Fractional Angular Momenta, Gouy and Berry Phases in Relativistic Bateman-Hillion-Gaussian Beams of Electrons.

A new Bateman-Hillion solution to the Dirac equation for a relativistic Gaussian electron beam taking explicit account of the four-position of the beam waist is presented. This solution has a pure Gaussian form in the paraxial limit but beyond it contains higher order Laguerre-Gaussian components attributable to the tighter focusing. One implication of the mixed mode nature of strongly diffracting beams is that the expectation values for spin and orbital angular momenta are fractional and are interrelated to each other by intrinsic spin-orbit coupling. Our results for these properties align with earlier work on Bessel beams [Bliokh et al., Phys. Rev. Lett. 107, 174802 (2011)PRLTAO0031-900710.1103/PhysRevLett.107.174802] and show that fractional angular momenta can be expressed by means of a Berry phase. The most significant difference arises, though, due to the fact that Laguerre-Gaussian beams naturally contain Gouy phase, while Bessel beams do not. We show that Gouy phase is also related to Berry phase and that Gouy phase fronts that are flat in the paraxial limit become curved beyond it.

Unprotected sex, underestimated risk, undiagnosed HIV and sexually transmitted diseases among men who have sex with men accessing testing services in a New England bathhouse.

American men who have sex with men (MSM) continue to have increased rates of HIV and sexually transmitted diseases (STD). Between 2004 and 2010, 1155 MSM were tested for HIV and/or STDs at Providence, RI bathhouse. The prevalence of HIV was 2.3%; syphilis, 2.0%; urethral gonorrhea, 0.1%; urethral chlamydia, 1.3%; 2.2% of the men had hepatitis C antibodies. Although 43.2% of the men engaged in unprotected anal intercourse in the prior 2 months, the majority of the men thought that their behaviors did not put them at increased risk for HIV or STDs. Multivariate analyses found that men who engaged in unprotected anal intercourse were more likely to have had sex with unknown status or HIV-infected partners; have sex although under the influence of drugs; tended to find partners on the internet; and were more likely to have a primary male partner. Men who were newly diagnosed with HIV or syphilis tended to be older than 30 years; had sex with an HIV-infected partner; had a prior STD diagnosis; and met partners on the internet. For 10.5% of the men, bathhouse testing was the first time that they had ever been screened for HIV. Of 24 men who were newly diagnosed with HIV infection, only 1 was not successfully linked to care. These data suggest that offering HIV and STD testing in a bathhouse setting is effective in attracting MSM who are at increased risk for HIV and/or STD acquisition or transmission.