages, 12 figures (2 in appendix), revised version, submitted to MNRA

Non-linear dynamic analysis of the response of moored floating structures

© 2016 Elsevier Ltd. The complexity of the dynamic response of offshore marine structures requires advanced simulations tools for the accurate assessment of the seakeeping behaviour of these devices. The aim of this work is to present a new time-domain model for solving the dynamics of moored floating marine devices, specifically offshore wind turbines, subjected to non-linear environmental loads. The paper first introduces the formulation of the second-order wave radiation-diffraction solver, designed for calculating the wave-floater interaction. Then, the solver of the mooring dynamics, based on a non-linear Finite Element Method (FEM) approach, is presented. Next, the procedure developed for coupling the floater dynamics model with the mooring model is described. Some validation examples of the developed models, and comparisons among different mooring approaches, are presented. Finally, a study of the OC3 floating wind turbine concept is performed to analyze the influence of the mooring model in the dynamics of the platform and the tension in the mooring lines. The work comes to the conclusion that the coupling of a dynamic mooring model along with a second-order wave radiation-diffraction solver can offer realistic predictions of the floating wind turbine performance.Postprint (published version

Model selection and averaging in the estimation of population parameters of Bemisia tabaci (Gennadius) from stage frequency data in sweet pepper plants

Bemisia tabaci is a significant pest for many crops, but there are few population studies of this insect on sweet pepper ( Capsicum annuum). In this study, stage frequency data were generated with B. tabaci in sweet pepper plants in various situations, and the Bellows and Birley method was used to obtain population parameters from the data. The Akaike Information Criterion (AIC) was used to select the best option of the Bellows and Birley method and, in some cases, to estimate the parameters of the population using model averaging. The ratios estimated/observed for each population parameter were calculated to assess bias and were used to correct the estimations if the ratios were different from 1. The effects of different factors on the estimations of population parameters were analysed. The total duration of development was affected by the experimental conditions (laboratory vs. greenhouse) and temperature, but it had the highest precision. The final survival rate was affected by temperature, and the estimation of individuals entering each stage was affected only by the options included in the Bellows and Birley method. AIC helped to detect differences in the daily survival rate among the different experiments between N1 (first instar) (range 0.842-0.923), and the egg (range 0.989-1.0) and N4 (fourth instar) (0.990). The methodology used can be employed in field population studies. For example, the final survival rate in the greenhouse experiments varied between 0.624 and 0.097, depending on if the parasitoids were present or not, and the total development varied between 420.6 and 440.7 degree days