Invariant Manifolds and Rate Constants in Driven Chemical Reactions

Reaction rates of chemical reactions under nonequilibrium conditions can be determined through the construction of the normally hyperbolic invariant manifold (NHIM) [and moving dividing surface (DS)] associated with the transition state trajectory. Here, we extend our recent methods by constructing points on the NHIM accurately even for multidimensional cases. We also advance the implementation of machine learning approaches to construct smooth versions of the NHIM from a known high-accuracy set of its points. That is, we expand on our earlier use of neural nets, and introduce the use of Gaussian process regression for the determination of the NHIM. Finally, we compare and contrast all of these methods for a challenging two-dimensional model barrier case so as to illustrate their accuracy and general applicability.Comment: 28 pages, 13 figures, table of contents figur

Invariant manifolds and rate constants in driven chemical reactions

Reaction rates of chemical reactions under nonequilibrium conditions can be determined through the construction of the normally hyperbolic invariant manifold (NHIM) [and moving dividing surface (DS)] associated with the transition state trajectory. Here, we extend our recent methods by constructing points on the NHIM accurately even for multidimensional cases. We also advance the implementation of machine learning approaches to construct smooth versions of the NHIM from a known high-accuracy set of its points. That is, we expand on our earlier use of neural nets and introduce the use of Gaussian process regression for the determination of the NHIM. Finally, we compare and contrast all of these methods for a challenging two-dimensional model barrier case so as to illustrate their accuracy and general applicability

Intracorporeal and Extracorporeal Anastomosis for Robotic-Assisted and Laparoscopic Right Colectomy: Short-Term Outcomes of a Multi-Center Prospective Trial

Background: Studies to date show contrasting conclusions when comparing intracorporeal and extracorporeal anastomoses for minimally invasive right colectomy. Large multi-center prospective studies comparing perioperative outcomes between these two techniques are needed. The purpose of this study was to compare intracorporeal and extracorporeal anastomoses outcomes for robotic assisted and laparoscopic right colectomy. Methods: Multi-center, prospective, observational study of patients with malignant or benign disease scheduled for laparoscopic or robotic-assisted right colectomy. Outcomes included conversion rate, gastrointestinal recovery, and complication rates. Results: There were 280 patients: 156 in the robotic assisted and laparoscopic intracorporeal anastomosis (IA) group and 124 in the robotic assisted and laparoscopic extracorporeal anastomosis (EA) group. The EA group was older (mean age 67 vs. 65 years, p = 0.05) and had fewer white (81% vs. 90%, p = 0.05) and Hispanic (2% vs. 12%, p = 0.003) patients. The EA group had more patients with comorbidities (82% vs. 72%, p = 0.04) while there was no significant difference in individual comorbidities between groups. IA was associated with fewer conversions to open and hand-assisted laparoscopic approaches (p = 0.007), shorter extraction site incision length (4.9 vs. 6.2 cm; p ≤ 0.0001), and longer operative time (156.9 vs. 118.2 min). Postoperatively, patients with IA had shorter time to first flatus, (1.5 vs. 1.8 days; p ≤ 0.0001), time to first bowel movement (1.6 vs. 2.0 days; p = 0.0005), time to resume soft/regular diet (29.0 vs. 37.5 h; p = 0.0014), and shorter length of hospital stay (median, 3 vs. 4 days; p ≤ 0.0001). Postoperative complication rates were comparable between groups. Conclusion: In this prospective, multi-center study of minimally invasive right colectomy across 20 institutions, IA was associated with significant improvements in conversion rates, return of bowel function, and shorter hospital stay, as well as significantly longer operative times compared to EA. These data validate current efforts to increase training and adoption of the IA technique for minimally invasive right colectomy

The influence of obesity and body mass index on the outcome of laparoscopic colorectal surgery: a systematic literature review

AIM: The relationship between obesity, body-mass index (BMI) and laparoscopic colorectal resection is unclear. Our object was to assess systematically the available evidence to establish the influence of obesity and BMI on the outcome of laparoscopic colorectal resection. METHOD: A search of PubMed/Medline databases was performed in May 2015 to identify all studies investigating the impact of BMI and obesity on elective laparoscopic colorectal resection performed for benign or malignant bowel disease. Clinical end points examined included operation time, conversion rate to open surgery, post-operative complications including anastomotic leakage, length of hospital stay, readmission rate, reoperation rate and mortality. For patients who underwent an operation for cancer, the harvested number of lymph nodes and long-term oncological data were also examined. RESULTS: 45 studies were analysed, the majority of which were Level IV with only four level III case-controlled studies. Thirty comparative studies containing 23649 patients including 17895 non-obese and 5754 obese showed no significant differences between the two groups with respect to intraoperative blood loss, overall postoperative morbidity, anastomotic leakage, reoperation rate, mortality and the number of retrieved lymph nodes in patients operated on for malignancy. Most studies, including 15 non-comparative studies, reported a longer operation time in patients who underwent a laparoscopic procedure with the BMI being an independent predictor in multivariate analyses for the operation time. CONCLUSION: Laparoscopic colorectal resection is safe and technically and oncologically feasible in obese patients. These results, however, may be different outside high volume centres of expertise. This article is protected by copyright. All rights reserved