937 research outputs found
Wave Dynamical Chaos in a Superconducting Three-Dimensional Sinai Billiard
Based on very accurate measurements performed on a superconducting microwave
resonator shaped like a desymmetrized three-dimensional (3D) Sinai billiard, we
investigate for the first time spectral properties of the vectorial Helmholtz,
i.e. non-quantum wave equation for a classically totally chaotic and
theoretically precisely studied system. We are thereby able to generalize some
aspects of quantum chaos and present some results which are consequences of the
polarization features of the electromagnetic waves.Comment: 4 pages RevTex; 4 postscript figures; to be published in Phys. Rev.
Lett.; Info: [email protected]
Thin-disk laser pump schemes for large number of passes and moderate pump source quality
Novel thin-disk laser pump layouts are proposed yielding an increased number
of passes for a given pump module size and pump source quality. These novel
layouts result from a general scheme which bases on merging two simpler pump
optics arrangements. Some peculiar examples can be realized by adapting
standard commercially available pump optics simply by intro ducing an
additional mirror-pair. More pump passes yield better efficiency, opening the
way for usage of active materials with low absorption. In a standard multi-pass
pump design, scaling of the number of beam passes brings ab out an increase of
the overall size of the optical arrangement or an increase of the pump source
quality requirements. Such increases are minimized in our scheme, making them
eligible for industrial applicationsComment: 16 pages, 9 figure
Modeling of field singularities at dielectric edges using grid based methods
Electric field singularities at sharp metallic edges or at a dielectric
contact line can be described analytically by asymptotic expressions. The a
priori known form of the field distribution in the vicinity of these edges
can be used to construct numerical methods with improved accuracy. This
contribution focuses on a modified Finite Integration Technique and on a
Discontinuous Galerkin Method with singular approximation functions. Both
methods are able to handle field singularities at perfectly electric
conducting as well as at dielectric edges. The numerical accuracy of these
methods is investigated in a number of simulation examples including static
and dynamic field problems
Compact 20-pass thin-disk amplifier insensitive to thermal lensing
We present a multi-pass amplifier which passively compensates for distortions
of the spherical phase front occurring in the active medium. The design is
based on the Fourier transform propagation which makes the output beam
parameters insensitive to variation of thermal lens effects in the active
medium. The realized system allows for 20 reflections on the active medium and
delivers a small signal gain of 30 with M = 1.16. Its novel geometry
combining Fourier transform propagations with 4f-imaging stages as well as a
compact array of adjustable mirrors allows for a layout with a footprint of 400
mm x 1000 mm.Comment: 7 pages, 6 figure
Investigation of Planar Pick-up and Kicker Electrodes for Stochastic Cooling
The success of stochastic cooling crucially depends on the interaction between the beam and high frequency devices for detection (pick-up electrodes) and deflection (kicker electrodes). This contribution shows the theoretical investigation of a planar electrode to be used for stochastic cooling of secondary particles with a beta of 0.83. The coupling to the beam is realised by a slot line. Transition networks are added to extract the signal. The detailed investigation is performed via a numerical electromagnetic field analysis. The longitudinal kick of the deflectors is calculated as a function of the beam position and scaled to the applied voltage. According to the Panofsky-Wenzel theorem the transverse kick is obtained simultaneously. The electromagnetic properties of the discussed electrode are compared to existing ones as currently in use in the ESR storage ring (GSI, Darmstadt)
Higher-order sensitivity analysis of periodic 3-D eigenvalue problems for electromagnetic field calculations
An algorithm to perform a higher-order sensitivity analysis for
electromagnetic eigenvalue problems is presented. By computing the eigenvalue
and eigenvector derivatives, the Brillouin Diagram for periodic structures
can be calculated. The discrete model is described using the Finite
Integration Technique (FIT) with periodic boundaries, and the sensitivity
analysis is performed with respect to the phase shift φ between the
periodic boundaries.
For validation, a reference solution is calculated by solving multiple
eigenvalue problems (EVP). Furthermore, the eigenvalue derivatives are
compared to reference values using finite difference (FD) formulas
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First steps in the logic-based assessment of post-composed phenotypic descriptions
In this paper we present a preliminary logic-based evaluation of the integration of post-composed phenotypic descriptions with domain ontologies. The evaluation has been performed using a description logic reasoner together with scalable techniques: ontology modularization and approximations of the logical difference between ontologies
Solubility of precursors and carbonation of waterglass-free geopolymers
Geopolymers have the potential to function as an environmentally friendly substitute for ordinary Portland cement, with up to 80% less CO emission during production. The effect is best utilized for geopolymers prepared with amorphous silica instead of waterglass (NaSiO) to adjust the Si:Al ratio. The reactivity of the precursors with the alkaline activator affects the final mineralogical properties of the binder. The purpose of the present study was to investigate the amount of different phases formed during geopolymerization and to understand the quantitative evolution of carbonation during geopolymer synthesis by determining the solubility of metakaolinite and amorphous SiO in NaOH at various concentrations. The solubility was studied by ICP-OES measurements. X-ray diffraction was used for qualitative and quantitative phase analysis of the geopolymers. The solubility of the precursors increased with calcination temperature of metakaolinite, reaction time for amorphous SiO, and at higher NaOH concentrations. Partial dissolution resulted in free Na, which is a source for the formation of carbonates in the geopolymers. Thermonatrite occurred prior to trona formation in all samples
Integrating protein-protein interactions and text mining for protein function prediction
<p>Abstract</p> <p>Background</p> <p>Functional annotation of proteins remains a challenging task. Currently the scientific literature serves as the main source for yet uncurated functional annotations, but curation work is slow and expensive. Automatic techniques that support this work are still lacking reliability. We developed a method to identify conserved protein interaction graphs and to predict missing protein functions from orthologs in these graphs. To enhance the precision of the results, we furthermore implemented a procedure that validates all predictions based on findings reported in the literature.</p> <p>Results</p> <p>Using this procedure, more than 80% of the GO annotations for proteins with highly conserved orthologs that are available in UniProtKb/Swiss-Prot could be verified automatically. For a subset of proteins we predicted new GO annotations that were not available in UniProtKb/Swiss-Prot. All predictions were correct (100% precision) according to the verifications from a trained curator.</p> <p>Conclusion</p> <p>Our method of integrating CCSs and literature mining is thus a highly reliable approach to predict GO annotations for weakly characterized proteins with orthologs.</p
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