Four-channel joint-polarization-frequency-multiplexing encryption meta-hologram based on dual-band polarization multiplexing meta-atoms.

Holography is an advanced imaging technology where image information can be reconstructed without a lens. Recently, multiplexing techniques have been widely adapted to realize multiple holographic images or functionalities in a meta-hologram. In this work, a reflective four-channel meta-hologram is proposed to further increase the channel capacity by simultaneously implementing frequency and polarization multiplexing. Compared to the single multiplexing technique, the number of channels achieves a multiplicative growth of the two multiplexing techniques, as well as allowing meta-devices to possess cryptographic characteristics. Specifically, spin-selective functionalities for circular polarizations can be achieved at lower frequency, while different functionalities can be obtained at higher frequency under different linearly polarized incidences. As an illustrative example, a four-channel joint-polarization-frequency-multiplexing meta-hologram is designed, fabricated, and characterized. The measured results agree well with the numerically calculated and full-wave simulated ones, which provides the proposed method with great potential in numerous opportunities such as multi-channel imaging and information encryption technology.

Dual-channel geometric meta-holograms with complex-amplitude modulation based on bi-spectral single-substrate-layer meta-atoms.

Metasurfaces with complex-amplitude modulation are superior in power regulation and hologram imaging resolution compared with those with phase-only modulation. Nevertheless, a single-cell metasurface with multi-band independent phase and amplitude controls is still a great challenge for the circularly polarized incidences. In this work, we propose and design a single-substrate-layer single-cell metasurface with independent complex-amplitude modulations at two discrete frequencies. Based on this emerging technique, a bi-spectral meta-hologram is designed and verified by both full-wave simulations and experiments, which could reconstruct two Chinese characters at the imaging plane at two frequencies. The proposed method shows great potential in multifunctional meta-devices with enhanced performance.

Broadband high-efficiency polarization-encoded meta-holograms based on 3-bit spin-decoupled reflective meta-atoms.

Metasurfaces are engineered planar surfaces consisting of arrays of resonators for tailoring the electromagnetic wavefronts in a desirable way. However, the spin-locked issue of the geometric metasurfaces hinders simultaneous manipulation of both spins. In this work, a spin-decoupled information metasurface composed of simple C-shaped resonators is proposed to realize two different information channels under the orthogonal circularly polarized (CP) incidences. Based on the encoded digit '0' or '1', the diffusion scattering or a holographic image could be realized under the CP excitation in a broadband frequency range from 9 to 12 GHz. As an illustrative example, a 3-bit polarization-encoded meta-hologram is designed, fabricated, and characterized. The measured results agree very well with the numerical results, which gives the proposed method great potential in numerous applications such as holographic displays and information processing.

Sexual and reproductive health correlates of polysubstance use among female adolescents who sell sex in the southwest of China.

BACKGROUND: Substance use and adverse sexual and reproductive health (SRH) outcomes continue to be significant threats to female adolescents' health and wellbeing, particularly to these marginalized subpopulations. Our research aimed to tackle knowledge gaps regarding the prevalence of concurrent substance use including alcohol, tobacco, illicit drug among Chinese adolescent female sex workers (AFSWs), while to assess the correlates between substance use and SRH risks; the needs for comprehensive SRH services were also examined in this study. METHODS: A cross-sectional study enrolled 310 AFSWs aged 15-19 years by using cluster sampling method in Kunming, China. Descriptive analysis was employed to characterize the participants who were regular-alcohol users, regular-tobacco users, illicit drug users and polysubstance users. Multivariable logistic regression analysis was performed to detect the SRH correlates of regular-alcohol use, regular-tobacco use, illicit drugs and polysubstance use respectively. RESULTS: There is a high prevalence of regular-alcohol drinking (83%, 257/310) among AFSWs, with 44% (136/310) smoking cigarettes regularly and 9% using illicit drug (27/310) in the past year. In multivariate analysis, AFSWs who had middle and high school education, had higher monthly income, experienced of sexual and gender based violence (SGBV) and prior abortion, and regular-tobacco smoking were associated with increased odds of regular-alcohol drinking; engaging in unprotected sex while drunk, having STIs symptoms and using illicit drugs were significantly associated with regular-tobacco smoking; while AFSWs who had an illicit drug using- intimate partner, experienced forced sexual initiation, accessed unsafe medical providers for STIs treatment were associate with increased odds of illicit drug use. Moreover, 35% (105/298) AFSWs sought unsafe medical care for STIs treatment, or no treatment at all, among them, majority were using polysubstance (87%; 91/105). CONCLUSIONS: Our findings reveal combined threats of substance use to AFSWs' SRH and wellbeing in China, this study emphasises that the coordinated efforts are needed to integrate SRH promotion and harm reduction service across sectors, and not only fragmented measures. An effective response should include an agreed framework, indicators and targets supported by political will, solid leadership and policy reform to deal with AFSWs' overlapping vulnerabilities in a systematic way.

Full control of dual-band vortex beams using a high-efficiency single-layer bi-spectral 2-bit coding metasurface.

Vortex beams (VBs) carrying orbital angular moment (OAM) modes have been proven to be promising resources for increasing communication capacity. Although considerable attention has been paid on metasurface-based VB generators due to the unprecedented advantages of metasurface, most applications are usually limited at a single band with a fixed OAM mode. In this work, an emerging dual-band reflection-type coding metasurface is proposed to mitigate these issues by newly engineered meta-atoms, which could achieve independent 2-bit phase modulations at two frequency bands. The proposed coding metasurface could efficiently realize and fully control dual-band VBs carrying frequency selective OAM modes under the linearly polarized incidence. As the first illustrative example, a dual-band VB generator with normal beam direction is fabricated and characterized at two widely used communication bands (Ku and Ka bands). Moreover, by encoding proper coding sequences, versatile beams carrying frequency selective OAM modes can be achieved. Therefore, by adding a gradient phase sequence to the first VB generator, the second one is designed to steer the generated beams to a preset direction, which could enable diverse scenarios. The measurement results of both VB generators agree very well with the numerical ones, validating the full control capability of the proposed approach.

[Cost-effectiveness of schistosomiasis monitoring in Rugao City from 2001 to 2010].

OBJECTIVE: To understand the cost-effectiveness of schistosomiasis monitoring in Rugao City, a schistosomiasis transmission interrupted area, so as to provide the evidence for improving schistosomiasis control. METHODS: According to the national and Jiangsu provincial working scheme of schistosomiasis monitoring and consolidation, the data of schistosomiasis monitoring were collected and the cost-effectiveness was analyzed in Rugao City from 2001 to 2010. RESULTS: During 10 years, the financial input for Oncomelania snail survey was 11.694 8 million Yuan, accounting for 92.9% of the total monitoring cost. In 6 years, a few remaining snails with low density and small area were detected, and per 100 m2 snail area spent 76 788 Yuan averagely. Totally 23 694 people were investigated with serological tests and 15 persons were positive, but no person was positive in feces tests, and the accumulative total cost was 410 350 Yuan. The average cost for detection of 1 person was 17.32 Yuan. Totally 454 heads of cattle were investigated but there was no positive, and the accumulative total cost was 18 716 Yuan and the average cost of detection of 1 case was 41.22 Yuan. The health education during the 10 years spent 172 500 Yuan, only accounting for 1.4% of the total monitoring funds. The awareness rate of schistosomiasis control knowledge and the health behavior formation rate increased year by year, and they were increased by 2.48 times and 2.71 times respectively from 2001 to 2010. CONCLUSIONS: In schistosomiasis transmission interrupted areas and areas with Oncomelania snails but without schistosomiasis, the monitoring index and monitoring method need to be studied and adjusted. Health education has a good cost-effectiveness.