Gap localization of multiple TE‐Modes by arbitrarily weak defects

This paper considers the propagation of TE‐modes in photonic crystal waveguides. The waveguide is created by introducing a linear defect into a periodic background medium. Both the periodic background problem and the perturbed problem are modelled by a divergence type equation. A feature of our analysis is that we allow discontinuities in the coefficients of the operator, which is required to model many photonic crystals. Using the Floquet–Bloch theory in negative‐order Sobolev spaces, we characterize the precise number of eigenvalues created by the line defect in terms of the band functions of the original periodic background medium for arbitrarily weak defects

On the Doppler effect for light from orbiting sources in Kerr-type metrics

A formula is derived for the combined motional and gravitational Doppler effect in general stationary axisymmetric metrics for a photon emitted parallel or antiparallel to the assumed circular orbital motion of its source. The same formula is derived from eikonal approximation and Killing vector approaches to elucidate connections between observational astronomy and modern Relativity. The formula yields expected results in the limits of a moving or stationary source in the exterior Kerr and Schwarzschild metrics and a moving source in flat space.Comment: Accepted for publication in in Monthly Notices of the Royal Astronomical Society Main Journal 1.23.15. This version has substantially shortened and clarified derivations and added content regarding applicability of the derivation

Absence of bound states for waveguides in 2D periodic structures

We study a Helmholtz-type spectral problem in a two-dimensional medium consisting of a fully periodic background structure and a perturbation in form of a line defect. The defect is aligned along one of the coordinate axes, periodic in that direction (with the same periodicity as the background), and bounded in the other direction. This setting models a so-called "soft-wall" waveguide problem. We show that there are no bound states, i.e., the spectrum of the operator under study contains no point spectrum.Comment: This is an updated version of our paper (in slightly different form in Journal of Mathematical Physics). An anonymous reviewer kindly made us aware that ref. 10 is not applicable in our situation. An application of the theorem in ref. 10 would have proved the absence of singular continuous spectrum also. Our result on the absence of point spectrum is not affected by thi

Prevention of HIV infection

W artykule przedstawiono podstawowe zagadnienia służące zapobieganiu rozprzestrzenianiu się wirusa HIV, profilaktykę i programy o charakterze prewencyjnym. Szczegółowiej omówiono czynniki społeczne powodujące podatność na HIV, oraz profilaktykę poekspozycyjną.This article presents basic facts that are helpful in the avoidance of HIV infection and preventive programmes. Social factors triggering susceptibility to HIV as well as post-exposure prophylaxis were discussed in greater detail

The role of a nurse in the prevention of HIV infection

Zadania stawiane przed pielęgniarkami w zakresie profilaktyki HIV skłaniają do zastanowienia się, w jakim stopniu partnerami w tych działaniach mogą być sami nosiciele wirusa HIV, a także młodzież. Dla wyjaśnienia tych wątpliwości autorzy podjęli badania własne, których celem było określenie stanu wiedzy grup badanych nosicieli wirusa HIV oraz młodzieży gimnazjalnej na temat zakażenia wirusem HIV. Materiał i metody. W badaniach udział wzięło 31 nosicieli wirusa HIV hospitalizowanych w jednym z warszawskich szpitali oraz 58 uczniów I klasy jednego z warszawskich gimnazjów. W badaniu posłużono się metodą sondażu diagnostycznego, techniką była autor-ska ankieta służąca ocenie stanu wiedzy na temat HIV. Wyniki i wnioski. Stan wiedzy na temat zakażenia HIV w grupie nosicieli wirusa jest wysoki, mimo to wymaga jeszcze uzupełnienia wiedzy. Wśród młodzieży natomiast wiedza jest obarczona wieloma mitami i negatywnymi stereotypami, co oznacza, że młodzież wymaga stałej edukacji w kierunku profilaktyki HIV/AIDS.The tasks that are expected of nurses as far as HIV prevention is concerned make one wonder to what degree HIV carriers and youth can partner those tasks. In order to clear those doubts the authors undertaken their self-developed research whose objective was to evaluate the state of knowledge on HIV infection among the interviewed HIV carriers and junior high school students. Materials and methods. 31 HIV carriers hospitalized in one of the hospitals in Warsaw and 58 1st grade students in one of the junior schools in Warsaw took part in the research. The diagnostic poll method was used, the research tool being a self-developed question-naire whose purpose was to assess the level of knowledge on HIV. Results and conclusion. The level of knowledge on HIV infection is high among HIV carriers; nevertheless, their knowledge still needs to be broadened. Among the youth there are many myths and negative stereotypes incorporated in the knowledge, which means that there is a need for constant education of youth on HIV/AIDS prevention

A new diversity index

We introduce here a new index of diversity based on consideration of reasonable propositions that such an index should have in order to represent diversity. The behaviour of the index is compared with that of the Gini-Simpson diversity index, and is found to predict more realistic values of diversity for small communities, in particular when each species is equally represented and for small communities. The index correctly provides a measure of true diversity that is equal to the species richness across all values of species and organism numbers when all species are equally represented, as well as Hill's more stringent 'doubling' criterion when they are not. In addition, a new graphical interpretation is introduced that permits a straightforward visual comparison of pairs of indices across a wide range within a parameter space based on species and organism numbers