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- Bengtsson, Linus, et al.
(författare)
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Implementation of Web-Based Respondent-Driven Sampling among Men Who Have Sex with Men in Vietnam
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:11, s. e49417-
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Lack of representative data about hidden groups, like men who have sex with men (MSM), hinders an evidence-based response to the HIV epidemics. Respondent-driven sampling (RDS) was developed to overcome sampling challenges in studies of populations like MSM for which sampling frames are absent. Internet-based RDS (webRDS) can potentially circumvent limitations of the original RDS method. We aimed to implement and evaluate webRDS among a hidden population. Methods and Design: criteria were men, aged 18 and above, who had ever had sex with another man and were living in Vietnam. Participants were invited by an MSM friend, logged in, and answered a survey. Participants could recruit up to four MSM friends. We evaluated the system by its success in generating sustained recruitment and the degree to which the sample compositions stabilized with increasing sample size. Results: Twenty starting participants generated 676 participants over 24 recruitment waves. Analyses did not show evidence of bias due to ineligible participation. Estimated mean age was 22 years and 82% came from the two large metropolitan areas. 32 out of 63 provinces were represented. The median number of sexual partners during the last six months was two. The sample composition stabilized well for 16 out of 17 variables. Conclusion: Results indicate that webRDS could be implemented at a low cost among Internet-using MSM in Vietnam. WebRDS may be a promising method for sampling of Internet-using MSM and other hidden groups.
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| 3. |
- Tran, Quoc Cuong, et al.
(författare)
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Novel Ensemble Landslide Predictive Models Based on the Hyperpipes Algorithm : A Case Study in the Nam Dam Commune, Vietnam
- 2020
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Ingår i: Applied Sciences. - Switzerland : MDPI. - 2076-3417. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- Development of landslide predictive models with strong prediction power has become a major focus of many researchers. This study describes the first application of the Hyperpipes (HP) algorithm for the development of the five novel ensemble models that combine the HP algorithm and the AdaBoost (AB), Bagging (B), Dagging, Decorate, and Real AdaBoost (RAB) ensemble techniques for mapping the spatial variability of landslide susceptibility in the Nam Dan commune, Ha Giang province, Vietnam. Information on 76 historical landslides and ten geo-environmental factors (slope degree, slope aspect, elevation, topographic wetness index, curvature, weathering crust, geology, river density, fault density, and distance from roads) were used for the construction of the training and validation datasets that are the prerequisites for building and testing the proposed models. Using different performance metrics (i.e., the area under the receiver operating characteristic curve (AUC), negative predictive value, positive predictive value, accuracy, sensitivity, specificity, root mean square error, and Kappa), we verified the proficiency of all five ensemble learning techniques in increasing the fitness and predictive powers of the base HP model. Based on the AUC values derived from the models, the ensemble ABHP model that yielded an AUC value of 0.922 was identified as the most efficient model for mapping the landslide susceptibility in the Nam Dan commune, followed by RABHP (AUC = 0.919), BHP (AUC = 0.909), Dagging-HP (AUC = 0.897), Decorate-HP (AUC = 0.865), and the single HP model (AUC = 0.856), respectively. The novel ensemble models proposed for the Nam Dan commune and the resultant susceptibility maps can aid land-use planners in the development of efficient mitigation strategies in response to destructive landslides.
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| 4. |
- Tokarski, Antek K., et al.
(författare)
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Active faulting and seismic hazard in the Outer Western Carpathians (Polish Galicia) : Evidence from fractured Quaternary gravels
- 2020
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141. ; 141
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Tidskriftsartikel (refereegranskat)abstract
- This report opens a new window on Quaternary tectonics of the Outer Western Carpathians. We discuss results of fractured clasts analysis in Quaternary fluvial gravels within a 4.500 km2 large area comprising a part of the Outer Carpathians including Nowy Sącz Intramontane Basin (NSIB) as well as in the innermost part of the Carpathian Foredeep. Quaternary gravels bearing fractured clasts are widespread within the area, we observed them in 180 exposures. In the Carpathian Foredeep and in the Outer Carpathians excluding the NSIB, the exposures of gravels bearing fractured clasts are located largely close to (<2 km) all major overthrusts and close to (<0.75 km) the cross-fold faults of the Skawa River Fault System (SRFS). The clast-cutting fractures are mostly joints attesting to widespread Quaternary tectonic activity of the faults. Moreover, the density of occurrence of gravels bearing fractured clasts is considerably higher within the NSIB than in other parts of the study area. Furthermore, our results shed new light on the seismic hazard in the study area. In our interpretation, the clast-cutting fractures are damage resulting from coseismic rupturing of underlying bedrock faults or from regional seismic shaking. We conclude that in the study area the seismic hazard posed by natural seismicity can matter only in case of planning there the erection of critical structures like nuclear power plants, nuclear waste repositories or gas storage facilities. On the other hand, we infer that the appreciable seismic hazard is near the cross-fold faults of the SRFS, due to the location of Świnna Poręba Artificial Lake there, which can lead to triggering significant seismicity in the area. Furthermore, we suggest that fractured clasts can serve worldwide as providers of information on paleoseismicity and can be useful for mapping blind faults.
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