A data assimilation technique applied to a predator-prey model

A new approach for data assimilation, which is based on the adjoint method, but allows the computer code for the adjoint to be constructed directly from the model computer code, is described. This technique is straightforward and reduces the chance of introducing errors in the construction of the adjoint code. Implementation of the technique is illustrated by applying it to a simple predator-prey model in a model fitting mode. A series of identical twin numerical experiments are used to show that this data assimilation approach can successfully recover model parameters as well as initial conditions. However, the ease with which these values are recovered is dependent on the form of the model equations as well as on the type and amount of data that are available. Additional numerical experiments show that sufficient coefficient and parameter recoveries are possible even when the assimilated data contain significant random noise. Thus, for biological systems that can be described by ecosystem models, the adjoint method represents a powerful approach for estimating values for little-known biological parameters, such as initial conditions, growth rates, and mortality rates.     

Conflicts of interest in e-cigarette research: A public good and public interest perspective

The tobacco industry’s involvement in the electronic cigarette research that informs public health policy is controversial. On the one hand, some are concerned that their involvement presents conflicts of interest that bias research outputs and invalidate the policies that use them. On the other hand, some have argued that the tobacco industry may support valid research and contribute to the goals of public health, for instance, if the interests of the e-cigarette industry could be part of a tobacco smoking cessation policy. We approach this debate from the ethical perspective of the public interest and the public good, considering how legitimate researchers can square their expert opinion with validating tobacco industry-funded research, given the perfidy of the tobacco industry and paucity of robust, conclusive evidence on the public health impacts of liberalizing e-cigarette use.     

Fat mass compared to four body condition scoring systems in the Asian elephant (Elephas maximus)

Captive elephant populations are not self‐sustaining due to health concerns possibly related to obesity. Categorizing obesity relies on qualitative analyses like body condition scores (BCS). However, elephant indices have not been validated against measured body composition. The objective was to compare BCS systems to body composition determined by deuterium dilution in 28 zoo‐kept Asian elephants. Elephants were weighed and given deuterated water orally (0.05 ml/kg). Blood was collected at ~0, 24, 120, 240, 360, and 480 hr after dosing. Photographs were taken to score the elephant based on four BCS systems (BCS_Wemmer [0 to 11 scoring], BCS_Morfeld [1 to 5 scoring], BCS_Fernando [0 to 10 scoring], BCS_Wijeyamohan [1 to 10 scoring]). Based on regression analysis, relative fat ranged from ?305 kg to 515 kg, where negative values indicate less and positive values indicate more fat than expected for the elephant's mass in this population. BCS_Fernando was associated with relative fat (p = .020, R² = 0.194). Relative fat, adjusted for sex and age in the statistical model, was associated with BCS_Wemmer (p = .027, R² = 0.389), BCS_Fernando (p = .002, R² = 0.502), and BCS_Wijeyamohan (p = .011, R² = 0.426). Inclusion of zoo and familial relatedness resulted in all BCS systems associated with relative fat (p ≤ .015). Only BCS_Fernando predicted relative fat, unadjusted, suggesting it is the most capable system for practical use. Compared to absolute fat, relative fat may be more biologically relevant as greater fat relative to body mass is more likely to lead to health issues.     

A New Chamber for Studying the Behavior of Drosophila

Methods available for quickly and objectively quantifying the behavioral phenotypes of the fruit fly, Drosophila melanogaster, lag behind in sophistication the tools developed for manipulating their genotypes. We have developed a simple, easy-to-replicate, general-purpose experimental chamber for studying the ground-based behaviors of fruit flies. The major innovative feature of our design is that it restricts flies to a shallow volume of space, forcing all behavioral interactions to take place within a monolayer of individuals. The design lessens the frequency that flies occlude or obscure each other, limits the variability in their appearance, and promotes a greater number of flies to move throughout the center of the chamber, thereby increasing the frequency of their interactions. The new chamber design improves the quality of data collected by digital video and was conceived and designed to complement automated machine vision methodologies for studying behavior. Novel and improved methodologies for better quantifying the complex behavioral phenotypes of Drosophila will facilitate studies related to human disease and fundamental questions of behavioral neuroscience.