Respondent driven sampling (RDS) is a relatively new method to sample hard-to-reach populations. Until this study, female sex workers (FSWs) in Vietnam were sampled using a variety of methods, including time location sampling (TLS), which may not access the more hidden types of FSWs. This paper presents an analysis from an HIV biological and behavioral surveillance survey to assess the feasibility and effectiveness of RDS to sample FSWs, to determine if RDS can reach otherwise inaccessible FSWs in Vietnam and to compare RDS findings of HIV risk factors with a theoretical TLS. Through face-to-face interviews with FSWs in Ho Chi Minh City (HCMC) and Hai Phong (HP), data were collected about the venues where they most often solicit their clients. These data were used to create three variables to assess whether FSWs solicit their clients in locations that are visible, semi-visible and nonvisible. For this analysis, the visible group simulates a sample captured using TLS. Survey results in HIV prevalence and related risk factors and service utilization, adjusted for sampling methodology, were compared across each of the three FSW visibility groups to assess potential bias in TLS relative to RDS. The number of selfreported visible FSWs (HCMC: n = 311; HP: n = 162) was much larger than those of the semi-visible (HCMC: n = 65; HP: n = 43) and non-visible (HCMC: n = 37; HP: n = 10) FSWs in HCMC and HP. Non-visible FSWs in both cities were just as likely as visible and semi-visible FSWs to be HIV positive (HCMC: visible 14.5%, semi-visible 13.8%, non-visible 13.5%, p value = 0.982; HP: visible 35.2%, semi-visible 30.2%, non-visible 30.0%, p value = 0.801), to practice behaviors that put them at risk for contracting and transmitting HIV (injecting drug use-HCMC: visible 13.8%, semivisible 12.3%, non-visible 5.4%, p value = 0.347; HP: visible 38.9%, semi-visible 23.3%, non-visible 30.0%, p value = 0.378, to have no condom use in the past month -HCMC only: visible 52.7%, semi-visible 63.1%, non-visible 48.6%, p value = 0.249) and to have symptoms of a sexually transmitted infection (STI) in the past year (HCMC: visible 16.1%, semi-visible 12.3%, non-visible 16.2%, p value = 0.742; HP: visible 13.6%, semi-visible 18.6%, non-visible 20.0%, p value = 0.640). There was a difference found among the visible, semi-visible and non-visible groups in HP for no past month condom use (visible 53.1%, semi-visible 79.1%, non-visible 60.0%, p value = 0.009). This study found that RDS was successful at recruiting hidden types of FSWs in Vietnam. Past reports of FSWs in Vietnam have assessed the more visible FSWs

Photocatalytic materials for photocatalysis is recently proposed as a promising strategy to address environmental remediation. Metal-free graphitic carbon nitride (g-C 3 N 4 ), is an emerging photocatalyst in sulfate radical based advanced oxidation processes. The solar-driven electronic excitations in g-C 3 N 4 are capable of peroxo (O-O) bond dissociation in peroxymonosulfate/peroxydisulfate (PMS/PDS) and oxidants to generate reactive free radicals, namely SO 4•− and OH • in addition to O 2 •− radical. The synergistic mechanism of g-C 3 N 4 mediated PMS/ PDS photocatalytic activation, could ensure the generation of OH • radicals to overcome the low reductive potential of g-C 3 N 4 and fastens the degradation reaction rate. This article reviews recent work on heterojunction formation (type-II heterojunction and direct Z-scheme) to achieve the bandgap for extended visible light absorption and improved charge carrier separation for efficient photocatalytic efficiency. Focus is placed on the fundamental mechanistic routes followed for PMS/PDS photocatalytic activation over g-C 3 N 4 -based photocatalysts. A particular emphasis is given to the factors influencing the PMS/PDS photocatalytic activation mechanism and the contribution of SO 4 •− and OH • radicals that are not thoroughly investigated and require further studies. Concluding perspectives on the challenges and opportunities to design highly efficient persulfateactivated g-C 3 N 4 based photocatalysts toward environmental remediation are also intensively highlighted.

Vietnam has had varying success over the past decade with its pesticides policy. Some of the most toxic pesticides have been banned from the market. But while many countries have successfully decreased agricultural pesticide use per hectare, this has not (yet) happened in Vietnam. Due to insufficient pesticide management capacity of the Vietnamese government, pesticide types and quantities registered and distributed on the market have substantially increased in Vietnam over the last 10 years. A 10-year monitoring programme at farm level showed that pesticide use follows the increasing pesticide availability on the market, and many toxic and illegal pesticides are still being used. In an agricultural country dominated by millions of small-scale farmers and with limited state capacity for control at farm level, reduction of the use of the most toxic pesticides can best be achieved by more effective pesticide market control through stricter and more effective state regulations and implementation, aimed at eliminating illegal, low quality and counterfeit pesticides from the market. But even then, better state and private extension services, and greater state capacity for control and enforcement remain essential in enabling farmers to make better decisions about pesticide use.

This study examined predictors of HIV testing, successful condom negotiation with clients, and self-reported sexually transmitted infections (STIs) among Vietnamese female sex workers (FSW). Data were collected by using face-to-face interviews from a community sample of 610 FSW from Nha Trang city during October-December, 2000. Having had an HIV test was associated with having spent time in a rehabilitation center. Consistently successful negotiation of condom use occurred most among FSW who had few clients, understood how HIV was not transmitted, and had not reported ever having any symptoms of STIs. Migration to Nha Trang for sex work was a risk factor for an STI diagnosis; successful negotiation of condom use had a protective effect. Our results suggest the need for voluntary HIV counseling and testing, further promotion of condom use among FSW populations, and better use of rehabilitation sites to promote HIV prevention.

Antibiotics are chemical compounds that are used to kill or prevent bacterial growth. They are used in different fields, such as the medical field, agriculture, and veterinary. Antibiotics end up in wastewater, which causes the threat of developing antibacterial resistance; therefore, antibiotics must be eliminated from wastewater. Different conventional elimination methods are limited due to their high cost and effort, or incomplete elimination. Semiconductor-assisted photocatalysis arises as an effective elimination method for different organic wastes including antibiotics. A variety of semiconducting materials were tested to eliminate antibiotics from wastewater; nevertheless, research is still ongoing due to some limitations. This review summarizes the recent studies regarding semiconducting material modifications for antibiotic degradation using visible light irradiation.