Field assessment of straw pellet combustion in improved heating stoves in rural Northeast China.

Straw pellets are widely promoted and expected to be a cleaner alternative fuel to unprocessed crop residues and raw coal in rural China. However, the effectiveness of these dissemination programs is not well evaluated. In this field study, emission characteristics of burning straw pellets, raw coal, and unprocessed corn cobs in heating stoves were investigated in a pilot village in Northeast China. Emission measurements covering the whole combustion cycle (ignition, flaming, and smoldering phases) shows the promotion of improved heating stoves and straw pellets could reduce pollutant emissions (e.g., SO2 and CO), but increase NOX and PM2.5 emissions compared to the initial stove-fuel use pattern in the studied area. There is a significant variance in emission characteristics between different combustion phases. The normalized emission concentrations of the different stove-fuel combinations were higher than the limits in the Chinese national standard for heating stoves, indicating that the standard is not met for real-world emissions. Coal consumption was lower than official data. Household surveys were conducted to identify the barriers to fuel and stove access associated with existing promotion strategies, management, and policies. The pilot program was of the typical "subsidy-and-policy-dependence" pattern and was unlikely to be implemented on a large scale. Technological innovation, operational optimization, and proper policies considering the local socioeconomic factors are needed to sustain the promotion of biomass straw pellets and stoves.

Continuous control of flagellar gene expression by the σ28-FlgM regulatory circuit in Salmonella enterica.

The flagellar genes in Salmonella enterica are expressed in a temporal hierarchy that mirrors the assembly process itself. The σ(28)-FlgM regulatory circuit plays a key role in controlling this temporal hierarchy. This circuit ensures that the class 3 genes are expressed only when the hook-basal body (HBB), a key intermediate in flagellar assembly, is complete. In this work, we investigated the role of the σ(28)-FlgM regulatory circuit in controlling the timing and magnitude of class 3 gene expression using a combination of mathematical modelling and experimental analysis. Analysis of the model predicted that this circuit continuously controls class 3 gene expression in response to HBB abundance. We experimentally validated these predictions by eliminating different components of the σ(28)-FlgM regulatory system and also by rewiring the transcriptional hierarchy. Based on these results, we conclude that the σ(28)-FlgM regulatory circuit continuously senses the HBB assembly process and regulates class 3 gene expression and possibly flagellar numbers in response.

Personal exposure to PM2.5 of indoor and outdoor origin in two neighboring Chinese communities with contrasting household fuel use patterns.

The Chinese government is replacing high-polluting, household coal heating stoves with electricity- and natural gas-powered heaters to improve ambient air quality. The evaluation of the intervention impact on outdoor PM2.5 and personal exposure in community level are in their initial stages. We compared outdoor air pollution and personal exposure in two neighboring communities (~2 km) in northern China with contrasting household fuel use patterns: one where residents primarily used coal for cooking and heating ("coal village") and one where natural gas was the dominant fuel ("gas village"). We collected 24-h outdoor gravimetric PM2.5 samples in each village and concurrently measured 48-h integrated exposures among 71 participants from 41 and 30 households in the coal and gas villages, respectively. PM2.5 samples were analyzed for mass and chemical composition. Daily outdoor PM2.5 concentrations in the coal village (mean ± standard deviation: 109 ± 41 µg/m3) were, on average, 1.3 ± 0.2 times higher than in the gas village (88 ± 38 µg/m3). However, personal PM2.5 exposures were lower in the coal village (116 ± 121 µg/m3 versus 156 ± 106 µg/m3). PM2.5 species that can serve as tracers for residential coal combustion (e.g., S, Se, Zn, Pb, etc.) and dust (Al, Ca, Mg, Fe, Si and Ti) were higher in the coal village, and the proportion of personal PM2.5 of outdoor origin in the coal village was nearly 2 times higher than the gas village. Our results suggest that ambient PM2.5 and its chemical composition can vary at relatively small spatial scales and may reflect community-level differences in the household energy use. However, personal PM2.5 exposures may not mirror between-village differences in outdoor air pollution if only PM2.5 mass is evaluated. Individual chemical composition of PM2.5 exposure can provide important insight in future studies on the effectiveness of source-targeted air quality interventions.

FliZ induces a kinetic switch in flagellar gene expression.

FliZ is an activator of class 2 flagellar gene expression in Salmonella enterica. To understand its role in flagellar assembly, we investigated how FliZ affects gene expression dynamics. We demonstrate that FliZ participates in a positive-feedback loop that induces a kinetic switch in class 2 gene expression.