Merging of the alpha and beta relaxations and aging via the Johari–Goldstein modes in rapidly quenched metallic glasses

This paper provides evidence that the physical aging of deeply and rapidly quenched metallic glasses is promoted by the Johari–Goldstein slow beta relaxation, resulting in a significant irreversible increase in the mechanical modulus on initial heating. Dynamic mechanical analysis has been used to characterize relaxation phenomena of a strong and a fragile metallic glass. In addition, we can extrapolate the temperature dependence of beta- and alpha-relaxation peaks to higher temperatures and calculate the merging temperature for both types of glasses

Mechanical spectroscopy of metallic glasses and copolymers

Das mechanische Verhalten eines Festkörpers bei verschiedenen Temperaturen und die Zeitskala auf der eine Verspannung abgebaut wird, werden bestimmt durch die Eigenschaften der vorherrschenden Relaxationsprozesse. In dieser Arbeit werden die zum Glasübergang führenden Relaxationen mittels mechanischer Spektroskopie experimentell untersucht. Als modellhaftes System harter Kugeln finden dabei ein starkes und ein fragiles metallisches Glas Anwendung. Entscheidend für den Erweichungsprozess von Polymeren ist deren Segmentbeweglichkeit. Diese kann durch "Chemical Confinements" gezielt beeinflusst werden.Speziell wird am System des metallischen Glases Pd77,5Cu6Si16,5 die Existenz einer sekundären Relaxation, der langsamen β-Relaxation, gezeigt und für das Glas Zr65Al7,5Cu27,5, bei den zu Vorgängerarbeiten niedrigeren Spektroskopiefrequenzen von einigen Hz, reproduziert. Das Vorkommen dieses Prozesses in sowohl fragilem als auch starkem metallischen Glas lässt darauf schließen, dass es sich bei der langsamen β-Relaxation um ein universelles Phänomen im Rahmen des Glasübergangs handelt. Darüber hinaus lässt sich ein direkter Zusammenhang der langsamen β-Relaxation mit dem beim ersten Aufheizen beobachtbarem Alterungsprozess zeigen.Eine selektive Beeinflussung der Segmentbeweglichkeit lässt sich im Copolymer Poly(Ethylen-co-Methacrylsäure) (EMAA) erreichen. Dieses wird bei Drücken von 1300 - 2300 bar und ca. 540 K mittels kontinuierlicher radikalischer Hochdruck-Hochtemperatur-Rührkessel-Synthese hergestellt. Bei hohem Synthesedruck zeigt das Copolymer eine statistische Verteilung der Monomereinheiten, während bei niedrigerem Synthesedruck eine nicht-zufällige Verteilung entsteht. Zwischen den über Wasserstoffbrückenbindungen wechselwirkenden Methacrylsäure-Blöcken kann das Schwingen der Ethylen-Blöcke zu einer weiteren Relaxationsmode führen. Dieser Effekt fehlt den Hochdruck-Proben, welche über eine statistische Monomerverteilung verfügen, ansonsten aber den Niederdruckproben chemisch gleichen. Eine Erhöhung des Methacrylsäure-Gehalts führt zu einer Verkürzung der Ethylen-Blöcke und verschiebt diesen "Chemical Confinement"-Effekt zu tieferen Temperaturen bzw. höheren Frequenzen

Improve hip fracture outcome in the elderly patient (iHOPE) : a study protocol for a pragmatic, multicentre randomised controlled trial to test the efficacy of spinal versus general anaesthesia

Introduction: Hip fracture surgery is associated with high in-hospital and 30-day mortality rates and serious adverse patient outcomes. Evidence from randomised controlled trials regarding effectiveness of spinal versus general anaesthesia on patient-centred outcomes after hip fracture surgery is sparse. Methods and analysis: The iHOPE study is a pragmatic national, multicentre, randomised controlled, open-label clinical trial with a two-arm parallel group design. In total, 1032 patients with hip fracture (>65 years) will be randomised in an intended 1:1 allocation ratio to receive spinal anaesthesia (n=516) or general anaesthesia (n=516). Outcome assessment will occur in a blinded manner after hospital discharge and inhospital. The primary endpoint will be assessed by telephone interview and comprises the time to the first occurring event of the binary composite outcome of all-cause mortality or new-onset serious cardiac and pulmonary complications within 30 postoperative days. In-hospital secondary endpoints, assessed via in-person interviews and medical record review, include mortality, perioperative adverse events, delirium, satisfaction, walking independently, length of hospital stay and discharge destination. Telephone interviews will be performed for long-term endpoints (all-cause mortality, independence in walking, chronic pain, ability to return home cognitive function and overall health and disability) at postoperative day 30±3, 180±45 and 365±60. Ethics and dissemination: iHOPE has been approved by the leading Ethics Committee of the Medical Faculty of the RWTH Aachen University on 14 March 2018 (EK 022/18). Approval from all other involved local Ethical Committees was subsequently requested and obtained. Study started in April 2018 with a total recruitment period of 24 months. iHOPE will be disseminated via presentations at national and international scientific meetings or conferences and publication in peer-reviewed international scientific journals. Trial registration number: DRKS00013644; Pre-result

Improve hip fracture outcome in the elderly patient (iHOPE): a study protocol for a pragmatic, multicentre randomised controlled trial to test the efficacy of spinal versus general anaesthesia

Introduction Hip fracture surgery is associated with high in-hospital and 30-day mortality rates and serious adverse patient outcomes. Evidence from randomised controlled trials regarding effectiveness of spinal versus general anaesthesia on patient-centred outcomes after hip fracture surgery is sparse. Methods and analysis The iHOPE study is a pragmatic national, multicentre, randomised controlled, open-label clinical trial with a two-arm parallel group design. In total, 1032 patients with hip fracture (>65 years) will be randomised in an intended 1: 1 allocation ratio to receive spinal anaesthesia (n=516) or general anaesthesia (n=516). Outcome assessment will occur in a blinded manner after hospital discharge and inhospital. The primary endpoint will be assessed by telephone interview and comprises the time to the first occurring event of the binary composite outcome of all-cause mortality or new-onset serious cardiac and pulmonary complications within 30 postoperative days. In-hospital secondary endpoints, assessed via in-person interviews and medical record review, include mortality, perioperative adverse events, delirium, satisfaction, walking independently, length of hospital stay and discharge destination. Telephone interviews will be performed for long-term endpoints (all-cause mortality, independence in walking, chronic pain, ability to return home cognitive function and overall health and disability) at postoperative day 30 +/- 3, 180 +/- 45 and 365 +/- 60. Ethics and dissemination iHOPE has been approved by the leading Ethics Committee of the Medical Faculty of the RWTH Aachen University on 14 March 2018 (EK 022/18). Approval from all other involved local Ethical Committees was subsequently requested and obtained. Study started in April 2018 with a total recruitment period of 24 months. iHOPE will be disseminated via presentations at national and international scientific meetings or conferences and publication in peer-reviewed international scientific journals