Polarization and diffraction peculiarities of optical media possessing simultaneously the properties of right and left substances

With the simultaneous presence of positive and negative components both in the permittivity tensor μij, and in the tensor of magnetic permeability μij, the propagation of an electromagnetic wave in optically homogeneous anisotropic media, and in periodically inhomogeneous media with a spiral structure is considere

Presenting a conceptual framework for an HIV prevention and care continuum and assessing the feasibility of empirical measurement in Estonia: A case study

Objective We aim to show the feasibility of using an integrated prevention and care continuum (PCC) model as a complete and improved tool for HIV control measurement and programming. Alignment of prevention and care continua is essential to further improve health outcomes and minimize HIV transmission risk. Design Cross-sectional study. Methods Data from 977 persons who inject drugs (PWID) collected in 2011-2016 in Tallinn, Estonia, were used to construct an HIV PCC for PWID, stratified by risk for acquiring or transmitting HIV infection and by coverage of combined interventions. We also estimated the average protective effect of current levels of intervention provision. Results 74.4%, 20.3% and 35.2% of PWID were currently using needle and syringe programmes (NSP), drug treatment and HIV testing, respectively. 51.1% of current PWID were HIV seropositive and of those 62.5% were currently on ART and 19.0% were virally suppressed. Across the PCC, individuals moved between categories of being aware and ever using drug treatment (resulting in -50% "leakage"); from ever having used to currently using drug treatment (-59%); between "ever testing"and "current (continuous) testing"(-62%); and from self-reported antiretroviral therapy (ART) adherence to viral suppression (-70%). Use of prevention services was higher among those at risk of transmission (HIV positive). The overall reduction in acquisition risk among HIV-negative PWID was 77.7% (95% CrI 67.8-84.5%), estimated by the modelled protective effects of current levels of NSP, drug treatment and ART compared to none of these services. Conclusions Our findings suggest that developing a cohesive model for HIV prevention and treatment is feasible and reflects the bi-directional relationships between prevention and care. The integrated continuum model indicates the major factors which may predict the epidemic course and control response. © 2020 Uusküla et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Negative Refraction of Infrared Waves and Rays in Sapphire α-Al2O3

The properties of refraction of extraordinary rays at principal surfaces of a uniaxial crystal having a strongly anisotropic dielectric dispersion are studied. Subject to optical nonabsorptivity of the crystal, the criteria for characterizing the refraction behavior are derived from Maxwell\u27s equations. The criteria reveal that in sapphire a variety of specific oblique-incidence reflection spectra arise from negative refraction and counterposition in the infrared region of multimode polar optical phonons. The effects of light dissipation due to damping of the phonons are explored further to interpret the oblique-incidence reflection spectrum measured for the c-surface of a synthetic crystal of sapphire. We pay attention to the directions of wave-normal and Poynting vectors of the infrared light transmitted into the crystal. It turns out that the damping of phonons gives rise to a true negative refraction that the two vectors are simultaneously refracted or deflected negatively in a certain frequency range