Switching and intrinsic position bistability of soliton beams in chiral nematic liquid crystals

We study theoretically and experimentally the propagation of light beams in chiral nematic liquid crystals. Despite the rather complex refractive index distribution of these crystals, their reorientational nonlinearity can compensate for diffraction, leading to robust solitonlike beams propagating along helical trajectories. We demonstrate that, due to a symmetry-breaking instability of the liquid crystal structure, these beams undergo abrupt switching and bistability, features that are of potential interest for applications to all-optical signal processing.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Transanal Versus Transabdominal Minimally Invasive (Completion) Proctectomy With Ileal Pouch-anal Anastomosis in Ulcerative Colitis A Comparative Study

Objective: This study aims to compare surgical outcome of transanal ileal pouch-anal anastomosis (ta-IPAA) with transabdominal minimal invasive approach in ulcerative colitis (UC), using the comprehensive complication index (CCI). Background: Recent evolutions in rectal cancer surgery led to transanal dissection of the rectum resulting in a better exposure of the distal rectum and presumed better outcome. The same approach was introduced for patients with UC, resulting in decreased invasiveness. Methods: All patients, undergoing minimally invasive restorative proctocolectomy in 1, 2, or 3 stages between January 2011 and September 2016 in 3 referral centers were included. Only patients who underwent either multiport, single port, single port with 1 additional port, hand-assisted, or robotic (R) laparoscopy were included in the analysis. CCI, registered during 90 days after pouch construction, was compared between the transanal and the transabdominal approach. Results: Ninety-seven patients (male: 52%) with ta-IPAA were compared to 119 (male: 53%) with transabdominal IPAA. Ninety-nine (46%) patients had a defunctioning ileostomy at time of pouch construction. A 2-step model showed that the odds for postoperative morbidity were 0.52 times lower in the ta-IPAA group (95% confidence interval [0.29; 0.92] P = 0.026). In patients with morbidity, mean CCI of the transanal approach was 2.23 points lower than the transabdominal approach (95% confidence interval: [-6.64-3.36] P = 0.13), which was not significant. Conclusions: Ta-IPAA for UC is a safe procedure, resulting in fewer patients with morbidity, but comparable CCI when morbidity is present. Overall, ta-IPAA led to lower CCI score