Background: Men who have sex with men (MSM) are highly vulnerable to HIV infection, but this population can be particularly difficult to reach in Thailand. This study aimed to estimate the number of MSM in Chiang Mai ...Background: Men who have sex with men (MSM) are highly vulnerable to HIV infection, but this population can be particularly difficult to reach in Thailand. This study aimed to estimate the number of MSM in Chiang Mai Thailand, in order to plan HIV control and prevention. Methods: The total of 348 potential MSM were identified at eight contact locations, including two public parks, two bars, two massage parlors and two pubs in Chiang Mai. Trained 16 research enumerators and 16 enumerators were trained to extend a recruitment of brooches to MSM. The MSMs were captured one week apart. A record was kept of when, where and by whom the invitation was extended and received, and of refusals. The total estimate of MSM was derived from capture-recapture calculation. Results: The total MSM in Chiang Mai Thailand estimated by capture and recapture method was 733 (95%CI = 480 - 948) or the estimate was 7.3% (95%CI = 7.1% - 14.1%). Conclusions: Capture and recapture method can be used to enumerate and provide accurate and reliable estimates of the MSM population in any area, provided that certain conditions are controlled. MSM who are engaged in personal community represent a sizeable population who urgently need to be targeted by HIV and STDs prevention strategies.展开更多
We consider the problem of population estimation using capture-recapture data, where capture probabilities can vary between sampling occasions and behavioural responses. The original model is not identifiable without ...We consider the problem of population estimation using capture-recapture data, where capture probabilities can vary between sampling occasions and behavioural responses. The original model is not identifiable without further restrictions. The novelty of this article is to expand the current research practice by developing a hierarchical Bayesian approach with the assumption that the odds of recapture bears a constant relationship to the odds of initial capture. A real-data example of deer mice population is given to illustrate the proposed method. Three simulation studies are developed to inspect the performance of the proposed Bayesian estimates. Compared with the maximum likelihood estimates discussed in Chao et al. (2000), the hierarchical Bayesian estimate provides reasonably better population estimation with less mean square error;moreover, it is sturdy to underline relationship between the initial and re-capture probabilities. The sensitivity study shows that the proposed Bayesian approach is robust to the choice of hyper-parameters. The third simulation study reveals that both relative bias and relative RMSE approach zero as population size increases. A R-package is developed and used in both data example and simulation.展开更多
Mark-recapture models are extensively used in quantitative population ecology, providing estimates of population vital rates, such as survival, that are difficult to obtain using other methods. Vital rates are commonl...Mark-recapture models are extensively used in quantitative population ecology, providing estimates of population vital rates, such as survival, that are difficult to obtain using other methods. Vital rates are commonly modeled as functions of explanatory covariates, adding considerable flexibility to mark-recapture models, but also increasing the subjectivity and complexity of the modeling process. Consequently, model selection and the evaluation of covariate structure remain critical aspects of mark-recapture modeling. The difficulties involved in model selection are compounded in Cormack-Jolly-Seber models because they are composed of separate sub-models for survival and recapture probabilities, which are conceptualized independently even though their parameters are not statistically independent. The construction of models as combinations of sub-models, together with multiple potential covariates, can lead to a large model set. Although desirable, estimation of the parameters of all models may not be feasible. Strategies to search a model space and base inference on a subset of all models exist and enjoy widespread use. However, even though the methods used to search a model space can be expected to influence parameter estimation, the assessment of covariate importance, and therefore the ecological interpretation of the modeling results, the performance of these strategies has received limited investigation. We present a new strategy for searching the space of a candidate set of Cormack-Jolly-Seber models and explore its performance relative to existing strategies using computer simulation. The new strategy provides an improved assessment of the importance of covariates and covariate combinations used to model survival and recapture probabilities, while requiring only a modest increase in the number of models on which inference is based in comparison to existing techniques.展开更多
Taking into account the effect of electron screening on electron energy and electron capture threshold energy, by using the method of Shell-Model Monte Carlo and random phase approximation theory, we investigate the c...Taking into account the effect of electron screening on electron energy and electron capture threshold energy, by using the method of Shell-Model Monte Carlo and random phase approximation theory, we investigate the capture rates of chromium isotopes with strong electron screening according to the linear response theory screening model. Strong screening rates can decrease by about 40.43% （e.g., for 6Cr at T9 = 3.44, Ye = 0.43）. Our conclusions may be helpful to researches on supernova explosions and related numerical simulation methods.展开更多
文摘Background: Men who have sex with men (MSM) are highly vulnerable to HIV infection, but this population can be particularly difficult to reach in Thailand. This study aimed to estimate the number of MSM in Chiang Mai Thailand, in order to plan HIV control and prevention. Methods: The total of 348 potential MSM were identified at eight contact locations, including two public parks, two bars, two massage parlors and two pubs in Chiang Mai. Trained 16 research enumerators and 16 enumerators were trained to extend a recruitment of brooches to MSM. The MSMs were captured one week apart. A record was kept of when, where and by whom the invitation was extended and received, and of refusals. The total estimate of MSM was derived from capture-recapture calculation. Results: The total MSM in Chiang Mai Thailand estimated by capture and recapture method was 733 (95%CI = 480 - 948) or the estimate was 7.3% (95%CI = 7.1% - 14.1%). Conclusions: Capture and recapture method can be used to enumerate and provide accurate and reliable estimates of the MSM population in any area, provided that certain conditions are controlled. MSM who are engaged in personal community represent a sizeable population who urgently need to be targeted by HIV and STDs prevention strategies.
文摘We consider the problem of population estimation using capture-recapture data, where capture probabilities can vary between sampling occasions and behavioural responses. The original model is not identifiable without further restrictions. The novelty of this article is to expand the current research practice by developing a hierarchical Bayesian approach with the assumption that the odds of recapture bears a constant relationship to the odds of initial capture. A real-data example of deer mice population is given to illustrate the proposed method. Three simulation studies are developed to inspect the performance of the proposed Bayesian estimates. Compared with the maximum likelihood estimates discussed in Chao et al. (2000), the hierarchical Bayesian estimate provides reasonably better population estimation with less mean square error;moreover, it is sturdy to underline relationship between the initial and re-capture probabilities. The sensitivity study shows that the proposed Bayesian approach is robust to the choice of hyper-parameters. The third simulation study reveals that both relative bias and relative RMSE approach zero as population size increases. A R-package is developed and used in both data example and simulation.
文摘Mark-recapture models are extensively used in quantitative population ecology, providing estimates of population vital rates, such as survival, that are difficult to obtain using other methods. Vital rates are commonly modeled as functions of explanatory covariates, adding considerable flexibility to mark-recapture models, but also increasing the subjectivity and complexity of the modeling process. Consequently, model selection and the evaluation of covariate structure remain critical aspects of mark-recapture modeling. The difficulties involved in model selection are compounded in Cormack-Jolly-Seber models because they are composed of separate sub-models for survival and recapture probabilities, which are conceptualized independently even though their parameters are not statistically independent. The construction of models as combinations of sub-models, together with multiple potential covariates, can lead to a large model set. Although desirable, estimation of the parameters of all models may not be feasible. Strategies to search a model space and base inference on a subset of all models exist and enjoy widespread use. However, even though the methods used to search a model space can be expected to influence parameter estimation, the assessment of covariate importance, and therefore the ecological interpretation of the modeling results, the performance of these strategies has received limited investigation. We present a new strategy for searching the space of a candidate set of Cormack-Jolly-Seber models and explore its performance relative to existing strategies using computer simulation. The new strategy provides an improved assessment of the importance of covariates and covariate combinations used to model survival and recapture probabilities, while requiring only a modest increase in the number of models on which inference is based in comparison to existing techniques.
基金supported in part by the National Natural Science Foundation of China (Grant Nos. 11565020 and 10773005)the Counterpart Foundation of Sanya (Grant 2016PT43)+2 种基金the Special Foundation of Science and Technology Cooperation for Advanced Academy and Region of Sanya (Grant 2016YD28)the Scientific Research Starting Foundation for 515 Talented Project of Hainan Tropical Ocean University (Grant RHDRC201701)the Natural Science Foundation of Hainan Province (Grant No. 114012)
文摘Taking into account the effect of electron screening on electron energy and electron capture threshold energy, by using the method of Shell-Model Monte Carlo and random phase approximation theory, we investigate the capture rates of chromium isotopes with strong electron screening according to the linear response theory screening model. Strong screening rates can decrease by about 40.43% （e.g., for 6Cr at T9 = 3.44, Ye = 0.43）. Our conclusions may be helpful to researches on supernova explosions and related numerical simulation methods.
