Noise-resistant phase imaging with intensity correlation.

Interferometric methods form the basis of highly sensitive measurement techniques from astronomy to bioimaging. Interferometry typically requires high stability between the measured and reference beams. The presence of rapid phase fluctuations washes out interference fringes, making phase profile recovery impossible. This challenge can be addressed by shortening the measurement time. However, such an approach reduces photon-counting rates, precluding applications in low-intensity imaging. We introduce a phase imaging technique which is immune to time-dependent phase fluctuations. Our technique, relying on intensity correlation instead of direct intensity measurements, allows one to obtain high interference visibility for arbitrarily long acquisition times. We prove the optimality of our method using the Cramér-Rao bound in the extreme case when no more than two photons are detected within the time window of phase stability. Our technique will broaden prospects in phase measurements, including emerging applications such as in infrared and x-ray imaging and quantum and matter-wave interferometry.

Sexual behavior among men who have sex with women, men, and Hijras in Mumbai, India--multiple sexual risks.

We describe the same-sex partnerships and sexual risk behavior of men attending sexually transmitted infection (STI) clinics in Mumbai, India. The HIV prevalence among 2,381 men sampled was 14%; 62% had a documented STI. Almost all men reported sex with women; additionally, 13% also reported having sex with other men, 13% reported sex with Hijras (male-to-female transgenders), and 11% had sex with all 3 genders. Men who had sex with men and/or Hijras as well as women, reported having greater numbers of partners, including female sex workers (FSW), and were more likely to engage in insertive anal and oral sex with women. The prevalence of HIV was higher among men having sex with Hijras (14%) or with all 3 genders (13%) than among men having sex with men and women (8%). A high proportion of men who attend STI clinics in Mumbai are behaviorally bi- or tri-sexual and have multiple partners with whom they engage in risky sex. STI/HIV prevention programs should not assume that men only have sex with women.