Search

Current guidelines consider endoscopic resection appropriate treatment for malignant colon polyps with negative margins, low-grade histology, and no lymphovascular invasion. While increasing literature demonstrates a worse prognosis for advanced stage right- versus left-sided colon cancers after curative treatment, there is paucity of data regarding prognostic effect of location in patients undergoing endoscopic resection of T1 polyps. We hypothesized the more aggressive biologic behavior observed in advanced right-sided cancers would be similarly represented in malignant polyps, and this location would be associated with lower overall survival.The National Cancer Database was queried for adults with T1NxMx tumors who underwent endoscopic polypectomy (2004-2017). Patients with positive margins or without follow-up information were excluded.A total of 2,337 patients met inclusion criteria; 22% had right-sided polyps. Endoscopically excised proximal tumors were more common in elderly, and those with public insurance and more comorbidities (all P.01). Among patients with complete pathologic data, there were no statistical differences between right- and left-sided polyps with 1 cm median size,92% without lymphovascular invasion, and 100% without tumor deposits. Univariate analysis showed 73% vs 86% 5-year overall survival for right versus left polyps (P.01). After adjustment for available confounders, right-sided location remained significantly associated with worse overall survival (hazard ratio 1.49, 95% confidence interval 1.21-1.83).In this national cohort of patients with endoscopically excised malignant polyps, we identified right colon location as an independent prognostic factor associated with increased risk of mortality. Our data suggest polyp location should be taken into consideration when making clinical decisions regarding treatment and/or surveillance.

Multigrid methods for two-body contact problems are mostly based on special mortar discretizations, nonlinear Gauss-Seidel solvers, and solution-adapted coarse grid spaces. Their high computational efficiency comes at the cost of a complex implementation and a nonsymmetric master-slave discretization of the nonpenetration condition. Here we investigate an alternative symmetric and overconstrained segment-to-segment contact formulation that allows for a simple implementation based on standard multigrid and a symmetric treatment of contact boundaries, but leads to nonunique multipliers. For the solution of the arising quadratic programs, we propose augmented Lagrangian multigrid with overlapping block Gauss-Seidel smoothers. Approximation and convergence properties are studied numerically at standard test problems.

Aims Woody plants represent the ancestral growth form in angiosperms with herbs evolving repeatedly from them. While there are a number of hypotheses about drivers of the evolution of the herbaceous habit, the ability to avoid frost damage in winter by discarding their aboveground biomass has often been invoked as the main force in their evolution. We propose instead that any unpredictable disturbance might have been much more important than the seasonal frost, as herbs easily survive repeated disturbance. Methods We tested this hypothesis by comparing herbs and woody plants in their ability to deal with three types of simulated disturbances, more predictable winter freezing, less predictable spring freezing and herbivory. Comparison was made in an experimental common garden setup with 20 species differing in woodiness. We evaluated the effects of these disturbances on mortality and regrowth of plants. Important Findings Herbs did not have an advantage over woody plants in survival when exposed to winter freezing. In less predictable conditions of spring freezing herbs survived the treatment better than woody plants and this advantage was even larger in case of the simulated herbivory treatment. The advantage of herbs over woody plants in less predictable conditions suggests that herbaceous growth form might be an adaptation to unpredictable disturbance, which herbs are able to tolerate thanks to their ability to survive loss of aboveground biomass. Consequently, factors such as mammal herbivory or fire might have been the most likely factors in the transition from woody species to herbs.

In angiosperms, herbs evolved from ancestral woody growth form. A number of hypotheses on what was the driver of their evolution have been proposed, but none of them has received clear support so far. We are putting forward a new hypothesis that an important advantage of the herbaceous growth form lies in its greater capacity for plastic response to neighbour shading. Since most herbs form aboveground structures only for 1 year, they can respond to light heterogeneity more plastically than woody plants with long-living structures which need to pursue long-term goals such as stability and upward growth. To test the hypothesis, we carried out an experiment comparing plastic response to directional green shading of 21 species of young herbaceous and woody plants. We measured change of their tilt and length and compared it between herbs and woody plants using phylogenetic techniques. Both herbs and woody plants in our experiment responded to directed green shading by growing away from the shading plastic film. Overall response of herbs was, in agreement with the hypothesis, slightly stronger than response of woody plants, although there was high interspecific variation. The data indicate that herbs indeed have greater plasticity of stem growth in response to neighbour shading than woody plants, although the overall difference is not very strong. This capacity for plastic response might have played a role as one of the drivers of the evolution of the herbaceous growth form.

The improvement of the high-temperature oxidation resistance remains an ambitious goal for the design of new γ/γ′-strengthened Co-base superalloys, since their oxidation resistance beyond 800 °C still ranks behind their Ni-base counterparts. To better understand the origin of the poor oxidation resistance at higher temperatures, this study focuses on early stages of oxidation of four quaternary (Co-Al-W-Ta system) Co-base model alloys with a two-phase γ/γ′-microstructure and varying γ′-volume fraction at 800 °C, 850 °C and 900 °C. Based on time-resolved isothermal gravimetric analysis (TGA) in synthetic air and detailed electron microscopic analysis, the role of the γ-channel width (or γ′-volume fraction), the surface preparation prior to exposure (polishing versus shot-peening), and the heating conditions (synthetic air versus argon) on protective alumina growth is elucidated. Firstly, for alloys of increased γ′-volume fractions slower oxidation kinetics prevailed. Secondly, the two-phase microstructure was found to decisively affect the propagation of the internal oxidation front at the early stages of oxidation. Thirdly, shot-peening prior to exposure together with a lack of oxygen availability during heating was identified to foster protective alumina growth, accompanied by TCP-phase formation in the substrate. The critical role of a high Al availability in the alloy for a rapid growth of protective alumina and the relating challenges in alloy development regarding, for example, phase stability in this relatively novel Co-base alloy class are discussed in detail.