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In an effort to reduce nitrogen oxide (NOx) emissions and other pollutants from heavy-duty vehicles (HDVs), regulators have been implementing more stringent regulations that have included a combination of significantly more stringent emissions standards with the introduction of battery electric vehicles (BEVs). This study analyzed in-use NOx emissions data from 63 HDVs across various vocations, model years, and engine technologies/fuels to assess which current technologies offer a realistic path toward reducing NOx emissions without significantly burdening fleet operators or electrical infrastructure. All 63 HDVs were equipped with portable emissions measurement systems when they were tested for in-use NOx emissions during their routine operation on California roadways. The data was analyzed using the moving average window method proposed by the Environmental Protection Agency (EPA) in which the in-use emissions are broken up into two bins dependent on the engine load: ≤6 % (idle) and >6 % of maximum rated power. It was found that diesel engines manufactured after 2020 and natural gas engines certified to the 0.02 g/bhp-h NOx standard met the 2027 and 2035 EPA in-use NOx standards for both bins even though the future standards do not apply to these older engines. In addition, over an 80 % reduction in average NOx emissions is seen in both bins and fuels as modern NOx and greenhouse gas standards were implemented in 2017. With the implementation of ultralow NOx diesel technology engines, capable of meeting 0.035 g/bhp-h NOx limits, it was found that reductions in the NOx emissions inventories from 90.0 to 91.9 % could be achieved by 2050, depending on the deployment of BEVs. In conclusion, current and upcoming engine technologies can serve as benchmark powertrain solutions for emissions inventory reductions in the near and intermediate terms solutions even to the extent that the transition to battery electric HDVs becomes more gradual. 

Plants synthesize thousands of volatile organic compounds (VOCs) (see Glossary), which mainly include isoprene (C5, hemiterpene) and monoterpenes (C10) from the methylerythritol-4-phosphate pathway (MEP) in chloroplasts (Figure 1). Sesquiterpenes and diterpenes are less volatile and are not discussed here. Global emissions are estimated to range from 300 to 440 Tg C·year–1 for isoprene and 90 to 100 Tg C·year–1 for monoterpenes [1., 2., 3.]. Biosynthesis of isoprenoids consumes 1–2% of carbon fixed by photosynthesis under normal conditions and >10% under stress, especially under high temperature [4., 5., 6.]. In nature, the highest emissions of isoprenoids are also detected during the hottest months of the year, as a result of an increase in the abundance of precursors, related enzyme activities, gene expression, and diffusion rates (of storage monoterpenoids) 

Isoprene is the most abundant nonmethane biogenic hydrocarbon emitted by some plants, mostly trees. It plays critical roles in atmospheric chemistry by contributing to ozone and aerosol formation. Isoprene also benefits plants, particularly under stress, through its signaling roles. Legume crops like soybean were thought to have evolutionarily lost isoprene synthase (ISPS) and are typically considered nonemitters. Here, we report that damage to soybean leaves by wounding or burning triggered a burst of isoprene emission from the undamaged part of the leaves. In silico analysis identified intactISPSgenes in the soybean genome, with features similar to known ISPSs. Protein made from these gene sequences catalyzed isoprene production in the presence of dimethylallyl diphosphate. Isoprene emission in soybeans was linked to reduced photosynthesis rates and stomatal conductance. Metabolomic analysis showed that leaf damage caused a surge in glyceraldehyde 3-phosphate and pyruvate levels, leading to an increase of most of the methylerythritol 4-phosphate pathway metabolites. 

ABSTRACT Follow-up observations of neutrino events have been a promising method for identifying sources of very-high-energy cosmic rays. Neutrinos are unambiguous tracers of hadronic interactions and cosmic rays. On 2020 June 15, IceCube detected a neutrino event with an 82.8 per cent probability of being astrophysical in origin. To identify the astrophysical source of the neutrino, we used X-ray tiling observations to identify potential counterpart sources. We performed additional multiwavelength follow-up with NuSTAR and the VLA in order to construct a broadband spectral energy distribution (SED) of the most likely counterpart. From the SED, we calculate an estimate for the neutrinos we expect to detect from the source. While the source does not have a high predicted neutrino flux, it is still a plausible neutrino emitter. It is important to note that the other bright X-ray candidate sources consistent with the neutrino event are also radio-quiet active galactic nuclei. A statistical analysis shows that 1RXS J093117.6+033146 is the most likely counterpart (87.5 per cent) if the neutrino is cosmic in origin and if it is among X-ray detectable sources. This result adds to previous results suggesting a connection between radio-quiet AGN and IceCube neutrino events. 

Isoprene, emitted by some plants, deters insect herbivory. However, the associated biochemical and physiological responses that confer herbivory resistance remain unknown. We used engineered isoprene-emitting (IE) and non-emitting (NE) control tobacco plants to interpret isoprene-mediated defense against herbivory in plants. Hornworm larvae raised on IE plants exhibited stunted growth compared to those raised on NE plants. Worms preferred to feed on NE rather than IE leaves, indicating deterrent effects of isoprene on insect feeding. Worm feeding induced a greater increase in jasmonic acid (JA), a crucial hormone for insect resistance, in IE leaves compared to that in NE leaves. Assimilation rates were stably maintained in IE plants, suggesting a protective role of isoprene in preserving photosynthetic efficiency during insect herbivory. Wound-induced increase in isoprene emission correlated with the elevation of key metabolites of the isoprene biosynthesis pathway. Our results highlight JA-priming functions of isoprene and provide insights into isoprene-mediated defense against insect herbivory.