Stable isotope characterisation of 3,4-methylenedioxyphenyl-2-propanone and 3,4-methylenedioxyamphetamine prepared from piperonal.

RATIONALE: Stable isotopic ratios can provide information for illicit drug profiling. The research presented here investigated the variations in stable isotopic ratios of hydrogen (δ2 H), carbon (δ13 C), nitrogen (δ15 N) and oxygen (δ18 O) during the synthesis of MDP2P (3,4-methylenedioxyphenyl-2-propanone) and MDA (3,4-methylenedioxyamphetamine) prepared via the 'nitrostyrene' route. METHODS: Samples of MDA and MDP2P were synthesised from two isotopically characterised starting materials, piperonal and nitroethane. The isotopic compositions of the nitrostyrene intermediate (3,4-methylenedioxyphenyl-2-nitropropene, MDP2NP) and products MDP2P and MDA were also measured by isotope ratio mass spectrometry. RESULTS: A significantly negative change occurred to δ2 H values during the production of MDP2NP, MDP2P and MDA, indicating a mechanism that favours inclusion or retention of 1 H over 2 H. This suggests that the δ2 H compositions of MDA/MDP2P prepared from piperonal will not provide information on the synthetic history. Minimal changes were observed in δ13 C composition during the synthesis of MDP2NP, MDP2P and MDA, and minimal δ15 N compositional changes occurred in MDP2NP and MDA. Progressing from piperonal to MDP2NP, a minimal change occurred to δ18 O composition. A variable change to δ18 O was observed from MDP2NP with one sample becoming more positive in δ18 O composition and two samples becoming more negative. Progressing from MDP2NP to MDA, a significant negative change occurred to δ18 O composition. CONCLUSIONS: The changes to stable isotopic ratios observed during the preparation of MDA and MDP2P from piperonal may prove useful when attempting to compare batch-to-batch variations between seizures and provide information with tactical intelligence applications.

Heat transfer analysis and resolution quantification of active dynamic thermography through human skin.

OBJECTIVES: Active dynamic thermography (ADT) is a non-contact imaging technique that characterizes non-homogeneities in thermal conductance through objects as a response to applied energy stimulus. The aim of this study was to (i) develop a heat transfer model to define the relationship between thermal stimulation and resolution and (ii) empirically quantify the resolution an ADT imaging system can detect through a range of depths of human skin. MATERIALS AND METHODS: A heat transfer model was developed to describe a thermally non-conductive object below a sheet of skin. The size and depth of the object were varied to simulate wound conditions, while the intensity and duration of thermal stimulation were varied to define stimulation parameters. The model was solved by numerical analysis. For ex vivo experimentation, freshly excised human pannus tissue was cut into sheets of thickness 2.54-6.35 × 10-4 m (0.010-0.025vinches) for a total of 48 grafts from 12 patients. Grafts were placed over a 3D printed resolution target with objects ranging from 0.445-0.125 LP/mm. Stimulation from a 300 W halogen lamp array was applied for 0.5-14 seconds for a total of 480 experiments. RESULTS: ADT resolved a peak of 0.428 ± 0.025 LP/mm for 2.54 × 10-4 m (0.010 inches) skin thickness, 0.384 ± 0.030 LP/mm for 3.81 × 10-4 m (0.015 inches), 0.325 ± 0.042 LP/mm for 5.08 × 10-4 m (0.020 inches) and 0.249 ± 0.057 LP/mm for 6.35 × 10-4 m (0.025 inches) skin thickness. Additionally, it was determined that the ideal duration of stimulation energy with a 300 W stimulation system was 4 seconds for 2.54 × 10-4 m, 6 seconds for 3.81 × 10-4 m, 8 seconds for 5.08 × 10-4 m, and 14 seconds for 6.35 × 10-4 m skin thickness. CONCLUSIONS: This study has characterized the correlation between thermal stimulus input and resolvable object size and depth for ADT. Through ex vivo experimentation it has also quantified the functional imaging depth to below the sub-cutis, beyond that of conventional imaging techniques. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.