3,948 research outputs found

    Book Review: Research Methods in Education, 7th Edition

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    This article reviews the book, “Research Methods in Education” by Louis Cohen, Lawrence Manion, Keith Morrison (Authors)

    Fidelity and visibility reduction in Majorana qubits by entanglement with environmental modes

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    We study the dynamics and readout of topological qubits encoded by zero-energy Majorana bound states in a topological superconductor. We take into account bosonic modes due to the electromagnetic environment which couple the Majorana manifold to above-gap continuum quasi-particles. This coupling causes the degenerate ground state of the topological superconductor to be dressed in a polaron-like manner by quasi-particle states and bosons, and the system to become gapless. Topological protection and hence full coherence is only maintained if the qubit is operated and read out within the low-energy spectrum of the dressed states. We discuss reduction of fidelity and/or visibility if this condition is violated by a quantum-dot readout that couples to the bare (undressed) Majorana modes. For a projective measurement of the bare Majorana basis, we formulate a Bloch-Redfield approach that is valid for weak Majorana-environment coupling and takes into account constraints imposed by fermion-number-parity conservation. Within the Markovian approximation, our results essentially confirm earlier theories of finite-temperature decoherence based on Fermi's golden rule. However, the full non-Markovian dynamics reveals, in addition, the fidelity reduction by a projective measurement. Using a spinless nanowire model with pp-wave pairing, we provide quantitative results characterizing these effects.Comment: 18 pages, 10 figure

    Phylogenetischer Vergleich von chromosomal- und plasmid-kodierten Genabschnitten in enterohÀmorrhagischen Escherichia coli

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    In einem reprĂ€sentativen Kollektiv HUS-assoziierter EHEC wurde untersucht, in welchem VerhĂ€ltnis sich das Plasmid und das Chromosom zueinander entwickelt haben. Dazu wurden 41 StĂ€mme hinsichtlich der plasmid-kodierten Gene EHEC-hlyA und espP untersucht und sequenziert. Diese plasmidalen Sequenzen sowie die konkatenierten Sequenzen der sieben chromosomalen Haushaltsgene aus dem E. coli-MLST-Schema wurden auf ihre Phylogenie untersucht um einen Vergleich der Entwicklung durchzufĂŒhren. Von den 42 untersuchten HUSEC-StĂ€mmen waren 23 EHEC-hlyA-positiv und 14 espP-positiv, darunter 12 sowohl EHEC-hlyA als auch espP-positiv. Der Vergleich der phylogenetischen BĂ€ume ergab, dass die Struktur der plasmidalen Sequenzen gegenĂŒber den chromosomalen Sequenzen keine signifikanten Übereinstimmungen aufweisen. Zusammenfassend haben sich somit die chromosomalen Gene unabhĂ€ngig von den plasmidalen Genen entwickelt.<br

    Effect of surface nanostructure on temperature programmed reaction spectroscopy: First-principles kinetic Monte Carlo simulations of CO oxidation at RuO2(110)

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    Using the catalytic CO oxidation at RuO2(110) as a showcase, we employ first-principles kinetic Monte Carlo simulations to illustrate the intricate effects on temperature programmed reaction spectroscopy data brought about by the mere correlations between the locations of the active sites at a nanostructured surface. Even in the absence of lateral interactions, this nanostructure alone can cause inhomogeneities that cannot be grasped by prevalent mean-field data analysis procedures, which thus lead to wrong conclusions on the reactivity of the different surface species.Comment: 4 pages including 3 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

    Property of the large format digital aerial camera dmc ii

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    Z/I Imaging introduced with the DMC II 140, 230 and 250 digital aerial cameras with a very large format CCD for the panchromatic channel. The CCDs have with 140 / 230 / 250 mega pixel a size not available in photogrammetry before. CCDs in general have a very high relative accuracy, but the overall geometry has to be checked as well as the influence of not flat CCDs. A CCD with a size of 96mm x 82mm must have a flatness or knowledge of flatness in the range of 1 mu m if the camera accuracy in the range of 1.3 mu m shall not be influenced. The DMC II cameras have been evaluated with three different flying heights leading to 5cm, 9cm and 15cm or 20cm GSD, crossing flight lines and 60% side lap. The optimal test conditions guaranteed the precise determination of the object coordinates as well as the systematic image errors. All three camera types show only very small systematic image errors, ranging in the root mean square between 0.12 mu m up to 0.3 mu m with extreme values not exceeding 1.6 mu m. The remaining systematic image errors, determined by analysis of the image residuals and not covered by the additional parameters, are negligible. A standard deviation of the object point heights below the GSD, determined at independent check points, even in blocks with just 20% side lap and 60% end lap is standard. Corresponding to the excellent image geometry the object point coordinates are only slightly influenced by the self calibration. For all DMCII types the handling of image models for data acquisition must not be supported by an improvement of the image coordinates by the determined systematic image errors. Such an improvement up to now is not standard for photogrammetric software packages. The advantage of a single monolithic CCD is obvious. An edge analysis of pan-sharpened DMC II 250 images resulted in factors for the effective resolution below 1.0. The result below 1.0 is only possible by contrast enhancement, but this requires with low image noise, demonstrating the very good radiometric image quality

    Concentrations of higher dicarboxylic acids C5 – C13 in fresh snow samples collected at the High Alpine Research Station Jungfraujoch during CLACE 5 and 6

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    Samples of freshly fallen snow were collected at the high alpine research station Jungfraujoch (Switzerland) in February and March 2006 and 2007, during the Cloud and Aerosol Characterization Experiments (CLACE) 5 and 6. In this study a new technique has been developed and demonstrated for the measurement of organic acids in fresh snow. The melted snow samples were subjected to solid phase extraction and resulting solutions analysed for organic acids by HPLC-MS-TOF using negative electrospray ionization. A series of linear dicarboxylic acids from C5 to C13 and phthalic acid, were identified and quantified. In several samples the biogenic acid pinonic acid was also observed. In fresh snow the median concentration of the most abundant acid, adipic acid, was 0.69 micro g L -1 in 2006 and 0.70 micro g L -1 in 2007. Glutaric acid was the second most abundant dicarboxylic acid found with median values of 0.46 micro g L -1 in 2006 and 0.61 micro g L -1 in 2007, while the aromatic acid phthalic acid showed a median concentration of 0.34 micro g L -1 in 2006 and 0.45 micro g L -1 in 2007. The concentrations in the samples from various snowfall events varied significantly, and were found to be dependent on the back trajectory of the air mass arriving at Jungfraujoch. Air masses of marine origin showed the lowest concentrations of acids whereas the highest concentrations were measured when the air mass was strongly influenced by boundary layer air

    Min-oscillations in Escherichia coli induced by interactions of membrane-bound proteins

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    During division it is of primary importance for a cell to correctly determine the site of cleavage. The bacterium Escherichia coli divides in the center, producing two daughter cells of equal size. Selection of the center as the correct division site is in part achieved by the Min-proteins. They oscillate between the two cell poles and thereby prevent division at these locations. Here, a phenomenological description for these oscillations is presented, where lateral interactions between proteins on the cell membrane play a key role. Solutions to the dynamic equations are compared to experimental findings. In particular, the temporal period of the oscillations is measured as a function of the cell length and found to be compatible with the theoretical prediction.Comment: 17 pages, 5 figures. Submitted to Physical Biolog

    Assessing the efficiency of first-principles basin-hopping sampling

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    We present a systematic performance analysis of first-principles basin-hopping (BH) runs, with the target to identify all low-energy isomers of small Si and Cu clusters described within density-functional theory. As representative and widely employed move classes we focus on single-particle and collective moves, in which one or all atoms in the cluster at once are displaced in a random direction by some prescribed move distance, respectively. The analysis provides detailed insights into the bottlenecks and governing factors for the sampling efficiency, as well as simple rules-of-thumb for near-optimum move settings, that are intriguingly independent of the distinctly different chemistry of Si and Cu. At corresponding settings, the observed performance of the BH algorithm employing two simple, general-purpose move classes is already very good, and for the small systems studied essentially limited by frequent revisits to a few dominant isomers.Comment: 11 pages including 8 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm
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