A machine learning method to estimate PM2.5 concentrations across China with remote sensing, meteorological and land use information.

BACKGROUND: Machine learning algorithms have very high predictive ability. However, no study has used machine learning to estimate historical concentrations of PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5 µm) at daily time scale in China at a national level. OBJECTIVES: To estimate daily concentrations of PM2.5 across China during 2005-2016. METHODS: Daily ground-level PM2.5 data were obtained from 1479 stations across China during 2014-2016. Data on aerosol optical depth (AOD), meteorological conditions and other predictors were downloaded. A random forests model (non-parametric machine learning algorithms) and two traditional regression models were developed to estimate ground-level PM2.5 concentrations. The best-fit model was then utilized to estimate the daily concentrations of PM2.5 across China with a resolution of 0.1° (≈10 km) during 2005-2016. RESULTS: The daily random forests model showed much higher predictive accuracy than the other two traditional regression models, explaining the majority of spatial variability in daily PM2.5 [10-fold cross-validation (CV) R2 = 83%, root mean squared prediction error (RMSE) = 28.1 µg/m3]. At the monthly and annual time-scale, the explained variability of average PM2.5 increased up to 86% (RMSE = 10.7 µg/m3 and 6.9 µg/m3, respectively). CONCLUSIONS: Taking advantage of a novel application of modeling framework and the most recent ground-level PM2.5 observations, the machine learning method showed higher predictive ability than previous studies. CAPSULE: Random forests approach can be used to estimate historical exposure to PM2.5 in China with high accuracy.

Estimating spatiotemporal distribution of PM1 concentrations in China with satellite remote sensing, meteorology, and land use information.

BACKGROUND: PM1 might be more hazardous than PM2.5 (particulate matter with an aerodynamic diameter ≤ 1 µm and ≤2.5 µm, respectively). However, studies on PM1 concentrations and its health effects are limited due to a lack of PM1 monitoring data. OBJECTIVES: To estimate spatial and temporal variations of PM1 concentrations in China during 2005-2014 using satellite remote sensing, meteorology, and land use information. METHODS: Two types of Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6 aerosol optical depth (AOD) data, Dark Target (DT) and Deep Blue (DB), were combined. Generalised additive model (GAM) was developed to link ground-monitored PM1 data with AOD data and other spatial and temporal predictors (e.g., urban cover, forest cover and calendar month). A 10-fold cross-validation was performed to assess the predictive ability. RESULTS: The results of 10-fold cross-validation showed R2 and Root Mean Squared Error (RMSE) for monthly prediction were 71% and 13.0 µg/m3, respectively. For seasonal prediction, the R2 and RMSE were 77% and 11.4 µg/m3, respectively. The predicted annual mean concentration of PM1 across China was 26.9 µg/m3. The PM1 level was highest in winter while lowest in summer. Generally, the PM1 levels in entire China did not substantially change during the past decade. Regarding local heavy polluted regions, PM1 levels increased substantially in the South-Western Hebei and Beijing-Tianjin region. CONCLUSIONS: GAM with satellite-retrieved AOD, meteorology, and land use information has high predictive ability to estimate ground-level PM1. Ambient PM1 reached high levels in China during the past decade. The estimated results can be applied to evaluate the health effects of PM1.

Effects of lamivudine on replication of hepatitis B virus in HIV-infected men.

BACKGROUND: Therapy for hepatitis B virus (HBV) infection is still unsatisfactory, particularly in patients who are co-infected with the human immunodeficiency virus (HIV). Lamivudine, a retroviral inhibitor, has been shown to have activity against HBV replication in vitro, in animal models, and in studies of immunocompetent persons. OBJECTIVE: To assess the efficacy of lamivudine in inhibiting HBV replication during a 12-month period in patients with both HBV and HIV infection. DESIGN: Prospective, open study. SETTING: University hospital. PATIENTS: 40 consecutive patients (39 men and 1 woman) infected with both HIV and HBV. All had progressive HIV disease; were refractory to or unable to tolerate therapies other than lamivudine; and received lamlvudine, 600 mg/d or 600 mg/d followed by 300 mg/d, as therapy for HIV disease. MEASUREMENTS: Serum concentrations of HBV DNA were assessed every 2 months by using molecular hybridization. Polymerase chain reaction (PCR) for HBV DNA was done at baseline and was done at months 2, 6, and 12 only if the HBV DNA concentration was less than 5 pg/mL. RESULTS: Two groups were retrospectively identified at baseline: patients with high HBV replication (serum HBV DNA concentrations > 5 pg/mL) (n = 30) and patients with low HBV replication (serum HBV DNA concentrations < 5 pg/mL) (n = 10). After 12 months of treatment, 26 of 27 patients (96.3% [95% Cl, 81% to 99.9%]) who had had high HBV replication at baseline had serum HBV DNA concentrations less than 5 pg/mL. However, PCR could still detect HBV DNA in serum in 11.5% (Cl, 2% to 30%) of these patients. Among patients who had had low HBV replication at baseline, the results of PCR for serum HBV DNA became negative in the 6 patients who had had a positive result on PCR at baseline. No serious adverse events occurred during treatment. CONCLUSION: Although this study was not a randomized, blinded trial, it suggests that lamivudine is active against.

Outcomes of the Minnesota Smoking Prevention Program.

1,320 seventh-graders from a large midwestern public school district participated in a 6-hr. session of the Minnesota Smoking Prevention Program. Responses from students of the four trained and three control junior high schools indicated that the Minnesota program did not prevent students from becoming new users but rather encouraged those who were regular users to quit.

The detergent scrub method for quantitative determination of Malassezia furfur on chest and back skin: comparative evaluation of three different media.

The quantitative determination of Malassezia furfur on normal human skin has been considered as difficult until recently. During the last years, however, several different media have been described which facilitate the quantification of M. furfur. As the efficacy of these media is still controversial, three different media were compared analyzing the chest and back of 20 healthy young adult volunteers. The highest counts of colony-forming units (CFU) per cm2 were found using a medium containing whole fat cow's milk as a major ingredient. At the chest the mean count read was 259, at the back 322. The corresponding figures related to other media were markedly lower (P less than 0.001). Hence, the use of the milk-containing medium for cultivation of M. furfur seems advisable for therapeutic trials.