On right-angled polygons in hyperbolic space

We study oriented right-angled polygons in hyperbolic spaces of arbitrary dimensions, that is, finite sequences (S0,S1,…,Sp−1) of oriented geodesics in the hyperbolic space HHn+2 such that consecutive sides are orthogonal. It was previously shown by Delgove and Retailleau (Ann Fac Sci Toulouse Math 23(5):1049–1061, 2014. https://doi.org/10.5802/afst.1435) that three quaternionic parameters define a right- angled hexagon in the 5-dimensional hyperbolic space. We generalise this method to right-angled polygons with an arbitrary number of sides p≥5 in a hyperbolic space of arbitrary dimension

Microbial colonization of the upper gastrointestinal tract in patients with Barrett's esophagus

Background. Barrett’s esophagus (BE) is a complication of chronic gastroesophageal reflux disease, in which patients are at greatly increased risk of esophageal dysplasia and adenocarcinoma. Over the past 2 decades, there has been an increase in the incidence of both BE and adenocarcinoma; however, the involvement of microorganisms in BE is uncertain. The aim of this study was to characterize microbial communities in esophageal aspirate specimens and on distal esophageal mucosal samples from patients with BE. Methods. Biopsy and aspirate specimens were obtained by endoscopic examination from 7 patients with BE and 7 control subjects without BE. Samples were cultured under aerobic, anaerobic, and microaerophilic conditions for yeasts and bacteria, including Helicobacter pylori. Bacterial isolates were identified by 16S ribosomal RNA gene sequencing. Fluorescence microscopic examination was also used to determine the spatial localization of these organisms on mucosal surfaces. Significant colonization was detected in 6 patients with BE and in 4 control subjects. Results. Overall, 46 bacterial species belonging to 16 genera were detected, with 10 species being common in both groups. Both aspirate and biopsy samples from patients with BE contained complex populations of bacteria. Uniquely, high levels of Campylobacter species (Campylobacter concisus and Campylobacter rectus), which have been linked to enteritis, periodontal infections, and tumor formation in animals, were found in 4 (57%) of 7 patient