Decoherence and relaxation of topological states in extended quantum Ising models

We study the decoherence and the relaxation dynamics of topological states in an extended class of quantum Ising chains which can present a manyfold ground state subspace. The leading interaction of the spins with the environment is assumed to be the local fluctuations of the transverse magnetic field. By deriving the Lindblad equation using the many-body states, we investigate the relation between decoherence, energy relaxation and topology. In particular, in the topological phase and at low temperature, we analyze the dephasing rates between the different degenerate ground states

Design study of a feedback control system for the Multicyclic Flap System rotor (MFS)

The feasibility of automatically providing higher harmonic control to a deflectable control flap at the tip of a helicopter rotor blade through feedback of selected independent parameter was investigated. Control parameters were selected for input to the feedback system. A preliminary circuit was designed to condition the selected parameters, weigh limiting factors, and provide a proper output signal to the multi-cyclic control actuators. Results indicate that feedback control for the higher harmonic is feasible; however, design for a flight system requires an extension of the present analysis which was done for one flight condition - 120 kts, 11,500 lbs gross weight and level flight

Technology and benefits of aircraft counter rotation propellers

Results are reported of a NASA sponsored analytical investigation into the merits of advanced counter rotation propellers for Mach 0.80 commercial transport application. Propeller and gearbox performance, acoustics, vibration characteristics, weight, cost and maintenance requirements for a variety of design parameters and special features were considered. Fuel savings in the neighborhood of 8 percent relative to single rotation configurations are feasible through swirl recovery and lighter gearboxes. This is the net gain which includes a 5 percent acoustic treatment weight penalty to offset the broader frequency spectrum noise produced by counter rotation blading

Verbesserte Dehnungsmessung im Betonbau durch verteilte faseroptische Sensorik

Die verteilte faseroptische Sensorik (VFOS) auf Basis von Rayleighstreuung stellt ein besonderes und vielversprechendes Verfahren zur Dehnungsmessung im Betonbau und im Structural Health Monitoring (SHM) dar. Neben einer hohen Ortsauflösung und Messempfindlichkeit kann sie geringste Dehnungsänderungen an jedem Punkt der Messfaser erfassen. Für einen zuverlässigen Einsatz fehlen aktuell Material- und Handlungsempfehlungen; in der Literatur finden sich widersprüchliche Aussagen zu den Dehnungsübertragungsverlusten zwischen Substrat und Messfaser. Diesbezüglich beschäftigt sich die vorliegende Arbeit mit der Validierung des Messverfahrens für Szenarien im Betonbau. Neben der Applikation auf Stahl- und Betonoberflächen wurde die Integration in der Matrix untersucht. Im Zuge dessen sollten die Dehnungsübertragungsverluste verschiedener Fasercoatings bzw. Fasercoating-Klebstoff-Kombinationen überprüft werden. Darüber hinaus wurde ein Auswerteverfahren mithilfe der Programmiersprache Python entwickelt, das eine automatisierte Datenaufbereitung und Substituierung der Messabweichungen der enormen Datenmengen ermöglicht. Im Zuge der Validierung auf der Stahloberfläche wurden die Dehnungswerte der verschiedenen Coating-Klebstoff-Kombinationen an Präzisionsflachstählen im 4-Punkt-Biegeversuch mit einer photogrammetrischen Dehnungsmessung verglichen. Im Rahmen der Validierung auf der Betonoberfläche kamen Betondruckzylinder zum Einsatz, an denen zusätzlich zu den Coating-Klebstoff-Kombinationen der Einfluss einer Grundierung untersucht wurde. Induktive Wegaufnehmer dienten im Verlauf der Druckversuche als Vergleichsmesstechnik. Die Validierung verschiedener Coatingmaterialien in der Matrix fand anhand von Schwindversuchen an Betonprismen statt; als Vergleichsmessmethode dienten digitale Messuhren. Zur Bewertung der aus den Validierungsversuchen abgeleiteten Material- und Handlungsempfehlungen wurden Bauteilversuche an Betonbalken durchgeführt. Die Auswertung der Validierungsversuche zeigte, dass vor allem mit einem Ormocer-Coating gute Ergebnisse hinsichtlich der Dehnungsübertragung erzielt werden konnten. Im Falle einer Applikation empfiehlt sich die Verwendung eines Cyanacrylatklebstoffs -- besonders der M-Bond 200 überzeugte durch geringe Dehnungsverluste. Betonoberflächen sollten vorher geschliffen und mit Epoxidharz grundiert werden. Im Falle einer Integration in die Betonmatrix zeigten auch die Ormocer-Fasern minimale Unterschiede zur Vergleichsmessung. Die Ergebnisse der Bauteilversuche verifizieren die Handlungs- und Materialempfehlungen: Die Dehnungswerte der Fasern decken sich mit denen der analytischen Bemessung der Betonbalken. Lediglich an den Lasteinleitungsstellen konnten Oszillationen des Dehnungsverlaufs durch Gefügestörungen festgestellt werden. Forschungsbedarf besteht v.a. hinsichtlich der Validierung weiterer Komponenten (Klebstoff, Coating, Grundierungsmittel) und deren Langzeitstabilität, insbesondere bei chemischen und dynamischen Beanspruchungen. Im Rahmen dieser Arbeit konnte ein Überblick über verschiedene Materialien geschaffen werden, jedoch ist das Repertoire an verfügbaren Komponenten immens, gerade bei den Klebstoffen. Bei der Validierung auf der Betonoberfläche und in der Matrix kam eine Feinkornbetonmischung zum Einsatz. Diesbezüglich sollten in weiteren Forschungen unterschiedliche Matrices und Korngrößen Untersuchungsgegenstand sein.Distributed fiber optic sensor (DFOS) technology based on Rayleigh scattering is a unique and promising method for strain measurement in concrete structures as well as structural health monitoring (SHM). It can detect the smallest strain changes at any point in the measuring fiber with a high spatial resolution and sensitivity. Currently, there exist no material and handling recommendations for a reliable application, and the literature contains contradictory statements on strain transfer losses between substrate and fiber. The present study deals with the validation of this measuring method for scenarios in concrete structures. Besides applications on steel and concrete surfaces, the integration in a concrete matrix was investigated. The validation yields results for strain transfer losses for different fiber coatings or fiber coating/adhesive combinations. Furthermore, the development of an evaluation method using the computer language Python provides automated data preparation and measurement error substitution of the enormous data volumes. For the validation on steel surfaces, the strain values of different coating-adhesive combinations on precision flat steels were compared in a 4-point bending test with a photogrammetric strain measurement. For the validation on concrete surfaces, concrete pressure cylinders were used to investigate the influence of a primer and different coating-adhesive combinations. Inductive displacement transducers served as a comparative measuring technique during the compression tests. Shrinkage tests allowed the validation of different coating materials in a matrix on concrete prisms. Digital dial gauges were used as a comparative measuring method. For evaluation purposes, the material and handling recommendations derived from the validation were tested on concrete beams. The results of the validation tests indicate good results regarding strain transfer with an Ormocer coating. For application as tested , the use of a cyanoacrylate adhesive is recommended -- especially M-Bond 200 was convincing due to its low strain losses. Concrete surfaces should be sanded and primed with epoxy resin. If integrated into a concrete matrix, the Ormocer fibers also showed minor differences from the comparative measurement. The results of the evaluation tests verify the handling and material recommendations: the strain values of the fibers correspond to the values obtained in concrete-beam analysis. Oscillations of the strain profile due to microstructural disturbances could only be detected at the load application points. Further research regarding the validation of additional components (adhesives, coating, primer) and their long-term stability, especially chemical and dynamic loads, is necessary. This study provides an overview of different coating and adhesives. However, the repertoire of available components is immense - especially for adhesives. During the validation on concrete surfaces and in matrix, a fine-grained concrete mixture was used. In this respect, different matrices and grain sizes should be the subject of further research

Decoherence in the quantum Ising model with transverse dissipative interaction in the strong coupling regime

We study the decoherence dynamics of a quantum Ising lattice of finite size with a transverse dissipative interaction, namely the coupling with the bath is assumed perpendicular to the direction of the spins interaction and parallel to the external transverse magnetic field. In the limit of small transverse field, the eigenstates and spectrum are obtained by a strong coupling expansion, from which we derive the Lindblad equation in the Markovian limit. At temperature lower than the energy gap and for weak dissipation, the decoherence dynamics can be restricted to take only the two degenerate ground states and the first excited subspace into account. The latter is formed by pairs of topological excitations (domain walls or kinks), which are quantum delocalized along the chain due to the small magnetic field. We find that some of these excited states form a relaxation-free subspace, i.e. they do not decay to the ground states. We also discuss the decoherence dynamics for an initial state formed by a quantum superposition of the two degenerate ground states corresponding to the orthogonal classical, ferromagnetic states

Ground state topology of a four-terminal superconducting double quantum dot

In recent years, various classes of systems were proposed to realize topological states of matter. One of them are multiterminal Josephson junctions where topological Andreev bound states are constructed in the synthetic space of superconducting phases. Crucially, the topology in these systems results in a quantized transconductance between two of its terminals comparable to the quantum Hall effect. In this work, we study a double quantum dot with four superconducting terminals and show that it has an experimentally accessible topological regime in which the non-trivial topology can be measured. We also include Coulomb repulsion between electrons which is usually present in experiments and show how the topological region can be maximized in parameter space.Comment: 18 pages, 9 figures, submitted to SciPost Physic

Weighted Total Least Squares (WTLS) Solutions for Straight Line Fitting to 3D Point Data

In this contribution the fitting of a straight line to 3D point data is considered, with Cartesian coordinates xi, yi, zi as observations subject to random errors. A direct solution for the case of equally weighted and uncorrelated coordinate components was already presented almost forty years ago. For more general weighting cases, iterative algorithms, e.g., by means of an iteratively linearized Gauss–Helmert (GH) model, have been proposed in the literature. In this investigation, a new direct solution for the case of pointwise weights is derived. In the terminology of total least squares (TLS), this solution is a direct weighted total least squares (WTLS) approach. For the most general weighting case, considering a full dispersion matrix of the observations that can even be singular to some extent, a new iterative solution based on the ordinary iteration method is developed. The latter is a new iterative WTLS algorithm, since no linearization of the problem by Taylor series is performed at any step. Using a numerical example it is demonstrated how the newly developed WTLS approaches can be applied for 3D straight line fitting considering different weighting cases. The solutions are compared with results from the literature and with those obtained from an iteratively linearized GH model.TU Berlin, Open-Access-Mittel – 202

Mammalian end binding proteins control persistent microtubule growth

© 2009 Komarova et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0. The definitive version was published in Journal of Cell Biology 184 (2009): 691-706, doi:10.1083/jcb.200807179.End binding proteins (EBs) are highly conserved core components of microtubule plus-end tracking protein networks. Here we investigated the roles of the three mammalian EBs in controlling microtubule dynamics and analyzed the domains involved. Protein depletion and rescue experiments showed that EB1 and EB3, but not EB2, promote persistent microtubule growth by suppressing catastrophes. Furthermore, we demonstrated in vitro and in cells that the EB plus-end tracking behavior depends on the calponin homology domain but does not require dimer formation. In contrast, dimerization is necessary for the EB anti-catastrophe activity in cells; this explains why the EB1 dimerization domain, which disrupts native EB dimers, exhibits a dominant-negative effect. When microtubule dynamics is reconstituted with purified tubulin, EBs promote rather than inhibit catastrophes, suggesting that in cells EBs prevent catastrophes by counteracting other microtubule regulators. This probably occurs through their action on microtubule ends, because catastrophe suppression does not require the EB domains needed for binding to known EB partners.This work was supported by the Netherlands Organization for Scientifi c Research grants to A.A., by Funda ç ã o para a Ci ê ncia e a Tecnologia fellowship to S.M. Gouveia, by a FEBS fellowship to R.M. Buey, by the National Institutes of Health grant GM25062 to G.G. Borisy and by the Swiss National Science Foundation through grant 3100A0-109423 and by the National Center of Competence in Research Structural Biology program to M.O. Steinmetz

SLAIN2 links microtubule plus end–tracking proteins and controls microtubule growth in interphase

SLAIN2’s interactions with multiple different microtubule plus end–tracking proteins stimulate processive microtubule polymerization and ensure proper microtubule organization