Metal-free design of a multilayered metamaterial with chirped Bragg grating for enhanced radiative cooling.

A wideband, all-dielectric metamaterial structure for enhancing radiative cooling is investigated. The structure is optimized to reflect most of the solar irradiance window (between 0.3 µm-3 µm), which is one of the biggest challenges in highly efficient radiative cooling coatings. The design is based on the principles of Bragg gratings, which constitutes a simple synthesis procedure to make a broadband reflector of reduced dimensions, without metallic layers, while keeping a flat enough response in the entire bandwidth. Numerical results show that reflection of solar irradiation can be easily tailored and maximized using this method, as well as the net cooling power of the device, about ∼79 W/m2 at daytime (about double at night-time) and a temperature reduction of 23 K (assuming no heat exchange) and 7 K assuming a heat exchange coefficient of 10 W/m2/K, for a device and ambient temperatures of 300 K and 303 K, respectively. This occurs even in detriment of absorption in the atmospheric window (8 µm-13 µm). Results also show the importance of efficiently reflecting solar irradiance for such technologies and its relevance in synthesis and design without using metallic components.

Syphilis in Men Who Have Sex With Men: A Warning Sign for HIV Infection.

OBJECTIVE: To describe the clinical and epidemiological characteristics of syphilis in men who have sex with men (MSM) in an area of Mallorca, Spain. METHODS: We performed a retrospective analysis of syphilis cases in MSM seen at a hospital in Mallorca between January 2005 and June 2013. RESULTS: Fifty-five cases of syphilis were recorded in MSM during the study period (34.3% of all cases diagnosed), and 74.5% of these patients had human immunodeficiency virus (HIV) coinfection. The two diseases had been diagnosed simultaneously in 70.7% of this population. Patients with HIV coinfection had a median CD4 count of 456cells/µL (range, 29-979 cells/µL). Syphilis was diagnosed clinically in 49.1% of cases and by screening in the remaining 50.9%. The most common form of syphilis was late latent or indeterminate syphilis (41.9% of cases). In the group of men with syphilis, MSM had a higher risk of HIV infection. CONCLUSIONS: A majority of MSM with syphilis had HIV coinfection. HIV screening is therefore essential in this population and could even result in early diagnosis.