Methods for specifying the target difference in a randomised controlled trial : the Difference ELicitation in TriAls (DELTA) systematic review

Peer reviewedPublisher PD

Micromechanical study of the warm-prestress (WPS) effect

The WPS effect has been shown to be beneficial in increasing the fracture toughness in the cleavage region after prestressing at elevated temperatures. This paper is concerned with experimental investigations to explain this phenomenon. CT specimens made of the steel 10 MnMoNi5-5 were broken at -120°C in prestressed, prestressed with subsequent stress relief annealing and nonprestressed condition, and an enhancenment of fracture toughness by a factor of 3 to 4 times after prestressing has been estimated. By X-ray measurements a characteristic compressive residual stress field could be found ahead of the crack tip after prestressing. Microfractographic observations showed clearly that the WPS-induced fracture initiation is more inhibited, and the cleavage trigger point distance can be obtained as characteristic length parameter. The study demonstrates that an apparent increase in the lower shelf toughness due to warm prestressing can be caused by the compressive residual stress field including the damage process at the crack tip

Werkstoffmechanisches Verhalten von postulierten Anrissen in druckfuehrenden Komponenten mit vorbeanspruchter Rissspitze bei Belastung infolge rascher Abkuehlvorgaenge: Schwerpunkt: Einfluss und Bedeutung der Mikrostruktur und der Mikrogeometrie Abschlussbericht

The safety analysis of nuclear reactor components requires an extensive knowledge about the reliability of the material also under the extreme loading conditions during fast cooling. The aim of this project was to evaluate the influence of the microstructure and microgeometry at a prestressed crack tip on the fracture behaviour in the lower shelf region. The fracture toughness of the pressure vessel steels 10MnMoNi5-5 and 17MoV8-4 in the lower shelf region after prestressing under quasi-static and impact loading has been estimated and correlations between microstructure, loading history and fracture mechanism in the lower shelf and in the transition region have been evaluated by metallographic, microfractographic and X-ray methods. The main factor the governing enhancement of fracture toughness after prestressing is the loss of constraint caused by compressive residual stresses in combination with the inhomogenious deformation field at the blunted crack tip. (orig.)Die Sicherheitsanalyse von Reaktordruckbehaeltern setzt umfassende Kenntnisse ueber die Zuverlaessigkeit der verwendeten Werkstoffe auch unter extremen Beanspruchungen bei raschen Abkuehlvorgaengen voraus. Das Ziel dieses Vorhabens bestand darin, die mikrostrukturellen und mikrogeometrischen Veraenderungen an der Rissspitze durch eine Vorbeanspruchung in der Zaehigkeitshochlage und ihre Auswirkungen auf das Sproedbruchverhalten von Druckbehaelterstaehlen aufzuklaeren. Dazu wurden an den Druckbehaelterstaehlen 10MnMoNi5-5 und 17MoV8-4 die Bruchzaehigkeit in der Zaehigkeitstieflage nach Vorbeanspruchung mit quasistatischer und schlagartiger Beanspruchung ermittelt und der Zusammenhang zwischen dem Werkstoffgefuege, der thermomechanischen Belastungsgeschichte und dem Bruchmechanismus in der Tieflage bzw. im Uebergangsbereich der Zaehigkeit mit Hilfe metallographischer, mikrofraktographischer und roentgenographischer Methoden untersucht. Als vorherrschender Faktor bei der durch die Vorbeanspruchung erzielten Steigerung der Bruchzaehigkeit wurde die Abnahme der Verformungsbehinderung infolge Druckeigenspannungen und der Ausbildung eines inhomogenen Verformungsfeldes an der abgestumpften Rissspitze erkannt. (orig.)Available from TIB Hannover: F98B1210+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Ermittlung bruchmechanischer Kennwerte im instrumentierten Kerbschlagbiegeversuch Abschlussbericht

The Charpy impact test is one of the most commonly used methods for evaluating the toughness of reactor pressure vessel steels. More fundamental characterization of toughness in terms of fracture mechanics concepts allows the instrumented Charpy test on precracked specimens (PICHT). The aim of this project was to consider the application of the PICHT in the upper shelf region (20...350 C) for different German and Russian reactor vessel steels (22NiMoCr3 7, 18Ch2MFA, 15Ch2NMFA-A) and the HSLA steel StE 460. Using the low-blow-technique dynamic R curves J-#DELTA#a and the crack initiation toughness values J_d_i have been determined and correlated with the parameters of the conventional Charpy test. A good correlation could be established between the energy absorbed to fracture and the produckt J_d_i'T_d"J"("#DELTA#"a"="0","5"). (orig.)Der Kerbschlagbiegeversuch ist die am haeufigsten angewandte Methode zur Charakterisierung der Zaehigkeit von RDB-Staehlen. Eine fundierte Aussage auf der Basis von Konzepten der Bruchmechanik ermoeglicht der instrumentierte Kerbschlagbiegeversuch unter Verwendung angerissener Proben (PICHT). Das Ziel dieses Forschungsvorhabens bestand darin, mit Hilfe des PICHT zaehbruchmechanische Kennwerte im Hochlagenbereich der Zaehigkeit (20...350 C) von verschiedenen deutschen und russischen RDB-Staehlen (22NiMoCr3 7, 18Ch2MFA, 15CH2NMFA-A) und einem Feinkornbaustahl StE 460 zu ermitteln. Dazu wurden mittels low-blow-Technik die dynamischen R-Kurven und die Werte der Risseinleitungszaehigkeit J_d_i bestimmt und mit den Kennwerten des konventionellen Kerbschlagbiegeversuchs korreliert. Eine gute Korrelation ergab sich zwischen der Kerbschlagarbeit und dem Produkt J_d_i'T_d"J"("#DELTA#"a"="0","5"). (orig.)SIGLEAvailable from TIB Hannover: F95B582+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Etanercept for the treatment of rheumatoid arthritis

BACKGROUND: Etanercept is a soluble tumour necrosis factor alpha-receptor DMARD for the treatment of rheumatoid arthritis (RA). OBJECTIVES: To assess the efficacy and safety of etanercept for the treatment of RA. SEARCH STRATEGY: Five electronic databases were searched from 1966 to February 2003 with no language restriction. SELECTION CRITERIA: All randomized controlled trials (minimum 6 month duration) comparing three possible combinations 1) etanercept (10 mg or 25 mg twice weekly) with methotrexate (MTX) to MTX alone 2) etanercept to MTX, or 3) etanercept to placebo were eligible. DATA COLLECTION AND ANALYSIS: Two reviewers extracted data and assessed the methodological quality of the trails. The American College of Rheumatology (ACR) core set of disease activity measures for RA clinical trials, radiographic, withdrawals and toxicity outcomes were analyzed. MAIN RESULTS: Three trials were included in this review. Two trials compared an experimental group who were started on etanercept compared to a control group; both groups had the same ongoing background therapy of nonsteroidals in both trials plus in one trial one group was on stable methotrexate. In these two trials the ACR 20, ACR 50 and ACR 70 response rates at 6 months were statistically significantly and clinically important with etanercept 25 mg subcutaneous injections (SC) twice weekly. Sixty-four percent of people receiving etanercept ache vied an ACR 20 response compared to 15% of controls and the number needed to treat (NNT) with etanercept is 2 people. Thirty-nine percent of those receiving etanercept achieved an ACR 50 response compared to 4% of taking control treatment and the NNT is three. Fifteen percent of people taking etanercept achieved an ACR 70 compared to 1% of controls with a NNT of 7 people. In the third trial of starting etanercept compared to starting methotrexate the number of participants who achieved an ACR 20, 50 or response at 6 and 12 months were not statistically significant for either etanercept dose. Etanercept treatment showed a statistically significantly and clinically important affect on joint damage as measured by the Sharp erosion score. Among participants who received etanercept 72% had no increase in their erosion score compared to 60% of participants in the methotrexate group. Withdrawal and toxicity results were acceptable. REVIEWER'S CONCLUSIONS: Etanercept 25 mg SC twice weekly was more efficacious than control treatment for ACR 20, 50 and 70 at 6 months, and over 12 months it slowed joint damage

Cartilage Oligomeric Matrix Protein Level in Rheumatic Diseases: Potential Use as a Marker for Measuring Articular Cartilage Damage and/or the Therapeutic Efficacy of Treatments

Cartilage oligomeric matrix protein (COMP) is a tissue-specific noncollagenous protein that was first detected in the serum and the synovial fluid of patients suffering from rheumatic disorders, such as rheumatoid arthritis, reactive arthritis, juvenile chronic arthritis, and osteoarthritis. In this review, the authors consider serum COMP levels in different diseases and discuss their study of patients with rheumatoid arthritis treated with anti-TNF-alpha, to evaluate whether COMP is able to predict a rapid and sustained clinical response to these drugs. They observe that patients with high COMP levels have a lower ACR 70 response independently of the state of systemic inflammation, and conclude that COMP seems to have a pathogenetic role that is independent of the mechanisms regulating inflammatory processes