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Recent developments in markerless tracking software such as DeepLabCut (DLC) allow estimation of skin landmark positions during behavioral studies. However, studies that require highly accurate skeletal kinematics require estimation of 3D positions of subdermal landmarks such as joint centers of rotation or skeletal features. In many animals, significant slippage between the skin and underlying skeleton makes accurate tracking of skeletal configuration from skin landmarks difficult. While biplanar, high-speed X-ray acquisition cameras offer a way to measure accurate skeletal configuration using tantalum markers and XROMM, this technology is expensive, not widely available, and the manual annotation required is time-consuming. Here, we present an approach that utilizes DLC to estimate subdermal landmarks in a rat from video collected from two standard cameras. By simultaneously recording X-ray and live video of an animal, we train a DLC model to predict the skin locations representing the projected positions of subdermal landmarks obtained from X-ray data. Predicted skin locations from multiple camera views were triangulated to reconstruct depth-accurate positions of subdermal landmarks. We found that DLC was able to estimate skeletal landmarks with good 3D accuracy, suggesting that this might be an approach to provide accurate estimates of skeletal configuration using standard live video. 

We present electronic spectra containing the Q x and Q y absorption bands of singly and doubly deprotonated protoporphyrin IX, prepared as mass selected ions in vacuo at cryogenic temperatures, revealing vibronic structure in both bands. We assign the vibronic progression of the Q x band using a Frank–Condon–Herzberg–Teller simulation based on time-dependent density functional theory, comparing the observed bands with those calculated for porphine. A comparison of the electronic spectra of the two charge states allows investigation of the electronic Stark effect with an electric field strength beyond the capabilities of typical laboratory setups. We analyze the differences in the electronic spectra of the two charge states using n-electron valence perturbation theory (NEVPT2) and simulated charge distributions.