Background The impact of HIV pre-exposure prophylaxis (PrEP) depends on uptake, adherence, and sexual practices. Methods Men and transgender women who have sex with men (MSM/TGW) previously enrolled in PrEP trials were enrolled in a 72 week open label extension (iPrEx OLE). Drug concentrations were measured in plasma and dried blood spots (DBS) in seroconverters and a random sample of seronegatives. Findings 1603 HIV uninfected persons were enrolled, of whom 76% received PrEP. PrEP uptake was higher among those reporting condomless receptive anal intercourse (ncRAI; P=0.003) and having serological evidence of herpes (P=0.03). Among those receiving PrEP, HIV incidence was 1.8/100PY, which was 49% (95% CI: −1 to 74%) lower than among those who concurrently did not choose PrEP after adjusting for sexual behavior, and 53% (95% CI: 26 to 70%) lower than in the placebo arm of the prior randomized phase (3.9/100PY). Among those receiving PrEP, HIV incidence was 4.7/100PY if drug was not detected in DBS, 2.3/100PY if drug concentrations indicated use of less than 2 tablets per week, 0.6/100PY for use of 2 to 3 tablets per week, and 0/100PY for use of 4 or more tablets per week (P<0.0001). PrEP drug concentrations were higher among people with older age, more schooling, ncRAI, more sexual partners, trans-identification, and a history of syphilis or herpes. Interpretation PrEP uptake was high when made available free of charge by experienced providers. PrEP impact is increased by greater uptake and adherence during periods of higher risk; disengagement after initial use is common. DBS drug concentrations are strongly correlated with PrEP’s protective benefit.

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A novel quantization-based data-hiding method, called Rational Dither Modulation (RDM), is presented. This method retains most of the simplicity of the conventional dither modulation (DM) scheme, which is largely vulnerable to amplitude scalings and modifies it in such a way that the result becomes invariant to gain attacks. RDM is based on using a gain-invariant adaptive quantization step-size at both embedder and decoder. This causes the watermarked signal to be asymptotically stationary. Mathematical tools are used to determine the stationary probability density function, which is later used to assess the performance of RDM in Gaussian channels. It is also shown that by increasing the memory of the system, it is possible to asymptotically approach the performance of DM, still keeping invariance against gain attacks. RDM is compared with improved spread-spectrum methods, showing that the former can achieve much higher rates for the same bit error probability. Experimental results confirm the validity of the theoretical analyses given in the paper. Finally, a broader class of methods, that extends gain-in- variance to quantization index modulation (QIM) methods, is also presented

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The adoption of aggressive frequency reuse schemes along with interference management techniques has become the leading paradigm in satellite communications to increase the spectral efficiency. In general terms, one cannot rely on precoding techniques in the absence of channel phase information. Nevertheless, the availability of channel magnitude information, makes it possible to explore power-based separation of superimposed signals. In this paper, rate splitting (RS) ideas are exploited, whereby the separation of messages into private and public parts serves to improve the performance of successive cancellation decoding (SCD). Numerical results reveal that in some pertinent system scenarios, the proposed schemes achieve a larger rate region than that of orthogonal schemes that do not exploit the interference and other strategies that either do not allow beam cooperation or do not apply RS.