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L-carnitine, a nutrient in red meat, was recently reported to accelerate atherosclerosis via a metaorganismal pathway involving gut microbial trimethylamine (TMA) formation and host hepatic conversion into trimethylamine-N-oxide (TMAO). Herein, we show that following L-carnitine ingestion, γ-butyrobetaine (γBB) is produced as an intermediary metabolite by gut microbes at a site anatomically proximal to and at a rate ∼1,000-fold higher than the formation of TMA. Moreover, we show that γBB is the major gut microbial metabolite formed from dietary L-carnitine in mice, is converted into TMA and TMAO in a gut microbiota-dependent manner (like dietary L-carnitine), and accelerates atherosclerosis. Gut microbial composition and functional metabolic studies reveal that distinct taxa are associated with the production of γBB or TMA/TMAO from dietary L-carnitine. Moreover, despite their close structural similarity, chronic dietary exposure to L-carnitine or γBB promotes development of functionally distinct microbial communities optimized for the metabolism of L-carnitine or γBB, respectively.

Currently, the electrochemical CO2 reduction reaction (CO2RR) can realize the resource conversion of CO2, which is a promising approach to carbon resource use. Important advancements have been made in exploring the CO2RR performance and mechanism because of the rational design of electrolyzer systems, such as H-cells, flow cells, and catalysts. Considering the future development direction of this technology and large-scale application needs, membrane electrode assembly (MEA) systems can improve energy use efficiency and achieve large-scale CO2 conversion, which is considered the most promising technology for industrial applications. This review will concentrate on the research progress and present situation of the MEA component structure. This paper begins with the composition and construction of a gas diffusion electrode. Then, the application of ion-exchange membranes in MEA is introduced. Furthermore, the effects of pH and the anion and cation of the anolyte on MEA performance are explored. Additionally, we present the anode reaction type in MEA. Finally, the challenges in this field are summarized, and upcoming trends are projected. This review should offer researchers a clearer picture of MEA systems and provide important, timely, and valuable insights into rational electrolyzer design to facilitate further development of CO2 electrochemical reduction. [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries (ZIBs) have emerged as the most promising candidate for large‐scale energy storage due to their inherent safety, environmental friendliness, and cost‐effectiveness. Simultaneously, the utilization of organic electrode materials with renewable resources, environmental compatibility, and diverse structures has sparked a surge in research and development of aqueous Zn‐organic batteries (ZOBs). A comprehensive review is warranted to systematically present recent advancements in design principles, synthesis techniques, energy storage mechanisms, and zinc‐ion storage performance of organic cathodes. In this review article, we comprehensively summarize the energy storage mechanisms employed by aqueous ZOBs. Subsequently, we categorize organic cathode materials into small‐molecule compounds and high‐molecular polymers respectively. Novel polymer materials such as conjugated polymers (CPs), conjugated microporous polymers (CMPs), and covalent organic frameworks (COFs) are highlighted with an overview of molecular design strategies and structural optimization based on organic cathode materials aimed at enhancing the performance of aqueous ZOBs. Finally, we discuss the challenges faced by aqueous ZOBs along with future prospects to offer insights into their practical applications. [ABSTRACT FROM AUTHOR]

BACKGROUND. L-Carnitine, an abundant nutrient in red meat, accelerates atherosclerosis in mice via gut microbiota- dependent formation of trimethylamine (TMA) and trimethylamine N-oxide (TMAO) via a multistep pathway involving an atherogenic intermediate, [gamma]-butyrobetaine ([gamma]BB). The contribution of [gamma]BB in gut microbiota- dependent L-carnitine metabolism in humans is unknown.METHODS. Omnivores and vegans/vegetarians ingested deuterium-labeled L-carnitine ([d.sub.3]-L-carnitine) or [gamma]BB ([d.sub.9]-[gamma]BB), and both plasma metabolites and fecal polymicrobial transformations were examined at baseline, following oral antibiotics, or following chronic ([greater than or equal to] 2 months) L-carnitine supplementation. Human fecal commensals capable of performing each step of the L-carnitine [right arrow] [gamma]BB [right arrow] TMA transformation were identified.RESULTS. Studies with oral [d.sub.3]-L-carnitine or [d.sub.9]-[gamma]BB before versus after antibiotic exposure revealed gut microbiota contribution to the initial 2 steps in a metaorganismal L-carnitine [right arrow] [gamma]BB [right arrow] TMA [right arrow] TMAO pathway in subjects. Moreover, a striking increase in [d.sub.3]-TMAO generation was observed in omnivores over vegans/vegetarians (>20-fold; P = 0.001) following oral [d.sub.3]-L-carnitine ingestion, whereas fasting endogenous plasma L-carnitine and [gamma]BB levels were similar in vegans/ vegetarians (n = 32) versus omnivores (n = 40). Fecal metabolic transformation studies, and oral isotope tracer studies before versus after chronic L-carnitine supplementation, revealed that omnivores and vegans/vegetarians alike rapidly converted carnitine to [gamma]BB, whereas the second gut microbial transformation, [gamma]BB [right arrow] TMA, was diet inducible (L-carnitine, omnivorous). Extensive anaerobic subculturing of human feces identified no single commensal capable of L-carnitine [right arrow] TMA transformation, multiple community members that converted L-carnitine to [gamma]BB, and only 1 Clostridiales bacterium, Emergencia timonensis, that converted [gamma]BB to TMA. In coculture, E. timonensis promoted the complete L-carnitine [right arrow] TMA transformation.CONCLUSION. In humans, dietary L-carnitine is converted into the atherosclerosis- and thrombosis-promoting metabolite TMAO via 2 sequential gut microbiota-dependent transformations: (a) initial rapid generation of the atherogenic intermediate [gamma]BB, followed by (b) transformation into TMA via low-abundance microbiota in omnivores, and to a markedly lower extent, in vegans/vegetarians. Gut microbiota [gamma]BB [right arrow] TMA/TMAO transformation is induced by omnivorous dietary patterns and chronic L-carnitine exposure.TRIAL REGISTRATION. ClinicalTrials.gov NCT01731236.FUNDING. NIH and Office of Dietary Supplements grants HL103866, HL126827, and DK106000, and the Leducq Foundation., IntroductionRecent studies identify a mechanistic link between a Western diet, gut microbiota-dependent metabolism, and development of both cardiovascular disease (CVD) and metabolic diseases (1-3). For example, the ingestion of trimethylamine-containing [...]

Intestinal microbiota metabolism of choline and phosphatidylcholine produces trimethylamine (TMA), which is further metabolized to a proatherogenic species, trimethylamine-N-oxide (TMAO). We demonstrate here that metabolism by intestinal microbiota of dietary L-carnitine, a trimethylamine abundant in red meat, also produces TMAO and accelerates atherosclerosis in mice. Omnivorous human subjects produced more TMAO than did vegans or vegetarians following ingestion of L-carnitine through a microbiota-dependent mechanism. The presence of specific bacterial taxa in human feces was associated with both plasma TMAO concentration and dietary status. Plasma L-carnitine levels in subjects undergoing cardiac evaluation (n = 2,595) predicted increased risks for both prevalent cardiovascular disease (CVD) and incident major adverse cardiac events (myocardial infarction, stroke or death), but only among subjects with concurrently high TMAO levels. Chronic dietary L-carnitine supplementation in mice altered cecal microbial composition, markedly enhanced synthesis of TMA and TMAO, and increased atherosclerosis, but this did not occur if intestinal microbiota was concurrently suppressed. In mice with an intact intestinal microbiota, dietary supplementation with TMAO or either carnitine or choline reduced in vivo reverse cholesterol transport. Intestinal microbiota may thus contribute to the well-established link between high levels of red meat consumption and CVD risk.

The drag of coaxial helicopter hub accounts is more than 50% of the total helicopter's waste drag, so it is necessary to research the drag characteristics and reduction design of the hub. Wind tunnel test is carried out for a coaxial helicopter hub model, drag reduction scheme and drag reduction scheme with vortex generator. The drag characteristics of coaxial helicopter hub is researched. The drag reduction effect of the drag reduction scheme and drag reduction scheme with vortex generator are verified. The results show that the azimuth, rotation speed and attack angle have little influence on the drag of hub and its drag reduction scheme, the gap between the upper and lower hub fairings and the shaft fairing has a relatively large impact on drag, the drag reduction scheme can reduce the drag by about 33%, and the drag effect of the vortex generator is not obvious.