335598 research outputs found
Sort by
Stochastic modelling of symmetric positive definite material tensors
No full textSpatial symmetries and invariances play an important role in the behaviour of materials and should be respected in the description and modelling of material properties. The focus here is the class of physically symmetric and positive definite tensors, as they appear often in the description of materials, and one wants to be able to prescribe certain classes of spatial symmetries and invariances for each member of the whole ensemble, while at the same time demanding that the mean or expected value of the ensemble be subject to a possibly ‘higher’ spatial invariance class. We formulate a modelling framework which not only respects these two requirements—positive definiteness and invariance—but also allows a fine control over orientation on one hand, and strength / size on the other. As the set of positive definite tensors is not a linear space, but rather an open convex cone in the linear space of physically symmetric tensors, we consider it advantageous to widen the notion of mean to the so-called Fréchet mean on a metric space, which is based on distance measures or metrics between positive definite tensors other than the usual Euclidean one. It is shown how the random ensemble can be modelled and generated, independently in its scaling and orientational or directional aspects, with a Lie algebra representation via a memoryless transformation. The parameters which describe the elements in this Lie algebra are then to be considered as random fields on the domain of interest. As an example, a 2D and a 3D model of steady-state heat conduction in a human proximal femur, a bone with high material anisotropy, is modelled with a random thermal conductivity tensor, and the numerical results show the distinct impact of incorporating into the constitutive model different material uncertainties—scaling, orientation, and prescribed material symmetry—on the desired quantities of interest
Xenotransplantation – ein möglicher Beitrag zur Lösung des Organmangels
No full textDie Xenotransplantation – die Übertragung lebender Zellen, Gewebe oder Organe zwischen unterschiedlichen Spezies – wird seit mehreren Jahrzehnten als potenzieller Beitrag zur Lösung für den anhaltenden Mangel an Spenderorganen diskutiert.
Nach Experimenten mit Organen von nichthumanen Primaten/Affen in den 1960er und 1980er Jahren gelten heute Schweine mit genetischen Veränderungen, um Abstoßungsreaktionen und die Übertragung bestimmter Viren zu verhindern, als aussichtsreichste Spendertiere. Dieser Ansatz hat durch die Entwicklung von Genome-Editing-Technologien neue Dynamik gewonnen. Ab 2021 wurden in den USA erstmals genetisch veränderte Schweineorgane, die kurzfristig funktionstüchtig waren, in hirntote Patient/innen sowie in einzelne Schwerkranke transplantiert. Anfang 2025 wurden erstmalig klinische Studien von der US-amerikanischen Arzneimittelbehörde Food and Drug Administration (FDA) genehmigt.
Die medizinischen Herausforderungen betreffen vor allem: Abstoßung, Langzeitfunktionalität und Infektionsrisiken. Durch Genom-Editierungs-Techniken möglich gewordene gezielte Modifikationen im Erbgut von Spenderschweinen und verbesserte Immunsuppression bei Patient/innen führten zu vielversprechenden Fortschritten. Noch fehlt es aber an belastbaren Daten zur Langzeitverträglichkeit und -funktionalität. Eine Prämisse für klinische Studien und eine zukünftig breitere Anwendung sind spezifisch-pathogenfreie (SPF) Zuchtanlagen, die in Euro¬pa bislang nicht vorhanden sind.
Gesellschaftlich und ethisch wird das Thema kontrovers diskutiert: Neben Tierschutz- und Akzeptanzfragen in verschiedenen Religionen betreffen Debatten auch die mögliche Verteilungsgerechtigkeit, den Umgang mit noch unausgereiften Technologien am Menschen sowie Fragen der Nachsorge und Datensicherheit
A Gd-Dimer Benchmark Study: Is DFT an accurate Method for the Prediction of Gadolinium Exchange Coupling Constants?
No full textHow Realistic Was the Threat of “Hitler’s Atomic Bomb”?
No full textUsing factual information on background knowledge, costs, personnel numbers, resources, and facilities from the Manhattan Project, we examine the feasibility of the development of nuclear weapons in Germany in World War II. We conclude that, while for various reasons, a uranium bomb would have been technically and economically out of reach in Germany, a few plutonium bombs might have been possible had a coordinated aggressive project been initiated no later than about mid-1940. However, the German scientists involved never established an understanding of the functioning of an atomic bomb as contained in the Frisch–Peierls memorandum and were never asked to provide such a basis on which a decision on an atomic bomb program could be based. This means that a German atomic bomb program did not fail as is often assumed; rather, it was never started. The German uranium project was never more than a scientific mission to study the possibilities offered by the newly discovered source of nuclear power
@kit-data-manager/react-search-component v0.4.2
No full textAll-in-one component for rendering an elastic search UI for searching anything. Includes an interactive graph of related records and unique identifier resolving
NovaCrate v1.8.0
No full textWebbasierter interaktiver Editor für die Erstellung, Bearbeitung, Validierung und Visualisierung von Research Object Crates
Development of a soda-lime glass feedstock for injection molding
No full textInjection molding has been used for many years in the fabrication of thermoplastic parts with different complexities. With metal and ceramic injection molding, it is possible to realize at the end of the related process chain sintered metal and ceramic parts. Parts made from glass are rather seldom realized applying powder technology methods. This work describes the production of devices made from a commercial soda-lime glass applying the process chain of powder injection molding, covering the individual process steps like compounding, shaping, debinding, and sintering. In the first step, a binder consisting of polyethylene glycol (PEG) with different average molecular masses (4000, 8000, and 20,000 g/mol), polyvinyl butyral (PVB), and stearic acid (SA) were used for compounding new feedstocks with a solid load of 55 Vol% and 60 Vol%. As filler, a soda-lime glass with an average particle size of 6.1 μm, an almost symmetrical particle size distribution, a specific surface area of 0.78 m2/g, and a spherical morphology was applied. The measured equilibrium torque during compounding was low, with values between 2.5 and 5.5 Nm depending on the solid load and average molecular mass of the investigated PEG. All feedstock possessed a pseudoplastic flow behavior in the shear rate range between 10 and 3500 1/s. Small disk-shaped parts, as well as large cuboids and plates, were injection molded to a good quality. These green bodies were pre-debinded in water to remove the PEG, subsequently followed by thermal debinding to eliminate the remaining organic moieties. The concluding sintering in the temperature range between 660 and 680 °C delivered glass parts with huge density values close to 100% of the theoretical value, as measured by the Archimedes method. The principal feasibility of glass injection molding with a suitable feedstock system could be demonstrated successfully
mnt: Affine Invariant Tests of Multivariate Normality
No full textVarious affine invariant multivariate normality tests are provided. It is designed to accompany the survey article Ebner, B. and Henze, N. (2020) titled "Tests for multivariate normality – a critical review with emphasis on weighted L^2-statistics". We implement new and time honoured L^2-type tests of multivariate normality, such as the Baringhaus-Henze-Epps-Pulley (BHEP) test, the Henze-Zirkler test, the test of Henze-Jiménes-Gamero, the test of Henze-Jiménes-Gamero-Meintanis, the test of Henze-Visage, the Dörr-Ebner-Henze test based on harmonic oscillator and the Dörr-Ebner-Henze test based on a double estimation in a PDE. Secondly, we include the measures of multivariate skewness and kurtosis by Mardia, Koziol, Malkovich and Afifi and Móri, Rohatgi and Székely, as well as the associated tests. Thirdly, we include the tests of multivariate normality by Cox and Small, the \u27energy\u27 test of Székely and Rizzo, the tests based on spherical harmonics by Manzotti and Quiroz and the test of Pudelko. All the functions and tests need the data to be a n x d matrix where n is the samplesize (number of rows) and d is the dimension (number of columns)
Measuring the muon content of inclined air showers using AERA and the water-Cherenkov detectors of the Pierre Auger Observatory
No full textWe present a novel approach for assessing the muon content of air showers with large zenith angles on a combined analysis of their radio emission and particle footprint. We use the radiation energy reconstructed by the Auger engineering radio array (AERA) as an energy estimator and determine the muon number independently with the water-Cherenkov detector array of the Pierre Auger Observatory, deployed on a 1500 m grid. We focus our analysis on air showers with primary energy above 4 EeV to ensure full detection efficiency. Over approximately ten years of accumulated data, we identify a set of 40 high-quality events that are used in the analysis. The estimated muon contents in data are compatible with those for iron primaries as predicted by current-generation hadronic interaction models. This result can be interpreted as a deficit of muons in simulations as a lighter mass composition has been established from measurements. This muon deficit was already observed in previous analyses of the Auger Collaboration and is confirmed using hybrid events that include radio measurements for the first time