Non-Zhang-Rice singlet character of the first ionization state of T-CuO

We argue that tetragonal CuO (T-CuO) has the potential to finally settle long-standing modelling issues for cuprate physics. We compare the one-hole quasiparticle (qp) dispersion of T-CuO to that of cuprates, in the framework of the strongly-correlated ($U_{dd}\rightarrow \infty$) limit of the three-band Emery model. Unlike in CuO$_2$, magnetic frustration in T-CuO breaks the $C_4$ rotational symmetry and leads to strong deviations from the Zhang-Rice singlet picture in parts of the reciprocal space. Our results are consistent with angle-resolved photoemission spectroscopy data but in sharp contradiction to those of a one-band model previously suggested for them. These differences identify T-CuO as an ideal material to test a variety of scenarios proposed for explaining cuprate phenomenology.Comment: 4 pages, 2 figure

A Deep Context Grammatical Model For Authorship Attribution

We define a variable-order Markov model, representing a Probabilistic Context Free Grammar, built from the sentence-level, delexicalized parse of source texts generated by a standard lexicalized parser, which we apply to the authorship attribution task. First, we motivate this model in the context of previous research on syntactic features in the area, outlining some of the general strengths and limitations of the overall approach. Next we describe the procedure for building syntactic models for each author based on training cases. We then outline the attribution process – assigning authorship to the model which yields the highest probability for the given test case. We demonstrate the efficacy for authorship attribution over different Markov orders and compare it against syntactic features trained by a linear kernel SVM. We find that the model performs somewhat less successfully than the SVM over similar features. In the conclusion, we outline how we plan to employ the model for syntactic evaluation of literary texts

Strukturgrößen zur Schwingfestigkeitsbewertung von Schweißverbindungen

Zur Schwingfestigkeitsbewertung wiederholt belasteter Schweißverbindungen können Anwender aus der industriellen Praxis auf Nachweisverfahren wie dem Nenn-, Struktur- und Kerbspannungskonzept zurückgreifen, die unter anderem in den Empfehlungen des International Institute of Welding (IIW) oder der Richtlinie des Forschungskuratoriums Maschinenbau e.V. (FKM) beschrieben sind. Zyklisch hochbeanspruchte geschweißte Bauteile mit Versagen im Kurzzeitfestigkeitsbereich können damit jedoch nicht bewertet werden, da dieser Lebensdauerbereich außerhalb der Anwendungsgrenzen der Regelwerke liegt. Eine auf Schweißverbindungen erweiterte Variante des Örtlichen Konzepts nach der FKM-Richtlinie Nichtlinear schließt diese Lücke. Allerdings erfordert dieses Verfahren ein aufwendig zu erstellendes detailliertes und fein vernetztes Finite-Elemente-Modell der untersuchten Struktur. Alternativ zu dieser Methode wird daher ein auf Strukturspannungen und -dehnungen basierendes "Strukturgrößenkonzept" vorgestellt, dem ein grob vernetztes Modell genügt. Durch die grobe Vernetzung können bei verhältnismäßig kurzen Rechenzeiten elastisch-plastisches Werkstoffverhalten und geometrische Nichtlinearität in der numerischen Rechnung berücksichtigt werden. Dies stellt auch bei hohen Beanspruchungen und größeren Deformationen eine realitätsnahe Simulation des Strukturverhaltens sicher. Zugunsten einer möglichst hohen Akzeptanz in der Praxis wird das Strukturgrößenkonzept an das Strukturspannungskonzept gemäß der FKM-Richtlinie angelehnt. Auf diese Weise lassen sich darin enthaltene praxiserprobte Einflussfaktoren und Handlungsanweisungen unmittelbar oder mit geringfügigen Anpassungen übertragen. Auch die zur Bewertung zyklischer Beanspruchungen erforderlichen Wöhlerlinien werden aus der Richtlinie abgeleitet. Die anschließende Validierung des Nachweisverfahrens und der Vergleich mit der zuvor erwähnten Variante des Örtlichen Konzepts erfolgt auf Basis selbst durchgeführter und in der Literatur beschriebener Ermüdungsversuche. Insgesamt werden hierfür 213 Versuche an Stumpf- und T-Stößen mit Blechdicken von 8 bis 40 mm aus ferritischen sowie austenitischen Stählen mit Fließgrenzen zwischen ca. 200 und 1000 MPa nachgerechnet. Anhand der Gegenüberstellung der rechnerischen und experimentell ermittelten Lebensdauern zeigt sich, dass alle untersuchten Schweißverbindungen im betrachteten Lebensdauerbereich von 10^0 bis 10^6 Lastwechseln mit dem Strukturgrößenkonzept sicher bewertet werden. Dabei sind im Vergleich zum Örtlichen Konzept insbesondere im Kurzzeitfestigkeitsbereich deutlich treffendere Lebensdauerabschätzungen bei zugleich wesentlich geringeren Streuungen zu beobachten

Thermophysical Properties of Air-PA66-Copper Plasmas for Low-Voltage Direct Current Switches

This paper presents the thermophysical properties of an air-PA66-copper mixture in thermal plasma. Equations based on mass action law, conservation of neutrality and perfect gas law are used to calculate particle number densities. Thermodynamic properties and transport coefficients were obtained from equilibrium compositions and computed using the Chapman-Enskog method. Radiative properties are described in terms of the total absorption coefficient and the net emission coefficien

Validation Approach for a Spatially and Temporally Resolved Fault Arc Model

This paper presents a method to validate arc models for fault arc applications by examining the effect of changed boundary conditions on arc parameters, e.g. voltage and pressure build-up. The study shows the impact of ignition location on arc voltage and pressure build-up and prediction accuracy of the presented model. The results indicate insufficient accuracy in predicting arc voltage during dynamic phases, while the pressure build-up prediction aligns well with the experimental results

The nature of the quasiparticles in two benchmark transition metal oxides:a spectroscopic study of anatase TiO₂ and tetragonal CuO

Transition metal oxides (TMOs) are emerging strong players in many domains, ranging from superconductivity, to microelectronics to spintronics to light harvesting for photovoltaics. Beyond their non-toxicity, low corrosiveness and low price, they exhibit a whole range of exciting electronic properties, which could be realistically exploited in new devices. Typically, TMOs are governed by strong correlation of its 3d electrons, often dressed by lattice or magnetic excitations and thus leading to complex electronic behavior. This work is focused on the electronic structure of two benchmark TMOs - anatase TiO₂ and tetragonal CuO - spectroscopically investigated by angle resolved photoemission (ARPES) and resonant inelastic x-ray scattering (RIXS). Anatase TiO₂, a 3d0 system, has been proposed for many applications from transparent conducting layers to photovoltaic- and photocatalytic- devices, as well as memristors. For the performance of these devices, the charge carrier lifetime and their control is of primordial importance. By means of ARPES, the possibility to achieve a fine control of the mobile charge carrier concentration through x-ray beam doping is demonstrated. We show that the conduction electrons in anatase, and their nature, is determined by significant electron-phonon-coupling and by the number of oxygen defects. At low defect densities, charge carriers behave as a gas of weakly interacting large polarons. At larger densities, the polarons spatially overlap and dissolve into a weakly correlated Fermi liquid. The role of the electron-lattice coupling is further resolved by RIXS. The spectral signatures of phonons hint towards isotropic electron-phonon-coupling in anatase. Phonon frequency and electron-phonon coupling both show low doping sensitivity. The cupric oxide CuO, a 3d9 system, exhibits an insulating ground state with a correlation-induced charge-transfer gap and antiferromagnetism. It is, in principle, the most straightforward parent compound of the doped cuprates, and therefore has been theoretically studied as a model material for high temperature superconductivity. Bulk CuO crystallizes in a low-symmetry monoclinic form, in contrast to the rocksalt structure typical of late 3d transition metal monoxides. In this work, CuO was synthesized by epitaxial growth on SrTiO3 substrates in a higher symmetry tetragonal structure (T-CuO) much closer to the one observed in most cuprates. ARPES identifies its first ionization state as a Zhang Rice Singlet (ZRS). This is the first observation of the ZRS on a quasi 2D edge-sharing cuprate system with possible implications for magnetism and potential superconductivity in the doped phase

Ectomycorrhiza succession patterns in Pinus sylvestris forests after stand-replacing fire in the Central Alps

Fires shape fundamental properties of many forest ecosystems and climate change will increase their relevance in regions where fires occur infrequently today. In ecosystems that are not adapted to fire, post-fire tree recruitment is often sparse, a fact that might be attributed to a transient lack of mycorrhizae. Ectomycorrhizal (EcM) fungi play an important role for recruitment by enhancing nutrient and water uptake of their hosts. The questions arise whether and for how long the EcM community is transformed by fire. We investigated the resistance and resilience of EcM fungal communities on a chronosequence of 12 Pinus sylvestris stands in Valais (Switzerland) and Val d'Aosta (Italy) affected by fire between 1990 and 2006. Soil samples from burnt and non-burnt forests were analyzed with respect to EcM fungi by means of a bioassay. The number of EcM species was significantly lower in samples from recently (2-5years) burnt sites than non-burnt forest, and increased with time since fire reaching levels of adjacent forests after 15-18years. Community composition changed after fire but did not converge to that of non-burnt sites over the 18year period. Only Rhizopogon roseolus and Cenococcum geophilum were abundant in both burnt sites and adjacent forest. Our data indicate fire resistance of some EcM fungal species as well as rapid resilience in terms of species number, but not in species composition. As long as the function of different EcM species for seedling establishment is unknown, the consequences of long-term shifts in EcM community composition for tree recruitment remain unclea