The contact geometry of the restricted 3-body problem

We show that the planar circular restricted three body problem is of restricted contact type for all energies below the first critical value (action of the first Lagrange point) and for energies slightly above it. This opens up the possibility of using the technology of Contact Topology to understand this particular dynamical system.Comment: 29 pages, 1 figur

Radiofrequency ablation is beneficial in simultaneous treatment of synchronous liver metastases and primary colorectal cancer

In patients with resectable synchronous colorectal liver metastases (CRLM), either two-staged or simultaneous resections of the primary tumor and liver metastases are performed. Data on radiofrequency ablation (RFA) for the treatment of CRLM during a simultaneous procedure is lacking. The primary aim was to analyze short-term and long-term outcome of RFA in simultaneous treatment. A secondary aim was to compare simultaneous resection with the colorectal-first approach.Retrospective analysis of 241 patients with colorectal cancer and synchronous CRLM between 2000-2016. Median follow-up was 36.1 months (IQR 18.2-58.8 months). A multivariable analysis was performed to analyze the postoperative morbidity, using the comprehensive complication index. A propensity matched analysis was performed to compare survival rates.In multivariable analysis, the best predictor of lower complication severity was treatment with RFA (p = 0.040). Higher complication rates were encountered in patients who underwent an abdominoperineal resection (p = 0.027) or age > 60 years (p = 0.022). The matched analysis showed comparable overall survival in RFA treated patients versus patients undergoing a liver resection with a five year overall survival of 39.4% and 37.5%, respectively (p = 0.782). In a second matched analysis, 5-year overall survival rates in simultaneously treated patients (43.8%) was comparable to patients undergoing the colorectal first approach (43.0%, p = 0.223).RFA treatment of CRLM in simultaneous procedures is associated with a lower complication severity and non-inferior oncological outcome as compared to partial liver resection. RFA should be considered a useful alternative to liver resection

Liver microwave ablation:a systematic review of various FDA-approved systems

ObjectivesThe aim of the present study is to analyze preclinical and clinical data on the performance of the currently US Food and Drug Administration (FDA)-approved microwave ablation (MWA) systems.MethodsA review of the literature, published between January 1, 2005, and December 31, 2016, on seven FDA-approved MWA systems, was conducted. Ratio of ablation zone volume to applied energy R(AZ:E) and sphericity indices were calculated for ex vivo and in vivo experiments.ResultsThirty-four studies with ex vivo, in vivo, and clinical data were summarized. In total, 14 studies reporting data on ablation zone volume and applied energy were included for comparison R(AZ:E). A significant correlation between volume and energy was found for the ex vivo experiments (r=0.85,

5-dimensional contact SO(3)-manifolds and Dehn twists

In this paper the 5-dimensional contact SO(3)-manifolds are classified up to equivariant contactomorphisms. The construction of such manifolds with singular orbits requires the use of generalized Dehn twists. We show as an application that all simply connected 5-manifoldswith singular orbits are realized by a Brieskorn manifold with exponents (k,2,2,2). The standard contact structure on such a manifold gives right-handed Dehn twists, and a second contact structure defined in the article gives left-handed twists.Comment: 16 pages, 1 figure; simplification of arguments by restricting classification to coorientation preserving contactomorphism

NDT of Composites by Thermography

This paper describes ongoing research efforts to evaluate thermographic techniques for locating flaws or damage in structural fiber composite laminates. An infra-red camera with video isotherm readout is used to identify perturbations in uniform or linear thermal fields which may be caused by presence of flaws or damage such as matrix cracks, delaminations, blind side impact damage, and partial through holes. This procedure has potential for rapid qualitative screening of large surface areas. Potential defective areas may then be analyzed by a more accurate (but more time consuming) method . Two techniques are discussed; externally applied thermal field (EATF) and stress-generated thermal field (SGTF). The EATF technique involves applying heat to a composite structure and observing theresulting transient thermal pattern. The SGTF technique requires stress cycling to create hot spots in regions of high stress concentrations adjacent to flaws or damage sites

Explaining individual differences in young English language learners’ vocabulary knowledge: The role of Extramural English Exposure and motivation

The role of motivation and extramural English exposure in explaining individual differences in young English language learners’ (YELLs’) English performance is unclear. In this study, we hypothesized that different types of extramural English exposure predict YELLs’ (Dutch, N = 262, 10 years old, grade 4) oral and written English receptive vocabulary knowledge, and that motivational factors act as mediators. A distinction was made between YELLs learning English only informally through extramural English exposure and YELLs learning English also formally at school. A path analysis showed that the total impact of familial extramural English exposure and extramural English exposure through entertaining media was greater for the YELLs learning English informally, compared to YELLs learning English also formally. While the sources of extramural English exposure were directly predictive of performance with regard to both oral and written English receptive vocabulary tests for YELLs’ learning English informally, linguistic self-confidence fully mediated these relationships for YELLs learning English formally. Our findings call for further development of theoretical frameworks explaining the relationship between YELLs’ motivation and exposure