4,506 research outputs found
Effect of Hydrogen on the Sintering of Pt-Black Catalyst and on its Activity in Skeletal Hydrocarbon Reactions*
Exceptional Points in Atomic Spectra
We report the existence of exceptional points for the hydrogen atom in
crossed magnetic and electric fields in numerical calculations. The resonances
of the system are investigated and it is shown how exceptional points can be
found by exploiting characteristic properties of the degeneracies, which are
branch point singularities. A possibility for the observation of exceptional
points in an experiment with atoms is proposed.Comment: 4 pages, 4 figures, 1 table, to be published in Physical Review
Letter
Fourier's Law from Schroedinger Dynamics
We consider a class of one-dimensional chains of weakly coupled many level
systems. We present a theory which predicts energy diffusion within these
chains for almost all initial states, if some concrete conditions on their
Hamiltonians are met. By numerically solving the time dependent Schroedinger
equation, we verify this prediction. Close to equilibrium we analyze this
behavior in terms of heat conduction and compute the respective coefficient
directly from the theory.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Let
WDX-Analysis of the New Superconductors RO(1-x)F(x)FeAs and Its Consequences on the Electronic Phase Diagram
Polycrystalline samples of RO1-xFxFeAs (0 < x < 0.25) (R = La, Sm, Gd) were
investigated by wavelength-dispersive X-ray spectroscopy (WDX) in the electron
microscope to determine the composition of the samples, in particular the
fluorine content. It was found that the measured fluorine content can deviate
considerably from the initial weight. In the lanthanum compound LaO1-xFxFeAs,
we found good agreement mainly for x > 0.05, but for x < 0.05 the fluorine
hardly goes into the sample. For the samarium compound we measured less than
half the fluorine in the sample as initially weighed at all fluorine
concentrations. These measured values are taken into account when drawing the
electronic phase diagrams of LaO1-xFxFeAs and SmO1-xFxFeAs. This leads to a
more consistent picture of both of the diagrams in comparison to the plot of
the initial weight.Comment: 5 pages, 4 figures, Accepted for publication in Journal of
Superconductivity and Novel Magnetis
Generation of specific antibodies against the rap1A, rap1B and rap2 small GTP-binding proteins. Analysis of rap and ras proteins in membranes from mammalian cells
Specific antibodies against rap1A and rap1B small GTP-binding proteins were generated by immunization of rabbits with peptides derived from the C-terminus of the processed proteins. Immunoblot analysis of membranes from several mammalian cell lines and human thrombocytes with affinity-purified antibodies against rap1A or rap1B demonstrated the presence of multiple immunoreactive proteins in the 22-23 kDa range, although at strongly varying levels. Whereas both proteins were present in substantial amounts in membranes from myelocytic HL-60, K-562 and HEL cells, they were hardly detectable in membranes from lymphoma U-937 and S49.1 cyc- cells. Membranes from human thrombocytes and 3T3-Swiss Albino fibroblasts showed strong rap1B immunoreactivity, whereas rap1A protein was present in much lower amounts. In the cytosol of HL-60 cells, only small amounts of rap1A and rap1B proteins were detected, unless the cells were treated with lovastatin, an inhibitor of hydroxymethylglutaryl-coenzyme A reductase, suggesting that both proteins are isoprenylated. By comparison with recombinant proteins, the ratio of rap1A/ras proteins in membranes from HL-60 cells was estimated to be about 4:1. An antiserum directed against the C-terminus of rap2 reacted strongly with recombinant rap2, but not with membranes from tested mammalian cells. In conclusion, rap1A and rap1B proteins are distributed differentially among membranes from various mammalian cell types and are isoprenylated in HL-60 cells
Geometry of inertial manifolds probed via a Lyapunov projection method
A method for determining the dimension and state space geometry of inertial
manifolds of dissipative extended dynamical systems is presented. It works by
projecting vector differences between reference states and recurrent states
onto local linear subspaces spanned by the Lyapunov vectors. A sharp
characteristic transition of the projection error occurs as soon as the number
of basis vectors is increased beyond the inertial manifold dimension. Since the
method can be applied using standard orthogonal Lyapunov vectors, it provides a
simple way to determine also experimentally inertial manifolds and their
geometric characteristics
Perspectives on organic light-emitting diodes for display applications
Herein, we describe a number of key issues that concern the commercialization of organic light-emitting diodes for display applications. We will firstly outline the historical and market contexts that show the potential for organic electronics as a viable display technology. Next, we will discuss the chemical structures for a range of both small-molecular and polymer organic semiconducting compounds, and how the electronic properties are governed thereof. Also we will briefly discuss various common film deposition and device fabrication strategies. Then, we will describe two factors that are highly relevant for commercially viable organic light-emitting diodes, namely charge balance, and device degradation. Finally, we will outline some methods for achieving the high-volume throughput of organic electronics via well-established technologies that are used in the printing industr
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