Rapid dark aging of biomass burning as an overlooked source of oxidized organic aerosol

Oxidized organic aerosol (OOA) is a major component of ambient particulate matter, substantially impacting climate, human health, and ecosystems. OOA is readily produced in the presence of sunlight, and requires days of photooxidation to reach the levels observed in the atmosphere. High concentrations of OOA are thus expected in the summer; however, our current mechanistic understanding fails to explain elevated OOA during wintertime periods of low photochemical activity that coincide with periods of intense biomass burning. As a result, atmospheric models underpredict OOA concentrations by a factor of 3 to 5. Here we show that fresh emissions from biomass burning exposed to NO₂ and O₃ (precursors to the NO₃ radical) rapidly form OOA in the laboratory over a few hours and without any sunlight. The extent of oxidation is sensitive to relative humidity. The resulting OOA chemical composition is consistent with the observed OOA in field studies in major urban areas. Additionally, this dark chemical processing leads to significant enhancements in secondary nitrate aerosol, of which 50 to 60% is estimated to be organic. Simulations that include this understanding of dark chemical processing show that over 70% of organic aerosol from biomass burning is substantially influenced by dark oxidation. This rapid and extensive dark oxidation elevates the importance of nocturnal chemistry and biomass burning as a global source of OOA.

Highly oxidized organic aerosol (OOA) is a dominant component of particulate matter air pollution globally (1–3); however, sources of OOA remain uncertain, limiting the ability of models to accurately represent OOA and thus predict the associated climate, ecosystem, and health implications (4, 5). The current conceptual model of OOA formation suggests that anthropogenic OOA predominantly originates from the oxidation of volatile (VOCs), intermediate volatility (IVOCs), and semivolatile (SVOCs) organic compounds by the OH radical, resulting in lower-volatility products that condense to the particle phase (6). As the OH radical is formed through photolysis and has a very short atmospheric lifetime [less than a second (7)], this oxidation mechanism only occurs in the presence of sunlight. Further, the time scale for OOA formation through oxidation with OH in models is on the order of a few days (8). While this understanding is sufficient in explaining OOA concentrations in summer or periods with high solar radiation, atmospheric models fail to reproduce the observed concentration of OOA in the ambient atmosphere during winter and low-light conditions (9, 10). Fountoukis et al. (9) found simulated OOA concentrations significantly underestimated in wintertime Paris. Tsimpidi et al. (10) also reported an underprediction of simulated OOA globally in winter, suggesting missing sources of both primary OA (POA) and secondary formation pathways. This underproduction suggests a possible overlooked conversion pathway of organic vapors or particles to OOA that is not accounted for in current chemical transport and climate models.As stricter controls on fossil fuel combustion are implemented, residential biomass burning (BB) as a source of heating or cooking is becoming an increasingly important source of OA in urban environments (1, 11, 12). Further, increasing rates of wildfires from climate change are increasing the frequency of smoke-impacted days in urban areas (12–14). BB emissions include high concentrations of POA, SVOCs, IVOCs, and VOCs (15, 16), thus making BB a key source of OOA. Previous research has focused on quantifying the concentration of OOA formed through photochemical oxidation reactions (i.e., OH) with BB emissions (17, 18). However, oxidation of BB emissions in low or no sunlight is less well understood and is not included in chemical transport models. As opposed to OH, the NO₃ radical is formed through reactions with NO₂ and O₃ and is rapidly lost in the presence of sunlight (19). Thus, the NO₃ radical is only available in significant concentrations at night or other low-light conditions (20, 21). Previous research has established that biogenic VOCs may undergo oxidation at night when mixed with anthropogenic emissions containing NO₂ and O₃ (19, 22–27). There have been only a few studies that consider that nighttime oxidation of residential wood combustion may proceed through similar pathways (28–31); however, the magnitude and relevance to observed OOA in the ambient atmosphere has not yet been established. By combining laboratory experiments and ambient observations to inform a chemical transport model, we present strong evidence that nighttime oxidation of BB plumes (proceeding through reactions with O₃ and the NO₃ radical) is an important source of OOA.     

Enhanced H2 sorption performance of magnesium hydride with hard-carbon-sphere-wrapped nickel

Magnesium hydride is regarded as one of the most ideal candidates for hydrogen storage, but its relatively high operating temperatures and slow kinetics always hinder its commercial applications. Herein, we first fabricated hard-carbon-sphere-wrapped Ni (Ni/HCS) via a mild chemical method; subsequently, the as-prepared additive was introduced to fabricate an Mg–Ni/HCS composite by using hydriding combustion synthesis. Hard carbon spheres (HCS) effectively inhibited the agglomeration of hydride particles during hydrogen storage cycling; they could also provide active sites to promote the nucleation of Mg-based hydrides. During the hydriding combustion synthesis procedure, in situ-formed Mg₂NiH₄ could induce the absorption of MgH₂, thus triggering its hydrogen properties. Remarkable enhancement in hydrogen absorption properties of the composite was found. The composite absorbed 6.0 wt% H₂ within 5 min at 275 °C; moreover, even at 75 °C, it could still absorb 3.5 wt% H₂. Furthermore, it delivered a high reversible hydrogen absorption capacity of 6.2 wt% and excellent rate capability at 350 °C. It was also demonstrated that the composite could release 6.2 wt% H₂ at 350 °C within 5 min. A rather low activation energy value (65.9 kJ mol⁻¹) for the dehydrogenation of MgH₂ was calculated as compared to that for commercial MgH₂ (133.5 kJ mol⁻¹).

Magnesium hydride is regarded as one of the most ideal candidates for hydrogen storage, but its relatively high operating temperatures and slow kinetics always hinder its commercial applications.     

顺铂化疗联合用药的增效减毒作用研究进展

摘 要 顺铂在临床上应用于多种肿瘤的治疗,也会引起广泛的不良反应如肾毒性、肝毒性、耳毒性等,限制了其临床应用,因此临床上主张联合用药以达到增效减毒的作用。本文概述了近些年来关于化学药及中药（中药成分、单味中药及中药复方）对顺铂的增效解毒作用方面的研究进展,为化疗药联合用药研究和临床给药方案的制定提供参考依据。     

An interprofessional approach to reducing hospital-onset Clostridioides difficile infections

BackgroundClostridioides difficile is the most prevalent hospital-onset (HO) infection. There are significant financial and safety impacts associated with HO-C. difficile infections (HO-CDIs) for both patients and health care organizations. The incidence of HO-CDIs at our community hospital within an academic acute health care system was continuously above the national benchmark.MethodsIn response to the high HO-CDI rates at our facility, an interprofessional team selected evidence-based interventions with the goal of reducing HO-CDI incidence rates. Interventions included: diagnostic stewardship, enhanced environmental cleaning, antimicrobial stewardship and education and accountability.ResultsAfter one year, we achieved a 63% reduction in HO-CDI and have sustained a 77% reduction. The infection rate remained below national benchmark for HO-CDI for over 4 years at a rate of 2.80 per 10,000 patient days and a SIR of 0.43 in 2020.DiscussionMultiple evidence-based interventions were successfully implemented over several service lines over a 4-year period through the collaboration of an interprofessional team. The addition of an accountability processes further improved compliance with standards of practice.ConclusionsCollaboration of an interprofessional team led to substantial and sustained reductions in HO-CDI.     

Flavonoids derived from liquorice suppress murine macrophage activation by up-regulating heme oxygenase-1 independent of Nrf2 activation

Liquiritigenin (LQG), isoliquiritin (ILQ) and isoliquiritigenin (ILG) are flavonoids derived from liquorice and all possess a similar chemical structural backbone. In the current study, we found that ILQ and ILG had suppressive effects on lipopolysaccharide (LPS)-induced inflammatory responses in murine macrophage by suppressing the iNOS and COX-2 proteins and mRNA expression. A mechanistic study indicated that the effect was associated with an induction of antioxidant and detoxification enzymes, including UGT1A1, NQO1, and heme oxygenase-1 (HO-1) mRNA expression. The regulator of these enzymes, nuclear factor-erythroid 2-related factor 2 (Nrf2), which plays a critical role in LPS-induced inflammatory responses, could be activated by ILQ and ILG. Additionally, ILQ and ILG promoted Nrf2 signaling activation by inhibiting the Kelch-like ECH-associated protein 1 (Keap1) and increasing Nrf2 translocation, inducing the expression of these antioxidant enzymes. We further found that ILQ and ILG induced HO-1 expression independent of Nrf2 expression. With respect to the effect of these compounds on NF-κB signaling, ILG was found to markedly inhibit IκBα degradation and phosphorylation, while LQG and ILQ had no significant effects. These results indicate that there are correlations between the anti-inflammatory responses and the chemical structural properties of these flavonoids.