On the Derivation of Vector Radiative Transfer Equation for Polarized Radiative Transport in Graded Index Media

Light transport in graded index media follows a curved trajectory determined by the Fermat's principle. Besides the effect of variation of the refractive index on the transport of radiative intensity, the curved ray trajectory will induce geometrical effects on the transport of polarization ellipse. This paper presents a complete derivation of vector radiative transfer equation for polarized radiation transport in absorption, emission and scattering graded index media. The derivation is based on the analysis of the conserved quantities for polarized light transport along curved trajectory and a novel approach. The obtained transfer equation can be considered as a generalization of the classic vector radiative transfer equation that is only valid for uniform refractive index media. Several variant forms of the transport equation are also presented, which include the form for Stokes parameters defined with a fixed reference and the Eulerian forms in the ray coordinate and in several common orthogonal coordinate systems.Comment: This paper has been submitted to JQSR

Sheffield Clinical Research Fellowship programme: A transferable model for UK gastroenterology

Out of programme (OOP) opportunities are to be encouraged. This article gives an insightful view of the Sheffield Clinical Research Fellowship Programme. Unique trainee feedback is provided. The take home message is clear - trainees should grab OOP experiences with both hands! For consultants the logistics described are potentially transferrable to their own regions

Diagnostic yield of magnetically assisted capsule endoscopy versus gastroscopy in recurrent and refractory iron deficiency anemia

BACKGROUND: Small-bowel capsule endoscopy is advocated and repeat upper gastrointestinal (GI) endoscopy should be considered for evaluation of recurrent or refractory iron deficiency anemia (IDA). A new device that allows magnetic steering of the capsule around the stomach (magnetically assisted capsule endoscopy [MACE]), followed by passive small-bowel examination might satisfy both requirements in a single procedure. METHODS: In this prospective cohort study, MACE and esophagogastroduodenoscopy (EGD) were performed in patients with recurrent or refractory IDA. Comparisons of total (upper GI and small bowel) and upper GI diagnostic yields, gastric mucosal visibility, and patient comfort scores were the primary end points. RESULTS: 49 patients were recruited (median age 64 years; 39 % male). Combined upper and small-bowel examination using the new capsule yielded more pathology than EGD alone (113 vs. 52; P < 0.001). In upper GI examination (proximal to the second part of the duodenum, D2), MACE identified more total lesions than EGD (88 vs. 52; P < 0.001). There was also a difference if only IDA-associated lesions (esophagitis, altered/fresh blood, angioectasia, ulcers, and villous atrophy) were included (20 vs. 10; P = 0.04). Pathology distal to D2 was identified in 17 patients (34.7 %). Median scores (0 - 10 for none - extreme) for pain (0 vs. 2), discomfort (0 vs. 3), and distress (0 vs. 4) were lower for MACE than for EGD (P < 0.001). CONCLUSION: Combined examination of the upper GI tract and small bowel using the MACE capsule detected more pathology than EGD alone in patients with recurrent or refractory IDA. MACE also had a higher diagnostic yield than EGD in the upper GI tract and was better tolerated by patients