Background: At present, the flexible endoscopic evaluation of swallowing (FEES) is one of the most commonly used methods for the objective assessment of swallowing. This multicenter trial prospectively collected data on the safety of FEES and also assessed the impact of this procedure on clinical dysphagia management. Methods: Patients were recruited in 23 hospitals in Germany and Switzerland from September 2014 to May 2017. Patient characteristics, professional affiliation of the FEES examiners (physicians or speech and language therapists), side-effects and cardiorespiratory parameters, severity of dysphagia and clinical consequences of FEES were documented. Results: 2401 patients, mean age 69.8 (14.6) years, 42.3% women, were included in the FEES-registry. The most common main diagnosis was stroke (61%), followed by Parkinson's disease (6.5%). FEES was well tolerated by patients. Complications were reported in 2% of examinations, were all self-limited and resolved without sequelae and showed no correlation to the endoscopist's previous experience. In more than 50% of investigations FEES led to changes of feeding strategies, in the majority of cases an upgrade of oral diet was possible. Discussion: This study confirmed that FEES, even when performed by less experienced clinicians is a safe and well tolerated procedure and significantly impacts on the patients' clinical course. Implementation of a FEES-service in different clinical settings may improve dysphagia care. Trial registration: ClinicalTrials.gov NCT03037762, registered January 31st 2017.
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.
Co-based superalloys have been developed as candidate materials to replace Ni-based superalloys in hot sections of turbine engines, however, their oxidation resistance is limited. Therefore, in this work chromium and aluminum diffusion coatings were developed via the pack cementation process for novel γ/γ′-strengthened superalloys of the Co–Ni–Al–W system. This alloy system also offers the opportunity to vary the cobalt-to-nickel ratio and the tungsten content systematically to investigate their influence on the coating process. The coating process was shown to successfully enrich the surfaces of such alloys either in aluminum or chromium. For Al, the result was the formation of (Co, Ni)Al on top of an interdiffusion zone, while for chromium a Cr-rich layer in solid solution with the substrate along with the formation of σ-phase were observed. The coating formation mechanisms are discussed for both coatings in the light of activities and phase formation.
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