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Individual tree detection for urban forests in subtropical environments remains a great challenge due to the various types of forest structures, high canopy closures, and the mixture of evergreen and deciduous broadleaved trees. Existing treetop detection methods based on the canopy-height model (CHM) from UAV images cannot resolve commission errors in heterogeneous urban forests with multiple trunks or strong lateral branches. In this study, we improved the traditional local-maximum (LM) algorithm using a dual Gaussian filter, variable window size, and local normalized correlation coefficient (NCC). Specifically, we adapted a crown model of maximum/minimum tree-crown radii and an angle strategy to detect treetops. We then removed and merged the pending tree vertices. Our results showed that our improved LM algorithm had an average user accuracy (UA) of 87.3% (SD± 4.6), an average producer accuracy (PA) of 82.8% (SD± 4.1), and an overall accuracy of 93.3% (SD± 3.9) for sample plots with canopy closures less than 0.5. As for the sample plots with canopy closures from 0.5 to 1, the accuracies were 78.6% (SD± 31.5), 73.8% (SD± 10.3), and 68.1% (SD± 12.7), respectively. The tree-height estimation accuracy reached more than 0.96, with an average RMSE of 0.61 m. Our results show that the UAV-image-derived CHM can be used to accurately detect individual trees in mixed forests in subtropical cities like Shanghai, China, to provide vital tree-structure parameters for precise and sustainable forest management. [ABSTRACT FROM AUTHOR]

The impervious surface area (ISA) is a key indicator of urbanization, which brings out serious adverse environmental and ecological consequences. The ISA is often estimated from remotely sensed data via spectral mixture analysis (SMA). However, accurate extraction of ISA using SMA is compromised by two major factors, endmember spectral variability and plant phenology. This study developed a novel approach that incorporates phenology with Fisher transformation into a conventional linear spectral mixture analysis (PF-LSMA) to address these challenges. Four endmembers, high albedo, low albedo, evergreen vegetation, and seasonally exposed soil (H-L-EV-SS) were identified for PF-LSMA, considering the phenological characteristic of Shanghai. Our study demonstrated that the PF-LSMA effectively reduced the within-endmember spectral signature variation and accounted for the endmember phenology effects, and thus well-discriminated impervious surface from seasonally exposed soil, enhancing the accuracy of ISA extraction. The ISA fraction map produced by PF-LSMA (RMSE = 0.1112) outperforms the single-date image Fisher transformed unmixing method (F-LSMA) (RMSE = 0.1327) and the other existing major global ISA products. The PF-LSMA was implemented on the Google Earth Engine platform and thus can be easily adapted to extract ISA in other places with similar climate conditions. [ABSTRACT FROM AUTHOR]

As Volatile Organic Compounds (VOCs) are one of the precursors of ozone, their distribution and variable concentrations are highly related to local ozone pollution control. In this study, we obtained vertical profiles of VOCs in Shanghai's Jinshan district on 8 September and 9 September in 2016 to investigate their distribution and impact on local atmospheric oxidation in the near surface layer. Vertical samples were collected from heights between 50 m and 400 m by summa canisters using an unmanned aerial vehicle (UAV). Concentrations of VOCs (VOCs refers to the 52 species measured in this study) varied minimally below 200 m, and decreased by 21.2% from 100 m to 400 m. The concentrations of VOCs above 200 m decreased significantly in comparison to those below 200 m. The proportions of alkanes and aromatics increased from 55.2% and 30.5% to 57.3% and 33.0%, respectively. Additionally, the proportion of alkenes decreased from 13.2% to 8.4%. Toluene and m/p-xylene were the key species in the formation of SOA and ozone. Principal component analysis (PCA) revealed that the VOCs measured in this study mainly originated from industrial emissions. [ABSTRACT FROM AUTHOR]

Background: Hepatitis B virus (HBV) flare can occur in HBV patients either naïve or have interruption to treatment. Bacterial infection (BI) is a common complication of cirrhosis with potential severe outcomes. We aimed to assess the impact of HBV flare on the outcome of patients with HBV‐related decompensated cirrhosis and BI. Methods: This was a retrospective study from 2 tertiary academic hospitals in Shanghai, China of HBV patients admitted with or developed BI during admission. The characteristics of BI, prevalence of HBV flare, its impact on organ failure, acute‐on‐chronic liver failure (ACLF) and 90‐day survival were evaluated. Results: A total of 360 hospitalized patients (median age: 50 years, male: 79%, BI: at admission: 58.6%; during admission: 41.4%) were included. All patients including those with HBV flare (21%) received antiviral therapy after admission. Patients with HBV flare and BI had significantly higher percentage of liver (93.3% vs 48.8%), coagulation (64.0% vs 39.6%), cerebral (40.0% vs 21.8%) (all P < 0.01), and kidney failure (38.7% vs 26.3%, P < 0.05) compared to BI alone, associated with a higher risk of developing ACLF with a subdistribution hazard ratio (sHR) of 2.23 (95% confidence interval [CI]: 1.68‐2.96). Multivariate analysis showed that ACLF development was the strongest risk factor for 90‐day mortality (sHR, 95%CI: 7.36, 4.12‐13.16). Conclusions: In HBV‐related decompensated cirrhosis patients admitted with BI, HBV flare increased the risk of additional organ failures and ACLF, raising the risk of 90‐day mortality by seven‐fold. Optimization of HBV treatment in these patients should minimize the risk of HBV flare with improved outcomes. [ABSTRACT FROM AUTHOR]

Due to the development of industrialization and urbanization, secondary pollution is becoming increasingly serious in the Yangtze River Delta. Volatile organic compounds (VOCs) are key precursors of the near-surface ozone, secondary organic aerosol (SOA), and other secondary pollutants. In this study, we chose a serious ozone pollution period (01 May–31 July 2017) in Jinshan, which is a petrochemical and industrial area in Shanghai. We explored the VOCs distribution characteristics and contribution to secondary pollutants via constructing a regional network based on wind patterns. We determined that dense pollutants were accumulated at adjacent sites under local circulation (LC), and pollution from petrochemical discharge was more serious than industry for all sites under southeast (SE) wind. We also found that cyclopentane, o-xylene, m/p-xylene, 1-3-butadiene, and 1-hexene were priority-controlled species as they were most vital to form secondary pollutants. This study proves that regional network analysis can be successfully applied to explore pollution characteristics and regional secondary pollutants formation. [ABSTRACT FROM AUTHOR]