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The decay of methyl chloroform, a banned ozone-depleting substance, has provided a clear observational metric of mean tropospheric hydroxyl radical (OH) abundance. Almost all current global chemistry models calculate about 15% too much OH and thus too rapid methane loss. Methane is a short-lived climate forcer, critical to achieving global warming targets, and this error affects our model projections of climate change. New observations of water vapor absorption in the ultraviolet region (290 to 350 nanometers) imply reductions in sunlight with key photolysis rates decreasing by 8 to 12% in the near-surface tropical atmosphere. Incorporation of this new mechanism in a chemistry-transport model reduces OH and methane loss by only 4%, but combined with other proposed mechanisms, such as tropospheric halogen chemistry (7%), we may be able to resolve this conundrum.

Dark aqueous-phase reactions involving the nitrosation and nitration of aromatic organic compounds play a significant role in the production of light-absorbing organic carbon in the atmosphere. This process constitutes a crucial aspect of tropospheric chemistry and has attracted growing research interest, particularly in understanding the mechanisms governing nighttime reactions between phenols and nitrogen oxides. In this study, we present new findings concerning the rapid dark reactions between phenols containing electron-donating groups and inorganic nitrite in acidic aqueous solutions with pH levels <3.5. This reaction generates a substantial amount of nitroso- and nitro-substituted phenolic compounds, known for their light-absorbing properties and toxicity. In experiments utilizing various substituted phenols, we demonstrate that their reaction rates with nitrite depend on the electron cloud density of the benzene ring, indicative of an electrophilic substitution reaction mechanism. Control experiments and theoretical calculations indicate that the nitrosonium ion (NO+) is the reactive nitrogen species responsible for undergoing electrophilic reactions with phenolate anions, leading to the formation of nitroso-substituted phenolic compounds. These compounds then undergo partial oxidation to form nitro-substituted phenols through reactions with nitrous acid (HONO) or other oxidants like oxygen. Our findings unveil a novel mechanism for swift atmospheric nitrosation and nitration reactions that occur within acidic cloud droplets or aerosol water, providing valuable insights into the rapid nocturnal formation of nitrogen-containing organic compounds with significant implications for climate dynamics and human health.

Intersections are essential road infrastructures for traffic in modern metropolises. However, they can also be the bottleneck of traffic flows as a result of traffic incidents or the absence of traffic coordination mechanisms such as traffic lights. Recently, various control and coordination mechanisms that are beyond traditional control methods have been proposed to improve the efficiency of intersection traffic by leveraging the ability of autonomous vehicles. Among these methods, the control of foreseeable mixed traffic that consists of human-driven vehicles (HVs) and robot vehicles (RVs) has emerged. We propose a decentralized multi-agent reinforcement learning approach for the control and coordination of mixed traffic by RVs at real-world, complex intersections—an open challenge to date. We design comprehensive experiments to evaluate the effectiveness, robustness, generalizablility, and adaptability of our approach. In particular, our method can prevent congestion formation via merely 5% RVs under a real-world traffic demand of 700 vehicles per hour. In contrast, without RVs, congestion will form when the traffic demand reaches as low as 200 vehicles per hour. Moreover, when the RV penetration rate exceeds 60%, our method starts to outperform traffic signal control in terms of the average waiting time of all vehicles. Our method is not only robust against blackout events, sudden RV percentage drops, and V2V communication error, but also enjoys excellent generalizablility, evidenced by its successful deployment in five unseen intersections. Lastly, our method performs well under various traffic rules, demonstrating its adaptability to diverse scenarios. Videos and code of our work are available at https://sites.google.com/view/mixedtrafficcontrol .

Biomass burning (BB) is a major source of trace gases and particles in the atmosphere, influencing air quality, radiative balance, and climate. Previous studies have mainly focused on the BB emissions of carbon and nitrogen species with less attention on chlorine. Reactive chlorine chemistry has significant effects on atmospheric chemistry and air quality. However, quantitative information on chlorine emissions from BB, particularly the long-term trend and associated atmospheric impacts, is limited both on regional and global scales. Here, we report a long-term (2001–2018) high-resolution BB emission inventory for the major chlorine-containing compounds (HCl, chloride, and CH3Cl) in Asia based on satellite observations. We estimate an average of 730 Gg yr−1 chlorine emitted from BB activity in Asia, with China contributing the largest share at 24.2% (177 Gg yr−1), followed by Myanmar at 18.7% and India at 18.3%. Distinct seasonal patterns and significant spatial and interannual variability are observed, mainly driven by human-mediated changes in agricultural activity. By incorporating the newly developed chlorine emission inventory into a global chemistry-climate model (CAM-Chem), we find that the BB-chlorine emissions lead to elevated levels of HCl and CH3Cl (monthly average up to 2062 and 1421 parts per trillion by volume (pptv), respectively), subsequently resulting in noticeable changes in oxidants (up to 3.1% in O3 and 17% in OH radicals). The results demonstrate that BB is not only a significant source of air pollutants but also of oxidants, suggesting a larger role of BB emissions in the atmospheric chemistry and oxidation process than previously appreciated. In light of the projected increase in BB activity toward the end of the century and the extensive control of anthropogenic emissions worldwide, the contribution of BB emissions may become fundamental to air quality composition in the future.

Relaxor ferroelectric polymers exhibiting a giant electrocaloric effect (ECE) can potentially be used to create next‐generation solid‐state coolers. Under an electric field, poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) terpolymer goes through a large dipolar entropy change producing a high adiabatic temperature change (ΔT_ECE). This work resolves the molecular origins of the large entropy change behind the electric field‐induced dipole switching. A Fourier transform infrared spectroscopy equipped with a high voltage source is used to operandoly observe the characteristic molecular vibrational modes. A short‐range trans (T) conformation of the CF₂‐CH₂dyads interrupted by a gauche (G) conformation, e.g., TTTG in the terpolymer chain, undergoes a dynamic transformation that leads to a corresponding ΔT_ECEwhenever an electric field is applied. The molecular dynamics simulation also proves that the energy barrier that the transformation from TTTGs into a long T sequence overcomes is smaller than that for all other conformations. A mixed solvent system is used to obtain T3G‐enriched terpolymer films exhibiting a 4.02 K ΔT_ECEat 60 MV m⁻¹and these films are employed to manufacture a 2‐layer‐cascaded cooling device that achieves a 6.7 K temperature lift, the highest reported value for a 2‐layer cascaded device made of fluoropolymers.

Side chain engineering of non-planar zinc(ii) complexes of azadipyrromethene enables either very high hole mobility, high electron mobility or both as estimated by the space-charge limited current (SCLC) method in diodes.

The sequential biochemical (SNAP-tag) and chemical (chelation-assisted copper-catalyzed azide–alkyne cycloaddition) reactions are applied in membrane protein labeling on live cells. The second, chemical step is rapid (within 1 minute) without any ill-effect to the labeled cells.

Poly(vinylidene fluoride) (PVDF)‐based polymers demonstrate great potential for applications in flexible and wearable electronics but show low piezoelectric coefficients (e.g., −d₃₃< 30 pC N⁻¹). The effective improvement for the piezoelectricity of PVDF is achieved by manipulating its semicrystalline structures. However, there is still a debate about which component is the primary contributor to piezoelectricity. Therefore, current methods to improve the piezoelectricity of PVDF can be classified into modulations of the amorphous phase, the crystalline region, and the crystalline–amorphous interface. Here, the basic principles and measurements of piezoelectric coefficients for soft polymers are first discussed. Then, three different categories of structural modulations are reviewed. In each category, the physical understanding and strategies to improve the piezoelectric performance of PVDF are discussed. In particular, the crucial role of the oriented amorphous fraction at the crystalline–amorphous interface in determining the piezoelectricity of PVDF is emphasized. At last, the future development of high performance piezoelectric polymers is outlooked.