1,629 research outputs found

    Investigation of the M-shell unresolved transition array of aluminium-like iron using monochromatic soft x-ray synchrotron radiation

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    In various astrophysical observations, the n = 2 → 3 transitions of highly charged iron appear in the soft x-ray region as an unresolved transition array (UTA). The structure of the UTA is directly related to the ionization balance of the plasma and is therefore of high astrophysical interest. The models used to analyse the astrophysical spectra are highly sensitive to the input atomic data, which is mainly based on theoretical calculations. Therefore high precision laboratory measurements are needed for benchmarking theory. Within this thesis, a systematic measurement over the whole UTA energy range has been conducted to determine the transition energies and rates for the thirteen-fold ionized iron (Fe13+), an important constituent of the UTA. The ions of interest were produced by an electron beam ion trap and resonantly excited by the synchrotron radiation of PETRA III. By utilizing an ion-extraction beamline, the radiative as well as the autoionization decay channels have been observed in parallel. 31 hitherto unexplored transitions of the UTA have been resolved with a relative accuracy on the level of 40 parts-per million, serveral orders of magnitude higher than the accuracy obtained in the astrophysical observations. An additional high resolution measurement lead to the extraction of the natural linewidth, which has been used to determine the absolute radiative and autoionization rates of two prominent lines of the UTA. A comparison with state-of-the-art theory revealed a significant 80(7)meV offset in transition energies as well as a three to four-fold smaller natural linewidth, leading to the question how reliable the astrophysical models are

    Performance measurements of mixed data acquisition and LAN traffic on a credit-based flow-controlled ATM network

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    Laser-Induced Skyrmion Writing and Erasing in an Ultrafast Cryo-Lorentz Transmission Electron Microscopy

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    We demonstrate that light-induced heat pulses of different duration and energy can write skyrmions in a broad range of temperatures and magnetic field in FeGe. Using a combination of camera-rate and pump-probe cryo-Lorentz Transmission Electron Microscopy, we directly resolve the spatio-temporal evolution of the magnetization ensuing optical excitation. The skyrmion lattice was found to maintain its structural properties during the laser-induced demagnetization, and its recovery to the initial state happened in the sub-{\mu}s to {\mu}s range, depending on the cooling rate of the system

    Experimental Signature of Medium Modifications for rho and omega Mesons in the 12 GeV p + A Reactions

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    The invariant mass spectra of e+e- pairs produced in 12-GeV proton-induced nuclear reactions are measured at the KEK Proton-Synchrotron. On the low-mass side of the omega meson peak, a significant enhancement over the known hadronic sources has been observed. The mass spectra, including the excess, are well reproduced by a model that takes into account the density dependence of the vector meson mass modification, as theoretically predicted.Comment: 4 pages, 3 figures, Version accepted for Physical Review Lette

    Nano-Hall sensors with granular Co-C

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    We analyzed the performance of Hall sensors with different Co-C ratios, deposited directly in nano-structured form, using Co2(CO)8Co_2(CO)_8 gas molecules, by focused electron or ion beam induced deposition. Due to the enhanced inter-grain scattering in these granular wires, the Extraordinary Hall Effect can be increased by two orders of magnitude with respect to pure Co, up to a current sensitivity of 1Ω/T1 \Omega/T. We show that the best magnetic field resolution at room temperature is obtained for Co ratios between 60% and 70% and is better than 1μT/Hz1/21 \mu T/Hz^{1/2}. For an active area of the sensor of 200×200nm2200 \times 200 nm^2, the room temperature magnetic flux resolution is ϕmin=2×10−5ϕ0\phi_{min} = 2\times10^{-5}\phi_0, in the thermal noise frequency range, i.e. above 100 kHz.Comment: 5 pages, 4 figure

    Análise e caracterização do gene de osmotina em cupuaçuzeiro.

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    O cupuaçuzeiro, Theobroma grandiflorum (Willd. ex Spreng.) Schum., pertence à família Malvaceae e é nativo da região Amazônica. A cultura do cupuaçuzeiro é afetada pela doença vassoura-de-bruxa, causada pelo fungo Moniliophthora perniciosa, provocando uma grande redução na produção de frutos. O conhecimento molecular da interação planta-patógeno é essencial para o desenvolvimento de ferramentas para o controle da doença, como por exemplo, a identificação de genótipos resistentes. Genes expressos em resposta ao ataque de patógenos são alvos de estudos desta interação. O objetivo do presente trabalho foi caracterizar um deles, o gene de osmotina, em cupuaçuzeiro. Sequências anotadas do transcriptoma de frutos de cupuaçuzeiro foram avaliadas quanto à presença deste gene. Os genes identificados foram comparados ao de osmotina de cacau pelo programa BLAST. Além disso, a organização do gene foi analisada por Southern blot, utilizando DNA genômico de cupuaçu. Identificaram-se duas sequências tipo osmotina: uma de 381 pb e outra de 477 pb, que correspondem a aproximadamente 63% e 79%, respectivamente, da região codificadora da proteína madura de cacau (607 pb). A comparação destas duas sequências com o gene de osmotina de cacau revelou identidade de cerca de 70%. Quanto à organização genômica em cupuaçu, foi observado que o gene está presente em múltiplas cópias. Estudos posteriores são necessários para investigar o envolvimento deste gene com os fenótipos de resistência à vassoura-de-bruxa

    Probing microwave fields and enabling in-situ experiments in a transmission electron microscope.

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    A technique is presented whereby the performance of a microwave device is evaluated by mapping local field distributions using Lorentz transmission electron microscopy (L-TEM). We demonstrate the method by measuring the polarisation state of the electromagnetic fields produced by a microstrip waveguide as a function of its gigahertz operating frequency. The forward and backward propagating electromagnetic fields produced by the waveguide, in a specimen-free experiment, exert Lorentz forces on the propagating electron beam. Importantly, in addition to the mapping of dynamic fields, this novel method allows detection of effects of microwave fields on specimens, such as observing ferromagnetic materials at resonance
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