Reachability Subspace Exploration Using Continuation Methods

Reachability manifold computation suffers from the curse of dimensionality and for large state spaces is computationally intractable. This paper examines the use of continuation methods to address this issue by formulating the reachability sub-space manifold calculation into a number of initial valued problems. As a result of computing the reachability manifold for a subspace of interest, an exponential improvement in computational cost occurs. This concept is applied to a position subspace reachability problem of a spacecraft in a Keplerian orbit under maximum thrust constraints. Future work includes a comparison of the proposed method with computing reachability manifolds using viscosity solutions of the Hamilton Jacobi Bellman partial differential equation

Spatial Coherence Properties of One Dimensional Exciton-Polariton Condensates

In this work, we combine a systematic experimental investigation of the power- and temperature-dependent evolution of the spatial coherence function, g(1)(r), in a one dimensional exciton-polariton channel with a modern microscopic numerical theory based on a stochastic master equation approach. The spatial coherence function g(1)(r) is extracted via high-precision Michelson interferometry, which allows us to demonstrate that in the regime of nonresonant excitation, the dependence g(1)(r) reaches a saturation value with a plateau, which is determined by the intensity of the pump and effective temperature of the crystal lattice. The theory, which was extended to allow for treating incoherent excitation in a stochastic frame, matches the experimental data with good qualitative and quantitative agreement. This allows us to verify the prediction that the decay of the off-diagonal long-range order can be almost fully suppressed in one dimensional condensate systems

Resolution of the Two Aluminum Sites in Ettringite by ²⁷Al MAS and MQMAS NMR at Very High Magnetic Field (22.3 T)

Ettringite (Ca₆[Al­(OH)₆]₂(SO₄)₃·26H₂O) is the first hydration product formed during Portland cement hydration. ²⁷Al MAS NMR has been used in a wide number of studies to detect and quantify ettringite in hydrated cement blends by the observation of a single, narrow resonance at 13–14 ppm. This work reports the first observation of resonances from two distinct Al sites in octahedral coordination for ettringite, employing ²⁷Al MAS and MQMAS NMR at an ultrahigh magnetic field (22.3 T). Thereby, the ²⁷Al NMR spectra are in agreement with the most accepted trigonal model for the ettringite structure. ²⁷Al quadrupole coupling parameters and isotropic chemical shifts for the two Al sites are determined from simulations and least-squares optimization of slow-speed ²⁷Al MAS NMR spectra of the satellite transitions. These data reveal that the local environments for the two octahedral Al sites are very similar, in accord with the most recent XRD refinements of the ettringite structure. Finally, the significant improvement in spectral resolution by the application of an ultrahigh magnetic field is illustrated by the detection of the two Al sites from ettringite in a hydrated cement mimicking the composition of a calcium sulfoaluminate cement

Sol\u2013gel processes at the droplet interface: hydrous zirconia and hafnia nanocapsules by interfacial inorganic polycondensation

We report a simple method to prepare nanocapsules of hydrous zirconia and hafnia by interfacial precipitation in water-in-oil miniemulsions. We show that the sol\u2013gel precipitation of transition metal hydroxides, exemplified for the cases of zirconium and hafnium, can be driven to the droplet interface by addition of an organic base. The prompt addition of triethylamine generates hydroxide ions at the interface, which initiate a polycondensation of the metal hydroxo species. Electron and X-ray diffractions indicate that the resulting materials are amorphous, but can be transformed to monoclinic ZrO2 or HfO2 upon thermolytic treatment. Mixed oxides of Hf and Zr with different compositions (HfxZr1 12xO2) can also be formed by using the desired ratios of precursors. Furthermore, the ability of the hollow particles to encapsulate efficiently hydrophilic materials without leakage has been proven with the example of a water-soluble dye (fluorescein isothiocyanate)

High Zn/Al ratios enhance dehydrogenation vs hydrogen transfer reactions of Zn-ZSM-5 catalytic systems in methanol conversion to aromatics

Two series of Zn-ZSM-5 catalysts were prepared by ion exchanging two commercial zeolites with different Si/Al ratios (40 and 15) with increasing Zn loadings. The nature of the Zn sites in the zeolite was studied by spectroscopy using laboratory and synchrotron techniques. All the evidences suggest that catalytic activity is associated with [Zn(H2O)n(OH)]+ species located in the exchange positions of the materials with little or no contribution of ZnO or metallic Zn. The effect of Zn/Al ratio on their catalytic performance in methanol conversion to aromatics has been investigated. In all cases, higher Zn content causes an increase in the yield of aromatics while keeping the production of alkanes low. For similar Zn contents, high densities of Al sites favour the hydrogen transfer reactions and alkane formation whereas in samples with low Al contents, and thus higher Zn/Al ratio, the dehydrogenation reactions in which molecular hydrogen is released are favoured

The anti-apoptotic Coxiella burnetii effector protein AnkG is a strain specific virulence factor

The ability to inhibit host cell apoptosis is important for the intracellular replication of the obligate intracellular pathogen Coxiella burnetii, as it allows the completion of the lengthy bacterial replication cycle. Effector proteins injected into the host cell by the C. burnetii type IVB secretion system (T4BSS) are required for the inhibition of host cell apoptosis. AnkG is one of these anti-apoptotic effector proteins. The inhibitory effect of AnkG requires its nuclear localization, which depends on p32-dependent intracellular trafficking and importin-α1-mediated nuclear entry of AnkG. Here, we compared the sequences of ankG from 37 C. burnetii isolates and classified them in three groups based on the predicted protein size. The comparison of the three different groups allowed us to identify the first 28 amino acids as essential and sufficient for the anti-apoptotic activity of AnkG. Importantly, only the full-length protein from the first group is a bona fide effector protein injected into host cells during infection and has anti-apoptotic activity. Finally, using the Galleria mellonella infection model, we observed that AnkG from the first group has the ability to attenuate pathology during in vivo infection, as it allows survival of the larvae despite bacterial replication.This work was supported by the Deutsche Forschungsgemeinschaft (DFG) through the grant LU1357/5-1 to AL. We thank Prof. Robert Heinzen, Dr. Alyssa Ingmundson, Prof. James Samuel and Prof. Thomas Stamminger for providing plasmids, and the Lührmann lab for discussion. Open Access funding provided by Projekt DEAL.info:eu-repo/semantics/publishedVersio

Inequality in Collective Action Problems

Rainer-Olaf Schultze was a second supervisor for my dissertation and he took this role very seriously. He showed me what to do and how, and more importantly: what not to do. I was very grateful for his advice, if not always in the very first moment, than surely later on. Looking back, I am still grateful because his level of engagement was not at all a matter of course. Although my ways led me elsewhere soon, geographically and academically, Rainer-Olaf further supported me in the early phases of my career and we never lost contact. There was one strong bond between us, namely our disagreement about the value of rational choice analysis. In what follows I do not strive to persuade Rainer-Olaf of the usefulness of this kind of reasoning; instead I want to demonstrate what I have learned at least: the rational actor is a fiction