Quantitative Assessment Method of Muzzle Smoke in a Field Environment.

The muzzle of barrel weapons produces a large amount of smoke (muzzle smoke), a major source of pollution in the battlefield. Quantitative assessment of muzzle smoke is an important support for the development of advanced propellants. However, due to the lack of effective measurement methods for field experiments, most of the previous studies were based on a smoke box, and few studies have focused on muzzle smoke in the field environment. In view of the nature of the muzzle smoke and the conditions of the field environment, the characteristic quantity of muzzle smoke (CQMS) was defined based on the Beer-Lambert law in this paper. CQMS is used to characterize the danger level of muzzle smoke produced by the propellant charge, and theoretical calculations indicated that when the transmittance is e -2, the impact of the measurement errors on CQMS can be minimized. Seven firings with the same propellant charge of a 30 mm gun were carried out in a field environment to verify the effectivity of CQMS. The measurement uncertainty analysis on the experimental results showed that the CQMS of the propellant charge used in this study was 2.35 ± 0.06 m2, which indicates that CQMS can be used to quantitatively assess muzzle smoke.

Ecological risk assessment for organophosphate esters in the surface water from the Bohai Sea of China using multimodal species sensitivity distributions.

Organophosphate esters (OPEs) as the foremost substitutes of brominated flame retardants have been ubiquitously found in the aquatic environment around the world. However, the information on the community-level risks induced by OPEs to the marine ecosystem remains scarce. This study adopted ten commonly used species sensitivity distribution (SSD) parametric statistical approaches coupled with the acute-to-chronic transformation for the toxicity data to fit the sensitivity distributions of different species to four major OPE congeners including triethyl phosphate (TEP), tri-n-butyl phosphate (TnBP), tri(2-chloroethyl) phosphate (TCEP), and tris(1-chloro-2-propyl) phosphate (TCPP) in the surface water of the Bohai Sea. All SSD models except Exponential for TnBP, TCEP, and TCPP fitted well the chronic toxicity data for the four OPE congeners. Discrepancies appeared among the best fitting models for different congeners, which also happened to the fitting results from the multiple SSD models for each congener. Based on the best fitting models, the hazard concentrations corresponding to the cumulative probability of 5% were 3.58 mg/L, 0.116 mg/L, 1.30 mg/L, and 1.44 mg/L for TEP, TnBP, TCEP, and TCPP, respectively. The risks induced by the four OPE congeners to the Bohai Sea ecosystem were negligible during the monitoring period because of both the risk quotients and the hazard indexes far <0.1. This study drew a clear picture of the joint ecological risks of TEP, TnBP, TCEP, and TCPP to the Bohai Sea environment. The application of multimodal SSD statistical methods will benefit the accurate derivation of water quality criteria and the community-level ecological risk assessment for pollutants.

Single-molecule tracking in live Yersinia enterocolitica reveals distinct cytosolic complexes of injectisome subunits.

In bacterial type 3 secretion, substrate proteins are actively transported from the bacterial cytoplasm into the host cell cytoplasm by a large membrane-embedded machinery called the injectisome. Injectisomes transport secretion substrates in response to specific environmental signals, but the molecular details by which the cytosolic secretion substrates are selected and transported through the type 3 secretion pathway remain unclear. Secretion activity and substrate selectivity are thought to be controlled by a sorting platform consisting of the proteins SctK, SctQ, SctL, and SctN, which together localize to the cytoplasmic side of membrane-embedded injectisomes. However, recent work revealed that sorting platform proteins additionally exhibit substantial cytosolic populations and that SctQ reversibly binds to and dissociates from the cytoplasmic side of membrane-embedded injectisomes. Based on these observations, we hypothesized that dynamic molecular turnover at the injectisome and cytosolic assembly among sorting platform proteins is a critical regulatory component of type 3 secretion. To determine whether sorting platform complexes exist in the cytosol, we measured the diffusive properties of the two central sorting platform proteins, SctQ and SctL, using live cell high-throughput 3D single-molecule tracking microscopy. Single-molecule trajectories, measured in wild-type and mutant Yersinia enterocolitica cells, reveal that both SctQ and SctL exist in several distinct diffusive states in the cytosol, indicating that these proteins form stable homo- and hetero-oligomeric complexes in their native environment. Our findings provide the first diffusive state-resolved insights into the dynamic regulatory network that interfaces stationary membrane-embedded injectisomes with the soluble cytosolic components of the type 3 secretion system.