Letter to the Editor

Page et al. appear to have missed our point that the teratogenic effects of oil on fish derive from embryonic exposure to environmentally persistent 3- and 4-ring polycyclic aromatic hydrocarbons (PAHs). They regard our conclusions as incorrect because we failed to demonstrate causality or a clear dose-response relationship. As evidence for lack of causality, they indicate that our data were not replicated. However, our report was a companion paper to a similar one demonstrating PAH-induced teratogenesis in herring embryos, also in the low ppb. Current literature corroborates our data and careful consideration of our conclusion demonstrates that their inclusion of low molecular weight PAHs in their dose-response relationship is counter to their thesis that dose measures should only include toxic compounds. When we published this work 12 years ago, the concept that PAHs with high octanol-partition coefficient (KOW) were teratogenic at concentrations below their solubility was considered novel. Since then, the sensitivity of developing fish embryos to ppb concentrations of PAHs dissolved in water has been confirmed for fish embryos exposed to oiled sediments, dissolved mixtures of PAHs derived from oiled sediments, and specific high molecular weight PAHs dissolved in water; additional references will be found in the Supplemental Data. More recently, experiments involving specific PAHs with partition-controlled delivery systems also have demonstrated toxic effects at levels below aqueous solubility limits. At least eleven reports replicate our findings in seven different fish species and support our conclusion that accumulation of PAHs by embryos depends on the kinetics of the transfer of PAHs from oil to egg rather than PAH solubility

Aryl Hydrocarbon Receptor–Independent Toxicity of Weathered Crude Oil during Fish Development

Polycyclic aromatic hydrocarbons (PAHs), derived largely from fossil fuels and their combustion, are pervasive contaminants in rivers, lakes, and nearshore marine habitats. Studies after the Exxon Valdez oil spill demonstrated that fish embryos exposed to low levels of PAHs in weathered crude oil develop a syndrome of edema and craniofacial and body axis defects. Although mechanisms leading to these defects are poorly understood, it is widely held that PAH toxicity is linked to aryl hydrocarbon receptor (AhR) binding and cytochrome P450 1A (CYP1A) induction. Using zebrafish embryos, we show that the weathered crude oil syndrome is distinct from the well-characterized AhR-dependent effects of dioxin toxicity. Blockade of AhR pathway components with antisense morpholino oligonucleotides demonstrated that the key developmental defects induced by weathered crude oil exposure are mediated by low-molecular-weight tricyclic PAHs through AhR-independent disruption of cardiovascular function and morphogenesis. These findings have multiple implications for the assessment of PAH impacts on coastal habitats

Simulations and analysis tools for charge-exchange (d,2He)(d,{}^{2}\text{He}) reactions in inverse kinematics with the AT-TPC

Charge-exchange $(d,{}^{2}\text{He})$ reactions in inverse kinematics at intermediate energies are a very promising method to investigate the Gamow-Teller transition strength in unstable nuclei. A simulation and analysis software based on the $\rm{\scriptsize ATTPCROOT}$ package was developed to study these type of reactions with the active-target time projection chamber (AT-TPC). The simulation routines provide a realistic detector response that can be used to understand and benchmark experimental data. Analysis tools and correction routines can be developed and tested from simulations in $\rm{\scriptsize ATTPCROOT}$, because they are processed in the same way as the real data. In particular, we study the feasibility of using coincidences with beam-like particles to unambiguously identify the $(d,{}^{2}\text{He})$ reaction channel, and to develop a kinematic fitting routine for future applications. More technically, the impact of space-charge effects in the track reconstruction, and a possible correction method are investigated in detail. This analysis and simulation package constitutes an essential part of the software development for the fast-beams program with the AT-TPC

Convolutional Neural Networks Applied to Neutrino Events in a Liquid Argon Time Projection Chamber

We present several studies of convolutional neural networks applied to data coming from the MicroBooNE detector, a liquid argon time projection chamber (LArTPC). The algorithms studied include the classification of single particle images, the localization of single particle and neutrino interactions in an image, and the detection of a simulated neutrino event overlaid with cosmic ray backgrounds taken from real detector data. These studies demonstrate the potential of convolutional neural networks for particle identification or event detection on simulated neutrino interactions. We also address technical issues that arise when applying this technique to data from a large LArTPC at or near ground level