Modeling the complicated chemical reactions in the interstellar medium and surface materials of Titan is nontrivial. Since both the atmosphere and the surface are rich in organic molecules, the chemistry may have important implications for the origin of biomolecules. Prebiotic synthesis of DNA nucleobases from simple molecules such as formamide has been known for more than half a century. In this study, new free radical pathways leading to the synthesis of guanine, hypoxanthine, purine, and adenine have been studied using density functional theory (B3LYP with the 6-311G(d,p) basis set). The pathways of the selected nucleobases demonstrate the importance of free radicals in the production of useful biomolecules under conditions appropriate for the interstellar medium or on Titan. The pathways may be universal in nature and proceed without solvent requirements. Calculations indicate that radical pathways yield lower reaction barriers as compared to previously reported pathways. Overall, these results suggest that the chemistry on Titan's surface and/or the growth of organic particulates in the haze layers in Titan's atmosphere likely involve free radicals. The mechanisms demonstrate that important prebiotic precursors can be predicted. The reaction sequences reported here may lead to the production and build-up of molecules with prebiotic relevance.

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The results demonstrate the importance of both charge-induced and charge-remote dissociations in RDX pathways. The ion structures identified along the pathways could be used as targets in analytical methods for reliable identification purposes.

Graft-versus-host disease (GVHD) is a major complication of bone marrow transplantation. Polymyositis with myonecrosis is a rare manifestation of GVHD. Here, we report the case of a 32-year-old man with acute myeloid leukemia who developed GVHD after transplant. He subsequently developed polymyositis, which was diagnosed on PET/CT and confirmed on pathology. Treatment with corticosteroids resulted in the resolution of the symptoms. Abnormal muscular FDG uptake resolved on the follow-up PET/CT.

Peritoneal scintigraphy, although rarely used, plays a vital role in the diagnosis of peritoneal dialysis catheter complications. Reported complications include spontaneous hydrothorax secondary to a pleuroperitoneal fistula, which requires the abandonment of peritoneal dialysis, given that a delay in diagnosis can lead to worsening clinical status. Previously reported peritoneal scintigraphy protocols recommended intraperitoneal instillation of radiotracer and moderate-to-large volumes of dialysate or sterile saline ranging from 350 to 2,000 mL. However, smaller volumes, in conjunction with the use of single-photon emission computed tomography/computed tomography, are not verified in patients receiving peritoneal scintigraphy imaging.