Experimental study on a breaking-enforcing floating breakwater

Floating breakwaters are moored structures that attenuate wave energy through a combination of reflection and dissipation. Studies into floating breakwaters have been generally restricted to optimising the attenuation performance. This study presents a novel floating breakwater type that was developed to have good attenuation performance while keeping wave drift loads as small as possible. The floating breakwater was designed as a submerged parabolic beach that enforces wave energy dissipation through breaking. The design was tested in a 3D shallow-water wave basin in captive and moored setups for regular and irregular wave conditions. Results are presented in terms of attenuation performance, motions, and (mooring) loads. The results show that the breaking of waves improves the attenuation performance of the floater in captive setup. However, in moored setup, the attenuation performance was dominated by diffraction and radiation of the wave field, with breaking being of secondary importance. This shows that breaking-enforcing floating breakwaters have potential, but require a high vertical hydrostatic and/or mooring stiffness in order to enforce intense breaking. Mean wave drift loads on the object showed significant difference between breaking and non-breaking waves in both setups, with breaking waves leading to lower normalized loads. This is attributed to breaking-induced set-up and set-down of the water level. As a result, the new breakwater design has a more favourable balance between wave attenuation and drift loads than common (i.e., box-, pontoon-, or mat-type) floating breakwater designs. Tests with varying surface roughness showed that floating breakwaters may benefit from dual-use functions that naturally increase the roughness (e.g., shellfish, vegetation), which have a marginal effect on the attenuation performance, but increase the added mass and hydrodynamic damping and as such, reduce mooring line loads

Preoperative stereotactic radiotherapy to prevent pancreatic fistula in high-risk patients undergoing pancreatoduodenectomy (FIBROPANC): prospective multicentre phase II single-arm trial

Background: Postoperative pancreatic fistula is the main driver of morbidity and mortality after pancreatoduodenectomy. In high-risk patients, the rate of postoperative pancreatic fistula approaches 50%, whereas it is below 5% in patients with pancreatic cancer who receive neoadjuvant chemoradiotherapy. The aim of this study was to evaluate the safety, feasibility, and efficacy of preoperative stereotactic body radiotherapy on the pancreatic neck transection margin in high-risk patients undergoing pancreatoduodenectomy to prevent postoperative pancreatic fistula. Methods: In this prospective multicentre open-label single-arm trial (progressing from a safety run-in phase to a phase II design), patients undergoing pancreatoduodenectomy for neoplasms other than pancreatic ductal adenocarcinoma received a single preoperative stereotactic body radiotherapy dose of 12 Gy. Primary endpoints included safety (less than or equal to 15% grade 3–5 toxicity), feasibility (a significant change in pancreatic texture measured using a durometer), and efficacy (a 15% reduction in the grade B/C postoperative pancreatic fistula rate compared with patients from the Dutch Pancreatic Cancer Audit who were eligible but not included in this study). Secondary endpoints assessed tissue fibrosis (collagen density). Results: Overall, 38 patients were included, of whom 33 (87%) completed the study protocol and were included in the per-protocol analysis. The safety cut-off was met, with 3% grade 3–5 toxicity. Pancreatic tissue treated with stereotactic body radiotherapy showed increased firmness using a durometer (median of 47 (interquartile range 36–57) versus 37 (interquartile range 30–41) Shore OO units; P < 0.001) and a higher collagen density (median of 6.1% (interquartile range 4.4%–9.5%) versus 4.6% (interquartile range 2.5%–7.4%); P = 0.003). The grade B/C postoperative pancreatic fistula rate with stereotactic body radiotherapy was 57.6% (95% c.i. 41% to 74%), compared with 34% (95% c.i. 27% to 42%) in audit controls (P = 0.011). Conclusion: Preoperative stereotactic body radiotherapy is safe in high-risk patients undergoing pancreatoduodenectomy and increases parenchymal firmness and fibrosis, but fails to show evidence of efficacy