Application of a Line Laser Scanner for Bed Form Tracking in a Laboratory Flume

A new measurement method for continuous detection of bed forms in movable bed laboratory experiments is presented and tested. The device consists of a line laser coupled to a 3-D camera, which makes use of triangulation. This allows to measure bed forms during morphodynamic experiments, without removing the water from the flume. A correction is applied for the effect of laser refraction at the air-water interface. We conclude that the absolute measurement error increases with increasing flow velocity, its standard deviation increases with water depth and flow velocity, and the percentage of missing values increases with water depth. Although 71% of the data is lost in a pilot moving bed experiment with sand, still high agreement between flowing water and dry bed measurements is found when a robust LOcally weighted regrESSion (LOESS) procedure is applied. This is promising for bed form tracking applications in laboratory experiments, especially when lightweight sediments like polystyrene are used, which require smaller flow velocities to achieve dynamic similarity to the prototype. This is confirmed in a moving bed experiment with polystyrene

Application of a line laser scanner for bed form tracking in a laboratory flume

In order to develop a measurement method that is fully non-invasive and able to capture the short timescale bed-form dynamics, tests have been performed with single-beam (Visconti et al., 2012) and multi-beam (Friedrichs and Graf, 2006; Peña González et al., 2007) laser scanners. However, these studies have only focused on a laser beam travelling vertically downward up till now. In the present study the full range of beams emitted by a multi-beam laser is taken into account, and corrections are quantified and performed in order to reduce the errors due to e.g. refraction. The applied corrections are used for measuring dunes and alternate bars under flowing water conditions

Map merging of multi-robot SLAM using reinforcement learning

Using 'Simultaneous Localization and Mapping' (SLAM), mobile robots can become truly autonomous in the exploration of their environment. However, once these environments becomes too large, Multi-Robot SLAM becomes a requirement. This paper will outline how a mobile robot should decide when best to merge its maps with another robot's upon rendezvous, as opposed to doing so immediately. This decision will be based on the current status of the mapping particle filters and the current status of the environment. Using Reinforcement Learning, a model can be established and then trained upon to determine a policy capable of deciding when best to merge. This will allow the robot to incur less error during a merge compared to simply merging immediately. This policy is trained and validated using simulated mobile robot datasets

Assessment of herd effects among women and heterosexual men after girls-only HPV16/18 vaccination in the Netherlands:A repeated cross-sectional study

Data on the impact of human papillomavirus (HPV) vaccination on the population HPV prevalence are largely obtained from women. We assessed the impact of the girls-only HPV16/18 vaccination program in the Netherlands that started in 2009, on trends in HPV prevalence among women and heterosexual men, using data from the PASSYON study. In this cross-sectional study, the HPV prevalence among 16- to 24-year-old visitors to sexually transmitted infection clinics was assessed in 2009, 2011, 2013, and 2015. We compared the genital postvaccination HPV prevalence with the prevaccination prevalence (2009) using Poisson GEE models. In total, we included 4,996 women and 1,901 heterosexual men. The percentage of women who reported to be vaccinated increased from 2.3% in 2009 to 37% in 2015. Among all women, the HPV16/18 prevalence decreased from 23% prevaccination to 15% in 2015 (adjusted prevalence ratio [aPR] 0.62, p(trend) <0.01). Among heterosexual men, the HPV16/18 prevalence decreased from 17% prevaccination to 11% in 2015 (aPR 0.52, p(trend) <0.01). Of the heterosexual men with a steady partner, HPV16/18 prevalence was lower among those whose steady partner had been vaccine-eligible in the national immunization program (aPR 0.13). Among unvaccinated women, the HPV16/18 prevalence in 2015 was not different from prevaccination. The decreasing HPV16/18 prevalence among heterosexual men and the reduced HPV16/18 prevalence among heterosexual men with a vaccine-eligible steady partner strongly suggests herd protection from girls-only vaccination. Absence of notable herd effects among unvaccinated women 6 years postvaccination may be due to the moderate vaccine uptake among girls in the Netherlands. What's new? Human papillomavirus (HPV) is a sexually transmitted virus that plays a causal role in the development of anogenital and oropharyngeal cancers in both men and women. The population-level impact of HPV vaccination programs on the HPV prevalence has however mainly been studied in women. This study shows decreasing trends in the HPV16 and HPV18 prevalence among both women and heterosexual men after the introduction of a girls-only HPV16/18 vaccination program in the Netherlands. The findings provide compelling evidence for herd protection in men. Because HPV16/18 are the most oncogenic types, HPV-related cancers are expected to decline in both sexes after girls-only HPV vaccination

No evidence for cross-protection of the HPV-16/18 vaccine against HPV-6/11 positivity in female STI clinic visitors

Objectives Data from a vaccine trial and from post-vaccine surveillance in the United Kingdom have suggested that the bivalent HPV-16/18 vaccine offers cross-protection against HPV-6/11 and protection against anogenital warts (AGW). We studied the effect of the bivalent vaccine on genital HPV-6/11 positivity and AGW in the Netherlands. Methods We included all vaccine-eligible women from the PASSYON study, a biennial cross-sectional study among 16- to 24-year-old sexually transmitted infection (STI) clinic attendants. Vaginal self-swabs were analyzed for type specific HPV and AGW were diagnosed at the STI-clinic. Prevalence of HPV-6 and/or HPV-11 and AGW were compared between self-reported vaccinated and unvaccinated women by log-binomial regression analysis, adjusted for demographics and risk behavior. Results Of the 1198 women included, 56% reported to be vaccinated at least once. Relative to unvaccinated women, the adjusted prevalence ratio (PR) for HPV-6/11 was 1.03 (95% confidence interval [CI] 0.74–1.43) for women vaccinated at least once. The crude PR for AGW was 0.67 (95% CI 0.22–2.07) for women vaccinated at least once. Adjustment did not change these results. Conclusions We observed no cross-protective effect of the bivalent vaccine on genital HPV-6/11 positivity and a non-significant partially protective effect on AGW