Untersuchung des Verhaltens und der Verarbeitung von Thin-Ply Prepreg mittels Fertigungsversuchen und Parameterstudien

Luft- und Raumfahrtkomponenten aus Faserverbundwerkstoffen besitzen im Vergleich zu metallischen Materialien bessere spezifische mechanische Eigenschaften; andererseits weisen sie eine tendenziell geringere Schadenstoleranz auf. In den letzten Jahren erfuhren so genannte „Thin-Ply“ Materialien (besonders dünne Faserlagen) zunehmend Aufmerksamkeit, nicht zuletzt aufgrund ihrer Fähigkeiten, die Festigkeit bei verschiedenen Belastungen im Vergleich zu Faserverbundwerkstoffen mit herkömmlichen Lagendicken zu verbessern und Mikrorisse wirksam zu unterdrücken. Obwohl Thin-Ply Materialien bereits in einigen Komponenten der Luft- und Raumfahrt eingesetzt werden, haben sie noch keine breite Anwendung in der automatisierten Fertigung gefunden. Bisher angewandte automatisierte Fertigungsverfahren resultierten in Qualitätsdefiziten. Die gegenwärtigen Risiken der automatisierten Fertigung mit Thin-Ply Materialien basieren auf einer bislang ungenügenden Forschung und damit verbundenen unzureichenden Erkenntnissen. Ziel dieser Arbeit ist es, das Potenzial der automatisierten Fertigung mit Thin-Ply Prepreg (vorimprägnierte Fasern) mittels einer Machbarkeitsstudie systematisch zu untersuchen. Dazu wird Thin-Ply Prepreg sowohl manuell als auch automatisiert per Automated Fiber Placement (AFP) abgelegt. Per Handablage werden Panels gefertigt, welche für zukünftige Zug- und Druckproben verwendet werden. Bei der AFP-Ablage werden verschiedene Verarbeitungsparameter variiert, um die Ablagequalität zu optimieren. Die Untersuchungen erfolgen sowohl im Versuchsmaßstab anhand einfacher Geometrien als auch an einem Demonstratorbauteil, welches komplexe Lagengeometrien aufweist. Aus den Erkenntnissen wird zudem ein industrielles Fertigungskonzept für die ebenfalls automatisierte Herstellung von Omega-Stringern erarbeitet. Die im Rahmen dieser Arbeit angefertigten Panels aus Thin-Ply Prepreg bieten die Grundlage für weitere Materialversuche. Sowohl bei der manuellen als auch bei der automatisierten Ablage wird festgestellt, dass die Haftung des Materials ohne Wärmeeinwirkung sehr gering ist. Erschwerend kommen bei der automatisierten Ablage Förderprobleme hinzu. Unter Berücksichtigung der durchgeführten Parameter-Optimierungen kann die Ablagequalität von Thin-Ply Prepreg per AFP dennoch gesteigert werden. Das vorgestellte Fertigungskonzept für Omega-Stringer reduziert die Komplexität deren Herstellung verbunden mit der Verwendung von Thin-Ply Prepreg. Es wird erwartet, dass die im Rahmen dieser Arbeit gewonnenen Erkenntnisse den Einsatz noch leistungsfähigerer Faserverbundwerkstoffe ebnen werden

(Infra-)Strukturelle Differenzen und deren Ursachen in peripheren Räumen – Aktuelle Beitrage des Lehrstuhls für Regionale Geographie

In Anlehnung an den Forschungsschwerpunkt der Universität beschäftigt sich der Lehrstuhl für Regionale Geographie mit der Analyse von Wirtschafts- und Gesellschaftsstrukturen vor dem Hintergrund der langfristigen Regionalentwicklung. Hierzu werden Strategien und Maßnahmen beleuchtet, welche der Infrastrukturentwicklung dienen und überdies zu einer Optimierung der Programmräume von Behörden sowie Unternehmen führen sollen. Der Untersuchungsgegenstand ist in Mecklenburg-Vorpommern, Nord- und Osteuropa sowie Russland zu verorten. Mit dem hier vorgelegten Band 49 der „Greifswalder Geographischen Arbeiten“ geben wir einen Einblick in unsere aktuellen Projekte am Lehrstuhl für Regionale Geographie. Mit der Auswahl an Themen ist gleichzeitig das Ziel verbunden, die inhaltliche Ausgestaltung des Lehrstuhls einem breiteren Publikum darzulegen und zusätzlich den wissenschaftlichen Diskurs zu bereichern. Dabei werden in den Beiträgen auch Sachverhalte und Kausalitäten gezeigt, die oftmals eine ungewohnte Sichtweise ermöglichen und somit eingeschliffene Denkweisen in Frage stellen.ISBN: 978-3-86006-414-6researc

Validation of the Endoscopic Part of the Spigelman Classification for Evaluating Duodenal Adenomatosis in Familial Adenomatous Polyposis:A Prospective Study of Interrater and Intrarater Reliability

INTRODUCTION: In patients with familial adenomatous polyposis, the Spigelman classification is recommended for staging and risk stratification of duodenal adenomatosis. Although the classification has been used for decades, it has never been formally validated. METHODS: We included consecutive FAP patients undergoing upper gastrointestinal endoscopic surveillance and evaluated the inter- and intrarater reliability of the Spigelman classification. RESULTS: The interrater reliability of the endoscopic parameters and the Spigelman classification was good and excellent, respectively. The intrarater reliability of the endoscopic parameters and the Spigelman classification was moderate and good, respectively. DISCUSSION: The results support continued use of the Spigelman classification as the primary end point for future studies and as key endoscopic performance measure

Thyroid autoimmunity in Greenlandic Inuit

OBJECTIVE: This study aimed to provide the first data on the occurrence of thyroid autoimmunity among Inuit in Greenland, a distinct ethnic group who is not iodine deficient. DESIGN: This study is a population-based cross-sectional study. METHODS: Data were collected in Nuuk in West Greenland and in Ammassalik district in East Greenland. Information on lifestyle, diet and diseases was obtained using questionnaires. Thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb) and thyroid-stimulating hormone (TSH) were measured in serum. Iodine and creatinine were measured in spot urine samples. RESULTS: The participation rate was 95% with 434 Inuit participants; 75% were smokers. Iodine excretion was 169 µg/24 h in urban West Greenland, 224 µg/24 h in the main town and 228 µg/24 h in settlements in rural East Greenland. TPOAb, TgAb or either of these was measured in the serum from 3.7, 5.9 and 8.3% of participants, respectively. TPOAb or TgAb was found in 9.3% of Inuit women and 7.5% of men and more frequently, in East Greenland Inuit with the higher iodine excretion (P  = 0.02). There was some evidence suggesting that thyroid autoimmunity was more frequent among non-smokers (12.5%) compared to smokers (7.0%). Harbouring a thyroid autoantibody was most frequent in participants with TSH above 3.6 mIU/L (P  < 0.001). CONCLUSION: Thyroid autoantibodies were rare among Greenland Inuit. While iodine nutrition was associated with autoimmunity similarly to other ethnic groups, the influence of sex and smoking was limited. This could suggest genetic component in Inuit, but the impact of cold, selenium and persistent organic pollutants needs to be elucidated

The Suction Panel - xHLFC and Structural Solution for Energy Efficient Aviation

Future energy-efficient aircraft requires a further drastic reduction in drag and weight. Is it contradictory to improve both at the same time? Is it possible to design a highly efficient HLFC system to be weight-neutral? The present study, performed within the Cluster of Excellence SE2A – Sustainable and Energy-Efficient Aviation, summarizes aspects and considerations of the contributing disciplines to derive a solution for a suction-based system on short-range aircraft wings with maximum efficiency, i.e. hybrid laminar flow control application capabilities at minimum weight penalty. Several new features – novel wing design and simulation tools, the potentials of thin plies for weigth saving and the 3D-printing possibilities for ventable core structures – are investigated to achive this goal

Periprosthetic Joint Infection After Total Knee Arthroplasty With or Without Antibiotic Bone Cement.

IMPORTANCE Despite increased use of antibiotic-loaded bone cement (ALBC) in joint arthroplasty over recent decades, current evidence for prophylactic use of ALBC to reduce risk of periprosthetic joint infection (PJI) is insufficient. OBJECTIVE To compare the rate of revision attributed to PJI following primary total knee arthroplasty (TKA) using ALBC vs plain bone cement. DESIGN, SETTING, AND PARTICIPANTS This international cohort study used data from 14 national or regional joint arthroplasty registries in Australia, Denmark, Finland, Germany, Italy, New Zealand, Norway, Romania, Sweden, Switzerland, the Netherlands, the UK, and the US. The study included primary TKAs for osteoarthritis registered from January 1, 2010, to December 31, 2020, and followed-up until December 31, 2021. Data analysis was performed from April to September 2023. EXPOSURE Primary TKA with ALBC vs plain bone cement. MAIN OUTCOMES AND MEASURES The primary outcome was risk of 1-year revision for PJI. Using a distributed data network analysis method, data were harmonized, and a cumulative revision rate was calculated (1 - Kaplan-Meier), and Cox regression analyses were performed within the 10 registries using both cement types. A meta-analysis was then performed to combine all aggregated data and evaluate the risk of 1-year revision for PJI and all causes. RESULTS Among 2 168 924 TKAs included, 93% were performed with ALBC. Most TKAs were performed in female patients (59.5%) and patients aged 65 to 74 years (39.9%), fully cemented (92.2%), and in the 2015 to 2020 period (62.5%). All participating registries reported a cumulative 1-year revision rate for PJI of less than 1% following primary TKA with ALBC (range, 0.21%-0.80%) and with plain bone cement (range, 0.23%-0.70%). The meta-analyses based on adjusted Cox regression for 1 917 190 TKAs showed no statistically significant difference at 1 year in risk of revision for PJI (hazard rate ratio, 1.16; 95% CI, 0.89-1.52) or for all causes (hazard rate ratio, 1.12; 95% CI, 0.89-1.40) among TKAs performed with ALBC vs plain bone cement. CONCLUSIONS AND RELEVANCE In this study, the risk of revision for PJI was similar between ALBC and plain bone cement following primary TKA. Any additional costs of ALBC and its relative value in reducing revision risk should be considered in the context of the overall health care delivery system

The use of antibiotic-loaded bone cement and systemic antibiotic prophylactic use in 2,971,357 primary total knee arthroplasties from 2010 to 2020: an international register-based observational study among countries in Africa, Europe, North America, and Oceania.

BACKGROUND AND PURPOSE Antibiotic-loaded bone cement (ALBC) and systemic antibiotic prophylaxis (SAP) have been used to reduce periprosthetic joint infection (PJI) rates. We investigated the use of ALBC and SAP in primary total knee arthroplasty (TKA). PATIENTS AND METHODS This observational study is based on 2,971,357 primary TKAs reported in 2010-2020 to national/regional joint arthroplasty registries in Australia, Denmark, Finland, Germany, Italy, the Netherlands, New Zealand, Norway, Romania, South Africa, Sweden, Switzerland, the UK, and the USA. Aggregate-level data on trends and types of bone cement, antibiotic agents, and doses and duration of SAP used was extracted from participating registries. RESULTS ALBC was used in 77% of the TKAs with variation ranging from 100% in Norway to 31% in the USA. Palacos R+G was the most common (62%) ALBC type used. The primary antibiotic used in ALBC was gentamicin (94%). Use of ALBC in combination with SAP was common practice (77%). Cefazolin was the most common (32%) SAP agent. The doses and duration of SAP used varied from one single preoperative dosage as standard practice in Bolzano, Italy (98%) to 1-day 4 doses in Norway (83% of the 40,709 TKAs reported to the Norwegian arthroplasty register). CONCLUSION The proportion of ALBC usage in primary TKA varies internationally, with gentamicin being the most common antibiotic. ALBC in combination with SAP was common practice, with cefazolin the most common SAP agent. The type of ALBC and type, dose, and duration of SAP varied among participating countries