Fiber-coupled balanced optical cross-correlator using PPKTP waveguides

We present a fiber-coupled balanced optical cross-correlator using waveguides in periodically-poled KTiOPO4 (PPKTP). The normalized conversion efficiency of the waveguide device is measured to be η0 = 1.02% / [W·cm2], which agrees well with theory and simulation. This result represents an expected improvement of a factor of 20 over previous bulk-optic devices. The sensitivity of the cross-correlator is characterized and shown to be comparable to the free-space bulk-optic version, with the potential for significant performance enhancements in the future

Long-term stable, large-scale, optical timing distribution systems with sub-femtosecond timing stability

Sub-fs X-ray pulse generation in kilometre-scale FEL facilities will require sub-fs long-term timing stability between optical sources over kilometer distances. We present here key developments towards a completely fiber-coupled, pulsed optical timing distribution system capable of delivering such stability. First, we developed a novel 1.2-km dispersion-compensated, polarization- maintaining fiber link to eliminate drifts previously induced by polarization mode dispersion. Link stabilization for 16 days showed 0.6 fs RMS timing drift and during a 3-day interval only 0.13 fs drift. Second, we verified that ultralow-noise optical master oscillators for sub-fs timing distribution are available today; the measured jitter for two commercial femtosecond lasers is less than 70 as for frequencies above 1 kHz. Lastly, we fabricated a hybrid-integrated, balanced optical cross- correlator using PPKTP waveguides to eliminate alignment drifts and for future reduction of the link operation power by a factor of 10-100

Towards a Large-Scale, Optical Timing Distribution System with Sub-Femtosecond Residual Timing Jitter

We present here key developments for an all-optical timing distribution system with sub-femtosecond precision. Timing distribution over a 1.2-km polarization-maintaining, fiber-optic link using balanced optical cross-correlators (BOC) for link stabilization was demonstrated for 16 days with 0.6 fs RMS timing drift and during a 3-day interval only 0.13 fs drift. Jitter characterization of two identical commercial femtosecond lasers using the BOC method verified sub-100-as timing jitter for frequencies greater than 1 kHz. Preliminary operation of a fiber coupled, hybrid-integrated BOC using periodically-poled KTiOPO4 (PPKTP) waveguides indicate great potential for improved BOC timing sensitivities and overall system efficiency

Stoma-free survival after anastomotic leak following rectal cancer resection: worldwide cohort of 2470 patients

Background: The optimal treatment of anastomotic leak after rectal cancer resection is unclear. This worldwide cohort study aimed to provide an overview of four treatment strategies applied. Methods: Patients from 216 centres and 45 countries with anastomotic leak after rectal cancer resection between 2014 and 2018 were included. Treatment was categorized as salvage surgery, faecal diversion with passive or active (vacuum) drainage, and no primary/secondary faecal diversion. The primary outcome was 1-year stoma-free survival. In addition, passive and active drainage were compared using propensity score matching (2: 1). Results: Of 2470 evaluable patients, 388 (16.0 per cent) underwent salvage surgery, 1524 (62.0 per cent) passive drainage, 278 (11.0 per cent) active drainage, and 280 (11.0 per cent) had no faecal diversion. One-year stoma-free survival rates were 13.7, 48.3, 48.2, and 65.4 per cent respectively. Propensity score matching resulted in 556 patients with passive and 278 with active drainage. There was no statistically significant difference between these groups in 1-year stoma-free survival (OR 0.95, 95 per cent c.i. 0.66 to 1.33), with a risk difference of -1.1 (95 per cent c.i. -9.0 to 7.0) per cent. After active drainage, more patients required secondary salvage surgery (OR 2.32, 1.49 to 3.59), prolonged hospital admission (an additional 6 (95 per cent c.i. 2 to 10) days), and ICU admission (OR 1.41, 1.02 to 1.94). Mean duration of leak healing did not differ significantly (an additional 12 (-28 to 52) days). Conclusion: Primary salvage surgery or omission of faecal diversion likely correspond to the most severe and least severe leaks respectively. In patients with diverted leaks, stoma-free survival did not differ statistically between passive and active drainage, although the increased risk of secondary salvage surgery and ICU admission suggests residual confounding

Stoma-free Survival After Rectal Cancer Resection With Anastomotic Leakage: Development and Validation of a Prediction Model in a Large International Cohort.

Objective:To develop and validate a prediction model (STOMA score) for 1-year stoma-free survival in patients with rectal cancer (RC) with anastomotic leakage (AL).Background:AL after RC resection often results in a permanent stoma.Methods:This international retrospective cohort study (TENTACLE-Rectum) encompassed 216 participating centres and included patients who developed AL after RC surgery between 2014 and 2018. Clinically relevant predictors for 1-year stoma-free survival were included in uni and multivariable logistic regression models. The STOMA score was developed and internally validated in a cohort of patients operated between 2014 and 2017, with subsequent temporal validation in a 2018 cohort. The discriminative power and calibration of the models' performance were evaluated.Results:This study included 2499 patients with AL, 1954 in the development cohort and 545 in the validation cohort. Baseline characteristics were comparable. One-year stoma-free survival was 45.0% in the development cohort and 43.7% in the validation cohort. The following predictors were included in the STOMA score: sex, age, American Society of Anestesiologist classification, body mass index, clinical M-disease, neoadjuvant therapy, abdominal and transanal approach, primary defunctioning stoma, multivisceral resection, clinical setting in which AL was diagnosed, postoperative day of AL diagnosis, abdominal contamination, anastomotic defect circumference, bowel wall ischemia, anastomotic fistula, retraction, and reactivation leakage. The STOMA score showed good discrimination and calibration (c-index: 0.71, 95% CI: 0.66-0.76).Conclusions:The STOMA score consists of 18 clinically relevant factors and estimates the individual risk for 1-year stoma-free survival in patients with AL after RC surgery, which may improve patient counseling and give guidance when analyzing the efficacy of different treatment strategies in future studies