2,154 research outputs found
Use of Equivalent Hermitian Hamiltonian for -Symmetric Sinusoidal Optical Lattices
We show how the band structure and beam dynamics of non-Hermitian
-symmetric sinusoidal optical lattices can be approached from the point of
view of the equivalent Hermitian problem, obtained by an analytic continuation
in the transverse spatial variable . In this latter problem the eigenvalue
equation reduces to the Mathieu equation, whose eigenfunctions and properties
have been well studied. That being the case, the beam propagation, which
parallels the time-development of the wave-function in quantum mechanics, can
be calculated using the equivalent of the method of stationary states. We also
discuss a model potential that interpolates between a sinusoidal and periodic
square well potential, showing that some of the striking properties of the
sinusoidal potential, in particular birefringence, become much less prominent
as one goes away from the sinusoidal case.Comment: 11 pages, 8 figure
Observation of two-dimensional lattice interface solitons
We report on the experimental observation of two-dimensional solitons at the
interface between square and hexagonal waveguide arrays. In addition to the
different symmetry of the lattices, the influence of a varying refractive index
modulation depth is investigated. Such variation strongly affects the
properties of surface solitons residing at different sides of the interface.Comment: 14 pages, 5 figures, to appear in Optics Letter
Scalable numerical approach for the steady-state ab initio laser theory
We present an efficient and flexible method for solving the non-linear lasing
equations of the steady-state ab initio laser theory. Our strategy is to solve
the underlying system of partial differential equations directly, without the
need of setting up a parametrized basis of constant flux states. We validate
this approach in one-dimensional as well as in cylindrical systems, and
demonstrate its scalability to full-vector three-dimensional calculations in
photonic-crystal slabs. Our method paves the way for efficient and accurate
simulations of lasing structures which were previously inaccessible.Comment: 17 pages, 8 figure
Prehospital fresh frozen plasma: Universal life saver or treatment in search of a target population?
Comparative analysis of marketed factor VIII products: comment
We read with interest the paper by Azengruber and colleagues recently published in the journal. The authors reported significant variation among the different recombinant concentrates in terms of content of soluble protein aggregates and subvisible particles. This could be important in explaining the differential immunogenicity, in terms of inhibitor development, among recombinant concentrates. We were, however, disappointed that the authors do not name the nine brands of recombinant FVIII concentrates they studied. By convention in scientific literature, authors are required to name their reagents and their source. We can not see any reason why the names of the concentrates were withheld and invite the authors to name the products now. This is particularly relevant as the studies cited by Anzengruber et al to demonstrate the different rates of inhibitor incidence relative to product type do cite the products used. This article is protected by copyright. All rights reserved
Testing the IONORT-ISP system: A comparison between synthesized and measured oblique ionograms
The three-dimensional (3-D) electron density representation of the ionosphere computed by the assimilative IRI-SIRMUP-P (ISP) model was tested using IONORT (IONOspheric Ray-Tracing), a software application for calculating a 3-D ray-tracing for high frequency (HF) waves in the ionospheric medium. A radio link was established between Rome (41.8°N, 12.5°E) in Italy, and Chania (35.7°N, 24.0°E) in Greece, within the ISP validity area, and for which oblique soundings are conducted. The ionospheric reference stations, from which the autoscaled foF2 and M(3000)F2 data and real-time vertical electron density profiles were assimilated by the ISP model, were Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E) in Italy, and Athens (38.0°N, 23.5°E) in Greece. IONORT was used, in conjunction with the ISP and the International Reference Ionosphere (IRI) 3-D electron density grids, to synthesize oblique ionograms. The comparison between synthesized and measured oblique ionograms, both in terms of the ionogram shape and the maximum usable frequency characterizing the radio path, demonstrates both that the ISP model can more accurately represent real conditions in the ionosphere than the IRI, and that the ray-tracing results computed by IONORT are reasonably reliable
Hybrid Adaptive Filter development for the minimisation of transient fluctuations superimposed on electrotelluric field recordings mainly by magnetic storms
The method of Hybrid Adaptive Filtering (HAF) aims to recover the recorded electric field signals from anomalies of magnetotelluric origin induced mainly by magnetic storms. An adaptive filter incorporating neuro-fuzzy technology has been developed to remove any significant distortions from the equivalent magnetic field signal, as retrieved from the original electric field signal by reversing the magnetotelluric method. Testing with further unseen data verifies the reliability of the model and demonstrates the effectiveness of the HAF method
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