43 research outputs found
Struktur der Energielandschaft und Relaxation von +/- J Spinglas-Modellen
Die komplizierte Struktur der Energielandschaft wurde am Beispiel des +/- J Spinglas-Modells untersucht. Sie ist in glasartigen Systemen der SchlĂŒssel zum VerstĂ€ndnis einer verlangsamten Dynamik. Es wurde ein enger Zusammenhang zwischen der Dynamik und der Energielandschaft nachgewiesen. Die Energielandschaft wird in +/- J Spinglas Modellsystemen durch Cluster charakterisiert, die infolge ihrer KonnektivitĂ€t gröĂere Objekte (z.B. TĂ€ler) bilden. Einzelne Cluster, aber auch ganze TĂ€ler, sind miteinander durch sogenannten Sattelcluster verknĂŒpft. Die physikalischen Eigenschaften werden durch die Strukturen der VerknĂŒpfungen und durch die innere Struktur der Cluster geprĂ€gt. Zur Beschreibung der Energielandschaften wurde die genaue Kenntnis der ZustĂ€nde benutzt. Auf der Grundlage des "branch-and-bound" Verfahrens war es möglich, fĂŒr kleine Systeme alle ZustĂ€nde bis zu der dritten Anregung zu bestimmen. Danach wurden die Konfigurationen so sortiert, dass die Beziehungen zwischen ihnen, wie z.B. Nachbarschaften und Clusterzugehörigkeiten, einfach zu finden waren. Es gelang, die exakte Landschaft fĂŒr Systeme bis L=6 aufzubauen. FĂŒr gröĂere Systeme ist es zur Zeit unmöglich, alle niederenergetischen ZustĂ€nde zu finden. Eine alternative Möglichkeit, die Struktur zu beschreiben, erhĂ€lt man durch Untersuchung der Verteilung der Overlap. An der Gestalt der Verteilung erkennt man, ob die niederenergetische Struktur kompliziert oder einfach ist. Bei genaueren Untersuchungen ist es sogar möglich, die Anzahl der existierenden TĂ€ler abzuschĂ€tzen. Die Untersuchungen der Overlap bei 8555 3D Systemen (L=4) weisen darauf hin, dass bei kleineren Grundzustandsenergien die Struktur durch zwei spiegelsymmetrische TĂ€ler geprĂ€gt ist. Mit wachsender Grundzustandsenergie wird die Struktur der Systeme immer komplizierter. Eine weitere wichtige Komponente der Energielandschaft ist die innere Struktur der Sattelcluster. Ein Sattelcluster besteht aus wenigstens drei Gruppen von Konfigurationen. Zwei Gruppen enthalten Konfigurationen, die mit den Grundzustandsclustern verbunden sind, und die dritte Gruppe verbindet die beiden. Es passiert oft, dass die Konfigurationsgruppen, die verschiedene Grundzustandscluster verbinden, weit voneinander entfernt liegen. Dies wurde als ein wichtiger Aspekt erkannt, der zu einer Verlangsamung dynamischer Prozesse fĂŒhrt. Der andere Aspekt der Energielandschaft ist ihr Zusammenhang mit dem Realraumbild. Das Realraumbild ist als die Lage der Spins auf dem Gitter zu verstehen. Spins kann man zu verschiedenen SpindomĂ€nen zusammenfassen, die dann auf natĂŒrliche Weise die Struktur der Energielandschaft generieren. FĂŒr die GröĂe der einzelnen Cluster sind die freien Spins verantwortlich. Es wurde bestĂ€tigt, dass die Existenz einzelner TĂ€ler durch SpindomĂ€nen erklĂ€rt werden kann. Dabei wird durch das kollektive Umdrehen aller Spins in einer solcher DomĂ€ne ein anderer Cluster in einem anderen Tal erzeugt. Neben dem Zusammenhang von SpindomĂ€nen und Energielandschaft konnte der Einfluss von bestimmten zusammenhĂ€ngenden Strukturen freier Spins genauer aufgeklĂ€rt werden. Hier ergeben sich Ansatzpunkte fĂŒr weitergehende Untersuchungen
Magnet-sleeve-sealed mini trochoidal-gear pump prototype with polymer composite gear
The trochoidal-gear technology has been growing in groundbreaking fields. Forthcoming applications are demanding to this technology a step forward in the conceiving stage of positive displacement machines. The compendium of the qualities and the inherent characteristics of
trochoidal-gear technology, especially towards the gerotor pump, together with scale/size factor and magnetic-driven transmission has led to the idea of a magnet-sleeve-sealed variable flow mini trochoidal-gear pump. From its original concept, to the last phase of the design development, the proof of concept, this new product will intend to overcome problems such as noise, vibration, maintenance, materials, and dimensions. The paper aims to show the technological path followed from the concept, design, and model, to the manufacture of the first prototype, where the theoretical and numerical approaches are not always directly reflected in the prototype performance results.
Early in the design process, from a standard-commercial sintered metal mini trochoidal-gear unit, fundamental characteristics and dimensional limitations have been evaluated becoming the strategic parameters that led to its configuration. The main technical challenge to confront is being sealed with non-exterior driveshaft, ensuring that the whole interior is filled and wetted with working fluid and helping the hydrodynamic film formation, the pumping effect, and the heat dissipation. Subsequently, the mini pump architecture, embodiment, methodology, materials, and manufacture are presented. The trend of applications of polymer composite materials and their benefits wanted to be examined with this new mini pump prototype, and a pure polyoxymethylene mini trochoidal-gear set has been designed and manufactured. Finally, both the sintered and the polymer trochoidal-gear units have been experimentally tested in an in-house full-instrumented mini test bench. Although the main goal of the presented work is the development of a new mini trochoidal-gear pump prototype rather than a numerical study, the results have been compared with numerical simulation. Subsequently, the prototype of the mini trochoidal-gear pump is a feasible proof of concept supported by functional indexes and the experimental results.Peer ReviewedPostprint (published version
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Provenance and paleoenvironmental context of the Late Pleistocene thin aeolian silt mantles in southwestern Poland â A widespread parent material for soils
Thin loess deposits are widespread soil parent materials and important archives for paleoenvironmental reconstruction. The origin of loess in SW Poland is attributed to the Great Odra Valley (GOV), following the general concept that large rivers play a major role in regional silt supply. Yet, the precise provenance (glacier sources and/or local rocks) of silts, possibly deflated from dry GOV braided riverbeds, is not clear. Our study of thin and thick loess mantles in SW Poland for the first time indicates the provenance of thin loess based on mineralogical (MLA-SEM) and isotopic analyses (143Nd/144Nd, 87Sr/86Sr). Luminescence ages of five localities point to thin loess mantle formation during and shortly (23.0 to 17.7 ka yr) after the Last Glacial Maximum (LGM). Our isotopic data indicate that thin loess deposits in SW Poland are the mixtures of two main components â local Sudetic and Scandinavian, the latter delivered by the Fennoscandian ice sheet (FIS). Also, detailed analyses of heavy minerals show that a single mineral (e.g., hornblende) may come from both Sudetic and Scandinavian sources. This research highlights the role of the (Pleistocene) GOV in collecting and homogenizing materials, while supplying the region with fine particles to be deflated by paleowinds from open surfaces. Anomalies in mineralogy and isotopic composition are connected with influence of Sudetic mountain rivers and locally blowing silt material by katabatic winds. Regional grain size differentiation of thin loess mantles explains transport distance and altitude. © 2021 The Author
Clinical influences on antibiotic prescribing decisions for lower respiratory tract infection: a nine country qualitative study of variation in care
Objectives: there is variation in antibiotic prescribing for lower respiratory tract infections (LRTI) in primary care that does not benefit patients. This study aims to investigate clinicians' accounts of clinical influences on antibiotic prescribing decisions for LRTI to better understand variation and identify opportunities for improvement.Design: multi country qualitative interview study. Semi-structured interviews using open-ended questions and a patient scenario. Data were subjected to five-stage analytic framework approach (familiarisation, developing a thematic framework from the interview questions and emerging themes, indexing, charting and mapping to search for interpretations), with interviewers commenting on preliminary reports.Setting: primary care.Participants: 80 primary care clinicians randomly selected from primary care research networks based in nine European cities.Results: clinicians reported four main individual clinical factors that guided their antibiotic prescribing decision: auscultation, fever, discoloured sputum and breathlessness. These were considered alongside a general impression of the patient derived from building a picture of the illness course, using intuition and familiarity with the patient. Comorbidity and older age were considered main risk factors for poor outcomes. Clinical factors were similar across networks, apart from C reactive protein near patient testing in TromsĂž. Clinicians developed ways to handle diagnostic and management uncertainty through their own clinical routines.Conclusions: clinicians emphasised the importance of auscultation, fever, discoloured sputum and breathlessness, general impression of the illness course, familiarity with the patient, comorbidity, and age in informing their antibiotic prescribing decisions for LRTI. As some of these factors may be overemphasised given the evolving evidence base, greater standardisation of assessment and integration of findings may help reduce unhelpful variation in management. Non-clinical influences will also need to be addresse
Ultra-Rare Mutation in Long-Range Enhancer Predisposes to Thyroid Carcinoma with High Penetrance
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