Social Network Strategy improves access to HIV testing and harm reduction programs for PWID and their partners in Kazakhstan.

INTRODUCTION: The region of Eastern Europe and Сentral Asia has a growing HIV epidemic. Kazakhstan is a country in Central Asia with an estimated 33,000 people living with HIV. The new HIV infections have increased by 29% since 2010. Evidence suggests that HIV testing strategies focused on social networks are effective methods to identify more people with undiagnosed HIV. We conducted a study to describe the optimized HIV case finding (OCF) intervention for people who inject drugs (PWID) and their partners in Kazakhstan. METHODOLOGY: The OCF is based on recruitment of the extended risk social networks of HIV-positive PWID, using a two-step recruitment algorithm. RESULTS: There were 5,983 PWIDs and their partners tested for HIV, of those 149 (2.5%) received HIV-positive test results and the majority 145 (97%) were newly identified HIV-positive. The characteristics which had a statistically significant positive association with HIV-positive test results included: age group 15-19 (OR 4.12, 95% CI 1.44-11.7); age group 20-24 (OR 1.97, 95% CI 1.03-3.8); age group 50+ (OR 2.45, 95% CI 1.48-4.1); male sex (OR 1.78; 95% CI 1.2-2.6), participants who have previously received harm reduction services (OR 1.48; 95% CI 1.0-2.2); partners from "other groups" (OR 2.31, 95% CI 1.3-4.2). CONCLUSIONS: Low-threshold HIV testing and harm reduction services, like OCF using directly assisted self-testing and social network strategies are essential in reaching key populations with HIV prevention, increasing access to HIV testing and care.

Observation of Dirac bands in artificial graphene in small-period nanopatterned GaAs quantum wells.

Charge carriers in graphene behave like massless Dirac fermions (MDFs) with linear energy-momentum dispersion 1, 2 , providing a condensed-matter platform for studying quasiparticles with relativistic-like features. Artificial graphene (AG)-a structure with an artificial honeycomb lattice-exhibits novel phenomena due to the tunable interplay between topology and quasiparticle interactions 3-6 . So far, the emergence of a Dirac band structure supporting MDFs has been observed in AG using molecular 5 , atomic 6, 7 and photonic systems 8-10 , including those with semiconductor microcavities 11 . Here, we report the realization of an AG that has a band structure with vanishing density of states consistent with the presence of MDFs. This observation is enabled by a very small lattice constant (a = 50 nm) of the nanofabricated AG patterns superimposed on a two-dimensional electron gas hosted by a high-quality GaAs quantum well. Resonant inelastic light-scattering spectra reveal low-lying transitions that are not present in the unpatterned GaAs quantum well. These excitations reveal the energy dependence of the joint density of states for AG band transitions. Fermi level tuning through the Dirac point results in a collapse of the density of states at low transition energy, suggesting the emergence of the MDF linear dispersion in the AG.

Solid-immersion imaging interferometric nanoscopy to the limits of available frequency space.

Imaging interferometric nanoscopy (IIN) is a synthetic aperture approach offering the potential of optical resolution to the linear-system limit of optics (~λ/4n). The immersion advantages of IIN can be realized if the object is in close proximity to a solid-immersion medium with illumination and collection through the substrate and coupling this radiation to air by a grating on the medium surface opposite the object. The spatial resolution as a function of the medium thickness and refractive index as well as the field-of-view of the objective optical system is derived and applied to simulations.

Optical resolution below lambda/4 using synthetic aperture microscopy and evanescent-wave illumination.

Evanescent-wave illumination is applied to synthetic-aperture microscopy on a transparent solid substrate to extend the resolution limit to lambda/2(n+1) (where n is the substrate refractive index) independent of the lens NA. Using a 633 nm source and a 0.4 NA lens, a resolution to 150 nm (lambda/4.2) is demonstrated on a glass (n = 1.5) substrate. Further extension to approximately 74-nm resolution (lambda/8.6) is projected with a higher index substrate (n = 3.3).

Structured illumination for the extension of imaging interferometric microscopy.

Structured illumination applied to imaging interferometric microscopy (IIM) allows extension of the resolution limit of low numerical aperture objective lenses to ultimate linear systems limits (

Imaging interferometric microscopy.

Imaging interferometric microscopy (IIM) is a synthetic aperture imaging approach providing resolution to the transmission medium (refractive index n) linear systems limit extending to greater, similarlambda/4n using only low-numerical-aperture (low-NA) optics. IIM uses off-axis illumination to access high spatial frequencies along with interferometric reintroduction of a zero-order reference beam on the low-NA side of the optical system. For a thin object normal to the optical axis, the frequency space limit is [(1+NA)n/lambda], while tilting the object plane allows collection of diffraction information up to the material transmission bandpass-limited spatial frequency of 2n/lambda. Tilting transforms the spatial frequencies; the algorithm to reset to the correct image frequencies is described. IIM involves combining multiple subimages; the image reconstruction procedures are discussed. A mean-square-error metric is introduced. For binary objects, sigmoidal filtering of the image provides significant resolution improvement.

Imaging interferometric microscopy-approaching the linear systems limits of optical resolution.

The linear systems optical resolution limit is a dense grating pattern at a lambda/2 pitch or a critical dimension (resolution) of lambda/4. However, conventional microscopy provides a (Rayleigh) resolution of only ~ 0.6lambda/NA, approaching lambda/1.67 as NA ?lambda1. A synthetic aperture approach to reaching the lambda/4 linear-systems limit, extending previous developments in imaginginterferometric microscopy, is presented. Resolution of non-periodic 180-nm features using 633-nm illumination (lambda/3.52) and of a 170-nm grating (lambda/3.72) is demonstrated. These results are achieved with a 0.4-NA optical system and retain the working distance, field-of-view, and depth-of-field advantages of low-NA systems while approaching ultimate resolution limits.

Imaging interferometric microscopy.

We introduce and demonstrate a new microscopy concept: imaging interferometric microscopy (IIM), which is related to holography, synthetic-aperture imaging, and off-axis-dark-field illumination techniques. IIM is a wavelength-division multiplex approach to image formation that combines multiple images covering different spatial-frequency regions to form a composite image with a resolution much greater than that permitted by the same optical system using conventional techniques. This new type of microscopy involves both off-axis coherent illumination and reinjection of appropriate zero-order reference beams. Images demonstrate high resolution, comparable with that of a high-numerical-aperture (NA) objective, while they retain the long working distance, the large depth of field, and the large field of view of a low-NA objective. A Fourier-optics model of IIM is in good agreement with the experiment.